An optimized direct control method applied to multilevel inverter for microgrid power quality enhancement

Multifunctional DGs and active power filters have become a mature technology in recent years, so in this paper, an optimized current control method for a multilevel converter is proposed. The control method will overcome harmonic current tracking inefficiency of previous control methods in online harmonic compensation applications in microgrids. This control method is applicable for grid-connected inverter-based multi-functional Distributed Generation (DG) converters. It could also be used in active power filter applications which need high-speed reference tracking ability. Having the advantages of current control methods like hysteresis band control, proportional-integral (PI) and proportional-resonant (PR) control methods, the proposed approach overcomes disadvantages of these methods especially in harmonic reference tracking as it will be discussed in detail. The main advantages of this method are the simplicity of implementation, calculation delay compensation and its fast response to changes. The power electronic circuit, operating principles, two-horizon predicted switching states of multilevel inverter, experimental results and applications of this control method will be discussed in the paper. For studying the feasibility of the control method, an experimental prototype is tested in a microgrid platform

Investigating Impacts of CVR and Demand Response Operations on a Bi-Level Market-Clearing With a Dynamic Nodal Pricing

This paper investigates the impacts of conservation voltage reduction (CVR) on electricity prices, the local market, and technical issues in distribution networks. An increase in electricity demand is one of the key challenges for developing sustainable societies. An increase in electric consumption puts immense pressure on electricity providers, which forces them to apply for load reduction programs during peak-demand time intervals. The CVR is one of the popular methods for load reduction, but how it would impact the pricing process and electricity market at the distribution level needs further investigation. The proposed methodology includes a power tracing and loss allocation-based pricing method. Since the distribution networks are going to be confronted by penetration of distributed energy resources (DER), prosumers, and microgrids, it is important to have a comprehensive methodology. This paper deploys a bi-level optimization algorithm to consider the financial benefits of all participating agents. In addition to CVR, the demand response (DR) programs are considered to shift and curtail flexible loads by the distribution system operator (DSO) and prosumers, respectively. The price sensitivity of prosumers toward change in the network’s voltage for better planning is calculated. The operation costs/profits of DSO/prosumers decrease/increase during CVR and DR programs by 4.63% / 3%, respectively.©2023 Authors. Published by IEEE. This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/fi=vertaisarvioitu|en=peerReviewed

An overview of power quality enhancement techniques applied to distributed generation in electrical distribution networks

It is obvious that power quality is an important characteristic of today's distribution power systems as loads become more sensitive on the other hand nonlinear loads are increasing in the electrical distribution system. Considering the distributed nature of harmonic loads, the need for distributed power quality improvement (PQI) is inevitable. From years ago, researchers have been working on various kinds of filters and devices to enhance the overall power quality of power system, but today the nature of distribution system has been changed and power electronic based DGs play an important role in distribution grids. In this paper, a thorough survey is done on power quality enhancement devices with emphasis on ancillary services of multi-functional DGs. A literature review is also done on microgrids concept, testbeds and related control methods. Although there were some applications of DGs for PQI improvement these applications were not defined multi-functional DGs. Various control methods are studied and categorized regarding different viewpoints in the literature. Finally, a couple of thorough comparisons are done between the available techniques considering the nature, capabilities, advantages and implementation costs

Coupled Inductor Assisted High-Voltage Gain Half-Bridge Z-Source Inverter

A half-bridge-based impedance-source inverter with two T-shaped coupled inductors is proposed in this article. Unlike the conventional half-bridge structure, the proposed topology can generate a zero-voltage level at its output stage. First, the proposed configuration and its modulation method are described, which will analyze the topology's various operational modes. Second, the boost factor is determined, and a way to design the necessary passive devices is found. Third, a power loss breakdown study is investigated in order to devise a solution to improve the efficiency of the proposed structure. Fourth, various comparisons show the benefits and drawbacks of the presented design. These comparisons show that the proposed topology can provide a high boost factor when coupled inductors are used. Furthermore, it has reduced voltage stresses on the components, resulting in a smaller size and lower cost. Finally, the experimental results are obtained by employing a prototype designed by the methodology presented in this article. These results are used as a benchmark to determine whether the proposed topology works well. In addition, the power loss analysis and efficiency comparison are displayed

Trans Z-source-based half-bridge inverter: A method for achieving high voltage gain

This article offers a modified trans Z-source-based half-bridge inverter topology. A suitable pulse width modulation (PWM)-based control method is applied on the proposed inverter. Regarding this control technique, the state of switches in each of the operational states is obtained, and their equivalent control circuits are demonstrated and examined in depth. With the help of the results of these analyses, the boost factor for the proposed structure can be calculated. Additionally, the necessary equations for designing the passive components, as well as the power ratings of the active components, are found. Then, in order to evaluate the advantages and disadvantages of the proposed topology, a comparative study is conducted in several aspects, including the boost factor, the voltage stresses on capacitors, and the voltage stresses on passive devices. This comparison demonstrates that the proposed topology provides a high boost factor while minimizing voltage stresses on the devices, resulting in a smaller volume and size and a lower cost. Once the proposed topology has been thoroughly analyzed, the total power losses and the percentages of power losses consumed by each component device are calculated to obtain efficiency. Finally, an experimental prototype based on the equations for passive and active components is developed. Experiments are used to verify the validity of the proposed topology and the accuracy of the equations. 2022 John Wiley & Sons Ltd.Scopu

Multi-objective model predictive control for microgrid applications

Integration of microgrids may introduce significant power quality challenges to the power distribution networks that may necessitate additional enforcement such as installing new Power Quality Improvement Devices (PQID), which is costly and not always possible option. This paper proposes a control approach that enables the existing power electronics devices within the microgrid to perform multiple functions to address the resultant power quality problems. The proposed method introduces flexibility in harmonic and fundamental power sharing and controlling switching frequency through an improved cost function. Grid connected operation-mode, harmonic compensation capabilities as well as improved dynamic response of controller to fast reference changes have been studied and experimentally verified on a microgrid prototype. Finally, the experimental results of the proposed control method are compared with the results from most recent relevant research activities in the field, evidencing its superiority as compared to the existing control methods presented in the literature

Multi-objective model predictive control for microgrid applications

Integration of microgrids may introduce significant power quality challenges to the power distribution networks that may necessitate additional enforcement such as installing new Power Quality Improvement Devices (PQID), which is costly and not always possible option. This paper proposes a control approach that enables the existing power electronics devices within the microgrid to perform multiple functions to address the resultant power quality problems. The proposed method introduces flexibility in harmonic and fundamental power sharing and controlling switching frequency through an improved cost function. Grid connected operation-mode, harmonic compensation capabilities as well as improved dynamic response of controller to fast reference changes have been studied and experimentally verified on a microgrid prototype. Finally, the experimental results of the proposed control method are compared with the results from most recent relevant research activities in the field, evidencing its superiority as compared to the existing control methods presented in the literature