Load distribution and bus voltage regulation method for photovoltaic power generation system based on hierarchical control

Abstract

The application relates to a layered control-based photovoltaic power generation system load distribution and bus voltage regulation method, which respectively comprises constructing a model for each distributed photovoltaic power generation unit in a photovoltaic power generation system, so as to realize primary droop control of the photovoltaic power generation system; and correcting bus voltage deviation based on output currents of adjacent photovoltaic power generation units. The application introduces distributed secondary control, effectively corrects load distribution errors existing in traditional droop control, effectively deals with voltage fluctuation in system operation, and thus ensures stable control of the bus voltage.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of load distribution and bus voltage stable operation in photovoltaic power generation system, and more particularly to a load distribution and bus voltage regulation method for photovoltaic power generation system based on hierarchical control. BACKGROUND

[0002] With the increasing popularity of distributed power generation, photovoltaic power generation has been proposed as an effective solution to regional power supply. Droop control is widely used to achieve current distribution between photovoltaic power generation units due to its simplicity and decentralization. However, the traditional droop control method cannot well coordinate current distribution and voltage regulation at the same time, and cannot achieve zero-error control.

[0003] For the control of load distribution and bus voltage of photovoltaic power generation system, centralized hierarchical control is mostly used, but centralized algorithm lacks flexibility and has large load distribution error; therefore, distributed algorithm based on communication network is gradually applied, but most of the distributed control algorithms of communication network require high bandwidth communication, which not only increases the burden of communication network, but also causes frequent data loss and communication delay, etc., affecting the overall stable operation of photovoltaic power generation system, and the uncertainty of these network systems will reduce the control performance, and even cause system failure. In addition, this method has not analyzed the closed-loop large signal stability of these distributed controllers, and cannot ensure that the two control targets can be achieved at the same time.

[0004] Therefore, how to solve the above problems and ensure the safe and stable operation of photovoltaic power generation system is a technical problem to be solved at present. SUMMARY

[0005] Therefore, in order to at least partially solve the above technical problems, the present application provides a load distribution and bus voltage regulation method for photovoltaic power generation system based on hierarchical control, mainly by introducing a distributed secondary event triggered controller to correct the load distribution and DC bus voltage deviation existing in droop control, so as to improve the current equalization distribution and bus voltage stable control.

[0006] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0007] A load distribution and bus voltage regulation method for photovoltaic power generation system based on hierarchical control, comprising:

[0008] A model is constructed for each distributed photovoltaic power generation unit in the photovoltaic power generation system, which is used to realize the primary droop control of the photovoltaic power generation system;

[0009] The output current of the adjacent photovoltaic power generation unit is used to correct the bus voltage deviation; the step comprises:

[0010] determining a current distribution error according to output currents of adjacent photovoltaic power generation units;

[0011] obtaining average output voltages of the distributed photovoltaic power generation units according to the current distribution error, and determining a voltage control error in combination with a current bus reference voltage;

[0012] updating the bus reference voltage of the photovoltaic power generation system at a stable time based on the current distribution error and the voltage control error.

[0013] Preferably, the model of the distributed photovoltaic power generation unit is:

[0014]

[0015] wherein, I DPPGi represents an output current of the i-th photovoltaic power generation unit, I Loadi represents a load current of the i-th photovoltaic power generation unit, G ij represents a tie-line conductance between the bus of the i-th photovoltaic power generation unit and the bus of the j-th photovoltaic power generation unit, U DPPGi represents a bus voltage of the i-th photovoltaic power generation unit, U DPPGj represents a bus voltage of the j-th photovoltaic power generation unit, represents a set of other distributed photovoltaic power generation units connected to the i-th photovoltaic power generation unit.

[0016] Preferably, when the model is used for once droop control, the load balancing distribution control target is:

[0017]

[0018] wherein, I DPPGi_max represents a maximum current capacity of the i-th photovoltaic power generation unit, I DPPGj_max represents a maximum current capacity of the j-th photovoltaic power generation unit, and Ne represents a number of nodes in the photovoltaic power generation system network.

