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By: Pravin Sankhwar.
1.Pravin Sankhwar,Independent Researcher, Electrical Engineering Consultant, WSP, USA.
The project analyzes the voltage fluctuations caused by any disturbance in a power system and minimizes the oscillations by controlling the excitement field using a feedback control loop. Adequate numbers of journal papers and literature materials were researched and reviewed to understand the principles of generator excitation and investigate various control systems which can be worked upon to keep the voltage output stabilized. It is known that Automatic Voltage Regulator cannot respond to the fluctuating generator voltage output fast enough resulting in voltage drop and other adverse effects in power system. Therefore, the project mainly considers the operation of AVR and verifies the improvement in the response time of the control system when a PI controller is added to the loop using EMTP-ATP. Due to unfamiliarity with using the TACS elements in ATP, there were problems in running the simulations without errors and even after that the solutions were intricate. But we were able to overcome the issue and generate the required output. For the project, the automatic voltage regulator control loop was developed and modelled in EMTP-ATP using transfer function blocks and the voltage regulation concept was used to control the excitation of a generator. The model uses transfer function blocks to mimic the functions of AVR, Exciter, Generator and Sensors. Separate cases were run for the system – one with no load changes and one with load changes. The fluctuations in voltage output of generator due to load changes, which overshoot by around 10%, were stabilized in 4 seconds and set to steady state value. A three-phase test system model was also developed to check the functioning of the exciter system for proper model of synchronous generator. The system also includes transmission lines and loads which are connected using switches. The voltage and associated parameters were selected to represent a basic transmission system and an LCC template is used to simulate the transmission line. TACS models were used for coding the AVR control loop of the exciter and defining the machine parameters. Both the cases of increase and decrease of load were tested by opening/closing the switches at different times and disturbances were observed in the voltage output. Here too, the bus voltage was stabilized effectively rendering it to steady state value.
Keywords: proportional integral control, voltage regulation, power system, synchronous generator, AVR control loop, TACS element, PI controller.
Citation:
Refrences:
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