Nicu Bizon | University of Pitesti (original) (raw)

Papers by Nicu Bizon

This paper proposes a method to minimize the inverter ripple by active compensation of the low fr... more This paper proposes a method to minimize the inverter ripple by active compensation of the low frequency harmonics using a buck current source with a bang-bang control. Remain power spectrum is spreading by chaotification of the buck voltage source command using a nonlinear transfer function for the control loop. Simulation results and designing methodology are presented.

In this paper we propose a fuzzy optimization of the bang-bang control using a fuzzy controller i... more In this paper we propose a fuzzy optimization of the bang-bang control using a fuzzy controller in the feedback loop. The nonlinear characteristic of the fuzzy controller is designed to minimize the output voltage ripple of the buck switching voltage regulator. Feedback signal is output voltage error gain by a value which is nonlinear dependent by output voltage ripple. Comparing this feedback signal with a dc offset level results the PWM command signal. The feasibility and effectiveness of this relative simple control method is shown by simulation. A comparison with the PI control method is included, too.

2008 13th International Power Electronics and Motion Control Conference, 2008

I. INTRODUCTION Power electronics is an interdisciplinary green technology with the main goal to ... more I. INTRODUCTION Power electronics is an interdisciplinary green technology with the main goal to convert electrical energy at high conversion efficiency from different (renewal) energy sources to loads. One problem appears when fuel cells (FC) as energy sources supply ...

In this paper a fuzzy averaging method for extraction of signal drowned in noise is proposed. The... more In this paper a fuzzy averaging method for extraction of signal drowned in noise is proposed. The fuzzy averaging method increases the Signal-to-Noise-Ratio (SNR) gain for an unknown signal drowned in noise, and obviously gives best results for different other signal processing applications, such as: extraction of periodic signals drowned in noise, signal shape reconstruction etc. The field of biosignals processing is explored using that fuzzy averaging method because of its limited frequencies band. Recommended sampling frequency is up to N s-times of frequency given by the Shannon's condition, where number of signal samples on one time stage, usually is N s =100 samples. The testing results obtained in simulations with basic signals and some applications concerning extraction of periodic signals drowned in noise and EKG biosignal processing are given, and compared with other similar results as SNR gain.

Energy, 2015

Four new energy control strategies are proposed here for the Fuel Cell Hybrid Power Source (FCHPS... more Four new energy control strategies are proposed here for the Fuel Cell Hybrid Power Source (FCHPS) used in stationary and mobile FC application (such as the FC backup source for a smart-house and FC vehicle, respectively) based on the Load Following (LF) control and Maximum Efficiency Point Tracking (MEPT) control of the fueling rates. The LF control approach is used to design simple strategies of the Energy Management Unit (EMU) that will assure a charge-sustaining mode for the batteries stack of the Energy Storage System (ESS). If a fueling rate is controlled based on the LF strategy, then the other is controlled based on MEPT strategy in order to maximize the FC net power available. The advantages of the proposed EMU strategies during an unknown load cycle are comparatively shown.

Energy Conversion and Management, 2015

interfaced to the common DC bus via power converters and then to the single-phase distribution gr... more interfaced to the common DC bus via power converters and then to the single-phase distribution grid through a voltage source inverter. RES/FC HPS seem to be an efficient alternative for supplying smart houses and isolated sites. This paper proposes a new supervision strategy of the Energy Management Unit (EMU) based on the LF control approach that assures a charge-sustaining (CS) mode for the Energy Storage System (ESS). So, the capacity of the batteries stack can be reduced at minimum if it is directly connected to the DC bus. The ultracapacitors stack compensates dynamically the power flow balance on the DC bus, regulating the DC voltage via a bidirectional buck-boost power converter. Thus, a semi-active hybrid topology is adopted for the ESS having the batteries stack. The MEPT loops ensure an optimized energy management of the RES/FC HPS. The LF strategy designed based on the power flow balance guarantees the load demand through the efficient management of the power flow from RES, FC and ESS, adapting FC energy production to load profile. The FC energy production is controlled via the fueling rates (one is controlled in the LF loop and the other is controlled in the MEPT loop) to maximize the energy consumption indicator: the ratio of the produced energy and the fuel consumed by the FC system during a load cycle. Thus, this paper evaluates the control performances of the four control topologies to fuel the FC stack during an variable RES and load profile. The MATLAB-Simulink® software package is used to model the RES/FC HPS and develop the four EMU strategies. Simulation results shown comparatively the performance of the EMU strategies proposed under different scenarios of RES power generation and load demand.

