Primal-Dual Interior Point Methods for Discrete Optimal Power Flow

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Solution Overview

Problem

Current optimal power flow (OPF) analysis in electrical power systems is hindered by the complexity of nonlinear variables and constraints, leading to time-consuming computations and convergence issues with nonlinear programming algorithms, limiting their adoption in real-time large-scale systems.

Innovation Solution

The OPF problem is reconfigured using the chain rule to transform it into a compact linear system of six equations, eliminating binary variables and introducing slack variables, allowing for the application of interior point methods and reducing the problem to an irreducible set of linear equations, thereby simplifying the analysis and resolution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If nonlinear programming algorithms are used to solve the OPF problem with nonlinear variables and constraints, then solution accuracy is improved, but computational time and convergence reliability deteriorate

Engineering Contradiction:
Improvesolution accuracyVSAvoidcomputational time
Core Design Contradiction:
Measurement precisionVSLoss of time

Solution Approach 1:

The patent transforms the original nonlinear OPF problem parameters into a different mathematical representation using the chain rule, converting nonlinear variables and constraints into a compact linear system of six equations with six unknowns. This parameter transformation maintains solution accuracy while dramatically reducing computational complexity and solving time.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent extracts and isolates the critical components of the OPF problem by reducing the complex system to an irreducible set of six linear equations containing the essential unknowns. By separating the core problem from the complex nonlinear constraints, the solution achieves both accuracy and efficiency.

Inventive Principle:
Principle #2Taking out (Extraction)

2Measurement precision

If nonlinear programming algorithms are used to solve the OPF problem, then solution accuracy is improved, but algorithm robustness and convergence reliability worsen

Engineering Contradiction:
Improvesolution accuracyVSAvoidconvergence reliability
Core Design Contradiction:
Measurement precisionVSReliability

Solution Approach 1:

By changing the mathematical parameters from nonlinear to linear form through chain rule application, the patent eliminates convergence issues inherent in nonlinear algorithms while preserving the ability to accurately represent the original problem constraints and objectives.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent introduces an intermediary mathematical transformation (the chain rule-based linear system) that mediates between the original nonlinear problem and the solution process. This intermediary representation maintains fidelity to the original problem while enabling reliable and robust solution through linear methods.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Measurement precision

If the original discrete OPF problem is solved directly, then solution equivalence is maintained, but problem complexity and computational burden increase

Engineering Contradiction:
Improvesolution equivalenceVSAvoidproblem complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts the essential elements of the discrete OPF problem and reformulates them into a compact continuous relaxation form. By taking out only the critical components needed for solution equivalence and expressing them through six linear equations, the complexity is dramatically reduced while maintaining solution accuracy.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The patent applies parameter changes by transforming discrete variables and nonlinear constraints into continuous variables with linear relationships. This transformation simplifies the problem structure while preserving the mathematical equivalence needed to solve the original discrete OPF problem.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentUS8775136B2Primal-dual interior point methods for solving discrete optimal power flow problems implementing a chain rule technique for improved efficiency
Publication Date: 2014.07.08 SIEMENS AG
  • US8775136B2 patent drawing
  • US8775136B2 patent drawing
  • US8775136B2 patent drawing

AI summary

A solution to the optimal power flow (OPF) problem for electrical generation and distribution systems utilizes a re-configuration of the OPF problem that allows for a simplified analysis and resolution of a network-based OPF problem in a minimal number of iterations. The standard mixed integer quadratic problem (MIQP) definition is be reconfigured, using the chain rule, to a relatively compact linear system of six equations with six unknowns (the smallest reducible (atomic) problem). Advantageously, the reduction in the complexity of the problem does not require any assumptions and yields a solution equivalent to the original problem.