Majid Mehrasa - Academia.edu (original) (raw)
Papers by Majid Mehrasa
2017 IEEE PES Innovative Smart Grid Technologies Conference Europe (ISGT-Europe), 2017
This paper deals with a synchronous active proportional resonant-based (SAPR) control technique f... more This paper deals with a synchronous active proportional resonant-based (SAPR) control technique for interfaced converters, enhancing the stable operation of the power grid under high penetration of distributed generation sources. By considering the grid specifications and load currents, both d and q axis of converter currents are obtained in terms of active and reactive power and also angular speed using small-signal linearization method. Then, swing equation is analyzed in detail to achieve the reference current components in the current control loop of the interfaced converter. By using the obtained swing equation and a non-ideal proportional resonant (PR) controller, a new control technique is proposed, which introduces the behavior of synchronous power generators based on power electronic converters in distributed generation (DG) technology. The effectiveness of the proposed control technique is verified through stringent simulation studies in MATLAB/SIMULINK.
2018 International Conference on Smart Energy Systems and Technologies (SEST), 2018
A synchronous generator (SG)-based control technique is proposed in this paper to force the grid ... more A synchronous generator (SG)-based control technique is proposed in this paper to force the grid voltage magnitude and frequency to follow the desired values under high penetration of renewable energy sources. The active and reactive power error-based curve of the proposed control technique is evaluated in detail. Besides, the grid angular frequency error based on the proposed control technique performance is assessed in the next step. Simulation is employed in Matlab/Simulink to verify operation of the proposed control technique in power converters for large-scale integration of renewable energy sources into the power grids.
2017 IEEE PES Innovative Smart Grid Technologies Conference Europe (ISGT-Europe), 2017
Renewable energy sources are normally connected to the power grid via power electronic converters... more Renewable energy sources are normally connected to the power grid via power electronic converters. High penetration of these energy sources into the power grid leads to high instability in voltage and frequency. This issue is caused by neglecting the inherent characteristics of synchronous generators i.e., inertia, damping and proper active and reactive power sharing in the structure of the used control technique in the control loop of the interfaced converter between power grid and renewable energy sources. This paper presents a powerbased control technique based on a double synchronous controller (DSC) for interfaced converter between the renewable energy sources and the power grid, including an active-reactive power based dynamic equation. Through the proposed DSC, a decoupled control method is performed in which both active and reactive power can be injected from renewable energy sources into the power grid by the interfaced power converter with the inherent features of synchronous power generators. By using the proposed control technique, a stable operation of the power grid can be guaranteed during the integration of large-scale renewable energy sources. Stringent simulation results performed in MATLAB/SIMULINK environment verify the proficiency of the proposed control technique. Index Terms-Large-scale renewable energy sources, double synchronous controller (DSC), active and reactive power. I.
2018 International Conference on Smart Energy Systems and Technologies (SEST), 2018
In this paper, an angular frequency dynamic-based control technique is proposed to control interf... more In this paper, an angular frequency dynamic-based control technique is proposed to control interfaced converters between the power grid and renewable energy sources. The proposed control technique can guarantee a stable operation of power grid under high penetration of renewable energy resources through providing the required inertia properties. The synchronous generator characteristics combined with the basic dynamic model of the interfaced converter can shape a second order derivative of the grid angular frequency consisted of converter power and virtual mechanical power derivative with embedded virtual inertia to prevent from the power grid instability as well as generate active and reactive power with appropriate inertia. Simulation analyses are performed in Matlab/Simulink to confirm high performance of the proposed control technique.
2018 IEEE International Conference on Environment and Electrical Engineering and 2018 IEEE Industrial and Commercial Power Systems Europe (EEEIC / I&CPS Europe), Jun 1, 2018
A single synchronous controller (SSC) technique is proposed in this paper for control of interfac... more A single synchronous controller (SSC) technique is proposed in this paper for control of interfaced converters under high penetration of renewable energy resources (RER) into the power grid. The proposed SSC is based on a new dynamic model concerning to the power grid stability (PGS) and modeled based on all features of a synchronous generator (SG), which can properly improve the performance of the power grid in those scenarios in which a large-scale penetration of RERs is considered. Different transfer functions are achieved to assess the high performance of the proposed control technique. Simulation results are presented to demonstrate the superiority of the proposed SSC in the control of the power electronic-based synchronous generator under high penetration of RERs into the power grid.
