Agileswari K. Ramasamy

Dynamic Voltage Restorer For Voltage Sag Compensation

The Dynamic Voltage Restorer (DVR) is a power electronic device that is used to inject 3-phase voltage in series and in synchronism with the distribution feeder voltages in order to compensate for voltage sag. In this paper the operation of a DVR is presented. The power circuit of a DVR together with the control techniques used for compensation is explained. The operation of the Software Phase Locked Loop (SPLL) and its stability are analyzed. The DVR control system is described and verified using simulation. The control algorithm implemented using DSP was tested using generated input voltage signals and the results are also presented. The micro-cycle effect of battery current for balanced and unbalanced sag is also investigated.

Control of Dynamic Voltage Restorer using TMS320F2812

Dynamic Voltage Restorer (DVR) is a custom power device that is used to compensate voltage sag. The DVR generally consists of voltage source inverter (VSI), injection transformers, passive filters and energy storage (battery). The efficiency of the DVR depends on the efficiency of the control technique involved in switching the inverters. The inverters are switched using Space Vector Pulse Width Modulation pulses (SVPWM) to maximize the usage of DC link voltage. The control strategy that is used to generate the pulses will be illustrated in this paper. The flow chart of the program and the modules involved in the implementation of the control algorithm using DSP board TMS320F2812 will be described in detail. The implementation of the control using TMS320F2812 is tested using a 3kVA lab prototype and the results are presented.

DSP based overcurrent relay using fuzzy bang–bang controller

Abstract Overcurrent relays are very important protection component that require high reliability to maintain high security in power systems. With the new numerical relay technology using digital signal processor (DSP), it is possible to improve the performance of the relay significantly. However, application of DSP in numerical overcurrent relays is limited especially in coordination among the group of relays. The relay must work proficiently to coordinate with the networks in order to avoid mal-operation. Therefore, in this paper, an implementation of overcurrent relay with improved coordination on a DSP, TMS320F2812 is described. The fuzzy bang–bang controller is used as the control strategy for the relay to provide efficient control for overcurrent protection. The performance evaluation of the proposed system is based on steady state analysis, transient state analysis, coordination and lastly the execution time of the DSP. The results obtained using this new proposed controller is very promising.

DSP based fuzzy and conventional overcurrent relay controller comparisons

Abstract Fuzzy logic control uses linguistic approach to solve complicated rules and ambiguous systems. This control strategy can be used to improve the overall performance of an overcurrent relay for power system protection compared to conventional relay. It is essential for a relay to work efficiently to trip the circuit breakers in the presence of faults and at the same time proficient to coordinate well with the networks to avoid mal-operation. There are two different types of fuzzy logic control strategies proposed for the relay, the Fuzzy Logic Controller (FLC) and Fuzzy Bang-Bang Controller (FBBC). The FBBC is the same as the conventional FLC except that the defuzzification method uses largest of maxima (LOM). Comparisons between the fuzzy controllers and conventional relay are based on IEC 255-3 standard. These relays are implemented on a DSP TMS320F2812 and their performance is evaluated which is based on operation time, DSP’s execution time and grading margin. The results obtained show a significant performance improvement compared to conventional relay.

Modelling of overcurrent relay using digital signal processor

Protective relays are used to detect any abnormalities in a power system and isolate the faulty section of the system in the shortest time, in order to minimize disturbances caused by failure in the system to ensure continuous power delivery. Protective relays for overcurrent protection are the most widely used relays in a power system. The implementation of overcurrent relay on digital signal processor (DSP) proficient to mitigate problems such as lack of memory capacity, lower speed and functionality, compared to conventional approach using microprocessor. The modelling of overcurrent relay for inverse definite minimum time (IDMT) type using DSP board TMS320F2812 will be discussed in the paper. Simulation results of the overcurrent relay from MATLAB/ Simulink and execution on TMS320F2812 will be presented.

Overcurrent time delay determination using gain scheduled PID controllers

The inverse time overcurrent relay operation is based upon the current setpoint and also the time multiplier setting. Depending on the ratio of the value of the current and the setpoint current together with the value of the time multiplier setting, the amount of time delay for the trip command is determined using the inverse time characteristics. This would mean that the relay is not of the adaptive type and would possibly give a maltripping. This paper uses the concept of PID controller to determine the time delay for the overcurrent relay.

Efficient illumination design and energy saving through occupancy control for building

In any nation, energy is the fuel for its economic development. Realizing the utmost importance of energy, enormous efforts have to be taken in order to secure the energy availability of a nation. Therefore, it is necessary to increase the efficiency of electric energy usage and make use of the renewable energy sources in order to extend the availability of these fuel resources. This paper focuses on the efficient illumination design and occupancy of the main building of Asia Pacific University of Technology & Innovation (APUTI). A detailed load and energy audit was done for APUTI main building. For efficient illumination design the existing lighting design was reviewed and the potential energy saving by delamping the lights were determined and validated with actual photometric measurements. The energy saving through occupancy control was also determined.

A study on FVSI index as an indicator for under voltage load shedding (UVLS)

In the time of rapid growth, there is an increase of demand for a reliable and stable power supply. Power utilities are pressured to cater the rising demand with the existing system. Thus, monitoring the voltage stability of the system has become crucial. Under Voltage Load Shedding (UVLS) is one of the many methods that are used to sustain voltage stability. On the other hand, Fast Voltage Stability Index (FVSI) index is proven to be a good indicator for voltage stability in a system. This paper will study on the correlation between FVSI index and UVLS scheme. From the simulation, the results clearly indicate that FVSI index can be used to indentify location to be load shed.

Automatic online signature verification: A prototype using neural networks

Signature verification is the process used to recognize an individuals handwritten signature to prevent fraud. In this paper pressure at the pen-tip together with the x, and y coordinates of the signature are measured and features extracted from these are used to verify the signature. A pressure pad was used to obtain signature samples. A signature verification system using SOM neural network was designed in MATLAB to verify the signatures. Results obtained using a prototype system are encouraging. The attractive features of this system are its low cost, low intrusion, good performance and use of an acceptable and natural biometric (the signature).

Determination of overcurrent time delay using fuzzy logic relays

The inverse definite minimum time relay has been used in the power distribution system in order to protect the system from power system faults.[1] These relays will function after a certain time delay when the current going through the relay exceeds a predefined set point. This time delay depends on the ratio of the fault current flowing through the relay with the setpoint current defined by the protection engineer[2]. The basic problem with these relays is that the relays will have a longer time delay for a less severe fault[3]. Another problem that these relays would face is when the impedence between the backup relay and the main relay is much smaller than the impedence between the fault and the main relay. In this paper, the possibility of using a fuzzy logic controller(FLC) is studied in order to determine the time delay of the overcurrent relay.