CN113054851A - Distributed voltage-sharing control circuit and control method - Google Patents

Distributed voltage-sharing control circuit and control method Download PDF

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Publication number
CN113054851A
CN113054851A CN202110426933.7A CN202110426933A CN113054851A CN 113054851 A CN113054851 A CN 113054851A CN 202110426933 A CN202110426933 A CN 202110426933A CN 113054851 A CN113054851 A CN 113054851A
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voltage
module
sharing control
output
controller
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朱明达
方毅
朱景璐
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China University of Petroleum Beijing
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China University of Petroleum Beijing
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/3353—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having at least two simultaneously operating switches on the input side, e.g. "double forward" or "double (switched) flyback" converter
    • 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
    • H02J1/00—Circuit arrangements for dc mains or dc distribution networks
    • H02J1/10—Parallel operation of dc sources
    • H02J1/102—Parallel operation of dc sources being switching converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The application provides a distributed voltage-sharing control circuit and a control method, which are applied to an IPOS combined system. The distributed voltage-sharing control circuit comprises a plurality of voltage-sharing control modules, wherein each voltage-sharing control module comprises a single-module LLC converter, an input voltage acquisition module, a first controller, an output voltage acquisition module, a second controller and a PFM pulse generation module. In the distributed voltage-sharing control circuit provided by the scheme, an independent controller is adopted for each LLC converter, and the PFM pulse generator generates corresponding driving signals to control the switching devices, so that the voltage on the input side is stable, and the output voltage of each voltage-sharing control module is balanced. Meanwhile, the control method is suitable for a plurality of voltage-sharing control modules, and coupling among the voltage-sharing control modules is not needed, so that the transmission efficiency of the system is effectively improved.

Description

Distributed voltage-sharing control circuit and control method
Technical Field
The application relates to the technical field of photovoltaic power generation, in particular to a distributed voltage-sharing control circuit and a control method.
Background
With the continuous progress of society and the increasing level of people, the demand of industry, national defense, medical treatment, daily life and the like on electric energy is also increasing. Photovoltaic Power generation has been vigorously developed in the Power electronics industry due to the characteristics of environmental protection and abundant reserves, a general photovoltaic Power generation system can be divided into two stages for transmission, a front-stage Direct-Current (DC/DC) converter and a rear-stage DC/DC converter, wherein the front-stage DC/DC converter is responsible for completing Maximum Power Point Tracking (MPPT) and converging voltage into a low-voltage Direct-Current bus or supplying the voltage to a Direct-Current load; and the later-stage DC/DC converter continuously boosts the electric energy of the low-voltage direct-current bus and then imports the electric energy into a high-voltage direct-current power grid or inverts the electric energy into alternating current for transmission. For a post-stage DC/DC boost part, a plurality of DC/DC converters are often combined in a mode that Input-Parallel Output-Series (IPOS) are connected in Series at an Input side, and the combination mode is suitable for high-voltage and high-power occasions, however, when parameters of sub-modules change during operation, voltage imbalance of each module is caused, so that Output efficiency is affected, equipment is damaged in severe cases, and therefore an IPOS combination system needs to be controlled.
In the prior art, a control method for an IPOS combined system is mainly output voltage-sharing control, and the method is composed of an output voltage closed loop and an output voltage-sharing closed loop and directly controls the output voltage of each module. For example, two modules are taken as an example, the output voltage closed loop ensures the stability of the output voltage, the output voltage equalizing closed loop ensures that the voltage of one module is 1/2 of the total output voltage, and the difference and the sum of the two are used as control signals of the modules to generate corresponding pulse signals.
However, the control method mainly aims at the control method of the output side fixed load, which is complex, and does not consider the variation situation of the input side voltage, so that the stability is poor.
Disclosure of Invention
The application provides a distributed voltage-sharing control circuit and a control method, which are used for solving the problems of high complexity and poor input side voltage stability of the existing control mode.
In a first aspect, an embodiment of the present application provides a distributed voltage-sharing control circuit, including:
the input sides of the voltage-sharing control modules are connected in parallel, and the output sides of the voltage-sharing control modules are connected in series;
each voltage-sharing control module comprises a single-module LLC converter, an input voltage acquisition module, a first controller, an output voltage acquisition module, a second controller and a PFM pulse generation module;
one end of the input voltage acquisition module is connected with the input of the single-module LLC converter and is used for acquiring the input voltage of the single-module LLC converter, the other end of the input voltage acquisition module is connected with the input end of the first controller, and the output end of the first controller is connected with the first input end of the PFM pulse generation module;
one end of the output voltage acquisition module is connected with the output of the single-module LLC converter and is used for acquiring the output voltage of the single-module LLC converter, the other end of the output voltage acquisition module is connected with the input end of the second controller, and the output end of the second controller is connected with the second input end of the PFM pulse generation module;
and the output end of the PFM pulse generation module is connected with the single-module LLC converter.
Optionally, the PFM pulse generating module is configured to generate a driving signal according to a frequency output by the first controller or a frequency output by the second controller, where the driving signal is used to control a switching device in the single-module LLC converter.
Optionally, the single-module LLC converter includes:
a controllable switching network, a resonant network, an ideal transformer and a rectifier network;
the input end of the controllable switch network is used for connecting an input power supply, the output end of the controllable switch network is connected with the input end of the resonance network, the output end of the resonance network is connected with the input end of the ideal transformer, and the output end of the ideal transformer is connected with the rectifier network;
wherein, the rectification network is a voltage doubling rectification circuit.
