Search

Two structures are proposed based on the quasi Z‐source inverter (qZSI), which can significantly raise the output voltage in applications, including photovoltaic and fuel cells, in which the input voltage is low. The proposed inverters provide a continuous input current and reduce the voltage stress on capacitor. Besides, the proposed switched‐capacitor‐inductor qZSI (SCL‐qZSI) can suppress inrush current at the start up moment as this current might damage the devices. The performance of the proposed structures is investigated at different operating modes, and the voltage equations are calculated. The voltage stress on switches, the voltage stress on capacitors, the voltage stress on diodes, and the current stress on inductor, as well as the average DC‐link current, the gain voltage (G), and the boost factor (B) of the proposed inverters, are analysed and derived. They are then compared with similar converters. To confirm the performance of the proposed converters, a laboratory sample of converters is made, which with output voltages, capacitors voltages, input and output current for the proposed converters. The DC‐link (Vi) voltage is 95 with boost factor 1.6 for SCL‐qZSI, and the DC‐link voltage is 216 with boost factor 3.6 for the enhance switched‐capacitor‐inductor qZSI (ESCL‐qZSI), which confirms the relationships obtained from the proposed converters. Also, the abbreviation for this paper is shown in table 1. [ABSTRACT FROM AUTHOR]

Very fast transient over voltage (VFTO) is a unique electromagnetic transient phenomenon occurring in Gas Insulated Substation (GIS), which determines the insulation level of the GIS (above 330 kV). Unfortunately, up to the present, there is no standard VFTO waveform to test the high voltage equipment to ensure the safety of power grid. For this reason, this paper focuses on obtaining the standard VFTO waveform through finding a method to fit the curve of VFTO. Hence, a UHV disconnector operation experiment of GIS was carried out on the UHV GIS test platform. The representative waveform of VFTO generated by a single SF6 gas discharge was extracted from the measured data. Furthermore, The Fast Fourier Transformer is applied to analyze the frequency features of VFTO. As one of the switchgear operation voltage, VFTO can be concluded to be a superposition of the power-frequency waveform with the non-periodic impulse waveform. Thus, it is found that The Squares Method is convenient for fitting the expression of VFTO according to its transient characteristics. Then the standard VFTO waveform can be obtained from the fitting expression, which coincides well with the measured waveform. The simulation results using ATP-EMTP software are compared with the calculation results and the measured results. [ABSTRACT FROM AUTHOR]

This paper proposes a technique for switch current stress reduction in a Switched Inductor DC‐DC Boost Converter (SIBC). The proposed technique comes up with a low‐cost design, high voltage conversion ratio with a less duty cycle value, and lower current stress without increasing the component count. This topology is basically a transformer‐less design where one diode of the traditional switched inductor configuration has been replaced with a switch, which is in parallel with the existing switch, resulting in a design that can incorporate active switches with a low current rating, since the total input current is equally shared by them. The detailed modes of operation in both continuous conduction mode (CCM) and discontinuous conduction mode (DCM) and steady‐state analysis, the non‐idealities' effect on voltage gain, design approach, and a comparative study with other DC‐DC converters for some significant performance characteristics are provided. The experimental validations for the performance and working of the 500 W designed prototype are presented. [ABSTRACT FROM AUTHOR]

Most matrix converters use indirect control, which includes a three‐phase virtual AC/DC converter and a virtual inverter, to control their nine AC switches. However, matrix converters do not use electrolytic capacitors to store energy. As a result, unbalanced three‐input voltages directly cause unbalanced three‐phase output voltages, which deteriorate the performance of IPMSM drive systems. To solve this problem, this paper proposes an improved method, which includes inverter stage control and AC/DC stage control, for matrix converter‐based IPMSM drive systems under unbalanced three‐phase input voltages. The inverter stage control adjusts the duty cycles of the virtual inverter to compensate for the fluctuations of the virtual DC‐bus voltage. Therefore, the harmonic currents of the IPMSM are significantly reduced, and the speed ripples of the IPMSM are reduced as well. The AC/DC stage control uses a virtual AC/DC converter to control the three‐phase input currents near sinusoidal waveforms with a unity power factor. Finally, a hybrid algorithm that combines the inverter stage control and the AC/DC stage control is demonstrated. A digital signal processor, type SH 7237, and a field programmable gate array, type 10M16SAU16917G, are used in parallel as the computational and control center. [ABSTRACT FROM AUTHOR]

This paper presents a novel converter topology for six-phase switched reluctance motor (SRM) drives, which reduces the number of switches and diodes by half, compared with the conventional asymmetric half-bridge (AHB) converter, and needs no additional energy storage component. A dynamic model of a six-phase SRM is developed in the MATLAB/SIMULINK environment and conventional control technique is applied to the proposed converter, demonstrating successful operation with modified conventional current control technique, lower converter losses, and higher system efficiency compared with the AHB converter. Furthermore, a direct torque control (DTC) method has been proposed for the novel converter to further reduce the torque ripple. Experimental tests comparing the proposed converter with the AHB are described and verify the predictions of the simulations. [ABSTRACT FROM AUTHOR]

