• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.2
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• pp.261-270
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• 2021

In this study, the design methodology of LCL filter for grid-connected three-phase inverter was studied. First, the advantages and disadvantages of applying typical filter structures as a filter for grid connection of a three-phase inverter were analyzed. Next, filter design methodologies for grid connection of a three-phase inverter were analyzed, and an effective filter design methodology was determined to satisfy the harmonic requirements in grid connection. In order to verify the effectiveness of the design methodology, EMTP models such as a three-phase inverter, a three-phase LCL filter, and a performance evaluation system to evaluate the performance of the designed filter were developed using EMTP-RV. Next, an LCL filter was designed for an application example of a three-phase inverter, and the waveforms of the output voltage and outage current of the three-phase inverter were checked through EMTP-RV simulation work. In particular, the validity of the design methodology was verified by confirming that the magnitude of the current ripple was reduced to a limited magnitude through waveform analysis of the output current.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.6
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• pp.1071-1079
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• 2007

In this paper, a novel space vector control method for isolated multi-level inverter using 3-phase low frequency transformers is proposed. This method is based on the simplification of the space-vector diagram of a five-level inverter using calculated table into fully programming method. The execution time of the proposed method is about same as that of the method using calculated table. Also, the proposed method is easily applied to other case level inverter. We applied this method into the 3-phase IHCML inverter using common arm. It makes possible to use a single DC power source due to employing low frequency transformers. In this inverter, the number of transformers could be reduced compare with an exiting 3-phase multi-level inverter using single phase transformer. In addition, this method generates very low harmonic distortion operation with nearly fundamental switching frequency. Finally, We tested multi-level inverter to clarify electric circuit and reasonableness through Matlab simulation and experiment by using prototype inverter.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.905-915
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• 2015

Two PWM techniques using space vector pulse-width modulation (SVPWM) are proposed for a two-phase permanent magnet synchronous motor (PMSM) driven by a two-phase eight-switch inverter. A two-phase motor with two symmetric stator windings is usually driven by a two-phase four-, six-, or eight-switch inverter. Compared with a four- and six-switch inverter, a two-phase eight-switch inverter can achieve larger power output. For two-phase motor drives, the SVPWM technique achieves more efficient DC bus voltage utilization and less harmonic distortion of the output voltage. For a two-phase PMSM fed by a two-phase eight-switch inverter under a normal SVPWM scheme, each of the eight PWM trigger signals for the inverter have to be changed twice in a cycle, causing a higher PWM frequency. Based on the normal SVPWM scheme, two effective SVPWM schemes are investigated in order to reduce the PWM frequency by rearranging four comparison values, while achieving the same function as the normal PWM scheme. A detailed explanation of the normal and two proposed SVPWM schemes is illustrated in the paper. The experimental results demonstrate that the proposed schemes achieve a better steady performance with lower switching losses compared with the normal scheme.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.5
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• pp.391-398
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• 2014

This paper presents a resonant step-down DC/DC converter to reduce the voltage stresses of a 3-phase inverter module under the three-phase AC utility line condition. Under this condition, a conventional 3-phase inverter module suffers from high voltage stresses as a result of the high rectified DC link voltage; hence, a high-cost high-voltage-rating inverter module must be used. However, using the proposed converter, a low-cost low-voltage-rating inverter module may be adopted to drive the motor even under the 3-phase AC line condition. The proposed converter, which can be realized with small size inductor and low-voltage-rating semiconductor devices, operates at a high-efficiency mode because of the zero-current switching operations of all the semiconductor devices. The operational principles are explained and a design example is provided in the study. Experimental results demonstrate the validity of the proposed converter.

• Journal of the Semiconductor & Display Technology
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• v.14 no.4
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• pp.72-77
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• 2015

Three-level diode clamped multilevel inverter, generally known as neutral point clamped (NPC) inverter, has an inherent problem causing neutral point (NP) potential variation. Until now, the NP potential problem of variation has been investigated and lots of solutions have also been proposed. This paper presents a neutral point voltage control technology using the anti-windup PI controller and offset technology of PWM (Pulse Width Modulation) to control the variation of NPC 3-phase three-level inverter neutral point voltage. And the proposed algorithm is tested and verified using a PLL (Phase Locked Loop) in order to synchronize the phase voltage from the line voltage of grid. It significantly improves the voltage balancing under a solar fluctuation conditions of the inverter. Experimental results show the good performance and effectiveness of the proposed method.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.2
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• pp.139-148
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• 2007

In this paper, we proposed the isolated multi-level inverter using 3-phase transformers. It makes possible to use a single DC power source due to employing low frequency transformers. In this inverter, the number of transformer could be reduced comparing with an exiting 3-phase multi-level inverter using single phase transformer. Also, using phase angle control method with switching frequency equal to output fundamental frequency, harmonics component of output voltage and switching losses can be reduced. Finally, we made a prototype inverter to clarify the proposed electric circuit and reasonableness of control signal.

• Journal of Power Electronics
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• v.18 no.3
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• pp.853-862
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• 2018

Frequency coupling in the phase domain is a recently reported phenomenon for phase locked loop (PLL) based three-phase grid-inverter systems. This paper investigates the mechanism and stabilization method for the frequency coupling to the stability of grid-inverter systems. Self and accompanying admittance models are employed to represent the frequency coupling characteristics of the inverter, and a small signal equivalent circuit of a grid-inverter system is set up to reveal the mechanism of the frequency coupling to the system stability. The analysis reveals that the equivalent inverter admittance is changed due to the frequency coupling of the inverter, and the system stability is affected. In the end, retuning the bandwidth of the phase locked loop is presented to stabilize the three-phase grid-inverter system. Experimental results are given to verify the analysis and the stabilization scheme.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.4
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• pp.538-550
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• 1998

The variable frequency and variable voltage AC source made by a conventional inverter which is composed of power semi-conductors includes much noises in sine wave due to high frequency switching of DC source. In this paper the 3rd low pass LC filter for a variable speed 3 phase induction motor driven by a full bridge inverter is introduced to solve the EMI problem by serious noise current. The utility of a modified 3rd order Butterworth LC filter is confirmed through FFT analysis of sine waves and noiseless ACsource can be obtained by the proposed LC filter. The speed of a 3 phase induction motor driven by a full bridge inverter with a LC filter is satisfactorily controlled by a digital PID controller under the condition of stepwise load and setpoint changes.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1995.10a
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• pp.80-84
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• 1995

ABSTRACT - This paper presents a software based 3 phase 5 level pulse-width modulation(PWM) inverter to reduce total harmonic distortion. The proposed modulation technique can reduce total harmonic distortion and significantly improve the performance of the inverter. In the modulation mode where the frequency ratio is 36 and modulation index is 1.2∼2.0, harmonic components have been mostly eliminated and the magnitude of fundamental component have been maximized by the 3 phase 5 level PWM inverter.

• Journal of Power Electronics
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• v.3 no.2
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• pp.90-98
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• 2003

This paper presents a performance analysis in steady-state of a novel type Auxiliary Resonant Commutation Snubber-linked 3-level 3-phase voltage source soft switching inverter suitable and acceptable for high-power applications in comparison with other three types of 3-level 3-phase voltage source soft switching inverters. This soft switching inverter operation which can operate under a condition of Zero Voltage Switching (ZVS). The practical steady -state performances of this inverter are illustrated and evaluated on the basis of the experimental results.