Multi-machine synchronous black start control method of optical storage hybrid control system

Abstract

The invention discloses a multi-machine synchronous black start control method of an optical storage hybrid control system, the optical storage hybrid control system comprises an energy storage system adopting network construction type control and a photovoltaic power generation system adopting network following type control, and the photovoltaic power generation system performs grid-connected operation through a phase-locked loop; the multi-machine synchronous black start control method comprises the step of analyzing multi-machine synchronous black start stability. The stability analysis comprises dynamic stability analysis of the phase-locked loop in the black start process and steady-state stability analysis of the phase-locked loop after the black start is completed; wherein in the black start process, when the active power generated by the photovoltaic power generation system meets # imgabs0 # after t0 (0 < = to < = Ts) and the active power generated by the photovoltaic power generation system after black start is completed meets # imgabs1 #, the optical storage hybrid control system can be stabilized to complete synchronous black start. The method has the advantages that the starting time can be shortened, and larger starting capacity can be provided.

Description

Technical Field

[0001] The present invention relates to the field of microgrids, and in particular to a multi-machine synchronous black start control method for a photovoltaic-storage hybrid control system. Background Art

[0002] With the rapid development of economy, the demand for electric energy has increased dramatically. Traditional thermal power generation has the disadvantages of high pollution and high cost. Distributed power sources have gradually attracted extensive attention from scholars due to their advantages of being renewable and low-pollution. According to local geographical conditions and resource conditions, the rational development and utilization of distributed power sources to form microgrids for power supply is an important direction for the future use of distributed power sources.

[0003] A microgrid is a small power system composed of distributed power sources, energy storage systems, loads, power electronic converters, etc. It has two operating modes: grid-connected operation and island operation. When the microgrid is in grid-connected operation, it can switch to island operation when the large grid fails or the power quality is poor. When the microgrid is in island operation, the system may lose power due to certain faults; in order to improve the power supply reliability of the system, the microgrid should have the ability to black start in the island operation state to quickly restore power supply to the load.

[0004] Microgrid black start means that after the entire microgrid stops operating due to external or internal faults and enters a completely black state, it does not rely on the help of the large power grid or other microgrids, but only starts the micro-sources with black start capability within the microgrid, thereby driving the micro-sources without black start capability within the microgrid, gradually expanding the recovery range of the system, and finally realizing the restart of the entire microgrid.

[0005] At present, the existing technology of microgrid black start research focuses on asynchronous black start, such as Figure 1 In the asynchronous black start two-machine system shown, when the lithium battery energy storage system is fully started, reaches the rated voltage and provides stable frequency support, the photovoltaic power generation system starts. However, in the case of asynchronous black start, when there are many devices, the black start time is very long, which is not conducive to the subsequent load recovery and will have a great impact on production and life; in addition, if it is a black start with load, once the energy storage capacity is insufficient to support the local load, it will cause black start failure. Summary of the invention

[0006] In order to at least partially solve the deficiencies in the prior art, the main purpose of the present invention is to provide a multi-machine synchronous black start control method for a photovoltaic-storage hybrid control system, which can shorten the start-up time and provide a larger start-up capacity.

[0007] In order to achieve the above main purpose, the present invention discloses a multi-machine synchronous black start control method of a photovoltaic storage hybrid control system, the photovoltaic storage hybrid control system includes an energy storage system using a grid-building type control and a photovoltaic power generation system using a grid-following type control, and the photovoltaic power generation system is connected to the grid through a phase-locked loop; wherein the multi-machine synchronous black start control method includes the step of analyzing the stability of the multi-machine synchronous black start;

[0008] Stability analysis includes:

[0009] Dynamic stability analysis of phase-locked loop during black start;

[0010] and, steady-state stability analysis of the locking loop after the black start is completed;

[0011] Among them, during the black start process, the active power generated by the photovoltaic power generation system is t 0 (o≤t o ≤T s ) after the time And after the black start is completed, the photovoltaic power generation system generates active power When the PV-storage hybrid control system is stable, it can complete the synchronous black start;

[0012] Among them, P PV =3V VSG I PV , P PV is the instantaneous value of active power output by the photovoltaic power generation system during the zero-starting voltage step-up process, V VSG is the effective value of the phase voltage output by the energy storage system during the zero-starting voltage step-up process, I PV is the effective value of the output current of the photovoltaic power generation system. The phase of the output current comes from the output of the phase-locked loop. line is the line impedance; P PVN =3U N I PVN , U N is the rated voltage of the photovoltaic power generation system, I PVN Output rated current for photovoltaic power generation system.

