The model of Voltage Source Converter (VSC) based HVDC in the synchronous dq reference frame is presented in this paper. The model includes the DC link model and the VSC models. The feedback linearization principle fo...
详细信息
The model of Voltage Source Converter (VSC) based HVDC in the synchronous dq reference frame is presented in this paper. The model includes the DC link model and the VSC models. The feedback linearization principle for Multi-input Multi-output plants is analyzed. Based on the analysis, nonlinear decoupling control strategies for the two VSCs are proposed. For one VSC, the proposed nonlinear control strategy enables it to decouple DC voltage and reactive powercontrol, and for the other one, the strategy guarantees the control of active power and that of reactive power independently. Simulation was conducted with MATLAB/Simulink software to verify the proposed control strategies. The simulation results prove that the nonlinear decoupling control strategies are able to provide good performance.
The electrical capacitance tomography (ECT) system was used to the visualization of the two-phase flow as well as the measurement of the film thickness in a pulsating heat pipe (PHP). The new-developed micro-sensor wa...
详细信息
The electrical capacitance tomography (ECT) system was used to the visualization of the two-phase flow as well as the measurement of the film thickness in a pulsating heat pipe (PHP). The new-developed micro-sensor was also applied as a part of the flow channel, with the characteristics of heat transfer and hydrodynamics similar to the measured tube. The measurement accuracy and the image resolving power were improved as compared with the conventional sensors. So the applied area of the ECT technology was widened. The experimental results indicate that there might exist three flow patterns, i.e. bubble-liquid slug flow, semi-annular flow and annular flow, corresponding to different operating conditions. The measurement results of the film thickness compare well with the actual conditions, and the trend of the film thickness can realize the identification of the flow patterns.
The Substation Automation system (SAS) is a crucial element of powersystemcontrol. The devices of SAS with remote-control functions are one of the main target of cyber attack. The vulnerability assessment for commun...
详细信息
The Substation Automation system (SAS) is a crucial element of powersystemcontrol. The devices of SAS with remote-control functions are one of the main target of cyber attack. The vulnerability assessment for communication network of SASs that supporting the analysis of control process, is an unsolved problem. Combined with the characteristics of SAS and the vulnerability assessment of the distributed systems, a vulnerability assessment method for communication nework of SASs to cyber attack is proposed. The substation communication system has been classified into six basic models used to construct vulnerability state graph (VSG). The vulnerability of single action is defined based on exponential distribution function including parameters called vulnerability factor and equivalent attacking cost, and then the vulnerability value of target systems are calculated by four connection types of VSG. Furthermore, a vulnerability factor quantity method based on AHP-TOPSIS is designed. An evaluation instance is constructed from IEC 61850 standard, the proposed method is applicable to evaluate the vulnerability of communication network of SASs.
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.
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 proposed a novel dynamic reactive power compensation circuit topology which is applicable to low voltage distribution system. It described the composition, features, and working principle of dynamic reactiv...
详细信息
This paper proposed a novel dynamic reactive power compensation circuit topology which is applicable to low voltage distribution system. It described the composition, features, and working principle of dynamic reactive power compensation system. Open-loop SPWM control strategy is applied for the inverter, by adjusting the inverter output voltage to dynamically regulate the absorption or emission of reactive power by SVC, zero reactive power compensation of the system can be achieved. With the combination of fixed compensation capacitor the capacity of the inverter can be smaller when it compensates the reactive powerdynamically, it can improve the power factor and voltage level fast, efficiently and reliably. It overcomes the switching oscillation and the shortcomings of inadequate compensation, at the same time, reduce power loss and improve the voltage quality.
A novel dynamic reactive power compensation circuit topology suitable for low voltage distribution system was proposed. The efficient compensation of unbalanced load could be realized by the structure of three-phase f...
详细信息
A novel dynamic reactive power compensation circuit topology suitable for low voltage distribution system was proposed. The efficient compensation of unbalanced load could be realized by the structure of three-phase four-leg inverter circuit. The sinusoidal pulse width modulation (SPWM) control of inverter could ensure the low distortion of voltage and current. Besides, by the regulation of the inverter's output voltage, the compensation reactive power could be dynamically regulated and the aim of system's zero reactive power compensation could be realized. Combined with fixed capacitor compensator, small capacity of inverter is required to compensate dynamic reactive power. The novel dynamic static var compensator (SVC) could improve the system's power factor and voltage stability. Finally, simulations are carried on the platform of PSCAD/EMTDC. The results show that the proposed control strategy is feasible and efficient.
With rapid development of wind power generation, the large capacity wind farms are built up and integrated into transmission network. The effect of wind farms on the grid becomes more serious and more extensive. In or...
详细信息
With rapid development of wind power generation, the large capacity wind farms are built up and integrated into transmission network. The effect of wind farms on the grid becomes more serious and more extensive. In order to investigate the dynamic performances of the grid-connected wind farm and the interaction of the wind farms, it is necessary to present the appropriate models of wind farms, which can present the wind power characteristics completely and are not too complicated. In this paper, based on the detailed model of the pitch angle controlsystem, two kinds of simplified pitch angle control models are deduced by mathematics equivalence method. Then the three models are adopted respectively, the relatively dynamic characteristics of the wind farm and the grid are compared. Later, the wind farm with different pitch angle control model is connected to the CIGRE B4-39 grid, and the simplified models are verified by simulation. Finally, the methods how to choice pitch angle control models are present.
The paper studies reactive power compensation strategy of wind farm based on optislip wound rotor induction generators (WRIGs). The WRIGs wind farm shares high market occupancy in China, but academic researches on thi...
详细信息
The paper studies reactive power compensation strategy of wind farm based on optislip wound rotor induction generators (WRIGs). The WRIGs wind farm shares high market occupancy in China, but academic researches on this grid-connected wind generation are few. Due to the WRIGs wind turbines not allowing the control of the reactive power, so it is necessary that reactive power compensation device is adopted in the large scale grid-connected wind farm. In the paper, from the perspective of system study, the compensation effects of three kind of static var compensation (SVC) are compared, and the influence of different ratings SVC on the voltage stability of the optislip wind farm is investigated. Finally, reactive power compensation strategy of the wind farm is proposed.
A novel SVC topology is proposed in this paper, firstly a multi-winding transformer is adopt to realize 12 ripple, secondly the 5th harmonic filter on system bus as the fundamental reactive power compensation, and con...
详细信息
ISBN:
(纸本)9781424427994
A novel SVC topology is proposed in this paper, firstly a multi-winding transformer is adopt to realize 12 ripple, secondly the 5th harmonic filter on system bus as the fundamental reactive power compensation, and control thyristor controlled reactor (TCR) to realize inflow system reactive power, thirdly modularization design is adopted, according to the compensation reactive power only one TCR module is phase controlled. Finally, the experimental result shows that the novel TCR without an additional filter has the advantages of low harmonic, good static and dynamic performance, small volume and etc, compared to traditional TCR.
暂无评论