Showing papers in "IEEE Transactions on Power Electronics in 2012"
TL;DR: In this paper, a detailed analysis of the main operation modes and control structures for power converters belonging to micro-grids is carried out, focusing mainly on grid-forming, grid-feeding, and grid-supporting configurations.
Abstract: The enabling of ac microgrids in distribution networks allows delivering distributed power and providing grid support services during regular operation of the grid, as well as powering isolated islands in case of faults and contingencies, thus increasing the performance and reliability of the electrical system. The high penetration of distributed generators, linked to the grid through highly controllable power processors based on power electronics, together with the incorporation of electrical energy storage systems, communication technologies, and controllable loads, opens new horizons to the effective expansion of microgrid applications integrated into electrical power systems. This paper carries out an overview about microgrid structures and control techniques at different hierarchical levels. At the power converter level, a detailed analysis of the main operation modes and control structures for power converters belonging to microgrids is carried out, focusing mainly on grid-forming, grid-feeding, and grid-supporting configurations. This analysis is extended as well toward the hierarchical control scheme of microgrids, which, based on the primary, secondary, and tertiary control layer division, is devoted to minimize the operation cost, coordinating support services, meanwhile maximizing the reliability and the controllability of microgrids. Finally, the main grid services that microgrids can offer to the main network, as well as the future trends in the development of their operation and control for the next future, are presented and discussed.
2,621 citations
TL;DR: In this article, a battery/ultracapacitor hybrid energy storage system (HESS) is proposed for electric drive vehicles including electric, hybrid electric, and plug-in hybrid electric vehicles.
Abstract: In this paper, a new battery/ultracapacitor hybrid energy storage system (HESS) is proposed for electric drive vehicles including electric, hybrid electric, and plug-in hybrid electric vehicles. Compared to the conventional HESS design, which uses a larger dc/dc converter to interface between the ultracapacitor and the battery/dc link to satisfy the real-time peak power demands, the proposed design uses a much smaller dc/dc converter working as a controlled energy pump to maintain the voltage of the ultracapacitor at a value higher than the battery voltage for the most city driving conditions. The battery will only provide power directly when the ultracapacitor voltage drops below the battery voltage. Therefore, a relatively constant load profile is created for the battery. In addition, the battery is not used to directly harvest energy from the regenerative braking; thus, the battery is isolated from frequent charges, which will increase the life of the battery. Simulation and experimental results are presented to verify the proposed system.
1,008 citations
TL;DR: In this article, the authors proposed an improved maximum power point tracking (MPPT) method for the photovoltaic (PV) system using a modified particle swarm optimization (PSO) algorithm.
Abstract: This paper proposes an improved maximum power point tracking (MPPT) method for the photovoltaic (PV) system using a modified particle swarm optimization (PSO) algorithm. The main advantage of the method is the reduction of the steady- state oscillation (to practically zero) once the maximum power point (MPP) is located. Furthermore, the proposed method has the ability to track the MPP for the extreme environmental condition, e.g., large fluctuations of insolation and partial shading condition. The algorithm is simple and can be computed very rapidly; thus, its implementation using a low-cost microcontroller is possible. To evaluate the effectiveness of the proposed method, MATLAB simulations are carried out under very challenging conditions, namely step changes in irradiance, step changes in load, and partial shading of the PV array. Its performance is compared with the conventional Hill Climbing (HC) method. Finally, an experimental rig that comprises of a buck-boost converter fed by a custom-designed solar array simulator is set up to emulate the simulation. The soft- ware development is carried out in the Dspace 1104 environment using a TMS320F240 digital signal processor. The superiority of the proposed method over the HC in terms of tracking speed and steady-state oscillations is highlighted by simulation and experimental results.
851 citations
TL;DR: In this paper, an extended phase-shift (EPSC) control of IBDC for power distribution in microgrid is proposed, which not only expands regulating range of transmission power and enhances regulating flexibility, but also reduces current stress and improves the system efficiency.
