• Title/Summary/Keyword: Unity power factor

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Development of Novel 3-Phase Line-interactive UPS System using 4-leg PWM Converter/Inverter and AC Reactor (4-레그 PWM 컨버터/인버터와 AC 리액터를 사용한 새로운 3상 라인 인터렉터브 무정전전원장치의 개발)

  • Ji Jun-Keun;Kim Hyo-sung;Sul Seung-Ki;Kim Kyung-Hwan
    • Proceedings of the KIPE Conference
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    • 2004.07a
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    • pp.77-81
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    • 2004
  • In this paper a novel line interactive UPS (Uninterruptible Power Supply) using the two 4-leg VSCs and AC line reactor is proposed. The 4-leg Voltage Source Converter(VSC) can use the DC link voltage effectively by the 3-D SVPWM method. Hence the DC battery voltage can be reduced by $15\%$ in comparison to that of the conventional line-interactive UPS system. One VSC is in parallel with the AC line reactor of the power source side, and the other is in series with the load. The parallel 4-leg voltage source inverter controls three-phase line voltage independently in order to control the line reactor current indirectly. It eliminates the neutral line current and the active ripple power of the source side using the pqr theory so that unity power factor and the sinusoidal source current can be achieved even though both the source and the load voltages have zero sequence components. The series 4-leg voltage source inverter compensates the line voltage and allows the load voltage to be balanced and harmonic-free. Both of parallel and series 4-leg voltage source inverters always act as independently controllable voltage sources, so that three-phase output voltage shows a seamless transition to the backup mode. The feasibility of the proposed UPS system has been investigated and verified through computer simulation results.

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A Study on Current Waveform Control and Performance Improvement for Inverter Arc Welding Machine (인버터 아크 용접기의 파형제어기법 및 성능향상에 관한 연구)

  • 채영민;고재석;김진욱;이승요;최해룡;최규하
    • The Transactions of the Korean Institute of Power Electronics
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    • v.4 no.2
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    • pp.128-137
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    • 1999
  • Recently the pelionnance of CO2 arc welding machine has been advanced significantly through the adoption of i invelter circuit topology. which made it possible to improve welding perfonnances such as spatter generation and bead s state. But the conventional inverter arc welding machine generates constant output voltage which cause much spatter g generation dUling short-circuit and arc start time because it is unable to control output current instantaneously. So this p paper representes wavefCnm controlled inverter arc welding machine which control the wavefonn of welding current and t thus to suppress the spatter generation. And the system designed in this paper is the digital controller using single chip m microprocessor of 80C196KC. As a result of perfonnance test for this system, the spatter generation is reduced and s shOlt-circuit time period is stabilized compared to conventional one. And more by using switched mode rectifier for A AC/DC power convelter. unity power factor is maintained and low order halmonic spectrum is supressed.

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Diminution of Current Measurement Error in Vector Controlled AC Motor Drives

  • Jung Han-Su;Kim Jang-Mok;Kim Cheul-U;Choi Cheol;Jung Tae-Uk
    • Journal of Power Electronics
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    • v.5 no.2
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    • pp.151-159
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    • 2005
  • The errors generated from current measurement paths are inevitable, and they can be divided into two categories: offset error and scaling error. The current data including these errors cause periodic speed ripples which are one and two times the stator electrical frequency respectively. Since these undesirable ripples bring about harmful influences to motor driving systems, a compensation algorithm must be introduced to the control algorithm of the motor drive. In this paper, a new compensation algorithm is proposed. The signal of the integrator output of the d-axis current regulator is chosen and processed to compensate for the current measurement errors. Usually the d-axis current command is zero or constant to acquire the maximum torque or unity power factor in the ac drive system, and the output of the d-axis current regulator is nearly zero or constant as well. If the stator currents include the offset and scaling errors, the respective motor speed produces a ripple related to one and two times the stator electrical frequency, and the signal of the integrator output of the d-axis current regulator also produces the ripple as the motor speed does. The compensation of the current measurement errors is easily implemented to smooth the signal of the integrator output of the d-axis current regulator by subtracting the DC offset value or rescaling the gain of the hall sensor. Therefore, the proposed algorithm has several features: the robustness in the variation of the mechanical parameters, the application of the steady and transient state, the ease of implementation, and less computation time. The MATLAB simulation and experimental results are shown in order to verify the validity of the proposed current compensating algorithm.

