It is a trend to construct unattended substation in power system *** paper systematically analyses the superiority and limitation of MATLAB and Visual C++ and illustrates how to compile m-files to cpp-files by MATLAB ...
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With rapid development of wind power generation, it's necessary to study the dynamic characteristics of wind power generators when a fault occurs in the grid to assure the safe and stable operation of the wind far...
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With rapid development of wind power generation, it's necessary to study the dynamic characteristics of wind power generators when a fault occurs in the grid to assure the safe and stable operation of the wind farm. At present, the widely used wind power generators in the whole world are squirrel cage induction generator (SCIG) and doubly fed induction generator (DFIG). The models of SCIG wind power generation system and DFIG wind power generation system connected with the grid are built, and their transient operation characteristics are studied. A new control measure is put forward to improve the transient performance of the DFIG, which is proved effective through the simulation. Also the impact of the control measure on the SCIG running in parallel with the DFIG is also investigated.
Distributed generation is regarded as the developing direction of the power system in 21 century. Because distributed generation always connects with the distribution system, which has great influence on every aspects...
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Distributed generation is regarded as the developing direction of the power system in 21 century. Because distributed generation always connects with the distribution system, which has great influence on every aspects of power system. This paper studied the influence of distributed generation on load modeling. When the influence of distributed generation is not negligible, the composite induction motor load model can't effectively describe the actual load characteristic. This paper proposes a new load model-asynchronous generator +ZIP. The validity of the proposed load model is also testified via the comparison and contrast from a great deal of simulations. Then, composite induction-motor and asynchronous generator +ZIP load models were unified in one program.
A new method for hybrid non-linear state estimation with phasor measurement unit (PMU) is proposed, in which the direct voltage phasor measurement is transformed into indirect equivalent branch current measurement to ...
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A new method for hybrid non-linear state estimation with phasor measurement unit (PMU) is proposed, in which the direct voltage phasor measurement is transformed into indirect equivalent branch current measurement to conduct the hybrid iteration with SCADA measurement. The indirect measurement errors caused by constructing the equivalent current modification are also analyzed and calculated in detail. The accuracy of the hybrid estimation algorithm is analyzed qualitatively and calculated quantitatively. The theoretic analysis and simulation results demonstrate that the proposed method has higher estimation precision and better performance in convergence time and filtering effect.
The paper presents the dynamic model and control schemes of a variable speed pitch wind turbine with permanent magnet synchronous generator (PMSG). The model includes a PMSG model, a pitch-angled controlled wind turbi...
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The paper presents the dynamic model and control schemes of a variable speed pitch wind turbine with permanent magnet synchronous generator (PMSG). The model includes a PMSG model, a pitch-angled controlled wind turbine model and a drive train model. The drive train model uses one-mass model to represent the mechanical characteristics of the generator set. The generator model is established in the dq-synchronous rotating reference frame. The wind turbine model details the mechanism of variable speed operation of the turbine by a pitch control. The control schemes in the paper include a pitch angle control for the wind turbine and a speed control for the generator. The pitch angle control uses wind speeds and electric power output as the input signals to ensure normal operation in high wind speed. The speed control is realized through field orientation where the d-axis current is set to zero and the q-axis current is used to control the rotational speed of the generator according to the variation of wind speed. In order to verify the presented model and the control strategy, simulations with MATLAB/Simulink software have been conducted. Simulation results prove the validity of the model and the control schemes.
In an AC/DC large-scale interconnection power grid, there are many problems to be solved. Among these, small-signal stability is extremely important. In this paper, based on the reallocating -damping theory of PSS, re...
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In an AC/DC large-scale interconnection power grid, there are many problems to be solved. Among these, small-signal stability is extremely important. In this paper, based on the reallocating -damping theory of PSS, reallocating-damping theory of HVDC modulation is proposed, that variation of gain of HVDC modulation doesn't influence the system general damping. It is also proved that reallocating-damping theory unifies PSS and HVDC modulation, which are both damping control measures. Mathematics deduction is given in detail. The possible negative effect caused by PSS and HVDC modulation is analyzed. A number of cases are tested such as a 12-generator system, 2DC system and a real power system.
In the paper multiterminal voltage source converter based HVDC (VSC-HVDC) is proposed to interconnect wind farms to AC grids. The method highlights the control at the level of wind generator cluster that comprises sev...
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In the paper multiterminal voltage source converter based HVDC (VSC-HVDC) is proposed to interconnect wind farms to AC grids. The method highlights the control at the level of wind generator cluster that comprises several permanent magnet synchronous generators without the primary converters on themselves. For the cluster control, active and reactive power decoupling scheme is applied to adjust the rotational speed of the cluster according to wind speed. The paper studies the schemes to control grid side converter based on the philosophy of linear decoupling control, which aims to control the DC voltage as well as the reactive power of VSC-HVDC. In the proposed control scheme, the two goals are achieved by controlling the q- and rf-axis components of the grid's fundamental current. Simulation has been performed using engineering software Matlab/Simulink to verify the interconnection method and validate the control scheme as well.
More and more IEDs have been commissioned in power systems, such as digital relays, PMUs, metering and control devices, fault recorders and so on. Once there is a disturbance (for example, fault, low-frequency oscilla...
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More and more IEDs have been commissioned in power systems, such as digital relays, PMUs, metering and control devices, fault recorders and so on. Once there is a disturbance (for example, fault, low-frequency oscillation, etc.), large amount of information will pour into the control center. Therefore, how to identify the disturbance and then take corresponding countermeasures is crucial for power system security and reliability. A multi-layer disturbance processing system based on multiple information sources is proposed in this paper. Firstly, the characteristics of different kinds of information sources, including PMUs, RTUs, digital relays and fault recorders, are analyzed. Secondly, according to the arrival times of the information, the framework and functions of multi-layer fault diagnosis system is presented in detail. After a disturbance occurs, the suggested system could realize disturbance identification, fault element diagnosis and detailed post-fault analysis in succession at different time frames with the information coming, which fits the needs of operators well.
Load modeling is very important for power system dynamic analysis and control. The composite load model widely applied recently in the power system operation centre consists of the static load and the equivalent motor...
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In the neutral ungrounded system, potential transformer (PT) ferro-magnetic resonance is a kind of interior overvoltage which is frequently appears and creates most of the accidents. Whether the elimination measures a...
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In the neutral ungrounded system, potential transformer (PT) ferro-magnetic resonance is a kind of interior overvoltage which is frequently appears and creates most of the accidents. Whether the elimination measures are reasonable and effective or not affects the security and stability of the power system directly. Fundamental research has been done on the resonance region changeable situation and the characteristics of each resonance region under different system parameter and PT saturation characteristics. According to the occurring principle of PT ferromagnetic resonance and the characteristics, a novel effective controllable damping device is designed, which will change the correlative parameter that lead to resonance to make the circuit parameter of the system get out of the resonance area to eliminate the resonance. The accuracy of the fundamental analysis and the effectiveness of the elimination measure have been verified by the digital simulation based on EMTDC/PSCAD and by the high voltage propotype experiment.
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