[0019] Preferably, when the model is used for once droop control, the bus voltage control target is:

[0020]

[0021] wherein, is an average output voltage of each distributed photovoltaic power generation unit, U n is a nominal voltage of the photovoltaic power generation unit, n is a number of photovoltaic power generation units, and U i is an output voltage of the i-th photovoltaic power generation unit.

[0022] Preferably, the current distribution error is defined as:

[0023]

[0024] where e DPPGIi (t) represents the current distribution error at time t, h ij represents the communication relationship between the ith photovoltaic power generation unit and the jth photovoltaic power generation unit, I DPPGi (t) is the output current of the ith photovoltaic power generation unit at time t, I DPPGj (t) is the output current of the jth photovoltaic power generation unit at time t, I DPPGi_max represents the maximum current capacity of the ith photovoltaic power generation unit, I DPPGj_max represents the maximum current capacity of the jth photovoltaic power generation unit.

[0025] Preferably, the average output voltage of the distributed photovoltaic power generation unit is collected according to the following formula:

[0026]

[0027] where U is the average output voltage of each distributed photovoltaic power generation unit at time t, U i (t) represents the output voltage of the ith photovoltaic power generation unit at time t; K I > 0 and K U > 0 is a control gain coefficient, e DPPGIi represents the current distribution error; e DPPGIi represents the current distribution error.

[0028] The voltage control error expression is:

[0029]

[0030] where U n is the nominal voltage of the photovoltaic power generation unit.

[0031] Preferably, the bus reference voltage of the photovoltaic power generation system is updated based on the current distribution error and the voltage control error according to the following formula:

[0032]

[0033] where U n (t) represents the updated nominal voltage of the photovoltaic power generation unit at time t, K r represents the droop coefficient of the voltage, L δDPPGi represents the current deviation, K I > 0 and K U > 0 is a control gain coefficient, e DPPGIi represents the current distribution error, e DPPGUi represents the voltage control error.

[0034] Preferably, an event triggering condition is introduced, when the condition is triggered, the connected photovoltaic power generation units exchange current distribution information to improve the communication bandwidth;

[0035] Preferably, when the event triggering condition is:

[0036]

[0037] In the formula, U represents a direct current bus voltage reference value, U i is the output voltage of the i th photovoltaic power generation unit, e tr represents an event triggering condition, K I > 0 and K U > 0 is a control gain coefficient, λ B_min is the minimum eigenvalue of the matrix B, B is a Laplace matrix L Ne and L Nc is the associated matrix of L Ne , L Nc is the node admittance matrix in the network theory of the photovoltaic power generation system, L and 0 < δ < 1 is a constant set, is the observed current distribution error between DPPG i and DPPG j . is the observed voltage distribution error between DPPG i and DPPG j .

[0038] The photovoltaic power generation system load distribution and bus voltage regulation method based on hierarchical control disclosed in the application has the following advantages:

[0039] 1. By introducing distributed secondary control, the load distribution error existing in the traditional droop control is effectively corrected, and more accurate current equalization distribution is realized;

[0040] 2. The bus reference voltage is updated in combination with the current distribution error and the voltage control error, so as to ensure the stable control of the bus voltage; by adjusting the bus reference voltage in real time, the voltage fluctuation in the system operation is effectively coped with, and the robustness of the voltage control is improved;

[0041] 3. The event triggering condition is used for information exchange, the unnecessary communication times are reduced, the burden of the communication network is reduced, and the communication bandwidth is improved.

[0042] Compared with the prior art,

[0043] Compared with the centralized algorithm, the distributed control algorithm is more flexible, can better adapt to system changes and uncertainties. At the same time, through the closed-loop large signal stability analysis of the distributed controller, the control target is ensured at the same time, and the reliability of the system is improved. At the same time, the high-bandwidth communication demand is avoided, and the problems such as data loss and communication delay are reduced, which provides a strong guarantee for the safe and stable operation of the photovoltaic power generation system. BRIEF DESCRIPTION OF DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the provided drawings.

