2020 3rd International Conference on Power and Energy Applications (ICPEA)
For low-voltage vibration energy harvesting, such as 0.5V@50Hz input, this paper presents a novel... more For low-voltage vibration energy harvesting, such as 0.5V@50Hz input, this paper presents a novel inductor-less step-up ac/dc converter. In the proposed ac/dc converter, high voltage gain can be achieved by combing a cross-coupled charge pump with a bipolar Cockcroft-Walton multiplier, where a rectifier-less design is realized by the bipolar Cockcroft-Walton multiplier. Furthermore, small EMI (Electro-Magnetic Interference) is provided by the inductor-less design. The performance of the proposed ac/dc converter with 12×step-up gain is evalutaed by theoretical analysis and SPICE (Simulation Program with Integrated Circuit Emphasis) simulations. The SPICE simulations demonstrated that the power efficiency of the proposed converter is about 88%@1mW with 1% ripple factor. Furthermore, breadboard experiments verify the feasibility of the proposed inductor-less topology.
2022 8th International Conference on Control, Instrumentation and Automation (ICCIA)
Today, the overuse of nonlinear loads in island microgrids (MGs) are created problems such as poo... more Today, the overuse of nonlinear loads in island microgrids (MGs) are created problems such as poor harmonic load distribution and voltage distortion. To solve these problems, this paper proposes a control method to reduce main voltage harmonics selectively. This method uses a virtual synchronous generator (VSG) based control to compensate the harmonic voltage created by the passing harmonic current in output impedance, via adding the appropriate amount of harmonic voltage to the inverter voltage reference. After examining the primary principles of power transmission to a constant current source, harmonic VSG controller is created, which significantly reduces total harmonic distortion (THD). To evaluate the performance of the harmonic VSG controller, this controller is compared with the droop controller. Simulation results show the improvement of power quality in terms of voltage THD using VSG-based harmonic mitigation strategy.
2021 7th International Conference on Control, Instrumentation and Automation (ICCIA), 2021
Today, with development of technologies and communication networks, cyber security is one of the ... more Today, with development of technologies and communication networks, cyber security is one of the challenges in widespread use of cyber-physical systems. Secondary control in microgrids is known as one of the potential targets of cyber-attacks, and these threats should be considered in the design of the controller. In this paper, the vulnerability of distributed secondary control against cyber-attacks has been proposed. This paper studies the performance and vulnerability of various distributed secondary control methods in AC microgrids under cyber-attacks. The purpose of this work is to identify the point of failure of each method against cyber threats in AC microgrids. In order to do this comparison study, three well-known attacks including false data injection, controller hijacking, and denial of service are evaluated for three secondary control methods so called distributed consensus, average distributed control, and distributed finite-time control. Simulation results are performed in MATLAB software to provide the comparison results.
Nowadays, the proliferation of distributed energy resources has the potential to overcome the maj... more Nowadays, the proliferation of distributed energy resources has the potential to overcome the majority of the environmental challenges associated with energy generation from non-renewable resources. Nonetheless, their generation capacity fluctuates constantly in response to the amount of energy received in peripheral conditions. To address this issue, maximum power point tracking (MPPT) algorithms must be used. There are several MPPT approaches; the majority of them either lack tracking accuracy at the maximum power point (MPP) or perform poorly, posing a fundamental challenge as steady-state response fluctuations. The purpose of this paper is to eliminate the shortcomings of conventional methods by introducing a data-driven control approach. The conventional MPPT methods are based on the system's model, and it is critical to consider an accurate model for the desired system. This paper proposes a data-driven method known as iterative feedback tuner (IFT) for achieving the MPP of a photovoltaic (PV) system using a PI controller. The proposed control approach is validated through simulation studies.
Today, with the development of the internet of things in industrial control, cyber security is on... more Today, with the development of the internet of things in industrial control, cyber security is one of the challenges in the widespread use of systems. Microgrids are known as one of the potential targets of cyberattacks, and these cyber threats should be considered in the design of future protection systems and controllers. In this paper, a method of detecting deception cyberattacks is designed for AC microgrids. This method uses a distributed and locally implemented estimator for the secondary control layer. The estimator is utilized to extract the system information from the secondary control point of view. Based on the characteristics extracted by the estimator, cyberattacks will be identifiable before the microgrid is disrupted. The simulation results performed in the MATLAB environment show the efficiency of the proposed method.
