• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.3
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• pp.365-373
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• 2015

The performance of 4-switch 3-phase inverter(FSTPI) is mainly affected by the unbalanced voltages between two capacitors which replace two switches of conventional 6-switch 3-phase inverter(SSTPI). This paper proposes a DC offset current injection method to compensate the capacitor voltage unbalance for FSTPI. A simplified SVPWM method which can be applied to FSTPI is also proposed. The validity of the proposed methods is verified by computer simulation.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.3
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• pp.283-292
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• 2016

The performance of 4-switch 3-phase inverter(: FSTPI) which replace two switches of 6-switch 3-phase inverter(: SSTPI) is mainly affected by the compensator unbalanced voltages and output voltage control method. This paper proposes a DC offset current injection method to compensate the capacitor unbalanced voltages for FSTPI. A simplified SVPWM method which can be applied to FSTPI is also proposed. The validity of the proposed methods is verified by simulation and experiment using SPMSM.

• Journal of Power Electronics
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• v.14 no.2
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• pp.383-391
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• 2014

For the digital control of systems such as grid-connected inverters, measuring inverter output currents accurately is essential. However, current measurement offsets are inevitably generated by current measurement paths and cause DC current components in real inverter output currents. Real inverter output currents with DC components cause the DC-link capacitor voltage to oscillate at the frequency of a utility voltage. For these reasons, current measurement offsets deteriorate the overall system performance. A compensation strategy to eliminate the effect of current measurement offsets in grid-connected inverters is proposed in this study. The validity of the proposed compensation strategy is verified through simulations and experiments. Results show that the proposed compensation strategy improves the performance of grid-connected inverters.

• Journal of Power Electronics
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• v.15 no.6
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• pp.1567-1576
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• 2015

Offline inductance identification of a permanent magnet synchronous motor (PMSM) is essential for the design of the closed-loop controller and position observer in sensorless vector controlled drives. On the base of the offline inductance identification method combining direct current (DC) offset and high frequency (HF) voltage injection which is fulfilled at standstill, this paper investigates the inverter nonlinearity effects on the inductance identification while considering harmonics in the induced HF current. The negative effects on d-q axis inductance identifications using HF signal injection are analyzed after self-learning of the inverter nonlinearity characteristics. Then, both the voltage error and the harmonic current can be described. In addition, different cases of voltage error distribution with different injection conditions are classified. The effects of inverter nonlinearities on the offline inductance identification using HF injection are validated on a 2.2 kW interior PMSM drive.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.4
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• pp.369-372
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• 2017

This paper presents a control scheme for three-level NPC inverters using small DC-link capacitors. To reduce the inverter system volume, the film capacitor with small capacitance is a promising candidate for the DC-link. When small capacitors are applied in a three level inverter, however, the AC ripple component increases in the DC-link NPV (neutral point voltage). In addition, the three-phase input grid currents are distorted when the DC-link capacitors are fed by diode rectifier. In this paper, the additional circuit is applied to compensate for small capacitor systems defect, and the offset voltage injection method is presented for the stabilization in NPV. These two proposed processes evidently ensure the quality improvement of the input grid currents and output load currents. The feasibility of the proposed method is verified by experimental results.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.1
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• pp.80-83
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• 2022

This paper proposes an initial rotor polarity detection algorithm of a single-phase permanent magnet synchronous motor (SP-PMSM) related to stable open-loop starting for sensorless operation. Generally, the SP-PMSM needs an asymmetric air-gap structure to can avoid the initial starting failure at zero torque point. Therefore, the rotor polarity information can be obtained by using the DC offset current direction of a stator current through a high frequency voltage injection into an SP-PMSM with an asymmetric air gap. In this paper, the proposed rotor initial polarity detection algorithm is verified through several experimental results.