In this first part of the paper, the architecture of the Hybrid Power Source based on Maximum Pow... more In this first part of the paper, the architecture of the Hybrid Power Source based on Maximum Power Point tracking controller to harvest the energy available from used Renewable Energy Sources is presented. Usually, the energy harvesting is based on Extremum Seeking Control (ESC) loop. Two ESC schemes are proposed and analyzed in relation with the classical ESC schemes: (1) the modified ESC scheme (named mESC scheme because is based on band-pass filter BPF use, instead of series connection of the high-pass and low-pass filters such as used in higher order ESC scheme) and (2) its equivalent representation (named EQmESC because is based on modified higher order ESC scheme). The cut-off frequency of low-pass filter is chosen larger than in higher order ESC schemes in both ESC schemes proposed. This improves the dither persistence on the proposed ESC schemes, so the search speed of the extremum increases accordingly.

Green Energy and Technology, 2013

Proceedings of the 2014 6th International Conference on Electronics, Computers and Artificial Intelligence (ECAI), 2014

This paper is focused on the nonlinear behavior of the DC-DC converters. In the first part of thi... more This paper is focused on the nonlinear behavior of the DC-DC converters. In the first part of this paper, the basic topologies of the DC-DC converters are analyzed and modeled. The general linear model for the Buck, Boost and Buck-Boost topologies is presented and used in the simulation performed in the second part of this paper. Also, the main tools used to study their nonlinear behavior are shown here, and applied and compared in the second part of this paper. The phase diagram, power spectrum, Poincaré map, bifurcation map, and Lyapunov exponent are briefly presented here as the most used tools to analyze the systems' stability.

2009 International Symposium on Signals, Circuits and Systems, 2009

In the present paper a fuzzy interpolation method is proposed of the average signal steps in each... more In the present paper a fuzzy interpolation method is proposed of the average signal steps in each processing stage, for extraction of signal drowned in noise. The fuzzy interpolation method increases the Signal-to-Noise-Ratio (SNR) gain for a periodic signal drowned in noise, and may give good results for various other signal processing applications, such as: extraction of periodic signals combination drowned in noise, signal shape reconstruction, etc. The recommended sampling frequency is up to N s times of frequency given by the Shannon's condition, where the number of signal samples for one time stage, N s , is usually in the order of hundreds or thousands. The simulation and experimental results obtained with periodic signals drowned in noise are given, using the Matlab© and a digital signal processing (DSP) platform, respectively. The proposed filtering method is compared with other similar methods by computing the SNR gain.

This paper presents an investigation of the fuel cell current ripple produced by inverters which ... more This paper presents an investigation of the fuel cell current ripple produced by inverters which use a fuel cell as DC energy source. Different method to limits that current ripple are analyzed by experiment and compared with simulation obtained results. The low pass filter used on the high DC bus must be carefully designed to reduce the current ripple at a low level without increasing the size and price of the inverter system. The experimental results show that the boost power interface between the fuel cell and DC-DC converter can reduce the fuel cell current ripple, but the overall energy efficiency decrease, so a direct connection of the inverter system to fuel cell is used. Experimental results are presented for a battery stack used as DC energy source, and it is shown that results are approximately the same as a case when the inverter is supplied from a fuel cell stack.

2014 International Conference on Applied Electronics, 2014

University of Pitesti, Scientific …, 2009

This paper presents a comparative study of the filtering techniques used for inverter input curre... more This paper presents a comparative study of the filtering techniques used for inverter input current ripple minimisation. The passive and active filters are used to reduce the inverter input current ripple effects on fuel cell operation as DC energy source. The proper design of the second order passive filter for the high DC voltage bus is presented. Also, different control methods for DC-DC converter, which are used as power interface between fuel cell stack and inverter system, are compared concerning the possibility to limit the fuel cell current ripple. The advantages of a fuzzy control surface, which has as one control variable just the fuel cell current ripple, are shown by simulation and experiment. Finally, an active filter is proposed as one of the best filtering technique.

2007 European Conference on Power Electronics and Applications, EPE, 2007

We analyze by simulations the nonlinear phenomena in the peak current mode controlled boost conve... more We analyze by simulations the nonlinear phenomena in the peak current mode controlled boost converter used as power interface into the energy generation system (EGS). Transition to chaos in one or more stages depends on the initial conditions and the bifurcation diagrams with the reference current as the variable parameter have been reported. The simulation results show that the EGS without large energy storage device (ESD) shift to chaos as the parameter is modified. The proposed fuzzy peak current controller provides better dynamic response, robustness against system uncertainty disturbances, and an implicit stability proof.