Optionally, the controllable switch network includes two groups of switch circuits, and each group of switch circuits includes a switch device and a diode;
the rectifier network comprises a switch circuit formed by a group of diodes and a group of capacitors.
Optionally, the first controller and the second controller are any one of the following controllers:
proportional integral PI controller, proportional integral derivative PID controller, active disturbance rejection controller ADRC.
In a second aspect, an embodiment of the present application provides a distributed voltage-sharing control method, where the method includes:
calculating a first deviation value between the input voltage and a preset input voltage reference value aiming at each voltage-sharing control module;
calculating a first frequency disturbance value according to the first deviation value;
after the first frequency disturbance value is superposed with a preset reference frequency, generating a first driving signal in a pulse frequency modulation mode;
and inputting the first driving signal into a single-module LLC converter in the voltage-sharing control module, wherein the first driving signal is used for controlling a switching device in the single-module LLC converter so as to stabilize the output voltage of the voltage-sharing control module.
Optionally, the method further includes:
when the output voltage of the voltage-sharing control module is detected to be unbalanced, calculating a second deviation value between the output voltage and a preset output voltage reference value;
calculating a second frequency disturbance value according to the second deviation value;
after the second frequency disturbance value is superposed with a preset reference frequency, a second driving signal is generated in a pulse frequency modulation mode;
and inputting the second driving signal into a single-module LLC converter in the voltage-sharing control module, wherein the second driving signal is used for controlling a switching device in the single-module LLC converter so as to stabilize the output voltage of the voltage-sharing control module.
Optionally, the method further includes:
and if the output voltage of the voltage-sharing control module is detected to be inconsistent with the output voltage reference value, determining that the output voltage of the voltage-sharing control module is unbalanced.
Optionally, the method further includes:
and collecting the input voltage of the voltage-sharing control module in real time.
Optionally, the method further includes:
and acquiring the output voltage of the voltage-sharing control module in real time, comparing the output voltage with the output voltage reference value, and determining that the output voltage of the voltage-sharing control module is balanced.
The distributed voltage-sharing control circuit and the control method provided by the embodiment of the application are applied to an IPOS system. The distributed voltage-sharing control circuit comprises a plurality of voltage-sharing control modules, wherein each voltage-sharing control module comprises a single-module LLC converter, an input voltage acquisition module, a first controller, an output voltage acquisition module, a second controller and a PFM pulse generation module. In the distributed voltage-sharing control circuit provided by the scheme, each LLC converter is provided with an independent controller, the PFM pulse generator generates a corresponding driving signal to control a switching device, the voltage on the input side is stable, the output voltage of each voltage-sharing control module is balanced, meanwhile, the control method is suitable for a plurality of voltage-sharing control modules, coupling among the voltage-sharing control modules is not needed, and the transmission efficiency of the system is effectively improved.
Drawings
Fig. 1 is a schematic diagram of a distributed voltage-sharing control principle provided in an embodiment of the present application;
FIG. 2 is a schematic diagram of a single-module LLC converter according to an embodiment of the present application;
fig. 3 is a schematic flowchart of a first embodiment of a distributed voltage-sharing control method according to an embodiment of the present application;
fig. 4 is a schematic flow chart of a second embodiment of a distributed voltage-sharing control method according to an embodiment of the present application;
FIG. 5 is a schematic structural diagram of an IPOS combined system according to an embodiment of the present application;
fig. 6A is a waveform diagram of an input voltage in the IPOS combined system according to the embodiment of the present application;
FIG. 6B is a waveform diagram of an input current in the IPOS combined system according to the embodiment of the present application;
FIG. 6C is a waveform diagram of output power in the IPOS combined system according to the embodiment of the present application;
fig. 7 is a waveform diagram of output voltages of voltage-sharing control modules in a normal operating condition in the IPOS combined system according to the embodiment of the present application;
fig. 8 is a waveform diagram of output voltages of voltage-sharing control modules when resonant inductors in an IPOS combined system are different according to an embodiment of the present application;
fig. 9 is a waveform diagram of operating frequencies of voltage-sharing control modules in an IPOS combined system according to an embodiment of the present application;
fig. 10 is a waveform diagram of voltages at the output side of voltage-sharing control modules when resonant capacitors in the IPOS combined system are different according to the embodiment of the present application;
fig. 11A is a waveform diagram of an output voltage of a photovoltaic MPPT module in the IPOS combined system according to the embodiment of the present application;
fig. 11B is a waveform diagram of an output current of a photovoltaic MPPT module in the IPOS combined system according to the embodiment of the present application;
fig. 11C is a waveform diagram of the output power of the photovoltaic MPPT module in the IPOS combined system according to the embodiment of the present application;
fig. 12 is a waveform diagram of a total output current in the IPOS combined system according to an embodiment of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
With the increasing energy crisis and environmental crisis, compared with the traditional fossil energy, solar energy is an ideal renewable energy, and because no pollution is generated in the development and utilization processes, photovoltaic power generation has been vigorously developed in the power and electronics industry. The Input-Parallel Output-Series (IPOS) combined converter is suitable for high-power occasions with high voltage difference between the Input side and the Output side, so that the IPOS combined converter can be applied to the photovoltaic power generation technology to boost and collect Output of a photovoltaic power generation board, and the energy utilization rate can be effectively improved. For stable operation of the IPOS system, voltage stabilization of an input side of the IPOS system and output voltage stabilization among modules are generally considered, and if parameters among the modules change in an operation process, voltage imbalance of each module is caused, so that output efficiency is affected, and equipment is damaged in severe cases. In the prior art, an output voltage-sharing control method is mainly used for keeping stability of an IPOS combined system, and the method is composed of an output voltage closed loop and an output voltage-sharing closed loop and directly controls output voltages of modules. For example, two modules are taken as an example, the output voltage closed loop ensures the stability of the output voltage, the output voltage equalizing closed loop ensures that the voltage of one module is 1/2 of the total output voltage, and the difference and the sum of the two are used as control signals of the modules to generate corresponding pulse signals. However, the method mainly aims at the condition that the output side is connected with a fixed load, and has the problems of high complexity and poor stability of the voltage of the input side, and certain potential safety hazards exist.
