Common DC Research Articles

Extension of Negative-Sequence Current Compensation Range Based on Negative- and Zero-Sequence Voltage Injection for Hybrid Cascaded STATCOM

Negative sequence voltage (NSV) injection is an effective cluster balancing control for CHB STATCOM, which has a higher capability in eliminating unbalanced active powers than zero sequence voltage (ZSV) injection. Unfortunately, NSV is employed for negative sequence current control under unbalanced current compensation applications, and only ZSV injection is used for cluster balancing, thereby seriously limiting negative sequence current compensation range (NCCR). To extend NCCR, the converter with a common DC link, called power exchange unit (PEU), is inserted into CHB to form a hybrid cascaded structure, which can freely exchange the unbalanced active powers via the common DC link. However, only ZSV injection method fails to take the advantage of this hybrid cascaded converter (HCC) to extend NCCR. In this paper, the NSV injection with a simple algorithm in dq frame is proposed for the HCC STATCOM with negative sequence current compensation. Owing to the PEU, the NSV of CHB for cluster balancing is counteracted by superposing an opposite NSV into PEU, thus transferring unbalanced active power from CHB to PEU and not affecting the negative sequence current control. Due to the limit of PEU capacity, the ZSV injection is also employed, and thus a novel cluster balancing control based on NSV and ZSV injection is proposed, based on which the NCCR is greatly extended. Finally, the proposed control is verified by the experimental results on a 400V / 7.5kvar HCC STATCOM.

Ultrathin tunable UWB metasurface absorber design by exciting plasmonic modes in bilayer graphene stack

This work presents a graphene-based ultra-wideband (UWB) tunable metasurface absorber (MSA) consisting of top patterned graphene (Gpat) and bottom continuous graphene (Gcont) separated by a 2 μm thick silicon dioxide (SiO2) substrate. An absorptivity (Af) ≥ 90 % from 0.1 to 14 THz (fractional bandwidth = 197.2 %) has been achieved in three steps: (i) Fabry-Perot cavity mode has been generated near 0.1 THz using bilayer graphene stack, (ii) multiple plasmonic modes have been excited by engraving resonant slots on Gpat and (iii) plasmonic coupling strength has been enhanced between Gpat and Gcont by adjusting SiO2 substrate's thickness. The excited plasmonic modes show high absorption due to the generation of localized surface plasmon polariton (LSPP) waves. The fourfold symmetry in design nullifies the effect of the polarization angle (ϕ). Interestingly, the orthogonal modes' excitation helps to achieve similar Af response under both transverse electric and transverse magnetic polarizations for incidence angle (θ) up to 60°. Further, an effective DC biasing mechanism has been devised to tune the chemical potential (μc) of the interconnected Gcont, which ensures common DC bias between unit cells. A DC voltage from 0 to 10.2 V can vary μc (Bottom) from 0 to 1 eV to provide frequency tunability.

Options for the structure of an autonomous electric power system with a battery of hydrogen fuel cells

Background. Recently, interest in the problem of reducing the emissions of hydrocarbon fuel combustion products into the atmosphere and the use of alternative and renewable energy sources has sharply increased. This problem is relevant to both stationary and transport energy. One of the ways to reduce the harmful impact of primary energy sources in autonomous transport power plants on the environment is their hybridization, i.e., use, along with traditional energy sources (turbogenerators and diesel generators), of hydrogen sources of electricity (fuel cell batteries).
 Aim. This study presents a justification of the optimal variant of the structure of an autonomous electric power system with a combined power plant based on hydrogen sources of electricity.
 Materials and Methods. To achieve this goal, a comparative analysis of the parameters and characteristics of the power system elements was performed, as well as a method for modeling processes in the power system under study using the MATLAB Simulink package. Two options for the structure of an autonomous electric power system are being considered, namely, a common AC and DC bus. An analysis of the parameters and characteristics of these options was performed for three typical operating modes, namely, turning on a static load, direct starting of an asynchronous motor with a load on the shaft, and transferring consumers from power from a diesel generator to power from a battery of hydrogen fuel cells.
 Results. In all considered modes, the VTE battery is characterized by a rapid response to load changes and stable efficiency. The nature of transient processes is aperiodic or low oscillatory, rapidly decaying. In terms of the number of semiconductor converters, filtering devices, and their total power, the structure of an autonomous power system with a common AC bus is more preferable.