2019 10th International Power Electronics, Drive Systems and Technologies Conference (PEDSTC), 2019
LCL filters are used in grid-connected voltage source inverters (GC-VSIs) due to their lower cost... more LCL filters are used in grid-connected voltage source inverters (GC-VSIs) due to their lower cost and higher efficiency. These filters attenuate high order harmonics effectively; however, the grid impedance fluctuations (GIFs) may cause resonance and system instability. The GIF can reduce the resonance frequency to lower than a permissible threshold, then, the resonance may happen and prevent some nonlinear loads from being fed. On the other hand, very high resonance frequencies cause capacitor of the filter being actually short circuited. Consequently, the nature of the filter changes and reduces the power quality of the network. In this paper, considering the possible range for GIFs and using Kharitonov control theorem (KCT), the coefficients of the PI controller and the current feedback of the filter capacitor are obtained simultaneously to ensure safe and desired operation of the GC-VSI against the GIFs. As a result, the proposed closed loop system shows optimal response to variation of the reference current. Genetic algorithm (GA) is used to determine optimal values of the coefficients and the gain. Simulation results carried out in MATLAB/SIMULINK show accuracy and effectiveness of the proposed method.
Abstract This paper presents a novel light emitting diode (LED) sink driver with a high voltage g... more Abstract This paper presents a novel light emitting diode (LED) sink driver with a high voltage gain for LED-based lighting applications. Unlike conventional LED sink drivers, the proposed driver has the nested switched-inductor/switched capacitor (SI/SC) topology consisting of an SI buck-boost converter block and a nesting-type SC cell. Owing to the nested SI/SC topology, the proposed driver offers not only a high voltage gain but also a flexible controllability of the LED currents and transformer-less structure. The effectiveness of the proposed driver is justified by some simulation results in SPICE software environment and laboratory experimental tests. In the performed simulations, the proposed driver in comparison of conventional drivers improved almost 6% power efficiency when the output power was 500 mW. Furthermore, in the performed experiments, the feasibility of the proposed topology is confirmed by demonstrating a high voltage gain and the output controllability.
2021 12th Power Electronics, Drive Systems, and Technologies Conference (PEDSTC), 2021
The fully-distributed secondary control can be regarded as a viable solution to achieve acceptabl... more The fully-distributed secondary control can be regarded as a viable solution to achieve acceptable voltage regulation and proper load-sharing of DC microgrids. Using this secondary controller, in addition to acceptable voltage regulation, the load is shared according to the nominal capacity of the distributed generation units. This manner is traditionally implemented as a time-triggered communication paradigm which causes a high communication load by sending and receiving unnecessary data among units. In this paper, to avoid unnecessary communication, the fully-distributed secondary controller is equipped with an event-triggered strategy based on a new pre-defined condition. The system stability under the proposed event-based control is analyzed using the Lyapunov theorem. The considered scheme is applied to a multi-agent DC microgrid to validate the system performance using Simulink/ MATLAB environment.
In this article, an improved robust control strategy for voltage stabilization and desired perfor... more In this article, an improved robust control strategy for voltage stabilization and desired performance satisfaction of islanded inverter-interfaced microgrids consisting of several distributed generations (DGs) with general topology is presented. The main advantages of the proposed control manner are as follows: 1) its structure is fully decentralized, 2) the design process is scalable, 3) it does not impose any limitations on the microgrid parameters and line dynamics, 4) it provides stability and the desired performance of nominal microgrid system, 5) it maintains robust stability as well as robust performance of the closed-loop system against microgrid topology changes, plug-and-play (PnP) operation of DG units, and load unmodeled dynamics, and 6) each local controller is obtained from a unique convex optimization problem which results in optimal performance of the system and also robustness to several sequential changes. To achieve these objectives, first, each DG subsystem is modeled as a linear time-invariant (LTI) system affected by disturbances caused by the local load current and the load voltages of its neighboring DGs. Next, the PnP functionality of DGs and the microgrid topology changes are modeled as a new polytopic-type uncertainty. Thereafter, the design problem is transformed into a dynamic output feedback controller for an LTI system subject to polytopic-type uncertainty with ${\boldsymbol{H}_\infty }$ performance criteria. Finally, a convex linear-matrix-inequality-based optimization problem with a noniterative direct synthesis process is proposed to solve the controller design problem. The performance of the presented controller is appraised via several simulation studies accomplished in MATLAB/SimPowerSystems Toolbox.
