AC Power Conversion Research Articles

Design and analysis of solitary AC–AC converter using reduced components for efficient power generation system

Considering different applications that require varied power and voltage conversion levels between AC grids and AC loads, AC–AC power conversion between AC grids has become an inevitable technology of energy management systems. An isolated converter for performing AC-to-AC transmission is proposed with minimal components for reduced losses and enhanced system efficiency. Single-phase direct buck-boost AC to AC converter with minimum components constituted with two dual IGBT control units (IGBT 1–IGBT 4), inductor (Lf), and capacitor (Cf) is proposed in this work. The MATLAB/Simulink platform is used to provide in-depth analysis of the circuit and components along with the design guidelines, and simulation outcomes of this proposed model. The voltage gains of G = 2.13, power factor of 0.97, and overall efficiency of 98% are achieved in the proposed system with minimum components of 4 switches, 2 conductors, and 1 capacitor and inductor respectively. The obtained results are compared with existing technology to evaluate the proposed system.

Feasibility Study of Three-Phase Modular Converter for Dual-Purpose Application in DC and AC Microgrids

The modern concept of a universal converter is intended as a power converter suitable for application in both dc or ac grids using the same external connectors. This novel family was recently proposed to allow an easier integration of renewable energy sources and energy storage systems, interfacing with dc/ac grids and/or loads with a minimum redundancy of power switches and passive elements. This kind of solution and applications are expected to be a reality in the nearest decade, as ac and dc low voltage distribution networks will coexist. Nevertheless, the initial solutions proposed as universal converter were focused on ac single-phase power conversion systems. In this sense, this article proposes and describes a new member of the universal converter family suitable for dc to dc and dc to ac power conversion (both in three-phase three-wire and in three-phase four-wire). The proposed power topology is derived as a modular extension from the single buck-boost bidirectional cell. Its main operation modes (buck and boost) are discussed, and a pulse-width-modulation technique is developed to generate the corresponding switching patterns. The proposed solution is successfully validated in open-loop mode both in simulation and experimentally with a laboratory prototype. The measured efficiency of the power converter was above 97% in the dc to ac mode and around 99% in the dc to dc mode.

The revolution of matrix converter: moving towards decarbonization technology

The matrix converter is a power electronic device that can be used to control the flow of electricity in various industrial and commercial applications. In recent years, the matrix converter has become increasingly popular as a means of decarbonizing energy production. One of the primary benefits of the matrix converter is its ability to efficiently convert AC power to DC power, and vice versa. This is critical in renewable energy systems that rely on DC power, such as solar panels and wind turbines. Therefore, this paper presents the revolution of the matrix converter, which focuses on the single-phase topology, and its applications, especially for renewable energy and battery storage. The operations of a matrix converter to convert DC power from solar panels and wind turbine sources to AC power suitable for use on the power grid are presented as well as the appropriate switching algorithms. To achieve this, the SPMC can be designed to handle multiple input voltages and frequencies and to generate multiple output voltages and frequencies. This can be done by using a combination of modulation techniques, such as carrier based PWM, along with appropriate switching patterns. Therefore, a multi-input multi-output converter (MIMO) using matrix converter is a power electronics converter that can handle multiple inputs and multiple outputs voltages and frequencies using only one circuit topology. Thus, the topology can offer several advantages over traditional power converters such as reduced size and cost, high efficiency, improved power quality and flexibility. This is crucial for a decarbonized energy system because it makes renewable energy sources more effective. Its ability to efficiently convert power, regulate power flows, and operate reliably makes it an important tool in the transition to a decarbonized energy system.

Low threshold DC–AC power converter with optimized standby power consumption

The quest for universal energy access continues to be a major concern globally. Renewable energy technologies such as solar PV are viable options to meet this energy poverty with DC–AC power converters playing a major role in solar PV systems. Current designs of these converters suffer from high standby energy consumption and high input threshold voltage. This paper presents the design and implementation of a single-phase DC–AC power converter with low threshold input voltage and optimized standby power consumption. A multivibrator, pulse width modulation signal generator, MOSFETs, and a multiple secondary winding center tap transformer were used in the system design. The results show an optimized power converter having a low input threshold voltage of 10.5V and power consumption of 9.49W.

