CN114678943A - Photovoltaic power generation energy storage circuit, control method and control system - Google Patents

Photovoltaic power generation energy storage circuit, control method and control system Download PDF

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Publication number
CN114678943A
CN114678943A CN202210595997.4A CN202210595997A CN114678943A CN 114678943 A CN114678943 A CN 114678943A CN 202210595997 A CN202210595997 A CN 202210595997A CN 114678943 A CN114678943 A CN 114678943A
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photovoltaic cell
output
buck
photovoltaic
voltage
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CN114678943B (en
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郑明才
廖永忠
郑钊
赵小超
郑金兵
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Hefei Boyi Network Operation Co.,Ltd.
NINGBO KELUN SOLAR ENERGY CO Ltd
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Hunan First Normal University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/34—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering
    • H02J7/35—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering with light sensitive cells
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/007—Regulation of charging or discharging current or voltage
    • H02J7/00712—Regulation of charging or discharging current or voltage the cycle being controlled or terminated in response to electric parameters
    • H02J7/007182—Regulation of charging or discharging current or voltage the cycle being controlled or terminated in response to electric parameters in response to battery voltage
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E70/00—Other energy conversion or management systems reducing GHG emissions
    • Y02E70/30—Systems combining energy storage with energy generation of non-fossil origin

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Charge And Discharge Circuits For Batteries Or The Like (AREA)
  • Dc-Dc Converters (AREA)
  • Control Of Electrical Variables (AREA)

Abstract

The invention discloses a photovoltaic power generation energy storage circuit, a control method and a control system, wherein the energy storage circuit comprises a photovoltaic cell, a BUCK module, a BOOST-BUCK combined module, a digital controller, a storage battery and a current sampling module, wherein the digital controller is used for controlling the BUCK module and the BOOST-BUCK combined module according to detected photovoltaic cell output voltage, photovoltaic cell output power, storage battery voltage and photovoltaic cell output current information, prompting the photovoltaic power generation energy storage circuit to be switched to a corresponding working state, implementing MPPT control on the photovoltaic cell output power, forcing the photovoltaic cell to work in an MPPT state in the whole process, completing the boosting or reducing output of the photovoltaic power generation energy storage circuit, storing collected electric energy in the storage battery, and realizing the maximum power output of the photovoltaic cell. The invention enables the photovoltaic cell to work in the MPPT state in the whole process, the output power of the photovoltaic cell is maximum, and the solar energy utilization rate is highest.

Description

Photovoltaic power generation energy storage circuit, control method and control system
Technical Field
The invention relates to the technical field of photovoltaic power generation, and particularly discloses a photovoltaic power generation energy storage circuit, a control method and a control system.
Background
The BUCK circuit and the BOOST circuit are typical non-isolated Power conversion circuits, and MPPT (Maximum Power Point Tracking) control is a commonly used control technology in a photovoltaic Power generation system. The BUCK circuit outputs the input electric energy of partial time period to the output end through the filter inductor by the on/off control of the switch tube, and the BUCK circuit is voltage-reducing, and the output voltage of the circuit is lower than the input voltage. The BOOST circuit outputs input electric energy through the BOOST inductor through the on/off control of the switch tube, and is BOOST. And the MPPT control enables the equivalent load of the photovoltaic cell to be matched with the equivalent internal resistance of the photovoltaic cell through the switching of the working state of the electric energy conversion circuit, so that the photovoltaic cell works in the maximum power output state.
The existing photovoltaic power generation and energy storage system has the following defects:
1. when the BUCK circuit is used as a solar electricity collection and energy storage circuit, the output voltage is low, the energy storage capacity is weak, the solar energy utilization rate is not high, and a single BUCK circuit cannot ensure that the photovoltaic cell works in the MPPT state in the whole process.
2. When the BOOST circuit is used as a solar energy electricity collection energy storage circuit, if the starting voltage of the energy storage container is low, the output current of the photovoltaic cell is out of control, the output power of the photovoltaic cell is small, the internal loss is large, the power generation capacity of the photovoltaic cell is influenced, the solar energy utilization rate is limited, and the single BOOST circuit can not guarantee that the photovoltaic cell works in the MPPT state in the whole process.
3. When the BOOST circuit and the BUCK circuit are simply combined to be used as the electricity collecting circuit of the photovoltaic cell, the photovoltaic cell cannot be guaranteed to work in the MPPT state in the whole process due to discontinuity of the output current of the photovoltaic cell under certain working conditions.
4. The existing MPPT control method for maximum power output of the photovoltaic cell is mostly based on the internal equivalent state of the photovoltaic cell, the power generation state and equivalent parameters of the photovoltaic cell need to be estimated, the calculation is generally too complex, the real-time performance is limited during actual implementation, the actual effect is lower than the theoretical effect, the cost is higher, and the cost performance of products is not high.
Therefore, the above-mentioned defects of the existing photovoltaic power generation energy storage system are a technical problem to be solved urgently.
Disclosure of Invention
The invention provides a photovoltaic power generation energy storage circuit, a control method and a control system, and aims to overcome the defects of the conventional photovoltaic power generation energy storage system.
One aspect of the invention relates to a photovoltaic power generation energy storage circuit, which comprises a photovoltaic cell, a BUCK module, a BOOST-BUCK combination module, a digital controller, a storage battery and a current sampling module, wherein,
a photovoltaic cell for converting solar energy into electrical energy;
the current sampling module is used for collecting the output current of the photovoltaic cell;
the digital controller is respectively connected with the current sampling module, the BUCK module, the BOOST-BUCK combined module and the storage battery, and is used for controlling the BUCK module and the BOOST-BUCK combined module by outputting PWM (Pulse Width Modulation) pulses according to the detected photovoltaic cell output voltage, the photovoltaic cell output power, the voltage of the storage battery and the photovoltaic cell output current information acquired by the current sampling module, prompting the photovoltaic power generation energy storage circuit to be switched to a corresponding working state, implementing MPPT control on the output power of the photovoltaic cell, forcing the photovoltaic cell to work in an MPPT state in the whole process, completing the boosting or reducing output of the photovoltaic power generation energy storage circuit, storing the collected electric energy in the storage battery, and realizing the maximum power output of the photovoltaic cell; the working state comprises a BUCK working state and a BOOST working state.
Furthermore, the BUCK module comprises a first switch MOS tube, a first diode, a second diode and a first inductor, wherein the drain electrode of the first switch MOS tube is connected with the photovoltaic cell, the grid electrode of the first switch MOS tube is connected with the digital controller through a first driving circuit, the source electrode of the first switch MOS tube is divided into two paths, one path is connected with the anode of the storage battery through the first inductor and the first diode which are connected in series, and the other path is connected with the cathode of the storage battery through the second diode which is reversely connected.
Furthermore, the BOOST-BUCK combined module comprises a second switch MOS tube, a third diode, a fourth diode and a second inductor, wherein the drain electrode of the second switch MOS tube is connected with the photovoltaic cell, the grid electrode of the second switch MOS tube is connected with the digital controller through a second driving circuit, the source electrode of the second switch MOS tube is divided into two paths, one path is connected with the anode of the storage battery through the second inductor and the third diode which are connected in series, and the other path is connected with the cathode of the storage battery through the fourth diode which is reversely connected; the drain electrode of the third switching MOS tube is connected with the anode of the third diode, the grid electrode of the third switching MOS tube is connected with the digital controller through the third driving circuit, and the source electrode of the third switching MOS tube is connected with the cathode of the storage battery.
