PHOTOVOLTAIC UNINTERRUPTIBLE POWER SUPPLY (UPS)

5 kWp PV Array

5 kVA UPS with modifications

[ User manual ]

Leverages existing UPS rectifier, inverter and charge controller
Low AH battery bank suffices for day-time use
Battery/ PV array voltages are matched, but much lower than dc-link voltage when ac ON (but sufficient for inverter operation)
Low-cost modular add-on controller (Smart Relay), based on linear relationship (irrespective of solar irradiance and ambient temperature) between PV array’s open circuit voltage, V_oc, and its peak power voltage, V_mp:

Automatically switches in the appropriate power source (PV array/ Utility)
Minimizes power outage probability
Maximizes expected solar power utilization
Minimizes expected grid power utilization
Minimizes expected life cycle costs (including capital amortization, battery replacement and system maintenance)

Changes to the UPS to interface PV array and Smart Relay are simple and fail-safe
Easy integration into Hybrid Systems (Wind/PV/Grid) for 24/7 operation
Diagnostics

Battery-operated hand-held PC may monitor PV/ UPS performance (through isolated com-port)
Faults that distort the V_oc vs V_mp relationship are identified by monitoring V_oc and V_dctime series
For example, a loose connection from the PV array to the UPS’s DC bus may be identified

Smart relay may be upgraded for additional features (e.g., demand side management)

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