In order to solve the above problems, the present application provides a distributed voltage-sharing control circuit and a control method, which are applied to an IPOS system. In the distributed voltage-sharing control circuit and the control method provided by the embodiment of the application, an independent controller is adopted for each single module Resonant circuit (LLC) converter, and a Pulse Frequency Modulation (PFM) Pulse generation module generates a corresponding driving signal to control a switching device, so as to ensure stable voltage on an input side and balanced output voltage of each voltage-sharing control module. The control method is suitable for a plurality of voltage-sharing control modules, coupling among the voltage-sharing control modules is not needed, and the transmission efficiency of the system is effectively improved. The technical solution of the present application will be described in detail below with reference to specific examples.
It should be noted that the following specific embodiments may be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.
Fig. 1 is a schematic diagram of a distributed voltage-sharing control principle provided in an embodiment of the present application. As shown in fig. 1, the distributed voltage-sharing control circuit of the present embodiment includes: the input sides of the voltage-sharing control modules 10 are connected in parallel, and the output sides of the voltage-sharing control modules 10 are connected in series.
Each voltage-sharing control module 10 includes an LLC converter 101, an input voltage acquisition module 102, a first controller 103, an output voltage acquisition module 104, a second controller 105, and a PFM pulse generation module 106.
One end of the input voltage acquisition module 102 is connected with the input of the single-module LLC converter 101, the other end of the input voltage acquisition module 102 is connected with the input end of the first controller 103, the output end of the first controller 103 is connected with the first input end of the PFM pulse generation module 106; one end of the output voltage acquisition module 104 is connected to the output of the single-module LLC converter 101, the other end of the output voltage acquisition module 104 is connected to the input end of the second controller 105, and the output end of the second controller 105 is connected to the second input end of the PFM pulse generation module 106.
The input voltage collecting module 102 is mainly used for collecting an input voltage value. In a specific embodiment, the input voltage acquisition module 102 uses an Analog-to-Digital converter (a/D) to convert the input voltage signal into an input voltage value, and subtracts the input voltage value from the input voltage reference value at the comparison point to obtain a difference value therebetween. The input voltage acquisition module 102 may also include an input voltage relay. The input voltage relay is a controller for reflecting voltage change, and when the voltage in the circuit exceeds the maximum steady-state voltage or is lower than a specified value, the voltage relay cuts off the circuit to play a role in protecting the safety of the circuit.
The single-module LLC converter 101 is mainly used to boost the power of the low-voltage dc bus and to merge into the high-voltage dc power grid, and to adjust the output voltage by adjusting the switching frequency, and the duty ratio remains unchanged at different input voltages, resulting in higher output power and conversion efficiency.
The first controller 103 is mainly configured to calculate a first frequency disturbance value according to a difference between an input voltage reference value and an input voltage value, superimpose the first frequency disturbance value and a reference frequency to obtain a current working frequency, and send the current working frequency to the PFM pulse generation module 106. Specifically, the reference frequency may be set to 10KHz, the main reason is that the frequency of the open-loop fixed-frequency operation of the single-module LLC converter 101 is the main resonant frequency of 10KHz, and the converter requires an operating frequency between 8KHz and 12 KHz.
Optionally, the first controller 103 may select a Proportional-Integral (PI) controller as the first controller 103, or may select a Proportional-Integral-derivative (PID) controller, an Active Disturbance Rejection Controller (ADRC), and the like, which is not limited in this embodiment.
The output voltage collecting module 104 is mainly used for collecting an output voltage value, and in a specific embodiment, the output voltage collecting module 104 converts an output voltage signal into an output voltage value by using an a/D converter, and subtracts the output voltage value from an output voltage reference value at a comparison point to obtain a difference value between the output voltage value and the output voltage reference value. The output voltage acquisition module 104 may also include an output voltage relay. The output voltage relay is a controller for reflecting voltage change, and when the voltage in the circuit exceeds the maximum steady-state voltage or is lower than a specified value, the voltage relay cuts off the circuit to play a role in protecting the safety of the circuit.
The second controller 105 is mainly configured to calculate a second frequency disturbance value according to a difference between the output voltage reference value and the output voltage value, superimpose the second frequency disturbance value and the reference frequency to obtain a current working frequency, and send the current working frequency to the PFM pulse generation module 106. For example, the second controller 103 may select a PI controller as the second controller 103, or may select a PID controller, ADRC, etc., which is not limited in this embodiment.
