Microgrid Controller Standards



 

Microgrid Controller Standards

Microgrids are a decades-old concept from the time before alternating current (AC) grids existed. The first microgrids were direct current (DC) in design, electrically disconnected and far apart from each other. With the introduction and expansion of AC grids in the early 1900s, the DC grid concept subsided.

Until a few years ago, AC grids were operated with the concept of one-way power flow; a utility generated energy at centralized plants and distributed that energy to customers (loads) via transmission and distribution lines. In today’s world, several factors have led to widespread integration of distributed energy resources (DERs) on the AC grid, thus challenging the concept of one-way power flow. The delivery of energy to customers now requires complex transmission and distribution line networks, communication equipment, protection equipment and energy management systems.

In the United States (US), DERs connected to the grid must comply with IEEE Standard 1547–2003 (Standard for Interconnecting Distributed Resources with Electric Power Systems). The standard provides guidance on voltage and frequency control, overcurrent protection, effective grounding, islanding prevention and synchronization thresholds, among other issues relevant to the microgrid, while connected to the grid [1].

As the penetration of DERs on the grid grows, the need for microgrid controllers to aggregate and manage DERs collectively and efficiently is more evident. While microgrid controllers were originally intended to enable reliable and flexible energy options to critical loads, today these controllers offer several additional advanced features to maximize revenue, support the grid and react to dynamic grid conditions. With several microgrid controllers available in the market today, it is important to use standards that provide functional and performance guidelines for these controllers.

IEEE Standard P2030.7 (Standard for the Specification of Microgrid Controllers) lists two core functions for microgrid controllers: transition and dispatch. With these two functions, the microgrid can operate as a self-managed system that can connect and disconnect from the grid. The core control functions ensure that the microgrid satisfies interconnection requirements, coordinates with existing grid protection schemes and is able to exchange energy with the grid.

IEEE Standard P2030.8 (Standard for the Testing of Microgrid Controllers) standardizes testing procedures and provides minimum performance requirements for the core functions of microgrid controllers listed in P2030.7. Several testing configurations are available to evaluate controllers:

  • Both the controller and the power system are in simulation (Figure 1(a)).
  • The controller is in hardware form and the power system is simulated (Figure 1(b)).
  • The controller is in hardware form, some components of the power system are in hardware form, while other components of the power system are simulated (Figure 1(c)).
  • Both the controller and the power system are in hardware form (Figure 1(d)).

P2030.7 and P2030.8 provide a method of standardizing the functions and performance of microgrid controllers, testing the controllers and evaluating them against quantitative minimum requirements. Many leaders from academia and industry (including ABB) have collaborated to help develop P2030.7 and P2030.8.

Fundamental standards like ANSI-C84.1 (American National Standard for Electric Power Systems and Equipment – Voltage Ratings (60 Hertz)) and IEEE-519 (IEEE Recommended Practice and Requirements for Harmonic Control in Electric Power Systems) are often used by utilities in the US. Utilities in other countries have equivalent standards for voltage ratings and harmonic levels. P2030.8 recommends that microgrid controllers be programmed to adhere to power quality standards that are specific to the local utility, region or country.

ABB’s state-of-the-art testing facilities in Raleigh (US), Genova (Italy) and Darwin (Australia) are used to test ABB’s microgrid controller in various configurations, including the ones shown in Figure 1.

Figure 1: Options for laboratory evaluations of microgrid controller compliance with site-specific requirements: (a) pure simulation, (b) CHIL (Controller hardware in the loop), (c) CHIL and PHIL (Power hardware in the loop), and (d) hardware only [1]

Several initiatives are being funded by the US Department of Energy (DOE), in collaboration with private and academic entities. One is the DOE funding opportunity announcement (DOE-FOA-997) titled “Microgrid Research Development and System Design.” FOA-997 provides minimum functions and performance metrics for microgrid controllers that deal with grid-connected dispatch operations, islanded dispatch operations, transition operations and power quality. It allows awardees to test their microgrid controllers in laboratory-based and/or field-based microgrid configurations.

Another initiative supported by the DOE, and led by the Massachusetts Institute of Technology (MIT), is using simulated DERs to test and compare commercially-available microgrid controllers (CHIL configuration). This initiative has been running for two years and is seeing increasing participation and interest from academia and industry. Typhoon HIL’s real time digital power system simulator is being used to simulate the DERs.

A future initiative supported by the DOE, and led by the National Renewable Energy Laboratory (NREL), will use a combination of simulated and real DERs to test and compare commercially-available microgrid controllers (CHIL and PHIL). RTDS’ real time digital power system simulator will be used to simulate the DERs in this instance.

Testing a microgrid controller against site-specific configurations (CHIL, PHIL or both) with site-specific performance requirements ensures that the controller is ready for a particular site. ABB’s testing facilities are able to test their microgrid controller against site-specific configurations before deploying the controller in the field, to ensure that the controller is ready to adhere to the specific functional and performance requirements of a site.

ABB’s M+ microgrid controller is able to manage power systems in both a grid-connected and islanded state, and transitions between the two states. The decentralized design of ABB’s controller can ensure that in the event of a failure of one or more DERs, or a break in communications between the controller and one or more DERs, the microgrid as a whole continues to function in a safe manner. Microgrid controllers using a centralized design have several disadvantages, including expensive hardware redundancy requirements, complex scalability and expansion requirements, limited options for network redundancy and catastrophic results if the controller were to fail. The robust decentralized architecture, reliability-focused control schemes and customer-focused objectives of ABB’s M+ controller has enabled ABB to deploy their microgrid products at over 40 sites worldwide. Watch this video to learn about how ABB microgrid controls help optimize renewable integration.

There is always more to learn about microgrid technologies.  If you’re considering whether to invest in a microgrid project or are building a microgrid, ABB’s Microgrid Advisory Group can help! Register to receive updates on ABB’s Microgrids Advisory services and be notified of newly available microgrids case studies, webinars and events. Visit our website, ABB microgrids solutions, to read about ABB’s experience in microgrid projects.

Written by:

Dr. Mohit Chhabra, Ph.D.

 

[1] Maitra A., Pratt A., Hubert T., Wang D., Prabakar K., Handa R., Baggu M., McGranahan M., “Microgrid Controllers : Expanding Their Role and Evaluating Their Performance”, IEEE Power and Energy Magazine, Volume 15, Issue 4, July-August 2017

[2] Chhabra M., Barnes F., “Robust and Optimal Current Controller Based Solar-Inverter System Used for Voltage Regulation at a Substation”, IEEE 40th Photovoltaic Specialists Conference (PVSC), Denver, Colorado, June 2014

[3] Joos G., Reilly J., Bower W., Neal R., “The Need for Standardization: The Benefits to the Core Functions of the Microgrid Control System”, IEEE Power and Energy Magazine, Volume 15, Issue 4, July-August 2017

[4] Tsikalakis A.G., Hatziargyriou N.D., “Centralized Control for Optimizing Microgrids Operation”, IEEE Transactions on Energy Conversion, Volume 23, Issue 1, March 2008