Frequency Responsive Charge Sustaining Control for Grid Ancillary Services
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Solution Overview
Problem
Energy storage technologies, such as batteries, struggle to reliably provide sustained frequency regulation and synchronized reserve services due to limitations in charge capacity and duration, leading to inefficiencies and increased costs in power grid management.
Innovation Solution
A control system that monitors and maintains the state of charge (SOC) of energy storage devices to ensure they can respond to moment-by-moment energy demands, using a programmable logic controller (PLC) and battery management system (BMS) to adjust charge levels within a specified range, ensuring the energy storage system can provide or absorb energy as needed for frequency regulation and other ancillary services.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If energy storage technologies are used to provide frequency regulation services, then the response speed and flexibility improve, but the duration of energy supply is limited due to charge capacity constraints
Solution Approach 1:
The system performs preliminary charging of the energy storage device during periods when frequency regulation is not needed or when frequency is within the deadband, so that charge is available when regulation is required. This advance preparation ensures rapid response capability is maintained without compromising duration of supply.
Solution Approach 2:
The control system continuously monitors grid frequency and continuously manages the charge state of the energy storage device, ensuring that the device remains in an optimal charge range for providing frequency regulation services. This continuous management maintains both response speed and supply duration.
2Productivity
If energy storage devices discharge to meet moment-by-moment energy demands, then frequency regulation capability improves, but the state of charge depletes and reliability decreases
Solution Approach 1:
The control system continuously monitors the state of charge of the energy storage device and uses this feedback to adjust charging and discharging operations. When SOC falls below a threshold, the system prioritizes recharging; when SOC is adequate, it prioritizes frequency regulation service, thus maintaining both productivity and reliability.
Solution Approach 2:
The system dynamically adjusts its operation between charging and discharging modes based on real-time conditions including grid frequency, SOC level, and regulation demands. This dynamic behavior allows the system to maintain reliability by recharging when necessary while providing regulation services when charge is available.
3Reliability
If the state of charge is maintained within a narrow range to ensure reliability, then service availability improves, but the flexibility to respond to varying energy demands decreases
Solution Approach 1:
The system maintains charge within an optimal range as a preliminary condition for providing frequency regulation services. This pre-established charge state ensures both reliability of service and flexibility to respond to varying demands, as the device is continuously prepared to charge or discharge as needed.
Data Source
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AI summary
Systems, apparatus, and methods are provided for maintaining the state of charge of energy storage devices such as batteries, flywheel, capacitors, or other technologies that are energetically coupled with the electricity grid to support ancillary services. To reliably respond to requests to regulate the grid, the charge on the energy storage device is sustained or restored to a specified range in a manner that optimizes the readiness of the energy storage device to supply ancillary services in light of the condition of the grid. A state of charge (SOC) of the energy storage device and the grid frequency may be monitored. When a request from the operator to regulate the grid frequency is not being serviced, the charge of the energy storage device may be increased or decreased so that the charge may be sustained within the specific range. Once the SOC falls outside of the first range, charge may be added to or removed from the energy storage device when the grid frequency has appropriate values, e.g. if the grid frequency is respectively above a first setpoint or below a second setpoint.