Available transfer capability (ATC) is defined as a measure of the system's capability for transfers of power for further commercial activity, over and above already committed uses. In practical power markets, ATC...
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DSR (dynamicsecurity region) is one of the direct methods focusing on the transient stability of powersystem. This paper focuses on the DSRs of powersystem with different load models, and explores the characteristi...
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DSR (dynamicsecurity region) is one of the direct methods focusing on the transient stability of powersystem. This paper focuses on the DSRs of powersystem with different load models, and explores the characteristic of the DSRs of the powersystem with constant impedance load and motor load. It deduces the algorithm for DSR of powersystem described with differential algebraic equation, after introducing the theory of DSR for powersystem with network-reduction model. And then, it presents the mathematical models for the constant impedance load and motor load. Based on the simulation results, it presents the DSRs for the powersystem with respect to constant impedance load and motor load, respectively. And furthermore, it compares the characteristic of the DSRs of powersystem with different loads, and summarizes the impact of different loads characteristic on the DSR.
Three single-phase H-bridge DVR is a kind of dynamic voltage restorer (DVR) which is used very widely. The traditional analysis method of compensation strategy has some shortcomings so that it is not suitable for this...
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Three single-phase H-bridge DVR is a kind of dynamic voltage restorer (DVR) which is used very widely. The traditional analysis method of compensation strategy has some shortcomings so that it is not suitable for this kind of DVR. A new analysis method which could overcome the shortcomings of the tradition method is proposed in the paper. The new method not only has definite physical concept but also could determine the compensation range easily when unbalanced voltage sag happened. More importantly, it could be applied to unbalanced load. Adopting the new method, the compensation strategy of three single-phase H-bridge DVR is studied. The simulation result shows the correctness of the theoretical analysis.
The electromechanical coupling model is employed to define the all-mode shape and torsional mode shape, and deduce the linear solutions of torques. Based on the solutions of torques, mode shapes of torques and mode co...
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In load model verification process, the accuracy of model and its parameters makes the actual operating conditions unable to reappear in simulation. The information deviation between measured data and verifiable simul...
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In load model verification process, the accuracy of model and its parameters makes the actual operating conditions unable to reappear in simulation. The information deviation between measured data and verifiable simulation data makes it impossible to ensure the descriptive power of measurement-based load model for real load characteristics. With this problem, the paper applies closed-loop verification approach to this question for the first time. The closed-loop verification approach is common in system identification study but newly used in load model comparison and validation. Two cases based on PSASP are studied in the paper. The object of this study is composite load model and the verification is carried out on a 10-generator, 39-bus New England powersystem. They both prove the validity of composite load model and the feasibility of this verification approach.
The removal of overload lines can cause power flow transferring, which may give rise to some transmission lines overload. By analysis of available methods of determining transmission sections with shortcomings, this p...
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The removal of overload lines can cause power flow transferring, which may give rise to some transmission lines overload. By analysis of available methods of determining transmission sections with shortcomings, this paper proposes a new way to determine transmissions section based on real-time power flows, and then deduce a new criterion of transmission section securityprotection based on the redundancy of normal line's power flows. A new transmission section securityprotectioncontrol scheme based on wide area measurement system (WAMS) is also proposed. When there is line overload, we should make a decision according to the protection criterion, if the transmission lines are safe after the overload removal, allow the backup protection to cut off the overload line; if not, block the protection. Therefore, it can avoid cascading overload tripping. At last, the validity of proposed algorithm is verified by the simulation results of CEPRI 36-bus system.
When taking emergency control measures to eliminate the overload circuits, it is necessary to ensure the normal lines of powersystem won't overload. Therefore, it's necessary to analyze the security of the no...
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When taking emergency control measures to eliminate the overload circuits, it is necessary to ensure the normal lines of powersystem won't overload. Therefore, it's necessary to analyze the security of the normal lines when take measures to eliminate overload. Based on the analysis of traditional methods of eliminating overload lines, this paper proposes an new overload control scheme based on wide area information, which can in parallel analyzing the impact of the normal line's redundancy on the regulated quantity of matching units, then the analysis results are sent to the control center, which finally determines the regulated quantity. It can ensure the normal lines won't overload when eliminating overload, and also can improve the computing speed of the whole control process. Therefore, it's very conducive to ensure the powersystem operating in a safe and stable state. Finally, simulation experiments verify the program is fast and reasonable.
A novel main circuit topology of voltage quality disturbance generator is proposed in this paper, composed of PWM rectifier and cascade H bridge inverter. The three phase inverter is decoupling controlled. The main ad...
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A novel main circuit topology of voltage quality disturbance generator is proposed in this paper, composed of PWM rectifier and cascade H bridge inverter. The three phase inverter is decoupling controlled. The main advantage of the topology is a hybrid structure, the mainly power of voltage quality disturbance generator is supplied by system source and the small power is supplied by inverter, so the capacitor generator is easy to realize larger because of lower active loss. PWM rectifier is adopted to maintain the dc-bus voltage stably, the later inverter is composed of cascade H-bridges. The inverter is controlled by carrier phase shifting with FPGA. The simulation model is set up on the platform of PSCAD/EMTDC, the problems of voltage fluctuation and flicker, sag and harmonic is researched by theoretical analysis and simulation. Finally, the simulation and experimental results show that the proposed main circuit topology and control strategy is feasible and efficient.
As a clean renewable energy, wind energy draws more and more attention around the world. In case of high wind speed or low speed but substantial installed wind power capacity, wind turbine generators (WTGs) will take ...
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As a clean renewable energy, wind energy draws more and more attention around the world. In case of high wind speed or low speed but substantial installed wind power capacity, wind turbine generators (WTGs) will take the place of traditional power plant partly. Under the circumstance, the transient stability will change. Therefore, in this article, the synthetical dynamic model of WTG is introduced first, and on the basis of it, the article focus on the comparison of transient stability characteristic between wind farm based on double fed induction generator (DFIG) and tradition power plant with the same capacity. Take an actual grid including wind farm as an example. The power factor of the wind farm is 1.00 and keeps constant during steady state. Under this control mode, the reactive power between wind farm and the grid is zero. The study indicates that, in this system, when the scale of wind farm connected is below 12.3%, the transient stability is better than synchronous generator integrated with the identical capacity. And with the increasing capacity of wind farm, the fault critical clearing time (CCT) is shorter, and it lasts longer time during the recovery. When the scale of wind farm exceeds 12.3%, the terminal voltage of point of common coupling (PCC) is below 0.95 p.u. The stability is inferior to the synchronous generator connected. Under the circumstance, the stability will be enhanced through adding the reactive power compensative device.
Based on the synthetic control of microgrid, a flexible power electronics interface is developed in this paper. Considering distributed generation types and storage devices, different control strategies are adopted in...
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Based on the synthetic control of microgrid, a flexible power electronics interface is developed in this paper. Considering distributed generation types and storage devices, different control strategies are adopted in controller design for different distributed generation units. The interface comprises a couple of back-to-back VSC converters, and exports variable active power and reactive power in order to maintain the power balance inside the microgrid. Apparently, the interface separates the microgird from the AC grid, prevent harmonic component transmitting from one side to the other side and control the active power precisely flowing between microgrid and main grid. Besides, it's also in charge of reactive power compensation and keeping the microgrid voltage stable. Simulation results can approve its superiority and validity comparing with direct connection.
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