Power Sharing Enhancement Strategies for Parallel-Connected Voltage Source Inverters With Common dc and ac Buses in Islanded Microgrids: Two New Control Schemes

Power Sharing Enhancement Strategies for Parallel-Connected Voltage Source Inverters With Common dc and ac Buses in Islanded Microgrids: Two New Control Schemes

Power quality stabilization system for grid connected large-scale solar power system

This paper presents solution to power quality issues when integrating a 1.5 MW photovoltaic array (PVA) with a unified power quality conditioner (UPQC) into the power grid. A modified unit vector template control scheme is used to generate a reference load voltage signal, and a synchronous reference frame (SRF) is created using a low-pass filter to control UPQC. Furthermore, the PVA is interfaced with the grid through a common DC link of shunt and series converters. The series converter mitigates power quality problems allied with the grid side, such as 3rd, 5th, and 7th harmonics, voltage sag, and voltage swell, by introducing signals in phase and out of phase voltage, respectively, at the point of common coupling (PCC). The shunt converter mitigates nonlinear load current harmonics and compensates for reactive power using SRF. The suggested methodology is implemented using MATLAB Simulink with both linear and nonlinear loads under different power quality conditions. Total harmonic distortions are maintained below 5% at PCC, as per IEEE-519 standards.

A novel fuzzy-logic controller-MDsUPQC topology for power quality improvement in multi-feeder distribution system

In the current situation, the significant usage of massive non-linear functioned power electronic loads has been increased in domestic and industrial applications. The main problem of power-quality (PQ) deterioration in both voltage quality and current quality from nominal values and also damaging the single/multi feeder distribution systems. The major contribution is to alleviate the PQ issues by employing novel multi-devices unified power-quality conditioner (MDsUPQC) topology in a multi-feeder distribution system. This MDsUPQC comprises multiple voltage source inverter (VSI) devices connected with a common direct current-link (DC-link) capacitor which is controlled by a proportional-integral (PI) controller. However, this controller has some technical issues that are not suited for the regulation of common DC voltage at the desired level because of improper selection of gain values. The contribution of this work is proposing an intelligent fuzzy-logic (FL) DC-link controller-driven MDsUPQC device which evidences the intelligent knowledge base for better regulation of PQ issues. The technique and performance of the suggested strategy for PQ improvement, load sharing between feeders, and simulation results are presented with comparative analysis utilizing the MATLAB/Simulink software tool.

Enhanced proportional integral controller for DSTATCOM with particle swarm optimization algorithm in power system

Power system expansion planning is supported by using distributed generation (DG) instead of installing new main power system generators. The portability and autonomous operation of the DG make it capable of integrating into the distribution system. Power electronics devices for home loads, mainly electric vehicles, mobile phones, and laptops, introduce harmonics and related power quality issues to the distribution system. This load creates power quality issues like an increase in total harmonic distortion (THD) and a reduction in power factor. This paper uses the DG to supply important power electronics devices for the mitigation of power quality problems in distributed systems with non-linear loads, such as electric vehicles, called the “distributed static compensator (DSTATCOM)”. Wind and photovoltaic (PV) generators supply power to a common DC source. To improve power quality D-STATCOM powered by PV and wind energy systems at the DC link is incorporated. The direct axis/quadrature axis method (DQ method) controls the real and reactive components of the power. Proportional integral (PI) and particle swarm optimization (PSO) based PI controller parameter estimation are developed, and results are compared for power quality performance. In terms of improving power quality, the PSO-based parameter estimate of the PI controller performs better than the traditional PI controller.<br /><div class="extension_reset_css AnnotateNet_widget AnnotateReviewNotesButton" style="display: none; z-index: 2147483644;" data-id="ExtensionWidget"><div class="extension_reset_css AnnotateNet_widget annotateclickable" style="z-index: 8; display: none;" title="Resize" data-id="Widget"> </div></div>

Zero-Sequence-Current Suppression of Open-End Winding PMSM With Common DC Bus Based on Virtual Vector Control

Zero-Sequence-Current Suppression of Open-End Winding PMSM With Common DC Bus Based on Virtual Vector Control

