Yao J.,Chongqing University of Technology |
Li H.,Hunan Electrical Power Research Institute |
Chen Z.,University of Aalborg |
Xia X.,Chongqing University of Technology |
And 3 more authors.
IEEE Transactions on Power Electronics | Year: 2013
This paper presents an enhanced control method for a doubly fed induction generator (DFIG)-based wind-power generation system with series grid-side converter (SGSC) under unbalanced grid voltage conditions. The behaviors of the DFIG system with SGSC during network unbalance are described. By injecting a series control voltage generated from the SGSC to balance the stator voltage, the adverse effects of voltage unbalance upon the DFIG, such as stator and rotor current unbalances, electromagnetic torque, and power pulsations, can be removed, and then the conventional vector control strategy for the rotor-side converter remains in full force under unbalanced conditions. Meanwhile, three control targets for the parallel grid-side converter (PGSC) are identified, including eliminating the oscillations in the total active power or reactive power, or eliminating negative-sequence current injected to the grid. Furthermore, a precise current reference generation strategy for the PGSC has been proposed for the PGSC to further improve the operation performance of the whole system. Finally, the proposed coordinated control strategy for the DFIG system with SGSC has been validated by the simulation results of a 2-MW-DFIG-based wind turbine with SGSC and experimental results on a laboratory-scale experimental rig under small steady-state grid voltage unbalance. © 2013 IEEE.
Liu Z.,North China Electrical Power University |
Pang C.,State Grid Corporation of China |
Wei J.,Chongqing Electrical Power Corporation |
He J.,Chongqing Electrical Power Corporation
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2012
In view of the load density selection problem in spatial load forecasting in the distribution network, a load density index selection method based on the interval analytic hierarchy process (IAHP) and technique for order preference by similarity to ideal solution (TOPSIS) methods is proposed. The method is an improvement on the traditional analytic hierarchy process for using interval data instead of dot data while effectively combining the theory of the IAHP method with the TOPSIS method, and the advantages of human expertise with quantitative calculation in rationally handling the uncertainties of decision factors and fuzziness of experts' judgment. This has enhanced the reliability of prediction results of load density. Finally, the method of similarity is used to correct the load density, further improving the precision of forecast. A case study shows that the method proposed has better prediction results and smaller errors. © 2012 State Grid Electric Power Research Institute Press.
Chen G.,Chongqing University |
Ma A.,Chongqing University |
Zhang J.,Chongqing Electrical Power Corporation |
Tang Y.,Chongqing University |
He G.,Communication Power Corporation
Dianwang Jishu/Power System Technology | Year: 2010
Voltage and reactive power control (VQC) in substations is an important component of automatic voltage control (AVC). In view of the defects that traditional VQC strategies are not adapted to AVC and their control effects are unsatisfied, in this paper a new VQC strategy for substation is proposed. According to this strategy and based on desired voltage value of AVC, adjusting times of on-load tap changer (OLTC) and switching times of capacitor banks, a multi-objective decision-making model is constructed. For the selectable schemes to solve the proposed model an objective decision matrix is built and through non-dimension treatment the objective decision matrix is changed into relative superior attribute degree matrix of all objectives. To overcome the shortcoming of single weight determination and make the determination of weight more effective and reasonable, the improved analytical hierarchy process (AHP), i.e., the subjective weight determining, and dispersion maximization, i.e., the objective weight determining, are integratively utilized to determine the weight the weights of indices. Finally, the optimal control strategy is solved by multi-objective decisionmaking based linear weighted sum. The feasibility and superiority of the proposed control strategy are verified by calculation example.
Li H.-W.,Southwest Petroleum University |
Li Y.-F.,Chongqing Electrical Power Co. |
Ma H.-B.,Petrochina |
Wang H.-C.,Southwest Petroleum University
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2011
Distribution power flow calculation is the base of distribution system analysis. Based on loop-analysis method, an efficient method for calculating the load flow solution of weakly meshed distribution systems is presented. In this algorithm, by using path matrix and loop matrix of the distribution network, the incident matrix of node voltages and injection currents is established based on circuit fundamental laws. Because the node voltages and load injection currents meet accurate linear relations by means of the incident matrix, the algorithm has a strong processing ability for meshed network. And because the incident matrix is constant if the distribution network structure remains, the algorithm has higher computational speed, clear and simple calculating process which makes programming easy. The test shows that the convergence of this algorithm becomes faster when more loops are closed in the same system. Test results also demonstrate the validity and universality of the proposed method.
Ma Y.-Q.,Yongchuan Power Bureau |
Zhang Y.-Y.,Chongqing University |
Wu J.,Chongqing Electrical Power Corporation
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2010
IEC recommended flickermeter takes incandescent flicker as the object of analysis, however, the fluorescent lights flicker and the incandescence lights flicker are different in their generation mechanism. So with a variety of large-scale use of fluorescent lamps, the limitations of this measurement principle then gradually emerge. In this paper, spectral analysis method is used to analyze the deficiencies of the IEC recommended flickermeter in the measurement of voltage flicker caused by the inter-harmonics, and then to draw attention to the issue, promoting voltage flicker measurement methods further improvedment.