Furthermore, the current sampling module adopts a current Hall, and the digital controller is a microcontroller for completing the energy storage function of photovoltaic power generation.
The invention also relates to a photovoltaic power generation and energy storage control method which is applied to the photovoltaic power generation and energy storage circuit and comprises the following steps:
detecting the output voltage of the photovoltaic cell, the output power of the photovoltaic cell, the voltage of a storage battery and collecting the output current information of the photovoltaic cell collected by a current sampling module;
according to the detected photovoltaic cell output voltage, the photovoltaic cell output power, the storage battery voltage and the photovoltaic cell output current information collected by the collected current sampling module, the BUCK module and the BOOST-BUCK combined module are controlled by outputting PWM pulses, the photovoltaic power generation energy storage circuit is switched to a corresponding working state, MPPT control is carried out on the photovoltaic cell output power, the photovoltaic cell is forced to work in an MPPT state in the whole process, the collected electric energy is stored in the storage battery, and the maximum power output of the photovoltaic cell is realized; the working state comprises a BUCK working state and a BOOST working state.
Further, according to the detected photovoltaic cell output voltage, the photovoltaic cell output power, the storage battery voltage and the photovoltaic cell output current information collected by the collected current sampling module, the BUCK module and the BOOST-BUCK combination module are controlled by outputting PWM pulses, the photovoltaic power generation energy storage circuit is enabled to be switched to a corresponding working state, MPPT control is implemented on the photovoltaic cell output power, the photovoltaic cell is forced to work in an MPPT state in the whole process, the collected electric energy is stored in the storage battery, and the step of realizing the maximum power output of the photovoltaic cell comprises the following steps:
primarily detecting the output voltage of the photovoltaic cell and the voltage of the storage battery;
comparing the primarily detected output voltage of the photovoltaic cell with the voltage of the storage battery, and entering a BUCK working state if the detected output voltage of the photovoltaic cell is greater than the voltage of the storage battery; if the detected output voltage of the photovoltaic cell is less than or equal to the voltage of the storage battery, entering a BOOST working state;
waiting for the next period to arrive, and detecting the output voltage of the photovoltaic cell, the output current of the photovoltaic cell, the output power of the photovoltaic cell and the voltage of the storage battery again;
if the photovoltaic power generation energy storage circuit is identified to work in the BUCK working state, comparing the output voltage of the photovoltaic cell detected again with the voltage of the storage battery, and if the output voltage of the photovoltaic cell detected again is larger than the voltage of the storage battery, controlling the photovoltaic power generation energy storage circuit to enter the interleaved parallel BUCK working state; if the output voltage of the photovoltaic cell detected again is less than or equal to the voltage of the storage battery, controlling the photovoltaic power generation energy storage circuit to enter a BOOST working state;
if the output power of the photovoltaic cell is increased in the BUCK working state, maintaining the BUCK working state unchanged; and if the photovoltaic cell output power is increased in the BOOST working state, maintaining the BOOST working state unchanged.
Further, if the output power of the photovoltaic cell is increased in the BUCK working state, maintaining the BUCK working state; if the photovoltaic cell output power is increased under the BOOST working state, the step of maintaining the BOOST working state unchanged comprises the following steps:
if the photovoltaic power generation energy storage circuit is identified to work in the BUCK working state, controlling the cut-off state of the third switch MOS tube to be unchanged, and alternately switching the states of the first switch MOS tube and the second switch MOS tube according to the output power variation trend; and if the photovoltaic power generation energy storage circuit works in a BOOST working state, controlling the cut-off state of the second switch MOS tube and the conduction state of the first switch MOS tube to be unchanged, and alternately switching the state of the third switch MOS tube according to the output power variation trend.
Another aspect of the present invention relates to a photovoltaic power generation and energy storage control system, which is applied to the above photovoltaic power generation and energy storage circuit, wherein the digital controller comprises:
the detection unit is used for detecting the output voltage of the photovoltaic cell, the output power of the photovoltaic cell, the voltage of the storage battery and the output current information of the photovoltaic cell collected by the current collection sampling module;
the control unit is used for controlling the BUCK module and the BOOST-BUCK combined module by outputting PWM pulses according to the detected output voltage of the photovoltaic cell, the output power of the photovoltaic cell, the voltage of the storage battery and the output current information of the photovoltaic cell collected by the collected current sampling module, so that the photovoltaic power generation energy storage circuit is switched to a corresponding working state, MPPT control is carried out on the output power of the photovoltaic cell, the photovoltaic cell is forced to work in an MPPT state in the whole process, the collected electric energy is stored in the storage battery, and the maximum power output of the photovoltaic cell is realized; the working state comprises a BUCK working state and a BOOST working state.
Further, the control unit includes:
the first detection subunit is used for primarily detecting the output voltage of the photovoltaic cell and the voltage of the storage battery;
the first comparison subunit is used for comparing the primarily detected output voltage of the photovoltaic cell with the voltage of the storage battery, and if the detected output voltage of the photovoltaic cell is greater than the voltage of the storage battery, the first comparison subunit enters a BUCK working state; if the detected output voltage of the photovoltaic cell is less than or equal to the voltage of the storage battery, entering a BOOST working state;
the second detection subunit is used for detecting the output voltage of the photovoltaic cell, the output current of the photovoltaic cell, the output power of the photovoltaic cell and the voltage of the storage battery again after waiting for the next period;
the second comparison subunit is used for comparing the output voltage of the photovoltaic cell detected again with the voltage of the storage battery if the photovoltaic power generation energy storage circuit is identified to work in the BUCK working state, and controlling the photovoltaic power generation energy storage circuit to enter the interleaved parallel BUCK working state if the output voltage of the photovoltaic cell detected again is greater than the voltage of the storage battery; if the output voltage of the photovoltaic cell detected again is less than or equal to the voltage of the storage battery, controlling the photovoltaic power generation energy storage circuit to enter a BOOST working state;
the switching subunit is used for maintaining the BUCK working state unchanged if detecting that the output power of the photovoltaic cell is increased in the BUCK working state; and if the photovoltaic cell output power is increased in the BOOST working state, maintaining the BOOST working state unchanged.
Further, the switching subunit is specifically configured to control the cut-off state of the third switch MOS transistor to be unchanged if it is identified that the photovoltaic power generation energy storage circuit operates in the BUCK operating state, and alternately switch the states of the first switch MOS transistor and the second switch MOS transistor according to the output power variation trend; and if the photovoltaic power generation energy storage circuit works in a BOOST working state, controlling the cut-off state of the second switch MOS tube and the conduction state of the first switch MOS tube to be unchanged, and alternately switching the state of the third switch MOS tube according to the output power variation trend.
The invention provides a photovoltaic power generation energy storage circuit, a control method and a control system, wherein the photovoltaic power generation energy storage circuit comprises a photovoltaic cell, a BUCK module, a BOOST-BUCK combined module, a digital controller, a storage battery and a current sampling module, wherein the digital controller is respectively used for controlling the BUCK module and the BOOST-BUCK combined module by outputting PWM (pulse width modulation) pulses according to detected photovoltaic cell output voltage, photovoltaic cell output power, photovoltaic cell output current information acquired by the storage battery voltage and current sampling module, so that the photovoltaic power generation energy storage circuit is switched to a corresponding working state, MPPT control is carried out on the output power of the photovoltaic cell, the photovoltaic cell is forced to work in an MPPT state in the whole process, the boosting or reducing output of the photovoltaic power generation energy storage circuit is completed, the collected electric energy is stored in the storage battery, and the maximum power output of the photovoltaic cell is realized. The photovoltaic power generation energy storage circuit, the control method and the control system provided by the invention have the following beneficial effects:
(1) compared with a single BUCK circuit or a BOOST circuit, the output state of the photovoltaic cell is controllable in the whole process, namely the output voltage, the output current and the output power of the photovoltaic cell are controllable in the whole process.
