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This paper proposes a medium-frequency (MF) solid-state transformer (SST) based grid interface for high-power multipulse rectifiers. In the proposed approach, the low-frequency ac (grid) voltage is transformed to MF voltage via front-end converters. The three single-phase MF outputs from these converters are fed to the primary side of a three-phase, five-limb multiwinding isolation transformer (or alternately three one-phase transformers). The secondary side windings from the transformer are configured in a certain “zig-zag” arrangement, which are connected to the inputs of three-phase diode rectifier modules as in a typical multipulse system. The proposed topology can better than double the power density by reducing volume (or weight) of the required front-end isolation transformer while maintaining the same input current quality as a conventional low-frequency transformer based approach. Usage of an open-loop square wave pulse width modulation for the front-end converters makes this approach simple to implement. This paper explains the proposed concept taking an adjustable speed drive application's perspective using modeling, simulation, and experimental results from a scaled down laboratory prototype. [ABSTRACT FROM AUTHOR]

In this paper, a fast detection method for voltage disturbances is explored. The proposed method provides reliable and fast detection for either single-phase or polyphase voltage disturbances such as voltage sags, voltage swells, flicker, frequency change in the utility voltage, and harmonic distortion. The algorithm is based on the theory that allows a set of three-phase voltages be represented as dc voltages in a d-q synchronous rotating frame. In this case, the utility input voltages are sensed and then converted to dc quantities in the d-q reference frame. Thus, any disturbance at the utility input voltages will be promptly reflected as disturbances in the d-q values. Further processing of the signals minimizes the point-on-wave effect and yields a trip signal indicating if the disturbance is a voltage sag or a voltage swell. Analysis, simulation, and experimental results are presented for a three-phase system. The proposed algorithm is implemented on a digital signal processor (DSP)-based system to provide ride-through for critical loads. [ABSTRACT FROM AUTHOR]

In this paper, a new control scheme is proposed for controlling multiple single-phase power-factor-correction (PFC) modules with a single low-cost digital signal processor (DSP). The proposed scheme allows for multiple PFC modules of different current ratings to be operated in parallel and controlled via a single DSP. DSP-based control handles simple current sharing and provides size reduction. The paper describes a current sense technique for each PFC module and a closed-loop control algorithm for output voltage and input current control for operating multiple modules. In the example design, switching frequency is set at 120 kHz and two continuous conduction mode PFC stages are operated in parallel and controlled via a single TMS320LF2407 DSP. Experimental results show that the proposed scheme is capable to be used for modern switching power supplies. [ABSTRACT FROM AUTHOR]

Discusses an approach to reduce common-mode voltage at the output of a matrix converter. Advantages of the proposed method; Information on the output voltage quality of the proposed modulation strategy; Details of the simulation and experimental results.

Presents an analysis of a voltage sag compensator for critical loads in electrical power distribution systems. Conceptual design of the proposed approach; Topology of the pulsewidth modulation ac-ac converter; Details of the simulation and experimental results.

Examines an approach to provide ride-through of an adjustable speed drive (ASD) with flyback converter modules powered by super capacitors. Significance of ASD; Difficulties caused by power disturbances to ASD; Use of super capacitors for ASD ride-through; Simulation and experimental results.

Presents a paper which proposed a three-phase power-factor correction (PFC) scheme using two single-phase PFC modules. Advantages of the proposed scheme; Equations for the equivalent circuits at each switching period; Inductor current waveforms for a switching period; Relationship between the sources and each single-phase PFC module.

Focuses on a study which presented a real-time space-vector-based control strategy for three-phase uninterruptible power supply systems that power nonlinear and unbalanced loads. System description; Details of the control strategy; Conclusion.

Presents information on a study which proposed an integrated single-switch approach to improve the harmonic performance of standard pulsewidth modulation adjustable-speed drives (ASD). Requirements for the three-phase rectifier used for ASDs; Proposed topology; Principle of harmonic reduction with the proposed scheme; Experimental results.

Presents information on a study which proposed a modular motor-modular inverter (MM-MI) concept for medium-voltage adjustable-speed drive (MV-ASD) systems. Background of the MV-ASD systems; Details on the winding connections of commercially available MV induction motors; Categories of MM-MI approach for MV-ASD; Analysis; Design example; Experimental results.

Details a a study which presented a critical evaluation of the effect of voltage sags on adjustable-speed drives. Information on the proposed integrated boost converter approach; Experimental results; Conclusions.

Assesses the industrial ride-through requirements through power quality surveys and the results of an adjustable-speed drive (ASD) ride-through questionnaire. Determination of the cost-effectiveness of ride-through solution in ASD; Modifications to existing ASD topologies; Description of the ASD ride-through using energy storage technologies.

Proposes a method to be used in avoiding acoustic-resonance-related instabilities in metal halide lamps when operated with a high-frequency electronic ballast. Methodology of the study; Results of the study; Conclusions.

Presents the design considerations for an inverter output filter to mitigate the effects of long motor leads in adjustable-speed drive applications. Two primary means of reducing the motor insulation stresses due to motor terminal over-voltages; Primary role of the inverter output filter; Comparison of first-order motor terminal filter; Experimental results; Conclusion.

Proposes an active interphase reactor for twelve-pulse diode rectifiers. Circuit diagram; Simulation results of the proposed approach; Interphase reactor; Implementation of the active current source.

In a three-phase four-wire utility system, three-phase unbalanced loads and many single-phase nonlinear loads result in a neutral line current that is zero-sequence current. To deal with unbalanced and nonlinear loads in a high power system, this paper suggests a multilevel four-leg pulsewidth modulation (PWM) voltage-source inverter (VSI) as a topology for the high power applications where a function is required to control the zero-sequence component as well as dq components. This paper proposes a carrier-based PWM method for a multilevel four-leg PWM VSI along with introducing a novel offset voltage. The proposed offset voltage makes it possible for the switching sequence of all the legs to be optimized for minimizing the harmonic distortion of the output voltage irrespective of the number of inverter levels. The proposed PWM method based on digital signal processors is implemented and tested by using a prototype three-level four-leg VSI. The feasibility of the proposed PWM method is verified by the spectral analysis, simulation, and experimental results. [ABSTRACT FROM AUTHOR]

Modern telecommunication power supply systems have several parallel-connected switch-mode rectifiers to provide -48 Vdc. A typical switch-mode rectifier configuration includes a three-phase diode rectifier followed by a dc-dc converter. Such a system draws significant harmonic currents for the utility, resulting in poor input power factor and high total harmonic distortion. In this paper, a three-phase active harmonic rectifier (AHR) scheme is proposed. In the AHR scheme, a diode rectifier module is replaced by a six-insulated-gate-bipolar-transistor pulsewidth-modulation rectifier to supply load harmonics as well as its own active power. Each dc-dc converter module is connected to a shared 48-V dc link. The AHR module together with parallel-connected switch-mode rectifiers is controlled to achieve clean input power characteristics. The VA ratings of the AHR scheme is compared with an active power filter approach. The control design is based on the synchronous reference frame approach. Analysis, simulation, and experimental results show that the AHR offers several advantages such as lower VA rating, better current control response, efficient use of the AHR dc link, small size, and stable dc-link voltage control. [ABSTRACT FROM AUTHOR]

Focuses on a study which presented a control method which enables equal sharing of linear and nonlinear loads in three-phase power converters. Discussion on the sharing of linear load; Use of droop coefficients in the sharing of harmonic load currents; Conclusion.