A Bidirectional Single-Stage DC/AC Converter for Grid Connected Energy Storage Systems

Abstract

In this paper, a unified control strategy using the current space vector modulation (CSVM) technique is proposed and applied to a bidirectional three-phase DC/AC converter. The operation of the converter changes with the direction of the power flow. In the charging mode, it works as a buck type rectifier; and during the discharging mode, it operates as a boost type inverter, which makes it suitable as an interface between high voltage AC grids and low voltage energy storage devices. This topology has the following advantages: high conversion efficiency, high power factor at the grid side, tight control of the charging current and fast transition between the charging and discharging modes. The operating principle of the mode analysis, the gate signal generation, the general control strategy and the transition from a constant current (CC) to a constant voltage (CV) in the charging mode are discussed. The proposed control strategy has been validated by simulations and experimental results obtained with a 1kW laboratory prototype using supercapacitors as an energy storage device.

Resonance Suppression Based on PR Control for Single-Phase Grid-Connected Inverters With Filters

“…2. The transfer functions of the grid current and the inverter current to the inverter voltage are derived, respectively, as [2] ( )…”

“…Rather than the L filter, the LCL filters are commonly used due to the advantages in the inductor size and the performance. One drawback of the LCL filters is to need the passive damping (PD) or active damping (AD) control to suppress the oscillations in the resonance frequency [2]- [19]. Recently, a topology of LLCL filters has been proposed, where a small inductor is added in series with the capacitor filter, so the grid-side inductor size can be reduced remarkably [13].…”