CN114552661B

CN114552661B - Light storage power generation system control method and storage medium

Info

Publication number: CN114552661B
Application number: CN202210426431.9A
Authority: CN
Inventors: 雷健华; 颜湘武; 秦赓; 王晨光; 贾焦心; 游泳亮
Original assignee: North China Electric Power University; Shenzhen Poweroak Newener Co Ltd
Current assignee: Shenzhen Delian Minghai New Energy Co ltd; North China Electric Power University
Priority date: 2022-04-22
Filing date: 2022-04-22
Publication date: 2022-07-29
Anticipated expiration: 2042-04-22
Also published as: CN114552661A

Abstract

A control method and a storage medium of a light storage power generation system are provided, the method is applied to the light storage power generation system based on a VF source type virtual synchronous machine and works in an off-grid state, and comprises the following steps: acquiring photovoltaic output power and load power of a light storage power generation system; judging whether the photovoltaic output power is greater than the load power; when the photovoltaic output power is smaller than the load power, setting a voltage component according to the direct-current voltage deviation of the optical storage power generation system; superposing a voltage component on the voltage loop, adjusting the output power of the optical storage power generation system, and matching the output power with the load power; when the photovoltaic output power is greater than or equal to the load power, if the state of charge of the energy storage battery reaches a limit value or the energy storage system cannot work normally, the photovoltaic working mode is converted into a variable power tracking mode, the photovoltaic output power is changed by adjusting the photovoltaic working voltage, and the balance between the photovoltaic output power and the load power is realized. The method can effectively ensure the power balance in the system and improve the stability of the system.

Description

Light storage power generation system control method and storage medium

Technical Field

The invention relates to the field of photovoltaic energy storage power generation system control, in particular to a control method and a storage medium for a photovoltaic energy storage power generation system.

Background

Terms and abbreviations illustrate:

photovoltaic (Photovaltaic, PV)

Energy storage system (Energy storage system, ESS)

Energy Management System (EMS)

Light storage power generation system (Photovoltaic-solar energy storage system, PV-BES)

Virtual Synchronous Generator (VSG)

Voltage/frequency control (VF control)

Maximum Power Point (MPP)

Maximum Power Point Tracking (MPPT)

State of charge (SOC)

Active power-frequency (P-f)

Reactive power-system voltage (Q-U).

Photovoltaic power generation generally adopts a Maximum Power Point Tracking (MPPT) operating mode, and in this mode, a photovoltaic cell always operates at a Maximum Power Point (MPP). The photovoltaic power generation has two characteristics of volatility and randomness, and the two characteristics determine the output characteristics of the photovoltaic power generation. And the uncertainty of the photovoltaic output causes that the reliability of load power supply is difficult to guarantee when the photovoltaic output is off-grid. Therefore, in practical use, photovoltaic and Energy Storage Systems (ESS) are commonly used together, and such ESS is called photovoltaic-based Energy Storage System (PV-BES).

Although the photovoltaic power generation system can be used completely off-grid, in most cases it is still necessary to incorporate the PV power into the grid, or to feed the PV power into the grid, or to absorb the energy from the grid to charge the energy storage battery. The operating state of the system can be divided into two operating modes depending on whether it is connected to the grid: 1 off-grid running state and 2 grid-connected running state. At present, a photovoltaic grid connection strategy still mostly adopts mode switching to realize a grid disconnection and connection function. A voltage source mode is adopted when the photovoltaic is in off-grid work, and the photovoltaic grid connection mode is switched to a current source control mode. The working mode has the advantages that the control structure is simple, the inner ring controls the inductive current and the outer ring controls the direct-current voltage after grid connection, and the PV power can be completely transmitted into a power grid. However, the disadvantage of this mode is that mode switching is required when the grid is disconnected, although some papers propose strategies that can make the mode switching process as smooth as possible, so that the system is not affected during switching to supply power to the load. However, in the case of unexpected grid disconnection such as grid failure, the local load is still powered off for a short time.

Since clean energy still needs to be connected to a synchronous grid for a long time, a Virtual Synchronous Generator (VSG) technology has been developed and has received much attention in recent years. The distributed power supply adopting the VSG technology has the same operation mechanism as that of a synchronous unit, can autonomously participate in the operation and management of a power grid, and makes corresponding response under the conditions of abnormal voltage/frequency and active power/reactive power of the power grid so as to actively deal with the transient and dynamic stability problems of the power grid. The VSG technology has the greatest advantage that the VSG is a voltage source in the off-grid and on-grid states, and mode switching during the off-grid and on-grid states can be avoided. In addition, the VF source type VSG has the droop characteristics of active-frequency and reactive-voltage, and can be conveniently connected in parallel with a plurality of machines and incorporated into a power grid.

However, based on the scenario and the requirement, in the existing related research, the topology and the control structure of the virtual synchronous machine are mainly directed to the case where the dc side is the energy storage system, that is, it is assumed that the dc side is a power source with constant voltage and infinite capacity, and the energy storage system operates in a mode with constant dc bus voltage, and the power of the dc side photovoltaic and the power of the inverter are balanced by the energy storage system. However, when the energy storage system does not operate in a mode of constant dc bus voltage, or the SOC of the energy storage system reaches a better level and stops operating, the problem caused by the photovoltaic property of the dc side will be highlighted, and therefore, the conventional virtual synchronous machine control ignores the influence of the dynamic characteristic of the dc side and is difficult to be applied to various operating modes of the PV-BES.

In addition, although the VSG technology avoids the need of strategy switching of the inverter under grid connection and grid disconnection, the VSG technology is faced to some conditions of unplanned grid disconnection or abnormal work of an energy storage system and the like. Under the condition, the grid is often in fault, and the light storage power generation system is cut off from the grid after anti-islanding protection is triggered. Therefore, when the energy storage system may not be started in time or the energy storage system cannot work normally due to a fault, a downtime and the like, the optical storage power generation system is already separated from the power grid, and the power inside the system is unbalanced, which causes the direct-current voltage to rise or fall rapidly. In addition, when the photovoltaic, energy storage and load power of the PV-BES are unbalanced in the off-grid operation state, the system may be unstable. In summary, based on the scenario and the requirement, the control strategy for various operation modes of the PV-BES in the related research is yet to be researched.

It is to be noted that the information disclosed in the above background section is only for understanding the background of the present application and thus may include information that does not constitute prior art known to a person of ordinary skill in the art.

Disclosure of Invention

The invention provides a control method of a light storage power generation system, which is used for ensuring the power balance in the system and improving the stability of the system.

In order to achieve the purpose, the invention adopts the following technical scheme:

a control method of a light storage power generation system is applied to the light storage power generation system based on a Voltage Frequency (VF) source type virtual synchronous machine and works in an off-grid state, and comprises the following steps:

acquiring photovoltaic output power and load power of the light storage power generation system;

judging whether the photovoltaic output power is greater than the load power;

when the photovoltaic output power is smaller than the load power, setting a voltage component according to the direct-current voltage deviation of the light storage power generation system;

superposing the voltage component on a voltage loop, adjusting the output power of the optical storage power generation system, and matching the output power with the load power;

when the photovoltaic output power is greater than or equal to the load power, if the state of charge of the energy storage battery reaches a limit value or the energy storage system cannot work normally, the photovoltaic working mode is converted into a variable power tracking mode, the photovoltaic output power is changed by adjusting the photovoltaic working voltage, and the balance between the photovoltaic output power and the load power is realized, wherein the target of variable power tracking is that the power of the energy storage battery is 0 or the energy storage battery discharges with set power.

A computer-readable storage medium storing a computer program which, when executed by a processor, implements the off-grid control method for a light storage power generation system.

Due to the adoption of the technical scheme, the invention has the following beneficial effects:

the invention provides a control method of a light storage power generation system based on a traditional VSG control method, which is suitable for off-grid control of a light storage power generation system (PV-BES). The method ensures power balance in the system and improves the stability of the system by superposing a voltage component which is related to direct-current voltage deviation and is preferably in direct proportion on a voltage loop and changing the operation mode of a Photovoltaic (PV).

According to the method provided by the embodiment of the invention, the energy storage system works in a constant direct current voltage mode in an off-grid running state, so that the direct current voltage of the PV-BES is ensured to be constant; when the photovoltaic output power is insufficient, a voltage component is superposed on a voltage loop according to the direct-current voltage deviation of the system, so that the output power is consistent with the load power. When the photovoltaic output power is sufficient, if the state of charge of the energy storage battery reaches a limit value or the energy storage system cannot work normally, the photovoltaic control strategy of the PV-BES is changed, the photovoltaic mode is changed from the maximum power point tracking mode to the variable power tracking mode, and the PV output power is changed by adjusting the operating point of the photovoltaic to balance the photovoltaic and the load power. The method of the invention can meet the working requirements of various working conditions of the PV-BES. The method of the invention considers the source end characteristic of PV-BES on the basis of VSG technology, and the control strategy can improve the operation flexibility and reliability of the optical storage power generation system. The method of the invention is subjected to simulation verification, and the result proves the correctness of the method.

The invention also provides another control method of the optical storage power generation system, which aims to solve the problem that the traditional virtual synchronous machine (VSG) strategy is difficult to meet the working requirements of multiple working conditions of the optical storage power generation system.

a control method of a light storage power generation system is applied to the light storage power generation system based on a VF source type virtual synchronous machine and works in a grid-connected state, and comprises the following steps:

acquiring direct-current voltage on the direct-current side of an inverter in the optical storage power generation system, and acquiring direct-current voltage deviation of the system according to a rated value of the direct-current voltage on the direct-current side of the inverter;

and according to the f-P droop characteristic curve of the VF source type virtual synchronous machine, changing the position of the primary frequency modulation curve according to the DC voltage deviation to carry out secondary frequency adjustment, thereby adjusting the output power of the optical storage power generation system.

A computer readable storage medium stores a computer program, which when executed by a processor, implements the control method of the optical storage power generation system as described above and is applied to an optical storage power generation system based on a VF source type virtual synchronous machine to operate in a grid-connected state.

The invention provides a control method of a light storage power generation system aiming at the light storage power generation system, which is applied to the light storage power generation system based on a virtual synchronous machine and works in a grid-connected state. The invention considers the source end characteristic of PV-BES on the basis of VSG technology, and the control strategy can improve the operation flexibility and reliability of the optical storage power generation system. By adjusting the output power of the VSG through the method, the excess PV power can be sent into the power grid after the system is connected to the power grid, or the power is absorbed from the power grid to meet the requirement of local load or charge the energy storage system.

Drawings

Fig. 1 is a flowchart of a control method of a photovoltaic power storage system, which is applied to a photovoltaic power storage system based on a virtual synchronous machine and works in a grid-connected state;

FIG. 2A is a block diagram of a classical optical storage power generation system applied in an embodiment of the present invention;

FIG. 2B is a schematic diagram illustrating switching control between grid-connected and grid-disconnected according to an embodiment of the present invention;

FIG. 2C is a control structure diagram based on a virtual synchronous machine according to an embodiment of the present invention;

FIG. 3 is a diagram illustrating the droop characteristics of a VF source VSG in accordance with an embodiment of the present invention;

FIG. 4 is a schematic diagram of the frequency quadratic adjustment to change the output power according to the embodiment of the present invention;

FIG. 5 shows the power, DC voltage and

f, a change map;

FIG. 6 shows the power, DC voltage and

f, graph of variation.

Fig. 7 is a flowchart of a control method for a photovoltaic power generation system, which is applied to a photovoltaic power generation system based on a virtual synchronous machine and operated in an off-grid state;

FIG. 8 is a photovoltaic variable power tracking control block diagram of an embodiment of the present invention;

9 (a) to 9 (c) are block diagrams of three different strategies for stabilizing the dc voltage of the inverter by varying the photovoltaic power according to the embodiment of the present invention;

FIG. 10 is a schematic diagram of a DC voltage stabilization strategy using FPPT according to an embodiment of the present invention;

FIG. 11 shows voltage components in an embodiment of the present invention

Calculating U and controlling VSG voltage structure chart;

FIG. 12 is a graph of active, reactive and DC voltage changes under the three control strategies provided by the embodiment of the present invention when the illumination is sufficient;

FIG. 13 is a graph of power versus voltage under control of the proposed strategy in the case of insufficient illumination according to an embodiment of the present invention;

FIG. 14 is a graph of power versus voltage without control when the illumination is insufficient in accordance with the present invention.

Detailed Description

The embodiments of the present invention will be described in detail below. It should be emphasized that the following description is merely exemplary in nature and is not intended to limit the scope of the invention or its application.

The embodiment of the invention provides a control method of a photovoltaic power storage and generation system, which is applied to a photovoltaic power storage and generation system based on a VF source type virtual synchronous machine (VSG) and works in a grid-connected state, and as shown in figure 1, the method comprises the following steps: step T1, acquiring direct-current voltage of the direct-current side of an inverter in the light storage power generation system, and acquiring direct-current voltage deviation of the system according to a rated value of the direct-current voltage of the direct-current side of the inverter; and T2, changing the position of the primary frequency modulation curve according to the f-P droop characteristic curve of the VF source type virtual synchronous machine to perform secondary frequency adjustment according to the direct-current voltage deviation, so as to adjust the output power of the optical storage power generation system, and sending redundant photovoltaic power to a power grid after the system is connected to the power grid, or absorbing power from the power grid to meet the requirement of a local load or absorbing power from the power grid to charge the energy storage system in a low-ebb period of the power grid load. The invention considers the source end characteristic of PV-BES on the basis of VSG technology, and the control strategy can improve the operation flexibility and reliability of the optical storage power generation system.

