EPE Association: EPE 2019 - DS3d: Standard and Advanced Control Techniques for Power Converters III

EPE 2019 - DS3d: Standard and Advanced Control Techniques for Power Converters III
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2019 ECCE Europe - Conference > EPE 2019 - Topic 03: Measurement and Control > EPE 2019 - DS3d: Standard and Advanced Control Techniques for Power Converters III

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   A NEW COMMON MODE VOLTAGE REDUCTION METHOD IN A GENERALIZED SPACE VECTOR MODULATOR FOR CASCADED MULTILEVEL CONVERTERS
By Gianmarco MARAGLIANO [View]
[Download]

Abstract: High switching frequency employed in modern power electronic converters is cause of important common mode electrical quantities, having as consequences the premature motor failure and other unwanted effects in drive systems. A new SVM scheme for cascaded multilevel converter, aimed to the attenuation of these consequences, is proposed.

   A Novel Approach of High Dynamic Current Control of Interior Permanent Magnet Synchronous Machines
By Jan DEGEL [View]
[Download]

Abstract: Harmonic-afflicted effects of permanent magnet synchronous machines with high power density arehardly faced by traditional current PI controllers, due to limited controller bandwidth. As a consequence,currents and lastly torque ripples appear. In this paper, a new deadbeat current controller architecturehas been presented, which is capable to encounter the effects of these harmonics. This new controlalgorithm, here named 'Hybrid-Deadbeat-Controller', combines the stability and the low steady-stateerrors offered by common PI regulators with the high dynamic offered by the deadbeat control.Therefore, a novel control algorithm is proposed, capable of either compensating the current harmonicsin order to get smoother currents or to control a varying reference value to achieve a smoother torque.The information needed to calculate the optimal reference currents is based on an online parameterestimation feeding an optimization algorithm to achieve an optimal torque output and will beinvestigated in future research. In order to ensure the stability of the controller over the whole area ofoperation even under the influence of effects changing the system's parameter, this work as wellfocusses on the robustness of the 'hybrid' dead beat controller.

   A Sensor-less Control Scheme for Grid Tied Inverters to Provide Phase Balancing Services to the Distribution Grid
By Lenos HADJIDEMETRIOU [View]
[Download]

Abstract: This work proposes a sensor-less controller for grid tied photovoltaic (PV) inverters to enable phase balancing functionalities for compensating asymmetric loading conditions imposed by building loads in low voltage distribution grids. For enabling such an advanced functional operation by PV inverter, the first step is to enable the inverter to estimate the equivalent grid impedance. Then, the grid impedance is utilized to approximate the nearby load asymmetries without using any additional current sensors. Finally, advanced control schemes have been developed for PV inverters in order to enable the new phase balancing operation mode, where the inverter can compensate the asymmetric loading conditions of a distribution feeder. The effectiveness of the proposed method has been experimentally validated in a prototype where the grid tied PV inverter is able to compensate nearby load asymmetries and maintain a purely symmetrical interaction with the grid. Further, a simulation-based investigation in a realistic distribution feeder has been performed in order to highlight the benefits of the proposed approach regarding the power quality, the energy losses and the effective utilization of distribution grid capacity.

   A Simplified Line-to-Line Space Vector Modulation for Multilevel Converter Applied for a Standalone Wind Energy Conversion System
By Tarek GHENNAM [View]
[Download]

Abstract: A new Simplified Direct Space Vector Modulation (SDSVM), based on a line-to-line space-vectordiagram, is proposed, in this paper, to control a three-level Neutral-Point-Clamped (NPC) Converterfor a standalone variable speed Wind Energy Conversion System (WECS). The frequency andmagnitude of the stator output voltage of the Doubly Fed Induction Generator (DFIG) are controlledand fixed at nominal values, despite the variable rotor speed, ensuring by that a continuous AC supplyfor three phase loads. The performance of the proposed SDSVM technique to control the standaloneDFIG based WECS is demonstrated through simulation results. The control strategy is implementedon a dSPACE DS 1104 board driving a 4.5 kW DFIG based wind system test bench. The obtainedexperimental results confirm the validity of the control.

   Active Damping based on the Capacitor Voltage Positive-Feedback for Grid-Connected Power Converters with LCL filter
By Javier SAMANES [View]
[Download]

Abstract: The capacitor voltage positive-feedback is a widely extended active damping strategy. It can effectively damp the LCL output filter resonant poles for low ratios of resonance to sampling frequencies. However, the existing delays in the control loop limit the applicability of the capacitor-voltage positive-feedback. For high ratios of resonance to sampling frequencies, it becomes ineffective and can even destabilize the system. This limitation is overcome in this paper by adjusting the delay in the feedback path. With the delay adjustment, a robust damping can be achieved if the delays are properly considered, including the filters, and the grid impedance variations are taken into account. Simulation results validate the proposed active damping strategy.

   An enhanced DC-link voltage controller for single phase AC/DC converters
By Meriem MERAI [View]
[Download]

Abstract: This paper presents a simple and efficient design methodology for the DC-link voltage control of a single-phase AC/DC converter. The DC-link voltage controller is made of a standard PI controller associated to a feed-forward control. The aim of the designed controller is to ensure three main objectives: i) the average value of the DC-link voltage must track with good accuracy a predefined reference value; ii) the DC-link voltage fluctuations must be minimized during transients and; iii) The grid current THD must be minimized during steady state operation.

   Closed-Loop Predictively Optimizing Control for Modular Multilevel Converter with Parallel Connectivity
By Chuang WANG [View]
[Download]

Abstract: This paper adopts the bilinear modeling method to design a coherent model for modular multilevel converters with parallel connectivity and proposes an optimized closed-loop control combining proportional resonant (PR) control, nearest level modulation, and online-optimization scheduling. A bilinear mathematical model of the MMSPC is developed to predict the behavior of MMSPC one step ahead and thus reduce the computation burden of the proposed closed-loop control. PR control guarantees small steady state error and rapid dynamic response. Thanks to PR control, simple nearest level modulation can replace digital pulse-width modulation or sigma-delta modulation and decrease switching loss sharply. Moreover, a novel online-optimization scheduler replaces previously used offline optimization to improve module balance. The effectiveness of the proposed closed-loop control is verified by an accurate circuit simulation setup that represents the experimental prototype.

   Comparison of Two Possible Solution for Reducing Over-voltages at the Motor Terminals in High-Speed AC Drives
By Riccardo LEUZZI [View]
[Download]

Abstract: This paper addresses the overvoltage issue occurring at the motor terminals in high-speed AC drives. Such phenomenon is substantially due to the voltage wave reflections across the connection cable occurring in presence of PWM motor supply. Moreover, such over-voltages are strictly related to the steepness of the PWM pulse and hence are more evident and severe in case a high-frequency inverter based on wide band gap devices is used to feed an AC high-speed machine. The main effect consists in a more severe stress of the motor winding insulation system which in turn may result in a major failure deeply affecting the system reliability. Two possible solutions, based on different converter topologies, are analyzed and compared in this paper in terms of overvoltage level, efficiency, encumbrance and system complexity. In particular, a Cascaded H-Bridge multilevel converter is compared with a SiC MOSFET two-level inverter equipped with active gate drivers capable of dynamically changing the switching features of the power devices.

   Constant Boost Control with Third Harmonic Injection for Quasi-Z Source Inverter used in PV Grid-connected System
By Zhengyu ZHAO [View]
[Download]

Abstract: Compared to the dual-stage inverter, quasi-Z-source inverter (qZSI) offers higher reliability and lowerswitch count but suffers from higher voltage stress on components. The qZSI is normally controlled by the simple boost control (SBC) method that adds reference signals to the sinusoidal PWM to generate the shoot-through state. This paper develops a constant boost control method with third harmonic injection. Compared to the SBC, the proposed control method increases the voltage boost and reduces the voltage stress on switches and passive components of the qZSI, making it suitable for PV gridconnected applications. The third harmonic signal is produced and injected in a way that keeps it in phase with the reference sinusoidal signals, regardless of the solar irradiance level. This reduces the total harmonic distortions (THD) and improves the output power quality. Simulation results are presented for validation of the theoretical analysis and controller design.

