Discontinuous Mode Operation Research Articles

Performance analysis of a Scalar Coupled and Decoupled PWM Technique for a Three Level symmetrical Dual Inverter Fed OEWIM Drive

Dual inverter fed IM drive is commonly employed in EV applications. In this application, SVPWM based PWM generator was utilised. However, they produce a high common-mode voltage(CMV). Because of this, bearing of motor will be affected and in turn, results in EMI problems. Hence, to overcome this problem, this work introduced a novel PWM generation techniques named scalar coupled and decoupled PWM topology to control a three-level symmetrical DI fed OEWIM. Hence, to find out the effectiveness of the proposed topologies, its operation is examined under both continuous and discontinuous modes of operation using MATLAB simulation. From the acquired results, it is concluded that this coupled PWM topology topology exhibits reduced CMV and harmonics when compared to decoupled topology

Novel high voltage gain dc–dc converter with dynamic analysis

This study proposes a non-isolated dc–dc converter based on a coupled inductor and switch-capacitor–boosting techniques. The goal of the proposed topology is to increase the voltage gain with low-duty cycle, so voltage stresses are decreased across power switches and diodes. The power switches are controlled by pulse width modulation. The common ground of input and output of the proposed converter makes it suitable for many applications such as photovoltaic systems. The proposed converter topology is discussed in continuous and discontinuous operation modes. A dynamic analysis of the proposed converter is also provided. Simulation and experimental verifications are presented to prove the effectiveness of the proposed topology.

A Scalar Decoupled PWM Technique for a Three-Level Symmetrical Dual Inverter Fed OEWIM Drive for Electric Vehicle

Induction motor is employed in electric vehicle to control the speed. Dual inverter fed drives are used for this purpose. Even though it finds application in many applications, high common-mode voltage (CMV) becomes a major problem and it results in EMI problems. Hence, to overcome this problem, this work introduced a novel PWM generation technique named scalar decoupled PWM topology to control a three-level symmetrical DI fed OEWIM. In this proposed topology, switching signals of the inverter 1 and 2 can be generated and controlled separately. To examine the efficiency of the proposed topology, its operation is examined under both continuous and discontinuous modes of operation and is carried out in both simulation and experimental set up. From the acquired results, it is concluded that this proposed topology exhibits reduced CMV and harmonics when compared to traditional PWM topology.

Alternative Control Approach to Achieve Fast Load-Transient Responses in DC–DC Converters

This article proposes a controller for dc-dc converters to achieve fast load-transient responses. The controller is developed for both continuous conduction mode (CCM) and discontinuous conduction mode (DCM) of operation. The main idea is developed for buck converters, but it is shown that the proposed controller can be applied to other topologies, such as the noninverting buck-boost converter. The controller derivation, analysis, and experimental verifications are provided in both CCM and DCM, and its performance is compared with other methods. The main advantage of the proposed controller is that it minimizes the recovery times associated with load-transient responses in dc-dc converters while maintaining component sizes and other system parameters within the acceptable range. The proposed controller can be used to minimize load transients in electronic portable devices and electric vehicle charging.

An efficient DC-DC boost converter for thermoelectric energy harvesting

In this paper, an efficient digitally controlled DC-DC boost converter for thermoelectric energy harvesting is presented. The proposed converter is based on the discontinuous mode (DCM) of operation. The efficiency of the converter is improved by using an adaptive pulse generator circuit and an active diode circuit. The adaptive pulse generator circuit reduces the dead time of the converter, whereas, the active diode circuit reduces the reverse current flow through the inductor to improve the conversion efficiency and the ripple voltage. The circuit is designed and simulated using 0.18 μm technology. Adaptive pulse generator circuit and active diode circuit provide an efficiency improvement of 15.31% and 5.74%, respectively, with respect to that of the existing boost converter circuit. Both circuits together provide 21% of improvement in efficiency. An efficiency of 72.59% is obtained using the proposed circuit as compared to 51.54% of the existing boost converter circuit.