Abstract: This paper points out a phenomenon of power backflow in traditional phase-shift (TPS) control of isolated bidirectional full-bridge DC-DC converter (IBDC), and analyzes the effects which backflow power act on power circulating flow and current stress. On this basis, the paper proposes a novel extended-phase-shift (EPS) control of IBDC for power distribution in microgrid. Compared with TPS control, EPS control not only expands regulating range of transmission power and enhances regulating flexibility, but also reduces current stress and improves the system efficiency. The operation principle of EPS control and the operation modes of IBDC are analyzed in the paper. By establishing mathematical models of transmission power, backflow power, and current stress, the paper comparatively analyzes control performances of TPS and EPS control. At last, experimental results verify the excellent performance of EPS control and correctness of the theoretical analysis.
623 citations
TL;DR: In this article, a comprehensive review on the unified power quality conditioner (UPQC) to enhance the electric power quality at distribution levels is presented, which is intended to present a broad overview on the different possible UPQC system configurations for single-phase and three-phase (threewire and four-wire) networks, different compensation approaches, and recent developments in the field.
Abstract: This paper presents a comprehensive review on the unified power quality conditioner (UPQC) to enhance the electric power quality at distribution levels. This is intended to present a broad overview on the different possible UPQC system configurations for single-phase (two-wire) and three-phase (three-wire and four-wire) networks, different compensation approaches, and recent developments in the field. It is noticed that several researchers have used different names for the UPQC based on the unique function, task, application, or topology under consideration. Therefore, an acronymic list is developed and presented to highlight the distinguishing feature offered by a particular UPQC. In all 12 acronyms are listed, namely, UPQC-D, UPQC-DG, UPQC-I, UPQC-L, UPQC-MC, UPQC-MD, UPQC-ML, UPQC-P, UPQC-Q, UPQC-R, UPQC-S, and UPQC-VA. More than 150 papers on the topic are rigorously studied and meticulously classified to form these acronyms and are discussed in the paper.
620 citations
TL;DR: A new grid synchronization method for three-phase three-wire networks, namely dual second-order generalized integrator (SOGI) frequency-locked loop, based on two adaptive filters, is presented, able to perform an excellent estimation of the instantaneous symmetrical components of the grid voltage under unbalanced and distorted grid conditions.
Abstract: Grid synchronization algorithms are of great importance in the control of grid-connected power converters, as fast and accurate detection of the grid voltage parameters is crucial in order to implement stable control strategies under generic grid conditions. This paper presents a new grid synchronization method for three-phase three-wire networks, namely dual second-order generalized integrator (SOGI) frequency-locked loop. The method is based on two adaptive filters, implemented by using a SOGI on the stationary αβ reference frame, and it is able to perform an excellent estimation of the instantaneous symmetrical components of the grid voltage under unbalanced and distorted grid conditions. This paper analyzes the performance of the proposed synchronization method including different design issues. Moreover, the behavior of the method for synchronizing with highly unbalanced grid is proven by means of simulation and experimental results, demonstrating its excellent performance.
620 citations
TL;DR: In this paper, the authors investigated how the arm currents and capacitor voltages interact when the submodules are connected and bypassed in a sinusoidal manner, and derived the analytical expression for the arm current.
Abstract: The fundamental frequency component in the arm currents of a modular multilevel converter is a necessity for the operation of the converter, as is the connection and bypassing of the submodules. Inevitably, this will cause alternating components in the capacitor voltages. This paper investigates how the arm currents and capacitor voltages interact when the submodules are connected and bypassed in a sinusoidal manner. Equations that describe the circulating current that is caused by the variations in the total inserted voltage are derived. Resonant frequencies are identified and the resonant behaviour is verified by experimental results. It is also found that the effective values of the arm resistance and submodule capacitances can be extracted from the measurements by least square fitting of the analytical expressions to the measured values. Finally, the analytical expression for the arm currents is verified by experimental results.
