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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 performance of a controller for adjusting the power generated by the permanent magnet generator (PMG) in a wind energy conversion system (WECS), which has generated-charged battery units (BUs). The proposed controller is based on the Lagrangian relaxation unit commitment (LRUC) method to determine a command value for the PMG electromagnetic torque ($T_{e}^{*}$) at each wind speed. The determined value of $T_{e}^{*}$ is set to calculate command values for $q$ -axis currents that are required by the controllers operating the generator-side and charging power electronic converters (PECs). The performance of the LRUC-based controller is experimentally evaluated for a grid-connected 7.5-kW PMG-based WECSs with 4.44-kW BUs, when operated under various wind speeds and/or charging and discharging modes of the BUs. Performance results show that the proposed controller is capable of initiating fast and accurate responses to adjust the power generation of the PMG to meet the demands of the generator-side and charging PECs for different wind speeds, and/or charging and discharging of the BUs. These performance features are found to have minor sensitivity to the changes in wind speed, and/or levels of charging the BUs. [ABSTRACT FROM AUTHOR]

This paper presents the development, implementation, and performance evaluation of a new active dc link for permanent magnet generator (PMG)-based wind energy conversion systems (WECSs). The proposed dc link is developed based on the multiport converter (MPC) topology with two dc–dc power electronic converters (PECs) that have separate inputs and parallel-connected outputs. The first dc–dc PEC is designed as a boost converter, while the second dc–dc PEC is designed as a flyback converter. Each dc–dc PEC is operated and controlled independently to facilitate processing continuous and/or discontinuous input dc voltages. The performance of the MPC active dc-link is experimentally evaluated using a grid-connected 7.5-kW PMG-based WECS, when operated under different wind speeds and/or levels of power delivery to the host grid. Test results show that the proposed dc link can produce a high-quality-regulated dc output voltage over a wide range of wind speeds and levels of power delivery to the host grid. Performance results also demonstrate that the operation of the MPC active dc link has minor impacts on the operation and control of the generator-side and grid-side PECs. [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 compact-converter-based power supply for plasma dielectric barrier discharge (DBD) devices. The developed power supply is designed to meet weight and size requirements for applications in aeronautical systems. Multistage and multilevel switch-mode converters are employed to construct the power supply. The multistage part of the power supply is constructed from multiple dc–dc boost converters that have their inputs fed by rechargeable batteries. The outputs of the dc–dc converters are used to feed different levels of a single phase cascaded $H$ -bridge (CHB) multilevel dc–ac converter. The switching signals for the CHB dc–ac converter are generated to facilitate the adjustments of the magnitude and/or frequency of the output voltage. Such adjustments are set to allow manipulating the generated plasma body force. A prototype for the multistage multilevel power supply is constructed for performance evaluation using a fiberglass DBD device. Performance results show an effective generation and control of plasma body force, which can be achieved by a modular, lightweight, and compact size power supply. [ABSTRACT FROM PUBLISHER]

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, development, and implementation of a new controller for microgrid systems. The developed controller is structured to produce command values for the active and reactive powers ( PC and QC ), and d– q-axis voltage components ( v\text{dC} and v\text{qC}) for each bus in the microgrid system at hand. Values for PC,QC,v\text{dC}, and v\text{qC} are obtained using a power flow formulated in the $d$– $q$-axis frame. The $d$–$q$-axis power flow (DQPF) produces values for PC,QC,v\text{dC} , and v\text{qC} that can meet load demands, respond to variations in power generation within the microgrid, and accommodate the mode of operating the microgrid (interconnected or standalone), while maintaining the voltage and frequency stability. The DQPF-based controller is implemented for performance evaluation using a five-bus microgrid system operated under various conditions, including changes in power generation, step changes in load demands, and changes in mode of operation. Test results demonstrate that the DQPF-based controller can offer simple implementation, accurate and fast responses, and negligible sensitivity to the mode of microgrid operation. [ABSTRACT FROM PUBLISHER]

In this paper, the performance of a passive anti-islanding method is experimentally tested for three phase (3\phi) cogeneration systems. The tested method is based on determining the wavelet packet transform (WPT) high-frequency subbands present in the d– q-axis components of instantaneous 3\phi, when evaluated at the point of common coupling (PCC). This passive anti-islanding method is founded based on the nature of instantaneous 3\phi apparent powers that have components continuously exchanged between both sides of the PCC. An islanding condition can be considered as a transient disturbance that creates nonperiodic and nonstationary high frequency components in sd and sq. These frequency components can be parameterized by WPT high-frequency subbands, which can provide accurate detection of the islanding condition. The $d$– $q$ WPT-based anti-islanding method is tested for a $3\phi$ cogeneration system under various loading and power delivery conditions. Performance results reveal accurate, fast, and reliable detection and response to the islanding condition. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) systems have become a popular type of distributed generation units (DGUs) for small and medium levels of renewable energy generation. When grid connected, these DGUs are designed and operated to deliver electric power to their host grid through power electronic converters. The nonlinear and switched natures, along with the control actions, of these PECs can influence the voltage–current behaviors during faults in grid-connected PV systems. This paper experimentally investigates the voltage–current behaviors during faults occurring in grid-connected PV systems. Results of these investigation show that voltages and currents at the point-of-common-coupling (PCC) experience changes in their magnitudes and harmonic distortions due to faults occurring on both sides of PCC. These results can be incorporated in the improvement of the accuracy and reliability of protective devices used for grid-connected PV systems. [ABSTRACT FROM PUBLISHER]

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]