FPGA‐based implementation of single‐phase seven‐level quasi‐Z‐source inverter

SummaryIn this paper, a new single‐phase seven‐level quasi‐Z‐source (qZs) inverter with reduced switch count for multistring photovoltaic applications is proposed, which is capable of supplying both direct current (dc) and alternating current (ac) loads simultaneously. The proposed configuration is derived from a combination of qZs networks and asymmetrical seven‐level inverter. The front‐end qZs converter boosts the input voltage obtained from the dc sources to the desired value, whereas the asymmetrical seven‐level inverter performs dc‐ac conversion with reduced switch count and provides better efficiency. The steady‐state performance of the model is evaluated in both continuous conduction mode (CCM) and discontinuous conduction mode (DCM) of operation. In addition, the dynamic performance of the model is tested for the load as well as input voltage changes. A simple proportional‐integral (PI) controller is implemented in FPGA Spartan‐6 Processor using Xilinx system generator blocks. An experimental prototype is also developed to validate the feasibility of the proposed topology. Finally, a brief comparative assessment is formulated with other topologies to show the merits of the proposed structure.

Weighted-$A^*$ Based Energy Efficient Resource Allocation in G.Fast

One of the key challenges in G.fast is to minimize the power consumption at distribution points. G.fast standards define Discontinuous Operation modes that provide avenues for power reduction by allowing intermittent transmission of users along time slots. In this paper, we formulate a power efficiency problem as a user-slot assignment problem, where we schedule users to time slots during discontinuous operation such that the total power consumption is minimized. Since the general user-slot assignment is NP hard, we propose a weighted $A^{*}$ algorithm based solution that achieves reasonable performance with limited computational resources. Further, the proposed user-slot assignment is also G.fast standards compliant and therefore can be implemented in practice. We also explore different precoding as well as user grouping strategies that can be employed while performing user-slot allocation. Finally, the main insight of this work is that on using our user-slot assignment algorithm and by only precoding during the normal operations, we achieve energy efficiency levels comparable to those achieved when precoding is applied during the discontinuous operations without the suggested user-slot allocation.

Modified multilevel buck–boost converter with equal voltage acrosseach capacitor: analysis and experimental investigations

Recently, the circuitry of Multilevel Buck-Boost Converter (here, called MBBC 1 ) is suggested in the literature to attain high inverting voltage by increasing the output levels of the classical buck-boost converter. However, the only circuitry is suggested and detail investigations are not provided. The major drawbacks of MBBC 1 are the voltages across the load capacitors side are unequal and the input current is not continuous. Therefore, the MBBC 1 is not well suited to feed multilevel inverter where a stack of capacitors is required with equal voltage across each capacitor. A new modified MBBC called MBBC 2 is proposed to achieve continuous input current and equal voltage across each capacitor. The circuitry of MBBC 1 and MBBC 2 configurations are analysed with non-idealities to investigate its effects on the voltage conversion ratio. The Continuous Conduction Mode (CCM) and Discontinuous Conduction Mode (DCM) boundary conditions and modes of operation for MBBC 1 and MBBC 2 configurations are presented. The procedure for basics design and components selection is elaborated. Additionally, comparison of MBBC 1 , MBBC 2 and recently proposed a non-isolated DC-DC configuration is provided. The performances of MBBC 1 and MBBC 2 configurations are tested with simulation and experimental work, and obtained results consistently show a good agreement with the theoretical approach..

Small Signal Model for PV Fed Boost Converter in Continuous and Discontinuous Conduction Modes

Small signal models are of high importance in power electronic systems which exhibit highly non-linear properties. They provide access to stability and help in tuning controllers. Small signal models for many power electronic converters are seen in the literature. However, specific applications like photovoltaic systems demand the addition of a capacitor at the terminals of photovoltaic (PV) panel. Since this capacitor is connected between the PV panel terminals and the input of power converter, it is termed as input capacitor. The effect of the addition of input capacitor on system stability has not been addressed yet. In this brief, we derive the small signal models for PV fed boost converter operating in both continuous conduction mode (CCM) and discontinuous conduction modes (DCM) of operation. The load is assumed as purely resistive; however, the analysis holds good for any practical loads. It is observed that in both CCM and DCM the stability of the maximum power point tracking (MPPT) system is independent of the input capacitance. It is also shown that the MPPT system is open loop stable for all operating conditions. The studied models are further validated with the experimental setup.