Two principal two-stage switch architectures (cascaded and parallel), both of which are composed of two identical optical crossbar switches with an extra set of inputs and outputs, are compared in terms of their number of crosspoints, switch control complexities, and key optical performances, such as insertion loss and crosstalk power, through theoretical analysis. The authors begin by briefly introducing a known N × N cascaded optical crossbar switch with N2/2 crosspoints, where N is the switch size, and present a new functional perspective based on quasi-bitonic sorting. Subsequently, the authors derive two types of two-stage parallel optical crossbar switches with reduced crosspoints from a conventional single-stage parallel crossbar switch with N2 + 2N crosspoints. The first type uses two N/2 × N asymmetric switches in parallel, both of which are embedded in a single N/2 × N/2 crossbar switch. It has (N2 + 2N)/2 crosspoints and suffers from a complex switch control of O(N2). The second type is equivalent to a three-stage Benes network and exploits bidirectional transmission to reduce the number of switching stages. It requires (N2 + 3N)/2 crosspoints, but has a dramatically reduced switch control complexity of O(N), and significantly improved optical performance. [ABSTRACT FROM AUTHOR]

This paper presents a novel voltage self‐balancing converter (VBC) applied to DC solid‐state transformer (DCSST), analyzes the operating principle of the proposed VBC, and proves the voltage balance performance. Based on this converter, a novel DCSST topology is proposed, which can be used in medium and low voltage DC distribution application, microgrid and medium and low voltage energy storage system. Compared with the previous work, under the same voltage level, it can effectively reduce the number of transformers and switches, reduce the voltage level of switches, and realize the soft switching of the VBC switches, so as to improve the system efficiency and power density, and then improve the system reliability. Meanwhile, the fault handling ability and fault tolerance ability of DCSST are improved, which makes DCSST more reliable when multiple isolated bi‐directional DC/DC Converters (IBDC) are connected in series. In addition, with this topology, the input voltage self‐balancing control strategy of the IBDC is not needed because of the voltage self‐balancing characteristic of VBC, which simplifies the control complexity and greatly improves the control accuracy of the control system. Experimental results agree well with the accuracy and correctness of the proposed topology. [ABSTRACT FROM AUTHOR]

Non‐isolated inverters have the disadvantage of large leakage current, which will damage the equipment and personal safety. In order to solve this problem, this paper proposes two H10 three‐phase inverter topologies named forward‐clamped and reverse‐clamped H10 inverters. Each of the topologies is composed of two DC bus switches, a clamping circuit and a traditional three‐phase inverter, but the clamping method of these two topologies is different. A general control strategy combining carrier modulation and logic operation for these two topologies are proposed. The control strategy allows the common‐mode voltage of these two topologies to vary between one third and two thirds of the DC bus voltage, but the frequency of the common‐mode voltage of the reverse‐clamped inverter is three times that of the forward‐clamped inverter. The loop impedance of the reverse‐clamped inverter increases significantly at high frequency, so the leakage current suppression capability is better. Simulation and experiment platforms of the inverter systems are built. The obtained results verify the correctness of the theoretical analysis. [ABSTRACT FROM AUTHOR]

The authors propose a phased patch-antenna array working in the X-band (i.e. 8-12 GHz), in which the beam-steering is obtained by means of two-terminal non-volatile resistive switches (or memristors). These novel components have a simple design and a tunable resistance (suitable for electromagnetic matching), and could replace other volatile switching-type devices (such as PIN diodes, MEMS, etc.), providing good radiofrequency (RF) performance and low-power consumption. They also offer the advantage of non-volatility state, i.e. the controlling signals do not need to be applied continuously, which entails a decrease of the power consumption and a reduction of antenna's sensitivity to power outages. The paper models a simple non- volatile resistive switch working in the microwave and millimetre frequency bands, then simulates, based on these switches, a frequency-tunable dipole antenna and a double patch-antenna array with beam steering capabilities. The authors obtained a multi-resonant array, which exhibits a maximum steering angle of ±28°. They also report the fabrication and characterisation of a resistive switch, based on TiO2-x that shows promising performance for high endurance and retention, with low insertion loss and high isolation. The results of this study represent the starting point for a new family of microwave tunable devices. [ABSTRACT FROM AUTHOR]

This paper presents an optimization analysis of an axial flux-switching hybrid excitation synchronous machine (AFHESM) to improve its no-load electromagnetic performances. The shapes of permanent magnet (PM), rotor-teeth and stator slot of AFHESM are investigated for a better design scheme by finite element analysis (FEA). Some optimal results under no-load are achieved, which mainly including the induced electromotive force (EMF), cogging torque and field control ability. Both FEA and experimental results show that the induced EMF can be improved when PM shape coefficient is 0.95 and the rotor-teeth bevel angle is 6°. [ABSTRACT FROM AUTHOR]

