Integrated DC Research Articles

A High-Efficiency Double-Side Silicon- Embedded Inductor for Integrated DC–DC Converter Applications

In this brief, a novel double-side silicon-embedded coreless inductor is proposed and demonstrated for integrated dc-dc converter applications. The inductor has double-side thick windings embedded into the silicon substrate and connected in parallel. Extremely large effective metal thickness of 300 μm can, therefore, be achieved. Consequently, the 0.8 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> inductor fabricated shows a low dc resistance of 42 mΩ. A large inductance to dc resistance ratio of 0.4 nH/ mΩ is then achieved with an inductance over 16.1 nH. The calculated peak effective inductor efficiency is 96.1% for 1.8-0.85 V, 100 MHz dc-dc conversion.

Adaptive energy management strategy for sustainable voltage control of PV-hydro-battery integrated DC microgrid

DC microgrid has relatively more advantages of power quality, not requirement of reactive power, higher operational efficiency compare to AC microgrid. DC microgrid can facilitate effective integration of distributed clean energy resources and efficient solution for providing electricity to remote areas (e.g. North Eastern States of India). Recently, India has commissioned small hydro, solar PV and battery storage integrated DC microgrids (MGs) to meet the locally increasing load demand of northeastern states. The sudden change in solar insolation during the load power dynamics can cause unbalanced power flow in such isolated MGs. Due to the slow response time of small hydro power plant (SHPP) and limited output power of battery storage with fixed C-rate, the unbalanced power flow, during load power dynamics, cannot be compensated. The unbalanced power flow may lead to unsustainable voltage control at the DC bus of MG. To prevent this, MG follows load shedding. But, load shedding reduces the reliability of MG. To achieve the sustainable voltage control of DC MG, a smart adaptive energy management strategy (AEMS) is proposed in this research work. The novel aspect of proposed AEMS is that it operates the SHPP despite its slow response time by estimating the load power dynamics on the iterative basis. The deep charging/deep discharging scenario of battery storage due to mismatch between the total generation with estimated load and the actual load is taken care by the adjustable energy controller of proposed AEMS. To justify the potential contributions of proposed AEMS, it is assessed against various dynamic test load cases. Based on the assessment of obtained results against various test load cases, in this work, a comparative analysis is carried out between the proposed AEMS and the existing control strategies in the literature. The comparative analysis reveals that with the proposed AEMS, voltage sustainability of MG is improved by 22.7% and the utilization factor of SHPP is enhanced by 55.27% with 98.17% reduction in current stress levels of battery storage system. Finally, the proposed AEMS is evaluated in MATLAB/Simulink as well as validated through OPAL-RT real time simulator.

A miniaturized low frequency (LF) magnetoelectric receiving antenna with an integrated DC magnetic bias

Due to the applications in meteorological broadcasts, radio navigation, and underwater communications, low-frequency (LF) receiving antennas have been actively studied. However, because the frequency range of LF antenna is 30 to 300 kHz, its electromagnetic wavelength is 1 to 10 km, which makes LF electromagnetic antennas difficult to be implemented in miniaturized or portable devices. This article presents a miniaturized LF magnetoelectric (ME) receiving antenna with an integrated DC magnetic bias. The antenna is based on the magnetoelectric effect and operates by resonance at its mechanical resonant frequency. Thus, compared with traditional LF wire antennas, the dimension of ME antenna is reduced significantly. Compared with prior art of ME antennas which do not have DC magnetic bias, higher performance can be achieved by integrating the miniaturized DC magnetic bias. Magnetostrictive TbDyFe2 (Terfenol-D) and piezoelectric lead zirconate titanate thin films are bonded together to form the 38 × 12 × 5.8 mm3 ME receiving antenna. Four 10 × 10 × 10 mm3 Rb magnets are implemented to provide an optimal DC bias for the antenna. A maximum operation distance of 2.5 m is demonstrated with the DC magnetic field bias, 2.27 times of the maximum operation distance of the antenna without DC magnet field bias. The efficiency, gain, and quality factor of the ME receiving antenna are also characterized. The miniaturized LF ME antenna could have potential applications in portable electronics, Internet of things, and underwater communications.

