A hierarchical control method for distributed energy resources

Abstract

The application relates to a hierarchical control method of a distributed energy source, which comprises bottom control logic, secondary control logic and top control logic; the bottom control logic uses a droop control method to adjust the output of active power by changing the frequency and to adjust the output of reactive power by changing the voltage amplitude, and the output power satisfies the P-f and Q-U decoupling required by the droop control; the secondary control logic compensates for the voltage and frequency deviation generated by the bottom control; the top control logic performs power flow control on the micro-grid in a grid-connected mode; when the distributed energy source operates in an island mode, the reference frequency f* and the reference voltage U* input by the secondary control are the frequency and the PCC voltage of the distributed energy source; when the distributed energy source is converted into a grid-connected mode, the top control adjusts the output frequency and voltage of the distributed energy source through a PI control process, so that the output frequency and voltage of the distributed energy source are equal to the PCC frequency and voltage.

Description

Technical Field

[0001] This application belongs to the field of new energy technology for power grids, and in particular relates to a hierarchical control method for distributed energy. Background Technology

[0002] Low-voltage distribution networks typically exhibit a radial topology, with power flow pointing from the power supply side to the power consumption side. With the integration of numerous distributed wind power plants and end-load nodes into the distribution network, power flow exhibits a bidirectional and even more complex trend. The intermittent nature of wind energy makes wind power generation highly sensitive to changes in environmental conditions. As wind inverters operate in different modes, voltage instability and voltage exceeding limits at wind power grid connection points, caused by the convergence of various factors, increasingly become major risks restricting the stability of low-voltage distribution network power supply. Distributed wind power will gradually be deployed on a large scale at the end-user side and integrated into the distribution network. The distributed nature and sheer scale of this technology lead to a continuous generation of massive electrical data sources. Traditional inverter control architectures or platforms cannot meet the demands of accessing and using such vast amounts of electrical data. This means that the traditional master-slave coordinated control mode cannot meet the actual needs of distributed wind power voltage control. From the perspectives of voltage and frequency regulation, power flow control, and cost control, wind inverters require hierarchical control methods to achieve safe grid connection operation.

[0003] Chinese patent publication CN 114696364 A discloses a distributed microgrid control strategy considering disturbance effects. It designs a network layer and physical layer control structure; designs a sliding mode consensus controller with a virtual leader node based on sliding mode control-discrete consensus theory; constructs a physical layer to complete primary control of the voltage and frequency of each distributed power source in the microgrid, and completes droop control through local information to maintain the stability of system voltage and frequency and output corresponding power according to instructions; constructs a network layer to complete distributed secondary control, treating each distributed power source as a multi-agent node, communicating only with adjacent nodes to form a sparse communication matrix with a spanning tree, and setting a virtual leader node to obtain global reference information; treats the droop control output voltage and frequency of each distributed power source as state variables, and designs secondary control to achieve voltage and frequency convergence to a given reference value. This reduces communication requirements and eliminates frequency and voltage deviations, while considering system disturbances and improving system robustness.

[0004] The above patented solutions have the following problems: the interfaces between levels are not clearly defined, making it impossible to modularize and standardize the inverter control algorithm; the control process cannot be flexibly accessed / detached, and it cannot meet the needs of distributed control. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a hierarchical control method for distributed energy resources in order to overcome the above-mentioned shortcomings of the existing distributed microgrid control strategies.

[0006] The technical solution adopted by this invention to solve its technical problem is:

[0007] A hierarchical control method for distributed energy, comprising bottom-level control logic, secondary control logic, and top-level control logic;

[0008] The underlying control logic uses a droop control method to adjust the output of active power by changing the frequency and the output of reactive power by changing the voltage amplitude. The output power meets the P-f and Q-U decoupling requirements of droop control. P and Q are the actual output active power and reactive power of the inverter; f is the actual output frequency of the converter, and U is the actual output voltage of the converter.

