The Research Of Active Power Filter Harmonic Detection And Control Algorithm

Along with the development of our society, electric power as a major energy is demand increasingly, and we need more and more high quality electric power at the same time. In power supply system, in order to guarantee the stability of the power supply, we generally want to get the symmetrical three-phase voltage and current, it means that the voltage and current for the constant frequency sine wave, thus reducing the load change on the impact of power quality. But with the device like FACTS used in power system, introducing serious harmonic problems into power grid, and it threats to the power quality, so in order to make the electrical equipment in the power system to obtain good power quality, efficient and fast measures must be taken to suppress the harmonic pollution.The active electric power filter have the advantages of overtone real-time track compensation, the wonderful dynamic stability performance, and the compensation precision higher merit, thus it has received the extensive research and the attention. But due to compensation of signal sampling and processing lag, how to control the switching converter power devices to eliminate compensation lags is still the emergency needs to study key technology for APF.This article mainly conducts the research to the shunt active power filter (SAPF), the design research mainly includes three modules, namely the harmonic detection module, the current compensation module, the capacitance control module. Harmonic current are detected from the grid power harmonic current detection module, and we use the instantaneous reactive power theory of ip-iq algorithm to design it. Current compensation module is tracking instruction current and compensation of harmonic current which is generated by the main circuit. The module is proposed in this paper advanced two repetitive control prediction algorithm to predict harmonic current and calculating the instructions voltage. Here we put forward the improvement method can make the prediction precision improved, which solves the harmonic compensation better due to delay in the compensation, and the compensation of power grid is still a large number of harmonic problems. Capacitance control module for compensation current output and stable operation environment, the module uses the energy balance principle, with PI control on DC side capacitor voltage in a stable range. For monitoring the power quality at the same time, this article will add Blackman window of double line interpolation FFT algorithm for embedded. When it comes to the difficulty in solving the complex structure of the interpolation function, we put forward a kind of cubic spline interpolation method, and the interpolation function to analyze every harmonic parameter accuracy is higher. It can monitor the active power filter harmonic compensation ability to the part for beyond the compensation ability of detection for the follow-up improvement and adjustment.Finally we model the simulation by MATLAB/Simulink platform, it first compares the advanced two pat repeated prediction algorithm with the Lagrange interpolation algorithm of harmonic prediction precision. The simulation results in the error precision lead two pat repeated superiority of the improved algorithm is proved, and it then for the design of the overall modeling and simulation of active power filter. In the case of the load stability and load mutation in various control parts, this paper verified the accuracy of the output harmonic compensation of active power filter system.