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An optimized configuration of bidirectional Z-source circuit breaker using a coupled inductor is introduced for the fault isolation in low-voltage dc microgrid. The proposed circuit breaker is designed to operate with a single coupled inductor for bidirectional power flow. Use of the single coupled inductor for the power flow in both the directions reduces the component count. In this article, the operating principle of the breaker is explained for a short-circuit fault condition and breaker design criteria are derived. The performance of the circuit breaker is evaluated by carrying out a MATLAB simulation study. The functional prototype is developed to validate the breaker capabilities. Experimental results show that the fault is cleared within few microseconds. Additionally, the breaker is tested under the step load change condition for a current five times the steady-state rated current of the breaker and results are satisfactory. [ABSTRACT FROM AUTHOR]

This article introduces a new lossless passive snubber for the bidirectional buck/boost converter. The proposed snubber comprises a low number of passive components which jointly contribute to achieve soft switching condition at both the buck and boost operations of the converter. Without using the auxiliary switch, soft switching condition is ensured over a wide load range with a relatively low circulating current. Also, there is no need for any complex control method to diminish circulating current at light loads. Consequently, by using a simple auxiliary circuit and the conventional control methods, excellent efficiency is acquired over a wide load range. The proposed topology is analyzed in detail and to confirm the theoretical analysis, the experimental results of a 500 W–100 kHz prototype for both the boost and buck modes in full-load and 20% of full-load are presented. [ABSTRACT FROM AUTHOR]

Wireless power transfer systems using coupled magnetic resonances are susceptible to the transfer distance variation between the transmitter (Tx) and receiver (Rx) since the coupling between Tx and Rx is highly position dependent. Once the transfer distance deviates from the optimum one, the coupling will be either excessive or weak, which results in power transfer efficiency (PTE) degradation. This article presents a Tx structure consisting of multiple subcoils oriented in opposite directions to keep the coupling relatively constant over an extensive range of transfer distances. The proposed design can achieve a PTE of 88–70% with a transfer distance varying from 0 to 70 mm and a PTE of 85–60% with a misalignment of 0–80 mm at a 40 mm transfer distance. The radius of the Tx and Rx is 84.6 and 45.1 mm, respectively. The measured PTE of the proposed design is better than 70% with a 0–50 mm transfer distance while the misalignment changing from 0 to 50 mm. The proposed system is much less sensitive to the transfer distance variation than the convention system and has a great potential for wireless charging applications. [ABSTRACT FROM AUTHOR]

This article introduces a zero voltage switching (ZVS) interleaved buck/boost bidirectional converter using the active-clamp technique. In the proposed converter, by utilizing a simple auxiliary circuit comprised of an auxiliary switch, an auxiliary inductor, and a clamp capacitor, ZVS condition is secured for both the boost and buck operation modes, regardless of the converter operating duty cycle or load condition. Furthermore, the converter can operate with the conventional fixed-frequency pulsewidth modulation (PWM) control procedure. The boost and buck modes of the proposed converter are analyzed in both conditions of D > 0.5 and D < 0.5. To confirm the theoretical analysis, the experimental results of a 350 W–100 kHz prototype are presented. [ABSTRACT FROM AUTHOR]

This paper discusses the analysis and experimental validation of bidirectional Z-source breaker and bidirectional Z-source breaker using coupled inductor for low-voltage dc microgrid application. The proposed topologies use an SCR as a switch to isolate the fault from the system, and LC network to generate required commutation conditions for the SCR under fault conditions. Thus, both topologies are able to isolate the fault naturally within a few microseconds without any fault detection and sensing circuit. In this paper, the breaker operating principle is discussed during fault condition and breaker design criteria are derived. When the breaker is connected in series with power electronic converter, Z-source components offer filtering characteristic. The filtering characteristic offered by the breaker components is analyzed. Functional prototypes are developed for both configurations to validate the breaker performance and experimental results are presented. [ABSTRACT FROM AUTHOR]

