Wind Turbine Pitch Drive Speed Control via Field Flux Regulation
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Solution Overview
Problem
Conventional pitch drive systems in wind turbines face challenges with speed regulation, particularly with series-wound DC motors that have high starting torque but poor speed regulation, and shunt-wound motors that lack starting torque but offer good speed regulation, necessitating a solution that balances these characteristics.
Innovation Solution
A pitch drive system incorporating a direct current (DC) motor with a series-field winding and a current-controlling device, such as a resistor or diodes, configured between the battery assembly and the series-field winding to ensure non-zero field flux, thereby improving speed control and flattening the speed versus torque curve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a series-wound DC motor is used in the pitch drive system, then high starting torque is achieved, but speed regulation deteriorates
Solution Approach 1:
A current-controlling device is introduced as an intermediary component between the power source and the series-field winding. This device regulates the field current independently, preventing field flux from reaching zero and thereby maintaining speed control while preserving the high starting torque characteristic of series-wound motors.
Solution Approach 2:
The invention dynamically controls the field current parameter through the current-controlling device. By adjusting the field current to maintain non-zero field flux, the system changes the magnetic field parameters to achieve both high starting torque and improved speed regulation that would otherwise be mutually exclusive.
2Speed
If a shunt-wound DC motor is used in the pitch drive system, then good speed regulation is achieved, but starting torque deteriorates
Solution Approach 1:
The motor winding system is segmented into separate armature and series-field components with independent current control. This segmentation allows the field current to be controlled independently to maintain torque while the armature current provides speed regulation, combining benefits of both motor types.
3Speed
If a compound DC motor is used to balance starting torque and speed regulation, then both characteristics are improved, but device complexity increases
Solution Approach 1:
The invention extracts the speed control function from the motor structure itself and places it in a separate current-controlling device. This allows the motor to maintain the simple series-wound structure while the external controller provides the speed regulation that would otherwise require a complex compound motor design.
Solution Approach 2:
The current-controlling device serves as an intermediary that decouples the relationship between field current and armature current. This intermediary control mechanism achieves compound motor performance without requiring the complex dual-winding structure of a true compound motor.
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
The proposed solution enhances speed regulation by preventing field flux from reaching zero, reducing maximum speed, and preventing power regeneration back into the battery, offering improved performance over conventional systems while being simpler and more economical than compound DC motors.
Implementation Method 1
A pitch drive system incorporates a direct current (DC) motor with a series-field winding and a current-controlling device, such as a resistor or diodes, configured between the battery assembly and the series-field winding to ensure non-zero field flux, thereby improving speed control
Data Source
AI summary
The present subject matter is directed to a system and method for improving speed control of a pitch drive system of a wind turbine. In one embodiment, the pitch drive system includes a direct current (DC) motor having an armature and a series-field winding, a battery assembly having a positive terminal and a negative terminal, and a current-controlling device configured in series between the positive terminal of the battery assembly and the series-field winding. The battery assembly is configured to supply power to the pitch drive system and the current-controlling device is configured to supply current to the series-field winding so as to ensure a field flux does not equal zero. Thus, the current-controlling device has the effect of limiting the maximum speed of the DC motor.