Traditionally, DC-coupled systems were used mainly in small domestic and off-grid applications. Systems using a charger controller to control the power into the chemical storage, or battery bank, were also not typically used commercially. The DC input voltage into the charger controller was close to the nominal battery voltage in the PWM types, and in the case of the MPPT types, the voltages were well above the nominal battery voltage, typically 80-150VDC in the most common type, and in the region of 600VDC in the more commercial units. In all cases of DC-coupling, the PV power was delivered directly to the battery bank. Commercially, and for utility-scale projects, the PV power was installed at much higher DC voltages (ranging from 300 VDC, and up 1500 VDC). These devices were essentially a source of AC current that went under the heading of grid-tied inverters. They operated without battery banks and delivered the PV power into AC current, injected into an existing AC source. This AC-source was in most cases the gird. The high DC voltages were applied to string and central inverters. Micro inverters are also in this group – where individual PV panel voltages or pairs of panels...