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In this paper, the procedure for designing a sliding-mode controller for maximum power point tracking photovoltaic (PV) applications is proposed. It is applied to a single-ended primary inductor converter, thus to a fourth-order topology, but it can be extended to a wide class of converters suitable for PV applications. The reachability and existence conditions give rise to a number of design inequalities that add to the classical steady-state conditions in order to have the desired closed-loop converter's performances. The superiority of the control technique over the classical tracking methods is analytically demonstrated through the procedure proposed in this paper. The analytical results have been validated by means of both simulations and experiments. [ABSTRACT FROM PUBLISHER]

The need for lighter and smaller railway traction drives and recent advances in power semiconductor technology have resulted in a new energy conversion paradigm, one without the classical heavy and bulky line-frequency transformer. Several multilevel topologies have been introduced over the past years, all having in common the use of medium-frequency (MF) energy conversion to reduce the weight and volume of the magnetic components. This paper is concerned with the design of the input filter for an MF traction converter, focusing on a solution that minimizes the filter's overall mass. Two filter topologies are investigated, namely a single-pole filter (inductor) and a passively damped $LCL$ filter. The paper first describes the requirements to be fulfilled, establishes the spectrum to consider for the design, and proposes a method to determine the initial parameters of the filter's components. The results show that an $LCL$ -type filter achieves considerable weight savings in comparison to the single-pole solution. [ABSTRACT FROM AUTHOR]

In this paper, a single-inductor dual-output (SIDO) dc–dc converter is proposed. The significant feature of the proposed converter is feeding a constant power load in low-voltage side (LVS) port, where even feeding a variable load at LVS does not have any cross regulation to high-voltage side port with the desired approximation. Magnificently, both merits are obtained in open-loop manner, which is an outstanding characteristic in comparison with that of the existed converters. In this paper, soft commutation and soft switching of switches and diodes are investigated along with the aforementioned main novelty. Moreover, detailed theoretical analyses of the proposed SIDO dc–dc converter in continuous conduction mode are presented besides the comparisons with some other structures. Finally, theoretical analyses are verified through a 1500 W experimental prototype results. [ABSTRACT FROM AUTHOR]

This paper proposes a novel isolated bidirectional two-switch flyback converter with two integrated non-dissipative inductor–capacitor–diode (LCD) snubbers. In the proposed topology, the main flyback transformer and the LCD snubbers are cross coupled to minimize circulating current that would occur in the non-cross-coupled case, in addition to recycle leakage energy and protect the power transistors. The same current circulation issue also occurs in the bidirectional flyback converter with conventional resistor–capacitor–diode (RCD) snubbers. The main objective of this paper is to illustrate this issue and propose an alternate circuitry to reduce the current circulation and improve the conversion efficiency. The experimental results of a laboratory prototype are reported to verify the design. [ABSTRACT FROM AUTHOR]

Single-stage power-factor-corrected (S2PFC) power supplies usually suffer from high voltage stress, due to lack of control on the intermediate bus capacitor voltage. In the past, analysis of such voltage stress was mostly based on steady-state condition without providing sufficient explanation during the transient circuit operation. This paper revisits the problem at circuit level and reports that the root cause is due to the inherent negative current feedback property of the output inductor or the transformer operating in continuous conduction mode (CCM). Based on the finding, this paper further proposes a new approach to reducing the voltage stress by adding an auxiliary circuit branch to existing S2PFC converters. The additional circuit branch limits the effect of negative current feedback by suppressing the change of output current slope due to change of load. This assists the pulsewidth modulation controller to track the change of load better such that the bus capacitor voltage range is reduced through duty cycle control. The auxiliary circuit branch also reduces reverse-recovery-related losses of the converter under CCM operation. A laboratory prototype using the popular boost PFC converter combined flyback dc/dc converter was built and tested to confirm the analysis and effectiveness of the approach. [ABSTRACT FROM AUTHOR]

A merit of the interleaving reducing the switching harmonics allows for the reduction of the filter inductance. However, in the case of direct parallel voltage source inverters (VSIs), a severe circulating current occurs. To suppress the high frequency circulating current, coupled inductors (CIs) for the high impedance is inserted. However, the employed CIs induce a positive- or negative-sequence circulating current (i.e., a cross current) besides the zero-sequence circulating current already mentioned in the other papers. Due to different impedances developed by the current characteristics and the cross current in the CIs, VSIs becomes unstable when the resonant controllers are applied for the harmonic compensation such as 5, and 7th harmonics. In this paper, the cross currents and the impedances of CIs varying with the current characteristics are mathematically analyzed, and a novel current controller is proposed to solve this stability problem. The experimental results validate the proposed control scheme. [ABSTRACT FROM PUBLISHER]

