K. R. Rajagopal

PM Synchronous Motor Speed Control Using Hybrid Fuzzy-PI With Novel Switching Functions

Vector control is one of the standard techniques used for the control of a permanent magnet synchronous motor (PMSM). The outer speed loop in vector controlled PMSM drive greatly affects the drive performance. In order to combine the advantages of proportional plus integral (PI) and fuzzy controllers, hybrid fuzzy-PI controllers are used in which the output can either be the outputs of the two, i.e. the PI or fuzzy units being switched as per the predetermined speed errors or be a combination of the two outputs with separate weights assigned to them with online calculations for the weights from the speed errors. The former method based on switching often causes chattering effects, and later method demands larger execution time because of inclusion of separate switching algorithms. This paper reports the vector control of PMSM with hybrid fuzzy-PI speed controller with switching functions calculated based on the weights for both the controller outputs using the output of (a) only the fuzzy controller, (b) only the PI controller and (c) a combination of the outputs of both the controllers. These switching functions are very simple and effective and do not demand any extra computations to arrive at the hybrid fuzzy-PI controller outputs. These control algorithms have been simulated and also implemented on hardware with TMS320F2812 digital signal processor, and it is observed that the performance of the vector controlled PMSM drive with these hybrid fuzzy-PI speed controllers in terms of the response and torque ripples is very promising.

A Novel Air-Gap Profile of Single-Phase Permanent-Magnet Brushless DC Motor for Starting Torque Improvement and Cogging Torque Reduction

We propose a new air-gap profile for single-phase permanent-magnet brushless dc (SP PM BLDC) motor to improve starting torque and to reduce cogging torque. We calculate starting torque and cogging torque using finite-element (FE) analysis. We perform a parametric analysis to study the effect of variation of proposed profile dimensions on cogging torque and starting torque. More than 70% improvement in starting torque and considerable reduction in magnitude of cogging torque is achieved compared to existing tapered air-gap profiles.

Nonlinear Dynamic Modeling of a Single-Phase Permanent-Magnet Brushless DC Motor Using 2-D Static Finite-Element Results

A nonlinear dynamic model is proposed for a single-phase permanent-magnet brushless DC (SP PM BLDC) motor to reduce simulation time compared to transient finite-element model and finite-element co-simulation model. The model uses a lookup table of EMF constant and cogging torque obtained from two-dimensional static finite-element analyses. A machine model based on a lookup table is coupled to an inverter model and a load model to form a complete motor model. Nonlinear effects such as cogging torque, magnetic saturation, armature reaction, and switching transients are considered in the model. The simulated results are validated experimentally with a prototype SP PM BLDC external rotor ceiling fan motor.

Permanent Magnet Synchronous Motor Drive Using Hybrid PI Speed Controller With Inherent and Noninherent Switching Functions

The performance of the fuzzy logic controller (FLC) is better under transient conditions, while that of the proportional plus integral (PI) controller is superior near the steady-state condition. The combined advantages of these two controllers can be obtained with hybrid fuzzy-PI speed controller. The computations involved with the FLC are much higher as compared to that of the PI controller. Generally, the FLC output is near the maximum permissible value at the beginning of a transient condition but reducing with the reduction in the speed error. In this paper, instead of the FLC, a fuzzy equivalent proportional (FEP) controller is used along with the PI controller to make it a hybrid PI (HPI) controller which eventually is much faster and less computation intensive. The performance of the vector-controlled permanent magnet synchronous motor drive with this HPI controller is obtained with six switching functions, namely: 1) saturation; 2) hyperbolic tangent; 3) polynomial S function; 4) output of FEP controller only; 5) output of PI controller only; and 6) combination of the outputs of both the PI and FEP controllers. From the results, it is observed that the polynomial S switching function based HPI controller is better in general for most of the performances.

Development of external rotor single-phase PM BLDC motor based drive for ceiling fan

Permanent magnet brushless dc (PM BLDC) motors offer various advantages such as high efficiency, compactness and easy controllability which are absolutely beneficial in domestic appliances. Ceiling fans, in general, are driven by single-phase induction motors with an overall system efficiency of about 30%. This paper presents the design, analysis, and development of a 170 V, 20 W, 360 rpm, single-phase PM BLDC motor meant for use in ceiling fan, which becomes a cost effective high efficiency solution for this high volume domestic appliance. The developed motor, on testing gave an efficiency of about 50% when fitted to a ceiling fan delivering the same air delivery.

