When it comes to photovoltaic (PV) design, there are always stumbling blocks for power electronics engineers to overcome. These are generally connected to maximising system efficiency levels while enabling greater miniaturisation and improved reliability.With solar-based generation, losses are experienced in the inverters used to convert the DC output of the PV panels into the AC required by the power grid. It is the inverter’s power transistors that prove to be among the main culprits for loss levels.
One means of increasing efficiency is to give each PV panel its own dedicated micro inverter (MI), rather than using one larger inverter to handle an entire installation. While this is intrinsically more costly in terms of the initial hardware investment, it significantly increases flexibility with regard to the choice of panels, which can each then be managed separately. The PVs may thus be of different types and deployed on to different planes (i.e. facing in different directions).
Another way of realising significant efficiency gains is to fabricate the constituent components from a material other than traditional silicon (Si). Semiconductors made from emerging wide bandgap materials, such as gallium nitride (GaN) or silicon carbide (SiC) will be smaller, faster and more efficient than their Si counterparts and are capable of withstanding higher temperature and voltage levels. They also offer far better switching performance too - but all this admittedly comes with a higher price tag.
Innovative circuit design offers yet another route through which to realise improvements in efficiency, but without the additional costs that wide bandgap materials present. One such design methodology centres on applying advanced synchronous reverse blocking (A-SRB) to the half bridges typically used in inverters for PV applications. Conventional SRB reduces the switching losses caused by blocking the reverse recovery charge (Qrr) through the free-wheeling diode, by means of adding a second switching transistor in series with the main switch. For its part, A-SRB minimises the effect of charging output capacitance (Coss) on switching losses by pre-charging the main switch to a lower voltage, using a charge pump in the gate driver IC.
A-SRB will help bring down heavy costs that currently accompany PV panels, so helping to further solar technology’s proliferation. It can be used not only in an MI context, but also with other power applications, delivering efficiency improvements in areas such as DC/DC conversion, power factor correction and motor drives.
You can learn all about the portfolio of A-SRB solutions that Toshiba has developed in order to boost PV inverter efficiency and enable more effective implementation of MIs. Just download the following whitepaper by clicking here: