Wind Turbine VSM Control for Generator Torque Gradient Reduction
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Solution Overview
Problem
Wind turbine generators using virtual synchronous machine control schemes experience high torque levels and high torque gradients due to sudden changes in grid voltage or phase, leading to mechanical stress and potential damage.
Innovation Solution
A method is introduced to reduce high torque levels and torque gradients by determining a generator torque and its surplus relative to a torque limit, calculating an active power surplus, and controlling the line-side converter based on this surplus within the virtual synchronous machine control scheme.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If virtual synchronous machine control scheme is used to enable wind turbine generator to emulate synchronous generator and provide grid-forming properties, then grid stability and renewable energy penetration are improved, but high torque levels and high torque gradients occur causing mechanical stress and potential damage
Solution Approach 1:
The patent introduces an intermediary control mechanism between the virtual synchronous machine control and the generator torque output. A torque limiting device is inserted that monitors and restricts the torque signal, preventing excessive torque levels and gradients from reaching the generator while maintaining the grid-forming capabilities of the VSM control scheme.
Solution Approach 2:
The patent dynamically adjusts the torque parameter by implementing a torque limit that prevents torque from exceeding a predetermined maximum value. This parameter change is achieved through continuous monitoring of the torque signal and applying limiting logic that modifies the torque output when thresholds are exceeded, thereby protecting the generator from mechanical stress.
2Duration of action of stationary object
If torque limit is imposed to protect generator from mechanical damage, then generator lifespan is extended, but torque control flexibility and response to grid conditions are reduced
Solution Approach 1:
The torque limiting mechanism is designed to be dynamic rather than static. The system continuously monitors torque levels and applies limiting only when necessary, allowing full torque control flexibility within safe operating boundaries. This dynamic approach preserves the adaptability of the VSM control while protecting the generator during abnormal conditions.
Solution Approach 2:
The patent implements a feedback mechanism where the torque signal is continuously monitored and fed back to the limiting device. This feedback loop enables the system to maintain optimal torque control within safe limits, automatically adjusting the torque output based on real-time conditions while ensuring the torque never exceeds the predetermined maximum value.
Data Source
AI summary
Aspects of the present invention relate to a method for reducing high torque levels and/or high rates of change of torque in a wind turbine generator that comprises a machine-side converter and a line-side converter connected by a DC link, and, wherein the line-side converter is operated according to a virtual synchronous machine control scheme. The method comprises: determining a generator torque; determining a torque surplus indicating the amount that the generator torque exceeds a torque limit; determining an active power surplus corresponding to the torque surplus; controlling the line-side converter according to the virtual synchronous machine control scheme using an input parameter configured to reduce the active power output of the line side converter by the active power surplus.