Space Vector Modulation Techniques for Multilevel Converters – a survey

This paper presents a survey of most recent, simple and efficient Space Vector Modulation algorithms for multilevel converters. These algorithms avoid trigonometric and other complex operations, leading to more simple and cost efficient implementations. They can be applied to multilevel topologies and present freedom degrees that can be Exploited in order to optimize system parameters in the system like: capacitors voltages balancing or voltage/current ripples. Experimental results are presented to show the good performance of the algorithms

A new space-vector-modulation algorithm for a three-level four-leg NPC inverter

For power conversion systems interfaced to 4-wire supplies, four-leg converters have become a standard solution. A four-leg converter allows good compensation of zero-sequence harmonics and full utilization of the dc-link voltage. These are very important features when unbalanced and/or non-linear loads are connected to the system. This paper proposes a 3D-SVM algorithm and provides a comprehensive analysis of the algorithm implemented on a three-level, four-leg NPC converter. The algorithm allows a simple definition of the different switching patterns and enables balancing of the dc-link capacitor voltages using the redundancies of the converter states. A resonant controller is selected as the control strategy to validate the proposed SVM algorithm in a 6kW experimental rig

Backstepping control of three-phase three-level four-leg shunt active power filter

In this paper, backstepping control for three-level four-leg shunt active power filter (SAPF) system is proposed. The adopted filtering topology requires both a three-dimensional space vector modulation (3DSVM) for controlling the three-level four-leg inverter as well as DC voltage and filter currents control. The regulation of the DC voltage and filter currents is accomplished by backstepping controllers. The voltage-balancing control of two split DC capacitors of the three-level four-leg SAPF is achieved using three-level three-dimensional space vector modulation equipped by a balancing strategy based on the effective use of the redundant switching states of the inverter voltage vectors. The simulation results show the effectiveness of the proposed filtering system in terms of the compensation of the harmonics and the zero sequence current and the operation at unity power factor.Keywords: shunt active power filter; three-dimensional space vector modulation; multilevel four-leg inverter; backstepping control; synchronous reference frame theory

A simplified space-vector modulation algorithm for four-leg NPC converters

To interface generation sources and loads to four-wire distribution networks is important to use power converters and modulation methods which provide high performance, flexi¬bility and reliability. To achieve these goals, this paper proposes a simple and efficient Space Vector Modulation (SVM) algorithm in α3-y coordinates for Neutral Point Clamped (NPC) converters. The proposed SVM method reduces a three-dimensional (α3-y) search of the modulating vectors into a simple two-dimensional (α3) problem. Moreover, the algorithm provides full utilisation of the dc-link voltage, full utilisation of the redundant vectors and it can be applied to any other four-leg converter topology. The proposed SVM has been successfully validated using a 6kW three-level four-leg NPC converter, achieving control over the voltages of the dc-link capacitors and simple definition of switching pattern for shaping frequency spectrum

A Hysteresis Current-Regulated Control for Multi-Level Drives

Most multi-level converters are controlled through the use of voltage-source based control techniques such as space-vector modulation or multi-level sine-triangle modulation. However, in many applications such as field oriented drives, a high bandwidth current-source inverter based control is more desirable. In this paper, the concept of a multi-level hysteresis current-source control is set forth. The new control is experimentally verified using a four-level converter/induction motor drive system and the results are compared to a space vector modulation controller. A dynamic study involving a step change in current command demonstrates the controls high bandwidth

MATLAB/SIMULINK BASED ANALYSIS OF VOLTAGE SOURCE INVERTER WITH SPACE VECTOR MODULATION

Space vector modulation (SVM) is the best modulation technique to drive 3-phase load such as 3-phase induction motor. In this paper, the pulse width modulation strategy with SVM is analyzed in detail. The modulation strategy uses switching time calculator to calculate the timing of voltage vector applied to the three-phase balanced-load. The principle of the space vector modulation strategy is performed using Matlab/Simulink. The simulation result indicates that this algorithm is flexible and suitable to use for advance vector control. The strategy of the switching minimizes the distortion of load current as well as loss due to minimize number of commutations in the inverter

Three Dimensional Space Vector Modulation Theory: Practices without Proofs

In three dimensional (3D) space vector modulation (SVM) theory with α-β-γ frame there are some issues which are well known and are widely practiced being quite obvious but without any proof so far. In this paper necessary scientific foundations to those issues have been provided. The foremost of these issues has been with the frame of reference to be considered in 3D SVM applications for unbalanced three phase systems. Although for balanced three phase systems there has been no controversy with α-β frame as the frame of reference but in 3D it has not yet been established which one, α-β-γ frame or the a-b-c frame, is mathematically correct. Another significant issue addressed in this work has been to ascertain the exact reason when a three phase system has to be represented in 2D or 3D space to apply SVM. It has been presented for the first time in this work that the key factor that determines whether 3D or 2D SVM has to be applied depends on the presence of time independent symmetrical components in a three phase ac system. Also it has been proved that the third axis, the Y–axis, represents the time independent quantity and that it must be directed perpendicular to the α-β plane passing through the origin

Feed-forward Space Vector Modulation for Single-Phase Multilevel Cascade Converters with any DC voltage ratio

Modulation techniques for multilevel converters can create distorted output voltages and currents if the DC link voltages are unbalanced. This situation can be avoided if the instantaneous DC voltage error is not taken into account in the modulation process. This paper proposes a feed-forward space vector modulation method for a single-phase multilevel cascade converter. Using this modulation technique, the modulated output voltage of the power converter always generates the reference determined by the controller even in worst case voltage unbalance conditions. In addition the possibility of optimizing the DC voltage ratio between the H-bridges of the power converter is introduced. Experimental results from a 5kVA prototype are presented in order to validate the proposed modulation technique