Thanks for the excellent presentation. I could use it in the classroom for apprentice electricians. The inverter in a PV system is the tradename of an integrated system which includes discrete electronic devices called inverters. The inverter is a common power device found in many types of equipment in an industrial facility but they are also beginning to appear in residential HVAC systems as small motor drives on fans and compressors. Electricians like this stuff.

Dr. Casey briefly mentioned the ability of an appropriately configured inverter system to match grid demand changes in microseconds rather than tens of seconds. This characteristic is widely used in Variable Frequency Drives, VFD's, for electric motors. Coupled with a rectifier and a DC filter circuit this device has been installed on hundreds of thousands of large motors, worldwide. The annual energy savings produced by these devices is difficult to quantify but probably exceeds the global production of wind and solar PV combined. Inverter improvements have enabled the emergence of grid-connected solar. There would be little discussion on these pages without the existence of the modern IGBT and the technique of PWM.

There is some disparity in what was stated about the response time being in uS and the relatively slow switching frequency of 5 KHz of this inverter. I have design many switching power supplies in the 60 KHz to 150 KHz (kilo Hertz) range. The response time of the control loops are usually 50 uS or slower. I expect this inverter to be around 500 uS at best though that certainly seems fast enough for 60 Hz lines.
Lets not confuse inverters with motor drives. Inverters take DC and "convert" it to AC. Converters are AC to DC, while inverters are DC to AC. A typical inverter is a battery backup system used for computers.

Motor drives gain efficiency by using pulse width modulation or some similar control to allow the motor speed to vary while maintain high torque. At full speed, the motor uses the same energy as it would just connected to the normal full voltage (AC or DC). At slower speeds you get higher efficiency by just providing enought power needed to support the load. This is done in the form of DC pulses (hence PWM). I did my first discrete PWM motor control in 1974 for a medical instrument. Most modern switching power supplies use FETs, but for high currents, IGBTs work better though at lower frequencies.

It is the worst design ever, I have been in service for many years, I do not want to troublesoot this type of inverter on the field. You have to go inside that box with you head in order to see the controller board. Good luck.

A very large American inverter manufacturer
and its equally large Japanese competitor decided
to hold a canoe race down the Charles River, with
the winner securing bragging rights for the following
year. Both teams were given 30 days to
develop their strategy and prepare their teams to
reach peak performance before the race. On the
big day, Team Japan won by a mile. Team
America, very discouraged and disappointed,
decided to investigate the reason for the crushing
defeat. A canoe steering committee of senior
managers was formed to investigate the root
cause and recommend appropriate action. Their
conclusion was that Team Japan had eight people
rowing and one person steering, while Team
America had eight people steering and one person
rowing.
Unsatisfied with the internal conclusions and
feeling that a deeper study was in order, Team
America's management hired a consulting company
and paid them a large amount of money for
a second opinion. After considerable time and
great expense, they advised, of course, that too
many people were steering the canoe, while not
enough people were rowing.
Not sure of how to utilize that information, but
wanting to prevent another loss to Team Japan,
the rowing team's management structure was
totally reorganized to four steering supervisors,
three area steering supervisors and one steering
manager brought from Tyco. They also implemented a new pay-for performance
program that would give the one
person rowing the canoe greater incentive to work
harder. The program was launched with much
fanfare and named "Team High Incentive Canoe
Kickoff" (THICK), with meetings, dinners and
free pens for the rower. There was discussion of
getting new-technology paddles, canoes and other
equipment, extra vacation days for practices, and
bonuses.
The next year, Team Japan won by two miles.
Humiliated, Team America's management laid
off the Canadian rower for poor performance, halted development
of a new canoe, s

sold the equipment, and
canceled all capital expenditures for new technology.
The money saved was distributed to the senior
executives as bonuses, and the following year
the racing team was outsourced to China.

This video gives a great in-depth description of Satcon's inverter. There's another great video with one of the top engineers at Satcon, who used to work for NASA: http://bit.ly/mHlPy which gives a more broad view of the different inverters carried by Satcon as well as the sustainability of the company itself.