Solar inverters play an important role!

If you open the inverter controller housing of a typical central inverter solar system, you will find digital isolation products in several places. These include isolation of gate drive signals, isolation of digital feedback in voltage control loops, and isolation of communication channels. ADI offers products that fully meet these design requirements.

First, all inverters have MOSFET or IGBT power transistors to do the heavy lifting of converting DC power into AC power. These power switches are driven by DC/AC controllers. Since most controllers are low-voltage devices and power transistors are relatively high-voltage devices, a digital isolated gate driver is required to achieve this conversion function. ADI’s iCoupler® technology forms the basis for several isolated gate drivers, such as the ADuM3220, which has two isolated drivers integrated in a single package with 4 A peak current drive capability. Two ADuM3220s can control four switches of an H-bridge output circuit.

In a typical inverter, there are usually at least two, if not three controllers. In the case of both a DC/DC controller and a DC/AC controller, communication between the two controllers is necessary to ensure that the entire system operates efficiently. However, DC/DC controllers are often electrically isolated from DC/AC controllers, or at least there is a high likelihood of large common-mode voltages between the two ground systems. Therefore, the communication between the two processors must be electrically isolated, and this is where multiple standard bidirectional isolators come into play.

Finally, a communication channel is needed to report the performance of the system to the central controller and receive instructions from the central controller. Differential data transmission performs better than single-ended transmission at high data rates or when communicating over long distances. Commonly used protocols for this communication task are RS-485 and CAN. The RS-485 specification conforms to the requirements of a true multipoint communications network, whereby up to 32 drivers and 32 receivers can be connected on a single (two-wire) bus, although typical solar installations generally do not need to push this performance to the extreme .