Investigation of a Non-isolated Reduced Redundant Power Processing DC/DC Converter for High-Power High Step-Up Applications

In this paper, a nonisolated high step-up dc/dc converter, belonging to the family of reduced redundant power processing converters (R2P2), is investigated for high-power applications. The selection of this topology as the most suitable for such applications among those belonging to the R2P2 family is justified. Emphasis is given on the theoretical analysis of the real step-up voltage ratio of the converter, and voltage and current stresses under continuous and discontinuous conduction modes of operation, taking into account the nonideality of the topology components, namely the parasitic resistances of semiconductor devices and inductors and the voltage drop of diodes. The theoretical analysis and the behavior of the selected converter are experimentally validated through a 2 kW prototype. Moreover, the overall efficiency of the chosen converter is experimentally investigated for various step-up voltage ratios and for a high-power range, considering a waste heat recovery system for a maritime application.

Structure and predictive functional profiling of microbial communities in two biotrickling filters treated with continuous/discontinuous waste gases

Two biotrickling filters were operated in continuous (BTF1) and discontinuous (BTF2) modes at a constant empty bed residence time of 60 s for 60 days. From day 60, the operation mode of each BTF was oppositely switched. Higher removal efficiencies of five aromatic pollutants were recorded with BTF1 (> 77.2%). The switch in the operation mode did not alter the removal performance of BTF1. Comparatively, BTF2 was not successfully acclimated in the discontinuous operation mode. Once the mode had been switched to continuous mode, the removal efficiencies of BTF2 on all pollutants increased drastically and finally exceeded the values observed in BTF1, with the single exception of p-xylene. Principle coordinate analysis and analysis of similarities (ANOSIM) showed that the structure of the microbial communities differed considerably between both BTFs (R = 1.000, p < 0.01) as well as before and after the switch in BTF2 (R = 0.996, p < 0.01). The random forest model demonstrated that Mycobacterium, Burkholderia, and Comamonas were the three most important bacterial genera contributing to the differences in microbial communities between the two BTFs. Metagenomics inferred by PICUSt (phylogenetic investigation of communities by reconstruction of unobserved states) indicated that BTF2 had high degradation potential for aromatic pollutants, although those genes involved in biofilm formation were less active in BTF2 than those in BTF1.

Analysis and Control of Enhanced Switched Boost Inverters for Wide Duty Cycle Operation

Switched boost inverter (SBI) is a high gain converter that uses the concept of Z-source inverter but with a reduced number of passive elements. The analysis and operation of SBI are already reported for continuous and discontinuous input current but these converters operate in the restricted range of duty cycle and load variation. In a certain duty cycle situation, the converter shows inadvertent behavior and the inductor current tends to become equal to the AC load current. This phenomenon creates a ripple in dc link voltage which causes increased THD at the output AC voltage. Moreover, the DC link capacitor undergoes higher voltage stress. In this paper, the duration for which this peculiar phenomenon lasts is termed as non-zero discontinuous current mode (NZ-DCM) of operation. The analytical expression during NZ-DCM is derived and analyzed in terms of peak to peak ripple inductor current. To overcome NZ-DCM, the authors propose a modified SBI which consists of an extra active switch antiparallel across the diode. The simulation and experimental results pertaining to the adverse effect of NZ-DCM and its mitigation in the form of the conventional and modified SBI are presented in this paper.

