Updating P-V Bus Voltages

It can be seen from Table 4.3 that even though the real power is specified for the P-V bus-5, its reactive power is unknown. Therefore to update the voltage of this bus, we must first estimate the reactive power of this bus. Note from Fig. 4.11 that

(4.16)

And hence we can write the k^th iteration values as

(4.17)

For the system of Fig. 4.1 we have

(4.18)

This is computed as 0.0899 per unit. Once the reactive power is estimated, the bus-5 voltage is updated as

(4.19)

It is to be noted that even though the power generation in bus-5 is 48 MW, there is a local load that is consuming half that amount. Therefore the net power injected by this bus is 24 MW and consequently the injected power P_{5, inj} in this case is taken as 0.24 per unit. The voltage is calculated as V₅⁽¹⁾ = 1.0169 < − 0.8894° . Unfortunately however the magnitude of the voltage obtained above is not equal to the magnitude given in Table 4.3. We must therefore force this voltage magnitude to be equal to that specified. This is accomplished by

(4.20)

This will fix the voltage magnitude to be 1.02 per unit while retaining the phase of − 0.8894 ° . The corrected voltage is used in the next iteration.