Search

This article proposes a novel three-port converter with a fault-tolerant (FT) capability to reconfigure automatically under different switching fault conditions, i.e., open circuit fault (OCF) and short circuit fault (SCF) of the power transistors, and to continue achieving different control objectives such as effective battery charging, maximum power point tracking (MPPT), and output voltage regulation. The proposed fault-tolerant design with a one-level redundancy structure enhances the reliability of traditional three-port converters (TPCs). Experimental results of a laboratory prototype has proven the effectiveness of the proposed converter.

Virtual inertia (VI) control of dc microgrids (dc MG) is a potential solution to the voltage stability issue caused by the intermittency of loads and renewable sources. Existing VI strategies for dc MG rely on a first-order differential equation relating voltage (speed) with current (torque) to control the grid-forming converters that are crucial in an autonomous dc MG. However, the output impedance of these converters can distort the inertial response. Existing research works overcome this by using a feed-forward controller (FFC) necessitating an accurate system model for proper compensation. Hence, in this article, a novel VI scheme based on capacitor current control, which does not rely on any differential equation, is proposed. The proposed VI scheme employs a static gain to restrict the capacitor current for inertia emulation without any additional FFC. Furthermore, the proposed VI scheme is extended to parallel-connected converters to study their steady-state and transient coordination. Finally, the proposed strategy is validated in simulation using MATLAB/Simulink and is also experimentally verified in a laboratory prototype using the TMS320F280049C controller.

To monitor the thermal performance of the battery, the surface temperature (ST) of the battery is normally directly measured by temperature sensors. As the number of battery cells or strings increases, the number of temperature sensors increases proportionally. This increases the cost and reduces the reliability of the battery systems. To solve this problem, this article introduces a method to accurately estimate the ST of lithium-ion batteries using a recurrent neural network (RNN) with gated recurrent unit (GRU). First, this article analyzes the battery ST distribution theory and proves that it is a time series task since the present ST is conditioned on the previous state. Second, a GRU-RNN model is adopted to estimate the battery ST as this model has the ability to automatically encode dependencies in time and accurately estimate the battery ST without using any physical battery models or filters. Third, an improved data normalization method is proposed to enhance the estimation accuracy and robustness. Fourthly, the proposed data normalization method is incorporated into the stacked GRU-RNN to estimate the battery ST from compulsory online signals. The proposed method is verified with LiFePO4 using US06 and Federal Urban Driving Schedule (FUDS) profiles under four fixed ambient temperatures and with LiNiCoAIO2 using a mixed dynamic profiles under varying ambient temperature ranges (from 10 °C to 25 °C). The estimation error using mean absolute error (MAE) is less than 0.2 °C over all the fixed ambient temperature conditions and 0.42 °C over the varying ambient temperature conditions.

Distributed generation systems integrated into the modern electrical grid demand novel circuit architectures that can combine high efficiency and high power density together. The transformerless highly efficient and reliable inverter concept (HERIC) topologies are notable due to their mitigated leakage current concerns, constant common-mode voltage, and high efficiency. Nonetheless, the HERIC-based structures feature a maximum of three-level ac output voltage, forcing the conversion system to integrate large output filters to meet the grid codes. This article introduces a novel HERIC active-clamped converter with bidirectional power flow and full reactive power capabilities that can achieve five-level output voltage. This is accomplished by means of a phase-shifted pulsewidth modulation technique that effectively doubles the apparent switching frequency of the inverter and improves the quality of the injected ac power. Consequently, the topology can achieve higher power conversion efficiency, while using the same or a smaller output filter. To verify the feasibility of the proposed converter, a 2.5-kW SiC-based prototype was built and tested in the laboratory under different operation conditions.