511 citations
TL;DR: In this article, an improved single-phase inverter topology is presented to eliminate the common-mode leakage current in the transformerless photovoltaic grid-connected system, and the high efficiency and convenient thermal design are achieved thanks to the decoupling of two additional switches connected to the dc side.
Abstract: To eliminate the common-mode leakage current in the transformerless photovoltaic grid-connected system, an improved single-phase inverter topology is presented. The improved transformerless inverter can sustain the same low input voltage as the full-bridge inverter and guarantee to completely meet the condition of eliminating common-mode leakage current. Both the unipolar sinusoidal pulsewidth modulation (SPWM) as well as the double-frequency SPWM control strategy can be applied to implement the three-level output in the presented inverter. The high efficiency and convenient thermal design are achieved thanks to the decoupling of two additional switches connected to the dc side. Moreover, the higher frequency and lower current ripples are obtained by adopting the double-frequency SPWM, and thus the total harmonic distortion of the grid-connected current are reduced greatly. Furthermore, the influence of the phase shift between the output voltage and current, and the influence of the junction capacitances of the power switches are analyzed in detail. Finally, a 1-kW prototype has been simulated and tested to verify the theoretical analysis of this paper.
507 citations
TL;DR: In this paper, a generalized mathematical model for MMC in HVDC applications under balanced and unbalanced grid conditions is presented, where the dynamics of the positive-, negative-, and zero-sequence components are derived from the model.
Abstract: The modular multilevel converter (MMC) is an emerging and attractive topology for the high-voltage direct-current (HVDC) transmission system. This paper presents a generalized mathematical model for MMC in HVDC applications under balanced and unbalanced grid conditions. The dynamics of the positive-, negative-, and zero-sequence components are derived from the model. Then, a dual current control scheme with positive- and negative-sequence current controllers is applied to MMC. The power controller to eliminate negative-sequence current components and the other one to eliminate double-line-frequency voltage ripple are compared. Moreover, a zero-sequence current controller is proposed in addition to the positive- and negative-sequence current controllers. Time-domain simulations on a 61-level MMC-HVDC test system are performed in the PSCAD/EMTDC software environment. The results demonstrate that the MMC-HVDC system with or without converter transformer is able to operate under unbalanced conditions by the use of the proposed control scheme.
490 citations
TL;DR: In this article, an optimal modulation scheme that enables minimum conduction and copper losses is presented for a bidirectional dual active bridge (DAB) dc-dc converter, which is employed for an automotive application.
Abstract: An optimal modulation scheme that enables minimum conduction and copper losses is presented for a bidirectional dual active bridge (DAB) dc-dc converter. The considered converter system is employed for an automotive application and comprises of a high voltage (HV) port with port voltage V1, 240V ≤ V1 ≤ 450 V, and a low voltage (LV) port with port voltage V2, 11 V ≤ V2 ≤ 16 V; the rated output power is 2 kW. The closed-form expressions for the optimal control parameters are derived and implementation details are presented in order to facilitate the direct application to a given DAB converter. The paper further details the properties of the presented modulation scheme with respect to switching losses. Experimental results confirm a considerable increase of the converter efficiency achieved with the proposed optimal modulation scheme, compared to the efficiency obtained with conventional phase shift modulation. The efficiency increase is most distinct at V1=450V and V2 = 11V with an increase from 78.6% to 90.6% at 1 kW output power and from 85.9% to 90.7% at rated output power as compared to conventional phase shift modulation.
476 citations
TL;DR: In this article, a ripple power port is proposed to manage energy storage and decouple capacitor ripple from power ripple, allowing the designer to make a choice of capacitor voltage independent of other system voltages.