Simulation and optimization of rectenna systems

In this paper, we present an entirely simulation-based method to predict the performance of a complete rectenna system that includes all its components: the receiving antenna, the matching circuits between the antenna and the rectification circuit, and the load circuit. Whereas previous efforts to predict the performance of a rectenna system subdivided the system into the antenna part (radiation to AC power conversion) and the circuit part (AC power to DC power conversion), and made assumptions about the performance of the non-linear part of the rectenna based on a specified power level and frequency, in this method, the radiation part of the system is incorporated into the simulation by using Thevenin theorem. The method proposed in this work enables the rectenna designer to predict the performance of the complete rectenna system, at the design stage, for variation in the incident field’s power density, angle of incidence, and operating frequency. Such performance prediction was not available before. Furthermore, the proposed method enables the rectenna designers to optimize the entire system over a portion of or the entire range of the operating frequency. Experimental results are provided to demonstrate the accuracy of the method.

Vibration Analysis of an On-Board Charger Assembly for Electrical Mobility

This article deals with the vibration analysis of an On-Board Charger assembly to check the strength of its components with respect to vibrational load. On-Board Charger (OBC) is a system which is built for electrical vehicles to charge high-voltage battery packs by converting AC power from an external charging source into a DC voltage. The primary role of an onboard charger is to manage the flow of electricity from the grid to the battery. This means that the OBC should fit the necessities of the grid in locations wherever it will be used. Onboard chargers enable plug-in hybrid and battery electric vehicles (BEV) to charge anywhere, not just at designated charging locations, wherever there is AC power. The OBC which is studied in this article is used in three-wheeler vehicles and the weight of this assembly is quite more because of the heat sink and other electronic components; so it is important to check its strength through a vibrational point of view, as induced vibrational load in the vehicle is more while driving the vehicle. Here, the focus will be on all housing and its internal components such as PCB (Printed Circuit Board) and its electrical components. Electrical components connect with PCB with solder joints which provide mechanical and electrical connections between components and PCB. Simulation of an OBC assembly is done by using the ANSYS tool in which modal and harmonic analysis is carried out to check assembly’s strength. The main focus will be on the natural frequencies of the assembly; the aim is to increase the natural frequencies of the assembly above 150 Hz to avoid the resonating condition. The frequency response analysis was done for the range of 50-150 Hz for the acceleration of 15g and stresses and deformation of OBC assembly components are observed after frequency response analysis.
 Keywords: On-Board Charger; Solder joint; Frequency; Vibration, Harmonic analysis, Electrical Mobility, Materials, NVH, Simulation

A New Flying Capacitor-Based Buck–Boost Converter for Dual-Purpose Applications

A novel dual-purpose common ground dc–dc/dc–ac power converter is proposed in this article. It is based on the flying capacitor circuit along with a boost circuit, which in turn provides a wide range of input voltage regulation with the capability of stepping up or down the output voltage. The same components are used under both dc–dc and dc–ac modes, which reduces the redundancy of the used devices. Particular attention is dedicated to the working modes of the proposed solution. The special control system is implemented to provide acceptable current and voltage quality in off-grid and grid-connected modes. To underline the pros and cons of the proposed solution, a comprehensive comparison is performed. Finally, the performance of the proposed dual-purpose power converter is investigated through an experimental 3.5-kW/5-kW setup, for dc–ac and dc–dc operating modes, respectively. Main oscillograms along with efficiency analysis are presented and discussed in conclusions.

Matrix Converter Based on Trapezoidal Current Injection

The matrix converter (MC) is a direct ac–ac power converter featuring high power density and high efficiency. However, the conventional MC (CMC) topologies require high control complexity and high transistor capacity, hindering the wide applications. An emerging MC topology (3CI-MC) based on the third-harmonic current injection (3CI) reduces the control complexity, but requires more transistors and a complex clamping circuit. This article proposes the trapezoidal current injection (TCI) technique to form a novel MC topology (TCI-MC), which consists of a line-commutated converter (LCC), a TCI circuit, and a voltage source converter (VSC). Compared with the 3CI-MC, the proposed TCI-MC not only maintains the advantages of simple modulation and independent voltage control but also achieves lower current stress on the LCC part of the circuit. The total transistor capacity (TTC) of the proposed TCI-MC is the lowest among all the considered MC topologies. The clamping circuit is also simplified and the bidirectional switches are eliminated, reducing the implementation cost. Simulation and experimental results have verified the validity of the proposed topology.

