予見サーボ系を用いたPWMインバータパルスパターンの設計

抄録

Systematical design method of pulse patterns of single phase PWM (Pulse Width Modulated) inverter is proposed in this paper on the basis of system control theory such as optimal preview servosystem, adaptive control system etc. Merits of the design by means of system control theory are as follows:
(1) Pulse patterns are designed with consideration on the load conditions and then, optimal pulse patterns are designed for the whole system.
(2) PWM inverter with low sensitivity for the system variations such as variations of the source voltage and load changes etc. is theoretically designed by means of the robust control theory.
(3) Output feedback control or partial state feedback control or observer application is effective when measurements of variables such as currents and/or voltages are difficult.
The first step of the procedure is the derivation of the state equations of the whole system with inverter circuit and the load. In the state equation, pulse width during one sampling period is taken to be control input variable of the state equations. In this paper, state equations for a full-bridge type inverter and a half-bridge type inverter are drived. Any control system design method can apply to the obtained state equations. Preview servo system is applied when the future desired signals are known in advance, which is possible in the case of application to UPS (Uninterruptible Power System). In this case, almost perfect generation of the desired sinusoidal voltage output is obtained by obtained PWM pulse patterns. Adaptive control system is effective for system changes or load changes.