Wind Turbine Converter Protection via Junction Temperature Estimation
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Solution Overview
Problem
Variable speed wind turbines with doubly fed induction generators face challenges in protecting semiconductor components from grid transients, which can cause overcurrents that exceed the operational range of current sensors, leading to potential damage and reduced output power.
Innovation Solution
A method to estimate the junction temperature of semiconductor components in real-time by determining associated currents and power losses, using a thermal model to trigger a protection mechanism if the temperature exceeds a threshold, even when currents are outside the sensor range, allowing for efficient protection during grid transients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current sensors are used to measure converter rotor currents, then measurement is possible under normal conditions, but measurement accuracy is lost when currents exceed the operational range during transients
Solution Approach 1:
The patent introduces an intermediary measurement approach by measuring voltages across known impedances (resistors or inductors) in the current path instead of directly measuring current with sensors that have limited range. This voltage measurement can then be converted to current value, allowing measurement of very high currents during transients without exceeding sensor operational ranges, thus maintaining measurement accuracy across all current conditions.
2Measurement precision
If temperature sensors with slow response time are used, then junction temperature can be measured under stationary conditions, but temperature increase during hard transients goes undetected
Solution Approach 1:
The patent performs preliminary action by continuously estimating junction temperature using a thermal model based on measured power losses and thermal parameters, rather than relying solely on slow-responding physical temperature sensors. This estimation provides real-time temperature data that can detect rapid temperature increases during hard transients, enabling timely protection activation before damage occurs.
Solution Approach 2:
The patent replaces the mechanical/physical temperature sensing system with a computational estimation system. Instead of using physical temperature sensors that have inherent response time limitations, the system uses a thermal model that calculates junction temperature based on electrical measurements and thermal parameters, providing much faster response capability.
3Reliability
If power converter handles total active power in full converter topology, then generator protection is improved, but converter size and costs increase
Solution Approach 1:
The patent extracts the protection function from the main power conversion path by implementing a separate protection mechanism that monitors thermal conditions and can quickly disconnect or limit power flow during transient events. This allows the main power converter to remain smaller (handling only partial power as in DFIG) while still providing generator protection through the dedicated protection system.
4Device complexity
If DFIG configuration is used to reduce converter size, then converter costs are reduced, but stator experiences grid transients causing overcurrents that can damage the converter
Solution Approach 1:
The patent applies preliminary anti-action by continuously monitoring estimated junction temperature and being prepared to activate protection measures before actual damage can occur. The system detects the thermal stress caused by grid transients through the thermal model and can preemptively limit power flow or activate protection circuits to prevent converter damage, countering the harmful effects before they manifest physically.
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
Enables real-time estimation and protection of semiconductor components, preventing damage and maintaining high output power by accurately measuring junction temperatures and triggering protective measures before component failure.
Implementation Method 1
using a thermal model of the one or more semiconductor components to estimate the junction temperature of at least one of the one or more semiconductor components based on the estimated power loss
Implementation Method 2
semiconductor components such as semiconductor switches provided for rectification and inversion of the electrical power
Implementation Method 3
a generator that converts mechanical power provided by the rotating shaft of the wind turbine into electrical power
Data Source
AI summary
A method of protecting a converter of a wind turbine and a respective protection system are provided. The converter is coupled to a generator of the wind turbine to perform conversion of electrical power produced by the generator, the converter including plural semiconductor components that are operational to provide the conversion of the electrical power. The method includes the performing of a step of estimating a junction temperature of at least one of the semiconductor components by determining a current in the converter associated with power loss in one or more of the semiconductor components; estimating power loss associated with the one or more semiconductor components based on the determined current and on a state of the one or more semiconductor components; and using a thermal model to estimate the junction temperature of the semiconductor components based on the estimated power loss. The estimating step is repeatedly performed.