Novel Control Strategy for Enhancing Microgrid Operation Connected to Photovoltaic Generation and Energy Storage Systems

Recently, the penetration of energy storage systems and photovoltaics has been significantly expanded worldwide. In this regard, this paper presents the enhanced operation and control of DC microgrid systems, which are based on photovoltaic modules, battery storage systems, and DC load. DC–DC and DC–AC converters are coordinated and controlled to achieve DC voltage stability in the microgrid. To achieve such an ambitious target, the system is widely operated in two different modes: stand-alone and grid-connected modes. The novel control strategy enables maximum power generation from the photovoltaic system across different techniques for operating the microgrid. Six different cases are simulated and analyzed using the MATLAB/Simulink platform while varying irradiance levels and consequently varying photovoltaic generation. The proposed system achieves voltage and power stability at different load demands. It is illustrated that the grid-tied mode of operation regulated by voltage source converter control offers more stability than the islanded mode. In general, the proposed battery converter control introduces a stable operation and regulated DC voltage but with few voltage spikes. The merit of the integrated DC microgrid with batteries is to attain further flexibility and reliability through balancing power demand and generation. The simulation results also show the system can operate properly in normal or abnormal cases, thanks to the proposed control strategy, which can regulate the voltage stability of the DC bus in the microgrid with energy storage systems and photovoltaics.

An Integrated DC Series Arc Fault Detection Method for Different Operating Conditions

Series arc fault (SAF) has severe impacts on the safety of dc power supply systems. Timely and accurate SAF detection under different operating conditions is an open and challenging problem. To address this problem, this article proposes an integrated SAF detection method for different operating conditions. In the proposed method, dual-tree complex wavelet transform (DT-CWT) is employed to obtain an accurate current signal decomposition. The singular values of each wavelet component are then extracted by using an improved matrix construction method, which can effectively reduce the computational cost of constructing the high-dimension features. Finally, the kernel extreme learning machine (KELM) is applied to fuse the feature information for SAF detection. A series of experiments are presented to demonstrate the effectiveness of the proposed method. The results of offline experiment show that the accuracy of the proposed method has higher detection accuracy than that of the six state-of-the-art methods under different operating conditions. In this article, the proposed method is then embedded into the hardware of the experimental platform for online in-service implementation. The online experimental results show that the proposed method achieves fast and accurate SAF detection and, at the same time, offers outstanding reliability and stability in system dynamic transients.

Decentralized Voltage Regulation and Energy Management of Integrated DC Microgrids Into AC Power Systems

This article proposes a control strategy for integrated dc microgrids (MGs) into power systems. In this method, the DC MGs are capable of importing or exporting energy from or to the AC grid based on the loading conditions. The DC MGs employ an interlinking converter (IC) as a bidirectional back-to-back converter for a distributed generator (DG) unit at the point of common coupling (PCC). In a multi-DG unit DC MG, an energy management strategy should be planned by sharing network loads among dispatchable DG units, and meanwhile, the dc network voltage should be regulated. The proposed control system utilizes an ac voltage superimposed on the nominal dc voltage of the network. The frequency of the superimposed ac voltage is used to modify the conventional droop control, which leads to simultaneous accurate load sharing and regulated voltage in a decentralized manner. The IC DG unit equipped with the proposed controller interfaces the dc network through a dc/dc buck converter and the ac grid through an active rectifier. This strategy provides a seamless transition between islanded and grid-connected modes for the DC MGs. The performance of the proposed control system is evaluated through simulations studies via PLECS and a set of experimental results.

An Integrated Cascade Structure-Based Isolated Bidirectional DC–DC Converter for Battery Charge Equalization

In this article, an isolated bidirectional dc-dc converter with an integrated cascade structure is proposed for a centralized charge equalization system. Compared with existing architectures, the proposed converter structure is equivalent to the integration of polarity switches and a bidirectional dc-dc converter. Equalization of cells with different voltage polarities can be realized by controlling the working state of the converter, which further improves the reliability and integration of the equalization system. The integrated cascade structure can not only increase the equalization current and make it work in a continuous state but also achieve a high voltage conversion ratio to improve the efficiency of the transformer. Theoretical derivations of the converter and the conditions of soft-switch implementation are analyzed in detail. Finally, equalization experiments on a 13-cell lithium-ion battery string are carried out, and a quantitative and comprehensive comparison of different centralized equalizer is conducted. The experimental and comparison results validate the superiorities of the proposed equalizer and demonstrate obvious performance enhancement over the conventional method.

Magnetic Functional Integrated DC Motor Drive

This paper presents the concept of magnetic functional integrated DC motor drive. It uses the field winding of a wound-field DC motor as the inductor of its drive circuit. The field winding in a wound-field DC motor not only builds the required magnetic field for the electric-mechanic energy conversion, but also acts as the inductor to buffer the energy for the drive circuit. One magnetic component is shared to realize different functions for motor and its drive circuit, simultaneously. The weight, loss and cost of the drive system can be reduced due to the saving of extra bulky inductors for the drive circuit. This concept can be applied to all DC-DC drive circuits using inductor as its energy buffer. An example of magnetic functional integrated DC motor drive using the buck-boost converter is used to explain the concept in detail. The feasibility and the new features are verified experimentally by comparing with the conventional motor drive.

