Wind Turbine Generator Heating via Converter Current Circulation
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Solution Overview
Problem
Permanent magnet synchronous generators in wind power plants face challenges in heating up after a period of inactivity, leading to moisture condensation and potential voltage flashovers when restarted, as they lack excitation windings and cannot operate at reduced power levels without risking short circuits.
Innovation Solution
A method involving the converter system to circulate stator current through the generator and converter system at low speeds and voltages, using field weakening control and chopper circuits to heat the generator and converter components without generating high power or voltage, thereby preventing moisture-related issues during startup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the generator is operated at normal power levels to generate voltage, then electrical power is produced, but moisture condensation causes voltage flashovers and short circuits
Solution Approach 1:
The generator is heated in advance before normal operation begins. The heating process removes moisture condensation from the generator components beforehand, eliminating the risk of voltage flashovers when the generator starts operating at normal power levels. This preliminary heating action prevents the harmful effect of moisture before it can cause damage.
Solution Approach 2:
The generator operates in a heating mode with modified parameters before transitioning to normal operation. During heating, the generator produces minimal electrical power while maintaining elevated temperature to evaporate moisture. This parameter change allows the generator to transition from a low-power heating state to a full-power operational state without the moisture-related risks present at normal operating temperatures.
2Temperature
If the generator is operated at reduced power levels to heat up, then moisture is evaporated, but insufficient voltage is generated for effective heating
Solution Approach 1:
A heating resistor connected in series with the generator stator windings serves as an intermediary heating element. This resistor generates additional heat when current flows through it, supplementing the minimal electrical power produced by the generator during low-speed operation. The combined heating effect from both the generator and the resistor enables effective moisture evaporation even at reduced power levels.
3Ease of operation
If excitation windings are added to the permanent magnet synchronous generator for heating, then heating capability is improved, but device complexity increases
Solution Approach 1:
The permanent magnet synchronous generator uses its own stator windings and converter system to generate heating current, eliminating the need for separate excitation windings. The converter system, already present for normal operation, is utilized to circulate current through the stator windings during heating mode. This self-service approach provides heating capability without adding external excitation components, maintaining simple generator structure.
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
Effectively heats the generator and converter system at low power and voltage levels, preventing condensate-related issues and ensuring safe startup by dissipating power within the system, thus minimizing the risk of voltage flashovers.
Implementation Method 1
the stator current, at least part of it, essentially circulates through the generator and the converter system in order to dissipate power in at least stator windings of the generator, thereby heating the generator
Implementation Method 2
the generator is a permanent magnet synchronous generator, which is designed to generate a stator current
Data Source
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AI summary
Method for heating a generator (202) of a wind turbine (100) during or before starting the wind turbine (100), wherein the generator (202) is a permanent magnet synchronous generator (PMG) configured to generate a stator current (ls), wherein the stator current (ls) is at least a three-phase current, and the wind turbine (100) is configured as a gearless wind turbine and is connected to an electrical supply network (204) for feeding electrical power into the electrical supply network (204), and the wind turbine (100) comprises: a rotor (106) with rotor blades (108) that can be operated at variable speed, a converter system (200) connected to the generator (202) to control the generator (202), and connected to the electrical supply network (204) to convert electrical power generated by the generator (202),The method comprises rotating the rotor (106) at a low speed below a first speed limit, operating the converter system (200) such that the generator (202) generates the stator current (IS) and electrical power, and no electrical power is fed into the electrical supply network (204), wherein the stator current (is), or at least a part thereof, circulates substantially through the generator (202) and the converter system (200) to consume power at least in stator windings of the generator in order to heat the generator (202).