| The development of Ultra High Voltage Interregional Grid will make it possible to transmit data over several thousands of kilometers. With wide application of new communication techniques, such as Automatically Switched Optical Networks (ASON), Software Defined Network (SDN), and Optical Transport Networks (OTN) to power systems, it is impossible to simply calculate their time delay and bit error because of the high complexity of path protection algorithm. Therefore, the effects of time delay and reliability of communication system on power grid operation control will become significant.The analysis and control of the conventional power system three-line of defense is limited to provincial grids, and the inter-station communication speed and reliability are all qualified. In the interregional and long-distance Ultra High Voltage AC-DC Hybrid power grid, the wide area control puts forward higher requirements for the real-time and reliability of communication system. To meet the demand for multi-source wide area information transmission required by the power system protection targeting on power systems stability, the existing fiber optic network combined with the latest technologies of protection and control for communication should be adopted in the power system protection. The techniques, such as cross-area coordination, accurate load shedding, AC/DC coordinated control and active splitting control are usually used to guarantee the security and stability of large-scale ultra-high voltage AC/DC power network. The existing communication systems are difficult to satisfy the high reliability, high real-time and high security for communication required by the power system protection. The communication system plays a role in supporting the power system protection, so the communication interrupt, time delay and bit error may exert an important influence to power systems operation and control.The modern power system has developed into a complex coupling network system, which is composed of power systems and communication system. Large-scale blackouts of power systems caused by communication failures and attacks from time to time around the world knoll alarm clock for China power systems. Therefore, constructing a cooperation defense between communication system and power system is urgently needed in guarantying power systems" safe and stable operation.This thesis studies the impacts of communication system on the stability control of power systems. The research work mainly focuses on the following aspects:(1) Four key techniques for the engineering software of adaptive closed-loop emergency control systems are proposed. In particular, the unified control strategy based on E format is proposed for stability control equipment and wide area monitoring analysis protection-control system. Independently separation technology of data inputting and internal implementation of configurable decision engineering software simplifies its complexity. To realize the on-line and off-line adaptive search of closed-loop emergency control systems, the reliability of communication systems must be guaranteed.(2) The effects of time delay and communication interrupt between various control-layers of power grid stability control system is qualitatively analysed. Based on the quantitative theory of transient angle stability. EEAC, the analytical expressions of generator tripping selectivity to time and stability margin selectivity to generator power in classical multi machine system are derived.(3) According to the three stages, namely before the fault happening, disappearance of evil consequence after the fault happening and appearance of evil consequence after the fault happening, classified by power systems three-line of defense, the definition of communication system three-line of defense and an overall framework of communication defense system are proposed in a creative way. The function structures of early-warning subsystem and control decision subsystem in the communication defense system are introduced.(4) The mechanism of negative effects of time delay on control is verified by the case studies of the switch tripping and generator tripping with time delays. Also, the effects of time delay on stability control measures and stability margin are simulated by using optimal control strategy algorithm based on generator tripping sensitivity in the co-simulation of Ultra High Voltage AC-DC Hybrid power grid and electric power communication network. Moreover, in the simulation the fixed time delay commonly used in past researches is replaced by real time delay in communication system and the time delay caused by bit error is considered.(5) Comprehensively considering topologies and physical properties of power systems and communication system, this thesis proposes a general mathematical model taking into account of the risk of communication and information system and the mutual influence between power systems and communication system, and points out the core technique of emergency control risk estimation considering communication issues is to calculate the probability matrix describing the communication between stability control devices in various substations. Taking power systems stability control as an example, the physical meaning of matrixes in the mathematical model and their calculation method are introduced in detail. Furthermore, the calculation method for the probability matrix describing the communication between stability control devices in various substations is illustrated by the 2-bus system and Jiangsu EACCS system.(6) This thesis analyzes the ways for communication system impacting power systems. It is found by the analysis that the key to the comprehensive analysis and control of power systems and communication system is the correlation analysis based on the contingencies of both power systems and communication system. Considering the communication demand of power systems and the effects of communication system on power systems, and taking power system emergency control as an example, the thesis proposes the rule of data exchange and the flow of coordinated control for power systems emergency control and communication systems defense system. Taking a provincial power grid including ultra-high voltage transmission lines as an example, the thesis compares three kinds of stability control strategy, namely the strategy considering conventional 200ms delay load shedding, the strategy considering actual time delay of communication and the strategy considering expected faults. It shows that, after communication is introduced into blackout defense systems, the load shedding amount and control costs are less than conventional blackout defense systems.(7) In practical engineering, the performances of various control strategies are calculated based on fixed fault set, and no time delay in control process is considered in the calculations. This thesis analyzes the calculation methods for off-line and on-line control strategies considering the risk of communication and information system. Because of the fact that the calculation of emergency control strategies in WARMAP neglects the difference of time delay considering the tripping times of various control measures, an adaptive searching method in WARMAP is proposed taking into account of communication failures. Furthermore, taking a provincial power grid including ultra-high voltage transmission lines as an example, the on-line check method for off-line control strategies and the optimization algorithm for on-line control strategies, both considering communication failures, are illustrated.This research work is supported by the State Grid Corporation of China project: Key Technologies for Power System Security and Stability Defense Considering the Risk of Communication and Information Systems. The research results are applied to the developments of communication security defense system and power systems security defense system considering communication and information risk in the project. An experimental verification system platform for the project is constructed based on WARMAP, communication security defense system and regional stability control system. Through the platform, the serviceability and effectiveness of the coordinated control between WARMAP and communication security defense system are verified. |
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