CN116505570B - Four-port intelligent soft switch system without central controller and control method thereof - Google Patents
Four-port intelligent soft switch system without central controller and control method thereof Download PDFInfo
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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
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/381—Dispersed generators
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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
- H02J1/00—Circuit arrangements for dc mains or dc distribution networks
- H02J1/10—Parallel operation of dc sources
- H02J1/109—Scheduling or re-scheduling the operation of the DC sources in a particular order, e.g. connecting or disconnecting the sources in sequential, alternating or in subsets, to meet a given demand
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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
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/008—Circuit arrangements for ac mains or ac distribution networks involving trading of energy or energy transmission rights
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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
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/04—Circuit arrangements for ac mains or ac distribution networks for connecting networks of the same frequency but supplied from different sources
- H02J3/06—Controlling transfer of power between connected networks; Controlling sharing of load between connected networks
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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
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
- H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
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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
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
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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
- H02J7/007—Regulation of charging or discharging current or voltage
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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
- H02J7/02—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries for charging batteries from ac mains by converters
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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
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
- H02J2300/22—The renewable source being solar energy
- H02J2300/24—The renewable source being solar energy of photovoltaic origin
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- 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
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
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- Engineering & Computer Science (AREA)
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- Supply And Distribution Of Alternating Current (AREA)
- Charge And Discharge Circuits For Batteries Or The Like (AREA)
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Abstract
The invention provides a four-port intelligent soft switching system without a central controller and a control method thereof. The distributed photovoltaic and energy storage are connected to a direct current chain of the intelligent soft switch, and a controller of the intelligent soft switch executes an optimization strategy according to the states of the energy storage unit and the photovoltaic unit and the current electricity price to output a control signal, so that the control of direct current voltage and regulation power is realized; and the energy storage unit determines a control strategy according to the direct-current voltage value to control the charge and discharge of the energy storage, and finally realizes the cooperative operation of all ports. According to the invention, the AC-DC converter of the intelligent soft switch is used as a grid-connected converter for photovoltaic and energy storage, so that the number of converters in the system is reduced, the system cost is reduced, meanwhile, the energy storage unit is utilized to discharge at peak electricity price, and is utilized to charge at valley electricity price, so that peak clipping and valley filling are realized, the electricity cost of a power distribution network is reduced, and the economy of the system is improved.
Description
Technical Field
The invention belongs to the technical field of power electronic control, and particularly relates to a four-port intelligent soft switching system without a central controller and a control method thereof.
Background
The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.
The increasingly diverse electrical loads and power demands make ac distribution networks a significant problem in terms of safety, reliability, economic applicability, and distribution efficiency. With the adjustment of energy structures and the development of power systems, the application of distributed photovoltaic, energy storage and novel power electronic equipment in the power systems is more and more extensive, so that the power distribution network has richer active adjustment capability. Among them, the smart soft switch SOP (Soft Open Point) receives more attention as a completely controlled power electronic device.
The distributed photovoltaic and energy storage access distribution network effectively relieves the problems of resource shortage and large load fluctuation. However, when the photovoltaic power grid is connected to a power distribution network, the distributed photovoltaic power grid and the energy storage are independently planned, independently designed and independently operated, coordination among systems is lacking, meanwhile, the problem of converter redundancy exists, and the economical efficiency and the stability of the systems are reduced. Meanwhile, due to the periodic characteristics of photovoltaic power generation and the periodic change of power load, the power flow size and direction of the power distribution network can be changed at any time, so that the fluctuation of the power transmission power is large, the running efficiency of the transformer is difficult to ensure, the running cost of the power distribution network is high, the generated energy and the consumed energy are difficult to match, and the economic applicability and the distribution efficiency of the power distribution network are difficult to ensure.
The SOP facing the power distribution level has flexible, rapid and accurate power exchange control and power flow optimization capability, and can realize integrated coordination optimization management of source-load-network-storage, so that the alternating current power distribution network can take account of safety and reliability, economic applicability and high power distribution efficiency. However, the SOP is mainly used for realizing fault isolation and power transfer, little research is conducted on a connection mode of a distributed power supply, energy storage and the SOP when the SOP is connected to a power distribution network and cooperative control among the three, and the problem of operation optimization of transformers at the position where the SOP is connected to the power distribution network is not considered, so that the number of transformers in the system is large, and the electricity cost is high.
Therefore, there is an urgent need for a connection mode and a cooperative control method capable of reducing the number of converters and improving the operation efficiency of the transformer.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides a four-port intelligent soft switch system without a central controller and a control method thereof, wherein the controller of the intelligent soft switch outputs control signals according to the states of an energy storage unit and a photovoltaic unit and the current electricity price execution optimization strategy to realize the control of direct current voltage and regulation power; and the energy storage unit determines a control strategy according to the direct-current voltage value to control the charge and discharge of the energy storage, so that the cooperative operation of all ports is finally realized, and the economy of the power distribution network is improved.