   Decoupled Control of the Arms of a Modular Multilevel Converter with Orthogonal Reference Signals
By Luca ZARRI [View]
[Download]

Abstract: The technology of modular multilevel converters has been proposed for high-power dc-ac applications. The modular structure of the converter, which is composed of floating capacitor converters connected in series, is one of its most appreciated advantages. However, the control of the energy stored in the floating capacitors is not simple, because it depends on the circulating current of each leg, i.e., the current that runs through the leg without affecting the power transferred to the load. The harmonic components of the circulating current can be employed to balance the arm energies, and several techniques have already been developed to address this control problem. This paper finds a solution to the control problem of the arm voltages by expressing the circulating current as a combination of orthogonal functions synthesized from the measured voltages and currents. As a result, the voltages of the upper and lower arms of each leg can be directly controlled, independently of one another. Experimental results confirm the feasibility of the developed approach.

   GaN E-HEMT based High Flatness Broadband Power Noise Source for Dynamic Identification of Mechatronic Systems and Batteries
By Pierluigi TENCA [View]
[Download]

Abstract: Still today the dynamic identification of mechatronic systems - in particular electrical machines - is often based on stimulating them with deterministic signals, being single sinusoidal tones, single steps or periodical pulse trains of fixed frequency the most common ones. Such methodologies were the most, when not the only, practicable ones when the instrumentation was limited to low frequency generators and analog oscilloscopes, at most. The modern metrological scenario allows to concretize way more sophisticated approaches nowadays, which can bring to Mechatronics more holistic and easily executable identification methods; like those based on flat noise sources traditionally used in Radio Frequency (RF). More in general, the adoption of SiC and GaN fully controllable switches demands that also Power Electronics become eventually permeated with the very different way of thinking peculiar of RF. Within the framework of such cultural and methodological evolution that Power Electronics must embrace, the paper describes the unconventional use of converters based on GaN switches as powerful high-flatness noise sources for broadband dynamic identification, here tailored for modern electrical machines and battery technologies. Indeed, owing to the much shorter raise and fall times, as well as much higher switching frequencies enabled by GaN, it is possible to greatly extend the upper boundaries of the frequency bands where desired spectra can be synthesized by commutating such fully controllable switches according to proper time-based patterns. The authors illustrate the use of a randomly PWM-modulated H-bridge employing GaN E-HEMTs as high-flatness noise source up to at least 200 kHz thanks to 1 MHz PWM carrier. Various selected experimental results from identifications of BLDC Motors and Lithium-Iron-Phosphate (LiFePo4) cells are shown. The details in the figures are fully visible by magnifying the electronic version of the paper, which represents the same approach when Microfilms were widely used.

   Improvement and Quantification of the Power Loop Robustness for Droop Controlled VSCs
By Steffen LAMPKE [View]
[Download]

Abstract: This paper studies the sensitivity of power dynamics for technically possible variations of operating point and line impedance of a droop controlled voltage source converter (VSC) connected to a stiff low voltage grid. The influence of the control parameters of traditional droop, improved droop and power-synchronizing control are analyzed by also considering their interaction with internal control dynamics and reactive power droop control. Finally, parameter selection rules are proposed that yield a robust behavior in all studied scenarios by quantifying the damping constant and finding it to be always equal to one.

   Model Predictive Control for Space Vector Modulation of a Three-Level ANPC Inverter for Efficient Loss Distribution and Neutral Point Balancing
By Umar RAUF [View]
[Download]

Abstract: This paper presents an efficient loss distribution and Neutral Point (NP) balancing method for a grid-connected Three-Phase Three-Level Active Neutral Point Clamped (3L-ANPC) inverter. A Finite Control Set Model Predictive Control (FCS-MPC) technique is used to select the optimum redundant active voltage vectors and redundant zero voltage vectors during the Space Vector Modulation (SVM). A direct discrete loss model is designed for the IGBT switches of the 3L-ANPC inverter, to calculate the junction temperature Tj of the IGBT switches for each sampling point, using information about conduction and switching losses, and thermal properties of the housing and cooling. To evaluate the performance of FCS-MPC, a Tj comparison is held out with a reference from literature. This reference utilizes a decision table based on an energy loss model. Furthermore, the performance of the FCS-MPC technique for loss distribution is analyzed during steady state. The FCS-MPC technique for NP balancing is evaluated during steady and transient states.

