Regional distributed power supply cooperative control system and method based on multistage layered optimization

Abstract

The invention discloses a regional distributed power supply cooperative control system and method based on multistage layered optimization. A distributed energy management system receives management and control equipment information of each distributed energy region and comprehensively monitors the state of each distributed power supply; giving reference values of active power and reactive power injected to each power distribution network by the main power grid at a point of common connection PCC to each distributed energy area management and control device; each distributed energy area management and control device receives distributed power supply grid-connected point information accessed by the corresponding integrated grid-connected device, information of other flexible loads on a feeder line and outlet power of the feeder line, uploads the information to the distributed energy management system, screens and controls required power signals through the corresponding integrated grid-connected device, and sends the screened power signals to the corresponding integrated grid-connected device. A distributed power supply and a flexible load are controlled through a regional cooperative control strategy; and each integrated grid-connected device receives a power target of the corresponding distributed energy region management and control device, and distributes power to each distributed power supply and flexible load connected with the integrated grid-connected device.

Description

Technical Field

[0001] The present invention relates to energy control technology, and more specifically, to a regional distributed power supply collaborative control system and method based on multi-level hierarchical optimization. Background Art

[0002] New energy sources, mainly renewable energy, have been developed on a large scale. Distributed power generation provides important support for the development and utilization of new energy sources. On the one hand, compared with centralized power generation, distributed power generation can reduce transmission losses, improve power supply reliability, and improve the disaster prevention level of the power grid. On the other hand, distributed power sources also have the advantages of small investment, quick results, easy start and stop, easy upgrade and expansion, and slight impact on the environment. Therefore, the application of distributed power sources is becoming more and more extensive.

[0003] However, the need for distributed power generation to participate in grid dispatching and the inherent uncertainty of new energy sources have brought challenges to the planning, operation and control of the coordinated control of the grid. On the other hand, with the advent of the information age characterized by digitization and networking, society has increasingly stringent requirements for power quality and power supply reliability, and users hope to interact with the grid in information and power more conveniently and flexibly. Therefore, the research on distributed power control based on new energy sources has received widespread attention.

[0004] Due to the intermittent characteristics of distributed power generation from new energy sources, researchers have focused on analyzing the control methods, peak-shaving and valley-filling operation mechanisms, and economic aspects of new energy sources for single states and conventional power generation forms. However, in distributed power sources, in addition to new energy sources, there are also various types of power sources such as internal combustion engines, cogeneration, and fuel cells. There are differences and clustering effects between different regulation objects. At the same time, in addition to the internal interaction and coordination of multiple types of power groups, there is also a need for interaction and coordination between them and the power grid. It can be seen that when carrying out regional distributed power supply management and control, the multi-level hierarchical optimization of multiple distributed power sources at different time scales should be comprehensively considered, and the impact of grid state perception should be considered. However, related research results are still rare. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and propose a regional distributed power supply collaborative control system and method based on multi-level hierarchical optimization. The multi-level hierarchical optimization of multiple distributed power supplies at different time scales is considered, and the influence of grid state perception is considered. The tolerance level of grid fluctuations is effectively improved, and the coordinated regulation of distributed power supplies in different regions can be achieved, thereby promoting the consumption of new energy, improving the economy and reliability of system operation, reducing power supply planning margin, and improving load access level.

[0006] The purpose of the present invention can be achieved through the following technical solutions.

[0007] The present invention is based on a regional distributed power supply collaborative control system with multi-level hierarchical optimization, and adopts a hierarchical control structure, including a distributed power supply management platform at the top level, a regional collaborative control function module at the middle level, and a local autonomous control function module at the bottom level. The distributed power supply management platform adopts a distributed energy management system, and each of the regional collaborative control function modules adopts a distributed energy regional management and control device, and each of the local autonomous control function modules adopts an integrated grid-connected device;

[0008] The distributed energy management system independently interacts with multiple distributed energy regional control devices, receives information from each distributed energy regional control device, comprehensively monitors the status of each distributed power source, and controls the entire system by giving each distributed energy regional control device a reference value of active power and reactive power injected by the main grid into each distribution network at the common connection point PCC;

[0009] Each of the distributed energy regional control devices exchanges information with an integrated grid-connected device respectively. Each of the distributed energy regional control devices receives the distributed power grid-connected point information, other flexible load information on the feeder, and the power at the outlet of the feeder to which the integrated grid-connected device in the corresponding region is connected, and uploads it to the distributed energy management system. The power signal required for control is screened by the corresponding integrated grid-connected device, and then the distributed power source and flexible load in the corresponding region are controlled through the regional collaborative control strategy.

[0010] Each of the integrated grid-connected devices is connected to a distributed power source and a flexible load. Each of the integrated grid-connected devices is used to receive the power target of the corresponding distributed energy area management and control device, and reasonably allocate power to each distributed power source and flexible load connected to it, and collect and upload the distributed power source grid connection point information connected to the area, other flexible load information on the feeder, and the power at the feeder outlet.

[0011] The purpose of the present invention can also be achieved through the following technical solutions.