Airport Microgrid and Its Incorporated Operations

This paper presents the development of an airport bipolar DC microgrid and its interconnected operations with the utility grid, electric vehicle (EV), and more electric aircraft (MEA). The microgrid DC-bus voltage is established by the main sources, photovoltaic (PV) and fuel cell (FC), via unidirectional three-level (3L) boost converters. The proposed one-cycle control (OCC)-based current control scheme and quantitative and robust voltage control scheme are proposed to yield satisfactory responses. Moreover, the PV maximum power point tracking (MPPT) with FC energy-supporting approach is developed to have improved renewable energy extraction characteristics. The equipped hybrid energy storage system (HESS) consists of an energy-type battery and a power-type flywheel; each device is interfaced to the common DC bus via its own 3L bidirectional interface converter. The energy-coordinated operation is achieved by the proposed droop control. A dump load leg is added to avoid overvoltage due to an energy surplus. The grid-connected energy complementary operation is conducted using a neutral point clamped (NPC) 3L three-phase inverter. In addition to the energy support from grid-to-microgrid (G2M), the reverse mcrogrid-to-grid (M2G) operation is also conductible. Moreover, microgrid-to-vehicle (M2V) and vehicle-to-microgrid (V2M) bidirectional operations can also be applicable. The droop control is also applied to perform these interconnected operations. For the grounded aircraft, bidirectional microgrid-to-aircraft (M2A)/aircraft-to-microgrid (A2M) operations can be performed. The aircraft ground power unit (GPU) function can be preserved by the developed microgrid. The MEA on-board facilities can be powered by the microgrid, including the 115 V/400 Hz AC bus, the 270 V DC bus, the switched-reluctance motor (SRM) drive, etc.

Simplified Phase Model Predictive Voltage Control for Half-Centralized Open-End Winding Permanent-Magnet Motor Systems

In order to obtain a wider speed range for the permanent-magnet linear motor drive system, a half-centralized open-end winding (OEW) topology is studied. In this topology, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> movers are supplied by <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> +1 voltage-source-inverters (VSIs), and all these VSIs share a common dc bus voltage. In order to reduce the computation burden, a simplified phase model predictive voltage control (S-PMPVC) is proposed in this paper. For S-PMPVC, the optimal and suboptimal base levels are defined. When the optimal base level cannot be implemented, the suboptimal base level is selected. As a result, S-PMPVC requires smaller computation burden while the performances are not degraded. By taking the advantage of the smaller computation burden, S-PMPVC can adopt higher control frequency to improve performances. The effectiveness of S-PMPVC has been verified by simulation and experimental results.

Simplified control of TAB converter for scalable multibattery charging system

SummaryThe integration of distributed energy resources (DERs) into DC microgrids has become commonplace in many applications, including electric vehicle (EV) systems that use batteries, fuel cells, and supercapacitors as energy storage systems. To make a sustainable charging system for electric vehicles, DERs can be used in conjunction with the grid. In many cases, charging systems based on isolated DC‐DC converters, such as the dual active bridge (DAB) converter, with various controls, are typically used. However, integrating multiple DERs at the common input DC link can result in a loss of isolation in the DAB converter and also leads to problems with circulating current. To maintain isolation, multiple DAB converters can be used, but this increases the system's size. Alternatively, the multiport isolated DC‐DC converter can address such issues but introduces complexities such as cross‐coupling between power flow. This paper proposes a hardware decoupling control methodology for a triple active bridge (TAB) based isolated DC‐DC converter, with power routing features for simultaneously charging two EV's battery stack. Through hardware decoupling control, appropriate passive components are designed and selected to connect with the individual H‐bridges of the TAB for power decoupling. The paper discusses the cross‐coupling issue in the TAB and describes a methodology derived from mathematical expressions for achieving power decoupling. For validation of the control, a 5 kW system is modeled in MATLAB Simulink, and the results demonstrate how the proposed approach overcomes cross‐coupling issues. Further, a 500 W hardware prototype has been developed to validate the proposed approach.

Classification Algorithm for DC Power Quality Disturbances Based on SABO-BP

To better address and improve the issues related to DC power quality, this paper proposes an identification method tailored for DC power quality disturbances. First, it explores the underlying mechanisms and waveform characteristics of common DC power disturbances. By integrating the results of time–frequency analysis obtained through the S-transform, five distinct features are designed and extracted to serve as classification indicators. The SABO algorithm is subsequently employed to optimize the BP neural network, assisting in determining the optimal input weights and hidden layer thresholds. This optimization technique helps prevent the network from becoming stuck in local minima, thereby enhancing its robustness and generalization capabilities. This paper presents a simulation system for AC/DC power systems to conduct experimental verification. The system simulates various DC power quality issues and monitors abnormal waveforms. According to the designated classification index, the features of simulated disturbance signals are extracted. The SABO-BP classification prediction model is then used to automatically classify and identify the samples. The experimental results demonstrate high accuracy in classification and identification using the proposed method. In comparison to the BP neural network method, the SABO-BP method demonstrates an 8.207% improvement in accurately identifying disturbance signals. It is capable of accurately identifying direct current power quality signals, thereby assisting in the evaluation and control of power quality issues.

