• 전력전자학회논문지
• /
• 제12권1호
• /
• pp.27-36
• /
• 2007

본 논문은 전원전압이 불평형이고 왜곡될 경우의 3상 PWM 컨버터의 전류제어기법을 제안한다. 전원전압의 왜곡에 대한 대책은 종래의 일반적인 전류 제어기에 5차, 7차 고조파 전류제어기를 추가하여 전원전류에 저차고조파가 나타나는 것을 제거한다. 그리고 전원전압 불평형의 경우, 역상분 전류제어기를 추가함으로써 전원전류를 평형으로 제어하거나 직류출력 전압의 리플을 감소시킬 수 있다. 제안된 제어 알고리즘의 타당성을 실험을 통하여 검증하였다.

• 전력전자학회논문지
• /
• 제12권3호
• /
• pp.234-240
• /
• 2007

본 논문에서는 비대칭 컨버터에 비하여 전력소자의 수를 감소하면서도, 고속 운전에 적합한 새로운 멀티레벨 인버터를 제안한다. 제안된 인버터는 기존의 비대칭 컨버터에 비하여 전력소자의 수를 감소시킬 수 있는 특징이 있으며, SRM의 감자구간에서 휠링되는 에너지와 전원에서 공급되는 에너지를 교차적으로 활용하는 방식을 적용함으로써, C-dump 인버터에 비해 커패시터의 정격전압을 낮출 수 있는 장점이 있다. 또한, 제안된 멀티레벨 인버터의 동작 모드는 비대칭 컨버터에 비하여, 충전 레벨의 전원을 정역으로 활용하여 빠른 여자(Excitation)와 감자(Demagnetization) 모드를 가지게 되므로, 제어의 활용성이 매우 높다. 따라서, SRM의 고속 운전에 필요한 여자전류의 빠른 확립을 통하여 응답시간을 개선시키며, 토크 발생구간을 확장시킬 수 있다. 제안된 멀티레벨 인버터 구동형 SRM의 운전특성은 시뮬레이션과 실험을 통해 검증하였다.

• Journal of Power Electronics
• /
• 제15권4호
• /
• pp.939-950
• /
• 2015

A single-stage AC-AC converter has been designed for a wind energy conversion system (WECS) that eliminates multistage operation and DC-link filter elements, thus resolving size, weight, and reliability issues. A simple switching strategy is used to control the switches that changes the variable-frequency AC output of an electrical generator to a constant-frequency supply to feed into a distributed electrical load/grid. In addition, a modified random sinusoidal pulse width modulation (RSPWM) technique has been developed for the designed converter to make the overall system more efficient by increasing generating power capacity and reducing the effects of inter-harmonics and sub-harmonics generated in the WECS. The technique uses carrier and reference waves of variable switching frequency to calculate the firing angles of the switches of the converter so that the three-phase output voltage of the converter is very close to a sine wave with reduced THD. A comparison of the performance of the proposed RSPWM technique with the conventional SPWM demonstrated that the power generated by a turbine in the proposed approximately increased by 5% to 10% and THD reduces by 40% both in voltage and current with respect to conventional SPWM.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2014년도 전력전자학술대회 논문집
• /
• pp.512-513
• /
• 2014

본 논문은 3상 인버터에서 직류단 션트 저항을 이용하여 전류를 복원하는 새로운 기법에 대하여 제안한다. 직류단 션트 저항을 이용하여 전류를 측정할 경우, 전동기의 구동에 따른 지령 전압 벡터의 변화에 따라 SVPWM 헥사곤 내부에는 전류의 측정이 불가능한 영역이 존재한다. 기존의 방법들은 지령 벡터가 전류 측정이 불가능한 영역에 위치할 때, 스위칭 패턴에 변화를 주는 방법들을 이용하였다. 그러나, 이 기법들은 스위칭 패턴을 바꾸기 때문에 소음 및 전류 왜곡의 원인이 된다. 본 논문에서는 스위칭 패턴의 변화 없이 전류를 추정할 수 있는 새로운 기법을 소개한다. 제안된 알고리즘의 효율성은 실험적 결과를 통해 증명한다.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2012년도 전력전자학술대회 논문집
• /
• pp.264-266
• /
• 2012

엘리베이터 제동 시 발생하는 인버터 회생 전류는 많은 고조파를 포함하고 있다. 기존의 회생용 인버터는 계통 측 필터로 L필터가 많이 사용되어 왔으나, 고조파를 저감하기 위해서 매우 큰 L값을 요구한다. 하지만 엘리베이터 회생용 인버터는 기설치된 DC Link 과전압 방지 방전회로가 동작되기 전에 회생을 실시하여야 하므로, 상대적으로 낮은 전압에서 회생되어야 하므로 큰 임피던스를 갖는 L필터를 사용하기 어렵다. 본 논문에서는 엘리베이터 회생용 인버터의 리플저감용 LCL 필터와 최근 제안된 LLCL 필터의 성능을 비교 분석하고 모의해석과 실험을 통해 그 타당성을 입증 하였다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1995년도 하계학술대회 논문집 A
• /
• pp.416-419
• /
• 1995

