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This paper proposes the predictive control with the discrete space-vector modulation (DSVM) for Vienna rectifier connecting to the permanent magnet synchronous generator (PMSG) of the wind turbine system (WTS). Since Vienna rectifier has the special operation principle, Vienna rectifier generates only the feasible eight voltage vectors, which can be a candidate vector for the predictive control, depending on the sign of the input currents. In the proposed predictive control, the feasible voltage vectors are extended from 8 to 19 consisting the 8 original voltage vectors and 11 virtual voltage vectors by using the DSVM for improving the current quality related to the torque ripple, vibration, and noise, and the neutral-point voltage balance with low voltage ripple is guaranteed by using the offset value calculated based on the model of two dc-link capacitors in Vienna rectifier. The scheme for reducing calculation burden is applied in selecting the candidate vector. In addition, the limited operation range for the maximum torque per ampere control of PMSG connected to Vienna rectifier is analyzed. The performance of the proposed predictive control with DSVM for Vienna rectifier with PMSGs is verified in simulation and experiment. [ABSTRACT FROM AUTHOR]

This paper proposes a generalized design framework for three-phase Vienna rectifiers to handle the neutral point voltage balance issue. On the basis of the design framework, it is convenient to construct various neutral point voltage balancing methods with the guarantee of stability. As demonstration, three representative neutral point voltage balance approaches are presented by choosing different zero-sequence voltages. A comprehensive comparison among the three approaches is given in the aspects of input current quality, capacitor voltage fluctuation, and system efficiency. The comparison results provide guidance for constructing the most appropriate approach based on the specific requirement. Finally, simulation and experimental results verify the correctness and effectiveness of the presented approaches and the related performance analysis. [ABSTRACT FROM AUTHOR]

The VIENNA rectifier is increasingly being considered as the active front-end converter in many applications that do not require regeneration or controllable input reactive power. In such applications, this rectifier is normally operated at unity source displacement factor, which derates its nominal voltampere (VA) rating. Moreover, in the “source voltage oriented” reference frame that is normally used for control, this rectifier has complex operating limits on the rectifier terminal voltage (imposed by the operating conditions), which needs to be computed online to avoid the line currents from going through zero-crossing distortions. Also, the source voltage has to be either measured or estimated, which further increases the cost and/or computational burden. This paper proposes a control method that eliminates the requirement of the input voltage sensors (or estimators) and makes the limits on the rectifier terminal voltage far simpler to compute. The control method is implemented in the input line current oriented reference frame, considering unity displacement factor at the rectifier input terminals, which minimizes the VA rating of the rectifier (for a given rated load power). The proposed sensorless current-oriented control approach is compared with the conventional voltage-oriented control strategy through experimental results. [ABSTRACT FROM AUTHOR]

This article proposes three-phase cascaded multilevel rectifiers for wind energy conversion system applications. These configurations operate as machine-side converters and play an essential role in the integration of wind power generation units. The proposed rectifiers are connected to a permanent magnet synchronous machine by an open-end winding arrangement, making the ac–dc conversion of the power delivered with high-power factor operation. Their structures are composed of a combination of a converter based on Vienna rectifiers and one H-bridge per phase with a floating capacitor. Compared with the conventional configurations, the proposed ones provide sinusoidal currents with lower harmonic distortion using, proportionally, a fewer number of controlled switches. Furthermore, they can operate with a lower switch blocking voltage. These features make them attractive options for industrial applications due to their good performance, providing an interesting cost–benefit. The system model, pulsewidth modulation technique, capacitor voltage balancing, and control strategy are detailed. Computer simulations and experimental tests are provided in order to validate their feasibility. [ABSTRACT FROM AUTHOR]

This article proposes three-phase configurations for wind energy conversion system applications. The proposed topologies are based on Vienna rectifiers and they have a reduced number of controlled switches, which may allow reducing size and costs. Despite they can work with other arrangements, the proposed structures operate at an open-end winding configuration in this article, providing some benefits over the traditional ones. Compared to the conventional topology, the proposed ones provide a better power quality employing, proportionally, a fewer number of controlled switches, offering a higher levels-per-switch ratio. Moreover, they can also operate at a lower switch blocking voltage. These features offer an interesting cost–benefit and make them attractive options to industry applications. The system model, modulation technique, and control strategy are discussed. Simulation and experimental results are provided in order to validate their performance and feasibility. [ABSTRACT FROM AUTHOR]

