EPE Association: EPE 2018 - DS2e: Standard and Advanced Control techniques for Power Converters II

EPE 2018 - DS2e: Standard and Advanced Control techniques for Power Converters II
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2018 ECCE Europe - Conference > EPE 2018 - Topic 03: Measurement and Control > EPE 2018 - DS2e: Standard and Advanced Control techniques for Power Converters II

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   A Proposal for Wireless Control of Submodules in Modular Multilevel Converters
By Baris CIFTCI [View]
[Download]

Abstract: The modular multilevel converter is one of the most preferred converters for high-power conversionapplications. Wireless control of the submodules can contribute to its evolution by lowering the material and labor costs of cabling. However, wireless control leads to many challenges for the control and modulation of the converter as well as for proper low-latency high-reliability communication. This paper investigates the tolerable asynchronism between phase-shifted carriers used in modulation from a wireless control point of view and proposes a control method along with communication protocol for wireless control. The functionality of the proposed method is validated by computer simulations in steady state.

   Baseband distortion compensation for high-precision power electronics using regular sampled pulse-width modulators with sawtooth carrier
By Bas VERMULST [View]
[Download]

Abstract: This paper presents a straight-forward method to compensate baseband distortion for regular sampled PWMs with a sawtooth carrier, for high-precision power electronics applications such as MRI and lithography. The method is computationally lightweight, and pseudo-code is given to simplify implementation. Measurements are conducted, which show that distortion can be reduced significantly by more than 40 dB.

   Current Control of LCL-Filtered Grid-Connected VSC using Model Predictive Control with Inherent Damping
By Jacob NORGAARD [View]
[Download]

Abstract: The advancement on penetration of renewable energy sources in the power system is, in part, tied to thecurrent control of grid-connected LCL-filtered voltage source converters. A challenge is current controlwith the addition of the LCL-filter resonance, which interacts with the digital converter-control switchingaction and creates the possibility for instability. In certain scenarios, active damping is needed tostabilize the system and ensure robust performance in steady-state and dynamic response. Another approach is detailed in this paper where a hybrid linear and nonlinear controller is implemented to ensure the dynamic current control performance. This is done by combining a linear outer-loop Proportional Resonant current controller with a nonlinear inner-loop Model Predictive voltage controller to replace the fixed switching-frequency Pulse Width Modulator. This allows for easy compensation of nonlinear effects, such as time delays and provides the controller with the ability to prioritize the dynamic performance during step changes. The details for implementing this control structure are provided, along with a discussion of the advantages, and guidelines for the design procedure of the hybrid control structure. Simulation results and experimental measurements are provided to illustrate the control performance and validate the proposed method. As a conclusion, the control method as a whole is discussed in relation to the presented work and further research options.

   Design and Analysis of Discrete Current Regulators for VSIs
By Michael SCHUETT [View]
[Download]

Abstract: This paper presents the implementation, analysis, and comparison of discrete synchronous frame current regulators for Voltage Source Inverters (VSIs). Both a two-level inverter and a Modular Multilevel Converter were used to emphasize the universality of the studied concepts. This work focuses on direct discrete modeling and in particular coupling effects that are unique to the discrete domain. The well-studied cross-coupling of the currents in the direct quadrature (dq) frame shows different behavior in discrete time. Further, this work studies a coupling of the latched output voltages (Zero Order Hold) in the dq-frame in the Z-domain and presents a consequent method for Manipulated Input Decoupling.

   Design of a DC Fault Current Reduction Control for Half-Bridge Modular Multi-Level Converters
By Firew Zerihun DEJENE [View]
[Download]

