Three-phase Converter Research Articles

Experimental validation of A robust integral terminal sliding mode control for three-phase voltage source converter in standalone microgrid

Experimental validation of A robust integral terminal sliding mode control for three-phase voltage source converter in standalone microgrid

Fuzzy Logic Controller Design for Circulating Current Control in Three-Phase Modular Multilevel Converter Fed by Fuel Cell

The Modular-Multilevel Converter (M-MC) has substantially contributed to the integration of non-conventional energy sources into grid systems, particularly Proton Exchange Membrane Fuel Cells (PEMFC). This paper proposes an M-MC system to interface PEMFC with the grid, focusing on controlling circulating currents and ensuring stability. A Fuzzy Logic is employed to mitigate circulating current (CC) harmonics. Phase-Shifted Carrier (PSC) modulation is used to improve capacitor voltage balancing, thus maintaining a constant input voltage. The boost converter enhances the input voltage to a higher level, which is essential for maintaining the necessary voltage margin in MMC. The main contribution of this paper is (I)The PSC-PWM was implemented for MMC to maintain a quality +y of output voltage by the control of capacitor voltages.(II)The proposed fuzzy logic controlled circulating current must be achieved in order to regulate the dc ripple component, arm current, and circulating current of MMC.(III)It is essential to regulate the SM capacitor voltages in order to provide a balanced and equal output while maintaining the ratings and limits of the SMs, and this will be accomplished.

Comparison of different control methods used in multi-frequency grid-forming converters

Abstract This article investigates and compares various control methods for a three-phase multi-frequency grid-forming converter tasked with producing a multi-frequency voltage profile comprising 50 Hz positive sequence and 150 Hz zero sequence signals. Different control strategies including proportional-integral (PI), proportional-resonant (PR), repetitive (RC) and state-feedback (SF) controllers are investigated to assess their efficacy in generating and regulating the desired multi-frequency voltage output. This study suggests that the PR-based control system exhibits notable potential due to its inherent frequency filtering capabilities and simplicity of the tuning and implementation, making it well-suited for multi-frequency applications. This approach effectively amplifies desired frequencies while suppressing others, showcasing superior multi-frequency performance compared to other mentioned methods. This ability of the PR controllers aligns well with the specific demands of the multi-frequency application. This contention is validated by simulating the multi-frequency grid-forming converter using the four mentioned control methods. Therefore, this paper provides crucial insights into control strategies for multi-frequency grid-forming converters, emphasizing the importance of control method selection based on application needs and performance metrics. Ultimately, these findings contribute significantly to advancing the development and refinement of multi-frequency grid-forming converters for microgrid and islanded mode scenarios.

A Low Harmonic Control Method of Bi-Directional Three- Phase Z- Sources

Three-phase Z-source inverters offer a voltage boosting solution of single-stage topology. They can also operate bidirectionally as rectifiers, hence have excellent potential for applications in the area of transportation electrification like Vehicle-to-Grid (V2G) chargers. In this paper, three new modulation schemes for three-phase Z-source converters are presented and analyzed. The best performed one is further extended to a closed-loop PI control technique. Although the voltage conversion ratio is adjustable, the output voltage. Total Harmonics Distortion (THD) is less than 3% between the voltage ratio range of 0.5 to 2.5. The effectiveness of the developed method has been completely verified in MATLAB/Simulink simulations and RT- LAB Hardware-In-Loop (HIL) experiments according to the real-time simulator OPAL-RT OP4510. The proposed one is compared with conventional control techniques operates better with lower harmonics, adjustable voltage gains, and less complex control algorithm. Index Terms—Z-source converter, Bi-directional converter, shoot-through states, voltage harmonics, closed-loop control. Key Words: Z-source inverter, power electronics, vehicle-to-grid (V2G), renewable energy, three-phase inverter, low harmonic control, power conversion efficiency, bidirectional operation.

Parallel operation of common PLL-based synchronverters under transient conditions

Generally, a parallel connection of generators is required to meet the power need to supply the load demand. As a preferable replacement for typical generation units, a topology based on three-phase voltage source converters has been proposed. This paper proposes an approach based on virtual synchronous generator-based synchronverters for parallel operation of alternators. This approach automatically exchanges active and reactive power between parallel operated inverters of the same kind. Furthermore, to serve the purpose of synchronization, a Phase Locked Loop (PLL) is used. To avoid the tuning complexities and stability margin issue, a common PLL is used for both the converters. The PLL detects the grid voltage angle and helps with initial synchronization of the synchronverter in an easier way. The simulation studies are carried out to validate the performance and control of the proposed system. In addition, stability analysis has been performed using a state space approach to prove the efficacy of the system.

