With Higher DC/AC Ratio: How Sigenergy’s DC-Coupled Architecture Redefines C&I Energy Solutions

Sigenergy C&I Energy Solution: Innovative DC-Coupled Architecture

In PV storage system design, the DC/AC ratio—the ratio between the total installed capacity of PV modules and the rated capacity of the inverter—is a key metric that directly influences system cost-effectiveness and return on investment (ROI). A well-optimized DC/AC ratio balances initial capital investment with long-term operation yields, reduces the levelized cost of electricity (LCOE), and enhances the ROI.

However, in practical applications, the inverter’s maximum AC output is often constrained by the capacity of grid-side step-up transformers, making it difficult to strike an optimal balance between economic performance and energy utilization efficiency.

Sigenergy’s C&I Energy Solution addresses this challenge with an advanced DC coupling design that supports a DC/AC ratio of up to 2—without power clipping. This design significantly boosts Round-Trip Efficiency (RTE) and solar energy utilization, enabling commercial and industrial users to greatly increase the proportion of their electricity consumption met by solar power.

A Real Case Study: Maximizing Solar Energy Utilization

A factory with a daily electricity demand of 18 MWh is equipped with a 2.5 MVA step-up transformer. For safe operation, the inverter’s output is limited to 80% of transformer capacity—around 2 MW. In a traditional AC-coupled setup, PV capacity is capped at 2.6 MWp, generating about 9.1 MWh per day. This meets only 50.56% of the factory’s energy needs with solar power.

Sigenergy’s DC-coupled architecture overcomes this limitation. With the same 2 MW inverter limit, the system supports a DC/AC ratio of up to 2, allowing 4 MWp of PV capacity. PV modules and batteries connect directly to the DC bus, enabling solar energy to charge the battery and supply loads simultaneously. Daily solar generation rises to 14 MWh, increasing the solar energy share to 77.8% and significantly reducing grid dependence.

Avoiding Power Clipping with DC-Coupled Design

In traditional AC-coupled systems, oversizing PV capacity is a common strategy to extend inverter full-load operation time, aiming to reduce the system’s LCOE. Even under low irradiance, the inverter can operate at full capacity for longer periods. However, during peak sunlight hours, the system may generate more power than the inverter can export, resulting in power clipping—where clipped power is occured, as shown in Figure 1.

Sigenergy’s DC-coupled system eliminates this issue. By connecting both PV modules and batteries directly to the DC bus, excess solar energy during peak hours can be stored in the battery without undergoing AC conversion. This means that even when PV generation exceeds the inverter’s output limit, the surplus energy is not wasted—it is efficiently stored and later used during high-demand periods or when solar production is low.

Figure 1

Higher Round-trip Efficiency and Less Complexity

Sigenergy’s DC-coupled architecture enhances the round-trip efficiency (RTE) of solar storage systems by keeping energy conversions entirely within the DC domain during charging, avoiding unnecessary AC-DC and DC-AC conversions. This minimizes energy losses caused by repeated energy conversions, increasing system RTE by up to 2%

In large-scale projects, DC-coupled systems offer less devices by eliminating the need for PV inverter and AC combiner. Fewer devices not only reduce initial capital expenditure but also lower maintenance costs and increase the overall revenue for project owners.

Sigenergy’s innovative modular BESS with DC-coupled architecture breaks through the capacity limitations of traditional solar storage systems, significantly increasing solar energy utilization and overall economic performance for project owners. Looking ahead, Sigenergy will continue to drive innovation in solar storage technologies, leading the industry toward more economical, efficient, and sustainable energy solutions.