International Journal of Electrical Power & Energy Systems, 2019
This paper addresses a single synchronous controller (SSC) for interfaced converters with high pe... more This paper addresses a single synchronous controller (SSC) for interfaced converters with high penetration of renewable energy resources (RERs) into a low inertia power grid. The SSC is modelled based on a comprehensive dependence between each operative feature of a synchronous generator (SG) and a power electronics converter. This can properly improve the performance of the power grid in such scenarios in which large-scale penetration of RERs are detected. The main contribution of this paper is representing an exhaustive relation between active components of the proposed SSC and SG features which enables the proposed SSC-based interfaced converter to more accurately mimic the behaviour of SGs during active power generating along with providing controllable inertia. Due to containing sufficient decoupling, both components of the proposed SSC have no impact on each other, also the proposed SSC has a superior operational flexibility within a wide range of inertia from very low to high values. Thus, two closed-loop control systems are considered to separately analyse the characteristic effects of SGs in active and reactive power sharing apart from the power grid stability challenges. In addition, the impacts of active power variations on reactive power are subsequently evaluated. To further analyse the operation of the system, the effects of the virtual mechanical power (VMP) error embedded in the SSC are considered as an alternative option for assessing the power grid stability. Also, the variations of the virtual angular frequency (VAF) error are carefully deliberated for more considerations associated with the active and reactive power performance of the SSC. Simulation results are presented to demonstrate the high performance of the SSC in the control of the power electronics-based SG when high-penetration renewable energy sources are integrated into the low inertia power grid.
Applied Sciences, 2019
This paper presents a virtual inertia and mechanical power-based control strategy to provide a st... more This paper presents a virtual inertia and mechanical power-based control strategy to provide a stable operation of the power grid under high penetration of renewable energy sources (RESs). The proposed control technique is based on a new active and reactive power-based dynamic model with the permanent magnet synchronous generator (PMSG) swing equation, in which all PMSG features i.e., inertia and mechanical power are embedded within the controller as the main contribution of this paper. To present an accurate analysis of the virtual PMSG-based parameters, the desired zero dynamics of the grid angular frequency are considered to evaluate the effects of virtual mechanical power (VMP) on the active and reactive power sharing, as well as the investigation of virtual inertia variations for the grid angular frequency responses. Moreover, by considering various active power errors and virtual inertia, the impacts of active power error on reactive power in the proposed control technique, ar...
Electric Power Systems Research, 2019
This paper deals with a control technique based on inherent characteristics of synchronous genera... more This paper deals with a control technique based on inherent characteristics of synchronous generators (SG) for control of interfaced converters with high penetration of renewable energy resources (RERs) into the power grid, as a new
IEEE Journal of Emerging and Selected Topics in Power Electronics, 2018
This paper aims to present a novel control strategy for Modular Multilevel Converters (MMC) based... more This paper aims to present a novel control strategy for Modular Multilevel Converters (MMC) based on differential flatness theory (DFT), in which instantaneous active and reactive power values are considered as the flat outputs. To this purpose, a mathematical model of the MMC taking into account dynamics of the ac-side current and the dc-side voltage of the converter is derived in a d-q reference frame. Using this model, the flat outputs-based dynamic model of MMC is obtained to reach the initial value of the proposed controller inputs. In order to mitigate the negative effects of the input disturbance, model errors, and system uncertainties on the operating performance of the MMC, the integral-proportional terms of the flat output errors are added to the initial inputs. This can be achieved through defining a control Lyapunov function which can ensure the stability of the MMC under various operating points. Moreover, the small-signal linearization method is applied to the proposed flat output-based model to separately evaluate the variation effects of controller inputs on flat outputs. The proficiency of the proposed method is researched via MATLAB simulation. Simulation results highlight the capability of the proposed controller in both steady-state and transient conditions in maintaining MMC currents and voltages, through managing active and reactive power. Index Terms-Modular Multilevel Converter (MMC), differential flatness theory (DFT), active and reactive power.
International Journal of Electrical Power & Energy Systems, 2018
A multi-loop control strategy based on a six-order dynamic model of the modular multilevel conver... more A multi-loop control strategy based on a six-order dynamic model of the modular multilevel converter (MMC) is presented in this paper for the high-voltage direct current (HVDC) applications. For the initial analysis of the operation of MMC, a capability curve based on active and reactive power of the MMC is achieved through a part of the six order dynamic equations. According to the MMC's control aims, the first loop known as the outer loop is designed based on passivity control theory to force the MMC state variables to follow their reference values. As the second loop with the use of sliding mode control, the central loop should provide appropriate performance for the MMC under variations of the MMC's parameters. Another main part of the proposed controller is defined for the third inner loop to accomplish the accurate generation of reference values. Also, for a deeper analysis of the MMC's dc link voltage stability, two phase diagrams of the dc-link voltage are assessed. Matlab/Simulink environment is used to thoroughly validate the ability of the proposed control technique for control of the MMC in HVDC application under both load and MMC's parameters changes.
Energies, 2018
This paper presents a synchronous resonant control strategy based on the inherent characteristics... more This paper presents a synchronous resonant control strategy based on the inherent characteristics of permanent magnet synchronous generators (PMSG) for the control of power converters to provide stable operating conditions for the power grid under high penetration of renewable energy resources (RERs). The proposed control technique is based on the small signal linearization of a dynamic model with grid specifications, load-current-based voltages, and power converter currents. A combination of the linearized dynamic model with the PMSG swing equation and resonant controller leads to a control technique with synchronous features and appropriate inertia for the control of converter-based power generators. As the main contribution of this work, an extra functionality is proposed in the control loop of the proposed model to solve the inherent inconveniences of conventional synchronous generators. Also, a comprehensive collaboration between interfaced converter specifications and PMSG fea...
IEEE Transactions on Power Systems, 2017
This article focuses on the control of Modular Multilevel Converters (MMC) for High Voltage DC (H... more This article focuses on the control of Modular Multilevel Converters (MMC) for High Voltage DC (HVDC) applications during unbalanced AC grid voltage sags where positive and negative sequence voltages are equal. The control scheme is based on six arm energy regulators, six independent current controllers and two reference calculation stages that convert the power references into grid and inner current references. Conventional inner AC currents reference calculation fails if the amplitude of the positive and the negative sequence AC grid voltages are equal, a state which is referred to in this paper as singular voltage condition. This article discusses the types of network faults that cause this condition and proposes three different solutions to operate the converter in such scenarios. The adequacy of the proposed solutions is validated through simulations considering each of the problematic fault scenarios.
Energies, 2016
In this paper, a novel modulation function-based method including analyses of the modulation inde... more In this paper, a novel modulation function-based method including analyses of the modulation index and phase is proposed for operation of modular multilevel converters (MMCs) in high voltage direct current (HVDC) transmission systems. The proposed modulation function-based control technique is developed based on thorough and precise analyses of all MMC voltages and currents in the a-b-c reference frame in which the alternating current (AC)-side voltage is the first target to be obtained. Using the AC-side voltage, the combination of the MMC upper and lower arm voltages is achieved as the main structure of the proposed modulation function. The main contribution of this paper is to obtain two very simple new modulation functions to control MMC performance in different operating conditions. The features of the modulation function-based control technique are as follows: (1) this control technique is very simple and can be easily achieved in a-b-c reference frame without the need of using Park transformation; and (2) in addition, the inherent properties of the MMC model are considered in the proposed control technique. Considering these properties leads to constructing a control technique that is robust against MMC parameters changes and also is a very good tracking method for the components of MMC input currents. These features lead to improving the operation of MMC significantly, which can act as a rectifier in the HVDC structure. The simulation studies are conducted through MATLAB/SIMULINK software, and the results obtained verify the effectiveness of the proposed modulation function-based control technique.
2016 7th Power Electronics and Drive Systems Technologies Conference (PEDSTC), 2016
A comprehensive dynamic model based on Direct-Quadrature (DQ) rotating frame is proposed in this ... more A comprehensive dynamic model based on Direct-Quadrature (DQ) rotating frame is proposed in this paper that is used along with a capability curve (CC) based on the active and reactive power to control a grid-connected single-phase voltagesource inverter (SPVSI). With the proposed dynamic model, a droop-passivity based controller can be designed for the gridconnected inverter in the presence of nonlinear loads. Stability analysis of the proposed control technique is also discussed in the paper as well as design principles. Moreover, an accurate performance area of SPVSI active and reactive power in dynamic transitions is achieved using the CC. Furthermore, an effective harmonic compensation scheme along with a proper active and reactive power sharing algorithm are performed by a welldesigned reference waveform generation process. Performance of the grid-connected SPVSI, under the proposed controller, is thoroughly evaluated in the Matlab/Simulink environment.
IEEE Transactions on Power Delivery, 2017
Energy, 2016
This paper introduces a control strategy for the assessment of SAPF (shunt active power filters) ... more This paper introduces a control strategy for the assessment of SAPF (shunt active power filters) role in the electrical power networks. The proposed control scheme is based on the Lyapunov control theory and defines a stable operating region for the interfaced converter during the integration time with the utility grid. The compensation of instantaneous variations of reference current components in the control loop of SAPF in ac-side, and dc-link voltage oscillations in dc-side of the proposed model, is thoroughly considered in the stable operation of interfaced converter, which is the main contribution of this proposal in comparison with other potential control approaches. The proposed control scheme can guarantee the injection of all harmonic components of current and reactive power of grid-connected loads, with a fast dynamic response that results in a unity power factor between the grid currents and voltages during the integration of SAPF into the power grid. An extensive simulation study is performed, assessing the effectiveness of the proposed control strategy in the utilization of SAPF in power networks.
2015 IEEE International Conference on Smart Energy Grid Engineering (SEGE), 2015
This paper presents a control technique for control of a Modular Multilevel Converter (MMC) based... more This paper presents a control technique for control of a Modular Multilevel Converter (MMC) based DG system in the grid-connected mode. Circulating currents of MMC are considered as a state variable, besides the AC currents and dc-link voltage of interfaced converter, which is the main novelty and contribution of the proposed control technique over the other potential control techniques in DG technology. By this assumption, the proposed control technique is included by three outer, central and inner control loops for regulating the operation of interfaced MMC under steady state operating conditions, and during load and parameter variations. Passivity based controller, sliding mode method and reference currents calculator are employed as outer loop controller (OLC), central loop controller (CLC) and inner loop controller (ILC), respectively, in the proposed control technique. Simulation results confirm the effectiveness of the proposed control technique in the proposed DG model during dynamic and steady-state operating conditions.
2015 Australasian Universities Power Engineering Conference (AUPEC), 2015
This paper presents a control technique for enhancing the stable operation of distributed generat... more This paper presents a control technique for enhancing the stable operation of distributed generation (DG) units during islanding and grid-connected modes. The compensation of instantaneous variations in the reference current components of DG units in ac-side, and dc-link voltage variations in dc-side of interfaced converters, are considered properly in the control loop of DG units, which is the main contribution and novelty of this control technique over other control techniques. By using the proposed control technique, DG units can provide the continuous injection of active power from DG sources to the local loads and/or utility grid. Moreover, by setting appropriate reference current components in the control loop of DG units, reactive power and harmonic current components of loads can be supplied with a fast dynamic response. The performance of the developed control is assessed through simulation results during dynamic and steady-state operating conditions. Keywords-Microgrid (MG); distributed generation (DG); droop control; grid-connected mode; islanding mode. I. NOMENCLATURE A. Indices i 1,2 w d,q B. Abbreviations DG Distributed Generation PI Proportional-Integral LPF Low Pass Filter VSC Voltage Source Converter PCC Point of Power Coupling STSs Static Transfer Switches BESS Battery Energy Storage System CC Capacity Curve C. Variables i cwi DG current components Instantaneous variations of DG currents Instantaneous variations of reference current cwi i Δ Deviation of DG currents i fwi Currents of capacitor filters R Radius of i cdi-i cqi curve (α,β) Centre of i cdi-i cqi curve v dci dc-link voltage v wi Voltage at the PCC Instantaneous variations of dc-link voltage u eqwi Equivalent switching state functions
Electric Power Systems Research, 2015
Maximum voltage amplitude at the PCC z , d q * fzi
2017 IEEE PES Innovative Smart Grid Technologies Conference Europe (ISGT-Europe), 2017
This paper deals with a synchronous active proportional resonant-based (SAPR) control technique f... more This paper deals with a synchronous active proportional resonant-based (SAPR) control technique for interfaced converters, enhancing the stable operation of the power grid under high penetration of distributed generation sources. By considering the grid specifications and load currents, both d and q axis of converter currents are obtained in terms of active and reactive power and also angular speed using small-signal linearization method. Then, swing equation is analyzed in detail to achieve the reference current components in the current control loop of the interfaced converter. By using the obtained swing equation and a non-ideal proportional resonant (PR) controller, a new control technique is proposed, which introduces the behavior of synchronous power generators based on power electronic converters in distributed generation (DG) technology. The effectiveness of the proposed control technique is verified through stringent simulation studies in MATLAB/SIMULINK.
2018 International Conference on Smart Energy Systems and Technologies (SEST), 2018
A synchronous generator (SG)-based control technique is proposed in this paper to force the grid ... more A synchronous generator (SG)-based control technique is proposed in this paper to force the grid voltage magnitude and frequency to follow the desired values under high penetration of renewable energy sources. The active and reactive power error-based curve of the proposed control technique is evaluated in detail. Besides, the grid angular frequency error based on the proposed control technique performance is assessed in the next step. Simulation is employed in Matlab/Simulink to verify operation of the proposed control technique in power converters for large-scale integration of renewable energy sources into the power grids.
2017 IEEE PES Innovative Smart Grid Technologies Conference Europe (ISGT-Europe), 2017
Renewable energy sources are normally connected to the power grid via power electronic converters... more Renewable energy sources are normally connected to the power grid via power electronic converters. High penetration of these energy sources into the power grid leads to high instability in voltage and frequency. This issue is caused by neglecting the inherent characteristics of synchronous generators i.e., inertia, damping and proper active and reactive power sharing in the structure of the used control technique in the control loop of the interfaced converter between power grid and renewable energy sources. This paper presents a powerbased control technique based on a double synchronous controller (DSC) for interfaced converter between the renewable energy sources and the power grid, including an active-reactive power based dynamic equation. Through the proposed DSC, a decoupled control method is performed in which both active and reactive power can be injected from renewable energy sources into the power grid by the interfaced power converter with the inherent features of synchronous power generators. By using the proposed control technique, a stable operation of the power grid can be guaranteed during the integration of large-scale renewable energy sources. Stringent simulation results performed in MATLAB/SIMULINK environment verify the proficiency of the proposed control technique. Index Terms-Large-scale renewable energy sources, double synchronous controller (DSC), active and reactive power. I.
2018 International Conference on Smart Energy Systems and Technologies (SEST), 2018
In this paper, an angular frequency dynamic-based control technique is proposed to control interf... more In this paper, an angular frequency dynamic-based control technique is proposed to control interfaced converters between the power grid and renewable energy sources. The proposed control technique can guarantee a stable operation of power grid under high penetration of renewable energy resources through providing the required inertia properties. The synchronous generator characteristics combined with the basic dynamic model of the interfaced converter can shape a second order derivative of the grid angular frequency consisted of converter power and virtual mechanical power derivative with embedded virtual inertia to prevent from the power grid instability as well as generate active and reactive power with appropriate inertia. Simulation analyses are performed in Matlab/Simulink to confirm high performance of the proposed control technique.
2018 IEEE International Conference on Environment and Electrical Engineering and 2018 IEEE Industrial and Commercial Power Systems Europe (EEEIC / I&CPS Europe), Jun 1, 2018
A single synchronous controller (SSC) technique is proposed in this paper for control of interfac... more A single synchronous controller (SSC) technique is proposed in this paper for control of interfaced converters under high penetration of renewable energy resources (RER) into the power grid. The proposed SSC is based on a new dynamic model concerning to the power grid stability (PGS) and modeled based on all features of a synchronous generator (SG), which can properly improve the performance of the power grid in those scenarios in which a large-scale penetration of RERs is considered. Different transfer functions are achieved to assess the high performance of the proposed control technique. Simulation results are presented to demonstrate the superiority of the proposed SSC in the control of the power electronic-based synchronous generator under high penetration of RERs into the power grid.
International Journal of Electrical Power & Energy Systems, 2019
This paper addresses a single synchronous controller (SSC) for interfaced converters with high pe... more This paper addresses a single synchronous controller (SSC) for interfaced converters with high penetration of renewable energy resources (RERs) into a low inertia power grid. The SSC is modelled based on a comprehensive dependence between each operative feature of a synchronous generator (SG) and a power electronics converter. This can properly improve the performance of the power grid in such scenarios in which large-scale penetration of RERs are detected. The main contribution of this paper is representing an exhaustive relation between active components of the proposed SSC and SG features which enables the proposed SSC-based interfaced converter to more accurately mimic the behaviour of SGs during active power generating along with providing controllable inertia. Due to containing sufficient decoupling, both components of the proposed SSC have no impact on each other, also the proposed SSC has a superior operational flexibility within a wide range of inertia from very low to high values. Thus, two closed-loop control systems are considered to separately analyse the characteristic effects of SGs in active and reactive power sharing apart from the power grid stability challenges. In addition, the impacts of active power variations on reactive power are subsequently evaluated. To further analyse the operation of the system, the effects of the virtual mechanical power (VMP) error embedded in the SSC are considered as an alternative option for assessing the power grid stability. Also, the variations of the virtual angular frequency (VAF) error are carefully deliberated for more considerations associated with the active and reactive power performance of the SSC. Simulation results are presented to demonstrate the high performance of the SSC in the control of the power electronics-based SG when high-penetration renewable energy sources are integrated into the low inertia power grid.
Applied Sciences, 2019
This paper presents a virtual inertia and mechanical power-based control strategy to provide a st... more This paper presents a virtual inertia and mechanical power-based control strategy to provide a stable operation of the power grid under high penetration of renewable energy sources (RESs). The proposed control technique is based on a new active and reactive power-based dynamic model with the permanent magnet synchronous generator (PMSG) swing equation, in which all PMSG features i.e., inertia and mechanical power are embedded within the controller as the main contribution of this paper. To present an accurate analysis of the virtual PMSG-based parameters, the desired zero dynamics of the grid angular frequency are considered to evaluate the effects of virtual mechanical power (VMP) on the active and reactive power sharing, as well as the investigation of virtual inertia variations for the grid angular frequency responses. Moreover, by considering various active power errors and virtual inertia, the impacts of active power error on reactive power in the proposed control technique, ar...
Electric Power Systems Research, 2019
This paper deals with a control technique based on inherent characteristics of synchronous genera... more This paper deals with a control technique based on inherent characteristics of synchronous generators (SG) for control of interfaced converters with high penetration of renewable energy resources (RERs) into the power grid, as a new
IEEE Journal of Emerging and Selected Topics in Power Electronics, 2018
This paper aims to present a novel control strategy for Modular Multilevel Converters (MMC) based... more This paper aims to present a novel control strategy for Modular Multilevel Converters (MMC) based on differential flatness theory (DFT), in which instantaneous active and reactive power values are considered as the flat outputs. To this purpose, a mathematical model of the MMC taking into account dynamics of the ac-side current and the dc-side voltage of the converter is derived in a d-q reference frame. Using this model, the flat outputs-based dynamic model of MMC is obtained to reach the initial value of the proposed controller inputs. In order to mitigate the negative effects of the input disturbance, model errors, and system uncertainties on the operating performance of the MMC, the integral-proportional terms of the flat output errors are added to the initial inputs. This can be achieved through defining a control Lyapunov function which can ensure the stability of the MMC under various operating points. Moreover, the small-signal linearization method is applied to the proposed flat output-based model to separately evaluate the variation effects of controller inputs on flat outputs. The proficiency of the proposed method is researched via MATLAB simulation. Simulation results highlight the capability of the proposed controller in both steady-state and transient conditions in maintaining MMC currents and voltages, through managing active and reactive power. Index Terms-Modular Multilevel Converter (MMC), differential flatness theory (DFT), active and reactive power.
