DC Load and Batteries Control Limitations for Photovoltaic Systems. Experimental Validation

Abstract

This study first presents an experimental control strategy of photovoltaic (PV) system composed of: PV array, dc-dc power converters, electrolytic storage, and programmable dc electronic load. This control aims to extract maximum power from PV array and manages the power transfer through the dc load, respecting the available storage level. The designed system allows simultaneously the supply of a dc load and the charge or the discharge of the storage during the PV power production. The experimental results obtained with a dSPACE 1103 controller board show that the PV stand-alone system responds within certain limits that appear as soon as one of the storage thresholds is reached: either loss of energy produced, or insufficient energy toward the load. In urban area, it is proposed to overcome these limitations by connecting the utility grid with the PV system while maintaining the priority for self-feeding. The experimental results of this PV semi-isolated system are shown and discussed. For this first approach, the goal was to verify the technical feasibility of the suggested system controls. The final results are energetically relevant.Index Terms-AC-DC power converters, batteries, dc-dc power converters, maximum power point tracking (MPPT), photovoltaic (PV) power system, power grid, power system control.

Influence of Dynamic Efficiency in the DC Microgrid Power Balance

“…If the power is well balanced, the bus voltage v BUS should be steady within an acceptable fluctuation scope, which is generally ±5% of the DC bus voltage reference v * BUS . In a previous work [19], without knowledge of the exact injected PV power p PV , the power balance is often realized by applying a voltage loop as follows:…”

Single-Source Multi-Battery Solar Charger: Analysis and Stability Issues

“…If during CV mode irradiation reduces such that maximum available power PPV,MAX is lower than charging power PB, no operation point would exist (see Figure 7) and SA voltage collapse to zero according to Equation (4). Therefore, such situation must be properly detected and the system should immediately switch back to CP mode to preserve operating point (note that such phenomenon does not take place in conventional, off-grid battery chargers [25]).…”

“…In grid-connected photovoltaic installations, the electrical network is perceived as a nearly-infinite storage capacity device, capable of absorbing all the energy generated by a solar array (SA). On the contrary, off-grid systems (often referred to as microgrids) fed by photovoltaic sources require careful sizing and energy management aimed to instantaneously match generation, storage and consumption [1][2][3][4][5][6][7][8].…”

Transient Analysis of Large Scale PV Systems with Floating DC Section

“…The power electronic converter must track the MPP of the PV cell [24][25][26] without modifying the mains voltage and frequency [13][14][15]. The conversion stage can be subdivided on the basis of the number of conversion stages (single or double) and on the basis of topology (e.g., centralized, string, modular, distributed).…”