Research On Energy Feedback Analog Load Used For PV Power Generation System Experiments

At present, the problem of energy shortage and environmental pollution has become increasingly prominent, energy saving and emission reduction is imperative. The energy feedback analog load is widely used as a new type of energy saving device. Aiming at the scene of the experiments of PV power generation system, the thesis researches a kind of AC / DC general energy feedback analog load. It realizes the characteristics of PV modules and off grid inverter tested simultaneously.According to the actual demand of PV power generation system experiments, the system structure with two independent load simulators and a common energy feedback unit is designed. Among them, the DC load simulator uses the quadratic Boost converter; The AC load simulator uses single-phase PWM rectifier circuit; The energy feedback unit uses a single phase full bridge inverter circuit.The single phase PWM rectifier uses hysteresis comparison control for the realization of AC load simulation function, and giving the design method of the PWM rectifier AC side filtering inductance and the hysteresis width combined with the power level and ripple current limit condition. To achieve DC load simulation function,the quadratic Boost converter uses current single closed-loop PI control. The quadratic Boost converter main circuit parameters is designed according to the requirements of the PV module power rating and voltage and current ripple coefficients. At the same time, establish the small signal mathematical model of the quadratic Boost converter based on the state-space average method and derive the transfer function from the power switch duty ratio to the input current. The PI regulator parameters are calculated according to the system transfer function. The energy feedback unit adopts double closed loop control. Establish double closed loop control system mathematical model and derive transfer functions from the reference feedback current to the actual feedback current and from the reference DC bus voltage to actual DC bus voltage. Then complete the design of the controller parameters according to the characteristics of transfer function.The system is simulated by Matlab software and the results show that the designed AC/DC general energy feedback analog load can meet the experimental demands of PV power generation system; The energy recovery efficiency of the system reach to 97.7%; The AC load simulator and the DC load simulator don’t influence each other while switching, so the system realizes AC source and DC source tested simultaneously; The double closed loop control based on PI and hysteresis comparison has more wide power regulation range than it based on two PI regulators.