The output end of the PFM pulse generating module 106 is connected to the single-module LLC converter 101, and is mainly used to generate a driving signal from the current operating frequency obtained by the first controller 103 or the second controller 105 and transmit the driving signal to the single-module LLC converter 101, so as to control a switching device in the single-module LLC converter 101.
The distributed voltage-sharing control circuit provided by the embodiment is applied to an IPOS system. The distributed voltage-sharing control circuit comprises a plurality of voltage-sharing control modules, wherein each voltage-sharing control module comprises a single-module LLC converter, an input voltage acquisition module, a first controller, an output voltage acquisition module, a second controller and a PFM pulse generation module. By adopting an independent controller for each single-module LLC converter and utilizing the PFM technology to control a switching device of the single-module LLC converter, the voltage on the input side is ensured to be stable, and the output voltage of each voltage-sharing control module is balanced, so that the power balance among the voltage-sharing control modules is achieved under the condition that the output side is clamped by a high-voltage direct-current power grid.
Fig. 2 is a schematic structural diagram of a single-module LLC converter provided in an embodiment of the present application, and as shown in fig. 2, the single-module LLC converter of the present embodiment includes: a controllable switching network 101-1, a resonant network 101-2, an ideal transformer 101-3, and a rectifier network 101-4.
The controllable switch network 101-1 includes a capacitor Ci, switching devices Q1, Q2, Q3, Q4, and diodes D1, D2, D3, and D4. Optionally, the switch device may be an Insulated Gate Bipolar Transistor (IGBT), a Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET), a Bipolar Junction Transistor (BJT), or the like, which is not limited in this embodiment.
The resonant network 101-2 comprises a resonant capacitor Cr, a resonant inductor Lr and an excitation inductor Lm.
The rectifying network 101-4 comprises diodes D5 and D6, capacitors C1 and C1, and resistors R1 and R2.
As can be seen from fig. 2, the input terminal of the controllable switching network 101-1 is used for connecting an input power supply, the output terminal of the controllable switching network 101-1 is connected to the input terminal of the resonant network 101-2, the output terminal of the resonant network 101-2 is connected to the input terminal of the ideal transformer 101-3, and the output terminal of the ideal transformer 101-3 is connected to the rectifier network 101-4.
The single-module LLC converter replaces a group of switching devices on the secondary rectification side of a common LLC resonant type unidirectional boosting DC/DC converter with a group of capacitors, so that the secondary rectification side is converted into voltage doubling rectification, the transformation ratio of the ideal transformer 101-3 is reduced, the actual production difficulty of the ideal transformer 101-3 is simplified, the cost is reduced, and the single-module LLC converter is more suitable for occasions with high voltage and high transformation ratio. Specifically, when the voltage V from the primary side to the secondary side of the ideal transformer 101-3 is measuredcdWhen the voltage is positive, negative, the diode D5 is turned on, and the diode D6 is turned off. Current flowing through D5 charges C1, so that voltage of C1 is VcdAnd the upper part is positive and the lower part is negative; all in onecdWith the positive upper, negative and lower, D6 is turned on, D5 is turned off, and current flows through D6 to charge C2, so that the voltage of C2 is VcdAnd is positive on top and negative on bottom, that is, the total output voltage is the sum of the two capacitor voltages. The main technical parameters of the single-module LLC converter are shown in the table below.
TABLE 1 Single Module LLC converter Main technical parameters
Rated power 62.5KW
Transformation ratio of converter 1/10.6
Rated voltage of low voltage side 820V
Rated current of low-voltage side 76.25A
Rated voltage of high voltage side 8750V±5％
Rated current of high-voltage side 7.2A
Main resonance frequency 10KHz
Fig. 3 is a schematic flow chart of a first embodiment of a distributed voltage-sharing control method provided in the embodiment of the present application, which includes the following specific implementation steps:
s101: and calculating a first deviation value between the input voltage and a preset input voltage reference value aiming at each voltage-sharing control module.
In this embodiment, an independent controller is adopted for each single-module LLC converter, and a PFM technique is used to control the switching devices of the single-module LLC converter, thereby ensuring the stability of the input voltage. The distributed voltage-sharing control method can complete component control, namely, signals output by the output regulator are superposed by control signals generated by a plurality of loops, and the superposition is equivalent to processing of a plurality of threads.
In this step, the current input voltage needs to be collected, and if the current input voltage is different from the reference value of the input voltage, the difference between the current input voltage and the reference value of the input voltage needs to be calculated. After the input voltage is collected by the input voltage collecting module, the input voltage signal is converted into an input voltage value. Meanwhile, an input voltage reference value registered in the input voltage acquisition module is read, and the input voltage value and the input voltage reference value are subtracted at a comparison point to obtain a first deviation value of the input voltage value and the input voltage reference value.
S102: and calculating a first frequency disturbance value according to the first deviation value.
In this step, the gain characteristic of the single-module LLC converter is known to be 0.8frTo 1.2frIn the range of (f)rAt resonant frequency) and the circuit gain is again broadly equal to the ratio of the output voltage to the input voltage (regardless of the effect of the ideal transformer and voltage doubling rectifier circuit). Therefore, in the case where the output voltage is clamped by the high voltage dc network, the frequency needs to be adjusted so that the circuit gain is changed to adjust the input voltage.
