Comprehensive control method of energy storage system to participate in primary frequency regulation with adaptive state of charge recovery

Abstract

This paper proposed a comprehensive control method for energy storage system (ESS) participating in primary frequency regulation (PFR). The integrated control strategy consists of PFR stage and "stage of charge" (SOC) recovery stage. In the PFR stage, the virtual droop control and virtual inertia control are combined and applied in the frequency deterioration phase to reduce the frequency deviation. The virtual negative inertia control coupled with virtual droop control is used in the frequency recovery phase to accelerate frequency recovery. In the SOC recovery stage, an adaptive SOC recovery control method is proposed. The SOC recovery control is performed while the frequency is within the dead zone, and the recovery power of ESS is based on the SOC to avoid overcharging and over-discharging. The proposed SOC recovery control can restore the SOC to a proper range which ensures the potential for ESS to participate in the next PFR process. It also reduces the number of SOC recovery starts compared with the fixed target SOC method and is beneficial to prolong the cycle life of ESS. Simulation outcomes demonstrate that the proposed comprehensive control method can efficiently enhance the frequency regulation performance and restore the SOC to the target range.

Adaptive Virtual Inertial Control and Virtual Droop Control Coordinated Control Strategy for Hybrid Energy Storage Taking into Account State of Charge Optimization

“…When the energy storage battery responds to the demand of system frequency regulation, if it has been operating with a given inertia/sag coefficient, it is very easy to saturate or exhaust the energy storage capacity due to the excessive frequency deviation in some time periods. In previous studies, many experts and scholars have improved the fixed inertia/sag coefficient control [22,23], and the more typical ones are the variable coefficient control [24], however, the previous control strategies focus on establishing a simple linear constraint between the storage inertia/sag coefficients K VIC B and K VDC B and the SOC. This alleviates the problem of overcharge and overdischarge of the energy storage battery to a certain extent, but at the same time, there are two main problems: one is weakening of the fast response characteristics of the energy storage battery, and the other is a secondary perturbation of the system frequency when its own SOC reaches the critical point.…”

Research on the Frequency Regulation Strategy of Large-Scale Battery Energy Storage in the Power Grid System

“…(1) Te system reference frequency f is set to 50 Hz; Δf is grid frequency deviation; the dead partition range of system frequency regulation is |Δf| ≤ 0.033 Hz, that is, when the system frequency is within ±0.033 Hz, the BESS does not participate in frequency regulation [24]. (2) If the system frequency fuctuation beyond the dead partition, it is necessary to judge the battery SOC.…”

Coordinated Frequency Control of an Energy Storage System with a Generator for Frequency Regulation in a Power Plant

“…In most studies, an SoC reference value required to regulate the SoC of the ESS is set as a constant. This fixed value must be adjusted to avoid frequent charging and discharging of the ESS because it is not the same as the target value [27]. Therefore, in this study, the operation of the ESS was subject to the SoC range constraint to limit its output power according to the SoC and prevent the aforementioned issue when it participates in FR.…”