Lcl Active Power Filter Based On Direct Power Control Research

This paper first introduces the formation and harm of harmonics, harmonic suppression method and the principle of active power filter. Direct current control of load current, APF compensating current or power supply current, is designed to restrain the harmonic pollution from harmonic current.The harmonic pollution caused from the harmonic voltage or harmonic current can be suppressed by direct power control. Direct power control has the advantage of fast response and simple control algorithm, it is convenient for hardware implementation, more suitable for APF control.The AC side of APF often use single inductor filter, the filtering effect is not ideal, and it is easy to cause the system volume too large. Shunt active power filter requires higher compensation bandwidth and lower switching ripple content, and LCL filter can give attention to both low-frequency gain and high frequency harmonic suppression. However, LCL filter is3order system, and there exists resonance points, so it is not easy to control. In this paper, the configuration of the virtual resistor instead of the actual damping resistor, can inhibit the occurrence of resonance phenomenon.Traditional DPC method uses hysteresis control to calculate the error between the instantaneous power and reference power, according to the error look-up table,then generate the APF reference voltage vector and the output. Traditional DPC method can achieve rapid control of power, but its steady-state characteristics is bad.The switching frequency is not fixed,so it is difficult to estimate the power loss, device selection and design the filter of network side. In this paper, a new APF control method named CSF-DPC (Constant Switch Frequency-Direct Power Control)is used, it is based on PI control and SVM technology, and constant frequency and active power damping control can increase the stability of the system.Compared to traditional direct power control strategy,CSF-DPC has good dynamic performance, the system sampling frequency is low, the loss is small, and it is useful for the design of the filter of the AC side.In the Matlab/Simulink environment, the simulation model of the APF is established, then the paper compare the speed of response and dynamic characteristics, the steady-state characteristics, robustness analysis, using different control strategies. Simulation conclusion confirmed the correctness and validity of the strategy by the direct power control based on constant switch frequency.