Multi-loop Switching Control for Doubly-fed Wind Turbines
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Solution Overview
Problem
Traditional vector control systems for doubly-fed wind turbines struggle to maintain stability during large disturbances, such as three-phase short circuit faults, due to their inability to fully utilize control energy and return the system to its original balance point quickly.
Innovation Solution
A multi-loop switching control system based on logic switch control is introduced, which enhances the robustness of doubly-fed wind turbines by using relative order information instead of precise system parameters, allowing for faster convergence to the balance point and switching between traditional vector control and logic switch control to optimize system performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If traditional vector control systems are used for doubly-fed wind turbines, then the control system is simple to implement, but the system cannot return to the original balance point quickly after large disturbances such as three-phase short circuit faults
Solution Approach 1:
The control system dynamically switches between traditional vector control mode and logic switch control mode based on system operating conditions. During normal operation, traditional vector control is used for simplicity. When large disturbances occur, the system transitions to logic switch control to achieve rapid convergence to the balance point, thus adapting the control strategy to different operational states.
Solution Approach 2:
The invention changes the control parameters by introducing logic switch control with binary control signals (u1, u2, u3, u4) that take values of 0 or 1. This parameter change enables the system to exert maximum control energy during disturbances, allowing rapid return to the balance point while maintaining manageable complexity through the binary nature of the control signals.
2Power
If traditional PI control is used to achieve maximum power tracking and active-reactive coordinated control, then the control parameter tuning considers rapidity and steady-state error synthetically, but the system cannot exert maximum control energy when deviating from the original operation point after great disturbances
Solution Approach 1:
The logic switch control applies partial control actions through binary signals (0 or 1) that selectively activate control components. This partial action approach allows the system to exert maximum necessary control energy during disturbances without requiring full continuous control, enabling reliable stable operation while recovering from deviations caused by great disturbances.
Solution Approach 2:
The control system is segmented into multiple independent logic switch control modules (u1, u2, u3, u4) that can be independently activated. This segmentation allows the system to apply control energy selectively to different aspects of the system state, improving reliability by addressing specific deviation components while maintaining overall system stability after disturbances.
3Loss of time
If switch control based on Hamiltonian equation is used to achieve time optimality, then the controlled system dynamically exhibits optimal time performance, but the Hamiltonian equation becomes very complicated when using all state variables of all parameters of the entire system
Solution Approach 1:
The invention extracts only the essential relative order information from the complete system state variables, eliminating the need to use all parameters in the Hamiltonian equation. By taking out only the critical information needed for control decisions, the system achieves rapid time-optimal convergence to the balance point while keeping the control logic simple and manageable.
Solution Approach 2:
The logic switch control uses simple binary control signals (u1, u2, u3, u4) that are computationally inexpensive and easy to implement. These simple control elements replace the complex continuous control required by full Hamiltonian equations, achieving comparable or superior time-optimal performance with much lower computational complexity and easier implementation.
Data Source
AI summary
A multi-loop switching control system for a doubly-fed wind turbine based on logic switch control. Output variables of the doubly-fed wind turbine may be used to form output feedback control channels. Each output feedback control channel may switch between a switch controller and a vector controller to form a multi-loop switching controller. When a power system associated with the doubly-fed wind turbine is subjected to a relatively large external disturbance, state variables and the output variables of the wind turbine deviate from an original balance point, and the output feedback control loops of the doubly-fed wind turbine are switched from the vector controller to the switch controller. Under control of the switch controller, the state variables and output variables return to a vicinity of the original balance point, and the output feedback control loops of the wind turbine are switched from the switch controller to the vector controller.