[0012] The present invention provides a regional distributed power supply coordinated control method based on multi-level hierarchical optimization, comprising the following contents:

[0013] The distributed energy management system independently interacts with multiple distributed energy regional control devices, receives information from each distributed energy regional control device, comprehensively monitors the status of each distributed power source, and controls the entire system by giving each distributed energy regional control device a reference value of active power and reactive power injected by the main grid into each distribution network at the public connection point PCC;

[0014] Each of the distributed energy regional control devices receives the distributed power grid connection point information, other flexible load information on the feeder, and the power at the outlet of the feeder to which the integrated grid-connected device in the corresponding region is connected, and uploads it to the distributed energy management system, and screens the power signal required for control through the corresponding integrated grid-connected device, and then controls the distributed power in the corresponding area through the regional collaborative control strategy;

[0015] Each of the integrated grid-connected devices receives the power target of its corresponding distributed energy area control device, and reasonably allocates power to each distributed power source and flexible load connected to it, collects and uploads the distributed power source grid connection point information connected to the area, other flexible load information on the feeder, and the power at the feeder outlet.

[0016] Furthermore, the regional collaborative control strategy adopts a distributed consistency algorithm, and through the collaborative control of each distributed power source in the distribution network, the injected power of the distribution network at the common connection point can track the power reference value given by the main power grid, so as to realize the distribution of active power among the distributed power sources in the same region and the balance of voltage at the grid connection point of each distributed power source; the regional collaborative control strategy includes injection power control at the common connection point of the distribution network, active power sharing of distributed power sources, voltage balance at the grid connection point of distributed power sources, and energy storage nuclear power status recovery;

[0017] ① Injection power control at the common connection point of the distribution network

[0018]

[0019]

[0020] Among them, P PCC and are the actual value and reference value of the active power injected by the main grid into the distribution network at the common connection point PCC, Q PCC and are the actual value and reference value of reactive power injected by the main grid into the distribution network at the common connection point PCC; P i and Q i ,i∈S L are the active and reactive power consumed by load node i, S L is a collection of load and energy storage nodes; P j and Q j ,j∈S E are the active and reactive power generated by distributed generation j or energy storage node j, S E It is a collection of distributed power sources and energy storage nodes; P loss and Q loss They are the active and reactive power losses of the distribution network system respectively;

[0021] ② Active power sharing of distributed power sources

[0022]

[0023] Among them, P i is the actual active output of distributed generation i, is the rated active output power of the converter of distributed generation i, S G Represents the set of distributed power sources excluding energy storage;

[0024] ③ Voltage balance at the distributed power grid connection point

[0025]

[0026] Among them, V i is the effective value of the voltage at the point where the distributed generation i is connected to the distribution network, are the lower limit and upper limit of the voltage fluctuation allowed by the distribution network at the point where the distributed generation i is connected to the distribution network;

[0027] ④ Energy storage nuclear power status recovery

[0028]

[0029] Among them, SoC i and are the actual value and reference value of the state of charge of energy storage i, S B Represents the set of energy storage nodes, S E =S B ∪S G .

[0030] Furthermore, each of the integrated grid-connected devices is used to receive the power target of the corresponding distributed energy regional control device, and reasonably allocate the power to each distributed power source and flexible load connected to it according to the local autonomous control strategy; the local autonomous control strategy includes distribution network port power control, active power sharing, voltage balancing control, and energy storage SOC recovery;

[0031] The local autonomous control strategy adopts hierarchical collaborative control: the first layer is the physical layer, which includes the hardware parts of the converters and other controllers of each distributed power source and energy storage unit. The converters all work in the PQ control mode, and the control signals are composed of the control signals generated by the second and third layers; the second layer is the PCC power control layer, which is responsible for controlling the injected power of the distribution network at the common connection point PCC so that it tracks the power reference value given by the distributed energy management system; the third layer is used to generate control signals for active power sharing, voltage balancing and energy storage SOC recovery among each distributed power source;

[0032] ①Power control of distribution network ports

[0033] Taking distributed power source i as an example, the active power reference value of distributed power source i is obtained as follows: and reactive power reference Then and Perform PI adjustment to obtain the PQ control signal of the converter of distributed power source i; and so on, obtain the PQ control signal of the converter of each distributed power source and energy storage unit in the same way as distributed power source i;

[0034]

[0035]

[0036] Among them, P iref- and Q iref-S are the control signals for the second-layer control of distributed generation i to realize the control of active power and reactive power injected into the distribution network at the common connection point PCC, P iref- and Q iref They are the control signals used in the third layer control of distributed power source i to realize the control of active power and reactive power injection at the common connection point PCC of the distribution network. When the power control of the distribution network port is performed, the control signal is only provided by the second layer control. At this time, P iref-T and Q iref-T All are 0;

[0037]

[0038]

[0039] in, and are the proportional control parameters of active power and reactive power injected by distributed generation i at the common connection point PCC, μ P-i and μ Q-i are the compensation adjustment factors for the active power and reactive power injected into the distributed generation i at the common connection point PCC, which are defined as follows:

[0040]

[0041]