Abstract-In this paper, the influence of one-sample delay for sampling and computation in digital control on the bandwidth of the inner current loop of a 400-Hz ground power unit (GPU) is analyzed first. The results show that it is difficult and even impossible for high-power 400-Hz GPUs to maintain low total harmonic distortion content in the output voltage with the conventional proportional-integral-based double-loop control. To improve the performance, resonant controllers with parallel structure which are widely used in active power filters are applied to the single-loop control of the 400-Hz GPU. The parameter design criterion for the parallel resonant controllers is discussed in the discrete time domain. Meanwhile, adoption of-proportional gain in the single-loop control is investigated. The results show that it can improve the performance little and may cause instability problems. Comparisons between different control methods for the 400-Hz GPU are also made, and the single-loop control method in this paper seems to be the most suitable one in terms of simplicity and performance. Experiments on a 16-b fixed-point DSP-controlled 90-kVA 400-Hz GPU prototype show satisfactory results of the single-loop method feeding linear/nonlinear and balanced/unbalanced loads. [ABSTRACT FROM AUTHOR]

In this paper, two structures are proposed for the switched-inductor quasi-Z-source inverter. In the proposed structures to extend the voltage gain of inverter, two new switched-inductor structures are used. In the proposed structures, voltage across the capacitors in the Z-source network and in the switched-inductor is symmetric and small. The other advantage of proposed inverters is known as achieving higher voltage gain per smaller duty cycle ratio (of shoot-through). Compared with a conventional continuous input current switched-inductor quasi-Z-source inverter at the same gain voltage, there is less of a ripple of input current in the proposed inverters. In this paper, at first the both the conventional and the proposed switched-inductor Z-source inventers are thoroughly investigated to find out their governing relations. Then, the proposed Z-source inverters are compared with the conventional ones by simulating them to assess their performance efficiency. Next, applying the simple boost pulse width modulation the simulation is carried out with PSCAD/EMTDC software. After that, to evaluate the obtained results, the prototypes of the proposed inverters with 48 Vdc input voltage are used. [ABSTRACT FROM PUBLISHER]

Microinverters require high voltage gain capability for interfacing the low dc voltage output of photovoltaic (PV) module to single-phase ac grid. A two-stage nonisolated inverter is proposed in this paper, with a first boost stage and a second traditional pulse width modulated grid-tied inverter stage. The proposed boost stage consists of a coupled inductor added with a voltage multiplier to achieve the required high voltage gain at high efficiency and to operate over a wide input voltage range. Among the coupled inductor topologies, adding a clamp circuit is a common solution to limit the voltage spike caused by leakage inductance. In the proposed converter, the resonance between the coupled inductor and voltage multiplier is used to address the issue of voltage spike, thereby reducing both component count and device voltage stress. Detailed analysis and design procedure of the proposed converter is presented in this paper. Experimental results of a 250-W microinverter are presented to validate the proposed converter. [ABSTRACT FROM PUBLISHER]

This paper proposes a wide-range zero-voltage-switching (ZVS) active-clamped current-fed push–pull converter for fuel cell application. The presented converter achieves ZVS for all of the primary switches and ZCS for secondary diodes from rated load to 10% full load over the wide input voltage variation, improving the overall efficiency. The ZVS of switches is realized by the energy stored in the transformer leakage inductance aided by the secondary parallel inductor. An additional active clamping circuit suppresses the voltage spike as well as assists in realizing ZVS of switches. Low-voltage-rated switches with low on-state resistance can be used. Moreover, the voltage-doubler rectifier is adopted to release the reverse-recovery problem of rectifier diodes and reduce turns ratio of the high-frequency transformer. Detailed steady-state operation, analysis, design, control, comparative study, and experimental results are discussed in depth in this paper. Finally, a 200-W prototype has been built in the laboratory to verify the effectiveness of the proposed converter. [ABSTRACT FROM PUBLISHER]

Connecting legs in parallel in a voltage source inverter is a way to increase the output current and, thus, its rated power. The connection can be made using either coupled or uncoupled inductors, and achieving an even contribution to the output current from all the legs is a crucial issue. Circulating currents produce additional losses and stress to the power devices of the converter. Therefore, they should be controlled and minimized. An efficient technique to attain such balance when coupled inductors are used is presented in this paper. The proposed technique can also be used when the inductors are uncoupled, since it is a particular case where the coupling coefficients are zero. This technique does not include proportional–integral controllers and does not require any parameter tuning either. The exact control action needed to reach current balance is straightforwardly calculated and applied. Experimental results are shown in this paper to verify the efficiency of the proposed balancing method. [ABSTRACT FROM PUBLISHER]

Domestic induction heating appliances are evolving from surfaces with three to five fixed cooking areas to flexible cooking zones. These are able to adapt to a number of vessels of any size and shape by using multiple coils. Some state-of-the-art induction systems make use of overlapped inductors in two layers, which combine the high efficiency of large inductors with the high flexibility of small adjacent coils. The main drawback of this concept is the unequal distance between different coils and the vessel, which implies that each coil presents a different impedance depending on its layer. This paper presents an induction system conformed by nonplanar inductors. These inductors are designed in such a way that they can be assembled in overlapping structures, while preserving equivalence among them, i.e., they all present the same impedance. This paper includes the finite-element method modeling of the nonplanar coil, an analysis on the an experimental verification. [ABSTRACT FROM AUTHOR]