Intelligent Information Systems and Knowledge Management for Energy

2015 7th International Conference on Electronics, Computers and Artificial Intelligence (ECAI), 2015

2014 International Conference on Applied Electronics, 2014

In the second part of this paper, the dither persistence on the Extremum Seeking Control (ESC) lo... more In the second part of this paper, the dither persistence on the Extremum Seeking Control (ESC) loop is analyzed. The ESC scheme is usually used on Maximum Power Point (MPP) tracking controller to harvest the energy available from used renewable or green Energy Sources (ES). Two ESC schemes are analyzed in relation with dither persistence on output reference current: (1) the modified ESC scheme (named mESC scheme because is based on band-pass filter BPF use, instead of series connection of the high-pass and low-pass filters such as used in higher order ESC scheme) and (2) its equivalent representation (named EQmESC because is based on modified higher order ESC scheme). The pass band (the cut-off frequency of low-pass filter) is chosen larger than in higher order ESC schemes in both ESC schemes proposed. Thus, dither persistence on the proposed ESC loop is improved. Consequently, the search speed of the extremum increases accordingly. These are shown by mathematical modeling and simul...

In this paper Pulse Width Modulation (PWM) and Peak Current Control (PCC) methods are analyzed by... more In this paper Pulse Width Modulation (PWM) and Peak Current Control (PCC) methods are analyzed by computer simulation as possible candidate for controlling with high dynamics performances of the controlled buck current source. These control performances are needed to compensate the low frequency PEMFC current harmonics produced by inverter system of the energy generation system with PEM fuel cell stack as energy source. The complex behavior of the buck current source with PWM and PCC control strategies are shown, and compared cu bang-bang control strategy. Used models and some designing rules are given, too.

This paper analyzes the possibility of using a nonlinear controller to mitigate the current rippl... more This paper analyzes the possibility of using a nonlinear controller to mitigate the current ripple of an inverter system powered by a Polymer Electrolyte Membrane Fuel Cell (PEMFC) stack. Hybrid and fuel cell technologies need to be merged in Hybrid Power Sources (HPS) to assure high performance regarding the PEMFC energy efficiency and PEMFC life cycle. The nonlinear controller is designed based on inverse gain that gives a constant answer for all levels of current ripple. Its advantages will be showed in comparison with hysteretic current control technique (that was shown in part I). Finally, a fuzzy logic controller is proposed to design the nonlinear control law.

This paper proposes a method to minimize the inverter ripple by active compensation of the low fr... more This paper proposes a method to minimize the inverter ripple by active compensation of the low frequency harmonics using a buck current source with a bang-bang control. Remain power spectrum is spreading by chaotification of the buck voltage source command using a nonlinear transfer function for the control loop. Simulation results and designing methodology are presented.

In this paper we propose a fuzzy optimization of the bang-bang control using a fuzzy controller i... more In this paper we propose a fuzzy optimization of the bang-bang control using a fuzzy controller in the feedback loop. The nonlinear characteristic of the fuzzy controller is designed to minimize the output voltage ripple of the buck switching voltage regulator. Feedback signal is output voltage error gain by a value which is nonlinear dependent by output voltage ripple. Comparing this feedback signal with a dc offset level results the PWM command signal. The feasibility and effectiveness of this relative simple control method is shown by simulation. A comparison with the PI control method is included, too.

2008 13th International Power Electronics and Motion Control Conference, 2008

I. INTRODUCTION Power electronics is an interdisciplinary green technology with the main goal to ... more I. INTRODUCTION Power electronics is an interdisciplinary green technology with the main goal to convert electrical energy at high conversion efficiency from different (renewal) energy sources to loads. One problem appears when fuel cells (FC) as energy sources supply ...

In this paper a fuzzy averaging method for extraction of signal drowned in noise is proposed. The... more In this paper a fuzzy averaging method for extraction of signal drowned in noise is proposed. The fuzzy averaging method increases the Signal-to-Noise-Ratio (SNR) gain for an unknown signal drowned in noise, and obviously gives best results for different other signal processing applications, such as: extraction of periodic signals drowned in noise, signal shape reconstruction etc. The field of biosignals processing is explored using that fuzzy averaging method because of its limited frequencies band. Recommended sampling frequency is up to N s-times of frequency given by the Shannon's condition, where number of signal samples on one time stage, usually is N s =100 samples. The testing results obtained in simulations with basic signals and some applications concerning extraction of periodic signals drowned in noise and EKG biosignal processing are given, and compared with other similar results as SNR gain.

