Grid-connected rooftop and ground-mounted solar photovoltaics (PV) systems have gained attraction globally in recent years due to (a) reduced PV module prices, (b) maturing inverter technology, and (c) incentives through feed-in tariff (FiT) or net metering. The large penetration of grid-connected PVs coupled with nonlinear loads and bidirectional power flows impacts grid voltage levels and total harmonic distortion (THD) at the low-voltage (LV) distribution feeder. In this study, LV power quality issues with significant nonlinear loads were evaluated at the point of common coupling (PCC). Various cases of PV penetration (0 to 100%) were evaluated for practical feeder data in a weak grid environment and tested at the radial modified IEEE-34 bus system to evaluate total harmonic distortion in the current (THD_i) and voltage (THD_v) at PCC along with the seasonal variations. Results showed lower active, reactive, and apparent power losses of 1.9, 2.6, and 3.3%, respectively, with 50% solar PV penetration in the LV network as the voltage profile of the LV network was significantly improved compared to the base case of no solar. Further, with 50% PV penetration, THD_i and THD_v at PCC were noted as 10.2 and 5.2%, respectively, which is within the IEEE benchmarks at LV.

Plug-in electric buses (PEBs) are a promising alternative to conventional buses to provide a sustainable, economical, and efficient mode of transportation. However, electrification of public transportation leads to a phenomenon of peak load that impacts the stability of low voltage (LV) feeders. In this context, the effective integration of an energy storage system (ESS) and photovoltaic (PV) in a bus depot charging ecosystem can lead to i) peak load reduction and ii) charging cost reduction with low carbon emission. Therefore, a limited PEB charge scheduling algorithm is proposed for: i) bus depot operator (BDO) profit maximization and ii) grid stability enhancement considering the constraints of PEB charging and grids. A mixed integer linear programming (MILP) model for BDO profit maximization has been formulated and analyzed using IBM ILOG studio with CPLEX solver. Simulation has been performed for SkyBus electric fleet using real-world data such as actual bus arrival and departure schedules under diverse traffic, number of passengers, trip duration, daily load profile, solar radiation profile, and benchmark storage price. The charging impact of PEBs was tested on one of the distribution feeders in Auckland, New Zealand. The BDO generates revenue by performing energy trading among PV, ESS, PEBs, and buildings after incorporating capital investment, operation and maintenance, and depreciation costs.

A number of mathematical models are available to model the performance of solar modules under varying operating conditions. Most commonly recognized and used models include (a) the basic three-parameter model, (b) the five-parameter model, and (c) the seven-parameter model. The basic three-parameter model does not incorporate series and shunt resistance for IV curves. The five-parameter model incorporates the effect of series and shunt resistance, and the seven-parameter model further includes the additional effect of temperature and irradiance variation on solar cell parameters. While all these models reasonably predict IV profiles of solar modules at small variations from standard testing conditions (STCs), their performance in modeling the module performance at low irradiances and high temperatures is far from ideal. This work primarily reviews the accuracy of available models for various module technologies not only under STC conditions but also over a wide range of operating conditions. The accuracy of modeled results is quantified (with datasheet results) for 10 crystalline silicon (c-Si) based modules as well as 9 thin film module (TF) samples (commercial modules) at multiple irradiance conditions. The results show that the three-parameter model generally overestimates the power output both for c-Si and TF modules. The five-parameter model predicts TF technology more accurately compared to the other two available models, whereas the seven-parameter model is most accurate for c-Si module modeling under varying operations.