A solid state Marx generator with a novel configuration

The new configuration proposed in this paper for Marx Generator (MG.) aims to generate high voltage for pulsed power applications through reduced number of semiconductor components with a more efficient load supplying process. The main idea is to charge two groups of capacitors in parallel through an inductor and take the advantage of resonant phenomenon in charging each capacitor up to a double input voltage level. In each resonant half a cycle, one of those capacitor groups are charged, and eventually the charged capacitors will be connected in series and the summation of the capacitor voltages can be appeared at the output of the topology. This topology can be considered as a modified Marx generator which works based on the resonant concept. Simulated models of this converter have been investigated in Matlab/SIMULINK platform and the acquired results fully satisfy the anticipations in proper operation of the converter

Enhancing the stability of an autonomous microgrid using DSTATCOM

This paper proposes a method for power sharing in autonomous microgrid with multiple distributed generators (DG). It is assumed that all the DGs are connected through voltage source converter (VSC) and all connected loads are passive, making the microgrid totally inertia less. The VSCs are controlled by either state feedback or current feedback mode to achieve desired voltage-current or power outputs respectively. A modified angle droop is used for DG voltage reference generation. Power sharing ratio of the proposed droop control is established through deriva-tion and verified by simulation results. A distribution static compensator (DSTATCOM) is connected in the microgrid to provide ride through capability during power imbalance in the microgrid, thereby enhancing the system stability. This is estab-lished through extensive simulation studies using PSCAD

A Modular Active Front-End Rectifier with Electronic Phase-Shifting for Harmonic Mitigation in Motor Drive Applications

In this paper, an electronic phase-shifting strategy has been optimized for a multiparallel configuration of line-commutated rectifiers with a common dc-bus voltage used in motor drive application. This feature makes the performance of the system independent of the load profile and maximizes its harmonic reduction ability. In order to further reduce the generated low-order harmonics, a dc-link current modulation scheme and its phase-shift values of multidrive systems have been optimized. Analysis, simulations, and experiments have been carried out to verify the proposed method

Analysis, Calculation and Reduction of Shaft Voltage in Induction Generators

Abstract. This paper presents analysis of shaft voltage in different configurations of a Doubly Fed Induction Generator (DFIG) and an Induction Generator (IG) with a back-to-back inverter in wind turbine applications. Detailed high frequency model of the proposed systems have been developed based on existing capacitive couplings in IG & DFIG structures and common mode voltage sources. In this research work, several arrangements of DFIG based wind energy conversion systems are investigated on shaft voltage calculation and its mitigation techniques. Placements of an LC line filter in different locations and its effects on shaft voltage elimination are studied with mathematical analysis and simulations

Power sharing and stability enhancement of an autonomous microgrid with inertial and non-inertial DGs with DSTATCOM

This paper proposes a method of enhancing system stability with a distribution static compensator (DSTATCOM) in an autonomous microgrid with multiple distributed generators (DG). It is assumed that there are both inertial and non-inertial DGs connected to the microgrid. The inertial DG can be a synchronous machine of smaller rating while inertia less DGs (solar) are assumed as DC sources. The inertia less DGs are connected through Voltage Source Converter (VSC) to the microgrid. The VSCs are controlled by either state feedback or current feedback mode to achieve desired voltage-current or power outputs respectively. The power sharing among the DGs is achieved by drooping voltage angle. Once the reference for the output voltage magnitude and angle is calculated from the droop, state feedback controllers are used to track the reference. The angle reference for the synchronous machine is compared with the output voltage angle of the machine and the error is fed to a PI controller. The controller output is used to set the power reference of the synchronous machine. The rate of change in the angle in a synchronous machine is restricted by the machine inertia and to mimic this nature, the rate of change in the VSCs angles are restricted by a derivative feedback in the droop control. The connected distribution static compensator (DSTATCOM) provides ride through capability during power imbalance in the microgrid, especially when the stored energy of the inertial DG is not sufficient to maintain stability. The inclusion of the DSATCOM in such cases ensures the system stability. The efficacies of the controllers are established through extensive simulation studies using PSCAD

