Loss of field protection is of great importance for the security of large-scale generators. With the development of large-scale generators and corresponding loss of field protection, the complicated structure leads to...
详细信息
ISBN:
(纸本)9781457710001
Loss of field protection is of great importance for the security of large-scale generators. With the development of large-scale generators and corresponding loss of field protection, the complicated structure leads to the high possibility of loss of field faults. According to the statistical data, more than sixty percentages of the synchronous generator faults are the excitation system faults, which might cause loss of load, tie-line tripping, instability, collapse and etc. Therefore, it is crucial to identify loss of field as early as possible and take countermeasures. In loss of field protection, the impedance boundary criterion of steady state stability limit is widely used to distinguish loss of field and normal condition. However, the steady state stability limit circle is affected by the system operating modes, which might result in mis-operation of the relay. In this paper, an approach for on-line identifying system equivalent impedance is presented based on PMU measurements. The steady state stability limit circle can be adaptively fit for operating modes. The computer simulation results demonstrate that the proposed method works well.
A three-terminal DC transmission system based on modular multilevel converter (MMC) is developed to solve the problem of power supply for distributed islands or *** system,with flexible features,may generate high qual...
详细信息
A three-terminal DC transmission system based on modular multilevel converter (MMC) is developed to solve the problem of power supply for distributed islands or *** system,with flexible features,may generate high quality output voltage and reduce construction costs and power losses in the converter ***,the three-terminal DC system based on MMC faces more complex situations in operation and its control *** this paper,the mathematic model of three-terminal DC system based on MMC is *** according to the structure of MMC,a method of carrier phase-shift SPWM is *** the system-level control,the decoupling controller for threeterminal DC system based on MMC is designed.A multi-point DC voltage control strategy based on DC voltage error method,which doesn't need communication between converter stations,is proposed to improve the system *** simulation with PSCAD/EMTDC,the feasibility and effectiveness of the proposed model and control strategies are verified.
The fault in any complex systems is inevitable. Fault detection is an important area in systems engineering. Different solution techniques using qualitative, semi-quantitative and quantitative methods have been propos...
详细信息
Service restoration is a problem with multiple objectives and constraints, when the distribution systems with DGs (distributed generators) come up large area blackout. In this article the model of multiple objective s...
详细信息
Service restoration is a problem with multiple objectives and constraints, when the distribution systems with DGs (distributed generators) come up large area blackout. In this article the model of multiple objective service restoration about distribution systems with DGs has been built, considering users’ priority, the action times of hand switches or tele-switches and network losses after service restoring. Multi-agent GA can be used to search the Pareto optimal solution set for the multiple objectives service restoration problem. Agent's competitive and selflearning actions reflect the principal of survival of the fittest and diversity. It can reduce complex rate and improve efficiency using challenge match method to form Pareto solution to store populations. At last the calculation example manifests the quickness and precision of the multiple objective service restoration for blackout based multi-agent GA, and it is better suit for the distribution system than single objective method.
The estimation of operating reserve to guarantee the system security and economic operation is an important task in powersystem operation. With the rapid increase of wind power installation and its large scale integr...
详细信息
The estimation of operating reserve to guarantee the system security and economic operation is an important task in powersystem operation. With the rapid increase of wind power installation and its large scale integration into powersystems, the uncertainty of wind power should be considered in operating reserve estimation. This paper discusses the risk from wind power forecast error and introduces the idea of wind power at risk. The total risk due to wind power forecast error is studied from two different aspects, and two sets of indices are proposed. Credibility theory is applied to get the comprehensive index which is used to estimate operating reserve. Numerical tests are done to compare the proposed approach with others. The results show that the proposed approach can give more economic operating reserve estimation without loss of system security, which may be a reference for the powersystems with large scale intermittent generation to estimate operating reserve.
dynamic security region (DSR), which describing the transient stability of powersystem from the parameter space, has attracted a lot of attentions. However, there are few literatures concerning the impact of generati...