In this paper, a three-phase, Y-connected, five-level static synchronous compensator with reduced number of switches is proposed for single phase and unbalanced three-phase loads. The level shifted carrier based sinusoidal pulse width modulation method is used for switching. The active and reactive powers demanded by the load are estimated for each phase independently to compensate the reactive power supplied from the power system. The simulation results obtained from Matlab are compared with the results of experimental work and dedicated model of the proposed system. The system is implemented in the laboratory by using DSP TMS320F28335. [ABSTRACT FROM AUTHOR]

In practical photovoltaic (PV) installations the operating conditions of the panels the PV array is made of are different owing to different factors. Such irregular conditions are known as 'mismatching conditions' and produce multiple maxima in the power-voltage curves of any PV array. The traditional maximum power point tracking (MPPT) techniques are able to track one of those maxima, but they cannot guarantee the extraction of the maximum power the PV array would be able to deliver. To overcome this problem, many techniques have been presented in the literature: they use one converter for the entire array (centralised MPPT), one converter for each part of the array (distributed MPPT) or they reconfigure the PV array (RMPPT). This paper presents the general architectures used by 61 different MPPT techniques, by discussing their main advantages and disadvantages, in order to give to the reader a comprehensive view of both the control strategies and the architectures for extracting the maximum power from a mismatched PV field. Moreover, the widely adopted techniques for each hardware structure are presented in a structured and compact way, thus providing to the reader some guidelines regarding the technique's operation principle and hardware requirements. [ABSTRACT FROM AUTHOR]

This paper proposes a high-power-factor electronic ballast for metal-halide (MH) lamps. In the proposed circuit, two buck-boost converters and a buck converter are integrated with a full-bridge inverter by sharing the four active switches of the full-bridge inverter. Two active switches are switched at high frequencies, while the other two are switched at lower frequencies. The buck converter is used to step down the DC-link voltage of the full-bridge inverter and filter out the high-frequency components to drive lamps with a low-frequency square-wave (LFSW) current. The buck-boost converters are operated at discontinuous-conduction mode to perform the function of power-factor correction (PFC) to ensure almost unity power factor at the input line. By tactful arrangement of diodes, the DC-link capacitors are discharged in parallel; this helps to operate the high-frequency active switches at a high duty ratio, achieving a small peak value of the PFC-converter current and correspondingly smaller conduction losses. Detailed operation modes and the design equations are provided. A prototype electronic ballast for a 70 W MH lamp is built and tested. Experimental measurements have proven that the proposed electronic ballast has the advantages of high-power factor and being free of acoustic resonance. By integrating the active switches of the converters and the inverter, the proposed electronic ballast is advantageous in terms of cost-effectiveness and high energy-conversion efficiency. [ABSTRACT FROM AUTHOR]

THD is the most common criterion to determine the harmonic content of each waveform. Conventional methods, which are usually used, result in approximate answers due to their inability to take all harmonic orders into account. This paper focuses on the three-phase two-level inverter and proposes two methods, founded on the basic definition of THD, to calculate its line voltage THD, precisely. The first method considers stepped essence of line voltage and the second uses its Fourier coefficients. By proposed methods, all harmonic orders of two-level inverter with any switching angles, named n-degree of freedom, are considered. Another feature of the introduced methods is deriving analytical formulas for line voltage THD. This helps some switching strategies like THD Minimisation (THDM) to get rid of heuristic methods, which find those switching angles that globally minimise THD. Superiority of the proposed methods for one and two degrees of freedom is verified by both numeric and graphic results, simulated in MATLAB. The comparison table is only used for higher degrees of freedom, because of impossibility of plotting n-dimensional space. Finally, experimental results for two sets of switching angles are compared with the results of proposed methods to evaluate the accuracy of introduced methods. [ABSTRACT FROM AUTHOR]

This paper proposes a reconfigurable beam-steering antenna using a bended dipole and a loop. The radiation patterns of the two antennas are cancelled or compensated, and headed towards a specific direction when the dipole and loop antenna are combined at a reasonable ratio. The proposed antenna can steer the beam directions by controlling the operation of two artificial switches. The proposed antenna was manufactured on a PCB (FR-4) and a flexible PCB (polyimide). In the case of the antenna that was fabricated on a PCB, the maximum beam directions were +50°, 0°, and -50° in the azimuth direction using the two artificial switches, and the antenna gain was 1.96 dBi to 2.48 dBi in the operation bandwidth of 2.47 GHz to 2.53 GHz. Also, the antenna was fabricated on a flexible PCB and measured under various bending conditions for wearable applications. [ABSTRACT FROM AUTHOR]

A novel, high-power optically controlled microwave switch is presented. The switch uses integrated illumination of a silicon superstate through a low-loss glass substrate which reduces losses related to the plasma conductivity tail in the silicon. Numerical electromagnetic modelling is used to design the switch and good agreement between measured and simulated results has been achieved. The switch is then characterised using a two-tone non-linearity test at 2 GHz and a third-order intercept point of +72 dBm is obtained with 10 W per tone. [ABSTRACT FROM AUTHOR]

