Isolated high-efficiency DC/DC converter for photovoltaic applications

While an increasing number of photovoltaic (PV) systems is installed, those systems typically use central inverters. In practical cases, output-power differences between PV modules will cause these central-inverter-based systems not to achieve Maximum Power Point (MPP) for each PV module. Furthermore, central-inverter-based systems feature limited modularity and single point-of-failure properties. These issues are, among other issues, addressed by the de-central inverter systems. The (patent pending) DC/DC stage topology presented in this paper has been developed to overcome issues that are experienced with the flyback and forward stages that are typically used for these de-central inverters and achieves very high efficiencies across the whole converter power range. A prototype has been built to verify the operation and shows promising results

A three-level three-phase dual active bridge DC-DC converter with a star-delta connected transformer

This paper investigates a three-level three-phase Dual Active Bridge (DAB) dc-dc converter with a star-delta connected transformer. The soft-switching region is analyzed for two and three-level operation, using symmetrical voltage waveforms, showing an increased ZVS range for three-level operation. A large number of switching modes are identified and are modeled with piecewise-linear equations. To facilitate a practical implementation of a controller, a modulation strategy is proposed that results in a Zero Voltage Switching (ZVS) operation and relies on analytical equations, using a small amount of switching modes, while obtaining close-to-minimal rms currents. The ZVS range and the proposed control strategy are supported by measurements obtained from an experimental setup

Reduction of thermal cycling to increase the lifetime of MOSFET motor drives

The variation of the temperature in semiconductors, caused by the load profile, results in the long term in material fatigue. A distinction can be made between the average temperature and the temperature swing, where the temperature swing has a significant effect on the lifetime of a semiconductor. Therefore, the auxiliary-pole topology is proposed to reduce the temperature swing of the MOSFETs in a motor drive. The auxiliary-pole topology divides the load current over two switching-legs and circulates a current when there is a low or zero load current. The conventional half bridge topology is used as a benchmark. Both topologies are simulated with the same load profile and with an equal total amount of silicon. The results show a reduction of the temperature swing and an increase in average temperature of the switches in the auxiliary-pole topology. This leads to an significant improvement in cycles to failure and time to failure. Index Terms—Thermal management of electronics, Thermal management, Thermal stresses, Power semiconductor switches, Lifetime estimation, Motor drive

Improved current estimation in paralleled half-bridge converters

When paralleling half bridges, their individual currents should be balanced to prevent large circulating currents. This paper improves an existing perturbation-based current estimation method by modifying the perturbation signal allowing a faster estimation of the currents, resulting in a reduction of current stress on components

A Switched-Mode Power Amplifier for Ion Energy Control In Plasma Etching

Plasma etching is an important process in the semiconductor manufacturing process. In order to precisely control the ion energy for better process quality, a tailored pulse-shape voltage waveform is applied to the plasma reactor table. Traditionally, a linear amplifier is used to generate this waveform, which results in poor efficiency. This paper proposes a switched-mode power amplifier as a substitute to the traditional linear amplifier. The electric equivalent circuit of the plasma reactor is introduced and a basic topology for the switched-mode power amplifier is derived. The basic topology is able to generate the required waveform but it has a low efficiency of charging the capacitive load in practice. Therefore, an efficiencyimproved topology is proposed by adopting resonant charging. A prototype is built in order to validate the research. The experiments show that the presented solution yields a significantly reduced input power compared to the normally used linear amplifier in this application

Exploring the Boundaries and Effects of the Discontinuous Conduction Mode in H-Bridge Inverter with Dead-time

Dead-time of an H-bridge inverter can cause nonlinear error on the inverter output. In different switching cycles during a fundamental period, the effect of dead-time might be different. The H-bridge inverter in different switching cycles can operate in three kinds of modes, including soft-switching continuous\u3cbr/\u3econduction mode, discontinuous conduction mode and hard-switching continuous conduction mode. In addition, the discontinuous conduction mode can be further classified into four different types, which have not been fully studied in previous research. In this paper, four different kinds of switching cycle in the discontinuous conduction mode are investigated. The effect of the dead-time on the voltage error is elaborated and the boundaries of each kind of switching cycle are determined by a series of constraint functions. Based on the analysis, a complete mathematical expression of the voltage error in a fundamental period is given and it yields a better accuracy compared to previous publications

