Line Side Converter Over-Modulation Control Strategy

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Solution Overview

Problem

Conventional control strategies for power converters in wind turbines are not suitable for testing and benchmarking performance in the over-modulation range, which can affect the stability and robustness of the power generation system.

Innovation Solution

A method of controlling the feedback control module of a line side converter by determining the modulation index within the over-modulation range and adjusting its operational state, either fully enabling or disabling it based on parameterised modulation index values, to ensure optimal performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional control strategies are used for power converters, then the control system is simple and easy to implement, but the performance in the over-modulation range cannot be properly tested and benchmarked, affecting system stability and robustness

Engineering Contradiction:

Improvesystem stability and robustnessVSAvoidcontrol strategy complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The feedback control module's activation is made dynamic by adjusting its operational state based on the modulation index. The controller dynamically switches between fully enabled and inactive states depending on whether the modulation index falls within specified ranges in the over-modulation region, allowing the system to adapt to varying operating conditions while maintaining stability.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention changes the operational parameters of the feedback control module by adjusting its activation state based on the modulation index parameter. By monitoring the modulation index and switching the feedback control module between enabled and inactive states, the system optimizes performance across different modulation ranges without requiring a completely new control architecture.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If the feedback control module is fully enabled, then the control precision is improved, but the system complexity increases and may affect performance in the over-modulation range

Engineering Contradiction:

Improvecontrol precisionVSAvoidcontrol system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

Instead of keeping the feedback control module fully enabled at all times, the invention applies partial action by selectively activating it only when the modulation index falls within specific ranges. This partial activation maintains control precision when needed while reducing unnecessary complexity and computational burden during over-modulation operations.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The feedback control module's activation state is made dynamic rather than static. The controller adjusts the module's operational state based on real-time modulation index values, switching between fully enabled and inactive states to optimize the balance between control precision and system complexity across different operating conditions.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS11502616B2Method of operating a power generation system in an overmodulation range

Publication Date: 2022.11.15 VESTAS WIND SYSTEMS AS

AI summary

This invention concerns a method of controlling a line side converter of a power converter system operating in an over-modulation range. The line side converter comprises a controller comprising a feedback control module configured to output a feedback control signal for modifying a drive signal received by a modulator. The method comprises determining a modulation index within the over-modulation range; and, controlling the feedback control module to adjust the feedback control signal based on the modulation index.