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Multilevel converters become visible to increase the working voltage of the power converter without exceeding the limits imposed by the semiconductor power devices. One of these multilevel converters is the three-level neutral point clamped converter, better known as NPC. This paper describes the most relevant modulation and control techniques of this converter and some of them are validated by simulations...
This paper concerns the application of three-level neutral point clamped (NPC) voltage source inverter (VSI) to electrical energy conversion of the photovoltaic (PV) power plant. The grid-connected 3-phase NPC inverter is powered via the split DC-link composed of the capacitive divider (Fig. 1). It enables the usage of two DC-buses independently which can be supplied by the separated boost-type DC-DC...
The voltage balancing of the dc-link capacitors in an electric drive system with five-level neutral-point-clamped converters is investigated in this paper. A properly modified space-vector-modulation technique is utilized in combination with a multilevel dc/dc converter for controlling the capacitor voltages. An advanced algorithm has been developed for reducing the losses of the electric drive system...
This paper presents a simple method for modulation in multilevel converters, which is hardly affected with the number of levels. The method is based on a simple graph, whose x-axis is directly related to the extra degree of freedom associated with component γ (in the αβγ reference frame) of the desired reference vector. In the y-axis, the different possibilities for the phase averaged references are...
A neutral point (NP) balancing modulation for a three-level inverter with cosϕ > 0.9 is presented. In the low modulation range, standard space vector modulation (SVM) is applied using the redundancy of the small space vectors (SV) for the NP balancing. In the high modulation range, the switching sequence is adapted so that the neutral-point voltage can be also balanced. The proposed method is compared...
In this paper, two control strategies based on space vector modulation (SVM) technique are developed for a five-level current source converter (CSC) based STATCOM. In case of control strategy-1, DC-link currents are kept constant, and the reactive power is varied by changing the modulation index. On the other hand, in case of control strategy-2, DC-link currents are varied in accordance with reactive...
Last few decades, multilevel converter topologies have gained a considerable attention. The multilevel converter designs promise a lot of advantages in high power applications, over the conventional converter design such as: lower THD (Total Harmonic Distortion) higher operational voltage ranges, lighter and cheaper topologies. However, due to its higher complexity, also the control algorithms are...
This paper presents a new, simple and generalized approach to calculate flying capacitor currents for an n-level flying capacitor converter without the use of look-up tables. The performance of the proposed method has been studied for a three-, four- and five-level flying capacitor converter in MATLAB/Simulink environment.
This paper proposes a new five-level voltage source converter (VSC) for medium-voltage high-power applications. The features and operation of the proposed converter is studied. The Space Vector Modulation (SVM) technique is developed to regulate voltages of flying capacitors. The performance of the proposed converter is evaluated by simulation and experimental results.
This paper proposes a systematic procedure to evaluate, compare and select different modulation techniques for a medium voltage variable speed drive. Several indicators are proposed to be analyzed, mainly based on thermal analysis, voltage limitations, dc bus evaluation and load current quality. The suggested procedure is evaluated on a simulation based analysis in a 6.6 kV adjustable speed drive...
The reduced capability of the 5L-NPC Inverter to balance the voltages of the four DC-bus capacitors makes this converter unattractive for real power applications. This is especially true if the load demands active power. The Back-to-Back (B2B) configuration of two 5L-NPC converters and the use of a Space Vector Modulation (SVM) that exploits the voltage balancing capabilities of the redundant switching...
This paper proposes the implementation of a space vector modulation (SVM) scheme to reduce the common-mode voltage of a symmetrical hybrid five-level inverter operating at high modulation index. The proposed modulation is implemented in a DSC-Digital Signal Controller. It employs vectors that prevent voltage vectors that impose high common-mode voltages at the converter load. Experimental results...
Open-end winding variable speed drives with dual-inverter supply have been extensively investigated for various applications, including series hybrid powertrains and propulsion motors. The topology is simple to realise while offering a higher number of switching states without the need for capacitor balancing algorithms, when compared to standard multilevel converters. The existing body of work is...
This paper presents a new control strategy for a high performance hybrid cascaded H-Bridge HB multilevel converter with integrated series Active Power Filter Stage APFS. Unequal DC voltage sources are used to energise the converter's HBs. This offers increased number of voltage levels using fewer number of series connected HBs. Simple hybrid stair-case/SVM modulation strategy is proposed to synthesise...
Multilevel converters are powerful converters in the medium/high power range. Inside this family of converters, the three-level neutral point clamped converter has its own importance. The main control methods associated with this converter are the carrier-based PWM with added homopolar components and the space vector PWM. One of the most important features of the NPC converter is the neutral point...
The three-level neutral point clamped converter is one of the most important multilevel converters. Two important features of the neutral point clamped converter are the neutral point balance and the output voltage characteristics. Carrier and space vector Pulse-Width Modulation control methods efficiently manage the two issues. This paper analyses the voltage balancing problem and shows that a simple...
The paper presents a comparative study of three different 3D-SVM techniques for the control of flying-capacitor multi-level inverters under both balanced and unbalanced operating conditions. Simulation results show that Direct 3D-SVM is the most efficient in computational effort. Application of this scheme to a three-level FCMI is simulated using the Alternative Transients Program (ATP). Output performance...
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