When the optical storage power generation system is in a grid-connected mode and an Energy Storage System (ESS) exits a working mode of constant direct-current bus voltage (the energy storage system can be an energy storage system)The system exits operation or enters a constant power mode, such as charging and discharging at constant power), at which time the PV-BES controls the state of charge (SOC) of the energy storage battery according to the Energy Management System (EMS), and provides primary frequency modulation and inertia support for the grid using the external characteristics of the VSG according to the frequency of the gridP _st =

P _st1 +

P _st2 (ii) a After PV-BES is merged into a power grid, the main control aim is to send surplus electric energy generated by photovoltaic into the power grid, or obtain electric energy from the power grid to meet local load or charge an energy storage system when the photovoltaic power is insufficientf ₀ Superpose a frequency offset on

fThe primary frequency modulation curve of the system is equivalent to moving upwards or downwards

fThus the system primary frequency modulation curve and the power grid frequencyf _g The intersection point of the three-phase converter is changed, namely, the multi-transmission to the power grid is realized

P or the active power absorbed from the grid, of a value of

P =k _f ×

fWhereink _f Is the f-P droop coefficient of VF controlled VSG.

In some embodiments, when the PV-BES is operated off-grid, the power supply quality of the system meets the requirement of the power quality standard, and the selected parameter is that the frequency deviation is within the rangef _N

In the range of 0.5Hz and the supply voltage isU _N

In the range of 7%, wherein f _N And U _N Rated frequency and rated voltage on the AC side of the inverter, frequency at the intersection of the f-P droop characteristic and the f-axisf ₀ = f _N -voltage at the intersection of the 0.5 and Q-U droop characteristic with the U-axisU ₀ = U _N -7％U _N 。

In some embodiments, adjusting the active power output by the PV-BES is achieved by shifting the position of the primary modulation curve upward when the PV-BES is operating on grid-tie. By controlling atf ₀ Frequency deviation superimposed on

fThe photovoltaic power can be completely output to the power grid when the photovoltaic power is sufficient, or the power can be absorbed from the power grid to meet the local load or charge the energy storage system when the photovoltaic power is insufficient.

In a preferred embodiment, a voltage dead band(s) is/are added to the DC voltage deviation u _dz ) When the system runs off the grid, the energy storage system works in a constant direct current bus voltage mode, secondary adjustment of the frequency does not work at the moment, only when the energy storage exits the constant voltage mode after grid connection, the direct current voltage deviation can exceed the dead zone range, and the secondary adjustment of the frequency can work at the moment. Thereby ensuring that the system is on-grid and off-gridThere is no need to switch control strategies.

When the system is in grid-connected operation, the output power of the ESS meets the primary frequency modulation and inertia requirements of the VSG strategy under the control of power, and in addition, the output power of the ESS is smaller than the maximum power of the ESS.

The following detailed description of the embodiments of the present invention and the working principle thereof will be made with reference to the accompanying drawings.

Fig. 2A shows a classical compact optical storage and power generation system to which an embodiment of the present invention is applied. Generally, when the system is in a grid-connected operation state, the photovoltaic mainly works in a Maximum Power Point Tracking (MPPT) mode. When the photovoltaic power is excessive (the photovoltaic power is larger than the local load) or insufficient (the photovoltaic power is smaller than the local load), the system can transmit or absorb power to or from the power grid. As shown in fig. 2B, in the grid-connected operation state, the power of the energy storage system is controlled by an Energy Management System (EMS), and in addition, the power of the energy storage system also needs to meet the requirement of the power quality standard, so as to provide primary frequency modulation and inertia support for the power grid.

The traditional control strategy of the optical storage system adopts a VF source type control strategy in an off-grid state, adopts a current control strategy in a grid-connected state, and needs to be switched among the strategies when the off-grid and the grid-connected conversion is carried out. If the system adopts the VF source type control mode under the conditions of off-grid and on-grid, the switching time between the traditional strategy modes can be saved, and the reliability of system power supply can be greatly improved.

The control structure of a VF source VSG is shown in fig. 2C. When the system runs off-grid, the voltage of the microgrid can be guaranteed to be stabilized at the rated voltage by adopting the control strategy, and the frequency of the microgrid is stabilized within the range of the rated frequency. WhereinDIs the damping coefficient of the VSG and,Jis the inertia coefficient of the VSG.

For the presynchronization component, the component is not 0 only during presynchronization, but is 0 when the system is incorporated into a grid or operates in an island.f-P droop control introduction

As frequency feedback, in comparison with

As frequency feedback, the method has the advantage of avoiding presynchronization process

The influence of the component. Parameter(s)P _N AndQ _N the active power and the reactive power of rated load in the system.

In practice, when the system is operated off-grid, the power supply quality of the system meets the requirement of the power quality standard. In one embodiment, the parameter is selected to be a frequency offset f _N

In the range of 0.5Hz and the supply voltage isU _N

Within the range of 7%. In one embodiment, the droop characteristic of the VF source is as shown in FIG. 3, with the frequency at the intersection of the f-P droop characteristic and the f-axisf ₀ (same as in the figure)f _max ) And the voltage at the intersection of the Q-U droop characteristic and the U axisU ₀ (same as in the figure)U _max ) Comprises the following steps:

sag factor of P-f sag characteristic curvek _f And droop coefficient of Q-U droop characteristick _u The following formula is satisfied:

wherein f is _N And U _N Respectively the rated frequency and the rated voltage of the inverter,P _N andQ _N the active power and the reactive power of rated loads in the optical storage power generation system.

Under the grid-connected state of the system, the working condition that the energy storage system exits the working mode of constant direct-current bus voltage exists. Because at this time, the system controls the SOC level of the energy storage system according to the EMS. For example, when the SOC reaches a predetermined level, the energy storage system may be taken out of operation or enter a butyl power mode to reduce losses. When the system is incorporated into a power grid, the system mainly aims to send redundant electric energy generated by photovoltaic into the power grid, or obtain energy from the power grid to meet local load or charge an energy storage system when the photovoltaic power is insufficient. Therefore, the control strategies of active power and reactive power can be divided from different control purposes.

When grid connection is carried out, the system needs to adjust the output power of the system to send the output power into the power grid or absorb power from the power grid. According to the f-P droop characteristic curve, the power output by the system can be adjusted by adjusting the position of the primary frequency modulation curve. As shown in fig. 4, point a is a grid-connected point, and at point a, the voltage, the phase angle and the frequency are consistent, so that the system grid connection without impact can be completed.

