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Stakeholder Comment and AESO Replies Matrix Proposed New ISO Rules Part 500 Facilities, Division 502 Technical Requirements, Section 502.13 Battery Energy Storage Facility Technical Requirements (“New Section 502.13”) Date of Request for Comment: Period of Comment: September 28, 2015 September 28, 2015 through October 26, 2015 1. ISO Rules Stakeholder Comments and/or Alternate Proposal AESO Replies a) New Capital Power Corporation (“Capital Power”) 1. Capital Power agrees with the proposed new Section 502.13, subject to the following clarifications: 1. The AESO is seeking comments from stakeholders with regard to the following matters: 1. Do you agree or disagree with the proposed New Section 502.13? If you disagree, please provide comments. 2. Are there any subsections where the language does not clearly articulate the requirement for either the AESO or a market participant? If yes, please indicate the subsections and suggest language that would improve the clarity. (a) 502.13, 5(1) – Voltage Ride-Through (VRT) Requirements Please explain the AESO’s rationale for using the difference between a battery storage facility’s maximum authorized charging power and its maximum authorized discharging power as the threshold for VRT requirements, as opposed to specifying a charging and discharging capacity. The difference between the maximum authorized charging power and maximum authorized discharging power is a single number that better reflects the overall size of the facility than specifying the charging and discharging capacities. (b) 502.13, 6 – Voltage regulating system; and 502.13, 7 – Governor System Requirements (b) 502.13, 6 – Voltage regulating system; and 502.13, 7 – Governor System Requirements It is not common for battery storage facilities to have both voltage and frequency regulating systems. Please confirm that according to the proposed Section 502.13 a battery storage facility must be set up with both a voltage regulating system and a governor (frequency regulating) system. If yes, please explain the reasoning for this requirement. AESO Replies to Stakeholder Comments: 2016-02-25 (a) 502.13, 5(1) – Voltage Ride-Through (VRT) Requirements The AESO disagrees that battery energy storage facilities do not commonly have both a voltage regulating system and a governor. Battery energy storage facilities can be used to provide voltage regulation/reactive power support and frequency support. These functions cannot be carried out without both a voltage regulating system and a governor, as described below. Accordingly, the AESO confirms that, in Page 1 of 7 accordance with subsections 6 and 7 of Section 502.13, a battery energy storage facility must haveboth a voltage regulating system and a governor. Voltage Regulation Systems Without a voltage regulating system, a battery energy storage facility will impact the voltage on the transmission system as the facility cycles from charge to discharge. Even a small battery energy storage facility in a weak area can have a significant impact on transmission system voltage. This cycling can occur quickly and several times an hour, depending on the use of the battery energy storage facility. As battery energy storage facilities grow in size and number (similar to wind facilities over the past 15 years) this impact will increase. Governing Systems Primary frequency control, which is provided by a governor system to assist in arresting and stabilizing abnormal frequency, is essential for maintaining the reliability of the Alberta interconnected electric system. In its Frequency Response Initiative Report, NERC recommends that all resources, including storage facilities, have a frequency responsive governor system. See the Report at page 3: http://www.nerc.com/pa/stand/project%20200712 %20frequency%20response%20dl/fri_report_1030-12_master_w-appendices.pdf In accordance with the AESO’s Generation and Load Interconnection Standard, conventional generation is currently required to have a governor system. In accordance with Section 502.1 of the ISO rules, Wind Aggregated Generating Facilities Technical Requirements (“Section 502.1”), wind facilities are required to AESO Replies to Stakeholder Comments: 2016-02-25 Page 2 of 7 have over-frequency controls so that they are able to provide primary frequency response to system disturbances. (c) 502.13, 17 – Synchrophasor Measurement System: Section 17 specifies Synchrophasor Measurement System (Power Quality). Capital Power requests that the AESO provide guidance for device selection for this measurement system. By taking synchrophasor measurements at both the low side and high side of the transmission system step-up transformer of the battery facility, is the intention to have one measurement system act as primary and a second to act as a backup? Please explain. (c) 502.13, 17 – Synchrophasor Measurement System: Some requirements of proposed Section 502.13 refer to the high side of the transmission system step up transformer of a battery energy storage facility, while others refer to the low side. As the transformer is an impedance, each side of the transformer behaves in a different way. By placing the synchrophasor on each side of the transformer, the exact behavior of the battery energy storage facility can be monitored. Wind facilities are also required to take synchrophasor measurements at both the high and low sides of the transformer in accordance with Section 502.1. Accordingly, no changes have been made to Section 502.13 in response to this comment. NextEra Energy Canada (“NextEra”) 2. Section 2(1): The ISO will likely receive a wide variance in the format and content of the “functional specifications” that must be submitted here, dependent on the submitting entity. The AESO should consider developing a template for this to ensure the ISO receives the level of detail that they require to perform and analysis and approve. 