2020 3rd International Conference on Power and Energy Applications (ICPEA)
For low-voltage vibration energy harvesting, such as 0.5V@50Hz input, this paper presents a novel... more For low-voltage vibration energy harvesting, such as 0.5V@50Hz input, this paper presents a novel inductor-less step-up ac/dc converter. In the proposed ac/dc converter, high voltage gain can be achieved by combing a cross-coupled charge pump with a bipolar Cockcroft-Walton multiplier, where a rectifier-less design is realized by the bipolar Cockcroft-Walton multiplier. Furthermore, small EMI (Electro-Magnetic Interference) is provided by the inductor-less design. The performance of the proposed ac/dc converter with 12×step-up gain is evalutaed by theoretical analysis and SPICE (Simulation Program with Integrated Circuit Emphasis) simulations. The SPICE simulations demonstrated that the power efficiency of the proposed converter is about 88%@1mW with 1% ripple factor. Furthermore, breadboard experiments verify the feasibility of the proposed inductor-less topology.
2022 8th International Conference on Control, Instrumentation and Automation (ICCIA)
Today, the overuse of nonlinear loads in island microgrids (MGs) are created problems such as poo... more Today, the overuse of nonlinear loads in island microgrids (MGs) are created problems such as poor harmonic load distribution and voltage distortion. To solve these problems, this paper proposes a control method to reduce main voltage harmonics selectively. This method uses a virtual synchronous generator (VSG) based control to compensate the harmonic voltage created by the passing harmonic current in output impedance, via adding the appropriate amount of harmonic voltage to the inverter voltage reference. After examining the primary principles of power transmission to a constant current source, harmonic VSG controller is created, which significantly reduces total harmonic distortion (THD). To evaluate the performance of the harmonic VSG controller, this controller is compared with the droop controller. Simulation results show the improvement of power quality in terms of voltage THD using VSG-based harmonic mitigation strategy.
2021 7th International Conference on Control, Instrumentation and Automation (ICCIA), 2021
Today, with development of technologies and communication networks, cyber security is one of the ... more Today, with development of technologies and communication networks, cyber security is one of the challenges in widespread use of cyber-physical systems. Secondary control in microgrids is known as one of the potential targets of cyber-attacks, and these threats should be considered in the design of the controller. In this paper, the vulnerability of distributed secondary control against cyber-attacks has been proposed. This paper studies the performance and vulnerability of various distributed secondary control methods in AC microgrids under cyber-attacks. The purpose of this work is to identify the point of failure of each method against cyber threats in AC microgrids. In order to do this comparison study, three well-known attacks including false data injection, controller hijacking, and denial of service are evaluated for three secondary control methods so called distributed consensus, average distributed control, and distributed finite-time control. Simulation results are performed in MATLAB software to provide the comparison results.
Nowadays, the proliferation of distributed energy resources has the potential to overcome the maj... more Nowadays, the proliferation of distributed energy resources has the potential to overcome the majority of the environmental challenges associated with energy generation from non-renewable resources. Nonetheless, their generation capacity fluctuates constantly in response to the amount of energy received in peripheral conditions. To address this issue, maximum power point tracking (MPPT) algorithms must be used. There are several MPPT approaches; the majority of them either lack tracking accuracy at the maximum power point (MPP) or perform poorly, posing a fundamental challenge as steady-state response fluctuations. The purpose of this paper is to eliminate the shortcomings of conventional methods by introducing a data-driven control approach. The conventional MPPT methods are based on the system's model, and it is critical to consider an accurate model for the desired system. This paper proposes a data-driven method known as iterative feedback tuner (IFT) for achieving the MPP of a photovoltaic (PV) system using a PI controller. The proposed control approach is validated through simulation studies.
Today, with the development of the internet of things in industrial control, cyber security is on... more Today, with the development of the internet of things in industrial control, cyber security is one of the challenges in the widespread use of systems. Microgrids are known as one of the potential targets of cyberattacks, and these cyber threats should be considered in the design of future protection systems and controllers. In this paper, a method of detecting deception cyberattacks is designed for AC microgrids. This method uses a distributed and locally implemented estimator for the secondary control layer. The estimator is utilized to extract the system information from the secondary control point of view. Based on the characteristics extracted by the estimator, cyberattacks will be identifiable before the microgrid is disrupted. The simulation results performed in the MATLAB environment show the efficiency of the proposed method.
2019 10th International Power Electronics, Drive Systems and Technologies Conference (PEDSTC), 2019
LCL filters are used in grid-connected voltage source inverters (GC-VSIs) due to their lower cost... more LCL filters are used in grid-connected voltage source inverters (GC-VSIs) due to their lower cost and higher efficiency. These filters attenuate high order harmonics effectively; however, the grid impedance fluctuations (GIFs) may cause resonance and system instability. The GIF can reduce the resonance frequency to lower than a permissible threshold, then, the resonance may happen and prevent some nonlinear loads from being fed. On the other hand, very high resonance frequencies cause capacitor of the filter being actually short circuited. Consequently, the nature of the filter changes and reduces the power quality of the network. In this paper, considering the possible range for GIFs and using Kharitonov control theorem (KCT), the coefficients of the PI controller and the current feedback of the filter capacitor are obtained simultaneously to ensure safe and desired operation of the GC-VSI against the GIFs. As a result, the proposed closed loop system shows optimal response to variation of the reference current. Genetic algorithm (GA) is used to determine optimal values of the coefficients and the gain. Simulation results carried out in MATLAB/SIMULINK show accuracy and effectiveness of the proposed method.
Abstract This paper presents a novel light emitting diode (LED) sink driver with a high voltage g... more Abstract This paper presents a novel light emitting diode (LED) sink driver with a high voltage gain for LED-based lighting applications. Unlike conventional LED sink drivers, the proposed driver has the nested switched-inductor/switched capacitor (SI/SC) topology consisting of an SI buck-boost converter block and a nesting-type SC cell. Owing to the nested SI/SC topology, the proposed driver offers not only a high voltage gain but also a flexible controllability of the LED currents and transformer-less structure. The effectiveness of the proposed driver is justified by some simulation results in SPICE software environment and laboratory experimental tests. In the performed simulations, the proposed driver in comparison of conventional drivers improved almost 6% power efficiency when the output power was 500 mW. Furthermore, in the performed experiments, the feasibility of the proposed topology is confirmed by demonstrating a high voltage gain and the output controllability.
2021 12th Power Electronics, Drive Systems, and Technologies Conference (PEDSTC), 2021
The fully-distributed secondary control can be regarded as a viable solution to achieve acceptabl... more The fully-distributed secondary control can be regarded as a viable solution to achieve acceptable voltage regulation and proper load-sharing of DC microgrids. Using this secondary controller, in addition to acceptable voltage regulation, the load is shared according to the nominal capacity of the distributed generation units. This manner is traditionally implemented as a time-triggered communication paradigm which causes a high communication load by sending and receiving unnecessary data among units. In this paper, to avoid unnecessary communication, the fully-distributed secondary controller is equipped with an event-triggered strategy based on a new pre-defined condition. The system stability under the proposed event-based control is analyzed using the Lyapunov theorem. The considered scheme is applied to a multi-agent DC microgrid to validate the system performance using Simulink/ MATLAB environment.
In this article, an improved robust control strategy for voltage stabilization and desired perfor... more In this article, an improved robust control strategy for voltage stabilization and desired performance satisfaction of islanded inverter-interfaced microgrids consisting of several distributed generations (DGs) with general topology is presented. The main advantages of the proposed control manner are as follows: 1) its structure is fully decentralized, 2) the design process is scalable, 3) it does not impose any limitations on the microgrid parameters and line dynamics, 4) it provides stability and the desired performance of nominal microgrid system, 5) it maintains robust stability as well as robust performance of the closed-loop system against microgrid topology changes, plug-and-play (PnP) operation of DG units, and load unmodeled dynamics, and 6) each local controller is obtained from a unique convex optimization problem which results in optimal performance of the system and also robustness to several sequential changes. To achieve these objectives, first, each DG subsystem is modeled as a linear time-invariant (LTI) system affected by disturbances caused by the local load current and the load voltages of its neighboring DGs. Next, the PnP functionality of DGs and the microgrid topology changes are modeled as a new polytopic-type uncertainty. Thereafter, the design problem is transformed into a dynamic output feedback controller for an LTI system subject to polytopic-type uncertainty with ${\boldsymbol{H}_\infty }$ performance criteria. Finally, a convex linear-matrix-inequality-based optimization problem with a noniterative direct synthesis process is proposed to solve the controller design problem. The performance of the presented controller is appraised via several simulation studies accomplished in MATLAB/SimPowerSystems Toolbox.
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