Anti-islanding method with reliable protection and reasonable control run an important role in grid connected PV power generation system. The detection and calculation of real and reactive power are the bases of many ...
详细信息
The circulating current on the delta side of wye-delta connected three-phase power transformer is hard to measure. The differential transformer protection has to adopt current phase compensation method to compensate t...
详细信息
ISBN:
(纸本)9781424452293
The circulating current on the delta side of wye-delta connected three-phase power transformer is hard to measure. The differential transformer protection has to adopt current phase compensation method to compensate the circulating current. However, the differential current hardly reflect the magnetic exciting current of transformer no matter what kind of current phase compensation methods used. It limits many algorithms of identifying inrush current, such as the promising one based on the equivalent instantaneous inductance. How to obtain the circulating currents in delta side has become a difficult problem in transformer protection. In this paper, based on the voltage equations of transformer, the calculation of the resistance and leakage inductance of winding is deduced. And then, a novel algorithm of calculating the circulating currents in delta side is proposed Simulation results of MATLAB verify the accuracy of this algorithm, which offers a new way to calculate the differential currents exactly.
In the powersystem, the controllable reactor can be used as reactive power compensation device to limit over-voltage operation, reduce no-load or light load loss and improve transmission capacity. It is with characte...
详细信息
In the powersystem, the controllable reactor can be used as reactive power compensation device to limit over-voltage operation, reduce no-load or light load loss and improve transmission capacity. It is with characters of simple structure, easy maintaining, low cost and high stability, etc. The magnetic field is closely related to the reactor performance. In this paper, aiming at a controllable saturated reactor prototype, using the finite elements method, the magnetic field is studied. Then, the precise 2-D prototype field-circuit coupling model is established based on the magnetic field analysis and the finite element analysis software - ANSYS. Using this model, the magnetic field and working currents concrete values under the condition that AC and DC excitations co-exist within the core are calculated. The analysis results indicate that finite element analysis theory can effectively analyze the magnetic field of the reactor.
In the future solar energy will be very important energy source. It is noticeable that the output characteristics of a PV array are influenced by the environment factors, and the conversion efficiency of PV arrays is ...
详细信息
In the future solar energy will be very important energy source. It is noticeable that the output characteristics of a PV array are influenced by the environment factors, and the conversion efficiency of PV arrays is very low. Therefore a Maximum power Point Tracking (MPPT) technique is needed to draw peak power from the solar array in order to maximize the produced energy. This paper introduces a novel MPPT control algorithm for photovoltaic (PV) power generation systems. The proposed algorithm based on numerical calculation is able to perform MPPT with only one step by quadratic interpolation. And a constant voltage tracking (CVT) startup is used in the MPPT method to enhance the accuracy and the speediness. The rationality and the feasibility of the algorithm developed in this paper are verified by building simulation model using MATLAB SIMULINK tool. The results indicate that the proposed approach can effectively improve the MPPT speed and accuracy simultaneously.
A novel voltage fluctuation and flicker generating main circuit topology is proposed in this paper, combined with passive and active to realize voltage fluctuation and flicker. The fundamental frequency power is suppl...
详细信息
A novel voltage fluctuation and flicker generating main circuit topology is proposed in this paper, combined with passive and active to realize voltage fluctuation and flicker. The fundamental frequency power is supplied by system source and the other frequency fluctuation power is supplied by active components, so the capacitor of generator is easy to realize larger because of lower active loss. Full-bridge diode rectifier is adopted to maintain the stable DC-bus voltage, the later inverter is controlled by instantaneous value voltage and current double closed-loop to make sure good static and dynamic performance. The inverter output two frequency voltage waveforms, and added to fundamental frequency sinusoidal voltage waveform by transformer so that the typical sinusoidal modulation voltage fluctuation and flicker waveform is obtained. The simulation model is set up on the platform of Matlab/Simulink. Finally, the simulation and experimental results show that the proposed main circuit and control strategy is feasible and efficient.
According to the definition of Available Transfer Capability by North America Electric Reliability Council (NERC), we know that ATC not only depends on the topology of power network but also on the parameters of compo...