A Power Management System for Electromagnetic Energy Harvesters in Battery/Batteryless Applications

This article presents a miniaturized and cost-effective power management system (PMS) for low-voltage electromagnetic energy harvesters (EMEHs) operating in both battery-powered and batteryless applications. The PMS consists of two converters and their associated controllers. The first converter converts EMEH’s ac voltage into a dc one in a single step and provides a maximum efficiency point tracking (MEPT) feature to maximize the harvested energy and can be used alone in battery-powered applications. The second converter provides tight output voltage regulation for batteryless applications. The MEPT converter utilizes a topology that uses a single inductor shared between the positive and negative half cycles of the EMEH voltage, unlike the majority of existing solutions, hence achieving system’s cost and size reductions. In addition, its control architecture is based on low-power comparators and does not require zero-crossing detection (ZCD) block, in contrast to many existing solutions, allowing for further reduction in cost, losses, and size. Moreover, the shared inductor is not only used by the power stage but also as a key element of the bias supply scheme allowing for voltage stepping up and hence providing sufficient voltage to supply the control circuits. The voltage regulation converter features a highly integrated dc–dc converter where the power inductor serves as normal inductor and a substrate for the converter. Experimental results show the effectiveness of the PMS with an EMEH that has a damped ac voltage characteristics ranging from 1.0 V to 10 mV for battery and batteryless applications. The presented MEPT converter, switching at 40 kHz, achieves 32.3-mm3 magnetics volume, which is the biggest contributor to the real estate of the PMS. Also, it can harvest up to 17 mJ out of 20 mJ available energy while achieving a BOM cost less than 0.7€. Moreover, the highly integrated buck converter, switching at 4 MHz, provides a tight regulated voltage of 1.2 V at 5 mA for a group of wireless sensors while achieving efficiency of 80% for load currents between $100~\mu \text{A}$ and 200 mA.

A Drivetrain Integrated DC Fast Charger With Buck and Boost Functionality and Simultaneous Drive/Charge Capability

Electric vehicles have the potential to change the global driving paradigm, significantly reducing the environmental impact of transportation systems. However, charging infrastructure cost and range anxiety impose challenges on rapid technology adoption. This paper proposes an onboard integrated dc charger, leveraging the traction inverter, and motor winding inductance to ensure the minimum incremental mass. The proposed circuit allows the vehicle to connect directly to emerging dc microgrids, utility storage, or renewable energy resources. The system is compatible with power supply voltages higher or lower than the vehicle battery, offering the possibility to charge 400-V batteries from emerging 1000-V supplies, as well as 800-V battery from the existing 600-V dc interfaces. The presented method also provides bidirectional fault blocking capability and bidirectional power transfer, suitable for V2G, G2V, or V2V operation. In addition, this paper proposes simultaneous driving and charging, especially useful for semitrailer trucks applications, significantly increasing operational range. The solution presented in this paper offers a simple and safe charging scheme with the potential to substantially reduce charging infrastructure cost and address range anxiety.

An Integrated DC Microgrid Solution for Electric Vehicle Fleet Management

The coordinated development of charging points reveals to be crucial in supporting the envisaged diffusion of electric vehicles, along with their proper design to ensure smart and fast charging performances and economic advantages for drivers. The integration of charging points with local generation and storage can enhance this process. In this paper, the structure of a modular electric vehicle supply infrastructure is proposed. It is based on the integration of photovoltaic rooftops, energy storage and electric vehicle stations in a dc microgrid, enabling coordination and control as well as the functions of bidirectional charging and the possibility to provide grid services at connection point. The main features of the technical demonstrator are described, along with the targeted innovations for system manager and final user, and the possible control functions involving operation planning, real-time control, and ancillary service market inclusion.

An Integrated DC–DC Converter With Segmented Frequency Modulation and Multiphase Co-Work Control for Fast Transient Recovery

This paper presents a fully integrated voltage-controlled oscillator (VCO)-based switched-capacitor (SC) 15-phase dc–dc converter in 65-nm CMOS. We propose two transient-enhancement techniques: segmented frequency modulation (SFM) and multiphase co-work (MCW) control to reduce the latency of the VCO-based control loop and shorten the SC dc–dc converter’s transient response time. The SFM can improve the heavy-to-light load transient by dynamically increasing the charge pump discharge current by nine times, while the MCW can enhance the light-to-heavy load recovery by synchronously combining three interleaved flying capacitors together during the transient state. We designed the 15-phase interleaved converter to support an output voltage of 1 V from a 2.4-V input supply, delivering up to 138 mA of load current, which takes only 25/29 ns for output voltage recovering to the steady state from heavy-to-light/light-to-heavy load transients, respectively. It obtains a peak efficiency of 82.8% and maintains the efficiency above 80% from 31 mA to the maximum load current. The SC dc–dc converter chip occupies 0.61 mm2, and its output power density is 240 mW/mm2.