[0013] According to a specific embodiment of the present invention, a grid-forming energy storage system has voltage support and active inertia characteristics through the control of a virtual synchronous generator, and has the ability to operate with load without the support of an external power grid, and externally exhibits voltage source characteristics; a grid-following photovoltaic power generation system injects or absorbs active and reactive power by tracking the voltage amplitude and angle of the energy storage, and externally exhibits current source characteristics; wherein, when the microgrid enters a completely black state, the grid-forming energy storage system is started up through the control of the virtual synchronous generator to provide voltage and frequency support, thereby driving the synchronous start-up of the grid-following photovoltaic power generation system to control the synchronous black start of multiple machines.

[0014] According to a specific embodiment of the present invention, the photovoltaic storage hybrid control system further includes a line module, a filter inductor and a load module, wherein the energy storage system directly supplies power to the load module via the line module, the output voltage of the photovoltaic power generation system is converted into AC current after inversion, and supplies power to the load module after being processed by the filter inductor; the phase-locked loop collects the grid-connected point voltage and outputs angle information, and generates a PWM drive signal through closed-loop control of the inductor current.

[0015] According to a specific embodiment of the present invention, the energy storage system includes an electromotive force generating layer, a virtual impedance control layer, a voltage and current dual closed-loop control layer, a dq inverse converter and a PWM modulator; wherein the electromotive force generating layer is used to generate the potential amplitude E and phase θ of the virtual synchronous generator, and the electromotive force E∠θ generated by it is processed by the virtual impedance control layer to obtain an output voltage, and the output voltage is passed through the voltage and current dual closed-loop control layer and the dq inverse converter to obtain an inverter output voltage modulation wave, and then the inverter drive signal is given through the PWM modulator.

[0016] According to a specific embodiment of the present invention, the energy storage system is provided with a zero-start boost module for suppressing the excitation inrush current of the distribution transformer in the microgrid during the black start micro-source startup process, wherein the zero-start boost control of the electromotive force amplitude is set as follows:

[0017]

[0018] Among them, E o is the voltage amplitude of the virtual synchronous generator when it is unloaded; k is the slope of the output potential amplitude increasing with time, k = E 0 / T s ; T s The output potential amplitude increases from 0 to E o The time required.

[0019] According to a specific implementation of the present invention, when the microgrid is black-started, the energy storage system uses a zero-start boost module to establish a voltage reference, generates an energy storage output active power reference value through primary and secondary frequency modulation, eliminates the frequency difference through an integral link, and then generates the phase of the virtual synchronous generator electromotive force through the rotor motion equation.

[0020] According to a specific implementation of the present invention, the primary frequency modulation is differential frequency modulation, which can be achieved through a proportional link; the secondary frequency modulation is non-differential frequency modulation, which eliminates the frequency difference through an integral link.

[0021] According to a specific implementation of the present invention, the photovoltaic power generation system implements the frequency modulation function through a PI regulator, and then generates a current instruction through a power loop to implement closed-loop control of the inductor current.

[0022] According to a specific embodiment of the present invention, the phase-locked loop transforms the voltage from the three-phase stationary coordinate system to the synchronous rotating dq coordinate system through dq transformation, and obtains the transformed voltage V q =V m sin(θ-θ′), where V m is the voltage amplitude at the grid connection point, θ is the actual voltage angle, and θ′ is the output estimated angle of the phase-locked loop;

[0023] Through PI regulation control, V q is 0, that is, the output estimated angle θ′ of the phase-locked loop is equal to the actual angle θ of the load voltage, so as to achieve phase locking.

[0024] According to a specific implementation of the present invention, the photovoltaic power generation system is equivalent to a current source and an equivalent circuit is obtained. The load voltage can be obtained by the superposition theorem:

[0025]

[0026] in,

[0027] The present invention has the following beneficial effects: It provides a multi-machine synchronous black start control method for a photovoltaic storage hybrid control system. Compared with asynchronous black start, the present invention mainly has the following advantages: 1) It speeds up the start time. The energy storage system and the photovoltaic power generation system are started at the same time, which can greatly shorten the black start time and speed up load recovery; 2) It provides a larger starting capacity to avoid the situation where the black start failure is caused by the inability to provide sufficient power using only energy storage under full load or heavy load conditions during load start.

