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Permanent magnet synchronous generator (PMG) based direct-drive wind turbines (DDWTs) have recently drawn the attention of the wind power market given their low operation and maintenance cost, reliability, and longer lifetime. In this paper, a zero dc-link impedance topology for DDWT-PMG systems is presented. The proposed topology eliminates the use of the failure-prone dc bus capacitor by replacing the grid-side converter with a phasor pulse-width modulation (PPWM) boost current source inverter (CSI), also referred to as indirect boost matrix converter. Furthermore, the novelty of the proposed topology lies in utilizing the synchronous inductance of the PMG as the dc-link inductor required by the boost-CSI, thus decreasing the overall system weight and size. In addition, the PPWM boost-CSI enables a high voltage-boosting ratio, which allows the design of a low-voltage PMG. As a result, the PMG size, weight, and high-cost PM material volume can be decreased. The feasibility of the low-voltage generator is investigated through finite-element computations using as a base for comparison an existing 1.5-MW DDWT-PMG. This comparison demonstrates a reduction in the generator volume, PM material, and the total weight of the generator. Finally, the proposed topology is validated through simulations and experiments. [ABSTRACT FROM AUTHOR]

A new topology is proposed for direct drive wind turbines that eliminates the use of the failure prone dc-bus electrolytic capacitor, avoids the need for a dc-link inductor by utilizing the synchronous inductance of the wind turbine permanent-magnet generator (PMG), and provides a low-voltage generator design, which decreases the amount of permanent-magnet material used in PMG, and reduces the volume and weight of the generator. [ABSTRACT FROM AUTHOR]

The phasor-PWM-based current source inverter (CSI) is a boost inverter. The difference between conventional CSIs and the boost inverter is that the boost ratio (VLLrms/Vdc ) in the boost inverter can easily be above 3.0, whereas this ratio is around 1 in conventional CSIs. In order to realize the potential capabilities of the boost inverter and to assist its penetration into renewable energy systems, the boost inverter dynamic behaviors are studied in this paper. First, the large- and small-signal models as well as the dq-equivalent circuits of the boost inverter are presented. Then, the developed models are verified using circuit simulations and experiments on a laboratory-scale 2-kW 208/240- V_{\rm LLrms} V_{\rm dc}=65\ \hbox{V} $ boost inverter made of reverse-blocking IGBTs. Finally, the developed small-signal model is used to study the stability of the boost inverter through root locus of small signal poles (eigenvalues) as control inputs, and load parameters vary within the boost inverter's operating limits. [ABSTRACT FROM PUBLISHER]

In many modern energy conversion systems, a dc voltage, which is provided from a sustainable energy source or energy storage device, must be boosted and converted to an ac voltage with a fixed amplitude and frequency. In this paper, a switching pattern based on the concept of the conventional space-vector pulsewidth-modulated (SVPWM) technique is developed for single-stage, three-phase boost-inverters using the topology of current-source inverters. The six main switching states, and two zeros, with three switches conducting at any given instant in conventional SVPWM techniques are modified herein into three-charging states and six discharging states with only two switches conducting at any given instant. The charging states are necessary in order to boost the dc input voltage. The developed switching pattern was experimentally verified through a laboratory-scaled three-phase 500-W boost inverter and the results are presented in this paper. [ABSTRACT FROM AUTHOR]