An improved differential variance bacterial colony chemotaxis (DVBCC) algorithm was presented for the urban power network substation planning. Bacterial colony chemotaxis (BCC) algorithm improves the speed of converge...
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An improved differential variance bacterial colony chemotaxis (DVBCC) algorithm was presented for the urban power network substation planning. Bacterial colony chemotaxis (BCC) algorithm improves the speed of convergence compared with bacterial chemotaxis (BC) algorithm through the introduction of perception in bacterial colony, and also increases the possibility of a local optimum. DVBCC adopts adaptive control perception scope according to colony' distribution condition, at the same time adds differential variance operator in order to increase the variety of bacterial colony and improves its robust and global optima searching capability. In this paper completed economy of substation optimization planning of 110 kV and 220 kV voltage grade in urban power network was taken as objective function, and factors of geographical effect was considered. The results indicated that DVBCC algorithm outperforms BCC and particle swarm optimization (PSO) algorithms in solving substation planning problem and the proposed model has good economy and practicability.
Frequency spectrum leakage caused by synchronous error in nonsynchronous sampling system reduces the accuracy of frequency spectrum analysis and harmonic measurement. A sampling frequency self-adapting software algori...
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Frequency spectrum leakage caused by synchronous error in nonsynchronous sampling system reduces the accuracy of frequency spectrum analysis and harmonic measurement. A sampling frequency self-adapting software algorithm in protection relay measure and controlsystem is presented in this paper. The sampling frequency self-adapting software algorithm obtained the actual signal frequency fairly accurately by calculating the sampling data from protection relay measure and controlsystem, and adjusted the sampling time interval according to the frequency which was calculated by the self- adapting software algorithm. The process of the software algorithm design is introduced, simulation and analysis are discussed. The results of simulation and analysis show that this software algorithm can improve the accuracy of frequency spectrum analysis and harmonic measurement for powersystem signal, and the algorithm can be realized easily.
With increasingly proportion of distributed generation (DG) in the powersystem, traditional powersystem planning has new challenges and demands. The necessity for flexible electric system, changing regulatory, energ...
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With increasingly proportion of distributed generation (DG) in the powersystem, traditional powersystem planning has new challenges and demands. The necessity for flexible electric system, changing regulatory, energy savings and environmental impact are providing impetus to the development of DG. Itpsilas critical that the powersystem impacts be assessed accurately so that DG can be applied in a manner that avoid degradation of power quality, assure reliability and control of the utility system. In recent years, wind energy has become an important part of DG in many countries and its importance is continuing to increase. This paper focuses on the capacity planning of wind power stations, considering technical constrains, like feeder voltage profile, harmonic distortion etc, and establishes a model based on improved genetic algorithm to solve, which produces chaotic initial population to start iteration to raise algorithm for the speed and accuracy. Through simulation and calculation, the two sets of results are compared, and the feasibility of the above model and algorithm is demonstrated.
A nonlinear control strategy based on Lyapunov stability theory is proposed to satisfy stability requirements under the external interference of the uncertainty condition. Due to the nonlinear of the DC voltage differ...
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A nonlinear control strategy based on Lyapunov stability theory is proposed to satisfy stability requirements under the external interference of the uncertainty condition. Due to the nonlinear of the DC voltage differential equation for VSC-HVDC, the control of DC voltage is transformed to the control of the q-axis component of AC current fundamental component. Suitable Lyapunov functions are adopted according to the difference between reference value and actual value. Two nonlinear control inputs to the converter are obtained based on Lyapunov stability criterion. Due to linear of active power differential equation, active power is controlled based on traditional proportional integral (PI). The simulation results performed on PSCAD/EMTDC verify the feasibility of the control strategies effectively under a short time (0.05s) single phase to ground fault in two terminal AC systems of VSC- HVDC.
A control scheme is described to charge series-connected super capacitors for photovoltaic generation systems. Based on the features of the super capacitors charge, the control scheme consists of three modes, i.e., th...
