Research on energy management of well grid photovoltaic power station
The energy management strategy of the photovoltaic power station is related to the large power grid and the automatic power generation control of the power station itself. It not only ensures the safe, reliable and efficient operation of the entire photovoltaic power generation system, but also enables the photovoltaic power station to obtain the greatest economic benefits. Due to the strong randomness and volatility of solar energy, the working state of photovoltaic modules is easily affected by changes in solar irradiance and load. Therefore, it is necessary to optimize energy management of photovoltaic power plants to determine the current available energy and energy of each component in the system. Use energy. Energy management is to adjust the charge and discharge of the energy storage battery in time when the output power of the photovoltaic unit changes within a certain period of time, to meet the demand for electric energy from the large power grid, and to make the amplitude and frequency of the photovoltaic power station meet the requirements to meet the requirements. requirements of large power grids.
From the perspective of mathematical models, photovoltaic modules and energy storage batteries are the basic units of photovoltaic power generation systems. First, it is necessary to master the basic characteristics of photovoltaic cells and batteries. Based on the above discussion, this chapter will focus on the mathematical model of energy scheduling. The energy management system analyzes and summarizes the current data and historical data of photovoltaic panels, battery units, load units, and large power grids, so as to evaluate their operating status, and comprehensively consider the forecast photovoltaic power generation, battery SOC, real-time electricity price of the grid, load Factors such as size, the system adopts an effective method to calculate the optimal operation mode of the photovoltaic power station in one day, and calculates the economic benefits of one day.
At present, the output of active power and reactive power of photovoltaic power plants is being studied at home and abroad, and further research is being carried out on energy storage units to improve the economic operation of power plants. Because the energy of the battery can flow in both directions and the power response is fast, this paper selects the lead-acid battery as the energy storage element. When the photovoltaic power station is running, the lead-acid battery can play a role in stabilizing the voltage and frequency. According to the photovoltaic power generation power and the remaining capacity of the battery to formulate different energy scheduling strategies, while realizing the real-time economic operation of photovoltaic power plants, it also plays the role of “peak shaving and valley filling” for the large power grid.
Establishment of System Energy Scheduling Model
The loss of produced power probability (L.PPP) and the loss of power supply probability (L.PSP) were used as the energy optimization indicators of photovoltaic power plants. During the operation of the photovoltaic power station, the energy loss rate RLppp is expressed as the ratio of the power lost by the photovoltaic power generation system ELpp to the total power generation Eg; the energy loss rate RLPSP is expressed as the ratio of the energy loss amont ELPS to the total load demand En.
Energy scheduling model one
The photovoltaic does not generate electricity or the photovoltaic power generation power is too low to be captured. If the remaining charge capacity of the battery is less than its maximum capacity, due to the low electricity purchase price during the valley period, the battery is charged with Pba. The constraints of Pba are shown in 7.3.3.2 Constraints Constraints, if the battery charging does not reach its maximum capacity after time, then the middle battery is charged with constant power throughout the time, if the remaining charge capacity of the battery is not less than its maximum capacity, then there is no energy exchange between the photovoltaic power station and the grid , i.e. OP2
Energy Scheduling Model II
In the energy dispatching model 2, it needs to be discussed in two cases: one is that the output power of photovoltaic is greater than the demand power of grid load; the other is that the output power of photovoltaic power generation is not greater than the demand power of grid load,
(1) The output power of the photovoltaic is greater than the demand power of the grid load
OP3 is very similar to OP1. Compared with OP1, the difference is that there are photovoltaic modules in the system to supply power to the grid load and the battery at the same time, and there will be energy loss at this time. ELpp(t) is the energy lost by the system in time period 1; esale is the electricity purchase price of the power station in the current period; Msale is the cost of electricity purchased by the photovoltaic power station. If the battery does not reach its maximum capacity after time, then the battery is charged with power Pba in the whole time t: OP4 is very similar to OP2, and the difference compared to OP2 is that there are photovoltaic modules in the system to load the grid Power supply, there is energy loss.
(2) The output power of photovoltaic power generation is not greater than the power required by the grid load. Photovoltaic modules only supply power to the grid load, and there is energy shortage, that is, OP5.
Energy dispatch model 3
Since the energy dispatching model 3 is in the peak period, everything is based on the large grid load, as shown in Figure 7-20, which is also considered in two cases:
①The output power of photovoltaic power generation is greater than the power demanded by the grid load, which is exactly the same as in the energy dispatching model 2, and will not be repeated here.
②The output power of photovoltaic power generation is not greater than the power demanded by the grid load. If the remaining charge capacity of the battery is greater than its minimum capacity, the battery will be discharged with power Pb due to the high price of electricity during the peak period. After t1<t, the battery will be discharged to the minimum capacity SOCmin. After (t – t1) time, the battery will stop. Supply power to the large grid load, namely OP6: If the remaining charge capacity of the battery is not greater than its minimum capacity, then only photovoltaics supply power to the grid load, which is the same as OP5.
Energy Scheduling Model Four
This model 4 is in the peak period from 19:00 to 23:00, and the electricity price is high, and everything is based on the large power grid load demand. According to the data monitored in Qinghai photovoltaic power station, at this time, the photovoltaic does not generate electricity or the photovoltaic power is too low to be captured.
Analysis and Research on the Objective Function and Constraints of System Operation
There are only photovoltaic modules and energy storage batteries in photovoltaic power plants, so compared with microgrids, the objective function of the energy management model of photovoltaic power plants mainly considers the cost of photovoltaic modules and their supporting equipment, as well as the cost of batteries and their supporting equipment.