Abstract: Converters with a dc port and a single-phase ac port must store energy to buffer the inherent double-frequency power flow at the ac port. The minimum energy storage required to isolate the power ripple from the dc port is presented, and leads to the minimum capacitance required for converters that use capacitive energy storage. This paper presents a ripple power port to manage energy storage and decouple capacitor ripple from power ripple. A ripple power port allows the designer to make a choice of capacitor voltage independent of other system voltages. A combination of an ac link converter and a ripple power port leads to a dramatic increase in reliability: it is shown that converters with nominal ratings up to 200 W can be designed with expected mean-time-between-failure ratings on the order of 1.4 × 106 h-sufficient for hundred-year operation in long-life applications such as photovoltaic converters and LED lamps. This large increase in life is achieved with minimal extra cost.
TL;DR: In this article, a synthesis of different electrical methods used to estimate the temperature of power semiconductor devices is presented, including voltage under low current levels, threshold voltage, voltage under high current level, gate-emitter voltage, saturation current, and switching times.
Abstract: This paper proposes a synthesis of different electrical methods used to estimate the temperature of power semiconductor devices. The following measurement methods are introduced: the voltage under low current levels, the threshold voltage, the voltage under high current levels, the gate-emitter voltage, the saturation current, and the switching times. All these methods are then compared in terms of sensitivity, linearity, accuracy, genericity, calibration needs, and possibility of characterizing the thermal impedance or the temperature during the operation of the converter. The measurement of thermo-sensitive parameters of wide bandgap semiconductors is also discussed.
TL;DR: In this paper, the design and performance of a 6-kW, full-bridge, bidirectional isolated dc-dc converter using a 20-kHz transformer for a 53.2-V, 2-kWh Li-ion battery energy storage system was described.
Abstract: This paper describes the design and performance of a 6-kW, full-bridge, bidirectional isolated dc-dc converter using a 20-kHz transformer for a 53.2-V, 2-kWh lithium-ion (Li-ion) battery energy storage system. The dc voltage at the high-voltage side is controlled from 305 to 355 V, as the battery voltage at the low-voltage side (LVS) varies from 50 to 59 V. The maximal efficiency of the dc-dc converter is measured to be 96.0% during battery charging, and 96.9% during battery discharging. Moreover, this paper analyzes the effect of unavoidable dc-bias currents on the magnetic-flux saturation of the transformer. Finally, it provides the dc-dc converter loss breakdown with more focus on the LVS converter.
TL;DR: In this paper, the authors proposed a full-order continuous-time average model using the dc terms and first order terms of transformer current and capacitor voltage as state variables, resulting in a thirdorder model, if capacitor equivalent series resistance (ESR) is not considered, and a sixth-order model if ESR is considered.
Abstract: Full-order continuous-time average modeling and dynamic analysis of bidirectional dc-dc dual active bridge (DAB) converters are studied. The transformer current in DAB converter is purely ac, making continuous-time modeling difficult. The proposed full-order continuous-time average model uses the dc terms and first order terms of transformer current and capacitor voltage as state variables, resulting in a third-order model, if capacitor equivalent series resistance (ESR) is not considered, and a sixth-order model if ESR is considered. A control-to-output-voltage transfer function is derived for DAB converters. Experimental results confirm that the proposed model correctly predicts the small-signal frequency response and an even more accurate prediction can be obtained if capacitor ESR is taken into account.
TL;DR: In this article, the authors proposed an enhanced control strategy that estimates the reactive power control error through injecting small real power disturbances, which is activated by the lowbandwidth synchronization signals from the central controller.
Abstract: For the operation of autonomous microgrids, an important task is to share the load demand using multiple distributed generation (DG) units. In order to realize satisfied power sharing without the communication between DG units, the voltage droop control and its different variations have been reported in the literature. However, in a low-voltage microgrid, due to the effects of nontrivial feeder impedance, the conventional droop control is subject to the real and reactive power coupling and steady-state reactive power sharing errors. Furthermore, complex microgrid configurations (looped or mesh networks) often make the reactive power sharing more challenging. To improve the reactive power sharing accuracy, this paper proposes an enhanced control strategy that estimates the reactive power control error through injecting small real power disturbances, which is activated by the low-bandwidth synchronization signals from the central controller. At the same time, a slow integration term for reactive power sharing error elimination is added to the conventional reactive power droop control. The proposed compensation method achieves accurate reactive power sharing at the steady state, just like the performance of real power sharing through frequency droop control. Simulation and experimental results validate the feasibility of the proposed method.
