High Voltage DC Bus Research Articles

Cutting-Edge Triple-Port Soft-Switching Converter for Seamless Renewable Energy Integration

Three-port converters with high voltage gain are desirable solutions for integrating renewable energy and energy storage devices into high voltage dc bus. A high gain three-port converter with soft switching is proposed in this paper, which can realize zero voltage switching (ZVS) for all switches and zero current switching (ZCS) for all diodes in various operating modes. Single coupled inductor is used to achieve high voltage gain and to reduce the voltage stress of switches so that switches with low on-resistance can be selected to reduce the conduction loss. In addition, the advantages of fewer components, higher voltage gain, and very low switch voltage stresses make the proposed converter more suitable for application in renewable energy systems than similar solutions. Various operating modes, performance analysis, design considerations, efficiency analysis, and control method of the proposed converter are discussed. A laboratory prototype with 30V renewable energy source, 48V energy storage device and 400V output is designed to verify the performance of the proposed three-port converter.

Research on Analysis and Suppression Methods of the Bearing Current for Electric Vehicle Motor Driven by SiC Inverter

The silicon carbide (SiC) inverter brings great advantages to the motor drive systems of new energy vehicles; however, severe challenges to the bearings also happen. The high dc bus voltage and switching frequency of SiC inverter can increase the discharge frequency and energy when the bearing grease film collapses. As a result, the bearing suffers severe electric corrosion, and the service life of the motor drive system can be shortened. In this paper, the characteristics of common-mode voltage and bearing voltage are analyzed, firstly under space vector pulse width modulation (SVPWM). After that, the common-mode equivalent circuit model of the motor drive system is established. The frequency characteristics of bearing voltage are revealed, and the safe working area is determined. Then, the frequency characteristics of bearing voltage and current are verified based on IGBT and SiC inverters in experiments. After that, by designing a common-mode filter, the bearing voltage and current are significantly attenuated. Furthermore, the active zero state PWM (AZSPWM) is adopted to reduce the common-mode voltage from the inverter. At the same time, combined with the common-mode filter, the bearing voltage and current are further reduced. The experimental results show that the switching frequency has a decisive effect on the amplitude of bearing voltage and current. The bearing voltage can be attenuated to around half of the reference bearing voltage by using the common-mode filter and AZSPWM strategy, respectively. The combination of the common-mode filter and AZSPWM strategy can reduce the bearing voltage to around one-fourth of the reference bearing voltage, which can effectively reduce the breakdown time and discharge energy of the grease oil film.

A Transformerless Photovoltaic System Employing a Cubic Cell Boost Converter for Low Voltage Application

A photovoltaic (PV) system is commonly used to satisfy the power demand of the utility. This paper investigates the utilization of a high voltage gain Cubic Cell Boost Converter (CCBC) in a transformerless photovoltaic (PV) system for low voltage applications. The proposed system is a combination of a CCBC and a three-phase inverter creating a two-stage three-phase PV system. The CCBC is linked with the low-scale PV sources to step up its input DC voltage and maintain a constant DC bus voltage by employing the Perturb and Observe (P&O) Maximum Power Point Tracking (MPPT) control algorithm. The DC bus is further connected to an LCL filter based three-phase inverter using a synchronous reference frame (dq) control scheme to power the three-phase utility. The proposed combination is validated by simulating in MATLAB/ SIMULINK environment for a 5.5 kW PV source and achieved an efficiency of 91% with 1.91% of inverter Total Harmonic Distortion (THD) at unity power factor. In the proposed system, CCBC with P&O MPPT control provides a high step-up DC bus voltage with less input current ripple and output voltage ripple and maintains a constant DC bus under variable solar irradiance. This work does not account for the common leakage current that is often produced in a transformerless PV system.

