Hidehiko Sugimoto

A new scheme for maximum photovoltaic power tracking control

It is shown that the derivative (dp/sub s//de/sub s/) of output power (p/sub s/) with respect to output voltage (e/sub s/) of a photovoltaic array is equal to zero at the maximum power point. This kind of relationship is independent of insolation and temperature. This property may be utilized to perform maximum power tracking control, that is, at all insolation and temperature levels, the maximum power point can be obtained by regulating dp/sub s//de/sub s/ toward zero. Based on this concept, a new scheme of maximum power tracking control is proposed and applied to a utility-interactive photovoltaic power conditioning system, where the boost chopper is responsible for maximum power tracking control and the inverter responsible for unity power factor control and constant DC input voltage control. The related design method is described. The usefulness and validity of the proposed method are verified by simulation. Compared to conventional methods, this method show a considerably high tracking performance.

A Speed Sensorless Induction Motor Control Method using Adaptive Flux Observer Improving Stability Around Zero Frequency

Authors have proposed the speed sensorless vector control method that can stabilize the speed estimator in regeneration region as well as in powering operation. However, actual experimental results showed there were problems when it is driven at unloaded or around zero frequency with heavy load. In this paper observer gains are reviewed and modified with considering the phase condition which they must satisfy. Finally, the proposed observer gain scheduling method is confirmed its effectiveness and performance with experiments.

A proposition of design method for modified repetitive control system with corrected dead time using sensitivity function shaping and its application to motor control system

Here, a new design method applicable both for the conventional modified repetitive motor control systems and the authors proposed modified repetitive control system with corrected dead time was proposed. This newly proposed design method is based on the calculation of its sensitivity function and design of the system so as to minimize its sensitivity function. In addition, investigation was finally carried out to prove that designing a modified repetitive control system with corrected dead time according to this newly proposed method provides for great improvement in its control performance. The overall results of the investigations thus conducted by the authors revealed that a modified repetitive control system with corrected dead time, if so designed using the newly proposed method as to minimize its sensitivity function, can achieve further improvement in its control performance.

Suppressive control of the resonance current between PV system and the power system

This paper proposes a new current control method that can keep high power factor and can suppress resonance current between photovoltaic power generation systems and the system that is generated when the system voltage changes suddenly. Resonance current suppression has been realized with state feedback control and with a prepositive compensator which frees the pole assignment. The ability of the original repetitive control is drawn by correcting the dead time, in the modified repetitive control.