Reduction in switching losses/DC bus requirement for a grid-connected inverter with minimal sensors using PMR-OCC

One cycle control (OCC) is widely used for grid current control owing to least number of sensors used, reduced complexities and cost. A proportional multi-resonant controller within the OCC is implemented in this paper for the purpose of further improvement in grid current THD. A trapezoidal PWM is proposed to reduce the DC voltage requirement for a grid-connected inverter as well as to reduce the switching losses of the inverter and hence improve the efficiency. No extra sensors are used for the implementation of trapezoidal modulation. Overall, the proposed modulation and control strategy for the inverters not only further reduces the DC voltage requirement, the number of sensors and the total switching loss, but also improves the grid current THD. Three cases are compared and verified experimentally. In Case I, a traditional PMR controller is used for the purpose of current control. In Case II, a trapezoidal PWM along with PMR control technique is proposed, whereas in Case III, trapezoidal modulation along with PMR-OCC is proposed. Experimental results and analysis show the superior performance of trapezoidal PWM along with the proposed PMR-OCC compared to that with the other two techniques.