An LCL-Filter Design with Optimum Total Inductance and Capacitance

LCL-filter is among the best performing filters for grid-connected voltage source inverters. Designing of the filter parameters (grid-side and inverter-side inductors and capacitor), takes an iterative approach due to the coherence between the parameters and design requirements such as IEEE-519 Std for harmonic current limitations, reactive power compensation limit, and maximum allowable voltage drop across the filter to limit the switching losses. Most of the proposed LCL-filter optimization strategies emphasize on reducing the total inductance and losses of the filter while meeting the design requirements. There is less emphasis given on the capacitor selection and optimizing its value. Therefore, this paper proposes a method to compute the optimum capacitance requirement of the LCL-filter based on reactive power compensation of the filter rather than calculating it as a percentage of base capacitance of the filter as found in the literature. The proposed design methodology compared to the previously proposed designs is capable of reducing filter capacitance by 50% while meeting the harmonic limitation demanded by IEEE-519 Std and also considers the impact of the total inductance on reactive power compensation. Based on the proposed methodology an LCL-filter with minimum total inductance and capacitance is realized. Functionality of the proposed LCL-filter is verified and validated through simulations and experimental results.