Page 260 - Mathematical Models and Algorithms for Power System Optimization

252 Chapter 7

From the system diagram, for the thermal generating unit:
αT RM p +1
G 1 ¼
ð
ð T S p +1Þ T CH p +1Þ T RH p +1Þ
ð
1
G 2 ¼
M 1 p + D 1
For the hydro generating unit:

ð
ð T 1 p +1Þ 1 T W pÞ
G 1 ¼
ð
ð T 1 p +1Þ T 2 p +1ð Þ 0:5T W p +1Þ
1
G 2 ¼
M 2 p + D
In Fig. 7.14, H Cj means the transfer function of the compensator.

1
H Cj ¼
G 1j
Obviously, if the corresponding compensation control law is as follows:

1
Δu j ¼ ΔP L ¼ H Cj ΔP Lj
G 1j

It is possible to fully compensate for the effect of the disturbance. However, this
complete compensation can only be achieved if the unit transfer function is reversible.
Experimental results show that H Cj ¼1 can achieve good control effect when G 1j is
irreversible.

When the digital control is achieved, it is required to transform the continuous differential
transfer function in Fig. 7.16 into the discrete difference transfer function, using the methods
proposed in the next section. After such transformation, it is quite easy to achieve this
compensation control with the help of a digital computer.

7.6.3 Simulation Procedure of Tracking Control

In the past, the feedback control was not necessary to understand the system perturbation, that
is, no compensation to the disturbance, and the control is only performed after the system
state changes. In general, the feedforward control is to perform compensation control after
measuring the disturbance. The tracking control of the power system can be achieved by
continuously measuring, estimating, forecasting, and controlling. The simulation test of
tracking control is shown in Fig. 7.17.