MNPC - Mixed Voltage Neutral Point Clamped
The classic MNPC stage is equipped with four IGBTs and four diodes. This topology is also known as T-type or NPC2. The blocking voltage is 600 V / 650 V for the horizontal (neutral point) switches and 1200 V for the outer switches. Some modules come with 1200 V and 1700 V components. All modules are equipped with an NTC or PTC alongside the power semiconductors.
Modules with an MNPC topology are used mainly in three-phase PV inverters and UPS.
How it works
An MNPC module is often referred to as a three-level module. Its topology goes by various names such as an NPC2, T-type, or MNPC topology.
When an MNPC module is used as an inverter, the DC voltage can be converted into a variable alternating voltage and variable frequency. In contrast to a half-bridge or sixpack, an MNPC topology offers an additional voltage level at the output. The potential not only jumps to DC+ and DC-; it can also have a status of 0. The neutral point IGBTs switch the middle-point of the DC-link voltage to the output. At real or active power, these are switched at just 50 Hz and thus correspond to the positive or negative sinusoidal half-wave. Usually operated at 8 kHz, the outer switches generate the sine wave.
Although the outer switches have to be designed to handle the full DC-link voltage, they are operated at just half the voltage. This is done by using the neutral switches of the circuit. Switching losses across the components also increase with increasing voltage. However, this topology is operated at just half the DC voltage, so it still achieves a high level of efficiency. Double the frequency is applied to the filter inductance, which is not the case with half-bridges and sixpack modules.
The NPC module is an alternative to the MNPC module. It also works with three levels at the output. Each topology has its advantages, depending on the switching frequency.
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