Energy, 2015

Four new energy control strategies are proposed here for the Fuel Cell Hybrid Power Source (FCHPS... more Four new energy control strategies are proposed here for the Fuel Cell Hybrid Power Source (FCHPS) used in stationary and mobile FC application (such as the FC backup source for a smart-house and FC vehicle, respectively) based on the Load Following (LF) control and Maximum Efficiency Point Tracking (MEPT) control of the fueling rates. The LF control approach is used to design simple strategies of the Energy Management Unit (EMU) that will assure a charge-sustaining mode for the batteries stack of the Energy Storage System (ESS). If a fueling rate is controlled based on the LF strategy, then the other is controlled based on MEPT strategy in order to maximize the FC net power available. The advantages of the proposed EMU strategies during an unknown load cycle are comparatively shown.

Energy Conversion and Management, 2015

interfaced to the common DC bus via power converters and then to the single-phase distribution gr... more interfaced to the common DC bus via power converters and then to the single-phase distribution grid through a voltage source inverter. RES/FC HPS seem to be an efficient alternative for supplying smart houses and isolated sites. This paper proposes a new supervision strategy of the Energy Management Unit (EMU) based on the LF control approach that assures a charge-sustaining (CS) mode for the Energy Storage System (ESS). So, the capacity of the batteries stack can be reduced at minimum if it is directly connected to the DC bus. The ultracapacitors stack compensates dynamically the power flow balance on the DC bus, regulating the DC voltage via a bidirectional buck-boost power converter. Thus, a semi-active hybrid topology is adopted for the ESS having the batteries stack. The MEPT loops ensure an optimized energy management of the RES/FC HPS. The LF strategy designed based on the power flow balance guarantees the load demand through the efficient management of the power flow from RES, FC and ESS, adapting FC energy production to load profile. The FC energy production is controlled via the fueling rates (one is controlled in the LF loop and the other is controlled in the MEPT loop) to maximize the energy consumption indicator: the ratio of the produced energy and the fuel consumed by the FC system during a load cycle. Thus, this paper evaluates the control performances of the four control topologies to fuel the FC stack during an variable RES and load profile. The MATLAB-Simulink® software package is used to model the RES/FC HPS and develop the four EMU strategies. Simulation results shown comparatively the performance of the EMU strategies proposed under different scenarios of RES power generation and load demand.

In this first part of the paper, the architecture of the Hybrid Power Source based on Maximum Pow... more In this first part of the paper, the architecture of the Hybrid Power Source based on Maximum Power Point tracking controller to harvest the energy available from used Renewable Energy Sources is presented. Usually, the energy harvesting is based on Extremum Seeking Control (ESC) loop. Two ESC schemes are proposed and analyzed in relation with the classical ESC schemes: (1) the modified ESC scheme (named mESC scheme because is based on band-pass filter BPF use, instead of series connection of the high-pass and low-pass filters such as used in higher order ESC scheme) and (2) its equivalent representation (named EQmESC because is based on modified higher order ESC scheme). The cut-off frequency of low-pass filter is chosen larger than in higher order ESC schemes in both ESC schemes proposed. This improves the dither persistence on the proposed ESC schemes, so the search speed of the extremum increases accordingly.

Green Energy and Technology, 2013

Proceedings of the 2014 6th International Conference on Electronics, Computers and Artificial Intelligence (ECAI), 2014

This paper is focused on the nonlinear behavior of the DC-DC converters. In the first part of thi... more This paper is focused on the nonlinear behavior of the DC-DC converters. In the first part of this paper, the basic topologies of the DC-DC converters are analyzed and modeled. The general linear model for the Buck, Boost and Buck-Boost topologies is presented and used in the simulation performed in the second part of this paper. Also, the main tools used to study their nonlinear behavior are shown here, and applied and compared in the second part of this paper. The phase diagram, power spectrum, Poincaré map, bifurcation map, and Lyapunov exponent are briefly presented here as the most used tools to analyze the systems' stability.

2009 International Symposium on Signals, Circuits and Systems, 2009

In the present paper a fuzzy interpolation method is proposed of the average signal steps in each... more In the present paper a fuzzy interpolation method is proposed of the average signal steps in each processing stage, for extraction of signal drowned in noise. The fuzzy interpolation method increases the Signal-to-Noise-Ratio (SNR) gain for a periodic signal drowned in noise, and may give good results for various other signal processing applications, such as: extraction of periodic signals combination drowned in noise, signal shape reconstruction, etc. The recommended sampling frequency is up to N s times of frequency given by the Shannon's condition, where the number of signal samples for one time stage, N s , is usually in the order of hundreds or thousands. The simulation and experimental results obtained with periodic signals drowned in noise are given, using the Matlab© and a digital signal processing (DSP) platform, respectively. The proposed filtering method is compared with other similar methods by computing the SNR gain.

