How load sharing can be done in ac mains and inverter?

Thread Starter

Arijeet

Joined Dec 27, 2019
78
I want to do load sharing in between ac mains and inverter? But How it can be done.

In the above line, many experts will not understand the question, so I am just explaining a simple example below:- Suppose we need to drive a load of 10 kW( load can anything or mostly all the loads are combined to form the 10 KW) in our household. But in my area, the utility sector provides only 5 KW to drive the load. but if I go above beyond this we need to pay for this extra.but in my home I have an inverter (inverter can be any type may be a solar or conventional system with battery) which is rated of 6KW, so why we will purchase extra energy from the utility sector if we have an inverter. so what we will do we want to share the power or bypass the load, in simple terms if we set the limit of ac mains to 4KW and after beyond going to 4Kw my power will be shared by the inverter which will 6 KW. Now this power distribution will be done by the microcontroller and some hardware apparatus (e.g.IC's, gates).
New update about the question -
There's a question to which I've been looking for an answer but I haven't found a clear one yet so I hope this forum will help.
How is the load shared between a grid-tie inverter and the grid? I understand that the inverter feeds the loads with all the available solar power and imports the remaining balance from the grid if needed or exports the excess if any. I would like to understand the technical details behind this process (how does the inverter have feeding priority over the grid?) because so far I haven't found a clear explanation online.


So I explain everything that I need to do. I request to all please kindly share me some basic ideas on this. I apologize for not posting any pictures or any code. because this is a practical question that I need to do.
 
Last edited:

BobaMosfet

Joined Jul 1, 2009
1,222
@Arijeet - You need to check what your local utility guidelines are for your country/area. There are safety concerns, as well as financial concerns. (for example if you generate power onto the grid, your local incumbent utility may have to pay you for the extra power you put into their system.

If all you're trying to do is supplement the power your utility provides into your own equipment (they provide 4K, and you provide 2K on top of that), you still have to have a way to monitor that to adjust that difference AND you must (more importantly) make your signal generation in sync with the utility generation.

While what you have in mind is sensible from one perspective, it is not something you have the skill or equipment to do. Lastly, as this is a MAINS related question, it is not really a topic that can be addressed in this forum (safety concerns/liability), per the TOS.
 
Last edited:

Thread Starter

Arijeet

Joined Dec 27, 2019
78
This sounds very much like a job for a professional, licensed electrician or electrical contractor. It is not a DIY project for beginners. Safety standards address this problem.

You may do well to read up on grid tied inverters https://woodstockpower.com/blog/generator-load-sharing-principle/
sir, I agree with your point. but I am a research engineer, pursuing research from the top institute in my country. my professor allows for this project, so I am doing this thing under government-recognized instructors.so I am not violating any rules and regulations, in the end, after successful of research, it will implement into public premises.
 

Thread Starter

Arijeet

Joined Dec 27, 2019
78
@Arijeet - You need to check what your local utility guidelines are for your country/area. There are safety concerns, as well as financial concerns. (for example if you generate power onto the grid, your local incumbent utility may have to pay you for the extra power you put into their system.

If all you're trying to do is supplement the power your utility provides into your own equipment (they provide 4K, and you provide 2K on top of that), you still have to have a way to monitor that to adjust that difference AND you must (more importantly) make your signal generation in sync with the utility generation.

While what you have in mind is sensible from one perspective, it is not something you have the skill or equipment to do. Lastly, as this is a MAINS related question, it is not really a topic that can be addressed in this forum (safety concerns/liability), per the TOS.
Sir, I am already working under the supervision of the utility sector. well, this project is not my individual. definitely, my team will verify for this project. but I need to start from scratch will end into advanced. I just need some topics where I can hold the topic.
 

Thread Starter

Arijeet

Joined Dec 27, 2019
78

nsaspook

Joined Aug 27, 2009
7,723
What you need is a smart inverter with load sharing. The inverter grid power control loop runs in AC current control mode and sees the grid as a infinite power sink when directly connected so you must have some method of inserting a balancing impedance or use droop control (voltage and frequency changes) with a fixed impedance between the grid and load while the inverter drives the load if you want so control the ratio of inverter to grid power to the load.

https://www.thierry-lequeu.fr/data/SLUP094.pdf
https://core.ac.uk/download/pdf/228550635.pdf

None of this is easy even in a lab environment to get right at reasonable power levels for a beginner.

Load share inverter example: https://www.vitronicscontrols.com/solar-grid-online.html
 

fourtytwo

Joined May 2, 2017
38
If I might make a small contribution to the OP I think some of the confusion arises from the use of the word inverter that is commonly used to describe a device producing grid like current suitable for powering a tv, toaster or other household appliance from some low voltage source such as a car battery.

Such a device (inverter) is completely incapable of being coupled to the national grid on account of its characteristic as a voltage source inverter (VSI), this means it controls the voltage of the load, its primary feedback network is to control the voltage of the load. When such a device is connected to the grid not only is it incapable of controlling the voltage such that large currents will flow it is also incapable of controlling the phase or frequency hence it will simply explode.