To achieve the above object, one or more embodiments of the present invention provide the following technical solutions:
one or more embodiments provide a four-port intelligent soft switching system without a central controller, comprising an intelligent soft switching unit, a photovoltaic unit and an energy storage unit;
the intelligent soft switch unit comprises a controller, a detection device, two alternating current ports and two direct current ports, wherein the two alternating current ports are directly connected with the power distribution network through an isolation transformer, the two direct current ports are led out by a direct current chain of the intelligent soft switch unit, and are externally connected with a DC-DC converter of the photovoltaic unit and the energy storage unit;
the intelligent soft switch unit collects state information of the isolation transformer and transmits the state information to the controller, and the controller determines an operation state based on the received state information of the isolation transformer; the controller outputs a control signal according to the states of the energy storage unit and the photovoltaic unit and the current electricity price execution optimization strategy, and the control signal is used for controlling the direct current voltage and the regulation power;
and the energy storage unit determines a control strategy according to the controlled direct-current voltage value and is used for controlling the charge and discharge of the energy storage.
Further, the intelligent soft switching unit further comprises two AC-DC converters, the two AC-DC converters are connected back to back, and the two AC-DC converters are three-phase four-bridge-arm AC-DC converters;
and an energy storage capacitor is connected to the direct current link which is connected back to back with the two AC-DC converters.
Further, the detection device comprises a voltage detection device and a current detection device;
the voltage detection device collects direct-current chain voltage and alternating-current side voltage signals connected with the power distribution network and transmits the direct-current chain voltage and alternating-current side voltage signals to the controller of the intelligent soft switching unit;
the current detection device collects alternating-current side current signals connected with the power distribution network and transmits the alternating-current side current signals to the controller of the four-port intelligent soft switching unit.
The photovoltaic units comprise a plurality of distributed photovoltaic units, and the distributed photovoltaic units are connected in parallel and then connected into a direct current chain of the intelligent soft switching unit through a DC-DC converter.
The energy storage unit comprises an energy storage battery, and the energy storage battery is connected into a direct current chain of the intelligent soft switching unit through a bidirectional DC-DC converter.
The isolation transformers comprise two isolation transformers, one end of each isolation transformer is connected with a power transmission line of the power distribution network, and the other end of each isolation transformer is connected with a user load and the intelligent soft switch unit respectively.
One or more embodiments provide a control method of a four-port intelligent soft switching system without a central controller, including:
the intelligent soft switch unit collects state information of the isolation transformer and transmits the state information to the controller, and the controller determines an operation state based on the received state information of the isolation transformer; the controller outputs a control signal according to the states of the energy storage unit and the photovoltaic unit and the current electricity price execution optimization strategy, and the control signal is used for controlling the direct current voltage and the regulation power;
the energy storage unit determines a control strategy according to the controlled direct current voltage value and is used for controlling the charge and discharge of the energy storage.
Preferably, the controller determines the operation state of the system based on the received state information of the isolation transformer, and specifically includes:
when the total load capacity of the two isolation transformers is smaller than the total rated capacity, determining that the two isolation transformers are in a normal running state;
when the total load capacity of the two isolation transformers is larger than the total rated capacity, determining an overload state;
when one of the load amounts of the two isolation transformers is zero, namely the power distribution network breaks down to disconnect one side of user load from the power distribution network, determining that the power distribution network is in a single side fault state;
the load capacity of the two isolation transformers is obtained according to the fact that the detection device collects alternating-current side voltage signals and current signals connected with the power distribution network.
Preferably, the optimization strategy executed by the controller according to the states of the energy storage unit, the photovoltaic unit and the current electricity price comprises: economic operation strategy under normal operation state, reliable operation strategy under overload state, and reliable operation strategy under single-side power distribution network fault state.
Preferably, the economic operation strategy in the normal operation state specifically includes:
when the peak electricity price is in, discharging the energy storage unit with maximum power when the charge state of the energy storage unit is larger than a first set threshold value, otherwise, not working;
when the electricity price is in the valley value, the energy storage unit is charged with the maximum power when the charge state of the energy storage unit is smaller than a second set threshold value, otherwise, the energy storage unit does not work;
wherein the first set threshold is less than the second set threshold.