(2) The BUCK circuit is used for limiting the output current of the photovoltaic cell, the output current of the photovoltaic cell is prevented from being too large, and the power generation performance of the photovoltaic cell is optimized.
(3) The output voltage of the energy storage circuit is improved by using the BOOST circuit, so that the energy storage is maximized.
(4) And the continuity of the output current of the photovoltaic cell is ensured by utilizing the interleaved BUCK circuit.
(5) Through the MPPT control algorithm, the photovoltaic cell is enabled to work in the MPPT state in the whole process, the output power of the photovoltaic cell is maximum, and the solar energy utilization rate is highest.
(6) In the MPPT control algorithm, basic control is directly carried out according to the change trend of the output power of the photovoltaic cell, complex calculation is avoided, the real-time performance of control is improved, and the implementation cost is reduced.
(7) The states of the switching tubes in the energy storage circuit are switched according to the change of the output power of the photovoltaic cell, the switching tubes work in a PWM control mode with unfixed frequency, and the states of the switching tubes are switched only when the output power of the photovoltaic cell is reduced, so that unnecessary switching state switching is avoided, the switching times of the switching states are reduced, and the switching loss is reduced.
(8) On the basis of an MPPT control algorithm based on output power, the output voltage, the output current and the voltage of the energy storage battery of the photovoltaic battery are monitored, so that the switching of the working state of the energy storage circuit is assisted, and the robustness and the reliability of control are improved.
Drawings
FIG. 1 is a functional block diagram of an embodiment of a photovoltaic power generation energy storage circuit provided by the present invention;
FIG. 2 is a schematic circuit diagram of an embodiment of a photovoltaic power generation energy storage circuit provided by the present invention;
FIG. 3 is a circuit diagram of an embodiment of the BUCK module shown in FIG. 2;
FIG. 4 is a circuit schematic of one embodiment of the BOOST-BUCK combining module shown in FIG. 2;
FIG. 5 is an equivalent circuit diagram of the photovoltaic power generation energy storage circuit provided by the invention when the photovoltaic power generation energy storage circuit works in a staggered parallel BUCK working state;
FIG. 6 is an equivalent circuit diagram of the photovoltaic power generation energy storage circuit provided by the invention when the photovoltaic power generation energy storage circuit works in a BUCK working state;
fig. 7 is an equivalent circuit diagram of the photovoltaic power generation energy storage circuit provided by the invention when the photovoltaic power generation energy storage circuit works in a BOOST working state;
fig. 8 is a schematic flow chart of an embodiment of a photovoltaic power generation and energy storage control method provided by the present invention;
FIG. 9 is a flow chart of an embodiment of an MPPT control algorithm provided by the present invention;
fig. 10 is a schematic flow chart of an embodiment of the step shown in fig. 8, in which the BUCK module and the BOOST-BUCK combination module are controlled by outputting PWM pulses according to the detected output voltage of the photovoltaic cell, the output power of the photovoltaic cell, the voltage of the storage battery, and the output current information of the photovoltaic cell collected by the collected current sampling module, so as to switch the photovoltaic power generation energy storage circuit to a corresponding working state, perform MPPT control on the output power of the photovoltaic cell, force the photovoltaic cell to work in an MPPT state in the whole process, store the collected electric energy in the storage battery, and implement the maximum power output of the photovoltaic cell;
FIG. 11 is a functional block diagram of an embodiment of a photovoltaic power generation and energy storage control system provided by the present invention;
FIG. 12 is a schematic flow chart of an embodiment of the control unit shown in FIG. 11;
FIG. 13 is a diagram of the photovoltaic cell output state of the BUCK circuit when the load is light in the photovoltaic power generation energy storage circuit provided by the invention;
FIG. 14 is a diagram of the output state of the photovoltaic cell of the BUCK circuit when the load is light to heavy in the photovoltaic power generation energy storage circuit provided by the invention;
fig. 15 is a diagram of the output state of the photovoltaic cell in the BOOST circuit in the photovoltaic power generation energy storage circuit provided by the present invention;
fig. 16 is a photovoltaic cell output state diagram of the photovoltaic power generation energy storage circuit provided by the invention.
The reference numbers illustrate:
10. a photovoltaic cell; 20. a BUCK module; 30. a BOOST-BUCK combination module; 40. a digital controller; 50. a storage battery; 60. a current sampling module; 41. a detection unit; 42. a control unit; 421. a first detection subunit; 422. a first comparison subunit; 423. a second detection subunit; 424. a second comparison subunit; 425. and switching the subunits.
Detailed Description
In order to better understand the technical solution, the technical solution will be described in detail with reference to the drawings and the specific embodiments.
As shown in fig. 1 and fig. 2, a first embodiment of the present invention provides a photovoltaic power generation energy storage circuit, which includes a photovoltaic cell 10, a BUCK module 20, a BOOST-BUCK combination module 30, a digital controller 40, a storage battery 50, and a current sampling module 60, wherein the photovoltaic cell 10 is configured to convert solar energy into electric energy; a current sampling module 60 for collecting the output current of the photovoltaic cell 10; the digital controller 40 is respectively connected with the current sampling module 60, the BUCK module 20, the BOOST-BUCK combination module 30 and the storage battery 50, and is used for controlling the BUCK module 20 and the BOOST-BUCK combination module 30 by outputting PWM pulses according to the detected photovoltaic cell output voltage, the detected photovoltaic cell output power, the detected storage battery voltage and the photovoltaic cell output current information collected by the current sampling module 60, so as to enable the photovoltaic power generation energy storage circuit to be switched to a corresponding working state, implement MPPT control on the photovoltaic cell output power, force the photovoltaic cell to work in an MPPT state in the whole process, complete the BOOST or BUCK output of the photovoltaic power generation energy storage circuit, store the collected electric energy in the storage battery 50, and realize the maximum power output of the photovoltaic cell; the working state comprises a BUCK working state and a BOOST working state. In the present embodiment, the photovoltaic power generation energy storage circuit is composed of a photovoltaic cell 10, a BUCK module 20, a BOOST-BUCK combination module 30, a digital controller 40, a storage battery 50 and a current sampling module 60. The photovoltaic cell 10 is used for converting solar energy into electric energy and has 2 electric energy output terminals; the BUCK module 20 completes the step-down output of the output electric energy of the photovoltaic cell, stores the collected electric energy in the storage battery 50, and has 2 electric energy input terminals and 2 electric energy output terminals; the BOOST-BUCK combination module 30 is used for completing the step-up or step-down output of the photovoltaic power generation energy storage circuit, storing the collected electric energy in the storage battery 50, and has 2 electric energy input terminals and 2 electric energy output terminals; the battery 50 is used for completing the electric energy storage function; the digital controller 40 finishes the MPPT control of the maximum power output of the photovoltaic cell 10 according to the detection signal, controls the corresponding BUCK module 20 and the BOOST-BUCK combined module 30 by outputting PWM pulses to realize the MPPT control of the maximum power output of the photovoltaic cell, has 3 signal detection input terminals for respectively detecting the output voltage, the output current and the voltage of a storage battery of the photovoltaic cell 10, has 3 PWM control pulse output terminals for respectively controlling 3 MOS switching tubes in the circuit module; the current sampling module 60 employs a current hall H, which is used to complete the photovoltaic cell output current sampling function. The digital controller 40 employs a microcontroller. In fig. 1, P1 is a control signal for the first switching MOS transistor Q1, P2 is a control signal for the second switching MOS transistor Q2, and P3 is a control signal for the third switching MOS transistor Q3; and the controller determines whether the corresponding control signal is high level or low level according to the change condition of the output power of the photovoltaic cell.