Grid-connected inverters with a multilevel output voltage and an integrated dynamic voltage boosting feature are promising to achieve higher overall efficiency/power density, reduced output filter size, and better power quality. However, the input current of such a single-stage system might be pulsating with low- and high-frequency ripple contents in a single-phase grid-connected application. To tackle this challenge, active power decoupling (APD) can be used to keep the input current flat and reduce the current stress of the devices with an efficient performance. On the other hand, the grid voltage is usually nonideal in practice, polluted with the harmonics. This causes additional complexity in the closed-loop control system to maintain the injected power quality. The aim of this article is to apply a tailored closed-loop APD control on a recently proposed single-source single-stage switched-boost (SB) five-level converter leading to further enhancing its overall efficiency without adding any extra circuit components. A distinctive feature of the proposed solution is using a single proportional-resonant controller with a filtered feedforward term to achieve APD, even under a distorted grid voltage condition. This solution can also be applied to other single-stage SB-based converters as long as their input current before integration of the APD control contains a low-frequency ripple content. A 2-kW SiC-based prototype is built to validate the feasibility and accurate performance of the proposed method via experiments when connected to a grid with harmonic pollution.

The impact of dust on photovoltaic (PV) panel output power performance and energy generation is investigated in this study. The characteristic of the PV panel is analyzed for the dusted and clean panel and then compared with similar PV panels that have been affected by dust for a long time in the south of Jordan in the middle of the desert. The examined PV panels, which were uncleaned for two months, show 13.08% less energy generation compared to clean panels where, some panels suffer from hot spots and cracks after six months. The cell temperature of the cracked and dusted PV panels is increased. A string of four PV panels containing three cracked panels generates 20% less energy than the sum of the generated power from the panels individually.

Model predictive control strategy is an advanced control algorithm for bidirectional active and reactive power flow in electric vehicles. However, tuning the weighting factor is a time-consuming process and its value is constant for various working conditions. To solve this problem, fuzzy control is applied to generate an adaptive weighting factor to meet all unexpected requirements. A two-stage bidirectional charger is built in Matlab/Simulink with the proposed fuzzy model predictive control. Simulation results show that dynamic performance can be achieved in the proposed method. The total harmonic distortion of the grid current is limited to 5%. The weighting factor can be adjusted online according to different demands. No tuning procedure of the weighting factor is required.

Transformerless grid-connected inverters with highly efficient and reliable inverter concept (HERIC) and positive-negative neutral point-clamped (PN-NPC) circuit configurations exhibit excellent performance in terms of overall efficiency, common-mode voltage, and alleviated leakage current concern. These inverters are designed to generate only a three-level (3L) output voltage waveform, thereby reducing the power density of a conversion system. On the other hand, it is well-known that increasing the inverter output voltage levels entails the reduction of the output filter size. In this regard, this article aims to develop a five-level (5L) inverter output voltage for the improved versions of HERIC-clamped and original PN-NPC inverters. This is achieved with either phase-shifted or level-shifted pulse width modulation technique leading to further quality improvement of ac voltage and current waveforms through increasing the number of output voltage levels. Therefore, a much smaller output filter size can be utilized, while the overall efficiency of the entire system is enhanced. Two laboratory-built SiC-based prototypes for both the proposed HERIC-clamped (1.8 kW) and PN-NPC-5L (2 kW) inverters have been fabricated to show the feasibility and effectiveness of the proposed solution via experiments.

In this article, we present a family of multilevel converters with the single-stage dynamic voltage-boosting feature, reduced number of circuit components, modular structure, bidirectional operation, continuous input current, and acceptable overall efficiency. The proposed structure is based on a three-level single-stage boost integrated inverter with an embedded quasi-H-bridge (QHB) cell. It is comprised of five unidirectional power switches and a floating capacitor. By differential connection of two or three QHB cells and with the aim of a single inductor/input dc source, several derived topologies for both the single and three-phase applications with different multilevel output voltage performances have been achieved. The aforementioned advantages make this converter a suitable candidate for renewable energy applications. Theoretical analysis, design consideration, comparative study, and several experimental results for a 3-kW laboratory-built system are presented to validate the effectiveness and feasibility of this proposal.

The voltage regulation of a grid-tied PV system is constantly perturbed for the maximum power point tracking (MPPT), the transients of which determine the dynamic MPPT efficiency. Meanwhile, the PV-link voltage ripple coupled from the DC to single-phase AC power conversion adversely affects the static MPPT efficiency. Thus, optimal dynamic and steady-state performance is necessary to maximize the solar energy harvest. This brief proposes a novel adaptive mechanism preserving the advantages of two observers: the classical extended state observer and reduced-order generalized proportional integral observer. Simulation and experimental results prove the enhanced performance regarding the overshoot-free fast transient response and steady state against disturbances, even with small input capacitance. Meanwhile, the observer switching happens seamlessly through the proposed mechanism, which is confirmed analytically and experimentally.

Complex coefficient filters (CCFs) are widely used for phase-locked loop (PLL) in three-phase power systems, while its usage is largely sparse in the single-phase domain. Single-phase CCF-PLLs so far reported in the literature do not yield satisfactory performances at off-nominal frequency conditions, which is a crucial PLL attribute. Whether they are a suitable filtering technique of choice for single-phase PLL is yet to be formally documented in a methodological way. In this regard, this article derives an enhanced version of the single-phase CCF-PLL (ECCF-PLL), which is able to provide accurate estimation of grid parameters in dynamically changing grid frequency environment. The proposed ECCF-PLL is then numerically and experimentally compared with few other single-phase PLLs to gauge its efficacy and suitability. The test shows the advantage of harmonic robustness from ECCF-PLL, which is specifically useful in a weak grid.

This paper presents a model predictive sliding control (MPSC) strategy with the dynamic reference tracking for cascaded H-bridge multilevel converters. The nonlinear predicted sliding mode control (PSMC) and linear model predictive control (MPC) are combined as a two-level cascaded control structure. The proposed approach aims to get rid of time-consuming tuning to reach the good performance in the presence of uncertainties and disturbances, such as proportional-integral (PI). The MPC scheme is designed to predict the future optimal current and voltage vectors with a designed cost function. The high level PSMC algorithm is proposed for the dynamic current reference with less chattering problems. The stability of the proposed strategy is analyzed with the Lyapunov direct method. The design principle of the system parameters is introduced with a step-by-step tuning procedure. With the proposed method, the response time can be reduced from 60 to 30 ms during the start-up conditions in the simulation tests. The overshoot of the cell voltages can be eliminated with low harmonics current and dc-link voltage targets tracking. The validity and effectiveness of the proposed method are implemented by the experimental tests on a laboratory two-cell CHB converter. Compared with the PI-based MPC approach, the current total harmonic distortion can be reduced and the DC side performance, including overshoot/undershoot and response speed, can be improved.

The software-assisted reliability assessment of power electronic converters is increasingly important due to its multi-domain nature and extensive parametric calculations. The rainflow counting algorithm is gaining popularity for its low relative error in device lifetime estimation. Nevertheless, the offline operation of the algorithm prevents most simulation software packages considering other parameters for the device under study, such as aging and the current state of health in the estimation, as it requires a complete loading profile to run recursive comparison. This also brings difficulties in realization in circuit simulators such as SPICE. To tackle the issue, an in-the-loop circuit-based rainflow counting algorithm is proposed in this paper, and applied to estimate the consumed lifetime of the MOSFET in a boost converter for illustration. Instantaneous electrical and thermal performances, and the accumulated stress of the device can be monitored. Not only does this assist in evaluating the state of health of a device, but also allows the possibility of integrating the aging into the lifetime evaluation. The method follows the four-point rainflow counting algorithms, which continuously compares three adjacent temperature fluctuations (Formula presented.) to select full cycles for two rounds, and the remaining cycles are counted as half cycles. To validate the performance, a comparative analysis in terms of counting accuracy and simulation speed was performed alongside the proposed method, MATLAB® and also with a well-accepted half-cycle counting method. Reported results show that the proposed method has an improved counting accuracy compared to the half-cycle counting from 24% to 3.5% on average under different load stresses and length conditions. The accuracy can be effectively improved by a further 1.3–2% by adding an extra comparison round.

