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ABSTRACT: This paper focuses on discussing the type selection, analysis and optimization design of the snubber in switching power amplifier (SPA). Based on the principle analysis of the selected snubber, its design is summarized as a multi-objective optimization problem (MOP). Then the proposed MOP is solved by the modified nondominated sorting genetic algorithm II (MNSGA-II), which is constructed by introducing to the NSGA-II four new schemes: the pointers grouping fast nondominated sort (PGFNS), the preaccelerating crowding distance assignment (PACDA), the chaotic factor based middle recombination (CFBMR), and the reproduction without duplicates (RWD). The results obtained from simulation and practical experiment show that the optimal snubber parameters sought out by the MNS GA-II make the snubber design attain the expectant goals.
Electrical Machines and Systems, 2009. ICEMS 2009. International Conference on; 12/2009
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ABSTRACT: The large capacity nuclear power plants have been widely constructed in recent years to cope with social economic development and electrical energy demands. Consequently, it is necessary to be aware of nuclear power plant (NPP) dynamic characteristics in order to study the transient and midterm dynamic process of power system. Due to lacking suitable NPP model which is described the detail characteristics of the Nuclear Power Unit in the power system simulation, at first, the paper presents functional description of nuclear power plant. Then a detailed pressurized water reactor (PWR) plant overall model for medium-term and long-term power system transient stability is proposed based on PSASP through user-defined modeling program. In the end, dynamic response characteristics of pressurized water reactor is presented. The simulation results are obtained.
Industrial Electronics and Applications, 2009. ICIEA 2009. 4th IEEE Conference on; 06/2009
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ABSTRACT: By defining the relationship between regular-sampled PWM and space vector PWM (SVPWM), the implied modulating waves in SVPWM technique is identified in this paper. Then a simulation model of SVPWM controlled three-phase voltage source inverter (VSI) is built under MatlabSimulink based on the explicit modulating waves. During the simulation, various possibilities of adding a zero-sequence component to the sinusoidal modulating waves are explored and the effects are discussed. It proves that the injection of zero-sequence components results in an extended linear modulation range and high output voltage in PWM inverters.
Industrial Electronics and Applications, 2009. ICIEA 2009. 4th IEEE Conference on; 06/2009
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ABSTRACT: An inverter designed for protective relay testing (PRT) purpose is modeled and analyzed in frequency domain, which is named as PRT inverter. By introducing the concepts of ldquobiased on-timerdquo and ldquotime-voltage transfer coefficientrdquo, a modified model is proposed, which realizes the linear transition from duty cycle to output voltage and breaks the frequency limitation of the linearized models. Quasi-PID controller that is able to eliminate the inherent tracking error of the PI controller was assigned to control the modified model. To deal with the impacts of parameters drifting on the controller, a single neuron adaptive quasi-PID controller based on perceptron supervised Hebb learning rule (PSHLR) is put forward, which ameliorates the control performance excellently and makes the strategy fulfill the accuracy requirements of PRT, especially electrical fault waveform regeneration (EFWR).
Power Electronics and Motion Control Conference, 2009. IPEMC '09. IEEE 6th International; 06/2009
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ABSTRACT: In this paper, we propose a dynamic mathematical model for nuclear power plant (NPP) reactor, and give an implementation in Power System Analysis Software Package (PSASP) through a user-defined program. NPP is modeled with a bipartite model that consists of the neutron dynamics module and thermodynamics module. Through the simulation results of NPP reactor under different disturbances, a conclusion can be drawn that the temperature effect and poisoning effect are crucial to the self-stability of reactor, which is not only the basis of safe operation of the nuclear power plant but also the aim of the designing. The simulation validated the proposed NPP reactor model, and it can be packaged with the other parts of the NPP detailed model in PSASP for further usage in dynamic calculation of the power system.
Power and Energy Engineering Conference, 2009. APPEEC 2009. Asia-Pacific; 05/2009
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ABSTRACT: The nuclear power plants are being constructed and operated widely in recent years. Consequently, it is necessary to study nuclear power plants (NPPs) dynamic characteristics and power system dynamics simulations with nuclear plant after NPPs has been introduced into power system. At first, the paper presents functional description of NPP. Then a detailed and new models of generating plant with PWR have been developed in PSASP through user-defined modeling program for medium- term and long-term power system transient stability analyse. In the end, the results for power system dynamics simulation with nuclear plant are presented.
Power and Energy Engineering Conference, 2009. APPEEC 2009. Asia-Pacific; 05/2009
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ABSTRACT: This paper presents a hybrid control strategy for photovoltaic (PV) simulator, which emulates the output characteristics of PV arrays under different irradiation, temperature, and loads. The mathematic modeling of the I-V curve of PV arrays is investigated in this paper, and accordingly the voltage control or current control method is worked out for different segments of PV output characteristics. The proposed hybrid control strategy divides the I-V characteristics of PV arrays into three segments, by measuring the output voltage and current of the PV simulator, the control unit which is based on TMS320LF2407 DSP calculates and controls the voltage or current respectively. A 2-kW prototype has been built and tested with a variable resistive load and a constant power load as well. Experiment results show that the PV simulator could shift smoothly on its I-V characteristics, which fits well for further experiments of inverters and the maximum power point tracking in the PV system.
