CN103457514B - Dual-mode solar photovoltaic power generation system - Google Patents

Abstract

The dual-mode solar photovoltaic power generation system consists of four parts: distributed photovoltaic power generation subsystem, energy storage subsystem, load, and integrated management subsystem. In the present invention, the energy storage subsystem device is used as the energy buffer public platform, and the integrated management subsystem is used as the comprehensive management platform to implement a unified optimization goal of maximizing efficiency power generation, maximizing economic benefit operation, and safe demand response for distributed solar photovoltaic power generation .

Description

Dual-mode solar photovoltaic power generation system

technical field

The present invention relates to a dual-mode solar photovoltaic power generation system, in particular to a dual-mode solar photovoltaic power generation system mainly applied to distributed rooftop photovoltaic power stations built on buildings in cities, parks, communities, etc.

Background technique

Solar power generation, wind power generation, tidal power generation and other renewable energy power generation provide an alternative solution idea and method to solve the increasingly tense energy crisis and environmental pollution problems in human society. Taking solar photovoltaic power generation as an example, with the increasing installed capacity in the world in recent years, it is becoming an important technical means for the utilization of renewable energy.

Solar photovoltaic power generation can be simply divided into two ways, one is centralized solar photovoltaic power station, through the construction of large-scale solar photovoltaic power stations with a scale of tens of megawatts or even hundreds of megawatts in a concentrated and contiguous manner, solar energy is collected and converted into electrical energy , after the transmission and deployment of the large power grid, it is provided to users. Centralized solar photovoltaic power plants, due to the intermittent and unstable characteristics of solar power generation, often have a great impact on the power grid and adversely affect the security of the power grid; and the centralized energy production method still does not get rid of the limitations of traditional electric energy. The production and use mode leads to a large amount of irreversible loss of a large amount of precious electric energy in the process of multi-level conversion and long-distance transmission. There is also a decentralized solar photovoltaic power station, ranging in size from several megawatts to several kilowatts, and is generally built on the roof of a building or on the ground close to the user. Distributed solar photovoltaic power plants, close to the user side, do not require high-voltage differential conversion and transmission, the loss in the process is reduced, and the utilization efficiency of new energy is improved. However, since solar power generation is still intermittent and unstable, it may have a negative impact on the user's power quality; and it can be used immediately, and cannot respond to demand; when a grid failure occurs, the decentralized solar photovoltaic power station must also stop running, the goal of off-grid autonomy cannot be achieved.

In the existing technical solutions, the distributed solar photovoltaic power generation system is generally built into a distributed integrated system of solar photovoltaic power generation and energy storage by configuring the energy storage system to solve the problem of unstable new energy. problem, and can solve the problem of off-grid autonomy. However, due to the need to configure a large-scale energy storage system, the cost has increased.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the above-mentioned defects in the prior art and provide a dual-mode solar photovoltaic power generation system with high energy utilization rate and stable operation.

The technical solution adopted by the present invention to solve the technical problem is: a dual-mode solar photovoltaic power generation system, which consists of four parts: a distributed photovoltaic power generation subsystem, an energy storage subsystem, a load, and an integrated management subsystem;

The distributed photovoltaic power generation subsystem includes a solar cell array, a DC power distribution cabinet, and a photovoltaic inverter. The solar cell array is electrically connected to the DC power distribution cabinet, and the DC power distribution cabinet is electrically connected to the photovoltaic inverter through a switch K1. The inverter is electrically connected to the AC power distribution cabinet through the switch K2, and the AC power distribution cabinet is connected to the external mains power through the switch K0; the distributed photovoltaic power generation sub-system mainly realizes the conversion of solar energy into DC power and further conversion into AC power.