Generalized Deadbeat Solution for Model Predictive Control of Five-Phase PMSM Drives

Model predictive control (MPC) has been widely emerged and applied on five-phase PMSM drives. However, the conventional MPC schemes have employed the high-complexity enumeration process and/or virtual voltage vector(s) (V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> (s)), which are designed offline in one subspace. Thus, the traditional MPC schemes may have a large computational burden, low tracking accuracy, and/or limited DC-bus voltage utilization. This article proposes a generalized low-complexity deadbeat (DB) solution for MPC schemes of the five-phase drives, which have a double-space control problem. In the proposed solution, the double-space control problem of the five-phase PMSM drive is formulated in a linear system of equations. To have a unique solution, five candidate real vectors are defined and solved for their duties during every sample interval. The optimal voltage vector(s) are directly selected without any enumeration process according to the highest duty cycle(s), which are designed online considering the control objectives of the two-subspace components. Hence, five different MPC schemes can be obtained from this solution. Compared with traditional MPC schemes, the salient features of the proposed DB-based schemes are a low computational burden, improved steady-state performance, high DC-bus voltage utilization, and a simple generalized execution. These features are verified using a five-phase PMSM drive experimental prototype.

Multi-Source Dual Active Bridge DC/DC Converter for More Electric Aircraft

The topology proposed in this paper aims for a multiple sources/loads integration to improve the power density of the electrical power distribution system (EPDS) of the more-electric aircraft (MEA) architecture. The different operating modes of the proposed topology add flexibility to the system enabling power flow between different sources, while controlling the power supplied to the low voltage (LV) network on the aircraft. Better system utilization is achieved as compared to conventional solutions. The system stability is improved considering that the multi-source DAB (MSDAB) topology can be configured to stabilize the high-voltage DC (HVDC) bus in case of voltage sag. A battery charging configuration utilizing the magnetizing inductance of the transformer is proposed and discussed as one of the operating modes of the converter. The power flow to the low-voltage bus network is controlled by phase shifting the gating signals between the two bridges. A design process using genetic algorithm (GA) optimization is introduced to optimally select the converter parameters to minimize the transformer RMS current. Simulation and experiments of the control schemes were performed to validate optimal operation of the proposed converter.

Design and test of a novel 1kw Stirling engine generator

This paper describes a practical design of a novel Stirling engine generator and 1kW machine test data. This machine’s configuration is a 4 cylinder double acting Stirling engine coupled with a Halback PM generator in line. This machine operates on the Stirling thermodynamic cycle and electromagnetic cycle established in 19th century by Carnot and Faraday. This machine’s unique function is bidirectional exchanging between thermal energy and electric power, as a same rotating direction of a same shaft. And the shaft speed can be controlled by three phases voltage source PWM inverter during both function such as the motor cooler mode and the engine generator mode. So, this unit can generate an electricity by using to many kinds of external heat source. As the heat source temperature changes as the shaft speed changes for the amount of absorbed heat changing in order to keep a cylinder temperature (700 ℃) and a heater tube temperature (<770 ℃). Consequently, the unit will achieve a highest efficiency keeping as a creep rapture strength limit level of the heater tubes. This unit has achieved 1.1 kW effective electric power, and 20.1% efficiency using LPG fuel, and 23.7 % thermal energy to electrical energy. This unit can connect to a commercial AC grid line by another inverter and, also connect a high voltage battery and a solar cell on the high voltage DC bus line in the PWM inverter.

Performance Analysis of a Relift Luo Converter-Derived Dual-Output DC to DC Converter for Microgrid Applications

A microgrid typically maintains multiple voltage bus bars with AC or DC or both. The various subsystems participating in the microgrid are connected to the appropriate voltage bus bars. Renewable energy sources like the wind energy or the solar photovoltaic energy may also be integrated to the microgrid. A battery-based energy storage system is also usually required. In this work, a dual-output DC to DC converter derived from the double lift or the relift Luo converter is proposed and validated. The proposed system uses a solar photovoltaic source and delivers a high-voltage DC output to deliver power to the high-voltage DC bus bar. A battery of medium voltage is connected across the second output of the dual-output converter. The proposed idea is validated using modeling and simulations in the MATLAB Simulink environment and an experimental prototype.

