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Asymmetrical cascaded multilevel converters can generate more number of voltage levels for the same number of switching devices. Binary, Trinary and other different forms are available in literature. This paper has critically investigated such converters from the point of view of optimizing the number of levels. A mathematical tool to analyze the possibility of any asymmetric ratio for various three-phase...
The growing availability of high power semiconductor devices and the increasing necessity of high power converters in power systems and industry applications demand the use of multilevel converters topologies, such as the 3-level neutral point clamped voltage source converter. The tradeoff in designing this kind of converter is between switching losses and fast dynamic control. The size and cost of...
This work compares multi-cell topologies based on Current Source Inverters (CSIs) which are connected in a Cascade H-Bridge (CHB), where the large DC inductor size needed to compensate the oscillating power drained by the inverter is the main drawback. In order to reduce the DC inductor size, two compensation methods which compensated the oscillating power are evaluated and compared with the basic...
This work presents a comparison between two adaptive filters applied to harmonic and reactive power detection in power electronics conditioners. The objective is to demonstrate their ability of tracking the signal variations without the use of synchronization techniques, with fast dynamic response and low computational burden. The algorithms are simulated and implemented in DSP TMS320F2812 for power...
In this paper, an active power filter (APF) based on a modified one-cycle control is proposed. This control method can be applied in a three-level three-phase four-wire system. By adding an additional current sensor to detect the fundamental component of the output current, the proposed APF is capable of compensating harmonic components independently from the VAR compensation so that the capacity...
This paper describes novel adaptive multiplicative general parameter finite impulse response filter with real coefficients (MGP-FIR). The MGP-FIR is adaptive, predictive digital FIR filter for fundamental harmonic estimation of distorted signal with small frequency fluctuations without phase shift (time delay). This property is necessary for high quality control of power converters connected to the...
In this work it is proposed a control strategy for a shunt Active Power Filter (APF) based on an One Cycle Control (OCC) Rectifier, implemented by DSR An input resistance controller to set up dc-link voltage and a lead-lag compensator to average grid current is part of this work. In addition, as DSP implementation can increase the possibilities of control of complex systems. An example of this feature...
This paper addresses the harmonic compensation error problem existing with parallel connected inverter in the same grid interface conditions by means of impedance-based analysis and modeling. Unlike the single grid connected inverter, it is found that multiple parallel connected inverters and grid impedance can make influence to each other if they each have a harmonic compensation function. The analysis...
The instantaneous output power of a two-stage single-phase inverter pulsates at twice the output voltage frequency, generating second harmonic current (SHC) in the front-end dc-dc converter. Though reducing the SHC of the output filter inductor of the dc-dc converter (FIDC) can reduce the input SHC effectively, it depends on the capacitance of DC bus capacitor totally. In order to reduce the SHC of...
The power handling capability of the state-of-the-art semiconductor devices is limited. Therefore, the Voltage Source Converters (VSCs) are often connected in parallel to realize high power converter. The switching frequency semiconductor devices, used in the high power VSCs, is also limited. Therefore, large filter components are often required in order to meet the stringent grid code requirements...
Grid-connected photovoltaic (PV) systems with power electronic interfaces are becoming popular since they do not contribute to environmental pollution. However, one of the issues with grid feeding inverter is the requirement of high dc-link voltage. In view of this, single stage solar inverters using conventional inverters may not be suitable, since they require input dc voltage higher than the peak...
This paper presents novel control algorithms for a transformerless hybrid active filter without current sensors. The hybrid active filter is composed of a shunt active filter in series with a passive filter tuned nearby 5th harmonic frequency. This structure allows reducing the DC-Link voltage, which is very important when the connection of hybrid active filters to power grids at medium voltage level...
There is an increasing interest in two-stage four-leg matrix converter (3×4TSMC) which provides a neutral connection for potential imbalanced loads. However, the fourth leg will worsen its operation performance unexpectedly, even if connected to the balanced loads. By means of analysis and calculation, it is found that the input filter capacitor voltage fluctuation will transfer to the output in the...
This paper presents a new control topology to reduce the effect of the fifth negative and seventh positive voltages harmonic in the Doubly Fed Induction Generator (DFIG) in wind power systems. The proposed control is based on the concept of active power filters. A rotor current is delivered in the opposite direction of the harmonic content to reduces its effect. A incremental fuzzy controller is used...
A new space vector modulation method for common-mode voltage reduction in four-level nested neutral point clamped (NNPC) inverter is proposed in this paper. The proposed method employs switching states with minimal absolute common-mode voltages to synthesize given reference vectors. A variety of virtual vectors are constructed to facilitate the synthesis. The effect of dead time on common-mode voltage...
The power losses of three-level neutral-point-clamped (NPC) converters and their AC-filters with iron and amorphous core inductors designed for a bipolar low voltage direct current (LVDC) distribution network are evaluated. The main objectives of the LVDC distribution network are improved energy efficiency, power quality and reliability and higher power transmission capacity and integration of ICT...
An adaptive delta-sigma modulator which can be utilized for the zero-cross switching control of resistive heaters with AC line for thermal control is proposed. By adjusting the horizon width for the cost function of the modulator control scheme according to the command signal, the modulator has both a good performance of quantum noise suppression and a wide operating range simultaneously. A numerical...
In this paper, voltage control of stand-alone "Photovoltaic (PV)-Diesel Generator (DG)-Battery" system is presented when subjected to faults on distribution feeders. During the period of occurrence of fault and opening of fuse, high current flows through inverter leg which stops its operation. Moreover, fault creates huge unbalance due to opening of fuse of faulty phase(s). Therefore, a...
This paper presents a modified synchronous reference frame for Active Power Filter control (APF) to compensate for harmonics and reactive power for both balanced and unbalanced non-linear loads. The proposed controller autonomously detects different power quality problems, filters out load created harmonics and compensates for unbalances and/or DC offsets resulting from non-linear loads connected...
In this paper, parallel operation of multiple inverters with a new control method for efficient utilisation of active power filters (APF) is proposed for varying load conditions. Suppression of current harmonics with parallel operation of multiple inverters has been introduced instead of the high capacity single units, to add flexibility and reliability to the system. The operation of the system is...
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