The ultra-high-frequency (UHF) method is efficient in partial discharges (PDs) detection in gas-insulated switchgear (GIS). The features extraction of UHF signals is significant for propagation characteristics analysis and PD pattern classification. The PD-induced UHF signals are acquired by the internal UHF sensors in an actual 252 kV L-shaped GIS. The short-time Fourier transform method is applied to process UHF signals and describe the propagation characteristics in L-shaped GIS. Hu's invariant moments of energy density distribution are extracted as features in time-frequency plane. The features are utilised to discriminate different PD defect patterns in actual GIS model by the support vector machine classifier and achieve good results. Finally, a novel system of features extraction and classification of UHF signals is summarised. [ABSTRACT FROM AUTHOR]

Power system (grid) impedance is time varying due to the changing structure of the power system configuration and it can have a considerable influence on the control and stability of grid connected converters. This study presents an online grid impedance estimation method using the output switching current ripple of a space vector pulse-width modulator-based grid connected converter. The proposed impedance estimation method is derived from the discretised system model using two consecutive samples within a single switching period. The estimated impedance is used for islanding detection and online current controller parameter tuning. Theoretical analysis and MATLAB simulation results are presented to verify the proposed method and its effectiveness is validated using experimental testing. [ABSTRACT FROM AUTHOR]

This study presents a novel single-switch high step-up dc–dc converter employing a quasi-resonant operation with high efficiency and low ripple continuous input current characteristics. In order to achieve a high voltage gain, a combination of coupled inductor and switched capacitor techniques is used in the proposed dc–dc converter. Moreover, utilising a series resonance capacitor with the leakage inductance of the coupled inductor leads to a resonant circuit. Subsequently, by employing a quasi-resonant operation, the switching loss of the proposed dc–dc converter has been reduced significantly. Operational analysis, mathematical derivation, component voltage and current ratings are well demonstrated in this study. Finally, the performance of the proposed circuit is evaluated through a 200 W laboratory prototype with 25 V input voltage and 400 V output voltage. The maximum efficiency achieved at full load is 96.4%. [ABSTRACT FROM AUTHOR]

A hybrid B4 active power filter (APF) with reduced switches is proposed in this study, which is composed of a inductance-capacitance (LC) passive filter and a four-switch three-phase inverter (B4 inverter) in series connection. The LC filter is used to supply reactive power, and the active filter is responsible for mitigating the harmonics. Compared with the previous proposed four-switch hybrid APF, it can overcome the drawback of large dc voltage components appearing in the ac capacitors. Basic principles and steady-state analysis of hybrid B4 APF are introduced in detail. A control scheme based on source current detection is presented. Multiple parallel vector resonance controllers are adopted in the current control loop, and the gains of these resonance controllers are optimised by a particle swarm optimisation approach. Experimental results have verified the effectiveness of the proposed hybrid B4 APF. [ABSTRACT FROM AUTHOR]

A correction is presented to the article "The experimental circuit uses bidirectional switches cause the battery to short-circuit during operation."

The interconnection of basic switching converters to increase power handling capabilities in dc applications has been widely reported in technical literature. This study presents a family of switching step-up dc-dc converters based on the principle of reduced redundant power processing (R²P²). This principle states that the power transfer from input port and output port on interconnected converters is reduced when a non-cascading connection is used. As shown in this study, the principle R²P² is useful for developing new converters. These have wide conversion ratios and quadratic dependence with respect to the duty ratio. In this study, the voltage conversion ratios, average models and steadystate operating conditions for proposed converters are derived, which are verified by experimental results. [ABSTRACT FROM AUTHOR]

In this study, a three-phase to three-phase matrix converter with eight switches in each phase is presented. In addition, a simple switching strategy is used to control switches based on the comparison of a reference output voltage value with 12 voltage values obtained from input voltage. One advantage of the simple switching approach is that it is suitable to step down input voltage frequency. So, it is applicable to interface microturbine generation and load. This converter can boost input voltage amplitude with variable reduced frequency with respect to conventional matrix converter using a simple switching technique. Other advantages of the suggested converter is that it is possible to obtain a voltage with low total harmonic distortion by applying the stated switching method as compared to conventional matrix converter. Simulation and experimental results are shown to validate the capability of the suggested converter in the boosting of input voltage at a variable frequency. [ABSTRACT FROM AUTHOR]

In this study, a new topology of semi-cascaded multilevel inverter is proposed which is a proper alternative to be used in medium voltage applications. This structure consists of series connected sub-multilevel inverters blocks. The proposed topology is based on the connections of several cell units in an appropriate scheme with the help of six power switches. Compared to the traditional cascaded multilevel inverter, in suggested topology the number of switches, inverter cost and installation area are reduced significantly. Also, in comparison with semi-cascaded multilevel inverter, the proposed inverter works with lower total peak inverse voltage. The proposed inverter is able to be used as an asymmetrical inverter. To verify the operation and good performance of the proposed inverter the simulation and experimental results are obtained. [ABSTRACT FROM AUTHOR]

