Page 153 - Mathematical Models and Algorithms for Power System Optimization

144 Chapter 5

of the load can be taken as a higher value, or the LC at this point is directly set as zero (P Ci ¼0);
the corresponding safety load multiple of the power supply line and transformer shall be
increased accordingly.

5.6 Calculation Procedure of Maximizing LSC

(1) Input data: Data input is the basis of the LSC calculation, including the network
connection relationship, type and output of bus, load constraints, line and transformer
capacity constraints, and impedance parameters.
T
(2) Formulate the linear programming model: Generate coefficient matrix A and C of the
linear programming model to formulate the linear programming model, where A ¼ B L
1
B T T
R ,C , where C is a [0, 1] vector; c i ¼1 for load-type buses; and c i ¼0 for
0
other buses.
(3) Execute the linear programming calculation. Solve the linear programming problem using
the simplex method.
(4) Output maximum LSC index of the network: output the solution to the linear
programming problem, including the LSC indicator, active power at buses in the network,
active power flow at branches (line and transformer), and load rate.
(5) Verify the method using the traditional power flow algorithm (LF). Specifically, substitute
each bus load obtained from Step (4) as known conditions into the traditional AC power
flow calculation model, then calculate power flow.

5.7 Implementation for Maximizing LSC

This section uses actual network data for a certain region in China as an example to demonstrate
the rationality and accuracy of assessing the maximum LSC of an urban grid with a linear
programming model.

5.7.1 Description of the Test System

This test system has a total of 35 buses, including 3 output buses, 16 load buses, and 16 link
buses (including buses without output or load and neutral points of a three-circuit transformer);
36 branches, including 8 110kV lines, 8 three-circuit transformers, and 4 two-circuit
transformers. In the network, the total 330kV transformation capacity is 300MVA, and total
110kV transformation capacity is 349MVA. Set the limit of power at each branch to 95% of its