[0009] Secondary control logic: The secondary control compensates for the voltage and frequency deviations generated by the lower-level control. The lower-level control acquires and calculates active and reactive power at the PCC position, and then transmits voltage control signals to the current-voltage dual closed-loop control loop after calculating the droop curve. The connection between the secondary control and the lower-level control is established by using the reference frequency f in the droop curve. ref and reference voltage U ref The method of establishing the PI control process using signals;

[0010] Top-level control logic: The top-level control performs power flow control on the microgrid in grid-connected mode. The connection between the secondary control and the top-level control is established by collecting and calculating the active and reactive power flow at the connection point between the microgrid and the external power grid, and adjusting the reference frequency in the secondary PI control. and reference voltage The method of establishing the PI control process using signals;

[0011] When the distributed energy source is operating in islanded mode, the reference frequency f* and reference voltage U* of the secondary control input are the frequency of the distributed energy source and the voltage of the PCC. When the distributed energy source switches to grid-connected operation, the top-level control adjusts the output frequency and voltage of the distributed energy source through the PI control process to make the output frequency and voltage of the distributed energy source equal to the frequency and voltage of the PCC.

[0012] Preferably, in the hierarchical control method for distributed energy of the present invention, the bottom-level control logic, the secondary control logic, and the top-level control logic are compiled into a control program by MATLAB Simulink m files or C / C++ language, and the data communication function is implemented by the S-function module compiled by the ZeroMQ network library.

[0013] Preferably, in the hierarchical control method for distributed energy of the present invention, when the distributed energy is operating in islanded mode, the grid-side converter adopts a droop control strategy, and the inverter output power is jointly determined by the droop coefficient and the load power, thereby adjusting the inverter output frequency reference value f. * Voltage amplitude reference value U * .

[0014] Preferably, in the hierarchical control method of distributed energy of the present invention, the energy storage device connected to the DC bus compensates for the power difference on both sides, and a compensation item is set in the voltage reference value of the droop control module according to the line impedance and the power flowing through the line.

[0015] Preferably, in the hierarchical control method for distributed energy of the present invention, the calculation formula for the compensation term is:

[0016] U cmp = U*=U0+U cmp -k(Q-Q0);

[0017] In the formula: U cmp For line voltage drop compensation; R and X are the line resistance and reactance, respectively; P and Q are the measured active and reactive power outputs of the inverter; U is the line terminal voltage; U0 is the rated voltage; Q0 is the rated reactive power of the inverter; k is the reactive power droop factor.

[0018] Preferably, in the hierarchical control method for distributed energy of the present invention, the drooping control equation in the bottom-level control logic is as follows:

[0019] f * =f0-k p (P-P0); U * =U0-k Q (Q-Q0);

[0020] In the formula, f * U * Reference values ​​for controlling the inverter output frequency and voltage; f0 and U0 are the grid rated frequency and no-load operating voltage, respectively; k p k Q These are the droop coefficients for active power and reactive power, respectively; P and Q are the actual active and reactive power outputs of the inverter; P0 and Q0 are the rated active and reactive power of the inverter.

[0021] Preferably, in the hierarchical control method for distributed energy of the present invention, when the distributed energy is switched to grid-connected operation, the generator-side converter adopts a dual closed-loop control structure; the outer loop adopts MPPT control and stator voltage control, the inner loop is implemented by a PI controller through a current control loop, and the grid-side converter adopts the droop control method.

[0022] Preferably, the hierarchical control method for distributed energy in this invention has the following droop control equation during grid-connected operation:

[0023] f*=f0+(k p1 + )(P m -P)-( kp3 + (U) ref- U dc )

[0024] U*=U0-( k p2 + )Q;

[0025] In the formula k pi k li P represents the proportional-integral coefficients of the proportional-integral converter, i = 1, 2, 3; m U represents the maximum active power output of the wind turbine when it is in maximum wind energy capture mode. ref This is the reference value for the DC bus voltage; U dc This is the actual value of the DC bus voltage.