And when the first controller receives the first deviation value, calculating to obtain a first frequency disturbance value according to the first deviation value. The first frequency disturbance value refers to fluctuation of frequency and is divided into a positive frequency disturbance value and a negative frequency disturbance value. For example, when the input voltage is less than the reference input voltage, the first frequency disturbance value is a forward frequency disturbance value; when the reference input voltage is smaller than the input voltage, the first frequency disturbance value is a negative frequency disturbance value.
S103: and after the first frequency disturbance value is superposed with a preset reference frequency, generating a first driving signal in a pulse frequency modulation mode.
In this step, after the first controller calculates the first frequency disturbance value, the first frequency disturbance value and the reference frequency are required to be superimposed, the frequency value in the circuit is adjusted, and the gain of the circuit is changed, so as to achieve the purpose of controlling the input voltage. After the first controller obtains the first frequency disturbance value, reading a preset reference frequency, superposing the preset reference frequency and the preset reference frequency to obtain a current working frequency, and sending the current working frequency to the PFM pulse generation module. And after receiving the current working frequency, the PFM pulse generation module generates a first driving signal through PFM. Specifically, PFM is a pulse modulation technique in which the frequency of the pulses varies with the object being controlled, but the duty cycle remains the same.
For example, the reference frequency may be set to 10KHz, the main reason is that the open-loop fixed-frequency operating frequency of the single-module LLC converter is 10KHz as the main resonant frequency, and the converter requires an operating frequency between 8KHz and 12 KHz.
S104: and inputting the first driving signal into a single-module LLC converter in the voltage-sharing control module.
In this step, the first controller generates the first drive signal and transmits the first drive signal to the single-module LLC converter to act on the switching devices Q1, Q2, Q3, Q4 in the single-module LLC converter, the switching devices being turned on or off in accordance with the first drive signal.
For example, if the input voltage is smaller than the input voltage reference value, the frequency needs to be increased to increase the input voltage under the condition that the output voltage is clamped by the high-voltage direct-current power grid. The input voltage value is therefore subtracted from the input voltage reference value to obtain a positive voltage deviation value. The PI controller obtains a forward first frequency disturbance value according to the positive voltage deviation value, superposes the first frequency disturbance value and the reference frequency to obtain a working frequency, and sends the working frequency to the PFM pulse generation module to generate a first driving signal. And after receiving the first driving signal, a switching device of the single-module LLC converter is switched on or switched off according to the first driving signal.
The distributed voltage-sharing control method is applied to the IPOS system, and the input voltage is collected by the input voltage collecting module and subtracted from the input voltage reference value at the comparison point to obtain a first deviation value of the input voltage and the input voltage. And a first frequency disturbance value is obtained after the first frequency disturbance value passes through the first controller, the first frequency disturbance value is superposed with a reference frequency value, and finally a driving signal is generated by the PFM pulse generator to control a switching device of the LLC converter. Compared with the prior art, the method and the device are equivalent to the addition of a feedforward link, and the stability of the input side voltage is effectively improved.
In order to prevent the circuit parameters of a single voltage-sharing control module from changing to influence the balanced distribution of the output voltage among the voltage-sharing control modules, the output voltage can be controlled, so that the voltage among all the voltage-sharing control modules is kept consistent under the clamping action of a high-voltage direct-current power grid.
Fig. 4 is a schematic flow chart of a second embodiment of the distributed voltage-sharing control method provided in the embodiment of the present application, which includes the following specific implementation steps:
s201: and when the output voltage of the voltage-sharing control module is detected to be unbalanced, calculating a second deviation value between the output voltage and a preset output voltage reference value.
In this embodiment, when voltage imbalance occurs between voltage equalizing control blocks, the voltage between voltage equalizing control blocks is adjusted by using the influence of the frequency on the circuit gain when the input voltage is stable, considering that the input voltage remains unchanged.
In this step, the current output voltage needs to be collected and compared with the registered preset output voltage reference value, and if the current output voltage is different from the output voltage reference value, the difference between the current output voltage and the output voltage reference value needs to be calculated. The output voltage is collected in real time through the output voltage collecting module, and the output voltage signal is converted into an output voltage value. And comparing the registered preset output voltage reference values, considering that the output voltage of the voltage-sharing control module is balanced if the two numerical values are consistent, and considering that the output voltage of the voltage-sharing control module is unbalanced if the two numerical values are inconsistent, and subtracting the output voltage from the output voltage reference value at a comparison point to obtain a second deviation value between the output voltage and the preset output voltage reference value.
S202: and calculating a second frequency disturbance value according to the second deviation value.
In this step, when the input voltage is stable, the frequency also needs to be adjusted, so that the circuit gain is changed, thereby adjusting the output voltage.
And when the second controller receives the second deviation value, calculating to obtain a second frequency disturbance value according to the second deviation value. The second frequency disturbance value refers to a fluctuation of the frequency and is divided into a positive frequency disturbance value and a negative frequency disturbance value. For example, when the output voltage is smaller than the reference output voltage, the second frequency disturbance value is a forward frequency disturbance value; when the reference output voltage is smaller than the output voltage, the second frequency disturbance value is a negative frequency disturbance value.
S203: and generating a second driving signal in a pulse frequency modulation mode after the second frequency disturbance value is superposed with a preset reference frequency.