Modeling and Analysis of a PCM-Controlled Boost Converter Designed to Operate in DCM

Peak current-mode (PCM) control has been a very popular control method in power electronic converters. The small-signal modeling of the dynamics associated with PCM control has turned out to be extremely challenging. Most of the modeling attempts have been dedicated to the converters operating in continuous conduction mode (CCM) and just a few to the converters operating in discontinuous operation mode (DCM). The DCM modeling method published in 2001 was proven recently to be very accurate when applied to a buck converter. This paper provides the small-signal models for a boost converter and analyses for the first time its real dynamic behavior in DCM. The objectives of this paper are as follows: (i) to provide the full-order dynamic models for the DCM-operated PCM-controlled boost converter; (ii) to analyze the accuracy of the full and reduced-order dynamic models; and iii) to verify the validity of the high-frequency extension applied in the DCM-operated PCM-controlled buck converter in the case of the boost converter. It is also shown that the DCM-operated boost converter can operate only in even harmonic modes, similar to all the CCM-operated PCM-controlled converters. In the case of the DCM-operated PCM-controlled buck converter, its operation in the odd harmonic modes is the consequence of an unstable pole in its open-loop power-stage dynamics.

Power Factor Correction in Modified SEPIC Fed Switched Reluctance Motor Drives

This paper presents a dual output power factor correction (PFC) converter for switched reluctance motor (SRM) drives. Here, a modified single-ended primary inductance converter (SEPIC) is proposed for a wide range of speed control and to achieve PFC at ac mains. The switching frequency of the converter is considered to be 20 kHz. The converter is designed to operate in the discontinuous conduction mode (DCM) of operation, which reduces the size of the output inductor. The DCM mode to obtain PFC also reduces the sensor requirement as compared to the continuous conduction mode (CCM), where two voltage sensors and one current sensor add to the drive cost. The drive is proposed for universal ac mains (90–270 V ac). Simulated and experimental results are demonstrated to validate the performance of the drive during different operating conditions. The input current total harmonic distortion is reduced to comply with an IEC 61000-3-2 standard.

Improving Line Current Distortion in Single-Phase Vienna Rectifiers Using Model-Based Predictive Control

Conventional single-phase Vienna rectifiers employ proportional-integral (PI) controllers which are appropriate for controlling DC components, to regulate their line currents. However, in the regions close to the line current’s zero-crossing point, the dynamics of PI controllers are too slow to respond to the reference current, which has an AC component. Hence, the power factor (PF) of the device is degenerated, and total harmonic distortion (THD) increases. A controller with a fast dynamic response is thus required to solve this problem. In this paper, we investigate the use of a model-based predictive controller (MPC), which has a faster dynamic response than a PI controller, to improve the line current quality of a single-phase Vienna rectifier. With this method, the average current in both the continuous current mode (CCM) and the discontinuous current mode (DCM) of operation are controlled using a mode detection method. Moreover, we calculate the optimized duty cycle for the single-phase Vienna rectifier, by predicting the next current state. We verify the operation of the proposed algorithm using a PSIM simulation, and a practical experiment conducted with a 1-kW-rated single-phase Vienna rectifier prototype. With the proposed method, the quality of the line current near the zero-crossing point is improved, and the PF is controlled to unity.

A modular transformerless DC-DC step-up converter with very high voltage gain and adjustable switch stress

According to limited voltage gain of the standard step-up converters, cascade connection of the boost choppers can be employed to increase voltage gain. However, negative impedance instability problem due to converters constant power characteristic will complicate closed loop control of the cascaded converters. To cope with the problem, switched capacitor/switched inductor (SC/SI) circuits can be employed for voltage gain increment in transformerless DC–DC converters. High gain DC–DC converter model includes several state variables; hence multiple voltage and current sensors are required in closed loop applications. In this paper, a novel transformerless DC–DC step-up converter with very high voltage gain is proposed using SC/SI circuits which mitigates negative impedance instability problem. By modular extension, more improvements in converter gain and switch voltage stress can be obtained. In the developed circuit, inductors currents (and voltages of the capacitors) are equal during transient and steady-state conditions. Thus, model complexity is similar to standard DC–DC converters. Experimental response of the designed system is investigated in both continuous and discontinuous conduction modes of operation. Considering different performance parameters, proposed DC–DC converter is compared with recently reported methods. Closed loop response of the presented regulator is studied using two-loop control strategy under load and line changes.

