Research on control method of photovoltaic battery power reduction
Abstract: A method for controlling the power output reduction of photovoltaic batterys is proposed. When the photovoltaic battery power is excessive, the method adds a voltage feedback signal to the original maximum power control output voltage reference signal, so that the photovoltaic battery operating point deviates from the maximum power point, thereby reducing its power output and maintaining the power balance in the system. stable. The photovoltaic battery system simulation was built on PSCAD/EMTDC, and the method was simulated and analyzed. The results show that the method can effectively realize the power reduction control of the photovoltaic system and ensure the stable operation of the system.
Keywords: photovoltaic battery; power surplus; power reduction control
CLC number: TB
Document code: A
As an important distributed power source, photovoltaic batterys have many uncontrollable output characteristics and are extremely complex nonlinear power generation devices. Traditionally, in order to maximize the power output of a photovoltaic system, it is necessary to track the maximum power point of the photovoltaic battery (MPPT). However, when the system power is excessive, the output power of the photovoltaic battery needs to be controlled to maintain the stability of the microgrid system. The paper takes photovoltaic batterys as the research object and analyzes the characteristics of MPPT algorithm based on traditional disturbance observation. The DC voltage feedback signal is added on the basis of the basic disturbance observation method to realize the power reduction control of the photovoltaic system.
1 Basic disturbance observation method
The realization of basic PVMP disturbance observation method is essentially a self-optimization process, which is to constantly change the terminal voltage at both ends of the photovoltaic, judge the change of the output power of the photovoltaic battery, and then guide Change the direction of change of the photovoltaic terminal voltage. Enables photovoltaic batterys to output maximum power Pm in changing sunlight and temperature environments.
2 power reduction control
The power reduction control strategy of photovoltaic power supply is shown in Figure 1. It mainly includes MPPT control and power reduction control based on disturbance observation method.
When the photovoltaic power supply performs MPPT control, the MPPT link obtains the voltage UPV and current IPV of the current photovoltaic array, and calculates the maximum reference voltage UMPPT of the photovoltaic array. Then, UMPPT is used as the control voltage U*PV of the chopper circuit and its sample value UPV, and then sent to the voltage PI regulator to obtain the IMPPT as the control reference signal of the current inner loop to drive the converter switching device.
In the constant voltage drop power control mode, the voltage reference signal U*PV is generated by adding the UMPPT generated by the MPPT link and the DC voltage feedback signal ΔU generated by the power down link. What needs to be explained here is ΔU ≤ 0, because the power reduction control link only works when the power surplus causes the DC voltage to rise.
3 Simulation Analysis
For the above photovoltaic battery control method, a bipolar simulation circuit is built on the PSCAD/EMTDC simulation platform. The short circuit voltage of the photovoltaic battery is 1.7kV, and the short circuit current is 0.16kA. The photovoltaic battery control module implements MPPT control and power reduction control. The DC voltage Udc has a stable value of 0.5 kV. Therefore, the DC chopper circuit uses a step-down chopper circuit.
It can be seen from Fig. 2 that the voltage rise of the DC voltage Udc in the system at 1 s is shown in Fig. 2(a). At this time, the photovoltaic battery control module reduces the voltage on both sides of the photovoltaic battery according to the power reduction control, as shown in Fig. 2(b). Thus the photovoltaic power PPV will decrease as seen in 2(c).
Power regulation. It improves the flexibility of photovoltaic battery regulation and gives the photovoltaic battery a certain power regulation capability. These have important engineering practical implications in the actual case of photovoltaic batterys.
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