1,721,118 research outputs found
Multileg interleaved buck converter for EV charging: Discrete-time model and direct control design
Full text linkThis paper presents the modeling and the implementation of the digital control of a multileg interleaved DC-DC buck converter for electrical vehicle (EV) charging. Firstly, we derive a discrete averaged model of an n-leg interleaved buck converter (IBC). Secondly, we present a direct tuning procedure for one primary discrete PIDF (PID + filter) and multiple secondary PI controller. The objective of the control system is to regulate the current flow in each leg of the converter. This task is accomplished by introducing a novel control paradigm that simultaneously addresses two aims: on the one hand, the control scheme must guarantee an acceptable level of robustness under load variations; while on the other, an even distribution of power on each leg must be ensured at any operational condition. The proposed strategy hinges on a technique that combines simplicity and precision in the fulfillment of design frequency specifications. We use simulations and a digital signal processor (DSP) based experimental implementation of the design technique to validate the proposed methodology
Common- and differential- mode HF current components in AC motors supplied by voltage source inverters
No full textIn this paper, an inverter-fed ac motor drive is analyzed in order to investigate the conducted electromagnetic interferences at both the input and output sides of the inverter. HF lumped equivalent circuits for the inverter and the motor stator windings are proposed. The overall circuit model allows time- and frequency-domain analysis to be performed with standard circuit simulators. The proposed model can also predict common- and differential-mode HF current components. The equivalent circuit is verified by experimental tests carried out on a prototype of ac motor drive
Double-Inverter Drive System for Electric Ship Propulsion
No full textIn this paper a new electric ship propulsion system is proposed as combination of a double generator set with a double inverter feeding a wound-rotor synchronous machine.
Each generator set is composed by a diesel engine directly coupled to a compact, permanent magnet, synchronous generator. A diode rectifier connects the output of the generator to a variable voltage dc bus. The dc bus feeds one of the input sides of the double inverter. The double inverter acts as a multilevel converter and it is able to drive the 3-phase, 6-wire motor coupled to the propeller. The two generator sets can operate either jointly or one at a time,
depending on the power demand from the drive system. The working point of each diesel engine is determined in order to supply power to the propeller with maximum efficiency
Modulazione vettoriale e ripartizione della potenza nei convertitori multilivello a doppio inverter con alimentazioni isolate
No full textL’attività di ricerca dell’Unità di Bologna nel settore degli inverter multilivello, già intrapresa da un paio d’anni, si è concentrata sulla configurazione a doppio inverter trifase, con carico a sei morsetti (tipicamente macchine elettriche del tipo open-winding)
Evaluation of DC-link Voltage Ripple in Seven-Phase PWM Voltage Source Inverters
No full textThe analysis of dc-link inverter current and voltage ripple is important for the optimization of the input components, mainly the dc-link capacitor. In this paper reference is made to two-level seven-phase PWM voltage source inverters with balanced load, typically multiphase ac motor. The peak-to-peak amplitude of the dc-link voltage switching ripple within the fundamental period is analytically determined as a function of operating conditions: modulation index, output currents amplitude and phase angle. The maximum of voltage switching ripple is also derived in order to help with choice of the dc-link capacitor. The two most popular inverter modulation techniques are considered: sinusoidal PWM and centered PWM (CPWM, equivalent to space vector modulation, SVM). A comparison between them is made in terms of the dc voltage switching ripple envelope. Numerical simulations are carried out by Matlab/Simulink in order to verify the analytical results
A Single-Phase Multilevel PV Generation System with an Improved Ripple Correlation Control MPPT Algorithm
Full text linkThe implementation of maximum power point tracking (MPPT) schemes by the ripple correlation control (RCC) algorithm is presented in this paper. A reference is made to single-phase single-stage multilevel photovoltaic (PV) generation systems, when the inverter input variables (PV voltage and PV current) have multiple low-frequency (ripple) harmonics. The harmonic analysis is carried out with reference to a multilevel configuration consisting of an H-bridge inverter and level doubling network (LDN) cell, leading to the multilevel inverter having double the output voltage levels as compared to the basic H-bridge inverter topology (i.e., five levels vs. three levels). The LDN cell is basically a half-bridge fed by a floating capacitor, with self-balancing voltage capability. The multilevel configuration introduces additional PV voltage and current low-frequency harmonics, perturbing the basic implementation of the RCC scheme (based on the second harmonic component), leading to malfunctioning. The proposed RCC algorithm employs the PV current and voltage harmonics at a specific frequency for the estimation of the voltage derivative of power dP/dV (or dI/dV), driving the PV operating point toward the maximum power point (MPP) in a faster and more precise manner. The steady-state and transient performances of the proposed RCC-MPPT schemes have been preliminarily tested and compared using MATLAB/Simulink. Results have been verified by experimental tests considering the whole multilevel PV generation system, including real PV modules, multilevel insulated-gate bipolar transistor (IGBT) inverters, and utility grids