In this letter, we introduce a simple turn-on snubber for the conventional bidirectional converter. This snubber notably reduces the current reduction rate of the converter main diodes at turn-off. Hence, the reverse recovery losses, which are the dominant losses in the bidirectional converter, are almost eliminated. These features are achieved with a minimum circulating current and no extra voltage or current stress. The conventional bidirectional converter with the proposed snubber is analyzed, and to confirm the analysis, the experimental results are presented. [ABSTRACT FROM AUTHOR]

A 1-MHz half-bridge high-gain multi-CLLC bidirectional resonant converter with (gallium nitride) GaN field effect transistor (FETs) and integrated planar magnetics is proposed in this paper. It presents excellent gain characteristic and high power density, which is very suitable for a distributed energy storage system. The operation principle, topology features, and parameter design method of the converter are discussed in detail. The improved winding method of integrated planar magnetics is also elaborated. And then, a 400-W prototype is established and the corresponding experiments are carried out in 1 MHz. Finally, the accuracy and correctness of the theory are verified and the highest efficiency of the converter can reach 94.3%. [ABSTRACT FROM AUTHOR]

Buildings consume quite a lot of energy; hence, the issue of building energy efficiency has attracted a great deal of attention in recent years. A key factor in achieving this objective is occupancy information that directly impacts on energy-related building control systems. In this paper, we leverage on environmental sensors that are nonintrusive and cost-effective for building occupancy estimation. Our result relies on feature engineering and learning. The conventional feature engineering requires one to manually extract relevant features without a clear guideline. This blind feature extraction is labor intensive and may miss some significant implicit features. To address this issue, we propose a convolutional deep bidirectional long short-term memory (CDBLSTM) approach that contains a convolutional network and a deep structure to automatically learn significant features from the sensory data without human intervention. Moreover, the long short-term memory networks are able to capture temporal dependencies in the data and the bidirectional structure can take the past and future contexts into consideration for the final identification of occupancy. We have conducted real experiments to evaluate the performance of our proposed CDBLSTM approach. Instead of estimating the exact number of occupants, we attempt to identify the range of occupants, i.e., zero, low, medium, and high, which is adequate for most of building control systems. The experimental results indicate the effectiveness of our proposed approach compared with the state-of-the-art methods. [ABSTRACT FROM AUTHOR]

Lithium (Li)-ion battery cells suffer from significant performance degradation at subzero temperatures. This paper presents a predictive control-based technique that exploits the increased internal resistance of Li-ion cells at subzero temperatures to increase the cell’s temperature until the desired power can be delivered. Specifically, the magnitude of a sequence of bidirectional currents is optimized such as to minimize total energy discharged. The magnitude of current is determined by solving an optimization problem that satisfies the battery manufacturer’s voltage and current constraints. Drawing bidirectional currents necessitates that a temporary energy reservoir for energy shuttling, such as an ultracapacitor or another battery, be available. When compared with the case when no penalty on energy withdrawn is imposed, simulations indicate that reductions of up to 20% in energy dispensed as heat in the battery as well as in the size of external storage elements can be achieved at the expense of longer warm-up operation time. [ABSTRACT FROM PUBLISHER]

In this paper, a decoupled controlled triport dc/dc converter is derived by combining two bidirectional single-phase buck–boost converters and one isolated full-bridge converter for multiple input source applications. The power density is improved, and the circuit structure is simplified because the power devices are completely shared in the primary side. Furthermore, the pulsewidth modulation plus phase-shift control strategy is introduced to provide two control freedoms and achieve the decoupled voltage regulation within a certain operating range. The duty cycle of the bidirectional buck–boost converters is adopted to balance the voltage between the two primary input terminals, while their phase angle is applied to regulate the accurate secondary voltage. Furthermore, zero-voltage-switching soft-switching operation is provided for all of the primary power switches due to the inherent phase-shift control scheme. Moreover, the two filter inductors in the bidirectional buck–boost converters and the isolated transformer in the full-bridge topology are integrated and replaced by the winding-cross-coupled inductors to reduce the component numbers and simplify the magnetic structure. Finally, a 1-kW prototype is built to verify all theoretical considerations, and it is shown that the proposed topology is particularly advantageous in the distributed power generation system with multiple energy sources. [ABSTRACT FROM PUBLISHER]

