Power System Stability Control By Using Superconducting Magnetic Energy Storage Technology

Rapid development of energy storage technology is potential solution to the problemthat large amount of energy cannot be stored in power system. In recent years, large scalerenewable power generation, with features of fluctuation and randomness has been put intoutility, which brings great challenges to the power system operation and stabilization. En-ergy storage is one of the most important technologies to face the challenges. Hence, energystorage plays an essential role in modern power systems. Firstly this thesis reviewed thehistory and recent development of energy storage applications in power system. Compari-sons of different types of energy storage are made. Techno-economical features shows thatsuperconducting magnetic energy storage (SMES) has bright future in system stability con-trol. Based on the literature review, this thesis systematically studies the application ofSMES in power system stability control including the aspects of mathematical modeling,digital simulation, theoretical analysis, control strategy and laboratorial prototype. This the-sis consists of following parts.In chapter2, a modified11-bus test system with both wind farm and SMES are im-plemented. The wind farm is represented as a doubly fed induction generator (DFIG) basedwind generator. A stochastic-based approach to evaluate the probabilistic transient stabilityindex of the power system is presented. Uncertain factors include both sequence of dis-turbance in power grid and stochastic generation of the wind farm. The spectrums of dis-turbance in the grid as the fault type, the fault location, the fault clearing time and the au-tomatic reclosing process with their probabilities of occurrence are used to calculate theprobability indices. With the proposed method based on Monte-Carlo simulation and bisec-tion method, system stability is "measured". Quantitative relationship of penetration level,SMES coil size and system stability is established. Considering the stability versus coil sizeto be the production curve, together with the cost function, the coil size is optimized eco-nomically.In addition, chapter3analyzes the impact of high penetration of grid-connected windfarm on power system small signal stability. Considering the fluctuation of wind power,effects of the variation of DFIG’s parameters on system linearization are investigated.Based on the damping characteristics of the system, a coordinated output feedback dampingcontroller of wind farm and energy storage is designed. The synthesis of the controller isdefined as a problem of mixed H2=H1output-feedback control with regional pole place- ment and is resolved by the linear matrix inequality (LMI) approach. Nonlinear simulationand eigenvalue analysis demonstrate the robustness of the controller designed with lineartechniques handling the fluctuation of wind generation which leads to the variation of pa-rameters and power output.Chapter4proposed an anti-windup compensator for energy storage applied as powersystem stabilizer, considering its limited power output. Without taking the capacity of en-ergy storage into consideration, linear controller can be designed. In this chapter, residuebased design method is used as the control group, which can damps the power oscillationeffectively. When facing limited capacity of energy storage, however, its output power isdifferent from the expected. This leads to degradation of system performances, even loss ofsynchronization. In this chapter, the capacity of energy storage is represented as actuatorsaturation and analyzed as constraint input system. An anti-windup scheme along with theappropriate linear matrix inequalities (LMIs) is adopted here to obtain the anti-windupcompensator. Under the test system, anti-windup scheme renders better performance andhas no influence on the linear controller.Chapter4designed the anti-windup compensator for the possible solution to the limi-tation of power output of the energy storage. The basic idea is to apply anti-windup whenthe performance of the saturated system faces degradation with saturation. For this, an an-ti-windup scheme along with the appropriate linear matrix inequalities (LMIs) is adoptedhere to obtain the gains. Under the test system, anti-windup scheme renders better perfor-mance and has no influence on the linear controller.Chapter5introduces the first moveable conduction-cooled high temperature super-conducting magnetic energy storage (M-SMES) in China, including schematic diagram,structure, as well as performance, laboratorial and field tests. The M-SMES is rated at380V/35kJ/7kW, consisting of the high temperature magnet confined in the Dewar, the cryo-genic unit, the converter, the monitoring and control unit, and the container, etc. The labor-atory and field test results were given. Test results indicate that the M-SMES is functionedwith energy storage, featuring with fast response to four-quadrant power regulation. Theaccessories for moveable feature and anti-shock property are well designed. The M-SMESperforms well during the field test. The power oscillation is damped and bus voltage is im-proved.