To solve the problem of low efficiency of the dual active bridge (DAB) converter under the traditional single‐phase‐shift control, a natural soft‐switching current stress optimisation (NSS‐CSO) method is proposed by considering the current stress optimisation and soft‐switching operation under dual‐phase‐shift (DPS) control. This study establishes the current stress and the soft‐switching analytical models of the DPS control global mode. Based on these models, the Karush–Kuhn–Tucker (KKT) condition is used to analyse the influence of the current stress optimisation methods on the efficiency when all switches achieve controlled soft‐switching or some switches achieve natural soft‐switching. It is found that the NSS‐CSO method is more efficient. Furthermore, the optimal phase‐shift ratio combinations and the corresponding current stress extremums of the NSS‐CSO method under various ranges of transmission power and voltage conversion ratio are deduced completely. The results of this study show that the NSS‐CSO method can effectively improve the operation efficiency of the DAB converter over the entire power range when the voltage conversion ratio does not match. Finally, experimental results confirm the accuracy of the theoretical analysis and the effectiveness of the proposed optimisation method. [ABSTRACT FROM AUTHOR]

Here, a new single stage single switch soft switching PFC (power factor correction) converter is presented and analysed. The proposed converter combines buck AC‐DC converter and forward DC‐DC converter and applies an auxiliary circuit to eliminate input current dead angle. Furthermore, soft switching is attained and switching losses are eliminated resulting in high efficiency. Another merit of the proposed converter is the partial direct transmission of input power to the output that helps to improve efficiency. Experimental results are presented which justify the above mentioned points and show less than 5% THD in the nominal load. Comparison with other similar single stage PFC converters is performed and shows the proposed converter provides the lowest THD while high efficiency is attained. [ABSTRACT FROM AUTHOR]

An attempt was made to establish self‐healing architecture using ordered element‐matching (OEM) technology for ageing or partially damaged components of digital‐to‐analogue converter (DAC) components used in communication equipment. Using OEM technology, damaged DAC components, such as memory cells, current cells and current cell control switches, can be healed. The performance before and after healing is compared in this work. The simulation results prove the feasibility of using the proposed technology to heal the DAC almost to achieve the original performance. [ABSTRACT FROM AUTHOR]

Two‐stage switch networks are an emerging design option for relatively small‐capacity space switches. They are classified into two categories: folded and unfolded. Although folded switches have been well studied, research on unfolded two‐stage switch networks (UTSNs) remains limited. Here, non‐blocking UTSNs are considered. First, a new UTSN design is presented that consists of input and output switch modules (ISMs and OSMs) using bidirectional switching techniques. The proposed UTSN is represented by B(n, m, r), where n, m, and r denote the number of input ports of the ISM, number of OSMs, and number of ISMs, respectively. Second, the maximum number of rearrangements for B(n, n, r) is proved to be ⌊(r−1)/2(n−1)⌋ in general, whereas it is limited to two when n ≥ r. The strictly non‐blocking condition for B(n, m, r) to be m ≥ n + 1 is also determined. Finally, it is shown that the switch hardware complexity becomes minimal at n=N/2 and saturates at N2/2 as N → ∞. [ABSTRACT FROM AUTHOR]

To date, numerous concepts for converter station designs for use in voltage source converter (VSC)-based high- voltage direct current (HVDC) systems have been proposed. These differ not only in converter circuit topology, sub-module design, and control scheme but also in AC-or-DC switchgear and other auxiliary equipment. In the main, the existing literature categorises these converter stations according to just the converter circuit technologies and controls. However, for the development of network codes and to enable systematic network studies, a system-focused and technology-independent classification is needed. As such a classification does not yet exist, this study proposes a new framework, which categorises VSC station designs according to their capabilities during a DC-side fault and the method by which post-fault restoration may be achieved, given that these are the main differentiating factors from a system perspective. The classification comprises six converter station types and three time-intervals through which to fully characterise a design. Many well-known forms of converters are used as case studies, and simulation results are used to exemplify the classification framework. The outcome is a generic and technology-independent way of characterising converter station designs that is useful in wider power-system analysis but also for putting proposed converter stations into context. [ABSTRACT FROM AUTHOR]

Fast load restoration based on network reconfiguration is a key step to enhance the resilience of distribution systems (DSs). For DSs equipped with remote-controlled switches (RCSs), the reconfiguration can be completed promptly. However, when the branch is equipped with manual switches only, it cannot be operated immediately, and its post-event state is determined by its pre-event state. Considering these facts, this study proposes a unified two-stage reconfiguration method for the resilience enhancement of DSs. In the pre-event stage, the allocation of RCSs and the reconfiguration of the network are determined to prepare the system for a set of possible fault scenarios caused by upcoming extreme weather. In the post-event stage, network reconfiguration based on the placed RCSs is performed for fast load restoration to minimise the loss of load expectation (LOLE). A new mathematical expression is proposed to ensure the radial operation of DSs with islanded DSs and islanded microgrids. To improve the computational efficiency, the scenario decomposition algorithm is employed to decompose the proposed model into several subproblems, which can be solved in parallel. The results show that the proposed method can significantly reduce the LOLE caused by extreme weather events, thus enhancing the resilience of DSs. [ABSTRACT FROM AUTHOR]