In this paper, several new coupled-inductor-based soft-switching dc–dc converters are proposed. These converters are obtained by changing the coupled branch of several existing dc–dc converters. Meanwhile they have similar characteristics to these existing converters, and provide more choices for the practical application. Then by applying an existing efficiency improvement method, which is used in the buck-type soft-switching converter, to all abovementioned converters, several new converters with efficiency improvement characteristics are obtained. This efficiency improvement method utilizes the low conduction performance of the transistor to reduce the loss. In addition, this method has the same control complexity to original topologies, because the auxiliary transistor has the same control timing to one of main transistors. The characteristic of new converters and efficiency improvement method are presented by analyzing two new topologies (boost-type converters). Finally simulation and experimental results are given and analyzed by designing a prototype. Based on these results, soft-switching conditions and efficiency improvement capability are verified. [ABSTRACT FROM AUTHOR]

A dual-active-bridge (DAB) converter with parallel-connected full bridges in low-voltage side is proposed in this paper. A coupling inductor is integrated into the two low-voltage-side full bridges for zero-voltage-switching (ZVS) operation throughout full-load range. By analyzing the working modes of the converter, the ZVS range of the converter is derived. To compromise the ZVS and the conduction loss caused by the coupling inductor, the modulation trajectory is designed in terms of the boundary conditions of the ZVS range. The conduction loss of the proposed converter is compared with the conventional parallel-connected DAB converter, which illustrates that the conduction loss of the proposed converter is only increased under light loads. Finally, a 1.2-kW experimental prototype is built to verify the proposed converter and the modulation scheme, which demonstrates the remarkable ZVS performance and efficiency improvement. [ABSTRACT FROM AUTHOR]

In this paper, a high-frequency ac-link photovoltaic (PV) inverter is proposed. The proposed inverter overcomes most of the problems associated with currently available PV inverters. In this inverter, a single-stage power-conversion unit fulfills all the system requirements, i.e., inverting dc voltage to proper ac, stepping up or down the input voltage, maximum power point tracking, generating low-harmonic ac at the output, and input/output isolation. This inverter is, in fact, a partial resonant ac-link converter in which the link is formed by a parallel inductor/capacitor (LC) pair having alternating current and voltage. Among the significant merits of the proposed inverter are the zero-voltage turn-on and soft turn-off of the switches which result in negligible switching losses and minimum voltage stress on the switches. Hence, the frequency of the link can be as high as permitted by the switches and the processor. The high frequency of operation makes the proposed inverter very compact. The other significant advantage of the proposed inverter is that no bulky electrolytic capacitor exists at the link. Electrolytic capacitors are cited as the most unreliable component in PV inverters, and they are responsible for most of the inverters' failures, particularly at high temperature. Therefore, substituting dc electrolytic capacitors with ac LC pairs will significantly increase the reliability of PV inverters. A 30-kW prototype was fabricated and tested. The principle of operation and detailed design procedure of the proposed inverter along with the simulation and experimental results are included in this paper. To evaluate the long-term performance of the proposed inverter, three of these inverters were installed at three different commercial facilities in Texas, USA, to support the PV systems. These inverters have been working for several months now. [ABSTRACT FROM PUBLISHER]

This paper presents a sinusoidal pulsewidth modulation (SPWM) based direct digital control with average-voltage model (AVM) and division–summation process for paralleled three-phase three-wire (3φ3W) grid-connected converters to reduce circulating currents. With the direct digital control, plant of each single-phase converter can be derived directly, and a controller is then designed to cover the variation effects of filter inductance and grid voltage. Based on SPWM and AVM over a switching cycle, each 3φ3W converter can be decomposed into three single-phase converters and each converter is controlled individually to track its sinusoidal reference current tightly, reducing circulating currents significantly. Equal current sharing is therefore also achieved. The control laws for achieving grid connection are derived in detail. In the design and implementation, the inductances corresponding to various inductor currents are measured offline and stored in the controller for scheduling loop gain cycle by cycle. Experimental and simulated results from a three-converter system confirm the analysis and discussion of the proposed control approaches. [ABSTRACT FROM AUTHOR]

A 1-MHz-modified single-ended primary-inductor converter (SEPIC) circuit is presented in this paper as an LED driver for automotive headlights. On the basis of traditional SEPIC, only a diode and two capacitors are added; therefore, the circuit structure is relatively simple and the volume is relatively small. High step-up capability is obtained with moderate duty cycle. Compared with traditional step-up circuit such as boost, low-voltage stress is gained which is beneficial to device selection. Zero-voltage switching is achieved at the same time to reduce switching loss. Planar inductors are used with the advantages of low profile and good thermal characteristic. Operational principle and parameters design process are introduced in detail. A 36-W prototype has been designed to demonstrate theoretical analysis. Obtained efficiency was up to 90.91% at full load. [ABSTRACT FROM AUTHOR]