The load, as the energy-consuming part, includes a class I load that cannot interrupt power supply (such as emergency lighting) and a class II load that can interrupt power supply (such as an air conditioner). Connection, the AC power distribution cabinet is electrically connected to a type of load through switch K4 and switch K8;

The energy storage subsystem includes a battery stack and a bidirectional energy storage inverter, the battery stack is bidirectionally electrically connected to the bidirectional energy storage inverter through a switch K5, and the bidirectional energy storage inverter is bidirectionally electrically connected to the AC power distribution cabinet through a switch K6 ; The energy storage subsystem is used as a buffer platform for energy and power, which is used to store solar power, which is further fed to the grid for use through a bidirectional energy storage inverter. At the same time, a part of the electric energy is used as a backup. Released to provide emergency power supply to a class of loads.

The integrated management subsystem implements the management and control of the entire dual-mode solar photovoltaic power generation system, and the command system works in various modes to realize functions such as energy collection, production, conversion, emergency power supply, energy storage subsystem management, and stored energy release.

The integrated management subsystem includes a mains power monitoring module, a new energy monitoring module, a BMS monitoring module, a ladder electricity price database, a load monitoring module and a working mode decision-making module, a mains electricity monitoring module, a new energy monitoring module, a BMS monitoring module, and a ladder electricity price Both the database and the load monitoring module are electrically connected to the working mode decision-making module in two directions, the new energy monitoring module is electrically connected to the distributed photovoltaic power generation subsystem in two directions, the BMS monitoring module is electrically connected to the energy storage subsystem in two directions, and the load monitoring module is electrically connected to the load in two directions , the mains monitoring module is electrically connected to the AC power distribution cabinet in two directions.

The mains monitoring module mainly monitors information related to power quality such as voltage, current, power, and power factor of the mains. The BMS monitoring module mainly monitors the voltage, current, temperature, SOC (state of charge), SOH (state of health) and other information of the energy storage subsystem. The ladder electricity price database stores the current ladder electricity price data. The load monitoring module monitors the energy consumption of loads and realizes the removal of non-class loads in emergency situations. The new energy monitoring module mainly monitors the input voltage, input current, input power, output voltage, output current, output power, solar irradiance and other information of the distributed photovoltaic power generation subsystem.

The working modes determined by the working mode decision-making module include: photovoltaic grid-connected power generation mode, smooth working mode, photovoltaic peak shifting mode and off-grid autonomous mode.

The capacity of the energy storage subsystem is set to be: more than 2 times the emergency energy required by the first-class load, and less than 10 times the emergency energy required by the first-class load; The maximum value between the power and 1.2 times the maximum power of the photovoltaic power generation array is taken as the minimum power of the energy storage subsystem; the minimum value between the maximum power of 3 times the maximum power of the first-class load and 1.5 times the maximum power of the photovoltaic power generation array is taken , as the maximum power of the energy storage subsystem; since the power of the energy storage subsystem takes the maximum value between 1.5 times the maximum power of a first-class load and 1.2 times the maximum power of the photovoltaic power generation array, as the minimum power of the energy storage subsystem, Therefore, it can meet the demand of the energy storage subsystem for the power balance of solar photovoltaic power generation, and at the same time, it can meet the demand for the starting power of a type of load in emergency situations. The purpose of specifying the maximum power of the energy storage subsystem is to meet the requirements of cost input and economy. The capacity of the energy storage subsystem is between 2 times and 10 times the emergency energy required by the first-class load, that is, it can meet the needs of emergency power supply, and there is still a certain surplus capacity to meet the peak shifting demand of photovoltaic power generation. The cost of the energy storage subsystem Not too high, controlled within a reasonable range.

During non-peak hours of mains power, the SOC (state of charge) of the energy storage subsystem operates at a high level, and the SOC (state of charge) is controlled at 70% to 90%; when the price of mains power is high, the SOC (state of charge) of the energy storage subsystem is at a low level State-of-the-art operation, the optimal SOC (state of charge) is controlled at 20%~50%. At this time, the charge of the energy storage subsystem in the lowest SOC state is greater than 1.5 times the emergency energy required by the first-class load. Through the energy storage subsystem, the valley storage and peak discharge can minimize the use of peak electricity, and at the same time realize the maximum economic value of the energy of photovoltaic power generation.