Modeling and analysis of hybrid energy storage systems used in Electric vehicles

This paper deals with the design and modelling aspects of hybrid energy storage system (HESS) used in Electric vehicles. Modelling of HESS includes modelling of battery, Ultra-capacitor and the vehicle load modelling for Light electric vehicle used in the work. A detailed analysis for vehicle load is carried out to find out capacity of motor, battery and ultra-capacitor in both acceleration and in regenerative braking. This paper also discusses different types of converters used in HESS for electric vehicle application along with its suitability to the light electric vehicles. The HESS in this work uses a bidirectional dc/dc converter along with battery and ultra-capacitor. A simple power sharing algorithm based on heuristic approach is presented to ensure the different modes of operation of electric vehicles. From the performance analysis at different speeds and at different gradients it is concluded that HESS reduces the size of the battery, weight of the system. Due to this the range of the vehicle can be improved in a single charge.

Compact regenerative braking scheme for a PM BLDC motor driven electric two-wheeler

Regenerative method of braking of an electric vehicle (EV) helps in efficient utilization of the battery power to increase the range of the vehicle. Methods described in literature for the regeneration use complex control algorithms to deal with the energy flow during the transition from the motoring mode to the regenerative braking mode of PM BLDC motor driven EV. In this paper, a simple method to control the power flow from the motor to the battery by changing the switching sequence given to the inverter used in the PM BLDC motor drive is presented. The newly presented method gives lower braking time and higher regeneration, and also does not necessitate any additional converters or ultra-capacitors.

PM synchronous motor drive with wavelet controller and fractional order integrator

Permanent magnet synchronous motor (PMSM) is widely used in low and medium power applications with vector control being a standard control technique. The speed controller is essential for obtaining the required drive performance. Proportional plus integral (PI) controllers were traditionally being employed as speed controllers. The performance degradation in the PI controller due to the fixed controller gains is a concern. This paper investigates the application of wavelet multi-resolution (MRW) speed controller for vector control of the PMSM. The MRW controller process the error input with the gains depending on the level of decomposition employed. In order to limit the number of gains, this paper analyzes MRW controller with a single gain constant. A separate fractional order integrator unit which enhances the controller performance with additional flexibility of tuning and also offers better steady state performance of the motor is introduced. The results show improved performance in terms of speed and current responses and also the ease of tuning.

Computer aided design of a compact doubly-fed induction generator for small wind power application

The doubly-fed induction generator (DFIG) has advantages in wind energy applications while considering for the economy, quality, and the controllability of the system at various speeds. So as to take advantage of these factors in an effective manner, the DFIG has to be designed with all the degrees of freedom available for the optimum design of the machine. This includes, stator to rotor turns ratio, integral and fractional slot winding and winding layers, apart from the conventional design variables such as magnetic loading, electric loading, stack length to bore diameter ratio, stator current density, rotor current density, stator slot opening to stator slot pitch ratio and rotor slot opening to rotor slot pitch ratio. This paper brings out a computer aided design approach for the design of an efficient and compact DFIG meant for small wind power generation to the tune of 2 kW. Comparison with the conventionally designed DFIG of the same rating reveals that the newly designed DFIG is better in term of lower volume and better efficiency. The new design logic has resulted in reduction in the active volume of the machine, lower airgap harmonics and higher variable speed efficiency.

A low cost position sensorless brushless DC motor drive

A low cost position sensorless brushless DC motor drive is presented in this paper. The motor starts with simple align and go methodology, to a speed where a traditional sensorless algorithm based on winding back EMF, detects accurate commutation instants and then filtered line to line back EMF crossings are utilized to find the rotor position. The speed and current are controlled with variable structure sliding mode control. The drive uses a low cost microcontroller and only one current sensor, which makes it a cost effective drive. The performance of the presented drive is proved by simulation and experimentally on low cost high performance DSP microcontroller. The presented control drive is useful for developing low cost commercial and domestic applications.