Modification of Beam Transport Line Design for Simultaneous Top-up Injection to PF and PF-AR

The High Energy Accelerator Research Organization (KEK) has two light sources: Photon Factory (PF, 2.5 GeV) and Photon Factory Advanced Ring (PF-AR, 6.5 GeV). In 2017, the operation of a new beam transport line (BT) of PF-AR was started, and the simultaneous top-up injection for both PF and PF-AR was realized. These days, there have been strong demands for the reduction of the operating cost of accelerators, and its importance is greater in PF-AR with higher ring-energy of 6.5 GeV. In 2019, the 5 GeV operation was started in PF-AR. However, the new BT of PF-AR (ARBT) was designed for the energy of 6.5 GeV, then the simultaneous top-up injection is no longer available under the condition of 5 GeV operation of PF-AR and 2.5 GeV operation of PF. In order to mitigate this impact, the pseudo-top-top injection has been employed by fine-tuning the current of a common DC bending magnet placed at the intersection of ARBT and the BT of PF (PFBT) within a given time frame. However, this scheme reduces the flexibility of the operation schedules, and will not be able to respond adequately to low emittance optics of PF-AR that may bring the shorter beam lifetime. In order to realize true-top-up injection, a modification of BTs’ optics design was carried out to add new horizontal steering magnets and a flattened-duct. The beam commissioning succeeded and the application to the user-run will start in this May. This time, details of modification and its extended plan will be presented.

Experimentation of Multi-Input Single-Output Z-Source Isolated DC–DC Converter-Fed Grid-Connected Inverter with Sliding Mode Controller

Converting devices are quickly becoming the most important part of renewable energy-producing systems that are linked to the grid. Applications that are linked to the grid are the most common place to find usage for two-port power converters that are built using single-input and single-output (SISO) ports. The incorporation of SISO power converters into the grid-connected hybrid system results in an increase in both its size and its cost. Multiple power sources may be connected to a single DC bus by means of hybrid power systems, which make use of multi-input power converters. To combine the hybrid wind and PV system with a common DC bus, this study suggests an isolated multi-input single-output (IMISO) Z-Source converter. It has been determined that the suggested system performs well in spite of dynamic load fluctuations and shifting input voltage circumstances. The sliding mode controller (SMC) has also been used to control a single-phase five-level (SPFL) inverter. The purpose of developing the laboratory prototype model was to verify the proposed IMISO Z-source converter-fed single-phase five-level (SPFL) inverter in the context of the circumstance that is being investigated.

Accurate voltage regulation for a DC microgrid using nonlinear state feedback controller

AbstractThe high penetration of distributed generation systems poses challenges in effectively managing both DC bus voltage and power‐sharing in DC microgrids (MGs). To ensure precise voltage regulation across various distributed generation systems and maintain overall system stability, this paper studies the modelling and control of an islanded DC MG described by a set of nonlinear‐nonaffine differential equations. In the proposed DC MG, a battery storage, a photovoltaic (PV) power plant, and a back‐end power converter with DC loads have been connected to a common DC bus. First, a dynamic model of a DC MG was developed. Then, to find the maximum power point of solar PV, a straightforward method based on an artificial neural net is employed. Afterward, a nonlinear local state feedback controller through output regulation theory is applied to achieve voltage stability, overcoming the drawbacks of droop‐based techniques. Moreover, partial state feedback capability simplifies controller design. To verify the effectiveness of the proposed approach, various scenarios, including sudden load variation, illumination change, and changes in the MG configuration, have been examined. Finally, numerical studies were carried out in a simulation environment to demonstrate the superiority of the proposed nonlinear control scheme over constant feedback control.

