Universal inverters for flexible power electronic test-bed implementation

Abstract

As the rapid development of electric grids, power electronic equipment has been widely deployed in modern power systems. The flexible operation of power electronic equipment has significantly complicated the grid operation, which enables different types of grid operation conditions that need to be emulated in the lab to facilitate the testing and development of advanced control diagram. Note that the fully controllable power electronic converters make it feasible to establish and simulate different operation conditions, which greatly diversifies the flexibility of conventional test-beds used for power electronics and power system research. In this paper, a generic three-leg converter is used and further functional expansion is implemented to make it a controllable unit for simulating different grid assets, including photovoltaics (PVs), batteries, etc. Hence, a universal inverter-based grid simulator is developed. Advanced control diagram is designed to achieve the flexible operation of the power-electronics-based grid simulators. Rather than relying on conventional synchronous-frame-based proportional-integral (PI) controllers, proportional-resonant (PR) controllers in stationary frame is used to avoid the coordinate transformation from a-b-c framework to d-q-0 framework. In other words, the coordinate transformation from stationary frame to rotational frame is eliminated. Test cases are established to test and validate the developed universal grid simulator.