Characteristic Analysis of Single Phase Line Start Synchrous Motor (단상 유도형 동기전동기의 동특성 해석)

  • Kim, Sol;Jang, Ki-Bong;Kim, Byung-Bok;Lee, Ju;Ko, Kwon-Min;Kim, Tea-Duk;Oh, Sang-Kyeong
    • Proceedings of the KIEE Conference
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    • 2002.07b
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    • pp.648-650
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    • 2002
  • SPLSSM may operate with very high efficiencies and near unity power factor, SPLSSM has been shown to be capable of desirable steady state performance, but is known to have undesirable staring performance because starting asynchronously by means of an induction cage, it operates in steady state performance of a PM motor. This combination provides the steady state performance of a permanent magnet motor without the need for an expensive drive system. However, that combination makes it difficult to analyze the transient behaviors. This paper investigates the behaviors of Single-Phase Line-Start Synchronous Motor using finite element method combined analytic method. It is shown that finite element modeling is capable of giving accurate prediction of performances. Varying the value of capacitance and material of permanent magnet shows the effect on the dynamic characteristics in this paper.

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The Study of 3-Phase Bi-Directional DC to AC Inverter for the Bi-Model PV PCS (자립형 태양광 발전 시스템을 위한 3상 양방향 DC-AC 인버터 연구)

  • Yang, Seung-Dae;Jung, Seung-Hwan;Choi, Ju-Yeop;Choy, Ick;Lee, Young-Kwon
    • 한국태양에너지학회:학술대회논문집
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    • 2012.03a
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    • pp.319-324
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    • 2012
  • This paper presents the study of 3-Phase bi-directional DC to AC inverter with unity power factor. 3-Phase bi-directional DC to AC inverter is important for the bi-modal PV PCS with an energy storage system. Both Inverting and converting are needed to connect between the grid side and boost converting side to charge and discharge the energy storage system. The paper proposes the appropriate circuit topology and proper control system for the bi-directional inverter. It also proposes the method of selecting the optimum control method considering system stability. PSIM simulation is used to validate the proposed algorithm.

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Classification Rule for Optimal Blocking for Nonregular Factorial Designs

  • Park, Dong-Kwon;Kim, Hyoung-Soon;Kang, Hee-Kyoung
    • Communications for Statistical Applications and Methods
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    • v.14 no.3
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    • pp.483-495
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    • 2007
  • In a general fractional factorial design, the n-levels of a factor are coded by the $n^{th}$ roots of the unity. Pistone and Rogantin (2007) gave a full generalization to mixed-level designs of the theory of the polynomial indicator function using this device. This article discusses the optimal blocking scheme for nonregular designs. According to hierarchical principle, the minimum aberration (MA) has been used as an important criterion for selecting blocked regular fractional factorial designs. MA criterion is mainly based on the defining contrast groups, which only exist for regular designs but not for nonregular designs. Recently, Cheng et al. (2004) adapted the generalized (G)-MA criterion discussed by Tang and Deng (1999) in studying $2^p$ optimal blocking scheme for nonregular factorial designs. The approach is based on the method of replacement by assigning $2^p$ blocks the distinct level combinations in the column with different blocks. However, when blocking level is not a power of two, we have no clue yet in any sense. As an example, suppose we experiment during 3 days for 12-run Plackett-Burman design. How can we arrange the 12-runs into the three blocks? To solve the problem, we apply G-MA criterion to nonregular mixed-level blocked scheme via the mixed-level indicator function and give an answer for the question.

Adoptive Feedback Linearization Control of Three-Phase AC/DC Voltage-Source Converter (적응 궤환 선형화를 이용한 3상 AC/DC 전압원 컨버터 제어)

  • Park, Young-Hwan;Park, Jang-Hyun;Kang, Moon-Ho
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.20 no.3
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    • pp.62-68
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    • 2006
  • In this paper, an adaptive input-output linearization and zero dynamics control of three phase AC/DC converter are proposed. For achieving output do voltage regulation with unity power factor, the q-axis current of the rotating d-q frame is regulated to zero and the output do voltage is controlled to track a given reference voltage $V_r$. The proposed scheme is robust to the parametric uncertainty md load current of the converter due to the adaptation process. The simulation results are presented to illustrate the performance and feasibility of the proposed control scheme.