In the above structure, please refer to fig. 1 to 7, in the photovoltaic power generation energy storage circuit provided in this embodiment, the BUCK module 20 includes a first switching MOS transistor Q1, a first diode D1, a second diode D2 and a first inductor L1, a drain of the first switching MOS transistor Q1 is connected to the photovoltaic cell 10, a gate of the first switching MOS transistor Q1 is connected to the digital controller 40 through a first Driver1, a source of the first switching MOS transistor is divided into two paths, one path is connected to an anode of the battery 50 through a first inductor L1 and a first diode D1 connected in series, and the other path is connected to a cathode of the battery 50 through a second diode D2 connected in reverse. The BOOST-BUCK combined module 30 comprises a second switch MOS tube Q2, a third switch MOS tube Q3, a third diode D3, a fourth diode D4 and a second inductor L2, wherein the drain electrode of the second switch MOS tube Q2 is connected with the photovoltaic cell 10, the grid electrode of the second switch MOS tube Q2 is connected with the digital controller 40 through a second driving circuit Driver2, the source electrode of the second switch MOS tube Q2 is divided into two paths, and one path is connected with the second switch MOS tube Q2 in seriesThe inductor L2 and the third diode D3 are connected with the anode of the battery 50, and the other path is connected with the cathode of the battery 50 through the reverse-connected fourth diode D4; the drain of the third switching MOS transistor Q3 is connected to the anode of the third diode D3, the gate of the third switching MOS transistor Q3 is connected to the digital controller 40 through the third Driver3, and the source of the third switching MOS transistor Q3 is connected to the cathode of the battery 50. As shown in fig. 1 to 7, PV is a photovoltaic cell 10, L2 is a BOOST inductor or a filter inductor of a BOOST-BUCK combined module 30, L1 is a filter inductor of a BUCK module 20, D1 to D2 are unidirectional isolation diodes which ensure directional output of electric energy, D3 to D4 are freewheeling diodes of a BUCK working circuit, Q1 to Q3 are MOS switch tubes, H is a current sampling hall, a/D is an analog-to-digital converter, "drivers 1 to Driver 3" are driving circuits of MOS transistors Q1 to Q3, respectively, and a "digital controller" is a microcontroller which completes a photovoltaic power generation and energy storage function; u. ofpv(t)For photovoltaic cell output voltage, ipv(t)For photovoltaic cell output current uc(t)Energy storage voltage i output by photovoltaic power generation energy storage circuitL1(t)For the current in the boost or filter inductor L1, iL2(t)Is the current in the filter inductor L2; u. ofpv(k)The method comprises the steps of sampling an analog-to-digital conversion value for output voltage of a photovoltaic cell, sampling an analog-to-digital conversion value for output current of the photovoltaic cell by ipv (k), and sampling an analog-to-digital conversion value for output voltage of a photovoltaic power generation energy storage circuit by uc (k).
The main circuit equivalent circuit of the photovoltaic power generation energy storage circuit is shown in figure 3. U shapeiIs the equivalent electromotive force of the photovoltaic cell, RiFor the equivalent internal resistance of the photovoltaic cell, when the parameters such as illumination intensity are different, the power generation state of the photovoltaic cell is different and is expressed as UiAnd RiAre different.
When the photovoltaic cell is in a power generation state of (U)i，Ri) When the photovoltaic cell is in the maximum power output state, the output voltage, the output current and the output power are respectively the values shown in the formulas (1) - (3), and when the photovoltaic cell is in the MPPT control, the output voltage, the output current or the output power of the photovoltaic cell can be kept near the values shown in the formulas (1) - (3) by switching the working state of the energy storage circuit.
Figure 227780DEST_PATH_IMAGE001
When photovoltaic cell output power MPPT control is performed on a photovoltaic cell according to photovoltaic cell MPPT voltage, MPPT current or MPPT power, the power generation state (U) of the photovoltaic cell needs to be estimated in real timei，Ri) The calculation amount is large, the accuracy is difficult to guarantee, and therefore the MPPT control method is not adopted in the embodiment, and MPPT control is directly carried out according to the change trend of the actual output voltage, the actual output current and the actual output power of the photovoltaic cell by analyzing the output behavior characteristics of the photovoltaic cell without estimating the internal equivalent state of the photovoltaic cell.
Compared with a single BUCK circuit or a single BOOST circuit, the photovoltaic power generation energy storage circuit and the energy storage control circuit provided by the invention have the advantages that the output state of the photovoltaic cell is controllable in the whole process, namely the output voltage, the output current and the output power of the photovoltaic cell are controllable in the whole process; the BUCK circuit is used for limiting the output current of the photovoltaic cell, so that the output current of the photovoltaic cell is prevented from being too large, and the power generation performance of the photovoltaic cell is optimized; the output voltage of the energy storage circuit is improved by using the BOOST circuit, so that the energy storage is maximized; the continuity of the output current of the photovoltaic cell is ensured by utilizing the interleaved BUCK circuit; through an MPPT control algorithm, the photovoltaic cell is enabled to work in an MPPT state in the whole process, the output power of the photovoltaic cell is maximum, and the solar energy utilization rate is highest; in the MPPT control algorithm, basic control is directly carried out according to the change trend of the output power of the photovoltaic cell, so that complex calculation is avoided, the real-time performance of control is improved, and the implementation cost is reduced; the states of the switching tubes in the energy storage circuit are switched according to the change of the output power of the photovoltaic cell, each switching tube works in a PWM control mode with unfixed frequency, and the states of the switching tubes are switched only when the output power of the photovoltaic cell is reduced, so that unnecessary switching state switching is avoided, the switching times of the switching states are reduced, and the switching loss is reduced; on the basis of an MPPT control algorithm based on output power, the output voltage, the output current and the voltage of the energy storage battery of the photovoltaic battery are monitored, so that the switching of the working state of the energy storage circuit is assisted, and the robustness and the reliability of control are improved.
The invention also relates to a photovoltaic power generation and energy storage control method which is applied to the photovoltaic power generation and energy storage circuit and comprises the following steps:
and S100, detecting the output voltage of the photovoltaic cell, the output power of the photovoltaic cell, the voltage of a storage battery and collecting the photovoltaic cell output current information collected by a current sampling module.
Step S200, controlling a BUCK module and a BOOST-BUCK combination module by outputting PWM pulses according to detected photovoltaic cell output voltage, photovoltaic cell output power, storage battery voltage and photovoltaic cell output current information collected by a collected current sampling module, enabling a photovoltaic power generation energy storage circuit to be switched to a corresponding working state, implementing MPPT control on the photovoltaic cell output power, forcing the photovoltaic cell to work in an MPPT state in the whole process, storing collected electric energy in the storage battery, and realizing the maximum power output of the photovoltaic cell; the working state comprises a BUCK working state and a BOOST working state.