[0042] Among them, a i-PCC The value of depends on the communication method used by the power control at the second-layer distribution network PCC in the local autonomous control strategy; when point-to-point communication is used, if there is a communication connection between the distributed generation i and the PCC, then a i-PCCThe value is 1, otherwise it is 0; when broadcast communication is used, the a of the distributed power source i participating in PCC power compensation i-PCC All are 1; is the reference value of the voltage at the point where the distributed generation i is connected to the distribution network;

[0043] ② Active power sharing

[0044] A distributed consensus algorithm is used to realize active power sharing of each distributed power source, so that the ratio of active power generated by all distributed power sources to the rated active output power of their respective converters is the same, that is, active power is distributed proportionally;

[0045] Taking distributed power source i as an example, a distributed consistency algorithm is used to design its active power sharing ratio, that is, the active power sharing consistency factor:

[0046]

[0047]

[0048] Among them, k is the time step of algorithm iteration, P iref-T (k+1) is the active power sharing control signal of distributed generation i at step k+1, P i (k) is the actual active power output of distributed generation i at step k, ρ is a fixed positive real number used to control the convergence speed of the algorithm, and n is the set S E The number of elements in l i,j is the i-th row and j-th column element of the Laplace matrix of the distribution network communication topology graph, λ P-i (K) is the active power sharing consistency factor of distributed generation i at step k;

[0049] In the iterative process of the algorithm, if the active power sharing consistency factor λ of distributed generation i P-i is less than the average value of the active power sharing consistency factor of its neighboring nodes, that is, the active power sharing ratio of distributed power source i is lower than that of its neighboring nodes, then the active power sharing control signal generated by formula (13) will increase, and then increase it, and vice versa;

[0050] In the process of active power sharing of distributed power sources, each participating distributed power source transmits its own active power sharing consistency factor to the neighboring node through the communication network, and substitutes the collected active power sharing consistency factor information of the neighboring node into equations (12) and (13) to generate active power sharing control signals for respective converter control. Finally, the active power sharing consistency factors of all participating distributed power sources will tend to be consistent.

[0051] ③Voltage balance control

[0052] Voltage balancing control requires that the injected reactive power of the distribution network at the common connection point PCC tracks the reference value given by the distributed energy management system;

[0053] Taking distributed power source i as an example, the distributed consistency algorithm is used to design its voltage balance consistency factor:

[0054]

[0055]

[0056] Among them, λ V-i (k) is the voltage balance consistency factor of distributed generation i at step k, Q iref-T (k+1) is the voltage balance reactive power control signal of distributed generation i at step (k+1), Q i (k) is the actual reactive power output of distributed generation i at step k, is a positive real number, which is used to control the convergence speed of the voltage balancing algorithm;

[0057] In the process of voltage balancing control of distributed power sources and energy storage units, each participating distributed power source and energy storage unit transmits its own voltage balancing consistency factor to its own neighboring node through the communication network, and generates a voltage balancing reactive power control signal for its own converter control according to formula (15);

[0058] ④ Energy storage SOC recovery

[0059] The energy storage SOC recovery means that the energy storage unit participates in the control of active power injection at the PCC by charging and discharging; the active power control signal generated by formula (16) is used to perform energy storage SOC recovery control on the converter of each energy storage unit;

[0060]

[0061] Among them, P iref- is the control signal for the third-layer control of energy storage unit i to realize the control of active power injection at the common connection point PCC of the distribution network, K p is the proportional control parameter, K i is the integral control parameter, SoC i and are the actual value and reference value of the state of charge of energy storage unit i respectively.

[0062] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0063] (1) The present invention proposes a regional collaborative control strategy to achieve coordinated regulation of distributed power sources in different regions, thereby promoting the consumption of new energy and improving the economy and reliability of system operation.

[0064] (2) The present invention considers the multi-level hierarchical optimization of multiple distributed power sources at different time scales, and takes into account the impact of grid state perception, effectively improving the tolerance level of grid fluctuations.

[0065] (3) The present invention focuses on analyzing the control method of new energy, which can reduce the power planning margin and improve the load access level. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 It is a schematic diagram of the regional distributed power supply collaborative control system based on multi-level hierarchical optimization of the present invention.

[0067] Figure 2 This is the converter control structure diagram of the distributed power supply.

[0068] Figure 3 Schematic diagram of the SOC recovery control signal generation mechanism. DETAILED DESCRIPTION

[0069] The present invention will be further described below in conjunction with the accompanying drawings.

[0070] The present invention proposes a regional distributed power supply coordinated control system based on multi-level hierarchical optimization, such as Figure 1 As shown, it includes a distributed power management platform at the top layer, a regional collaborative control function module at the middle layer, and a local autonomous control function module at the bottom layer. Taking into account the complexity of the distributed power source itself, a hierarchical control structure is adopted to realize the information interaction between the distributed power management platform, the regional collaborative control function module, and the local autonomous control function module. One distributed power management platform corresponds to multiple regional collaborative control function modules, and one regional collaborative control function module corresponds to one local autonomous control function module. The distributed power management platform adopts a distributed energy management system, each of the regional collaborative control function modules adopts a distributed energy regional management and control device, and each of the local autonomous control function modules adopts an integrated grid-connected device.

