Frequency Control Performance Measurement and Requirements

Abstract

Frequency control is an essential requirement of reliable electric power system operations. Determination of frequency control depends on frequency measurement and the practices based on these measurements that dictate acceptable frequency management. This report chronicles the evolution of these measurements and practices. As technology progresses from analog to digital for calculation, communication, and control, the technical basis for frequency control measurement and practices to determine acceptable performance continues to improve. Before the introduction of digital computing, practices were determined largely by prior experience. In anticipation of mandatory reliability rules, practices evolved from a focus primarily on commercial and equity issues to an increased focus on reliability. This evolution is expected to continue and place increased requirements for more precise measurements and a stronger scientific basis for future frequency management practices in support of reliability.Frequency Control Performance Measurement and Requirements iii

Use of Frequency Response Metrics to Assess the Planning and Operating Requirements for Reliable Integration of Variable Renewable Generation

“…The discussion of the first topic draws from two technical reports commissioned for this study that are published separately (Martinez et al 2010, Illian 2010. The second discussion is based on interviews conducted by the project team with power system operators.…”

“…As a result, these practices target predominantly the average performance of reserves for secondary frequency control and permit operation beyond pre-established thresholds for some portion of time. The historic reasons for this are discussed in Illian (2010).…”

“…The large, interconnected power systems of the U.S. (and Europe) developed comparatively tighter ranges for acceptable system frequency to enable the entities within the interconnection to control power flows among themselves equitably, based on closely managing the balance between the loads they serve and the generation they procure. As discussed earlier in this section (and by Illian [2010]), the basic design of U.S. frequency control practices has been predicated on this requirement. Ireland, as noted, is essentially an electrical island; interchange with Great Britain is controlled directly as a result of the transmission technology employed (high voltage DC).…”

Dynamic frequency regulation resources of commercial buildings through combined building system resources using a supervisory control methodology

“…Frequency rate of change is determined by the inertia of all generators and rotating loads on the grid [2]. The frequency must be strictly maintained within a very narrow range in order to comply with the control performance standards (CPS) and the balancing authority ACE Limit (BAAL) reliability criteria [3]. Traditionally, FR is supplied by directing dedicated generators in response to a signal sent by the independent system operator (ISO) or the regional transmission organization (RTO).…”

“…(2) Heating systems, such as electric boilers and resistance heaters; these resources vary the heater electric consumption (i.e., adjusting the heating capacity) in response to the FR signal [8]. (3) Independent systems with variable frequency drives (VFD), such as wastewater treatment pumps and supply fans in air-handling units (AHU); these resources vary the motor electric consumption (i.e., adjusting the motor rotating speed) in response to the FR signal [9,10]. These three types of resources typically have smaller capacity than generators but can ramp much faster and respond to the FR signal more accurately and thereby offer better performance.…”