Showing papers by "Neville R. Watson published in 2010"

Power quality state estimation

Abstract: Due to the size and complexity of modern electrical power networks and the cost of monitoring and telecommunication equipment, it is unfeasible to fully monitor the system state. For this reason state estimation techniques are used. With strategically placed measurements, estimation techniques can determine the parameters at unmonitored locations. Fundamental frequency state estimation is now a standard tool in modern power systems. The emission and immunity levels of modern electrical equipment are different to that of the past, and this has resulted in power quality issues have become important. Knowledge of the source and location of the disturbances is desirable so that remedial action can be taken promptly. Recent contributions have extended the concept to: harmonic state estimation (HSE) and identification of harmonic sources, transient state estimation (TSE) and voltage sag state estimation (VSSE), which are all types of power quality state estimation (PQSE). This paper provides an overview of the state-of-the-art techniques currently available for PQSE in a large electrical power system. Copyright © 2009 John Wiley & Sons, Ltd.

The effect of new residential appliances on Power Quality

Abstract: The changing nature of residential network loads means that Power Quality is becoming a significant issue in New Zealand and internationally. Many residential appliances have electronic power converters that characteristically draw a non-sinusoidal current waveform. This results in increased harmonic voltage levels in the distribution network. The total impact depends on the number of appliances, their power ratings, and their harmonic diversity. A measurement survey has been performed of different categories of modern appliances to determine their Power Quality characteristics. In addition, computer modelling of the appliances on a typical distribution feeder shows their relative harmonic voltage impact.

The characteristics of CFLs; beyond the harmonics

Abstract: Large numbers of Compact Fluorescent Lamps (CFLs) are entering the power system and therefore it is important to understand their behaviour and possible detrimental impact. The main area of concern to-date has been the possible negative impact they will have on harmonic levels in the distribution system. This paper investigates some of the characteristics of CFLs that are often overlooked, or of which little is known. In particular; interference with Infrared Remote Controlled Devices, Conducted Radio Frequency Interference (RFI), inrush current at switch ON and failure modes are investigated.

Review of Power Quality State Estimation

Abstract: Fundamental frequency state estimation is now a standard tool in modern power systems. Research now is focused of extending state estimation to power quality issues. With strategically placed measurements, estimation techniques can be exploited to determine the power quality parameters at unmonitored locations. Power Quality State Estimation (PQSE) is significantly different from fundamental frequency state estimation and requires new formulations and methods. PQSE is not only one particular type of analysis but encapsulates many different types. This paper introduces the concept of PQSE and reviews and categorizes the contributions in this area.

Impact of the Darfield earthquake on the electrical power system infrastructure

Abstract: This paper gives a brief summary of the performance of the electrical infrastructure in the earthquake that struck Christchurch and surrounding regions on 4th September 2010.

Power Quality implications of new residential appliances

Abstract: Power Quality (or more accurately Voltage Quality) has become a significant issue in New Zealand with the changing nature of the loads. In the residential sector, many home appliances being bought now have electronic power converters which characteristically draw a non-sinusoidal current waveform. This results in increased harmonic levels in the distribution network. Unfortunately, some of these appliances are also relatively heavy loads, and many of the lighter loads have little harmonic diversity between them. An investigation is in progress by the EPECentre and University of Canterbury (funded by Foundation for Research, Science and Technology (FRST) and the EEA) to develop Power Quality guidelines. As part of this, characterisation of the harmonic emissions from home appliances being sold and used is required so that the possible effect on distribution networks can be determined. Moreover, this will point to possible mitigation options that can be implemented. This paper gives an overview of the home appliances tested so far, so as to provide some insight into how they will impact Power Quality levels in a distribution network.

Power system state estimation using equivalent measurement models and rectangular coordinates

Abstract: This paper presents a new state estimation method based on the concepts of equivalent measurement model and rectangular coordinate state variables. The bus voltage phasors in rectangular form are considered as the states to be estimated. Actual measurement of voltage magnitude, real and reactive power, and the estimated bus voltage phasors are employed to compute the equivalent measurements, i.e. real part of voltage phasors, and current phasors measurements. With this formulation, the measurement equations can be formulated in a form of linear measurement model. The solution method based on fixed-point iteration technique is also proposed. The error propagation of these equivalent measurements is described. Several IEEE test systems have been used to verify the performance of the proposed method. Numerical experimental results indicate that the proposed method can perform better than the conventional power system state estimation method which uses state variables in polar form.

Frequency-to-voltage conversion using OTA

Abstract: In recent years Operational Transconductance Amplifier (OTA) based integrated circuits, filters and analog circuits have been widely investigated. The usefulness of OTAs over conventional OP-Amps in the design of active circuits are well documented. This paper presents a new sinusoidal frequency-to-voltage converter which can linearly convert low voltage signals which is not possible with commercial converter ICs such as LM2917. This converter is based on an OTA based differentiator and an OTA based half wave rectifier.

Simulation of Voltage Controlled Tunable All Pass Filter Using LM13700 OTA

Abstract: In recent years Operational Transconductance Amplifier based high frequency integrated circuits, filters and systems have been widely investigated. The usefulness of OTAs over conventional OP-Amps in the design of both first order and second order active filters are well documented. This paper discusses some of the tunability issues using the Matlab/Simulink® software which are previously unreported for any commercial OTA. Using the simulation results two first order voltage controlled all pass filters with phase tuning capability are proposed. Keywords—All pass filter, Operational Transconductance Amplifier, Simulation.

Wide tunable all pass filter using OTA as active component

Abstract: A new tunable all pass filter is presented. It is based on the simple op-amp based filter with a programmable floating capacitor and a programmable resistor. The proposed floating capacitor value can be widely varied by adjusting the transconductance parameter which depends on bias current. The floating capacitor consists of only five OTAs. Using simulation results a first order all pass filter with phase tuning capability is proposed.

Electronically tunable PLL controller design using OTA

Abstract: This paper presents an electronically tunable Proportional Integral (PI) controller employing Operational Transconductance Amplifiers (OTA) for use in a Phase Lock Loop (PLL). Bandwidth, time constants, phase margin, cross-over frequency, damping factor can all be electronically tuned by the use of OTA based PI controller. Parameter design equations based on OTA bias currents, and results are presented. OTAs have the advantage that they are free from input voltage linearity restriction and temperature dependence.

Voltage controlled tunable all pass filter using LM13700 Operational Transconductance Amplifier

Abstract: In recent years Operational Transconductance Amplifier based high frequency integrated circuits, filters and systems have been widely investigated. The usefulness of OTAs over conventional OP-Amps in the design of both first order and second order active filters are well documented. This paper proposes two first order voltage controlled all pass filters with phase tuning capability. Simulation results are obtained in TINA® and verified by experimental results.

Two-quadrant Power Control for Large-current, Low-voltage Rectification with Reference to Aluminium Smelters

Abstract: Large-current, low-voltage applications such as aluminium smelters use diode-saturable reactors or thyristor-based rectification to control the DC current. Transformer on-load tap-changers are also used to minimise the steady-state reactive power requirements. This paper describes a new double-group, two-quadrant thyristor-based concept suitable for high current, where several thyristor and insulated gate bipolar transistor bridges are paralleled. By using a combination of leading and lagging firing angles, high power-factor is maintained and supplying bridges via phase shifting transformers enables continuous high-pulse operation. The theory is verified by EMTDC simulation.