Studies On Wide-Area Damping Control For Large-Scale Power System With Wind Power Integration

With the development and utilization of large-scale new energy and rapid advance of UHV power grid interconnection corridor construction, the scale and the dynamic characteristics of interconnected power systems is becoming increasingly complex, the effect of different kinds of uncertain factors in large power grid on stable operation of the interconnected power system is increasing, it becomes more and more difficult to rely barely on the local area controller which is based on local signals to suppress low-frequency oscillations in the interconnected power systems. Development of wide area measurement system provides a powerful guarantee for dynamic stability analysis and research on network-source coordination damping control technology in interconnected power system, but due to the widespread distribution of large interconnected power systems, wide area signal delays in the transmission channel inevitably, so it is necessary to consider the impact of the time-varying and time-lag effect of the wide area signal when using wide area signal for additional damping control.In this paper, new ideas, new theories and new methods are explored based on stability analysis related to wide-area power system time-delay, the effect of wide-area damping control measures on improving the dynamic characteristics of interconnected power systems and network source coordination control technology are the emphases, the main contents of this paper are as follows:In the first part, a time-delay power system model which take the time-varying and time-lag characteristics of wide-area signal into account based on the wide-area damping control structure of the large-scale interconnected power system is proposed, which is the base of the time-delay stability analysis and damping control in the subsequent chapters. Also a reduction method of power system model based on LMI technique is proposed. This method increases the consistency of the reduced model in the low frequency range with full-order model, having the better approximation performance compared to the traditional method. This reduction method is the basis for the design of damping controller in the subsequent chapters.In the second part, a maximum time-delay stability upper bound calculation method of the power system based on comprehensive approach is proposed, which overcomes the problems of presence of a large number of decision variables and low computational efficiency in the traditional methods. A stability criterion which has better decision variable and higher computational efficiency based on Jensen integral inequality is derived without increasing the conservative of the stability criterion. Also a method to determine the time-lag initial value which is based on the relationship between the maximum time-delay stability upper bound and the system's unstable poles is proposed, further reducing the number of iterations and computation. The simulation examples show that the proposed method has good potential of applicability and practical application.In the third part, the impact of the increasing wind power proportion on the damping characteristics of interconnected power system is analyzed, on which a wide-area control strategy of wind farm based on reactive power compensation equipment and a wide-area control strategy of synchronization unit related to grid-side based on the additional excitation control are proposed, and then the thought of wide-area time-delay Robust coordination control in power system concluding wind power is proposed comprehensively. A new design method of wide-area time-delay damping controller which bind free-weighting matrix method and the state observer theory is proposed, which can easily obtain the maximum time-delay stable upper bound of wide-area power system through the iterative algorithm in the design of wide-area controller.In the fourth part, a model of power system which take the feedback signal's time-varying and time-delay characteristics and the effect of external random disturbance into account is established. A robust performance index of the closed-loop time-delay power system and delay-dependent robust stability criterion are proposed. Using binary search technology can help obtain the minimum robust performance index easily. Binding improved taper complementary algorithm and binary search technique, the delay-dependent robust damping controller design method which meet the requirements of the minimum robust performance index is presented. The simulation example shows that this method can not only improve the dynamic stability of the closed-loop time-delay power system, but also fully guarantee the best attenuation performance of the closed-loop system for external random disturbances.