Nirmal Nair

Systematic development of Low Voltage Ride-Through (LVRT) envelope for grids

Increased penetration of wind generation into high voltage transmission systems necessitates development of grid integration standards. One of them is Fault Ride-Through (FRT) or Low Voltage Ride-Through (LVRT) guidelines. Development of the voltage envelope depends on the transmission network characteristics along with considerations like contingency and protective relay settings. This paper outlines a systematic method for establishing LVRT criteria through a set of analysis involving contingency analysis, static and dynamic scenario based system simulations. Wind turbine technology is also discussed in context of development of LVRT criteria for large wind farms. The development of voltage envelope for LVRT criteria is shown through the case study for New Zealand transmission system.

Distance protection of transmission line with infeed based on real-time simulator

In this paper real-time simulation, analysis, and validation of the conventional distance relay based on MATLAB/simulink and Real-Time LABoratory (RT-LAB) is presented. In addition to the detailed model of six impedance measuring units of distance relay, power system model is implemented in Opal-RTs RT-LAB simulator. Some cases are highlighted to illustrate the modelling performance. Moreover, the effect of infeed current, which is an emerging issue for power system protection, using conventional distance relay in real-time environment is evaluated.

An optimal reactive power dispatch (ORPD) for voltage security using particle swarm optimization (PSO) in graph theory

The stochastic nature of the wind and the highly non linear transform from wind speed to electrical energy makes it more difficult to determine how to dispatch the power in order to guarantee both operational cost reduction and power system security. From a network constraint perspective for the economic dispatch problem one of the factors to be accounted for is voltage security, which impacts both active and/or reactive power dispatch. In this paper, an Optimal Reactive Power Dispatch based on Particle Swarm Optimization (PSO) using Graph Theory has been proposed to overcome the above-mentioned problem. Graph Theory has been used since it becomes very useful in cases of fault detection and isolation or to shed unbalanced nodes in case of excessive or insufficient supply. Simulation studies on the modified IEEE-14 Bus System have been conducted to show the effectiveness of the proposed method.

Renewable generation and its integration in New Zealand power system

The New Zealand power system has a peak demand of 3500 MW in the south island and 4500 MW in the north island, thus a total of 8000MW. In 2010, approximately 74.6% of energy came from different renewable sources where hydro alone represents about 57%. The NZ government has announced that the renewable target of 90% needs to be fulfilled by 2025. It seems this target is easily achievable because there is significant additional wind plant and geo-thermal plants under construction or planned for the near future. The installed capacity of wind generation is 565 MW at present and it is expected that this capacity will increase significantly. Thus it will bring with it “intermittency”. This paper describes the New Zealand power system and its market operation. Next it describes the methods by which the wind generation intermittency can be overcome considering New Zealand river chain system and also by Demand Management. A mathematical model is presented showing how the demand response could bridge the intermittency created by wind generation. Result of a case study is summarized and presented.