Inverters

A full-bridge (H-bridge) inverter switches the DC bus alternately across the load. Waveform quality:

• Square wave — simple, high harmonics.
• Modified sine — square wave with a zero step; cheap home inverters.
• Pure sine (SPWM) — a sinusoidal reference compared with a triangular carrier; after filtering, a clean sine.

For sinusoidal PWM with modulation index $m_a$ (linear range, $m_a \le 1$), the fundamental phase voltage peak is $m_a V_{dc}/2$ for a half-bridge leg. Space-vector PWM utilises the DC bus about 15 % better. Grid-tied solar inverters also synchronise to the grid, track the maximum power point and must disconnect when the grid fails (anti-islanding).