Park Transformation Research Articles

Observer Based Current Controlled Single Phase Grid Connected Inverter

This paper describes a decoupled current control of single phase grid connected inverter achieved through d-q control via observer. The d-q control enables to set zero steady state error. Observer helps in giving a very pure in phase and quadrature components of the fundamental load current, which is being converted into d-q frame through Park transformation and used as the feed-back signal for the control system. In addition to the fundamental component the observer extracts the DC component of the grid current. Injection of these DC component into the grid has been prevented by these controller. This decoupled control has helped in controlling active and reactive components of grid current individually. Therefore by controlling the active and reactive power injected into the grid, the power factor of the grid can be improved. The Simulation study is conducted using MATLAB, considering the grid as a constant voltage source and the results are also incorporated. The performance of the control technique for sudden changes in grid voltage, variation in inductance has been shown through simulation. This control strategy enables in reducing the harmonics in current because of the observer used in feed-back.

Sustaining a legacy – from Sydney 2000's environmental guidelines to the Commission for a Sustainable London 2012

The so-called Green Olympic movement had its origins in one of the five winning designs for the Sydney Olympic Village by two architects associated with Greenpeace Australia. This led to the development of a set of Environmental Guidelines for the Summer Olympic Games. The Sydney Olympics provided a benchmark for sustainable design and construction in Australia and also a template for future Games. London's successful bid for the 2012 Games took these principles further with a focus on legacy as its core mission. A comprehensive London 2012 Sustainability Plan was developed. The Commission for a Sustainable London 2012 was established to provide on-going independent sustainability assurance of all aspects of Games developments, the event itself and the legacy transformation of the Olympic Park. This paper explores the evolution of environmental and sustainability concerns in the Olympic movement and how these have altered the staging of the Games and the associated physical developments. It examines whether the lessons from the Sydney and London Olympics can be more widely applied in urban renewal and regeneration schemes in both Australia and the UK.

Modélisation forward-backward des machines synchrones à pôles saillants en régime stationnaire

This paper presents a diphase analytical modelling of salient pole synchronous machines aiming at studying 'accurately' the operating of these structures. Based on the Park transformation and the concept of forward and backward currents, the proposed model differs from usual approaches by the fact it introduces the e.m.f. into the different relations. This model is then used to study different motor and generator operating modes of salient pole synchronous machines and buried permanent magnet synchronous machines. The results confirm known practical results and also show a certain number of non trivial features.

Performance Evaluation of Computer Simulated Extracted Features of Induction Motor with Intermediate State of Degradation Present in Any-One Phase

The state of degradation of stator groundwall insulation in induction motor results in the state of unbalance in three-phase stator current at fundamental frequency. In this investigation, the computer simulation model to determine this state of unbalance is developed. On the basis of park's transformation model the unbalanced stator current data in three-phase machine variable ('abc') form is first transformed into equivalent two-phase ('dq') model form. The park's current vector components are then presented in a graphical dq- data pattern form and certain mathematical parameters are deduced. The computer simulation model is designed to extract simulated electrical variables and mathematical parameters of induction motor under test. The practical assumption of stator winding of induction motor being star (Y) connected with isolated neutral is considered. The extracted features of induction motor for particular case of variation in the state of degradation of stator groundwall insulation occurring in respective phases is presented. The performance evaluation of extracted features for the variation in the state of degradation of insulation in one particular phase from healthy to worst-case state along with an arbitrary intermediate state of degradation of insulation present in other two-phases is presented. On the basis of performance evaluation, it is possible to determine the appropriate selection of specific input parameter for optimal design of suitable artificial neural network classifier to distinguish the probable states of degradation of insulation.

Monitoring of inter-turn insulation failure in induction motor using advanced signal and data processing tools

Detection of stator winding inter-turn insulation failure at early stages is crucial for promoting safe and economical use of induction motors in industrial applications. Whereas major insulation failures involving larger percentages of winding are easily discernible from magnitude of supply current, minor inter-turn insulation failures involving less than 5% of turns often go undetected. The present contribution reports experimental results of minor faults due to inter-turn insulation failures in stator windings of induction motor under different loading conditions being analyzed using data and signal processing tools combining Park's Transform and Cross Wavelet Transform. Rough Set Theory (RST) based classifier has been used for fault severity monitoring.

An Efficient Synchronous Machine Model for Electromagnetic Transients

This paper proposes a new synchronous machine model based on the application of Park's transformation to the discretized equations of the phase-domain model. The proposed approach maintains the precision of the phase-domain model and eliminates its computational inefficiencies through a constant admittance matrix. The model includes magnetic saturation. Precision analysis is performed within the accuracy constraints of the surrounding network.