[0028] In order to more clearly illustrate the purpose, technical solutions and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of a prior art asynchronous black start two-machine system;

[0030] Figure 2 It is a topological diagram of the photovoltaic storage hybrid control system of the present invention;

[0031] Figure 3 It is a framework diagram of grid-type energy storage control;

[0032] Figure 4 It is a framework diagram of active power control of grid-type energy storage;

[0033] Figure 5 This is the framework diagram of grid-based photovoltaic control;

[0034] Figure 6 It is the framework diagram of phase-locked loop control;

[0035] Figure 7 It is a linearized model diagram of the phase-locked loop control structure;

[0036] Figure 8 It is the equivalent circuit diagram of the photovoltaic power generation system;

[0037] Fig. 9 It is the synchronous stability analysis model diagram of the photovoltaic storage hybrid control system;

[0038] Fig.10 It is the waveform of the output voltage of the energy storage system;

[0039] Fig.11 It is the frequency waveform of the output voltage of the energy storage system;

[0040] Fig.12 It is the waveform of the output power of the energy storage system;

[0041] Fig.13 It is a waveform diagram of the output power of the photovoltaic power generation system. DETAILED DESCRIPTION

[0042] In the following description, many specific details are explained in conjunction with the embodiments to facilitate a full understanding of the present invention. However, it should be understood that the following embodiments and detailed descriptions are only for illustrative purposes and do not limit the scope of protection of the present invention.

[0043] An embodiment of the present invention provides a multi-machine synchronous black start control method for a photovoltaic-storage hybrid control system, wherein the photovoltaic-storage hybrid control system is a multi-machine system. The following is a specific description based on the photovoltaic-storage hybrid control system specifically including an energy storage system using a grid-building type control and a photovoltaic power generation system using a grid-following type control, and the photovoltaic power generation system is connected to the grid through a phase-locked loop.

[0044] The energy storage system adopts grid-type control, specifically adopts virtual synchronous generator control and has voltage support and active inertia characteristics, has the ability to operate with load without the support of the external power grid, does not require a phase-locked loop, and shows voltage source characteristics to the outside; the photovoltaic power generation system adopts grid-following control, depends on the grid voltage, and must be connected to the grid through a phase-locked loop. It injects or absorbs active and reactive power by tracking the voltage amplitude and angle of the energy storage, and shows current source characteristics to the outside. In the embodiment, when the microgrid enters a completely black state, the grid-type energy storage system is started through virtual synchronous generator control to provide voltage and frequency support, thereby driving the synchronous start of the grid-following photovoltaic, that is, the grid-type energy storage system and the grid-following photovoltaic power generation system are started at the same time, and finally the multi-machine synchronous black start control is realized.

[0045] The photovoltaic-storage hybrid control system further includes a line module, a filter inductor and a load module, wherein the energy storage system directly supplies power to the load module via the line module, the output voltage of the photovoltaic power generation system is converted into AC current after inversion, and supplies power to the load module after being processed by the filter inductor; the phase-locked loop collects the grid-connected point voltage and outputs angle information, and generates a PWM drive signal through closed-loop control of the inductor current.

[0046] The topology diagram of the photovoltaic storage hybrid control system is as follows: Figure 2 As shown in the figure, the energy storage system controlled by the virtual synchronous generator has a stable output voltage and frequency, so the AC voltage source V VSG (θ 1 ) instead of (where θ 1 is the voltage source phase), the energy storage system passes through the line z line Give load z L The core of this embodiment is the grid-connected operation of the photovoltaic power generation system, so the photovoltaic DC side is equivalent to a DC voltage source to simplify the analysis. PV After inversion, the output AC current i abc , after filtering inductor L f Give load z L Power supply; PLL is a phase-locked loop, which collects the grid voltage V L Then output angle information θ 2 , a PWM drive signal is generated through closed-loop control of the inductor current.