A circuit configuration, a circuit topological family, a buck-mode active clamped circuit, and an instantaneous output voltage feedback control strategy of combined bidirectional buck–boost dc–dc chopper-mode inverter with high-frequency (HF) link (HFL) were proposed and fully investigated in this paper. The steady principle characteristic and the design criteria for the key circuit parameters were given in this paper. The circuit configuration is composed of two identical isolated bidirectional buck–boost dc–dc choppers with the same input and output filters. These two choppers in parallel at input end and in series at output end generate unipolarity sinusoidal pulsewidth modulation current waveforms with positive and negative half low-frequency cycles separately. The circuit topological family includes four circuit topologies, such as one-transistor mode. Taking the one-transistor mode circuit topology as an example, the 750VA48VDC/220V50HzAC prototype is designed and implemented. The theoretical analysis and principle test show the inverters have excellent performance. [ABSTRACT FROM PUBLISHER]

This paper presents a review of the current state of the art in terms of practical matrix converter technologies. Present solutions to the numerous technological issues and challenges faced when implementing viable matrix converters are discussed. The reported use of the matrix converters in different applications is also presented together with a review of current industrial applications. [ABSTRACT FROM PUBLISHER]

This paper suggests a two-stage isolated/bidirectional dc/dc converter with hybrid-switching technique. High-frequency bidirectional resonant converter with a fixed gain can reduce the bulky transformer size by minimizing Insulated Gate Bipolar Junction Transistor (IGBT) turn-off loss due to tail current, and it forms bidirectional power flow without any control operation. Pulsewidth-modulation nonisolated converter takes in charge of bidirectional control, and its serious turn-off switching loss is alleviated using MOSFET-assisted hybrid-switching structure. The proposed scheme provides low switching loss and removes snubber circuitry so a high efficiency and a high power density can be obtained in high-voltage/high-power bidirectional applications. [ABSTRACT FROM PUBLISHER]

This paper presents a magnetically coupled feedback-clamped optimal bidirectional battery charger. The proposed charger acts as a current source, i.e., acts in constant-current (CC) mode with a controlled output current in case of deep discharge of a battery, and as a voltage source, i.e., acts in constant-voltage (CV) mode with a controlled output voltage for near-100% battery state of charge. The proposed circuit is universal from the battery voltage point of view, i.e., can charge a battery with any given voltage rating, and adaptive from the optimum charging current requirement viewpoint, i.e., can adapt to the optimum battery charging current. The presented solution uses a magnetically coupled bidirectional converter topology. In order to make the system feedback controlled during the whole cycle of charging, the regulation loop is clamped, and hence, automatic and smooth transition from the CC to CV mode is achieved without the need of any extra switching circuit or control loop. Experimental and simulation results for a 250-W prototype are presented to verify the proposed system. The prototype shows maximum efficiencies of 90.24% under boost mode and 92.7% under buck mode of operation. The performance of the charger is verified using two different 12-V–7-Ah and 12-V–32-Ah lead–acid batteries. [ABSTRACT FROM PUBLISHER]

Bidirectional inductive power transfer (IPT) systems are attractive for applications such as electric vehicles and vehicle-to-grid systems which preferably require “contactless” and two-way power transfer. However, in contrast to unidirectional IPT systems, bidirectional IPT systems require more sophisticated control strategies to control the power flow. An indispensible component of such control strategies is the robust and accurate synchronization between the primary- and pickup-side converters, without which the transfer of real power in any direction cannot be guaranteed. This paper proposes a novel technique that synchronizes converters on both the primary and pickup sides of bidirectional IPT systems. The technique uses an auxiliary winding, located on the pickup side, to produce a synchronizing signal which, in turn, can be utilized to regulate the real power flow. This paper also presents a mathematical model for the proposed technique and investigates its sensitivity for component tolerances. The viability of the technique, which is applicable to both single- and multiple-pickup IPT systems, is demonstrated through both simulations and experimental results of a 1-kW prototype bidirectional IPT system. [ABSTRACT FROM PUBLISHER]