Based on air clearance discharge characteristic curve and insulation coordination method, it is pointed out that the minimum air clearance of 1000 kV ultra-high voltage (UHV) AC substation can be further optimised. On the basis of analysis of the merits and demerits of the two insulation coordination methods for air clearances of UHV substation stated in the national standard GB/Z 24842–2009, it is concluded that using statistical method for insulation coordination is more reasonable and feasible. The minimum air clearance of UHV substation is optimised with the statistical method based on 1000 μs switching impulse characteristic test results. According to the study results, the phase-to-earth air clearance A1′ can be 1 m less than that specified in standard, the air clearance between conductors 0.5 m less than that specified in standard, and the phase-to-phase air clearance of grading ring and tubular bus 0.6 and 1.8 m, respectively, less than that specified in standard. [ABSTRACT FROM AUTHOR]

This study introduces a novel method called overlap onset control (OOC) to balance and maintain alternate arm modular multilevel converter (AAC) submodule capacitor voltages at their desired value. OOC performs zero-current switching and controls the timing of AAC commutation to regulate submodule voltages while retaining output voltage quality. The study uses steady-state converter models to develop the mathematical foundations behind the proposed capacitor voltage regulation method and then presents electromagnetic transient simulation results in PSCAD /EMTDC to demonstrate OOC's ability to extend the AAC operating range. [ABSTRACT FROM AUTHOR]

With the increase of the load of the switchgear, the overheating of the switchgear is more and more serious. In this article, the authors give the primary heat sources in the electrical equipment. According to these sources, they explore the reason of why the switchgear can be overheated during operation. Then, they build a 3D model in the Comsol & Multiphysics® and analyse the temperature state of the switchgear from the simulation. They also carry out temperature test on KYN28 switchgear to summarise the laws of the temperature change of the switchgear. Finally, they propose a brief method to monitor the temperature and realise the function of temperature warning to avoid accidents caused by overheating. [ABSTRACT FROM AUTHOR]

To improve the reliability and intelligent level of the AC transmission system, the radial basis function-based proportional-integral-derivative (RBF-PID) control method for the motor actuator used in the 550 kV gas-insulated switchgear (GIS) disconnector is proposed. According to the dynamic mathematical model of the motor actuator, the main structure of the RBF neural network based on the gradient descent method for learning algorithm is constructed. An identification function is formed by taking values of the output error square, and then by gathering information on the real-time tuning parameters of PID. Based on that, the simulation of the control system is constructed. The comparative analyses of the tracking control characteristics and the servo following error of the disconnector's contact speed between double-loop PID and RBF-PID are done through the computational and experiment methods, respectively. The results show that 550 kV GIS disconnector with the motor actuator by the RFB-PID control method has better controllability, and the servo following error is controlled within 0.1 m/s. [ABSTRACT FROM AUTHOR]

The non-inverting buck boost (NIBB) converter has attracted significant attention in recent years, as it shares ground between input and output, and the voltage stress of switches is lower. In order to investigate the differences between NIBB and conventional buck boost converters, a comprehensive comparison and analysis of these two converters were conducted in terms of their operation principles, which includes multi-mode control strategy and dual-edge modulation here, and also the characteristics of switches and passive components in the two converters were analysed. The results show that NIBB is better than conventional buck boost circuit in these aspects of electrical stress, power loss, cost, passive component volume, and so on. Two prototypes for the two converters with 10 kW/20 kHz were designed and simulated, respectively, for verifying the results. Analytical and simulated results confirmed the conclusions. [ABSTRACT FROM AUTHOR]

The aim of this study is to present a new cost effective topology for Symmetric multilevel inverters (SMLIs) configurations, which can generate a great number of output voltage levels with a least of switching devices. The proposed structure contains a novel switched-dc-source (SDCS) sub-module that can produce three positive output voltage levels with a contribution of four equal dc voltage sources, two unidirectional, and one bi-directional power switches. Accordingly, to create a uniform staircase output voltage with multiple levels, the proposed SDCS sub-module is integrated into a new design. Therefore, a new family of reduced switch-count (RSC)-SMLIs is derived, which is capable of generating at least 13- and 15-level output voltages using only ten power switches and nine gate drivers. Furthermore, when employing several of the proposed SDCS sub-modules in series, a new generalised RSC-SMLI topology is obtained. Comparisons with prior-art SMLIs structures are done, which also highlights the beneficial potential of the proposed topology. To demonstrate the superior performance of the proposed topology, several simulation and experimental results have been provided. [ABSTRACT FROM AUTHOR]

