in the smart grids context, the phovoltaic systems could be required to provide ancillary services, such as: voltage regulatio and generation of reactive power.
The operation at a power factor different from 1 would introduce higher power losses in the PV inverters and so it can justify a price for the prevision of such services.
Efficiency Solar PV inverters is contributed by MPPT efficiency and conversion efficiency. MPPT efficiency is not affected by power factor whereas conversion efficiency is impacted by operating power factor of inverter.
There are two new conversion efficiency method named as EURO and CEC
efficiency introduced to world for calculation of conversion efficiency.
Euro efficiency is a weighted conversion efficiency. Which is used irradiation
data in watts per meter square, hourly for Europe as raw data and defined weight age for calculation of conversion efficiency. This conversion efficiency was more appropriate approach for calculation of conversion efficiency.
Same as EURO efficiency, Californian efficiency is introduced which
considered irradiation profile of California for a year. This time sample rate of raw data
was minute wise instead of hourly.
I hope it will help you.
PV inverter efficiency is firstly influenced by the loading and the DC input voltage. Efficiency can be defined in several ways:
- EURO efficiency (weighted average between efficiency at different loadings, i.e. 0,03xeff5% + 0,06xeff10% + 0,13xeff20% + 0,10xeff30% + 0,48xeff50% + 0,20xeff100%, where effX% is the inverter efficiency at loading X%)
- California Energy Commission (CEC) efficiency (weighted average between efficiency at different loadings, i.e. 0,04xeff10% + 0,05xeff20% + 0,12xeff30% + 0,21xeff50% + 0,53xeff75% + 0,20xeff100%, where effX% is the inverter efficiency at loading X%). This means that CEC efficiency weights more medium-high levels of irradiation
- maximum efficiency (highest value obtained varying both the loading and the DC voltage)
- rated efficiency (defined by standards).
In addition, some technical journals realize tests on inverters to verify their efficiency depending on the influence factors (loading and DC voltage), as in the attached screen-shot.
Thank you for your kind and detailed answers.
However I would like to focus on the impact of power factor on inverter efficiency. The power factor impacts the efficiency as, given the real power, when the reactive power changes the current changes as well so the power losses related with the change.
There are already in literature some models where the efficiency is a function of S, the apparent power and a parameter a. I guess that there are other impacts. So I am looking for literature and experimental data in thi subject.
i think that this paper can help you
Valentini, M., Raducu, A., Sera, D., Teodorescu, R., 2008. PV inverter
test setup for European efficiency, static and dynamic MPPT efficiency
evaluation. In: Optimization of Electrical and Electronic Equipment,
OPTIM 2008. 11th International Conference, pp. 433–438.
I think that there only two types of inverter losses. The first one is the switching losses which is associated with the operation of the electronic switches. The second one is losses associated with operating the internal control circuits within the inverter. Both losses are active power losses regardless of the phase shift between the outpyAC voltage and current. Consequently, the operation power factor setting will not affect the losses.