In this step, after the second controller calculates the second frequency disturbance value, the second frequency disturbance value needs to be superimposed with the reference frequency, so as to adjust the frequency value in the circuit, change the gain of the circuit, and achieve the purpose of adjusting the output voltage. And after the second controller obtains a second frequency disturbance value, reading a preset reference frequency, superposing the preset reference frequency and the preset reference frequency to obtain a current working frequency, and sending the current working frequency to the PFM pulse generation module. And after receiving the current working frequency, the PFM pulse generation module generates a second driving signal through PFM.
S204: and inputting the second driving signal into a single-module LLC converter in the voltage-sharing control module.
In this step, after the second controller generates the second driving signal, the second driving signal is sent to the single-module LLC converter, and acts on the switching devices Q1, Q2, Q3, Q4 in the single-module LLC converter, and the switching devices are turned on or off according to the second driving signal to adjust the output voltage by adjusting the switching frequency.
For example, if the output voltage is smaller than the output voltage reference value, the frequency needs to be increased to increase the output voltage when the input voltage is stable. Therefore, the output voltage value needs to be subtracted from the output voltage reference value to obtain the positive voltage deviation value. The PI controller obtains a forward second frequency disturbance value according to the positive voltage deviation value, the second frequency disturbance value and the reference frequency are overlapped to obtain a working frequency, and the working frequency is sent to the PFM pulse generation module to generate a second driving signal. And after receiving the first driving signal, the switching device of the single-module LLC converter is switched on or switched off according to the second driving signal.
When the output voltage among the voltage-sharing control modules is unbalanced, the input voltage can be considered to be kept unchanged, and the output voltage is adjusted by utilizing the influence of frequency on the circuit gain. The main reason is that in the distributed voltage-sharing control method of the first embodiment, the oscillation of the output voltage of the voltage-sharing control module is large in an initial stage, so that a generated frequency disturbance value also generates large oscillation, and the output frequency is greatly influenced. Therefore, the influence can be greatly reduced through the amplitude limiting function, and in addition, the voltage distribution can be completed very well to reach the balance due to the fact that the output side is clamped by the high-voltage direct-current power grid, so that the voltage stabilizing function of the distributed voltage-sharing control method in the first embodiment cannot be influenced to a great extent.
In addition, after the circuit is initially stable in operation, the input voltage is basically stable at the moment, and the unequal output voltages among the voltage-sharing control modules caused by parameter imbalance are also basically stable. Therefore, the output voltages of the voltage-sharing control modules can be adjusted to be equal through the distributed voltage-sharing control method of the second embodiment, and voltage sharing among the voltage-sharing control modules is finally completed under the clamping action of the high-voltage direct-current power grid, so that balanced output of power is achieved, and the output efficiency of the system is maintained.
In addition, in practical application, a circuit generally has parameter mutation in a steady-state operation process, at this time, the input voltage is kept stable, the output frequency is stable, and if parameter imbalance occurs between voltage-sharing control modules at this time, so that the output voltage mutation is caused, only the distributed voltage-sharing control method of the second embodiment is used, so that the distributed voltage-sharing control methods of the first embodiment and the second embodiment are designed to meet practical conditions.
The distributed voltage-sharing control method provided by the embodiment of the application is applied to an IPOS system. When the output voltage of the voltage-sharing control module is detected to be unbalanced, a second deviation value between the output voltage and a preset output voltage reference value is calculated, and then a second frequency disturbance value is calculated according to the second deviation value. And then, after the second frequency disturbance value is superposed with a preset reference frequency, a second driving signal is generated in a pulse frequency modulation mode, and finally, the second driving signal is input into a single-module LLC converter in the voltage-sharing control module. By controlling the output voltage, the voltage among all voltage-sharing control modules is kept consistent under the clamping action of the high-voltage direct-current power grid, and the output efficiency of the system is improved.
Fig. 5 is a schematic structural diagram of an IPOS combination system provided in an embodiment of the present application, and as shown in fig. 5, the embodiment provides a specific implementation manner, and the IPOS combination system is built in Matlab/Simulink, where the IPOS combination system includes: photovoltaic MPPT module 20, voltage-sharing control module 10.
It should be noted that the photovoltaic MPPT module 20 and the voltage grading control module 10 may include at least one photovoltaic MPPT module and a voltage grading control module. Fig. 5 illustrates that the photovoltaic MPPT module 20 includes 5 photovoltaic MPPT modules and the voltage-sharing control module 10 includes 2 voltage-sharing control modules, which are respectively the voltage-sharing control module 10-1 and the voltage-sharing control module 10-2, and the specific number may be limited according to actual requirements, which is not limited in this scheme.
Photovoltaic MPPT module 20 is mainly used for simulating the preceding stage part of photovoltaic direct current boost grid-connected system, exports about 125 KW's power altogether. The MPPT algorithm selects a disturbance observation method, a low-voltage direct-current bus is 820V, a high-voltage direct-current power grid is 17500V, and the voltage stabilizing effect and the voltage equalizing effect of the control method are verified respectively.
Fig. 6A is a waveform diagram of an input voltage in the IPOS combined system provided in the embodiment of the present application, fig. 6B is a waveform diagram of an input current in the IPOS combined system provided in the embodiment of the present application, and fig. 6C is a waveform diagram of an output power in the IPOS combined system provided in the embodiment of the present application. As shown in fig. 6A, 6B, and 6C, the horizontal axis of fig. 6A, 6B, and 6C represents time (S), and the vertical axis represents voltage (V), current (a), and power (W). Under standard environmental conditions (light illumination is S)refTemperature of Tref) After the input voltage of the IPOS combined system (i.e., the total output voltage of the photovoltaic MPPT module 20) is stabilized, 820V required by the low-voltage dc bus is reached, and the power of 125KW is output by the whole front-stage portion, which proves that the first controller 103 has the function of stabilizing the input voltage of the IPOS combined system under the normal illumination condition.