Recently, a photovoltaic (PV) emulator based on a combination of a constant current source and a semiconductor string, i.e., transistors or diodes, has demonstrated much faster dynamics than switching mode power supply (SMPS) based solution and shown also compatible performance with that of a real PV system. While it has high power efficiency at the maximum power point (MPP), the power loss of the emulator increases beyond the MPP and is at the highest at the open-circuit voltage (OCV) operation condition. This paper presents a hybrid solution where the semiconductor string works in the current-source region of the I-V curve and a new switching circuit, which sits in parallel with the semiconductor string, activates in the voltage-source region. Experimental results show that the efficiency and temperature of the PV emulator based on transistor string alone configuration reach 4.8% and 93.5°C, respectively, in the worst-case scenario, i.e., OCV condition, compared to 88.3% and 26.3°C, respectively, for the proposed solution. The switching circuit handles only a fraction of the rated emulator power and has much narrower control bandwidth requirement than pure switching converter based solution. A new control algorithm is proposed to manage the transition between the two regions seamlessly.

Single-inductor multi-input single-output (SI-MISO) switching DC-DC power converter architecture is a cost effective solution to applications where multiple input sources are required to be managed with a limited space and cost. This paper presents a new time-multiplexed hysteretic control (TMHC) scheme for SI-DISO topology to decouple the power sharing among two input sources. Unlike previously reported solutions with discontinuous conduction or pseudo-continuous conduction operation of the inductor, this paper focuses on how to keep the inductor current in a continuous conduction mode (CCM) and proposed a control scheme with considerably lower ripple current with fast transition time upon switching and higher efficiency. The mathematical proof using the expressions of inductor ripple current, comparison between efficiency and transition time from one level to other, is derived. Additionally, a low-cost analog circuitry has been implemented to incorporate the proposed control scheme. Experimental results from the hardware prototype are given to verify the proposed control scheme.

All-pass filter (APF) offers a simpler implementation for orthogonal signal generation (OSG) and has widely featured in single-phase phase locked loop (PLL) applications. However, they have two prominent issues, the absence of filtering capability and reliance on grid frequency information for yielding 90° phase shifted signal. This paper proposes an enhanced APF-PLL based on frequency fixed configuration for abnormal grid voltage scenarios addressing both the aforementioned concerns. The suggested structure utilizes a modified transformation for attaining frequency-independent APF-PLL, while a frequency-fixed bandpass filter (BPF) is appended as a prefilter to serve the filtering objective. Thus obtained PLL structure, is then evaluated against some recently proposed OSG-PLLs. The simulation and experimental results demonstrate improved performance (dynamic and steady-state) in different operating scenarios.

This paper presents the four-quadrant operation modes of bidirectional chargers for electric vehicles (EVs) framed in smart car parks. A cascaded model predictive control (MPC) scheme for the bidirectional two-stage off-board chargers is proposed. The controller is constructed in two stages. The model predictive direct power control for the grid side is applied to track the active/reactive power references. The model predictive direct current control is proposed to achieve constant current charging/discharging for the EV load side. With this MPC strategy, EV chargers are able to transmit the active and reactive powers between the EV batteries and the power grid. Apart from exchanging the active power, the vehicle-for-grid (V4G) mode is proposed, where the chargers are used to deliver the reactive power to support the grid, simultaneously combined with grid-to-vehicle or vehicleto-grid operation modes. In the V4G mode, the EV battery functions as the static var compensator. According to the simulation results, the system can operate effectively in the full control regions of the active and reactive power (PQ) plane under the aforementioned operation modes. Fast dynamic response and great steady-state system performances can be verified through various simulation and experimental results.