Dual-Input Grid-Connected Photovoltaic Inverter With Two Integrated DC–DC Converters and Reduced Conversion Stages

A dual-input dual-buck inverter (DI-DBI) with integrated boost converters (IBCs) is proposed for grid-connected applications. The proposed DI-DBI is composed of two buck-type inverter-legs and two IBCs. Two renewable dc sources, with independent maximum power point tracking, can be realized with the DI-DBI. The IBCs are used to provide a constant and stable dc-bus voltage for the inverter-legs, enabling the inverter to operate well, even when the dc source voltage varies widely and is lower than the peak amplitude of the grid voltage. Unlike a conventional two-stage dc–ac inverter, only a small ratio of the input power needs to be processed by the IBCs. The other part of the input power is directly fed to the grid through the inverter-legs; therefore, in comparison with a conventional dc–dc converter and inverter cascaded two-stage solution, the conversion stages of the DI-DBI, power rating, and losses of the IBCs are all reduced. The switching loss can be reduced as well because of the multivoltage-level characteristics of the proposed DI-DBI. As a result, a higher efficiency is achieved. Modulation and control strategies are proposed to realize independent regulation of the two dc inputs. Operation principles and characteristics of the proposed DI-DBI are analyzed in detail. Experimental results have been provided to verify the effectiveness and advantages of the proposed method.

Programmable Topology Derivation and Analysis of Integrated Three-Port DC-DC Converters with Reduced Switches for Low-Cost Applications

Thanks to the favorable advantage of low cost, integrated three-port dc–dc converters with reduced switches have attracted extensive attention. In order to provide more new topologies, this paper aims to propose a programmable topology derivation method, which effectively simplifies the cumbersome process of the conventional combination method. Instead of the manual connection and examination, the proposed alternative can quickly and rigorously derive multiple viable integrated three-port dc–dc topologies from a great number of possible connections with the aid of computer program. Besides, generalized analysis is also accomplished, with which performance characteristics of all derived converters are simultaneously obtained and then a comprehensive comparison can be easily conducted to select a preferred one for the practical application. Finally, an example-specific application with one input and two outputs is given, with topology selection, design, and experimental results demonstrated in detail.

Virtual Resistor-Based Integrated DC Bus Voltage Conditioner for Stability Improvement of Cascaded Power Converters

A bidirectional integrated bus voltage conditioner (IBVC) for an isolated phase-shifted full bridge (PSFB) dc/dc converter is proposed to reduce the dc bus voltage oscillations in a cascaded power converter system, where a load converter is controlled tightly with high-control bandwidth. In the proposed method, unlike conventional dc bus voltage stabilization methods for which auxiliary switches are used, the multiplexing utilization of the full bridge switches at the primary side of a PSFB is adopted. In this paper, to improve the dc bus voltage stability, an equivalent virtual resistor is implemented by applying the duty cycle regulation for both legs of the PSFB. The effectiveness of the proposed method on the dc voltage stabilization is examined through simulations and experiments. The achieved results reveal that the dc bus voltage stability is significantly improved with the proposed method.

Integrated DC Electrical Machine for All-Electric and Hybrid-Electric Vehicles

In the paper a concept and physical and mathematical models of the integrated DC electrical machine for automotive vehicles with the electromechanical or hybrid-electromechanical drive is presented. The DC electrical machine under consideration is a double DC-AC/AC-DC commutator synchronous motor/generator with electronic commutators and an electromagnetic exciter on a common shaft. The paper contains a short description of the mechatronic control system of this DC electrical machine, operating both as an electromechanical motor and/or a mechanoelectrical generator. Besides, the oscillograms from the laboratory tests of this electrical machine are also presented. The analysis of the operation of this DC electrical machine is facilitated by the physical and mathematical models presented in the paper. Thanks to the use of an innovative electronic AC-DC commutator, operating as a transistor AC-DC rectifier, the energy efficiency and reliability of this electrical machine was improved during operation as a mechanoelectrical generator.

