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Summary: A Vienna rectifier is a kind of three‐phase converter with complex operation constraints. Traditional control methods suffer from poor dynamic responses and total harmonic distortion (THD), particularly when operating with adjustable wide‐range power. A novel low‐complexity model predictive control (LC‐MPC) algorithm is proposed based on the optimal switching vector sequence in this paper. First, a model predictive optimization control (MPOC) method is designed to search for the voltage vector sequence and its acting time. Second, the equivalent transformation and coordinate mapping of MPOC are efficiently achieved through the derived correlation factors and lookup table. Supported by the correlation factors, the redundant objective function calculation and repetitive online optimization are eliminated. Meanwhile, the simplified optimal over‐modulation strategy is implemented. Finally, the effectiveness and superiority of the algorithm are verified by comparative experiments. The results show that the proposed LC‐MPC is beneficial in terms of the computation time, dynamic response, over‐modulation, and harmonic content reduction. [ABSTRACT FROM AUTHOR]

This paper proposes an offset voltage injection method to compensate for AC voltage ripple at the neutral-point of a Vienna rectifier. The proposed method leads to sinusoidal input currents and has a suppression effect on the AC voltage ripple at the neutral-point by injecting three offset voltages to remove both the zero current distortion and voltage unbalance (both DC voltage and AC voltage ripple) at the neutral-point. This can result in an improvement in the Total Harmonic Distortion (THD) of the input current. The offset voltage to realize the suppressing of the AC voltage ripple is defined based on a neutral-point voltage equivalence model of a Vienna rectifier. The priority of the offset voltages is considered to avoid over-modulation. In addition, incompatibility between offset voltages is analyzed to guarantee sinusoidal input currents. By considering both of these characteristics, the proposed method injects the offset voltages in order from the higher priority to the lower priority. The performance and effectiveness of the proposed method are verified with simulation and experimental results. [ABSTRACT FROM AUTHOR]

The VIENNA rectifier is of high reliability, high power density, and low complexity, which has been widely applied in telecommunication systems. However, it has 25 switching states complicating the control design. Besides, it is easy for the VIENNA rectifier to distort the input currents at zero‐crossing points, which will degrade the grid power quality. To address these problems, a novel mode‐reduction space vector pulse width modulation (SVPWM) control method is proposed in this paper. By analyzing the switching states of the VIENNA rectifier, 3‐mode, 6‐mode, and 18‐mode control framework are compared, and it is found that the 18‐mode has advanced features. Specifically, the proposed 18‐mode control algorithm will have fewer calculation steps and a simpler processing flow. More importantly, it can eliminate the input current distortions for power quality improvement. A 4 kW hardware prototype of the VIENNA rectifier is developed, and experiments have been performed to verify the harmonic reduction feature of the proposed 18‐mode control. [ABSTRACT FROM AUTHOR]

This paper presents a novel fault ride-through (FRT) capability with the use of active converters (Vienna rectifier-I and five-level three-phase modular multilevel converter (MMC)) integrated with permanent magnet synchronous generator (PMSG) supplying AC load. The DC-link fault is controlled with the use of fault blocking diode and MMC sub-module (SM) based wind power plant (WPP). A 16 kW, 60 Hz, PMSG and wind turbine (WT) integrated with the machine-side converter (MSC), and grid-side converter (GSC) are utilized as wind farm components, along with direct current (DC) transmission grid. This topology contributes to the stability and reliability of the system by ensuring continuous output power under transient fault conditions. The functional response of the system is presented using power simulator (The PowerSim, Rockville, USA) software to demonstrate the performance of the proposed controller. [ABSTRACT FROM AUTHOR]