A model predictive control (MPC) strategy based on optimal switching sequence concepts is presented for direct power control of grid-connected three-level neutral-point clamped converters. The proposed control strategy explicitly considers the modulator in its formulation along with the model of the system. Through two well-formulated optimal control problems, the proposed strategy is shown to optimally achieve control of the average trajectory of the active and reactive powers as well as the dc-link capacitor voltages without using weighting factors to tradeoff both control targets. Experimental results demonstrate this strategy produces improved steady-state performance with a well-defined output voltage spectrum and fixed-switching frequency while maintaining the inherent fast dynamic responses of MPC strategies.

Lifetime estimation of power semiconductor devices have been widely investigated to improve the reliability and reduce the cost of maintenance of power converters. However in most reported work, the aging effect is not considered in the lifetime evaluation process due to the omission or limitation of thermal cycle counting method. Additionally, the electrical/thermal simulation and lifetime estimation are usually implemented in different simulators/platforms, for the same reason. Thus, to tackle these problems, a concise but comprehensive MOSFET model that enables electro-thermal modeling, aging and lifetime estimation on LTspice® circuit simulator is proposed in this paper. The idea comes from the fact that, MOSFET on-state resistance R_{ds,on} is not only temperature dependent, but also widely accepted as the device failure precursor. In other words, as it carries critical information about instantaneous temperature and aging progress. Hence, co-simulation can be achieved by constructing electrical, thermal, and aging and lifetime sub-modules exclusively first, and using R_{ds,on} , to build linkages among them. Averaged modeling technique is adopted due to the ease of establishing links among these three sub-modules, and fast simulation speed as compared to a switched converter model. Behavioral models are employed to realize the thermal cycles counting, stress accumulation and degradation evaluation. This paper demonstrates that it is possible to use a single simulation software to monitor performances of devices and circuits, and their lifetime estimation simultaneously. High-stress thermal cycling and long-term random mission profiles are applied to verify the correctness of the model and to mimic a 10-year load respectively. An accelerated aging trend can be observed in the long-term mission profile simulation, which is in agreement with the theory. Facilitated by the employment of averaged circuits, the proposed method is a good simulation/analytical tool to

The conventional online battery impedance measurement method works by perturbing the duty cycle of the DC-DC power converter and measuring the response of the battery voltage and current. This periodical duty cycle perturbation will continuously generate large voltage ripples at the output of power converters. These large ripples will not easily be removed due to the high amplitude and wide frequency range and would be a challenge to meet tight output regulation. To solve this problem, this paper presents a new online battery impedance measurement technique by inserting a small switched resistor circuit (SRC) into the converter. The first contribution of this work is that the perturbation source is moved from the main switch to the input-side of the converter, so the ripples are reduced. The analysis and experimental results of the proposed method show a reduction of 16-times compared with the conventional method. The second contribution tackles the possible change of the battery state of charge (SOC) during the online battery measurement process, which will inevitably influence the impedance measurement accuracy. In this proposed method, battery impedance at multiple frequencies can be measured simultaneously using only one perturbation to accelerate measurement speed and minimize possible SOC change. The experimental impedance results coincide with a high-accuracy laboratory battery impedance analyzer.

This paper presents a systematic topological study to derive all possible basic and non-isolated three-port converters (TPCs) using power flow diagrams. Unlike most reported TPCs with one bidirectional port, this paper considers up to two bidirectional ports and provides a comprehensive analytical tool. This tool acts as a framework for all power flow combinations, selection, and design. Some viable converter configurations have been identified and selected for further analysis.

Non-frequency-dependent transfer delay (NTD) approach is one of the simplest and the fastest solution for single-phase AC systems to achieve phase-locked loops (PLLs). It also exhibits immunity to error in estimated quantities in grid frequency variations. However it is susceptible to grid voltage disturbances, such as DC offset and distortions. This paper proposed an improved NTD scheme to achieve both fast dynamic response and operational robustness against abnormal grid conditions. The solution is based on a digital phase lead compensator (PLC), which is cascaded with the MAF inside the PLL control loop to enhance dynamic response and mitigate disturbance, DC offset, and harmonics. The filtering structure is also designed to be adaptive to grid frequency variations. The effectiveness of the proposed solution is verified via simulation and experimental results.