[0026] Preferably, in the hierarchical control method for distributed energy of the present invention, the connection between secondary control and lower-level control is established through the following relationship:

[0027] ;

[0028] In the formula: and These are the proportional and integral coefficients for the frequency PI control process. and These are the proportional and integral coefficients for the voltage PI control process. and This is the PCC reference voltage. and For PCC voltage acquisition, Additional parameters for maintaining synchronization are measured by the phase-locked loop (PLL) circuit. This is a frequency control signal. This is a voltage control signal.

[0029] Preferably, in the hierarchical control method for distributed energy of the present invention, the connection between secondary control and top-level control is established through the following relationship:

[0030] ;

[0031] In the formula: and These are the proportional and integral coefficients for the frequency PI control process. and These are the proportional and integral coefficients for the voltage PI control process. and P' and Q' are the active power reference values ​​and reactive power reference values ​​of the PCC, respectively, and are the active power and reactive power measured by the PCC.

[0032] The beneficial effects of this invention are:

[0033] This paper proposes a hierarchical control method with nested control loops based on an improved droop control strategy to address voltage instability and voltage exceeding limits at the wind power grid connection point caused by the connection of numerous distributed permanent magnet wind power systems to the distribution network in low-voltage distribution networks. When the direct-drive distributed wind power system is operating in islanded mode, a line impedance voltage drop compensation method is used to increase the converter output voltage and offset the line voltage drop, achieving equal potential at the line ends. This effectively suppresses reactive power circulation and ensures precise distribution of reactive power to the load. During grid-connected operation, a decoupling control method based on the droop method is employed to ensure that the grid-side inverter output voltage tracks the grid voltage amplitude, phase, and frequency, guaranteeing that the grid-side output frequency and voltage are consistent with the voltage and frequency at the grid PCC or within the nationally required error range. The hierarchical control method applied to direct-drive distributed wind power provides a clear hierarchy and well-defined interfaces between levels. Multiple control paths are added for system voltage and frequency, and the operating points for voltage and frequency are refined, resulting in better control performance.

[0034] The hierarchical control method proposed in this invention is implemented on a distributed control platform based on the IEC 61499 standard. This method helps to modularize and standardize the inverter control algorithm, and allows for convenient module reuse and replacement. It enables the hierarchical control process to be freely adjusted and replaced, and improves reconfigurability, thus providing conditions for a large number of distributed energy interactive control practices. Attached Figure Description

[0035] The technical solution of this application will be further described below with reference to the accompanying drawings and embodiments.

[0036] Figure 1 This is a schematic diagram of a distributed energy hierarchical control method according to an embodiment of this application;

[0037] Figure 2 This is a block diagram of the sag control of a wind power microgrid according to an embodiment of this application;

[0038] Figure 3 This is a block diagram of droop control during the operation of a microgrid island in an embodiment of this application. Detailed Implementation

[0039] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0040] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the scope of protection of this application. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0041] In the description of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances. In this embodiment, if the X, Y, Z directions or X, Y, Z axes are involved, they are all based on the Cartesian coordinate system.

[0042] The technical solution of this application will now be described in detail with reference to the accompanying drawings and embodiments.

[0043] Explanation of relevant terms:

[0044] IEC 61499 standard: is a modeling standard applicable to the field of distributed industrial control systems, and is widely used in manufacturing plants and motor control.

[0045] ZeroMQ is a multi-threaded network library based on message queues that abstracts the underlying details of socket types, connection handling, frames, and even routing, providing sockets across multiple transport protocols.

[0046] PCC (Point of Common Coupling): Common Coupling Point.

[0047] Example

[0048] This embodiment proposes a hierarchical control method with nested control elements based on an improved droop control strategy for a microgrid system composed of permanent magnet direct-drive wind power generation:

[0049] (1) such as Figure 1 As shown, the underlying control uses a droop control method to control the system.

