DC Coupling VS. AC Coupling, How to Choose the Right ...

DC Coupling VS. AC Coupling: How to Choose the Right Configuration A photovoltaic (PV) energy storage system comprises components such as solar modules, controllers, inverters, batteries, loads, and other equipment. Regardless of the technical route, the core aim is to capture and store energy effectively. There are predominantly two topologies in the market: DC coupling and AC coupling. The big question is: which configuration should you choose, AC or DC coupling? Let’s delve into the pros and cons of each. DC Coupling In a DC coupling system, the DC power generated by the PV modules is stored directly into the batteries through a controller. The grid can also charge the battery through a bidirectional DC-AC battery inverter. Here, the energy gathering point is at the DC battery end. The working principle of DC coupling involves the use of an MPPT controller to charge the batteries when the PV system is operational. Power is released from the batteries as required by the electrical load. The energy storage system is grid-connected. If the load capacity is small and the batteries are fully charged, excess power from the PV system is supplied to the grid. Conversely, when load demand exceeds PV generation, both the grid and PV system can supply power concurrently. The battery balances energy within the system since PV generation and load consumption fluctuate. AC Coupling Contrarily, in an AC coupling system, the DC power generated by PV modules is converted into AC through an inverter. This AC power is then either fed directly to the load or sent to the grid. The grid can also charge the batteries through a bidirectional DC-AC inverter. Here, the energy gathering point is at the AC end. The working principle of AC coupling includes a PV power supply system and a battery power supply system. The PV system consists of PV arrays and grid-connected inverters, while the battery system comprises battery packs and bidirectional inverters. These systems can either operate independently without interfering with each other or be isolated from the main grid to form a micro-grid system. Comparison of DC Coupling and AC Coupling In a DC coupling system, components are connected in series, providing close connectivity but less flexibility. On the other hand, AC coupling involves parallel connections, offering better flexibility and fewer interconnections. AC coupling is particularly suitable for scenarios where grid-connected inverters are already installed, and users wish to upgrade their systems with energy storage capabilities. DC coupling is more appropriate for new installations. Application of DC Coupling in the HPS System Our Hybrid Power Solutions (HPS) system integrates a PV controller and a bidirectional battery inverter. The electricity generated by PV modules can charge the battery via an MPPT controller and can also be converted into AC for load usage. When PV power generation falls short, the battery compensates by discharging stored energy. The HPS can connect to the grid, enabling the grid to charge the battery or supply power to loads. In the HPS system, the energy gathering point is the battery. Our HPS systems offer seamless on-grid and off-grid switching, catering to a wide range of user needs. However, the PV controller’s capacity limits the size of PV panels it can connect to. Application of AC Coupling in the HPS System Historically, many users have installed grid-connected inverters that require a reference voltage to operate. If the grid fails, these inverters stop running. Our HPS can function off-grid. Customers often inquire about enabling grid-connected inverters to use HPS output voltage as a reference for generating power, thereby leveraging existing PV systems and reducing investment costs. This is achievable via AC coupling. The method involves connecting the grid-connected inverter to the HPS load end. After matching the communication protocols, the grid-connected inverter adjusts its power generation according to HPS instructions, enabling off-grid operation. Application of DC Coupling in the PCS System In the Power Conversion System (PCS), DC coupling is heavily utilized. The PV module-generated power charges the battery through a PV controller (PBD) or converts it into AC via PCS to power loads or the grid. Unlike the HPS system, the PCS system allows users to configure an optimal number of PV controllers and batteries for maximum economic benefit due to the separated PV controller PBD and bidirectional inverter CS. Application of AC Coupling in the PCS System AC coupling in the PCS system is considered during product design. A PV inverter interface on the bypass cabinet connects to grid-connected inverters. However, these inverters must match our communication protocols. At present, only certain SUNSPEC member brands ensure direct compatibility. Final Thoughts ATESS products efficiently support both DC coupling and AC coupling configurations, with the optimal solution varying by project. While our expertise lies in DC coupling systems, we also offer AC coupling solutions per customer demands. Contact us to discuss your requirements of Micro AC coupled inverter. For additional details, visit High surge capacity grid connected inverter. ATESS is always here to assist you. If you are looking for a Compact single phase string inverter, check out our best offerings. 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