The electronic realization of synchronous machines: model matching, angle tracking and energy shaping techniques

Abstract

In this paper, we investigate grid-following and grid-forming control strategies starting from the nonlinear dynamics of the DC/AC converter. An electronic synchronous machine is an inverter whose the integral of the DC-bus measurement generates the angle of the instantaneous modulation vector. We show how this minimal augmentation represents an exact physical realization without requiring inner current loops. The DC-link capacitance becomes the equivalent rotational inertia of the converter. Additional features such as a novel phase-locked-loop design, a voltage controller and a power set-point tracking mechanism are then designed via two energy-shaping techniques. One energy function is used to implement a grid-following control scheme, via the inherent synchronizing torque, while the other is used to implement a grid-forming control scheme, by uncovering active-power droop. The results are first derived systematically, and then evaluated experimentally on a front-to-front setup.