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Can grid-tied inverter operate in parallel with diesel generator?

Updated: Sep 15, 2021

The sole purpose of the grid-tied inverter is to convert DC [Direct Current] power generated from solar panels into AC [Alternate Current] power in synchronization with a reference power source electrically paralleled with it. Most of the time, this reference power source is a grid but if you want to use a diesel generator as a reference power source then there is some protection you will be required to successfully operate.

I heard this question lot of time from lots of creative people who think beyond the market standard practice and want to achieve something out of the textbook.

Here I am going to answer the question “Can grid-tied inverter operate in parallel with diesel generator?”.

The grid-tied inverter can be used in parallel with a diesel generator, but you will require a device called ZED advance to protect your diesel generator from the reverse power generated from the grid-tied solar power plant. Grid-Tied solar power plants produce reverse power during the excess power generation (that is when power generation > load demand) and this reverse power will burn down the diesel generator. ZED Advance protect diesel generator from this reverse power by ramping down the power generation from the solar inverter as per the load demand.

The above diagram shows how you can use the generator as a reference power source and run your grid-tied solar power plant.

As shown in the above diagram, you will be required the following.

Transfer switch to select a power source from Grid or Generator.

  • Input#1 with CT [current transformer] from Generator

  • Input#2 from Grid

  • Output#A to Input#2 of Combiner Box

The current transformer at Input#1 of the Transfer switch sends the load feedback to ZED Advance.

Combiner Box to combine the power from transfer switch (Grid/Generator) with Grid tie inverter.

  • Input#1 from Grid Tie Solar Inverter.

  • Input#2 from Output#A of Transfer Switch.

  • Output#A to Home Load.

10 Core, 1.5 Sqmm Cable: For connecting Current transformers with ZED Advance.

3 Core, 1.5 Sqmm Cable: For Voltage feedback as well as a power source to ZED Advance.

CAT6 LAN Cable: To connected ZED Advance with the Solar inverter as well as with local area internet for remote monitoring of the Solar power plant as well as the Generator.

When grid power is not available select a power source from the generator (Input#1) via transfer switch and starts your generator.

CT (at Input#1) will measure the current flows and feedback to ZED Advance.

For the first few minutes, the whole load will be served by Generator. During this time ZED advance to analyze the load and start the Grid-tie PV inverter.

After a few minutes your solar power plant will start running again but in synchronization with a generator.

Curious about ZED Advance? Click here to know more

Related post:

Key features of ZED Advance

  1. With ZED Advance you can go Solar without Net Metering or Gross Metering.

  2. With ZED Advance you can Syn your Generator with your Gird connected Solar power plant

  3. With ZED Advance you can monitor your PV plant, Generator and Grid.

  4. With ZED Advance you can use your Grid-tie PV plant even in Power cuts.

  5. ZED Advance is compatible with 17 plus makes of Solar inverters.


How does ZED Advance work with Generator?

For the synchronization of PV plant (solar plant) with Generator, ZED Advance is required, with the set the sharing point at 30%.

30% of sharing points means that ZED advance will make sure that Generator will be 30% loaded and rest of the load will be served by PV plant. ​

But why 30% ??, operating a Generator at a load less than 30% of rated capacity for extended time periods impacts the unit negatively.

These impacts include engine exhaust slobber, which is also known as exhaust manifold slobber or wet stacking. Engine slobber is a black, oily liquid that can leak from exhaust manifold joints due to extended low- or no-load scenarios.

Running at high idle with little or no load reduces the heat in the cylinder, allowing unburned fuel and oil deposits to leak through the exhaust slip joints. Click here to learn more about the same.

To understand the sharing of load between the Generator and the PV plant during a power failure, let's take an example, where the PV plant is producing 100kW, Generator Rating is 250kVA (200kW) and the total load is 120kW then suddenly power failed.

For the first few minutes, the whole load is shifted on the Generator because Solar inverters take few minutes to restart or start producing power

During these few minutes, the integrated power analyzer of ZED Advance monitor the load and communicate with the solar inverter, so that during starting Solar inverter produce power as per the setpoint to keep Generator set 30% loaded.

So 120kW of load will be shared between Generator and PV plant, i.e 60kW on Generator (30% of 200kW or 250kVA) and PV plant will produce 60kW instead of 100kW.

Now either Load varies or PV plant's output power varies.

In case of the load varies, if the load goes below 30% of the Generator rating, ZED Advance will completely Shutoff the PV plant.

And when the power comes back, the PV plant will start running normally.


1 Comment

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Jun 11, 2023
Rated 5 out of 5 stars.

Thank you dude, your animation wrap up all the good and easy explanation. It made my day.

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