This paper presents a new average electrothermal model of the inductor dedicated to the computer analysis of dc–dc converters, such as a boost converter. The proposed model takes into account the influence of power losses in the ferromagnetic core on frequency and temperature. The considered model includes parameters, values of which are estimated on the basis of the catalog data of the inductor components—the core and the winding. To prove the usefulness of the average electrothermal model of the inductor, calculations of the characteristics of the boost converter are performed. The results of calculations are compared with the results of measurements and the good agreement between these results is achieved for two types of ferromagnetic cores made of powdered iron or ferrite. [ABSTRACT FROM AUTHOR]

In this paper, a sequence switching control (SSC) scheme based on an auxiliary parallel inductor is proposed to improve the transient performance of buck converters. The proposed SSC scheme introduces a small controlled inductor in parallel with the output inductor, so as to increase the inductor-current slew rate when it is activated during a load transient. Furthermore, an “n+ 1” sequence switching strategy is proposed to control the auxiliary parallel inductor. The proposed scheme divides the transient event inton+ 1 periods. In the formernperiods, the same small output voltage deviations are designed, while in the last period, a smaller deviation is done for a smooth transition from the transient to the steady state. The switching sequence is derived applying the capacitor–charge balance principle for each ofn+ 1 periods. For a given buck converter in the experiment, the settling time and the output voltage deviation of the proposed SSC scheme enhance more than 50% and 67%, respectively, over those of the time-optimal control for a 3-A load step. [ABSTRACT FROM AUTHOR]

In this paper, a new control strategy for single-inductor multiple-output (SIMO) converters is proposed. The strategy is based on the hybrid control scheme. Switched linear equations of the converter are used in the design procedure. As a result, the cross regulation is suppressed inherently. A minimum dwell-time constraint is considered to suppress the switching loss and electromagnetic interference. The proposed scheme can control both minimum phase and nonminimum phase SIMO converters. It will be shown that the system is robust to input voltage and load variations. In order to compare the results, a recent pulsewidth-modulation-based control system is considered. Performance of the system is evaluated by a number of simulations and experiments. [ABSTRACT FROM AUTHOR]

In this paper, an integrated double buck–boost (IDBB) converter is proposed as a high-power-factor offline power supply for power-LED lamps. The IDBB converter features just one controlled switch and two inductors and is able to supply a solid-state lamp from the mains, providing high power factor and good efficiency. In this paper, the IDBB converter is analyzed, and a design methodology is proposed. It is demonstrated that, with a careful design of the converter, the filter capacitances can be made small enough so that film capacitors may be used. In this way, the converter mean time between failures can be made as high as that of the solid-state lamp. A design example for a 70-W converter supplied from a 230 V/50 Hz mains for street lighting applications is shown. Finally, experimental results from a laboratory prototype are also presented. [ABSTRACT FROM AUTHOR]

This paper proposes a novel family of cascade three-level (TL) ac–ac direct converters based on ac switch cells, which transfer unsteady high ac voltage with distortion into regulated sinusoidal voltage with low total harmonic distortion (THD). The topological family includes buck TL–boost, buck–boost TL, and buck TL–boost TL modes. In order to achieve a reliable TL ac–ac conversion, a double transient voltage feedback control strategy of the output voltage and the voltage across the flying capacitor is introduced in this paper. A 500-VA 220-V \pm10% 50-Hz ac/220-V 50-Hz ac prototype is presented with the experimental results to prove that the converters have four improved advantages simultaneously, including lower voltage across power switches, bidirectional power flow, low THD of output voltage, and higher input power factor. [ABSTRACT FROM AUTHOR]

In this paper, a new nonisolated high step-up dc–dc converter is proposed. Active–passive inductor cells (APICs) are used to extend the topology. The ability to achieve high gains is the main merit of the proposed topology. The proposed converter operates based on parallel charging and series discharging of the inductors. The converter also achieves high step-up voltage gain with appropriate duty cycle and low voltage and current stress on the power switches and diodes. The proposed converter is analyzed in operation modes. The main parameters of the converter such as voltage gain, voltage stress of semiconductor devices are calculated to compare with other structures. Considering the output voltage ripple and filter size, the proposed converter is designed. Moreover, the losses and efficiency of the converter are calculated. The performance of the proposed converter is validated by experimental results. [ABSTRACT FROM AUTHOR]

A new single inductor dual buck full-bridge inverter is proposed in this paper. The inverter is improved on the basis of a dual buck inverter, and it retains the advantage of a no reverse recovery of body diode. The dc voltage utilization rate can be increased by adopting the voltage commutation bridge instead of the voltage-dividing capacitors in the inverter. In addition, comparing with other dual buck inverters, the inverter has just one filter inductor, which can make the volume and weight of the system decreased observably and improve the integration. The controlling method, combining the high- and low-frequency modulation, is adopted to weaken the complexity of control and improve the reliability and stability of the system. The operating principle, characteristic analysis, simulation and experiment are provided in this paper. A 1-kW prototype is established and tested, and the results of simulation and experiment verify the correctness of the theoretical analysis. [ABSTRACT FROM PUBLISHER]

