# Topology choices for retrofit PV: AC coupling, DC-side paralleling and online-UPS schemes Both the LEONA-B750K and LEONA-H135K explicitly support AC coupling to existing PV inverters and also document DC-side PV-storage-diesel-charging schemes, one-cluster-one-management DC coupling and online-UPS microgrids. The decision is not about which topology is newer but about whether the legacy inverters stay, where the genset and chargers connect, and which unit establishes voltage during an outage. Both the LEONA-B750K and LEONA-H135K explicitly support AC coupling to existing PV inverters and also document DC-side PV-storage-diesel-charging schemes, one-cluster-one-management DC coupling and online-UPS microgrids. The decision is not about which topology is newer but about whether the legacy inverters stay, where the genset and chargers connect, and which unit establishes voltage during an outage. Keeping legacy inverters: AC coupling The B750K brochure lists AC-coupled compatibility among the ten features of the split architecture: it accepts existing PV inverters while the storage converter provides voltage and frequency support plus energy management. The typical arrangement puts GRID/GEN through an ATS, an STS isolating critical loads, and the existing PV inverter in parallel with the B750K on the AC bus. This minimises rework and leaves the original strings and grid approval untouched, which suits C&I rooftop storage retrofits. New build: DC-side paralleling and cluster management When PV, batteries, genset and DC chargers are all new, the B750K documentation gives a one-cluster-one-management DC-coupled scheme and a DC-side PV-storage-diesel-charging scheme: six 261 kWh battery clusters, six MPPT units, DC Charge and an ATS on the same DC side, with the PCS handling grid-forming and grid connection. DC coupling removes one conversion stage and enables active SOC balancing per cluster; the price is a complete DC busbar, QF breaker and SPD design. Expansion and continuity: paralleling and UPS Several B750K units form a 2.25 MW multi-unit microgrid and can also be extended through communication-free VSG paralleling. The online-UPS microgrid scheme keeps critical loads on a continuous inversion path and, with the H135K sub-10 ms transfer and AC/DC charger integration, addresses weak grids, missing phases and near-zero interruption requirements. Write the duties and timing of the ATS (grid or genset selection), STS (transfer) and PCS (voltage establishment) into the single-line diagram; an STS is not a substitute for a grid-forming PCS. Frequently asked questions Can any existing PV inverter be connected directly? Check its anti-islanding behaviour, voltage and frequency tolerance and grid approval. In island mode the grid-forming PCS establishes voltage and the legacy inverter must follow that source stably. Should chargers sit on the DC or AC side? B750K and H135K natively support DC-DC chargers, so a DC connection removes a conversion stage. Existing AC chargers stay on the AC bus and are coordinated by the EMS dispatch logic. Related equipment and guides [SP750H54PSTD](/en/product/sp750h54pstd-2) · [SP135HAPSS](/en/product/sp135hapss) · [SP125HCPS](/en/product/sp125hcps) · [SP200/150HAPV](/en/product/sp200-150hapv) · [All technical guides](/en/blog/category/blog) · [Product catalogue](/en/products)。 ## Can any existing PV inverter be connected directly? Check its anti-islanding behaviour, voltage and frequency tolerance and grid approval. In island mode the grid-forming PCS establishes voltage and the legacy inverter must follow that source stably. ## Should chargers sit on the DC or AC side? B750K and H135K natively support DC-DC chargers, so a DC connection removes a conversion stage. Existing AC chargers stay on the AC bus and are coordinated by the EMS dispatch logic.