Reactive Power Optimization for Integrated Transmission Distribution Networks

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Solution Overview

Problem

In active distribution networks with integrated distributed renewable energy resources, there is a lack of coordination between transmission and distribution networks, leading to power mismatch losses, overvoltage issues, and suboptimal economic objectives due to the tight coupling and independent reactive power control modes.

Innovation Solution

A reactive power optimization method using a generalized Benders decomposition method with second-order cone relaxation is applied to establish a model that optimizes reactive power output across transmission and distribution networks, minimizing total network loss and addressing non-convex constraints through relaxation techniques.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If independent reactive power control mode is used in transmission and distribution networks, then operational simplicity is maintained, but power mismatch loss increases significantly at the network boundary

Engineering Contradiction:

Improveindependent reactive power controlVSAvoidpower mismatch loss

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

The patent merges the transmission network and distribution network into an integrated system for coordinated reactive power optimization. The optimization model jointly determines reactive power outputs of generators in both networks, eliminating the boundary between independent control zones and preventing power mismatch losses at the interface.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent segments the integrated network into transmission network subsystem and distribution network subsystem, each with its own constraints and objectives. The generalized Benders decomposition method enables independent optimization of each subsystem while coordinating through iterative information exchange, combining benefits of both centralized and decentralized approaches.

Inventive Principle:

Principle #1Segmentation

2Power

If massive distributed renewable energy resources are integrated in distribution network, then energy production capacity increases, but overvoltage problems occur at power injection nodes

Engineering Contradiction:

Improveenergy production capacityVSAvoidovervoltage

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The optimization model incorporates voltage constraints at distribution network nodes, including power injection nodes with renewable energy resources. The coordinated optimization provides feedback control on reactive power outputs to maintain voltages within acceptable ranges, preventing overvoltage problems while maximizing renewable energy integration.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent changes the operating parameters of generators by optimizing their reactive power outputs. By adjusting reactive power injection from generators in both transmission and distribution networks, the system controls voltage levels at distribution nodes, especially at points with high renewable energy penetration, thereby eliminating overvoltage issues.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If transmission and distribution networks are optimized independently, then computational complexity is reduced, but coordination between networks is lacking and economic objectives are suboptimal

Engineering Contradiction:

Improveoptimization computationVSAvoidcoordination between networks

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent uses the generalized Benders decomposition method as an intermediary approach. The method introduces master problem and sub-problems that act as intermediaries between transmission and distribution network optimizations. The master problem coordinates overall reactive power optimization while sub-problems handle local constraints, enabling coordinated optimization without requiring complete centralization.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The optimization approach is dynamic and iterative. The generalized Benders decomposition method iteratively updates solutions between master problem and sub-problems, allowing the system to adaptively find optimal coordinated solutions. This dynamic process maintains computational tractability while achieving network coordination, unlike static independent optimization.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS10673237B2Reactive power optimization method

Publication Date: 2020.06.02 TSINGHUA UNIVERSITY

AI summary

A reactive power optimization method for integrated transmission and distribution networks related to a field of operation and control technology of an electric power system is provided. The reactive power optimization method includes: establishing a reactive power optimization model for a transmission and distribution network consisting of a transmission network and a plurality of distribution networks, in which the reactive power optimization model includes an objective function and a plurality of constraints; performing a second order cone relaxation on a non-convex constraint of a plurality of distribution network constraints of the plurality of constraints; and solving the reactive power optimization model by using a generalized Benders decomposition method so as to control each generator in the transmission network and each generator in the plurality of distribution networks.