A comparative evaluation of series-resonant, bidirectional optimal trajectory controlled isolated DC-DC converters

\u3cp\u3eRecently, a new dynamic control algorithm was proposed for a series-resonant converter, i.e. bidirectional optimal trajectory control. It regulates the amount of charge that is drawn from, or supplied to, the sources that are connected to the primary and secondary input ports of the converter. Additionally, it realizes a dead-beat control while guaranteeing zero voltage switching of all switches over the entire input and output voltage range. This paper presents a comparative evaluation of a bidirectional optimal trajectory controlled, series-resonant converters with four different switching leg configurations. The comparison comprises an analysis of bidirectional optimal trajectory control on the semiconductor chip area, the resonant tank volume and losses, and the operating frequency range of the converter. Also included is the implementation complexity, which covers both the measurement and computational effort. Evaluating all advantages and drawbacks of the compared switching leg configurations, the 3-level full-bridge full-bridge series-resonant converter shows the most advantageous properties for a series-resonant, bidirectional optimal trajectory controlled isolated DC-DC converter.\u3c/p\u3

Scalable multi-port active-bridge converters: modelling and optimised control

This study presents the tools required to create a modular and scalable multi-port converter structure, suitable for bidirectional power flow. A class of converters is defined based on the active bridge as basic building block. Any number of active bridges can be combined to form a multi-port converter with any number of ports. For modelling of the converter, a Fourier-based method is introduced to find an analytical converter model. Moreover, a scalable control method is proposed for these multi-port converters: power-balance control. The method uses Newton-optimisation in order to reduce the circulating currents. Experimental verification on a prototype shows the methods operate as expected. This study presents the tools required to create a modular and scalable multi-port converter structure, suitable for bidirectional power flow. A class of converters is defined based on the active bridge as basic building block. Any number of active bridges can be combined to form a multi-port converter with any number of ports. For modelling of the converter, a Fourier-based method is introduced to find an analytical converter model. Moreover, a scalable control method is proposed for these multi-port converters: power-balance control. The method uses Newton-optimisation in order to reduce the circulating currents. Experimental verification on a prototype shows the methods operate as expected

Dual voltage source inverter topology extending machine operating range

Field weakening operation of an electrical machine is a conventional method to extend the angular velocity range of a system above the peak output voltage of the inverter. A downside, however, is that an increased reactive current is required that creates losses but no output torque. A dual voltage source inverter topology is proposed, capable of driving an electrical machine without weakening its field in an extended speed range. For this purpose, a second inverter fed by a capacitor only is connected to the open-end side of the machine windings. Charging the floating capacitors is realized by adding an AC zero sequence current to the regular machine currents. The operating principles of the presented topology are demonstrated, showing their possible advantages when driving an electrical machine. Simulation results confirm the proposed ideas

Modulation strategy for wide-range ZVS operation of a three-level three-phase dual active bridge DC-DC converter

The modulation strategy proposed in this paper enables wide-range zero voltage switching (ZVS) operation of a three-level three-phase dual active bridge (DAB) dc-dc converter. The circuit topology is analyzed and piece-wise linear equations are derived for most appropriate switching modes. Based on the results of a numerical optimizer a modulation scheme is derived, utilizing analytic equations. Compared to optimal control variables, the proposed modulation scheme generates a higher transformer rms current for low power transfers, however, for high power levels it operates with a close-to-optimal transformer rms current. Simulations of the converter, obtained using the proposed modulation strategy, verify zero voltage switching (ZVS) operation and demonstrate an accurate power transfer for the full voltage range. Finally, experimental results, obtained from a high-power prototype, support the theoretical model and confirm correct operation of the proposed modulation strategy