• Title/Summary/Keyword: power system equivalent

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PWM-Based Sliding Mode Controller for Three-Level Full-Bridge DC-DC Converter that Eliminates Static Output Voltage Error

  • Liu, Jilong;Xiao, Fei;Ma, Weiming;Fan, Xuexin;Chen, Wei
    • Journal of Power Electronics
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    • v.15 no.2
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    • pp.378-388
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    • 2015
  • This paper proposes a pulse width modulation (PWM)-based sliding mode controller (SMC) for a full-bridge DC-DC converter that can eliminate static output voltage error. Hysteretic SMC in DC-DC converter does not have a fixed switching frequency, and applying hysteretic SMC to full-bridge converters is difficult. Fixed-frequency SMC, which is also called PWM-based SMC, based on equivalent control overcomes these shortcomings. However, the controller order reduction in equivalent control in PWM-based SMC causes static output voltage error. To resolve this issue, an integral item is added to the PWM-based SMC. Sliding mode coefficients are designed by applying a standard second-order system to the sliding mode surface. The effect of adding an integral item on the controller is analyzed, and an integral coefficient design method is proposed. Experiment results on a three-level full-bridge DC-DC converter verify the control scheme and design method proposed in this paper.

Equivalent Stiffness Modeling of Isolators to Consider Wave Effects in Multi-dimensional Vibration Isolation Analysis, via Vibrational Power (진동파워를 이용한 다차원 진동절연계 해석시 절연요소의 파동효과를 고려한 등가강성화)

  • 최규상;이호정;김광준
    • Journal of KSNVE
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    • v.9 no.3
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    • pp.517-524
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    • 1999
  • Mathematical formulas for multi-dimensional isolation analysis via vibrational power transmission can be derived in a rather simple form when the wave effects of the isolators are completely neglected. With increase of frequency range of interest, however, the wave effects play a very important role and hence cannot be neglected. The formulas get involved accordingly. In this study, a method of equivalent stiffness modeling of the isolators to include the wave effects is proposed in such a way that not only the complexity of the mathematical expressions but also that of experiments of necessity can be reduced. This method is illustratively applied to a two-dimensional vibration isolation system with nonrigid source and base structures.

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Statistical comparison of morphological dilation with its equivalent linear shift-invariant system:case of memoryless uniform soruces (무기억 균일 신호원에 대한 수리 형태론적인 불림과 등가 시스템의 통계적 비교)

  • 김주명;최상신;최태영
    • Journal of the Korean Institute of Telematics and Electronics S
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    • v.34S no.2
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    • pp.79-93
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    • 1997
  • This paper presents a linear shift-invariant system euqivalent to morphological dilation for a memoryless uniform source in the sense of the power spectral density function, and comares it with dialtion. This equivalent LSI system is found through spectral decomposition and, for dilation and with windwo size L, it is shown to be a finite impulse response filter composed of L-1 delays, L multipliers and three adders. Th ecoefficients of the equivalent systems are tabulated. The comparisons of dilation and its equivalent LSI system show that probability density functions of the output sequences of the two systems are quite different. In particular, the probability density functon from dilation of an independent and identically distributed uniform source over the unit interval (0, 1) shows heavy probability in around 1, while that from the equivalent LSI system shows probability concentration around themean vlaue and symmetricity about it. This difference is due to the fact that dilation is a non-linear process while the equivalent system is linear and shift-ivariant. In the case that dikation is fabored over LSI filters in subjective perforance tests, one of the factors can be traced to this difference in the probability distribution.

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A Study on Photovoltaic/Wind/Diesel Hybrid Power System

  • Jeong, Byung-Hwan;Cho, Jun-Seok;Gho, Jae-Seok;Choe, Gyu-Ha;Kim, Eung-Sang;Lee, Chang-Sung
    • Journal of Power Electronics
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    • v.3 no.1
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    • pp.40-48
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    • 2003
  • In this paper, a hybrid power system with photovoltaic/wind/diesel generators is proposed to solve the defect of stand-alone type power system in a remote area. A hybrid power system has a power-balanced controller to equilibrate generation power with a given load demand and which is composed of common DC power system. To execute a power-balanced control, a hybrid power system is assumed that all of power generators have the characteristics of an equivalent current-source and load sharing control technique must be needed at the same time. So this paper discusses the structure of power-balance control for hybrid power system. And through the results of simulation, the proposed scheme was verified.