TL;DR: In this paper, the authors proposed a new carrier-based pulsewidth modulation (CB-PWM) strategy for a three-level neutral-point-clamped (NPC) converter, which is based on a zero-sequence voltage injection.
Abstract: Performance of a carrier-based pulsewidth modulation (CB-PWM) strategy can be improved by the inclusion of a zero-sequence voltage in the modulation-reference signal. This paper proposes a new CB-PWM strategy for a three-level neutral-point-clamped (NPC) converter, which is based on a zero-sequence voltage injection. By inclusion of the zero-sequence voltage, the sinusoidal-modulation reference is modified to 1) carry out the voltage-balancing task of the dc-link capacitors, with no additional control effort, 2) reduce the switching losses, and 3) reduce the low-frequency voltage oscillations of the neutral point. The proposed strategy is an alternative approach to the nearest three-vector (NTV) space-vector modulation (SVM) strategy and is obtained by the analysis of the NTV-SVM strategy and establishing a correlation between the NTV-SVM and the CB-PWM strategies. The salient features of the proposed scheme, as compared with the NTV-SVM strategy, are: 1) its reduced computational processing time which is attractive for digital implementation and 2) its reduced switching losses. Compared with the existing CB-PWM strategies, the proposed strategy offers 1) capability to balance the capacitor voltages and reduce the NP voltage oscillations and 2) reduced switching losses. Performance of the proposed CB-PWM strategy for a three-level NPC converter based on time-domain simulation studies in the MATLAB/SIMULINK environment is evaluated and also experimentally verified.
TL;DR: In this paper, the authors investigated both the conventional and a novel vector control mechanism for a PMSG wind turbine that has two side-by-side voltage source pulsewidth modulation converters.
Abstract: With the advances of power electronic technology, direct-driven permanent magnet synchronous generators (PMSGs) have increasingly drawn the interest of wind turbine manufacturers. At the present time, a commercial PMSG wind turbine primarily makes use of a passive rectifier followed by an insulated gate bipolar transistor (IGBT) inverter. Although a PMSG wind turbine with two back-to-back voltage source IGBT converters is considered more efficient, it has not been widely adopted by the wind power industry. This paper investigates both the conventional and a novel vector control mechanism for a PMSG wind turbine that has two side-by-side voltage source pulsewidth modulation converters. The proposed approach is based on a direct-current vector control mechanism for control of both machine- and grid-side converters of a PMSG wind turbine. Then, an optimal control strategy is developed for integrated control of PMSG maximum power extraction, reactive power, and grid voltage support controls. A transient system simulation using SimPowerSystem is built to investigate the performance of the conventional and proposed control techniques for the PMSG wind turbine under steady and gusty wind conditions. This paper shows that when using the direct-current vector control structure, a PMSG system has excellent performance in various aspects.
TL;DR: In this paper, an improved finite control set-model predictive control (FCS-MPC) with an optimized weighting factor is presented, which is based on dividing the control interval into two parts.
Abstract: In this paper, an improved finite control set-model predictive control (FCS-MPC) with an optimized weighting factor is presented. The main goal of this paper is reducing the torque ripples when the FCS-MPC is implemented by means of the two-level inverter. For this purpose, the weighting factor is calculated via an optimization method. The optimization is based on dividing the control interval into two parts: active time for applying the active voltage vectors and zero time for applying the zero voltage. With this technique, the torque ripple is calculated as a function of weighting factor and it is optimized. The method is validated by simulations and experiments, using two-level inverter, at two speed regions (nominal speed and low speed). The results are compared with conventional FCS-MPC.