[0050] 1. Sagging control principle

[0051] Based on the fundamental principle of droop control, a control method for a direct-drive wind power generation system based on voltage and current dual closed-loop droop control is presented. The control block diagram is as follows: Figure 2 As shown.

[0052] Droop control is primarily used to control the parallel operation of multiple distributed generation (DG) sources in a microgrid. When the load of the microgrid system changes, load distribution can be achieved without communication between the multiple parallel DGs. Since the transmission lines in a microgrid are relatively short and the inverter output impedance is mainly inductive, active power output is adjusted by changing the frequency, and reactive power output is adjusted by changing the voltage amplitude. The output power satisfies the P-f and Q-U decoupling required for droop control. The droop control equation is as follows:

[0053] f * =f0-k p (P-P0) U * =U0-k Q (Q-Q0) (1)

[0054] In the formula, f * U * Reference values ​​for controlling the inverter output frequency and voltage; f0 and U0 are the grid rated frequency and no-load operating voltage, respectively; k p k Q These are the droop coefficients for active power and reactive power, respectively; P and Q are the actual active and reactive power outputs of the inverter; P0 and Q0 are the rated active and reactive power of the inverter.

[0055] 2. Microgrid Island Operation Control Principle

[0056] When the microgrid is operating in islanded mode, the inverter on the motor side of the direct-drive wind turbine unit still uses the control strategy employed during grid-connected operation, and the power output of the wind turbine is determined by wind energy. The grid-side inverter requires a droop control strategy, where the inverter output power is determined by both the droop factor and the load power, thereby adjusting the inverter output frequency reference value f. * Voltage amplitude reference value U * .

[0057] Since neither converter on either side has the function of controlling the DC bus voltage, voltage fluctuations and other problems will occur. Therefore, an energy storage device needs to be added to the DC bus to compensate for the power difference between the two sides and maintain DC voltage stability. To suppress circulating current, a compensation term is set in the voltage reference value of the droop control module based on the line impedance and the power flowing through the line. The calculation formula is as follows.

[0058] U cmp = U*=U0+U cmp -k(Q-Q0) (2)

[0059] In the formula: U cmp This is the line voltage drop compensation term; R and X are the line resistance and reactance, respectively; P and Q are the measured starting power; U is the line terminal voltage, and the line voltage U is calculated. cmp When applied to the rated voltage U0, the converter output voltage increases, offsetting the line voltage drop and achieving equal potential at the line ends. This effectively suppresses reactive circulating current and allows for precise distribution of reactive power from the load.

[0060] 3. Microgrid grid-connected operation control

[0061] The direct-drive wind turbine generator is in grid-connected operation. The generator-side converter adopts a dual closed-loop control structure. The outer loop uses MPPT control and stator voltage control, while the inner loop is a current control loop implemented using a PI controller to eliminate steady-state errors in current tracking. The grid-side converter still uses droop control. At this time, the DC microgrid system is supported by the grid, with the grid-side converter acting as a power balance point to ensure stable system operation. When using droop control during grid-connected operation, Q0 should be 0, and the AC main grid can be treated as an infinite power source. During normal operation, the microgrid's frequency and voltage are consistent with the grid. Voltage, frequency fluctuations, and load fluctuations in the microgrid are all borne by the main grid. At this time, the generator-side converter is in maximum power point tracking control, and the grid-side converter controls the stability of the DC bus voltage. Therefore, a DC bus voltage control unit is added on top of the frequency control. The droop control equation during grid-connected operation is as follows:

[0062] f*=f0+(k p1 + )(P m -P)-( k p3 + (U) ref- U dc )

[0063] U*=U0-( k p2 + )Q; (4)

[0064] In the formula k pi k li (i=1, 2, 3) are the proportional-integral coefficients of the proportional-integral converter; Pm is the maximum active power output of the wind turbine when it is in maximum wind energy capture mode; U ref This is the reference value for the DC bus voltage; U dc This is the actual value of the DC bus voltage.