The reliable operation strategy under the overload state is divided into two situations that only one isolation transformer is overloaded and two isolation transformers are overloaded, and specifically comprises the following steps:
when only one isolation transformer is overloaded, if the charge state of the energy storage unit is greater than a first set threshold, the energy storage unit discharges with maximum discharge power, and the intelligent soft switching unit performs active power adjustment to deliver power to the overload side so as to relieve the overload condition;
when overload occurs to the two isolation transformers, if the charge state of the energy storage unit is greater than a first set threshold, the energy storage unit discharges with maximum discharge power, the intelligent soft switch unit does not perform active power adjustment, and only the output power of the photovoltaic unit and the output power of the energy storage unit are distributed to two sides, so that the load rates of the transformers at the two sides are the same or similar.
Preferably, the reliable operation strategy in the fault state of the single-side power distribution network is that the energy storage unit discharges with maximum power, the intelligent soft switching unit operates on the fault side to perform constant voltage constant frequency control, and the other side performs a control mode of constant direct current voltage and reactive power control, so as to ensure uninterrupted power supply on the fault side.
The energy storage unit transmits a control signal generated by the intelligent soft switching unit to the bidirectional DC-DC converter of the energy storage unit in the form of direct current link voltage under the condition of no central controller and additional signal lines according to a control strategy determined by the controlled direct current voltage value, and specifically comprises the following steps:
determining a maximum charge and discharge power value of the energy storage unit and a direct current chain voltage interval when the four-port intelligent soft switching system can stably run;
the intelligent soft switch unit determines the charge and discharge power values of the energy storage unit according to the optimization strategies under different running states, converts the charge and discharge power values into voltage values, and transmits voltage value signals to the energy storage unit through a direct current chain;
the DC-DC converter of the energy storage unit converts the voltage value signal into a power value signal, and absorbs or outputs corresponding power.
The one or more of the above technical solutions have the following beneficial effects:
(1) According to the invention, a plurality of small-capacity energy storage units are replaced by one large-capacity energy storage unit, and distributed photovoltaic is connected with the grid through the AC-DC converter of the intelligent soft switch, so that the number of grid-connected inverters is reduced, the system cost is reduced, and the topological structure of the system is simpler.
(2) According to the invention, the load rate of the transformer at the access position is adjusted through the intelligent soft switch, so that the operation efficiency of the transformer is improved, and the loss of a system is reduced; and the charge and discharge states of the energy storage units are adjusted, so that the electricity cost of the power distribution network is reduced, and the economical efficiency of the system is improved.
(3) The controller of the intelligent soft switch is used as a master controller of the system to generate a control signal, a system central controller is not required to be additionally arranged, and the direct current chain is used as a signal transmission path to control the energy storage unit.
Additional aspects of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention.
FIG. 1 is a schematic diagram of a four-port intelligent soft switching system topology without a central controller according to the present invention;
FIG. 2 is an optimized control block diagram of a four-port intelligent soft switching system without a central controller of the present invention;
FIG. 3 is an operational criteria of an energy storage unit;
fig. 4 is a schematic diagram of a simulation result of a four-port intelligent soft switching system without a central controller accessing to a power distribution network 24 h;
fig. 5 is a schematic diagram of a state switching simulation of a four-port intelligent soft switching system without a central controller.
Detailed Description
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present invention.
Embodiments of the invention and features of the embodiments may be combined with each other without conflict.
The invention provides a general idea:
based on the existing intelligent soft switch, the distributed photovoltaic and the energy storage are connected to a direct current chain of the intelligent soft switch, the output characteristics of the distributed photovoltaic, the efficiency characteristics of a transformer and the peak-valley electricity price policies are comprehensively considered, the optimization strategies under different running states of the system are determined to realize the control of direct current voltage and regulation power, the control strategy of the energy storage charging and discharging is realized to realize the control of the energy storage charging and discharging, the cooperative running of all ports is finally realized, and the economical efficiency of the power distribution network is improved.
Example 1
Referring to fig. 1, the embodiment discloses a four-port intelligent soft switching system without a central controller, which comprises an intelligent soft switching unit, a photovoltaic unit and an energy storage unit;
the intelligent soft switch unit is shown as a dotted line frame in the figure and comprises two AC-DC converters which are connected back to back, and the two AC-DC converters are three-phase four-bridge arm AC-DC converters; and an energy storage capacitor is connected to the direct current link which is connected back to back with the two AC-DC converters.
The intelligent soft switch unit is provided with four ports, wherein two alternating current ports are directly connected with the power distribution network through an isolation transformer, two direct current ports are led out by a direct current chain, and the intelligent soft switch unit is externally connected with a DC-DC converter of the photovoltaic unit and the energy storage unit;
the intelligent soft switch unit is used as a core component of the system, not only controls the running states of the two AC-DC converters, but also determines an optimization strategy according to the state information of each port to generate a control signal, and then controls the bidirectional DC-DC converter of the energy storage unit through direct current link voltage.