This paper investigates a Vienna rectifier as a charger for series-connected battery packs. Focusing on carrier-based pulsewidth modulation (CBPWM), the ripple current flowing through the neutral point (NP) results in the voltage oscillation if the loads are resistive. To reduce the ripple of average NP current with mitigated distortion under balanced and unbalanced dc-link voltages conditions, a novel CBPWM with segmented component injection scheme (SCIS) is proposed in this paper. After dc component injection, continuous intervals for optimized component injection and clamping intervals for compensation component injection are identified. Optimized components are calculated originally based on unbalanced factor to make the average NP current zero-size in one switching period. Moreover, unique compensation components generate suitable NP current to shape the sinusoidal input currents according to the circuit analysis. In consequence, the SCIS not only keeps the input current with low-harmonic distortion, but also minimizes the oscillation of dc-link voltage under balanced and unbalanced conditions. In addition, the value of the NP current during the clamping intervals is analyzed under various operating conditions. The effectiveness and the performance of the proposed SCIS are verified by simulation and experiments. [ABSTRACT FROM AUTHOR]

Worldwide increasing energy demands promote development of environment-friendly energy sources. As consequences, ocean wave is exploited as an ideal energy source to mitigate greenhouse gas emissions. In this paper, a hydraulic energy-storage wave energy conversion system is constructed, and a mathematical model of main components is built for analysis. Control strategies of generator-side and grid-side are defined for the system, where a Vienna rectifier is applied to converter of generator-side. A two-level space vector plane simplified modulation method for Vienna rectifier is designed for the three-level system and a modulation algorithm is detailed, which has lower complexity compared with traditional three-level space vector pulse width modulation (SVPWM) algorithm. An improved adjusting factor method is proposed to solve the potential imbalance of neutral point caused by uneven charging to the upper and lower capacitors in the three-level structure, which optimizes sector division and inhibits the neutral-point potential offset and fluctuation effectively. Using Matlab/Simulink, the intermittent and continuous power conversion modes of the system under different wave conditions are simulated. The results indicate stable operation of the system, feasible topology scheme, modulation algorithm and control strategy, and effective suppression of AC-side harmonics. [ABSTRACT FROM AUTHOR]

This paper deals with nonlinear control and optimal management of wind energy conversion systems connected to HVDC transmission lines. Specifically, the energy system under study consists of a wind turbine driving a permanent magnet synchronous generator, the latter supplies energy to a power grid through a Vienna rectifier and a DC link. To compensate for intermittent nature of wind power and load demand variations, we design a voltage controller as well as a novel energy management strategy that accounts for the available wind power and DC load demands. In the considered management, distinction is made between two operation modes: i) the maximum power point tracking mode using an intelligent adaptive optimizer, where only electrical parameter measurements are used to ensure maximum power extraction; ii) the adaptive power point tracking mode employing demand-driven production. In both modes, the power factor requirement is ensured, regardless the weather conditions and load demand variations, enhancing thus the aerogenerator's efficiency. One more novelty of the proposed control and management system is the online estimation of the DC voltage, avoiding thus the use of a physical sensor. The performances of the control and management system are highlighted by several simulations, showing the achievement all control objectives. • SVPWM applied to the Vienna rectifier. • WECS recursive backstepping nonlinear control design. • ANFIS algorithm-based speed optimizer. • Adaptive high gain observer for HVDC transmission lines. [ABSTRACT FROM AUTHOR]

This paper presents a novel sensorless high-gain observer for wind energy conversion systems (WECS) incorporating Vienna rectifiers. Vienna rectifiers offer several advantages for WECS, including improved efficiency and signal quality. The main contribution of this study is the design of a high-gain observer that provides online estimates of magnetic and mechanical variables, such as rotor speed and load torque, based solely on electrical parameters. Addressing the challenges posed by the nonlinearity and relatively high dimensionality of the system dynamics, the proposed observer's effectiveness is demonstrated through simulations and theoretical analysis. Furthermore, experimental validation using the RTDS (Real-Time Digital Simulator) platform further confirms the performance and reliability of the observer. • Observability analysis. • Online Estimation of Magnetic and Mechanical Variables. • Sensorless control of WECS involve a Vienna rectifier. • Experimental Validation: RTDS (Real-Time Digital Simulator). [ABSTRACT FROM AUTHOR]