详细信息
dynamic security region (DSR), which describing the transient stability of powersystem from the parameter space, has attracted a lot of attentions. However, there are few literatures concerning the impact of generation system model on the DSR. This paper focuses on the impact of generation system model including high order model of generator, excitation system, speed governor, on DSR, based on the extension of DSR theory from the powersystem with ordinary differential structure to the powersystem with differential-algebraic equation(DAE). The simulation results investigate impact of generation system, especially exciter magnitude and the governor system to DSR, i.e. DSR with different generation system model.
dynamic economic dispatch (DED) is a high-dimensional, non-convex, multi-constrained optimization problem. With the increase of wind power penetration into powersystems, the DED problem becomes more difficult. In the...
详细信息
dynamic economic dispatch (DED) is a high-dimensional, non-convex, multi-constrained optimization problem. With the increase of wind power penetration into powersystems, the DED problem becomes more difficult. In the mathematical model, the constraints of wind farm output and spinning reserve are proposed to deal with the random and unpredictable nature of wind power. In the powersystem with large-scale wind farm, wind power should be adjusted according to available spinning reserve capacity. To improve the searching capability of binary differential evolution (BDE) algorithm, an adaptive adjusting strategy for control parameters is adopted. At the same time, the constraints are solved by some new strategies, which can make all the particles feasible, then searching efficiency is greatly improved. The presented method is proved effective by some numerical examples.
Studying the HVDC typical fault-the commutation failure and its protection measures will give some guidance for HVDC engineering,also,it will improve the AC-DC powersystem safety and reliability with great *** on the...
详细信息
Studying the HVDC typical fault-the commutation failure and its protection measures will give some guidance for HVDC engineering,also,it will improve the AC-DC powersystem safety and reliability with great *** on the analysis of commutation failure of HVDC,the article studies the effect of the commutation failure when the commutation buses have different kinds of AC faults on the base of CIGRE HVDC benchmark model,with the simulation of PSCAD/*** in-depth analysis of the causes of commutation failure,the type and characteristics of the fault will be done in this *** for the characteristics of HVDC system,combined with AC transmission relay protection tuning principle,conservation and protection action principle approach,are given to promoting HVDC transmission should take measures to return to *** simulation results show that the HVDC transmission recovers from commutation failure effectively after the fault is cleared due to the high controllability of the system and the reasonable protection strategies.
A novel scheme based on generalized leakage inductance (GLI) to distinguish the inrush current from the internal fault current in the power transformer is proposed. By eliminating the mutual flux linkage in the transf...
详细信息
ISBN:
(纸本)9781457710001
A novel scheme based on generalized leakage inductance (GLI) to distinguish the inrush current from the internal fault current in the power transformer is proposed. By eliminating the mutual flux linkage in the transformer loop equation and adopting the trapezoid principle, the GLI is calculated in the real time. According to the difference between the GLI and the leakage inductance obtained from transformer manufacturer, the criterion to identify the internal fault is developed. A total of 162 experimental cases have been tested and the proposed method is able to reliably and accurately discriminate internal faults from inrush currents with easy implementation. Also, the method is suitable if it is not possible to measure the currents in the delta winding. Furthermore, the method is independent of the B-H curve and iron losses.
This paper presents two novel topologies on precharge and submodule capacitor voltage balancing schemes of Modular Multilevel Converter (MMC) for VSC-HVDC application respectively. Firstly, A traditional precharge pro...
详细信息
ISBN:
(纸本)9781424462537
This paper presents two novel topologies on precharge and submodule capacitor voltage balancing schemes of Modular Multilevel Converter (MMC) for VSC-HVDC application respectively. Firstly, A traditional precharge process of MMC was modeled in PSCAD/EMTDC, its drawbacks were summarized and a novel topology was proposed based on submodules charged synchronously;Secondly, we analyzed the principles of a traditional submodule capacitor voltage balancing scheme, clarified its limitations and another novel topology based on the essential objectives of the balancing schemes was proposed. The topology is with Double DC Bus Bars, external DC voltage source and antiparallel thyristors. Detailed analysis and simulations indicated that the two topologies presented here not only can make up the drawbacks of the conventional schemes to a certain extent, but also have great potentiality in the application of VSC-HVDC projects in the future.
暂无评论