The photovoltaic units comprise a plurality of distributed photovoltaic units, and the distributed photovoltaic units are connected in parallel and then connected into a direct current chain of the intelligent soft switching unit through a DC-DC converter to provide certain electric energy support for the system; the output power of the photovoltaic unit is limited by natural resource conditions and can be regarded as a relatively uncontrollable power source, so that the power source can provide electric energy support for the system and reduce the electricity consumption of the system.
The energy storage unit comprises an energy storage battery, and the energy storage battery is connected into a direct current chain of the intelligent soft switching unit through a bidirectional DC-DC converter; the distributed energy storage is replaced by a large energy storage unit, so that the energy storage cost is saved; the energy storage unit can release electric energy when the power consumption is high and absorb electric energy when the power consumption is low by changing the charge and discharge state, so that the transfer of the power consumption load in a time scale is realized, and the charge and discharge control of the energy storage unit can be realized by controlling the bidirectional DC-DC converter.
The isolation transformers comprise two isolation transformers, one end of each isolation transformer is connected with a power transmission line of the power distribution network, and the other end of each isolation transformer is connected with a user load and the intelligent soft switch unit respectively.
Example two
Referring to fig. 2, the embodiment discloses a control method of a four-port intelligent soft switching system without a central controller, which comprises the following steps:
the intelligent soft switch unit collects state information of the isolation transformer and transmits the state information to the controller, and the controller determines an operation state based on the received state information of the isolation transformer; the controller outputs a control signal according to the states of the energy storage unit and the photovoltaic unit and the current electricity price execution optimization strategy, and the control signal is used for controlling the direct current voltage and the regulation power;
the energy storage unit determines a control strategy according to the controlled direct current voltage value and is used for controlling the charge and discharge of the energy storage.
In the figure, pg1 and Pg2 respectively represent output power of two isolation transformers, E1 and E2 respectively represent rated capacity of the two isolation transformers, pe represents charge and discharge power values of the energy storage unit, SOC represents charge states of the energy storage unit, PV represents output power values of the photovoltaic unit, vdc_value represents direct current voltage control signals generated by the intelligent soft switching unit through an optimization strategy, psop and Qsop respectively represent control signals of active power and reactive power generated by the intelligent soft switching unit through the optimization strategy, and Vdc represents direct current chain voltage values of the intelligent soft switching unit.
In the figure, the controller of the intelligent soft switching unit in the part (1) determines the running state based on the collected state information of the isolation transformer, and divides the running state into three different running states according to the state information of the isolation transformer, and the intelligent soft switching unit specifically comprises:
when the total load capacity (sum of output power Pg1 and Pg 2) of the two isolation transformers is smaller than the total rated capacity (sum of E1 and E2), determining that the two isolation transformers are in a normal operation state;
when the total load capacity of the two isolation transformers is larger than the total rated capacity, determining an overload state;
when one of the load amounts of the two isolation transformers is zero, namely Pg1=0 or Pg2=0, the power distribution network breaks down to cause disconnection of one-side user load and the power distribution network, and the fault state of the one-side power distribution network is determined;
the output power Pg1 and Pg2 of the isolation transformer are obtained by collecting an alternating-current side voltage signal and a current signal connected with the power distribution network according to the detection device.
And then, the controller of the intelligent soft switching unit executes corresponding optimization/control strategies according to the PV, the SOC and the Pe to generate control signals Psop, qsop and vdc_value.
The optimization strategies under different operation states comprise an economic operation strategy under a normal operation state, a reliable operation strategy under an overload state and a reliable operation strategy under a single-side power distribution network fault state.
The economic operation strategy in the normal operation state comprehensively considers the peak-valley electricity price policy and the efficiency characteristic of the transformer, realizes the time transfer of the electricity load by using the energy storage unit, and realizes the space transfer of the electricity load by using the power regulation and control function of the intelligent soft switch;
specifically, when the SOC is greater than a first set threshold value while the peak electricity price is in, the energy storage unit discharges at maximum power, otherwise, the energy storage unit does not work; when the SOC is lower than a second set threshold value, the energy storage unit is charged with the maximum power, and otherwise, the energy storage unit does not work;
the first set threshold is smaller than the second set threshold, and the first set threshold and the second set threshold are respectively 0.2 and 0.9.
And then, by establishing a consumption characteristic model of the isolation transformers, determining output power values of the two isolation transformers and the power value transferred by the intelligent soft switching unit under the condition of a certain net load, and outputting a control signal, the total efficiency of the two isolation transformers is highest, and the total electricity consumption is lowest.