[0045] Figure 1 The flow chart of the load distribution and bus voltage regulation method of the photovoltaic power generation system based on hierarchical control of the present application;

[0046] Figure 2 The hierarchical control diagram of the photovoltaic power generation system of the present application;

[0047] Figure 3 The event-triggered controller of the photovoltaic power generation system of the present application;

[0048] Figure 4 The principle diagram of the event-triggered time of the present application;

[0049] Figure 5 The output power transformation curve diagram of the four distributed power sources of the present application;

[0050] Figure 6 The distributed power source DC bus voltage distributed power source output power curve diagram of the present application;

[0051] Figure 7 The droop coefficient change curve diagram of the distributed power source of the present application;

[0052] Figure 8 The output power change curve diagram of the distributed power source when the load suddenly drops of the present application;

[0053] Figure 9 The output voltage change curve diagram of the distributed power source when the load suddenly drops of the present application;

[0054] Figure 10 The droop coefficient change curve diagram when the load suddenly drops of the present application;

[0055] Figure 11 The voltage control distributed event-triggered time diagram of the present application;

[0056] Figure 12 The power control distributed event-triggered time diagram. DETAILED DESCRIPTION

[0057] The technical solutions in the embodiments of the present application will be clearly and completely described with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the protection scope of the present application.

[0058] The present application is directed to the load distribution and bus voltage stable operation in the photovoltaic power generation system, and the communication burden problem between the various unit controllers. First, a hierarchical control structure photovoltaic power generation system is designed, considering different line impedance, a network model composed of distributed photovoltaic power generation units is established; secondly, according to the operation characteristics of the photovoltaic power generation system, the control target of the load distribution and bus voltage is determined; thirdly, a secondary distributed voltage controller is designed on the basis of the primary droop control in the photovoltaic power generation system, and the direct current bus voltage deviation existing in the droop control is corrected by the introduced controller.

[0059] In order to further reduce the communication demand, the event-triggered condition is introduced, each local controller only exchanges the current distribution information with the adjacent controller connected thereto when the triggering condition is met, thereby improving the communication bandwidth problem. The present application provides a certain research value for the stable operation of the photovoltaic power generation system.

[0060] In an embodiment, the photovoltaic power generation system load distribution and bus voltage regulation method based on hierarchical control disclosed by the present application comprises the steps of Figure 1 , including:

[0061] The model is constructed for each distributed photovoltaic power generation unit in the photovoltaic power generation system, for realizing the primary droop control of the photovoltaic power generation system;

[0062] The bus voltage deviation is corrected based on the output current of the adjacent photovoltaic power generation unit; the steps include:

[0063] The current distribution error is determined according to the output current of the adjacent photovoltaic power generation unit;

[0064] The average output voltage of the distributed photovoltaic power generation unit is obtained according to the current distribution error, and the voltage control error is determined in combination with the current bus reference voltage;

[0065] The bus reference voltage of the photovoltaic power generation system is updated based on the current distribution error and the voltage control error.

[0066] According to the structure characteristics and control principle of the photovoltaic power generation system, the photovoltaic power generation system is divided into one-layer control and two-layer control by using the distributed hierarchical control structure, as shown in the figure. Figure 2 Each layer of control has its own implementation function, and the distributed hierarchical control can eliminate the deviation of system parameters and the load and communication distribution problems between nodes. The embodiment mainly includes the following two parts:

[0067] I. According to the structure of the distributed photovoltaic power generation system, a model of each distributed photovoltaic power generation unit is established, and then according to the operation characteristics of the photovoltaic power generation system, the control target of load distribution and bus voltage is determined, and then the primary droop control of the photovoltaic power generation system is realized;

[0068] In this embodiment, the model of the distributed photovoltaic power generation unit is:

[0069]

[0070] In the formula, I DPPGi represents the output current of the i-th photovoltaic power generation unit, I Loadi represents the load current of the i-th photovoltaic power generation unit, G ij represents the tie line conductance between the bus of the i-th photovoltaic power generation unit and the bus of the j-th photovoltaic power generation unit, U DPPGi represents the bus voltage of the i-th photovoltaic power generation unit, U DPPGj represents the bus voltage of the j-th photovoltaic power generation unit, represents the set of other distributed photovoltaic power generation units connected to the i-th photovoltaic power generation unit.

