Off-grid - Genset Grid forming: How to efficiently manage microgrids

Kiesse Sita-Kengue

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Welcome back to our four-part series on how to effectively manage microgrids to power Commercial and Industrial buildings. 

This series focuses on the best practices for different types of microgrids systems. 

Our latest articles were: How to efficiently manage microgrids: Load Shifting for Grid-tied System and How to efficiently manage microgrids: Solar + BESS system with Genset Backup. 

Todays’ article will tackle off-grid PV diesel systems coupled with BESS and more particularly the ones that have Gensets as a Grid forming unit. 

 

Before diving into the core of the subject, let’s define what is a microgrid.

Feel free to jump to the next section if you are already familiar with this concept.

A microgrid is an energy distribution network that relies on local means of producing electricity. It is designed to operate independently or in synchronization with the national grid within a defined area.

It is necessary to ensure electricity production and distribution to enable areas or buildings to secure their economic activity and benefit from reliable energy. It is also an opportunity to profit from clean distributed and renewable energy. 

A microgrid can be typically composed of renewable energy sources, BESS, utility grid (when available), diesel generators, or gensets. 

Depending on the grid availability two types of sites emerge; Off-grid and Grid-tied ones.  

In grid-tied applications, the national DSO needs to reduce the intermittency of solar production. The battery can be seen as an alternative to provide further services for this national entity.

In off-grid applications such as; cities, islands, or mining, electricity comes mainly from thermal plants. However, fuel prices are high and uncertain due to oil price variation, logistics, and security costs. A local energy provision can be seen as a solution to solve this fuel dependency. Thus, energy suppliers tend to add solar plus storage systems to the existing gensets. We will focus on such a site in this article. 

If you want to dive deeper into the microgrid topics, here are two articles that might interest you:

What is a solar hybrid microgrid?

What is a solar hybrid system?

Microgrid controller operational mode

When the microgrid is islanded, only one energy source can be grid forming meaning that it sets the voltage and frequency of the whole grid. 

In a microgrid several energy systems can be grid forming such as genset or BESS. In this article we will focus on a microgrid where the genset plant will always be the grid forming unit and the BESS and PV will be grid following. 

 

As an example, you can find below one of our projects which represents the solar-diesel-BESS off grid configuration where the genset is always grid forming

Use Case

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Hotel Resort – Bahamas

  • PV – 74 kWp 
  • Gensets – 108 kVA 
  • Storage – 80 kWh
 
On this off-grid site, several gensets have to be controlled independently in a system with SMA Sunny Island ESS inverters coupled with Tesvolt Batteries. 
Enviroearth_Malawi 1

Remote Village – Malawi

  • PV – 100 kWp 
  • Gensets – 225 kVA 
  • Storage – 936 kWh
 
In this village in Malawi, the ePowerControl MC allows PV and storage integration with an existing diesel plant through a DC hybrid inverter architecture to supply stable power.

Why should you choose this configuration?

The decision on which device will be grid forming or grid following is most of the time a matter of the feature of your devices or the configuration of your project. Indeed, the nature of your on-site devices is primordial in this matter. 

There are three main reasons to chose this configuration:  

  1. In a hybrid project, genset plants are usually existing and have always formed the grid. It is therefore easier for the final client to accept an adding of PV+BESS plant without changing the grid forming unit
  2. The BESS can only be grid forming if its power conversion system (PCS) allows it. If the project doesn’t incorporate an advanced grid-forming power conversion system that permits the BESS to be grid forming. 
  3. Sometimes the genset controller doesn’t allow it to be grid-following. In this case, the genset is required to be grid-forming. 
  4. Changing the mode of the BESS can sometimes induce blackout depending on the devices. 
 
 
 

To optimize your microgrid use and maximize your system’s performance and profitability, request a call with one of our microgrid experts.

Schedule a demo

We will release the third article about off-grid Solar BESS Genset applications in the next few weeks. 

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