• Journal of Electrical Engineering and Technology
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• 제13권3호
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• pp.1212-1222
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• 2018

This paper presents a model predictive control (MPC) method to reduce the common-mode voltage (CMV) for inverters connected in parallel, which increase the capacity of energy storage systems (ESSs). The proposed method is based on subdivided voltage vectors, and the resulting algorithm can be applied to control the inverters. Furthermore, we use more voltage vectors than the conventional MPC algorithm; consequently, the quality of grid currents is improved. Several methods were proposed in order to reduce the CMV appearing during operation and its adverse effects. However, those methods have shown to increase the total harmonic distortion of the grid currents. Our method, however, aims to both avoid this drawback and effectively reduce the CMV. By employing phase difference in the carrier signals to control each inverter, we successfully reduced the CMV for inverters connected in parallel, thus outperforming similar methods. In fact, the validity of the proposed method was verified by simulations and experimental results.

• Journal of Power Electronics
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• 제6권3호
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• pp.195-204
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• 2006

This paper presents a new compensating system, consisting of series and shunt active filters, for mitigating voltage and current disturbances. The shunt filter is used to compensate for unbalanced and distorted load currents. The series filter comprises two inverters, used to suppress voltage disturbances and handle source currents independently. This configuration is devised to reduce the overall cost of active compensators by using low-frequency high-current switches for the latter inverter. The filters are controlled separately using a novel control strategy. Since voltages at the point of common coupling contain interharmonics, conventional methods cannot be used for extracting voltage references. Therefore, voltage references are obtained from generated sinusoidal waveforms by a phase-locked loop. Current references are detected based on rotating frame vector mapping. Simulation results are presented to verify the system.

• Journal of Power Electronics
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• 제17권1호
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• pp.190-199
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• 2017

In this paper, a predictive direct power control (DPC) method based on a Kalman filter is presented for three-phase pulse-width modulation (PWM) rectifiers to improve the performance of rectifiers with source voltages that are distorted with harmonic components. This method can eliminate the most significant harmonic components of the source voltage using a Kalman filter algorithm. In the process of predicting the future real and reactive power to select an optimal voltage vector in the predictive DPC, the proposed method utilizes source voltages filtered by a Kalman filter, which can mitigate the adverse effects of distorted source voltages on control performance. As a result, the quality of the source currents synthesized using the PWM rectifier is improved, and the total harmonic distortion (THD) values are reduced, even under distorted source voltages.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 추계학술대회 논문집 학회본부
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• pp.159-161
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• 1994

A new control technique which generates high-quality sinusoidal output voltage from a single-phase resonant do link inverter suitable for the UPS systems is presented. The inverter output voltage control system has the PID controller with a minor loop of the filter inductor current and tile feedforward controller. The proposed control scheme also solves resonant voltage overshoot without any additional switch or passive component, resulting in pulses with uniform amplitude and high efficiency. Experimental results in the case of linear and nonlinear loads are presented to confirm the usefulness of the Proposed control algorithms.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.325-329
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• 2000

An effective Carrier-Based PWM scheme that enables the instantaneous quality of each branch point voltage of a diode clamped 4-level inverter to be reduced at a low modulation index is described. This scheme presents a computed zero sequence voltage of PWM by the feedback of both DC-link voltages and load currents. The proposed PWM scheme enables to increase the controllable region of DC-link voltage and makes it possible to operate with small DC-link capacitors. The validity of the proposed PWM scheme is verified by simulation results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 A
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• pp.164-167
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• 2001

In resent years, electric power quality has become an important issue in power system. Voltage variation and compensation countermeasures of KEPCO system in west Gyeongnam have been simulated using PSS/E. In this paper, in the abnormal power system, the adaption of SVC, high speed and continuous control are simulated for voltage compensation. It is shown that the SVC is the optimal voltage compensation method in loop power system or 2 lines radial system.

• 전력전자학회논문지
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• 제17권5호
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• pp.377-387
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• 2012

A single-phase grid-connected PV system is known as suitable for housing of less than 3 kW. The DC link voltage in a single-phase PV system has necessarily twice component of fundamental wave. It makes high THD in the grid current. According to the problem, power quality is lower. Many engineers have studied about this problem. The most simple method is to use low pass filter on DC link voltage control. However it is affected by DC link voltage control bandwidth. If cutoff frequency is reduced to increase the performance of low pass filter, it also lowers DC link voltage control bandwidth. Second method is using band stop filter, it works good on steady state but not good on transient state. This paper proposes the new method for removing ripple voltage to get an exact current reference. It improves the responses on steady state and transient state. The performance was verified through computer simulation using MATLAB and actual experiments.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2012년도 전력전자학술대회 논문집
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• pp.359-360
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• 2012

This paper proposes a scheme of auto-tuning fuzzy PI controller and input voltage feed forward to control the output voltage of a three-phase Z-source inverter (ZSI). The proposed scheme adjusts the ts (Kp and Ki) in real time in order to find the most suitable Kp and Ki for PI controller and to simplify the controller design. The proposed scheme is verified the validity by experiment and co-simulation in PSIM and MATLAB/SIMULINK both load step change and input DC voltage variation in Z-source inverter, and has compared with the conventional PID control scheme. The experiment results involve of three-phase output voltage, Z-network capacitor voltage and dc-link peak voltage value. By those analysis and comparison, the availability of the proposed method in output voltage transient response quality improving has been verified. Compared with conventional PID method, the proposed method showed a more effective and robust control performance for coping with the severe disturbance conditions.

• 한국산학기술학회논문지
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• 제10권1호
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• pp.81-90
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• 2009

전력산업의 구조개편과 더불어 분산전원의 배전계통연계운용 및 전력품질이 전력회사의 배전사업자, 구역전기사업자, 전기공급 신뢰도와 밀접한 관계에 있는 산업용 수용가들에게 많은 관심을 불러일으키고 있다. 이러한 주변정세는 차세대의 배전계통이 다수의 Micro-grid들로 구성될 것이라고 하는 예상을 전문가들로부터 제기되기에 이르렀다. 그러나, 제안된 Micro-grid는 몇몇의 분산전원과 전력품질을 보상하는 기기, 그리고 통신제어설비와 부하들로 구성된다는 기본적인 내용에 지나지 않는다 따라서, 본 논문에서는 수용가에 고신뢰 고품질의 전력공급을 가능하게 하는 차세대 전력공급네트워크인 Micro-grid의 적정전압유지를 위한 자율분산협조 운용제어 알고리즘을 제안한다.

• 전력전자학회논문지
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• 제6권2호
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• pp.173-179
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• 2001

본 논문은 배전계통의 전력품질 개선을 위한 순시 전압강하 보상기의 제어 알고리즘에 대한 연구를 수행하였다. 특별히 순시적인 전압강하의 원인중 가장 대표적인 1선 지락사고 시에 발생하는 불평형과 비대칭 문제를 해석하기 위하여 새로운 대칭성분 검출 기법을 제안하였다. 제안되 방법은 간단한 연산만을 사용하며, 전압보상을 위한 대칭성분의 제어 기준값이 별도의 위상검출 과정을 거치지 않고도 직류 값으로 표현되도록 하였다. 그리고 기준전압의 발생 시에 IEC에서 규정하고 있는 UF와 MF를 사용하도록 하였다. 제안된 제어기법을 사용하면 보상장치는 매우 빠른 응답특성을 가지고 보상된 전압 파형의 총고조파왜형률(THD)도 매우 낮게 된다. 마지막으로 EMTDC 시뮬레이션과 실험을 통하여 제안된 방법의 타당성을 입증하였다.