Fuzzy logic based online adaptation of current and speed controllers for improved performance of IPMSM drive

Precise torque and speed control of electric motors is a key issue in industries for variable speed drives (VSD). Over the years the induction motors have been widely utilized in industries for VSD applications. However, induction motor has some significant drawbacks like low efficiency, lagging power factor, asynchronous speed, low torque density etc. Nowadays the interior permanent magnet synchronous motor (IPMSM) is becoming popular for high performance variable speed drive (HPVSD) due to its high torque-current ratio, large power-weight ratio, high efficiency, high power factor, low noise and robustness as compared to conventional induction and other ac motors. Smooth torque response, fast and precise speed response, quick recovery of torque and speed from any disturbance and parameter insensitivity, robustness in variable speed domain and maintenance free operations are the main concerns for HPVSD. This work proposes a closed loop vector control of an IPMSM drive incorporating two separate fuzzy logic controllers (FLCs). Among them one FLC is designed. to minimize the developed torque ripple by varying online the hysteresis band of the PWM current controller. Another Sugeno type FLC is used to tune the gains of a proportional-integral (PI) controller where the PI controller actually serves as the primary speed controller. Thus, the limitations of traditional PI controllers will be avoided and the performance of the drive system can be improved. A flux controller is also incorporated in such a way that both torque and flux of the motor can be controlled while maintaining current and voltage constraints. The flux controller is designed based on maximum-torque- per-ampere (MTPA) operation below the rated speed and flux weakening operation above the rated speed. Thus, the proposed drive extends the operating speed limits for the motor and enables the effective use of the reluctance torque. In order to verify the performance of the proposed IPMSM drive, first a simulation model is developed using Matlab/Simulink. Then the complete IPMSM drive has been implemented in real-time using digital signal processor (DSP) controller board DS1104 for a laboratory 5 HP motor. The effectiveness of the proposed drive is verified both in simulation and experiment at different operating conditions. In this regard, a performance comparison of the proposed FLC based tuned PI and adapted hysteresis controllers based drive with the conventional PI and fixed bandwidth hysteresis controllers based drive is provided. These comparison results demonstrate the better dynamic response in torque and speed for the proposed IPMSM drive over a wide speed range

Design, Analysis, Implementation and Operation of a Brushless Doubly Fed Reluctance Motor Drive

The permanent magnet synchronous motor (PMSM) is a popular choice for variable speed drive (VSD) applications. However, concerns regarding the low availability and price volatility of rare earth permanent magnet materials are encouraging researchers to reduce or even remove the permanent magnets from electrical machines without significantly compromising their performance. The Brushless Doubly Fed Reluctance Machine (BDFRM) can be a promising prospect with its unique advantageous features over other conventional machines. The BDFRM has two stator windings and a reluctance type rotor. It does not consist of brushes, rotor circuits or magnets. This makes the BDFRM an attractive prospect of a controllable, low cost, low maintenance machine which can be even more robust and versatile than the PMSM. If such a machine is commercially realized, it will be highly suitable to operate in locations of limited accessibility or harsh climate. With proper control technique being utilized, it can be an attractive replacement for two important electrical applications: wind power system and electric vehicle. The concept of Brushless Doubly Fed Machine (BDFM) was first introduced more than a century ago. Much of the published literature has analyzed existing designs, rather than focusing on the design process and effective operation of possible commercial machines. This work describes the complete evaluation of a ducted rotor BDFRM design process through time-stepped finite element analysis (FEA), a prototype machine built based on the design, and two-converters based operation of the BDFRM drive in three different operating modes. In this regard, theoretical aspects and control approach are also discussed and explained. Another objective of this work is to investigate the two-converters based frequency sharing operation (Mode-3) of the prototype BDFRM drive. In this case, the total applied frequency is split between the two stator windings with a specific ratio. Thus, the frequency dependent core loss can be reduced. Besides, this approach can provide additional degrees of freedom for control, extend the constant torque region, and increase the machine power density