Fig. 7 is a waveform diagram of output voltages of the voltage equalizing control modules in a normal operating condition in the IPOS combined system according to the embodiment of the present application, as shown in fig. 7, a horizontal axis represents time (S), a vertical axis represents voltage (V), a dark line represents a change of the output voltage of the voltage equalizing control module 10-1 with time, and a light line represents a change of the output voltage of the voltage equalizing control module 10-2 with time. Under the normal working condition, the voltage of each voltage-sharing control module 10 is stable and is controlled to be about 8750V, which is 1/2 of the voltage of the high-voltage direct-current power grid, and at the moment, the voltage-sharing control modules 10 are voltage-sharing and can work normally.
Fig. 8 is a waveform diagram of output voltages of voltage-sharing control modules when resonant inductors in an IPOS combined system are different, as shown in fig. 8, a horizontal axis represents time (S), a vertical axis represents voltage (V), and a dark line represents the output voltage of the voltage-sharing control module 10-1 along with timeThe light line represents the change in the output voltage of the voltage sharing control module 10-2 over time. Fig. 9 is a waveform diagram of the operating frequency of each voltage equalizing control module in the IPOS combined system according to the embodiment of the present application, as shown in fig. 9, the horizontal axis represents time (S), the vertical axis represents frequency value (HZ), the dark line represents the change of the frequency value of the voltage equalizing control module 10-1 with time, and the light line represents the change of the frequency value of the voltage equalizing control module 10-2 with time. In FIGS. 8 and 9, the resonant inductor C of the voltage-sharing control module 10-1 is maintainedr1The resonance inductance of the voltage-sharing control module 10-2 is set to be Cr2＝110％Cr1The other parameters are the same. It can be seen that, when parameters change between the voltage-sharing control modules 10, the output voltages of the voltage-sharing control modules 10 are unbalanced, but after the output-side voltage-sharing second controller 105 is added, the second controller 105 can adjust the operating frequencies of the voltage-sharing control modules 10 according to the difference of the output-side voltages, so that the output voltage-sharing stabilizing system between the voltage-sharing control modules 10 operates normally, which indicates that the second controller 105 plays a role in sharing the output-side voltage among the voltage-sharing control modules 10.
Fig. 10 is a waveform diagram of voltages at the output side of each voltage-sharing control module when the resonant capacitors in the IPOS combined system are different, as shown in fig. 10, a horizontal axis represents time (S), a vertical axis represents voltage (V), a dark line represents a change of the output voltage of the voltage-sharing control module 10-1 with time, and a light line represents a change of the output voltage of the voltage-sharing control module 10-2 with time. Keeping the resonance inductance C of the voltage-sharing control module 10-1 under the standard environmental conditionr1The resonance inductance of the voltage-sharing control module 10-2 is set to be Cr2＝110％Cr1And the other parameters are the same. It can be seen that the voltage equalization between the voltage equalization control modules 10 is not performed due to the difference in resonant capacitance between the voltage equalization control modules 10, and the voltage equalization is completed under the adjustment of the output side second controller 105.
Fig. 11A is a waveform diagram of an output voltage of a photovoltaic MPPT module in an IPOS combined system according to an embodiment of the present application, fig. 11B is a waveform diagram of an output current of a photovoltaic MPPT module in an IPOS combined system according to an embodiment of the present application, and fig. 11C is a waveform diagram of an output current of an IPOS combination according to an embodiment of the present applicationAnd (3) a waveform diagram of the output power of the photovoltaic MPPT module in the system. In fig. 11A, 11B, and 11C, the horizontal axis represents time (S), and the vertical axis represents voltage (V), current (a), and power (W). Fig. 12 is a waveform diagram of a total output current in the IPOS combined system according to an embodiment of the present application. The horizontal axis represents time (S) and the vertical axis represents current (a). As shown in fig. 11A, 11B, 11C, and 12, the initial light intensity S is setrefAre all 1000W/m2After 0.5S, the intensity of light became 500W/m2The 1S light intensity becomes 800W/m2. It can be seen that the output voltage of the photovoltaic MPPT module 20 changes due to sudden change of illumination, the reason is that the photovoltaic MPPT module 20 needs to search for the maximum power point again when the illumination changes, and the circuit gain of the IPOS combined system changes with the change of the switching frequency, so that the voltage on the input side is caused under the condition that the voltage on the output side of the IPOS combined system is clamped, that is, the output voltage of the photovoltaic MPPT module 20 changes, but the change range is within the range of 15V, and the voltage continuously approaches to the reference value 820V along with the control of the first controller 103 on the input side, which indicates that the voltage stabilizing effect of the IPOS combined system is basically completed.
In addition, it can be known that the power transmission of the photovoltaic dc boost grid-connected system is basically determined by the current, and the voltage of each part in the circuit is clamped near the reference value due to the relationship between the high-voltage dc bus and the circuit gain along with the change of the operating frequency, wherein this is well demonstrated in fig. 8 and 9.