A youth perspective on Leisure, livability, and Ottawa’s Lansdowne Park

Residents of the Canadian Capital City – Ottawa − have been caught up in an intense debate about the transformation of Lansdowne Park, a multi-purpose city-run open space that is home to heritage buildings, an arena and stadium as well as several weekly and annual community events. In the last decade, the Canadian Football League (CFL) franchise and the south side of the stadium crumbled and then collapsed. In 2009, a group of local business owners presented the Lansdowne Live ! proposal to raise the CFL franchise and to build a large-scale hotel and shopping centre at the park. This proposal, the only one to be considered by the City Council, has become a lightning rod for debate about the park’s ‘potential’ and ‘real’ contributions to the livability of the city, the quality of life of its inhabitants, and the experiential environment for visitors. The transformation of Lansdowne Park has split the community, heritage supporters, sports fans, leisure experts, city planners, political leaders, and citizen advocates who have long worked together to contribute to the livability of the City of Ottawa. During a period of active community debate in 2009, leisure students at the University of Ottawa developed their own transformation plans based on the key issues revealed by the community discourse. Apart from being future experts in the field, the students are past, present and future stakeholders in whatever the park’s fate may be. A content analysis of the student briefs, informal review of their transformation plans and informal focus group discussions, reveals that the support and opposition for Lansdowne Park is directly linked to the livability of the city and that the youth perspective could inform the development of a solution for Ottawa’s Lansdowne Park.

Nonlinear Estimation of Synchronous Machine Parameters Using Operating Data

This paper presents a nonlinear parameter estimator for synchronous machines based on the unscented Kalman filter. The proposed methodology uses voltages and current signals recorded from the stator and the field winding to update the parameters of the classical model of the synchronous machine for stability studies. The methodology can be applied without interrupting the normal operation of the generator. Park's Transformation is included in the estimation process to relate the stator measurements (in abc components) to the nonlinear voltage equations in the qd0 reference frame. The proposed robust methodology has been validated using real and simulated data to estimate the model parameters of a 483-MVA round rotor machine.

Modeling and Control of a Three-Phase Four-Switch PWM Voltage-Source Rectifier in d-q Synchronous Frame

Controller design for six-switch pulse width-modulated (PWM) voltage source rectifiers (VSRs) is often accomplished in the rotating d-q frame coordinates in order to achieve a high-performance control. In contrast, the development of a d-q frame controller for a four-switch PWM VSR is rarely reported in the literature. In this regard, this paper introduces a control design approach in rotating d-q frame for the four-switch PWM VSRs. For this purpose, a mathematical model of the four-switch PWM VSR in rotating d-q frame is first derived. Its success is relied on performing a so-called “reduced Park Transformation” on switching functions. The derived model shares much structural property with that of a six-switch VSR. Then, two d-q frame current controller designs, input-output feedback linearization (IOFL) and linear proportional-plus-integral (LPI) control, are performed based on the derived model as application examples. Their effectiveness is verified via computer simulation and hardware experiment. Responses of an LPI a-b-c frame controller originated from the six-switch VSR are also documented for comparative study. Test results evidence the superiority of the d-q frame controllers.

Modification of Park variable transformation for wye‐connected winding without neutral wire

PurposeThe purpose of this paper is to present a modification of the Park variable transformation for a three‐phase wye‐connected winding without neutral wire. A new physical interpretation of the winding equivalent circuit is proposed.Design/methodology/approachAn equivalent circuit representing reluctance motor stator winding is rearranged to enable easier physical interpretation of obtained voltage equation. The Park transformation and constraints resulting from Kirchhof's laws are then applied to obtain a two‐axis mathematical model of the motor.FindingsA new physical two‐phase interpretation of the voltage equation for a three‐phase wye‐connected winding without neutral wire is proposed. A novel two‐axis transformation is formulated for all variables. Compared to the Park transformation, which is the same for all variables, in the proposed transformation its matrices for currents and voltages/flux linkages are different, yet strongly interconnected.Research limitations/implicationsThe proposed transformation is formulated for a specific type of winding connection scheme. Therefore, it is limited in its application.Practical implicationsFrom the practical point of view, the proposed transformation could be very useful as it applies to the most popular stator winding connection scheme. Its main advantages are fewer number of trigonometric parameters in the matrices and measurability of all currents and voltages present in its voltage equations. It could be of special importance for electric machines with non‐sinusoidal field distribution (e.g. Brushless DC).Originality/valueThe paper presents a new type of variable transformation for three‐phase electric machines with wye‐connected windings without neutral wire. Proposed transformation combines different transformations for currents and voltages/flux linkages.