3. Section 2(3): “maximum charging power” could include auxiliary loads (lighting, HVAC, etc.) which are required for the facility to operate but not AESO Replies to Stakeholder Comments: 2016-02-25 2. The AESO develops the functional specification with information received from the market participant. Therefore, there is no need for a template to be supplied to the market participant, and no changes have been made to Section 502.13 in response to this comment. 3. The AESO assumes that NextEra’s comment is in regard to subsection 3. The AESO agrees with NextEra’s comment and has revised Page 3 of 7 directly associated with the charging of the batteries (this is dependent on where the auxiliary load transformers are tapped relative to the metering location). NextEra would like to suggest adding a sentence stating “This maximum charging power is not inclusive of any auxiliary power utilized in the operation of the facility”. 4. Section 4(1): NextEra would like to suggest adding language to clarify that for ULTC transformers, the 1.00 per unit voltage should be calculated with the ULTC at neutral tap, or the normal operating tap if not at neutral. subsection 3 accordingly. 4. In the AESO’s view, the 1.00 per unit voltage is a design value that is independent of the tap setting. Studies performed during the connection process will determine the tap settings used to achieve the 1.00 per unit voltage. The taps may be adjusted from time to time in consultation with the AESO (see OPP 1304) to assist in operating the facility closer to the 1.00 per unit voltage value. Accordingly, no changes have been made to Section 502.13 in response to this comment. 5. Section 4(2): it is feasible that if a battery energy storage facility is co-located with an existing generation resource such as wind, they may share a common voltage/reactive control system if they share a common point of interconnection. If this is the case, it may not be desirable to have a separate manually controllable set point of the battery energy storage facility that is separate from the control for the aggregate facility. NextEra would like the AESO to please consider this scenario in determining the requirements in section 4, as to whether you may include an exception process to exclude certain battery energy storage facilities from these requirements in certain scenarios. 6. Section 7(1, 8(1) and 8(2): although capable of AESO Replies to Stakeholder Comments: 2016-02-25 5. The scenario described by NextEra is covered by subsection 4(4). Accordingly, no changes have been made to Section 502.13 in response to this comment. 6. The AESO does not agree that governor Page 4 of 7 simulating a typical generators governor response, inverter based technologies such as battery energy storage facilities provide a unique capability not available with traditional generation in their ability to respond very quickly (within cycles) to either an input signal or a fluctuation in a transmission system parameter such as voltage or frequency. These capabilities can be utilized to more quickly arrest frequency declines or loss of large loads more efficiently than the slower typical governor response. A number of ISO’s have seen value in this type of response and have established markets for this type of service. If AESO is considering this direction now or in the future, the governor requirements as well as the ramp rate limitations in these sections would prohibit implementing a market design or ancillary service such as this. requirements or ramp rate limitations will limit the participation of battery energy storage facilities in any potential markets. Subsection 7(1) has been included to prevent a large withdrawal or injection of real power into the transmission system in a very small time frame, and to provide a reasonable automated response to frequency excursions. As battery systems grow in size and number (similar to wind facilities over the past 15 years) such large changes taking place over a few cycles could result in significant issues on the local transmission system. Subsections 8(1) and 8(2) are in place to prevent similar issues from arising as a result of a directive or dispatch. Note that subsection 8(3) allows for ramp rates that may exceed those specified in subsection 8(2) if the ancillary service requires a different ramp rate. Accordingly, no changes have been made to Section 502.13 in response to this comment. AESO Replies to Stakeholder Comments: 2016-02-25 7. Section 12(1) and 12(2): our interpretation is that these breaker controls, remote functionality, etc can be shared if the battery energy storage facility is co-located with an existing generating site and shares a common point of interconnection. Could the AESO verify that our interpretation is accurate? 