Whats the difference between a grid tie dc ac inverter and a normal dc ac inverter for 12 v or 24 v batteries?

Question

what are technically the differences between a grid tie solar inverter, which takes as much power from the connected solar cells as possible, on the dc side, to convert it into 230v ac power and a normal battery ppwered inverter, which converts the energy from batteries to 230v ac as required.

What would be the major differences when both inverters would be teared down and the electronic components would be compared on 1 on 1?

How does a grid tie inverter manage to "pull" all the energy possible from the cells? Which component is responsible for that behavior?

Thanks to all those who honestly try to help in advance.

Answer 1

To answer all three of those questions completely wouid require a very long answer so I have tried to hit a scope that I thought made sense here.

A grid tie inverter makes sure:

• the inverter output matches the phase of the grid power
• the inverter has a voltage slightly above the grid voltage
• the power factor is unity
• is powered down when the grid goes down so line workers can safely make repairs

A non grid tied inverter just creates a voltage that's within tolerance, at the correct frequency

The major differences between the two in terms of components would be that the grid tied version would have circuitry/firmware to sense the grid voltage to sync to it and shut down when not present. It would also have a power factor correction circuit to achieve unity. Specific component differences I suspect would be dependent on the particular implementation.

To '"pull" energy from the solar cells, the inverter presents a low impedance load to the cells. It may, for example charge an inductor from the cells and then discharge it into the load repeatedly via a transformer.

The inductor is initially connected from the solar panel output to ground, causing current to build in the inductor. After a period of time the inductor is connected to the output and current then flows to the output. This is simplified but that's the concept. The average current in thr inductor csn be increased until the solar panel voltage there are various schemes for this, read more about PWM and MPPT inverters to learn more.

Answer 2

What would be the major differences when both inverters would be teared down and the electronic components would be compared on 1 on 1?

There would not be really major differences that you can see. Both the battery-powered inverter and the grid-tied solar MPPT inverter will have two power converters, a DC/DC voltage boost converter and a DC/AC inverter.

In the solar inverter, the DC/DC converter is operated as a current source. It "pushes" to the inverter the level of current that results in the maximum power being drawn or "pulled" from the solar panel that the panel can produce with the given illumination. In order to do that, there is a difference in the voltage and current sensing and a difference in the control strategy programmed into the MCU. What is being done is to make the DC/DC converter look to the solar panel like the optimum load for the illumination conditions.

The inverter must be synchronized and coordinated with the grid. That too requires different sensing and different MCU programming. The inverter essentially "pushes" to the grid whatever power it receives from the DC/DC converter. So it is also acting as a current source with respect to the grid. The grid acts like an ideal voltage source that will supply or receive whatever power that the load wants to receive or supply.

Summary

There may be some differences in the power components, but the topology will be generally similar to the battery inverter. The voltage and current sensing will be a little different but similar. The MCU programming will be similar, but quite different in the essential control strategy.