• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.1937-1939
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• 1998

This paper presents a simple switching method to generate a PWM pattern mostly relevant to signle-phase three-level PWM rectifier. The adopted PWM switching pattern is performed in a manner similar to the space vector PWM method, which is popularly used in the three-phase rectifier and inverter. A set of possible voltages has been selected so that an equation with a time integral considered within a sampling period should be satisfied every sampling time. The simulation result shows that the proposed control scheme is good in some performance criteria such as unity power factor, low harmonic distortion of input current, dynamic response and voltage balancing of two series-connected DC capacitors.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.368-370
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• 1995

A new three-level push-pull type quantum series resonant rectifier for the power factor correction is proposed. The proposed single phase rectifier enables a zero-current switching operation of all the power devices allowing the circuit to operate at high switching frequencies and high power levels. With the proposed control technique, an unity power factor and greatly reduced line current harmonics can be obtained.

• Journal of Power Electronics
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• v.16 no.2
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• pp.480-489
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• 2016

A novel hybrid carrier-based pulse width modulation (CBPWM) scheme that combines unipolar and dipolar modulations is proposed for single-phase three-level rectifiers, which are widely applied in railway traction drive systems. The proposed CBPWM method can satisfy the volt-second balancing principle in the complete modulation index region through overmodulation compensation. The modulation scheme features two modulation modes: unipolar and dipolar. The operation range limits of these modulation modes can be modified by changing the separation coefficient. In comparison with the traditional unipolar CBPWM, the proposed hybrid CBPWM scheme can provide advantageous features, such as lower high-order harmonic distortion of the line current and better utilization of switching frequency. The separation coefficient value is optimized to achieve the maximum utilization of these advantages. The experimental results verify the feasibility and effectiveness of the proposed hybrid CBPWM scheme.

• Journal of the Korean Society for Railway
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• v.19 no.5
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• pp.617-628
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• 2016

This paper proposes the structure of a smart transformer to improve the performance of the 60Hz main power transformer for rolling stock. The proposed smart transformer is a kind of solid state transformer that consists of semiconductor switching devices and high frequency transformers. This smart transformer would have smaller size than the conventional 60Hz main transformer for rolling stock, making it possible to operate AC electrified track efficiently by power factor control. The proposed structure employs a cascade H-Bridge converter to interface with the high voltage AC single phase grid as the rectifier part. Each H-Bridge converter in the rectifier part is connected by a Dual-Active-Bridge (DAB) converter to generate an isolated low voltage DC output source of the system. Because the AC voltage in the train system is a kind of medium voltage, the number of the modules would be several tens. To control the entire smart transformer, the inner DC voltage of the modules, the AC input current, and the output DC voltage must be controlled instantaneously. In this paper, a control algorithm to operate the proposed structure is suggested and confirmed through computer simulation.