This paper is focused on core size optimization of power inductors in bidirectional dc–dc converters. It presents an experimental large-signal characterization procedure for power inductors in electric vehicle applications and a method to obtain an inductance reference value for the power inductor in dc–dc converters' simulation studies. It discusses the importance of the inductor design project by describing important constraints such as core size and saturation. The main contribution of this paper is related to the proposed dc flux cancelation technique in the bidirectional converter. A variable inductor prototype is used to replace the power inductor in order to decrease core size by improving the ripple content of the inductor current. The saturation level of the core is controlled by means of an auxiliary winding whether the converter operates in buck or boost mode. Experimental results validate the proposed methodology showing more than 50% reduction in magnetic material for similar current levels. [ABSTRACT FROM PUBLISHER]

In applications where the high voltage gain is required, such as photovoltaic grid-connected system, fuel-cell and high-intensity discharge lamps for automobile, high step-up dc-dc converters have been introduced to boost the low voltage to a high bus voltage. The voltage gain of traditional boost converter is limited, considering the issues such as the system efficiency and current ripple. This paper proposes a class of hybrid switched-inductor converters (H-SLCs) for high step-up voltage gain conversion. First, the topological derivation of H-SLCs is deduced by combining the passive and active switched-inductor unit; second, this paper illustrates the operation modes of the proposed asymmetrical and symmetrical converters; third, the performance of the proposed converters is analyzed in detail and compared with existing converters; finally, a prototype is established in the laboratory, and the experimental results are given to verify the correctness of the analysis. [ABSTRACT FROM PUBLISHER]

This paper presents a circuit structure with a novel inverter that is applicable to arc welding machines. The output rectifier configuration adopts the current doubler rectifier with two coupled inductors. The proposed inverter topology can keep the energy stored in the coupled inductor until the next commutation interval. Moreover, the conduction loss will be lower, which improve the conversion efficiency of the arc welding machine. The operation principle, control circuit, and inverter design example are also described in detail. Experimental results demonstrate the feasibility and efficiency of the proposed inverter topology. [ABSTRACT FROM PUBLISHER]

In this paper, a simple digital hysteresis current control (DHCC) with quasi-constant switching frequency (SF) for the current control of a single-phase grid-connected inverter (SPGI) is proposed. The hysteresis band is cancelled, and the SF is fixed by online adjusting the sampling period. The principle of the DHCC with constant sampling period is analyzed, and the distribution of the switching period (SP) corresponding to the phase angle of the grid is derived. The rule of online adjusting the sampling period to fix SF is then determined according to the former theoretical analysis results. Furthermore, the effect of variation of the filter inductor on the SP is analyzed. An online estimation of the filter inductor based on the linear model of the current increment within one switching cycle is developed to eliminate this kind of effect. The proposed scheme shows the features of simple control, easy implementation in a digital way, robust to the filter inductor, and excellent steady and dynamic performance. The detailed simulation and experimental results verify its accuracy and feasibility. [ABSTRACT FROM PUBLISHER]

Electric bicycles (EBs) are becoming increasingly popular in some regions such as China and Europe. However, wireless power transfer (WPT) for charging massive EBs poses a challenge related to the cost of WPT system (WPTS), especially in China, where EBs application is so sensitive to the product price. This paper presents an optimization method of the passive components for the S-LCC topology to decrease the cost of the overall system. With the novel method, the number of passive components can be optimized to the minimum and still with constant current and constant voltage outputs. A novel compensation method with an inductor array is also proposed to guarantee an inductive input impedance of WPTS, achieving soft switching and reducing the high switching losses of the high-frequency inverter (HFI). To demonstrate the validity of the proposed methods, an experimental setup is built. The performance of two WPTS indicates that massive EBs can be charged with only one HFI, and the cost of the overall system decreases accordingly. [ABSTRACT FROM PUBLISHER]

This paper presents a new interleaved coupled-inductor nonisolated bidirectional dc–dc converter that provides high voltage gain ratio (VGR), low ripple current at the low-voltage side (LVS), and soft switching. The high VGR is obtained by connecting in series the outputs of an interleaved bidirectional buck–boost converter and a dual-active half-bridge converter, using the turns ratio of a coupled inductor. Since the voltage of the high-voltage side is shared between the converters outputs, the voltage stress across the active switches decrease. The active switches turn ON under zero-voltage switching condition in both directions. Moreover, the low current ripple at the LVS is achieved due to the applied interleaved technique. By employing the phase-shift angle modulation, the output voltage is regulated. The proposed converter is analyzed in details and a 900-W experimental prototype with 48-V input voltage and 400-V output voltage under 100-kHz switching frequency is implemented to verify the theoretical results. [ABSTRACT FROM PUBLISHER]