After the grid connection, no active power flows between the system and the power grid. At this moment, if the active power is required to be transmitted to or absorbed from the power grid, the active power can be transmitted to or absorbed from the power gridf ₀ Is superposed with one

fThe primary frequency modulation curve of the system is equivalent to moving

f（

fIf the current is positive, the current moves upwards;

fnegative, moving down). Thus, the primary frequency modulation curve and the power grid frequency of the systemf _g (i.e. the intersection point of)The operating point of the system) is changed from point a to point B. When the system operates at the point B, more transmission is carried out to the power grid compared with the point A

PActive power or absorption from the grid

PThe active power of which has a value of

P =k _f ×

f。

The excess photovoltaic power is transmitted to the power grid or absorbed from the power grid to satisfy the load or energy storage power supplyf ₀ Frequency deviation superimposed on

fThe following formula:

wherein the content of the first and second substances,u _dc a dc voltage representing the dc side of the inverter; u _dc,N Indicating the DC rated voltage of the DC side of the inverter;k _dc,f the proportionality coefficient between frequency and voltage in the frequency quadratic adjustment is shown.

When the system is in a grid-connected state, when the energy storage system works in a working mode of constant direct-current bus voltage, the system voltage is constant at a rated voltage, and according to the formula, secondary adjustment of the frequency does not work. The deviation of the DC voltage can occur only when the energy storage system goes out of the working mode of constant DC bus voltage after grid connection: (u _dc -u _dc,N Not equal to 0) the second adjustment of the frequency is effected.

In order to ensure that the system does not need to switch the control strategy during grid connection and grid disconnection, the method is as above

fThe voltage deviation in the formula adds a dead zone as follows:

whereinU _dz The voltage dead zone is a value, such as 20V, according to the actual situation. This is to consider that the dc side voltage of the system will change slightly during off-grid switching. When the system runs off the grid, the energy storage system works in a working mode of constant direct current bus voltage, and the system voltage is constant at the rated voltage at the moment. The second adjustment of the frequency does not work at this time according to the above formula. When the system is changed from off-grid to grid-connected, the direct-current voltage deviation of the system cannot exceed the dead zone range, and the secondary adjustment of the frequency does not work; only when the energy storage system exits the working mode of constant direct current bus voltage after grid connection, the direct current voltage deviation can exceed the dead zone range, and the secondary adjustment of the frequency can play a role.

The VSG output power is adjusted according to the above equation, and in fact the control is a differential regulation. Under this strategic control, the dc voltage will be at different levels at different times. By passingk _dc,f The value of (a) ensures that the direct-current voltage cannot exceed the maximum value (such as a collecting device, a direct-current capacitor, a power tube, a protection device and the like) borne by hardware (related to the direct-current voltage)u _dc,max ) The values are as follows:

wherein the content of the first and second substances,P _max the maximum output power of photovoltaic plus stored energy. The result calculated by the above formula isk _dc,f The minimum value of the values.

From the point of view of grid loss, it is more desirable for the grid to reduce the unnecessary flow of reactive power within the grid. Therefore, after the system is merged into the power grid, the strategy ensures that the reactive power on the connecting line of the system and the power grid is 0. Therefore, the reactive power control target after grid connection is as follows:

whereinQ _g The reactive power exchanged by the system and the power grid. At the same time, the reactive power output by the inverter must be within its rated capacity, soQ _VSG Must be smaller thanQ _limit ，Q _limit The calculation formula of (a) is as follows:

wherein the content of the first and second substances,Q _VSG representing the reactive power output by the inverter/virtual synchronous machine, S representing the capacity of the inverter,P _VSG representing the active power output by the virtual synchronous machine.

When the system is in grid-connected operation, the output power of the ESS meets the requirements of primary frequency modulation and inertia of a VSG strategy, and the output power is as follows:

Wherein, P _st Representing the output power, k, of the energy storage system _f Droop coefficient, k, representing the P-f droop characteristic _H Representing coefficient of inertia, f _g Representing the grid frequency, f _N Which is indicative of the rated frequency of the inverter,

P _st1 the requirement for a primary frequency modulation is indicated,

P _st2 representing the inertia requirement.

There is also a condition in addition to: the output power of the ESS should be less than its maximum power.

In order to verify the stability of the method and the system provided by the invention, a simulation model is built in Matlab-Simulink according to the graph shown in FIGS. 2A to 2C.

TABLE 1 detailed parameters of PV-BES System

Control parameters for the methods set forth in Table 2

The rated active power of the local load of the system in the simulation model is 10kW, and the reactive power is 2 kVar. The maximum power of the energy storage battery is 10kW, and the discharge power is 15 kW. The maximum possible power of the photovoltaic panel is 15kW, so the maximum possible active power output by the inverter is 30kW and the maximum possible active power absorbed is 10 kW. The normal working range of the DC voltage is selected to be 700-900V, so that the power and the range of the DC voltage can be calculatedk _dc,f The value of (D) is 0.025. Wherein the detailed parameters of the PV-BES system are shown in table 1 and the parameters of the proposed strategy are shown in table 2.

In order to verify the correctness of the method, the grid connection process of the system is verified by simulation. And respectively setting working conditions such as load or power demand change, photovoltaic maximum available power change and the like aiming at different processes. Specific simulation analysis is given below.

In the grid connection process, power is mainly transmitted to a power grid or energy storage batteries in an energy storage system are mainly charged, and two working conditions are set to verify a grid connection strategy.

Working condition 1: the temperature of the illumination of the photovoltaic is constant, i.e. the maximum power of the photovoltaic is constant. And when the system is incorporated into a power grid in 1s, and the energy storage battery stops running after grid connection. Local load active power of 0-2s time systemThe rate and the reactive power are respectively 5kW and 1kVar, and local loads with power of 5kW and 1kVar are input again at 2s, so that the local loads are 10kW and 2kVar at 2-3 s. The simulation result under this condition is shown in fig. 5, where (a) in fig. 5 shows the variation of the output power of the photovoltaic and energy storage system (i.e., energy storage battery), where the power of the stored energy is set to emit positive and absorb negative. FIG. 5 (b) shows the secondary adjustment of the DC voltage and frequency of the inverter

fAnd (d) in fig. 5 shows the active and reactive power output by the VSG and the active and reactive power exchanged between the system and the grid.