A Vienna rectifier has been widely applied when power density is a design objective and usually works with a high switching frequency. Therefore, it is necessary to decrease the switching loss to reduce the temperature of the device. Discontinuous pulse width modulation (DPWM) is able to reduce the switching loss of power of the device. However, the five‐stage vector synthesis method of DPWM will increase the current harmonics. To reduce the current harmonic distortions caused by the DPWM method and reduce the switching loss of a Vienna rectifier, a modified DPWM modulation method with minimum switching loss for a Vienna rectifier is proposed in this paper, and the reduction of current harmonic is achieved by injecting the optimal zero‐sequence component into three‐phase modulation waves in the subsectors at the large‐sector transitional area. Furthermore, the three‐level topology has a problem of unbalanced neutral point potential. By changing the clamp mode in each subsector leading to different currents, leading to the neutral point, the neutral point potential is balanced. Finally, all these proposed modulation and control strategies are verified by simulation and experiment results. © 2020 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

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]

In this paper, a control scheme is proposed for maximum power point tracking (MPPT) in a variable speed standalone wind energy conversion system (WECS) with permanent magnet synchronous generator. A MPPT algorithm is designed trying to eliminate the main deficiency of the conventional perturbation and observation (P&O) method, which is the challenge of choosing a proper step size and the unwanted trade-off between accuracy and speed. The designed algorithm properly addresses this drawback and significantly improves the MPPT performance. Another important issue is to ensure fast and accurate tracking of the optimal reference point obtained from the MPPT algorithm and improve the performance and efficiency of the control system for transferring maximum possible power to the load. To this end, a Vienna rectifier is used in the designed WECS and a multiobjective model predictive control scheme is designed to properly control the converter with fast response, high accuracy, and, at the same time, the lowest possible switching frequency. The performance of the proposed control scheme has been studied for two different wind speed profiles with different behaviors. Moreover, a comparison is made between the proposed MPPT algorithm and the conventional P&O method. The results support the proper performance of the proposed system in extraction and transfer of the maximum possible power from the wind to the load. This aim is achieved because of the significant advantages of the designed system in terms of fast and accurate tracking of the optimal point and having higher efficiency. [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]

• Development of the PMSG model related to the Vienna rectifier for analytical investigation of the effect of switching vectors. • Improved look-up table-based direct torque control was developed to control a permanent magnet synchronous generator using Vienna rectifier. • Model-based computational delay compensation approach for the digital implementation of direct torque control. • Irregular torque and stator flux ripples especially during unbalance DC load connection was addressed. • Laboratory scale model developed using Texas Instrument TMS320F28335 and tested with wind turbine emulator as a wind energy conversion system. This paper presents an improved look-up table-based direct torque control of the permanent magnet synchronous generator using Vienna rectifier for a wind energy conversion system. A stator voltage model for the system was developed to allow an in-depth analysis of the effect of the switching vectors for the Vienna rectifier on the performance of direct torque control. The developed generator model is dedicated to reducing the complexity of look-up table development. Subsequently, an improved look-up table was designed to enhance the overall performance of the permanent magnet synchronous generator in both torque and stator flux ripples, along with the investigation of the computation delay compensation for the digital implementation. The performance was first investigated through Matlab / Simulink before being further validated using a small-scale prototype and a wind turbine emulator. Both simulation and experimental results obtained were compared with the existing direct torque control approach to verify the effectiveness of the proposed system for wind energy extraction. The results show that the enhanced look-up table generates lower ripples in torque and stator flux while improving their reference tracking, especially during unbalanced DC load scenarios. This achievement can be clearly seen by the lower discrepancy percentage between the reference and actual value in the generated torque and stator flux by 6.35% and 0.47%, respectively. [ABSTRACT FROM AUTHOR]