[0071] 1. Distributed Energy Management System

[0072] The distributed energy management system is the core of the entire control system of the present invention. It independently exchanges information with multiple distributed energy regional control devices, receives information from each distributed energy regional control device, comprehensively monitors the status of each distributed power source, and controls the entire system by giving each distributed energy regional control device a reference value of the active power and reactive power injected by the main power grid into each distribution network at the common connection point PCC.

[0073] (II) Distributed energy regional control equipment

[0074] Each of the distributed energy regional control devices serves as the manager of the autonomous area and exchanges information with an integrated grid-connected device respectively. Each of the distributed energy regional control devices receives the distributed power grid connection point information, other flexible load information on the feeder and the power at the feeder outlet connected to the corresponding integrated grid-connected device in the region, and uploads it to the distributed energy management system. The power signals required for control (such as active power signals and reactive power signals, etc.) are screened and controlled through the corresponding integrated grid-connected device, and then the distributed power sources and flexible loads in the corresponding area are controlled through the regional collaborative control strategy.

[0075] The purpose of the regional collaborative control strategy is to achieve intensive integrated coordination of controllable distributed power sources inside and outside the region. This strategy enables the injected power of the distribution network at the common connection point to track the power reference value given by the main power grid through the collaborative control of each distributed power source in the distribution network. At this time, from the perspective of the entire power system, the distribution network (an integrated grid-connected and its connected distributed power sources and flexible loads together constitute a distribution network) can be equivalent to a controllable PQ load node, thereby reducing the uncertainty of the distribution network flow changes caused by the access of a large number of distributed power sources to the distribution network, and giving the distribution network a certain power scheduling capability. At the same time, this strategy can achieve the distribution of active power among the distributed power sources in the same region and the balance of voltage at the grid connection points of each distributed power source.

[0076] The regional collaborative control strategy adopts a distributed consensus algorithm that only relies on communication between neighboring nodes and does not require global information of the system. The regional collaborative control strategy will make the active and reactive power injected at the common connection point of the distribution network, the output of distributed power sources and energy storage meet the requirements of equations (1)-(5), mainly including the injection power control at the common connection point of the distribution network, the active power sharing of distributed power sources, the voltage balance at the grid connection point of distributed power sources, and the recovery of the energy storage nuclear power state;

[0077] ① Injection power control at the common connection point of the distribution network

[0078]

[0079]

[0080] Among them, P PCC and are the actual value and reference value of the active power injected by the main grid into the distribution network at the common connection point PCC; Q PCC and are respectively the actual value and reference value of the reactive power injected by the main grid into the distribution network at the common connection point PCC; and It is the result of the scheduling and planning of the distributed energy management system according to the actual situation; i and Q i ,i∈S L are the active and reactive power consumed by load node i, S L is a collection of load and energy storage nodes; P j and Q j ,j∈S E are the active and reactive power generated by distributed generation j or energy storage node j, S E It is a collection of distributed power sources and energy storage nodes; P loss and Q loss They are respectively the active and reactive power losses of the distribution network system. When planning and dispatching electricity, the distributed energy management system sends reference signals of active and reactive power to the distribution network and coordinates the distributed power sources in the distribution network to control the injected power at the PCC of the distribution network to meet the demand, thereby coordinating with the dispatching of the main grid.

[0081] ② Active power sharing of distributed power sources

[0082]

[0083] Among them, P i is the actual active output of distributed generation i, is the rated active output power of the converter of distributed generation i, S G Represents the set of distributed power sources excluding energy storage. It should be noted that energy storage units do not participate in the sharing of active power.

[0084] Within the allowed range of the converter capacity of the distributed power source, if equation (3) cannot be satisfied due to the power limit of the maximum power point of the distributed power source (that is, when the active control signal of the distributed power source participating in active power sharing is greater than the output power at its maximum power point), the distributed power source will exit active power sharing and operate at the maximum power point.

[0085] ③ Voltage balance at the distributed power grid connection point

[0086]

[0087] Among them, V i is the effective value of the voltage at the point where the distributed generation i is connected to the distribution network, They are the lower and upper limits of voltage fluctuations allowed by the distribution network for distributed generation i to access the distribution network. When the reactive power control signal exceeds the reactive capacity of the converter, the distributed generation will exit voltage balancing control.

[0088] ④ Energy storage nuclear power status recovery

[0089]

[0090] Among them, SoC i and are the actual value and reference value of the state of charge of energy storage i, S B Represents the set of energy storage nodes, S E =S B ∪S G , (Because the energy storage unit is different from distributed power sources such as photovoltaic and wind power, it can both emit power and absorb power, and whether it can work normally is related to its charge state. Therefore, energy storage is not included in the distributed power supply in the mathematical expression).

[0091] (III) Integrated grid-connected equipment

[0092] Each of the integrated grid-connected devices is connected to multiple distributed power sources and flexible loads. The distributed power sources include photovoltaic, wind power, and combined heat and power systems. The flexible loads include loads and energy storage units.

