RESEARCH
Frequency Behavior and Its Stability of Grid-Interface Converter in Distributed Generation Systems
Year: 2012
Fig. 1. Grid-interface converter under study.
As shown in Fig. 3, the proposed model consists of two feedback systems. In addition to the typical negative feedback system, the frequency positive-feedback mechanism in the converter system is proposed and quantified in the model. The nonlinear behavior of the PLL under weak grid conditions can be accurately predicted, and the large-signal frequency stability region can be also estimated by the proposed model. It shows that large penetration of distributed generation (DG) units, a large reactive power variation, and a weak grid tend to destabilize the converter frequency operation. The proposed model can help study electric power system or microgrid operation under a large penetration of renewable energy resources with power electronic interfaces.
Fig. 2. Synchronous reference frame PLL.
Fig. 3. Proposed PLL model.
Fig. 4. Switching converter simulation results ω2 (purple) [5 Hz/DIV], one-phase current ia (blue) [25A/DIV], and proposed PLL model output ω2 (dark blue).