   Model Predictive Control for Three-Phase Four-Wire Voltage Source Converters in Standalone Mode
By Yu LI [View]
[Download]

Abstract: This work proposes a new model predictive control for three-phase four-wire voltage source convertersoperated at standalone mode. The proposed solution uses single cost function to deal with output filtervoltage and current to improve output voltage quality, meanwhile, resonant energy oscillation betweeninductance and capacitance is effectively suppressed. Enhanced performance in both steady state andtransient has been demonstrated by simulation data under nonlinear and unbalanced load condition.

   Modeling and Stability Analysis of Advanced PLLs Based on LTP Theory
By Huoming YANG [View]
[Download]

Abstract: A novel linear time-periodic (LTP) model for advanced PLLs is presented, demonstrating superior accuracy over the conventional linear time-invariant (LTI) models. Applying eigenvalues analysis, a general parameter design procedure is proposed and the effect of voltage unbalance is investigated. The effectiveness of the theoretical analysis is verified by time-domain simulation results.

   The Generalized Bode Criterion: application to the dc voltage control of a three-phase photovoltaic grid-tied inverter
By David LUMBRERAS [View]
[Download]

Abstract: As renewable energies are becoming more important in the electrical generation system, powerelectronic converters are facing new design issues related not only to their components but also to theircontrol loops. In this context, the Generalized Bode Criterion (GBC) appears as a good tool to correctlydetermine stability and to help the controller design. In order to show the potential of the GBC and howit can be applied, this paper studies a dc voltage regulation with compensation of the photovoltaic powerin a three-phase photovoltaic grid-tied inverter.

   Voltage control for VSI using load current observer
By Henrique MAGNAGO [View]
[Download]

Abstract: This paper proposes a voltage controller with disturbance observer for VSI. A discrete time dead-beatinner current loop is used to regulate and limit the inverter current. The outer voltage control loopincludes the closed loop dynamic of the current controller and, in order to reduce the THD of the outputvoltage under non-linear loads, a load current observer is included. The controller and observers havetheir dynamic behavior set through the DLQR. An interactive scan of the DLQR's Q and R matricesvalues is implemented to optimize the obtained gains. HIL results are given to support the theoreticalanalysis and to demonstrate the performance of the system.

EPE 2019 - DS3d: Standard and Advanced Control Techniques for Power Converters III
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2019 ECCE Europe - Conference > EPE 2019 - Topic 03: Measurement and Control > EPE 2019 - DS3d: Standard and Advanced Control Techniques for Power Converters III
	[return to parent folder]

	A NEW COMMON MODE VOLTAGE REDUCTION METHOD IN A GENERALIZED SPACE VECTOR MODULATOR FOR CASCADED MULTILEVEL CONVERTERS By Gianmarco MARAGLIANO	[View] [Download]
Abstract: High switching frequency employed in modern power electronic converters is cause of important common mode electrical quantities, having as consequences the premature motor failure and other unwanted effects in drive systems. A new SVM scheme for cascaded multilevel converter, aimed to the attenuation of these consequences, is proposed.

	A Novel Approach of High Dynamic Current Control of Interior Permanent Magnet Synchronous Machines By Jan DEGEL	[View] [Download]
Abstract: Harmonic-afflicted effects of permanent magnet synchronous machines with high power density arehardly faced by traditional current PI controllers, due to limited controller bandwidth. As a consequence,currents and lastly torque ripples appear. In this paper, a new deadbeat current controller architecturehas been presented, which is capable to encounter the effects of these harmonics. This new controlalgorithm, here named 'Hybrid-Deadbeat-Controller', combines the stability and the low steady-stateerrors offered by common PI regulators with the high dynamic offered by the deadbeat control.Therefore, a novel control algorithm is proposed, capable of either compensating the current harmonicsin order to get smoother currents or to control a varying reference value to achieve a smoother torque.The information needed to calculate the optimal reference currents is based on an online parameterestimation feeding an optimization algorithm to achieve an optimal torque output and will beinvestigated in future research. In order to ensure the stability of the controller over the whole area ofoperation even under the influence of effects changing the system's parameter, this work as wellfocusses on the robustness of the 'hybrid' dead beat controller.