[0071] Further, according to the operation characteristics of the photovoltaic power generation system, the control target of load distribution and bus voltage is determined, which specifically includes:

[0072] The control target of load balanced distribution is set as:

[0073]

[0074] In the formula, I DPPGi_max represents the maximum current capacity of the i-th photovoltaic power generation unit, I DPPGj_max represents the maximum current capacity of the j-th photovoltaic power generation unit, and Ne is the number of nodes in the photovoltaic power generation system network.

[0075] The randomness of the load will cause the bus voltage to fluctuate constantly, in order to ensure the stability of the bus voltage, the control target of the bus voltage is set as:

[0076]

[0077] In the formula, U represents the average output voltage of each distributed photovoltaic power generation unit. n U is the nominal voltage of the photovoltaic power generation unit, which is usually taken as a specific value, where n is the number of photovoltaic power generation units. i Let be the output voltage of the i-th photovoltaic power generation unit.

[0078] II. In one embodiment, a secondary distributed voltage controller is designed based on the primary droop control in a photovoltaic power generation system. The introduced controller corrects the DC bus voltage deviation that exists in the droop control.

[0079] First, during droop control, the photovoltaic (PV) power generation unit transmits its respective load current ratio to its neighboring units. Therefore, the current distribution error between the various PV power generation units can be defined as:

[0080]

[0081] In the formula, h ij This represents the communication relationship between the i-th photovoltaic power generation unit and the j-th photovoltaic power generation unit. In this embodiment, the vertex of the communication network is the controller of the local distributed photovoltaic power generation unit, and the connecting edge of the communication network is the communication line. If there is a connection, h > 0, which is a user-defined communication weight; otherwise, h = 0. DPPGi Let I be the output current of the i-th photovoltaic power generation unit. DPPGi_max I represents the maximum current capacity of the i-th photovoltaic power generation unit. DPPGj_max Let represent the maximum current capacity of the j-th photovoltaic power generation unit, and t represent the time corresponding to the current distribution error.

[0082] Secondly, the system's voltage controller controls its voltage to the set bus reference voltage, therefore the voltage control error is:

[0083]

[0084] In the formula, Let U be the average output voltage of each distributed photovoltaic power generation unit at time t. n This is the nominal voltage of the photovoltaic power generation unit.

[0085] In this embodiment, the voltage of each photovoltaic power generation unit needs to be collected when calculating the voltage control error, and then... The value is calculated. The data collection and calculation can be performed using the following formula:

[0086]

[0087] In the formula, U i (t) represents the output voltage of the i-th photovoltaic power generation unit at time t; K I> 0 and K U > 0 is the control gain coefficient, e DPPGIi represents the current distribution error. The average voltage calculation only uses the DPPG i current voltage and its connected controller's load current distribution error information.

[0088] Here the integral is called convolution integral, the result of which is a function of t, where τ is a dummy variable used in the integral calculation. Convolution operation satisfies the commutative law, associative law and distribution law, which can be flexibly applied when dealing with complex signals.

[0089] Further, in combination with the voltage and current droop control, the bus reference voltage of the photovoltaic power generation system is updated.

[0090] Regarding the voltage and current droop control, in the photovoltaic power generation system DPPG i , the power and voltage and current satisfy the following relationship:

[0091]

[0092] In the formula, I δDPPGi is the current deviation, P δDPPGi is the power deviation, U DPPGi is the bus voltage of the i-th photovoltaic power generation unit.

[0093] In order to make the power in each DPPG system reach balance, when the power provided by the distributed power supply and the load power produce a difference, the bus voltage will fluctuate. Therefore, the bus voltage and the power difference P δDPPGi satisfy the following formula of the droop relationship:

[0094] U DPPGi = U n -D r (P Loadi -P DPPGi )

[0095] In the formula, D r is the droop coefficient of power, U n is the nominal voltage of the photovoltaic power generation unit.