Applied Power Electronics Conference and Exposition, 2009. APEC 2009. Twenty-Fourth Annual IEEE; 03/2009
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ABSTRACT: This paper presents a quasi-Z-source inverter (qZSI) that is a new topology derived from the traditional Z-source inverter (ZSI). The qZSI inherits all the advantages of the ZSI, which can realize buck/boost, inversion and power conditioning in a single stage with improved reliability. In addition, the proposed qZSI has the unique advantages of lower component ratings and constant dc current from the source. All of the boost control methods that have been developed for the ZSI can be used by the qZSI. The qZSI features a wide range of voltage gain which is suitable for applications in photovoltaic (PV) systems, due to the fact that the PV cell's output varies widely with temperature and solar irradiation. Theoretical analysis of voltage boost, control methods and a system design guide for the qZSI in PV systems are investigated in this paper. A prototype has been built in the laboratory. Both simulations and experiments are presented to verify the proposed concept and theoretical analysis.
Applied Power Electronics Conference and Exposition, 2009. APEC 2009. Twenty-Fourth Annual IEEE; 03/2009
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ABSTRACT: A quasi-PID controller for complex waveform generating inverters that is derived from further analysis of the commonly used pulse width modulation (PWM) method of triangular carrier comparison is proposed in this paper. Firstly, the accurate theoretical formulas are obtained for the parameter turning of the PI controller, so as to make the normally cumbersome adjusting process much more readily. Due to the satisfactorily good performance of the quasi-PID controller, it can be either introduced into traditional inverters directly, or adopted as the initial state machine (ISM) of high accuracy intelligent-PID control inverters for the purpose of ensuring system stability and safety at start-up and also making the intelligent control algorithm operate more smoothly and effectively. Moreover, the proposal of the quasi-PID controller also presents a compelling answer to the interesting question: why do almost all the inverters adopt P or PI controller primarily but do not consider the strict PID controller? The answer is that the strict proportional, integral and derivative (PID) controller is not suitable for the PWM inverter, and only the quasi-PID controller is workable. This argument is verified in this paper.
Industrial Electronics, 2008. IECON 2008. 34th Annual Conference of IEEE; 12/2008
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ABSTRACT: An electrical fault-waveform regenerator (EFWG) is proposed in this paper originally, including its hardware structure and software flow chart. And the EFWG is mainly relying on a power amplifier (PA) to regenerate the electrical fault waveforms recorded by fault recorders (FR), so a digital closed-loop modification technique (DCLMT), which is distinct from the predistortion technique (PDT) widely used nowadays, is conceived to counteract the inherent nonlinear distortions of the PA. The EFWG is actually designed to serve as a novel and more effective alternative to the common used protection-relay testing apparatuses (PRTA).
Electrical Machines and Systems, 2008. ICEMS 2008. International Conference on; 11/2008
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ABSTRACT: The precise linearization method based on the theory of differential geometry is used in TCSC stabilized controller's design. It is mainly considered that TCSC stabilized controller is designed with linear quadratic optimal control theory after the one machine - infinity bus system with TCSC is precisely linearized, compared with traditional PID controller in MATLAB/Simulink simulation. The results of computer simulation indicate that TCSC nonlinear controller based on differential geometry can not only improve the static stability of system, but also effectively damp power oscillation and enhance the transient stability of system when the power system suffers small disturbance and short circuit. In addition, it also illuminates that nonlinear control is more effective than traditional PID control, and possess certain robustness and self- adaptability.
Electric Utility Deregulation and Restructuring and Power Technologies, 2008. DRPT 2008. Third International Conference on; 05/2008
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ABSTRACT: The residual flux of transformer ferromagnetic-core is not random when it enters into power system without load form last cutting off. Firstly, the relationship between residual fluxes and the last exciting current was discussed, then hysteresis loop was divided into three antisymmetric sections according to reversibility of magnetic domains; methods were proposed to calculate residual flux approximately section by section based on the principle of similar-shape and ferromagnetic characters. Combined with time-character of ferromagnetic material, a phase control tactic to eliminate inrush current was developed, finally EMTP simulation was taken to testify its rationality, and in this simulation, according to inrush current overshoot limited to 115%, the ranges of phase at different ratios of residual flux was measured, which is useful in device design.
Power System Technology, 2006. PowerCon 2006. International Conference on; 11/2006
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ABSTRACT: When transformer enters into power system without load form last cutting off, which because of action of protective device in answer to system fault and changes of system framework structure, the residual flux of ferromagnetic-core is of no randomicity. Firstly on the basis of time-character of ferromagnetic material analysis, combined with Preisach model, a way to calculate residual flux is proposed in this paper. After this, an expression between residual flux and entering-phase is educed to eliminate inrush current in single phase transformer, then its rationality has been testified by an EMTP test. Meanwhile, the simulation has discovered some rules between residual flux and the range of entering-phase at a given overshoot limit of inrush current. Finally these rules have been used to propose a control tactic about entering phase in sections to design a device to eliminate inrush current
Environmental Electromagnetics, The 2006 4th Asia-Pacific Conference on; 09/2006
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ABSTRACT: A dynamic phasors model for TCSC is proposed in this paper to understand the interactions between TCSC and power system better. The distinguishing feature of the model is that the harmonics characteristics are considered in the derivation of the model. The order of the model is maintained to a second-order state-space equation. Validation of the model is performed and the results show that the proposed model has a good agreement with the waveforms of the simulation results of the time-domain model. This model has an accurate simulation of the dynamic process of the power system which can be more valuable for transient simulation and control design.
Energy and Environment Technology, International Conference on. 2:176-179.
