Wiki describes high end inverters as a device that produce waveforms which are closer to the sine wave produced by a utility!
https://en.wikibooks.org/wiki/Basic_Electrical_Generation_and_Distribution
Basic Electrical Generation and Distribution
Inverters and Battery Based AC[edit]
An inverter is a circuit for converting direct current to alternating current. An inverter can have one or two switched-mode power supplies (SMPS).
Early inverters consisted of an oscillator driving a transistor as an on/off switch, that is used to interrupt the incoming direct current to create a square wave. This is then fed through a transformer to smooth the square wave into a sine wave and to produce the required output voltage.
More efficient inverters use various methods to produce an approximate sine wave at the transformer input rather than relying on the transformer to smooth it. Capacitors can be used to smooth the flow of current into and out of the transformer. It is also possible to produce a more sinusoidal wave by having split-rail direct current inputs at two voltages, (positive and negative inputs with a central ground). By connecting the transformer input terminals in a timed sequence between the positive rail and ground, the positive rail and the negative rail, the ground rail and the negative rail, then both to the ground rail, a 'stepped sinusoid' is generated at the transformer input and the current drain on the direct current supply is less variable.
Modified Sine Wave inverters convert the (usually 12 V DC) battery voltage to high frequency (20 kHz) AC, so that a smaller transformer can be used for stepping up to a higher voltage (say 160 V) AC. This output is converted to DC at the same voltage, and then inverted again to a quasi sine wave output (about 120 V RMS). A disadvantage of the modified sine wave inverters is that the output voltage depends on the battery voltage.
It is quite difficult to obtain a good sine wave from an inverter. The quoted accuracy (harmonic distortion) for most is less than 60%, and will have an effect on the appliances connected to the output of the inverter. This might mean noisy operation in some appliances and/or damaged electric motors, because they will run less efficiently and could overheat. High end inverters (> $2,000) produce waveforms which are closer to the sine wave produced by a utility.
Ok got it now let's put it to work to produce waveforms which are closer to the sine wave produced by a utility aka your own mini microgrid that has options. To accomplish this task there are 2 usual options (1) high end micro inverters that produce dc to ac voltage with no battery banking (2) high end inverters that require dc battery banking options. Each has it's own pros and dislikes but the better option is usually (2) as the storage capabilities give more options. Inverter dc to ac electrical power that can match utility power with battery banking gives endless options as system design for power need can be easily matched to load.
High end inverters are usually microprocessor controlled for 2 ac inputs, 1 for grid 1 for auto start generator or 1 for grid 1 for ATS automatic transfer switch, once again it is the way the setup configuration is installed for each individual system. Either way the power transfer is so fast that computer or clock resets are not needed.
Any Basic Electrical Generation and Distribution needs control and protection to provide the safety required for efficient operation and this is achieved by being able to turn the power off by either automatically by fault or manually for service.
By having total electrical power control gives even more choices to switching and automation arrangements in voltage and wattage inputs and outputs. Matching clients utility wattage loads can be easily matched and sized to their battery banking requirements to stop the utility meter from spinning for days or weeks at a time. Building the battery bank above the required load needed makes like a very large capacitor that is a source of free electrical power when solar-wind-hybrid is added into the mix.
A simple way to look at trying to match the utility power is it is just another switching point that can be ATS controlled in normally open or normally closed system design. With high end inverters it is very easy to use and switch the utility grid power as a battery charger.
In short high end inverters are well worth the investment for free electrical power when solar-wind-hybrid charging is added into the mix.
Consulting options available for online/onsite for homes, cabins, ranches, farms, telecom, remote off grid, grid tied inverter power, auto start generator. By retired master electrician that offers quality craftsmanship into high end inverter pre built systems matched to clients wattage requirements.
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