A Modified Interleaved Capacitor Clamped DC–DC Converter With Non-Resonant Soft Switching

Since the solar panels and fuel cells have low output voltage, which need to be converted to the 400 V or higher dc bus voltage in the renewable energy power generation systems, where, the high gain dc–dc converter plays a key role. Furthermore, with the requirement of the converter in low cost and high efficiency, the soft-switching interleaved boost-type converters based on switched-capacitor and voltage multiplier cell as the high gain dc–dc converters have been widely applied. However, the above-mentioned soft-switching interleaved boost-type converters in literature have resonant spikes on the switches or there are coupled inductors, which will cause the high cost due to the large stresses of the switches or low efficiency due to the high core losses of the coupled inductors. To solve the above-mentioned problems, a modified interleaved capacitor clamped (MICC) dc–dc converter with non-resonant soft-switching (NRSS) is proposed, in which only an auxiliary inductor operating in discontinuous conduction mode with few μH is used to achieve the zero-current-switching for all switches and diodes. Furthermore, the operating principle of the proposed converter is given, the interleaved boost structure is used as the front stage of the proposed converter to reduce the input current ripple and lighten the current stress on all switches and magnetic components, the MICC structure with NRSS as the output stage is proposed as a voltage multiplier module to achieve the high voltage gain. Then, the circuit parameter design for this converter is presented. Finally, a 400 W experimental prototype is built to verify the correctness and the effectiveness of the proposed topology.

Modular DC Circuit Breaker With Master−Slave Concept for Gate Driver Simplification: Topology and Implementation

DC circuit breaker is the key equipment to deal with the interruption of short-circuit current. Compared with the mechanical switch, the solid circuit breaker and the hybrid circuit breaker using the semiconductor device to interrupt the short-circuit current exhibit superiorities in response duration and arc-less characteristics. Massive power devices controlled by corresponding gate drivers which make the semiconductors-based dc circuit breaker bulky and costly are required to withstand the high dc-bus voltage. In this article, the master−slave concept based modular circuit breaker is proposed to simplify the gate driver topology. Only one single gate driver is required to control highly compact modular submodules consisting of power devices, passive components, and diodes. Moreover, the proposed topology can be easily implemented with high flexibility and low cost. Specifically, the gate control function and voltage equalization for series-connected devices can be realized reliably. The master−slave concept and operation principle of the proposed topology are elaborated and the effectiveness has been demonstrated by both simulation and experimental test.

Z-Source-Based High Step-Up DC–DC Converters for Photovoltaic Applications

This article proposes three high step-up Z-source (ZS)-based dc–dc converters by integrating the conventional ZS network with switched-capacitor (SC) cells. The proposed converters offer a simple structure with a smooth input current, a high-voltage gain, and low voltage stress on the semiconductor devices. In addition, the proposed converters, unlike some existing ZS-based topologies in the literature, do not impose any limitation on the duty cycle of the power switch. These characteristics make the proposed converters excellent candidates to interface a low-voltage solar photovoltaic (PV) panel with a high-voltage dc bus in PV applications. Among the proposed three converters, the operating principles and steady-state analysis of the one with more components are presented in detail. However, the steady-state voltage and current relationships are also tabulated for two other proposed converters. In addition, design considerations are presented. The performance of the proposed converters is compared against similar existing high step-up dc–dc converters with regards to the component count, normalized voltage stress on the power switch and diodes, and voltage gain. Finally, the theoretical analyses and calculations are validated through experimental results using a 400-W/400-V laboratory prototype.

