Pekik Argo Dahono

Damping of transient oscillations on the output LC filter of PWM inverters by using a virtual resistor

This paper presents a method to damp transient oscillations on the output LC filter of PWM inverters by using a virtual resistor. A virtual resistor is an additional control algorithm that simulates the roles of a resistor in the output LC filters. Because no real resistor is used, the oscillations can be damped effectively without sacrificing the power efficiency. The implementation of the virtual resistor is determined by how the resistor is connected to the LC filter. Experimental results are included to verify the proposed method.

A control method to damp oscillation in the input LC filter

A control method to damp oscillation in the input LC filter of AC-DC PWM converters is proposed in this paper. The oscillation in the input LC filter of AC-DC PWM converters is damped by using a virtual resistor that can be connected either in series to or parallel with filter inductor or capacitor. Because no real resistor is used, the efficiency of the converters is not sacrificed. The required additional sensor and implementation of the virtual resistor in the control algorithm is strongly influenced by how the virtual resistor is connected to the LC filter. We need an additional current sensor if the virtual resistor is connected in series to the filter inductor or capacitor and an additional voltage sensor if connected in parallel. Simulated and experimental results are included to verify the proposed method.

Analysis and minimization of ripple components of input current and voltage of PWM inverters

Analysis and minimization of the ripple components of the input current and voltage of three-phase voltage-source pulsewidth modulated (PWM) inverters are presented in this paper. The analytical expressions for the rms values of the input current and voltage ripples as a function of the shape of the PWM reference signal are derived. It is found that the reference signal which produces a minimum ripple in the input voltage varies as a function of the load power factor. It is also found that the rms value of the inverter input current ripple does not depend on the shape of the reference signal. In respect of the inverter input current and voltage ripples, the addition of harmonics other than the third into the sinusoidal reference is neither useful nor necessary. Experimental results are included to verify the derived expressions.

An LC filter design method for single-phase PWM inverters

In this paper, an analysis and design method of the output LC filter of single-phase PWM inverters is presented. At first, the analytical expressions for the total harmonics of the inductor current and capacitor voltage of the LC filter are derived. As the unique values of the parameters of the LC filter cannot be specified based on the total harmonic of the capacitor voltage alone an additional criterion based on the minimum reactive power of the LC filter is used to specify these parameters. Experimental results are included to verify the derived expressions.<<ETX>>

A control method for DC-DC converter that has an LCL output filter based on new virtual capacitor and resistor concepts

An LCL output filter is commonly used to minimize the output current ripple of DC-DC converters. A large LCL filter, however, may makes the output current response oscillatory and slow. This paper presents a current control method for DC-DC converter that has an LCL output filter. The proposed control method is based on new virtual capacitor and resistor concepts. Virtual capacitor is used to ensure that the steady-state error of the output current is zero. Virtual resistor is used to damp the oscillations in LCL output filter. Experimental results are included to show the validity of the proposed method.

Output ripple analysis of multiphase DC-DC converters

This paper presents an output ripple analysis of multiphase DC-DC power converters having an output LC filter. Analytical expressions for the output voltage ripple of two- and three-phase DC-DC power converters are derived. Influence of the coupling coefficient of the output filter inductor on the output ripple is investigated. Because the unique parameters of the LC filter cannot be determined solely based on the specified maximum output ripple, an additional criterion based on minimum energy storage is introduced. A comparative evaluation of single-phase, two-phase, and three-phase DC-DC power converters is presented. The validity of the proposed analysis method is verified by experimental results.

A transformer connection for multipulse rectifier applications

In this paper, a polygon-connected transformer for multipulse rectifier applications is proposed. By using the polygon form on the secondary windings, the windings can be designed to have the same voltage and impedance. The proposed transformer connection can also be extended to autotransformer connection if a galvanic isolation is not required. By using the proposed autotransformer, the required kVA rating can be much smaller compared to the rated load.. The design and analysis of the proposed transformer connection are detailed. Several experimental results are included to show the effectiveness of the proposed method.

Output Current-Ripple Analysis of Five-Phase PWM Inverters

An output current ripple analysis of five phase PWM inverters under sinusoidal and nonsinusoidal operations is presented in this paper. A general expression of output current ripple of five-phase PWM inverters under nonsinusoidal operation is first derived. Under sinusoidal operation it is found that the optimum reference signal that results in minimum output current ripple is a sinusoidal reference signal. Under nonsinusoidal operation, however, it is found that fifth harmonic injection can be used to reduce the output current ripple. Moreover, fifth harmonic injection is useful to increase the maximum modulation index of five-phase PWM inverter. Simulation and experimental results are included to show the validity of the derived expressions.

A practical approach to minimize the zero-sequence current harmonics in power distribution systems

In this paper, a simple and practical approach to minimize the zero-sequence current harmonics in three-phase four-wire power distribution systems is proposed. The zero-sequence current harmonics are minimized by using a combination of a very low zero-sequence impedance transformer and a very high zero-sequence impedance transformer. The very low zero-sequence-impedance transformer is shunt connected to the load and the very high zero-sequence impedance transformer is series connected to the source. The series connected transformer will act as a zero-sequence current isolator between the source and load and, therefore, almost all of zero-sequence currents which are generated by the load will flow through the shunt connected transformer. Experimental results are included to verify the proposed approach.

New current controllers for single-phase full-bridge inverters

Two new current controllers for single-phase full-bridge inverters are proposed in this paper. At first, a new hysteresis-type current controller that has a capability to ensure equal switching frequencies among the inverter switching devices is proposed. In this paper, the proposed hysteresis-type current controller is analyzed and compared to the conventional single-band and double-band hysteresis-type current controllers. A new discrete-pulse current controller that has also a capability to ensure equal switching frequencies is then proposed. Different to the hysteresis-type, the discrete-pulse current controller has maximum switching frequency that can be predetermined. Several experimental results are included to show the performance of the proposed current controllers.