Test Specification 16.02
Test Rationale
Once the BS generator is started by the BS controller to reenergize the grid, an interval follows within which several resources are reconnected. The main challenge that the BS generator and the system itself faces is the stability of frequency and voltage. Due to its nature, the requirements for this operating state should not be very strict. Nevertheless, rudimentary stability should always be maintained in order to avoid a new blackout. This test aims at evaluating the system’s capability to cope with the imbalances and maintain frequency as well as voltage stability within the required limits.
Specific Test System
The above test system is based on the MV distribution network benchmark application example by CIGRE1
Target measures
- ΔVmax=+5% to -5% of nominal voltage
- Δfmax= from 47.5 to 52 Hz with a ROCOF <2 Hz/s.
Input and output parameters
Input parameters
- Solar irradiance
- Wind speed
- Ambient temperature
- Load consumption
- Breaker state
Output parameters
- Frequency
- Voltages
Test Design
The test is carried out in a way that emulates the system behaviour after a black out. This implies the initial disconnection of lines and loads through the controllable circuit breakers and the start-up of the BS generator (BESS on Bus B-5). In this way, the system is sectionalized to its minimal connectivity state.
Initial system state
- All circuit breakers are open
- The BS generator is not running
Evolution of system state and test signals
- At a specific time within 1 min from the beginning of the test, the BS generator is started up
- Frequency and voltages at various points of the grid are continuously monitored
- After another time interval (e.g., 2-5 minutes) the first set of circuit breakers is reclosed to add the extra generation/load to the system. The time interval allowed for reconnection should be enough for quasi-stabilization of the system.
- The previous step is repeated as many times as the number of circuit breaker groups are reclosed
Other parameters
N/A
Temporal resolution
A sampling time of <100 ms is required for the accurate measurement of frequency and voltage variations.
Source of uncertainty
Apart from the measurement uncertainties due to the instruments’ accuracy, additional uncertainties may be introduced by the communication channel delays between the controller and the DER units. In addition to that, the system operation is subject to uncertainties due to:
Environmental conditions
Consumers’ demand
Grid parameters variability, i.e., resistance and inductance
Suspension criteria / Stopping criteria
The test should be suspended and restarted if one of the quality attributes described in the TC is not met. If stability is not ensured during the various reconnection actions, the control parameters should be readjusted and the test repeated.