Análise dos impactos das correntes harmônicas nas redes de distribuição causados pela grande penetração de geração fotovoltaica

Abstract

In this work, the effects of harmonic currents in a distribution network system with several photovoltaic inverters were analyzed. In the first part, the inductivecapacitiveinductive (LCL) filter sizing methodology was carried out for inverters connected to a “strong” grid, according to the established parameters of total harmonic distortion of current ( 𝑇𝐻𝐷𝑖), resonant frequency (𝑓𝑟𝑒𝑠), damping coefficient (𝜉) and the power factor at the common connection point (𝑓𝑝). To verify the proposed methodology of the filter, the measurement of the harmonic content is used in the simulation of the photovoltaic system connected to the distribution network in the PSIM software. In the second part, four threephase secondary distribution network systems with photovoltaic generation are adopted, consisting of: 1) five photovoltaic generators with nominal power of 15 kW and five loads with a nominal apparent power of 15 kVA and unity power factor, 2) five photovoltaic generators with a nominal power of 15 kW and five loads with a nominal apparent power of 15 kVA and 0.98 inductive power factor, 3) five photovoltaic generators with nominal power 15 kW and five loads with a nominal apparent power of 15 kVA and 0.98 capacitive power factor, 4) two photovoltaic generators of 12 kW, two photovoltaic generator of 15 kW and one photovoltaic generator of 24 kW; two loads with nominal apparent power of 12 kVA and 0.95 and 0.98 inductive power factor, two loads with nominal apparent power of 15 kVA and 0.98 inductive and unitary power factor and one load with a nominal apparent power of 24 kVA and unitary power factor. The total harmonic distortion of current (𝑇𝐻𝐷𝑖 ) and voltage (𝑇𝐻𝐷𝑣) were investigated in 28 cases in systems 1, 2 and 3 based on the amounts of generated and consumed power with variation of the distances between the buses; and in 5 cases for system 4 based on the power generated according to the PVDG (Photovoltaic Distributed Generation) curve and on the power consumed according to typical values of residential demand, obtained by the IEA (International Energy Agency). Inverters were designed with 𝑇𝐻𝐷𝑖 current generation equal to 4.35% below the reference value of 5.0%, respecting the IEEE 5192014 standard for “weak” and “strong” networks. What affected the waveforms of the distribution network currents and the phase voltages on the buses, caused by the presence of harmonic frequencies in the system. It was found that the beginning of the day is one of the worst periods for photovoltaic energy generation, due to the low solar irradiance, consequently, the currents generated by the inverters presented greater total harmonic distortion. However, when inverters with current generation of 𝑇𝐻𝐷𝑖 equal to 0.50% were designed, the impacts of harmonic currents on distribution networks were contained.