Regulating Energy Storage


Increasing demands from utility companies on the energy industry have once again placed distributed energy resources, including renewable energy, in the spotlight as a significant regulatory issue. This is because utility companies require the ability to accurately forecast connection with the grid in a safe, reliable, and efficient way. These requirements, coupled with issues of grid connectivity, smart grids and micro grids, are bringing major changes to the power generation, renewable energy, and energy storage industries.

This environment has created tremendous growth potential for the energy storage industry, which is currently equivalent to 2.3 percent of energy capacity in the United States. Energy storage systems (ESS) provide many benefits to the industry through integration of different components and technologies such as power conversion, utility grid connection, cooling, and communication and control. These components include equipment for charging, discharging, protection, and fluid movement and containment, and can come in the form of battery, stored/pumped hydroelectric, compressed air, gaseous system, ultracapacitor, and flywheel devices.

With these capabilities, however, come strict requirements on ESS equipment. ESS evaluation involves an assessment of individual equipment and of the system as a whole, including consideration of the final connection, installation, application, and environment of the system. Any potential safety concerns for ESS also receive intense scrutiny and are considered on electrical, mechanical, energy and chemical levels.

In light of this, efforts are underway to develop and apply suitable safety standards for the rapidly evolving energy storage and renewable energy industries.

ANSI/UL 9540 currently serves as the “umbrella” standard for ESS, applying broad requirements for ESS equipment. Published in 2014, ANSI/UL 9540 covers ESS that store energy from various sources and provide energy to loads or power conversion equipment. The standard establishes general requirements for ESS, as well as more specific measures for safety analysis and control systems, safety critical electrical and electronic controls, as well as electrical, mechanical, and environmental tests.

In addition to the requirements placed on ESS and associated equipment, standards have been established for interconnection, with a focus towards general construction, safety and grid protection, and power quality requirements. IEEE 1547-2003 and IEEE 1547.1-2003, both published in 2003, serve as the current standards for grid connection requirements. The requirements of IEEE 1547-2003 Standard for Interconnecting Distributed Resources with Electric Power Systems, are concerned with performance, operation, testing, safety considerations, and maintenance of the interconnection. IEEE 1547.1-2003, the Standard for Conformance Test Procedures for Equipment Interconnecting Distributed Resources with Electric Power Systems, specifies the type, production, and commissioning tests that must be performed to demonstrate that the interconnection functions, and distributed energy resources (DER) equipment comply with IEEE 1547-2003.

The latest amendments to these standards, IEEE 1547a and 1547.1a respectively, are short-term permissible revisions to the established standards. Currently, manufacturers may opt for the existing IEEE 1547 and 1547.1 standards with or without considering the amendments IEEE 1547a and 1547.1a. These amendments are not mandated and will be cancelled after new version IEEE 1547 and 1547.1 standards are released.

Under IEEE 1547a, voltage regulation is allowed, assuming coordination with, and approval of, the area electric power systems (EPS) and DER operators. In addition, the requirement for field adjustable voltage settings is reduced from 30kW to 300W, and the requirement for field adjustable frequency settings now applies to equipment with any power level.

In response to requirements of IEEE 1547a for “modulated power output as a function of frequency,” IEEE 1547.1a presents real power reduction tests where equipment under test (EUT) responds to over frequency, and real power increase tests where EUT responds to under-frequency. IEEE 1547.1a also responds to the “permitted voltage regulation” requirement in IEEE 1547a with four categories of voltage regulation testing. These will test the manufacturer claimed response characteristics of the EUT where it actively participates to regulate the voltage by changes of real and reactive power.

The goal of the new version of IEEE 1547 is to address DER interconnection and interoperability, including associated interfaces. Under this version, the interoperability and associated interfaces aspects will build from the IEEE 2030 standard (Guide for Smart Grid Interoperability of Energy Technology and Information Technology Operation with the Electric Power System (EPS), and End-Use Applications and Loads, published in 2011), in addition to the IEEE 1547 series. As mandated by IEEE, these must be completed by 2018.

Additionally, the updated version of IEEE 1547 will bring an increased focus to criteria such as the introduction and incorporation of advanced evaluation and testing approaches, such as enhanced modeling and simulation requirements, interoperability and intelligent devices integration, and the potential interactive effects among advanced requirements and specifications, among others.

Along with these more general requirements for ESS, there are also specific requirements for certain areas that manufacturers will want to examine when attempting to enter those markets. California, for example, has established Rule 21 for generating facility interconnections within the state.

Rule 21 is generally harmonized with IEEE 1547-2003, and in the event of any conflicts with other standards, Rule 21 takes precedence. The rule includes many smart inverter functions, and manufacturers must claim what function their inverter can provide. For a specific test item, Rule 21 provides flexibility for manufacturers to make set points themselves or by agreement with their local utility.

Hawaii is another state, which, in addition to the IEEE 1547-2003 and IEEE 1547.1-2003 standards, establishes local requirements for grid connection. Locally, these requirements are stated through Standard Interconnection Agreement Rule 14H. The inverter requirements of the rule are intended to be consistent with IEEE 1547-2003 and 1547a. In the event of a conflict between Rule 14H and IEEE 1547-2003, Rule 14H takes precedence.

Together with Rule 14H, File TrOV-2 states two part requirements for the Hawaiian market. The first, transient over-voltage (TrOV) is a test to verify the effects of the DER system on overvoltage on the area EPS. The second, frequency and voltage ride-through (FVRT) testing can be conducted under a similar procedure as abnormal voltage and frequency testing in the existing IEEE 1547.1-2003. It does, however, contain different requirements on voltage and frequency tripping percentage magnitude and tripping time than are currently featured in IEEE 1547-2003.

In addition to these regional requirements, there are additional standards specific to batteries that manufacturers should be aware of when bringing ESS to market. Different standards are currently established for a wide variety of battery products including lithium batteries (ANSI/UL 1642), household and commercial batteries (ANSI/UL 2054), uninterruptable power systems (UPS) batteries (ANSI/UL 1989), and batteries for electric vehicles (ANSI/UL 2580/2271).

To bring energy storage solutions to market across rapidly growing and changing industries, it is crucial for manufacturers to understand all global and regional regulatory requirements. Having an in depth knowledge of what is required will improve speed to market and ensure that you are bringing safe, high-quality, and high-performing products to market.


Henry Sapiecha

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