During the period of time before sunrise and sunset, the sun's irradiance is low, and the power generated by the distributed photovoltaic power generation subsystem is generally less than 5% of the rated power of the photovoltaic inverter. At this time, the inverter efficiency of the photovoltaic inverter is low or even It cannot be started, and the power quality is also very poor. During this period, the photovoltaic power generation is directly stored in the energy storage subsystem, which improves the overall power generation efficiency of solar photovoltaic power generation.

Define the generating power of the distributed photovoltaic power generation sub-system at a certain moment as P1; define the load power at the same moment as P2; define the rated power of the photovoltaic inverter as P3, then the conditions that need to be met in various operating modes are described in turn as follows:

The conditions that must be met in the photovoltaic grid-connected power generation mode are: (1) the power generation P1/load power P2 of the distributed photovoltaic power generation subsystem is less than 0.2; (2) the electricity price is the peak price; (3) the city power is normal; ( 4) The power generation P1 of the distributed photovoltaic power generation subsystem/the rated power P3 of the photovoltaic inverter is greater than 0.05; the switch status in this mode: switch K0, switch K4, switch K5, switch K6, switch K7, switch K8, switch K1, The switch K2 is closed, and the switch K3 is opened;

The conditions that must be met in the smooth working mode are: (1) the power generation P1/load power P2 of the distributed photovoltaic power generation subsystem is greater than 0.2; (2) the electricity price is the peak electricity price; (3) the mains power is normal; (4) the distribution The power generation power P1 of the type photovoltaic power generation subsystem/the rated power P3 of the photovoltaic inverter is greater than 0.05; the switch state in this mode: switch K0, switch K4, switch K5, switch K6, switch K7, switch K8, switch K1, switch K2 are closed , the switch K3 is disconnected;

The conditions that must be met in the photovoltaic peak-shifting mode are: (1) the electricity price is the electricity price during off-peak hours or the power generation P1 of the distributed photovoltaic power generation subsystem/the rated power P3 of the photovoltaic inverter is less than 0.05; (2) the mains power is normal; Switch state in mode: switch K0, switch K5, switch K6, switch K8, switch K7, switch K4, switch K3 are closed, switch K1, switch K2 is open;

The conditions that must be met in the off-grid autonomous mode are: (1) The mains power is abnormal; the switch status in this mode: switch K4, switch K6, switch K8, switch K5, switch K3 are closed, switch K0, switch K1, switch K2 , The switch K7 is disconnected.

In the present invention, the energy storage subsystem device is used as the energy buffer public platform, and the integrated management subsystem is used as the comprehensive management platform to implement the unified optimization goal of maximizing efficiency power generation, maximizing economic benefit operation, and safe demand response for distributed solar photovoltaic power generation .

Compared with the prior art, the dual-mode solar photovoltaic power generation system of the present invention has the following advantages: (1) Based on the energy buffering and power buffering functions of the energy storage subsystem, the distributed photovoltaic power generation subsystem is smoothly connected and paralleled. (2) Based on the energy buffer and power buffer public platform of the energy storage subsystem, as well as the management and coordination of the whole system, the off-grid autonomous operation of the distributed photovoltaic power generation subsystem is realized to meet the emergency needs; (3) through the use of weak Photovoltaic power generation improves the overall efficiency of distributed photovoltaic power generation and increases the amount of photovoltaic power generation; (4) By transferring part of the power generated by solar energy to use during peak hours, the economic benefits of distributed photovoltaic power generation are improved and the economy is improved.

Description of drawings

Fig. 1 is a structural block diagram of a dual-mode solar photovoltaic power generation system according to an embodiment of the present invention;

Fig. 2 is a block diagram of the operation decision-making of the dual-mode solar photovoltaic power generation system according to the embodiment of the present invention.

Detailed ways

The implementation method of the present invention will be described in detail below in conjunction with the accompanying drawings.

Referring to Figure 1, the present invention consists of four parts: distributed photovoltaic power generation subsystem, energy storage subsystem, load, and integrated management subsystem.