Thermal Analysis of Water Cooled ISG Based on a Thermal Equivalent Circuit Network

  • Kim, Kyu-Seob;Lee, Byeong-Hwa;Jung, Jae-Woo;Hong, Jung-Pyo
    • Journal of Electrical Engineering and Technology
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    • v.9 no.3
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    • pp.893-898
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    • 2014
  • Recently, the interior permanent synchronous motor (IPMSM) has been applied to an integrated starter and generator (ISG) for hybrid electric vehicles. In the design of such a motor, thermal analysis is necessary to maximize the power density because the loss is proportional to the power of a motor. Therefore, a cooling device as a heat sink is required internally. Generally, a cooling system designed with a water jacket structure is widely used for electric motors because it has advantages of simple structure and cooling effectiveness. An effective approach to analyze an electric machine with a water jacket is a thermal equivalent network. This network is composed of thermal resistance, a heat source, and thermal capacitance that consider the conduction, convection, and radiation. In particular, modeling of the cooling channel in a network is challenging owing to the flow of the coolant. In this paper, temperature prediction using a thermal equivalent network is performed in an ISG that has a water cooled system. Then, an experiment is conducted to verify the thermal equivalent network.

S-Domain Equivalent System for Electromagnetic Transient Studies PART I : Frequency Dependent Network Equivalent (전자기 과도현상 해석을 위한 S 영역 등가시스템 PART I : 주파수 의존 시스템 등가)

  • 왕용필
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.52 no.11
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    • pp.632-638
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    • 2003
  • Modern power systems are very complex and to model them completely is impractical for electromagnetic transient studies. Therefore areas outside the immediate area of interest must be represented by some form of frequency dependent equivalent. The s-domain rational function form of frequency dependent equivalent does not need refitting if the simulation time-step is changed in the electromagnetic transient program. This is because the s-domain rational function coefficients are independent of the simulation time-step, unlike the z-domain rational function coefficients. S-domain rational function fitting techniques for representing frequency dependent equivalents have been developed using Least Squares Fitting(LSF). However it does not suffer the implementation error that exited in this work as it ignored the instantaneous term. This paper Presents the formulation for developing 1 Port Frequency Dependent Network Equivalent(FDNE) with the instantaneous term in S-domain and illustrates its use. This 1 port FDNE have been applied to the CIGRE Benchmark Rectifier test AC system. The electromagnetic transient package PSCAD/EMTDC is used to assess the transient response of the 1 port (FDNE) developed with Thevenin and Norton Equivalent network. The study results have indicated the robustness and accuracy of 1 port FDNE for electromagnetic transient studies.

A Mathematical Modeling on Battery Charging Circuit for the Power Storage of Wind Power Generation (풍력발전의 전력저장을 위한 베터리 충전회로에 관한 수학적인 모델링)

  • Ko, Seok-Cheol;Lee, Jae;Lim, Sung-Hun;Kang, Hyeong-Gon;Han, Byoung-Sung
    • Proceedings of the KIEE Conference
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    • 2001.10a
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    • pp.301-304
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    • 2001
  • Wind power generation system is one of the most useful energy resource using natural environment. One of the biggest problem we encountered is toot the wind speed is fluctuating sharply according to the weather conditions rather than it is stable. In this paper we do the equivalent modeling the mechanical energy of wind power turbine according to wind speed into the synchronous generator. We analyse the equivalent modeling output part of rectifier into DC/DC converter input part theoretically. We analyse a battery charging characteristics for power storage enabling the supply of stable power to the load. We design a system and do the modeling of it analytically so that it supplies a stable power to the load by constructing a DC-AC inverter point. Also we make a small size model usable in actual wind power generation system of 30kw and make an experiment and confirm its validity.