In this paper, an active electromagnetic interference (EMI) choke for both common-mode (CM) and differential-mode (DM) noise suppression is proposed. Three isolated windings with a different number of turns are wound on the same magnetic core. One of the windings is served as the auxiliary winding connecting to an active circuit called the negative impedance circuit. The inductance of the EMI choke is substantially boosted up to effectively attenuate the low-frequency noise. This technique leads to a greater inductance but fewer turns and smaller size of the EMI choke. Different from the design of a conventional EMI filter, which uses separated CM and DM chokes, this proposal saves the cost and space of the EMI filter. The enhancement to the CM and DM impedance is individually analyzed and experimentally confirmed. Based on the classical CM and DM noise models, CM and DM noise insertion losses are predicted using computer simulation. The simulation results are validated by a network impedance analyzer. Finally, conducted EMI tests are carried out to verify the effectiveness of the proposed technique. [ABSTRACT FROM PUBLISHER]

Due to the global environmental issues and energy crisis, the injection of renewable energy sources (RESs) into the power system is continuously increasing. As the interface between RESs and power grid, grid-tied inverters using MOSFET switches, without traditional line frequency transformers, show some potential advantages, in terms of low cost, high efficiency, and lightweight and small size. Among several proposed configurations, the Aalborg inverter was proposed as a new family of high efficiency MOSFET-switch-based hybrid source inverters. For a conventional “half bridge” type Aalborg inverter, due to the imbalance of two independent dc sources, the input dc energies may not be fully utilized, which may reduce the efficiency of whole system. In order to extract the maximum energy from two independent dc sources, a coupled-inductor-based “half bridge” type Aalborg inverter is proposed in this paper. The principle of operation is presented and demonstrated through equivalent circuits. The effectiveness of a new energy balancing technique has been validated through simulations and experiments on a 110 V/ 500 W prototype. [ABSTRACT FROM PUBLISHER]

In this paper, a new nonisolated high-voltage-gain boost converter is proposed. The proposed converter is constructed by adding an additional inductor to a conventional three-level-boost (TLB) converter. When compared with the conventional boost and TLB converters, the proposed converter can achieve higher voltage conversion ratio with reduced voltage and current stresses in the switches. In particular, the proposed converter can reduce the losses of active devices by reducing the current of the switch compared to conventional converters, thus, can achieve high efficiency. In addition, the proposed converter automatically balances the output voltages for an unbalanced load without the need for any additional control strategy or auxiliary circuit. A 2-kW prototype converter was built and tested to verify performances of the proposed converter. [ABSTRACT FROM PUBLISHER]

In this paper, a new structure for high step-up dc–dc converters is proposed. In the proposed structure, it is possible to extend the topology by increasing the number of active–passive inductor cells. High voltage gain with lower duty cycle, low-current and -voltage stresses on switches, small inductors, and small size of filter are the main advantages of the proposed structure. The proposed converter is analyzed in different operating modes. In order to design the components’ values of the proposed converter, the equations of output voltage ripple are calculated in each operating mode and a design procedure is proposed based on the aforementioned equations. Moreover, the losses and efficiency of the converter are calculated. In order to validate the correctness of calculations and analyses, the experimental results are given. [ABSTRACT FROM PUBLISHER]

In an asymmetrical pulse-width-modulated half-bridge (APWM HB) series resonant converter, an auxiliary LC network is provided for ensuring zero-voltage switching (ZVS) over a wide range of line and load variations. However, it comes at the cost of increased number of components and reduced efficiency and reliability. This paper presents a novel design methodology for the standard APWM HB resonant topology, which uses the magnetizing current and eliminates the need for extra components. The converter with the proposed design methodology operates at the resonant frequency of the tank and features load-independent ZVS for a wide range of input voltage variation with minimal magnetizing current. Empirical formulae are derived to design the resonant network and the magnetizing inductance of the high-frequency transformer systematically in a flowchart-based manner. The proposed design is validated by using simulations as well as experiments and is compared with a reference APWM HB series resonant converter design that uses an auxiliary LC circuit for ZVS. Two separate experimental prototypes of the two converters rated for 30 W, 48 V/5 V with a switching frequency of 500 kHz were built and tested in the laboratory. It was found that the converter with the proposed design methodology, apart from having lower component count, is about 3% more efficient than the reference topology at the rated power. [ABSTRACT FROM PUBLISHER]

This paper proposes a current control method for discontinuous current mode (DCM) in order to achieve the same control performance as continuous current mode (CCM) in a boost converter. By utilizing the duty ratio at the previous calculation period to compensate for a DCM nonlinearity, the controller, which is designed for CCM, can also be used in DCM. In the frequency analysis, the cutoff frequency of the proposed DCM current control agrees exactly to the design value, which is 2 kHz, whereas the cutoff frequency of the conventional DCM current control results in high error of 47.5%. In the current step response experiment with a 360-W prototype and the switching frequency of 20 kHz, the experimental DCM current response almost agrees with the conventional CCM current response, which are 380-μs rise time for both CCM and DCM, 9% and 8% overshoot for CCM and DCM, respectively. Furthermore, the computation time of the proposed DCM current control is shorter 35% than the conventional DCM current control. [ABSTRACT FROM AUTHOR]