[0065] (2) Secondary control. The secondary control compensates for the voltage and frequency deviations generated by the lower-level control. The lower-level control collects and calculates the active and reactive power at the PCC (Point of Common Coupling) position, and then transmits the voltage control signal to the current and voltage dual closed-loop control loop after calculating the droop curve. The connection between the secondary control and the lower-level control is established by using the reference frequency in the droop curve. and reference voltage The signal establishes the PI control process, as shown in equation (5), which is the frequency and voltage control signal. and This enables the tracking and compensation of the PCC voltage.

[0066] (5)

[0067] In the formula: and These are the proportional and integral coefficients for the frequency PI control process. and These are the proportional and integral coefficients for the voltage PI control process. and This is the PCC reference voltage. and For PCC voltage acquisition, Additional parameters for maintaining synchronization are measured by the phase-locked loop (PLL) circuit.

[0068] (3) Top-level control. When the distributed energy system is operating in islanded mode, the reference frequency f* and reference voltage U* of the secondary control input are the distributed energy frequency and PCC voltage. When switching to grid-connected mode, the top-level control adjusts the output frequency and voltage of the distributed energy system to be equal to the PCC frequency and voltage through the PI control process of equation (6).

[0069] Top-level control enables power flow control of microgrids in grid-connected mode. The connection between secondary control and top-level control is established by collecting and calculating the active and reactive power flow at the connection point between the microgrid and the external power grid, and adjusting the reference frequency in the secondary PI control. and reference voltage The signal establishes the PI control process as shown in equation (6).

[0070] (6)

[0071] In the formula: and These are the proportional and integral coefficients for the frequency PI control process. and These are the proportional and integral coefficients for the voltage PI control process. and P and Q are the active and reactive power values ​​for the PCC reference, respectively. P and Q are the measured active and reactive power outputs of the inverter, respectively. P' and Q' are the active and reactive power values ​​measured by the PCC.

[0072] (4) The above implementation method is compiled into a control program by MATLAB Simulink m file or C / C++ language. The data communication function is implemented by the S-function module compiled by ZeroMQ network library. The control program is applied to the IEC 61499 standard function block platform to implement control.

[0073] The invention proposed in this paper implements this hierarchical control method based on the IEC 61499 standard distributed control platform, which helps to modularize and standardize the inverter control algorithm. It enables convenient module reuse and replacement, allowing the hierarchical control process to be freely adjusted and replaced, and improving reconfigurability, thus providing conditions for a large number of distributed energy interactive control practices.

[0074] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0075] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0076] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0077] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A hierarchical control method for distributed energy resources, characterized in that, This includes lower-level control logic, secondary control logic, and upper-level control logic; The underlying control logic uses a droop control method to adjust the output of active power by changing the frequency and the output of reactive power by changing the voltage amplitude. The output power meets the P-f and Q-U decoupling requirements of droop control. P and Q are the actual output active power and reactive power of the inverter; f is the actual output frequency of the converter, and U is the actual output voltage of the converter. Secondary control logic: The secondary control compensates for the voltage and frequency deviations generated by the lower-level control. The lower-level control acquires and calculates active and reactive power at the PCC position, and then transmits voltage control signals to the current-voltage dual closed-loop control loop after calculating the droop curve. The connection between the secondary control and the lower-level control is established by using the reference frequency f in the droop curve. ref and reference voltage U ref The method of establishing the PI control process using signals; Top-level control logic: The top-level control performs power flow control on the microgrid in grid-connected mode. The connection between the secondary control and the top-level control is established by collecting and calculating the active and reactive power flow at the connection point between the microgrid and the external power grid, and adjusting the reference frequency in the secondary PI control. and reference voltage The method of establishing the PI control process using signals; When the distributed energy system is operating in islanded mode, the reference frequency f* and reference voltage U* of the secondary control input are the distributed energy frequency and PCC voltage. When the distributed energy system switches to grid-connected operation, the top-level control adjusts the output frequency and voltage of the distributed energy system through the PI control process to make the output frequency and voltage of the distributed energy system equal to the PCC frequency and voltage. The underlying control logic, secondary control logic, and top-level control logic are compiled into a control program by MATLAB Simulink m-files or C / C++ language, and the data communication function is implemented by the S-function module compiled by the ZeroMQ network library. The droop control equation during grid-connected operation is as follows: f*=f0+(k p1 + )(P m -P)-( k p3 + )(U ref- U dc ) U*=U0-( k p2 + )Q ; In the formula k pi k li P represents the proportional-integral coefficients of the proportional-integral converter, i = 1, 2, 3; m U represents the maximum active power output of the wind turbine when it is in maximum wind energy capture mode. ref This is the reference value for the DC bus voltage; U dc This is the actual value of the DC bus voltage.