Specifically, the consumption characteristic model established according to the efficiency characteristic curve of the transformer is represented by the following formula (1):
wherein F is i Representing the input power of the i-side isolation transformer, P Oi Representing no-load loss at rated voltage of i-side isolation transformer, P ki The short-circuit loss when the i-side isolation transformer is rated current is shown. Obtaining micro increment lambda of two isolation transformers by deriving the formula (1) 1 And lambda is 2 The following formula (2) shows:
the output power Pg1 and Pg2 of the two isolation transformers can be determined according to the inequality constraint in the formula (1) and the micro increment of the two transformers in the formula (2); at this time, the total efficiency of the two isolation transformers is the highest and the loss is the smallest.
The reliable operation strategy under the overload state is divided into two conditions that only one isolation transformer is overloaded and two transformers are overloaded:
when only one isolation transformer is overloaded, if the SOC is larger than a first set threshold, the energy storage unit discharges with maximum discharge power, and the intelligent soft switching unit performs active power adjustment to deliver power to an overload side so as to relieve overload; the value for power regulation by the intelligent soft switching unit satisfies the formula (3):
P sop_value ＝P e +P V +E 1 -P L1 (3)
wherein P is Li Representing the user load on the i-side.
When overload occurs to the two isolation transformers, if the SOC is greater than a first set threshold, the energy storage unit discharges with maximum discharge power, the intelligent soft switch unit does not perform active power adjustment, only the output power of the photovoltaic unit and the energy storage unit is distributed to two sides, so that the load rates of the transformers at the two sides are the same or similar, and the method comprises the following specific steps:
firstly, determining a power value which needs to be distributed to one side with high load ratio when the load ratio of the transformers at two sides is the same, and recording as Pdo;
and then distributing the residual power of the direct current chain according to the condition that the load rates of the two sides are the same.
When the output power of the energy storage unit and the output power of the photovoltaic unit cannot enable the load rates of the transformers at the two sides to be the same, the value of the control signal is shown as a formula (4); when the output power of the energy storage and photovoltaic unit can make the load ratios of the transformers at the two sides the same, the value of the control signal is shown as the formula (5).
P sop_value ＝P e +P V (4)
The reliable operation strategy under the fault state of the single-side power distribution network is that when the user load at one side is disconnected from the power distribution network due to the fault of the power distribution network, the energy storage unit discharges with maximum power, the intelligent soft switching unit operates on the fault side to perform constant voltage and constant frequency control, and the other side performs a VdcQ-Vf control mode of constant direct voltage and reactive power control, so that uninterrupted power supply of the fault side is ensured.
In the figure, the part (2) is a hardware structure part, and is a carrier and a target of optimal control.
In the figure, the part (3) is a hardware control strategy, which specifically comprises:
firstly, controlling the operation of two AC-DC converters of an intelligent soft switching unit according to control signals Psop, qsop and vdc_value generated in the part (1), wherein one converter operates in a VdcQ control mode of constant direct current voltage and reactive power control, and the other converter operates in a PQ control mode of active power and reactive power control or a Vf control mode of constant voltage and constant frequency control; when the power supply operates in the Vf control mode, the given reference signal is 220V and 50Hz of the standard value of the mains voltage;
and then realizing charge and discharge control of the energy storage unit according to the direct current chain voltage value.
As shown in fig. 3, the charge-discharge control strategy of the energy storage unit is a bidirectional DC-DC converter that transmits a control signal generated by the intelligent soft switching unit to the energy storage unit in the form of a DC link voltage without a central controller and an additional signal line, and specifically includes the following steps:
the energy storage unit determines a working state according to state information acquired by a controller of the intelligent soft switching unit, when the total output power of the two isolation transformers at the current moment is larger than the total rated capacity, the energy storage unit discharges when the SOC of the energy storage unit is more than 0.2 in order to improve the stability and the service life of the transformers, the discharge power is shown as a formula (6), otherwise, the energy storage unit does not work; when the total output power of the two isolation transformers at the current moment is smaller than the total rated capacity, if the peak power price is set and the SOC is more than 0.2, the energy storage unit discharges, the discharge power is shown as a formula (7), and if the SOC is less than or equal to 0.2, the energy storage unit does not work; if the power is not at the peak power price and the SOC is less than 0.9, the energy storage unit is charged, the charging power is shown as a formula (8), and if the SOC is more than or equal to 0.9, the energy storage unit does not work.
P e ＝min{P cnmax ,P L1 +P L2 -E 1 -E 2 -P V }(6)
P e ＝P cnmax (7)
P e ＝min{P cnmax ,-P L1 -P L2 +E 1 +E 2 +P V }(8)
Wherein, pcnmax is the maximum charge-discharge power value of the energy storage unit.