Inductive power transfer (IPT) technology is a well-recognized technique for supplying power to a wide range of applications with no physical contacts. With the emergence of applications such as electric vehicles and vehicle-to-grid systems, IPT systems with bidirectional power flow have become a recent focus. In contrast to simple unidirectional IPT systems, bidirectional systems are complex in nature and essentially require more sophisticated and robust control strategies. This paper proposes a new controller, which is based on power–frequency droop characteristics of IPT systems, to regulate its power flow in both directions without a dedicated communication link. The proposed controller is applicable to unidirectional as well as bidirectional IPT systems with either single or multiple loads and ensures that power intake by the load side is always kept within the capability of the supply side. Analysis, together with both experimental and simulated results, of a 1-kW single-load bidirectional IPT system is presented with discussions to show that the proposed droop controller can successfully be used to regulate the two-way power flow. [ABSTRACT FROM PUBLISHER]

This paper presents a novel switched Z-source isolated bidirectional dc–dc converter. The converter employs two unique switched impedance networks to couple the main circuit and the power source and load. Compared with the traditional isolated bidirectional dc–dc converter, the proposed converter has a wider regulation range of voltage. In addition, due to the fully symmetrical circuit configuration, there is neither a high-voltage side nor a low-voltage side in the circuit structure, and the sources connected to the dc side of each H-bridge can be both voltage sources and current sources. At the same time, the converter can bear shoot-through phenomenon in H-bridges, so it has high reliability. The topology configuration and operating principle of this converter are analyzed, and a unique phase-shifting shoot-through bivariate coordinated control strategy is designed and implemented. Both simulation and experimental results verify the analytical results. [ABSTRACT FROM PUBLISHER]

In this paper, a novel Zeta-mode three-level ac direct converter is proposed. The converter realizes three-level voltage waveforms before the output filter, which can get a better harmonic spectrum and reduce the bulk of the filter. Compared with two-level ac choppers, voltage stresses of the converter can be lowered. Compared with ac–dc–ac converters with no isolation and low- or middle-frequency isolation, the converter has single power stage and bidirectional power flow. Moreover, compared with buck-mode three-level ac choppers, it can realize buck and boost output voltage. The converter has four operation states in one period of input voltage and three different operation modes in one switching period. To ensure that the converter operates reliably, the noncomplementary control strategy is presented, which can make the converter switch smoothly between different modes in bidirectional power flow. Therefore, the converter is suitable to different kinds of loads. Principle analysis and experiment results of the prototype well verify the advantages of the proposed converter. [ABSTRACT FROM PUBLISHER]

Demand for supplying contactless or wireless power for various applications, ranging from low-power biomedical implants to high-power battery charging systems, is on the rise. Inductive power transfer (IPT) is a well recognized technique through which power can be transferred from one system to another with no physical contacts. This paper presents a novel bidirectional IPT system, which is particularly suitable for applications such as plug-in electric vehicles (EVs) and vehicle-to-grid (V2G) systems, where two-way power transfer is advantageous. The proposed IPT system facilitates simultaneous and controlled charging or discharging of multiple EVs through loose magnetic coupling and without any physical connections. A mathematical model is presented to show that both the amount and direction of power flow between EVs or multiple systems can be controlled through either phase or/and magnitude modulation of voltages generated by converters of each system. The validity of the concept is verified by theoretical analysis, simulations, and experimental results of a 1.5-kW prototype bidirectional IPT system with a 4-cm air gap. Results indicate that the proposed system is an ideal power interface for efficient and contactless integration of multiple hybrid or EVs into typical power networks. [ABSTRACT FROM AUTHOR]

This letter suggests a two-stage isolated/bidirectional dc/dc converter with three bridges. Two bridges are used for electrical isolation and constant gain, and the bidirectional control is accomplished through only a single bridge. RMS currents in the high-voltage source and link capacitor can be alleviated by capacitor division and synchronizing operation of both stages. This structure provides a simple control scheme and removes snubber circuitry, so a high efficiency can be obtained under a high switching frequency regardless of operational modes. [ABSTRACT FROM AUTHOR]