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http://hdl.handle.net/10985/13677
Impact of control algorithm solutions on Modular Multilevel Converters electrical waveforms and losses
GRUSON, François; FREYTES, Julian; SAMIMI, Shabab; DELARUE, Philippe; GUILLAUD, Xavier; COLAS, Frédéric; BELHAOUANE, Mohamed Moez
Modular Multilevel Converters (MMC) are becoming increasingly popular with the development of HVDC connection and, in the future, Multi Terminal DC grid. A lot of publications have been published about this topology these last years since it was first proposed. Many of them deal with converter control methods, other address the method of estimating losses. Usually, the proposed losses estimation techniques are associated to simple control methods For VSC (Voltage Sources Converters) topology, the losses minimization is based on the limitation of the RMS currents values. This hypothesis is usually extended to the control of MMC, by limiting the differential currents to their DC component, without really being checked. This paper investigates the impact of two control algorithms variants on electrical quantities (currents, capacitor voltages ripple, losses). From the published results, it is shown that in some cases the usual choice is not the best one.
Thu, 01 Jan 2015 00:00:00 GMThttp://hdl.handle.net/10985/136772015-01-01T00:00:00ZGRUSON, FrançoisFREYTES, JulianSAMIMI, ShababDELARUE, PhilippeGUILLAUD, XavierCOLAS, FrédéricBELHAOUANE, Mohamed MoezModular Multilevel Converters (MMC) are becoming increasingly popular with the development of HVDC connection and, in the future, Multi Terminal DC grid. A lot of publications have been published about this topology these last years since it was first proposed. Many of them deal with converter control methods, other address the method of estimating losses. Usually, the proposed losses estimation techniques are associated to simple control methods For VSC (Voltage Sources Converters) topology, the losses minimization is based on the limitation of the RMS currents values. This hypothesis is usually extended to the control of MMC, by limiting the differential currents to their DC component, without really being checked. This paper investigates the impact of two control algorithms variants on electrical quantities (currents, capacitor voltages ripple, losses). From the published results, it is shown that in some cases the usual choice is not the best one.Synthesis of different types of energy based controller for a Modular Multilevel Converter integrated in a HVDC link
http://hdl.handle.net/10985/10783
Synthesis of different types of energy based controller for a Modular Multilevel Converter integrated in a HVDC link
SAMIMI, Shabab; GRUSON, François; DELARUE, Philippe; GUILLAUD, Xavier
Modular Multilevel Converters are becoming increasingly popular with the development of HVDC connection and, in the future, Multi Terminal DC grid. A lot of publications have been published about this topology these last years since it was first proposed. Few of them are addressing explicitly the 2 different roles that are held by this converter in a HVDC link: controlling the power or controlling the DC voltage level. Moreover, for a given function, different ways of controlling this converter may be considered. This paper proposes an overview of the different solutions for controlling the MMC and proposes a methodology to synthesize the control architecture.
Thu, 01 Jan 2015 00:00:00 GMThttp://hdl.handle.net/10985/107832015-01-01T00:00:00ZSAMIMI, ShababGRUSON, FrançoisDELARUE, PhilippeGUILLAUD, XavierModular Multilevel Converters are becoming increasingly popular with the development of HVDC connection and, in the future, Multi Terminal DC grid. A lot of publications have been published about this topology these last years since it was first proposed. Few of them are addressing explicitly the 2 different roles that are held by this converter in a HVDC link: controlling the power or controlling the DC voltage level. Moreover, for a given function, different ways of controlling this converter may be considered. This paper proposes an overview of the different solutions for controlling the MMC and proposes a methodology to synthesize the control architecture.Distributed Economic Dispatch of Embedded Generation in Smart Grids
http://hdl.handle.net/10985/11353
Distributed Economic Dispatch of Embedded Generation in Smart Grids
DIBANGOYE, Jille; GUILLAUD, Xavier; COLAS, Frédéric; FAKHAM, Hicham; DONIEC, Arnaud
In a Smart Grid context, the increasing penetration of embedded generation units leads to a greater complexity in the management of production units. In this arti- cle, we focus on the impact of the introduction of decentralized generation for the unit commitment problem (UC). Unit Commitment Problems consist in finding the optimal schedules and amounts of power to be generated by a set of gen- erating units in response to an electricity demand forecast. While this problem have received a significant amount of attention, classical approaches assume these problems are centralized and deterministic. However, these two assumptions are not realistic in a smart grid context. Indeed, finding the optimal schedules and amounts of power to be generated by multiple distributed generator units is not trivial since it requires to deal with distributed computation, privacy, stochastic planning, ... In this paper, we focus on smart grid scenarios where the main source of complexity comes from the proliferation of distributed generating units. In solving this issue, we consider distributed stochastic unit commitment prob- lems. We introduce a novel distributed gradient descent algorithm which allow us to circumvent classical assumptions. This algorithm is evaluated through a set of experiments on real-time power grid simulator.
