• Journal of Power Electronics
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• v.19 no.6
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• pp.1351-1365
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• 2019

This paper proposes two modified Z-source inverter topologies, namely an embedded L-Z-source inverter (EL-ZSI) and a coupled inductor L-Z source inverter (CL-ZSI). The proposed topologies offer a high voltage gain with a reduced passive component count and reduction in source current ripple when compared to conventional ZSI topologies. Additionally, they prevent overshoot in the dc-link voltage by suppressing heavy inrush currents. This feature reduces the transition time to reach the peak value of the dc-link voltage, and reduces the risk of component failure and overrating due to the inrush current. EL-ZSI and CL-ZSI possess all of the inherent advantages of the conventional L-ZSI topology while eliminating its drawbacks. To verify the effectiveness of the proposed topologies, MATLAB/Simulink models and scaled down laboratory prototypes were constructed. Experiments were performed at a low shoot through duty ratio of 0.1 and a modulation index as high as 0.9 to obtain a peak dc-link voltage of 53 V. This paper demonstrates the superiority of the proposed topologies over conventional ZSI topologies through a detailed comparative analysis. Moreover, experimental results verify that the proposed topologies would be advantageous for renewable energy source applications since they provide voltage gain enhancement, inrush current, dc-link voltage overshoot suppression and a reduction of the peak to peak source current ripple.

• Proceedings of the KIEE Conference
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• 2006.10d
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• pp.19-21
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• 2006

This paper presents the control method that inverter output keeps to linear to reference voltage of Synchronous Reluctance Motor using DC Link voltage Synthesis. The Inverter output voltage cannot be displayed to linear about inverter reference voltage if Real DC Link voltage is different from DC Link voltage of PWM amplitude. Also, the overmodulation that there is linearity broken if reference voltage is out of range that inverter can output voltage. Torque ripple generates the vibration and noise of a motor. This paper proposes the control method so that torque ripple decreases and the linearity of inverter output keeps using the DC Link voltage Synthesis.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.5
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• pp.427-433
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• 2016

This paper proposes a new method for the current ripple reduction of a three-phase interleaved bidirectional DC-DC converter. Usually, the three-phase interleaved bidirectional DC-DC converter is used for battery charging and discharging to reduce battery current ripple. In V2G application, a PWM AC-DC converter is used to connect the AC power grid and three-phase interleaved bidirectional DC-DC converter for battery charging and discharging. The magnitude of DC link voltage affects the battery current ripple magnitude. Therefore, the magnitude of the battery ripple current is analyzed with variations of battery and DC link voltages. The ripple current magnitude is found to be minimized by controlling the DC link voltage. Simulation and experimental results show the usefulness of the proposed method.

• Proceedings of the KIEE Conference
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• summer
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• pp.872-874
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• 2004

This paper presents a charcteristcic analysis switched reluctance motor (SRM) considering hard chopping and DC link voltage ripple by using time-stepped voltage source finite element method in which the magnetic field is combined with drive circuit. We also examine the influence of freewheeling diodes and DC link voltage ripple on the performance of the SRM such as torque ripples and radial force on the surface of the teeth The freewheeling diodes and DC link voltage ripples must be taken into account in predicted the performance of SRM

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.117-122
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• 2018

A large-capacity three-phase system air conditioner recently includes an inverter circuit to reduce power consumption. The inverter circuit uses a DC voltage that comes from DC-link power capacitor with the function of rectifying, which means AC voltage to DC voltage using a diode. An electrolytic capacitor is generally used to satisfy the voltage ripple and current ripple conditions of a DC-link power capacitor used for rectifying. Reducing the capacitance of the capacitor decreases the size, weight, and cost of the circuit. This paper proposes an algorithm to reduce the input ripple current by combining the minimum point estimation phase locked loop (PLL) phase control and the average voltage d axis current control technique. When this algorithm was used, the input ripple current decreased by almost 90%. The current ripple of the DC-link capacitor decreased due to the decrease in input ripple current. The capacitor capacity can be reduced but the electrolytic capacitor has a heat generation problem and life-time limitations because of its large equivalent series resistance (ESR). This paper proposes a method to select a film capacitor considering the current ripple at DC-link stage instead of an electrolytic capacitor. The capacitance was selected considering the voltage limitation, RMS (Root Mean Square) current capacity, and RMS current frequency analysis. A $1680{\mu}F$ electrolytic capacitor can be reduced to a $20{\mu}F$ film capacitor, which has the benefit of size, weight and cost. These results were verified by motor operation.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.5
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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.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.317-320
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• 2000

This paper proposes a voltage compensation method to improve the control performance of B4 inverter which is studied for low-cost drive systems. The B4 inverter employs only four switches and it has a center-tapped connection in the split dc-link capacitors to one phase of a three-phase motor. In the B4 topology unbalan-cd three-phase voltages will be generated by the dc link voltage ripple. To solve this problem we present a voltage compensation method which adjusts switching times considering dc link voltage ripple. The proposed method is verified by simulation results,

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.7
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• pp.59-66
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• 2013

This paper proposes a new voltage reference generation method for Four-Switch Inverters(FSI) with compensation of the neutral DC-link voltage variation. Since FSIs have the split DC-link causing the inherent problem of voltage fluctuations in the upper and lower capacitors, it is required to take account the voltage difference between the top and bottom capacitors. In this paper, to reduce the effect by the voltage variation, reference voltages are modified by adding compensation voltages proportional to the voltage difference between upper and lower capacitors. Simulation results showing control performance of induction and permanent magnet motors demonstrate the validity of the proposed method.

• Journal of Power Electronics
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• v.10 no.3
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• pp.328-333
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• 2010

A photovoltaic power conditioning system (PV PCS) that contains single-phase dc/ac inverters tends to draw an ac ripple current at twice the output frequency. Such a ripple current perturbs the operating points of solar cells continuously and it may reduce the efficiency of the current based maximum power point tracking technique (CMPPT). In this paper, the ripple current generation in a dc link and boost inductor is analyzed using the ac equivalent circuit of a dc/dc boost converter. A new feed-forward ripple current compensation method to incorporate a current control loop into a dc/dc converter for ripple reduction is proposed. The proposed feed-forward compensation method is verified by simulation and experimental results. These results show a 41.8 % reduction in the peak-to peak ac ripple. In addition, the dc/ac inverter control system uses an automatic voltage regulation (AVR) function to mitigate the ac ripple voltage effect in the dc link. A 3kW PV PCS prototype has been built and its experimental results are given to verify the effectiveness of the proposed method.

• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.419-420
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• 2015

In this paper, a low-cost single-phase PWM rectifier with small DC-link capacitors is proposed, where a buck-boost converter with a low power rating is added at the DC link. By controlling the auxiliary circuit so as to absorb the voltage ripple in the DC link, the second-order voltage ripple in DC-link capacitor can be reduced significantly. Therefore, a small film capacitor can be utilized to replace the bulky electrolytic capacitors. The simulation results are shown to verify the validity of the proposed method.