• 전력전자학회논문지
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• 제25권6호
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• pp.490-495
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• 2020

The power loss of large-capacity systems using single-phase inverters has attracted considerable attention. In this study, optimal switching sequence model prediction control at a low switching frequency is proposed to reduce the power loss in a high-power inverter system, and a compensation method that can be utilized for model prediction control is developed to reduce errors in accordance with sampling values. When a three-level, single-phase inverter using a switching frequency of 600 Hz and a sampling frequency of 12 kHz is adopted, the power factor is improved from 0.95 to 0.99 through 3 kW active power control. The performance of the controller is also verified.

• Journal of Power Electronics
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• 제15권3호
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• pp.741-752
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• 2015

This study proposes a new solution for the parallel operation of microgrid inverters in terms of circuit topology and control structure. A combined three-phase four-wire inverter composed of three single-phase full-bridge circuits is adopted. Moreover, the control structure is based on adaptive three-order sliding-mode control and wireless load-sharing control. The significant contributions are as follows. 1) Adaptive sliding-mode control performance in inner voltage loop can effectively reject both voltage and load disturbances. 2) Virtual resistive-output-impedance loop is applied in intermediate loop to achieve excellent power-sharing accuracy, and load power can be shared proportionally to the power rating of the inverter when loads are unbalanced or nonlinear. 3) Transient droop terms are added to the conventional power outer loop to improve dynamic response and disturbance rejection performance. Finally, theoretical analysis and test results are presented to validate the effectiveness of the proposed control scheme.

• 전기학회논문지
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• 제64권5호
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• pp.718-725
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• 2015

This paper proposes a novel level-shifted PWM (LS-PWM) strategy for fault tolerant cascaded multilevel inverter. Most proposed fault-tolerant operation methods in many of studies are based on a phase-shifted PWM (PS-PWM) method. To apply these methods to multilevel inverter systems using LS-PWM, two additional steps will be implemented. During the occurrence of a single-inverter-cell fault, the carrier bands scheme is reconfigured and modulation levels of inverter cells are reassigned in this proposed fault-tolerant operation. The proposed strategy performs balanced three-phase line-to-line voltages and line currents when a switching device fault occurs in a cascaded multilevel inverter using LS-PWM. Simulation and experimental results are included in the paper to verify the proposed method.

• Journal of Power Electronics
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• 제13권5호
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• pp.806-813
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• 2013

This paper aims to compare the performance of three phase induction motor drives using Five Leg Inverter (FLI) and Three Leg Inverter (TLI) configurations. An Indirect Field Oriented Control (IFOC) method using a TLI is well established and incorporated for high performance speed drives in various industries. The FLI dual motor drive system on the other hand shows good workability in the independent control of two induction motor drives simultaneously. In this experiment, the IFOC method is utilized for both drive systems, and Space Vector Pulse Width Modulation (SVPWM) is used to generate pulses for both inverters. For the FLI, the Double Zero Sequence (DZS) Injection technique is used to generate the modulation signal. The complete experiment setup is done by using a DSpace 1103 controller board. The individual motor performances are analyzed using similar schemes, equipment setups and controller parameter values. The results show similar speed performance response capability between the single motor operation using a TLI system and the two motor operation using a FLI system based on the variable speed range either in forward or reverse operation. They also show similar load rejection abilities. However, the single motor with a TLI has a better power quality aspect such as ripple current and total harmonics distortion (THD).

