Takao Kawabata

Dead beat control of three phase PWM inverter

This paper proposes new method of high performance current and/or voltage control of three phase PWM inverter, especially suitable for high speed switching devices such as Transistor and BIMOS. As the controller for calculation of the dead beat algorism, a high speed digital controller, such as the digital signal processor is assumed. Following new methods are successfully adopted and combined to realize high quality. (1) Three phase inverter current and voltage are transformed to synchronizing d-q-0 frame, and discretized equations of current and voltage are derived, which clearly reveal coupling of voltage and current of inverter on d-q frame. (2) Using above discretized equation of main circuit, algorism of Dead Beat control with compensation for decoupling is developed. (3) New method for compensation of computing time delay and full utilization of sampling interval for inverter output pulse width is developed, which utilizes 2nd order load current prediction and discretization with twice time of sampling period. (4) Double Dead Beat control system is developed for sinusoidal output voltage inverter, which has high speed current minor loop to constrain inverter current within safety limit. Validity of these techniques has been confirmed by simulation using a hybrid computer.

Parallel processing inverter system

A novel method of instantaneous voltage and power balance control of a parallel processing inverter system is proposed. It consists of a high-speed switching PWM (pulsewidth modulated) inverter with an instantaneous current minor loop controller, a voltage major loop controller, and a power balance controller. This system realizes the following functions with only one inverter: constant AC output voltage control with reactive power control, active filtering to absorb load current harmonics, DC voltage and current control as AC-to-DC converter, and uninterruptible power supply (UPS) for stand-alone operation. This system covers a wide application range, including UPS systems, new energy systems, and active filters with voltage control functions. >

Digital control of three-phase PWM inverter with LC filter

A digital control algorithm for the three-phase sinusoidal voltage inverter with an output LC filter has been developed. To take the transient of the LC filter during the discretization time into consideration, a fourth-order matrix state equation of the current and the voltage on the d-q frame is discretized. Precise discrete equations for the inverter are introduced. Using these equations, a deadbeat controller consisting of a d-g current minor loop and a d-q voltage major loop, with precise decoupling of the d-q components, was developed. The voltage major loop controller assures the sinusoidal output voltage and stabilizes the system. A deadbeat controller is used because both the current minor loop and the voltage major loop can used one sampling response. The validity of these techniques is confirmed by simulation studies. This method is expected to be useful for direct digital control of large-capacity sinusoidal voltage inverters using low-switching-frequency devices. >

Digital control of three phase PWM inverter with L-C filter

An algorithm for digital control of a three-phase sinusoidal voltage inverter having an output L-C filter has been developed. The transient of the L-C filter during the discretization time has been taken into account by discretizing the fourth-order matrix state equation of the current and the voltage of the d-q frame and precise discrete equations of the inverter have been introduced. Using these equations, a deadbeat controller consisting of a d-q current minor loop and a d-q voltage major loop, with precise decoupling of the d-q components, has been developed.<<ETX>>