A simplified current control method which enables an inverter to generate 20 kinds of space voltage vectors is developed, and a digital signal processing (DSP) based software field oriented induction motor drive system using this method is also presented. In this system, a particular sampling technique is used to shorten the dead time in the current control system. Furthermore, a current prediction technique is adopted to force the dead time to equal zero theoretically. The test results of the laboratory model drive system verify the validity of this simplified current control method. >

A new simplified current control method for field-oriented induction motor drives

The stability of an induction motor driven by pulsewidth modulated current-source inverters (CSI) is considered in the paper. The effects of capacitors connected in parallel with induction motor, to bypass the commutating energy, can not be assessed by conventional analysis methods. To overcome this limitation, a method based on a rigorous state-space analysis is presented and compared with the more usual approximate analysis by means of dominant roots of the system. The results confirm the feasibility of pulsewidth modulated CSIs and show that larger bypass capacitors cause oscillating unstable operations, even with constant V/f control.

Stability of induction motor drive controlled by current-source inverter

A novel suppression scheme for switching known as the limit cycle in a hysteresis current controller is presented. The proposed method is based on the concept of superimposing a common offset signal, which has both proper amplitude and pattern, on three-phase current references, and does not need any additional circuit. It is verified that the switching interference occurs more easily and directly depends on the period of the delay time. Moreover, the switching delay time also significantly influences the effect of limit cycle suppressions. It is seen that with the proposed method the switching interference is greatly suppressed even if the switching delay time exists. Simulations and experiments are performed to verify the effectiveness of the proposed method, and some results are presented. >

A simple limit cycle suppression scheme for hysteresis current controlled PWM VSI with consideration of switching delay time

The waveforms and power factor of an ordinary line-commutated thyristor inverter can be improved by adding one bypass GTO (gate-turn-off) thyristor and a small AC filter unit. Possible transitions between the switching states of the inverter are investigated on the basis of instantaneous voltage and current vectors. The extended freedom from adding the GTO is clearly shown. Restrictions for the pulse width-modulation (PWM) pattern are also shown, and an example pattern is deduced. A criterion for the design of the AC filter parameters is given. The validity of the method is confirmed by simulation and experimental results. >

PWM thyristor inverter with one bypass GTO utilizing line and device commutations

The stability of pulse width modulated current-source rectifier/inverter fed induction motor drives is considered in the paper. Rectifier/inverter operations are considerably complicated because of the high frequency pulse width modulated switching of power devices. To investigate the system stability successfully, an analysis without a complete simulation is performed by introducing synchronously rotating reference frames at the input and output terminals. The linearised equations are easily obtained so the intrinsic open-loop instability and the effects of circuit parameters under closed-loop operation can be made clear by determination of their dominant roots. The relevance of the results is verified by the transient characteristics of the nonlinear model, with and without a PI controller for constant V/f control.

Stability of a PWM current-source rectifier/inverter fed induction motor drive

/pdf/a-novel-current-control-technique-for-voltage-source-4ef0aw6ce4.pdf

Masakatsu Daijou

Papers

A Novel Current Control Technique for Voltage Source Inverter in Field Oriented Control

PWM Method of current Source Inverter for Induction Motor Drive

A PWM control method of current source inverter for induction motor drive