Extending the Operation Range of Electric Spring With Dual Inverters

As an emerging technology for power demand side management, electric spring (ES) is used to improve the power quality of the grid containing a high proportion of renewable energy sources (RES). Most of the existing ESs are connected in series with noncritical loads (NCL) to form smart loads, whose power consumption can follow the variation of RES power generation automatically. However, the structure of the direct series connection between ES and NCL limits the operating range of ES. In order to solve this problem, an improved ES topology based on dual inverters, called DI-ES, is proposed. The structure of the dual inverters allows DI-ES to have two output ports, one of which is connected in series with NCL for reactive power compensation and the other output port is connected in parallel with the NCL for active power compensation. DI-ES changes the traditional structure of ES in series with NCL, and improves the power compensation capability and flexibility of ES. In this work, the topology, operating principle, and control method of DI-ES are introduced in detail. The effectiveness of DI-ES has been verified by simulation and experiment results.