Abstract: HVDC DC grids composed of half-bridge modular multi-level converters (HB MMC) can be protected against DC faults using DC circuit breakers (DCCBs). However, the rapid increase of DC fault currents during DC pole-to-pole faults on symmetric monopolar HVDC systems or DC pole-to-ground faults on bipolar HVDC systems poses a challenge on the design of DCCBs due to the requirement on handling very large amount of energy during the DC fault clearing process.Blocking of the MMC converters immediately after the DC fault stops the fault current contribution of the HB MMC submodules, and reduces the design requirement of the DCCBs (energy absorption and interruption capability), but at the cost of disrupting continuous operation of the Hybrid AC/DC grid and potentially deteriorating stable post fault system recovery.This paper introduces a method that helps to reduce the DC fault current contribution of the HB MMC submodule capacitors using the converter controls of the MMCs within the HVDC grid in order to reduce the requirements of DCCB designs. The proposed method achieves this during a DC pole-to-pole fault on a symmetric monopolar HVDC system or a DC pole-to-ground fault on bipolar HVDC system through the use of modified circulating current controls of the MMC HVDC. The parameters of the proposed controller are selected taking into consideration the operational limits of the converters.

   Explicit Computation of Indirect Hybrid MPC for Voltage Control in Multilevel DC-DC Converters
By Mattia ROSSI [View]
[Download]

Abstract: This paper extends indirect model predictive control (MPC) to the design of a three-level neutral pointclamped (3L-NPC) step-down dc-dc converters. A hybrid model is used to map the switching pattern oftwo switches only and to build piecewise affine (PWA) decoupled models with reduced complexity. Twoconstrained optimization problems are explicitly solved offline to provide two explicit MPCs driven bya wake-up logic. The resulting approach represents a first step towards the extension of explicit MPC tomore complex multilevel topologies, when a reduced computational effort is required.

   Impact of the Prediction Error on the Performance of Model Predictive Controllers with Long Prediction Horizons for Modular Multilevel Converters - Linear vs. N
By Simon FUCHS [View]
[Download]

Abstract: The closed loop control performance of MMCs can be significantly improved by using Model Predictive Control (MPC). This paper evaluates an MPC algorithm based on a linearised MMC model regarding the performance limits caused by the prediction error due to the linearisation. To decrease the prediction error to a minimum and to improve the performance it is proposed to use a nonlinear MMC model as a prediction model for the MPC. The steady state and transient performance of the MPC with both MMC models is compared in detail using simulations to analyse the effect of the prediction error on the control performance.

   Influence of Dynamic Misorientation of PLL for Small-Signal Analysis of Converter Control in Weak Grids
By Magdalena GIERSCHNER [View]
[Download]

Abstract: This paper gives a systematic approach to develop the complete state space representation of a voltagesource converter using Voltage Oriented Control. It is shown that the dynamic misorientation of the phase-locked loop plays a significant role in stability analyses and its input has to be a state.

   Interleaved boost converter operating near BCM with improved control technique to reduce current ripple
By Kaspars KROICS [View]
[Download]

Abstract: The paper discusses design of the multiphase interleaved converter which operates near the boundary conduction mode in order to reduce costs and remove the current control loop in each phase. The paper presents the control principle of the multiphase DC-DC converter that reduces input and output current and voltage ripple. The principle is based on changing of number of active phases during the operation of the converter. The experimental results of six-phase interleaved converter prototype are presented in the paper and confirms possibility to reduce current ripples by utilizing proposed method.

   Loss-Surface-Based Iron Loss Prediction for Fractional Horsepower Electric Motor Design
By Hannes GRUEBLER [View]
[Download]

Abstract: A modified loss-surface approach for iron loss prediction in fractional horsepower motors is proposed which is especially suitable when the flux density distribution contains a high number of harmonics, and/or when only insufficient datasheet values are available. The requirements on such loss-surface determination and specific aspects of its realization are investigated. The approach is validated experimentally by investigation of a toroidal iron stack of similar size as that of fractional horsepower machines which motivated this research. The predicted and the measured iron losses differ at a maximum of 4.6\%.

   Transitional Average Current Sensorless Control during Peak-to-Peak Value Changes
By Alexander SUZDALENKO [View]
[Download]

Abstract: The current feedback is considered as unavoidable part of all control system driving power electronic converters. However, if properly calculated volt-second balance is applied to input inductor, it is possible to eliminate the use of current sensor. Previously known solutions described in literature define only sensorless current control in discontinuous and continuous current mode. This paper contains explanation of various current trajectories that allows transition between different peak-to-peak values keeping inductor's average current at a reference value. The analytical study of proposed solution is verified with simulation results.