详细信息
According to the definition of Available Transfer Capability by North America Electric Reliability Council (NERC), we know that ATC not only depends on the topology of power network but also on the parameters of components. So a series of adequacy indices are proposed to evaluate ATC. Through thorough analyses on these indices, the sensitivities of components parameters to these adequacy indices are deduced. The impact of components parameters’ small variations on ATC can be reflected by these sensitivities, the importance degree of each component can be embodied. Furthermore, by sensitivity analysis we can effectively identify ATC bottlenecks and get important guide information for operation and planning. The algorithm based on MATLAB 6.5 is developed. The correctness and effectiveness of the proposed sensitivity analysis method are verified using IEEE-RTS79 test system.
This paper studies the voltage stability problems of wind farm access to electric grid. Based on the equivalent circuit of asynchronous machine, it deduces the relationship of wind turbine angular velocity rotation wi...
详细信息
ISBN:
(纸本)9781424427994
This paper studies the voltage stability problems of wind farm access to electric grid. Based on the equivalent circuit of asynchronous machine, it deduces the relationship of wind turbine angular velocity rotation with the induction generator terminal voltage. Aiming at wind power for 10 kV distribution grid, a novel SVC is proposed to replace the fixed capacitors compensating devices. The reactive power can be detected based on the instantaneous reactive power theory and with this method the reactive power compensation is fast and continuous. The voltage level of wind farm access system is stable with a voltage feedback control strategy. The new SVC winding structure can achieve a multi-pulse, injecting the system small harmonic current component. Research results show that a corresponding control strategy of the novel SVC compensation device can be very good to improve voltage stability of wind farm access to the grid.
In this paper, a new dynamic voltage-var compensator is introduced, compared to the traditional SVC, the new voltage source of continuous two-way adjustable SVC has significant advantages. This paper has introduced th...
详细信息
In this paper, a new dynamic voltage-var compensator is introduced, compared to the traditional SVC, the new voltage source of continuous two-way adjustable SVC has significant advantages. This paper has introduced the fundamental of the SVPWM; SVPWM control technology is an optimized PWM control technology, compared with the traditional PWM technology, SVPWM with a high utilizationrate, less harmonic control simple, easy-to-digital realization of the advantages. The simulink is used to simulation and analysis. The simulation results show this SVC has its own advantage. It can regulate the voltage smoothly and continually.
A novel main circuit topology of voltage quality compensator (VQC) is proposed in this paper, composed of PWM rectifier and cascade H-bridges inverter. The three phase inverter is decoupling controlled. PWM rectifier ...
详细信息
A novel main circuit topology of voltage quality compensator (VQC) is proposed in this paper, composed of PWM rectifier and cascade H-bridges inverter. The three phase inverter is decoupling controlled. PWM rectifier is adopted to maintain the dc-bus voltage stably and provide or absorb real power. The inverter is controlled by carrier phase shifting with FPGA. The simulation model is set up on the platform of PSCAD/EMTDC, the voltage sag, swell and harmonic compensation is researched by theoretical and simulation. Finally, the simulation results show that the proposed main circuit topology and control strategy is feasible and efficient for multi objectives voltage quality compensation.
This paper proposes a protection scheme for transmission lines based on nature frequency of fault-generated travelling wave. The fault component of current signals are first computed and decoupled into their modal com...
详细信息
ISBN:
(纸本)9781424449347
This paper proposes a protection scheme for transmission lines based on nature frequency of fault-generated travelling wave. The fault component of current signals are first computed and decoupled into their modal components, and then the mode spectrums are computed by FFT to extra the fundamental frequency of nature frequencies, through comparing the fundamental frequency at both ends of lines to identify internal and external faults. The scheme operates rapidly, reliably and is immune to CT saturation, operation mode and transient resistance; it can endure the influences of various fault inception angles, fault location, The performance of scheme is investigated for various faults on a typical Electro-Magnetic Transient Program/Alternative Transients Program (EMTP/ATP) simulated transmission feeder.
暂无评论