Song Yunting

PMU placement based on power system characteristics

We present a novel method for placing PMU in power systems based on power system intrinsic characteristics. In the method power system was first analyzed for find out the major or critical interchanges and major load areas, major control systems, critical equipments and power plants in the power system. The overall PMU facilities should provide comprehensive information of line flows, bus conditions, and control actions for power system dispatcher. Then based on coherent characteristics of rotor angles as well as bus voltages, placement of PMU is optimized. All potentially critical-modes, critical bus-clusters and generators are identified by transient stability evaluation and small signal stability analysis, and then PMU are assigned to those critical buses or power plants. The effectiveness of the proposed approach is verified with a real large-scale power system. PMU placement scheme is being implemented in Northwest China power grid. The proposed approach can also be used to different sized power systems. As the power systems become more populated by PMU, the proposed novel method is a useful and convenient tool for systematic installation of PMU around the network, which may assist system planners in deciding on the location of new PMU installments for better dynamic monitoring and control.

Optimal reliability of composite power systems using genetic algorithms

The purpose of this paper is to develop an optimal reliability framework of composite power systems using genetic algorithms. In the competitive power market environment, there might be trade-off between system installation cost and power interruption cost. Interruption cost can be obtained through quantitative reliability indices of probabilistic adequacy evaluation. Through applying the genetic algorithms to solve the kind of complex discontinuous problems, the optimal reliability indices of components are obtained, which minimize the total cost comprising apparatus investment cost and interruption cost. The numerical results show that significant savings can be achieved. The proposed method is a valuable and powerful tool for power system planning.

Probabilistic Security Evaluation of Bulk Power System Considering Cascading Outages

This paper proposed an overall framework of probabilistic security evaluation considering cascading outages for bulk power system based on enumeration approach, which takes into account several uncertainty factors in power system. The quantitative probabilistic security indices obtained by this approach can reflect power system stability and security clearly. A case study of the IEEE-RTS test system is presented to demonstrate the effectiveness and feasibility of the proposed algorithm. The proposed method adopts the enumeration approach is a valuable and powerful tool for power system planning, and it makes research results of reliability evaluation become more practical in the competitive market environment. The results presented are helpful to electric power utilities in the decision making process at the planning stage.

Stability Analysis of Power System with Under-excitation Limiter in Generator Excitation Control System

The objectives of setting under-excitation limiter (UEL) of generator excitation control system are to prevent excessive stator end-core heating and to prevent the generator from operating beyond the steady state stability limit when the generator operates in the leading reactive power region. But many oscillation cases caused by UEL happened in power system recently. This paper analyses the impact of important parameters of UEL to the system dynamic stability in-depth by using electromagnetic torque analysis method and time domain simulation method. It is concluded that the root causes of system oscillation are the negative damping provided by UEL and the effect of weakening the damping of PSS by UEL. The effective control strategy of optimizing the parameters of UEL to improve the system damping is proposed, which provides an important reference for good performance of UEL.

Identification of Critical Branch in Weakness Section Based on Disturbed Tie-Line Electrical Characteristic

Fast automatic recognition helps to find out vulnerable branch in weakness section. Taking timely control strategies after recognition is good for maintaining power system stability. At first, sending and receiving system is used to prove the phenomenon that two peaks appear in active power trajectory when it is disturbed to stability margin. Secondly, fast identification method is put forward to find out critical branch. In order to facilitate its online usage, judge formula and flow chart is given to help to make the decision. Finally, computing example of New England system is used to prove theory above and to verify control effect.

Study on frequency and voltage regulation strategy of thermal power generating units in wind power uniting thermal power outgoing system

In order to make full use of the voltage and frequency regulating ability of thermal generator in wind-thermal-bundled power delivery system, taking Jiuquan wind-thermal-bundled system as an example, the study on strategies of voltage and frequency regulating is carried out. The characteristics and typical structure of the boiler turbine coordinated control system (CCS) of modern large-scale thermal power units are analyzed, the simulation model of the CCS control mode based on boiler following (CBF) which has wide in-situ application is built. Based on the analysis and the CCS simulation model, the frequency regulation characteristic of thermal power units is studied in the case of disconnection fault occurrence in regional grid. The optimization strategies for the frequency regulation of thermal power generating units are given. The basic types and characteristics of the excitation system in large thermal power generating units are analyzed and the simulation model of self-shunt excitation system is built. On the basis of analysis and simulation model above, the thermal power unit voltage regulation strategies are studied under wind turbine generators group tripping accident.

Research on the DC access grid security and stability analysis

This article research on the DC access grid security and stability analysis. It combed the stability and security of electrified weak link, revealing the power grid dynamic characteristics of evolution mechanism. It study and formulation of reservoir in the power grid security and stability control strategy of DC power transmission system, the access of power grids in Tibet, AC / DC hybrid power grid by the end of security and stability control measures. The conclusion of the study, for reservoirs in AC DC hybrid power grid by the end of the safe and stable operation and control measures for reference to make the reasonable.

Optimal reliability evaluation method of bulk power system based on IGA

Combined with risk indices of comprehensive reliability assessment and economic assessment theory, there may be trade-off between system installations cost and power interruption cost in the competitive power market environment. To coordinate reliability and economy, this paper proposed an overall framework of optimal reliability algorithm for bulk power system based on total owning cost (TOC). Interruption cost can be obtained through quantitative reliability indices of probabilistic security and probabilistic adequacy comprehensive evaluation based on Monte-Carlo simulation. Through applying improved genetic algorithm (IGA) to solving these kinds of complex discontinuous reliability optimization problems, the optimal reliability indices of components are obtained, which minimize the total owning cost comprising apparatus investment cost and interruption cost. A case study of the IEEE-RTS test system is presented to demonstrate the effectiveness and feasibility of the proposed algorithm. The proposed method is a valuable and powerful tool for power system planning, and it makes research results of reliability evaluation become more practical in the competitive market environment.