Solar photovoltaic inverter grid layout and safety issues

Today's solar grid tie inverter layout needs to be based current sensor compact, low-cost and reliable ground current detection scheme. LEM which specially designed CT series sensors. They are rated range of 100mA, 200mA and 400mA different current device, provided at rated current 5 volt linear output. 80% of the rated current and 90% of the conditions, the response time of less than 20 ms and 60 ms. Using high-tech design ("flux gate") is the key to the low-offset or drift conditions accurately measure small AC or DC current is especially true; measure DC and AC currents up to 18 kHz. CT can be mounted on the PCB, small size, light weight, for the phase line through the hole. Mounted on a PCB CAS / CASR / CKSR closed-loop current sensor using the same flux gate technology; can be isolated AC and DC current measurement, they cover the range from 6 to 50Arms rated, the highest rating of three times the measured value, same frequency up to 300 kHz (+ /-3dB). Accordance with the latest requirements of the inverter design trends they have been specifically designed to improve performance in the following areas: common mode interference, temperature drift (offset and gain; Depending on the model, the maximum temperature drift from 7 to 0:00 30ppm / K), the response time (less than 0.3 microseconds), the insulation level, the +5 volt supply and compact size.

In order to synchronize with the grid, the inverter requires special control output. Must output sinusoidal AC inverter, so to minimize harmonics, while the side of the current changes on the grid to make a quick response. The sensors must be used here have fast response time and low zero drift. Reduces zero drift caused by temperature changes also help to reduce the complex algorithms required compensation. In contrast, the sensor monitors the MPPT DC input terminal of the inverter, the current becomes less relevant, thus a low cost open-loop sensors.

No access to the grid inverters, such as battery backup system, free from the national grid, but must comply with many of the same safety and efficiency requirements.

PV inverters must comply with the specifications of the designer is likely to become more stringent. For example, the DC input power and limitations as may be the inverter output current harmonics of the total allowable level of the kind of consensus; existing situation according to the layout with a variety of local restrictions. This requires much more than 50 or 60 Hz line frequency current to be measured accurately.

Lyme and other sensor manufacturers and photovoltaic inverter close collaboration between manufacturers, will lay the foundation for technology development. A combination of these techniques will be growing solar industry to achieve real competitive advantage and market share.