Thu, 01 Jan 2015 00:00:00 GMThttp://hdl.handle.net/10985/113532015-01-01T00:00:00ZDIBANGOYE, JilleGUILLAUD, XavierCOLAS, FrédéricFAKHAM, HichamDONIEC, ArnaudIn a Smart Grid context, the increasing penetration of embedded generation units leads to a greater complexity in the management of production units. In this arti- cle, we focus on the impact of the introduction of decentralized generation for the unit commitment problem (UC). Unit Commitment Problems consist in finding the optimal schedules and amounts of power to be generated by a set of gen- erating units in response to an electricity demand forecast. While this problem have received a significant amount of attention, classical approaches assume these problems are centralized and deterministic. However, these two assumptions are not realistic in a smart grid context. Indeed, finding the optimal schedules and amounts of power to be generated by multiple distributed generator units is not trivial since it requires to deal with distributed computation, privacy, stochastic planning, ... In this paper, we focus on smart grid scenarios where the main source of complexity comes from the proliferation of distributed generating units. In solving this issue, we consider distributed stochastic unit commitment prob- lems. We introduce a novel distributed gradient descent algorithm which allow us to circumvent classical assumptions. This algorithm is evaluated through a set of experiments on real-time power grid simulator.Energetic Macroscopic Representati on and Inversion Based Control of a Modular Multilevel Converter.
http://hdl.handle.net/10985/10045
Energetic Macroscopic Representati on and Inversion Based Control of a Modular Multilevel Converter.
DELARUE, Philippe; GRUSON, François; GUILLAUD, Xavier
This papers deals with the Modular Multilevel Converter (MMC). This structure is a real breakthrough which allows transmitting huge amount of power in DC link. In the last ten years, lots of papers have been written but most of them study some intuitive control algorithms. This paper proposes a formal analysis of MMC model which leads to the design of a control algorithm thanks to the inversion of the model. The Energetic Macroscopic Representation is used for achieving this goal. All the states variables are controlled to manage the energy of the system, avoid some instable operational points and determine clearly all the dynamics of the different loops of the system.
Wed, 01 Jan 2014 00:00:00 GMThttp://hdl.handle.net/10985/100452014-01-01T00:00:00ZDELARUE, PhilippeGRUSON, FrançoisGUILLAUD, XavierThis papers deals with the Modular Multilevel Converter (MMC). This structure is a real breakthrough which allows transmitting huge amount of power in DC link. In the last ten years, lots of papers have been written but most of them study some intuitive control algorithms. This paper proposes a formal analysis of MMC model which leads to the design of a control algorithm thanks to the inversion of the model. The Energetic Macroscopic Representation is used for achieving this goal. All the states variables are controlled to manage the energy of the system, avoid some instable operational points and determine clearly all the dynamics of the different loops of the system.Laboratory-based test bed of a three terminals DC networks using power hardware in the loop
http://hdl.handle.net/10985/10300
Laboratory-based test bed of a three terminals DC networks using power hardware in the loop
AMAMRA, Sid-Ali; COLAS, Frédéric; GUILLAUD, Xavier; NGUEFEU, Samuel
In this paper a three stations MTDC grid is presented, providing a specific application of our work. The experimental platform is intended to combine electrical power components and communication/control equipment with real-time simulation tools. In this way the platform can test grid elements and evaluate different operation scenarios under various conditions.
