Question 1 [10 marks]:

1. A 50-Hz system consists of two interconnected areas, as shown in Figure 1. Area 1 has an

electric vehicle (EV) charging station and Area 2 has a wind farm. The parameters for both

areas are given in the table below:

Area

Speed regulation, R

Frequency sensitive load, D

Frequency Bias constant, B

Base power

Area 1

EV charging

station

APtie1

1

2

R₁ = 0.04 pu| R2 = 0.05 pu

D₁ = 2 pu

D₂ = 1 pu

B₁ = 3 pu

B₂ = 5 pu

100 MVA

100 MVA

APtie2

Area 2

FŰ

Wind farm

Figure 1

Initially, the generators in both areas are operating in parallel at the nominal

frequency and the tie-line is unloaded when the EV charging power suddenly

increases by 90 MW and the wind farm power suddenly increases by 30 MW

simultaneously. (Hint: assume wind farm power as a negative load change.)

(a) Calculate the new steady-state system frequency in Hz.

[2 marks]

(b) Calculate the change in mechanical power and change in frequency-sensitive

load in each area. Express your answers in per-unit.

[2 marks]

(c) Calculate APtie1 and APtie2 by forming power balance equation in each area.

Hence, or otherwise, determine the area control error (ACE) for each area.

Express your answers in per-unit.

[4 Marks]

(d) Explain how load frequency control (LFC) can eliminate the tie-line error and

area control error for each area in part (c). [No calculations needed]

[2 marks]