Indirect Matrix Converter-Based Grid-Tied Photovoltaics System for Smart Grids

This paper proposes an Indirect Matrix Converter (IMC)-based grid-tied Photovoltaic (PV) system for Smart Grids (SGs). The PV array injects current in the ‘dc link’ of the IMC through an inductive link, and is connected to the SG with shunt and series connections, allowing for the compensation of current- and voltage-related Power Quality (PQ) issues, respectively, for the sensitive loads and the SG connection. A direct sliding mode-based controller is proposed to guarantee nearly sinusoidal currents in the connection to the SG, and sinusoidal voltages guaranteeing compliance with international standards, when supplying the sensitive loads. Additionally, a novel control approach for the ‘dc link’ voltage is synthesised to allow for the control of both the PV array current and the power flow to the SG. To guarantee the semiconductors safe commutation an asynchronous commutation strategy is derived. Simulation and experimental results show that the proposed system significantly improves PQ in the SG, minimizing the total harmonic distortion of the currents injected in the SG, and guaranteeing the quality of the voltage supplied to the sensitive loads, even in the occurrence of voltage sags or overvoltages

Application of Ant Colony Optimization for Co-Design of Hybrid Electric Vehicles

One key subject matter for effective use of Hybrid Electric Vehicles (HEVs) is searching for drivetrains which their component dimensions and control parameters are co-optimally designed for a desired performance. This makes the design challenge as a problem, which needs to be addressed in a holistic way meeting various constraints. Along this line, the strong coupling between components sizes of a drivetrain and parameters of its controllers turns the optimal sizing and control design of HEVs into a Bi-level optimization problem. In this chapter, an important application of continuous Ant Colony Optimization (ACOR) for integrated sizing and control design of HEVs is thoroughly discussed for minimizing the drivetrain cost, minimizing the fuel consumption and addressing the control objectives at the meantime. The outcome of this chapter provides useful information related to incorporation of soft-computing, modeling and simulation concepts into optimization-based design of HEVs from all respects for designers and automotive engineers. It brings opportunities to the readers for understanding the criteria, constraints, and objective functions required for the optimal design of HEVs. Via introducing a two-folded iterative framework, fuel consumption and component sizing minimizations are of the main goals to be simultaneously addressed in this chapter using ACOR

Smart matrix converter-based grid-connected photovoltaic system for mitigating current and voltage-related power quality issues on the low-voltage grid

The increasing penetration of distributed energy resources, in particular Photovoltaic (PV) production units, and the ever-growing use of power electronics-based equipment has led to specific concern about Power Quality (PQ) in the Low-Voltage (LV) grid. These include high- and low-order current harmonics as well as voltage distortion at the point of common coupling. Solutions to overcome these issues, meeting international grid codes, are being proposed in the context of smart energy management schemes.This work proposes a novel three-phase topology for a PV system with enhanced PQ mitigation functionality, tackling the corresponding control challenges.First, a single-stage current-source inverter PV system with active filtering capability is preferred to the more common two-stage voltage-source inverter topology with additional voltage-step-up converter. The system also guarantees a nearly unitary displacement power factor in the connection to the grid and allows for Maximum Power Point Tracking (MPPT) with direct control of the PV array power. The grid-synchronised dq-axis grid current references are generated for the mitigation of nonlinear load low-order current harmonics, without the need for additional measurements. Active damping is used to minimise grid-side filter losses and reduce high-order harmonics resulting from the converter switching.Results on a 500W laboratory prototype confirm that active damping reduces the switching harmonics in the grid currents and active filtering properly mitigates the low-order current harmonics. The MPPT algorithm works effectively for various irradiance variations. Second, a PV system with a novel Indirect Matrix Converter (IMC)-based unified power quality conditioner topology is developed for enhanced current and voltage compensation capability, with compactness and reliability advantages. PQ issues such as current harmonics, and voltage sags, swells, undervoltage and overvoltage are mitigated by the shunt and series converters, respectively.The more common Space Vector Modulation (SVM) method used in IMCs is developed for this specific topology. In particular, a new shunt converter modulation method is proposed to additionally control the PV array current with zero switching vectors, resulting in a specific switching sequence.A direct sliding mode control method is also studied separately for the shunt and series converters, so that the zero-vector modulation method of the shunt converter can be used, with no sensitive synchronisation of the switching signals; this contrasts with the SVM method. A new dc link voltage modulation method with 12 voltage zones, instead of 6, is proposed to help overcome the limitation in the choice of shunt converter switching vectors due to the positive dc link voltage constraint.Results are obtained for the direct method on a 1 kW laboratory prototype with optimised IMC dc link connection and alternative shunt converter switching transitions to guarantee a positive dc link voltage. Current and voltage compensation capabilities are confirmed by tests in various operating conditions.Doctorat en Sciences de l'ingénieur et technologieinfo:eu-repo/semantics/nonPublishe