An Examination of Power Converter Architectures for Utility-Scale Hybrid Solar Photovoltaic and Battery Energy Storage Systems: The Features of Several Power Conversion Architectures

Recently, the falling costs of photovoltaic (PV) and battery storage (BS) technologies have raised interest in the creation of hybrid PV+BS power plants. Together with increasing energy storage capacity by storing clipped energy, hybrid plants broaden a power plant’s grid services by featuring fast dispatch flexibility and voltage-ampere reactive support. Although many proposed PV plants are being developed with colocated batteries, the dominant architecture of ­utility-scale PV+BS power plants is uncertain. Moreover, power architectures are expected to evolve over time based on future trends. The primary goal of this article is to critically examine and compare several dc–dc and dc–ac power converter architectures that are suitable candidates for hybrid PV+BS power plants. In particular, the article presents characteristics of several power conversion architectures from the point of view of power semiconductor requirements, efficiency, reactive component requirements, modularity, control complexity, and so forth. Detailed analytical models are utilized, along with a benchmark design example to present a comparative evaluation of the alternatives for performing engineering tradeoff studies.

Cascaded AC-DC Power Conversion Interface for Charging Battery

This paper develops a cascaded AC-DC power conversion interface (CADPCI) to convert AC power to charge the battery set. The proposed CADPCI is composed of a cascaded converter (CC) and a dual-input buck converter (DIBC). The CC is formed by connecting a full-bridge converter (FBC) and a bridgeless rectifier (BLR) in series. The CADPCI generates an 11-level input voltage and performs unity power factor correction. The switching loss is reduced because only the FBC with a lower DC port voltage is switched at a high frequency. The DIBC uses a buck converter and a selection switch set to generate a two-level DC voltage on the DC port of the BLR. By controlling the DC input voltage of the buck converter, the injected power of the BLR can match the input power of the utility. Therefore, the FBC does not require to handle the real power, saving an isolated converter for regulating the DC port voltage of the FBC, thus simplifying the power circuit of the CC. The buck converter also acts as a DC active filter to filter out low-frequency ripples of the charging current. A prototype is constructed to verify the performance of the proposed CADPCI.

Saturating PI Control of Stable Nonlinear Systems Using Singular Perturbations

This article presents an antiwindup propor- tional-integral (PI) controller, using a saturating integrator, for a single-input and single-output (SISO) stable nonlinear plant, whose steady-state input–output map is increasing. We prove that, under reasonable assumptions, there exists an upper bound on the controller gain such that for any constant reference input, the corresponding equilibrium point of the closed-loop system is exponentially stable, with a “large” region of attraction. When the state of the closed-loop system converges to this equilibrium point, then the tracking error tends to zero. The closed-loop stability analysis employs Lyapunov methods in the framework of the singular perturbations theory. Finally, we show that if the plant satisfies the asymptotic gain property, then the closed-loop system is globally asymptotically stable for any sufficiently small controller gain. The effectiveness of the proposed PI controller is proved by showing how it performs as part of the control algorithm of a synchronverter (a special type of dc to ac power converter).

THD Minimization and Reliability Analysis of Cascaded Multilevel Inverter

Inverters are DC to AC power converters that are widely used in AC motor drives and distributed energy generation systems. Multi-Level Inverters (MLIs) have emerged as the preferred inverter technology because of their advantages of reduced switching losses and better harmonic profile. This paper deals with the Minimization of Total Harmonic Distortion (MTHD) of Symmetric Cascaded H-bridge Multi-Level Inverter (SCMLI) and Asymmetric Cascaded H-bridge Multi-Level Inverter (ACMLI). A hybrid memetic algorithm composed of heuristic PSO (Particle Swarm Optimization) algorithm and traditional MAS (Mesh Adaptive direct Search) is proposed to optimize the switching angles. In Photo Voltaic (PV) system, the input DC voltage generally varies from its nominal value due to the change in temperature and irradiance. Thus, the sensitivity analysis of THD and harmonics is also carried out considering the variations with non-integer magnitudes of input DC sources. The experimental prototype of SCMLI and ACMLI topology is developed and validated with simulation results. The reliability and Mean Time to Failure (MTTF) of SCMLI and ACMLI are investigated based on power losses of the MOSFET and thermal parameters.