This paper proposes a novel modular multilevel dc–dc converter intended for transforming dc voltage and interconnecting dc grids for medium-voltage networks. The converter is composed by two strings of submodules, each of which consists of an upper arm and a lower arm with their middle points crossly connected through a dc capacitor. With assistant of the cross-connected capacitors, dc and ac power loops are formed for the dc–dc converter, leading to the power balance between primary and secondary sides, as well as between upper and lower arms. The avoidance of transformer brings the favorable features of low cost and light weight to the proposed dc–dc converter. In order to guarantee the normal operation of the dc–dc converter, a control strategy with focus on converter power balance control is presented. Simulation performed in MATLAB/SIMULINK validates the operation principle of the dc–dc converter. Experimental results obtained from a 300-V 3.6-kW downscaled laboratory prototype also prove the effectiveness of the proposal. [ABSTRACT FROM AUTHOR]

This paper presents a finite-control-set model predictive control (FCS-MPC) for grid-tied packed U cells (PUC) multilevel inverter (MLI). The system under study consists of a single-phase 3-cells PUC inverter connected to the grid through filtering inductor. The proposed competitive topology allows the generation of 7-level output voltage with reduction of passive and active components compared to the conventional MLIs. The aim of the proposed FCS-MPC technique is to achieve, under various operating conditions, grid-tied current injection with unity power factor and low total harmonic distortion while balancing the capacitor voltage. Parameters’ sensitivity analysis was also conducted. The study is conducted on a low-power case study single-phase 3-cells PUC inverter and with possible extension to higher number of cells. Theoretical analysis, simulation, and experimental results are presented and compared. [ABSTRACT FROM AUTHOR]

A new single-phase \uppi-\texttype 5-level inverter using 3-terminal switch-network (3TSN) is proposed in this paper. The topology is considered as a variant of T-type 3-level structure or dual-buck inverter with coupled inductors. This new inverter is suitable for multilevel power inversion with low dc-bus voltage. The merit of the proposed topology is to apply only four active power switches to achieve 5-level operation. Other benefits include double frequency operation of output inductor and equal division of the current that flows through power switches and filter inductor. Hence, it leads to high efficiency and low harmonics. These characteristics allow improvement of losses distribution and volume reduction of output filter inductor. The operation scenario with sinusoidal pulsewidth modulation (SPWM) is described in details. Meanwhile, the magnetic analysis and design are studied and discussed. Finally, a prototype is built to verify the theoretical analysis and demonstrate the benefits of the proposed topology. [ABSTRACT FROM AUTHOR]

This paper proposes a large-signal stabilization method for the dc power system with a constant power load (CPL), which is detrimental to system stability due to its negative incremental resistance (NIR). The proposed method utilizes a shunt active damper at the point of common coupling of the dc bus and controls it as a parallel set of a virtual capacitor, virtual inductor, and resistor. The Takagi–Sugeno fuzzy model is employed with the Lyapunov stability theorem to verify the asymptotic stability of the system and to estimate the region of asymptotic stability. Improvements on the dc-bus voltage stability are evaluated based on dc-bus voltage deviation or dc-bus capacitance reduction. The performance of the proposed shunt active damper is verified by simulation and experimental results. [ABSTRACT FROM PUBLISHER]

The main objective of this paper is to detect faults in induction machines using a condition monitoring architecture based on stator current measurements. Two types of fault are considered: bearing and broken rotor bars faults. The proposed architecture is based on high-resolution spectral analysis techniques also known as subspace techniques. These frequency estimation techniques allow to separate frequency components including frequencies close to the fundamental one. These frequencies correspond to fault sensitive frequencies. Once frequencies are estimated, their corresponding amplitudes are obtained by using the least squares estimator. Then, a fault severity criterion is derived from the amplitude estimates. The proposed methods were tested using experimental stator current signals issued from two induction motors with the considered faults. The experimental results show that the proposed architecture has the ability to efficiently and cost-effectively detect faults and identify their severity. [ABSTRACT FROM PUBLISHER]

This paper describes an alternative to connect power converters to a direct-current network with an inductor circuit. The circuit allows the connection of converters through a coil and avoids short-circuit currents with different instantaneous values of voltage output. A description of the calculation and the choice of components together with a real implemented example in a dc network within Smart City project (Endesa Utility) is presented. [ABSTRACT FROM PUBLISHER]