Novel Discrete-time Frequency-locked Loop for Three-phase Grid-connected Power Converters*

Novel Discrete-time Frequency-locked Loop for Three-phase Grid-connected Power Converters*

Enhanced Control Strategy for Three-Level T-Type Converters in Hybrid Power-to-X Systems

This paper presents a dual-loop control system designed for three-level three-phase T-type converters, optimizing their performance in the hybrid operation of Power-to-X systems. Due to the increasing of distributed power generation based on renewable energy sources, Power-to-X systems convert surplus renewable energy into other forms of energy, such as hydrogen, synthetic fuels, or chemical storage, which can be stored and later converted back to electricity or used in other applications. Bidirectional converters play a crucial role in hybrid system operation, which requires an efficient and reliable power conversion to maintain stability and performance. The proposed dual-loop control system includes an inner current loop for fast current regulation and an outer voltage loop to maintain stable voltage levels, ensuring precise control of the output of the converter and enhancing its response to dynamic changes in load and generation. Additionally, the control system incorporates a technique to balance the split DC-link capacitors voltages, a major challenge in three-level converters. Comprehensive simulation and experimental results demonstrate the efficacy of the proposed control system in maintaining high power quality and supporting the hybrid operation of Power-to-X systems.

Stationary-frame power regulation for controlling grid-connected three-phase modular multilevel converter with low harmonic under unbalanced voltage

Electronic power converters play an essential role in power grids, aiming to improve the electrical energy quality and also enabling bidirectional energy transfer between DC lines and circuits. They facilitate the achievement of a sinusoidal current waveform and effective power transfer control with a high power factor. This paper introduces a stationary reference frame based control strategy for grid-connected three phase modular multilevel converters (MMC). This strategy employs conventional PI controllers to track the instantaneous power components that include intentional oscillations at double grid frequency. By employing this method, the MMC converter can maintain an output sinusoidal waveform even under unbalanced grid voltage conditions. Also, there is no need for a transformation from a stationary frame to a synchronous frame, eliminating the requirement for a PLL to estimate the grid voltage phase angle. Furthermore, the use of MMC converter over common two-level and three-level VSC converters is proposed since MMC converters offer merits such as low harmonic components, no need for filters at the DC terminals, no need for filters at the AC side, and low losses, despite some drawbacks such as a large number of IGBT switches or a higher amount of stored energy in the sub-module capacitors. Therefore, the voltage THD and consequently active and reactive powers of the converter have been impressively mitigated by using MMC. To confirm the capability and effectiveness of the proposed method, various simulations are performed in MATLAB/Simulink software. Finally, the results are compared with common methods.

Control strategy for three-phase converters under unbalanced grid conditions with closed-loop compensation

Control strategy for three-phase converters under unbalanced grid conditions with closed-loop compensation

Advanced thyristor-based cycloconverter for efficient three-phase conversion with low THD

Advanced thyristor-based cycloconverter for efficient three-phase conversion with low THD

Effects of Modulator-Injected Zero-Sequence Signals on System Stability in Three-Phase Voltage Source Converters

Effects of Modulator-Injected Zero-Sequence Signals on System Stability in Three-Phase Voltage Source Converters

Consolidated Carrier-Based Discontinuous PWM Strategies for DC-Link Capacitance Reduction in Three-Phase Three-Level Converters

Consolidated Carrier-Based Discontinuous PWM Strategies for DC-Link Capacitance Reduction in Three-Phase Three-Level Converters

Self-Measurement of Three-Phase Converter Impedance with Virtual Excitation Source

Self-Measurement of Three-Phase Converter Impedance with Virtual Excitation Source

Grid-Forming Fuel Cell System for an Islanded AC Grid

This paper proposes a two-stage converter that can black start an isolated AC Microgrid with a Fuel Cell (FC) as the primary energy source. The first stage is connected to the FC and employs a Three-Leg Interleaved Boost DC/DC Converter (IBC), while the second is a Three-Phase Voltage Source Converter (VSC). The DC/DC stage utilizes a Cascade Voltage Control (CVC) to mitigate voltage fluctuations in the DC-link caused by the variability of the FC voltage. For the DC/AC stage, three distinct grid-forming (GFM) strategies are implemented with two of them with multi-loop cascaded structure and one with a single-loop structure. The power circuit of the system is simulated using the Real-Time Simulator (RTS) HIL 602+ from Typhoon-HIL, with the control strategies embedded on the Digital Signal Processor (DSP) TMS320F28379D - F28379D LaunchPad from Texas Instruments (TI). The performance of the cases are verified through CHIL simulations for a balanced and unbalanced inductive load steps. The results demonstrate that for both tests the GFM single loop structure presents smoother transients and shorter recovery times. Additionally, for the unbalanced loads, all the cases present similar results for the DC variables with more pronounced differences at the AC side.