As can be seen from (a) in fig. 5, the photovoltaic output in this condition is always 13.2 kW. The energy storage system absorbs about 8.2kW of power in the first 1s, and the power of the energy storage system is adjusted to 0 after grid connection. Under the working condition, after the grid connection, the energy storage system is withdrawn, so that the input power of the inverter is greater than the output power, and the direct-current voltage of the inverter can be continuously increased. As can be seen from (b) in fig. 5, the direct voltage exceeds the voltage dead zone (i.e., 800V) at about 1.06s,

fAnd begins to vary with voltage. Finally, when the DC voltage reaches 832.8V,

fWhen the voltage reaches 0.82, the system is stable, and the power of the alternating current side and the direct current side of the inverter is balanced. As can be seen from (c) in fig. 5, the output power of the inverter after grid connection is the output power of the photovoltaic, so the output power of the VSG is almost unchanged. The local load is 5kW and 1kVar at 1-2s, so the system transmits power to the power grid by about 8kW after the voltage is stabilized. The local load is 10kW and 2kVar at 2-3s, so the system outputs power to the power grid from 8kW to 3 kW. Since the objective of the reactive control strategy is to minimize the reactive exchange between the grid and the system, it can be seen from (d) in fig. 5 that the VSG changes when the local reactive load changesThe output reactive power of (1) is changed from 1kVar to 2kVar, and the reactive power output by the system to the power grid is always 0.

Working condition 2: the local load is constant all the time, and the active power and the reactive power are 5kW and 1kVar respectively. And when the system is incorporated into a power grid at 1s, and the energy storage battery is charged with the maximum power after grid connection. At 2-4s, the illumination is from 800W/m ² Gradually become 100W/m ² . The simulation result under this condition is shown in fig. 6, where (a) in fig. 6 shows the variation of the output power of the photovoltaic and energy storage system (i.e., energy storage battery), where the power of the stored energy is set to emit positive and absorb negative. FIG. 6 (b) shows the secondary adjustment of the DC voltage and frequency of the inverter

fAnd (c) in fig. 6 and (d) in fig. 6 show the active and reactive power output by the VSG and the active and reactive power exchanged between the system and the grid.

As can be seen from (a) in fig. 6, the initial photovoltaic output in this condition is about 8.16 kW. The photovoltaic power gradually decreases at 2-4s, and decreases to about 0.92kW at 4 s. The energy storage system absorbs about-3.24 kW of power in the first 1s, and the energy storage system is charged with 10kW of power after grid connection. After grid connection, the energy storage system is charged with the maximum power, so that the input power of the inverter is insufficient, and the direct-current voltage of the inverter is continuously reduced. As can be seen from (b) in fig. 6, the direct voltage exceeds the voltage dead zone (i.e., 760V) at about 1.06s,

fand begins to vary with voltage. The DC voltage reaches 732.5V at about 1.2s,

f reaches-0.69, and the power of the alternating current side and the direct current side of the inverter is basically balanced. After 4s of back illumination reaches 100W/m 2, the photovoltaic output power does not drop any more. At this time, the DC voltage reaches 703.4V,

fThe power on the ac and dc sides of the inverter reaches a new point of equilibrium, reaching-1.415. It can be seen from (c) in fig. 6 that the local load is always 5kW, 1kVar between 0 and 5s, and the output power of the system to the grid is always 5kW lower than the output power of the VSG. After about 1.2s of voltage stabilization, the system delivers about-6.9 kW of power to the grid. At 4s the illumination is no longer changing and the system finally delivers about-14.1 kW to the grid. It can be seen from (d) in fig. 6 that the reactive power output by the system to the grid is always 0.

The simulation experiment result verifies the correctness of the method, and the method can meet the actual requirements aiming at different processes, various set load or power demand changes, photovoltaic maximum available power changes and other working conditions.

The embodiment of the present invention further provides another control method for an optical storage power generation system, which is applied to an optical storage power generation system based on a VF source type virtual synchronous machine and working in an off-network state, as shown in fig. 7, the method includes the following steps:

step S1, acquiring photovoltaic output power and load power of the light storage power generation system;

step S2, judging whether the photovoltaic output power is larger than the load power;

step S3, when the photovoltaic output power is smaller than the load power, setting a voltage component according to the DC voltage deviation of the light storage power generation system;

step S4, superimposing the voltage component on a voltage loop, adjusting the output power of the light storage power generation system, and enabling the output power to be matched with the load power;

and step S5, when the photovoltaic output power is greater than or equal to the load power, if the state of charge of the energy storage battery reaches a limit value or the energy storage system cannot work normally, converting the photovoltaic working mode into a variable power tracking mode, and changing the photovoltaic output power by adjusting the photovoltaic working voltage to realize the balance between the photovoltaic output power and the load power, wherein the variable power tracking aims at that the power of the energy storage battery is 0 or the energy storage battery discharges with set power.

The limit value in the invention refers to a charging limit value, namely when the SOC of the energy storage battery exceeds the charging limit value, the optical storage power generation system does not charge the energy storage battery any more.

There are generally two cases when the system is disconnected from the grid. One is normal grid disconnection or planned grid disconnection, under the condition, the system starts the energy storage device and works in a constant voltage state, and then the system is disconnected from the power grid to realize the grid disconnection. Another situation is unplanned off-grid, in which the grid often fails, and the system is removed from the grid after anti-islanding protection is triggered. Under such conditions, the energy storage device may not be started in time, which results in the system being disconnected from the grid and an imbalance in power within the system, which results in a rapid rise or fall in the dc voltage. In addition, there may be over-discharge or overshoot of stored energy when the system is in an off-grid operating state. When the stored energy cannot keep the DC bus voltage constant, the DC voltage is too high or too low if the load fluctuation occurs.

When the photovoltaic output power is insufficient, the photovoltaic system and the energy storage system cannot provide enough energy, the output voltage of the VSG can influence the load power under the off-grid working condition, and a voltage component is superposed on a voltage loop

By adjusting the voltage component

The output voltage may be adjusted to achieve a match or match of the output power with the load power.

In some preferred embodiments, the virtual synchronous machine-based optical storage power generation system operates in an off-grid state by superimposing a voltage component proportional to the dc voltage deviation on the voltage loop when the photovoltaic output power is less than the load power

And U, the voltage component is adjusted to realize the consistency of the output power and the load power.Meanwhile, the coordination of photovoltaic power, load and energy storage power is realized through a photovoltaic variable power tracking strategy, wherein the system is directed at the state of charge of the energy storage battery if the system works in an off-grid stateSOC(t) Rise to the limitSOC _max The control strategy of the photovoltaic is improved. When state of charge of stored energySOC(t) Rise to the limitSOC _max When the SOC is too high, the two conditions can be divided according to the photovoltaic power: 1) when the photovoltaic power is less than the load power, the energy storage battery begins to dischargeSOC(t) Will gradually decrease. 2) When the photovoltaic power is greater than the load power, the photovoltaic working mode is converted into a variable power tracking mode, and the target of variable power tracking is that the power of the energy storage battery is 0 or the energy storage battery discharges with a specific power. According to the method, the output power of the photovoltaic is actively reduced through a variable power tracking technology, wherein a control block diagram of a variable power tracking strategy is shown in fig. 8, and the target power is tracked by adjusting the working voltage of the PV according to the comparison between the current power of the photovoltaic and the target power and the information of the current photovoltaic working point. In the invention, the photovoltaic working point refers to a position on a photovoltaic characteristic curve corresponding to the current photovoltaic output voltage power.

