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A topology and switching algorithm are presented for producing split-phase output voltages using a current-sourced inverter (CSI). Split-phase generation has previously been accomplished using voltage-sourced inverters (VSIs). There are some advantages to instead using CSIs, such as improved output voltage waveform quality and built-in overcurrent protection; however, two issues have prevented their adoption to date. First, while a CSI does not require the input boost converter used by a VSI when fed from a low-voltage source, it may require a preconditioning circuit to provide the required dc current. Second, no algorithm for producing split-phase outputs with a CSI presently exists. This paper's two major contributions aim to solve these problems. A simple preconditioning circuit is presented to provide the necessary dc current and store energy in a capacitor bank for use during load transients. A switching algorithm is written to produce balanced split-phase output voltages under a variety of unbalanced loading conditions. It is demonstrated using simulation and experimental results on a 400-W prototype that the proposed system is able to successfully generate balanced output voltages under unbalanced, inductive, nonlinear, and transient loading conditions, while equalizing switch utilization and minimizing output voltage ripple. Index Terms--Current supplies, inverters, pulsewidth modulated inverters, pulsewidth modulation.

In this paper, the control of an ac-dc-ac converter with a front-end diode rectifier and reduced dc-link capacitor based on the space vector modulation strategy is investigated. The modulation index is time-varying and determined by the instantaneous value of the dc voltage measured by a voltage sensor. Using a small bipolar capacitor, instead of a large electrolytic capacitor on the dc-link, increases the lifetime of the converter and reduces its size. The input current quality of this converter has been shown to be superior to that of the conventional ac-dc-ac converter with front-end diode rectifier. The perfectly sinusoidal local average output voltage can still be achieved under unbalanced input voltage condition by implementing a time-varying modulation index. The rule for determining the dc capacitance has also been studied in this paper. The simulation results obtained from PSIM simulation software and experimental results obtained from the lab prototype are used to verify the theoretical expectations. Index Terms--AC-DC-AC converter, front-end diode rectifier, reduced dc capacitor, space vector modulation, unbalanced input voltage.

The research on direct ac/ac conversion in the past twenty years has been following two major directions: 1) improving the performance of the original nine-bidirectional-switch matrix converter topology; 2) using converter topologies composed of unidirectional switches only. In this paper, a direct ac/ac converter topology based on current-source converter modules is proposed. It is shown, through analysis and simulation, that the proposed topology is free of any switching difficulties and gives high-quality sinusoidal waveforms on both sides. Furthermore, with the same number of semiconductor devices as in the original nine-bidirectional-switch matrix converter topology, it is able to perform all aspects of frequency changing, real power flow control, and independent reactive power flow control on both sides. The proposed topology finds applications in electric drive industry, as an ac motor drive, and power system industry, as an asynchronous link. Index Terms--AC/AC converter, CSC, frequency changer, high-quality sinusoidal waveforms, independent reactive power flow control, L-C filter, nine-bidirectional-switch, NPT IGBT, real power flow control, semiconductor devices, SVC, THDs, topology.

Three-phase voltage- and current-source converters are the building blocks of a great number of power electronic systems. The origin of difficulties in the control of the above converters is in their nonlinear nature. In this paper, a novel modeling technique is introduced to derive the linear models of the converters from the nonlinear transformations of the conventional nonlinear models. Then, based on the derived linear models, a high-performance linear controller with satisfactory performances is designed. The bold feature of the new model is the independence of the controller design from the operating point. A DSP-based control system has been built in the lab to verify the performance of the new models and the control algorithm. The simulation and experimental results are in close agreement. The results show that the dc term and the ac-side reactive power can be controlled independently in less than one cycle. Index Terms--Control algorithm, converter, DSP, nonlinear, PWM, reactive power.

Wind farms featuring a series-connected dc collection system have been shown to offer advantages in terms of total conversion efficiency and amount of offshore-deployed equipment. To ensure proper exploitation of these benefits, it is necessary to determine the ratings of wind turbine converters. These ratings must be sufficient to cover the expected operating conditions over the life of the wind farm, without unnecessarily oversizing the equipment. As shown in this article, the variable string current results in an interdependence of operating points among wind turbines that has to be considered for sizing these converters. This article proposes a generic sizing framework for such single-string, series-connected dc wind farms. This framework is applied to three wind farm configurations featuring differential power processing, voltage-source converters, and diode-bridge rectifiers and buck converters. Finally, a case study for a 450 MW offshore wind farm demonstrates the implementation of this sizing methodology and quantifies the design tradeoffs between converter ratings and energy production enabled from those converters. In two of the studied wind farm configurations, significant rating reductions are achievable while still avoiding energy curtailment for >99.7% of the energy production of an equivalent ac wind farm. [ABSTRACT FROM AUTHOR]

In this paper, the control of an ac-dc-ac converter with a front-end diode rectifier and reduced dc-link capacitor based on the space vector modulation strategy is investigated. The modulation index is time-varying and determined by the instantaneous value of the dc voltage measured by a voltage sensor. Using a small bipolar capacitor, instead of a large electrolytic capacitor on the dc-link, increases the lifetime of the converter and reduces its size. The input current quality of this converter has been shown to be superior to that of the conventional ac-dc-ac converter with front-end diode rectifier. The perfectly sinusoidal local average output voltage can still be achieved under unbalanced input voltage condition by implementing a time-varying modulation index. The rule for determining the dc capacitance has also been studied in this paper. The simulation results obtained from PSIM simulation software and experimental results obtained from the lab prototype are used to verify the theoretical expectations. [ABSTRACT FROM AUTHOR]

Presents information on a study that introduced a modeling technique to derive the linear models of the converters from the nonlinear transformations of the conventional nonlinear models. Derivation of improved models of voltage-source and current-source converters; Controller design for the converters; Conclusion of the study.