Coordinated Frequency and State-of-Charge Control with Multi-Battery Energy Storage Systems and Diesel Generators in an Isolated Microgrid

Abstract

Recently, isolated microgrids have been operated using renewable energy sources (RESs), diesel generators, and battery energy storage systems (BESSs) for an economical and reliable power supply to loads. The concept of the complementary control, in which power imbalances are managed by diesel generators in the long time scale and BESSs in the short time scale, is widely adopted in isolated microgrids for efficient and stable operation. This paper proposes a new complementary control strategy for regulating the frequency and state of charge (SOC) when the system has multiple diesel generators and BESSs. In contrast to conventional complementary control, the proposed control strategy enables the parallel operation of diesel generators and BESSs, as well as SOC management. Furthermore, diesel generators regulate the equivalent SOC of BESSs with hierarchical control. Additionally, BESSs regulate the frequency of the system with hierarchical control and manage their individual SOCs. We conducted a case study by using Simulink/MATLAB to verify the effectiveness of the proposed control strategy in comparison with conventional complementary control.

Distributed Control Strategy for an Isolated Electrical Hybrid Power System

“…In [6], [20] and [21] the control action for the next time step is obtained by solving an online finite horizon open-loop optimal control problem, using the current state of the plant as the initial state, known as Model Predictive Control (MPC). In [22], [23], [24], [25] and [26] the EMS is carried out from a dynamic control model of the elements in the microgrid, which calculates the optimal operation taking into account stability and frequency constraints.…”

Improved Feeder Flow Control Method for a Virtual Power Plant With Various Resources to Reduce Communication Dependency

“…An ESS consists of a battery (i.e., a power source) and an inverter that is required for interfacing a battery to the power system as shown in Fig. 2(b) [15]. As the output of an ESS can be controlled by an inverter, an ESS can be used to mitigate the variable outputs of REGs and maintain the VPP output at the contracted value.…”

“…Furthermore, because an ESS is usually based on a Li-ion battery source that has a fast response time of less than 1 ms [28], the bandwidth of an inverter controller can be large; hence, the ESS has a very fast response time. Generally, the bandwidth of the power controller for an ESS could be over a thousand [15]. However, an ESS has a state of charge (SOC) limitation due to the battery capacity.…”

“…However, an ESS has a state of charge (SOC) limitation due to the battery capacity. Therefore, thorough SOC management for an ESS is essential [15].…”

Cooperative Frequency Control of a Small-Scale Power System between Diesel Engine Driven Adjustable Speed Generator and Battery

“…Against this background, various design methods of microgrids, which include diesel power plants, energy storage systems and renewable energy sources, have been proposed that consider various viewpoints. Most of these studies are premised on the utilization of energy storage devices, and stabilization control studies using batteries for the balance between supply and demand in the microgrid have also been reported [1][2][3][4][5][6]. In some cases, flywheel energy storage systems are introduced into diesel power generator-based microgrids instead of chemical batteries [7,8].…”