Direct Torque and Indirect Flux Control of Brushless DC Motor

In this paper, the position-sensorless direct torque and indirect flux control of brushless dc (BLDC) motor with nonsinusoidal back electromotive force (EMF) has been extensively investigated. In the literature, several methods have been proposed for BLDC motor drives to obtain optimum current and torque control with minimum torque pulsations. Most methods are complicated and do not consider the stator flux linkage control, therefore, possible high-speed operations are not feasible. In this study, a novel and simple approach to achieve a low-frequency torque ripple-free direct torque control (DTC) with maximum efficiency based on dq reference frame is presented. The proposed sensorless method closely resembles the conventional DTC scheme used for sinusoidal ac motors such that it controls the torque directly and stator flux amplitude indirectly using d-axis current. This method does not require pulsewidth modulation and proportional plus integral regulators and also permits the regulation of varying signals. Furthermore, to eliminate the low-frequency torque oscillations, two actual and easily available line-to-line back EMF constants ( kba and kca) according to electrical rotor position are obtained offline and converted to the dq frame equivalents using the new line-to-line park transformation. Then, they are set up in the look-up table for torque estimation. The validity and practical applications of the proposed sensorless three-phase conduction DTC of BLDC motor drive scheme are verified through simulations and experimental results.

A Study on the Historical Transformation and Spatial Composition of the Southern Canal Belt Park in Shenyang China

A Study on the Historical Transformation and Spatial Composition of the Southern Canal Belt Park in Shenyang China

Variable-Frequency Grid-Sequence Detector Based on a Quasi-Ideal Low-Pass Filter Stage and a Phase-Locked Loop

This paper proposes a filtered-sequence phase-locked loop (FSPLL) structure for detection of the positive sequence in three-phase systems. The structure includes the use of the Park transformation and moving average filters (MAF). Performance of the MAF is mathematically analyzed and represented in Bode diagrams. The analysis allows a proper selection of the window width of the optimal filter for its application in the dq transformed variables. The proposed detector structure allows fast detection of the grid voltage positive sequence (within one grid voltage cycle). The MAF eliminates completely any oscillation multiple of the frequency for which it is designed; thus, this algorithm is not affected by the presence of imbalances or harmonics in the electrical grid. Furthermore, the PLL includes a simple-frequency detector that makes frequency adaptive the frequency depending blocks. This guarantees the proper operation of the FSPLL under large frequency changes. The performance of the entire PLL-based detector is verified through simulation and experiment. It shows very good performance under several extreme grid voltage conditions.

Determination of $d{\hbox{-}}q$ Axis Parameters of Interior Permanent Magnet Machine

In this paper, a new approach is presented for extracting saturated parameters Ld , Lq and permanent-magnet flux linkage λ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">md</i> with arbitrary load conditions for interior permanent-magnet (IPM) synchronous machines. The procedure starts with the parameter extraction in actual <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">abc</i> reference frame based on transient finite element analysis (FEA) in time domain. Then, the parameters in <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">abc</i> reference frame are transformed to <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> - <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> axis reference frame via Park transformation. This approach is able to provide better accuracy and allow easy implementation because the parameters are derived from a realistic physical representation and the effects of the slot leakage and phase-spread harmonic fields are included in the simulation.

Processamento eletrônico da energia solar fotovoltaica em sistemas conectados à rede elétrica

Este artigo apresenta um sistema fotovoltaico conectado à rede elétrica comercial em configuração centralizada e construído com um inversor trifásico de dois estágios capaz de extrair a máxima potência do arranjo de painéis fotovoltaicos. O algoritmo P&amp;O é adotado como técnica de MPPT. O isolamento é realizado por um transformador de alta frequência. O conversor que compõe o estágio CC-CC dispensa a estrutura de controle, pois funciona com razão cíclica e frequência constantes ao longo de toda a faixa de operação. Isto viabiliza o uso de conversores CC-CC ressonantes, cujo rendimento é elevado em altas frequências, favorecendo a compactação da estrutura de potência. Assim, o conversor trifásico série ressonante é escolhido para compor este estágio. O MPPT é transferido para o estágio CC-CA, que, invariavelmente, possui um controlador para a corrente injetada na rede elétrica. O inversor trifásico PWM alimentado em tensão, que compõe o estágio CC-CA, é controlado e modulado vetorialmente. O controle vetorial impõe a transformação de Park as correntes de linha, de onde resulta a corrente de eixo direto. O MPPT utiliza as mesmas variáveis do controlador de corrente e maximiza a corrente de eixo direto, a qual reflete a potência extraída do arranjo fotovoltaico. Assim, nenhuma medição específica para o MPPT é realizada, resultando em economia de sensores.

