Avr control system generator#

Why should we use AVR in industrial plants? What are the factors that must be considered while selecting a voltage regulator?

Drop characteristic for reactive load showing among the generators operating in parallel.

Avr control system generator#

It should provide the stator and rotor current limiters in order to utilize the capability of the generator properly.It should be able to do the transformer drop compensation.It must be able to apply positive ceiling voltage across the generator field winding for a quick increase in the terminal voltage of the generator.It should be able to apply the negative sealing voltage across the generator field winding for a quick de-excitation of the generator.What are the technical requirements for an AVR? If the generator operates in light load and if an additional load is applied to the generator then there would be a quick drop of the generator’s terminal voltage, so during this situation, our major choice is to apply voltage in addition to the existing field voltage. So in order to decrease the excitation voltage very quickly, a negative voltage can be applied to the DC voltage. So the AVR would detect this increase in the voltage level, so this problem must be solved quickly and the AVR operation is not quick enough for this and if this fault is not cleared quickly then the generator could become unstable. In case if the generator load is disconnected or thrown off due to some reason and this would cause a sudden increase in the voltage level. This is the input regulation, this is the percentage of the output voltage change with the input. The load regulation can also be described as the load voltage percentage change. There would be a change in the output voltage in case if there is a change in the load current and this must be regulated. There are two types of voltage regulation and they are The output voltage of a power supply would change according to the load and it would also vary according to the input.

AVR would maintain the generator’s output power.It would support controlling the frequency for large interconnections.It can suppress the overvoltage on the load rejection.The stability of the power system will be improved, transient stability and dynamic stability can be achieved with the help of AVR.It would adjust the reactive power by doing the voltage regulation in the generator.The AVR can regulate the generator terminal voltage, the terminal voltage will be detected by the AVR, and then it would be compared with the setter.The voltage at the terminals of all the equipment of the system would be in the acceptable limits.It would help to achieve the reliable operation of the power system.This in turn will reduce the terminal voltage and will try to make it stable at 21 kV.What are the major functions of a voltage regulator? Thus AVR will reduce the field current I f to reduce the value of air gap flux. Suppose V ref = 21 kV and due to some reason the terminal voltage V t = 25 kV. The output of Transfer Function is the fed to Thyristor Bridge Rectifier to change firing angle and hence field excitation. The controller in the diagram is denoted by its Transfer Function. The Error Signal (V ref-V t) is fed to Controller. But for this discussion we will eliminate the effect of PSS and assume that V ref is constant. This reference voltage is also dynamically changed around the manually set V ref by Power System Stabilizer (PSS). Reference voltage Vref is manually set in AVR. For simplicity we will assume only two inputs V ref and V t. AVR takes three inputs namely reference voltage V ref, terminal voltage V t and limiting signals.