• Journal of Electrical Engineering and Technology
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• v.9 no.4
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• pp.1324-1331
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• 2014

This paper proposes a compensation PWM technique for the extension of output voltage ranges in three-phase VSI applications using three shunt resistors. The proposed technique aims to solve the dead zone, which occurs in high modulation indexes. In the dead zone, two phase currents cannot be sampled correctly, so that the three-phase VSI cannot be operated up to the maximum output voltage. The dead zone is analyzed in detail, and the compensation PWM algorithm is developed. The proposed algorithm is verified by numerical analysis and experimental results.

• Proceedings of the KIEE Conference
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• 2003.04a
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• pp.154-156
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• 2003

3상 4레그(leg) VSI(Voltage Source Inverter)는 독립된 3개의 출력전압을 합성할 수 있다. 따라서 전압 합성에 있어서 3개의 자유도를 갖는다. 본 논문에서는 3상 4레그 VSI를 위한 PWM방법에 대해서 설명한다. 3상 4레그 VSI를 위한 기존의 PWM기술은 3-D SVPWM으로 그 구현 방법에 있어서 많은 양의 계산과 테이블을 필요로 하였다. 하지만, 본 논문에서 제안 한 방법은 3상 3레그 VSI경우에 적용되었던 옵셋(offset) 전압의 개념을 사용한다. 또한 단일 반송파를 이용하여 폴(Pole)전압과 비교함으로써 PWM을 구현하기 때문에 그 적응이 매우 간단하다. 본 논문에서는 기존의 3-D SVPWM과 제안한 방법이 해석적으로 동일한 방법임을 증명하였으며, 3상 4레그 VSI에서 합성가능한 3자유도의 전압범위를 계산하였다. 마지막으로 이를 실험을 통하여 검증하였다.

• Proceedings of the KIPE Conference
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• 2013.11a
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• pp.111-112
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• 2013

The three-phase four-leg voltage source inverter (VSI) topology can be an interesting option for the three phase-four wire system. With an additional leg, this topology can handle the neutral current, hence the DC link capacitance can be reduced significantly. In this paper the three dimensional space vector modulation (3D SVM) in ${\alpha}{\beta}{\gamma}$ coordinates for the three-phase four-leg VSI is presented. By using the 3D SVM method, the DC link voltage can be reduced by 16% compared with the split DC link capacitor topology and the output distortion can also be reduced under the unbalanced load condition.

• 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.

• Journal of Power Electronics
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• v.10 no.1
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• pp.91-96
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• 2010

In this paper, a simplified control algorithm for a three-phase, four-wire unified power quality conditioner (UPQC) is presented to compensate for supply voltage distortions/unbalance, supply current harmonics, the supply neutral current, the reactive power and the load unbalance as well as to maintain zero voltage regulation (ZVR) at the point of common coupling (PCC). The UPQC is realized by the integration of series and shunt active filters (AFs) sharing a common dc bus capacitor. The shunt AF is realized using a three-phase, four leg voltage source inverter (VSI) and the series AF is realized using a three-phase, three leg VSI. A dynamic model of the UPQC is developed in the MATLAB/SIMULINK environment and the simulation results demonstrating the power quality improvement in the system are presented for different supply and load conditions.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.965-968
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• 2003

This paper describes the PWM-VSI controller of three-phase UPS system using stationary reference frame. This controller meets the specification the UPS inverter output voltage even under the unbalanced or nonlinear load. This controller is also constructed with duble control loop of the outer voltage control loop and the inner current control loop. For the fast response of the output voltage control, yhr inner current control loop of the capacitor current os used. To get the good property against overshoot, the If controller us used. The outer voltage controller is designed with P controller and the high gain transfer function is used for the zero steady state error. All control gains of both controller is designed base on the CDM method.

• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.489-500
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• 2014

This paper presents a simple modified unipolar carrier-based pulsewidth modulation (CB-PWM) strategy for the three-level neutral-point-clamped (NPC) voltage source inverter (VSI). Analytical expressions for the relationship between modulation reference signals and output voltages are derived. The proposed modulation technique for the three-level NPC VSI includes the maximum and minimum of the three-phase sinusoidal reference voltages with zero-sequence voltage injection concept. The proposed modified CB-PWM strategy incorporates a novel method that requires only of one triangular carrier wave for generate the gating pulses in three-level NPC VSI. It has the advantages of being simplifying the algorithm with no need of complex two/multi-carrier pulsewidth modulation or space vector modulation (SVM) and it's also simple to implement. The possibility of the proposed CB-PWM technique has been verified though computer simulation and experimental results.

• Journal of Power Electronics
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• v.14 no.6
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• pp.1272-1280
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• 2014

This paper presents solutions for fault detection and diagnosis of two-level, three phase voltage-source inverter (VSI) topologies with IGBT devices. The proposed solutions combine redundant standby VSI structures and contactors (or relays) to improve the fault-tolerant capabilities of power electronics in applications with safety requirements. The suitable combination of these elements gives the inverter the ability to maintain energy processing in the occurrence of several failure modes, including short-circuit in IGBT devices, thus extending its reliability and availability. A survey of previously developed fault-tolerant VSI structures and several aspects of failure modes, detection and isolation mechanisms within VSI is first discussed. Hardware solutions for the protection of power semiconductors with fault detection and diagnosis mechanisms are then proposed to provide conditions to isolate and replace damaged power devices (or branches) in real time. Experimental results from a prototype are included to validate the proposed solutions.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.2
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• pp.40-46
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• 2015

This paper presents a method of controlling a three-phase VSI (Voltage Source Inverter) using MPC (Model Predictive Control) designed using Laguerre functions. It also provides a model of the three-phase VSI and its resistive-inductive load and then an overview of MPC design using Laguerre functions. The biggest challenge in using MPC is the high number of computations involved, which makes online implementation difficult. On the other hand, the LMPC (Laguerre Model Predictive Control) reduces the number of computations made and so online implementation becomes possible where traditional MPC would be unteneble. The simulation results from MATLAB are also provided.

• Journal of Power Electronics
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• v.9 no.3
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• pp.365-376
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• 2009

In this paper, the implementation of a three-phase shunt active power filter is presented. The filter is essentially three independent single-phase current-controlled voltage source inverters (CC-VSI) with a common DC bus. The CC- VSI is operated to directly control the AC grid current to be sinusoidal and in phase with the grid voltage without detecting the load currents. The APF consists of a current control loop, which shapes the grid currents to be sinusoidal and a voltage control loop, which regulates the active power balance of the system. The experimental results indicate that the active filter is able to handle predominantly the harmonics, as well as the unbalance and reactive power, so that the grid currents are sinusoidal, in phase with the grid voltages and symmetrical.