Referring to fig. 10, fig. 10 is a schematic flowchart illustrating an embodiment of step S200 shown in fig. 8, in the present embodiment, step S200 includes:
and step S210, primarily detecting the output voltage of the photovoltaic cell and the voltage of the storage battery.
Step S220, comparing the primarily detected output voltage of the photovoltaic cell with the voltage of a storage battery, and entering a BUCK working state if the detected output voltage of the photovoltaic cell is greater than the voltage of the storage battery; and if the detected output voltage of the photovoltaic cell is less than or equal to the voltage of the storage battery, entering a BOOST working state.
And step S230, waiting for the next period to arrive, and detecting the output voltage of the photovoltaic cell, the output current of the photovoltaic cell, the output power of the photovoltaic cell and the voltage of the storage battery again.
Step S240, if the photovoltaic power generation energy storage circuit is identified to work in the BUCK working state, comparing the output voltage of the photovoltaic cell detected again with the voltage of the storage battery, and if the output voltage of the photovoltaic cell detected again is larger than the voltage of the storage battery, controlling the photovoltaic power generation energy storage circuit to enter the interleaved parallel BUCK working state; and if the output voltage of the photovoltaic cell is detected again and is less than or equal to the voltage of the storage battery, controlling the photovoltaic power generation energy storage circuit to enter a BOOST working state.
Step S250, if the output power of the photovoltaic cell is increased in the BUCK working state, maintaining the BUCK working state unchanged; and if the photovoltaic cell output power is increased in the BOOST working state, maintaining the BOOST working state unchanged.
If the photovoltaic power generation energy storage circuit works in the BUCK working state, controlling the cut-off state of the third switching MOS tube Q3 to be unchanged, and alternately switching the states of the first switching MOS tube Q1 and the second switching MOS tube Q2 according to the output power variation trend; if the photovoltaic power generation energy storage circuit works in a BOOST working state, the cut-off state of the second switch MOS tube Q2 and the conduction state of the first switch MOS tube Q1 are controlled to be unchanged, and the state of the third switch MOS tube Q3 is alternately switched according to the output power variation trend.
Compared with a single BUCK circuit or BOOST circuit control method, the photovoltaic power generation energy storage circuit and the energy storage control method provided by the invention have the advantages that the output state of the photovoltaic cell is controllable in the whole process, namely the output voltage, the output current and the output power of the photovoltaic cell are controllable in the whole process; the BUCK circuit is used for limiting the output current of the photovoltaic cell, so that the output current of the photovoltaic cell is prevented from being too large, and the power generation performance of the photovoltaic cell is optimized; the output voltage of the energy storage circuit is improved by using the BOOST circuit, so that the energy storage is maximized; the continuity of the output current of the photovoltaic cell is ensured by utilizing the interleaved BUCK circuit; through an MPPT control algorithm, the photovoltaic cell is enabled to work in an MPPT state in the whole process, the output power of the photovoltaic cell is maximum, and the solar energy utilization rate is highest; in the MPPT control algorithm, basic control is directly carried out according to the change trend of the output power of the photovoltaic cell, so that complex calculation is avoided, the real-time performance of control is improved, and the implementation cost is reduced; the states of the switching tubes in the energy storage circuit are switched according to the change of the output power of the photovoltaic cell, each switching tube works in a PWM control mode with unfixed frequency, and the states of the switching tubes are switched only when the output power of the photovoltaic cell is reduced, so that unnecessary switching state switching is avoided, the switching times of the switching states are reduced, and the switching loss is reduced; on the basis of an MPPT control algorithm based on output power, the output voltage, the output current and the voltage of the energy storage battery of the photovoltaic battery are monitored, so that the switching of the working state of the energy storage circuit is assisted, and the robustness and the reliability of control are improved.
As shown in fig. 11 and fig. 12, the present invention further provides a photovoltaic power generation energy storage control system, which is applied to the above photovoltaic power generation energy storage circuit, wherein the digital controller 40 includes a detection unit 41 and a control unit 42, where the detection unit 41 is configured to detect the output voltage of the photovoltaic cell, the output power of the photovoltaic cell, the voltage of the storage battery, and the output current information of the photovoltaic cell collected by the current collection module; the control unit 42 is used for controlling the BUCK module and the BOOST-BUCK combination module by outputting a PWM pulse according to the detected photovoltaic cell output voltage, the detected photovoltaic cell output power, the detected storage battery voltage and the detected photovoltaic cell output current information collected by the current sampling module, so as to switch the photovoltaic power generation energy storage circuit to a corresponding working state, implement MPPT control on the photovoltaic cell output power, force the photovoltaic cell to work in an MPPT state in the whole process, store the collected electric energy in the storage battery, and realize the maximum power output of the photovoltaic cell; the working state comprises a BUCK working state and a BOOST working state.
Further, referring to fig. 12, in the photovoltaic power generation and energy storage control system provided in this embodiment, the control unit 42 includes a first detection subunit 421, a first comparison subunit 422, a second detection subunit 423, a second comparison subunit 424, and a switching subunit 425, where the first detection subunit 421 is configured to primarily detect the output voltage of the photovoltaic cell and the voltage of the storage battery; the first comparison subunit 422 is configured to compare the primarily detected output voltage of the photovoltaic cell with the voltage of the storage battery, and enter a BUCK operating state if the detected output voltage of the photovoltaic cell is greater than the voltage of the storage battery; if the detected output voltage of the photovoltaic cell is less than or equal to the voltage of the storage battery, entering a BOOST working state; the second detection subunit 423 is configured to detect the output voltage of the photovoltaic cell, the output current of the photovoltaic cell, the output power of the photovoltaic cell, and the voltage of the storage battery again after the next period comes; the second comparison subunit 424 is configured to, if it is identified that the photovoltaic power generation energy storage circuit operates in the BUCK operating state, compare the output voltage of the photovoltaic cell detected again with the voltage of the storage battery, and, if the output voltage of the photovoltaic cell detected again is greater than the voltage of the storage battery, control the photovoltaic power generation energy storage circuit to enter the interleaved parallel BUCK operating state; if the output voltage of the photovoltaic cell detected again is less than or equal to the voltage of the storage battery, controlling the photovoltaic power generation energy storage circuit to enter a BOOST working state; a switching subunit 425, configured to maintain the BUCK operating state unchanged if it is detected that the output power of the photovoltaic cell increases in the BUCK operating state; and if the photovoltaic cell output power is increased in the BOOST working state, maintaining the BOOST working state unchanged. The switching subunit 425 is specifically configured to, if it is identified that the photovoltaic power generation energy storage circuit operates in a BUCK operating state, control the off state of the third switching MOS transistor Q3 to be unchanged, and alternately switch the states of the first switching MOS transistor Q1 and the second switching MOS transistor Q3 according to the output power variation trend; if the photovoltaic power generation energy storage circuit works in a BOOST working state, the cut-off state of the second switch MOS tube Q2 and the conduction state of the first switch MOS tube Q1 are controlled to be unchanged, and the state of the third switch MOS tube Q3 is alternately switched according to the output power variation trend.
