Flywheel Energy Storage Technology And Its Application In Power System Control

The security and stability of the power system have been concerned widely. The rapid development of energy storage technologies provides an effective means to improve the power system security and stability. The flexible power conditioner (FPC) is a novel FACTS device which integrating both the characteristics of flywheel energy storage and the doubly-fed induction generator. It can perform multi-functions including energy storage, dynamic active and reactive power conditioning. In this dissertation, the flywheel energy storage technology represented as FPC and its application in power system control are researched.At first, the overview of background and research status of using energy storage technology to improve the power system stability is given in the dissertation. The characteristics of several major energy storage technologies and its current applications on improveing power system stability are analyzed and compared. And the result illustrate that the flywheel energy storage technology is a more suitable energy storage technology for improving power system stability. The principle, constitution and research situation of the FPC are described as well.The rest of the dissertation is organized as follows:(1) In Chapter 2, a 380V/4kW FPC prototype has been developed and detailed laboratory test of the dynamic operation characteristics of the prototype is performed. The test results show that the prototype can perform frequency conversion start without supplementary starting equipment, and exchange the active power and reactive power with the grid independently and quickly at both the sub-synchronous and super-synchronous operation states. The feasibility of the FPC is validated. Satisfactory characteristics dynamic operations are obtained.(2) The electromechanical wave propagation, which is a new idea for analyzing and studying active power oscillations, is applied to the analysis and control of the power system with FPC in Chapter 3. The characteristic of the electromechanical wave propagation on the system with single generator is analyzed as well the control method of the FPC based on the electromechanical wave propagation is proposed. The corresponding controller of 380V/4kW FPC prototype is designed as the proposed method. The test results show that the FPC can effectively improve the system stability. The feasibility of the proposed control method based on electromechanical wave propagation is validated.(3) Chapter 4 proposes a novel control method for improving AC interconnected grids stability based on flywheel energy storage, by configuring the inter-area mode corresponding eigenvalue and damping the inter-area mode effectively even in the case of the capacity of the flywheel energy storage device is limited. The optimization of the control coefficients and the selection of the position are discussed. The influence of the response time on control effect is analyzed and the practical control strategy is proposed. The validation of the control method is verified by digital simulations. Satisfactory results in the case of limited the flywheel energy storage device output power are obtained.(4) The dynamic stability of the interconnection grids would be affected by AC interconnection. By comparisons between the AC and DC interconnection, Chapter 5 proposes a novel method by which the region decoupling control for AC interconnected girds could be achieved by using flywheel energy storage, that is, the stability control of the region gird could be implemented just according to its own characteristic, by that the flywheel energy storage device eliminates the mutual influence between the interconnected girds. The feasibility of the region decoupling control is proved by theoretical analysis. The influences of the flywheel energy storage device location, output power and response time on the proposed control are discussed. The practical control strategy is proposed. Its validity is verified by simulations in two power system.(5) Flywheel energy storage technology has become a new means for frequency regulation, and has been running live on the grids and earning revenue. Chapter 6 describes the 20 MW Frequency Regulation Plant in ISO-NY in USA. The emissions and cost comparison for the flywheel energy storage technology for frequency regulation and other frequency regulation technologies are analyzed. The highly favorable emissions and cost performances of the flywheel-based frequency regulation technology are obtained.