1. Project Overview

This project involves the deployment of an AC-coupled photovoltaic-storage integrated system at a client’s 4S dealership in Cambodia. It incorporates a 125kW photovoltaic inverter and a newly added energy storage system, enabling dual functionality: ‘self-generation for self-consumption with surplus feed-in to the grid’ and ‘off-grid backup power’. The system design fully accounts for the client’s electricity consumption patterns (average daily usage of approximately 14.8kWh, operating hours 8:00–20:00) and supports the sale of up to 15kWh of surplus electricity to the grid daily.

2. Project Details

Application

The system operates in two modes:

Grid-connected mode:

– Daytime loads prioritise photovoltaic power;

– Excess PV generation charges storage batteries first;

– Upon battery full charge , surplus PV power may be sold to the grid (capped at 15kWh/day);

During night-time or overcast conditions, battery discharge supplies power until SOC drops below 10%, at which point the system shuts down and switches to mains supply;

Charging batteries from mains supply is prohibited.

Off-Grid Standby Mode:

During mains power outages, the energy storage system automatically switches to off-grid operation to supply critical loads;

The system shuts down when battery discharge reaches SOC < 10%, resulting in load disconnection.

Installed Capacity

Photovoltaic side: 125kW inverter

Energy storage side: 100kW / 215kWh

Supporting equipment: 1 x 200kVA static transfer switch (STS)

Principal Equipment

Photovoltaic inverter

Power conversion system (PCS)

Static transfer switch (STS)

Battery management system (BMS)

Air conditioning

Metering equipment

Communication Interface: Reserved RS485 (PV Inverter & Grid Connection Meter)

3. Project Advantages

Economic Optimisation: Maximises self-generation and self-consumption to reduce electricity expenditure; supports daily fixed-quota surplus feed-in for additional revenue.

Energy Security: Provides off-grid backup power during mains outages, ensuring short-term operation of critical loads.

Intelligent Scheduling: Automatically switches charge/discharge strategies based on SOC thresholds (10%–100%) to extend battery lifespan.

High Compatibility: Reserved standard communication interfaces facilitate integration with existing PV systems and grid metering equipment.

Local Adaptation: Customised control logic tailored to customers’ low average daily consumption (approx. 14.8kWh) and operating hours, preventing over-provisioning.