EPE 2018 - DS2e: Standard and Advanced Control techniques for Power Converters II
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2018 ECCE Europe - Conference > EPE 2018 - Topic 03: Measurement and Control > EPE 2018 - DS2e: Standard and Advanced Control techniques for Power Converters II
	[return to parent folder]

	A Proposal for Wireless Control of Submodules in Modular Multilevel Converters By Baris CIFTCI	[View] [Download]
Abstract: The modular multilevel converter is one of the most preferred converters for high-power conversionapplications. Wireless control of the submodules can contribute to its evolution by lowering the material and labor costs of cabling. However, wireless control leads to many challenges for the control and modulation of the converter as well as for proper low-latency high-reliability communication. This paper investigates the tolerable asynchronism between phase-shifted carriers used in modulation from a wireless control point of view and proposes a control method along with communication protocol for wireless control. The functionality of the proposed method is validated by computer simulations in steady state.

	Baseband distortion compensation for high-precision power electronics using regular sampled pulse-width modulators with sawtooth carrier By Bas VERMULST	[View] [Download]
Abstract: This paper presents a straight-forward method to compensate baseband distortion for regular sampled PWMs with a sawtooth carrier, for high-precision power electronics applications such as MRI and lithography. The method is computationally lightweight, and pseudo-code is given to simplify implementation. Measurements are conducted, which show that distortion can be reduced significantly by more than 40 dB.

	Current Control of LCL-Filtered Grid-Connected VSC using Model Predictive Control with Inherent Damping By Jacob NORGAARD	[View] [Download]
Abstract: The advancement on penetration of renewable energy sources in the power system is, in part, tied to thecurrent control of grid-connected LCL-filtered voltage source converters. A challenge is current controlwith the addition of the LCL-filter resonance, which interacts with the digital converter-control switchingaction and creates the possibility for instability. In certain scenarios, active damping is needed tostabilize the system and ensure robust performance in steady-state and dynamic response. Another approach is detailed in this paper where a hybrid linear and nonlinear controller is implemented to ensure the dynamic current control performance. This is done by combining a linear outer-loop Proportional Resonant current controller with a nonlinear inner-loop Model Predictive voltage controller to replace the fixed switching-frequency Pulse Width Modulator. This allows for easy compensation of nonlinear effects, such as time delays and provides the controller with the ability to prioritize the dynamic performance during step changes. The details for implementing this control structure are provided, along with a discussion of the advantages, and guidelines for the design procedure of the hybrid control structure. Simulation results and experimental measurements are provided to illustrate the control performance and validate the proposed method. As a conclusion, the control method as a whole is discussed in relation to the presented work and further research options.

	Design and Analysis of Discrete Current Regulators for VSIs By Michael SCHUETT	[View] [Download]
Abstract: This paper presents the implementation, analysis, and comparison of discrete synchronous frame current regulators for Voltage Source Inverters (VSIs). Both a two-level inverter and a Modular Multilevel Converter were used to emphasize the universality of the studied concepts. This work focuses on direct discrete modeling and in particular coupling effects that are unique to the discrete domain. The well-studied cross-coupling of the currents in the direct quadrature (dq) frame shows different behavior in discrete time. Further, this work studies a coupling of the latched output voltages (Zero Order Hold) in the dq-frame in the Z-domain and presents a consequent method for Manipulated Input Decoupling.

	Design of a DC Fault Current Reduction Control for Half-Bridge Modular Multi-Level Converters By Firew Zerihun DEJENE	[View] [Download]
Abstract: HVDC DC grids composed of half-bridge modular multi-level converters (HB MMC) can be protected against DC faults using DC circuit breakers (DCCBs). However, the rapid increase of DC fault currents during DC pole-to-pole faults on symmetric monopolar HVDC systems or DC pole-to-ground faults on bipolar HVDC systems poses a challenge on the design of DCCBs due to the requirement on handling very large amount of energy during the DC fault clearing process.Blocking of the MMC converters immediately after the DC fault stops the fault current contribution of the HB MMC submodules, and reduces the design requirement of the DCCBs (energy absorption and interruption capability), but at the cost of disrupting continuous operation of the Hybrid AC/DC grid and potentially deteriorating stable post fault system recovery.This paper introduces a method that helps to reduce the DC fault current contribution of the HB MMC submodule capacitors using the converter controls of the MMCs within the HVDC grid in order to reduce the requirements of DCCB designs. The proposed method achieves this during a DC pole-to-pole fault on a symmetric monopolar HVDC system or a DC pole-to-ground fault on bipolar HVDC system through the use of modified circulating current controls of the MMC HVDC. The parameters of the proposed controller are selected taking into consideration the operational limits of the converters.