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Eddy Loss Analysis and Parameter Optimization of the WPT System in Seawater

  • Zhang, Ke-Han;Zhu, Zheng-Biao;Du, Luo-Na;Song, Bao-Wei
    • Journal of Power Electronics
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    • v.18 no.3
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    • pp.778-788
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    • 2018
  • Magnetic resonance wireless power transfer (WPT) in the marine environment can be utilized in many applications. However, energy loss in seawater through eddy loss (EL) is another consideration other than WPT in air. Therefore, the effect of system parameters on electric field intensity (EFI) needs to be measured and ELs calculated to optimize such a system. In this paper, the usually complicated analytical expression of EFI is simplified to the product of frequency, current, coil turns, and a coefficient to analyze the eddy current loss (ECL). Moreover, as the calculation of ECL through volume integral is time-consuming, the equivalent eddy loss impedance (EELI) is proposed to help designers determine the optimum parameters quickly. Then, a power distribution model in seawater is conceived based on the introduction of EELI. An optimization flow chart is also proposed according to this power distribution model, from which a prototype system is developed which can deliver 100 W at 90% efficiency with a gap of 30 mm and a frequency of 107.1 kHz.

On-line Remote Diagnosis System for DC Bus Capacitor of Power Converters Using Zigbee Communication (Zigbee통신을 이용한 전력변환기기의 DC Bus 커패시터의 온라인 원격 고장진단 시스템)

  • Chung, Wan-Sup;Shon, Jin-Geun
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.64 no.1
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    • pp.29-34
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    • 2015
  • DC bus electrolytic capacitors are used in variety of equipments as smoothing element of the power converters because it has high capacitance for its size and low price. It is responsible for frequent breakdowns of many static converters and inverter drive systems. Therefore it is important to diagnosis monitoring the condition of an electrolytic capacitor in real-time to predict the failure of power converter. In this paper, the on-line remote diagnosis monitoring system for DC BUS electrolytic capacitors of power converter using low-cost type Zigbee communication modules is developed. To estimate the health status of the capacitor, the equivalent series resistor(ESR) of the component has to be determined. The capacitor ESR is estimated by using RMS computation using AC coupling method of DC link ripple voltage/current. The Zigbee communication-based experimental results show that the proposed remote DC capacitor diagnosis monitoring system can be applied to DC/DC converter and UPS successfully.

A study on characteristics of three phase induction motor by #Kr{\ddot}{a}mer# system (#Kr{\ddot}{a}mer# 시스템에 의한 3.phi.유도전동기의 특성에 관한 연구)

  • 노창주;유춘식;정경열
    • Journal of Advanced Marine Engineering and Technology
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    • v.9 no.1
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    • pp.61-73
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    • 1985
  • The induction motor is widely used in the power equipments of the ship and the various industrial drive applications because it is robust and relatively simple and cheap to manufacture, but it has a disadvantage that the speed of induction motor is not controlled in wide range such as d.c motor. In this paper, the characteristics relating to the Kramer system that the speed of three phase wound type induction motor is controlled by changing the exciting e.m.f. of the secondary circuit is described. In order to analyze the characteristics, a new simplified and approximated T-type equivalent circuit from the Kramer circuit with three phase graetz connection and d.c machine is proposed. The stator current, motor torque and mechanical output power are computed by the current, torque and power equations derived by its equivalent circuit. Through the experiments, the $I_f-N$, torque-slip and current-slip characteristic curves of the tested motor are obtained and the various needed constants are determined. The numerical values obtained from the above method are compared with experimental values under the same conditions. As a result of the above investigation, it is found that the induction motor speed by the Kramer system is controlled by 28 per cent under the rated speed by changing the field current of d.c motor and the values computed by the current and torque equations derived by the simplified and approximated T-type equivalent circuit generally come to approach the experimental values.

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