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In microgrid systems one or more inverters should be grid-forming in order to control the voltage during island mode operation. Usually the voltage regulation is operated controlling the capacitor voltage of the LCL filter interconnected between the converter and the load. In the present paper a cascade control is proposed for a Three-Level Neutral Point Clamped (3L-NPC) inverter where the voltage...
Reactive power handling by distributed power generation systems (DPGS) was prevented in the past in order to avoid additional power losses in the distribution feeders, however several new national grid codes request reactive power generation/absorption by the converters of active users. Actually almost no literature is focused on power losses analysis in case of reactive current circulation from the...
A combined centralized/decentralized reactive power control strategy for PV systems connected to LV distribution networks is discussed in the present paper. The proposed solution is based on a centralized control performed by the Distribution System Operator (DSO) coordinated with a local/decentralized control operated at the PV converter level. The proposed strategy ensures high performance in terms...
In the More-Electric-Aircrafts the role of the power converters is fundamental and in the last years the amount of electric power has increased rapidly. In this paper a power conversion stage is proposed and controlled for the Ground Power Unit of a More-Electric-Aircraft. The power conversion topology is based on paralleled converters with interleaved modulation which allows to overcome constraints...
DC Microgrids have recently received a lot of attention in the last years due to high penetration of renewable energy sources as well as distributed energy storage systems. In the future DC microgrids could be preferable respect to AC microgrids in terms of redundancy since multi-DC-Bus solutions could provide a continuative power supply to the loads. An overview of Multi-DC-Bus solutions is presented...
Fast change of the irradiance conditions entails failure of the maximum power point tracking (MPPT) algorithm in a photovoltaic system (PVS). In this paper it is proposed the combination of a modified Perturb and Observe (P&O) distributed MPPT and an adaptive algorithm. The MPPT has been tested in case of hard mismatch conditions through simulation showing high performance in terms of efficiency.
Transformer-less photovoltaic (PV) inverters specifically designed to achieve high efficiency shall also comply with leakage current limits, low current harmonic distortion and reactive power handling capability. This paper aims at benchmarking some recently published or patented topologies with the most successful industrial products and it offers a complete trends scenario and a critical comparison...
Transformer-less photovoltaic (PV) inverters offer better efficiency compared to inverters connected to the grid through a transformer providing galvanic isolation. However, in case the transformer is omitted, the generated common-mode voltage greatly influences the leakage current flowing to ground through the parasitic capacitance of the PV array. Hence, both the power stage and the modulation strategy...
Distributed power generation systems may be required to work in both grid-connected and stand-alone modes for ensuring the supply of critical local loads, maybe organized in micro-grids. Every time the micro-grid is disconnected and reconnected from the grid, a change in the control scheme is required leading to undesired transients and even lost of stability. In this paper, the use of the droop control...
Universal operation of small-power wind turbine systems (grid-connected and island mode) may increase their penetration in the power systems. This paper proposes the use of gain scheduling to adapt the droop control gains to the different operation modes. It allows to achieve fast dynamic response in grid-connected mode and small voltage and frequency variations in island mode. An energy storage system...
Universal wind power generation systems (WPGS) should be able to operate both grid-connected and in island mode without compromising the power quality. The control system of a universal WPGS has to manage the different connections and provide harmonic disturbances compensation. This paper proposes the use of resonant filters for harmonics rejection both in grid-connected and island operation mode...
Distributed power generation systems (DPGS) are based on the grid-converters as interface between the source and the grid. They require a control strategy is designed in order to guarantee system stability and reliability. The effect of converter outages should be properly studied as well as the effect of power quality disturbances. The aim of this paper is to provide a comprehensive analysis of these...
Universal inverters will be the future interface of distributed generation to power systems based on active distribution grid where island operation should be allowed. Universal inverters should be able to work both connected to the grid both in island mode. A self-commissioning process based on advanced optimization algorithms should tune the parameters of the controllers to manage the different...
Inverters are a universal interface to inject the power produced by distributed power generation in stand-alone loads, micro-grid or the main electrical grid. The control system of a universal inverter should be designed in order to manage the different connections. This paper is an attempt to provide an overview with attention paid to current/voltage control of the converter and direct/inverse droop...
In order to meet standard specifications in terms of power quality and safety for grid-connected systems the phase angle, the amplitude and the frequency of the grid voltage are a critical piece of information. Phase locked loop (PLL) algorithms are very important for grid synchronization and monitoring in most of the grid-connected power converters system. This paper presents a performance comparison...
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