Single-Step Current Control for Voltage Source Inverters With Fast Transient Response and High Convergence Speed

Current control loop response in voltage source inverters impacts the quality of output current and output voltage waveforms. Parabolic current control provides a fast transient response with approximate-constant switching frequency, solving the frequency variation problem of hysteresis current control. This makes it a good candidate for the current control loop of voltage source inverters to achieve a good system performance. Yet, parabolic current control is often implemented with digital-to-analog converters, analog comparators, and field-programmable gate array circuits where increasing switching frequency pushes update speed and bandwidth requirements. Concurrently, even if the transient response of parabolic current control is fast, it can still take up several switching cycles converging to steady state. In order to solve both problems, a new current control strategy, motivated by the convergence analysis of parabolic current control but with a convergence process that takes just one switching operation, is proposed: single-step current control. Since single-step current control samples two data points in a switching cycle instead of using continuous parabolic carriers, it can be easily implemented in a digital microcontroller then high switching frequency can be achieved. The small signal model, dead-time compensation, and stability analysis are also studied in this paper. The convergence speed of the algorithm is verified with experimental hardware prototype and the transient performance of the designed voltage source inverter meets expectation.