Development of an Aircraft Electric Power Architecture With Integrated Ground Power Unit

This article presents a switch-mode rectifier-based electric power architecture with an integrated ground power unit for more electric aircraft. The well-regulated high-voltage dc-bus is established from the aircraft generator. And the conventional major 270-Vdc, 28-Vdc, and 115-Vac/400-Hz buses are also preserved. In landed conditions, the ground power unit function powered by the mains is inherently possessed thanks to the proposed integrated schematic. First, the developed switch-mode rectifier using a silicon-carbide device with a wide frequency range covering utility line frequency and aircraft generated varied high frequency is presented. The allowable energy storage inductances using the embedded generator armature winding are derived. Good generator armature power quality and well-regulated dc output voltage are preserved by the designed current and voltage control schemes. Next, the utility grid-powered ground power unit established by the embedded schematic is introduced. Finally, the inverter for generating the 115-Vac/400-Hz three-phase source and the dc–dc converter for establishing the 270-Vdc bus are constructed. Normal operations, good dynamic, and steady-state performances of all the constructed power stages are verified experimentally, which can confirm the feasibility of the proposed aircraft power architecture.

Thirteen-Level Multilevel Inverter Structure Having Single DC Source and Reduced Device Count

This article proposes a single dc source-based hybrid three-phase thirteen-level inverter suitable for medium voltage applications. The multilevel structure is composed of a three-level T-type neutral point clamped (NPC), half-bridge, and three-level Flying capacitor converter with optimal switch count and high dc bus voltage utilization as high as 0.63 times the dc-link voltage. This requires a special attention to a novel capacitor balancing method using redundant switching states in order to operate at any power factor under grid-connected mode. A unified common-mode voltage is injected in the carrier based pulse width modulation (PWM) technique to maintain the voltage balance in dc-link capacitors as well as floating capacitors. Simulation results are presented under different operating conditions that include unity power factor operation with passive load as well as grid-connected inverter mode. The performance of the proposed multilevel inverter in the grid-connected mode is also validated with experimental results using a lab prototype.

Autonomous DC-Bus Voltage Regulation in DC Microgrid Using Distributed Energy Storage Systems

A DC microgrid has many advantageous features, such as low power losses, zero reactive power, and a simple interface with renewable energy sources (RESs). A bipolar DC microgrid is also highlighted due to its high-power quality, improved reliability, and enhanced system efficiency. However, the bipolar DC microgrid has high DC bus voltage fluctuation due to the load power unbalance between the poles. Therefore, this paper analyzes the DC bus voltage fluctuation that can occur in the bipolar DC microgrid. An autonomous grid voltage regulation method is introduced to regulate the DC bus voltage of a bipolar DC microgrid using distributed energy storage systems (ESSs). The proposed grid voltage regulation scheme using the distributed ESSs could regulate DC bus voltage in real time, regardless of the structure of the DC microgrid without external communication. Lastly, experimental results using a lab-scale bipolar DC microgrid prototype verified the proposed method.

A V2G Enabled Bidirectional Single/Three-Phase EV Charging Interface Using Modular Multilevel Buck PFC Rectifier

The battery charging power electronics interface of an electric vehicle (EV) must be capable of bidirectional power flow to enable both grid-to-vehicle (G2V) and vehicle-to-grid (V2G) operations. In the presence of a single/three-phase AC supply, the front-end of the EV charger employs a power factor correction (PFC) rectifier, which should have the bidirectional capability to facilitate V2G mode. A conventional active rectifier functions in boost mode while performing PFC and voltage regulation. In most of the currently available EVs, however, the battery nominal voltage is low and, hence, a downstream high step-down DC-DC converter and high voltage DC bus capacitor are required in the charging interface. To overcome these issues, this work proposes a bidirectional AC-to-DC buck rectifier topology that can operate in G2V and V2G modes, both in single- and three-phase versions. The proposed topology utilizes the switched capacitors principle to achieve self-balancing of voltages in the capacitors. In addition, it is highly modular in structure. This paper describes the proposed topology, its working and modulation and its applications. The hardware proto model is used to validate the proposed power converter and the control approach to achieve PFC and voltage regulation. In addition, a comparison with other topologies is presented to demonstrate its competence.