2. The hierarchical control method for distributed energy resources according to claim 1, characterized in that, When distributed energy islands are in operation, the grid-side converter adopts a droop control strategy. The inverter output power is determined by both the droop coefficient and the load power, thereby adjusting the inverter output frequency reference value f. * Voltage amplitude reference value U * .

3. The hierarchical control method for distributed energy resources according to claim 2, characterized in that, The DC bus is connected to an energy storage device to compensate for the power difference between the two sides. Based on the line impedance and the power flowing through the line, a compensation item is set in the voltage reference value of the droop control module.

4. The hierarchical control method for distributed energy resources according to claim 3, characterized in that, The calculation formula for the compensation term in the voltage reference value of the droop control module is as follows: U cmp = ; U*=U0+U cmp -k(Q-Q0) ; In the formula: U cmp For line voltage drop compensation; R and X are line resistance and reactance, respectively; P and Q are the actual active power and reactive power output of the inverter; U is the line terminal voltage; U0 is the rated voltage; Q0 is the rated reactive power of the inverter; k is the reactive power droop factor.

5. The hierarchical control method for distributed energy resources according to claim 4, characterized in that, In the underlying control logic, the droop control equation is: f * =f0-k p (P-P0) ; U * =U0-k Q (Q-Q0); In the formula, f * U * Reference values ​​for controlling the inverter output frequency and voltage; f0 and U0 are the grid rated frequency and no-load operating voltage, respectively; k p k Q These are the droop coefficients for active power and reactive power, respectively; P and Q are the actual active and reactive power outputs of the inverter; P0 and Q0 are the rated active and reactive power of the inverter.

6. The hierarchical control method for distributed energy resources according to claim 5, characterized in that, When distributed energy sources are switched to grid-connected operation, the generator-side converter adopts a dual closed-loop control structure; the outer loop uses MPPT control and stator voltage control, while the inner loop is implemented using a PI controller through a current control loop, and the grid-side converter adopts the aforementioned droop control method.

7. The hierarchical control method for distributed energy resources according to any one of claims 1-6, characterized in that, The connection between secondary control and lower-level control is established through the following relationship. ； In the formula: and These are the proportional and integral coefficients for the frequency PI control process. and These are the proportional and integral coefficients for the voltage PI control process. and This is the PCC reference voltage. and For PCC voltage acquisition, Additional parameters for maintaining synchronization are measured by the phase-locked loop (PLL) circuit. This is a frequency control signal. This is a voltage control signal.

8. The hierarchical control method for distributed energy resources according to any one of claims 1-6, characterized in that, The connection between secondary control and top-level control is established through the following formula. ； In the formula: and These are the proportional and integral coefficients for the frequency PI control process. and These are the proportional and integral coefficients for the voltage PI control process. and P' and Q' are the active and reactive power reference values ​​of the PCC, respectively, and are the active and reactive power measured by the top-level control PCC (point of common coupling).

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