| Abstract |
Renewable energy resources are usually needed to be connected to the distribution grids through a power electronics converter with an appropriate filter in the output. Therefore, harmonics injected to the grid by converters must be handled to maintain power quality indices within standard limits. LCL filters with passive damping resistors are the most reliable and efficient devices to fulfill the standards. The main objectives in the design of an efficient LCL filter are to reduce the cost and weight of the filter, as well as to increase robustness and stability. Due to the outstanding ability of multilevel inverters in diminishing the output voltage harmonics, conventional 2-level inverters are being replaced with them. However, the output filter design for inverters based on multilevel Pulse Width Modulation algorithms (PWM) has not yet been considered in the literature. Hence, exact formulas should be derived to design each element in the filter considering N-levels of the output voltage. In this paper, a comprehensive and mathematical approach is proposed to calculate the maximum current ripple of a PWM-based N-level cascaded inverter, which helps to precisely calculate the size of the inverter-side inductor. Finally, an algorithm is proposed to design an LCL or LCCL filter step-by-step by modification of previous algorithms. |