This paper presents an investigation of the fuel cell current ripple produced by inverters which ... more This paper presents an investigation of the fuel cell current ripple produced by inverters which use a fuel cell as DC energy source. Different method to limits that current ripple are analyzed by experiment and compared with simulation obtained results. The low pass filter used on the high DC bus must be carefully designed to reduce the current ripple at a low level without increasing the size and price of the inverter system. The experimental results show that the boost power interface between the fuel cell and DC-DC converter can reduce the fuel cell current ripple, but the overall energy efficiency decrease, so a direct connection of the inverter system to fuel cell is used. Experimental results are presented for a battery stack used as DC energy source, and it is shown that results are approximately the same as a case when the inverter is supplied from a fuel cell stack.

2014 International Conference on Applied Electronics, 2014

University of Pitesti, Scientific …, 2009

This paper presents a comparative study of the filtering techniques used for inverter input curre... more This paper presents a comparative study of the filtering techniques used for inverter input current ripple minimisation. The passive and active filters are used to reduce the inverter input current ripple effects on fuel cell operation as DC energy source. The proper design of the second order passive filter for the high DC voltage bus is presented. Also, different control methods for DC-DC converter, which are used as power interface between fuel cell stack and inverter system, are compared concerning the possibility to limit the fuel cell current ripple. The advantages of a fuzzy control surface, which has as one control variable just the fuel cell current ripple, are shown by simulation and experiment. Finally, an active filter is proposed as one of the best filtering technique.

2007 European Conference on Power Electronics and Applications, EPE, 2007

We analyze by simulations the nonlinear phenomena in the peak current mode controlled boost conve... more We analyze by simulations the nonlinear phenomena in the peak current mode controlled boost converter used as power interface into the energy generation system (EGS). Transition to chaos in one or more stages depends on the initial conditions and the bifurcation diagrams with the reference current as the variable parameter have been reported. The simulation results show that the EGS without large energy storage device (ESD) shift to chaos as the parameter is modified. The proposed fuzzy peak current controller provides better dynamic response, robustness against system uncertainty disturbances, and an implicit stability proof.

Intelligent Information Systems and Knowledge Management for Energy

2015 7th International Conference on Electronics, Computers and Artificial Intelligence (ECAI), 2015

2014 International Conference on Applied Electronics, 2014

In the second part of this paper, the dither persistence on the Extremum Seeking Control (ESC) lo... more In the second part of this paper, the dither persistence on the Extremum Seeking Control (ESC) loop is analyzed. The ESC scheme is usually used on Maximum Power Point (MPP) tracking controller to harvest the energy available from used renewable or green Energy Sources (ES). Two ESC schemes are analyzed in relation with dither persistence on output reference current: (1) the modified ESC scheme (named mESC scheme because is based on band-pass filter BPF use, instead of series connection of the high-pass and low-pass filters such as used in higher order ESC scheme) and (2) its equivalent representation (named EQmESC because is based on modified higher order ESC scheme). The pass band (the cut-off frequency of low-pass filter) is chosen larger than in higher order ESC schemes in both ESC schemes proposed. Thus, dither persistence on the proposed ESC loop is improved. Consequently, the search speed of the extremum increases accordingly. These are shown by mathematical modeling and simul...

In this paper Pulse Width Modulation (PWM) and Peak Current Control (PCC) methods are analyzed by... more In this paper Pulse Width Modulation (PWM) and Peak Current Control (PCC) methods are analyzed by computer simulation as possible candidate for controlling with high dynamics performances of the controlled buck current source. These control performances are needed to compensate the low frequency PEMFC current harmonics produced by inverter system of the energy generation system with PEM fuel cell stack as energy source. The complex behavior of the buck current source with PWM and PCC control strategies are shown, and compared cu bang-bang control strategy. Used models and some designing rules are given, too.

This paper analyzes the possibility of using a nonlinear controller to mitigate the current rippl... more This paper analyzes the possibility of using a nonlinear controller to mitigate the current ripple of an inverter system powered by a Polymer Electrolyte Membrane Fuel Cell (PEMFC) stack. Hybrid and fuel cell technologies need to be merged in Hybrid Power Sources (HPS) to assure high performance regarding the PEMFC energy efficiency and PEMFC life cycle. The nonlinear controller is designed based on inverse gain that gives a constant answer for all levels of current ripple. Its advantages will be showed in comparison with hysteretic current control technique (that was shown in part I). Finally, a fuzzy logic controller is proposed to design the nonlinear control law.