TL;DR: The LLCL filter as mentioned in this paper inserts a small inductor in the branch loop of the capacitor in the traditional LCL filter to compose a series resonant circuit at the switching frequency, which attenuates the switching-frequency current ripple components much better than an LCL filtering.
Abstract: This paper presents a new topology of higher order power filter for grid-tied voltage-source inverters, named the LLCL filter, which inserts a small inductor in the branch loop of the capacitor in the traditional LCL filter to compose a series resonant circuit at the switching frequency. Particularly, it can attenuate the switching-frequency current ripple components much better than an LCL filter, leading to a decrease in the total inductance and volume. Furthermore, by decreasing the inductance of a grid-side inductor, it raises the characteristic resonance frequency, which is beneficial to the inverter system control. The parameter design criteria of the proposed LLCL filter is also introduced. The comparative analysis and discussions regarding the traditional LCL filter and the proposed LLCL filter have been presented and evaluated through experiment on a 1.8-kW-single-phase grid-tied inverter prototype.
TL;DR: In this paper, a generalized closed-loop control (GCC) scheme was proposed for voltage source converters (VSCs) with LC or LCL output filters, which has a singleloop control of inverter output (voltage or current) and two parallel virtual impedance terms using additional measurements.
Abstract: In this paper, a generalized closed-loop control (GCC) scheme is proposed for voltage source converters (VSCs) with LC or LCL output filters. The proposed GCC scheme has a single-loop control of inverter output (voltage or current) and two parallel virtual impedance terms using additional measurements. The virtual impedance can be the equivalent internal impedance or external impedance (or both), depending on their control term and feedback variable selection. The internal impedance term is mainly responsible for providing desired damping to the filter circuit, and the external virtual impedance term can effectively adjust the converter system closed-loop output impedance. As each term in the GCC scheme can be controlled independently, the proposed GCC scheme has great flexibility and can easily realize and explain the performances of the traditional single- and multiloop control schemes and their different variations. Moreover, the GCC scheme provides a distinct physical meaning of each control term, which makes the control parameter tuning more straightforward and robust. Additionally, as shown in this paper, the proposed GCC scheme can tackle some traditionally challenging control objectives by avoiding the harmonics filtering or derivative terms. Experimental results from laboratory VSC prototypes are obtained to validate the proposed GCC scheme.
TL;DR: In this paper, a series battery string or supercapacitor string automatic equalization system based on quasi-resonant switched-Capacitor converter is presented, where all switches are MOSFET and controlled by just a pair of complementary signals in synchronous trigger pattern and the resonant tanks operate alternatively between the two states of charging and discharging.
Abstract: The series battery string or supercapacitor string automatic equalization system based on quasi-resonant switched-capacitor converter is presented in this paper. It realizes the zero-voltage gap between cells and allows maximum energy recovery in a series battery system or supercapacitor system. It not only inherits the advantage of conventional switched-capacitor battery cell balancing system, but also overcomes the drawback of conduction loss, switching loss, and finite voltage difference among battery cells. All switches are MOSFET and controlled by just a pair of complementary signals in synchronous trigger pattern and the resonant tanks operate alternatively between the two states of charging and discharging. Zero-current switching and zero-voltage gap are achieved in this paper. Different resonant tank designs can meet the needs of different balancing time to meet the needs of different energy storage devices. Experimental results indicate that the efficiency of the system is high exceeding 98%. The system is very suitable for balancing used in battery management system.
TL;DR: In this paper, the dc component in the input signal of the phase-locked loop (PLL) and notch filter algorithms applied to filtering and synchronization applications is addressed, based on adding a new loop inside the PLL structure.