[0047] The energy storage system includes an electromotive force generation layer, a virtual impedance control layer, a voltage and current double closed-loop control layer, a dq inverse converter and a PWM modulator; wherein the electromotive force generation layer is used to generate the potential amplitude E and phase θ of the virtual synchronous generator, and the electromotive force E∠θ generated by it is processed by the virtual impedance control layer to obtain the output voltage, and the output voltage is passed through the voltage and current double closed-loop control layer and the dq inverse converter to obtain the inverter output voltage modulation wave, and then the inverter drive signal is given through the PWM modulator. Specifically, the grid-type energy storage control structure is as follows Figure 3 As shown, the purpose of the electromotive force generation layer is to generate the potential amplitude E and phase θ of the virtual synchronous generator. The generated electromotive force E∠θ is controlled by virtual impedance to obtain the output voltage u oabc After voltage and current dual closed-loop control and dq inverse transformation, the inverter output voltage modulation wave is obtained and then modulated to the inverter drive signal through PWM.

[0048] Furthermore, the energy storage system is provided with a zero-start boost module for suppressing the excitation inrush current of the distribution transformer in the microgrid during the black start micro-source startup process. The zero-start boost module enables the energy storage system to have a zero-start boost function; wherein the zero-start boost control of the electromotive force amplitude is set as follows:

[0049]

[0050] Among them, E o is the voltage amplitude of the virtual synchronous generator when it is unloaded; k is the slope of the output potential amplitude increasing with time, k = E 0 / T s ; T s The output potential amplitude increases from 0 to E o Specifically, in order to ensure the rapidity of energy storage startup and the non-saturation of transformer flux at any time, the potential amplitude rise time T s Generally it should be greater than 38.2ms.

[0051] When the microgrid is black-started, the energy storage system uses the zero-start boost module to establish a voltage reference. Figure 4 The active control shown establishes a stable frequency reference; this control generates the energy storage output work reference value through primary and secondary frequency modulation, eliminates the frequency difference through the integral link, and then generates the phase of the virtual synchronous generator electromotive force through the rotor motion equation. Among them, the primary frequency modulation is differential frequency modulation, which can be achieved through the proportional link; the secondary frequency modulation is non-differential frequency modulation, and the frequency difference is eliminated through the integral link.

[0052] The grid-following control framework of photovoltaic power generation system is as follows: Figure 5 As shown in Figure 2, this control enables the photovoltaic power generation system to have a frequency modulation function; Figure 5 In the process, the frequency modulation function is realized by the PI regulator, and then the current command I is generated by the power loop. ref To achieve closed-loop control of the inductor current.

[0053] Furthermore, the multi-machine synchronous black start control method includes a step of analyzing the stability of the multi-machine synchronous black start, and the stability analysis includes a dynamic stability analysis of the phase-locked loop during the black start process and a steady-state stability analysis of the phase-locked loop after the black start is completed; the details are as follows:

[0054] The phase-locked loop control structure is as follows: Figure 6 As shown, its main function is to extract Figure 2 The grid voltage V L The phase of (θ) is determined by the phase-locked loop. The voltage V L (θ) is transformed from the three-phase stationary abc coordinate system to the synchronous rotating dq coordinate system to obtain V q =V m sin(θ-θ′), where V m is the voltage amplitude at the grid connection point, θ is the actual voltage angle, and θ′ is the estimated angle of the phase-locked loop output. Through PI regulation control, V q is 0, that is, the output estimated angle θ′ of the phase-locked loop is equal to the actual angle θ of the load voltage, so as to achieve phase locking.

[0055] The linear model of this structure is as follows Figure 7 As shown, PD is a phase detector, and its output is V q .

[0056] In the embodiment, the photovoltaic power generation system is equivalent to a current source and an equivalent circuit is obtained. The equivalent circuit obtained is as follows: Figure 8 As shown, I PV is the effective value of the output current of the photovoltaic power generation system, and the phase of the current θ 2 From the output of the phase locked loop.

[0057] According to the superposition theorem, the load voltage can be obtained as:

[0058]

[0059] in,

[0060] In the embodiment, the phase-locked loop synchronization stability analysis model of the photovoltaic storage hybrid control system is as follows: Fig. 9 As shown, in Fig. 9 middle:

[0061]

[0062]

[0063]

[0064] It can be seen that the existence of the current source provides a positive feedback to the phase-locked loop; to ensure the stability of the phase-locked loop, it is necessary to ensure that V q+ <V q- . Due to the existence of the sine function, Therefore, when the phase-locked loop is stable, the following conditions must be met:

[0065]

[0066] In an embodiment, the stability analysis of the multi-machine synchronous black start of the photovoltaic-storage hybrid control system includes dynamic stability analysis and steady-state stability analysis, wherein dynamic stability refers to the stability of the phase-locked loop during the black start process, and steady-state stability refers to the stability of the phase-locked loop after the black start is completed.