Control Methodologies to Mitigate and Regulate Second-Order Ripples in DC–AC Conversions and Microgrids: A Brief Review

Second-order ripples occur in the voltage and current during any DC–AC power conversion. These conversions occur in the voltage source inverters (VSIs), current source inverters (CSIs), and various single-stage inverters (SSIs) topologies. The second-order ripples lead to oscillating source node currents and DC bus voltages when there is an interconnection between the AC and DC microgrids or when an AC load is connected to the DC bus of the microgrid. Second-order ripples have various detrimental effects on the sources and the battery storage. In the storage battery, they lead to the depletion of electrodes. They also lead to stress in the converter or inverter components. This may lead to the failure of a component and hence affect the reliability of the system. Furthermore, the second-order ripple currents (SRCs) lead to ripple torque in wind turbines and lead to mechanical stress. SRCs cause a rise in the temperature of photovoltaic panels. An increase in the temperature of PV panels leads to a reduction in the power generated. Furthermore, the second-order voltage and current oscillations lead to a varying maximum power point in PV panels. Hence, the maximum power may not be extracted from it. To mitigate SRCs, oversizing of the components is needed. To improve the lifespan of the sources, storage, and converter components, the SRCs must be mitigated or kept within the desired limits. In the literature, different methodologies have been proposed to mitigate and regulate these second-order ripple components. This manuscript presents a comprehensive review of different effects of second-order ripples on different sources and the methodologies adopted to mitigate the ripples. Different active power decoupling methodologies, virtual impedance-based methodologies, pulse width modulation-based signal injection methodologies, and control methods adopted in distributed power generation methods for DC microgrids have been presented. The application of ripple control methods spans from single converters such as SSIs and VSIs to a network of interconnected converters. Furthermore, different challenges in the field of virtual impedance control and ripple mitigation in distributed power generation environments are discussed. This paper brings a review regarding control methodologies to mitigate and regulate second-order ripples in DC–AC conversions and microgrids.

Design & Development Of a Dc Charging Unit For Various Engineering Applications

In this paper, the design & development of a DC charging unit for various engineering applications is presented. The DC Charger project is the creation of a charging system that converts AC power from the mains into a steady DC output for charging batteries and devices. The process involves using a transformer to step down the mains voltage, followed by a bridge rectifier that converts AC to pulsating DC. Smoothing capacitors then refine the DC waveform, which is further stabilized by voltage regulators to provide a consistent 12V output. A relay that manages the charging process. When the battery is fully charged, the relay disconnects the charging current. LED indicators provide visual cues for charging status. Protection mechanisms prevent issues such as overcurrent and overvoltage, ensuring safety. The project teaches about the basics of DC power electronics and how to design, build, components, and test a DC charger. It will also give you the opportunity to apply your skills in electronics and problem-solving. The work carried out is the second semester mini-project by the students of Electronics & Communication Engineering under the guidance of the faculties.

A Common-Ground-Type Five-Level Inverter with Dynamic Voltage Boost

Today, transformerless inverters (TIs) are widely applicable in different solar photovoltaic (PV) grid-connected applications owing to their promising features, such as higher efficiency and power density. However, high-frequency common-mode voltage (CMV) in these topologies can result in high leakage current, electromagnetic interference, and lack of safety, reducing the whole system’s reliability. To resolve the problems associated with TIs, this paper proposes a novel hybrid switched capacitor (SC)-based common-ground (CG) transformerless inverter (TI) topology, which can be applied in grid-connected photovoltaic (PV) applications. The boost inductor is integrated to achieve continuous input current and dynamic voltage gain. In addition, the proposed circuit comprises nine switches and two SCs with a single input DC source. It can generate five-level AC voltage with voltage boosting within a single-stage DC–AC power conversion. The working principles of the proposed topology, circuit description, and control technique are presented. Furthermore, the proposed inverter is comprehensively compared with other five-level TIs to show its superiority. Finally, a laboratory prototype is developed and tested to validate the practical viability of the proposed configuration.