[0096] The droop relationship of voltage and current is obtained in combination with the above formula:

[0097] U DPPGi = U n -K r I δDPPGi

[0098] In the formula, K r represents the droop coefficient of voltage, I δDPPGi is the current deviation.

[0099] To achieve the control target of voltage and load distribution, the control error of voltage and current must be equal to zero in steady state operation. Therefore, the derivative of the DC bus voltage reference value can be designed by the current and voltage error as follows:

[0100]

[0101] Integrating the above equation, we get:

[0102]

[0103] Therefore, in this embodiment, the updated system stable bus reference voltage can be expressed as:

[0104]

[0105] In the formula, U n (t) represents the updated nominal voltage of the photovoltaic power generation unit at time t, K r represents the droop coefficient of voltage, I δDPPGi represents the current deviation, K I > 0 and K U > 0 are control gain coefficients, e DPPGIi represents the current distribution error, e DPPGUi represents the voltage control error.

[0106] To further optimize the above technical solution, in an embodiment, an event-triggered control technology is used, that is, only when the preset condition is reached, the adjacent controller connected thereto exchanges current distribution information, thereby significantly reducing the burden of the communication network, reducing the communication demand, and improving the communication bandwidth.

[0107] In this embodiment, according to the system load change condition, an event-triggered controller is used to realize current equalization distribution and bus voltage stability control, and the control process refers to Figure 3 The trigger condition of this algorithm can be evaluated based on the information of the local and adjacent subsystems.

[0108] Specifically, at the time t k corresponding to the set trigger condition, the controller updates the local load current distribution information and then transmits it to the connected controller. Before the next trigger time arrives, this information is in a holding state, and at the time t k+1 corresponding to the next trigger condition, the above process is repeated.

[0109] In an embodiment, according to the above process, the current distribution error between DPPG i and DPPG j is:

[0110]

[0111] In the formula, Indicates at t k DPPG i Updated current observations. Indicates at t k DPPG j Updated current observations.

[0112] Similarly, the average voltage is:

[0113]

[0114] In the formula, Indicates at t k DPPG i Updated global average voltage observations.

[0115] The observed voltage error is:

[0116]

[0117] Based on the above formula, the distributed event triggering controller is:

[0118]

[0119] Integrating, we get:

[0120]

[0121] in, For DPPG i and DPPG j The observed current distribution error between them For the observed voltage error, This is the reference value for the DC bus voltage.

[0122] when hour, U represents the reference value of the DC bus voltage. i Let e ​​be the output voltage of the i-th photovoltaic power generation unit. tr This indicates the event triggering condition, which is:

[0123]

[0124] In the formula, e tr Indicates the event triggering condition, K I >0 and K U >0 represents the control gain coefficient, λ B_min Let L be the smallest eigenvalue of matrix B, where B is a Laplace matrix. Ne and L NcThe correlation matrix, L Ne L is the node admittance matrix in photovoltaic power generation system network theory. Nc For the Laplace matrix of the communication network, in this embodiment, L Ne =L Nc , λ B_min =1,ζ l >0、 And 0 < δ < 1 are set constants. Photovoltaic power generation network L Ne and its communication network L Nc Certain conditions must be met to achieve the control objective.

[0125] e tr Ultimately, it becomes a curve, such as Figure 4 As shown, the event-triggered controller designed in this invention also exhibits excellent control performance when the load changes.

[0126] To further verify the effectiveness of this application, the following simulation analysis was conducted on droop control and event-triggered control:

[0127] Objects: Four distributed photovoltaic power generation units, of which DPPG1 and DPPG2 have the same load, and DPPG3 and DPPG4 have the same load.

[0128] At the initial moment of the simulation, under the droop control mode, the power output quickly reaches a stable state, such as... Figure 5 As shown, P1, P2, P3, and P4 represent the power curves of four distributed photovoltaic power generation units. When t = 1s, the event-triggered controller starts working, and the output power recovers to a stable output after a short period of fluctuation.

