Modern data centers have to rely on continuous power to provide reliable and trustable services to their end users. Such power which comes from the main energy provider is most of the times supported by local uninterruptable power supply devices (UPS) which should therefore have a higher order of magnitude in terms of exploitability and reliability with respect to the hardware they are locally supporting. The reliability and availability performance of such systems must be therefore analyzed on both perspectives; the first one centered on the end user possibility to rely on a device every time it is needed and the second one aiming at a constant product performance improvement. These two different viewpoints can be far enough to lead to different product development strategies. In this manuscript a high efficiency modular UPS based on multicore control system for datacenter applications is presented and its reliability and availability figures discussed both from the designer and end user standpoints, under different operating conditions.

The incomplete knowledge of the power distribution grid status and in particular the impossibility to constantly monitor the number of subjects (feeder) able to inject current autonomously at a known time can represent a hazardous condition for the main utility provider operators’ safety. Whenever an unexpected islanding condition is induced on the utility grid, every subject injecting power on the grid should stop such injection switching to a safety shut down condition. Due to the presence of multi injecting sources on the utility grid it is possible that one or more feeders do not recognise such event and continue to supply energy to a portion of the utility grid, keeping the main provider operators unaware of such condition. Such situation is the islanding condition. The present work aims, starting from a previous paper Fort et al. (2010) at assessing the robustness of an anti-islanding detection system in presence of a uniform distributed noise sources on the grid. The anti islanding detection system is based on the injection of an interharmonic component on the grid. The single phase case is considered. In this paper it is considered the optimum tradeoff between the harmonic distortion injection of a component which is required to be both meaningful from a signal to noise ratio standpoint and low enough not to affect the overall grid THD. The aim of this paper is to prove that such device will constitute a low cost, stand alone, and reliable automatic detection system for grid disconnection detection, to be supplied in conjunction with devices like the photovoltaic (PV) inverters in order to minimise their islanding non-detection zone.

This paper presents an analysis about the performance of bang-bang controllers used on a static machine for energy conversion (inverter) showing their robustness with respect to some key parameters and to some operating conditions. In particular a quasi sliding mode solution is proposed supported by sensitivity analysis able to allow the choice of proper operative parameters set for in field testing. Moreover a comparison between two different sliding surfaces proposal is presented.

The renewable energy based on photovoltaic (PV) has been growing remarkably in the last years with many investments in new and bigger plants worldwide. A PV plant is a complex system composed by several devices. Among these, a fundamental equipment is represented by the inverter, the fault or failure of which can lead to looses in the electricity production of the plant. For this reason an important task to take into account in the design of PV plant is the performance optimization of this equipment in order to guarantee a high efficiency level of the whole plant. In this paper a study of the critical components from the thermal point of view of a PV inverter is proposed. The final aim is a proposal of a reliable design solution considering the real condition of use for the plant and, consequently, an improvement of the PV inverter yield. At the same time, the study allows to optimize both the availability and the maintainability of the inverter hence of the whole PV plant.

The incomplete knowledge of the power distribution grid status and in particular the impossibility to constantly monitor the number of subjects (feeder) able to inject current autonomously at a certain time can represent a hazardous condition for the provider operators safety. Whenever an unexpected islanding condition is induced on the utility grid, every subject injecting power on the grid should stop such injection switching to a safety shut down condition. Due to the presence of multi injecting sources on the utility grid it is possible that, one or more feeders do not recognize such islanding event and continue to supply energy to a portion of the utility grid, keeping the main provider operators unaware of such condition. The present work aims at describing an anti-islanding DSP based device able to satisfy the measurement time constraints (2 seconds) introduced by the reference standards, and to allow the identification of masked islanding conditions by means of both traditional techniques (frequency shift, over/under voltage frequency jumps etc.) and interharmonic voltage measurements. Such device will constitute a low cost, stand alone, automatic detection system for grid disconnection detection, to be supplied in conjunction with devices like the photovoltaic inverters (PV) in order to minimize their islanding non detection zone (NDZ).

The main objective of static power inverters is to produce an AC output waveform from a DC power supply. These are the types of waveforms required in adjustable speed drives (ASDs), uninterruptible power supplies (UPS), static VAR compensators (SVC), active filters, flexible AC transmission systems, and voltage compensators, which are only a few of the possible applications. For sinusoidal AC outputs, the magnitude, frequency, and phase should be controllable. The purpose of this research, in collaboration with Astrid Energy Enterprises, is to design and realize an innovative method of feedback control for inverter systems based on a single voltage sensor. This paper gives a detailed description of the system carried out and its potentiality as compared to the state of the art.