In the operation process of the intelligent soft switch unit, the direct current chain voltage can maintain the stable operation of the system in a certain range, so that the energy storage unit can determine different operation modes and charge and discharge power values through different direct current voltage values, and the determination mode is as follows:
firstly, determining a maximum charge and discharge power value of an energy storage unit and a section Vdcmin-Vdcmax of direct current chain voltage when a system can stably run;
the intelligent soft switch unit determines the charge and discharge power value Pe of the energy storage unit according to system optimization strategies under different running states, converts the value of the Pe into a voltage value, transmits signals to the energy storage unit through direct-current voltage, and then the DC-DC converter of the energy storage unit converts the direct-current voltage signals into power value signals to absorb or output corresponding power.
For example, in a 380V distribution network, the DC voltage can maintain stable operation of the system within the range of 750VDC to 850 VDC. When the DC-DC converter of the energy storage unit detects that the DC link voltage is 780-820 VDC, the energy storage unit does not work; when the direct current chain voltage is 820 VDC-850 VDC, the energy storage unit is in a constant power discharge mode, and the power is [ (VDC-820)/30 ] Pcnmax; when the direct current chain voltage is 750 VDC-780 VDC, the energy storage unit is in a constant power charging mode, and the power is [ (VDC-780)/30 ] Pcnmax.
Fig. 4 is a schematic diagram showing a simulation result of the four-port intelligent soft switching system without the central controller accessing the power distribution network 24 h. The photovoltaic output curve in fig. 4 (a) is 24h, the peak electricity price time is 8:00-22:00, the electricity price is 0.5769, the valley electricity price time is 0:00-8:00 and 22:00-24:00, and the electricity price is 0.3769. Fig. 4 (b) shows the user load curves on both sides and the optimized output power curve of the transformer. FIG. 4 (c) is a system electricity cost curve, wherein the solid line represents 24h electricity cost without energy storage, without SOP optimization strategy; the broken line represents the 24h electricity cost with stored energy without SOP optimization strategy optimization; the dash-dot line represents the 24h electricity cost of the system after adding the SOP optimization strategy. The overall electricity cost reduction after optimization by the optimization strategy can be observed.
Fig. 5 is a schematic diagram of a state switching simulation of a four-port intelligent soft switching system without a central controller. Fig. 5 (a) to fig. 5 (c) are a waveform diagram of a dc link voltage and an ac side current of the intelligent soft switching unit, a state diagram of the energy storage unit, and a power variation diagram of the system when the optimization strategy is executed and a new control signal is generated in a normal operation state and a system overload state of the system. In the time of 0-5s, the system is not optimally regulated by an optimization strategy, at the moment, the direct-current voltage is 800V, the energy storage does not work, and the output power of the two transformers and the power allocated by the intelligent soft switching unit are not changed. When t=5s, the controller of the intelligent soft switching unit generates a new control signal according to an optimization strategy, the direct-current voltage reaches a new reference value after being regulated briefly, the energy storage unit is charged, the output power of the two transformers is transferred through the intelligent soft switching unit, and the operation efficiency of the system is improved.
Fig. 5 (d) -fig. 5 (f) are waveforms of direct current chain voltage and alternating current side current of the intelligent soft switch unit, a state diagram of the energy storage unit and a voltage waveform diagram of a fault side user load when the system is switched from a normal operation state to a fault state of the power distribution network. In the time of 0-5s, the system is not optimally regulated by an optimization strategy, at the moment, the direct-current voltage is 800V, the energy storage does not work, and the output power of the two transformers and the power allocated by SOP are not changed. When t=5s, the power distribution network faults occur, the user load at the fault side is disconnected from the power distribution network, the intelligent soft switching unit is changed from the VdcQ-PQ operation mode to the VdcQ-Vf operation mode, the direct current voltage rapidly reaches a new steady state, the energy storage discharges with the maximum power, and the user load at the fault side rapidly enters the steady state after short-time oscillation.
Therefore, the control strategy provided by the invention can quickly respond to the optimization strategy in a short transient time, and the cooperative operation of a plurality of ports in the system is realized.
While the foregoing description of the embodiments of the present invention has been presented in conjunction with the drawings, it should be understood that it is not intended to limit the scope of the invention, but rather, it is intended to cover all modifications or variations within the scope of the invention as defined by the claims of the present invention.