Optimal Dynamic and Steady-State Performance of PV-Interfaced Converters Using Adaptive Observers

The voltage regulation of a grid-tied PV system is constantly perturbed for the maximum power point tracking (MPPT), the transients of which determine the dynamic MPPT efficiency. Meanwhile, the PV-link voltage ripple coupled from the DC to single-phase AC power conversion adversely affects the static MPPT efficiency. Thus, optimal dynamic and steady-state performance is necessary to maximize the solar energy harvest. This brief proposes a novel adaptive mechanism preserving the advantages of two observers: the classical extended state observer and reduced-order generalized proportional integral observer. Simulation and experimental results prove the enhanced performance regarding the overshoot-free fast transient response and steady state against disturbances, even with small input capacitance. Meanwhile, the observer switching happens seamlessly through the proposed mechanism, which is confirmed analytically and experimentally.

Three-Level T-Type qZ Source Inverter as Grid-Following Unit for Distributed Energy Resources

Distributed energy resources (DERs), such as solar photovoltaics (PVs), are required to achieve a high performance and an efficient use of generated renewable power in grid-integrated applications, both in normal and fault operating conditions. In this article, a grid-following (GFL) multifunctional control strategy for a three-phase three-level T-type quasi-impedance source inverter (3L-T-type qZSI) is studied through simulation and experimental tests. The GFL functionality is achieved by a proportional–integral (PI)-based dq current controller for the active and the reactive power tracking. A PI-based dc controller is used for the dc-link voltage control by taking advantage of the quasi-impedance source (qZS) network ability for input voltage boosting. The dc–ac power conversion is accomplished through a space vector pulsewidth modulation (SVPWM) with inner capacitors voltages balancing capability and minimum common-mode voltage (CMV) generation. Besides, a low-voltage ride-through (LVRT) strategy was implemented to fulfill the fault requirements imposed by the Spanish standard. The simulation and experimental results demonstrate the abovementioned functionalities and validate the stability and good dynamic response of the grid-connected 3L-T-type qZSI. Thus, this work supposes a novel contribution due to the few works previously reported in the literature concerning the performance of this relatively recent inverter topology in grid-tied applications.

A generalized switched‐capacitor‐based modular T‐type inverter topology with reduced switch count

SummarySwitched‐capacitor (SC)‐based multilevel inverters (MLIs) have gained great attention in renewable energy applications owing to their self‐balancing of capacitor voltage and ac voltage boosting. Using SCMLI, single‐stage dc–ac power conversion is made possible without needing a front‐end dc–dc boost converter that improves overall system efficiency, reliability, and power density. However, in most existing SCMLIs, the discharging duration of the rear‐end SCs is much longer than its charging duration, especially when a high number of SC units are adopted. While a high number of level generation is expected to produce a better resolution ac voltage, a significant increase in capacitor's voltage ripple, in contrast, distorts the ac voltage despite using large capacitors. Recently, the switched‐capacitor modular t‐type inverter (SC‐MTI) topology resolved the problem by extending the charging period of all SCs to at least half of the fundamental switching period. However, the high switch count of SC‐MTI introduces a trade‐off in terms of efficiency and cost. In this paper, a new SCMLI topology that retains the good traits of SC‐MTI with switch count reduction is proposed. The merits and feasibility of the proposed SCMLI are verified through simulation and further validated through experimental results for seven‐level considering various operating conditions.

Performance Investigations of Novel PWM Control Strategies for Fundamental Fortification in Single-Phase Matrix Converter for Cyclo-Conversion Operation and FPGA Implementations

Matrix converter is a class of AC–AC power converters, which facilitates variable voltage and frequency control without intermediate conversion like pulse width modulated [PWM] inverters. Traditional control strategies for variable frequency control for AC–AC conversion can be extended for matrix converters. This research work proposes two PWM strategies with an objective of enhanced fundamental voltage and reduced THD for low-frequency operation. The concept behind the approach is concatenating both fundamental switching and PWM pulses. The fundamental switching reduces switching losses and enhances fundamental output voltage which is equal to the instantaneous values of fundamental component in that particular segment. On the other hand, the variation of pulse width using PWM has a control in the harmonic content which reduces THD. The simulation and experimental results prove the competencies of the proposed strategies in real-time application.

AC Voltage Synthesis Using Arbitrary Two-Phase Voltages: Frequency, Phase, and Amplitude Modulation for Direct AC–AC Power Conversion

AC Voltage Synthesis Using Arbitrary Two-Phase Voltages: Frequency, Phase, and Amplitude Modulation for Direct AC–AC Power Conversion