• 전력전자학회논문지
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• 제25권4호
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• pp.319-328
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• 2020

The recent use of distributed power generation systems constructed with DC-DC converters has become extremely popular owing to the rising need for environment friendly energy generation power systems. In this study, a new single-phase five-level inverter for off-grid applications constructed with a multilevel DC-DC step-up converter is proposed to boost a low-level DC voltage (36 V-64 V) to a high-level DC bus (380 V) and invert and connect them with a single-phase 230 V rms AC load. Compared with other traditional multilevel inverters, the proposed five-level inverter has a reduced number of switching devices, can generate high-quality power with lower THD values, and has balanced voltage stress for DC capacitors. Moreover, the proposed topology does not require multiple DC sources. Finally, the performance of the proposed topology is presented through the simulation and experimental results of a 400 W hardware prototype.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 전력전자학술대회
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• pp.144-146
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• 2018

In order to meet the harmonics standards such as IEEE 519 and P1547 the output quality of a grid connected inverter should satisfy a certain level of Total Harmonic Distortion (THD) value. However, the output quality of an inverter gets degraded due to the grid voltage harmonics, the dead time effects and the nonlinearity of the switches, which all contributes to a higher THD value of the output. In order to meet the required THD value for the inverter output under the distorted grid condition the use of harmonic controller is essential. In this paper a novel feedforward harmonic compensation method is proposed in order to effectively eliminate the low order harmonics in the inverter current to the grid. In the proposed method, unlike the conventional harmonic control methods, the hamonic components are directly compensated by the feedforward terms generated by the PR controller with the grid current in the stationary frame. The proposed method is simple in implementation but powerful in eliminating the harmonics from the output. The effectiveness of proposed method is verified through the PSIM simulation and the experiments with a 5kW single phase grid connected inverter.

• 전력전자학회논문지
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• 제23권2호
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• pp.129-138
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• 2018

Previous single-phase transformerless inverters used active bypass switching circuits that need auxiliary power switches to minimize ground leakage current. However, switching and gate driving losses are increased due to the use of additional power switches. To cope with this drawback, this work proposes a transformerless inverter using a passive bypass filter without any auxiliary power switch. The operation and control of the proposed inverter are described. The ground leakage current characteristics are analyzed for the proposed inverter with the passive bypass filter. The experimental results of the proposed inverter for a 1.0kW prototype system are presented.

• 전력전자학회논문지
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• 제24권3호
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• pp.215-227
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• 2019

Grid-connected inverters should satisfy a certain level of total harmonic distortion (THD) to meet harmonics standards, such as IEEE 519 and P1547. The output quality of an inverter is typically degraded due to grid voltage harmonics, dead time effects, and the device's turn-on/turn-off delay, which all contribute to increasing the THD value of the output. The use of a harmonic controller is essential to meet the required THD value for inverter output under a distorted grid condition. In this study, an improved feedforward harmonic compensation method is proposed to effectively eliminate low-order harmonics in the inverter current to the grid. In the proposed method, harmonic components are directly compensated through feedforward terms generated by the proportional resonant controller with the grid current in a stationary frame. The proposed method is simple to implement but powerful in eliminating harmonics from the output. The effectiveness of the proposed method is verified through simulation using PSIM software and experiments with a 5 kW single-phase grid-connected inverter.

• Journal of Power Electronics
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• 제9권3호
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• pp.365-376
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• 2009

In this paper, the implementation of a three-phase shunt active power filter is presented. The filter is essentially three independent single-phase current-controlled voltage source inverters (CC-VSI) with a common DC bus. The CC- VSI is operated to directly control the AC grid current to be sinusoidal and in phase with the grid voltage without detecting the load currents. The APF consists of a current control loop, which shapes the grid currents to be sinusoidal and a voltage control loop, which regulates the active power balance of the system. The experimental results indicate that the active filter is able to handle predominantly the harmonics, as well as the unbalance and reactive power, so that the grid currents are sinusoidal, in phase with the grid voltages and symmetrical.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2002년도 추계종합학술대회
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• pp.425-429
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• 2002

In this paper, a single-phase inverter using a diode bridge-type resonant circuit to implement ZVT(Zero Voltage Transition) switching is presented. The current control algorithm is analyzed about how to design the circuit with auxiliary switch which can ZVT operation for the main power switch. The simulation and experimental results would be shown to verify the proposed current algorithm, because the main power switch is turn on with ZVT and the hi-directional inverter is operated.