Virtual Synchronous Wind Turbine Inverter Control for Torque Peaks
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Solution Overview
Problem
Wind turbines configured as virtual synchronous machines experience high mechanical loads in response to grid disturbances due to high generator power and torque peaks, which can be exacerbated by phase jumps and overcurrent thresholds.
Innovation Solution
A method to limit generator power and torque by determining adaptive maximum grid current values based on generator load, using virtual impedance and impedance-based control to manage grid current, incorporating virtual synchronous machine principles to stabilize the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a high overcurrent threshold is used in VSM configured wind turbine, then the wind turbine can operate with higher current capacity, but grid disturbances such as phase jumps can lead to high peak in generator power and generator torque causing undesired mechanical peak load
Solution Approach 1:
The patent applies dynamics by making the maximum grid current value adaptive rather than fixed. The control system continuously adjusts the maximum grid current value based on the current generator load, allowing the threshold to dynamically respond to changing operating conditions. This resolves the contradiction by enabling high current capacity during normal operation while automatically limiting peak currents during disturbances that cause mechanical stress.
Solution Approach 2:
The patent changes the parameter of maximum grid current value from a constant high threshold to a variable parameter that adapts based on generator load. By modifying this critical parameter dynamically, the system achieves both high current capacity utilization and protection against mechanical peak loads during grid disturbances.
2Object-affected harmful factors
If the maximum grid current value is limited to protect against mechanical loads, then generator load peaks are reduced, but the system may require very small or very large threshold values which can be problematic
Solution Approach 1:
The patent implements feedback by continuously monitoring the generator load and using this information to adjust the maximum grid current value. The control system measures the current generator load, compares it with the maximum generator load, and accordingly determines an appropriate maximum grid current value. This feedback mechanism avoids the need for manually tuned extreme threshold values and automatically adapts to operating conditions.
Solution Approach 2:
The control system performs self-service by autonomously determining appropriate current limits based on its own operating state. The system uses its measured generator load to automatically set its own maximum grid current value without requiring external intervention or complex external control mechanisms, thereby simplifying the overall system architecture.
Data Source
AI summary
Limiting generator loads in a wind turbine having a power converter with a line side inverter configured as a grid forming inverter. A maximum grid current value is determined based on a measured generator load and a limit function. A virtual impedance value and a virtual voltage drop over the virtual impedance value are determined. A virtual synchronous machine angle is determined based on a power reference and the virtual grid power. The voltage reference for controlling the line side inverter is determined based on the virtual synchronous machine angle, the virtual voltage drop and the voltage magnitude reference.