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Medium/High power converters usually employ low switching frequency to reduce power loss, resulting in large system delay in their control system. The multi-sampling technique is an effective method to reduce the system delay while this will make the system a Linear Periodic Time Varying (LPTV) system. Modeling this kind of system by using LTI modeling method, such as Laplace transform, Z-transform,...
The paper deals with a high efficiency boost rectifier for high rotational speed Gen-Set applications. It is tailored around a permanent magnet synchronous generator (PMSG) featuring an open end winding configuration. According to such a configuration the generator stator windings are connected on one side to a three level T-type unidirectional rectifier, and on the other side, to an auxiliary two-level...
A model predictive control system for delta-connected modular multilevel converter is proposed in this paper. The control system is based on offline computed optimal pulse patterns, which are modified online using model predictive control. Optimized pulse patterns facilitate the shaping of the grid current spectrum at low switching frequencies. Unlike conventional control methods with optimal pulse...
The advantages of the Modular Multilevel Converter (MMC) as a Voltage Source Converter (VSC) is well known. These includes scalability, increased reliability, lower Total Harmonic Distortion (THD) in output variables, fault tolerance and so forth. The MMC has found its most application in High Voltage DC (HVDC) systems again because of the stated advantages. In the analysis of such systems, because...
This paper investigates the influence of converter-fed operation on magnetic forces and radial vibration in a hydrogenerator. Flux density distribution is computed using time-stepping finite element (FE) analysis and used to calculate force density distribution based on Maxwell stress tensor. Both temporal and spatial characteristics of selected flux density and force density waves are studied. Important...
With regard to the pulse width modulation (PWM) of seven-phase motor system if the three-phase space vector pulse width modulation (SVPWM) is simply extended to the seven phase motor system that is the seven phase of the traditional SVPWM it will produce a great harmonic current. In order to restrain the harmonic content of phase current the voltage vector synthesized in the 3rd harmonic subspace...
In this paper, the circuit topology of single-stage isolated charging/discharging DC-AC converter with second harmonic current suppression is proposed. Based on which an analogous-rectifying unipolar phase-shifted control strategy with constant charging/discharging current is also proposed, which rectifies the Sinusoidal Pulse Width and Position Modulation(SPWPM) wave of high-frequency(HF) transformer...
Obtaining better harmonic profile at relatively lower switching frequencies is one of the key tasks in the present day power electronics world. Several pulse width modulation (PWM) techniques have been developed earlier in time, to reduce the harmonic content from the output of the inverter. Dodecagonal space vector generation scheme is one of them, which eliminates the most dominant lower order harmonics...
This paper presents a selective harmonics reduction for a 3(n+1) shared switch inverter topology utilizing optimal arrangement of the n-modulated signal. Under different modulation indices and operating power frequencies the purpose of the proposed procedure is to select an optimal load connection and/or modulation offsetting based on the desired objective function. Three performance indices are studied...
The star-configured modular multilevel converter is a promising topology for grid-connected storage as well as power-quality applications and motor drives. During operation, the ac output power generates substantial current pulsation at twice the output frequency in the modules, which causes additional loss and requires an increase of the module capacitance. This paper presents a common-mode voltage...
Multilevel current source converter (MCSC) is an effective way to increase the power rating of conventional current source-fed motor drive, especially its current rating. However, there are still several challenges existing in this kind of configuration, which mainly focus on its space vector modulation (SVM) technique and the inherent DC current imbalance issue. In this paper, an SVM scheme with...
A hybrid modulation approach is proposed in this work, which allows to modulate the switches of the five level neutral point clamped inverter (5LANPC) with different switching frequencies. Some of the switches are controlled with a low switching frequency using six-step modulation and Optimized Pulse Patterns (OPPs), whereas the rest are modulated with a high switching frequency using Carrier-Based...
Parallel Neutral-Point Clamped (NPC) inverters are commonly employed in medium voltage high power applications, such as wind energy system, smart transformer, and power conditioners. In literature, it is shown that the Phase Disposition modulation (PD) strategy provides better performance in terms of harmonic profile and current ripple for single NPC application. Therefore, the PD has been commonly...
This paper proposes an induction motor drive scheme generating multilevel twenty-four sided voltage space vector structure using single DC source. The topology consists of basic units with DC-source fed main three-level flying-capacitor (FC) inverter cascaded with two low-voltage floating-capacitor fed H-Bridge cells (CHB). The generated space vector structure has six concentric 24-sided polygons...
Advent of Modular multilevel converters (MMC) made the voltage sourced high voltage direct current (HVDC) transmission systems a reality mainly due to its modular structure, scalability and reliability. For these converters, minimization of sub-module (SM) capacitor voltage spread without increasing the switching frequency is the biggest challenge as it directly affects the efficiency and cost. Moreover,...
This paper presents the analysis of harmonic and switching loss for two-level space vector based pulse width modulation (PWM) schemes. The harmonic performance of the inverter is evaluated through weighted voltage total harmonic distortion for different modulation indices. To calculate switching loss, analytical expressions for switching instants are generated by comparing the triangular carrier signal...
The Particle Swarm Optimization (PSO) has been widely used to solve the selective harmonic elimination (SHE) problem, however, the executing efficiency is not very good if it is implement on the traditional Central Processing Units (CPUs). In this paper, the PSO is parallel implemented on the Graphical Processing Unit (GPU) under the Compute Unified Device Architecture (CUDA). Then, the GPU-accelerated...
This paper proposes a method for zero-crossing approximation of a band-limited sinusoidal signal embedded by a white Gaussian noise-like distortion. It consists of passive low-pass filter and dynamic-hysteresis comparator circuits. Simplicity and wide dynamic range are the main goal of the proposed approach. Theoretical calculations were formulated to select proper circuit components values. Simulation...
This paper proposes the pulse width modulation (PWM) technique for the five-phase open-end winding induction motor (FPOEWIM) drive fed from five-phase dual inverter (FPDI) with a single dc source. The selected method gives the advantages of reduced switching losses specifically for induction motor drives working with higher power factors with the elimination of common-mode current (CMC). The method...
A well-known problem of three-level neutral point clamped (NPC) inverter is the voltage imbalance in the dc-link capacitors. This paper proposes the dc-link capacitor voltage balancing method where a common offset voltage is injected. The offset voltage consists of a harmonic voltage and a magnitude difference between the upper and the lower capacitors. Theoretical analysis is provided to balance...
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