The distributed photovoltaic power generation subsystem includes a solar cell array, a DC power distribution cabinet, and a photovoltaic inverter. The solar cell array is electrically connected to the DC power distribution cabinet, and the DC power distribution cabinet is electrically connected to the photovoltaic inverter through a switch K1. The inverter is electrically connected to the AC power distribution cabinet through the switch K2, and the AC power distribution cabinet is connected to the external mains power through the switch K0; the distributed photovoltaic power generation sub-system mainly realizes the conversion of solar energy into DC power and further conversion into AC power.

The load, as the energy-consuming part, is divided into a type of load that cannot interrupt power supply (such as emergency lighting) and a type II load that can interrupt power supply (such as an air conditioner). The AC power distribution cabinet communicates with the type II load through switch K4 and switch K7. Electrically connected, the AC power distribution cabinet is electrically connected to a type of load through switch K4 and switch K8;

The energy storage subsystem includes a battery stack and a bidirectional energy storage inverter, the battery stack is bidirectionally electrically connected to the bidirectional energy storage inverter through a switch K5, and the bidirectional energy storage inverter is bidirectionally electrically connected to the AC power distribution cabinet through a switch K6 ; As a buffer platform for energy and power, the energy storage subsystem can store solar power, and can also be further fed to the grid for use through a bidirectional energy storage inverter. At the same time, a part of the electric energy is used as a backup. , released to provide emergency power supply to a class of loads.

The integrated management subsystem implements the management and control of the entire dual-mode solar photovoltaic power generation system, and the command system works in various modes to realize functions such as energy collection, production, conversion, emergency power supply, energy storage subsystem management, and stored energy release.

The integrated management subsystem includes a mains power monitoring module, a new energy monitoring module, a BMS monitoring module, a ladder electricity price database, a load monitoring module and a working mode decision-making module, a mains electricity monitoring module, a new energy monitoring module, a BMS monitoring module, and a ladder electricity price Both the database and the load monitoring module are electrically connected to the working mode decision-making module in two directions, the new energy monitoring module is electrically connected to the distributed photovoltaic power generation subsystem in two directions, the BMS monitoring module is electrically connected to the energy storage subsystem in two directions, and the load monitoring module is electrically connected to the load in two directions , the mains monitoring module is electrically connected to the AC power distribution cabinet in two directions.

The mains monitoring module mainly monitors information related to power quality such as voltage, current, power, and power factor of the mains. The BMS monitoring module mainly monitors the voltage, current, temperature, SOC (state of charge), SOH (state of health) and other information of the energy storage subsystem. The ladder electricity price database stores the current ladder electricity price data. The load monitoring module monitors the energy consumption of loads and realizes the removal of non-class loads in emergency situations. The new energy monitoring module mainly monitors the input voltage, input current, input power, output voltage, output current, output power, solar irradiance and other information of the distributed photovoltaic power generation subsystem.

The capacity of the energy storage subsystem is set to be: more than 2 times the emergency energy required by the first-class load, and less than 10 times the emergency energy required by the first-class load; The maximum value between the power and 1.2 times the maximum power of the photovoltaic power generation array is taken as the minimum power of the energy storage subsystem; the minimum value between the maximum power of 3 times the maximum power of the first-class load and 1.5 times the maximum power of the photovoltaic power generation array is taken , as the maximum power of the energy storage subsystem; since the power of the energy storage subsystem takes the maximum value between 1.5 times the maximum power of a first-class load and 1.2 times the maximum power of the photovoltaic power generation array, as the minimum power of the energy storage subsystem, Therefore, it can meet the demand of the energy storage subsystem for the power balance of solar photovoltaic power generation, and at the same time, it can meet the demand for the starting power of a type of load in emergency situations. The purpose of specifying the maximum power of the energy storage subsystem is to meet the requirements of cost input and economy. The capacity of the energy storage subsystem is between 2 times and 10 times the emergency energy required by the first-class load, that is, it can meet the needs of emergency power supply, and there is still a certain amount of surplus capacity to meet the peak shifting demand of photovoltaic power generation. The cost of the energy storage subsystem Not too high, controlled within a reasonable range.

