Many people in the wind energy industry use the term “pitch control system” in place of “pitch actuator system,” and vice versa. They’re not quite interchangeable, though.
The blade pitch actuator is a subsystem of a wind turbine’s pitch control system. For a pitch-regulated turbine, you need a pitch control element within the overall control system. The pitch control system creates pitch angle demands through the actuator subsystem.
That doesn’t mean the pitch actuator’s less important. It includes everything from the motor itself to the hardware that runs the motor to the AC main power connection.
The Job of a Pitch Actuator System
A pitch actuator has several responsibilities. The more developed the actuator, the greater its capabilities: Here’s what your actuator is ideally doing for your turbine’s success:
1. Ensuring the Safety of the Turbine
The actuator must act as an independent safety brake for the entire system. This includes slowing or stopping the turbine during a malfunction. Nothing else can shut it down -- your pitch actuator is your last line of defense.
2. Guaranteeing Pitch Angle Demands Set by the Main Control System
Putting these demands into action happens in one of two ways:
The traditional way: Most control systems have to account for errors instantaneously. They only have a closed-loop response to the issue and don’t include a command generator. This can unnecessarily “excite” the blade, hampering efficiency.
The better way: A more advanced and sophisticated response system constrains the rate of change in the pitch angle according to the windmill’s physical capabilities. This creates a nice, smooth trajectory and a less “excited” blade.
3. Apply Commands in a Way That Supports the Turbine
Your actuator response behavior should be matched and harmonize with the:
- And more!
The actuator should support zero-volt and low-volt ride-through. This means that if electrical power is intermittent or totally out, your system will run from a backup power source without faulting.
Turbines are often in volatile and remote environments, so it’s essential that they can handle situations that aren’t ideal.
4. Grid Connection Compatibility
Early systems transferred at the slightest hint of grid loss. With more wind power penetration on the grid these days, a short power drop (think of your lights flickering in your house) isn’t a cause for panic.
If you have a 1,500 MW wind power plant operating on a grid, you could lose 100 MW. Obviously, electric utilities couldn’t handle that. This is why an actuator needs to be able to function without the grid.
5. Providing Feedback to the Main Controller
The actuator provides feedback such as:
- Pitch angle
- Pitch torque
- A whole lot of status data
Beyond that, the pitch actuator should give real time condition monitoring data. It’s a health report of sorts on your windmill. Real time operating data can be sent back and checked by main controller to allow for preventative maintenance and optimal performance.
Availability is huge in the industry. If you can detect an issue ahead of time, that’s huge!
6. Surveilling Protection Parameters Within the Actuator Itself
An actuator has a few options if something’s not right with your turbine.
- The actuator can let you know something needs attention. Your turbine will continue running in this scenario.
- In “operating fault conditions,” the actuator tells you it must shut down the turbine. Fortunately, you have a chance to do so in a controlled fashion.
- In “emergency fault conditions,” the actuator will declare an emergency and will shut down the turbine. Whether you like it or not.
7. Condition-Based Historical Monitoring
Electrical utilities have SCADA systems -- SCADA stands for supervisory control and data acquisition. Tons of data is coming out of that pitch actuator -- so much so that there’s a bottleneck. SCADA might really only see what’s going on in that turbine every 10 minutes.
In a more advanced pitch actuator, intelligence and memory processor resources compile data about historical conditions of the actuator:
- What’s its lifetime average speed?
- What’s its lifetime average torque?
- What’s the highest torque it’s ever experienced?
- Other historian format data
You can then use this analysis to your turbine’s benefit.
Pay Now or Pay Later
The pitch actuator design process allows for cost-efficient use of ultracapacitor power backup. The process and technology offer reliable and maintenance-free solutions at the lowest possible cost.
The seven points above underline how crucial a high-quality pitch system to the success of your wind energy efforts. Price should never be the sole factor in your equipment purchase decisions!