A Novel Impedance-Network-Based Electric Spring

Abstract

An electric spring (ES) can well maintain the balance between supply and demand to compensate for the intermittent nature of small-scale renewable energy resources (RES). Despite its popularity, the second generation of ES (ES-2) is deemed to have a few practical problems. The most conspicuous one is the requirement of accurate dead-time control is in the ES circuit to avoid bridge shoot-through problem, which is necessitated by the series-connection of multiple voltage sources and/or converters to realize a wide voltage range. This however could cause output voltage waveform distortions. In this study, inspired by the Z-source network structure, we propose a novel ES topology with a specifically designed impedance network, i.e., an impedance-network-based (i.e., a network of passive devices such as inductors and capacitors) ES (IN-ES), which intrinsically has a wide voltage range and is immune to the bridge shoot-through issue (i.e., switch tubes on the same bridge arm of the inverter are turned ON/OFF at the same time). Detailed theoretical derivation, simulation and experimentation are conducted in this study, which verify the unique advantageous features of the proposed IN-ES, demonstrating a wide voltage operation range, undistorted waveforms and safe operations.