Fig. 2 is a block diagram of the operation decision-making of the dual-mode solar photovoltaic power generation system according to the embodiment of the present invention, which is the core operation logic of the integrated management subsystem. Various operating states and modes of the system are described below in conjunction with FIG. 2 .

The working modes determined by the working mode decision-making module include: photovoltaic grid-connected power generation mode, smooth working mode, photovoltaic peak shifting mode and off-grid autonomous mode.

Define the power generation power of the distributed photovoltaic power generation subsystem at a certain moment as P1, which is the power generation power of the solar photovoltaic array in this embodiment; define the power consumption of the load at the same time as P2; define the rated power of the photovoltaic inverter as P3. The conditions to be met by various working modes are described in turn as follows.

Photovoltaic grid-connected power generation mode: the conditions that must be met in this mode are (1) the power generation P1/load power P2 of the distributed photovoltaic power generation subsystem is less than 0.2; (2) the electricity price is the peak price; (3) the city power is normal ; (4) The power generation P1 of the distributed photovoltaic power generation subsystem/the rated power P3 of the photovoltaic inverter is greater than 0.05. Switch state in this mode: switch K0, switch K4, switch K5, switch K6, switch K7, switch K8, switch K1, switch K2 are closed, switch K3 is open. This working mode has the following characteristics: the power generation P1 of the distributed photovoltaic power generation subsystem/the rated power P3 of the photovoltaic inverter is greater than 0.05, indicating that the lighting conditions are good, and the photovoltaic inverter can start normally to perform MPPT (maximum efficiency point tracking) maximum Efficient power generation; the power generation P1/load power P2 of the distributed photovoltaic power generation subsystem is less than 0.2, indicating that the load demand is large, and the proportion of solar power generation to the total supply is low, which is not likely to cause adverse effects on the safety of load power consumption; electricity price It is the electricity price during peak hours, and the electric energy generated by solar energy can be used with the maximum economic value; the mains power is normal, and the necessary condition for solar grid-connected power generation.

Smooth working mode: the conditions that must be met in this mode are (1) the power generation P1/load power P2 of the distributed photovoltaic power generation subsystem is greater than 0.2; (2) the electricity price is the peak electricity price; (3) the utility power is normal; (4) ) The power generation P1 of the distributed photovoltaic power generation subsystem/the rated power P3 of the photovoltaic inverter is greater than 0.05. Switch state in this mode: switch K0, switch K4, switch K5, switch K6, switch K7, switch K8, switch K1, switch K2 are closed, switch K3 is open. This working mode has the following characteristics: the power generation P1 of the distributed photovoltaic power generation subsystem/the rated power P3 of the photovoltaic inverter is greater than 0.05, indicating that the lighting conditions are good, and the photovoltaic inverter can start normally to perform MPPT (maximum efficiency point tracking) maximum Efficient power generation; the power generation P1/load power P2 of the distributed photovoltaic power generation subsystem is greater than 0.2, indicating that the load demand is small, and the proportion of solar power generation to the total supply is high, which may have a negative impact on the safety of load power consumption. The energy storage system needs to be used to smooth the power, and the two-way energy storage inverter works; the electricity price is the peak period electricity price, and the electric energy generated by the solar energy can be used with the maximum economic value; the mains power is normal, and the necessary condition for solar grid-connected power generation.

Photovoltaic peak-shifting mode: The conditions that must be met in this mode are (1) the electricity price is the electricity price during off-peak hours or the power generation P1 of the distributed photovoltaic power generation subsystem/the rated power P3 of the photovoltaic inverter is less than 0.05; (2) the mains power is normal . Switch state in this mode: switch K0, switch K5, switch K6, switch K8, switch K7, switch K4, switch K3 are closed, switch K1, switch K2 is open. This working mode has the following characteristics: the electricity price is at a par price period, and the electricity generated by the solar energy cannot be utilized with the maximum economic value. Therefore, the electricity generated by the solar energy is stored in the energy storage subsystem, and the load is supplied with power after the peak electricity price period. Reduce the usage of mains power during peak hours, and maximize the economic value of solar energy; normal mains power is a necessary condition for solar grid-connected power generation.

