A DC Capacitor-Less Two-Terminal Unified Active Capacitor and Inductor

The emulation of passive components by power electronics converter (PEC) has gained significant popularity in recent times. Apart from improving the power density, it offers the flexibility to vary capacitance and inductance values within a specific range. However, any PEC emulating the behaviour of a capacitor or an inductor also requires passive filters, which can outweigh the power density enhancement achieved by the emulation effort. In particular, for the two-terminal active capacitor inductor (ACI), which is operationally similar to a single-phase STATCOM, DC capacitance requirement of the PEC is substantial. A more compact filter is achieved if a higher ripple is allowed across the DC bus while not compromising the desired emulation objective. The present work proposes a DC capacitor-less topology for realising an active, two-terminal capacitor and inductor unified in a single unit. Continuous control of the unified ACI converter is developed to achieve a smooth transition from capacitive to inductive characteristics and vice versa. A laboratory-scale prototype is developed to verify the concept and functionality of the proposed circuit.