Zero Export Limit Control System
Here is how the system responds to changes in load, PV/Photovoltaic solar power generation, and battery to maintain grid export at 0kW.
Key Concepts with an Example:
Grid < 0: Exporting power (not allowed under 0 export limit)
Grid > 0: Importing power (system tries to minimise this)
Grid = 0: Target state (zero export, zero import)
Battery > 0: Charging
Battery < 0: Discharging
Why Short Export Bursts Occur:
Response Time Components:
- Control Loop: Time for system to detect grid export and calculate response (typically 1s in our system)
- Communication Delay: Time to send commands to inverters/battery (varies by protocol)
DER Response: Time for inverters/battery to physically adjust output (200ms - 5s depending on device)
During sudden load changes (like a large appliance turning off), there's an inevitable lag between the disturbance and the corrective action, resulting in brief export periods. With our 1s control loop plus communication and device response times, total response time is typically 1-6 seconds.
How to implement Multi-PV Site Export Limit Controller in Stormcloud
Use Case:
This Multi-Inverter controller maintains grid export below a threshold by limiting the PV output
Please note that this controller also comes with an artificial grid offset
- (test_grid_offset parameter is added to allow offsetting the grid measurement for testing/certification purposes) to observe PV curtailment even if the site was importing
This controller can coexist with a Peak Shaving controller to allow sites to have both an export limit and import limit at the same time.
Step 1: Click on plus to add a new controller
Step 2: Select Multi-PV Site Export Limit in Controller type and enter the required parameters.
- Note that Grid offset is 0 by default.