[0093] Each of the integrated grid-connected devices manages all controllable distributed power sources and flexible loads under the same integrated grid-connected device (such as distribution room / switch station / ring main unit, etc.). Each of the integrated grid-connected devices is used to receive the power target of its corresponding distributed energy area management and control device, and reasonably allocate power to each distributed power source and flexible load connected to it according to the local autonomous control strategy, collect and upload the distributed power grid connection point information connected to this area, other flexible load information on the feeder, and the power at the feeder outlet.

[0094] The local autonomous control strategy includes four types of control: distribution network port power control, active power sharing, voltage balancing control, and energy storage SOC recovery.

[0095] The local autonomous control strategy adopts a hierarchical collaborative control structure, which is different from the traditional hierarchical control structure in terms of hierarchical functions. The first layer of the hierarchical collaborative control structure of the local autonomous control strategy is the physical layer, which includes the hardware parts of the converters and other controllers of each distributed power source and energy storage unit. The converters all work in the PQ control mode, and the control signals are composed of the control signals generated by the second and third layers. The second layer is the PCC power control layer, which is responsible for controlling the injected power of the distribution network at the common connection point PCC so that it tracks the power reference value given by the distributed energy management system. The third layer is used to generate control signals for active power sharing, voltage balancing and energy storage SOC recovery among the distributed power sources.

[0096] ①Power control of distribution network ports

[0097] The converter structure of the distributed power source and energy storage unit is uniformly represented by a typical bidirectional AC / DC converter. Taking distributed power source i as an example, the control structure diagram of its converter after adding the control strategy is as follows: Figure 2 As shown, R a , L a , C a They are the resistance, inductance and capacitance of the filter. line and L line are line resistance and line inductance respectively, and the short line on the signal connection line represents the number of signal paths. The power reference value of the converter is composed of the power signals of the second layer and the third layer. In the entire collaborative control system, the control signals generated by the second layer and the third layer are transmitted to the first layer respectively, and then merged in the first layer to form the converter PQ control signal, that is,

[0098]

[0099]

[0100] in, is the active power reference value of distributed generation i, is the reactive power reference value of distributed generation i, P iref- and Q iref- are the control signals for the second-layer control of distributed generation i to realize the control of active power and reactive power injected into the distribution network at the common connection point PCC, P iref-T and Q iref- They are the control signals used in the third layer control of distributed power source i to realize the control of active power and reactive power injection at the common connection point PCC of the distribution network. When the power control of the distribution network port is performed, the control signal is only provided by the second layer control. At this time, P iref- and Q iref-T Both are 0.

[0101] Control signal P iref-S and Q iref-S It is the PCC power compensation signal, which is used to make the active and reactive power at the PCC track the reference value given by the main grid dispatching center. iref-S and Q iref-S The expression is as follows:

[0102]

[0103]

[0104] in, and are the proportional control parameters of active power and reactive power injected by distributed generation i at the common connection point PCC, μ P-i and μ Q-i are the compensation adjustment factors for the active power and reactive power injected into the distributed generation i at the common connection point PCC, which are defined as follows:

[0105]

[0106]

[0107] Among them, a i-PCC The value of depends on the communication method used by the power control at the second-layer distribution network PCC in the local autonomous control strategy; when point-to-point communication is used, if there is a communication connection between the distributed generation i and the PCC, then a i-PCC The value is 1, otherwise it is 0; when broadcast communication is used, the a of the distributed power source i participating in PCC power compensation i-PCC All are 1; is the reference value of the voltage at the point where distributed generation i is connected to the distribution network.

[0108] According to the above formulas (6) to (11), the active power reference value of distributed power source i is obtained: and reactive power reference Then and PI regulation is performed to obtain the PQ control signal of the converter of distributed power source i. Similarly, the PQ control signals of the converters of each distributed power source and energy storage unit are obtained in the same manner as distributed power source i.

[0109] ② Active power sharing

[0110] A distributed consistency algorithm is used to realize active power sharing of each distributed power source, so that the ratio of the active power emitted by all distributed power sources to the rated active output power of their respective converters is the same, that is, the active power is distributed proportionally.

[0111] Taking distributed power source i as an example, when designing a distributed consistency algorithm, we must first determine the consistency factor and define its active power sharing ratio as:

[0112]

[0113] This ratio is used as the consistency factor of the consistency algorithm. If the consistency factors of all distributed power sources tend to be consistent in steady state, the purpose of active power sharing is achieved. The distributed consistency algorithm is used to design its active power sharing ratio, that is, the active power sharing consistency factor:

[0114]

[0115]

[0116] Among them, k is the time step of algorithm iteration; P iref-T (k+1) is the active power sharing control signal of distributed generation i at step k+1; P i (k) is the actual active power output of distributed generation i at step k; ρ is a fixed positive real number, which is used to control the convergence speed of the algorithm; n is the set S E The number of elements in l i,j is the i-th row and j-th column element of the Laplace matrix of the distribution network communication topology graph; P-i (k) is the active power sharing consistency factor of distributed generation i at step k.

