Marian Raducu

Evaluation of the performance of new extremum seeking control algorithm to locate accurately the peaks on multimodal functions

A new Extremum Seeking Control (ESC) scheme is proposed in this paper for multimodal function with two dimension (2D), named as ESC 2D — scheme. This ESC 2D-scheme is a Single Input — Double Outputs (DISO) control system that combine two ESC 1D-schemes of asymptotic perturbed type. Each ESC 1D-scheme has two control loop. The scanning loop generates the signal that sweep the searching space in order to locate the desired peak on the multimodal pattern. The tuning parameter (k2) will define the space of searching. The locating loop generates the gradient signal that will find accurately this peak. The tuning parameter (k1) will define the searching speed under the constraint of stability of the ESC loop. The performance obtained for the ESC 2D scheme proposed is evaluated on multimodal benchmark patterns.

Fuel cell current ripple minimization using a bi-buck power interface

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.

Energy efficiency analysis of various topologies, control techniques and technologies used for photovoltaic panels Part I: On thePV modeling and problem of extracting the maximum power

This part of the paper presents the problem of solar energy conversion into electricity using photovoltaic cells. The mathematical study of PV cells could be made by two models: single diode model and double diode model. By connecting in series several PV cells a PV panel is obtained. Small PV power generators are made by connecting multiple PV modules to form a PV array. Photovoltaic panels can be arranged in various configurations. Besides the insolation level (G) and ambient temperature (T), the PV cell power output depends a lot on panel orientation during a day. Thus the maximum power point (MPP) depends on panel orientation that can be controlled via the sun tracking control schemes. This part of the paper presents a review of the sun tracking systems at level of modeling and performances comparison of the main configurations used in PV systems to connect the PV modules.

On the search speed for the Extremum Seeking Control 2D-schemes. Part II - performances estimation

In this paper a performances analysis of the Extremum Seeking Control (ESC) scheme applied to the dual-inputs single-output (DISO) systems is presented. These ESC 2D-schemes contain two ESC 1D-schemes that have a common input: the output of the DISO system. The performance of the basic high-order ESC (bhoESC) and band-pass filter ESC (bpfESC) 2Dschemes will be analyzed here based on the two orthogonal dither signals. The ratio of the search speeds for these 2D-schemes is estimated analytically during the search speed based on the partial derivatives of the unknown DISO map. The relation of the search speeds ratio related to these partial derivatives and control parameters of the ESC 2D-scheme is shown. The proposed bpfESC 2D-scheme has higher search speed than the bhofESC 2D-scheme, and this is clearly highlighted in this paper based on the simulation performed.

Energy efficiency analysis of various topologies, control techniques and technologies used for photovoltaic panels Part II: Maximum power point tracking algorithms

The second part of the paper presents the MPPT systems for extracting maximum power from a photovoltaic installation. The maximum transfer between generator and receiver is obtained by interconnecting a DC-DC converter which performs continuous adaptation of load to a PV generator. This principle represents the basis of the MPPT systems. The PV cell power output mainly depends on two variables: insolation level (G) and ambient temperature (T). Thus the maximum power point (MPP) depends on these variables for a panel orientation set. After reaching the maximum power the transfer between the PV generator and receiver is done with MPP tracking (MPPT) control schemes. This part of the paper presents a review of the main MPPT control schemes at level of operating and performances comparison.

Energy efficiency of the PV panels using a MPPT controller with improved search speed: Part I: Modeling of the PV power system under extremum seeking control

In first part of this paper the Maximum Power Point Tracking (MPPT) technique for photovoltaic (PV) panels based on Extremum Seeking Control (ESC) scheme is analyzed. It is important to know how much energy can be harvested from a PV that uses a MPPT controller. In this paper, the ESC schemes are analyzed in the frequency domain. The modified ESC (mESC) and high-order ESC (hoESC) schemes are considered in this study. The mESC scheme is based on a band pass filter (BPF), while the hoESC scheme is based on a series connection of the high pass (HP) and the low pass (LP) filters. Because the BPF topology may be represented as an equivalent series combination of the HP and LP filters, the equivalence of these topologies is shown for the same cut-off frequencies used. The simulations performed shows that the mentioned equivalence is effective. Also, the design condition to obtain the highest value of the search speed for the mESC scheme is shown when the HP cut-off frequency is known.

