Inversor fotovoltaico operando nos modos ilhado e conectado à rede com armazenamento de energia

Abstract

The advancement of renewable energy sources, such as solar power, is rapidly increasing in Brazil and worldwide. These renewable sources are an alternative for reducing greenhouse gás emissions as they represent clean energy options. With the growing demand for clean energy, the integration of energy storage significantly contributes to enhancing the stability and efficiency of the electrical system, promoting more effective management of available energy resources. This study proposes a power management strategy and DC bus voltage control based on photovoltaic generation with a Battery Energy Storage System (BESS), operating in both grid-connected and islanded modes. Additionally, the system includes an active power filter (APF) strategy for mitigating current harmonics in the electrical grid. The dynamic model of linearized photovoltaic modules is implemented alongside the Perturb and Observe (P&O) Maximum Power Point Tracking (MPPT) algorithm in a dual-stage topology, where the Boost converter connects the modules to the DC bus. A bidirectional Buck-Boost converter is used to manage the BESS charge and discharge processes via hysteresis-based State of Charge (SOC) control. Furthermore, a DC-AC converter employing a grid-following strategy with a Phase-Locked Loop (PLL) algorithm tracks the grid frequency, controls active and reactive power at the Point of Common Coupling (PCC), operates as an APF mitigating grid current harmonics, and regulates the DC bus voltage. The proposed system achieved significant results, such as maintaining the DC bus voltage regulated in islanded mode while the photovoltaic generation provides active power. The APF performance evaluation showed a reduction in Total Harmonic Distortion (THD) of grid current from 17.86% to 3.83%, meeting the IEEE 519:2014 standard recommendation of less than 5%. The bidirectional converter with BESS operated in grid-connected mode by exchanging power during reduced irradiance levels and in islanded mode by regulating the DC bus voltage at 800V with variations smaller than 10%, supplying power to resistive and non-linear AC loads. It is noteworthy that the power factor remained unity during all operation modes. The proposed system is a viable alternative to ensure energy balance and a more reliable power supply, addressing the intermittency of photovoltaic generation caused by irradiance fluctuations and grid disconnections.