Huang M.,Chongqing University |
Li W.,BC Hydro |
Yan W.,Chongqing University |
Zhang H.,Chongqing Electric Power Company |
Xu J.,Chongqing Electrical Power Corporation
Dianwang Jishu/Power System Technology | Year: 2012
A method to accurately estimate parameters of d-axis equivalent circuit of synchronous generator by operational inductance model obtained from the identification is proposed. Due to the errors in the parameters of operational inductance model obtained from identification in general, the parameters of equivalent circuit directly solved by analytical formulae may be far from their true values. To obtain more accurate parameters of equivalent circuit, firstly the values of equivalent circuit parameters calculated by analytical formulae are taken as initial values, then based on the hybrid state model of generator these parameters of equivalent circuit are estimated by prediction error method. Simulation results show that the proposed method is effective.
Liao R.-J.,Chongqing University |
Sun H.-G.,ABB |
Yuan Q.,Chongqing University |
Yuan Q.,Chongqing Electrical Power Corporation |
And 4 more authors.
Gaodianya Jishu/High Voltage Engineering | Year: 2011
In order to obtain non-destructive diagnosis of the aging state of power transformer insulation by the recovery voltage method (RVM), the variation of the RVM parameters of oil-paper insulations with the aging degrees was investigated using the accelerated thermal aging and the recovery voltage method tests. On the basis of the effect of water on RVM parameters, RVM parameters of aged oil-paper samples before and after drying treatment were comparatively analyzed. A new RVM parameter, namely, relatively constant voltage, was proposed to assess the aging state of oil-paper insulation. The new parameter is able to characterize the longer portion of the RVM curves and is highly related to both the aging stage and the moisture of the oil-paper insulation. Results show that there is a close linear relation between each RVM parameter and the aging stage, but the goodness of linearity decreases with the increase of the moisture content; With the increasing of aging degree, the maximum of RVM as well as the initial slope and relatively constant voltage increases, but the central time constant decreases; Charging time also has effect on the RVM parameters.
Li L.-B.,Chongqing Electrical Power Corporation |
Liu Y.-G.,Chongqing University
Gaoya Dianqi/High Voltage Apparatus | Year: 2011
In order to study the causes of the lightning trip for 35 kV power grid in mountainous area, and to bring up effective lightning protection, the scene testing of electric parameter to 35 kV grounding grid in mountainous area is carried out and the actual parameter for the calculation, study, operation, maintenance and design of 35 kV system in mountainous area is gotten. The results show that the single phase grounding capacitive current of 35 kV power grid in mountain exceeds 10 A, so the neutral point for the 35 kV power system should be grounding through the arc suppression coil. Because the 35 kV transmission lines is not transposition, the capacitances to ground of the three conductors and the three phase voltages are asymmetry. It is difficult to select the arc suppressing coil winding to satisfy the requirements of system, and the suppressing coil cannot extinguish grounding arc effectively in fault.
Lin L.,Chongqing University |
Wang J.-B.,Chongqing University |
Tang F.-Y.,Chongqing Electrical Power Corporation |
Hu Z.-J.,Chongqing Electrical Power Corporation |
Mou D.-H.,Chongqing University
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2012
Aiming at the adjusting parameters theory of avoiding ferroresonance in neutral ungrounded system recently, we analyze the series and parallel resonance conditions when single-phase earth fault happens in neutral ungrounded system and conclude that the parallel resonance circuit can reflect actual operation situation of network. Simulation and computational analysis have been done in Elector-Magnetic Transient Program (ATP-EMTP) according to the experimental parameters of JDZJ-10 of potential transformer. The results show that decreasing capacitive reactance parameters in 10 kV system cannot avoid the resonance, but will lower harmonic order, and even will increase the impulse current on capacitor of fault phase when the single-phase earth fault takes place suddenly and increase the overcurrent of potential transformer of fault phase as the fault disappears in an instant.
Chen H.,University of Sichuan |
Zhang Y.-M.,University of Sichuan |
He Y.,Chongqing Electrical Power Co. |
Li X.-Y.,University of Sichuan |
And 2 more authors.
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2011
After the Ya'an-Jingmen 1000 kV UHVAC is put into operation, there will be a world wide unique UHV AC/DC hybrid transmission system in Sichuan power grid. To assess the impact of UHVAC operation on multi-send HVDC system of Sichuan power grid, this paper, based on 2012 high water level and peak load operation mode of Sichuan power grid, uses evaluation indicators like multi-infeed interaction factor and multi-infeed operating short-circuit ratio, and through small disturbance stability analysis and simulation, to compare two running modes which are putting Ya'an-Jingmen 1000 kV UHVAC into operation and not putting it into operation. The results show that UHVAC operation can effectively increase the sending end AC system strength, decrease the interaction among sending-end converter stations, improve small disturbance stability, increase the level of short circuit current and reduce the level of transient overvoltage of three HVDC systems of Sichuan power grid.