On the search speed for the Extremum Seeking Control 2D-schemes. Part I - signal processing using orthogonal dither signals

In this paper an analysis of the Extremum Seeking Control (ESC) 2D-scheme for the dual-inputs single-output (DISO) systems is presented. The ESC 2D-schemes have two loops where the output signal is obtained based on two different ESC algorithms proposed in the literature. The basic high-order ESC (bhoESC) 2D-scheme and an improved ESC variant will be analyzed here based on the two orthogonal dither signals. The proposed ESC scheme is based on a band-pass filter (BPF) instead of the series combination of high-pass (HP) and low-pass (LP) filters used in the bhoESC scheme. The processing of the output signal shows that the search speed in both bpfESC loops depends on the BPF cut-off frequencies. So, besides the gradient signals, the injected signals on the both bhoESC inputs contain the Low Frequencies (LF) components from the BPF band. Thus the dither persistence in the bpfESC loops is improved in comparison with the bhoESC scheme. The relations between the search speeds and the partial derivatives of an unknown DISO map are shown.

FSK transmission circuit for remote sensors integration in distributed measurement systems

In this paper is presented an innovative design and the practical implementation of a communication circuit intended to be used for long distances transmission of the signals from sensors. The circuit is suitable for integration within the conditioning modules that are used for processing of signals from sensors that are connected to remote data acquisition systems. Regarding his structure, the proposed circuit is composed by two modules: the transmitter and the receiver. The transmission part operates with FSK (Frequency Shift Keying) modulation technique having two discrete transmission frequencies of 400kHz and 800kHz respectively. The receiver part of the circuit is implemented as an asynchronous FSK demodulator. The maximum data transmission rate obtained with the proposed circuit is around 100kbits/s but this value can be improved by using more rapid circuits and increasing the carrier frequency. By using the robust FSK modulation for sensors signal transmission, the circuit achieves an improved immunity to electrical noises and spurious signals. This is an important advantage because interference problems are very frequently meet in the industrial environments where operates remote data acquisition systems. Another advantage of the proposed circuits is the possibility to multiplex signals from multiple sensors in order to be transmitted on the same physical channel.

Real-time strategy to optimize the operation of fuel cell hybrid power source under variable load cycle

A real-time optimization (RTO) strategy for Fuel Cell Hybrid Power Sources (FCHPS) based on the control of the boost converter is proposed in this study. The reference current for boost controller is generated by the optimization strategy based on the Global Extremum Seeking (GES) scheme. The GES scheme will track the maximum value of the optimization function considered for the FC system. The second input of the boost controller is the FC current. Because the fuel flow rate is controlled by the FC current, the optimization loop is closed via the fuel flow rate. The Load-Following (LF) control is used for the air flow rate to adjust the FC power to variable load demand. The performance of the proposed Boost_GES-RTO strategy is shown in comparison with the sFF-RTO strategy for constant and variable load based on the following performance indicators: the FC net power (PFCnet), the fuel consumption efficiency (Fueleff), the FC system efficiency (ηsys), and Total Fuel consumption (FuelT).

Energy Harvesting from the Photovoltaic Hybrid Power Source Based on Extremum Seeking Control Schemes

The energy harvesting is known as the conversion process of ambient energy into usable electrical energy. The energy of the renewable and green Energy Sources (ES) is free and available without territorial restrictions. In this chapter the possibility to use the Extremum Seeking Control schemes for harvesting the solar energy via a Photovoltaic Hybrid Power Source is presented. The new ESC schemes based on a band-pass filter instead of the series combination of high-pass and low-pass filters are analyzed in order to evaluate their performance. The performance indicators used are the search speed and the tracking accuracy. The simulations performed highlight the advantages of the Extremum Seeking Control schemes based on a band-pass filter in comparison with the classical Extremum Seeking Control schemes. A Maximum Power Point tracking technique based on a modified Extremum Seeking Control slightly improves the energy efficiency of the Photovoltaic Hybrid Power Source. The advanced Extremum Seeking Control scheme reduces the power ripple, so the energy efficiency of the Photovoltaic Hybrid Power Source increases as well. The analysis of the dither persistence in the Extremum Seeking Control loop scheme shows the relations between the search speed and the derivatives of the Photovoltaic power. The ratio of these search speeds is also used as the performance indicator. Finally, the dynamical operation of the Photovoltaic Hybrid Power Source under variable irradiance profile is shown.