Marco Lixia

Impact of the Model on the Accuracy of Synchrophasor Measurement

Phasor measurement units (PMUs) are becoming one of the key issues of power network monitoring. They have to be able to perform accurate estimations of quantities of interest either under steady-state or transient conditions. Among all the sources which may contribute to the uncertainty introduced by PMUs, this paper analyzes the impact of the phasor estimation models on the accuracy of these devices, focuses on algorithms proposed in the literature for the estimation of dynamic phasors, and studies their performances under several different conditions.

A software-only PTP synchronization for power system state estimation with PMUs

Synchronized Phasor Measurement Units (PMUs) are becoming a key element of monitoring, protection, control and state estimation applications in power systems and are the basis for the implementation of Wide Area Monitoring Systems (WAMSs). This paper investigates the possibility of using a software-only PTP (Precision Time Protocol) synchronization method to synchronize different Phasor Measurement Units (PMUs) and how this synchronization impacts the State Estimation. In this context, as a case study, the output data of the PMUs have been used to estimate the state of a power system of reduced size and complexity. A laboratory experimental setup has been built to evaluate the performance achievable with the proposed synchronization solution. The results thus obtained and the performance analysis are discussed in this paper.

Application of IEEE 1588 to the measurement of synchrophasors in electric power systems

This paper investigates the possibility of using the PTP (Precision Time Protocol) defined in the Standard IEEE 1588 for applications in electric power system, with reference to one of the most challenging measurement problems, i.e. the measurement of synchrophasors. The proposed approach refers to situations in which many measurement devices, connected to each other by suitable communication links, are located in a geographically limited sub-area of the power system. A laboratory experimental setup has been built to evaluate the performance achievable with this solution in terms of both accuracy and robustness. A detailed analysis of the obtained results is presented.

Adaptive Taylor-Fourier synchrophasor estimation for fast response to changing conditions

This paper proposes a modified version of the synchrophasor estimation algorithm which uses the non-orthogonal transform defined as a Taylor-Fourier Transform (TFT) and which is based on a Weighted Least Squares (WLS) approximation respect to a second order of Taylor model. The aim of the proposed changes is to improve the performance of the algorithm in presence of fast transient events. Several tests are presented, in different test conditions, to show the improvements achievable with the proposed method.

PAPR reduction in multicarrier modulations using Genetic Algorithms

This work presents a novel approach to the reduction of Peak-to-Average Power Ratio (PAPR) in multicarrier modulation: Partial Transmit Sequence (PTS) is optimized by opportune tailored Genetic Algorithms (GA) which allow achieving solution with pre-selected accuracy and reduced computational burden. A comparative study on both Orthogonal Frequency Division Multiplexing (OFDM) and Wavelet Packets Multi-Carrier Modulation (WP-MCM) has been conducted. Results show that although WP-MCM outperforms conventional OFDM schemes in terms of PAPR, GA applied to PTS are more effective in reducing PAPR for OFDM rather than for WP-MCM.

On the accuracy specifications of Phasor Measurement Units

A critical overview of the accuracy specifications of Phasor Measurement Units in the measurement of synchrophasors is presented in this work. The focus is both on the possible ambiguity arising from the definition of Total Vector Error (TVE), provided by the IEEE Standard C37.118-2005, and on the lack of homogeneity in the information provided by PMU manufacturers, that makes a very difficult task the comparison of the performance ensured by the different commercial devices. The discussion is based on both theoretical considerations and experimental results on PMU prototypes.

Impact of PMU sychronization on wide area state estimation

This paper investigates the impact of the PTP (Precision Time Protocol) synchronization method, used to synchronize different Phasor Measurement Units (PMUs), on a state estimation application. As a case of study, the output data of the PMUs, synchronized by means of a software-only implementation of the PTP, have been used to estimate the state of an IEEE 57-bus power system.

Optimized APSK bit allocation for satellite communication

In this paper a novel optimal bit allocation for APSK modulation is proposed. Optimization is done by GA according to the satellite channel error sensitivity of the data. Furthermore, a new bit mapping is proposed for 16-APSK and 32-APSK. Results show the improvement of the proposed scheme with respect to the state of the art of the APSK modulation.

Adaptive Wavelet Modulation for Cognitive Radio

Wavelet Modulation (WM) has been investigated in the past as multi-rate transmission technique on channels unknown in time or bandwidth. Such a channel conditions are common in Dynamic Spectrum Access (DSA) networks where secondary users aim to opportunistically transmit alongside primaries. In this paper, WM is opportunely designed to exploit channel opportunities avoiding interferences with the primary users of the spectrum. Unequal power allocation is performed according to both channel availability and data sensitivity to channel errors: zero power (i.e., carrier suppression) is assigned to potentially harmful wavelets whereas the power budget is distributed on safe wavelets in order to optimize the minimum square error between transmitted and received data. As to optimization Genetic Algorithms (GA) are used due to their capacity to solve complex problems with reduced convergence time and predefined accuracy when tailored to specific cases.

Adaptive Wavelet Modulation with Unequal Power Allocation for DSA Networks

Nowadays, the spread of wireless applications has led to the need of new spectrum resources and to the need to exploit in a more dynamic and efficient way those already in use. Several recent research works have confirmed the presence of unused spectrum portions in the range 30 MHz-3 GHz. As a consequence, developing new techniques to assure the utilization of these unused resources has become a key issue for telecommunications engineers. Wavelet Modulation has some characteristic that makes it suitable to exploit channel opportunities avoiding interferences with the primary users of the spectrum. In this paper we propose an Adaptive Wavelet Modulation with Unequal power allocation. Unequal power allocation is performed according to both channel availability and data sensitivity to channel errors: zero power (i.e., carrier suppression) is assigned to potentially harmful wavelets whereas the power budget is distributed on safe wavelets in order to optimize the minimum square error between transmitted and received data. Genetic Algorithms have been used to solve the optimization problem of the weights.