Solar photovoltaic power generation is one of the important components to realize the sustainable development strategy of energy and electricity in my country.
Due to the strong fluctuation and randomness of photovoltaic output power, the instability of photovoltaic power seriously restricts the access and transmission of photovoltaic power. Energy storage technology can realize functions such as peak shaving, load tracking, frequency regulation and voltage regulation, and power quality control. The photovoltaic energy storage system can also store excess energy into the energy storage battery when the photovoltaic power station encounters the curtailment of power generation, and when the photovoltaic power generation is lower than the limit value or the peak power consumption at night, the energy in the battery is converted into the battery through the energy storage inverter. It is fed into the power grid, and the energy storage system participates in peak shaving and valley filling of the power grid. The energy storage system can also use the peak-valley electricity price difference to create greater economic benefits and improve the system’s own adjustment capability; An effective support technology.
The main modes of the energy storage system are the energy storage system configured on the DC side of the power supply, the energy storage system configured on the AC side of the power supply, and the energy storage system configured on the load side.
1. Energy storage system configured on the DC side of the power supply
The energy storage system configured on the DC side of the power supply can be mainly installed in the DC system such as photovoltaic power generation. This design can control the connection and control of the battery combined photovoltaic power generation array in the DC section of the inverter.
The photovoltaic power generation system and the battery energy storage system in this system share an inverter, but due to the large difference between the charging and discharging characteristics of the battery and the output characteristics of the photovoltaic power generation array, the maximum power of the photovoltaic grid-connected inverter in the original system The tracking system (MPPT) is specially designed to match the photovoltaic output characteristics, and cannot meet the output characteristic curve of the energy storage battery at the same time.
Therefore, such systems need to transform or redesign and manufacture the original system inverter, not only to make the inverter meet the inverter requirements of the photovoltaic array, but also to add a charge and discharge controller for the battery pack, and battery energy management. and other functions. Generally speaking, the system is one-way output, that is to say, the battery in the system is completely charged by photovoltaic power generation, and the power from the grid cannot charge the battery.
The power generated by the photovoltaic power generation array of the system is automatically DC balanced with the battery at the front end of the inverter. The main feature of this mode is that the system has high efficiency. The power generation output of the power station can be dispatched from the photovoltaic power station, which can achieve seamless connection and output power. Good quality, very small output fluctuation, etc., can greatly improve the smoothness, stability and controllability of photovoltaic power output. Make an upgrade. Another disadvantage is that the battery pack in the energy storage system can only accept the power of this power generation unit to charge it, and the excess power of other adjacent photovoltaic power generation units or power stations cannot charge it. That is to say, this scheme lacks the function of internal power allocation of large power stations.