Compared with a single BUCK circuit or a single BOOST circuit, the photovoltaic power generation energy storage circuit, the control method and the control system provided by the invention have the advantages that the output state of the photovoltaic cell is controllable in the whole process, namely the output voltage, the output current and the output power of the photovoltaic cell are controllable in the whole process; the BUCK circuit is used for limiting the output current of the photovoltaic cell, so that the output current of the photovoltaic cell is prevented from being too large, and the power generation performance of the photovoltaic cell is optimized; the output voltage of the energy storage circuit is improved by using the BOOST circuit, so that the energy storage is maximized; the continuity of the output current of the photovoltaic cell is ensured by utilizing the interleaved BUCK circuit; through an MPPT control algorithm, the photovoltaic cell is enabled to work in an MPPT state in the whole process, the output power of the photovoltaic cell is maximum, and the solar energy utilization rate is highest; in the MPPT control algorithm, basic control is directly carried out according to the change trend of the output power of the photovoltaic cell, so that complex calculation is avoided, the real-time performance of control is improved, and the implementation cost is reduced; the states of the switching tubes in the energy storage circuit are switched according to the change of the output power of the photovoltaic cell, each switching tube works in a PWM control mode with unfixed frequency, and the states of the switching tubes are switched only when the output power of the photovoltaic cell is reduced, so that unnecessary switching state switching is avoided, the switching times of the switching states are reduced, and the switching loss is reduced; on the basis of an MPPT control algorithm based on output power, the output voltage, the output current and the voltage of the energy storage battery of the photovoltaic battery are monitored, so that the switching of the working state of the energy storage circuit is assisted, and the robustness and the reliability of control are improved.
Referring to fig. 1 to fig. 16, the working principle of the photovoltaic power generation energy storage circuit, the control method and the control system provided in this embodiment is as follows:
the main circuit of the photovoltaic power generation energy storage circuit is formed by connecting a BOOST-BUCK combined module 30 and a BUCK module 20 in parallel. A schematic diagram of the BOOST-BUCK combination module 30 is shown in fig. 4, and a schematic diagram of the BUCK module 20 is shown in fig. 3.
For the BOOST-BUCK combined module circuit shown in fig. 4, when the storage battery voltage u isc(t)At lower times, to limit the inductor current iL1(t)When the voltage is too large, the third switching MOS tube Q3 is cut off, the working circuit is a typical BUCK circuit, and the inductive current i is adjusted through the high-frequency PWM control of the second switching MOS tube Q2L2(t)The energy storage battery 50 is charged with energy at a lower voltage; when the voltage u of the energy storage batteryc(t)At higher times, to avoid inductor current iL2(t)When the voltage is too small, the second switching MOS tube Q2 is conducted, the working circuit is a typical BOOST circuit, and the inductive current i is adjusted through the high-frequency PWM control of the third switching MOS tube Q3L2(t)The energy storage battery is charged and stored with higher voltage, so that the energy storage of the battery is as much as possible.
The BUCK module circuit shown in fig. 5 is a typical BUCK circuit when the storage battery voltage u isc(t)At lower times, to limit the inductor current iL2(t)When the current is too large, the inductor current i is adjusted through the high-frequency PWM control of the first switching MOS tube Q1L2(t)The energy storage battery is charged and stored with lower voltage; when the voltage uc (t) of the energy storage battery is higher, the second switching MOS tube Q2 is cut off, and the BUCK module circuit does not work.
For making the output current of the photovoltaic cellIn succession, the BUCK circuit of the BOOST-BUCK combination module 30 and the BUCK circuit of the BUCK module 20 operate alternately. When the energy storage voltage uc(t)When the voltage is lower than a certain value, the third switch MOS tube Q3 is cut off, the BOOST-BUCK combined module 30 works in a BUCK circuit state, meanwhile, a BUCK circuit of the BUCK module 20 works to form a BUCK state working circuit, and the BUCK circuits in the two modules work alternately; when the energy storage voltage uc(t)When the voltage is higher than a certain value, the second switch MOS transistor Q2 is turned on, the BOOST-BUCK combination module 30 works in a BOOST circuit state, and the BUCK module 20 does not work (the first switch MOS transistor Q1 is turned off) at the same time, so that a BOOST state working circuit is formed. Namely: when the energy storage voltage uc(t)When the voltage is lower than a certain value, the photovoltaic power generation energy storage circuit works in a BUCK output energy storage state that the two BUCK circuits are connected in parallel in a staggered mode, namely, the BUCK working state; when the energy storage voltage uc (t) is higher than a certain value, the photovoltaic power generation energy storage circuit works in a BOOST output energy storage state of the BOOST circuit, namely, the BOOST working state.
Working principle of BUCK state working circuit
When the energy storage voltage uc(t)When the working voltage is lower than a certain value, the energy storage circuit works in a BUCK working state, the working principle diagram of the BUCK working circuit is shown in fig. 6, 2 BUCK circuits are connected in parallel, Q1, L1, D1 and D2 form 1 BUCK circuit, and Q2, L2, D3 and D4 form the other 1 BUCK circuit; the 2 BUCK circuits work alternately, and the Q1 and the Q2 are switched on or off alternately, so that the output current of the photovoltaic cell is continuous.
When the energy storage circuit works in the BUCK state working circuit, the output current of the photovoltaic cell is equal to the inductive current i in turnL1(t)Or the inductor current iL2(t)As in equation (4).
Figure 676078DEST_PATH_IMAGE002
(4)
Working principle of (IV) BOOST state working circuit
When the energy storage voltage uc(t)When the voltage is higher than a certain value, the tank circuit works in a BOOST working state, and the working principle diagram of the BOOST working circuit is shown in fig. 7, and the BOOST working circuit consists of a second inductor L2, a third diode D3, a third switch electrodeTube Q3. When the third switching MOS tube Q3 is conducted under the control of the high-frequency PWM pulse, the inductive current iL2(t)When the third switch MOS transistor Q3 is turned off, the second inductor L2 inductor current is decreased by iL2(t)Small, can ensure the output current of the photovoltaic cell to be continuous. At this time, the photovoltaic cell output current is equal to the inductor current, i.e.:
Figure 986974DEST_PATH_IMAGE003
(5)
(V) MPPT control algorithm
For the photovoltaic power generation energy storage circuit shown in fig. 2, in order to maximize the solar energy utilization rate, MPPT control is implemented on the output power ppv (k) of the photovoltaic battery by switching the operating state of the photovoltaic power generation energy storage circuit, so that the photovoltaic battery is forced to operate near the MPPT state in the whole process, and the MPPT control algorithm flowchart is shown in fig. 9.
The control basis is as follows:
the output power and the output current of the photovoltaic cell have a curve relation similar to a parabola, a maximum value point exists, the current value when the output power is maximum is the MPPT output current value, when the output current of the photovoltaic cell is increased from small to small on the left side of the MPPT current value, the output power of the photovoltaic cell is also increased from small to small, and when the output current of the photovoltaic cell is continuously increased from small to small on the right side of the MPPT current value, the output power of the photovoltaic cell is decreased from large to small. Therefore, the output power of the photovoltaic cell can be maximized as long as the output current of the photovoltaic cell can be controlled to be maintained near the MPPT current value. The MPPT control algorithm is mainly realized in 2 aspects: the photovoltaic cell output current is controllable in the whole process near the MPPT current value, and the photovoltaic cell output current is adjusted in real time according to the real-time output power and the variation trend of the photovoltaic cell to ensure the maximization of the output power of the photovoltaic cell.