Accurate estimation of grid voltage parameters (phase, frequency and amplitude) from Phase Locked Loop (PLL) is a challenging task under distorted and abnormal grid conditions. To equip PLLs in such scenarios, additional filters can be appended inside the control loop. The improvement in steady-state accuracy then comes in exchange of reduced control bandwidth because of phase delay introduced by filters. To boost the dynamic response, a preferred solution is cascading phase lead compensator (PLC) (with filters), while maintaining the disturbance rejection capability. This paper assesses performance of two types of PLCs (standard and digital) which are designed to minimize the phase delay of in-loop filters employed in PLL. These two approaches are compared by evaluating their dynamic response, steady-state accuracy and implementation complexity. The paper also provides design guidelines for both types of PLC along with its effect on controller design. The discussions presented are validated via simulation and experimental results.

© 2020 Institution of Engineering and Technology. All rights reserved. With the increasing integration of photovoltaic power generation in the low-voltage distribution network, the grid voltage regulation becomes critical, which demands support from different resources. This study presents the feasibility study of home appliance to be applied for appliance to grid mode of operation. The analysis includes the amendments in topology and control to support the concept of supportive platform provided by smart home and smart grid. Home appliances are then proposed as new distributed reactive sources, which are utilised to resolve the issue of voltage regulation, as well as produce reactive power locally for voltage stability. This study discusses the technical transitions in current home appliance to accommodate auxiliary functionality of grid reactive power support (RPS) and how it can fit in the home energy management system architecture to provide the required RPS.

© 1982-2012 IEEE. This article proposes a robust control strategy for five-level T-type (5L-T) hybrid power converters to achieve superior dynamic performance for effectively regulating the dc-bus voltage under external disturbances and generating high-quality grid current at the same time. A new filter-less dc-bus ripple voltage estimation method and a simple technique to remove this ripple component from the measured dc-bus voltage of a single-phase converter are developed. A sliding-mode control (SMC) incorporated with an extended-state observer (ESO) is employed for the outer voltage control loop, and to dynamically calculate the input (i.e., the active power reference) for the inner current-tracking controller. The proposed SMC-ESO approach presents a high disturbance rejection capability and robustness against the dc-bus load variation, and thus, significantly improves the dynamic and steady-state performance during system uncertainties. Moreover, a finite control set-model predictive control algorithm is derived as the inner current controller to track their references while balancing the dc-bus capacitor voltages. The effectiveness of the proposed controller is demonstrated and verified through measurement results.

© 2019 IEEE. This paper proposes a distributed control strategy for coordination of distributed energy resources (DERs) in low-voltage resistive microgrids. The proposed framework consists of two level structures; primary and secondary control. Unlike the existing distributed control solutions, the proposed method is based upon the practical assumption of network impedance being resistive. The primary control level consists of a V-I droop mechanism, where GPS timing is used to synchronize the control agents. A consensus-based distributed secondary control method is introduced to improve the voltage regulation and load sharing accuracy of the V-I droop method. In the proposed approach, the d-axis component of the voltage is altered so as to regulate the average microgrid voltage to the rated value while guarantying proper sharing of active power among the DERs. Additionally, the q-axis component of voltage is adjusted to perform proper current and, accordingly reactive power sharing. The proposed control methodology accounts for the distribution line impedances. It features a plug-and-play environment; prior system knowledge is not required, and an arbitrary DER can enter the microgrid without any need for additional synchronization. An ac microgrid is prototyped to experimentally demonstrate the efficacy of the proposed method.

