Project Background

With the large-scale grid integration of renewable energy, the demand for FM capacity of power grids is increasing. A provincial power grid company invested in the construction of a 100MWh grid-level energy storage power station, which is used for new energy consumption, peak-frequency regulation and power auxiliary services. The power station adopts lithium iron phosphate battery technology, with a total installed capacity of 100MW/100MWh, consisting of 40 clusters of 2.5MWh batteries.

System specifications requirements:

• Single cluster rated current: 1500A
• Current measurement accuracy: ±0.5% (to meet the power trading metering requirements)
• Supports bi-directional current measurement: -1500A ~ +1500A
• Design life: 15 years
• Ambient temperature: -10℃ ~ +55℃ (inside the battery compartment)

Technical challenges faced

1. High-precision measurement requirements

The participation of energy storage power stations in power market trading, whether for peak and frequency regulation gains or peak and valley arbitrage, requires accurate power measurement. The current measurement accuracy requirement of ±0.5% places high demands on both the shunt and the entire measurement system.

2. High-current heat dissipation problems

At 1500A rated current, the power loss of the shunt is more than 100W, so how to dissipate heat effectively is the core challenge. If the temperature is too high due to poor heat dissipation, it not only affects the measurement accuracy, but also may affect the life of the shunt.

3. Long-term stability

The design life of the energy storage power plant is 15 years, and the current detection accuracy cannot be significantly degraded during the entire life cycle. This imposes strict requirements on the material stability of the shunt and the quality of the welding process.

4. Multi-channel coherence

With 40 cell clusters requiring highly consistent current measurements, any deviation between channels can affect cell equalization control and overall performance evaluation.

Technical Solutions

1. Shunt sizing

Each cell cluster is configured with one FL-2 shunt, key parameters:

• Resistance value: 50µΩ ±0.3% (optional accuracy level)
• Rated current: 2000A (33% margin for 1500A operating current)
• Rated voltage drop: 100mV @2000A, 75mV @1500A
• Temperature coefficient:<20ppm>
• Power loss: 112.5W @1500A

2. Thermal system design

Custom aluminum heat sink module for a tight fit to the bottom of the shunt:

• Heat sink module material: 6063 aluminum alloy, anodic oxidation treatment
• Thermally conductive silicone grease on contact surfaces, thermal resistance<0.1°C/W
• The heat dissipation module cooperates with the ventilation system of the battery cabinet, utilizing the air conditioner inside the cabinet to dissipate the heat by convection.
• Measured at 1500A continuous operation, the surface temperature rise of the shunt is controlled within 50℃.

3. Accuracy assurance measures

• Shunt factory 100% testing, accuracy screening to ±0.3% grade
• Matching ADI AD7175-2 24-bit sigma-delta ADC with 21-bit effective resolution
• The system supports online temperature compensation, NTC measurement of shunt temperature, DSP algorithm dynamic correction of resistance drift
• Regular annual calibration against a standard meter to ensure long-term accuracy

4. Batch consistency control

• 40 sets of shunts selected from the same production lot
• Resistance deviation control within ±0.1%
• Factory paired test, provide complete sets of test reports

Project results

• Measurement accuracy:Current measurement accuracy of ±0.3%, better than the design target of ±0.5%
• Heat dissipation effect:Shunt temperature rise at 1500A continuous operation<50°C, stable long-term operation
• Running record:The plant has been in stable operation for more than 3 years with no significant degradation in shunt accuracy
• Economic benefits:Accurate power metering has given the power station a competitive advantage in spot power market transactions, reducing metering losses by approximately 500,000 RMB per year
• Return on Investment:Highly accurate current detection system pays for itself in less than 8 months

Summary of technical parameters