• Journal of Power Electronics
• /
• v.9 no.5
• /
• pp.718-725
• /
• 2009

To get instantaneous reference data in a single power system with vector space phasors, the instantaneous load current is adopted as a phase and another new signal, which is delayed through filtering by the phase-delay property of a low-pass filter, is used as the secondary phase. Because the two-phases have a different phase, the instantaneous value of the harmonic current can be obtained without a time-delay in calculation. The reference voltage is created by multiplying the coefficient k by the compensation current using the rotating reference frame synchronized with the source-frequency. To verify the validity of the proposed control method, experiments are carried out on a prototype of the single-phase hybrid active power filter system.

• Journal of Electrical Engineering and Technology
• /
• v.8 no.5
• /
• pp.1062-1069
• /
• 2013

This paper proposes a simple current compensation method to improve the control performance of B4 inverters. Four-switch inverters so called B4 inverters employ only four switches. They have a split dc-link and one phase of three-phase motors is connected to the center-tap of split dc-link capacitors in B4 inverters. The voltage ripples in the center tap of the dc-link generate unbalanced three-phase voltages causing current ripples. To solve this problem, this paper presents a simple compensation method that adjusts switching times considering dc-link voltage ripples. The validity of the proposed method is verified by simulations and experiments carried out with a 1 HP induction machine.

• Journal of Institute of Control, Robotics and Systems
• /
• v.9 no.12
• /
• pp.1001-1008
• /
• 2003

A time-delay compensation method for vector control system is proposed that can compensate for voltage and current distortions resulting from a time delay in the overall system due to the low pass filter, hysteresis control inverter, microprocessor program computation time, and so on. The proposed scheme estimates the time delay using the difference between the Q-axis stator current command and the time-delayed actual Q-axis stator current in a synchronous reference frame, then compensates the time delay in the voltage and current using the angular displacement of a DQ transformation. Accordingly, the proposed scheme can accurately compensate for the time delay related to the overall system, thereby significantly improving the performance of the vector control system, as verified by simulation and experiment.

• Proceedings of the KIPE Conference
• /
• 2002.07a
• /
• pp.580-583
• /
• 2002

An improved MPPT converter with current compensation method for small-scaled PV-applications is presented in this paper. The proposed method implements maximum power point tracking (MPPT) by variable reference current which is continuously changed during one sampling period. Therefore, the power transferred to the load is increased above $9\%$ by the proposed MPPT converter with current compensation method. As a result, the utilization efficiency of Photovoltaic (PV)-panel can be increased. In addition, as it doesn't use digital signal processor (DSP), this MPPT method has the merits of both a cost efficiency and a simple control circuit design. Therefore, it is considered that the proposed MPPT method is proper to low power, low cost PV-applications. The concept and control principles of the proposed MPPT method are explained in detail and its validity of the proposed method is verified through several simulated results.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.48 no.6
• /
• pp.330-335
• /
• 1999

This paper proposed the p-q-r coordinate system where the instantaneous active power p, and the two instantaneous reactive powers qq, qr were defined. The three power components are linearly independent, so the compensation for the two instantaneous reactive powers leads to control the two components of the current space vector. With the theory, the neutral current of a three-phase four-wire system can be eliminated by only compensating the instantaneous reactive power using no energy storge element.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.17 no.1
• /
• pp.8-13
• /
• 2012

DSTATCOM is active filter that reduces nonlinear and unbalanced currents. Researches about DSTATCOM are mainly divided two parts, one is the reference value calculation of compensation current depending on the calculation of the load-side average active power and dc-link capacitor average voltage, the other part is actual current control depending on the reference value of compensation current. This paper proposes a calculation of dc-link capacitor average voltage ripple voltage extraction instead of conventional method using LPF. The utility of the proposed algorithm is verified through the theoretical analysis and the experiment under unbalance loads and non-linear load.

• Proceedings of the KIPE Conference
• /
• 2013.07a
• /
• pp.130-131
• /
• 2013

In this paper, it suggests offset compensation method of output current in single phase PV-BES system which is connected with grid. The algorithm applied removes grid's frequency ingredient using a notch filter and it extracts only DC offset current. It can reduce problems as saturation of power transformer cause by DC current when it is indoctrinated to grid.

• Proceedings of the KIEE Conference
• /
• 2005.04a
• /
• pp.149-151
• /
• 2005

This paper deals with the novel control algorithm of single-phase hybrid active power filter for the compensation of harmonic current components in nonlinear R-L load with passive active power filters. To construct two-axes coordinate, an imaginary second phase was made by giving time delay to line current. In this proposed method, the new signal, which was the delayed through the filtering by the phase-delay property of low-pass filter, is used as the secondary phase. Because two phases have different phase, instantaneous calculation of harmonic current is possible. In this paper, a reference voltage is created by multiplying gain of filter by compensation current using the rotating reference frames that synchronizes with source-frequency, not applying to instantaneous reactive power theory which has been used with the existing fixed reference frames. This paper shows the experimental results, which provide a high accuracy and extremely fast response of single-phase hybrid active Bower filter under the operation with the proposed control method.

• Journal of Power Electronics
• /
• v.16 no.1
• /
• pp.1-8
• /
• 2016

Dead time is typically incorporated in voltage source inverter systems to prevent short circuit cases. However, dead time causes an error between the output voltage and reference voltage. Hence, voltage equation-based algorithms, such as motor parameter estimation and back electromotive force (EMF)-based sensorless algorithms, are prone to estimation errors. Several dead-time compensation methods have been developed to reduce output voltage errors. However, voltage errors are still common in zero current crossing areas, and an effect of the error is much worse in a low speed region. Therefore, employing voltage equation-based algorithms in low speed regions is difficult. This study analyzes the conventional dead-time compensation method and output voltage errors in low speed operation areas. A current shaping method that can reduce output voltage errors is also proposed. Experimental results prove that the proposed method reduces voltage errors and improves the accuracy of the parameter estimation method and the performance of the back EMF-based sensorless algorithm.

• Journal of Electrical Engineering and Technology
• /
• v.6 no.5
• /
• pp.647-657
• /
• 2011

The present paper proposes a sliding mode control with fixed switching frequency for three-phase three-leg voltage source inverter based four-wire shunt active power filter. The aim is to improve phase current waveform, neutral current mitigation, and reactive power compensation in electric power distribution system. The performed sliding mode for active filter current control is formulated using elementary differential geometry. The discrete control vector is deduced from the sliding surface accessibility using the Lyapunov stability. The problem of the switching frequency is addressed by considering hysteresis comparators for the switched signals generation. Through this method, a variable hysteresis band has been established as a function of the sliding mode equivalent control and a predefined switching frequency in order to keep this band constant. The proposed control has been verified with computer simulation which showed satisfactory results.