Page 149 - Mathematical Models and Algorithms for Power System Optimization

140 Chapter 5

The analysis and calculation of the three states of the 5-bus system reveals: the result of LCO for
system states 1 and 2 is 0, that is, there is no need for LC; for state 3, curtailment of 21.879MW
at bus 1 and 21.879MW at balance bus 5 are needed, in which the line load rate between buses 1
and 3 is up to 100%, that is, the LC is minimized when the load at bus 1 is curtailed until the line
between buses 1 and 3 is at full rate without violation.
Meanwhile, the static security analysis of the three states show only that state 3 cannot pass and
the line load rate between buses 1 and 3 reaches 122%. This also verifies the conclusion that the
LCO model supplements improve the static security analysis.

5.5.2 Basic Conditions of a Real-Scale System

In an actual case, there are 74 buses and 91 branches, and 0.90 is selected as the branch safety
load ratio.

Fig. 5.4 shows the geographical single line diagram of 110kV or above grid in an actual case.
The main grid power supply consists of a 500kV XIJIANG substation and two unified
dispatched power plants, FUNENG and XINTIAN, with a total capacity of 2760MVA; local
power plants include HENGYI, JIANGNAN, CHANGHAI, SHAKOU, HUANBAO,
FOSHAND, and FOSHANE with a total installed capacity of 656MW, but in summer’s heavy
load mode, the total output is 484MW. The main network is constructed by interconnecting six
220kV substations, such as ZHUYUAN, ZIDONG, NANHAI, HONGXING, FENGJIANG,
and FOSHAN, and power supply points (FOSHAN and HONGXING substations originally
formed a ring through TENGSHA and JI-AN) with a total capacity of 2580MVA. Each 220kV
substation radially supplies power to 110kV HV distribution network substations. The network
data are given in Tables 5.16–5.18.

5.5.3 Results of the Real-Scale System

Different postfault operating states and different load levels at each substation in a zone are
given. The grid risk index data by circular call of the optimization calculation procedure are
given. The input/output data for a certain state are presented in Section 5.7.

According to project requirements, the weights at each load point are equal (default value of 1.0
used for column 86–90), the upper limit of branch capacity is 0.9, the upper limit of local plant
outputisgivenaconservativevalue,anditslowerlimitistakenasdefaultvalueof0.Therefore,this
model directly uses the BPA data from FOSHAN Power Supply Bureau for its calculation. First,
simulateacertainsystemstatethroughMonteCarlo,thenconductstaticsafetyanalysisbyscanning
calculation; for states that cannot pass, modify the current load of BPA by adding “.” before each
data row. The output result for each state are written out using the field in the result of LCO.

For this particular state, the data output consists of four components: