Feb 21, 20219 min read

3 ways to use grid-tied solar during power outage [without replacing PV inverter]

Updated: Jun 9

Content Table

Reliability of Grid Connected PV Plant during a power outage.
3 Ways to use Grid-connected power plant during a power outage

A power outage is a nightmare of the modern lifestyle, electricity has many uses in our day-to-day life.

We use electricity for lighting our rooms, cooling or heating our rooms, and running our domestic appliances like microwaves, electric shavers, computers, and more. We use lots of electricity-driven appliances to provide comfort to our lives.

As our need for luxury appliances increases, unit chargers of this precise source of energy called electricity increase too.

Now the harsh truth, the environment is paying much more than us for our need for electricity.

As I read on world-nuclear.org, and I quote exactly “When the coal of say 2.5 percent sulfur is used to produce the electricity for one person in an industrialized country for one year, then about 9 tonnes of CO2 and 120 kg of SO2 are produced” read more on their site.

This lust for comfort, the desire for savings, and the necessity of saving the environment generates the requirement for solar power plants to reduce our electricity bills and make electricity affordable for us.

This demand for affordable electricity and saving the environment fuel the massive growth of the solar industry. And in just 9 years the total installed capacity of solar power has increased by 14.3%.

Here is the big question,

How much is grid-connected solar power reliable during a power outage?

Grid-connected solar power plants are not as reliable as off-grid solar power plants. but with ZED advance Grid-connected PV plants can work off-grid and become reliable as an off-grid solar power plant.

Now here is an in-depth answer and the solution you are looking for.

The two main parts of an On-grid solar power plant are solar panels and an on-grid [grid tie] solar inverter. These type of PV plants is suitable for areas with low or negotiable power failure.

But, during power outrage, the grid-connected solar power plant is impractical even on the sunniest days of the year. Because on gird solar power plants can't generate electricity without reference power source [grid].

Grid is not the only option available to generate a reference power source for girding tie solar power plants. Other options like home inverters, UPS with batteries, or generators can also generate reference power for the grid-tie solar power plant.

Now, the problem with these other options is that If the PV plant generates excess power. Then this excess power will be reversed back to the source of reference power.

Expect grid, none of the other options of reference power source can take this reverse power and survive.

But with the right equipment and knowledge, anyone can generate electricity from an On-grid solar power plant on the grid.

How to use a grid-connected solar power plant during a power outage?

The answer is here: You can use your grid-connected solar power plant during a power outage with the help of ZED Advance. With ZED advance you can use your home inverter/ups and generator as a reference power source for your grid-connected solar power plant.

Way#1: Use a generator as a reference power source
Way#2: Use Home inverter/UPS are reference power
Way#3: Use both generator and home inverter/UPS are reference power.

ZED advance monitors the power demand at the coupling point and controls the power generation from the solar inverter as per the set point. Setpoints of ZED advance can vary [in percentage] from 0 to 100.

The value of the setpoint depends upon the type of reference power source available. However, the criteria of the setpoint for the generator are completely different from the criteria of the setpoint for home ups/inverter.

ZED Advance set point for Home inverter/UPS

If the home ups or inverter is available as a reference power source then setpoint will be a percentage of the load. This will be the minimum load shared by the home inverter or UPS. For home UPS/inverter recommended step point depends upon the load variation.

If the frequency of load changing is low, the setpoint can be as low as 2 to 5%. And if the load variation is high, the setpoint can be between 10 to 20%.

ZED Advance set point for Generator

If the generator is available as a reference power source then the setpoint will be a percentage of generator size. This will be the minimum load shared by the generator.

It is recommended to keep the generator 30% loaded, thus recommended step point for the generator is 30%

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

Curious about ZED Advance? We make a whole page on “ZED Advance” go and checkout and it will help you will be able to select the correct solution for your need.

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 impact of running the generator at a low load.

This process of closed-loop control of solar power generation [Power generation as per demand] eliminates any possibility of excess power generation. And without excess power generation, you can use any non-grid reference power source to sync with a grid-connected solar power plant.

Use a Generator as a reference power source, to start On-grid Solar Power Plant During Power Outage

The above diagram shows how you can use the generator as a reference power source and run your grid-connected solar power plant during a power outage with ZED Advance.

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

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

Input#1 with CT [current transformer] from Generator
Input#2 from Grid
Output#A to Input#2 of Combiner Box

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.

During Power outage

When grid power is not available select a power source from the generator (Input#1) via the transfer switch and start 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 analyzes the load and starts the Grid-tie PV inverter.

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

Grid Power is available.

When the grid power is available, just stop your generator first and transfer the power source from a generator (Input#1) to the grid (Input#2).

In the absence of Load feedback to ZED Advance, it won’t control the output power of the Gird tie solar inverter.

Hence Gird tie PV inverter will work normally and excess power will be injected back to the grid.

Curious about ZED Advance? We make a whole page on “ZED Advance” go and checkout and it will help you will be able to select the correct solution for your need.

Use a Home inverter/UPS are reference power to start an On-grid Solar Power Plant During a Power Outage

Using a Home inverter/UPS as a reference power source is different from using a generator.

