Model-Free Fast Frequency Control Support With Energy Storage System

With the advantage of quick response and flexible ramp, energy storage system (ESS) offers a promising capability of fast frequency control for power systems, especially under a severe disturbance. This paper proposes an ESS control strategy using local measurement in order to provide fast frequency support right after a sufficiently severe disturbance is observed. The proposed strategy includes online frequency characteristic estimator and online optimization controller. Distinguished from existing approaches, no prior knowledge of power system model is required in this work, including generator configuration, operation condition, and frequency response of each component. Instead, the overall system frequency characteristic is approximated online by the proposed estimator. Then, the power setpoint of ESS is determined adaptively to participate in frequency control by the proposed model predictive controller. Finally, the effectiveness of the proposed method is verified via real-world data of a provincial power grid in China.

I. Introduction

As A Clean and sustainable energy, renewable power generation has received wide attention and rapid development around the world. However, most wind power or solar generation operates at maximum power point tracking (MPPT) mode and decouples from system frequency. As a result, it leads to very limited inertial response and primary frequency regulation compared to conventional generators [1], [2]. Thus large-scale renewable power integration brings significant challenge to fast frequency control of power system [3], [4]. Following a fault such as a generator trip, frequency of a system with high penetration of renewable power generation is likely to drop rapidly and then gets to a low nadir. When the frequency drops below the preset threshold for under frequency load-shedding (UFLS), a certain amount of load will be shed immediately and automatically so as to maintain system security. However, it decreases the reliability of power supply and results in large economic losses.