Charging Electric Vehicle Batteries: Wired and Wireless Power Transfer: Exploring EV charging technologies

Due to the environmental concerns about CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -caused global warming, policymakers are pushing electrified vehicles (EVs) to reduce these emissions. For passenger vehicles only, the electrified fleet is forecasted to reach 80 million in the U.S. and 500 million globally by 2040. Key enablers for such rapid EV adoption include the improvement of battery energy density, lifespan and safety, and drastic cost reduction of batteries and power electronics. The technology of power electronics nowadays can be found in many aspects of EVs. It alters and transforms the energy from the power source to different forms to feed the loads. For example, the on-board charger (OBC) accepts ac input and converts it to high voltage (HV) dc to charge the propulsion battery. An auxiliary power module (APM) steps down the HV battery voltage to low voltage (LV) to charge the LV battery <xref ref-type="bibr" rid="ref1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[1]</xref> . The HV dc bus voltage is converted to an ac form to drive the propulsion motor, forming the motor drive inverter. Putting the power electronics system and the batteries together, the typical structure of an EV is shown in <xref ref-type="fig" rid="fig1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Figure 1</xref> . In addition, power electronics can be found in other onboard auxiliary circuits, such as LED lighting and battery management system (BMS).

Weighting Factor Free Model Predictive Control for a Flying Capacitor Converter in a DC Microgrid

This paper presents a single-objective model predictive control for a bidirectional DC-DC flying capacitor (FC) converter, which integrates a battery to the microgrid. The presence of multiple FCs facilitates the converter to interface a low-voltage battery to a high-voltage DC bus at reduced voltage stress on its power switches. However, such converter requires a controller that fulfils multiple objectives, namely DC bus and FC voltage regulations, and bidirectional power flow. The key feature of the proposed controller is that it utilizes a model predictive control with a single-objective cost function based on battery current and a redundant state selection scheme to attain these multiple objectives. Adopting such a strategy not only reduces computational burden but also eliminates the need for weighting factors and requirement of complex numerical models for its estimation. Another notable aspect is that the controller employs an improved dynamic reference model to generate appropriate battery current reference for the DC bus voltage regulation, without necessitating a secondary control loop and additional current sensors. Finally, experimental results of the proposed system for a step-response of the DC bus voltage, varying PV power, and loads are validated and compared against finite control set model predictive control.

Integration of air-cooled multi-stack polymer electrolyte fuel cell systems into renewable microgrids

Currently, there is a growing interest in increasing the power range of air-cooled fuel cells (ACFCs), as they are cheaper, easier to use and maintain than water-cooled fuel cells (WCFCs). However, air-cooled stacks are only available up to medium power (<10 kW). Therefore, a good solution may be the development of ACFCs consisting of several stacks until the required power output is reached. This is the concept of air-cooled multi-stack fuel cell (AC-MSFC). The objective of this work is to develop a turnkey solution for the integration of AC-MSFCs in renewable microgrids, specifically those with high-voltage DC (HVDC) bus. This is challenging because the AC-MSFCs must operate in the microgrid as a single ACFC with adjustable power, depending on the number of stacks in operation. To achieve this, the necessary power converter (ACFCs operate at low voltages, so high conversion rates are required) and control loops must be developed. Unlike most designs in the literature, the proposed solution is compact, forming a system (AC-MSFCS) with a single input (hydrogen) and a single output (high voltage regulated power or voltage) that can be easily integrated into any microgrid and easily scalable depending on the power required. The developed AC-MSFCS integrates stacks, balance of plant, data acquisition and instrumentation, power converters and local controllers. In addition, a virtual instrument (VI) has been developed which, connected to the energy management system (EMS) of the microgrid, allows monitoring of the entire AC-MSFCS (operating temperature, purging, cell voltage monitoring for degradation evaluation, stacks operating point control and alarm and event management), as well as serving as a user interface. This allows the EMS to know the degradation of each stack and to carry out energy distribution strategies or specific maintenance actions, which improves efficiency, lifespan and, of course, saves costs. The experimental results have been excellent in terms of the correct operation of the developed AC-MSFCS. Likewise, the accumulated degradation of the stacks was quantified, showing cells with a degradation of >80%. The excellent electrical and thermal performance of the developed power converter was also validated, which allowed the correct and efficient supply of regulated power (average efficiency above 90%) to the HVDC bus, according to the power setpoint defined by the EMS of the microgrid.