[0117] Algorithms (13)-(14) are driven by the deviation between the distributed consistency factors. In the iterative process of the algorithm, if the active power sharing consistency factor λ of distributed power source i P-i is less than the average value of the active power sharing consistency factor of its neighboring nodes, that is, the active power sharing ratio of distributed generation i is lower than that of its neighboring nodes, then the active power sharing control signal generated by formula (14) will increase, and then increase it, and vice versa.

[0118] In the process of active power sharing of distributed power sources, each participating distributed power source transmits its own active power sharing consistency factor to the neighboring node through the communication network, and substitutes the collected active power sharing consistency factor information of the neighboring nodes into equations (13) and (14) to generate active power sharing control signals for their respective converter control. It can be seen from equation (14) that when the active power sharing consistency factor of distributed power source i is greater than the average value of the neighboring nodes, it will become smaller, causing the active power sharing ratio of distributed power source i to decrease. Ultimately, the active power sharing consistency factor (i.e., active power sharing ratio) of all participating distributed power sources will tend to be consistent.

[0119] When the active power control signal of the distributed power source is greater than the output power at its maximum power point, the distributed power source will exit the active power sharing and output the power at the maximum output power point. At this time, the exiting node only receives but does not send the active power sharing consistency factor in the communication network until the active power sharing state can be carried out.

[0120] ③Voltage balance control

[0121] Voltage balancing control requires that the reactive power injected by the distribution network at the common connection point PCC tracks the reference value given by the distributed energy management system, and each distributed power source needs to bear reactive compensation.

[0122] In order to simultaneously achieve voltage balancing of distributed generation and compensation for PCC power deviation, this paper designs a voltage balancing algorithm based on reactive power control of distributed generation.

[0123] Taking distributed power source i as an example, similar to the design of distributed power source active power sharing algorithm, in order to achieve voltage balance, the normalized value of the effective value of the voltage at the point where the distributed power source is connected to the distribution network is taken as the consistency factor, that is,

[0124]

[0125] The voltage balancing consistency factor is designed using a distributed consistency algorithm:

[0126]

[0127]

[0128] Among them, λ V-i (k) is the voltage balance consistency factor of distributed generation i at step k, Q iref- (k+1) is the voltage balance reactive power control signal of distributed generation i at step (k+1), Q i (k) is the actual reactive power output of distributed generation i at step k, is a positive real number used to control the convergence speed of the voltage balancing algorithm.

[0129] In the process of voltage balancing control of distributed power sources and energy storage units, each participating distributed power source and energy storage unit transmits its own voltage balancing consistency factor to its own neighboring node through the communication network, and generates a voltage balancing reactive power control signal for its own converter control according to formula (17). When the reactive control signal of the distributed power source exceeds the reactive capacity limit, the distributed power source exits voltage balancing and uses the reactive capacity saturation value as the reactive control signal.

[0130] ④ Energy storage SOC recovery

[0131] The energy storage SOC recovery means that the energy storage unit participates in the control of active power injection at the PCC by charging and discharging. However, the energy storage unit cannot be continuously charged and discharged to obtain reliable and continuous power regulation capabilities. Therefore, in the third-level control, the energy storage participates in voltage balancing control but not in active power sharing. In order to make the energy storage work in an ideal state and prevent the energy storage SOC from exceeding the limit, it is necessary to introduce an energy storage SOC recovery mechanism in the third-level control. The energy storage SOC recovery can be implemented using a simple PI controller. The active power control signal of the third layer of energy storage is

[0132]

[0133] Among them, Piref-T is the control signal for the third-layer control of energy storage unit i to realize the control of active power injection at the common connection point PCC of the distribution network, K p is the proportional control parameter, K i is the integral control parameter, SoC i and are the actual value and reference value of the state of charge of energy storage unit i respectively. The generation mechanism of energy storage SOC recovery control signal is as follows: Figure 3 The active power control signal generated by formula (18) is used to perform energy storage SOC recovery control on the converter of each energy storage unit.

[0134] Based on the above system principle, the present invention also proposes a regional distributed power supply coordinated control method based on multi-level hierarchical optimization, which mainly includes the following aspects:

[0135] The distributed energy management system independently interacts with multiple distributed energy regional control devices, receives information from each distributed energy regional control device, comprehensively monitors the status of each distributed power source, and controls the entire system by giving each distributed energy regional control device a reference value of active power and reactive power injected by the main grid into each distribution network at the public connection point PCC;

[0136] Each of the distributed energy regional control devices receives the distributed power grid connection point information, other flexible load information on the feeder, and the power at the outlet of the feeder to which the integrated grid-connected device in the corresponding region is connected, and uploads it to the distributed energy management system, and screens the power signal required for control through the corresponding integrated grid-connected device, and then controls the distributed power in the corresponding area through the regional collaborative control strategy;

[0137] Each of the integrated grid-connected devices receives the power target of its corresponding distributed energy area management and control device, and reasonably allocates the power to each distributed power source and flexible load connected to it according to the local autonomous control strategy, and collects and uploads the distributed power grid connection point information connected to the area, other flexible load information on the feeder, and the power at the feeder outlet.