[0129] When only one layer of droop control is used at the initial moment of the simulation, such as Figure 6 U1, U2, U3, and U4 represent the voltage variation curves of four distributed photovoltaic power generation units, respectively. Figure 6 It is known that after each distributed power source is connected to its corresponding load, the bus voltage will deviate significantly from the rated value, which is detrimental to the stable control of the bus voltage. By introducing a two-layer distributed event-triggered control method at t=1s, the output voltage of the four distributed power sources begins to rise under the action of the distributed event-triggered controller, ultimately achieving zero-deviation voltage control and overcoming the voltage deviation defect of droop control.

[0130] further, Figure 7For droop coefficient change curve, KP1, KP2, KP3, KP4 represent the droop control change curve of four distributed photovoltaic power generation units respectively, at the initial time of simulation, the droop controller starts to work, the droop output value of voltage power difference gradually rises to 0.375 and remains stable, at t=1s, the distributed event triggered controller starts to work to change the droop coefficient, under the action of two-layer controller, the voltage deviation is corrected, and finally when the bus voltage restores to the rated voltage, the droop coefficient remains unchanged.

[0131] The volatility of load is the main reason for the fluctuation of DC microgrid bus voltage, the control performance of event triggered controller when the load changes is analyzed as follows. Figures 8-10 is the change of distributed power output power P, bus voltage U and droop coefficient KP when the load of distributed photovoltaic power generation system suddenly decreases. When t=3s, the load of distributed power supply suddenly decreases, the output of each distributed power supply changes under the joint action of one-layer droop control and two-layer event triggered controller, and after a short time, the output power reaches stability. The bus voltage also stabilizes around the rated voltage after a small fluctuation, which also well explains that the distributed event triggered controller can maintain power balance and bus voltage stability when the load changes.

[0132] Figures 11-12 , is the distributed event triggered time diagram of voltage and power control of four distributed power supplies, DPPG1 is black curve, DPPG2 is red curve, DPPG3 is blue curve, and DPPG4 is green curve; in order to maintain the voltage at the set value, the controller triggers the comparison evenly. In order to maintain the stability of output power, the trigger control is intensive at the initial time of event triggered controller (t=1s) and the initial time of power change (t=3s), and gradually flat with the change of power, and the number of event triggering is gradually reduced. This shows that the event triggered controller designed in this paper only transmits voltage and load ratio information between the connected distributed power supply controllers when the event triggering condition is met, which greatly reduces the burden of communication system while achieving the control target of DC microgrid, which is conducive to the stable operation of microgrid.

[0133] The distributed event triggered controller in this application can realize the balanced distribution of load among different power sources, well correct the bus voltage deviation in traditional droop control, and also has good control performance when the load changes.

[0134] At the same time, the event triggered controller of the application only transmits information between distributed power supplies when the triggering condition is met, greatly reduces the communication burden between distributed power supply controllers under the premise of ensuring load distribution and bus voltage stability.

[0135] The various embodiments described in this specification are implemented in a progressive manner, each embodiment focusing on the differences from other embodiments, and the same or similar parts between embodiments can be mutually referred to. For the apparatus disclosed by the embodiments, since it corresponds to the method disclosed by the embodiments, the description is relatively simple, and the relevant parts can be referred to the description of the method part.

