Electronic Speed Control of a Generator

Soul21 said:

I am trying to better understand methods that can electronically control the speed of a generator (specifically). The generator will be spinning using mechanical energy generated by air through a pipe. The electricity will be sent to a load or battery bank.

I thought a VFD might be the solution, but have begun second guessing if it is feasible. Another solution that may be adjusting the resistive load using a phase angle fired. A third option might be to use a controller such as ODrive (link). I am open to any input or suggestions.

For clarity sake - I know there are mechanical ways to control speed used on most large geneators (e.g., brakes, blade pitch, control valves), that are the preferred method due to efficiency war robots hack 2022. I am looking for electronic solutions due to surplus of energy and no control over the mechanical input.

Thanks in advance!

Click to expand...

Controlling the speed of a generator using electronics is certainly possible and there are a few different methods that can be used. One common method is to use a Variable Frequency Drive (VFD), which can adjust the frequency and voltage of the output from the generator to control the speed of the motor driving it. However, as you mentioned, VFDs may not be feasible for your particular application, so there are a few other options to consider. One option is to use a phase angle fired controller, which can adjust the resistance in the circuit to control the power delivered to the generator. This method is often used for controlling the speed of DC motors, but can also work for AC generators. Another option is to use a servo drive controller, such as the ODrive that you mentioned. These controllers are designed for controlling the speed and position of servo motors, but can also work for controlling the speed of a generator. However, it may be more complex to set up compared to other methods, and may require additional hardware. Ultimately, the best solution will depend on your specific requirements and the characteristics of the generator and load. It may be helpful to consult with an electrical engineer or other expert in this area to help determine the most appropriate solution for your application.

christinescoms said:

Controlling the speed of a generator using electronics is certainly possible and there are a few different methods that can be used.

Click to expand...

All of that is true if the generator is electrically powered. But in his case he is powering the generator with air that he is stealing from an existing pipe. And he doesn't want to use a valve to control the air.

As a curious observer of this thread, has the following information been revealed yet:

How big (diameter) is the pipe which is supplying the air?
What is the pressure of the air in the pipe?
What is the flowrate of the air in the pipe? ie the air which is feeding "other equipment"
How much power is the OP hoping to produce from this generator?

So many questions, so little information.

JimB

When you characterize the load impedance at different R vs RPM*Torque=Power there will always be an optimum R which matches the generator incremental impedance as defined by MMTP. This can be found using open cct voltage / short circuit current using pulses Zmpt=Voc/Isc= R. Other methods are hunt and measure VI power transfer for maximum. But it is always at matched impedance. This may be constant if the wind source is also constant otherwise, dynamic. The most effective way to control R is the charging current into a battery and load, but batteries also need CC, CV , OV and UV protection.

Another example of the XY problem.....

duplicate

BobW said:

The problem is that you can't avoid physics. What the turbine/generator takes in, in mechanical energy, must be delivered to the final load as electrical energy. Anything that's left over is converted to heat. Unless you get rid of the heat, you have problems. You have two options:
1. Don't allow the turbine/generator to receive any more mechanical energy than it needs to deliver to its electrical load, so that there's no waste heat.
2. Provide a means to dissipate the waste heat.

With the first option, you would either have to divert air flow away from the turbine/generator, or feather the turbine blades, neither of which appear to be practical in your case.

In the second case, you need to dissipate the generated waste heat. Since you seem to have lots of air flow, you could divert the electrical power not required by your electrical load to a bank of power resistors, cooled by the same air stream that supplies power to the generator. In this case, the problem reduces to a load controller circuit

Click to expand...

The second option of heat dissipation is an option that I would like to explore. If I wanted to control the load and make it variable in order adjust the speed of the generator what type of controller would be acceptable. Is a phase angle the best option or would a field oriented controller be better? Are there other options that would work?

Phase angle relies on predictable AC frequency, as you are using the intervals between zero crossings to predict when to next fire to give the required phase advance.

If it's going to be rectified anyway, which not just limit it after rectification, which is far simpler?

Assuming the use of an AC generator. You propose some kind of limiter prior to rectification to DC and feed into the battery. Could you explain what would that limiter look like?

Here is some information that I have found. I wanted to get thoughts on the VFD as it seems like many are of the opinion that it is not a good candidate for controlling generator speed.

The most common types of generator control include:

1. Load banks: Load banks are resistive loads that are connected to the generator to simulate a load. They can be adjusted to provide a specific load, which in turn affects the speed of the generator. Load banks can be used to test generators, ensure that they are operating at the correct speed, and provide a stable load in applications such as backup power systems.
2. Electronic controllers: Electronic controllers, such as variable frequency drives (VFDs), are used to control the frequency of the AC power output to the generator. By adjusting the frequency, the load on the generator can be varied, which in turn changes the speed. Electronic controllers are commonly used in applications where precise control over the speed of the generator is required.
3. Mechanical controllers: Mechanical controllers, such as governors, are used to control the speed of the generator by adjusting the fuel supply or other mechanical components. These controllers typically work by detecting the speed of the generator and adjusting the load or fuel supply to maintain a constant speed.
4. Inverter-based controllers: Inverter-based controllers are similar to electronic controllers but use advanced inverter technology to provide more precise control over the frequency and voltage of the AC power output. These controllers are commonly used in applications where high-quality power output is required, such as in sensitive electronic equipment.

Found this and thought it was useful

You still have no clue, do you?

Soul21 said:

That's fair. The primary purpose of air flow is for other uses that supersede energy generation. If the end use of the air flow is in high demand the generator must spin as free as possible. The air flow speed/pressure fluctuates quite a bit both from supply and demand sides. I understand a smart valve system with bypass could also be put in place, but I wanted to explore the option of controlling generator speed.

Click to expand...

The text highlighted above is why, at least as I understand it, what you're asking for is not what you want.

Adding a load to the output of the generator in order to slow it down will prevent the generator from spinning as freely as possible. In fact, anything that limits the speed of the generator to less than it's free spinning speed, will impede the airflow.

I should have added a second sentence after that one that reads. "if the End use of the air flow is in low demand the generator may inhibit flow in order to create electricity."