Multifunctional photovoltaic inverters : harmonic current support effects and operation limits

• Autor(a) principal: Victor Magno Rodrigues de Jesus
• Data de Publicação: 2023
• Tipo de documento: Tese
• Idioma: eng
• Título da fonte: Repositório Institucional da UFMG
• Texto Completo: http://hdl.handle.net/1843/55633
• topic: Ancillary services; Capability curves; Harmonic current support; Multifunctional inverters; Passive filters; Power quality; Engenharia elétrica; Energia elétrica - Qualidade - Monitoramento; Energia elétrica - Distribuição - Equipamentos e acessórios, etc.; Filtros elétricos passivos

Renewable energy sources have significantly contributed to the new form of power generation that is connected to distribution and transmission systems. The distributed energy generation provided by renewable sources has been receiving increased investment, particularly photovoltaic (PV) solar energy. Power inverters play a key role in these grid-tied systems and their multifunctional operation has become a focus for achieving better cost-benefit. Multifunctional inverters are capable of attend various needs of the electrical grid, which contributes to greater efficiency and system optimization. The main objective of a PV inverter is to inject active power into the ac-grid, however due to variations in solar irradiance, they often operate below their rated current. This current margin can be used for ancillary services, such as reactive power and harmonic current support (HCS). This thesis investigates the impact of HCS on the design, operation, and control of grid-tied PV systems. The work focuses on exploring the effects of ancillary services, which can interfere with the correct functioning of distributed generation (DG) systems. Key contributions of this thesis include an algorithm for determining the limits of HCS, guidelines to obtain the voltage and current capability curves for PV inverters, analysis of nonlinear inductors impact on capability curves, and recommendations for optimal LCL filter component selection based on total system losses and HCS effects. The presented methodology enables the evaluation of passive filter and dc-link voltage designs, providing designers with a trade-offs among various performance metrics, such as efficiency and volume. The work demonstrates that it is possible to achieve a PV system with enhanced capability for HCS without compromising system efficiency. In one condition of the study case, when employing the same passive filter conditions and switching frequency, the multifunctional operation results in a decrease of 0.11% in efficiency and 0.09 kW/dm³ in power density. The findings and recommendations presented in this thesis can aid in the design and optimization of grid-tied PV systems, ultimately contributing to the efficient and reliable integration of renewable energy into the grid.