[0136] The above description of disclosed embodiments enables one of ordinary skill in the art to make or use the application. Various modifications to these embodiments will be readily apparent to those of ordinary skill in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Therefore, the application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A hierarchical control based load distribution and bus voltage regulation method for a photovoltaic power generation system, characterized by, Comprise: A model is constructed for each distributed photovoltaic power generation unit in the photovoltaic power generation system, which is used to realize the primary droop control of the photovoltaic power generation system; The output current of the adjacent photovoltaic power generation unit is used to correct the bus voltage deviation; the steps comprise: According to the output current of the adjacent photovoltaic power generation unit, the current distribution error is determined; According to the current distribution error, the average output voltage of the distributed photovoltaic power generation unit is obtained, and the voltage control error is determined in combination with the current bus reference voltage; Based on the current distribution error and the voltage control error, the bus reference voltage of the photovoltaic power generation system at the stable time is updated; An event trigger condition is introduced, when the condition is triggered, the adjacent photovoltaic power generation units exchange current distribution information to improve the communication bandwidth; When the event trigger condition is: In the formula, U is the reference value for the DC bus voltage. i Let e ​​be the output voltage of the i-th photovoltaic power generation unit. tr K is the event triggering condition. I >0 and K U >0 represents the control gain coefficient, λ B_min Let L be the smallest eigenvalue of matrix B, where B is a Laplace matrix. Ne and L Nc The correlation matrix, L Ne L is the node admittance matrix in photovoltaic power generation system network theory. Ne (i, i) represents the self-admittance of node i, L Nc Let ζ1 be the Laplace matrix of the communication network, where ζ1 > 0. And 0 < δ < 1 is a set constant. For DPPG i and DPPG j The observed current distribution error between them For DPPG i and DPPG j The observed voltage distribution error between them.

2. The method of claim 1, wherein, The model of the distributed photovoltaic power generation unit is: In the formula, I DPPGi represents the output current of the i-th photovoltaic power generation unit, I Loadi represents the load current of the i-th photovoltaic power generation unit, G ij represents the tie line conductance between the bus of the i-th photovoltaic power generation unit and the bus of the j-th photovoltaic power generation unit, U DPPGi represents the bus voltage of the i-th photovoltaic power generation unit, U DPPGj represents the bus voltage of the j-th photovoltaic power generation unit, represents the set of other distributed photovoltaic power generation units connected to the i-th photovoltaic power generation unit.

3. The method of claim 2, wherein, When the model is used for primary droop control, the load balancing distribution control target is: In the formula, I DPPGi_max represents the maximum current capacity of the i-th photovoltaic power generation unit, I DPPGj_max represents the maximum current capacity of the j-th photovoltaic power generation unit, and Ne is the number of nodes in the photovoltaic power generation system network.

4. The method of claim 2, wherein, When the model is used for primary droop control, the bus voltage control target is: wherein is the average output voltage of the individual distributed PV power generation units, U n is the nominal voltage of the PV power generation unit, n is the number of PV power generation units, U i is the output voltage of the i-th PV power generation unit.

5. The method of claim 1, wherein, The current distribution error is defined as: wherein e DPPGIi (t) represents the current distribution error at time t, h ij represents the communication relationship between the i-th photovoltaic power generation unit and the j-th photovoltaic power generation unit, I DPPGi (t) is the output current of the i-th photovoltaic power generation unit at time t, I DPPGj (t) is the output current of the j-th photovoltaic power generation unit at time t, I DPPGi_max represents the maximum current capacity of the i-th photovoltaic power generation unit, I DPPGj_max represents the maximum current capacity of the j-th photovoltaic power generation unit.

6. The method of claim 1, wherein, The average output voltage of the distributed photovoltaic power generation unit is collected according to the following formula: wherein, U (t) is the average output voltage of each distributed photovoltaic power generation unit at time t i (t) represents the output voltage of the i-th photovoltaic power generation unit at time t; K I > 0 and K U > 0 is a control gain coefficient, e DPPGIi represents the current distribution error; The voltage control error expression is: In the formula, U n is the nominal voltage of the photovoltaic power generation unit.

7. The method of claim 1, wherein, Based on the current distribution error and the voltage control error, the bus reference voltage of the photovoltaic power generation system at the stable time is updated according to the following formula: wherein U n (t) denotes the updated t-moment photovoltaic power generation unit nominal voltage, K r denotes the droop coefficient of the voltage, I δDPPGi denotes the current deviation, K I > 0 and K U > 0 is the control gain coefficient, e DPPGIi denotes the current distribution error, e DPPGUi denotes the voltage control error.

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