7. The AESO agrees with NextEra’s interpretation. 8. Section 17: It is not clear in section 17 as to whether or not continuous syncrophasor measurement data must be kept for at least one 8. Syncrophasor measurement data is to be measured and stored continuously, not just for triggered events (see Section 502.9 of the ISO Page 5 of 7 calendar year, or if the intent is that this data is available for any event that results in a trip of the battery energy storage facility (similar to the SER requirements in section 18). If the intent of the requirement is to store the syncrohphasor measurements only during the events in which the battery energy storage facility experiences a trip, and to then keep each of these trip event records for a duration of one calendar year, the language might be modified to state “17(1) A battery energy storage facility must be equipped with a syncrhophasor measurement system that triggers and event record for every event that results in a trip of the battery energy storage facility.” If the intent is to have continuous PMU data stored for the entire calendar year, we would like the AESO to explain the value that this provides. TransAlta Corporation (“TransAlta”) 9. TransAlta supports the AESO’s development of technical and operating standards for battery energy storage facilities. AESO Replies to Stakeholder Comments: 2016-02-25 rules, Syncrophasor Measurement Unit Technical Requirements) and must be kept for one year from the date of data collection pursuant to subsection 7 of Section 502.14. A similar requirement exists for wind aggregated generating facilities in accordance with Section 502.1. The synchrophasor will provide valuable information to both the operator of a battery energy storage facility and the AESO regarding the performance of the battery energy storage facility for post-contingency analysis and model validation. Accordingly, no changes have been made to Section 502.13 in response to this comment. 9. The AESO acknowledges TransAlta’s support. 10. TransAlta is seeking that battery energy storage facilities receive the same treatment as generating units to the extent possible. If provisions in the proposed generating unit operating requirement rule (proposed section 502.5 of the ISO rules) are changed and are applicable to battery energy storage facilities, TransAlta requests that those changes also be reflected in proposed section 502.13. 10. The AESO acknowledges TransAlta’s comment, but notes that the ISO rules applicable to battery energy storage facilities may be different from those relating to generating units to reflect differences in the technologies. 11. TransAlta is concerned that the voltage ridethrough requirements for battery energy storage facilities are significantly different than those for 11. The proposed voltage ride-through requirements for battery energy storage facilities in Section 502.13 are in alignment with NERC Page 6 of 7 wind aggregated generating facilities (see subsection 6 of section 502.1 of the ISO rules and associated Appendix 1). TransAlta would like to clarify whether the proposed ISO rule would require that a battery energy storage facility and a wind aggregated generating facility with a common point of connection should individually trip for differing voltage ride-through requirements. Differing voltage ride-through requirements could create issues and TransAlta would like to explore the possibility of coordinating the voltage ridethrough requirements for a wind aggregated generating facility and a battery energy storage facility with a common point of connection. 12. Can the requirement in subsection 17(2)(a) for a synchrophasor measurement system at the low side of the transmission system step-up transformer be fulfilled with a synchrophasor for a generating asset with the same point of connection as the battery energy storage facility? PRC-024 Generator Frequency and Voltage Protective Relay Settings. NERC PRC-024 is currently scheduled to be considered for adoption in Alberta later in 2016. Differences in voltage ride-through requirements arising as a result of a common point of connection will be addressed through the connection process at the time a battery is added to an existing facility. 12. Generally a synchrophasor measurement system can be shared by various technologies within a common facility. However, dedicated voltage and current channels will be required for the battery energy storage facility. Subsection 17 has been revised for clarity. 13. Can the requirement in subsection 17(2)(b) for a synchrophasor measurement system at the high side of the transmission system step-up transformer be fulfilled with a synchrophasor for a generating asset with the same point of connection as the battery energy storage facility? AESO Replies to Stakeholder Comments: 2016-02-25 13. Please refer to AESO Response #12. Page 7 of 7