Who can Industrial Microgrid Design: Solar VFD Loads First, Export Excess PV to Generator-Based Grid

Q&A and troubleshooting DESS
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1

Hello,

I own a stone and marble cutting factory equipped with several three-phase 380V electric motors.

My motors are:

- One 75kW motor

- Two 22kW motors

- Two 15kW motors

- Two 7kW motors

- Several smaller motors ranging from 1.5kW to 3kW

The actual measured power consumption during normal operation is approximately 80 to 100kW, even when the 75kW motor is running.

I want to install a solar power system without batteries (except for a small battery for nighttime lighting).

My goals are:

1. To power all factory loads directly with solar energy using a phased start/variable frequency control system for the larger motors.

2. To use the 265kW diesel generator only as a backup during cloudy weather or at night.

3. Exporting surplus solar energy to a local grid powered by diesel generators (250 kW and 500 kW generators).

4. Prioritizing factory loads and automatically exporting only unused solar energy.

5. In the event of factory closure, I want to export all available solar energy to the local grid as needed.

6. I do not want to import energy from the grid.

A supplier has offered me the following:

- A 154 kW photovoltaic solar panel system (214 panels x 720 W)

- A 160 kW solar pump/variable frequency inverter

My question is:

What is the best system design to achieve:

“Prioritizing loads and exporting surplus energy”?

Can this be achieved using solar variable frequency inverters in addition to a grid-tied inverter and an energy management system controller?

Or is there a better solution for a small industrial grid?

Additional Requirements:

I want to integrate a 265 kVA diesel generator into the system so that it automatically starts when solar power drops due to cloud cover, low solar irradiance, or high power demand.

My main objective is to ensure all motors operate continuously without interruption.

When solar power output falls below the required load, the generator should automatically start to meet the load.

When sufficient solar power is available and stabilizes, the generator should automatically shut down.

Is it possible to achieve seamless automatic generator start/stop using Victron equipment while ensuring all motors operate continuously without any interruption?

The motors must continue to operate during the transition between solar and generator power.

Thank you.

2

Its not possible with victron equipment without batterys… they are battery based systems

For such a large system contact your local official victron dealer, they can help you with system design

3

Based on your requirements and the consolidated load characteristics, I can assure you this is an HV system. The use of LV equipment in this case would be entirely impractical.

Without 800V battery arrays, no UPS function for uninterrupted operation or seamless transfer to the generator set can be achieved.

The PV arrays to be deployed will operate at 1500V.

Altogether, this falls under the class of industrial systems, and there are not many manufacturers of such systems when we speak of quality. Beyond that, you will need to begin with an engineering audit of the existing technical conditions, followed by ordering the design documentation, equipment specification, procurement, installation, commissioning, adjustment, and final handover into service.

That is the plan of action.

You may provide me with your GRID CODE and location details in a private message, and we may then be able to discuss prospects for cooperation.
I hold the appropriate qualifications and authorisations for the design and management of such projects. My portfolio includes systems up to 0.6 MW.

4

Thank you for your feedback.

My main goal is not to operate the entire factory from batteries.

I have a stone and marble processing factory with several VFD-controlled motors. The actual power consumption is usually between 80 and 100 kW.

What I am looking for is a system where:

Solar PV supplies the loads first during the day.

Excess solar power can be exported to the generator-based grid when available.

A 265 kVA diesel generator starts automatically when solar production drops due to cloud cover or insufficient irradiation.

The transition must be seamless, without stopping, tripping, or restarting the motors and VFDs.

5

Thank you for your detailed response.

I would like to clarify that the concept of operating the factory from solar power has already been implemented successfully in similar industrial applications.

My main question is not about whether the factory can run on solar power, but about two specific functions:

  1. Exporting excess PV energy to the generator-based grid when solar production exceeds the load demand.
  2. Automatic generator start and stop based on solar availability and load demand, without interrupting the operation of the motors or causing VFD trips during cloud passages.

The generator is rated at 265 kVA, and I am looking for a seamless transition between solar and generator operation.

Is this functionality achievable with Victron DESS/ESS architecture, or would another control strategy be required?

Thank you for your time and expertise.

6

Yes thats possible, but not without batterys

7

Everything you need to know and take into account has already been stated above. Furthermore, it is not only me who has pointed out that some of your requirements, particularly:

cannot be achieved without battery energy storage systems.

Once again, I would like to emphasise the key point: in this case, low-voltage energy storage and conversion systems are less efficient. In addition, it is more than likely that your case will require parallel segments responsible for portions of the load, and proper load balancing will be essential.

Only a high-voltage system!

Good luck.

8

Like others have stated you will need a battery backup to achieve your goals. When operating VFD’s, the battery part can be actually a simple solution. Most VFD’s are equipped with a DC link input. When you choose the battery voltage within the nominal link voltage (dependent on your normal grid voltage; eg. at 480Vac, link voltage is around 650Vdc ).

The solar will charge the battery direct at very high efficiency (>95%), and since the VFD’s run on DC, you’ll need a much smaller AC-inverter to run the other loads.

Both the grid and the generator can than be coupled to the DC-bus with a suitable rectifier and charger.