[0067] During the black start process, the photovoltaic power generation system output power P PV =3V VSG I PV , where P PV is the instantaneous value of active power output by the photovoltaic power generation system during the zero-starting voltage step-up process, V VSG It is the effective value of the phase voltage output by the energy storage system during the zero-starting voltage step-up process. When , the phase-locked loop can be relatively stable.

[0068] Since sin(p 2 )<1, it can be approximately considered

[0069] In steady state, the output power and output current of the photovoltaic power generation system are stable, and the output power and output voltage of the energy storage system are stable; the rated power of the photovoltaic output is P PVN =3U N I PVN , U N is the system rated voltage, I PVN The output current of the photovoltaic system is rated. At this time, the stability of the phase-locked loop must meet

[0070] In summary, considering the dynamic stability conditions and steady-state stability conditions of the photovoltaic power generation system, it can be concluded that during the black start process, the active power generated by the photovoltaic power generation system is 0 (o≤t o ≤T s ) after the time And after the black start is completed, the photovoltaic power generation system generates active power At this time, the photovoltaic-storage hybrid control system can be stable to complete the synchronous black start of the photovoltaic-storage hybrid control system.

[0071] Based on the above content, a simulation model of the photovoltaic-storage hybrid control system is built in Simulink, and the system parameters are shown in Table 1.

[0072] Table 1 Parameters of the photovoltaic and energy storage hybrid control system

[0073]

[0074] The output voltage waveform of the energy storage system is as follows: Fig.10 As shown, it can be seen that the output voltage amplitude increases linearly, and the voltage amplitude reaches 311V at 1s, which can complete the zero-starting voltage boost.

[0075] The output voltage frequency waveform of the energy storage system controlled by virtual synchronous machine is as follows: Fig.11 As shown, the frequency deviation is within 0.1Hz.

[0076] The output power waveform of the energy storage system is as follows: Fig.12 As shown, the output active power is controlled at 10KW after the zero-starting voltage boost is completed, and the output reactive power is controlled at 0 after the zero-starting voltage boost is completed.

[0077] The output power waveform of the photovoltaic system is as follows: Fig.13 As shown, the output active power is controlled at 10KW after the zero-starting voltage boost is completed, and the output reactive power is controlled at 0 after the zero-starting voltage boost is completed.

[0078] The above simulation results show that the embodiments of the present invention can realize the synchronous black start of multiple machines in the photovoltaic-storage hybrid control system.

[0079] Although the present invention has been described above through embodiments, the above embodiments are only used to exemplarily describe the feasible implementation schemes of the present invention, and are not used to limit the protection scope of the present invention. Any equivalent substitutions or changes made by those skilled in the art in accordance with the present invention should also be covered by the protection scope defined by the claims of the present invention.

Claims

1. A multi-machine synchronous black start control method for a photovoltaic storage hybrid control system, wherein the photovoltaic storage hybrid control system includes an energy storage system using a grid-building type control and a photovoltaic power generation system using a grid-following type control, and the photovoltaic power generation system is connected to the grid through a phase-locked loop; the method is characterized in that: The multi-machine synchronous black start control method includes the steps of analyzing the stability of the multi-machine synchronous black start; Stability analysis includes: Dynamic stability analysis of phase-locked loop during black start; and, steady-state stability analysis of the locking loop after the black start is completed; Among them, during the black start process, the photovoltaic power generation system generates active power at t0 (0≤t0≤T s ) after the time And after the black start is completed, the photovoltaic power generation system generates active power When the PV-storage hybrid control system is stable, it can complete the synchronous black start; Among them, P PV =3V VSG I PV , P PV is the instantaneous value of active power output by the photovoltaic power generation system during the zero-starting voltage step-up process, V VSG is the effective value of the phase voltage output by the energy storage system during the zero-starting voltage step-up process, I PV is the effective value of the output current of the photovoltaic power generation system. The phase of the output current comes from the output of the phase-locked loop. line is the line impedance; P PVN =3U N I PVN , U N is the rated voltage of the photovoltaic power generation system, I PVN Output rated current for photovoltaic power generation system.