Flying Start of a Permanent Magnet Wind Power Generator Based on a Discontinuous Converter Operation Mode and a Phase-Locked Loop

Flying start of a wind generator is a common requirement in wind turbine applications. This paper proposes a novel method for allowing the flying start of a permanent magnet generator (PMG). The proposed method is based on the discontinuous mode of operation of the converter and the phase-locked loop (PLL). During the discontinuous mode of operation, a series of zero-voltage pulses is applied to the generator, causing the occurrence of the short-circuit current, and thereby employing the PLL structure to estimate the rotor speed and angle. Also, a short-circuit current control structure with automatic adjustment of the reference value is proposed. The input signal to a PLL structure is adequately selected in order to enable a continuous mode of operation of the PMG. Simulation results demonstrate the applicability of the proposed method on the surface and interior PMGs, as well as on low- and high-power PMGs. The estimation accuracy does not depend on changes in the PMG parameters. The proposed method was implemented in a digital control system and experimentally verified on a 375 kW interior PMG. Experimental responses referring to the flying start of the PMG demonstrate the effectiveness of the proposed method.

Power Factor Correction in Cuk–SEPIC-Based Dual-Output-Converter-Fed SRM Drive

In this paper, a power factor correction (PFC)-based switched reluctance motor (SRM) drive is proposed. Generally, the SRM drive is fed with a simple diode bridge rectifier followed by a bulky capacitor, which draws peaky current at low power factor and high-input-current total harmonic distortion (THD). Here, a dual output converter is proposed to control the SRM and to provide power quality improvement as well. This converter is a combination of Cuk and SEPIC converters, which produces two equal output voltages with neutral point N, to feed a midpoint converter of the SRM drive. The converter is designed to operate in discontinuous conduction mode of operation to obtain inherent PFC at supply side. The motor control is attained by regulating dc link voltage over a wide range. Test results on a prototype of the SRM drive demonstrate the excellent performance with high power factor and reduced input current THD. The observed power quality indices depict the improved power quality as per the standard IEC 61000-3-2.

Decentral Control Strategies for Demand-side Management by Industrial Heating and Cooling Devices with Discontinuous Operation Mode

In future energy systems with a high share of fluctuating energy sources like wind and solar power, keeping the balance between power generation and consumption will be a challenge. In this context, cost-efficient solutions for moving the electrical energy demand to times with a high availability of renewable energy sources are needed. In this paper, a decentral control approach for demand-side management by a multi-agent system of industrial supply technologies for heating and cooling with discontinuous operation mode is presented. By this approach, the devices are enabled to stabilize the power system without a central control unit, which calculates the individual operation strategy of each device. Furthermore, no process-specific internal information has to be revealed and no direct remote control of devices is required from external service providers.

Incorporation of Harmonic Injection in an Interleaved Flyback Inverter for the Implementation of an Active Anti-Islanding Technique

Over recent years, the output power of micro-inverters [module-incorporated inverter (MIC)] is progressively pushed to higher levels, following the current photovoltaic (PV) modules market trends. The interleaved Flyback inverter—under discontinuous conduction mode of operation (DCM)—is an appealing solution for PV applications which are based on MIC technology. This topology provides increased power level for distributed PV generation exploitation with simple control configuration, high efficiency, and reduced filter size. In this paper, the harmonic injection capability is incorporated into the interleaved Flyback inverter for the implementation of an active anti-islanding scheme. A suitable technical solution is proposed that bypasses the unfolding H-bridge, without affecting the active power generation of the inverter and without requiring any hardware modification. In addition, a mathematical model based on the instantaneous power balance theory is presented, being a powerful analysis tool for inverters operating under complete magnetic discharge such as the Flyback inverter (either conventional or interleaved) under DCM or boundary conduction mode of operation. The proposed model predicts accurately the steady-state operational behavior of the Flyback inverter under current harmonic injection, either in grid-tied or islanding operation. The proposed technical implementation method and mathematical model are verified through simulation and experimental results. Finally, an anti-islanding set-up based on the proposed harmonic injection technique is presented and implemented into the Flyback micro-inverter. The proposed set-up is verified through experimental results on various quality factor values, as well as for weak grid conditions.