The control process comprises the following steps:
setting an initial state of a switch tube: when the third switching MOS transistor Q3 is cut off, the states of Q1 and Q2 are opposite; when the third switching MOS transistor Q3 is turned on, the second switching MOS transistor Q2 is turned off, and the first switching MOS transistor Q1 is turned on.
② detecting the photovoltaic cellOutput voltage upv(k)Output current of the power supplyipv(k)And the output power ppv(k)。
Thirdly, according to the output voltage u of the photovoltaic cellpv(k)And the voltage uc (k) of the storage battery determines whether the photovoltaic power generation energy storage circuit works in a BUCK working state or a BOOST working state.
And when the photovoltaic power generation energy storage circuit works in the BUCK working state, the third switching MOS tube Q3 is cut off, and the states of the second switching MOS tube Q2 and the first switching MOS tube Q1 are alternately switched according to the variation trend of the output power ppv (k).
When the photovoltaic power generation energy storage circuit works in a BOOST working state, the second switch MOS tube Q2 and the first switch MOS tube Q1 are cut off, and the state of the third switch MOS tube Q3 is switched according to the change trend of output power ppv (k).
Returning to the photovoltaic cell output state detection position, and circularly performing photovoltaic cell output MPPT control of the next period.
(VI) comparison of energy storage Effect
(1) BUCK structure energy storage circuit
Fig. 13 and 14 show the photovoltaic cell output states (output voltage, output current, output power) corresponding to the BUCK-structured tank circuit under a certain scene. As can be seen from the figure, the output voltage, the output current, and the output power of the photovoltaic cell are in the MPPT state at a certain time point, and the output power is low in other long time periods, so that the photovoltaic cell cannot work in the MPPT state, the output power of the photovoltaic cell is very low, and the solar energy utilization rate is not high. Especially, when the load carried by the energy storage circuit is heavy, the output current of the photovoltaic cell is in a discontinuous state, as shown in fig. 13. Wherein u ispv(t) is the output voltage of the photovoltaic cell; p is a radical ofpv(t) is the output power of the photovoltaic cell; i.e. ipv(t) is the output current of the photovoltaic cell; sQAnd (t) is the on/off state of the switching tube.
(2) BOOST structure energy storage circuit
In order to maximize the utilization rate of solar energy, the traditional photovoltaic power generation energy storage circuit is mostly born by a BOOST circuit. Under the same scenario, a graph of the output state (output voltage, output current, output power) of the photovoltaic cell of the BOOST structure energy storage circuit is shown in fig. 15. As can be seen from the figure, in the initial stage of energy storage (at this time, the voltage of the energy storage battery is low), the output current of the photovoltaic cell is overshot for a period of time, and in this period of time, the output power of the photovoltaic cell is low and is far lower than the due maximum output power of the photovoltaic cell, and the full-range MPPT output capability is not provided.
(3) Energy storage circuit
Fig. 16 shows the output states (output voltage, output current, and output power) of the photovoltaic cells corresponding to the photovoltaic power generation energy storage circuit used in this embodiment under the same scenario. It can be seen from the figure that the output voltage, the output current and the output power of the photovoltaic cell fluctuate around the maximum power output state of the photovoltaic cell in the whole process, the output power of the photovoltaic cell fluctuates around the due maximum output power of the photovoltaic cell in a small range, the maximum output power is approximately maximized, the solar energy utilization rate is undoubtedly enabled to be the highest, the energy storage of the energy storage circuit is maximized, and the MPPT output capability in the whole process is achieved.
Compared with the traditional photovoltaic energy storage and MPPT control, the photovoltaic power generation energy storage circuit and the MPPT control algorithm have the following benefits:
(1) compared with a single BUCK circuit or a BOOST circuit, the output state of the photovoltaic cell is controllable in the whole process, namely the output voltage, the output current and the output power of the photovoltaic cell are controllable in the whole process.
(2) The BUCK circuit is used for limiting the output current of the photovoltaic cell, the output current of the photovoltaic cell is prevented from being too large, and the power generation performance of the photovoltaic cell is optimized.
(3) The output voltage of the energy storage circuit is improved by using the BOOST circuit, so that the energy storage is maximized.
(4) And the continuity of the output current of the photovoltaic cell is ensured by utilizing the interleaved BUCK circuit.
(5) Through the MPPT control algorithm, the photovoltaic cell is enabled to work in the MPPT state in the whole process, the output power of the photovoltaic cell is maximum, and the solar energy utilization rate is highest.
(6) In the MPPT control algorithm, basic control is directly carried out according to the change trend of the output power of the photovoltaic cell, complex calculation is avoided, the real-time performance of control is improved, and the implementation cost is reduced.
(7) The states of the switching tubes in the energy storage circuit are switched according to the change of the output power of the photovoltaic cell, the switching tubes work in a PWM control mode with unfixed frequency, and the states of the switching tubes are switched only when the output power of the photovoltaic cell is reduced, so that unnecessary switching state switching is avoided, the switching times of the switching states are reduced, and the switching loss is reduced.
(8) On the basis of an MPPT control algorithm based on output power, the output voltage, the output current and the voltage of the energy storage battery of the photovoltaic battery are monitored, so that the switching of the working state of the energy storage circuit is assisted, and the robustness and the reliability of control are improved.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention. It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims (10)

1. A photovoltaic power generation energy storage circuit is characterized by comprising a photovoltaic cell (10), a BUCK module (20), a BOOST-BUCK combined module (30), a digital controller (40), a storage battery (50) and a current sampling module (60),
the photovoltaic cell (10) is used for converting solar energy into electric energy;
the current sampling module (60) is used for collecting the output current of the photovoltaic cell (10);
the digital controller (40) is respectively connected with the current sampling module (60), the BUCK module (20), the BOOST-BUCK combined module (30) and the storage battery (50), is used for detecting the output voltage of the photovoltaic cell, the output power of the photovoltaic cell, the voltage of the storage battery and the output current information of the photovoltaic cell collected by the current sampling module (60), the BUCK module (20) and the BOOST-BUCK combined module (30) are controlled by outputting PWM pulses to cause the photovoltaic power generation energy storage circuit to be switched to a corresponding working state, MPPT control is carried out on the output power of the photovoltaic cell, the photovoltaic cell is forced to work in an MPPT state in the whole process, the boosting or voltage reduction output of the photovoltaic power generation energy storage circuit is completed, the collected electric energy is stored in the storage battery (50), and the maximum power output of the photovoltaic cell is realized; the working state comprises a BUCK working state and a BOOST working state.
2. The photovoltaic power generation energy storage circuit according to claim 1, wherein the BUCK module (20) comprises a first switch MOS transistor, a first diode, a second diode and a first inductor, wherein a drain electrode of the first switch MOS transistor is connected with the photovoltaic cell (10), a gate electrode of the first switch MOS transistor is connected with the digital controller (40) through a first driving circuit, a source electrode of the first switch MOS transistor is divided into two paths, one path is connected with an anode of the storage battery (50) through the first inductor and the first diode which are connected in series, and the other path is connected with a cathode of the storage battery (50) through the second diode which is connected in reverse.
3. The energy storage circuit of claim 2, wherein the BOOST-BUCK combination module (30) comprises a second switch MOS transistor, a third diode, a fourth diode and a second inductor, wherein a drain electrode of the second switch MOS transistor is connected with the photovoltaic cell (10), a gate electrode of the second switch MOS transistor is connected with the digital controller (40) through a second driving circuit, a source electrode of the second switch MOS transistor is divided into two paths, one path is connected with an anode of the storage battery (50) through the second inductor and the third diode which are connected in series, and the other path is connected with a cathode of the storage battery (50) through the fourth diode which is connected in reverse; the drain electrode of the third switch MOS tube is connected with the anode of the third diode, the grid electrode of the third switch MOS tube is connected with the digital controller (40) through a third driving circuit, and the source electrode of the third switch MOS tube is connected with the cathode of the storage battery (50).
