What is Grid Forming vs Grid Following, and what does it mean for a net zero grid?

GRID FORMING

is a term that refers to the ability of an inverter-based energy source, such as solar, wind, or battery, to provide voltage and frequency support to the grid, especially during disturbances or outages. Grid forming inverters can operate independently or in coordination with other sources, and can help restore the grid after a blackout. Grid forming is a key technology for integrating more renewable energy into the grid and ensuring its reliability and stability.

Grid Forming inverters have different modes of operation, such as droop control, virtual synchronous machine, or hierarchical control, depending on the grid conditions and the desired performance. Grid forming inverters can also provide various ancillary services to the grid, such as inertia, system strength, voltage regulation, and frequency response. These services are essential for maintaining the power quality and security of the grid, especially when there is a high penetration of variable renewable energy sources, such as wind and solar. Grid forming inverters can adjust their output power and voltage in response to grid conditions and coordinate with other sources to balance supply and demand.

Grid Forming is an emerging and promising technology that is being researched and developed by various institutions and organizations. It has potential applications in microgrids, islanded grids, and large-scale grids. However, there are also some challenges and barriers for its widespread adoption, such as technical standards, regulatory frameworks, modeling techniques, and system coordination.

Grid Forming helps with renewable energy integration by enabling inverter-based resources, such as solar, wind, or battery, to provide voltage and frequency support to the grid, especially during disturbances or outages. This means that these resources can act like synchronous generators, which are the traditional sources of power that maintain grid stability and reliability. Grid forming inverters can also help restore the grid after a blackout, by creating a stable voltage and frequency reference for other sources to synchronize with.

Grid Forming is an emerging and promising technology that is being researched and developed by various institutions and organizations. It has potential applications in microgrids, islanded grids, and large-scale grids. However, there are also some challenges and barriers for its widespread adoption, such as technical standards, regulatory frameworks, modeling techniques, and system coordination.

SOME EXAMPLES OF GRID FORMING INVERTERS ARE:

The PowerFlex 755T from Rockwell Automation, which is a low-voltage AC drive that can operate in grid-following or grid-forming modes. It can provide voltage and frequency support, fault ride-through, and black start capabilities for microgrids and distributed energy resources.
The Sunny Island from SMA Solar Technology, which is a battery inverter that can form an AC grid in off-grid or grid-connected applications. It can supply reliable power to critical loads, manage energy flows, and communicate with other inverters and devices.
The PowerStore from ABB, which is a grid-stabilizing generator that can integrate renewable energy sources into the grid. It can operate as a grid-forming or grid-supporting device, and provide fast frequency response, voltage regulation, and power quality improvement.
The GridMaster from Ideal Power, which is a bi-directional power converter that can connect any type of energy storage to the grid. It can operate in grid-forming or grid-following modes, and provide peak shaving, demand response, and microgrid support.

These are just some of the examples of grid forming inverters that are available in the market or under development. Grid forming inverters are an emerging and promising technology that can enable more renewable energy integration and grid reliability.

GRID FOLLOWING 

Grid following is a term that refers to the control strategy of an inverter-based energy source, such as solar, wind, or battery, that synchronizes its output with the grid voltage and frequency. Grid following inverters are current sources that track the grid angle and magnitude to inject or absorb active and reactive power. Grid following inverters depend on the grid to provide a stable voltage and frequency reference, and cannot operate in islanded or off-grid mode.

Grid following inverters are the most common type of inverters used in grid-connected applications, such as renewable energy generation, energy storage, and electric vehicle charging.

Grid following inverters have some advantages and disadvantages compared to grid forming inverters, which are another type of control strategy that can create and regulate the grid voltage and frequency. Grid forming inverters are voltage sources that can operate independently or in coordination with other sources, and can help restore the grid after a blackout. Some of the advantages of grid following inverters are:

They are simpler and cheaper to implement than grid forming inverters.
They can achieve faster power control and response than grid forming inverters.
They can avoid some technical challenges and regulatory barriers that grid forming inverters face, such as synchronization, protection, coordination, and standards.

SOME OF THE DISADVANTAGES OF GRID FOLLOWING INVERTERS ARE:

They cannot operate in islanded or off-grid mode, which limits their flexibility and resilience.
They cannot provide voltage and frequency support to the grid, especially during disturbances or outages.
They cannot provide ancillary services to the grid, such as inertia, system strength, voltage regulation, and frequency response.
They may cause stability and security issues for the grid, especially when there is a high penetration of renewable energy sources.
Grid following is an established and widely used technology that is suitable for many grid-connected applications. However, as the share of renewable energy sources increases in the grid, there is a need for more grid forming inverters that can provide voltage and frequency support and ancillary services to the grid. Grid forming is an emerging and promising technology that is being researched and developed by various institutions and organizations. It has potential applications in microgrids, islanded grids, and large-scale grids

The grid-forming control adjusts the modulated voltage with respect to the grid voltage at PCC, whereas the grid-following control adjusts the injected power with respect to the grid voltage at the PCC (point of common coupling).

GRID FORMING vs GRID FOLLOWING

Grid forming and grid following are two different control strategies for inverters, which are devices that convert direct current (DC) to alternating current (AC). Inverters are used to connect various energy sources, such as solar, wind, or battery, to the grid.

Grid forming and grid following inverters have different characteristics and capabilities, and they can affect the grid stability and reliability in different ways. Here is a brief comparison of grid forming and grid following inverters:

Grid forming inverters can create and regulate the grid voltage and frequency, while grid following inverters synchronize their output with the grid voltage and frequency.
Grid forming inverters can operate independently or in coordination with other sources, while grid following inverters depend on the grid to provide a stable voltage and frequency reference.
Grid forming inverters can provide voltage and frequency support to the grid, especially during disturbances or outages, while grid following inverters cannot.
Grid forming inverters can provide various ancillary services to the grid, such as inertia, system strength, voltage regulation, and frequency response, while grid following inverters cannot.
Grid forming inverters are more complex and expensive to implement than grid following inverters.
Grid forming inverters can achieve slower power control and response than grid following inverters.
Grid forming inverters face some technical challenges and regulatory barriers, such as synchronization, protection, coordination, and standards, while grid following inverters avoid some of these issues.

Grid forming and grid following inverters are both important technologies for integrating renewable energy sources into the power system. However, as the share of renewable energy sources increases in the grid, there is a need for more grid forming inverters that can ensure the grid reliability and security.