International Journal of Electrical Power & Energy Systems, 2018
A multi-loop control strategy based on a six-order dynamic model of the modular multilevel conver... more A multi-loop control strategy based on a six-order dynamic model of the modular multilevel converter (MMC) is presented in this paper for the high-voltage direct current (HVDC) applications. For the initial analysis of the operation of MMC, a capability curve based on active and reactive power of the MMC is achieved through a part of the six order dynamic equations. According to the MMC's control aims, the first loop known as the outer loop is designed based on passivity control theory to force the MMC state variables to follow their reference values. As the second loop with the use of sliding mode control, the central loop should provide appropriate performance for the MMC under variations of the MMC's parameters. Another main part of the proposed controller is defined for the third inner loop to accomplish the accurate generation of reference values. Also, for a deeper analysis of the MMC's dc link voltage stability, two phase diagrams of the dc-link voltage are assessed. Matlab/Simulink environment is used to thoroughly validate the ability of the proposed control technique for control of the MMC in HVDC application under both load and MMC's parameters changes.
Energies, 2018
This paper presents a synchronous resonant control strategy based on the inherent characteristics... more This paper presents a synchronous resonant control strategy based on the inherent characteristics of permanent magnet synchronous generators (PMSG) for the control of power converters to provide stable operating conditions for the power grid under high penetration of renewable energy resources (RERs). The proposed control technique is based on the small signal linearization of a dynamic model with grid specifications, load-current-based voltages, and power converter currents. A combination of the linearized dynamic model with the PMSG swing equation and resonant controller leads to a control technique with synchronous features and appropriate inertia for the control of converter-based power generators. As the main contribution of this work, an extra functionality is proposed in the control loop of the proposed model to solve the inherent inconveniences of conventional synchronous generators. Also, a comprehensive collaboration between interfaced converter specifications and PMSG fea...
IEEE Transactions on Power Systems, 2017
This article focuses on the control of Modular Multilevel Converters (MMC) for High Voltage DC (H... more This article focuses on the control of Modular Multilevel Converters (MMC) for High Voltage DC (HVDC) applications during unbalanced AC grid voltage sags where positive and negative sequence voltages are equal. The control scheme is based on six arm energy regulators, six independent current controllers and two reference calculation stages that convert the power references into grid and inner current references. Conventional inner AC currents reference calculation fails if the amplitude of the positive and the negative sequence AC grid voltages are equal, a state which is referred to in this paper as singular voltage condition. This article discusses the types of network faults that cause this condition and proposes three different solutions to operate the converter in such scenarios. The adequacy of the proposed solutions is validated through simulations considering each of the problematic fault scenarios.
Energies, 2016
In this paper, a novel modulation function-based method including analyses of the modulation inde... more In this paper, a novel modulation function-based method including analyses of the modulation index and phase is proposed for operation of modular multilevel converters (MMCs) in high voltage direct current (HVDC) transmission systems. The proposed modulation function-based control technique is developed based on thorough and precise analyses of all MMC voltages and currents in the a-b-c reference frame in which the alternating current (AC)-side voltage is the first target to be obtained. Using the AC-side voltage, the combination of the MMC upper and lower arm voltages is achieved as the main structure of the proposed modulation function. The main contribution of this paper is to obtain two very simple new modulation functions to control MMC performance in different operating conditions. The features of the modulation function-based control technique are as follows: (1) this control technique is very simple and can be easily achieved in a-b-c reference frame without the need of using Park transformation; and (2) in addition, the inherent properties of the MMC model are considered in the proposed control technique. Considering these properties leads to constructing a control technique that is robust against MMC parameters changes and also is a very good tracking method for the components of MMC input currents. These features lead to improving the operation of MMC significantly, which can act as a rectifier in the HVDC structure. The simulation studies are conducted through MATLAB/SIMULINK software, and the results obtained verify the effectiveness of the proposed modulation function-based control technique.
