The Study On Coordinated Control Of Energy Storage Technology Applied In Power System

Energy Storage (ES) technology can respond to exchange active and reactive power independently with ac power grid connected. It can contribute to increasing the stabilization of the power system, improving the electric power quality, and applying in renewable power generations. Hence, ES technology will play an important role in the future power system. Currently, most research on ES control methods is about a single device for a single objective. However, for ES applications in actual power grid, there is an important and difficult problem need to be solved, including the coordinated control between the ES device and the existing power system stability control device, and the coordinated control of multiple different ES devices, which has great theoretical significance and application value. The main work and innovative results are as follows.For single machine infinite bus power system with ES, based on adaptive back-stepping technique and passive theory, a coordinated control scheme of ES device and generator excitation is proposed to improve the stability of both generator angle and voltage. Analysing the influence of the ES on the system power-angle performance, fifth-order nonlinear model is built. Taking the generator damping coefficient uncertainty into consideration, active and reactive power control strategies of ES device are designed by adaptive back-stepping means, and excitation control strategy is achieved based on coordinated passivity. So the feedback passivity of whole system is obtained and the closed-loop system is asymptotically stable. The controller makes full use of the nonlinear property of the dynamic system, and it also has strong robustness for system parameters variation. Simulations have proved the effectiveness of the coordinated control scheme.For multi-machine power system with ES, energy function methods are still adopted. A coordinated control scheme of ES devices and generator excitations based on Hamilton theory is proposed for improving the power system transient stability. Considering the interaction of every generator and the coupling effects between ES devices and generators, the generalized dissipation Hamilton realization is achieved. Then, taking the model error and external noise into account, the robust coordinated controller of ES and excitations is designed combined with adaptive control. Simulation results demonstrate that the coordinated controller is able to strength the power system transient stability significantly.Since no single type of ES element can satisfy all diverse demands of power system simultaneously, the paper proposes a hybrid energy storage system (HESS) based on superconducting magnetic energy storage (SMES) and battery because of their complementary characteristics for the grid integration of wind power generations. The mathematical model and the topology of the proposed HESS is investigated. The advanced coordinated control strategies comprised of device-level and system-level are designed. The control strategy for the converters which can be considered as device-level is briefly discussed. The significant contribution is proposing a novel system-level control strategy for reasonable and effective power allocation between SMES and battery. According to the control objectives, a fuzzy logic (FL) controller optimized with genetic algorithm (GA) is adopted. The detailed controller designs are described, meanwhile system stability and HESS operation performance are evaluated. Simulations are presented to demonstrate the effectiveness of the proposed strategies.Because the ES device capacity will affect the ES controller performance, the paper will also attempt to study how to optimize ES device capacity. A method is proposed to determine the optimal capacity allocation of HESS which consists of distributed SMES device and battery device for enhancing the rotor angle stability of multi-machine power system. The optimization process is divided into two steps--preliminary optimization and comprehensive optimization. Considering both the stability of power system and the economy of ES devices, multi-objective evolutionary algorithm is used to acquire optimal capacity of HESS. The proposed method is simple and convenient to use. Simulation with IEEE three-machine nine-bus power system is presented to demonstrate its usefulness and flexibility.