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This article presents the implementation and performance evaluation of a model predictive control (MPC) for three-phase (3σ) transformerless interconnected five-level power electronic converters (PECs). The proposed MPC employs a discrete-time model of five-level PECs to predict future values of the grid-injected currents and ground potential. Predicted values of the grid-injected currents and ground potential are used to set the reference signals to minimize a cost function, which is formulated in terms of the command and actual values of grid-injected current and ground potential. The proposed MPC is implemented for transformerless interconnected diode-clamped and flying-capacitor five-level PECs under different conditions. Test results show that the developed MPC can operate transformerless interconnected PECs to ensure accurate, dynamic, and fast responses to changes in the power delivered to the host grid. Furthermore, the MPC demonstrates a good ability to minimize ground potentials during steady state and step changes in the power delivered to the host grid. [ABSTRACT FROM AUTHOR]

This paper presents the development and performance evaluation of a new approach for detecting voltage flicker events in power systems hosting distributed generating units. The proposed approach is based on extracting the magnitudes and phases of the different frequency sub-band contents present in the voltage signal(s). Desired magnitudes and phases are extracted by processing the voltage signal(s) using nine phaselet frames that are realized by a modulated filter bank. The modulated filter bank is designed using nine digital high-pass filters (HPFs), each of which implements one phaselet frame. The coefficients of HPFs are determined by bi-orthogonal phaselet basis functions. Extracted high-frequency sub-band contents provide signature information for accurate detection and quantification of voltage flickers. The performance of a phaselet transform based approach is experimentally tested for different conditions, including voltage flicker events that are triggered by an interconnected photovoltaic system. Performance results show accurate, reliable, and fast detection and quantification of voltage flickers, along with a negligible sensitivity to the source producing voltage flicker events. [ABSTRACT FROM AUTHOR]

This paper presents the development and performance evaluation of a direct torque controller (DTC) for permanent-magnet synchronous motor (PMSM) drives fed by a 3\phi 6-pulse wavelet-modulated dc–ac power electronic converters. The developed DTC is designed to adjust the d-q-axis components of stator voltages (vd and vq) of a PMSM in response to changes in the load torque or drive speed. The desired adjustments in vd and vq are achieved by changing the angle $\vartheta$ of a frame created by \text{-hp} PMSM drive system. The performance of the frame-angle-based DTC is investigated for different changes in the command torque and drive speed. Simulation and experimental test results demonstrate stable, fast, and accurate responses that are complimented by negligible sensitivity to variations in the system parameters. [ABSTRACT FROM PUBLISHER]

This paper presents the development and performance testing of a modified bus-split method for aggregating interconnected distributed generation units (DGUs). The modified bus-split method is developed by introducing power-based models for interconnected DGUs. The introduced power-based models are used to replace admittance-based models used in the original bus-split method. The developed power-based models are generalized for DGUs that are interconnected to a $1\phi$ or a $3\phi$ distribution network. The modified bus-split aggregation method can be beneficial for determining possible offsets of conventional power generation, as well as improving the management of peak-demand conditions. The injected power-based bus-split aggregation method is implemented for performance testing using collected data from several wind and photovoltaic energy conversion systems, which are interconnected at different locations of the distribution network. Test results demonstrate accurate and reliable aggregation without sensitivity to the interface type, power ratings, location, voltage level at the interconnection node, and/or configuration ($1\phi$ or $3\phi$). [ABSTRACT FROM AUTHOR]

A digital predictive current controller for a single-phase grid-side power electronics converter employed in photovoltaic (PV) systems is presented in this paper. A disturbance estimator is employed with the controller in order to minimize its sensitivity to any parameter variation, as well as to reject grid-side disturbances. The design of the controller and the estimator are carried out using the pole placement method. The performance of the developed current controller was tested and verified experimentally using a 5.4-kW grid-connected PV system. These experiments are carried out for different levels of power delivered to the grid under different variation in the system parameters. In addition, other controllers used for interconnected PV systems are also tested to highlight the advantages of the developed current controller. The testing results illustrate the capability of the developed current controller to provide accurate, fast, and robust responses with negligible sensitivity to parameters variations and disturbances on the grid side. [ABSTRACT FROM AUTHOR]

This paper presents the analysis and development of a new approach to monitor and update the on–off status of appliances in residential loads (RSLs). The proposed approach is structured to employ power meter readings P to determine the values for the magnitude \vert \bar{S}\vert and phase \theta of the apparent power. The value of \vert \barS\vert , associated with a value of P, is determined using Newton iterations, where a value of \theta is calculated using six phaselet frames during each iteration. Once the iterations converge, the values of P and \theta are used to construct the ZIP model (polynomial model) for the RSL, from which P and K_{qf} that relate the change in frequency to the active and reactive power demands of the modeled load. The obtained values of K_{pf}$ and K_{qf} are compared to standardized values that are defined for each appliance in an RSL. The ZIP model-phaselet frame approach is implemented as an algorithm for monitoring the on–off status of appliances in RSLs. The algorithm for the proposed approach is developed without a need to collect data for training. Test results show simple implementation, good accuracy, and insensitivity to variations in energy demands. [ABSTRACT FROM PUBLISHER]