© 1963-2012 IEEE. The recent trend in the design of the high-power density power converter generally reduces the rate of the device cooling process. As a result, increased thermal coupling among devices exists. Based on measurements, a thermal coupling resistances network (TCRN) model is proposed in this article. Considering different spacings and current values at a fixed value of case temperature ( T _text c ), the relationships between the case-to-ambient thermal resistance ( R _text ca ) of individual power devices and their thermal coupling resistance ( R _text cp ) to the adjacent device are established. The close correspondence of T _text c from the calculation of the different spacing and experimental results obtained from a thermal coupling measurement platform confirms the established TCRN model and the relationships. Traditional thermal models do not consider the changes of R _text ca and also ignore the effect of thermal coupling among the adjacent devices. Compared with these models, the proposed thermal resistances modeling approach provides a better understanding of the thermal behavior of power devices.

© 2018 IEEE. In this paper, a grid-tied residential smart microgrid topology is proposed, which integrates energies of a photo-voltaic (PV), a fuel cell, and a battery bank to supply the local loads through a combination of electric and magnetic buses. In contrast to multiple-converter-based microgrids with a common electric bus, using a multiport converter with a common magnetic bus can effectively reduce the number of voltage conversion stages, size, and cost of the renewable energy system and isolates the conversion ports. The resultant topology utilizes a centralized system level control that leads to a faster and more flexible energy management. The proposed microgrid is able to operate in multiple grid-connected and off-grid operation modes. A fuzzy controlled energy management unit (EMU) is designed to select the appropriate operation mode considering both real-time and long-term predicted data of the energy generation and consumption. A mode transition process is designed to smooth the mode variation by using a state transition diagram and bridging modes. To improve the microgrid operation performance, appropriate control techniques, such as synchronized bus-voltage balance, are used. A prototype of the proposed microgrid and the EMU are developed and experimentally tested for three different energy management scenarios. Energy distribution and energy cost analysis are performed for each scenario to validate the proposed control method.

© 2013 IEEE. This paper presents a modified model predictive control (MMPC) for bidirectional power flow control between the electric vehicle (EV) chargers and the main grid. In contrast to the conventional finite control set MPC which selects an optimal switching state from eight possible voltage vectors, the proposed MMPC is based on the application of an optimal voltage vector chosen from an extended set of 20 modulated voltage vectors with a fixed duty ratio. To reduce the computational burden introduced by the increased number of voltage sets, a preselection algorithm is developed for the MMPC method. Six voltage vectors are preselected from the 20 sectors. Due to the increased number of the voltage space vectors, the grid currents and active and reactive power performance can be improved by using the proposed MMPC scheme. Both the conventional and proposed methods are compared through experimental test results of a two-level three-phase off-board EV charger.

© 2013 IEEE. The single-vector-based model-predictive-based direct power control (MPDPC) is commonly used for control of three-phase full-bridge ac/dc converters, but it could only select the best switching vector to be implemented. Due to the limited number of voltage vectors in a two-level three-phase converter, the sampling frequency needs to be high to achieve an acceptable performance. Also, it bears variable switching frequency that causes spread spectrum nature of harmonics. In this paper, a three-vector-based simplified model predictive duty cycle control (SMPDCC) is proposed. The adjacent two nonzero vectors are selected by evaluating the effects of each vector pairs based on the revised cost function. The duration calculation is simplified compared with the conventional predictive duty cycle control (CPDCC) by allocating a control period in reciprocal proportion with the corresponding cost function value of the selected vectors. Besides, the negative duration issue of CPDCC could be completely avoided and the mutual influence elimination ability could be realized. A comparative study with MPDPC and CPDCC has been conducted to verify the superiority of the proposed scheme by the simulation and experimental results. It shows that the SMPDCC has the advantages of lower power ripple, fixed switching frequency, lower total harmonic distortion, and mutual influence elimination ability.

© 2019 IEEE This paper presents a topological study using power flow diagrams to derive all possible basic and non-isolated double-input single-output (DISO) converters. Unlike most reported DISO converters with one bidirectional port, this paper considers up to two bidirectional ports. The paper focuses on providing a general guideline of all power flow combinations and corresponding converter configurations. After eliminating the impractical configurations due to their indirect connection to some ports and their multiple conversion stages, three converter configurations have been identified and corresponding circuit realizations are demonstrated.

