Sliding-Mode Direct-Voltage Control of Voltage-Source Converters With LC Filters for Pulsed Power Loads

This article proposes a direct-voltage controller, based on sliding modes, for regulating the output voltage of voltage-source converters (VSCs) equipped with LC filters. Grid-forming VSCs used in microgrids with pulsed loads must provide fast dynamic response and strong rejection of load perturbations. The new voltage control scheme uses a single-stage sliding-mode voltage controller with state feedback. The typical two-loop cascaded topology using a current controller in the inner loop and a voltage controller in the outer loop is not employed. The sliding-mode control (SMC) contains three components: 1) a feedforward effort that sets the ideal operating point, 2) a switching control law based on SMC, and 3) a sliding-mode equivalent control. The sliding variable is defined with proportional-derivative (PD) dynamics, and thus, it provides inherent active damping properties. The SMC improves the robustness with respect to load perturbations and modeling errors, whereas the equivalent control adds damping and reduces the response time to large load transients. The article describes the design and gain selection, and provides a simulation-based sensitivity analysis for this scheme. Two variants are tested in standalone operation: with and without the P term of the PD component. Experimental results show that, in both cases, the response to pulsed loads is very fast (about 1 ms) and accurate.