Abstract: This paper presents a method for addressing the dc component in the input signal of the phase-locked loop (PLL) and notch filter algorithms applied to filtering and synchronization applications. The dc component may be intrinsically present in the input signal or may be generated due to temporary system faults or due to the structure and limitations of the measurement/conversion processes. Such a component creates low-frequency oscillations in the loop that cannot be removed using filters because such filters will significantly degrade the dynamic response of the system. The proposed method is based on adding a new loop inside the PLL structure. It is structurally simple and, unlike an existing method discussed in this paper, does not compromise the high-frequency filtering level of the concerned algorithm. The method is formulated for three-phase and single-phase systems, its design aspects are discussed, and simulations/experimental results are presented.
TL;DR: This paper presents the Bee optimization method for harmonic elimination in a cascaded multilevel inverter, based on the food foraging behavior of a swarm of a honeybees, which has higher precision and probability of convergence than the genetic algorithm (GA).
Abstract: This paper presents the Bee optimization method for harmonic elimination in a cascaded multilevel inverter. The main objective in selective harmonic elimination pulsewidth modulation strategy is eliminating low-order harmonics by solving nonlinear equations, while the fundamental component is satisfied. In this paper, the Bee algorithm (BA) is applied to a 7-level inverter for solving the equations. The algorithm is based on the food foraging behavior of a swarm of a honeybees and it performs a neighborhood search combined with a random search. This method has higher precision and probability of convergence than the genetic algorithm (GA). MATLAB software is used for optimization and comparison of GA and BA. Simulation results show superiority of BA over GA in attaining accurate global minima and higher convergence rate. Also, its performance in 10 times run is the same as in 1 time run. Finally, for verifying purposes, an experimental study is performed.
TL;DR: In this article, a generalized mode analysis is presented that provides highly accurate prediction on resonant current and voltage behavior and dc gain characteristic, and an approximation method is developed to estimate the peak gain point, which is useful in LLC design.
Abstract: With the advantage of achieving zero voltage switching for a wide input voltage range, the LLC resonant topology has become increasingly popular for use in high power density and high-efficiency power converter applications. However, when the LLC converter is applied to wide input voltage range applications, the widely used fundamental harmonic approximation is incapable of guiding the design due to its inaccuracy. Thus an accurate LLC converter model is desired. In this paper, a generalized mode analysis is presented that provides highly accurate prediction on resonant current and voltage behavior and dc gain characteristic. Also, because operation modes are affected by load, frequency, and gain conditions, the boundaries and distribution of modes are discussed and illustrated. Based on the mode analysis, an approximation method is developed to estimate the peak gain point, which is useful in LLC design. This approximation demonstrates high accuracy within the simulation results. An experimental prototype is built to verify the analysis.
TL;DR: In this paper, a three-input dc-dc boost converter is proposed for hybridizing alternative energy sources such as photovoltaic (PV) source, fuel cell (FC) source and battery.
Abstract: A new three-input dc-dc boost converter is proposed in this paper. The proposed converter interfaces two unidirectional input power ports and a bidirectional port for a storage element in a unified structure. This converter is interesting for hybridizing alternative energy sources such as photovoltaic (PV) source, fuel cell (FC) source, and battery. Supplying the output load, charging or discharging the battery can be made by the PV and the FC power sources individually or simultaneously. The proposed structure utilizes only four power switches that are independently controlled with four different duty ratios. Utilizing these duty ratios, tracking the maximum power of the PV source, setting the FC power, controlling the battery power, and regulating the output voltage are provided. Depending on utilization state of the battery, three different power operation modes are defined for the converter. In order to design the converter control system, small-signal model is obtained in each operation mode. Due to interactions of converter control loops, decoupling network is used to design separate closed-loop controllers. The validity of the proposed converter and its control performance are verified by simulation and experimental results for different operation conditions.
TL;DR: In this paper, a multidevice structure with interleaved control is proposed to reduce the input current ripples, the output voltage ripples and the size of passive components with high efficiency compared with the other topologies.
