Linear Asymmetric Method for AC Power Network Security
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Solution Overview
Problem
Existing methods for examining branch-outage-type steady-state security in AC power networks are either inaccurate due to approximate or locally linear expressions, or time-consuming due to complete power flow calculations, failing to meet the requirements of modern power networks with rapid response power electronics.
Innovation Solution
A linear asymmetric method that establishes two linear expressions of bus injection active and reactive powers in terms of translation voltages and voltage angles, forming a linear asymmetric matrix-equation model, and modifies the bus impedance matrix to calculate branch-outage-type translation-voltage increments and voltage-angle increments, reducing computational effort and ensuring accurate power flow values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If DC power flow equations are used to establish approximate linear expressions, then computational speed is improved, but accuracy deteriorates due to ignored reactive power impacts
Solution Approach 1:
The patent transforms the traditional DC power flow parameters by introducing translation voltages and incorporating reactive power effects into the linear expressions. This changes the parameter representation from pure active power-based DC equations to a hybrid model that includes both active and reactive power components, achieving faster computation than full AC power flow while maintaining higher accuracy than traditional DC equations.
2Measurement precision
If complete AC power flow calculation is used, then accuracy is improved, but computational time increases making it impractical
Solution Approach 1:
The patent segments the complex AC power flow calculation into two distinct linear expressions: one for active power considering voltage angles, and another for reactive power considering translation voltages. This segmentation allows each expression to be solved independently and more efficiently, avoiding the iterative complexity of complete AC power flow while capturing essential accuracy requirements for branch outage security assessment.
3Productivity
If Jacobian matrix of AC power flow equations is used for local linearization, then computational speed is improved, but accuracy deteriorates due to local linearity limitations
Solution Approach 1:
The patent creates universal linear expressions that function for both normal operating conditions and branch outage scenarios. The two linear expressions (active power with voltage angles, reactive power with translation voltages) serve multiple purposes: they can assess security under various outage conditions and provide accurate power flow values globally, not just locally around an operating point like traditional Jacobian-based methods.
Data Source
AI summary
A linear asymmetric method for examining branch-outage-type steady-state security of AC power networks is provided. Two linear expressions of bus injection active and reactive powers in terms of translation voltages and voltage angles of all buses are established. Then a linear asymmetric matrix-equation model for the steady state of the network is built considering the reference bus number. Manipulating this model produces the matrix expression of branch-not-outage-type translation voltages and voltage angles of non-reference buses and the bus impedance matrix with the reference bus discarded. The branch-outage-type translation-voltage increments and voltage-angle increments of non-reference buses are then obtained by the bus impedance matrix and the outage branch using the calculation formula of ordinary inverse of a modified matrix. The examination of the steady-state security of the network is achieved using these increments. The present application provides a fast and accurate method for examining branch-outage-type steady-state security of AC power networks.