2016 7th Power Electronics and Drive Systems Technologies Conference (PEDSTC), 2016
A comprehensive dynamic model based on Direct-Quadrature (DQ) rotating frame is proposed in this ... more A comprehensive dynamic model based on Direct-Quadrature (DQ) rotating frame is proposed in this paper that is used along with a capability curve (CC) based on the active and reactive power to control a grid-connected single-phase voltagesource inverter (SPVSI). With the proposed dynamic model, a droop-passivity based controller can be designed for the gridconnected inverter in the presence of nonlinear loads. Stability analysis of the proposed control technique is also discussed in the paper as well as design principles. Moreover, an accurate performance area of SPVSI active and reactive power in dynamic transitions is achieved using the CC. Furthermore, an effective harmonic compensation scheme along with a proper active and reactive power sharing algorithm are performed by a welldesigned reference waveform generation process. Performance of the grid-connected SPVSI, under the proposed controller, is thoroughly evaluated in the Matlab/Simulink environment.
IEEE Transactions on Power Delivery, 2017
Energy, 2016
This paper introduces a control strategy for the assessment of SAPF (shunt active power filters) ... more This paper introduces a control strategy for the assessment of SAPF (shunt active power filters) role in the electrical power networks. The proposed control scheme is based on the Lyapunov control theory and defines a stable operating region for the interfaced converter during the integration time with the utility grid. The compensation of instantaneous variations of reference current components in the control loop of SAPF in ac-side, and dc-link voltage oscillations in dc-side of the proposed model, is thoroughly considered in the stable operation of interfaced converter, which is the main contribution of this proposal in comparison with other potential control approaches. The proposed control scheme can guarantee the injection of all harmonic components of current and reactive power of grid-connected loads, with a fast dynamic response that results in a unity power factor between the grid currents and voltages during the integration of SAPF into the power grid. An extensive simulation study is performed, assessing the effectiveness of the proposed control strategy in the utilization of SAPF in power networks.
2015 IEEE International Conference on Smart Energy Grid Engineering (SEGE), 2015
This paper presents a control technique for control of a Modular Multilevel Converter (MMC) based... more This paper presents a control technique for control of a Modular Multilevel Converter (MMC) based DG system in the grid-connected mode. Circulating currents of MMC are considered as a state variable, besides the AC currents and dc-link voltage of interfaced converter, which is the main novelty and contribution of the proposed control technique over the other potential control techniques in DG technology. By this assumption, the proposed control technique is included by three outer, central and inner control loops for regulating the operation of interfaced MMC under steady state operating conditions, and during load and parameter variations. Passivity based controller, sliding mode method and reference currents calculator are employed as outer loop controller (OLC), central loop controller (CLC) and inner loop controller (ILC), respectively, in the proposed control technique. Simulation results confirm the effectiveness of the proposed control technique in the proposed DG model during dynamic and steady-state operating conditions.
2015 Australasian Universities Power Engineering Conference (AUPEC), 2015
This paper presents a control technique for enhancing the stable operation of distributed generat... more This paper presents a control technique for enhancing the stable operation of distributed generation (DG) units during islanding and grid-connected modes. The compensation of instantaneous variations in the reference current components of DG units in ac-side, and dc-link voltage variations in dc-side of interfaced converters, are considered properly in the control loop of DG units, which is the main contribution and novelty of this control technique over other control techniques. By using the proposed control technique, DG units can provide the continuous injection of active power from DG sources to the local loads and/or utility grid. Moreover, by setting appropriate reference current components in the control loop of DG units, reactive power and harmonic current components of loads can be supplied with a fast dynamic response. The performance of the developed control is assessed through simulation results during dynamic and steady-state operating conditions. Keywords-Microgrid (MG); distributed generation (DG); droop control; grid-connected mode; islanding mode. I. NOMENCLATURE A. Indices i 1,2 w d,q B. Abbreviations DG Distributed Generation PI Proportional-Integral LPF Low Pass Filter VSC Voltage Source Converter PCC Point of Power Coupling STSs Static Transfer Switches BESS Battery Energy Storage System CC Capacity Curve C. Variables i cwi DG current components Instantaneous variations of DG currents Instantaneous variations of reference current cwi i Δ Deviation of DG currents i fwi Currents of capacitor filters R Radius of i cdi-i cqi curve (α,β) Centre of i cdi-i cqi curve v dci dc-link voltage v wi Voltage at the PCC Instantaneous variations of dc-link voltage u eqwi Equivalent switching state functions
Electric Power Systems Research, 2015
Maximum voltage amplitude at the PCC z , d q * fzi