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/10985/103002013-01-01T00:00:00ZAMAMRA, Sid-AliCOLAS, FrédéricGUILLAUD, XavierNGUEFEU, SamuelIn this paper a three stations MTDC grid is presented, providing a specific application of our work. The experimental platform is intended to combine electrical power components and communication/control equipment with real-time simulation tools. In this way the platform can test grid elements and evaluate different operation scenarios under various conditions.MMC Stored Energy Participation to the DC Bus Voltage Control in an HVDC Link
http://hdl.handle.net/10985/12895
MMC Stored Energy Participation to the DC Bus Voltage Control in an HVDC Link
SAMIMI, Shabab; GRUSON, François; DELARUE, Philippe; COLAS, Frédéric; BELHAOUANE, Mohamed Moez; GUILLAUD, Xavier
The modular multilevel converter (MMC) is becoming a promising converter technology for HVDC transmission systems. Contrary to the conventional two- or three-level VSC-HVDC links, no capacitors are connected directly on the dc bus in an MMC-HVDC link. Therefore, in such an HVDC link, the dc bus voltage may be much more volatile than in a conventional VSC-HVDC link. In this paper, a connection between the dc bus voltage level and the stored energy inside the MMC is proposed in order to greatly improve the dynamic behavior in case of transients. EMT simulation results illustrate this interesting property on an HVDC link study case.
Fri, 01 Jan 2016 00:00:00 GMThttp://hdl.handle.net/10985/128952016-01-01T00:00:00ZSAMIMI, ShababGRUSON, FrançoisDELARUE, PhilippeCOLAS, FrédéricBELHAOUANE, Mohamed MoezGUILLAUD, XavierThe modular multilevel converter (MMC) is becoming a promising converter technology for HVDC transmission systems. Contrary to the conventional two- or three-level VSC-HVDC links, no capacitors are connected directly on the dc bus in an MMC-HVDC link. Therefore, in such an HVDC link, the dc bus voltage may be much more volatile than in a conventional VSC-HVDC link. In this paper, a connection between the dc bus voltage level and the stored energy inside the MMC is proposed in order to greatly improve the dynamic behavior in case of transients. EMT simulation results illustrate this interesting property on an HVDC link study case.Improving Small-Signal Stability of an MMC With CCSC by Control of the Internally Stored Energy
http://hdl.handle.net/10985/12894
Improving Small-Signal Stability of an MMC With CCSC by Control of the Internally Stored Energy
FREYTES, Julian; BERGNA, Gilbert; JON ARE, SUUL; D'ARCO, Salvatore; GRUSON, François; COLAS, Frédéric; SAAD, Hani; GUILLAUD, Xavier
The DC-side dynamics of Modular Multilevel Converters (MMCs) can be prone to poorly damped oscillations or stability problems when the second harmonic components of the arm currents are mitigated by a Circulating Current Suppression Controller (CCSC). This paper demonstrates that the source of these oscillations is the uncontrolled interaction of the DC-side current and the internally stored energy of the MMC, as resulting from the CCSC. Stable operation and improved performance of the MMC control system can be ensured by introducing closed loop control of the energy and the DC-side current. The presented analysis relies on a detailed state-space model of the MMC which is formulated to obtain constant variables in steady state. The resulting state-space equations can be linearized to achieve a Linear Time Invariant (LTI) model, allowing for eigenvalue analysis of the small-signal dynamics of the MMC. Participation factor analysis is utilized to identify the source of the poorly damped DC-side oscillations, and indicates the suitability of introducing control of the internal capacitor voltage or the corresponding stored energy. An MMC connected to a DC power source with an equivalent capacitance, and operated with DC voltage droop in the active power flow control, is used as an example for the presented analysis. The developed small-signal models and the improvement in small-signal dynamics achieved by introducing control of the internally stored energy are verified by time-domain simulations in comparison to an EMT simulation model of an MMC with 400 sub-modules per arm.