Study in Post-Assembly Magnetization of Line Start Permanent Magnet Motor (영구자석 매입형 유도동기전동기의 조립 후 착자에 대한 연rn)

  • 이철규;권병일
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.52 no.8
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    • pp.373-380
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    • 2003
  • This paper consists of a study in post-assembly magnetization of LSPM (Line Start Permanent Magnet Motor). Recently, LSPM is noted as an alternative to the induction motor because it offers a very high efficiency and unity power factor, And it is necessary for permanent magnets to be magnetized by means of post-assembly magnetization in LSPMS because of the manufacturing cost involved. The manufacturing process is also simpler in post-assembly magnetization than in pre-assembly magnetization. Generally, permanent magnet motors are magnetized by their own stator coil or by magnetizing fixtures. However, the permanent magnet in a LSPM is scarcely magnetized by using them because of the eddy current of the rotor bar. Hence, it is necessary to design a magnetizing fixture that overcomes this problem. In this paper, the author analyses the post-assembly magnetization of a LSPM and proposes a method for designing the magnetizing fixture. The method that the author proposes is to make the number of coil turns greater in order to reduce the effect of the eddy current of the rotor bars.

Numerical Simulations of Subcritical Reactor Kinetics in Thermal Hydraulic Transient Phases

  • J. Yoo;Park, W. S.
    • Proceedings of the Korean Nuclear Society Conference
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    • 1998.05a
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    • pp.149-154
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    • 1998
  • A subcritical reactor driven by a linear proton accelerator has been considered as a nuclear waste incinerator at Korea Atomic Energy Research Institute(KAERI). Since the multiplication factor of a subcritical reactor is less than unity, to compensate exponentially decreasing fission neutrons from spallation reactions are essentially required for operating the reactor in its steady state. furthermore, the profile of accelerator beam currents is very important in controlling a subcritical reactor, because the reactor power varies in accordance of the profile of external neutrons. We have developed a code system to find numerical solutions of reactor kinetics equations, which are the simplest dynamic model for controlling reactors. In a due course of our previous numerical study of point kinetics equations for critical reactors, however, we learned that the same code system can be used in studying dynamic behavior of the subcritical reactor. Our major motivation of this paper is to investigate responses of subcritical reactors for small changes in thermal hydraulic parameters. Building a thermal hydraulic model for the subcritical reactor dynamics, we performed numerical simulations for dynamic responses of the reactor based on point kinetics equations with a source term. Linearizing a set of coupled differential equations for reactor responses, we focus our research interest on dynamic responses of the reactor to variations of the thermal hydraulic parameters in transient phases.

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The Research On the Energy Storage System Using SuperCapacitor (슈퍼커패시터를 적용한 에너지 저장시스템 설계에 관한 연구)

  • Kim, IL-Song
    • Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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    • v.8 no.11
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    • pp.215-222
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    • 2018
  • In this paper, the research on the energy storage system adapting super-capacitor has been performed. The most advanced features compared to the conventional lead-acid battery systems is that it can obtain high power capability due to the super capacitor power characteristics. The suggested system can attain high power in short times and achieve high power quality improvements. The application areas are power quality improvement system, motor start power which requires high power during transient times. The energy conversion system consists of bi-directional converter and inverter and advantages of high speed, high power charging and discharging performances. The design steps for the two loop controller of the bi-directional inverter are suggested and verified by the experiment and manufacturing. The two loop controller design starts from linearized transfer function which is calculated from the state averaging model including state decoupling method. The current controller requirements are 20% overshoot and settling time and voltage controller are no overshoot and settling time which is 10 times longer than current controller. The design is verified from the step input response. The designed controllers have unity power factor characteristics and thus can improve the power quality of the grid. It also has fast response time and zero steady state error.