A special kind of inverter known as a grid tie inverter that is capable of shared connection with the grid has completely different characteristics, the first and foremost is that it is a current source inverter (CSI) meaning its primary control loop is current feedback, secondly it senses the load voltage (most usually zero-cross) to ensure that it remains in phase with the grid and does not try to defeat it (an argument it will always loose). In order to provide some slack in the system between an immovable grid and a puny inverter some coupling impedance is normally used consisting of a fairly large inductor that is often integrated into the necessary harmonic reduction filter and is commonly called an LCL filter.

The mathematics involved in making all this work in practice is not simple and the energy and safety concerns are not for the feint hearted, you should have experience of designing and building direct grid powered switching power supplies before considering such a project.
 

Audioguru again

Joined Oct 21, 2019
2,048
Over there, people make their own wiring connections on the electricity poles (see the jungles of wires on Google) to avoid paying for electricity. The electrical wires on my street are hidden underground.
Here in Canada I pay a little more for any amount of electricity I use during daytime hours and less at night.
 

Thread Starter

Arijeet

Joined Dec 27, 2019
78
What you need is a smart inverter with load sharing. The inverter grid power control loop runs in AC current control mode and sees the grid as an infinite power sink when directly connected so you must have some method of inserting a balancing impedance or use droop control (voltage and frequency changes) with a fixed impedance between the grid and load while the inverter drives the load if you want to control the ratio of the inverter to grid power to the load.

https://www.thierry-lequeu.fr/data/SLUP094.pdf
https://core.ac.uk/download/pdf/228550635.pdf

None of this is easy even in a lab environment to get right at reasonable power levels for a beginner.

Load share inverter example: https://www.vitronicscontrols.com/solar-grid-online.html
sir,
What you need is a smart inverter with load sharing. The inverter grid power control loop runs in AC current control mode and sees the grid as an infinite power sink when directly connected so you must have some method of inserting a balancing impedance or use droop control (voltage and frequency changes) with a fixed impedance between the grid and load while the inverter drives the load if you want to control the ratio of the inverter to grid power to the load.
I agree with your explanation, actually, I need to work on the smart inverter but before doing automation or make smart the inverter first I need to do the load sharing but I have some basic idea on this. but after sharing your content I will read and start my work.
Thanks.
 

Thread Starter

Arijeet

Joined Dec 27, 2019
78
If I might make a small contribution to the OP I think some of the confusion arises from the use of the word inverter that is commonly used to describe a device producing grid-like current suitable for powering a tv, toaster, or other household appliance from some low voltage source such as a car battery.

Such a device (inverter) is completely incapable of being coupled to the national grid on account of its characteristic as a voltage source inverter (VSI), this means it controls the voltage of the load, its primary feedback network is to control the voltage of the load. When such a device is connected to the grid not only is it incapable of controlling the voltage such that large currents will flow it is also incapable of controlling the phase or frequency hence it will simply explode.

A special kind of inverter known as a grid-tie inverter that is capable of shared connection with the grid has completely different characteristics, the first and foremost is that it is a current source inverter (CSI) meaning its primary control loop is current feedback, secondly it senses the load voltage (most usually zero-cross) to ensure that it remains in phase with the grid and does not try to defeat it (an argument it will always loose). In order to provide some slack in the system between an immovable grid and a puny inverter, some coupling impedance is normally used consisting of a fairly large inductor that is often integrated into the necessary harmonic reduction filter and is commonly called an LCL filter.

The mathematics involved in making all this work in practice is not simple and the energy and safety concerns are not for the faint-hearted, you should have experience of designing and building direct grid powered switching power supplies before considering such a project.
sir, I agree with your point. but I am a research engineer, my team and institutes allow me for doing this project because after successfully doing this project, it will implement in a commercial area. I just need the advice of you's how should I proceed.
 

Papabravo

Joined Feb 24, 2006
14,655
sir, I agree with your point. but I am a research engineer, my team and institutes allow me for doing this project because after successfully doing this project, it will implement in a commercial area. I just need the advice of you's how should I proceed.
I guess you can learn the hard way by smoking a few devices that you build. That might not impress your colleagues, so maybe some diligent research on the matter would be a good course of action. I see several posts with good advice for further research on your part.
 

Thread Starter

Arijeet

Joined Dec 27, 2019
78
I guess you can learn the hard way by smoking a few devices that you build. That might not impress your colleagues, so maybe some diligent research on the matter would be a good course of action. I see several posts with good advice for further research on your part.
yes sir, but I have already started hunting on the research papers, reading materials.
 

Thread Starter

Arijeet

Joined Dec 27, 2019
78
Research and technical journals. I am retired, so you probably have more access to equipment than I do as well.
No sir, I do not have exact journal papers but sir I am a beginner in the research domain. I assume you have a lot of experience in this field.
 
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