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This paper presents an ac ripple repression method for neutral-point voltage of three-level inverter system with electrolytic capacitor less. To reduce the volume of three-level inverter system, electrolytic capacitor with huge capacitance is must eliminated from dc-link. In the inverter system applying film capacitors, however, the ac ripple component in neutral-point voltage of dc-link is increased...
This study investigates the cell voltages and arm currents in double-star modular multilevel converters (DSMMCs) based on power balance and current tracking control law. DSMMCs have been widely applied to static synchronous compensators, high-voltage direct-current transmission, back-to-back power transfer systems, wind/solar power generation and battery storage systems. The size of capacitors in...
We push forward setting of the elevator for barrier-free and exchanging of the LED light for energy saving in stations. But harmonic currents may increase by these facilities in the power distribution network. It is effective to take measures for harmonic currents from the design phase. In this paper, the method of this report can estimate harmonic current emissions in case of stations improved by...
Modulation techniques for the modular multilevel converter consider that the total number of sub-modules in the phase-leg is, either instantaneously or on average, equal to N balancing the capacitor voltages to a constant reference. This paper proposes an offset PWM technique that utilises the total number of the SMs in the arms of the MMC, particularly under low modulation indices. The result is...
In the literature, passive filters have been commonly used to mitigate the harmonic currents in industrial distribution systems because they are inexpensive, simple, and reliable. The aim of this paper is presenting different design methods for multiple-arm shunt passive filters based on various reactive power sharing approaches for an industrial distribution system of a petrochemical plant in Egypt...
This paper presents high-power-density inverter with pulse current injection power decoupling method. In order to reduce the dc-link capacitor significantly, dc-link current is fully analyzed with double Fourier method in theory. Compared with the traditional 2nd harmonic power decoupling method, the pulse current injection method considers not only 2nd order harmonic but also the higher order harmonics...
The grid connectivity requirements imposed today, ask for an accurate controller design able to deal with system constraints and nonlinearities. In order to fulfill grid international standards, this paper details a Finite control set model predictive controller called FCS-MPC as part of controlling an energy conversion system. It uses a discrete time 3L-NPC inverter model (in the α-β frame) to predict...
This paper presents the simulation of different types of single as well as composite power quality events (PQ) for analysis and characterization. Most of the power quality problems (the transient and steady state disturbances), which can occur in the distribution system, have been obtained. Six single PQ event such as voltage sag, voltage swell, interruption, transients, voltage notch and harmonics...
This paper focuses on the determination of suitable carrier based pulse width modulation (PWM) switching and control methods for grid connected modular multilevel converters (MMCs). Characterization of various level-shifted and phase-shifted carrier based PWM methods are provided in terms of output voltage waveforms both for N+1 and 2N+1 level output phase voltages. Carrier based PWM method based...
This paper deals with a computing simulation for an offshore wind energy system taking into account the influence of the marine waves action throughout the floating platform. The wind energy system has a variable-speed turbine equipped with a permanent magnet synchronous generator and a full-power fivelevel converter, injecting energy into the electric grid through a high voltage alternate current...
This paper proposes a control method of DC-link shunt compensator (DSC) located to DC-node in three-phase diode rectifier system. The circuit can substitute for bulky components such as DC reactor filter and DC-link capacitor from conventional three-phase system. Hence the system can be miniaturized and becomes lighter by reducing heavy passive components. DSC supplies harmonic current into diode...
This paper describes a novel family of modified quasi-Z-source buck-boost multilevel inverters with reduced switch count. The inverters are derived by means of the modified inverter configuration with quasi-Z-source networks. The main benefits of the proposed solutions lie in the increased amount of levels with all possible sequences: reduced THD, reduced voltage stress on the transistors and size...
As it was mentioned in the first part, this paper is focused on the nonlinear behavior of the DC-DC converters. The Buck converter was chosen to apply different tools in order to analyze the stability of operation under voltage and current control. Also, besides the qualitative information given by the graphical methods used, the performances of the control techniques are evaluated in time and frequency...
Bulky capacitors are often needed in DC systems to smooth voltage ripples, which reduces the power density and system reliability considerably. In this paper, a Ripple Eliminator (RE) that is a bidirectional buck-boost converter terminated with an auxiliary capacitor is proposed to reduce voltage ripples after connecting it to the DC bus. A controller is proposed to transfer the voltage ripples on...
This paper presents a unique control scheme for achieving power balancing in a recently proposed multilevel inverter topology. Moreover, this strategy can be extended to any type of topology and to any number of output levels of multilevel inverter (MLI). A comparison is made between the power delivered by sources with and without applying proposed strategy.
This paper presents the design and implementation of a modular single phase multilevel inverter using the asymmetric cascade multilevel converter type. The converter output allows 7, 15 and 31 levels and use the step modulation strategy. The selective harmonic elimination (SHE) technique was used for the computation of the firing angles. All the results were simulated in MATLAB professional software...
Active Power Filter (APF) is an important power electronic device to compensate the load harmonic current so as to improve power quality of the system. Stability of voltage across the capacitor in DC side of APF is one of the key factors which determine the compensation effect. Therefore voltage ripple should be controlled within allowed range. This paper firstly deduced theoretical expressions of...
Due to voltage limitation of available semiconductor switches, multicell converters are required for high-power medium-voltage applications. One of the most significant types of multicell converters is cascade multicell converter categorized into symmetrical and asymmetrical ones. This paper first presents a new symmetrical cascade multicell converter in which the number of switches is optimized....
A new method for reducing harmonics involved in output voltages of a three-phase voltage source inverter is proposed. It is applied to the conventional 6-step inverter with a three-phase autotransformer. By injecting harmonics to the neutral point of the autotransformer from an auxiliary circuit, output voltages of the proposed inverter can be almost the same as a conventional 24-step inverter. In...
This paper describes the operation of modular multilevel converter (MMC). A control method of adding the feed-forward current is introduced. Another strategy of removing the second harmonic current is also described in order to improve the arm currents. Simulation results based on a detailed PSIM model prove the effectiveness of the two methods. The paper presents principle of parameters selection...
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