4. The photovoltaic power generation energy storage circuit according to claim 1, wherein the current sampling module (60) adopts a current hall, and the digital controller (40) is a microcontroller for performing photovoltaic power generation energy storage function.
5. A photovoltaic power generation and energy storage control method is applied to the photovoltaic power generation and energy storage circuit according to any one of claims 1 to 4, and is characterized by comprising the following steps:
detecting the output voltage of the photovoltaic cell, the output power of the photovoltaic cell, the voltage of a storage battery and collecting the output current information of the photovoltaic cell collected by the current sampling module;
according to the detected output voltage of the photovoltaic cell, the output power of the photovoltaic cell, the voltage of a storage battery and the collected output current information of the photovoltaic cell, which is collected by the current sampling module, PWM pulses are output to control the BUCK module and the BOOST-BUCK combined module, so that the photovoltaic power generation energy storage circuit is switched to a corresponding working state, MPPT control is carried out on the output power of the photovoltaic cell, the photovoltaic cell is forced to work in an MPPT state in the whole process, the collected electric energy is stored in the storage battery, and the maximum power output of the photovoltaic cell is realized; the working state comprises a BUCK working state and a BOOST working state.
6. The photovoltaic power generation energy storage control method according to claim 5, wherein the step of controlling the BUCK module and the BOOST-BUCK combination module by outputting PWM pulses according to the detected photovoltaic cell output voltage, photovoltaic cell output power, battery voltage and the collected photovoltaic cell output current information collected by the current sampling module to cause the photovoltaic power generation energy storage circuit to switch to a corresponding working state, implementing MPPT control on the photovoltaic cell output power to force the photovoltaic cell to work in an MPPT state in the whole process, storing the collected electric energy in the battery, and implementing the maximum power output of the photovoltaic cell comprises:
primarily detecting the output voltage of the photovoltaic cell and the voltage of the storage battery;
comparing the primarily detected output voltage of the photovoltaic cell with the voltage of the storage battery, and entering a BUCK working state if the detected output voltage of the photovoltaic cell is greater than the voltage of the storage battery; if the detected output voltage of the photovoltaic cell is less than or equal to the voltage of the storage battery, entering a BOOST working state;
waiting for the next period to arrive, and detecting the output voltage of the photovoltaic cell, the output current of the photovoltaic cell, the output power of the photovoltaic cell and the voltage of the storage battery again;
if the photovoltaic power generation energy storage circuit is identified to work in a BUCK working state, comparing the output voltage of the photovoltaic cell detected again with the voltage of the storage battery, and if the output voltage of the photovoltaic cell detected again is larger than the voltage of the storage battery, controlling the photovoltaic power generation energy storage circuit to enter a staggered parallel BUCK working state; if the output voltage of the photovoltaic cell is detected again to be less than or equal to the voltage of the storage battery, controlling the photovoltaic power generation energy storage circuit to enter a BOOST working state;
if the output power of the photovoltaic cell is increased in the BUCK working state, maintaining the BUCK working state unchanged; and if the photovoltaic cell output power is increased in the BOOST working state, maintaining the BOOST working state unchanged.
7. The photovoltaic power generation energy storage control method according to claim 6, wherein if an increase in the photovoltaic cell output power in the BUCK operating state is detected, the BUCK operating state is maintained; if the photovoltaic cell output power is detected to be increased in the BOOST working state, the step of maintaining the BOOST working state unchanged comprises the following steps:
if the photovoltaic power generation energy storage circuit is identified to work in a BUCK working state, controlling the cut-off state of the third switch MOS tube to be unchanged, and alternately switching the states of the first switch MOS tube and the second switch MOS tube according to the output power variation trend; and if the photovoltaic power generation energy storage circuit works in a BOOST working state, controlling the cut-off state of the second switch MOS tube and the conduction state of the first switch MOS tube to be unchanged, and alternately switching the state of the third switch MOS tube according to the output power variation trend.
8. A photovoltaic power generation and energy storage control system applied to the photovoltaic power generation and energy storage circuit according to any one of claims 1 to 4, wherein the digital controller (40) comprises:
the detection unit (41) is used for detecting the output voltage of the photovoltaic cell, the output power of the photovoltaic cell, the voltage of the storage battery and collecting the output current information of the photovoltaic cell collected by the current sampling module;
the control unit (42) is used for controlling the BUCK module and the BOOST-BUCK combination module by outputting PWM pulses according to the detected output voltage of the photovoltaic cell, the output power of the photovoltaic cell, the voltage of the storage battery and the collected output current information of the photovoltaic cell collected by the current sampling module, so that the photovoltaic power generation energy storage circuit is switched to a corresponding working state, MPPT control is carried out on the output power of the photovoltaic cell, the photovoltaic cell is forced to work in an MPPT state in the whole process, the collected electric energy is stored in the storage battery, and the maximum power output of the photovoltaic cell is realized; the working state comprises a BUCK working state and a BOOST working state.
9. The photovoltaic power generation and energy storage control system of claim 8, wherein the control unit (42) comprises:
a first detection subunit (421) for primarily detecting the output voltage of the photovoltaic cell and the voltage of the storage battery;
the first comparison subunit (422) is used for comparing the primarily detected photovoltaic cell output voltage with the storage battery voltage, and entering a BUCK working state if the detected photovoltaic cell output voltage is greater than the storage battery voltage; if the detected output voltage of the photovoltaic cell is less than or equal to the voltage of the storage battery, entering a BOOST working state;
the second detection subunit (423) is used for detecting the output voltage of the photovoltaic cell, the output current of the photovoltaic cell, the output power of the photovoltaic cell and the voltage of the storage battery again after the next period comes;
the second comparison subunit (424) is used for comparing the output voltage of the photovoltaic cell detected again with the voltage of the storage battery if the photovoltaic power generation energy storage circuit is identified to work in a BUCK working state, and controlling the photovoltaic power generation energy storage circuit to enter a staggered parallel BUCK working state if the output voltage of the photovoltaic cell detected again is greater than the voltage of the storage battery; if the output voltage of the photovoltaic cell is detected again to be less than or equal to the voltage of the storage battery, controlling the photovoltaic power generation energy storage circuit to enter a BOOST working state;
a switching subunit (425) for maintaining the BUCK operating state unchanged if it is detected that there is an increase in the photovoltaic cell output power in the BUCK operating state; and if the photovoltaic cell output power is increased in the BOOST working state, maintaining the BOOST working state unchanged.
10. The photovoltaic power generation and energy storage control system according to claim 9, wherein the switching subunit (425) is specifically configured to, if it is identified that the photovoltaic power generation and energy storage circuit operates in the BUCK operating state, control the off state of the third switching MOS transistor to be unchanged, and alternately switch the states of the first switching MOS transistor and the second switching MOS transistor according to the output power variation trend; and if the photovoltaic power generation energy storage circuit works in a BOOST working state, controlling the cut-off state of the second switch MOS tube and the conduction state of the first switch MOS tube to be unchanged, and alternately switching the state of the third switch MOS tube according to the output power variation trend.
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