Abstract: Multiphase converter topologies for use in high-performance applications have received increasing interest in recent years. This paper proposes a novel multidevice interleaved boost converter (MDIBC) that interfaces the fuel cell with the powertrain of hybrid electric vehicles. In this research, a multidevice structure with interleaved control is proposed to reduce the input current ripples, the output voltage ripples, and the size of passive components with high efficiency compared with the other topologies. In addition, low EMI and low stress in the switches are expected. The proposed dc/dc converter is compared to other converter topologies such as conventional boost converter (BC), multidevice boost converter (MDBC), and two-phase interleaved boost converter (IBC) to verify its dynamic performance. Furthermore, a generalized small-signal model is derived for these dc/dc converters, which has not been previously discussed. A digital dual-loop control is designed to achieve the proper regulator for the converters with fast transient response. The dc/dc converter topologies and their controller are designed and investigated by using MATLAB/Simulink. Finally, the proposed converter (MDIBC) is experimentally validated with results obtained from a 30-kW prototype that has been built and tested in our laboratory based on TMS320F2808 DSP. The simulation and experimental results have demonstrated that the proposed converter is more efficient than other dc/dc converter topologies in achieving high performance and reliability for high-power dc/dc converters.
TL;DR: In this paper, a fault-tolerant control scheme for multiphase induction motor drives is presented and assessed, which is valid either in transient or steady-state operating conditions.
Abstract: In this paper, a control scheme for multiphase induction motor drives is presented and assessed. This control scheme ensures the operation of a multiphase drive under an open-circuit phase fault that can occur in one or more phases at the same time. A fault-tolerant control strategy is developed. The mathematical analysis is based on the space vector representation of the multiphase system and is valid either in transient or steady-state operating conditions. The feasibility of the drive is verified by means of experimental tests carried out on a prototype of seven-phase induction motor.
TL;DR: In this article, a summary of published techniques for power conditioning within energy harvesting systems is presented, where the focus is on low power systems, e.g., <;10 mW, for kinetic energy harvesting.
Abstract: In this paper, a summary of published techniques for power conditioning within energy harvesting systems is presented. The focus is on low-power systems, e.g, <;10 mW, for kinetic energy harvesting. Published concepts are grouped according to functionality and results contrasted. The various techniques described are considered in terms of complexity, efficiency, quiescent power consumption, startup behavior, and utilization of the harvester compared to an optimum load. This paper concludes with an overview of power management techniques that aim to maximize the extracted power and the utilization of the energy harvester.
TL;DR: In this paper, the authors gave the detailed theoretical and experimental analyses of the transmission power of the isolated bidirectional dual-active-bridge dc-dc converter under dual-phase shift (DPS) control.
Abstract: Compared to the traditional single-phase-shift control, dual-phase-shift (DPS) control can greatly improve the performance of the isolated bidirectional dual-active-bridge dc-dc converter (IBDC). This letter points out some wrong knowledge about transmission power of IBDC under DPS control in the earlier studies. On this basis, this letter gives the detailed theoretical and experimental analyses of the transmission power of IBDC under DPS control. And the experimental results showed agreement with theoretical analysis.
TL;DR: In this article, a modulation method for the modular multilevel converter is proposed based on a fixed pulse pattern where harmonic elimination methods can be applied to achieve stable operation at the fundamental switching frequency without measuring the capacitor voltages or using any other form of feedback control.
Abstract: This paper presents a new modulation method for the modular multilevel converter. The proposed method is based on a fixed pulse pattern where harmonic elimination methods can be applied. In the proposed modulation method, the pulse pattern is chosen in such a way that the stored energy in each submodule remains stable. It is shown that this can be done at the fundamental switching frequency without measuring the capacitor voltages or using any other form of feedback control. Such a modulation scheme has not been presented before. The theoretical results are verified by both simulations and experimental results. The simulation results show successful operation at the fundamental switching frequency with a larger number of submodules. When a smaller number of submodules are used, harmonic elimination methods may be applied. This is verified experimentally on a converter with eight submodules per phase leg. The experimental results verify that stable operation can be maintained at the fundamental switching frequency while successfully eliminating the fifth harmonic in the ac-side voltage.