Method for obtaining symmetric power transfer coefficients under simultaneous change of sources and loads in AC power networks

Patent metadata

Field	Value
Publication number	US-9774188-B2
Application number	US-201414772610-A
Country	US
Kind code	B2
Filing date	Nov 18, 2014
Priority date	Nov 18, 2014
Publication date	Sep 26, 2017
Grant date	Sep 26, 2017

Abstract

The present invention belongs to electric power engineering field, relates to a method for obtaining a set of symmetric power transfer coefficients under simultaneous change of sources and loads in AC power networks, which comprises the steps of: firstly establishing a linear function of a lossy branch transferred power in terms of buses voltage angles according to a nonlinear function of a branch transferred power, parameters and operation features of the AC power network; then establishing symmetric linear functions of buses injection powers of power sources and loads in terms of buses voltage angles by combining the linear function of the lossy branch transferred power in terms of buses voltage angles and buses injection powers of power sources and loads, in turn establishing symmetric linear functions of buses voltage angles in terms of buses injection powers of power sources and loads; and finally obtaining the symmetric power transfer coefficients from buses injection powers of power sources and loads to the lossy branch transferred power under simultaneous change of sources and loads by using the linear functions just mentioned above. The obtained set of symmetric power transfer coefficients is unique, follows electric circuit laws, is applicable for the practical situations that power sources and loads change at the same time and transmission losses need considering in the AC power network, and truly reflects the substantive characteristics of the power transfer from bus injection powers to branch transferred powers.

First claim

What is claimed is:

1. A method for obtaining a set of symmetric power transfer coefficients under simultaneous change of sources and loads in alternating current (AC) power networks, which comprises:
establishing a linear function of a lossy branch transferred power in terms of buses voltage angles according to given AC power network parameters, a nonlinear function of a branch transferred power in the AC power network, and operation features of the AC power network;
establishing symmetric linear functions of buses injection powers of power sources and loads in terms of buses voltage angles according to the linear function of the lossy branch transferred power in terms of buses voltage angles and given buses injection powers of power sources and loads;
establishing symmetric linear functions of buses voltage angles in terms of buses injection powers of power sources and loads according to the symmetric linear functions of buses injection powers of power sources and loads in terms of buses voltage angles;
obtaining the symmetric power transfer coefficients from buses injection powers of power sources and loads to the lossy branch transferred power under simultaneous change of sources and loads according to the symmetric linear functions of buses voltage angles in terms of buses injection powers of power sources and loads and the linear function of the lossy branch transferred power in terms of buses voltage angles.

2. The method for obtaining a set of symmetric power transfer coefficients under simultaneous change of sources and loads in AC power networks according to claim 1 , wherein the step of establishing a linear function of the lossy branch transferred power in terms of buses voltage angles according to the given AC power network parameters, the nonlinear function of the branch transferred power in the AC power network, and operation features of the AC power network comprises the step of:
according to the given AC power network parameters, the nonlinear function of the branch transferred power in the AC power network, and the operation features of the AC power network, establishing a linear function of the lossy branch transferred power in terms of buses voltage angles by the following equation:
P ij =−b ij (θ i −θ j )

where i and j are the numbers of two arbitrary buses in the AC power network respectively, i and j are natural numbers and equal to 1, 2 . . . , n, n is the total number of buses in the AC power network, n is natural number and is the given AC power network parameter; ij is the branch between bus i and bus j; P ij is the lossy branch transferred power entering branch ij from bus i; θ i and θ j are voltage angles at bus i and bus j respectively; b ij is a constant determined by the formula of

b
ij

=

-

0.5
⁢

⁢

r
ij

⁡

(

θ
i
′

-

θ
j
′

)

+

x
ij

r
ij
2

+

x
ij
2

 and is a pseudo branch susceptance of branch ij, where r ij and x ij are the resistance and reactance of branch ij respectively and are the given AC power network parameters; θ′ i and θ′ j are the initial buses voltage angles at bus i and bus j respectively and are the given AC power network parameters.

3. The method for obtaining a set of symmetric power transfer coefficients under simultaneous change of sources and loads in AC power networks according to claim 2 , wherein the step of establishing symmetric linear functions of buses injection powers of power sources and loads in terms of buses voltage angles according to the linear function of the lossy branch transferred power in terms of buses voltage angles and the given bus injection powers of power sources and loads comprises the steps of:
according to the linear function of the lossy branch transferred power in terms of buses voltage angles and the given bus injection powers of power sources and loads, establishing the linear function of particular bus injection power of power sources and loads in terms of buses voltage angles by the following equation:

P
Gi

-

P
Di

=

-

∑

k
=
1

,

k
≠
i

n

⁢

b
ik

⁡

(

θ
i

-

θ
k

)

where P Gi and −P Di are the bus injection powers of power sources and loads connected to bus i respectively; k is the number of each bus in the AC power network; k is natural number and k is equal to 1,2 . . . , n; θ k is the bus voltage angle at bus k; ik is the branch between bus i and bus k; b ik is the pseudo branch susceptance of branch ik determined by the formula of

b
ik

=

-

0.5
⁢

r
ik

⁡

Assignees

• Univ Shenzhen

Inventors

• Peng Jianchun
• Jiang Hui

Classifications

• H02J2103/30

  Simulating, planning, modelling, reliability check or computer assisted design [CAD] of electric power networks · CPC title

• H02J3/12 Primary

  Arrangements for adjusting voltage in AC networks by changing a characteristic of the network load · CPC title

• H02J3/0073 Primary

  by providing alternative feeding paths when the main path fails · CPC title

• Y04S40/22

  Cross-Sectional Technologies · mapped topic

• Y04S10/525

  Cross-Sectional Technologies · mapped topic