• Title/Summary/Keyword: inverter system.

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An Improved Central 60° Synchronous Modulation for High Transient Performance with PMSM Stator Flux Control Used in Urban Rail Transit Systems

  • Fang, Xiaochun;Lin, Fei;Yang, Zhongping
    • Journal of Power Electronics
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    • v.16 no.2
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    • pp.542-552
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    • 2016
  • Central 60° synchronous modulation is an easy pulse-width modulation (PWM) method to implement for the traction inverters of urban rail trains at a very low switching frequency. Unfortunately, its switching patterns are determined by a Fourier analysis of assumed steady-state voltages. As a result, its transient responses are not very good with over-currents and high instantaneous torque pulses. In the proposed solution, the switching patterns of the conventional central 60° modulation are modified according to the dynamic error between the target and actual stator flux. Then, the specific trajectory of the stator flux and current vector can be guaranteed, which leads to better system transients. In addition, stator flux control is introduced to get smooth mode switching between the central 60° modulation and the other PWMs in this paper. A detailed flow chart of the control signal transmission is given. The target flux is obtained by an integral of the target voltage. The actual PMSM flux is estimated by a minimum order flux state observer based on the extended flux model. Based on a two-level inverter model, improved rules in the α-β stationary coordinate system and equations of the switching patterns amendment are proposed. The proposed method is verified by simulation and experimental results.

Control Strategy for Selective Compensation of Power Quality Problems through Three-Phase Four-Wire UPQC

  • Pal, Yash;Swarup, A.;Singh, Bhim
    • Journal of Power Electronics
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    • v.11 no.4
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    • pp.576-582
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    • 2011
  • This paper presents a novel control strategy for selective compensation of power quality (PQ) problems, depending upon the limited rating of voltage source inverters (VSIs), through a unified power quality conditioner (UPQC) in a three-phase four-wire distribution system. The UPQC is realized by the integration of series and shunt active power filters (APFs) sharing a common dc bus capacitor. The shunt APF is realized using a three-phase, four-leg voltage source inverter (VSI), while a three-leg VSI is employed for the series APF of the three-phase four-wire UPQC. The proposed control scheme for the shunt APF, decomposes the load current into harmonic components generated by consumer and distorted utility. In addition to this, the positive and negative sequence fundamental frequency active components, the reactive components and harmonic components of load currents are decomposed in synchronous reference frame (SRF). The control scheme of the shunt APF performs with priority based schemes, which respects the limited rating of the VSI. For voltage harmonic mitigation, a control scheme based on SRF theory is employed for the series APF of the UPQC. The performance of the proposed control scheme of the UPQC is validated through simulations using MATLAB software with its Simulink and Power System Block set toolboxes.

Deadbeat Control with a Repetitive Predictor for Three-Level Active Power Filters

  • He, Yingjie;Liu, Jinjun;Tang, Jian;Wang, Zhaoan;Zou, Yunping
    • Journal of Power Electronics
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    • v.11 no.4
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    • pp.583-590
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    • 2011
  • Three-level NPC inverters have been put into practical use for years especially in high voltage high power grids. This paper researches three-level active power filters (APFs). In this paper a mathematical model in the d-q coordinates is presented for 3-phase 3-wire NPC APFs. The deadbeat control scheme is obtained by using state equations. Canceling the delay of one sampling period and providing the predictive value of the harmonic current is a key problem of the deadbeat control. Based on this deadbeat control, the predictive output current value is obtained by the state observer. The delay of one sampling period is remedied in this digital control system by the state observer. The predictive harmonic command current value is obtained by the repetitive predictor synchronously. The repetitive predictor can achieve a better prediction of the harmonic current with the same sampling frequency, thus improving the overall performance of the system. The experiment results indicate that the steady-state accuracy and the dynamic response are both satisfying when the proposed control scheme is implemented.