In this paper, an efficient zero-voltage-switching (ZVS) synchronous buck converter with extended duty cycle and low-current ripple is proposed for voltage regulator module (VRM) applications. By combining series capacitor and coupled inductors, operating duty cycle is extended considerably. Also, soft switching condition for all switches is provided without any auxiliary circuit and as a result, overall efficiency is improved. In addition, by complementary operation of the main switches of the interleaved modules, the resulting output current ripple is reduced. The converter operating modes are discussed and experimental results are presented to verify the theoretical analysis. [ABSTRACT FROM PUBLISHER]

This paper proposes some topologies for developing electronic ballasts, supplying high-intensity discharge lamps fed by a pulsewidth-modulation ac–ac converter, implemented with bidirectional switches. The lamp operates directly from the ac mains; thus, operation with low frequency so as to prevent the occurrence of destructive acoustic resonance is provided. The features of the proposed solution are high efficiency, high power factor, low cost, and the absence of electrolytic capacitors. This paper includes the design of passive elements, the transfer function, and the development of the control strategy. The experimental results qualify the viability of the system feasibility. [ABSTRACT FROM AUTHOR]

Pulsewidth modulation (PWM) strategies and methods for multilevel converters are usually developed for series converters. One of the aims of this paper is to show that they may be applied to parallel converters using interleaving techniques, given that these converters also have multilevel characteristics. PWM methods based on carriers' disposition and on zero sequence injection are studied for parallel multilevel inverters. Analysis show that the best method in terms of load current ripple (phase disposition (PD) centered space vector PWM) has, nevertheless, a bad influence on the current balancing between commutation cells of the same phase. Another objective is to analyze these problems and to propose a solution to cancel current imbalance when using PD strategy. Experimental results validate the analysis presented in this paper as well as the compensation of band transition of the differential mode current observed when PD strategy is used. [ABSTRACT FROM PUBLISHER]

In this paper, the effect of equivalent series resistance (ESR) of an output capacitor on the performance of a constant-on-time (COT)-controlled buck converter is studied, and a pulse bursting phenomenon is revealed. It indicates that the ESR of the output capacitor is one of the key factors causing pulse bursting phenomenon in COT-controlled buck converters, and the critical ESR is derived via time-domain analysis and stability analysis in the s-domain. It is pointed out that, when the ESR of the output capacitor is smaller than the critical ESR, pulse bursting phenomenon occurs; otherwise, it disappears. Simulation and experimental results are provided to verify the theoretical analysis results. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive physical characterization and modeling of the three-phase common-mode (CM) inductors along with the equivalent circuits that are relevant for their design. Modeling issues that are treated sparsely in previous literature are explained in this paper, and novel insightful aspects are presented. The calculation of the leakage inductance is reviewed, along with the magnetic core saturation issues, and a new expression for the leakage flux path is derived. The influence of the core material characteristics on the performance of the component is discussed, and a new method for the selection of the material for the minimized volume CM inductors is proposed in order to simplify the design procedure. Experimental results which validate the model are presented. [ABSTRACT FROM PUBLISHER]

In this paper, a direct ac–dc power electronic converter topology is proposed for efficient and optimum energy harvesting from low-voltage microgenerators. The converter utilizes the bidirectional current-conduction capability of MOSFETs to avoid the use of a front-end bridge rectifier. It is operated in discontinuous conduction mode and offers a resistive load to the microgenerator. Detailed analysis and modeling of the converter is presented. In such low-power applications, the power consumption of gate drive and control circuits should be minimal. In this paper, they are specifically designed to consume very low power. A suitable startup circuit and auxiliary dc supply circuit is proposed for the implementation of the converter. A low-voltage microgenerator is used to verify the performance and operation of the converter and the gate drive circuits. [ABSTRACT FROM AUTHOR]

This paper introduces an alternative implementation of the traditional LC filter, called hybrid LC filter (HLCF). The construction described in this paper contains two foil windings that integrate inductance and capacitance into one unit. The main aspects of the HLCF design are considered. The experimental data show that the device proposed here can be used, instead of traditional LC filters, as an alternative solution for the mitigation of the adverse effects of the pulse-width modulation (PWM). [ABSTRACT FROM AUTHOR]

This paper describes the design procedure and performance of an LCL grid filter for a medium-voltage neutral-point clamped converter to be adopted for a multimegawatt (multi-MW) wind turbine. The unique filter design challenges in this application are driven by a combination of the medium-voltage converter, a limited allowable switching frequency, component physical size and weight concerns, and the stringent limits for allowable injected current harmonics. Traditional design procedures of grid filters for lower power and higher switching frequency converters are not valid for a multi-MW filter connecting a medium-voltage converter switching at low frequency to the electric grid. This paper demonstrates a frequency-domain-model-based approach to determine the optimum filter parameters that provide the necessary performance under all operating conditions given the necessary design constraints. To achieve this goal, new concepts, such as virtual-harmonic content and virtual filter losses are introduced. Moreover, a new passive-damping technique that provides the necessary damping with low losses and very little degradation of the high-frequency attenuation is proposed. [ABSTRACT FROM AUTHOR]