Medaon: Magazin für Jüdisches Leben in Forschung und Bildung

This paper deals with the development of a Photovoltaics (PV) emulator for testing grid-connected in-verters, taking the shading effect on the panels into account. The Single Exponential Model (SEM) of a PV array is used with appropriate approximations. The shading effect is modeled for a configuration of series connected panels, with bypass diodes, and two irradiance levels. This PV modeling is used in a retroactive loop in order to output a voltage reference corresponding to the current measured at the output of the emulator. After being regulated by a Proportional-Integral (PI) controller, this reference produces the duty cycle for the Pulse Width Modulation (PWM) of the DC/DC converter, whose objective is to reproduce this voltage. The emulation is tested first with a resistive load, where it is observed that the characteristic curves of the panels are accurately reproduced, and then on a commercial grid-connected inverter. A Graphical User Interface (GUI) is developed to allow modifying online the test parameters and observe the results in a convenient way so as to properly assess the response of the inverter and its Maximum Power Point Tracking (MPPT) capability. In particular, several tests validate the operation of the emulator, in a reference situation, at the start-up of the inverter and for changing atmospheric conditions.info:eu-repo/semantics/publishe

Current Source Inverter-Based PV System with Enhanced Active Filtering Functionalities

This study proposes a three-phase photovoltaic (PV) inverter, with active power filtering capability that allows for maximum power point tracking (MPPT) and a nearly unitary power factor (PF) in the connection to the low voltage grid. A single-stage current source inverter, with an inductive DC link, connects the PV array to the three-phase grid for reduced cost and improved performances, and the MPPT algorithm controls directly the power of the PV array. On the basis of the power balance of the whole system, the grid current references are generated in a grid-synchronised dq frame allowing for the mitigation of low-frequency current harmonics introduced by a non-linear load connected at the point of common coupling, without the need for additional measurements. Active damping is used to minimise filter losses and reduce the high-frequency harmonics that result from the semiconductors switching. Simulation and experimental results are presented in unloaded and loaded situations, and with varying irradiance, to confirm the active filtering, PF regulation and MPPT operate correctly.info:eu-repo/semantics/publishe

Direct control method for a PV system integrated in an Indirect Matrix Converter-based UPQC

This paper proposes a direct control method for a three-phase Photovoltaic (PV) system integrated on the Low-Voltage grid, using an Indirect Matrix Converter (IMC)-based Unified Power Quality Conditioner topology. This topology adds enhanced Power Quality functionality to the PV inverter when connected to a sensitive non-linear load, such as load current harmonics mitigation and voltage sags, swells and harmonics compensation. The PV array is inserted in the DC link of the IMC, which is controlled with a direct sliding mode control method. This direct control allows using a specific modulation method for the shunt converter that guarantees the DC link voltage is adequate for the operation of the IMC. Simulation results are presented to confirm the proper operation of the system under a variety of operating conditions.info:eu-repo/semantics/publishe

Assessment of grid-side filters for three-phase Current-Source Inverter PV systems

In this paper, three grid-side filter topologies for grid-connected three-phase Photovoltaic Current-Source Inverters are sized and assessed based on the Total Harmonic Distortion of the grid currents, on the power factor in the connection to the grid, and on the filter losses. A second-order LC filter with passive damping resistors in parallel with the filter inductors is first sized and evaluated. It is then improved by removing the resistors and using active damping, with the virtual resistor method and feedback of the inductor voltages requiring no additional measurements. The analysis is conducted taking into account the delays introduced in the control circuit and the relation between the synchronously rotating d and q components of the grid currents. A fourth-order LCLC filter is also sized and considered as an alternative grid-side filter topology to reduce the switching harmonics. Simulation and experimental results obtained with a direct control approach confirm the proper sizing and operation of the filters. Based on the Total Harmonic Distortion (THD) of the grid currents and filter losses, the second-order filter with active damping presents the best results with a THD lower than 5 % and nearly negligible losses.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Unified Power Quality Conditioner: The Indirect Matrix Converter Solution

Power Quality (PQ) parameters such as voltage RMS value, Total Harmonic Distortion (THD), and Power Factor (PF) are main topics to be considered in the connection of sensitive loads to the grid. In this paper, a Unified Power Quality Conditioner (UPQC) based on an Indirect Matrix Converter (IMC) is proposed to address some PQ issues as mitigation of voltage harmonics and compensation of sags and swells when supplying a sensitive load. Also, it allows the mitigation of grid current harmonics in the Point of Common Coupling (PCC). The control of the converter is performed using the sliding mode control method, associated to the state-space vector representation, allowing fast response times to disturbances in the grid. The whole system is tested in MATLAB Simulink software, and the obtained results show that it guarantees PQ improvement in the PCC.Key-Words:info:eu-repo/semantics/publishe

An Indirect Matrix Converter-based Unified Power Quality Conditioner for a PV inverter with enhanced Power Quality functionality

This paper introduces an Indirect Matrix Converter (IMC)-based Unified Power Quality Conditioner topology for a Photovoltaic (PV) system and sensitive load, with enhanced Power Quality functionalities. In particular, the proposed system is able to compensate grid voltage sags, swells and harmonics in the sensitive load, and non-linear load current harmonics in the Low-Voltage (LV) grid, in addition to the common PV inverter functionalities. The modulation of the shunt converter is developed specifically to control the PV array current and the grid currents amplitude, as opposed to the common IMC modulation methods. The IMC modulation is synchronized with the series inverter modulation in order for the system to operate as a whole. Simulation results are presented to confirm the proper operation of the system under a variety of operating conditions.info:eu-repo/semantics/publishe