Sensorless and efficiency optimized induction machine control with associated converter PWM modulation schemes

The PWM modulation techniques for the three-phase voltage source inverter are extended to the multi-phase systems in the examples of five and six phases. The generalized transformation is used to synthesize the reference voltages, which could have more components than the fundamental component. The zero sequence voltage expressions are calculated and generalized by choosing the appropriate active and null states. The switching signals are generated using carrier-based PWM, which is easy to implement compared with the space vector approach and can be used for any multi-phase system.; The induction machine model, reference frame transformation and determination of the machine parameters are presented and used for the rotor flux oriented control of the induction machine. The design of the cascaded speed control scheme is illustrated and the implementation procedures are presented in detail, which are useful for the design and implementation of any other control system. The proposed scheme has been verified through computer simulations and experiments.; The natural variables of the machine are defined independent of any reference frame and used to formulate the speed control for the induction machine. The efficiency of the induction machine is improved through the minimum electrical loss strategy formulated using the same variables. The optimum rotor flux is obtained from the strategy and is used as the reference flux in the speed control. The rotor speed estimation using both rotor voltage equations is proposed and computer simulation results show much better estimation result. Experiments are conducted to verify the proposed formulation and the sensorless speed control method.; The closed-loop rotor speed estimation using the full-order flux observer is designed for the speed control. Inclusion of the reactive power in the error function for the speed estimation improves the performance in the low speed range. The observer gains are determined using the 4th order Butterworth polynomial and the control parameters for the speed estimation are selected using the D-decomposition method to ensure the system stability. Simulation results show that the same set of parameters can be chosen from the proposed method to make the system stable under both motoring and regenerating modes.; The open-loop voltage generation in the over-modulation region using carrier-based PWM and space vector PWM is presented. A new over-modulation scheme is proposed using the concept of space vector, which has a higher voltage gain compared with the traditional scaling method. The application for the current regulation is generalized for both modulation methods and the harmonic current is eliminated from the feedback current in order to use the linear controller structure. Both PWM methods are implemented for the current regulation of the R-L load and the induction machine with a converter operating in the over-modulation region.