The Research Of SHEPWM Applied In PV Grid Inverter

Selective Harmonic Elimination Pulse Width Modulation (SHEPWM) is a modulation technique of ideal sine wave. Comparing with Space Vector Modulation (SVM) or Sine Pulse Width Modulation (SPWM), SHEPWM has low equivalent switching frequency, low switching loss and high power quality.Based on the grid inverter with conventional SHEPWM, grid current is distorted by the background grid voltage harmonic seriously. In addition, under the same conditions of equivalent switching frequency and current quality, SHEPWM is expected to find a way to reduce the filter to achieve the lower cost of PV grid inverters. Therefore this article mainly about the background harmonic problem and reducing filter has an application research in PV grid inverter with SHEPWM. The main contents are as follows:The first part, to solve the problem of the grid background harmonic voltage, the article proposes a scheme that SHEPWM generate harmonic voltage. Then it expands the storage capacity of the controller to achieve harmonic with storage. Finally, simulation and experiments confirmed the feasibility of the scheme, and reach the grid current harmonic suppression purposes.The second part, for the decreasing of the filter of PV grid inverter, the article has theoretical analysis and experiments with harmonic performance and efficiency to different SHEPWM solutions and SVM. In the same case of equivalent switching frequency and current quality, this paper analyzes the harmonic performance and efficiency to SHEPWM with the inductor reduced by 30% theoretically and experimentally.