Requirement #4
Updated by Michelle Bausager about 2 months ago
# Requirement statement The system shall support a nominal HVDC bus voltage of 750Vdc. 800Vdc. ## Rationale A nominal voltage of 800 V enables efficient power transfer with reduced conductor losses and aligns with modern high-power conversion components and insulation practices. Nominal DC current with a 1.5mm² wire is around 15A-20A, this means around 12kW-16kW. A typical solar PV installation in Denmark is 6kW, next to 10kW installation. This means 100% solar utilization still allows a 100% equivalent battery utilization and for a 10kW system a battery equivalent of 60%. This is under the assumption of everything is on one cable string. The highest dc voltage required for any modules on the HVDC is for a 4-wire 480Vac inverter, which typically needs 678Vdc (480V*sqrt(2)). This leaves 122 Vdc (800Vdc-678Vdc) ad a buffer for voltage drop and tolerances. This means all converters/inverters should only be of the step-down/buck typologies when takes energy from the HVDC and step-up/boost typologies when supplying energy to the HVDC. ## Definition Nominal HVDC bus voltage is defined as the steady-state average DC voltage measured at the HVDC bus terminals under normal operating conditions over a sample window of 200ms with a minimum sample-rate of 50kHz. ## Notes Nominal voltage definition does not imply allowable operating range