The aim of this article is to help all those who, like me, have worked for a long time in the photovoltaic world, acquired knowledge and accurate practices, and wish to enter the marvelous world of solar pumping.
Specifically, this article deals with the variable speed drive as the main element for the search for the mppt of the panels and the control of the pump at the same time.
Not all drives are suitable for this, of course, but it is perfectly possible. It is a great option, because having the control of the pump and the photovoltaic field in the same microcontroller, everything is done faster and more efficiently.
If you add the possibility of managing an electronic group (and its heating during the start), or the electricity grid, as support for the solar contribution, we have a very powerful product.
I emphasize, the word “support“, which means to provide the missing energy with the group, not to commutate from one system to another.
I will then detail the main points to be taken into account:
- Normally with a solar inverter we inject energy from the panels to the grid. The main idea is to understand that managing the electrical network to inject energy is not the same as managing a pump, and if we do not take the necessary care with the pump, the result will be damage.
- The continuous (DC) input voltage ranges of an inverter are not the same as those of a solar inverter. Not because of limitations of the inverter, but because the operating voltages of the pump must be respected, and for this purpose the recommendations of the inverter manufacturer must be strictly followed.
- Always respect the motor distances recommended by the manufacturer of the inverter, because they depend on its filters.
- Make sure the drive is ready to work on this application, not everyone is.
- Continuous (DC) protections are very important, and should include an isolation guard.
- It is not possible to use photovoltaic panels by connecting one of their poles to earth. The pumps have a bad habit of short-circuiting, which would cause a damage inside the drive.
- My recommendation is to start through a radiation probe. A pump, unlike an inverter, needs a minimum power to reach the minimum speed for water extraction and cooling. Thus, the proper starting of that pump is vital, and without the probe, false starts can occur that will result in a reduction in its useful life.