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Mitesh B. Astik, Praghnesh Bhatt and Bhavesh R. Bhalja

Abstract

The observer design for estimation of back EMF to control the Brushless DC (BLDC) motor is proposed in this paper. Rotor position of the BLDC motor is estimated using the sequence of estimated back EMF. During speed reversal of motor, the actual and estimated values of speed fail to track the reference speed and if corrective action is not taken by the observer, the motor goes into the unstable region. To overcome this problem, the speed estimation algorithm is proposed for BLDC motor control during its speed reversal operation. Infinite Impulse Response (IIR) Butterworth first order low-pass filters are used in the observer for smoothing the estimated back EMFs of the BLDC motor. A new controller scheme based on Modified Hybrid Fuzzy PI (MHFPI) controller is proposed to control the speed of the BLDC motor. The effectiveness of the proposed method has been validated through simulations for different disturbances such as step changes in the reference speed and load torque of the motor and results are compared with the existing methods.

Open access

Mitesh B. Astik, Praghnesh Bhatt and Bhavesh R. Bhalja

Abstract

A sensorless control scheme based on an unknown input observer is presented in this paper in which back EMF of the Brushless DC Motor (BLDC) is continuously estimated from available line voltages and currents. During negative rotation of motor, actual and estimated speed fail to track the reference speed and if the corrective action is not taken by the observer, the motor goes into saturation. To overcome this problem, the speed estimation algorithm has been implemented in this paper to control the dynamic behavior of the motor during negative rotation. The Ackermans method was used to calculate the gains of an unknown input observer which is based on the appropriate choice of the eigenvalues in advance. The criteria to choose eigenvalue is to obtain a balance between faster convergence rate and the least noise level. Simulations have been carried out for different disturbances such as step changes in motor reference speed and load torque. The comparative simulation results clearly depict that the disturbance effects in actual and estimated responses minimizes as observer gain setting increases.

Open access

Ujjaval J. Patel, Nilesh G. Chothani and Praghnesh J. Bhatt

Abstract

Impedance reach of numerical distance relay is severely affected by Fault Resistance (RF), Fault Inception Angle (FIA), Fault Type (FT), Fault Location (FL), Power Flow Angle (PFA) and series compensation in transmission line. This paper presents a novel standalone adaptive distance protection algorithm for detection, classification and location of fault in presence of variable fault resistance. It is based on adaptive slope tracking method to detect and classify the fault in combination with modified Fourier filter algorithm for locating the fault. To realize the effectiveness of the proposed technique, simulations are performed in PSCAD using multiple run facility & validation is carried out in MATLAB® considering wide variation in power system disturbances. Due to adaptive setting of quadrilateral characteristics in accordance with variation in fault impedance, the proposed technique is 100 % accurate for detection & classification of faults with error in fault location estimation to be within 1 %. Moreover, the proposed technique provides significant improvement in response time and estimation of fault location as compared to existing distance relaying algorithms, which are the key attributes of multi-functional numerical relay