No abstract

We propose a simple dc voltage sensorless single phase PFC converter by detecting an ac line voltage waveform. Both dc voltage and ac current sensors used in the conventional PFC converter are not required to construct the control system. The conventional converter circuit with a boost chopper circuit in the dc side from a rectifier circuit is used as the main PFC converter circuit. In the control system, the circuit parameters such as a series inductance and equivalent load resistance value are used to generate the sinusoidal current waveform. The dc voltage is directly controlled by the command input signal (= ) for the boost chopper circuit. The dc voltage regulation is small because of the feed forward control for the ac line voltage and no dependence of the circuit parameters. The sinusoidal current waveform in phase with the ac line voltage can be obtained. The feasibility of the proposed control system is verified by some simulation and experimental results.Index Terms-ac line voltage, dc voltage regulation, PFC converter.

A new PWM method for Neutral-Point-Clamped (NPC) inverters is introduced. The method is based on closedloop control of the line-to-line voltage vectors. It uses independent hysteresis comparator controllers to regulate the direct and quadrature axis components of the three phase output voltages. The controllers select the appropriate output voltagevector through an EPROM table. The closed-loop control allows a high performance over the whole range of operation, even when low speed devices such as the GTO are used. A neutral-point potential control is described, which is capable of stabilizing the variations within k e d limits during steady and transient states. The principle of the method is discussed and the vector selection technique is presented. The effectiveness in the output-voltagewaveform generation and the balance of the DC-link capacitor voltages are verified by simulation and experiment.

SummaryVarious PWM techniques for three-phase power converters, such as the AC to DC converter and the DC to AC inverter, have been proposed and increasingly used with the development of the switching power devices. These are discussed separately for the types of the voltage source and the current source. This paper proposes a new PWM technique for the three-phase inverter/converter applicable to the above both types. The output characteristics of the new PWM technique are excellent in thee low-order harmonic elimination and the output gain to the DC power source. In this paper, the method to obtain the switching timing, the switching pulse pattern for the each power source, the frequency spectrum and the characteristics for the PWM output waveform are described. And they are verified by the experimental results for the voltage source inverter and the current source AC to DC converter.

No abstract