	A Sensor-less Control Scheme for Grid Tied Inverters to Provide Phase Balancing Services to the Distribution Grid By Lenos HADJIDEMETRIOU	[View] [Download]
Abstract: This work proposes a sensor-less controller for grid tied photovoltaic (PV) inverters to enable phase balancing functionalities for compensating asymmetric loading conditions imposed by building loads in low voltage distribution grids. For enabling such an advanced functional operation by PV inverter, the first step is to enable the inverter to estimate the equivalent grid impedance. Then, the grid impedance is utilized to approximate the nearby load asymmetries without using any additional current sensors. Finally, advanced control schemes have been developed for PV inverters in order to enable the new phase balancing operation mode, where the inverter can compensate the asymmetric loading conditions of a distribution feeder. The effectiveness of the proposed method has been experimentally validated in a prototype where the grid tied PV inverter is able to compensate nearby load asymmetries and maintain a purely symmetrical interaction with the grid. Further, a simulation-based investigation in a realistic distribution feeder has been performed in order to highlight the benefits of the proposed approach regarding the power quality, the energy losses and the effective utilization of distribution grid capacity.

	A Simplified Line-to-Line Space Vector Modulation for Multilevel Converter Applied for a Standalone Wind Energy Conversion System By Tarek GHENNAM	[View] [Download]
Abstract: A new Simplified Direct Space Vector Modulation (SDSVM), based on a line-to-line space-vectordiagram, is proposed, in this paper, to control a three-level Neutral-Point-Clamped (NPC) Converterfor a standalone variable speed Wind Energy Conversion System (WECS). The frequency andmagnitude of the stator output voltage of the Doubly Fed Induction Generator (DFIG) are controlledand fixed at nominal values, despite the variable rotor speed, ensuring by that a continuous AC supplyfor three phase loads. The performance of the proposed SDSVM technique to control the standaloneDFIG based WECS is demonstrated through simulation results. The control strategy is implementedon a dSPACE DS 1104 board driving a 4.5 kW DFIG based wind system test bench. The obtainedexperimental results confirm the validity of the control.

	Active Damping based on the Capacitor Voltage Positive-Feedback for Grid-Connected Power Converters with LCL filter By Javier SAMANES	[View] [Download]
Abstract: The capacitor voltage positive-feedback is a widely extended active damping strategy. It can effectively damp the LCL output filter resonant poles for low ratios of resonance to sampling frequencies. However, the existing delays in the control loop limit the applicability of the capacitor-voltage positive-feedback. For high ratios of resonance to sampling frequencies, it becomes ineffective and can even destabilize the system. This limitation is overcome in this paper by adjusting the delay in the feedback path. With the delay adjustment, a robust damping can be achieved if the delays are properly considered, including the filters, and the grid impedance variations are taken into account. Simulation results validate the proposed active damping strategy.

	An enhanced DC-link voltage controller for single phase AC/DC converters By Meriem MERAI	[View] [Download]
Abstract: This paper presents a simple and efficient design methodology for the DC-link voltage control of a single-phase AC/DC converter. The DC-link voltage controller is made of a standard PI controller associated to a feed-forward control. The aim of the designed controller is to ensure three main objectives: i) the average value of the DC-link voltage must track with good accuracy a predefined reference value; ii) the DC-link voltage fluctuations must be minimized during transients and; iii) The grid current THD must be minimized during steady state operation.

	Closed-Loop Predictively Optimizing Control for Modular Multilevel Converter with Parallel Connectivity By Chuang WANG	[View] [Download]
Abstract: This paper adopts the bilinear modeling method to design a coherent model for modular multilevel converters with parallel connectivity and proposes an optimized closed-loop control combining proportional resonant (PR) control, nearest level modulation, and online-optimization scheduling. A bilinear mathematical model of the MMSPC is developed to predict the behavior of MMSPC one step ahead and thus reduce the computation burden of the proposed closed-loop control. PR control guarantees small steady state error and rapid dynamic response. Thanks to PR control, simple nearest level modulation can replace digital pulse-width modulation or sigma-delta modulation and decrease switching loss sharply. Moreover, a novel online-optimization scheduler replaces previously used offline optimization to improve module balance. The effectiveness of the proposed closed-loop control is verified by an accurate circuit simulation setup that represents the experimental prototype.