A multi-pulse AC-DC converter fed space vector modulation (SVM) controlled neutral point clamped (NPC) inverter based vector control induction motor drive (VCIMD) is proposed here for medium power rating applications. To improve the power quality at supply side, a 12-pulse AC-DC converter is used and to meet the IEEE-519 standard, a high-pass filter is also used along with it. A three-level NPC inverter is utilised on the motor side to enhance the required performances of an induction motor drive (IMD). A modified SVM strategy is proposed to balance the capacitor voltages of the NPC inverter and to switch this inverter at very low switching frequency. The neutral point voltage balancing is achieved by the time adjustment between positive and negative small vectors. The model of proposed IMD is developed using the Simulink/MATLAB platform, and simulated response is validated with test results on a developed prototype in the laboratory to demonstrate its usefulness for medium power applications. [ABSTRACT FROM AUTHOR]

A new 11-level inverter using a coupled inductor and a transformer is proposed. The proposed inverter increases maximum output voltage and decreases current stress on switches. A comprehensive comparison is conducted among the proposed inverter and some of the recent presented inverters in terms of number of components, maximum output voltage, and voltage and current stresses on the switches. Moreover, the design calculations of a single-phase inverter in addition to the transformer and coupled inductor design are given. In order to verify the performance of the proposed topologies, the experimental results are presented. [ABSTRACT FROM AUTHOR]

The study introduces a bidirectional dc-dc converter with current- and voltage-fed (VF) ports that features soft switching in both buck and boost operating modes. The converter can be used for integration of low-voltage DC sources, such as batteries into a dc bus of considerably higher voltage or a dc link of a grid side inverter. Zero current switching, assisted with the leakage inductance of the isolation transformer, can be achieved at the current-fed side along with zero voltage switching of the VF side, assisted by snubber or intrinsic capacitances of the transistors. Soft switching can be maintained over a wide range of voltage and power levels, regardless of the energy transfer direction. Converter operation is described and theoretical findings were verified with experimental results obtained by means of a 300 W prototype operating at a switching frequency of 100 kHz and designed for integration of a 24 V battery into 400 V dc bus. The converter proposed is compared in terms of efficiency to other competing soft-switching full-bridge topologies implemented with the same components. [ABSTRACT FROM AUTHOR]

This study discusses the derivation of the continuous input current high-voltage gain DC-DC converters. These converters are very suitable for renewable energy sources such as photovoltaic power systems since high-output-voltage gain is required for grid connection and continuous input current is necessary for better input current regulation. In these structures, coupled inductors are used along with voltage multiplier cells to improve the voltage gain. Passive clamps are also applied to recover the remained energy in the coupled inductors and improve the efficiency. Regenerative snubbers mitigate the voltage stress on the main switch. Various advantages of the studied converters make them suitable for renewable energy sources with low-output DC voltage. A thorough comparison section is provided to assess the performance of the presented converters. For simplicity, a converter is selected and analysed in details and design guidelines are presented. The experimental setup is implemented in the laboratory to prove the proper operation of the converter. [ABSTRACT FROM AUTHOR]

Nowadays, low power factor (PF) is a serious problem that has gained more importance in power electronics area. In this study, a unity PF control (UPC) strategy for boundary conduction mode (BCM) buck-buck/boost PF correction converter is proposed. The proposed control strategy can achieve high PF and low total harmonic distortion by utilising the input and output voltages to modulate the on-time of both buck and buck/boost switches. The operating principles and comparative analysis of BCM buck-buck/boost converter with conventional non-UPC and UPC are analysed. For verifying the effectiveness of the proposed control strategy, the experimental verifications are carried out from a 100 W universal input prototype. [ABSTRACT FROM AUTHOR]

This study proposes a novel isolated bidirectional DC/DC converter for micro-grid system, which can fulfil battery charging and discharging. Even though the proposed converter only employs four active switches and a coupled inductor, it can achieve high-voltage ratio without excessive duty ratio or high transformer turns ratio. The power stage of the converter is mainly developed by integrating a three-winding coupled inductor, three-switched capacitors, and a flyback-behaviour converter into a novel structure. The energy stored in the leakage inductance can be totally recycled for efficiency improvement. The operation principle, steady-state analysis, and design considerations of the proposed converter are described in detail. Finally, a laboratory prototype is built to validate the converter. The measured results have verified the correctness and the theoretical analysis. [ABSTRACT FROM AUTHOR]

The new emerging topologies in multilevel inverter field with reduced dc voltage sources and device counts, offer high power capability with less commutation losses and less harmonics in output voltage. However, these topologies have some disadvantages such as voltage balancing problem, increased number of electronic components, larger in size and complex control techniques. This study proposes a new asymmetrical multilevel inverter topology which requires less number of switching devices and driver circuits as compared to conventional multilevel inverter topologies. In the proposed topology, eight switches are required for generation of 15-level single phase output voltage. The proposed topology is simple and can be extended easily to get more number of levels in the output voltage. Therefore, there is a significant reduction in size, cost and complexity for higher number of levels in output voltage. All positive and negative levels as well as performance parameter in term of Total Harmonic Distortion in the output voltage generated by proposed MLI have been evaluated using simulation in MATLAB environment. Various simulation and experimental results are presented to verify the operational accuracy of the proposed topology for a single phase 15-level inverter. [ABSTRACT FROM AUTHOR]