Smart Panel Board for EV Standard Chargers and Its Control Method (전기자동차 완속충전기용 스마트 분전반 및 그 제어방법)

  • Kim, Myeong-Soo;Hong, Soon-Chan
    • The Transactions of the Korean Institute of Power Electronics
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    • v.19 no.6
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    • pp.511-521
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    • 2014
  • This study proposes an electric vehicle (EV) smart panel board and its control method on the basis of charging scheduling. The proposed system consists of batteries, a three-phase battery charger, three single-phase inverters, transfer switches for electric power distribution, and a controller. The three-phase battery charger usually charges the batteries at midnight when electric rates are cheap and in light load. When the electric power consumption of the EV standard chargers connected to one phase of the power line is relatively large or when a blackout occurs, the electric power stored in the battery is supplied by discharging through the inverters to the EV standard chargers. As a result, the value of peak load and the charging electric power quantity supplied from a utility grid are reduced, and the current unbalance is improved. The usefulness of the proposed system is confirmed through simulations, experiments, and case studies.

EMI Noise Reduction with New Active Zero State PWM for Integrated Dynamic Brake Systems

  • Baik, Jae-Hyuk;Yun, Sang-Won;Kim, Dong-Sik;Kwon, Chun-Ki;Yoo, Ji-Yoon
    • Journal of Power Electronics
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    • v.18 no.3
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    • pp.923-930
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    • 2018
  • Based on the application of an integrated dynamic brake (IDB) system that uses a PWM inverter fed-AC motor drive to operate the piston, a new active zero state PWM (AZSPWM) is proposed to improve the stability and reliability of the IDB system by suppressing the conducted electro-magnetic interference (EMI) noise under a wide range of load torque. The new AZSPWM reduces common-mode voltage (CMV) by one-third when compared to that of the conventional space vector PWM (CSVPWM). Although this method slightly increases the output current ripple by reducing the CMV, like the CSVPWM, it can be used within the full range of the load torque. Further, unlike other reduced common-mode voltage (RCMV) PWMs, it does not increase the switching power loss. A theoretical analysis is presented and experiments are performed to demonstrate the effectiveness of this method.

A Study on Output Characteristics of the CO2 Laser by DC-DC Converter System (DC-DC Converter System에 의한 CO2 레이저 출력 특성에 대한 연구)

  • Kim, Geun-Yong;Chung, Hyun-Ju;Min, Byoung-Dae;Kim, Yong-Cheol;Lee, Yu-Soo;Kim, Hee-Je
    • Proceedings of the KIEE Conference
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    • 2002.07c
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    • pp.1816-1819
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    • 2002
  • Nowadays, CO2 lasers are used widely in many applications such as materials fabrication, communications, remote sensing and military purpose etc. It is important to control the laser output power in those fields. In this paper, current resonant half-bridge inverter and Cockcraft-Walton circuit are used to vary the laser output power. This laser power supply is designed and fabricated which has less switching losses and compact size. Also we used an IGBT(Insulated Gate Bipolar Transistor) as a switching device of a power supply and PIC one-chip microprocessor are used to control the gate signal of the IGBT precisely. We investigated the output characteristics of this CO2 laser. As a result, the maximum laser output power of 26[W] is obtained at the resonant frequency of about 13[kHz].

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Development of the 3kW Class Low Cost Fuel Inverter System for Residential Power Generation - DC-DC Converter Design and Control for Fuel Cell System (3kW급 주택용에 사용되는 저가의 연료전지용 인버터 시스템 - 연료전지 시스템용 DC-DC 컨버터 설계 및 제어)

  • Lee, S.H.;Cho, M.C.;Hwang, G.D.;Mun, S.P.;Suh, K.Y.;Kwon, S.K.
    • Proceedings of the KIEE Conference
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    • 2006.07b
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    • pp.1161-1162
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    • 2006
  • 본 논문은 3[kW]급 연료전지와 연료전지의 저전압$[40{\sim}60[Vdc]$)을 승압(380vdc)하기 위한 풀-브리지 DC-DC 컨버터, 그리고 승압된 링크전압을 교류 상용전압(220[Vac], 60[Hz)으로 변환하기위한 단상 풀-브리지 인버터로 구성된 연료전지 발전용 전력변환시스템 중 연료전지 시스템용 DC-DC 컨버터를 제안하였다. 제안한 연료전지 시스템용 DC-DC 컨버터는 변압기 2차측에 배전류 정류회로를 삽입하여 기존의 고주파 변압기 보다 간단하면서 무게 및 부피를 줄였다. 그리고 위상 천이 PWM 제어로 출력 전압을 가변시켜 영전압 스위칭을 달성 함으로써 스위칭 손실을 줄였으며. 효율을 95%이상 달성 하였다.

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A Study on Improved Operation of Apartment Heating System in a Machine Room (공동주택 기계실 난방설비 운전 개선 연구)

  • Seo, Jeong-Ah;Shin, Younggy;Kim, Yong-Ki;Lee, Tae-Won
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.29 no.1
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    • pp.38-42
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    • 2017
  • This study proposes an idea for energy saving in apartment machine rooms. A conventional district heating system is equipped with constant-flow pumps and bypass valves to regulate pump differential pressure. Each family unit is equipped with a constant-flow on/off valve. This leads to excessive hot water circulation and a high return temperature. To reduce energy loss, this study assumes that each family unit is renovated with a heating valve which regulates the return temperature at $35^{\circ}C$. The hot water supply pump is also replaced with a pump with an inverter to vary flow rate. Expected energy savings is then estimated from field test data. According to the results, pump electricity consumption was reduced by 6,100 kWh for a family unit building over about half a year. The supply temperature can also be lowered by $5^{\circ}C$, which can contribute to a production of electricity of 10.3 kWh/ton of hot water.

Advanced Maximum Power Point Tracking Method for the Series Operation Strategy of Grid-Connected Small Wind Turbines (계통연계형 소형풍력발전 시스템의 직렬운전을 고려한 개선된 MPPT 방법)

  • Kim, Yong-Hyu;Heo, Hong-Jun;Kim, Jang-Mok
    • The Transactions of the Korean Institute of Power Electronics
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    • v.21 no.6
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    • pp.497-505
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    • 2016
  • Operating wind turbine generators at maximum power point requires maximum power point tracking (MPPT) control methods. However, conventional methods cannot track the appropriate maximum power point in situations involving wind turbine systems based on a series operation strategy. These systems comprise one or more local maximum power points, and conventional methods can detect only one local maximum power point closed by a current operation point. This study proposes an advanced MPPT method for the series operation strategy of a small, grid-connected wind turbine system. In determining the appropriate maximum point, operations at certain local maximum power points are analyzed. The results show one appropriate point, which is tracked by the proposed MPPT method. The effectiveness of the proposed method is verified by the experimental results.

Static Analysis of AT Feeding Systems considering the Limited Rise of Regenerative Voltage (회생 차량의 전압 상승 한도를 고려한 AT 급전시스템 정태해석)

  • Kim, B;Moon, Y.-H
    • Proceedings of the KSR Conference
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    • 2004.10a
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    • pp.1322-1327
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    • 2004
  • There are some previous studies that utilize constant impedance models or constant current models for electric trains to perform the static analysis of AT feeding systems. These mentioned models have some merits of linear systems but yield erroneous results because of the innate restraints of the models since linear models cannot represent the features of constant power in inverter-driven trains. From these reasons, it is suitable that the train be considered as a constant load model when it drives or as a constant source model when it applies regenerative brake. However, excessive rise of regenerative voltage during the braking may damage the vehicle itself and the feeding systems so the voltage must be restricted below a certain value. Keeping these facts in minds, we suggest new methods of analyzing AT feeding systems using the constant power models with the conditions of voltage constraints. The simulation results from a sample system using the proposed method illustrate both the states of system variables and the supply-demand relation of power among the trains and the systems very clearly, so it is believed that the proposed method yields more accurate results than conventional methods do.

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