In simple terms, the three-phase four-leg technology is an advanced topology based on the traditional three-phase three-leg inverter, with an additional independent fourth leg specifically designed to control the neutral wire (N wire) current.

Traditional Three-Phase Three-Leg Inverter: It has only three legs (U, V, W), with each leg outputting one phase line. It typically requires a line-frequency or high-frequency isolation transformer to provide a neutral point and achieve electrical isolation and level conversion. Without a transformer, its neutral point potential is floating, making it impossible to directly connect the load's neutral wire and difficult to handle three-phase unbalanced loads.

Three-Phase Four-Leg Inverter: It features four independent H-bridge or half-bridge units. The first three legs are still responsible for outputting the U, V, W three-phase lines, while the newly added fourth leg directly generates and controls the current and voltage of the neutral wire (N wire).

The advantages are:

① Exceptional capability to handle three-phase unbalanced loads.

② Elimination of issues caused by neutral wire current.

③ Elimination of the need for a line-frequency transformer, achieving high efficiency and high power density.

④ Strong reactive power compensation and harmonic suppression capabilities.

⑤ Better support for microgrid operation.

In inverters, SiC components primarily refer to power devices made from silicon carbide (SiC), a wide-bandgap semiconductor material. They replace traditional silicon (Si)-based IGBTs and conventional silicon diodes.

Compared to IGBT-based products, those utilizing SiC offer the following advantages:

① Improved system efficiency, increasing power plant revenue

② Reduced size and weight, lowering system costs

③ Higher switching frequency, optimizing filtering performance

④ Enhanced system reliability

EMC is divided into two parts: EMI (Electromagnetic Interference), which refers to the electromagnetic interference emitted by the equipment, and EMS (Electromagnetic Susceptibility), which refers to the equipment's ability to resist external interference.

The Inpower inverter module has built-in AC and DC filtering units, eliminating the need for external magnetic rings or additional filtering modules. The unit itself directly passes the IEC 61000-6-2/-4 electromagnetic compatibility tests.

Meanwhile, electromagnetic-related requirements also become an industry challenge when integrating BESS. For example, the Radio Equipment Directive (RED) is a mandatory certification directive for radio equipment in the European Union. System-level testing involves evaluating the entire energy storage system (including the wireless communication module) for electromagnetic compatibility (EMC) and wireless performance, rather than testing only the independent communication module. Given the complexity of electromagnetic issues during system integration, a PCS with a greater EMC margin significantly reduces the overall difficulty of system integration.

During integrated cabinet assembly, facing complex electromagnetic issues and stricter Class A tests, Inpower PCS more effectively suppresses conducted and radiated interference at the source, providing a larger margin for overall cabinet testing. This avoids common issues such as "layout chaos and maintenance difficulties caused by external filtering devices," thereby improving system integration efficiency and reducing debugging costs.