An analysis of a new load resonant inverter considering stray inductance is given. There are several different types for load resonant inverters. They can offer zero turn-on as well as zero turn-off switching losses, yielding high efficiency at high power and high frequencies. However, they didn't consider the influences of stray inductance. In conventional topology using lossless snubber capacitor, stray inductances result in very high frequency resonant current. Especially, these influences can be problematic in high power system such as induction heating system with large current of some 10A associated with it. These currents increase EMI problem, give harmful effects in gate driver's operation and increase loss of dc-link capacitor as well as snubber capacitor. Therefore, the effect of stray inductances should be treated and reduced. This paper presents a new load resonant inverter topology, which can reduce the effect of stray inductances.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2015년도 추계학술대회 논문집
• /
• pp.95-96
• /
• 2015

In this paper, a single-sourced PV PCS using the trinary asymmetric MLI with a single-ended pre-regulator is proposed. Trinary based asymmetric CHB inverters provide higher output levels for the same number of cells compared to other CHB inverters. However, there is an issue of regeneration with trinary asymmetric inverters and this complicates the system with requirement of bi-directional converters at the input. Modified commutation strategies have been used to remove the regeneration issue with compromise in THD. The single-ended pre-regulator provides the isolated dc-link voltage for the individual H-bridge cells with the advantage of having a single switch and magnetic component. This implementation increases the magnetic utilization of the inductor core and reduces the switching loss in the pre-regulator and also the reduced parts count contributes to the cost competiveness of the proposed PCS. The proposed PV PCS has been verified using simulation results in this paper.

• Journal of Power Electronics
• /
• 제19권6호
• /
• pp.1536-1543
• /
• 2019

This paper presents an improved torque predictive control (TPC) for permanent magnet synchronous motors (PMSMs) using an indirect matrix converter (IMC). The IMC has characteristics such as a high power density and sinusoidal waveforms of the input-output currents. Additionally, this configuration does not have any DC-link capacitors. Due to these advantages of the IMC, it is used in various application field such as electric vehicles and railway cars. Recently, research on various torque control methods for PMSM drives using an IMC is being actively pursued. In this paper, an improved TPC method for PMSM drives using an IMC is proposed. In the improved TPC method, the magnitudes of the voltage vectors applied to control the torque and flux of the PMSM are adjusted depending on the PMSM torque control such as the steady state and transient response. Therefore, it is able to reduce the ripples of the output current and torque in the low-speed and high-speed load ranges. Additionally, the improved TPC can improve the dynamic torque response when compared with the conventional TPC. The effectiveness of the improved TPC method is verified by experimental results.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2019년도 전력전자학술대회
• /
• pp.71-73
• /
• 2019

The output current of the Grid Connected Inverter (GCI) can be polluted with harmonics mainly due to i) dead time in switches, ii) non-linearity of switches, iii) grid harmonics, and iv) DC link fluctuation. Therefore, it is essential to design the robust Harmonic Compensation (HC) technique for the improvement of output current quality and fulfill the IEEE 1547 Total harmonics Distortion (THD) limit i.e. <5%. The conventional harmonic techniques often are complex in implementation due to their i) additional hardware needs, ii) complex structure, iii) difficulty in tuning of parameters, iv) current controller compatibility issues, and v) higher computational burden. In this paper, to eliminate the harmonics from the GCI output current, a novel Digital Lock-In Amplifier (DLA) based harmonic detection is proposed. The advantage of DLA is that it extracts the harmonic information accurately, which is further compensated by means of PI controller in feed forward manner. Moreover, the proposed HC method does not require additional hardware and it works with any current controller reference frame. To show the effectiveness of the proposed HC method a 5kW GCI prototype built in laboratory. The output current THD is achieved less than 5% even with 10% load, which is verified by simulation and experiment.

• 한국초전도ㆍ저온공학회논문지
• /
• 제24권4호
• /
• pp.50-54
• /
• 2022

High temperature superconducting (HTS) magnets for large-capacity energy storage system need to be composed of toroid magnets with high energy density, low leakage magnetic fields, and easy installation. To realize such a large capacity of a toroid HTS magnet, an HTS cable with large current capacity would be preferred because of the limited DC link voltage and instantaneous high power required for compensation of the disturbance in the power grid. In this paper, the optimal operating strategies of the SMES for peak load reduction of the microgrid system were calculated according to the load variation characteristics, and the effect of compensation of the frequency change in microgrid with a SMES were also simulated. Based on the result of the simulation, key design parameters of SMES coil were presented for two cases to define the specification of the HTS cable with large current capacities for winding of HTS toroid coils, which will be need for development of the HTS cable as a future work.