High step-up DC-DC converter based on double self-lift switched-coupled-inductor

ABSTRACT This paper presents a novel switched-inductor based DC-DC converter with high step-up capability for interfacing the low voltage input from renewable energy sources to a high voltage DC bus. In the proposed converter, coupled inductors (CIs) are employed in lieu of discrete switched inductors to enhance the voltage gain and reduce the voltage stress on the switches. The number of turns in the CI windings is properly designed and one diode-capacitor multiplier cell (DCM) is connected at each of the two secondary windings to obtain the desired high voltage gain value. Since the required voltage conversion ratio value of 15.833 is obtained by employing CIs, the switches experience only lower voltage stress levels of about 5.79% and 26.3% of output voltage under practical conditions. Experimental results obtained from 24 V-380 V, 175 W prototype converter confirm that it operates at 93.6% full-load efficiency. Further, the supply current drawn by the converter is continuous with 15.4% ripple. Simple closed-loop control is implemented to regulate the converter’s output voltage against variations in line voltage and load current.

The Impact of an Overlaid Ripple Current on Battery Aging: The Development of the SiCWell Dataset

Fast-switching semiconductors induce ripple currents on the high-voltage DC bus in the electric vehicle (EV). This paper describes the methods used in the project SiCWell and a new approach to investigate the influence of these overlaid ripples on the battery in EVs. The ripple current generated by the main inverter is demonstrated with a measurement obtained from an electric vehicle. A simulation model is presented which is based on an artificial reference DC bus, according to ISO 21498-2, and uses driving cycles in order to obtain current profiles relevant for battery cycling. A prototype of a battery cycling tester capable of high frequency and precise ripple current generation was developed and is used to cycle cells with superimposed ripple currents within an aging study. To investigate the impact of the frequency and the amplitude of the currents on the battery’s lifetime, these ripple parameters are varied between different test series. Cell parameters such as impedance and capacity are regularly characterized and the aging of the cells is compared to standard DC cycled reference cells. The aging study includes a total of 60 automotive-sized pouch cells. The evaluation of ripple currents and their impact on the battery can improve the state-of-health diagnosis and remaining-useful life prognosis. For the development and validation of such methods, the cycled cells are monitored with a measurement system that regularly measures current and voltage with a sampling rate of 2 MHz. The resulting dataset is suitable for the design of future ripple current aging studies as well as for the development and validation of aging models and methods for battery diagnosis.

Multiple output high gain DC-DC converter

Multiple output DC-DC converters with high gain are the most cost-effective development in improving renewable energy applications. The high gain DC-DC boost converters can convert low voltage from renewable energy sources to high DC bus voltage level. The multiple output high gain converter has advantage of multilevel outputs which eliminate the requirement of individual converters for each voltage level. The DC-DC boost converter with multiple outputs provides boost outputs with different gains at low duty ratios with higher efficiency. The non-isolated multiple output DC-DC converter works on switched-capacitor and switched-inductor technique with a wide input voltage range. The dual power switches are driven with a single PWM drive signal. The voltage stress across components is less than half of the main output voltage. The dual outputs with single input reduce size and cost of the high gain converters in modern power electronics. The operation of DC-DC converter analysed in continuous conduction mode. The performance study of the multiple output high gain DC-DC converter is carried out with MATLAB/SIMULINK R2017b for 100W/20kHz.