According to the embodiment of the application, through building the IPOS combined system, the analysis and simulation result proves that the feasibility of the distributed voltage-sharing control circuit provided by the application can achieve the effects of voltage stabilization at the input side and voltage sharing at the output side, the voltage-sharing control modules do not need to be coupled, the distributed voltage-sharing control circuit is also suitable for multiple voltage-sharing control modules, the transmission efficiency of the system is improved to a great extent, and unnecessary electric energy waste is reduced. The independent control of each voltage-sharing control module ensures the working redundancy of the whole system, simplifies the design difficulty, and can continue working only by overhauling the rest voltage-sharing control modules after one voltage-sharing control module breaks down.
The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims (10)

1. A distributed voltage sharing control circuit, comprising:
the input sides of the voltage-sharing control modules are connected in parallel, and the output sides of the voltage-sharing control modules are connected in series;
each voltage-sharing control module comprises a single-module resonant circuit LLC converter, an input voltage acquisition module, a first controller, an output voltage acquisition module, a second controller and a Pulse Frequency Modulation (PFM) pulse generation module;
one end of the input voltage acquisition module is connected with the input of the single-module LLC converter and is used for acquiring the input voltage of the single-module LLC converter, the other end of the input voltage acquisition module is connected with the input end of the first controller, and the output end of the first controller is connected with the first input end of the PFM pulse generation module;
one end of the output voltage acquisition module is connected with the output of the single-module LLC converter and is used for acquiring the output voltage of the single-module LLC converter, the other end of the output voltage acquisition module is connected with the input end of the second controller, and the output end of the second controller is connected with the second input end of the PFM pulse generation module;
and the output end of the PFM pulse generation module is connected with the single-module LLC converter.
2. The distributed voltage sharing control circuit according to claim 1, wherein the PFM pulse generating module is configured to generate a driving signal according to a frequency output by the first controller or a frequency output by the second controller, and the driving signal is configured to control a switching device in the single-module LLC converter.
3. A distributed voltage grading control circuit according to claim 1 or 2, wherein said single module LLC converter comprises:
a controllable switching network, a resonant network, an ideal transformer and a rectifier network;
the input end of the controllable switch network is used for connecting an input power supply, the output end of the controllable switch network is connected with the input end of the resonance network, the output end of the resonance network is connected with the input end of the ideal transformer, and the output end of the ideal transformer is connected with the rectifier network;
wherein, the rectification network is a voltage doubling rectification circuit.
4. The distributed voltage-sharing control circuit according to claim 3, wherein the controllable switch network comprises two groups of switch circuits, each group of switch circuits is composed of a switch device and a diode;
the rectifier network comprises a switch circuit formed by a group of diodes and a group of capacitors.
5. The distributed voltage-sharing control circuit according to claim 4, wherein the first controller and the second controller are any one of:
proportional integral PI controller, proportional integral derivative PID controller, active disturbance rejection controller ADRC.
6. A distributed voltage-sharing control method applied to the distributed voltage-sharing control circuit according to any one of claims 1 to 5, the method comprising:
calculating a first deviation value between the input voltage and a preset input voltage reference value aiming at each voltage-sharing control module;
calculating a first frequency disturbance value according to the first deviation value;
after the first frequency disturbance value is superposed with a preset reference frequency, generating a first driving signal in a pulse frequency modulation mode;
and inputting the first driving signal into a single-module LLC converter in the voltage-sharing control module, wherein the first driving signal is used for controlling a switching device in the single-module LLC converter so as to stabilize the output voltage of the voltage-sharing control module.
7. The method of claim 6, further comprising:
when the output voltage of the voltage-sharing control module is detected to be unbalanced, calculating a second deviation value between the output voltage and a preset output voltage reference value;
calculating a second frequency disturbance value according to the second deviation value;
after the second frequency disturbance value is superposed with a preset reference frequency, a second driving signal is generated in a pulse frequency modulation mode;
and inputting the second driving signal into a single-module LLC converter in the voltage-sharing control module, wherein the second driving signal is used for controlling a switching device in the single-module LLC converter so as to stabilize the output voltage of the voltage-sharing control module.
8. The method of claim 7, further comprising:
and if the output voltage of the voltage-sharing control module is detected to be inconsistent with the output voltage reference value, determining that the output voltage of the voltage-sharing control module is unbalanced.
9. The method according to any one of claims 6 to 8, further comprising:
and collecting the input voltage of the voltage-sharing control module in real time.
10. The method according to claim 7 or 8, characterized in that the method further comprises:
and acquiring the output voltage of the voltage-sharing control module in real time, comparing the output voltage with the output voltage reference value, and determining that the output voltage of the voltage-sharing control module is balanced.
CN202110426933.7A 2021-04-20 2021-04-20 Distributed voltage-sharing control circuit and control method Pending CN113054851A (en)

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107947588A (en) * 2017-12-05 2018-04-20 南京航空航天大学 With the ISOP systems and its control method for pressing characteristic naturally
CN112467986A (en) * 2020-09-30 2021-03-09 中国电力科学研究院有限公司 Unidirectional LLC resonant converter, variable frequency control method thereof and IPOS direct current converter

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107947588A (en) * 2017-12-05 2018-04-20 南京航空航天大学 With the ISOP systems and its control method for pressing characteristic naturally
CN112467986A (en) * 2020-09-30 2021-03-09 中国电力科学研究院有限公司 Unidirectional LLC resonant converter, variable frequency control method thereof and IPOS direct current converter

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Application publication date: 20210629