Advanced Materials Research Vols. 945-949

Abstract: With the rapid development of city construction, contradiction between power supply and demand becomes more marked, so the idea of building 500kV terminal substation is put forward. This paper analyzes the design principle of main electrical connection of 500kV terminal substation, introduces several typical main electrical connection forms and compares the reliability and economy of referred forms between traditional schemes with circuit breakers and disconnecting switches and new schemes with disconnecting circuit breakers (DCB). The new scheme of transformer line block connection with disconnecting circuit breaker is recommended as the prior of 500kV main electrical connection in 500kV smart terminal substation.

Abstract: Electric vehicle (EV) is the greatest potential production of new energy vehicles. It plays a very important role in the area of energy conservation and reduction of pollutant emissions. In order to accelerate EV industrialization, the paper proposed a motor design method,which need to combine the automobile theory with the design permanent machine (PM). The paper considered the vehicle’s dynamic parameters, defined the motor’s basic parameters and designed the dimensions of electromagnetic structure, and then analyzed the field of the motor using finite element method (FEM). The paper firstly presents that drive motor’s design should consider two respects: one is the vehicle and another is the drive motor. In view of length of paper, only the no-load field analysis was proposed in this paper. The effectiveness of the proposed method is verified by the analysis results.

Abstract: In order to obtain the low synchronous speed, fractional slot concentrated winding is adopted in generation system. This paper analyzed the pole/slot combination rule, and studied the electromagnetic design method. By the finite element software, the characteristics is analyzed for this fractional-slot concentrated-winding permanent magnet generator, the result shows that this generator has a good performance, thus yet proves that fractional slot concentrated winding scheme is feasible.

Abstract: It is very common that the power consumption is too high and the efficiency ratio is too low in the field of the current full-bridge ZVZCS Converter, thus a practical circuit topology is designed and its working process is analyzed to solve the problem. The converter lead pipe can achieve a zero voltage turn-on and turn-off by using MOSFET, and a zero current turn-on and turn-off lagging by using IGBT. By analyzing the relevant waveform of the converter, the correctness of the converter designed is verified.

Abstract: In the process of designing high performance switch power, need to establish the accurate mathematical model of converter. The DC/DC converter generally has the characteristics of nonlinear, multimodal, time-varying, so need to use new methods to study it. The work of this paper aimed at non isolated DC / DC converter, established the mathematical model of Boost converter circuit by using the state space average method. Then design the closed-loop PI controller based on the Boost converter model, the closed-loop system has good static and dynamic performance, to meet the requirements of use.

Abstract: The application of traditional distance relay for four-parallel transmission lines is adversely affected by the mutual coupling between the lines. The result will lead to not achieved measured impedance calculation. And it has an effect on the operation of ground protection. In this paper, A new ground distance algorithm is proposed for single-phase grounding fault of four-parallel transmission lines. Based on the case of single-phase grounding fault, The first the relationship between fault point voltage and the voltage at protection installed location is presented by twelve-sequence component method. In the basis, According to the relationship of phase corner between the fault voltage and the fault current to eliminate the effect of fault voltage. The simulation results show that the new scheme has high sensitivity and reliability under different single-phase grounding fault of four-parallel transmission lines.

Abstract: This paper presents an equivalent circuit model of photovoltaic cells, and then discusses the photovoltaic (PV) grid power generation system in the maximum power point tracking (MPPT) control principle of the boost circuit. The MATLAB/Simulink software was used to model and simulate MPPT verification of the system. The simulation results showed the effectiveness of the control Strategy. As a conlusion, potential solution to MPPT The BOOST circuit adopts the MPPT control in photovoltaic power generation system, not only can improve the efficiency of photovoltaic cells, and thus improve the efficiency of the photovoltaic power generation systems.

Abstract: Unbalance of dc-link capacitor voltage is an key technical problem of multi-level inverter, this paper presents a novel method to solve it. According to the the new approach, a balancing capacitor is in turn connected in parallel with each dc-link capacitor in a sampling time, exacting charges from the capacitors with higher voltage and putting them into the capacitors with lower voltage.Thus the charges of all dc-link capacitors are refreshed constantly and the voltages can be kept balanced on the whole. This method only needs to add a simple hardware circuit and will not increase the complexity of modulation algorithm. In addition, the method is universal for N-level. Simulation experiments under several different conditions were made and the results verified the validity of the proposed approach.

Abstract: From a theoretical perspective, this paper develops a systematic approach to analyze the transient characteristics of the low voltage ride through in three-phase short-circuit rotor current. Firstly, the steady state current mathematical model of the system is described. And then, the short-circuit rotor current dynamic characteristic during the low voltage fault is analyzed, the resistance value and switching strategy of crowbar are discussed. Finally, the simulation results and the theoretical analysis manifest that appropriate crowbar reactance value and switching time can improve LVRT control characteristic and grid stability.

Abstract: Load forecasting is the foundation of power system planning, accurate load forecasting results can ensure the quality of power supply requirements under the premise of maximum avoid the waste of power grid construction fund, realize the maximization of the social benefits of limited investment. This paper in smart grid environment to load forecast of load signal at the same time, increasing the reliability of the forecast results. The discrete wavelet transform smooth wavelet transform, stationary wavelet transform the redundancy and panning invariability of the time frequency transform, in the process,to avoid the sampling processing signal distortion. In the load forecast this step,use wavelet clustering of data load classification,then use Elman neural network algorithm forecast. The main method is to use wavelet clustering algorithms for load classification. It will greatly enhance the load forecasting results accuracy and dependability.