Advanced Materials Research Vols. 986-987

Abstract: Analog Excitation regulation system is applied in No.3 turbine generator unit of Harbin No.3 power plant, Huadian Energy Group, and the system has several problems such as high failure rate, poor regulating performance and low level automation. As a solution, the static self-shunt excitation system is used to replace the analog excitation regulation system, UNITROL 5000 all-digital excitation system is adopted. With specific field situation, the paper introduces the structure and application of the system in details. Compared with the conventional A.C. exciting system, the all-digital excitation system has effectively improved the stability and reliability of the generator, with the advantages of more flexibility of the start-up modes and undisturbed switching. It is also reliable and convenient for the switching of PSS additional regulation unit.

Abstract: As the key technology of the electric vehicle, more and more research on battery management system has been done. And the balancing technology is the important part of battery management system. In this paper, a multi-inductor balancing method based on the Buck-Boost topological structure is used to improve batteries’ inconsistencies by obtaining parameters of the battery pack in real time. The proposed balancing method can improve batteries’ inconsistencies so as to increase the capacity utilization rate of the battery pack and prolong the battery lifespan. And in this paper a series of bench experiments were done to examine the effectiveness of the balancing method.

Abstract: Through the analysis of harmonics caused by transformer, capacitor, electromagnetic voltage transformer and other accident, harmonics is an important indicator of power quality, which has been included in the “pollution" of power grid is found. In order to understand the harmonic, this paper from the concept of quality of electric energy, and then gradually extended to the field of harmonics. This paper firstly introduces the various reasons and equipment may produce harmonic, Secondly, illustrate harm of harmonic to operation of transformers, capacitors, electromagnetic voltage transformers and other electrical equipment, let more people know and understand the relevant knowledge of the harmonic, In order to save technical force and provide scientific basis for future effective harmonic.

Abstract: In order to achieve high voltage, high-power,two-level inverter need to switch in series which results switch static, dynamic-pressure problems. Three-level inverter solve this problem for its circuit, but this circuit has the midpoint potential imbalances of the DC side, we propose to charge balance theory based on the three-level inverter midpoint potential algorithm to solve the problem, build simulation model to validate the algorithm on the midpoint potential in MATLAB.

Abstract: The function generator is the classic analog adder circuit, either independently or as an intermediate for its links embedded in complex circuits, have a very wide range of applications. Function generator can be used as the signal source to produce for research, teaching, experimental signals for different purposes such as how to make it more accurate and stable signal generation, has been widespread concern and research; Similarly, construction work adder circuit commonly used as a module, accurate input-output relationship is also very worth exploring. Therefore, this paper, on both a profound theoretical analysis, based on the modeling and simulation through the more figurative exposition of both operating characteristics, application to increase its theoretical basis.

Abstract: This paper focuses on the digital experimental system for neutral-point-clamped three-level converter. First, SVM’s digital implementation method is studied. As neutral-point voltage unbalance is an inherent problem for this topology, a practical capacitor voltage balance method is present. This method uses a variable factor as the small vectors’ adjustment coefficient, which is calculated by PI controller with capacitor voltage deviation. Then, a digital modular control system is proposed, in which both hardware and software system structures are designed in modular. The digital control system adopts high speed optical-fiber communication between a master controller and multiple sub-controllers, and realized the effective and rapid control of the experimental prototype finally.

Abstract: According to the structure of grounding resistor, the flow-current experiments of alloy materials which have different performance and specification have been done in the condition of simulation grounding fault. Based on the experiments, the simulation models of temperature field have been constructed; the distribution characteristics of the transient temperature field and the structure optimization of Grounding Resistor have been studied and discussed by the simulation models. The research results have a great engineering application value on the optimization of performance, the choice of the materials, the cost saving and the improvement of design efficiency to grounding resistor.

Abstract: By comprehensive analyzing the lead-acid batteries development situation of electric vehicle at first, and making a comprehensive comparison for the performances and features of the lead-acid batteries, nickel hydrogen batteries and lithium-ion batteries, then studying the charge and discharge performance of the lithium batteries which provides technical support and references for the application and popularization of lithium-ion batteries in electric vehicles.

Abstract: Based on the study of dielectric response theory and equivalent circuit of oil-paper insulation medium, this paper deduces the exponential decay type return voltage function model.It also proposes that rhe function can be resolved with the application of optimization algorithm. Finally, the paper takes a return voltage curve which is tested by the oil-immersed transformer for example.Fitting results verify the accuracy of the calculation. Further more,it also explains that return voltage function model is reliable and practical. Therefore,the model plays a crucial role in the follow-up study of topological structure of equivalent circuit of oil-paper insulation.

Abstract: A new-type LED switching power supply circuit using flyback converter is designed based on current-mode PFC controller chip L6562. The circuit has some characteristics such as simple structure, wide input voltage range, output stability and reliable operation. The experimental results show that the system efficiency is up to 89.46% when the input voltage changes from 85V to 265V(AC), meanwhile the system works stably with constant current and constant voltage output.