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LCL filter is becoming an attractive choice over conventional L filters for grid-connected voltage source inverters (VSI) due to smaller inductor size and better attenuation of the ripple components in the grid current. The modulation of the VSI generates switched voltages which results in distorted currents. In this paper, a simple closed form analytical expression is derived for the higher order...
This paper proposes a novel direct torque control (DTC) scheme to reduce the torque and stator flux ripples for permanent-magnet synchronous motor (PMSM) drives using a relatively low sampling frequency. Unlike the conventional DTC in which the voltage vectors are determined by hysteresis controllers, the proposed DTC uses nonlinear saturation comparators and a duty ratio modulation scheme for switch...
The main objective of this paper is to study a seven level multi string converter topology for distributed energy resources based DC-AC conversion system. This paper proposes the Karnaugh mapping technique (which was rarely used in power electronic converters) for modeling the multi string seven level converter. The proposed method can also be extended to ‘n’ level converter. This paper also proposes...
This paper proposes a digital online efficiency optimization technique for DC/DC Dual Half-Bridge Series Resonant Converters. The proposed technique implements an advanced modulation scheme which exploits the degrees of freedom inherently available in the converter modulation space in order to simultaneously regulate the output voltage and maintain the system in its maximum efficiency point. Furthermore,...
A traditional half-bridge three-phase inverter topology can achieve zero voltage switching by implementing BCM operation which requires no additional power devices or magnetic components. In this paper a variable boundary dualmode current modulation method that combines ZVS and ZCS is proposed in order to improve the efficiency of the BCM current controlled micro-inverter. Decreasing output current...
This paper introduces a novel isolated hybrid resonant converter with smooth transition between multiple operating modes. With the simple addition of a bidirectional ac switch, the highly-efficient series resonant converter operating in the discontinuous conduction mode (DCM) is combined with a phase-shifted full-bridge buck converter and a pulse width modulated (PWM) boost converter in order to provide...
Non-isolated single-inductor three-port converters (SI-TPCs) are the cost-effective way to connect the renewable source, energy-stored component and load for those stand-alone applications without isolation requirements. However, the dynamic features of SI-TPCs are complicated due to the multiport, bidirectional energy flowing and a variety of energy management modes. To facilitate the control-loop...
This paper presents a new method of current control that employs burst mode in order to balance the dc-side capacitor voltages of split phase inverters. By alternating the inductor current in every switching period, zero-voltage switching (ZVS) can be achieved, which avoids the reverse recovery issue of power MOSFETs. As a result, super-junction MOSFETs instead of IGBTs can be employed to achieve...
The inverter often connects to load or grid through inductor-capacitor (LC) filter for feeding the filtered voltage and current. The carrier based modulation techniques, such as sinusoidal pulse width modulation (SPWM) and space vector modulation (SVM), require some kind of current control in LC filter connected inverter to damp out the LC resonance. The major advantage of flux vector modulation for...
In this paper, a new post-fault modulation strategy is proposed to operate the direct matrix converter (MC) as close as possible to its desired normal operating under an open-switch fault condition. The proposed strategy determines the switching states of the eight, out of the nine, remaining healthy switches of the converter, to generate the reference voltage. The corresponding duty cycles of the...
Three-phase single-stage boost inverter requires narrow pulses, thus a low resolution DSP can cause some pulse droppings which results in asymmetries in the output waveforms of the boost inverter. This leads to an increase in the total harmonic distortion (THD) of the output waveforms. In order to solve this problem, a modified version of the phasor pulse width modulation (PPWM) switching pattern...
Presently, multi-string topology is considered the state of the art for grid integration of high power photovoltaic (PV) systems. In this paper, an improvement of the basic multi-string topology is presented which uses a three-level neutral point clamped (3L-NPC) converter as central grid tied inverter. Each of the two capacitors of the split dc link in 3L-NPC converter is fed from a separate multi-string...
This paper proposes a new technique for enhancement of energy extraction capabilities in wind energy conversion systems with low cut-in speed. The dc-link voltage is maintained by the grid-side converter in wind energy systems equipped with back-to-back three-phase inverters. This voltage is required to be higher than a certain value to ensure proper operation of the grid-side converter. On the other...
This work introduces three-phase unidirectional buck-type unity power factor rectifiers. The proposed rectifiers are assembled by incorporating auxiliary circuit branches into standard three-phase buck-type PFC topologies, each comprising an active switch and three diodes. These circuits can operate as active third harmonic current injection PFC systems. The characteristics of the buck-type converters,...
In traction inverters of hybrid electric vehicles (HEVs), DC-link capacitors, which are usually bulky and expensive, present an obstacle for improving the power density and reliability. This paper introduces an interleaving scheme to reduce the DC-link current harmonics of dual traction inverters in HEVs. The DC-link current expression is derived considering the modulation schemes, modulation index,...
DC capacitor voltage balance is one of the key issues in the control of five-level NPC (neutral point clamped) converter. In this paper, it analyses the influence of space vectors to the DC voltage balance in five-level NPC converter SVM (space vector modulation) strategy and present a novel DC capacitor voltage self-balancing SVM strategy. The novel strategy divides the whole five-level space vector...
This paper proposes an improved space vector modulation (SVM) method for the 3-level neutral point clamped (NPC) inverter that serves as a bidirectional power conversion system for renewable energy micro-grid. Conventional SVM for the NPC converter majorly deals with neutral point (NP) balance issue without considering switching loss. The proposed SVM method balances the NP voltage and minimize the...
Power Electronic Transformer (PET) is one of the most prospective components for future power electronics based power distribution systems. In this paper, the issue of the series-connected voltage sharing and the parallel-connected current sharing of a three-stage H-bridge based PET is discussed. Based on the present overall control strategy and application, it finds that the output-stage parallel-connected...
Space Vector Modulation (SVM) is a powerful method which enables some freedom to generate the modulation sequences and modify the performances of converter. However, in the multi-level converter structures, the number of switching state redundancies significantly increases, and the determination of modulation sequences becomes ambiguous because there are too many possible combinations and arrangements...
This paper presents a review of modulation strategies that can be applied to a novel large power voltage source converter arrangement. This arrangement has been used in a 47 MVAR SSSC demonstrator connected to the 220 kV Spanish transmission network, for power flow control purposes. It employs four standard 3-Level Neutral-Point Clamped (3L-NPC) Power Electronic Building Blocks (PEBB), of well-proven...
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