	Comparison of Two Possible Solution for Reducing Over-voltages at the Motor Terminals in High-Speed AC Drives By Riccardo LEUZZI	[View] [Download]
Abstract: This paper addresses the overvoltage issue occurring at the motor terminals in high-speed AC drives. Such phenomenon is substantially due to the voltage wave reflections across the connection cable occurring in presence of PWM motor supply. Moreover, such over-voltages are strictly related to the steepness of the PWM pulse and hence are more evident and severe in case a high-frequency inverter based on wide band gap devices is used to feed an AC high-speed machine. The main effect consists in a more severe stress of the motor winding insulation system which in turn may result in a major failure deeply affecting the system reliability. Two possible solutions, based on different converter topologies, are analyzed and compared in this paper in terms of overvoltage level, efficiency, encumbrance and system complexity. In particular, a Cascaded H-Bridge multilevel converter is compared with a SiC MOSFET two-level inverter equipped with active gate drivers capable of dynamically changing the switching features of the power devices.

	Constant Boost Control with Third Harmonic Injection for Quasi-Z Source Inverter used in PV Grid-connected System By Zhengyu ZHAO	[View] [Download]
Abstract: Compared to the dual-stage inverter, quasi-Z-source inverter (qZSI) offers higher reliability and lowerswitch count but suffers from higher voltage stress on components. The qZSI is normally controlled by the simple boost control (SBC) method that adds reference signals to the sinusoidal PWM to generate the shoot-through state. This paper develops a constant boost control method with third harmonic injection. Compared to the SBC, the proposed control method increases the voltage boost and reduces the voltage stress on switches and passive components of the qZSI, making it suitable for PV gridconnected applications. The third harmonic signal is produced and injected in a way that keeps it in phase with the reference sinusoidal signals, regardless of the solar irradiance level. This reduces the total harmonic distortions (THD) and improves the output power quality. Simulation results are presented for validation of the theoretical analysis and controller design.

	Decoupled Control of the Arms of a Modular Multilevel Converter with Orthogonal Reference Signals By Luca ZARRI	[View] [Download]
Abstract: The technology of modular multilevel converters has been proposed for high-power dc-ac applications. The modular structure of the converter, which is composed of floating capacitor converters connected in series, is one of its most appreciated advantages. However, the control of the energy stored in the floating capacitors is not simple, because it depends on the circulating current of each leg, i.e., the current that runs through the leg without affecting the power transferred to the load. The harmonic components of the circulating current can be employed to balance the arm energies, and several techniques have already been developed to address this control problem. This paper finds a solution to the control problem of the arm voltages by expressing the circulating current as a combination of orthogonal functions synthesized from the measured voltages and currents. As a result, the voltages of the upper and lower arms of each leg can be directly controlled, independently of one another. Experimental results confirm the feasibility of the developed approach.

	GaN E-HEMT based High Flatness Broadband Power Noise Source for Dynamic Identification of Mechatronic Systems and Batteries By Pierluigi TENCA	[View] [Download]
Abstract: Still today the dynamic identification of mechatronic systems - in particular electrical machines - is often based on stimulating them with deterministic signals, being single sinusoidal tones, single steps or periodical pulse trains of fixed frequency the most common ones. Such methodologies were the most, when not the only, practicable ones when the instrumentation was limited to low frequency generators and analog oscilloscopes, at most. The modern metrological scenario allows to concretize way more sophisticated approaches nowadays, which can bring to Mechatronics more holistic and easily executable identification methods; like those based on flat noise sources traditionally used in Radio Frequency (RF). More in general, the adoption of SiC and GaN fully controllable switches demands that also Power Electronics become eventually permeated with the very different way of thinking peculiar of RF. Within the framework of such cultural and methodological evolution that Power Electronics must embrace, the paper describes the unconventional use of converters based on GaN switches as powerful high-flatness noise sources for broadband dynamic identification, here tailored for modern electrical machines and battery technologies. Indeed, owing to the much shorter raise and fall times, as well as much higher switching frequencies enabled by GaN, it is possible to greatly extend the upper boundaries of the frequency bands where desired spectra can be synthesized by commutating such fully controllable switches according to proper time-based patterns. The authors illustrate the use of a randomly PWM-modulated H-bridge employing GaN E-HEMTs as high-flatness noise source up to at least 200 kHz thanks to 1 MHz PWM carrier. Various selected experimental results from identifications of BLDC Motors and Lithium-Iron-Phosphate (LiFePo4) cells are shown. The details in the figures are fully visible by magnifying the electronic version of the paper, which represents the same approach when Microfilms were widely used.