Mon, 01 Jan 2018 00:00:00 GMThttp://hdl.handle.net/10985/128942018-01-01T00:00:00ZFREYTES, JulianBERGNA, GilbertJON ARE, SUULD'ARCO, SalvatoreGRUSON, FrançoisCOLAS, FrédéricSAAD, HaniGUILLAUD, XavierThe DC-side dynamics of Modular Multilevel Converters (MMCs) can be prone to poorly damped oscillations or stability problems when the second harmonic components of the arm currents are mitigated by a Circulating Current Suppression Controller (CCSC). This paper demonstrates that the source of these oscillations is the uncontrolled interaction of the DC-side current and the internally stored energy of the MMC, as resulting from the CCSC. Stable operation and improved performance of the MMC control system can be ensured by introducing closed loop control of the energy and the DC-side current. The presented analysis relies on a detailed state-space model of the MMC which is formulated to obtain constant variables in steady state. The resulting state-space equations can be linearized to achieve a Linear Time Invariant (LTI) model, allowing for eigenvalue analysis of the small-signal dynamics of the MMC. Participation factor analysis is utilized to identify the source of the poorly damped DC-side oscillations, and indicates the suitability of introducing control of the internal capacitor voltage or the corresponding stored energy. An MMC connected to a DC power source with an equivalent capacitance, and operated with DC voltage droop in the active power flow control, is used as an example for the presented analysis. The developed small-signal models and the improvement in small-signal dynamics achieved by introducing control of the internally stored energy are verified by time-domain simulations in comparison to an EMT simulation model of an MMC with 400 sub-modules per arm.Direct AC Voltage Control for Grid-Forming Inverters
http://hdl.handle.net/10985/17961
Direct AC Voltage Control for Grid-Forming Inverters
QORAI, Taoufik; LI, Chuanyue; OUE, Ko; GRUSON, François; COLAS, Frédéric; GUILLAUD, Xavier
Grid-forming inverters usually use inner cascaded controllers to regulate output AC voltage and converter output current. However, at the power transmission system level where the power inverter bandwidth is limited, i.e., low switching frequency, it is difcult to tune controller parameters to achieve the desired performances because of control loop interactions. In this paper, a direct AC voltage control-based state-feedback control is applied. Its control gains are tuned using a linear quadratic regulator. In addition, a sensitivity analysis is proposed to choose the right cost factors that allow the system to achieve the imposed specifcations. Conventionally, a system based on direct AC voltage control has no restriction on the inverter current. Hence, in this paper, a threshold virtual impedance has been added to the state-feedback control in order to protect the inverter against overcurrent. The robustness of the proposed control is assessed for diferent short-circuit ratios using smallsignal stability analysis. Then, it is checked in diferent grid topologies using time domain simulations. An experimental test bench is developed in order to validate the proposed control.
Tue, 01 Jan 2019 00:00:00 GMThttp://hdl.handle.net/10985/179612019-01-01T00:00:00ZQORAI, TaoufikLI, ChuanyueOUE, KoGRUSON, FrançoisCOLAS, FrédéricGUILLAUD, XavierGrid-forming inverters usually use inner cascaded controllers to regulate output AC voltage and converter output current. However, at the power transmission system level where the power inverter bandwidth is limited, i.e., low switching frequency, it is difcult to tune controller parameters to achieve the desired performances because of control loop interactions. In this paper, a direct AC voltage control-based state-feedback control is applied. Its control gains are tuned using a linear quadratic regulator. In addition, a sensitivity analysis is proposed to choose the right cost factors that allow the system to achieve the imposed specifcations. Conventionally, a system based on direct AC voltage control has no restriction on the inverter current. Hence, in this paper, a threshold virtual impedance has been added to the state-feedback control in order to protect the inverter against overcurrent. The robustness of the proposed control is assessed for diferent short-circuit ratios using smallsignal stability analysis. Then, it is checked in diferent grid topologies using time domain simulations. An experimental test bench is developed in order to validate the proposed control.Critical clearing time determination and enhancement of grid-forming converters embedding virtual impedance as current limitation algorithm
http://hdl.handle.net/10985/17951
Critical clearing time determination and enhancement of grid-forming converters embedding virtual impedance as current limitation algorithm
QORIA, Taoufik; GRUSON, François; COLAS, Frédéric; DENIS, Guillaume; PREVOST, Thibault; GUILLAUD, Xavier
The present paper deals with the post-fault synchronization of a voltage source converter based on the droop control. In case of large disturbances on the grid, the current is limited via current limitation algorithms such as the virtual impedance. During the fault, the power converter internal frequency deviates resulting in a converter angle divergence. Thereby, the system may lose the synchronism after fault clearing and which may lead to instability. Hence, this paper proposes a theoretical approach to explain the dynamic behavior of the grid forming converter subject to a three phase bolted fault. A literal expression of the critical clearing time is defined. Due to the precise analysis of the phenomenon, a simple algorithm can be derived to enhance the transient stability. It is based on adaptive gain included in the droop control. These objectives have been achieved with no external information and without switching from one control to the other. To prove the effectiveness of the developed control, experimental test cases have been performed in different faulted conditions.
Tue, 01 Jan 2019 00:00:00 GMThttp://hdl.handle.net/10985/179512019-01-01T00:00:00ZQORIA, TaoufikGRUSON, FrançoisCOLAS, FrédéricDENIS, GuillaumePREVOST, ThibaultGUILLAUD, XavierThe present paper deals with the post-fault synchronization of a voltage source converter based on the droop control. In case of large disturbances on the grid, the current is limited via current limitation algorithms such as the virtual impedance. During the fault, the power converter internal frequency deviates resulting in a converter angle divergence. Thereby, the system may lose the synchronism after fault clearing and which may lead to instability. Hence, this paper proposes a theoretical approach to explain the dynamic behavior of the grid forming converter subject to a three phase bolted fault. A literal expression of the critical clearing time is defined. Due to the precise analysis of the phenomenon, a simple algorithm can be derived to enhance the transient stability. It is based on adaptive gain included in the droop control. These objectives have been achieved with no external information and without switching from one control to the other. To prove the effectiveness of the developed control, experimental test cases have been performed in different faulted conditions.Confidence Level Optimization of DG Piecewise Affine Controllers in Distribution Grids
http://hdl.handle.net/10985/17725
Confidence Level Optimization of DG Piecewise Affine Controllers in Distribution Grids
BUIRE, Jerome; COLAS, Frédéric; DIEULOT, Jean-Yves; DE ALVARO, Leticia; GUILLAUD, Xavier
Distributed generators (DGs) reactive powers are controlled to mitigate voltage overshoots in distribution grids with stochastic power production and consumption. Classical DGs controllers may embed piecewise affine laws with dead-band terms. Their settings are usually tuned using a decentralized method which uses local data and optimizes only the DG node behavior. It is shown that when short-term forecasts of stochastic powers are Gaussian and the grid model is assumed to be linear, nodes voltages can either be approximated by Gaussian or sums of truncated Gaussian variables. In the latter case, the voltages probability density functions (pdf) that are needed to compute the overvoltage risks or DG control effort are less straightforward than for normal distributions. These pdf are used into a centralized optimization problem which tunes all DGs control parameters. The objectives consist in maximizing the confidence levels for which voltages and powers remain in prescribed domains and minimizing voltage variances and DG efforts. Simulations on a real distribution grid model show that the truncated Gaussian representation is relevant and that control parameters can easily be updated even when extra DGs are added to the grid. The DG reactive power can be reduced down to 50% or node voltages variances can be reduced down to 30%.
Tue, 01 Jan 2019 00:00:00 GMThttp://hdl.handle.net/10985/177252019-01-01T00:00:00ZBUIRE, JeromeCOLAS, FrédéricDIEULOT, Jean-YvesDE ALVARO, LeticiaGUILLAUD, XavierDistributed generators (DGs) reactive powers are controlled to mitigate voltage overshoots in distribution grids with stochastic power production and consumption. Classical DGs controllers may embed piecewise affine laws with dead-band terms. Their settings are usually tuned using a decentralized method which uses local data and optimizes only the DG node behavior. It is shown that when short-term forecasts of stochastic powers are Gaussian and the grid model is assumed to be linear, nodes voltages can either be approximated by Gaussian or sums of truncated Gaussian variables. In the latter case, the voltages probability density functions (pdf) that are needed to compute the overvoltage risks or DG control effort are less straightforward than for normal distributions. These pdf are used into a centralized optimization problem which tunes all DGs control parameters. The objectives consist in maximizing the confidence levels for which voltages and powers remain in prescribed domains and minimizing voltage variances and DG efforts. Simulations on a real distribution grid model show that the truncated Gaussian representation is relevant and that control parameters can easily be updated even when extra DGs are added to the grid. The DG reactive power can be reduced down to 50% or node voltages variances can be reduced down to 30%.