In addition, the embodiment of the invention provides an improved PV-BES off-grid control strategy aiming at the possible problem when the system is converted from grid connection to off-grid state, so as to solve the problem of unbalanced system power under the condition that the stored energy can not work normally when the system is off-grid. The problem can be still researched in two conditions, namely when the illumination is sufficient and when the illumination is insufficient, the two working conditions that the photovoltaic power is greater than the load power and the photovoltaic power is less than the load power are also corresponding to each other.

Under the condition of sufficient illumination, the photovoltaic power is greater than the load power under the working condition, and the system is at the risk of overhigh direct-current voltage. Because the system has no power shortage under the working condition, the stability of the direct-current voltage can be ensured only by relying on a strategy. And adjusting the output power of the photovoltaic by adjusting the working voltage of the PV according to the photovoltaic characteristic curve. The photovoltaic has two operating regions on both the left and right sides of the Maximum Power Point (MPP). When photovoltaic output powerP _pv Increased photovoltaic voltageU _pv PV curve d of the region to the left of MPP, which decreasesP _pv /dU _pv Above 0, the PV voltage drop will result in a further drop in PV power. This creates a positive feedback between the PV power and the PV voltage, and the system must have a device (energy storage or inverter) that uses a constant dc voltage strategy to operate the PV to the left of the MPP. And PV curve d of the area to the right of MPP P _pv /dU _pv Less than 0, therefore when PV works in MPP right side, whether have the device work in invariable direct current busbar voltage mode can guarantee the system stability all the time. Because the energy storage under the working condition can not ensure the voltage stability of the direct current bus, the PV in the embodiment of the invention can only work on the right side of the MPP.

The embodiment of the invention provides three control strategies, namely three variable power tracking modes; the principles of the three control strategies are shown in fig. 9 (a) to 9 (c).

Strategy 1: and a PI controller is adopted to directly adjust the duty ratio D of the Boost circuit according to the deviation of the direct-current voltage. The method changes the photovoltaic voltage by adjusting D, and has the advantages of simple control structure and clear target. But due to the existence of direct current capacitance, the dynamic response process of the strategy is slow and the recovery time is long. In addition, when the unbalanced power between the photovoltaic and the load is too large, the photovoltaic voltage is close to the open-circuit voltage of the photovoltaic panel, and d is near the open-circuit voltage of the photovoltaic panelP _pv /dU _pv This too large will affect the stability of the system.

Strategy 2: the strategy is proposed based on a Maximum Power Point Tracking (MPPT) strategy. And judging the direct current voltage on the basis of the MPPT strategy, and increasing the photovoltaic voltage when the direct current voltage is higher than the target voltage. Executing MPPT strategy when the DC voltage is lower than the target voltage according to the current working point

P _pv /

u _pv Judging whether the photovoltaic voltage is increased or decreased; wherein the content of the first and second substances,

P _pv representing the difference in photovoltaic output power before and after the disturbance,

u _pv representing the difference in photovoltaic voltage before and after the perturbation,

P _pv and

u _pv can be used to infer the current operating position of the photovoltaic.

P _pv And

u _pv the expression of (a) is as follows:

and the strategy adopts the DC voltage deviation to adjust the tracking step lengthu _step The following formula is shown in the specification,

wherein the content of the first and second substances,u _step in order to track the step size,u _dc （k) Is a reference value of the direct-current voltage,u _dc,ref in order to be the target voltage, the voltage of the power supply,P _pv in order to output the power for the photovoltaic system,P _VSG in order for the virtual synchronous machine to output power,k ₁ andk ₂ is to set a coefficient, alpha is a step changeThe long factor can achieve better tracking effect by adjusting the numerical value of the long factor. The strategy also incorporates a judgment on the PV output current to prevent the output current of the PV from being too small. Since a smaller output current of the photovoltaic indicates a closer PV operating point to the PV open point, there is a risk that the photovoltaic voltage approaches the open circuit voltage when the PV operating point is too close to the open circuit point of the photovoltaic panel.

The strategy has the advantages that the PV can be accurately controlled to work in the area on the right side of the MPP, and the condition that the photovoltaic voltage is close to the open-circuit voltage is avoided. But the strategy still has the problem of slow dynamic response. As shown in FIG. 10 (a), the

strategies

1 and 2 are essentially based on

u _dc To adjust the photovoltaic power when

u _dc <Increase photovoltaic power when 0

u _dc >And (4) cutting the photovoltaic power at 0.

Strategies

1 and 2 take into account dc voltage deviations but do not take into account the rate of change of the dc voltage, which results in strategies that do not allow for fast and accurate control of the dc voltage.

Strategy 3: as shown in fig. 9(c), the strategy is improved on the basis of the strategy 2. The change rate of the direct-current voltage deviation is added into the judgment condition, and the judgment condition is as follows:

the region corresponding to the above formula in fig. 10 (b) is the region below the straight line in the figure, and the region corresponding to the above formula when the formula is less than 0 is the region above the straight line in fig. 10 (b). Wherein the slope of the two region dividing lines is-k。

When the above formula is satisfied, the photovoltaic power should be increased, and the photovoltaic voltage is increased according to the characteristics of the curve on the right side of the MPPThe power is cut down. Executing MPPT strategy when the above formula is not satisfied, according to the current working point

P _pv /

u _pv The information is used to select whether to increase the photovoltaic voltage or decrease the photovoltaic voltage. In addition, the modified variable step formula is as follows:

wherein the content of the first and second substances,k ₃ andkit is to set the coefficients of the coefficients,

in order to be able to measure the dc voltage deviation,u _step in order to track the step size of the step, P _pv in order to output the power for the photovoltaic system,P _VSG in order to output the power for the VSG,β ₁ andβ ₂ respectively, are the acceleration factors for the different terms, S(k) Is a switching function only when the photovoltaic power and VSG power deviation is greater thanThr2 and PV operating Point to the right of MPPS(k) Is 1 and is 0 otherwise. The variable step formula not only considers the direct-current voltage deviation and the direct-current voltage change rate, but also considers the deviation between the VSG output power and the photovoltaic power.

Wherein, executing the MPPT strategy specifically includes: judging the current operating point

P _pv /

u _pv If not, according to the tracking step lengthu _step Reducing the photovoltaic voltage, otherwise according to the tracking step lengthu _step Increasing photovoltaic voltage。

Wherein when the change rate of the DC voltage deviation satisfies

During, according to the characteristic increase photovoltaic voltage of maximum power point MPP right side curve, specifically include: judgment of i _pv Whether or not greater thanThr1If yes, according to the tracking step lengthu _step Increasing the photovoltaic voltage; otherwise, judging the current working point

P _pv /

u _pv If the tracking step length is larger than 0, the tracking step length is determinedu _step Increasing photovoltaic voltage, otherwise according to tracking step lengthu _step Reducing the photovoltaic voltage; wherein i _pv Which is representative of the photovoltaic output current,Thr1is the set current limit. When i is _pv When the photovoltaic operation point is too small, the photovoltaic operation point is close to the rightmost vertex of the P-U curve, and d is positioned at the rightmost vertexP _pv /dU _pv Excessive values can cause power oscillations by setting current limitsThr1Can limit i _pv Not too small.