Performance Enhancement of Microgrid Systems Using Backstepping Control for Grid Side Converter and MPPT Optimization

Microgrid networks represent a crucial model in the field of power transmission and distribution, integrating renewable energy sources with modern control technologies. This research focuses on enhancing the performance of a microgrid system connected to the main grid through a three-phase converter controlled using Voltage Oriented Control (VOC). The microgrid comprises a storage element and a photovoltaic (PV) generation system. To improve system efficiency and power quality, backstepping (BS) controllers are implemented and compared with traditional control methods. Three control systems are evaluated: a conventional system using Perturb and Observe (P&O) algorithm for Maximum Power Point Tracking (MPPT) and Proportional-Integral (PI) controllers for grid-side converter (GSC) control, a hybrid system with BS-modified P&O (BS-P&O) for MPPT and PI controllers for GSC, and an advanced system employing BS-P&O for MPPT and BS controllers for GSC. The research demonstrates that BS controllers exhibit superior dynamic performance, contributing to improved regulation of DC-link voltage, active and reactive powers. Additionally, they achieve lower Total Harmonic Distortion (THD) values and increase the overall efficiency of the PV system. The proposed advanced control strategy shows particular effectiveness in tracking speed, disturbance rejection, and power quality enhancement. This study underscores the potential of nonlinear control techniques in optimizing microgrid operations and facilitating the integration of renewable energy sources into the main grid.

An Analysis of Case Study Utilizing Distributed Power Flow Controllers Which Improves and Mitigates Power Quality

Abstract—Providing high-quality electrical power should be taken into consideration in light of the rising demand for electricity and the rise in non-linear loads in power systems. This research examines power quality concerns related to voltage sag and swell and uses a distributed power flow controller (DPFC) to reduce voltage deviation and enhance power quality. A novel FACTS device, the DPFC shares structural similarities with the unified power flow controller (UPFC). Despite UPFC, DPFC separates the three-phase series converter into many single-phase series dispersed converters via the line and removes the common dc-link between the shunt and series converters. A DPFC located in a single-machine infinite bus power system with two parallel transmission lines is included in the case study. The MATLAB/Simulink environment was to model the system. The simulation findings that are shown confirm that DPFC may raise power quality.

IMPLEMENTAÇÃO DE MODULAÇÃO VETORIAL APLICADA AO CONVERSOR CC-CA TRIFÁSICO VSI EMPREGANDO CÉLULA DE COMUTAÇÃO COM QUATRO ESTADOS

Este artigo apresenta a implementação de modulação vetorial espacial aplicada ao conversor VSI trifásico com célula comutação com quatro estados. A metodologia utilizada é mostrada em detalhes, indicando os vetores usados, sequência de comutação aplicada e os cálculos dos tempos de acionamentos dos vetores. Além disso contém o resultado do funcionamento do conversor em simulação, mostrando as principais formas de ondas. Na sequência traz os resultados obtidos por experimentação com o protótipo montado.

Research on a coordinated control strategy of three-phase photovoltaic converters based on a buck–boost DC link

Research on a coordinated control strategy of three-phase photovoltaic converters based on a buck–boost DC link

An inherent fault current blocking modular series multilevel converter using half-bridge sub-modules for grid integration

This paper proposes an inherent fault current blocking modular series multilevel converter (MSMC) using half-bridge (HB) sub-modules (SMs) for grid integration. The proposed converter uses passive filters to decouple the AC and DC side. Compared to conventional three-phase modular multilevel converters (MMCs) that use half-bridge sub-modules (HBSMs), the new MSMC design significantly reduces the number of switching devices required. Furthermore, one of the features of the proposed MSMC is its inherent ability to limit fault currents, which is achieved through its unique topological configuration whereas the conventional HB-MMC is susceptible to DC and AC faults. Despite these advancements, the new MSMC design retains all the desirable characteristics of conventional HB-MMCs, ensuring compatibility and ease of adoption. The paper thoroughly examines the operation of the MSMC under both steady-state and fault conditions. It also discusses the equivalent voltage decoupling circuit, energy balancing which is essential for the proper functioning of the converter. Additionally, the pre-charging process of the sub-module capacitors, a critical step for ensuring the safe start-up of the converter, is discussed in detail. Furthermore, Extended topologies can be derived from proposed topology for different applications.

Three-Phase Single-Stage AC-DC Converter Using Series–Series Compensation Circuit in Inductive-Power-Transfer-Based Small Wind Power Generation System

In this paper, a three-phase single-stage AC-DC converter for an IPT-based small wind power generation system (WPGS) with an S-S compensation circuit is proposed. It applies a three-phase single-stage AC-DC converter to improve the input power factor (PF), efficiency, and reliability in small WPGSs. Also, inductive power transfer (IPT) was applied to compensate for brush wear in the nacelle of small and medium-sized wind turbines while ensuring electrical safety. In conditions of the three-phase Permanent Magnet Synchronous Generator (PMSG) voltage (80~260 Vrms) for the wind turbine and the load (150~1000 W), it was verified that the desired output voltage below 3% can be controlled through the fixed link voltage (VLink) control without wireless communication. A 1 kW prototype was built and tested to demonstrate its applicability to the rotation of small and medium-sized wind turbine nacelles instead of brushes and slip rings.