	Improvement and Quantification of the Power Loop Robustness for Droop Controlled VSCs By Steffen LAMPKE	[View] [Download]
Abstract: This paper studies the sensitivity of power dynamics for technically possible variations of operating point and line impedance of a droop controlled voltage source converter (VSC) connected to a stiff low voltage grid. The influence of the control parameters of traditional droop, improved droop and power-synchronizing control are analyzed by also considering their interaction with internal control dynamics and reactive power droop control. Finally, parameter selection rules are proposed that yield a robust behavior in all studied scenarios by quantifying the damping constant and finding it to be always equal to one.

	Model Predictive Control for Space Vector Modulation of a Three-Level ANPC Inverter for Efficient Loss Distribution and Neutral Point Balancing By Umar RAUF	[View] [Download]
Abstract: This paper presents an efficient loss distribution and Neutral Point (NP) balancing method for a grid-connected Three-Phase Three-Level Active Neutral Point Clamped (3L-ANPC) inverter. A Finite Control Set Model Predictive Control (FCS-MPC) technique is used to select the optimum redundant active voltage vectors and redundant zero voltage vectors during the Space Vector Modulation (SVM). A direct discrete loss model is designed for the IGBT switches of the 3L-ANPC inverter, to calculate the junction temperature Tj of the IGBT switches for each sampling point, using information about conduction and switching losses, and thermal properties of the housing and cooling. To evaluate the performance of FCS-MPC, a Tj comparison is held out with a reference from literature. This reference utilizes a decision table based on an energy loss model. Furthermore, the performance of the FCS-MPC technique for loss distribution is analyzed during steady state. The FCS-MPC technique for NP balancing is evaluated during steady and transient states.

	Model Predictive Control for Three-Phase Four-Wire Voltage Source Converters in Standalone Mode By Yu LI	[View] [Download]
Abstract: This work proposes a new model predictive control for three-phase four-wire voltage source convertersoperated at standalone mode. The proposed solution uses single cost function to deal with output filtervoltage and current to improve output voltage quality, meanwhile, resonant energy oscillation betweeninductance and capacitance is effectively suppressed. Enhanced performance in both steady state andtransient has been demonstrated by simulation data under nonlinear and unbalanced load condition.

	Modeling and Stability Analysis of Advanced PLLs Based on LTP Theory By Huoming YANG	[View] [Download]
Abstract: A novel linear time-periodic (LTP) model for advanced PLLs is presented, demonstrating superior accuracy over the conventional linear time-invariant (LTI) models. Applying eigenvalues analysis, a general parameter design procedure is proposed and the effect of voltage unbalance is investigated. The effectiveness of the theoretical analysis is verified by time-domain simulation results.

	The Generalized Bode Criterion: application to the dc voltage control of a three-phase photovoltaic grid-tied inverter By David LUMBRERAS	[View] [Download]
Abstract: As renewable energies are becoming more important in the electrical generation system, powerelectronic converters are facing new design issues related not only to their components but also to theircontrol loops. In this context, the Generalized Bode Criterion (GBC) appears as a good tool to correctlydetermine stability and to help the controller design. In order to show the potential of the GBC and howit can be applied, this paper studies a dc voltage regulation with compensation of the photovoltaic powerin a three-phase photovoltaic grid-tied inverter.

	Voltage control for VSI using load current observer By Henrique MAGNAGO	[View] [Download]
Abstract: This paper proposes a voltage controller with disturbance observer for VSI. A discrete time dead-beatinner current loop is used to regulate and limit the inverter current. The outer voltage control loopincludes the closed loop dynamic of the current controller and, in order to reduce the THD of the outputvoltage under non-linear loads, a load current observer is included. The controller and observers havetheir dynamic behavior set through the DLQR. An interactive scan of the DLQR's Q and R matricesvalues is implemented to optimize the obtained gains. HIL results are given to support the theoreticalanalysis and to demonstrate the performance of the system.