The Vienna rectifier can produce three voltage levels, however only the connection to the neutral-point is fully controllable using the bidirectional switches. When the neutral-point voltage is not imposed in a phase-leg, the polarity of the pulses generated depends on the diode that is conducting in that phase-leg, which is defined by the current direction. As a result, the voltage pulses generated can go in the opposite direction to what is demanded by the controller, and the current becomes distorted. This can be mitigated by injecting a particular zero sequence so that the reference voltage is clamped to the neutral-point during the intervals, where the current of a phase-leg has the opposite sign than its reference voltage. However, the converter is at risk of entering into overmodulation when operating with high modulation indices. In this article, a hybrid modulation strategy is introduced where a calculated minimal amount of reactive current depending on the operating conditions is injected to avoid overmodulation. The reduction of reactive current required compared to the state-of-the-art solutions is up to 100% in certain operating conditions. With the proposed method, the Vienna rectifier can operate in a wide range of power factors without compromising the quality of the source currents. The concept is verified by simulation and in a 1-kW Vienna rectifier experimental setup. [ABSTRACT FROM AUTHOR]

Neutral-point (NP) voltage imbalance is an inherent issue of three-level converters. The alternating input current distortion is generated by using the conventional discontinuous pulsewidth modulation (DPWM) scheme without NP voltage balance control. In this article, the deviation vector between the synthesis vector and the reference vector, which is the fundamental cause of alternating input current distortion under NP voltage unbalance conditions, is revealed. Then, by optimizing the subsector division and the switching state sequence, a dynamic-space-vector DPWM (DSV-DPWM) is proposed to eliminate the deviation vector. Further, the comparisons of the proposed DSV-DPWM, the conventional DPWM, and an existing triangle carrier-based DPWM (TCB-DPWM), are addressed. Finally, a 10-kW prototype was built to verify the effectiveness of the proposed DSV-DPWM scheme. Experimental results show that, compared with the conventional DPWM scheme and the TCB-DPWM scheme, both the current THD performance and efficiencies can be significantly improved by the proposed DSV-DPWM scheme under unbalanced NP voltage conditions. [ABSTRACT FROM AUTHOR]

Compared with continuous pulsewidth modulation (PWM), discontinuous PWM (DPWM) is a preferred solution in high-frequency Vienna-type rectifiers due to its inherent characteristics of less commutation number and higher efficiency. In this article, redundant clamping modes at the same subsector with opposite effects on the neutral point (NP) voltage are presented. Then, a modified DPWM (MDPWM) scheme is proposed to regulate the NP voltage by using redundant clamping modes. Thus, the NP voltage can be controlled in each switching period to lower the NP voltage fluctuation. The implementation of the proposed MDPWM is given with variable power factors analysis. Further, the switching loss comparison of conventional space vector PWM (SVPWM), hybrid DPWM (HDPWM), and proposed MDPWM is presented as well. A simulation model was built to verify the proposed NP voltage balance with different modulation indices and variable power factors. Finally, a 10-kW prototype is built to evaluate the proposed MDPWM scheme at conversion efficiency and current total harmonic distortion (THD). Experimental results and analysis show that comparing conventional SVPWM and HDPWM, the efficiency of MDPWM is the highest. The THD of DPWM is slightly higher than that of SVPWM, and it is only 2.5% at rated output power. [ABSTRACT FROM AUTHOR]

Vienna rectifier, which is a nongenerative-boost-type rectifier, is widely used in industrial applications, such as wind turbine systems. However, the Vienna rectifier will face the challenge of reducing common-mode voltage (CMV), maintaining the sinusoidal input currents, and balancing neutral-point (NP) voltage in practice. As these issues are mutually coupled, the conventional space vector modulation (SVM) and various types of enhanced schemes cannot solve these problems properly, especially under nonunity power factor operation. To overcome these limitations, a two-layer pulsewidth modulation scheme through vector selection is developed. In the first layer of the proposed strategy, the NP voltage oscillations are mitigated by adjusting the switching sequence and dwell time of large, medium, small, and zero vectors with reduced CMV as the same in large, medium, and zero vector modulation. In the second layer of the proposed strategy, the switching states are reselected, and the dwell times are real time adjusted to eliminate the distortions in input currents. Through the aforementioned two-layer control method, CMV reduction, input current distortion elimination, and NP voltage balancing in Vienna rectifier can be realized simultaneously. The correctness and effectiveness of the proposed SVM method are verified by the experiment. [ABSTRACT FROM AUTHOR]