	Explicit Computation of Indirect Hybrid MPC for Voltage Control in Multilevel DC-DC Converters By Mattia ROSSI	[View] [Download]
Abstract: This paper extends indirect model predictive control (MPC) to the design of a three-level neutral pointclamped (3L-NPC) step-down dc-dc converters. A hybrid model is used to map the switching pattern oftwo switches only and to build piecewise affine (PWA) decoupled models with reduced complexity. Twoconstrained optimization problems are explicitly solved offline to provide two explicit MPCs driven bya wake-up logic. The resulting approach represents a first step towards the extension of explicit MPC tomore complex multilevel topologies, when a reduced computational effort is required.

	Impact of the Prediction Error on the Performance of Model Predictive Controllers with Long Prediction Horizons for Modular Multilevel Converters - Linear vs. N By Simon FUCHS	[View] [Download]
Abstract: The closed loop control performance of MMCs can be significantly improved by using Model Predictive Control (MPC). This paper evaluates an MPC algorithm based on a linearised MMC model regarding the performance limits caused by the prediction error due to the linearisation. To decrease the prediction error to a minimum and to improve the performance it is proposed to use a nonlinear MMC model as a prediction model for the MPC. The steady state and transient performance of the MPC with both MMC models is compared in detail using simulations to analyse the effect of the prediction error on the control performance.

	Influence of Dynamic Misorientation of PLL for Small-Signal Analysis of Converter Control in Weak Grids By Magdalena GIERSCHNER	[View] [Download]
Abstract: This paper gives a systematic approach to develop the complete state space representation of a voltagesource converter using Voltage Oriented Control. It is shown that the dynamic misorientation of the phase-locked loop plays a significant role in stability analyses and its input has to be a state.

	Interleaved boost converter operating near BCM with improved control technique to reduce current ripple By Kaspars KROICS	[View] [Download]
Abstract: The paper discusses design of the multiphase interleaved converter which operates near the boundary conduction mode in order to reduce costs and remove the current control loop in each phase. The paper presents the control principle of the multiphase DC-DC converter that reduces input and output current and voltage ripple. The principle is based on changing of number of active phases during the operation of the converter. The experimental results of six-phase interleaved converter prototype are presented in the paper and confirms possibility to reduce current ripples by utilizing proposed method.

	Loss-Surface-Based Iron Loss Prediction for Fractional Horsepower Electric Motor Design By Hannes GRUEBLER	[View] [Download]
Abstract: A modified loss-surface approach for iron loss prediction in fractional horsepower motors is proposed which is especially suitable when the flux density distribution contains a high number of harmonics, and/or when only insufficient datasheet values are available. The requirements on such loss-surface determination and specific aspects of its realization are investigated. The approach is validated experimentally by investigation of a toroidal iron stack of similar size as that of fractional horsepower machines which motivated this research. The predicted and the measured iron losses differ at a maximum of 4.6\%.

	Transitional Average Current Sensorless Control during Peak-to-Peak Value Changes By Alexander SUZDALENKO	[View] [Download]
Abstract: The current feedback is considered as unavoidable part of all control system driving power electronic converters. However, if properly calculated volt-second balance is applied to input inductor, it is possible to eliminate the use of current sensor. Previously known solutions described in literature define only sensorless current control in discontinuous and continuous current mode. This paper contains explanation of various current trajectories that allows transition between different peak-to-peak values keeping inductor's average current at a reference value. The analytical study of proposed solution is verified with simulation results.