The reason is that you will be required Home inverter/UPS to charge from the Grid during normal days. So, you can’t keep the Home inverter/UPS completely isolated from the grid just like you can do with the Generator.

As shown in the above diagram you will require.

Transfer the switch to select a power source from UPS or Grid + UPS.

Input#1 with CT [current transformer] from Home inverter/UPS.
Input#2 from Output#A Combiner Box#1.
Output#A to Input#2 of Combiner Box#2.

Combiner Box#1 to combine the power from Gird and Home inverter/UPS.

Input#1 from Home inverter/UPS.
Input#2 from Grid
Output#A to Input#2 of Transfer Switch.

Combiner Box#2 to combine the power from the Transfer Switch and Solar Inverter.

Input#1 from Gird Tie Solar Inverter.
Input#2 from Output#A of Transfer Switch.
Output#A to Home Load.

During Power outage

When grid power is not available select a power source from Home Inverter (Input#1) via a transfer switch.

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 Home Inverter. During this time ZED advance analyzes the load and starts the Grid-tie PV inverter.

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

Grid Power is available

When the grid power is available, just stop your Home Inverter first and transfer the power source from the Home Inverter (Input#1) to the Home Inverter + grid (Input#2) via a transfer switch.

In the absence of Load feedback to ZED Advance, it won’t control the output power of the Gird tie solar inverter.

Hence Gird tie PV inverter will work normally and excess power will be injected back into the grid.

Curious about ZED Advance? We make a whole page on “ZED Advance” go and checkout and it will help you will be able to select the correct solution for your need.

Use both generator and home inverter/UPS as reference power to start an On-grid Solar Power Plant During a Power Outage

If you have both generator and home inverter/ups and you want to use both as a reference power source for your grid-connected solar power plant.

Then there are three things you need to consider.

You can use both generator and home inverter at a time you can only either one of them at a time.
The home inverter should get charged with both girds as well as generator power.
Home inverter and generator require different set points hence two different load feedbacks (two sets of current transformers) are required.

As shown in the above diagram you will require.

Transfer switch#1 has the following input and outputs.

Input#1 with CT [current transformer] from Home inverter/UPS.
Output#A to Input#2 of Combiner Box#2.
Output#B to Input#1 of Transfer Switch#2.

Transfer switch#1 is used to select either of the following options.

a. Home inverter + Gird or Generator operation

b. Home inverter + Solar Operation

When Input#1 is connected with Output#A, a Home inverter + Gird/Generator operation will be performed.

When Input#1 is connected with Output#B, Home inverter + Solar Operation will be performed.

Transfer switch#2 has the following input and outputs.

Input#1 from Transfer Switch#1.
Input#2 with CT [current transformer] from the Generator.
Output#A to Transfer switch#3.

Transfer switch#2 is used to select either of the following options.

a. Home inverter + Solar Operation

b. Generator + Solar Operation

When Input#1 is connected with Output#A, a Home inverter + Solar operation will be performed.

When Input#2 is connected with Output#A, Generator + Solar Operation will be performed.

Transfer switch#3 has the following input and outputs.

Input#1 from Transfer Switch#2.
Input#2 from Grid.
Output#A to Combiner Box.

Transfer switch#3 is used to select either of the following options.

a. Home inverter or Generator + Solar Operation

b. Grid + Solar Operation

When Input#1 is connected with Output#A, a Home inverter or Generator + Solar operation will be performed.

When Input#2 is connected with Output#A, Grid + Solar Operation will be performed.

Combiner Box has the following inputs and outputs.

Input#1 from Solar inverter.
Input#2 from Transfer Switch#1.
Input#3 from Transfer Switch#3.
Output#A to Home Load.

A Combiner Box is used to combine the power from the Home Inverter, Solar inverter, and grid/generator as per the selection from Transfer switches.

During Power outage

During a power outage, you have two options for selecting power sources

a. Solar + Home invert and

b. Solar + generator

To select solar + home inverter following procedures are required:

Transfer Switch#1 : Input#1 + Output#B

Transfer Switch#2 : Input#1 + Output#A

Transfer Switch#3 : Input#1 + Output#A

CT [Current transformer] at Output#B of Transfer Switch #1 will measure the load on the Home inverter and feedback to ZED Advance.

ZED Advance controls the output power of the solar inverter so that no excess power can be generated.

To select a solar + generator following procedures are required:

Transfer Switch#2 : Input#2 + Output#A

Transfer Switch#3 : Input#1 + Output#A

CT [Current transformer] at Input#2 of Transfer Switch #1 will measure the load on the Generator and feedback to ZED Advance.

ZED Advance controls the output power of the solar inverter so that no excess power can be generated.

If you want to charge your Home inverter from the Generator, you can select Input#1 of Transfer switch#1 with Output#A.

Grid Power is available

When grid power is available you want to use grid power with a solar power plant to take advantage of NET metering.

As well as you want to charge the batteries of your home inverter. Just follow the below procedures.

Transfer Switch#1 : Input#1 + Output#A

Transfer Switch#3 : Input#2 + Output#A

Curious about ZED Advance? We make a whole page on “ZED Advance” go and checkout and it will help you will be able to select the correct solution for your need.