Performance of an Isolated Induction Generator Under Unbalanced Loads

In this paper, the performance of an isolated self-excited induction generator driven by a wind turbine under unbalanced loads is studied. First, the whole system, including the induction generator, the capacitors, and the loads, is modeled. The model used for the isolated induction generator is a diphase one obtained, using the Park transformation. This model allows the saturation effect to be taken into account, assuming certain simplifying hypotheses. Then, the developed model is validated comparing simulation and experiment results at no load and for balanced load cases. Finally, the same model is used to study the performance of the isolated induction generator under unbalanced load cases. Compared to the experiments, the simulation results show a good prediction of the electrical variable waveforms. Furthermore, it can be seen that the magnitude and frequency of the voltages do not vary a lot even if the load is hardly unbalanced.

Sensorless V/f control of high-speed surface permanent magnet synchronous motor drives with two novel stabilising loops for fast dynamics and robustness

This study introduces a novel fast dynamic sensorless control for high-speed surface permanent magnet synchronous motor (SPMSM) drives based on a V/f control with two stabilising loops to correct the stator voltage amplitude and phase by a closed loop for zero interior reactive power (implicitly pure i q control). This solution avoids Park transformations, speed and current closed-loop control - typical for vector control, and also rotor position and speed observers. It is robust to stator resistance and PM flux variations. Comprehensive experimental test results are given with a 50 Vdc MOSFET inverter and a SPMSM with very low electrical time constant of 0.5 ms and low inertia. Fast speed reversal of +10 000 rpm within 160 ms with good load rejection, starting from any initial rotor position and running to 20 000 rpm constitute the paper core. The speed (torque) dynamics are similar to those of vector control method with encoder, but online computation effort is notably lower, with superior control robustness. This solution should be particularly suitable for very high-speed drives with rated frequency of 0.5-10 kHz, where online computation time cycle is inherently small.

An Enhanced Inverter Controller for PV Applications Using the dSPACE Platform

This paper presents the simulation modeling and prototype development of an inverter controller for photovoltaic (PV) applications using the dSPACE DS1104 controller platform. The controller platform can link the simulation model developed in the MATLAB/SIMULINK environment to its prototype hardware. In the dSPACE controller, the voltage regulator controls the inverter by employing a proportional integral (PI) controller and the Park transformation method to generate sinusoidal pulse-width modulation (SPWM) signals. The SPWM signals switch the insulated gate bipolar transistor (IGBT) to stabilize the 50-Hz sinusoidal AC output voltages of the inverter. The simulation was performed with a DC power supply that acts as the PV generator to supply the power to the inverter. The simulation model was then translated into the inverter prototype using the dSPACE platform and tested in the laboratory to prove the efficacy of the proposed controller. The experimental results for the inverter system demonstrated the feasibility of the proposed control strategy by maintaining the THD of the output voltage at 4.6%.

Fully Integrated FPGA-Based Controller for Synchronous Motor Drive

The aim of this paper is to present a fully integrated solution for synchronous motor control. The implemented controller is based on Actel Fusion field-programmable gate array (FPGA). The objective of this paper is to evaluate the ability of the proposed fully integrated solution to ensure all the required performances in such applications, particularly in terms of control quality and time/area performances. To this purpose, a current control algorithm of a permanent-magnet synchronous machine has been implemented. This machine is associated with a resolver position sensor. In addition to the current control closed loop, all the necessary motor control tasks are implemented in the same device. The analog-to-digital conversion is ensured by the integrated analog-to-digital converter (ADC), avoiding the use of external converters. The resolver processing unit, which computes the rotor position and speed from the resolver signals, is implemented in the FPGA matrix, avoiding the use of external resolver-to-digital converter (RDC). The sine patterns used for the Park transformation are stored in the integrated flash memory blocks.

A Recursive Park Transformation to Improve the Performance of Synchronous Reference Frame Controllers in Shunt Active Power Filters

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Load harmonic currents and load unbalances reduce power quality (PQ) supplied by electrical networks. Shunt active power filters (SAPFs) are a well-known solution that can be employed to enhance electrical PQ by injecting a compensation current at the point of common coupling (PCC) of the SAPF, the load, and the electrical grid. Hence, SAPF controllers must determine the instantaneous values of the compensation reference current, including nondesirable components of the load current. A family of SAPF controllers, which evaluates the compensation reference current using synchronous rotating frames (SRFs), employs a structure based on Park transformations: direct transform, low-pass filtering (LPF), and inverse transform. The cutoff frequency and the filter order of the LPF stage must be designed properly in order to obtain an accurate reference current and a fast dynamic response of these SAPF controllers. This paper proposes a recursive implementation of the direct Park transformation that avoids the filtering stage and allows accurate SRF controllers to be designed. Moreover, the proposed implementation is not dependent on PCC conditions. The proposed implementation is evaluated using a three-phase, three-wire SAPF and compared with LPF-based controllers by simulation and experiment. </para>