Power Network Harmonic Analysis And The Design And Research Of Active Power Filter

With the development of power electronics technology, non-linear loads are in large-scale use. But massive harmonic components generated by the non-linear loads, which is leading to distortion of grid voltage and current, has threatened power quality and power use safety seriously. Therefore, Harmonic suppression has become the key technology urgent to solve in modern power production. Active Power Fliter (APF) can be used to suppress the harmonic of grid and compensate reactive power of grid. APF device aslo has an excellent performance of dynamic compensation.In order to achieve high harmonics effective compensation, switch component need to work in the high frequency. However, the switching losses of power electronic devices are increaseing with the switching frequency. It means that the power losses are increaseing with the switching frequency. This article has carried on the comparison to the type and topology of APF, and then proposes2H bridge cascaded type shunt APF which is suitable in three-phase three-wire system system. Meanwhile, this article has analyzed five level triangle carrier phase shifting PWM control technology in detail, the simulation improves that the control technology can make the component achieving the high switching frequency effect under low switching frequency, reduce the switching losses and increase the capacity of APF compensation.p-q harmonic detection method and ip-iq harmonic detection method based on instantaneous reactive power theory can detect the load current in the positive sequence active power, reactive power and harmonic components, but they do not apply to the situation of supply voltage distortion and asymmetric. The reference sine and cosine signals are obtained by a phase voltage PLL, while ignoring the other two-phase voltage phase information in ip-iq harmonic detection method. So the ip-iq harmonic detection method will bring the error, when the three-phase voltage is not completely symmetrical. At that time, this article proposed one kind improved ip-iq harmonic current detecting method which is suitable for the cascaded APF. This method can detect any of the grid harmonic current, when the three-phase voltage is not completely symmetrical. At the same time, this article presents the mathematical model, and proves the harmonic current detecting method by mathematical derivation.To achieve effective harmonic compensation effect, this article design the hardware circuit of cascaded shunt APF based on the type of TMS320F28335DSP. Because three-phase voltage, current testing requires high precision and good real-time, this article use external expansion AD sampling chip. This method not only solves the problem of insufficient accuracy of the DSP internal sampling module, but also has good real time. In order to solve the problem of DSP PWM output interface insufficient, this article Uses the DSP+FPGA to Constitute pulse circuit. DSP is responsible for the sampling and the computation, FPGA is only responsible for the PWM signal production, the circuit improves raised the efficiency of algorithm.This article uses MATLAB to carry on the simulation analysis to the2H bridge cascaded shunt APF. The improved ip-iq harmonic current detecting method can detect the grid harmonic current accurately. The simulation achieves a good harmonic compensation effect.