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A Brief Description Of The Working Mode Of Photovoltaic Energy Storage System
- Aug 09, 2018 -

The photovoltaic power generation has the characteristics of high energy level in the short time in the afternoon, low output in other periods and no force at night and no force at night. The energy storage technology has the time and space shift characteristic of electric energy. Give up light.


In order to prolong the service life of the battery energy storage system, the charge and discharge times of the battery energy storage system should be minimized. During the peak period of photovoltaic power generation, the battery charging system is controlled to reduce the output of the PV power station. After the peak period of photovoltaic power generation, the battery energy storage system is controlled to discharge the energy storage system. The discharge control of the energy storage system can help to smooth the fluctuation of the photovoltaic output and the peak adjustment of the auxiliary system, so as to maximize the energy storage function. According to the different functions of energy storage discharge, three working modes of energy storage system can be divided, namely peak clipping, peak clipping + suppression and peak clipping + transfer.


01 Working mode a peeling


In the peak period of the PV power station, the battery energy storage system is charged with the peak cutting peak as the application target. After the peak period of the PV output, the power amplification of the battery energy storage system is controlled, and the discharge to the lower limit of the SOE operating range of the battery energy storage system is controlled, and the energy storage system stops working. The working time of the energy storage system in the photovoltaic power generation time does not increase the working time of the photovoltaic power plant, and reduces the impact of the configuration of the energy storage system on the work arrangement of the photovoltaic power station.


02 Working mode two peeling + smoothing


In the peak period of PV power station output, the battery charging system is controlled by cutting the peak as the application target. The output fluctuation of large scale photovoltaic power stations can be divided into two types, one is the slow change of the output of the photovoltaic power station, such as the periodic variation of the output of the photovoltaic power station caused by the alternation of day and night; the other is the sudden change of the output of the photovoltaic power station, such as the sudden drop of the output of the photovoltaic power station caused by the floating cloud occlusion. The first round of change is large, but the change is slow; the second kind of change is unforeseeable and sudden, and the force is reduced from full hair to below 30% rating in 1~2s. After the peak period of PV output, in the process of smooth day and night alternation, the descending fluctuation of the photovoltaic power station output is the target control of the energy storage system discharge and the discharge to the lower limit of the SOE operating range of the battery energy storage system. If the output of the photovoltaic power station is reduced to 0 at night, the SOE of the energy storage system is still greater than 0.2, and the storage system is controlled. Discharge to SOE at rated power and constant power to 0.2, then control the energy storage system to stop working.


03 Working mode three peeling + transfer


In the peak period of PV power station output, the battery charging system is controlled by cutting the peak as the application target. The output period of the Qinghai photovoltaic power station is 8:30~18:30, and the late peak of Qinghai load appears between 18:00~22:00. In this period, the photovoltaic power station has no force. It can control the discharge of the battery energy storage system to assist the system peak adjustment, in order to reduce the operation times of the energy storage system and simplify the operation of the battery energy storage system. Control the battery energy storage system with constant power discharge, discharge in the battery energy storage system SOE operating range lower limit, and then the energy storage system stops working.


Summing up


The working mode of the photovoltaic energy storage system is based on the requirements of the owner and the characteristics of the local project. The specific control strategy plays a vital role in the selection of the working mode of the photovoltaic energy storage.