Model Predictive Control With Duty Ratio Modulation for Open-Winding PMSM Drives With Common DC Bus

Model Predictive Control With Duty Ratio Modulation for Open-Winding PMSM Drives With Common DC Bus

Comparative evaluation by two different hybrid power flow controller topologies of transient stability of machine system connected to wind-PV sources

The Hybrid Power Flow Controller (HPFC) has a simple design configuration, where the upgrading of the line functionality and controller can be performed in stages. This paper applies two HPFC configurations to a multi-machine power network. The first HPFC is a combination of two static synchronous series compensators (SSSC) connected in series, and a Static Var compensator (SVC). The second one consists of two shunt Static synchronous compensators (STATCOM) connected through a Thyristor controlled series compensator (TCSC), across a coupling transformer in a common DC link. The HPFC topologies are tested with a multi-machine power network with faults, in the presence of solar and wind energy sources. The overall model is simulated using SimPowerSystems toolbox and the performance of the two HPFC topologies is compared under various operating conditions. The comparison of simulation results shows that the second HPFC gives a better view than the first in analyzing the power system transient stability.

Improved Zero-Sequence Current Hysteresis Control-Based Space Vector Modulation for Open-End Winding PMSM Drives With Common DC Bus

Through the zero-sequence current (ZSC) hysteresis controller, the existing ZSC hysteresis control-based space vector modulation (SVM) strategy can provide a satisfactory ZSC suppression effect and greatly reduce the complexity for the open-end winding permanent magnet synchronous machine (OW-PMSM) drive with common dc bus. However, the corresponding linear modulation range is reduced by 12.7% compared with the middle hexagon space vector modulation (MH-SVM) for the OW-PMSM drive. To this end, this letter improves the linear modulation range of the existing strategy. The candidate voltage vectors for each sector are re-selected, and three active voltage vectors will be employed in the extended feasible region. While ensuring the ZSC hysteresis control, the linear modulation range of the proposed strategy is the same as the MH-SVM. At last, experimental results verify the feasibility and effectiveness of the proposed strategy. The proposed strategy can suppress the ZSC effectively, and the corresponding maximum speed is the same as the counterpart of the MH-SVM.

Design of a Three-Port Integrated Topology to interface electric vehicles and renewable energy sources

This work proposes the design and analysis of an off-board Three-Port Integrated Topology (TPIT). TPIT is used to interface Electrical Vehicles (EVs) and Renewable Energy Sources (RES) from solar electrical phenomenon (PV) panels with the power grid. The TPIT consists of three power converters sharing one common DC link. It can be operated in four completely different modes towards the long run sensible grids. The EV battery area unit is charged with energy from the power grid through the Grid-to-Vehicle (G2V) operation mode. The EV batteries deliver a part of the stored energy back to the power grid through the Vehicle-to-Grid (V2G) operation mode. The energy created by the PV panels is delivered to the electrical grid through the Renewable-to-Grid (R2G) operation mode and the energy created by the PV panels is employed to charge the EV batteries through the Renewable-to-Vehicle (R2V) operation mode. In addition to individual action, the reorganization of those modes leads to hybrid operational modes. This work plan is to propose a power theory to regulate the TPIT and this current control strategy controls the current in AC and DC sides of the TPIT respectively. Also, the features of the developed TPIT prototype, including the hardware and the digital control system are designed. The result portrays the analysis of TPIT operation modes are presented.

Implementation and Control of Multiport Grid Integrated Hybrid Energy Interface for EV Charging Application

EV charging combined with distributed energy storage (ES) devices could be utilized to send power to the grid during peak hours, mitigating the effects of load shedding. In order to achieve these goals, a hybrid multi-port charging system is developed in this study to properly manage power flows and balance energy. It is made up of a PFC bridge rectifier that is linked to an isolated three-port dc-dc converter that includes a series resonant (SRC) and a DAB converter for fast and slow charging applications, respectively. To maximize efficiency and power density, the ports share a 400 V common DC link. Grid-to-vehicle (G2V) mode is used to charge EV and ES vehicles from the utility grid; PV-to-grid (PV2G) mode is used to deliver PV energy to the grid; renewable-to-vehicle (R2V) mode is used to charge EV and ES batteries; and vehicle-to-grid (V2G) mode is used by EV and ES to deliver stored energy to the grid. The charging system’s performance and operation are validated in real time using MATLAB/Simulink under various operating situations. The system’s total harmonic distortion (THD) for the supply current is 2.07%. The suggested system is also compared against a state-of-the-art multiport charging system to assess its performance.