There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

On robust estimation of the location parameter

In the world, wind power is rapidly becoming a generation technology of significance. Unpredictability and variability of wind power generation is one of the fundamental difficulties faced by power system operators. Good forecasting tools are urgent needed under the relevant issues associated with the integration of wind energy into the power system. This paper gives a bibliographical survey on the general background of research and developments in the fields of wind speed and wind power forecasting. Based on the assessment of wind power forecasting models, further direction for additional research and application is proposed.

A review on the forecasting of wind speed and generated power

http://pierrepinson.com/31761/Literature/foley2012.pdf

Current methods and advances in forecasting of wind power generation

In this paper we present a new approach to detect, localize, and investigate the feasibility of classifying various types of power quality disturbances. The approach is based on wavelet transform analysis, particularly the dyadic-orthonormal wavelet transform. The key idea underlying the approach is to decompose a given disturbance signal into other signals which represent a smoothed version and a detailed version of the original signal. The decomposition is performed using multiresolution signal decomposition techniques. We demonstrate and test our proposed technique to detect and localize disturbances with actual power line disturbances. In order to enhance the detection outcomes, we utilize the squared wavelet transform coefficients of the analyzed power line signal. Based on the results of the detection and localization, we carry out an initial investigation of the ability to uniquely characterize various types of power quality disturbances. This investigation is based on characterizing the uniqueness of the squared wavelet transform coefficients for each power quality disturbance.

Power quality assessment via wavelet transform analysis

The goal of this work is to develop and validate a time-domain simulation model which can emulate the reclosing capabilities of an overcurrent and reclosing relay. The model is capable of performing multiple reclosing shots and can be programmed to operate on standard TCC curves by specifying the desired equations. The duration of the reclose intervals can also be specified. The performance of the model is compared to the performance of the reclosing relay by simulating the same fault scenarios on each and comparing the resulting fault current waveforms. Specifically, the operating times of the time-overcurrent trip function and duration of the reclose intervals are compared. The operating times are also compared with the theoretical values from the TCC curve equations. The accuracy of the reclosing relay model is compared to the actual relay for similar fault scenarios. The results show that both the model and the reclosing relay operate close to the expected theoretical values.

/pdf/time-domain-modeling-and-validation-of-overcurrent-reclosing-3p4piy8458.pdf

Time-domain modeling and validation of overcurrent/reclosing relay operation

Low-frequency high-voltage alternating-current (LF-HVac) transmission scheme has been recently proposed as an alternative solution to conventional 50/60-Hz HVac and high-voltage direct-current (HVdc) schemes for bulk power transfer. This paper proposes an optimal planning and operation for loss minimization in a multi-frequency HVac transmission system. In such a system, conventional HVac and LF-HVac grids are interconnected using back-to-back (BTB) converters. The dependence of system MW losses on converter dispatch as well as the operating voltage and frequency in the LF-HVac is discussed and compared with that of HVdc transmission. Based on the results of the loss analysis, multi-objective optimization formulations for both planning and operation stages are proposed. The planning phase decides a suitable voltage level for the LF-HVac grid, while the operation phase determines the optimal operating frequency and power dispatch of BTB converters, generators, and shunt capacitors. A solution approach that effectively handles the variations of transmission line parameters with the rated voltage and operating frequency in the LF-HVac grid is proposed. The proposed solutions of the planning and operation stages are evaluated using a multi-frequency HVac system. The results show a significant loss reduction and improved voltage regulation during a 24-hour simulation.

Optimal Planning and Operation of Multi-Frequency HVac Transmission Systems

The power swing phenomenon is characterized by oscillations in power flow between two areas of a power system due to an abrupt imbalance in mechanical and electrical power. Unintentional operation of distance relays during power swings can propagate a disturbance and result in a cascading outage. It is therefore critical that relays operate securely under such conditions. Modern distance relays can provide a function for power swing blocking (PSB). However, the PSB settings can be difficult to calculate without extensive stability studies and may fail to block if the slip frequency is too fast. In this work, we investigate the application of a model-based relaying framework applied to power swing blocking. The framework is named Model-Based Distributed Intelligence (MBDI) because it integrates, at the relay level, real-time knowledge of the network structure and system state in the form of simulation circuit models. We investigate the efficacy of a relay equipped with MBDI to supervise PSB operation during power swing and fault scenarios.

Supervision of power swing blocking using model-based distributed intelligence relaying framework

Starting with rotor blade performance and permanent magnet synchronous machine data, a series of equations for determining preliminary aerodynamic and electrical design parameters of a direct-drive wind turbine with a given converter topology is presented in this paper. Serving as a case study, these equations, derived based on aerodynamic, circuit analysis and electric machine theories, can determine blade radius, expected cut-in, rated, and cut-out wind speeds, sizes of inline inductors on machine and grid sides and the DC capacitor, and controller limits accurately. The efficacy of the method is demonstrated by modeling and simulating a complete Type 4 wind turbine based on the derived design parameters. It is shown that performance and response of the simulated wind turbine model meet the design criteria.

Determination of design parameters for direct-drive wind turbines

This paper provides 240 V ac air conditioning load data collected during summer peak heat load in Austin, TX. Air conditioning load profiles are studied in high, one-minute data resolution over the course of a typical, representative work-week where both electrical power and power factor are displayed. While THDv is 3.35%, TDDI is more concerning at 11.17% due to odd harmonics out to the 9th order. Load harmonics are tabulated, along with a discussion as it relates to IEEE Std 519–2014 harmonic limits. Lastly, the cyclical nature of air conditioning cycling is captured during a turn-on transient state so inrush current, voltage fluctuations, and electrical system parameters may be viewed. Voltage dips to 0.062 pu for 5 cycles while inrush current and power draw increase nearly 6 fold.

Surya Santoso

Papers

Time-domain modeling and validation of overcurrent/reclosing relay operation

Optimal Planning and Operation of Multi-Frequency HVac Transmission Systems

Supervision of power swing blocking using model-based distributed intelligence relaying framework

Determination of design parameters for direct-drive wind turbines

Profiles, harmonics, and transient analysis of 240 V air conditioning load during peak demand