© 2004-2012 IEEE. In this brief, an analog, bipolar junction transistor (BJT)-tuned voltage reference maximum power point tracking (MPPT) method for photovoltaic modules is proposed. The conventional fixed voltage reference method is the simplest method for tracking, but it does not obtain good MPPT efficiency because the maximum power point (MPP) voltage changes at different insolation levels. In reality, an approximately linear slope is formed when connecting the MPPs measured from the highest insolation level to the lowest. Utilizing this characteristic, a BJT, which has a similar electrical property, is used to implement a variable voltage reference that improves the accuracy of the MPP voltage when the insolation changes. The proposed circuit is simple and easy to implement, and it can track the MPP very quickly without the need for a digital controller or PID controller. Hence, the circuits cost and complexity are reduced. Experimental results are given to verify the feasibility of the proposed MPPT method.

© 1982-2012 IEEE. This paper presents a new approach to controlling and optimizing a single-stage boost-integrated full-bridge dc-dc converter for a stand-alone photovoltaic-battery-powered dc motor system by combining pulse-frequency modulation (PFM), pulsewidth modulation (PWM), and phase angle shift (PAS). Unlike most of the existing multiport dc-dc converters, which aim at regulating the output voltage (first-or second-quadrant operation), the dc motor load requires both voltage and current reversals (four-quadrant operation). The converter is able to perform three tasks simultaneously: maximum power point tracking (MPPT), battery charging/discharging, and driving the dc motor at variable speeds including bidirectional and stall motions. To achieve these control objectives, the boost inductor and the motor inductance operate in different modes such that PFM and PWM can be used to achieve MPPT and a wide motor voltage range, respectively. By properly adjusting the PAS of the duty cycles, the capacitor and battery rms current value can be reduced, while the operation of the converter remains unchanged, hence improving the conversion efficiency. Experimental results of a 26-W laboratory prototype converter confirmed the proposed design and operation and the efficiency improvement by 2-6%.

© The Institution of Engineering and Technology 2019. Solar cell power performance is greatly affected by two critical factors ageing and crack. In order to mitigate their negative effects on the solar system, these cells are to be substituted by new cells, thus, replacing the panels. This study presents an active crack detection method that detects the cracked cells within a solar string by using AC parameter characterisation without a need to have a physical inspection. The mathematical module of the solar cell shows that it constitutes of series and parallel resistors in addition to a parallel capacitor and that their values change by ageing and crack. In addition to studying the effects of the crack on the solar cell, it is verified by the experiment that the solar cells behave as a capacitive circuit, and their capacitance increases when the cell gets cracked, getting higher as the crack becomes more serious. The experiment is extended to investigate the effect of series and parallel PV strings, which are affected by cracked and partially shaded cells to evaluate their criticality levels. By monitoring the AC parameter of the solar cell and the change of the capacitance, it is easy to detect the crack when it occurs.

© 2018 IEEE. The conventional predictive duty cycle control (CPDCC) of three-phase full-bridge ac/dc converters selects adjacent nonzero vector pair based on the grid-voltage vector location, then the duration for each vector is calculated. Though the vector selection method is quite simple, it has a significant disadvantage that the values of calculated durations could be frequently less than zero due to nonoptimal vector selection, which results in high current harmonics and power notches. It could be improved with improved predictive duty cycle control (IPDCC) by reselecting the nonzero vector pair when negative duration exists; however, the whole vector selection and calculation procedure are repeated. By theoretical verification that the power variation rates of reversible vector pair are symmetrical with respect to that of zero vector, this paper proposes the reversible predictive duty cycle control (RPDCC) simply by replacing the original vector with its opposite vector and the recalculation of vector duration is eliminated compared with IPDCC. Thus, the calculation effort is almost not increased compared with CPDCC while system performance is significantly improved. The proposed control is theoretically derived and verified with the simulation and experimental results showing that RPDCC has better steady and dynamic performance than CPDCC and IPDCC methods.