In FIG. 9(c), u _pv Representing the actual photovoltaic voltage u _pv,ref A reference value representing the DC voltage, which can be based on the reference value u _pv,ref To control the photovoltaic voltage u _pv Changing the reference value u _pv,ref Regulating photovoltaic voltage u _pv The reference value is tracked and at steady state both are substantially the same.

The strategy has the advantages that the condition that the photovoltaic voltage is close to the open-circuit voltage can be avoided, the direct-current voltage can be rapidly stabilized, and the dynamic response speed of the direct-current voltage is greatly improved compared with the

strategies

1 and 2.

And under the condition of insufficient illumination, the photovoltaic power is smaller than the load power under the working condition, and the system cannot provide enough energy. At this time, the load can only be maintained without power failure as much as possible, and the energy storage is added to provide energy support for the load. Therefore, the system can be ensured not to be disconnected, the power supply voltage can be quickly recovered after the energy storage is put into use, and the reliability of the system power supply can be effectively improved.

Consider that the load power of a system operating off-grid is voltage dependent (even the actual power of a resistive load is often dependent on the voltage across the load). Therefore, under the off-grid operation condition, the VSG output power can be adjusted by reducing the output voltage, so that the output power and the load power are well matched. In the embodiment of the invention, one voltage loop is superposed on the voltage loop

UThe control structure of the component, which is proportional to the dc voltage deviation, is shown in fig. 11. The voltage component

UThe value is 0 when the system is connected to the grid, and the value exists only when the system is operated off the grid.

In order to avoid the influence of load switching and energy storage power controller overshoot on the strategy when the system is off-grid, the embodiment of the invention adds a voltage dead zone (in the DC voltage deviation)u _dz ) When the DC voltage deviation exceeds the dead zone control range, the secondary adjustment of the frequency is effected, and the secondary adjustment of the frequency is effected, the voltage component

The formula for U is:

wherein the content of the first and second substances,u _dz in order to provide a voltage dead zone,u _dc is a voltage on the direct-current side,u _dc,N is a reference voltage on the direct-current side,k _dc,u adjusting the coefficient for the DC side voltage

In some embodiments, the energy storage system operates in a constant direct current voltage mode in an off-grid operating state to ensure the linearity of the photovoltaic energy storage and generation system PV-BESThe current voltage is maintained at a rated level, and the output power is maintainedP _st The following formula:

，

wherein the content of the first and second substances,k _p,dc andk _i,dc for the PI regulator parameters, 1/s represents the frequency domain integration segment,u _dc is the voltage of the direct current side,u _dc,N is a dc side reference voltage.

In order to verify the stability of the method and the system provided by the embodiment of the invention, a simulation model built in Matlab-Simulink is shown in fig. 2A to 2C.

TABLE 3 detailed parameters of PV-BES System

Control parameters for the methods set forth in Table 4

The rated active power of the local load of the system in the simulation model is 10kW, and the reactive power is 2 kVar. The maximum power of the energy storage cell is 10kW, while the discharge power is 15 kW. The maximum possible power of the photovoltaic panel is 15kW, so the maximum possible active power output by the inverter is 30kW and the maximum possible active power absorbed is 10 kW. The normal operating range of the selected DC voltage is 700-900V, wherein the detailed parameters of the PV-BES system are shown in Table 3, and the parameters of the proposed strategy are shown in Table 4.

In order to verify the correctness of the method provided by the embodiment of the invention, the process of system off-network is verified by utilizing simulation. And respectively setting working conditions such as load or power demand change, photovoltaic maximum available power change and the like aiming at different processes. Specific simulation analysis is given below.

The unplanned off-grid process mainly ensures stable power supply of the system, or under the condition that stable power supply cannot be ensured, the system is ensured not to collapse to wait for new power supply to be put into operation. And setting two working conditions according to the illumination conditions for the unplanned off-grid condition to verify the off-grid strategy.

And (3) under the working condition of sufficient illumination: the local load is constant all the time, and the active power and the reactive power are 5kW and 1kVar respectively. And unplanned off-grid occurs at 1s, and the system is changed from grid-connected state to off-grid operation state. The illumination is always 1000W/m under the working condition ² The output of the photovoltaic is about 10.2kW under the illumination, and the stored energy is always in a non-working state. For this condition, fig. 12 shows the response process of the system output power and voltage under the control of three different control strategies. Wherein (a) and (d) of fig. 12 are response processes of the PV power and the inverter dc voltage of the system under the control of the strategy 1. Similarly, (b) and (e) of fig. 12 are response procedures under the control of the policy 2, and (c) and (f) of fig. 12 are response procedures under the control of the policy 3. Fig. 12 (g) and (h) show the VSG and the active and reactive changes between the system and the grid, respectively, under this operating condition.

Under the working condition, the power of the stored energy is always 0, so that the output power of the grid-connected system is 10.2kW of photovoltaic power. When the VSG is disconnected from the power grid, the output power of the VSG is changed into load power, namely 5 kW. At this time, the output power of the PV is still 10.2kW, so the dc voltage of the inverter rapidly increases. Comparing the response processes of the system under the control of the three strategies, it can be seen that the dynamic response process under the control of the strategy 3 considering the voltage change rate is the best. As can be seen from (a) of fig. 12, the strategy 1 does not consider the PV characteristics, so the power of the PV oscillates when the voltage of the PV approaches the open circuit voltage. While

strategies

2 and 3, which take PV characteristics into account, are controlled to avoid this problem. Comparing (d), (e) and (f) of fig. 12, it can be seen that the dc voltage is increased to different degrees under the control of the three strategies. The direct current voltage under the control of the strategy 1 exceeds 9.55V, the direct current voltage under the control of the strategy 2 exceeds 17.95V, and the direct current voltage under the control of the strategy 3 only exceeds 4.95V. It can be seen that the effect of strategy 3 is the best of the three strategies, not only having a fast response speed but also having a short time required for stabilizing the dc voltage.

And (3) under the condition of insufficient illumination: the local load is constant all the time, and the active power and the reactive power are 10kW and 2kVar respectively. And unplanned off-grid occurs at 1s, and the system is changed from grid-connected state to off-grid operation state. The illumination is always 600W/m under the working condition ² The output of the photovoltaic is about 6.1kW under the illumination, and the stored energy is always in a non-working state. In order to compare the effectiveness of the proposed strategy, the proposed strategy and the situation under the control of no control strategy are respectively simulated aiming at the working condition. Under the strategy control provided by the embodiment of the invention, the simulation result of the working condition is shown in fig. 13. And under the condition of not adding the control strategy, the simulation result of the working condition is shown in FIG. 14. Fig. 13 and 14 (a) show the active and reactive power output by the VSG and the active and reactive power exchanged between the system and the grid. Fig. 13 and 14 (b) show the change of the inverter dc voltage. Fig. 13 and 14 (c) show the change of the voltage per unit of the ac side of the VSG, and the line voltage reference value of the voltage is 380V.

As can be seen from fig. 13, the system finally reaches a steady state under the control of the proposed strategy, and finally the dc voltage is maintained at 682.3V. As can be seen from (a) and (c) of fig. 13, the load power decreases as the ac voltage decreases. When the ac voltage is reduced to about 0.776, the load power and the photovoltaic power reach equilibrium, and the dc voltage no longer drops to a steady value.

Fig. 14 shows the simulation result of the non-controlled strategy, and it can be seen that the dc voltage of the inverter finally decreases to around 330V, which is lower than the lowest voltage at which the inverter can normally operate. Therefore, the ac side voltage and the output power of the inverter are oscillating in the end. Comparing the simulation results of fig. 13 and fig. 14, it can be seen that the control strategy provided by the embodiment of the present invention plays a role when the illumination is insufficient, and the expected target is achieved.

Embodiments of the present invention further provide a non-volatile computer-readable storage medium, in which an executable computer program is stored, and when the computer program is executed, the steps of the above-mentioned method embodiments can be implemented. Wherein the computer program comprises computer program code, which may be in the form of source code, object code, an executable file or some intermediate form, etc. The computer-readable storage medium may include at least: any entity or apparatus capable of carrying computer program code to a terminal device, recording medium, computer Memory, Read-Only Memory (ROM), Random Access Memory (RAM), electrical carrier wave signals, telecommunications signals, and software distribution medium. Such as a usb-disk, a removable hard disk, a magnetic or optical disk, etc.

The background of the present invention may contain background information related to the problem or environment of the present invention and does not necessarily describe the prior art. Accordingly, the inclusion in the background section is not an admission of prior art by the applicant.

The foregoing is a more detailed description of the invention in connection with specific/preferred embodiments and is not intended to limit the practice of the invention to those descriptions. It will be apparent to those skilled in the art that various substitutions and modifications can be made to the described embodiments without departing from the spirit of the invention, and these substitutions and modifications should be considered to fall within the scope of the invention. In the description of the present specification, reference to the description of "one embodiment," "some embodiments," "preferred embodiments," "example," "specific example," or "some examples" or the like means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Various embodiments or examples and features of various embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction. Although embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the scope of the claims.

Claims

1. A control method of a light storage power generation system is applied to the light storage power generation system based on a voltage frequency source type virtual synchronous machine and works in an off-grid state, and is characterized by comprising the following steps:

judging whether the photovoltaic output power is greater than the load power;

when the photovoltaic output power is greater than or equal to the load power, if the state of charge of the energy storage battery reaches a limit value or the energy storage system cannot work normally, the photovoltaic working mode is converted into a variable power tracking mode, the photovoltaic output power is changed by adjusting the photovoltaic working voltage, and the balance between the photovoltaic output power and the load power is realized, wherein the variable power tracking aims at that the power of the energy storage battery is 0 or the energy storage battery discharges with set power;

further comprising: setting a voltage dead zone for the direct current voltage deviation, wherein the expression of the voltage component is as follows:

Wherein the content of the first and second substances,

in order to be a component of the voltage,u _dz in order to provide a voltage dead zone,u _dc is the voltage of the direct current side,u _dc,N is a reference voltage on the direct-current side,k _dc,u for regulating the voltage at the DC sideAnd (4) the coefficient.

2. The light storage and power generation system control method of claim 1, wherein when the photovoltaic output power is greater than the load power, the following photovoltaic control strategy is implemented:

and a PI controller is adopted to adjust the duty ratio of a Boost circuit according to the DC voltage deviation so as to change the photovoltaic working voltage.

3. The light storage and power generation system control method of claim 1, wherein when the photovoltaic output power is greater than the load power, the following photovoltaic control strategy is implemented:

increasing the photovoltaic voltage when the dc voltage is above the target voltage; and executing a maximum power point tracking strategy when the direct-current voltage is lower than the target voltage, wherein in the executed maximum power point tracking strategy, a tracking step length is adjusted according to the direct-current voltage deviation, and the tracking step length expression is as follows:

wherein, the first and the second end of the pipe are connected with each other,u _step in order to track the step size,u _dc （k) Is a reference value of the direct-current voltage,u _dc,ref for the target voltage, alpha is a variable step factor,P _pv is the photovoltaic output power of the solar cell,P _VSG in order for the virtual synchronous machine to output power,k ₁ andk ₂ to set the coefficients.

4. The light storage and power generation system control method of claim 1, wherein when the photovoltaic output power is greater than the load power, the following photovoltaic control strategy is implemented:

When the change rate of the DC voltage deviation satisfies

According to the characteristics of the curve on the right side of the maximum power pointIncreasing photovoltaic voltage to reduce power;

otherwise, executing a maximum power point tracking strategy; in the executed maximum power point tracking strategy, the tracking step length is adjusted according to the direct current voltage deviation and the change rate thereof, and the tracking step length expression is as follows:

in order to be able to measure the dc voltage deviation,u _step in order to track the step size, P _pv in order to output the power for the photovoltaic system,P _VSG in order to output the power for the VSG,β ₁ andβ ₂ respectively, are the acceleration factors for the different terms,S(k) Is a switching function.

5. The light storage and power generation system control method according to claim 4, wherein the executing of the maximum power point tracking strategy specifically comprises: judging the current operating point

P _pv /

u _pv If not, according to the tracking step lengthu _step Reducing the photovoltaic voltage, otherwise according to the tracking step lengthu _step Increasing the photovoltaic voltage, wherein,

u _pv representing the difference in photovoltaic voltage before and after the perturbation.

6. The light-storing electricity generating system control method according to claim 4, wherein the dc voltage deviation has a rate of change satisfying

P _pv /

u _pv If the tracking step length is larger than 0, the tracking step length is determinedu _step Increasing photovoltaic voltage, otherwise according to tracking step lengthu _step Reducing the photovoltaic voltage; wherein i _pv Which is representative of the photovoltaic output current,Thr1is the set current limit value and is,

7. The method of claim 1, wherein the energy storage system operates in a constant dc voltage mode with output power during off-grid operationP _st The following formula:

8. A computer-readable storage medium storing a computer program, wherein the computer program, when executed by a processor, implements the light storage power generation system control method according to any one of claims 1 to 7.