[0138] Although the functions and working processes of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned specific functions and working processes. The above-mentioned specific implementation methods are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, which are all within the protection of the present invention.

Claims

1. A regional distributed power supply coordinated control system based on multi-level hierarchical optimization, characterized in that: A hierarchical control structure is adopted, including a distributed power management platform at the top layer, a regional collaborative control function module at the middle layer, and a local autonomous control function module at the bottom layer. The distributed power management platform adopts a distributed energy management system, each of the regional collaborative control function modules adopts a distributed energy regional management and control device, and each of the local autonomous control function modules adopts an integrated grid-connected device; The distributed energy management system independently interacts with multiple distributed energy regional control devices, receives information from each distributed energy regional control device, comprehensively monitors the status of each distributed power source, and controls the entire system by giving each distributed energy regional control device a reference value of active power and reactive power injected by the main grid into each distribution network at the common connection point PCC; Each of the distributed energy regional control devices exchanges information with an integrated grid-connected device respectively. Each of the distributed energy regional control devices receives the distributed power grid-connected point information, other flexible load information on the feeder, and the power at the outlet of the feeder to which the integrated grid-connected device in the corresponding region is connected, and uploads it to the distributed energy management system. The power signal required for control is screened by the corresponding integrated grid-connected device, and then the distributed power source and flexible load in the corresponding region are controlled through the regional collaborative control strategy. Each of the integrated grid-connected devices is connected to a distributed power source and a flexible load. Each of the integrated grid-connected devices is used to receive the power target of the corresponding distributed energy area management and control device, and reasonably allocate power to each distributed power source and flexible load connected to it, and collect and upload the distributed power source grid connection point information connected to the area, other flexible load information on the feeder, and the power at the feeder outlet.

2. A regional distributed power supply coordinated control method based on a multi-level hierarchical optimization regional distributed power supply coordinated control system as described in claim 1, characterized in that: Includes the following: The distributed energy management system independently interacts with multiple distributed energy regional control devices, receives information from each distributed energy regional control device, comprehensively monitors the status of each distributed power source, and controls the entire system by giving each distributed energy regional control device a reference value of active power and reactive power injected by the main grid into each distribution network at the public connection point PCC; Each of the distributed energy regional control devices receives the distributed power grid connection point information, other flexible load information on the feeder, and the power at the outlet of the feeder to which the integrated grid-connected device in the corresponding region is connected, and uploads it to the distributed energy management system, and screens the power signal required for control through the corresponding integrated grid-connected device, and then controls the distributed power in the corresponding area through the regional collaborative control strategy; Each of the integrated grid-connected devices receives the power target of its corresponding distributed energy area control device, and reasonably allocates power to each distributed power source and flexible load connected to it, collects and uploads the distributed power source grid connection point information connected to the area, other flexible load information on the feeder, and the power at the feeder outlet.

3. The regional distributed power supply coordinated control system based on multi-level hierarchical optimization according to claim 1 or 2, characterized in that: The regional collaborative control strategy adopts a distributed consistency algorithm, and through the collaborative control of each distributed power source in the distribution network, the injected power of the distribution network at the common connection point can track the power reference value given by the main power grid, so as to realize the distribution of active power among the distributed power sources in the same region and the balance of voltage at the grid connection point of each distributed power source; the regional collaborative control strategy includes injection power control at the common connection point of the distribution network, active power sharing of distributed power sources, voltage balance at the grid connection point of distributed power sources, and energy storage nuclear power state recovery; ① Injection power control at the common connection point of the distribution network Among them, P PCC and are the actual value and reference value of the active power injected by the main grid into the distribution network at the common connection point PCC, Q PCC and are the actual value and reference value of reactive power injected by the main grid into the distribution network at the common connection point PCC; P i and Q i ,i∈S L are the active and reactive power consumed by load node i, S L is a collection of load and energy storage nodes; P j and Q j ,j∈S E are the active and reactive power generated by distributed generation j or energy storage node j, S E It is a collection of distributed power sources and energy storage nodes; P loss and Q loss They are the active and reactive power losses of the distribution network system respectively; ② Active power sharing of distributed power sources Among them, P i is the actual active output of distributed generation i, is the rated active output power of the converter of distributed generation i, S G Represents the set of distributed power sources excluding energy storage; ③ Voltage balance at the distributed power grid connection point Among them, V i is the effective value of the voltage at the point where the distributed generation i is connected to the distribution network, V i , are the lower limit and upper limit of the voltage fluctuation allowed by the distribution network at the point where the distributed generation i is connected to the distribution network; ④ Energy storage nuclear power status recovery Among them, SoC i and are the actual value and reference value of the state of charge of energy storage i, S B Represents the set of energy storage nodes, S E =S B ∪S G .

