Each BESS consists of the NaS battery modules and battery management system, SMS (including the inverter and master control unit), transformer and isolation switches. For the Field system, an IntelliRupter PulseCloser provides the intelligence and point of isolation required for the islanding operation. A small propane generator is required for backup station
The islanding function of the Field battery is enabled by IntelliTeam software running on the IntelliRupter and SMS to isolate the load and reroute the power supply. In the event of a fault between the Golden substation and the IntelliRupter, the upstream feeder protection opens to clear the fault and the SMS anti-islanding protection trips the battery unit off-line. The IntelliRupter detects a lack of upstream voltage, waits a preset amount of time to confirm the fault is permanent and then opens to isolate the portion of the feeder to be islanded. It then sends a signal to the SMS, causing it to close the main SMS breaker and start supplying power to the community of Field.
Customers experience a short outage during the switching, after which the battery provides power until either the system is restored or the battery is depleted. On system restoration, the IntelliRupter detects voltage on the upstream side and signals the SMS. The SMS again isolates the battery, causing another momentary outage for the customers before the IntelliRupter closes, allowing power from the grid to flow to the community. Another signal to the SMS initiates recharging the battery.
During peak-shaving control mode, the SMS can control the batteries based on either a scheduled charge and discharge cycle or input setpoints to the controller. To optimize the life of the batteries, BC Hydro contemplated developing an advanced control algorithm to charge and discharge the batteries based on measured load at the Golden substation transformers. The design would call for the peak-shaving control setpoints to be calculated at the Golden substation and communicated to the battery sites with default local control patterns should the communications links fail.
The battery located in Golden would be discharged based on a certain load threshold being reached at the substation, with the battery at Field only discharged at a higher, more critical level. Developing the algorithm was complicated by the load profile of the Golden substation, which shows long, shallow peaks not easily covered by a battery discharge and charge cycle.
In addition, the algorithm had to account for the possibility of an outage on the distribution line between Golden and Field. In this event, it would be preferred that the Field battery be in a fully charged condition and able to support the community load for as long as possible until the distribution from Golden was restored. The algorithm also would need to recognize maximum and minimum states of charge for the batteries and the preferred charging and discharging profiles to maintain the life of the battery. A regular-forced deep discharge and charge would be scheduled to confirm battery health.
The extent of definition and development required for this algorithm and control function was estimated as beyond what was possible for the team, and the decision was made to revert to the default scheduled charge and discharge cycle.
Construction and Learning
Despite its best efforts, BC Hydro’s inexperience with BESS and a lack of defined standards for required components meant extensive delays to the project. The team was forced to learn and innovate at every stage. In some cases, this meant backtracking or redefining when a process, procedure or standard thought to be suitable turned out to be inappropriate. Finally, 18 months after receiving the award for funding, construction began at both the Golden and Field sites.
By October 2011, the concrete foundations for the batteries had been poured at both Golden and Field, and the team expected to complete the installation before winter weather and snow conditions became too severe to continue. Construction of the battery enclosures was set to start when BC Hydro received notification from NGK that a NaS battery in Japan had caught fire. NGK recommended that BC Hydro suspend construction until the cause of the fire could be determined and the project was put on hold.
During the next six months, NGK and BC Hydro met several times to review the results of NGK’s fire investigation and the proposed design modifications to mitigate future fire risk. BC Hydro now faced the prospect of another 12 months of delay before the batteries could be in service. A review of the business case indicated the risk of overcapacity at the Golden substation had diminished because of several other upgrades to the system, so the utility decided to reduce the installed battery capacity from 2 MW to 1 MW.
The 1-MW battery system would be installed at the Field site. This change meant revisiting the original contracts before remobilizing construction teams. During this time, NGK showed the utmost integrity in working through the changes and was able to deliver newly modified battery modules in time for the summer construction window.
The final challenge came in preparing the system for operation. BC Hydro had no prior experience to draw on and initially treated the system as an interconnection to an independent power producer. However, that only worked to the point of energizing the site. For ongoing operation, the site had to be treated more like a substation with established operating and maintenance orders.
BC Hydro’s NaS battery installation is now in service in Field. The team will continue to monitor the performance over the life of the battery, however, the experience and knowledge gained through its deployment can be applied immediately.
Helen Whittaker (email@example.com) is manager of technology innovation in the office of the CTO at BC Hydro. She is responsible for BC Hydro’s corporate technology road map and manages projects demonstrating new and emerging technologies. Whittaker holds a bachelor’s degree in aeronautical engineering from Loughborough University in the United Kingdom and a MBA degree from Simon Fraser University in Canada. She is a registered professional engineer in British Columbia and a certified project management professional.
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