Autonomous Power Control and Management Between Standalone DC Microgrids

Renewable integrated dc Microgrids (DCMGs) are gaining popularity by feeding remote locations in qualitative and quantitative manner. Reliability of autonomous dc microgrids depend on battery capacity and size due to stochastic behavior of renewables. Over charging and discharging scenarios compel the microgrid into insecure zone. Increasing the storage capacity is not an economical solution because of additional maintenance and capital cost. Thus, interconnecting neighbor microgrids increases virtual storing and discharging capacity when excess power and deficit scenario arises respectively in any of the DCMG. Control strategy plays vital role in regulating the power within and between microgrids. Power control and management technique is developed based on bus signaling method to govern sources, storages, and loads to achieve effective coordination and energy management between microgrids. Proposed scheme is simple and reliable since bus voltages are utilized in shifting the modes without having dedicated communication lines. Proposed scheme is validated through real time simulation of two autonomous dc grids in real time digital simulator (RTDS) and its results are verified by hardware experimentation.

An Integrated DC–DC Boost Converter Having Low-Output Ripple Suitable for Analog Applications

This paper presents an integrated boost converter having very low output voltage ripple making it suitable for analog applications, which are sensitive to supply noise. Architecturally, the converter consists of a conventional boost converter followed by an L–C filter, which drastically reduces the output ripple. The L–C filter has been realized using 30-nH bondwire inductance and 0.54-nF on-chip capacitance. The converter switches at 118 MHz and produces a regulated 3.2-V output from an input voltage ranging from 1.0 to 2.7 V. The converter is able to deliver up to 65-mA current for input voltage $\geq$ 2.4 V. The prototype has been implemented in 0.18- $\mu$ m standard digital CMOS process and the entire design consumes only 0.52-mm $^2$ chip area resulting in a maximum power density of 0.387 W/mm $^2$ . Peak efficiency of the converter is 77.4% at 32.2-mA current for 2.7-V input supply. The measured maximum output ripple noise is 21 mV that is less than 0.65% of the regulated output voltage.

0.45 v and 18 μA/MHz MCU SOC with Advanced Adaptive Dynamic Voltage Control (ADVC)

An ultra-low-power MicroController Unit System-on-Chip (MCU SOC) is described with integrated DC to DC power management and Adaptive Dynamic Voltage Control (ADVC) mechanism. The SOC, designed and fabricated in a 40 nm ULP standard CMOS technology, includes the complete Synopsys ARC EM5D core MCU, featuring a full set of DSP instructions and minimizing energy consumption at a wide range of frequencies: 312 K–80 MHz. A number of unique low voltage digital libraries, comprising of approximately 300 logic cells and sequential elements, were used for the MCU SOC design. On-die silicon sensors were utilized to continuously change the operating voltage to optimize power/performance for a given frequency and environmental conditions, and also to resolve yield and life time problems, while operating at low voltages. A First Fail (FFail) mechanism, which can be digitally and linearly controlled with up to 8 bits, detects the failing SOC voltage at a given frequency. The core operates between 0.45–1.1 V volts with a direct battery connection for an input voltage of 1.6–3.6 V. Measurement results show that the peak energy efficiency is 18μW/MHz. A comparison to state-of-the-art commercial SOCs is presented, showing a 3–5× improved current/DMIPS (Dhrystone Million Instructions per second) compared to the next best chip.

Online Built-In Self-Test of High Switching Frequency DC–DC Converters Using Model Reference Based System Identification Techniques

A built-in self-test (BIST) technique that enables tracking of loop parameters of integrated DC–DC converters without affecting the normal mode of operation is presented. A digital pseudo-noise based stimulus and a mixed signal cross-correlation based analysis technique is used to derive on-chip impulse response, with minimum computational requirements in comparison to a digital correlator approach. Using measured impulse response, open-loop phase margin and closed-loop unity-gain frequency are estimated within 5.2% and 4.1% error, respectively, for the load current range of 30 mA to 200 mA. Converter parameters, such as natural frequency, $Q$ -factor, and center frequency are estimated within 3.6%, 4.7%, and 3.8% error, respectively, over load inductance of 4.7 $\mu \text{H}$ to 10.3 $\mu \text{H}$ , and filter capacitance of 200 nF to 400 nF. A 5 MHz switching frequency, 5 V to 8.125 V input voltage range, voltage-mode controlled DC-DC buck converter is designed for the proposed model reference based parametric and non-parametric BIST analysis. The converter output voltage range is 3.3 V to 5 V and supported maximum load current is 450 mA with a peak efficiency of 87.93%. The proposed converter is fabricated on a 0.6 $\mu \text{m}$ 6 layer-metal SOI technology with a die area of 9 mm2. The system identification circuitry occupies 3.8% of the converter area with 530 $\mu \text{A}$ quiescent current during operation.