Disturbance properties of photovoltaic appliances and its interaction with low-voltage grids
The compliance of the transformer-less topologies of small-scale photovoltaic (PV) appliances is individual from the viewpoints of filter manufacturers, filter designers, or distribution network operators. Based on this fact, the systematic approach should be applied to investigate the disturbance properties and their effects on the whole frequency range. In which, disturbance properties of the pulse width modulation (PWM) employed in a DC/AC inverter (PV-inverter) play an important role in the satisfaction of standard limits. The uncertainty of parameters and tolerance can be addressed effectively by the probabilistic approach based on the statistical data.
This thesis focuses on the power quality and electromagnetic compatibility issues of the PV integration in real conditions. It covers certain factors from the noise source property (PV-inverter) and its propagation path to the actual impedance characteristic of low-voltage grids (system level). Based on the experimental measurement data and statistical results following a probabilistic approach, some deterministic values and stochastic models of system parameters are considered investigating the harmonic interaction and potential remaining noises of PV appliances connection. Then, some issues of the PV appliance integration are clarified as control schemes of transformer-less topologies, optimal parameters and performance prediction of EMI filters, leakage current issue, voltage distortion, the effect of actual termination impedances, parasitic components. Based on simulation results, analytical recommendations are deduced to the compliance of new PV appliances to LV grids.