In a special case, when the power generation P1 of the distributed photovoltaic power generation subsystem/the rated power P3 of the photovoltaic inverter is less than 0.05, it indicates that the lighting conditions are poor, and the photovoltaic inverter may not be able to start normally at this time to perform MPPT (Maximum Efficiency Point Tracking) maximum efficiency working power generation, or even if it can start normally, but the efficiency of inverter power generation is also very low, at this time, the solar energy can be directly stored through the energy storage subsystem. On the contrary, the charging efficiency of the system is higher, so even under low light conditions, the power generation of the distributed photovoltaic power generation subsystem can still be realized and stored in the battery energy storage system. In this way, the overall power generation capacity of solar energy can be increased by more than 5%.

Off-grid autonomous mode: Conditions that must be met in this mode (1) Mains power is abnormal. Switch state in this mode: switch K4, switch K6, switch K8, switch K5, switch K3 are closed, switch K0, switch K1, switch K2, switch K7 are open. This working mode has the following characteristics: when the mains power is abnormal, under the energy allocation and buffering of the energy storage subsystem, the distributed photovoltaic power generation subsystem and the energy storage subsystem jointly provide emergency power to a class of loads to ensure the safety of important loads. Electricity demand and electricity safety.

In a word, compared with the prior art, the building energy storage emergency energy-saving system provided by the present invention has the following characteristics and advantages:

(1) Based on the energy buffering and power buffering functions of the energy storage subsystem, the smooth access and grid-connected operation of the distributed photovoltaic power generation system are realized;

(2) Based on the energy buffer and power buffer public platform of the energy storage subsystem, as well as the management and coordination of the whole system, the off-grid autonomous operation of the distributed photovoltaic power generation subsystem is realized to meet the emergency needs;

(3) By using weak light to generate electricity, the overall efficiency of distributed photovoltaic power generation is improved, and the amount of photovoltaic power generation is increased;

(4) By transferring part of the power generated by solar energy to use during peak hours, the economic benefits of distributed photovoltaic power generation are improved, and the economy is improved.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, these improvements and modifications It should also be regarded as the protection scope of the present invention.

Claims (2)