2. The multi-machine synchronous black start control method of the photovoltaic storage hybrid control system according to claim 1 is characterized by: The grid-forming energy storage system has voltage support and active inertia characteristics through the control of a virtual synchronous generator, as well as the ability to operate under load without the support of an external power grid, and it exhibits voltage source characteristics to the outside. The grid-following photovoltaic power generation system injects or absorbs active and reactive power by tracking the voltage amplitude and angle of the energy storage, and it exhibits current source characteristics to the outside. Among them, when the microgrid enters a completely black state, the grid-forming energy storage system is started up through the control of a virtual synchronous generator to provide voltage and frequency support, thereby driving the synchronous start-up of the grid-following photovoltaic power generation system to control the synchronous black start of multiple machines.

3. The multi-machine synchronous black start control method of the photovoltaic storage hybrid control system according to claim 2 is characterized by: The photovoltaic-storage hybrid control system further includes a line module, a filter inductor and a load module, wherein the energy storage system directly supplies power to the load module via the line module, the output voltage of the photovoltaic power generation system is converted into AC current after inversion, and supplies power to the load module after being processed by the filter inductor; the phase-locked loop collects the grid-connected point voltage and outputs angle information, and generates a PWM drive signal through closed-loop control of the inductor current.

4. The multi-machine synchronous black start control method of the photovoltaic storage hybrid control system according to claim 3 is characterized in that: The energy storage system includes an electromotive force generation layer, a virtual impedance control layer, a voltage and current dual closed-loop control layer, a dq inverse converter and a PWM modulator; wherein the electromotive force generation layer is used to generate the potential amplitude E and phase θ of the virtual synchronous generator, and the electromotive force E∠θ generated by it is processed by the virtual impedance control layer to obtain the output voltage, and the output voltage is passed through the voltage and current dual closed-loop control layer and the dq inverse converter to obtain the inverter output voltage modulation wave, and then the inverter drive signal is given through the PWM modulator.

5. The multi-machine synchronous black start control method of the photovoltaic storage hybrid control system according to claim 4 is characterized in that: The energy storage system is provided with a zero-start voltage-boosting module for suppressing the excitation inrush current of the distribution transformer in the microgrid during the black-start micro-source starting process, wherein the zero-start voltage-boosting control of the electromotive force amplitude is set as follows: Among them, E o is the voltage amplitude of the virtual synchronous generator when it is unloaded; k is the slope of the output potential amplitude increasing with time, k = E0 / T s ; T s It is the time required for the output potential amplitude to increase from 0 to E0.

6. The multi-machine synchronous black start control method of the photovoltaic storage hybrid control system according to claim 5 is characterized in that: During the black start of the microgrid, the energy storage system uses the zero-start boost module to establish a voltage reference, generates the energy storage output active power reference value through primary and secondary frequency modulation, eliminates the frequency difference through the integral link, and then generates the phase of the virtual synchronous generator electromotive force through the rotor motion equation.

7. The multi-machine synchronous black start control method of the photovoltaic storage hybrid control system according to claim 6 is characterized by: The primary frequency modulation is differential frequency modulation, which can be achieved through a proportional link; the secondary frequency modulation is differential frequency modulation, which eliminates the frequency difference through an integral link.

8. The multi-machine synchronous black start control method of the photovoltaic storage hybrid control system according to claim 3 is characterized by: The photovoltaic power generation system realizes the frequency modulation function through the PI regulator, and then generates current instructions through the power loop to achieve closed-loop control of the inductor current.

9. The multi-machine synchronous black start control method of the photovoltaic storage hybrid control system according to claim 8 is characterized in that: The phase-locked loop transforms the voltage from the three-phase stationary coordinate system to the synchronous rotating dq coordinate system through dq transformation, and obtains the transformed voltage V q =V m sin(θ-θ′), where V m is the voltage amplitude at the grid connection point, is the actual voltage angle, and θ′ is the output estimated angle of the phase-locked loop; Through PI regulation control, V q is 0, that is, the output estimated angle θ′ of the phase-locked loop is equal to the actual angle θ of the load voltage, so as to achieve phase locking.

10. The multi-machine synchronous black start control method of the photovoltaic-storage hybrid control system according to claim 9 is characterized in that: The photovoltaic power generation system is equivalent to a current source and an equivalent circuit is obtained. The load voltage can be obtained by the superposition theorem: in,

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