This paper presents the performance evaluation of the extended Newton-phaselet method for determining the reactive power using only the active power in single-phase systems. The presented method is structured to use one value of the active power P to calculate one value of the apparent power \vert \bar{S}\vert , while it employs six phaselet frames to calculate a value of the angle \theta (the phase of \barS). Calculated \vert \barS\vert and \theta are used to determine a value of the active power P_{C}, which is compared to P in order to adjust \vert \barS\vert for the next Newton iteration. Furthermore, calculated values of PC,\vert \barS\vert , and \theta at each iteration are employed to determine a value of the reactive power Q_{C} at that iteration. The extended Newton-phaselet method is implemented for performance evaluation using the measured active power supplied to different 1\phi$ loads. Performance results of the developed method demonstrate simple implementation and high accuracy with minor sensitivity to load types or power factor status (lagging or leading). [ABSTRACT FROM AUTHOR]

One of the requirements for safe, stable, sustainable, and profitable operation of doubly fed induction generators (DFIGs)-based wind energy conversion systems (WECSs) is the accurate and reliable protection against electrical faults, in particular, ground faults. The performance of protective devices employed to achieve this requirement is highly dependent on the grounding configuration of the DFIG-based WECS. This paper investigates impacts of the grounding configuration on the performance of protective devices used to protect DFIGs-based WECSs from electrical ground faults. Investigated grounding configurations include solid grounding, low-resistance grounding, high-resistance grounding, and no grounding. This paper also investigates the use of a capacitor in parallel with a low resistance, as a grounding configuration, to limit ground potentials, reduce ground currents, and minimize impacts on responses of ground protective relays. The impacts of the grounding configurations on protective devices are observed through their ability to identify faults, as well as their speed to respond to identified faults. Simulation and experimental results reveal that adequately designed low-resistance grounding offers the minimum impacts on protective devices used for ground protection of DFIG-based WECSs. [ABSTRACT FROM PUBLISHER]

This paper proposes a new passive antiislanding method for three-phase (3φ) distributed generation units (DGUs). The proposed method is based on extracting signatures from the instantaneous 3φ apparent powers determined at the point of common coupling (PCC). This new method is found on the fact that the instantaneous 3φ apparent powers have components continuously exchanged between loads and sources. The islanding condition creates transient high-frequency components in the instantaneous 3φ apparent powers.These high-frequency components contain signature information capable of identifying the islanding condition. These transient high-frequency components can be extracted using the wavelet packet transform (WPT), when applied to the direct and quadrature (d-q-axis) components of the instantaneous 3φ apparent powers. The d-q WPT-based antiislanding method is implemented for testing on a 3φ permanent magnet generator-based wind energy conversion system. Test results demonstrate an accurate, fast, and reliable response to the islanding condition occurring when supplying different load types at different levels of power delivery to the host grid. [ABSTRACT FROM AUTHOR]

The switching pulses of the wavelet modulation technique are generated as sets of dilated and shifted scale-based linearly combined synthesis wavelet functions. The duration and location of each switching pulse are set by the scale (resolution level) at which its associated synthesis wavelet function is generated. In this paper, a novel controller is developed and tested for three phase (3\phi) voltage source (VS) six-pulse wavelet-modulated ac–dc converters. The proposed controller is structured to adjust the maximum value reached by the scale. This maximum value, J, is adjusted based on two angles. The first angle, \thetaI, maps changes in the 3\phi supply voltages to adjustments in J, while the second angle, \thetaO, maps changes in the dc output voltage to adjustments in J. The net adjustment in J is optimized based on the mapped changes by \thetaI and \thetaO. The optimal resolution-level controller is implemented in order to evaluate its performances for operating 3\phi VS six-pulse ac–dc converters. The performances of the proposed controller are tested when the converter is supplied with balanced, unbalanced, and distorted 3\phi voltages for feeding static and dynamic loads. Test results demonstrate fast and accurate responses, stable functioning, and good dynamics to ensure that the output dc voltage follows its command value for different supply and loading conditions. [ABSTRACT FROM PUBLISHER]

This paper presents the development, implementation, and performances of a resolution-level vector controller (RLVC) for three-phase induction motor (IM) drive systems. The RLVC is structured to adjust the output voltages of a three-phase voltage-source wavelet-modulated inverter which is used to supply a three-phase IM. The objectives of the RLVC are established by controlling the quadrature axis component of the stator currents while maintaining a constant direct axis component of the stator currents. The complete IM drive system incorporating the RLVC is successfully implemented in real time for performance testing using a three-phase squirrel-cage IM. The performances of the proposed IM drive system are tested for sudden changes in load torque and command speed. Simulated and experimental performances demonstrate reliable, stable, fast, and accurate responses of the proposed controller under various operating conditions. [ABSTRACT FROM PUBLISHER]