Claims (8)
1. A four-port intelligent soft switching system without a central controller comprises an intelligent soft switching unit, a photovoltaic unit and an energy storage unit;
the intelligent soft switch unit comprises a controller, a detection device, two alternating current ports and two direct current ports, wherein the two alternating current ports are directly connected with the power distribution network through an isolation transformer, the two direct current ports are led out by a direct current chain of the intelligent soft switch, and are externally connected with a DC-DC converter of the photovoltaic unit and the energy storage unit;
the intelligent soft switch unit collects state information of the isolation transformer and transmits the state information to the controller, and the controller determines the running state of the system based on the received state information of the isolation transformer; the controller outputs a control signal according to the states of the energy storage unit and the photovoltaic unit and the current electricity price execution optimization strategy, and the control signal is used for controlling the direct current voltage and the regulation power;
the energy storage unit determines a control strategy according to the controlled direct-current voltage value and is used for controlling the charge and discharge of the energy storage;
the controller determines the operation state of the system based on the received state information of the isolation transformer, and specifically comprises the following steps:
when the total load capacity of the two isolation transformers is smaller than the total rated capacity, determining that the two isolation transformers are in a normal running state;
when the total load capacity of the two isolation transformers is larger than the total rated capacity, determining an overload state;
when one of the load amounts of the two isolation transformers is zero, namely the power distribution network breaks down to disconnect one side of user load from the power distribution network, determining that the power distribution network is in a single side fault state;
the load capacity of the two isolation transformers is obtained according to the fact that the detection device collects alternating-current side voltage signals and current signals connected with the power distribution network;
the energy storage unit transmits a control signal generated by the intelligent soft switching unit to the bidirectional DC-DC converter of the energy storage unit in the form of direct current link voltage under the condition of no central controller and additional signal lines according to a control strategy determined by the controlled direct current voltage value, and specifically comprises the following steps:
determining a maximum charge and discharge power value of the energy storage unit and a direct current chain voltage interval when the four-port intelligent soft switching system can stably run;
the intelligent soft switch unit determines the charge and discharge power values of the energy storage unit according to the optimization strategies under different running states, converts the charge and discharge power values into voltage values, and transmits voltage value signals to the energy storage unit through a direct current chain;
the DC-DC converter of the energy storage unit detects the difference of direct current voltage, determines different running modes and charge-discharge power values of the energy storage unit, converts a voltage value signal into a power value signal, and absorbs or outputs corresponding power.
2. The four-port intelligent soft switching system without a central controller of claim 1, wherein the intelligent soft switching unit further comprises two AC-DC converters, the two AC-DC converters are connected back-to-back, and the two AC-DC converters are three-phase four-leg AC-DC converters;
and an energy storage capacitor is connected to the direct current link which is connected back to back with the two AC-DC converters.
3. The four-port intelligent soft switching system without the central controller according to claim 1, wherein the photovoltaic units are a plurality of distributed photovoltaic units, the distributed photovoltaic units are summarized after being connected in parallel, and the distributed photovoltaic units are connected into a direct current chain of the intelligent soft switching unit through a DC-DC converter.
4. A four-port intelligent soft switching system without a central controller as claimed in claim 1, wherein the energy storage unit comprises an energy storage battery which is connected to the DC link of the intelligent soft switching unit via a bi-directional DC-DC converter.
5. A four-port intelligent soft switching system without a central controller as claimed in claim 1, wherein said isolation transformers comprise two, one end of each isolation transformer is connected to the power line of the power distribution network, and the other end is connected to the user load and the intelligent soft switching unit, respectively.
6. A control method of a four-port intelligent soft switching system without a central controller comprises the following steps:
the intelligent soft switch unit comprises a controller, a detection device, two alternating current ports and two direct current ports, wherein the two alternating current ports are directly connected with the power distribution network through an isolation transformer, the two direct current ports are led out from a direct current chain of the intelligent soft switch, and are externally connected with a DC-DC converter of the photovoltaic unit and the energy storage unit;
the intelligent soft switch unit collects state information of the isolation transformer and transmits the state information to the controller, and the controller determines an operation state based on the received state information of the isolation transformer; the controller outputs a control signal according to the states of the energy storage unit and the photovoltaic unit and the current electricity price execution optimization strategy, and the control signal is used for controlling the direct current voltage and the regulation power;
the energy storage unit determines a control strategy according to the controlled direct-current voltage value and is used for controlling the charge and discharge of the energy storage;
the controller determines an operation state based on the received state information of the isolation transformer, and specifically comprises the following steps:
when the total load capacity of the two isolation transformers is smaller than the total rated capacity, determining that the two isolation transformers are in a normal running state;
when the total load capacity of the two isolation transformers is larger than the total rated capacity, determining an overload state;
when one of the load amounts of the two isolation transformers is zero, namely the power distribution network breaks down to disconnect one side of user load from the power distribution network, determining that the power distribution network is in a single side fault state;
the load capacity of the two isolation transformers is obtained according to the fact that the detection device collects alternating-current side voltage signals and current signals connected with the power distribution network;
the energy storage unit transmits a control signal generated by the intelligent soft switching unit to the bidirectional DC-DC converter of the energy storage unit in the form of direct current link voltage under the condition of no central controller and additional signal lines according to a control strategy determined by the controlled direct current voltage value, and specifically comprises the following steps:
determining a maximum charge and discharge power value of the energy storage unit and a direct current chain voltage interval when the four-port intelligent soft switching system can stably run;
the intelligent soft switch unit determines the charge and discharge power values of the energy storage unit according to the optimization strategies under different running states, converts the charge and discharge power values into voltage values, and transmits voltage value signals to the energy storage unit through a direct current chain;
the DC-DC converter of the energy storage unit detects the difference of direct current voltage, determines different running modes and charge-discharge power values of the energy storage unit, converts a voltage value signal into a power value signal, and absorbs or outputs corresponding power.
