In short. A microgrid is a defined group of loads and energy sources, such as diesel or gas generators, batteries and solar, inside a clear electrical boundary, controlled so that it can operate as one system. It is defined by that boundary and by its controls, not by how many technologies it contains. Most microgrids must handle grid-connected operation, islanded operation, the transition between them and resynchronisation, and each mode needs a source that holds voltage and frequency.
What separates a microgrid from a collection of assets
Many Indian industrial sites already have a DISCOM supply, two or three diesel sets, a rooftop solar plant and perhaps a UPS bank. That is not yet a microgrid. Each asset runs on its own logic: the generators start on mains failure through AMF panels, the solar inverters shut down when the grid disappears, and nobody coordinates them. A microgrid adds three things: a defined point of common coupling with the utility, a supervisory controller that sees every source and controllable load, and a control philosophy that states which source does what in each operating mode. Only with those three in place can the site keep its solar running through an outage, hold a battery reserve, or shed the right loads in the right order.
Typical architecture
At the top sits the utility connection through the point of common coupling (PCC), normally a breaker with its own protection and synchronising check. Below it is the site bus, often split into sections. Connected to the bus are generators with their synchronising panels, a battery with its PCS, PV inverters, and loads grouped by priority. The microgrid controller communicates with every generator controller, the PCS, the inverters, the PCC breaker and the load-shedding relays. See microgrid controller architecture for the control hierarchy.
Operating modes
| Mode | What holds voltage and frequency | Main control task |
|---|---|---|
| Grid-connected | The utility | Dispatch sources for economics; respect import and export limits |
| Transition to island | Handover from utility to local grid-forming source | Detect the event, open the PCC, stabilise the bus |
| Islanded | Grid-forming generator or battery | Balance generation and load; hold reserve; shed load if short |
| Resynchronisation | Local source, matched to returning utility | Match voltage, frequency and phase angle; close PCC |
| Black start | First local source onto a dead bus | Restore auxiliaries and loads in stages |
The grid-connected and islandable pages go deeper into the first four modes.
Who forms the grid
In an island, at least one source must set voltage and frequency, and the others must follow. A diesel generator in isochronous mode can do this, as can a grid-forming battery inverter. PV inverters normally cannot. When several sources can form the grid, they must share the job through droop control or a master controller; two sources trying to regulate the same bus without coordination will fight, oscillate and trip. Deciding this is the core engineering decision of any microgrid and is covered in grid-forming and grid-following coordination.
Δf = −R × ΔP
Here Δf is the frequency change, R the droop setting and ΔP the change in a source’s output as a fraction of its rating. With 4 percent droop on a 50 Hz bus (R = 2 Hz per unit), a source picking up an extra 25 percent of its rating lets frequency fall by 0.5 Hz to 49.5 Hz (illustrative), and parallel sources with equal droop share load in proportion to their ratings.
Where microgrids fit in Telangana and Andhra Pradesh
The strongest cases are sites where outages are costly and long enough that diesel alone becomes expensive: process plants, cold chains, hospitals, campuses, data centres and remote mining or quarry sites. Industrial parks with rooftop solar and frequent short grid interruptions are another good fit, because a microgrid lets solar keep producing through outages that would otherwise shut the inverters down. Sites with a reliable grid and few outages rarely justify the control investment. Sector detail is in industrial microgrids.
Protection in a microgrid
Fault levels change with the operating mode. Grid-connected, the utility contributes high fault current; islanded on a battery, fault current may be little more than the inverter rating. Protection that works in one mode may not operate in the other, so settings groups that change with mode, or protection based on voltage and directional elements, are often needed. Anti-islanding requirements from the DISCOM must also be met at the PCC.
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Common mistakes
- Calling a site with uncoordinated generators and solar a microgrid. Solar still trips on every outage and the expected benefit never appears.
- Leaving two grid-forming sources without a sharing scheme. They fight over frequency and the island collapses.
- Using one set of protection settings for all modes. Faults in island mode are not cleared.
- Skipping resynchronisation design. Return to the grid needs a full outage every time.
What to send us
Send the single-line diagram, details of every source including generator nameplates, PV and battery ratings, an hourly load profile, outage records for the past year and the loads that must stay on. State whether grid paralleling or export is permitted. Use the application engineering enquiry and we will propose an architecture and control philosophy.
Questions engineers ask
Is a microgrid controller a single box?
It can be, but it is better understood as a function: supervisory control coordinating sources and loads within the boundary. It may be a dedicated controller, a PLC or a function within a power management system.
Can my existing generators become part of a microgrid?
Usually yes, if their controllers support synchronising, load sharing and remote setpoints. Older mechanical-governor sets may need controller upgrades.
Does a microgrid need a battery?
Not always. A generator-only microgrid can island and resynchronise. A battery adds fast response, the ability to switch generators off and a seamless transition, which is why most modern designs include one.
Do I need DISCOM approval?
Any arrangement that parallels with the utility or exports needs the DISCOM’s approval and the protection it specifies. A microgrid that only islands via an open transition may need less, but confirm with the utility.
Technical content reviewed by Srinivas Reddy, Managing Partner, Reddy Generators. Last updated 19 October 2026.