To solve the problem that three-to-five-phase matrix converter (MC) cannot supply symmetrical voltages to unbalanced loads, a topology of five-phase six-bridge indirect MC and a carrier-based pulse-width modulation (PWM) method are proposed. A midline bridge is added to the neutral point of five-phase loads in inverter stage. The neutral point voltage is analysed and derived by space vector PWM (SVPWM) method for calculating the duty ratio of midline bridge. Calculations of other five-phase bridge duty ratios of SVPWM method remain unchanged. All of the duty ratios are used to calculate modulation waves of rectifier stage and inverter stage. Driving signals of two-stage power switches are generated by comparing the modulation waves with a carrier, which are used to control the neutral voltage as corresponding zero-sequence voltage. Therefore, five symmetrical output voltage sinusoids are obtained under both balanced and unbalanced loads. Finally, simulation and experimental results are provided to verify the feasibility and validity of the proposed method. [ABSTRACT FROM AUTHOR]

This study introduces a new dual switches converter with a high voltage gain and reduced power device voltage stress. Using a three-winding coupled inductor and voltage multiplier, the proposed converter achieves a high step-up voltage gain without a large duty cycle. However, unlike other converters with coupled inductor, the power device voltage stress in the proposed converter is dramatically reduced. The two clamped diodes not only alleviate the voltage spike across the metal-oxide-semiconductor field-effect transistor (MOSFET), but also reduce the diode reverse recovery issue. The efficiency can be improved as circuit allows the use of low on-resistance MOSFETs and Schottoky diodes in applications where this might not have been possible with conventional topologies. The basic operational principle and relevant theoretical analysis are presented in this study. Finally, practical results from a laboratory prototype are presented to verify the performance of the proposed converter. [ABSTRACT FROM AUTHOR]

In this study, a new modified switched boost inverter (MSBI) is proposed. The proposed inverter presents higher voltage gain in comparison with conventional Z-source inverter and switched boost inverter. Moreover, the proposed inverter provides zero voltage switching turn-off of input voltage source side switches. In this study, the proposed converter is theoretically analysed in different operational modes along with design procedure and ripple analysis. The proposed MSBI is compared with similar works to evaluate its capabilities. Finally, a 50 kHz experimental prototype with input voltage of 40 V is used to verify the analysis and simulation results. [ABSTRACT FROM AUTHOR]

Inverters, as one of the key components of electrical systems, have experienced a great evolution in the last decade, and their performance improvement is a challenge even today, leading to many researches on topologies and control schemes. This study introduces a new multilevel converter topology which is able to supply bidirectional current loads. The proposed structure has fewer power electronic devices such as power switches, driver circuits, power diodes, and DC voltage sources and, can be designed in both symmetric and asymmetric structures. In order to increase the number of output levels and the proposed basic unit development, modular expansion or cascading methods can be used. This study demonstrates that the aforementioned methods have the best results in asymmetric and symmetric structures of the proposed topology, respectively. The comparison between the proposed converter and some previous topologies shows that it has better conditions with respect to the used semiconductor count, switching and conduction losses, and total blocking voltage. The operation and performance of the proposed multi-level converter have been ascertained through simulations and verified experimentally for a single-phase symmetric thirty-one-level inverter which shows the proposed converter's ability in smooth sinusoidal output voltage generation with minimum total harmonic distortion. [ABSTRACT FROM AUTHOR]

To analyse stability and non-linear behaviour of the sliding mode controlled non-isolated grid-connected inverter with H6-type (SMCNGCI-H6) system, the discrete model of the SMCNGCI-H6 system is first established based on the quasi-static theory and stroboscopic map method. With the case of folded diagram, a particular non-linear behaviour (state-mutation phenomenon) is observed that the state variable changes from the period-1 state to the period-2 state at a certain switching cycle. Then the root cause of state-mutation phenomenon is explored. Meanwhile, regarding the variation of state-mutation switching cycle with the parameters of sliding mode controller (SMC), a novel criterion (state-mutation switching cycle criterion) is proposed to determine state-mutation switching cycle of the state variable. Finally, the simulation and experimental results prove the validity of the discrete modelling of SMCNGCI-H6 system and the state-mutation switching cycle criterion. [ABSTRACT FROM AUTHOR]

To extend the operating range of the snubber assisted zero-voltage and zero-current transition dual-interleaved boost converter beyond its inherent soft-switching limit of D = 0.5, a resonant pulse transformer is proposed instead of the resonant inductor. The 1 : 2 turns ratio of the transformer ensures full discharge of the snubber capacitor at all duty ratio values to facilitate zero-voltage zero-current switching at turn on of the main switching devices. The effectiveness of the topology has been confirmed by SPICE simulation and demonstrated by a 20 kW SiC metal--oxide--semiconductor field-effect transistor converter. The prototype operated at 20 kW, 112 kHz, 320--600 V achieving 98.7% efficiency and achieved 98.2% efficiency at 6 kW. Taking the additional losses in the auxiliary circuit into account, the switching losses at 20 kW are reduced by 74% compared with hard-switching operation, representing a 54% reduction in overall losses. [ABSTRACT FROM AUTHOR]