C. Di Perna

Methods for Assessing the Robustness of Electrical Power Systems Against Voltage Dips

Electrical power system robustness is defined as the intrinsic capacity of an electrical power system to maintain assigned disturbance levels when external conditions change. This paper compares two methods for estimating voltage dip severity: the critical distance method and the fault position method. Their differences are not linked to the type of network but to the type of results which we are searching for. This paper proposes a graphical color visualization of the during fault voltage matrices that immediately correlates dip severity with colors defined by a proper scale. New robustness indices are also proposed to synthesize bus performance in terms of affected and exposed areas. Numerical applications refer to real transmission and real distribution systems.

User friendly smart distributed measurement system for monitoring and assessing the electrical power quality

This paper presents an innovative smart measurement system, as well as investigates the challenges and trends in the development of distributed Power Quality (PQ) smart measurement systems. PQ monitoring is getting importance for the customers even for the more sensitive modern equipment. Up today, the control and supervision of an industrial process has mainly been focused on the electrical protection, and little attention has been paid to the quality of the electrical supplies. Nowadays, measurement and communication systems have advanced to enable the installation of web-based sensors within a PQ assessment scenario. In this perspective, we propose a measurement instrument easy to use, chip, flexible, and with advanced world wide web capability. This paper also shows the first releases of prototypes already realised.

Power converters for fuel-cells based UPS to improve power quality

The paper deals with the power converter to be used in realising small scale UPS based on fuel cell. Different structures of standard UPS are analysed and modified to consider the presence of fuel cell as DC current energy source. The control of the DC/AC converter interfacing the fuel cell based UPS with the AC grid is based on feed-forward action able to minimize the time delay in reconstructing the AC voltage at the load bus whichever UPS structure is used. The realised 1.2 kW prototype is also shown demonstrating the actual possibility of realizing the proposed system using commercial converters

Fast Probabilistic Assessment of Voltage Dips in Power Systems

The stochastic prediction of voltage dips due to faults in transmission and distribution systems can be effected applying the fault position method. Also assuming deterministic operating condition before the faults and pre-assigned failure rates of the faulted components, this method may require severe computational efforts in case of high dimension power systems. In the paper a Monte Carlo simulation procedure which properly include the fault position method is proposed to evaluate the voltage dip indices taking into account also the randomness of the pre-fault conditions and the uncertainties that can characterize the failure rate values. To reduce the computational efforts, a complete matrix formulation of the fault position method is used. Several numerical applications are presented and discussed with reference to a test system

Power Converters for Fuel-Cells Based Micro-Cogeneration Units

The paper deals with the power converter to be used in realising small scale generation units of electric and thermal energy. Polymeric fuel cells supplied with hydrogen obtained with natural gas reforming are considered as the most adequate fuel cell type for low and medium size applications. The complete structure of multistage converters is presented together with proper modelling of fuel cell. The model of fuel cell accounts for parameter variations with temperature and with reformer output. The simulations are performed using also experimental data obtained at Department of Industrial Engineering with existing 1.2 kW polymeric fuel cell system.

On Energy Recovery Possibility at Test Facility of Generator Sets

Actual Standards require specific tests on the generator sets to be overcome before introducing them into the market. During these tests, synchronous machines produce electrical energy that, in traditional test facilities, is dissipated on resistors. In this paper the realization of a no dissipative test facility able to recover this produced electrical energy is proposed. Energy recovery estimation is based on real data of an existing generator set manufacturer.

On robustness of distribution systems against voltage dips

The concept of the system robustness against voltage dips is firstly analysed evidencing the main parameters it depends on. Then, the link between short circuit power and robustness is dealt with using also some numerical results obtained on a medium voltage distribution test system. Finally some considerations are offered with the aim to contribute for enhancing knowledge on this topic