Research Of Power Quality Comprehensive Compensation Strategy

With the rapid development of China's economy, many industrial and household electrical equipment access to the grid, these devices with low power factor, asymmetric and nonlinear characteristics, will directly will lead to the continuous decline in the quality of the power. Therefore, reasonable and effective control of power quality, harmonics and reactive power in power grid is the key problem of the current research. Active power filter for power compensation, which can eliminate harmonic and compensate the reactive power, balancing three-phase current role, which is the improvement of power quality is the most effective means. However, the application of APF in China's power grid has not reached a mature stage, there are still a lot of problems have not been resolved. Therefore, this paper focuses on the APF in the harmonic detection methods and control strategies in depth analysis and research.In this paper, the generation and harm of harmonic are introduced. The harmonic detection methods and control methods of active power filter are analyzed. Then, the detection method of instantaneous reactive power is analyzed, and the limitation of the detection method is analyzed in different situations. And then put forward a kind of improved harmonic current detection method, the method mainly for phase locked loop (PLL) was improved and the unbalanced grid voltage and distortion occurs when the established simulation model is validated by simulation. The simulation results of the surface of the the detection method in a kind of any possible the detection results are very good. In this paper, also for three-phase four wire mid point capacitor and four bridge arm parallel type APF two topology are analyzed, and of shunt three-phase four bridge arm APF in three kinds of coordinate system established mathematical model, the current and voltage controller design provides theory basis. Not only the real-time phase information of power grid voltage is needed in harmonic detection, but also the real-time phase information of the three-phase voltage must be obtained accurately in the control of APF. So the voltage phase which is needed to control the APF can be improved by the method of phase locked loop which is proposed by the previous harmonic detection. In this paper, the control scheme based on dq rotating coordinate system, the inner current loop of control (PI) controller design and stability analysis, the outer voltage loop controller with PI control, and verify the correctness of the simulation. Three dimensional SVPWM analysis of commonly used space vector modulation is carried out. Finally, through the combination of PSIM and MATLAB simulation, simulation results verify the feasibility of the detection method and control method in this paper. In order to further verify the dynamic tracking performance of the system, the original stable load is changed to the fluctuating load, and the compensation accuracy and rapidity of the system under load fluctuation are detected by simulation.