P. Linga Reddy

Hybrid random PWM algorithm for direct torque controlled induction motor drive for reduced harmonic distortion

The basic direct torque control has more torque, flux and current ripples in steady state, which results in acoustical noise and increased harmonic distortion. The standard space vector pulse width modulation (SVPWM) algorithm distributes the zero state time equally between the two possible zero voltage vectors. To reduce the complexity involved in the conventional space vector approach, the proposed pulse width modulation (PWM) algorithm uses instantaneous sampled reference phase voltages to calculate the actual switching times of the devices. The proposed PWM algorithm modifies the time duration of application of vector V0 (000) by using a factor µ by which various switching sequences can be derived. By comparing the instantaneous ripple values in each sampling time interval, the suitable sequence is selected resulting in minimum current ripple. Thus, the proposed algorithm gives reduced harmonic distortion when compared with the SVPWM algorithm. As the zero state time is varied randomly according to the operating sequence, randomization effect will occur, which results in reduced dominating harmonics and hence reduced acoustical noise. The simulation results validate the proposed algorithm.

An active dynamic LVRT solution for balanced and unbalanced grid faults in a power system by using “Sen” Transformer

In the recent trends the electrical grid is being interconnected with various types of non-conventional energy sources like solar, wind, etc. Some of the sources like wind turbine generators are vulnerable to grid side voltage sags and short circuits. This paper provides the new LVRT (Low Voltage Ride Through) solution for balanced and unbalanced grid faults in an electrical power system network. Till now “Sen” Transformer was used as a power flow controller. In this paper the Sen Transformer is used as a series voltage compensator under fault condition. The simulated model of the “Sen” Transformer during the balanced and unbalanced grid faults for maintaining the voltage stability of the system is presented so that the sensitive load will stay connected to the grid and the grid will not lose its synchronism during the fault and normal operation can be continued after the fault .The proposed solution is proven to be reliable and cost-effective when compared with the emerging technology of dynamic voltage restorer (DVR).

Robustness Study of Fractional Order PID Controller Optimized by Particle Swarm Optimization in AVR System

Received Mar 26, 2016 Revised Jul 14, 2016 Accepted Jul 30, 2016 In this paper a novel design method for determining fractional order PID (PID) controller parameters of an AVR system using particle swarm optimization algorithm is presented. This paper presents how to employ the particle swarm optimization to seek efficiently the optimal parameters of PID controller. The robustness study is made for this controller against parameter variation of AVR system. This work has been simulated in MATLAB environment with FOMCON (Fractional Order Modeling and Control) tool box.The proposed PSOPID controller has superior performance and robust compared to GA tuned PID controller. The results are also compared with PSO tuned PID controller. Keyword: