• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.4
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• pp.275-282
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• 2022

In this study, an inverter system connected to a grid through a paralleled LCL filter is proposed. The system consists of two inverters paralleled and operated with interleaved PWM for powering up and performance improvement. Two LCL filters have two separate filter inductors and one set of filter capacitor and grid inductor in common. The differential mode current circulates through two inverters and two filter inductors. The differential mode current is removed from the filter capacitor and the power grid. Accordingly, performance improvement can be achieved due to the reduced currents in the filter capacitor and the reduced harmonics into a grid. A single-phase prototype has been made and tested, and the proposal has been verified.

• Proceedings of the KIEE Conference
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• 1999.11b
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• pp.398-402
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• 1999

In PWM inverter fed traction motor drive systems, the switching frequency is restricted and thus the electromagnetic acoustic noise is generated. To reduce such an audible noise, we propose the modified RSF(Randomized Switching Frequency)-PWM method. In the proposed RSF-PWM method, both triangular wave and sawtooth wave are used in one period as carrier waves. Because the proposed method has inherently the same property as sinusoidal PWM method, there is no problem of linearity. To verify the validity of the modified RSF-PWM method, computer simulations are carried out.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.774-777
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• 2005

In this paper, a constant frequency phase shifting PWM controlled voltage source full bridge-type series load resonant high-frequency inverter using the IGBT power modules is presented for innovative consumer electromagnetic induction heating applications such as a hot water producer, steamer and super heated steamer. The full bridge arm side link passive quasi-resonant capacitor snubbers in parallel with the each power semiconductor device and high frequency AC load side linked active edge inductive snubber-assisted series load resonant tank soft switching inverter with a constant frequency phase shifted PWM control scheme is discussed and evaluated on the basis of the simulation and experimental results. It is proved from a practical point of view that the series load resonant and edge resonant hybrid high-frequency soft switching PWM inverter topology, what is called class DE type. including the variable-power variable-frequency(VPVF) regulation function can expand zero voltage soft switching commutation range even under low output power setting ranges, which is more suitable and acceptable for induction heated dual packs fluid heater developed newly for consumer power utilizations. Furthermore, even in the lower output power regulation mode of this high-frequency load resonant tank high frequency inverter circuit it is verified that this inverter can achieve ZVS with the aid of the single auxiliary inductor snubber.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.2
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• pp.178-186
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• 2004

This paper proposes a two-phase RCD-PWM scheme which is much better than a three-phase RCD-PWM scheme from the standpoint of the broadening and linearizing effect of the power spectrum. To implement the proposed scheme and conventional scheme, the experiment based on the SAB-Cl67 micro-controller was executed. Based on the space vector modulation technique, the duty ratio of the pulses is calculated using the SAB-Cl67 and each of PWM pulses is located randomly in each switching interval. The power spectrum of the output voltage, output current, the d.c link current and the acoustic noise radiated from inverter drives are experimentally investigated. 1'hen, the performance of the proposed scheme was compared and discussed with the conventional scheme.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.9 no.5
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• pp.51-56
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• 1995

The transistors of single phase 3 level PWM Inverter compose output power transistors and neutral point clamping transistors, which are NPN transistors. Waveforms of driving signals for this are PWM waves for power transistors and period operating waves for neutral point clamping transistors, which signals made W-type modulation from rectangular and sine wave. The output power transistors operate at ON-time complementary and neutral point clamping transistors operate at OFF-time complementary respectively. Therefore, each transistors operate in half period at parallel. Characteristics of this inverter circuit is parallel switching method about series switching method of general inverter. As modulation of 3 level drive signals made from full-wave rectifier of sine wave and rectangular wave, which are level wave about 3 level of complementary transistor inverter. So, this circuit composed complementary operation inverter of NPN transistors only compare with PNP-NPN complementary inverter, which have high power 3 level inverter of complementary operation.

• Journal of Advanced Marine Engineering and Technology
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• v.19 no.3
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• pp.99-106
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• 1995

PWM(Pluse Width Modulation) induction motor drives are being used in greater numvers through a wide variety of industrial and commercial applications. In this paper, a new speed control algorithm (hybrid algorithm) for induction motor drives that uses regular sampled PWM and harmonic elimination PWM is presented. The hybrid algorithm in implemeted on the computer to obtain solutions from the calculation equations of the width of the pulses and the firing angles for the selected harmonic elimination. this paper describes the time delay effects and the suitable compensating methods moreover, optical transmission system for driving signals is proposed and is compared with general trnasmission system. The hybrid inverter was tested with induction motor, and these test results are shown that this hybrid inverter closely approximates and exhibits many of the desirable performance characteristic distortions and eliminated the objectionable harmonics. Finally, detailed experimental investigation of the proposed hybrid scheme in presented.

• Proceedings of the KIPE Conference
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• 2004.07b
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• pp.620-624
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• 2004

Th is paper presents a systematical approach to study carrier based PWM techniques (CPWM) in diode-clamped and cascade multilevel inverters by using the proposed multi-modulating pattern method. This method is based on the vector correlation between CPWM and space vector PWM (SVPWM) and applicable to both multilevel inverter topologies. The CPWM technique can be described in a general mathematical equation, and obtain the same outputs similarly as of corresponding SVPWM. Control of the fundamental voltage, vector redundancies and phase redundancies in multilevel inverter can be formulated separately in the CPWM equation. The deduced CPWM can obtain a full vector redundancy control, and fully utilize phase redundancy in a cascade inverter. In the paper, CPWM equations and corresponding algorithm for generating multi-modulating signals will be performed, in which SVPWM attributes will be presented by corresponding controllable factors.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.296-298
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• 1995

This paper proposes a new filter topology that suppresses the high voltage gradient(dv/dt) in ac motor terminals. The high voltage gradient(dv/dt) causes over voltages on the motor windings, the degradation or motor insulation, and the bearing failure. Moreover surge voltage with high voltage gradient(dv/dt) in the PWM inverter red drive system where long line cables are required causes more serious problem to the motor. Thus, the most advisable method is attaching output filter to the inverter output terminals. The conventional output filters have several problems such as bulky size, difficulty or parameter tuning. The proposed filter can be relatively smaller than the conventional filters. By the proposed filter, the shaping or PWM waveform can considerably suppress high dv/dt in motor feeding cable from the inverter. The effectiveness or the proposed filter is compared with that or the conventional one and is verified by the computer simulation.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.971-982
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• 2015

In order to improve the quality of the billet continuous casting, a two-phase orthogonal power supply (TPOPS) for electromagnetic stirrer is researched, which is composed of three-phase PWM rectifier and three-leg inverter. According to the power analysis of system, the ripple of dc-link voltage is analyzed and its analytical expression is derived. In order to improve the performance of electromagnetic stirring, an integrated control method with feedforward control is proposed for PWM rectifier to suppress the fluctuations of dc-link voltage and provide a stable dc source for inverter. According to the simplified equivalent model, a composite current control method is proposed for inverter. This proposed method can combine the merits of feedforward control with feedback control to effectively improve the dynamic output performance of TPOPS. Finally, a 300kVA prototype of TPOPS is developed, and the results have verified the analysis and control method.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.333-336
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• 2003

Designed transformer-less inverter for photovoltaic and small unit windturbine power system. This system consisted of boost chopper circuit of multiple-switching method and foil bridge PWM inverter. Transformer-less system was adapted to reduce cost and size. But in this system, earth-leakage current have to be considered. So, to solve this problem, we used PWM inverter switching method to reduce the earth-leakage current which flows in accordance with the variation of DC input common mode voltage.