1. The dual-mode solar photovoltaic power generation system is characterized in that it consists of four parts: a distributed photovoltaic power generation subsystem, an energy storage subsystem, a load, and an integrated management subsystem; The distributed photovoltaic power generation subsystem includes a solar cell array, a DC power distribution cabinet, and a photovoltaic inverter. The solar cell array is electrically connected to the DC power distribution cabinet, and the DC power distribution cabinet is electrically connected to the photovoltaic inverter through a switch K1. The inverter is electrically connected to the AC power distribution cabinet through the switch K2, and the AC power distribution cabinet is connected to the mains through the switch K0; the distributed photovoltaic power generation sub-system mainly realizes the conversion of solar energy into DC power and further conversion into AC power; The loads include Class I loads that cannot interrupt power supply and Class II loads that can interrupt power supply. The AC power distribution cabinet is electrically connected to the Class II loads through switch K4 and switch K7, and the AC power distribution cabinet is connected to Class I loads through switch K4 and switch K8. load electrical connection; The energy storage subsystem includes a battery stack and a bidirectional energy storage inverter, the battery stack is bidirectionally electrically connected to the bidirectional energy storage inverter through a switch K5, and the bidirectional energy storage inverter is bidirectionally electrically connected to the AC power distribution cabinet through a switch K6 ; The energy storage subsystem is used as a buffer platform for energy and power, which is used to store solar power, which is further fed to the grid for use through a bidirectional energy storage inverter. At the same time, a part of the electric energy is used as a backup. Released to provide emergency power supply to a class of loads; The integrated management subsystem implements the management and control of the entire dual-mode solar photovoltaic power generation system; The integrated management subsystem includes a mains power monitoring module, a new energy monitoring module, a BMS monitoring module, a ladder electricity price database, a load monitoring module and a working mode decision-making module, a mains electricity monitoring module, a new energy monitoring module, a BMS monitoring module, and a ladder electricity price Both the database and the load monitoring module are electrically connected to the working mode decision-making module in two directions, the new energy monitoring module is electrically connected to the distributed photovoltaic power generation subsystem in two directions, the BMS monitoring module is electrically connected to the energy storage subsystem in two directions, and the load monitoring module is electrically connected to the load in two directions , the mains monitoring module is electrically connected to the AC power distribution cabinet in two directions; The mains monitoring module monitors the voltage, current, power, and power quality related information of the mains; the BMS monitoring module monitors the voltage, current, temperature, charging status, and health status information of the energy storage subsystem; the stepped electricity price database stores the current The ladder electricity price data; the load monitoring module monitors the energy consumption of the load, and realizes the removal of non-class loads in emergency situations; the new energy monitoring module monitors the input voltage, input current, input power, output voltage, Output current, output power, solar irradiance information; The working modes determined by the working mode decision-making module include: photovoltaic grid-connected power generation mode, smooth working mode, photovoltaic peak shifting mode and off-grid autonomous mode; The capacity of the energy storage subsystem is set to: greater than 2 times the emergency energy required by the first-class load, and less than 10 times the emergency energy required by the first-class load; the power of the energy storage subsystem is set to: take 1.5 times the maximum energy for the first-class load The maximum value between the power and 1.2 times the maximum power of the solar cell array is used as the minimum power of the energy storage subsystem; take the minimum value between the maximum power of 3 times the maximum power of the first-class load and 1.5 times the maximum power of the solar cell array , as the maximum power of the energy storage subsystem; During non-peak hours of mains electricity, the charging state of the energy storage subsystem is running at a high level, and the charging state is controlled at 70% to 90%; 20%~50%, at this time, the charge of the energy storage subsystem in the lowest state of SOC is greater than 1.5 times the emergency energy required by the first-class load. 2. The dual-mode solar photovoltaic power generation system according to claim 1, characterized in that, defining the generating power of the distributed photovoltaic power generation sub-system at a certain moment is P1; defining the load power at the same moment as P2; defining the rated power of the photovoltaic inverter The power is P3; then the conditions to be met in various working modes are described in turn as follows: The conditions that must be met in the photovoltaic grid-connected power generation mode are: (1) the power generation P1/load power P2 of the distributed photovoltaic power generation subsystem is less than 0.2; (2) the electricity price is the peak price; (3) the city power is normal; ( 4) The power generation P1 of the distributed photovoltaic power generation subsystem/the rated power P3 of the photovoltaic inverter is greater than 0.05; the switch status in this mode: switch K0, switch K4, switch K5, switch K6, switch K7, switch K8, switch K1, The switch K2 is closed, and the switch K3 is opened; The conditions that must be met in the smooth working mode are: (1) the power generation P1/load power P2 of the distributed photovoltaic power generation subsystem is greater than 0.2; (2) the electricity price is the peak electricity price; (3) the mains power is normal; (4) the distribution The power generation power P1 of the type photovoltaic power generation subsystem/the rated power P3 of the photovoltaic inverter is greater than 0.05; in this mode, the switch status: switch K0, switch K4, switch K5, switch K6, switch K7, switch K8, switch K1, switch K2 are closed , the switch K3 is disconnected; The conditions that must be met in the photovoltaic peak-shifting mode are: (1) the electricity price is the electricity price during off-peak hours or the power generation P1 of the distributed photovoltaic power generation subsystem/the rated power P3 of the photovoltaic inverter is less than 0.05; (2) the mains power is normal; Switch state in mode: switch K0, switch K5, switch K6, switch K8, switch K7, switch K4, switch K3 are closed, switch K1, switch K2 is open; The conditions that must be met in the off-grid autonomous mode are: (1) The mains power is abnormal; the switch status in this mode: switch K4, switch K6, switch K8, switch K5, switch K3 are closed, switch K0, switch K1, switch K2 , The switch K7 is disconnected.