7. The control method of the four-port intelligent soft switching system without the central controller according to claim 6, wherein the optimization strategies executed by the controller according to the states of the energy storage unit and the photovoltaic unit and the current electricity price comprise an economic operation strategy in a normal operation state, a reliable operation strategy in an overload state and a reliable operation strategy in a fault state of the single-side power distribution network.
8. The control method of the four-port intelligent soft switching system without the central controller according to claim 7, wherein the economical operation strategy in the normal operation state specifically comprises:
when the peak electricity price is in, discharging the energy storage unit with maximum power when the charge state of the energy storage unit is larger than a first set threshold value, otherwise, not working;
when the electricity price is in the valley value, the energy storage unit is charged with the maximum power when the charge state of the energy storage unit is smaller than a second set threshold value, otherwise, the energy storage unit does not work;
wherein the first set threshold is less than the second set threshold.
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Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108695875A (en) * | 2018-06-28 | 2018-10-23 | 华北电力大学（保定） | The power distribution network running optimizatin method of intelligent Sofe Switch and energy storage device joint access |
| CN109120008A (en) * | 2018-09-05 | 2019-01-01 | 东北大学 | A kind of energy router apparatus and control method applied to honourable energy storage |
| CN112436547A (en) * | 2020-11-17 | 2021-03-02 | 青岛大学 | Double-grid-connected interface medium-voltage photovoltaic power generation system with SOP function |
| CN113690873A (en) * | 2021-08-16 | 2021-11-23 | 三峡大学 | Photovoltaic direct-current micro-grid coordination control method containing hybrid energy storage |
| CN114006371A (en) * | 2021-10-28 | 2022-02-01 | 国网天津市电力公司 | Flexible power distribution network electric energy transaction method and device oriented to intelligent energy storage soft switch |
| CN114629174A (en) * | 2022-04-21 | 2022-06-14 | 广东电网有限责任公司 | Microgrid operation control method and device and microgrid |
| CN115425691A (en) * | 2022-10-09 | 2022-12-02 | 东南大学 | Multi-voltage-level flexible interconnection device |
| CN115441498A (en) * | 2022-08-25 | 2022-12-06 | 国电南瑞科技股份有限公司 | Platform area micro-grid system based on flexible direct current interconnection and control method thereof |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115085245A (en) * | 2021-03-10 | 2022-09-20 | 台达电子工业股份有限公司 | Photovoltaic energy storage system and applicable control method thereof |
-
2022
- 2022-12-20 CN CN202211646075.8A patent/CN116505570B/en active Active
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108695875A (en) * | 2018-06-28 | 2018-10-23 | 华北电力大学（保定） | The power distribution network running optimizatin method of intelligent Sofe Switch and energy storage device joint access |
| CN109120008A (en) * | 2018-09-05 | 2019-01-01 | 东北大学 | A kind of energy router apparatus and control method applied to honourable energy storage |
| CN112436547A (en) * | 2020-11-17 | 2021-03-02 | 青岛大学 | Double-grid-connected interface medium-voltage photovoltaic power generation system with SOP function |
| CN113690873A (en) * | 2021-08-16 | 2021-11-23 | 三峡大学 | Photovoltaic direct-current micro-grid coordination control method containing hybrid energy storage |
| CN114006371A (en) * | 2021-10-28 | 2022-02-01 | 国网天津市电力公司 | Flexible power distribution network electric energy transaction method and device oriented to intelligent energy storage soft switch |
| CN114629174A (en) * | 2022-04-21 | 2022-06-14 | 广东电网有限责任公司 | Microgrid operation control method and device and microgrid |
| CN115441498A (en) * | 2022-08-25 | 2022-12-06 | 国电南瑞科技股份有限公司 | Platform area micro-grid system based on flexible direct current interconnection and control method thereof |
| CN115425691A (en) * | 2022-10-09 | 2022-12-02 | 东南大学 | Multi-voltage-level flexible interconnection device |
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