Implementation of carrier-based optimized centered PWM in three-phase three-level inverters
No full textCarrier-based modulation is widely adopted since it offers some benefits compared to space-vector modulation in both two-level and multilevel inverters, such as inherent simplicity, flexibility, reduced computational times, and possibility of implementation on industrial DSPs. Among the numerous types of PWM techniques, the centered PWM (CPWM) is nearly optimal modulation, since it minimizes the RMS of output current harmonics. Despite of CPWM is easy to implement in two-level inverters, the complexity increases in case of three-level and multilevel inverters. In this paper a simplified straight procedure to implement carrier-based optimized CPWM for three-level inverter is presented, equivalent to centered space vector modulation. The proposed method has been implemented by numerical simulations, considering the comparison of resulting modulating signals with the other methods existing in literature and verifying the pulse centering in the output phase voltage waveforms
Analysis and Minimization of Output Current Ripple for Discontinuous Pulse-Width Modulation Techniques in Three-Phase Inverters
Full text linkThis paper gives the complete analysis of the output current ripple in three-phase voltage source inverters considering the different discontinuous pulse-width modulation (DPWM) strategies. In particular, peak-to-peak current ripple amplitude is analytically evaluated over the fundamental period and compared among the most used DPWMs, including positive and negative clamped (DPWM+ and DPWM-), and the four possible combinations between them, usually named as DPWM0, DPWM1, DPWM2, and DPWM3. The maximum and the average values of peak-to-peak current ripple are estimated, and a simple method to correlate the ripple envelope with the ripple rms is proposed and verified. Furthermore, all the results obtained by DPWMs are compared to the centered pulse-width modulation (CPWM, equivalent to the space vector modulation) to identify the optimal pulse-width modulation (PWM) strategy as a function of the modulation index, taking into account the different average switching frequency. In this way, the PWM technique providing for the minimum output current ripple is identified over the whole modulation range. The analytical developments and the main results are experimentally verified by current ripple measurements with a three-phase PWM inverter prototype supplying an induction motor load
Evaluation of current ripple amplitude in five-phase PWM voltage source inverters
No full textMultiphase systems are nowadays considered for various industrial applications. Numerous PWM schemes for multi-phase voltage source inverters with sinusoidal outputs have been developed, but no detailed analysis of the impact of these modulation schemes on the output peak-to-peak current ripple amplitude has been reported.
Determination of current ripple in five-phase PWM voltage source inverters is important for both design and control purposes. This paper gives the complete analysis of the peak-to-peak current ripple distribution over a
fundamental period. In particular, peak-to-peak current ripple
amplitude is analytically determined as a function of the modulation index, and a simplified expression to get its maximum value is carried out. Reference is made to centered symmetrical PWM, being the most simple and effective solution to maximize the dc bus utilization, leading to a nearly-optimal modulation to minimize the rms of current ripple. However, the analysis can be easily extended to either discontinuous or asymmetrical modulation, both carrier-based and space vector PWM. The analytical developments for all the different sub-cases are verified by numerical simulations
A Comprehensive AC Current Ripple Analysis and Performance Enhancement via Discontinuous PWM in Three-Phase Four-Leg Grid-Connected Inverters
Full text linkA complete analysis of the ac output current ripple in four-leg voltage source inverters considering multiple modulation schemes is provided. In detail, current ripple envelopes and peak-to-peak profiles have been determined in the whole fundamental period and a comprehensive method providing the current ripple rms has been achieved, all of them as a function of the modulation index. These characteristics have been determined for both phase and neutral currents, considering the most popular common-mode injection schemes. Particular attention has been paid to the performance of discontinuous pulse width modulation (DPWM) methods, including DPWMMAX and DPWMMIN, and their four most popular combinations DPWM0, DPWM1, DPWM2, and DPWM3. Furthermore, a comparison with a few continuous techniques (sinusoidal, centered pulse width modulations, and third harmonic injection) has been provided as well. Moreover, the average switching frequency and switching losses are analyzed, determining which PWM technique ensures minimum output current ripple within the linear modulation range at different assumptions. Numerical simulations and laboratory tests have been conducted to extensively verify all the analytical claims for all the considered PWM injections
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