A novel communication-less control method to improve DC microgrid performance based on AC signal injection

Abstract

DC bus voltage restoration, proportional load/power-sharing, and batteries’ SOC balancing are some of the most critical challenges of DC microgrids. The utilization of communication links and the central controller eliminate these problems. Nevertheless, microgrids controlled in this way, have low modularity, flexibility, reliability, and high costs and complexity. This paper proposes a novel communication-less control method, which solves the mentioned concerns and problems. The energy storage units are controlled by local parameters in order to guarantee the system stability. In this method, a unit (sender unit) estimates the DC bus voltage deviation and injects an AC signal to the DC bus. The droop curve of the units is shifted based on the AC signal and their SOC. The shifted values are specified such that the higher SOC units inject (absorb) more (less) power, and the DC bus voltage is restored. The stability analysis and step response of the system show that the proposed method benefits from an acceptable stability and satisfactory speed. Simulation results confirm that the proposed method can regulate the DC bus voltage and reduce the units’ SOC imparity without any communication links and central controller.