Parallel Damping Circuit for Subsynchronous Resonance in Power Transmission

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Solution Overview

Problem

Power transmission systems face issues with voltage flicker, ferroresonance, self-excitation, and subsynchronous resonance due to series capacitors, which can cause damage to equipment and are challenging to manage, especially with the integration of non-conventional power sources like wind turbines and solar farms.

Innovation Solution

A system comprising a series compensation circuit and a parallel damping circuit is introduced to reduce subsynchronous series resonance, featuring a resistor, capacitor, and inductor configuration that can be tuned for broadband response and includes a switch for isolation during failures or maintenance, allowing for the connection of multiple disparate generation sources without extensive coordination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If series capacitors are used to raise power limits of long transmission lines, then power transmission capability is improved, but subsynchronous resonance oscillations occur that can damage equipment

Engineering Contradiction:

Improvepower transmission capabilityVSAvoidsubsynchronous resonance oscillations

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

A damping circuit is introduced as an intermediary component connected in parallel with the series capacitor. This damping circuit acts as a mediator that absorbs and dissipates the harmful subsynchronous resonance oscillations while allowing the series capacitor to continue providing its beneficial power transmission enhancement. The damping circuit includes resistive elements that convert the oscillation energy into heat, effectively eliminating the resonance problem.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The damping circuit converts the harmful subsynchronous resonance oscillations into beneficial thermal energy through resistive dissipation. By intentionally providing a controlled path for the oscillation current through the damping circuit, the harmful electrical oscillations are transformed into harmless heat, protecting the transmission line and connected equipment from damage.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Stability of the object's composition

If distribution series capacitors are used to solve voltage flicker problems, then voltage stability is improved, but ferroresonance and self-excitation phenomena occur that can damage equipment

Engineering Contradiction:

Improvevoltage stabilityVSAvoidferroresonance and self-excitation

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The damping circuit serves as an intermediary that intervenes between the series capacitor and the harmful resonance phenomena. When ferroresonance or self-excitation occurs, the damping circuit provides a controlled discharge path that prevents the oscillations from building up to damaging levels, while not interfering with the voltage stabilizing function of the series capacitor under normal operating conditions.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If multiple non-conventional power sources are connected to existing transmission lines, then power generation diversity is improved, but coordination complexity increases

Engineering Contradiction:

Improvepower generation diversityVSAvoidcoordination complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The damping circuit is designed with universal applicability that can handle multiple types of non-conventional power sources (wind turbines, solar farms, etc.) without requiring source-specific configuration. The broadband damping characteristic allows the same damping circuit design to protect against subsynchronous resonance from various generation types, simplifying the integration process and reducing coordination complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The system effectively dampens subsynchronous resonance, preventing equipment damage and enabling the stable integration of non-conventional power sources into existing transmission lines, reducing the need for costly and complex coordination efforts.

Implementation Method 1

The damping circuit reduces subsynchronous series resonance caused by the series compensation circuit on the power transmission line

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

The series capacitors can cause series-resonant oscillations, which have been known to cause damage to generator shafts. This effect has become known as subsynchronous resonance (SSR)

Methodology Applied

Scientific EffectElectrical resonance: Resonance

Data Source

PatentUS8106540B2Compensation system for power transmission

Publication Date: 2012.01.31 GE INFRASTRUCTURE TECH LLC

AI summary

A system is provided for compensating a power transmission line having one or more non-conventional power generating sources connected to the power transmission line. At least one series compensation circuit is connected to a portion the power transmission line, and at least one damping circuit is connected in parallel with the series compensation circuit. The damping circuit reduces subsynchronous series resonance caused by the series compensation circuit on the power transmission line, and the series compensation circuit compensates the power transmission line.