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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.

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.

Li H.-W.,Southwest Petroleum University | Li Y.-F.,Chongqing Electrical Power Corporation | 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.

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.

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