• Journal of Power Electronics
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• v.17 no.2
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• pp.464-475
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• 2017

This study examines a P+multi resonant-based voltage control for voltage harmonics compensation under the islanded mode of a microgrid. In islanded mode, the inverter is defined as a voltage source to supply the full local load demand without the connection to the grid. On the other hand, the output voltage waveform is distorted by the negative and zero sequence components and current harmonics due to the unbalanced and nonlinear loads. In this paper, the P+multi resonant controller is used to compensate for the voltage harmonics. The gain tuning method is assessed by the tendency analysis of the controller as the variation of gain. In addition, this study analyzes the slight voltage magnitude drop due to the practical form of the P+multi resonant and proposes a counter method to solve this problem by adding the PI-based voltage restoration method. The proposed P+multi resonant controller to compensate for the voltage harmonics is verified through the PSIM simulation and experimental results.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.537-538
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• 2008

A step-down DC-DC converter with On-chip Compensation for battery-operated portable electronic devices which are designed in 0.18um CMOS standard process. In an effort to improve low load efficiency, this paper proposes the PFM (Pulse Frequency modulation) voltage mode 1MHz switching frequency step-down DC-DC converter with on-chip compensation. Capacitor multiplier method can minimize error amplifier compensation block size by 20%. It allows the compensation block of DC-DC converter be easily integrated on a chip and occupy less layout area. But capacitor multiplier operation reduces DC-DC converter efficiency. As a result, this converter shows maximum efficiency over 87% for the output voltage of 1.8V (input voltage : 3.3V), maximum load current 500mA, and 0.14% output ripple voltage. The total core chip area is $mm^2$.

• Journal of Power Electronics
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• v.17 no.1
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• pp.294-304
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• 2017

This paper proposes a point of common coupling (PCC) voltage compensation method for islanding microgrids using an improved power sharing control scheme among distributed generators (DGs) without communication. The PCC voltage compensation algorithm is implemented in the droop control scheme to reduce the PCC voltage deviation produced by the droop controller itself and the voltage drop on the line impedance. The control scheme of each individual DG unit is designed to use only locally measured feedback variables and an obtained line impedance to calculate the PCC voltage. Therefore, traditional voltage measurement devices installed at the PCC as well as communication between the PCC and the DGs are not required. The proposed control scheme can maintain the PCC voltage amplitude within an allowed range even to some extent assuming inaccurate line impedance parameters. In addition, it can achieve proper power sharing in islanding microgrids. Experimental results obtained under accurate and inaccurate line impedances are presented to show the performance of the proposed control scheme in islanding microgrids.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.3
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• pp.211-218
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• 2000

The performance and dynamic characteristics of three-phase active power filter with PCC voltage compensation is presented and analyzed in this paper. The characteristics of parallel active filter are discussed when they are applied to nonlinear loads with current source and voltage source type, the characteristics of voltage compensator and comparison of two functions are discussed. The proposed scheme in this paper employs a PWM voltage-source inverter and has two operation modes. First, it operates as a conventional active filter with reactive power compensation while PCC voltage is in a certain range. Second, is operates as a voltage compensator while PCC voltage is out of range. Finally, the validity of this scheme is investigated through analysis of simulation and experimental results for a prototype active power filter system rated at 10KVA.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.1
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• pp.46-52
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• 2021

This study proposes a feedforward compensation control method to reduce 120 Hz output voltage ripple in a single-phase AC/DC rectifier system composed of PFC and LLC resonant converters. The proposed method compensates for the voltage ripple of the DC-link by using the AC input and DC output power difference, and then reduces the final output voltage ripple component of 120 Hz through feedforward compensation based on the linearized frequency gain curve of the LLC resonant converter. Through simulation and experimental results, the validity of the ripple reduction performance was verified by comparing the conventional PI controller and the proposed feedforward compensation method.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.876-881
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• 1998

The compensation strategy of shunt active power filters is one of the most important link that determine its compensation characteristics. In this paper, a new interpretation of the instantaneous reactive power theory in three-phase circuits was proposed. A compensation strategy (ip, iq mode) was introduced on the basis of the new interpretation. This compensation strategy was compared with other two compensation strategies(P, q mode and UPF mode). When source voltage is distorted, a sinusoidal, the three compensation strategies are equivalent to each other. When source voltage is distorted, a sinusoidal source current may result only by using ip, iq mode. This is the advantage of ip, iq mode. The result is verified by simulation.

• Journal of Power Electronics
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• v.15 no.3
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• pp.763-774
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• 2015

This study investigates the inherent influence of a DC-link voltage controller on both DC-link voltage control and the compensation performance of a three-phase, four-wire shunt active power filter (APF). A nonlinear variable-parameter DC-link voltage controller is proposed to satisfy both the dynamic characteristic of DC-link voltage control and steady-state compensation performance. Unlike in the conventional fixed-parameter controller, the parameters in the proposed controller vary according to the difference between the actual and the reference DC-link voltages. The design procedures for the nonlinear voltage controller with variable parameters are determined and analyzed so that the proposed voltage controller can be designed accordingly. Representative simulation and experimental results for the three-phase, four-wire, center-spilt shunt APF verify the analysis findings, as well as the feasibility and effectiveness of the proposed DC-link voltage controller.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.586-590
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• 2001

In this paper, a novel control scheme compensating source voltage unbalance and harmonic currents for hybrid active power filters is proposed, where no low/high-pass filters are used in compensation voltage composition. The phase angle and compensation voltages for source harmonic current and unbalanced voltage components are derived from the positive sequence component of the unbalanced voltage set, which is simply obtained by using digital all-pass filters. Since a balanced set of the source voltage obtained by scaling the positive sequence components is used as reference values for source current and load voltage, it is possible to eliminate the necessity of low/high-pass filters in the reference generation. Therefore the control algorithm is much simpler and gives more stable performance than the conventional method. In addition, the source harmonic current is eliminated by compensating for the harmonic voltage of the load side added to feedback control of the fundamental component.

• 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.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.6
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• pp.544-551
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• 2000

In this paper, 3-phase hybrid series active power filter for compensate current harmonics, voltage drop and unbalanced voltage in the network presented. The proposed system is implemented with a space vector modulation voltage source inverter and a high pass filter connected in parallel to the power system. Here the load is six-pulses thyristor rectifier. The phase angle detected in order to generation reference voltage at load terminal is synchronized with the positive sequence component of the unbalanced source by using symmetrical component transformation. The proposed system has an function harmonic isolation between source and load, voltage regulation, and unbalance compensation. Therefore, what the power system is improved quality, the source current is maintained as a nearly sinusoidal waveform and the load voltage is regulated with a rated voltage regardless of the source variation condition. To verify the validity of the proposed compensating system, the computer simulation and experiment are carried out.