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A control scheme is described to charge series-connected super capacitors for photovoltaic generation systems. Based on the features of the super capacitors charge, the control scheme consists of three modes, i.e., the constant current charge mode, the constant power charge mode, and the constant voltage charge mode. The shift of three modes can be realized by controlling the duty of IGBT in the Boost-Buck converter system. Meanwhile, the high voltage, which is more suitable for application, can be obtained. Compared with the normal charge method with series-connected current-limiting resistance and the charge method with the constant current charge mode and the constant voltage charge mode, the proposed charging control scheme can shorten the charging time and improve the usage of the electric power generated from the PV arrays. The advantage described above is verified by simulations.
This paper puts forward an auxiliary fuzzy logic controller for the Voltage Source Converter based HVDC transmission system, VSC-HVDC, to improve the stability of the AC/ DC system by damping the oscillation effective...
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This paper puts forward an auxiliary fuzzy logic controller for the Voltage Source Converter based HVDC transmission system, VSC-HVDC, to improve the stability of the AC/ DC system by damping the oscillation effectively after disturbance. The fast control capability of the VSC-HVDC and the process of area mode oscillations are analyzed. No detailed model of the system is required for the design of the proposed control scheme. The controller judges the operation states and the control effect and accordingly adjusts its active power order in an adaptive way by using fuzzy rules, so as to damp out the area mode oscillation. Simulation results on the IEEE 4-generator AC/DC powersystems have shown that the controller can enhance the dynamic stability of interconnected powersystems effectively and is robust to the variation of system operating conditions and oscillation modes.
Thyristor controlled series capacitor (TCSC) used in power transmission line can increase the transportability and the stability of system, and decrease the system loss significantly. At the same time, TCSC brings man...
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Thyristor controlled series capacitor (TCSC) used in power transmission line can increase the transportability and the stability of system, and decrease the system loss significantly. At the same time, TCSC brings many serious problems to transmission lines fault location and protective relaying. This paper analyzes the influence of TCSC to EHV transmission line protection, especially to the high-frequency directional protection. It can be obtained from the analyzing that the addition of TCSC to EHV transmission line would make the high-frequency directional protection unwanted operation or failure to operate. In order to solute the problems TCSC caused, this paper presents a novel transient protection scheme based on wavelet transform (WT). The simulation tests have proved that the analyzing and solution of the appearance of TCSC in EHV transmission line are correct.
It is of great importance to study the dynamic behavior of distributed generation (DG), which might affect the fault level and protectionsystem of distribution network greatly. In this paper, the transient stability ...
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It is of great importance to study the dynamic behavior of distributed generation (DG), which might affect the fault level and protectionsystem of distribution network greatly. In this paper, the transient stability of asynchronous type of DG is comprehensively analyzed. The critical shedding time and corresponding slip of DG are calculated. It is pointed out that the fault clearing time of existing relays cannot guarantee DG operates stable when a fault occurs in distribution network. The countermeasures to low down the possibility of instability of DG are suggested. Finally, case studies are carried out using PSCAD to demonstrate the viewpoint of this paper.
This paper proposes a fault classification scheme for transmission lines based on spectrum of fault component. First it analyses the spectrum of fault component, then the characters of power frequency and nature frequ...
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This paper proposes a fault classification scheme for transmission lines based on spectrum of fault component. First it analyses the spectrum of fault component, then the characters of power frequency and nature frequencies in two data windows are used to identify fault type and fault phase respectively. The scheme performance was proven using ATP/EMTP simulations in a 500-kV powersystem considering different fault types and fault locations. The results show that the scheme works quickly and is not impacted by harmonics and the DC offset. It is also not sensitive to sampling rate and fault inception angle.
When faults occur in transmission lines, the high frequency signals are caused by fault generated traveling waves and the spectrum is a series of harmonic in frequency domain. This paper utilizes lumped and distribute...
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When faults occur in transmission lines, the high frequency signals are caused by fault generated traveling waves and the spectrum is a series of harmonic in frequency domain. This paper utilizes lumped and distributed parameter models to express transmission lines respectively, analyzes the character of nature frequencies. Different influencing factors including different fault conditions, source impedance, bus capacitance, series compensated capacitance and shunt reactor are discussed in this paper. The results have been proven by ATP procedure in a typical 500- Kv power transmission line.
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