Alternative energy sources such as photovoltaic (PV) and wind power generation are becoming more commonplace in the global effort to conserve energy, move away from fossil fuels, become more self-reliant, and to reduce carbon footprints. Most alternative energy sources are intrinsically DC current sources. However, the modern commercial, industrial, and residential world runs almost entirely on AC current, including the power grid that distributes the power to consumers. Thus a grid-interactive inverter, or grid-tie inverter (GTI), is used to invert the DC current to an AC current. A significant cost element of the alternative energy solution is the GTI that converts the DC current supplied by the PV panels or wind turbine to AC current used by the utility power grid. As the price of PV panels falls, the inverter(s) will become a more significant fraction of the total lifecycle cost of the alternative energy system. Additionally, many PV systems operate at high voltages that subsequently require trained installers and maintenance workers familiar with the hazards of high voltage, thereby adding to the cost of the alternative energy system.
Some inverter designs use a transformer while others use no transformer (transformerless), and have a corresponding lower weight. High-frequency transformers follow an unconventional pattern of converting the DC into a high frequency AC, then back to DC, then finally to the desired line frequency AC. Transformerless inverters are less favored because of the possibility of transmitting DC faults directly into the AC grid, which could cause subsequent problems to the substation and the system at large.
Most inverters use maximum power point tracking (MPPT) that aligns the voltage and the current such that the product of the two, equal to the power, is maximized. Misalignment between the two could otherwise result in a high level of current being multiplied by a low voltage level, and vice versa, with the overall product resulting in a substantially reduced power output.
Residential electricity users in North America utilize a split single-phase AC line comprising a neutral line and two lines called phase and antiphase, which are sometimes inaccurately referred to as a two-phase line. The split single AC phase has a line voltage of 120 volts AC (VAC) root mean square (RMS) with an actual peak voltage of 170 volts (120 volts * √2) relative to neutral and a “peak-to-peak” voltage of 340 V. Traditional methodology involves converting the DC input source to drive the phase and antiphase lines via power semiconductor electronics that should be capable of withstanding the peak system voltage