4. The regional distributed power supply coordinated control system based on multi-level hierarchical optimization according to claim 1 or 2, characterized in that: Each of the integrated grid-connected devices is used to receive the power target of the corresponding distributed energy regional control device, and reasonably allocate the power to each distributed power source and flexible load connected to it according to the local autonomous control strategy; the local autonomous control strategy includes distribution network port power control, active power sharing, voltage balancing control, and energy storage SOC recovery; The local autonomous control strategy adopts hierarchical collaborative control: the first layer is the physical layer, which includes the hardware parts of the converters and other controllers of each distributed power source and energy storage unit. The converters all work in the PQ control mode, and the control signals are composed of the control signals generated by the second and third layers; the second layer is the PCC power control layer, which is responsible for controlling the injected power of the distribution network at the common connection point PCC so that it tracks the power reference value given by the distributed energy management system; the third layer is used to generate control signals for active power sharing, voltage balancing and energy storage SOC recovery among each distributed power source; ① Power control of distribution network ports Taking distributed power source i as an example, the active power reference value of distributed power source i is obtained as follows: and reactive power reference Then and Perform PI adjustment to obtain the PQ control signal of the converter of distributed power source i; and so on, obtain the PQ control signal of the converter of each distributed power source and energy storage unit in the same way as distributed power source i; Among them, P iref-S and Q iref-S are the control signals for the second-layer control of distributed generation i to realize the control of active power and reactive power injected into the distribution network at the common connection point PCC, P iref and Q iref- They are the control signals used in the third layer control of distributed power source i to realize the control of active power and reactive power injection at the common connection point PCC of the distribution network. When the power control of the distribution network port is carried out, the control signal is only provided by the second layer control. At this time, P iref- and Q iref- All are 0; Among them, K p-Pi and K p-Qi are the proportional control parameters of active power and reactive power injected by distributed generation i at the common connection point PCC, μ P-i and μ Q-i are the compensation adjustment factors for the active power and reactive power injected into the distributed generation i at the common connection point PCC, which are defined as follows: Among them, a i-PCC The value of depends on the communication method used by the power control at the second-layer distribution network PCC in the local autonomous control strategy; when point-to-point communication is used, if there is a communication connection between the distributed generation i and the PCC, then a i-PCC The value is 1, otherwise it is 0; when broadcast communication is used, the a of the distributed power source i participating in PCC power compensation i-PCC All are 1; V i * is the reference value of the voltage at the point where the distributed generation i is connected to the distribution network; ② Active power sharing A distributed consensus algorithm is used to realize active power sharing of each distributed power source, so that the ratio of active power generated by all distributed power sources to the rated active output power of their respective converters is the same, that is, active power is distributed proportionally; Taking distributed power source i as an example, a distributed consistency algorithm is used to design its active power sharing ratio, that is, the active power sharing consistency factor: Among them, k is the time step of algorithm iteration, P iref- (k+1) is the active power sharing control signal of distributed generation i at step k+1, P i (k) is the actual active power output of distributed generation i at step k, ρ is a fixed positive real number used to control the convergence speed of the algorithm, and n is the set S E The number of elements in , l i,j is the i-th row and j-th column element of the Laplace matrix of the distribution network communication topology graph, λ P-i (K) is the active power sharing consistency factor of distributed generation i at step k; In the iterative process of the algorithm, if the active power sharing consistency factor of distributed generation i is λ P-i is less than the average value of the active power sharing consistency factor of its neighboring nodes, that is, the active power sharing ratio of distributed power source i is lower than that of its neighboring nodes, then the active power sharing control signal generated by formula (13) will increase, and then increase it, and vice versa; In the process of active power sharing of distributed power sources, each participating distributed power source transmits its own active power sharing consistency factor to the neighboring node through the communication network, and substitutes the collected active power sharing consistency factor information of the neighboring node into equations (12) and (13) to generate active power sharing control signals for respective converter control. Finally, the active power sharing consistency factors of all participating distributed power sources will tend to be consistent. ③Voltage balance control Voltage balancing control requires that the injected reactive power of the distribution network at the common connection point PCC tracks the reference value given by the distributed energy management system; Taking distributed power source i as an example, the distributed consistency algorithm is used to design its voltage balance consistency factor: Among them, λ V-i (k) is the voltage balance consistency factor of distributed generation i at step k, Q iref-T (k+1) is the voltage balance reactive power control signal of distributed generation i at step (k+1), Q i (k) is the actual reactive power output of distributed generation i at step k, is a positive real number, which is used to control the convergence speed of the voltage balancing algorithm; In the process of voltage balancing control of distributed power sources and energy storage units, each participating distributed power source and energy storage unit transmits its own voltage balancing consistency factor to its own neighboring node through the communication network, and generates a voltage balancing reactive power control signal for its own converter control according to formula (15); ④ Energy storage SOC recovery The energy storage SOC recovery means that the energy storage unit participates in the control of active power injection at the PCC by charging and discharging; the active power control signal generated by formula (16) is used to perform energy storage SOC recovery control on the converter of each energy storage unit; Among them, P iref- is the control signal for the third-layer control of energy storage unit i to realize the control of active power injection at the common connection point PCC of the distribution network, K p is the proportional control parameter, K i is the integral control parameter, SoC i and are the actual value and reference value of the state of charge of energy storage unit i respectively.

Images