Distributed Secondary Control With an Event-Triggered Consensus-Based Observer for Energy Storage Systems in Islanded DC Microgrids

This paper proposes a distributed secondary control strategy with an event-triggered consensus-based observer. Firstly, a voltage-shifting term is introduced in the proposed control strategy to ensure accurate current sharing, faster state-of-charge (SOC) balancing and bus voltage restoration. Since the SOC balancing speed becomes very slow when the difference in SOC between battery energy units (BEUs) is small, and SOC balancing of BEUs with low power is difficult. Therefore, an adaptive SOC balancing factor to improve the balancing speed is proposed in this control strategy. In addition, communication delay can lead to large errors in traditional consensus-based observers, and continuous communication can bring a significant burden. Considering these issues, the event-triggered consensus-based observer is proposed. This observer can achieve accurate average consensus under communication delay and greatly reduce communication burden. The convergence of the proposed observer under communication delay is theoretically proven, and the Zeno behavior is excluded. At last, the effectiveness of the proposed control strategy has been verified in MATLAB/Simulink and RT-LAB experiments.

I. Introduction

In Recent years, distributed power generation based on renewable energy sources (RESs), such as photovoltaic (PV) and wind power, has been growing rapidly due to the attention given to environmental pollution [1], [2]. However, the intermittency of RESs leads to a mismatch between power generation and demand in the power system. Therefore, in order to maintain reliable operation, it requires the ESSs to achieve peak shaving and valley filling [3], [4], [5]. Microgrid, as a small-scale power system that integrates RESs, ESSs, and loads, has been widely studied [6], [7]. In particularly, DC microgrid can directly connect the DC sources, ESSs and DC load without DC-AC converters, and, compared to AC microgrid, there are no issues with harmonics, phase synchronization, reactive power, and frequency. Thus, the application of ESSs in DC microgrids has attracted widespread attention [8], [9].