Cross voltage control with inner hysteresis current control for multi-output boost converter

Multi-output boost (MOB) converter is a novel DC-DC converter unlike the regular boost converter, has the ability to share its total output voltage and to have different series output voltage from a given duty cycle for low and high power applications. In this paper, discrete voltage control with inner hysteresis current control loop has been proposed to keep the simplicity of the control law for the double-output MOB converter, which can be implemented by a combination of analogue and logical ICs or simple microcontroller to constrain the output voltages of MOB converter at their reference voltages against variation in load or input voltage. The salient features of the proposed control strategy are simplicity of implementation and ease to extend to multiple outputs in the MOB converter. Simulation and experimental results are presented to show the validity of control strategy

Enhanced Phase-Shifted Current Control for Harmonic Cancellation in Three-Phase Multiple Adjustable Speed Drive Systems

A phase-shifted current control can be employed to mitigate certain harmonics induced by the diode rectifiers and silicon-controlled rectifiers as the front ends of multiple parallel adjustable speed drive (ASD) systems. However, the effectiveness of the phase-shifted control relies on the loading condition of each drive unit as well as the number of drives in parallel. In order to enhance the harmonic cancellation by means of the phase-shifted current control, the currents drawn by the rectifiers should be maintained almost at the same level. Thus, this paper first analyzes the impact of unequal loading among the parallel drives, and a scheme to enhance the performance is introduced to improve the quality of the total grid current, where partial loading operation should be enabled. Simulation and experimental case studies on multidrive systems have demonstrated that the enhanced phase-shifted current control is a cost-effective solution to multiple ASD systems in terms of harmonic cancellation

Operation and control of single phase micro-sources in a utility connected grid

This paper proposes operation and control of converter based single phase distributed generators (DG) in a utility connected grid. A common utility practice is to distribute the household single-phase loads evenly between the three phases. The voltage unbalance between the phases remains within a reasonable limit. However the voltage unbalance can be severe if single-phase rooftop mounted PVs are distributed randomly between the households. Moreover, there can also be single-phase nonlinear loads present in the system. The cumulative effect of all these will cause power quality problem at the utility side. The problem can be macabre if three-phase active loads (e.g., induction motors) are connected to the utility feeder. To counteract this problem, we have proposed two different schemes. In this first scheme a distribution static compensator (DSTATCOM) is connected at the utility bus to improve the power quality. The DSTATCOM only supplies reactive power and no real power. In the second scheme, a larger three-phase converter controlled DG is placed that not only supplies the reactive power but also provides active power. The efficacies of the controllers have been validated through simulation for various operating conditions using PSCAD

Effects of modulation techniques on the input current interharmonics of Adjustable Speed Drives

Adjustable speed drives (ASDs) based on a three-phase front-end diode rectifier connected to a rearend inverter may generate interharmonic distortion in the grid. The interharmonic components can create power quality problems in the distribution networks such as interference with the ripple control signals, and consequently they can hamper the normal operation of the grid. This paper presents the effect of the symmetrical regularly sampled space vector modulation and discontinuous pulse width modulation-30° lag (DPWM2) techniques, as the most popular modulation methods in the ASD applications, on the drive's input current interharmonic magnitudes. Further investigations are also devoted to the cases where the random modulation technique is applied to the selected modulation strategies. The comparative results show how different modulation techniques can influence the ASD's input current interharmonics and consequently may not be a suitable choice of modulation from an interharmonics perspective. Finally, the theoretical analysis and simulation studies are validated with obtained experimental results on a 7.5-kW motor drive system

Improving 9-150 kHz EMI Performance of Single-Phase PFC Rectifier

In order to improve the Electromagnetic Interference (EMI) performance of grid-connected power electronics converters within the new 9-150 kHz frequency range, this digest investigates feasible solutions through modifying the EMI filter and applying spectral shaping method. The proposed solutions are validated based on a 1 kW single-phase Power Factor Correction (PFC) rectifier prototype. Moreover, frequency domain modeling approach is utilized as a virtual-oriented methodology in order to analyze the converter behavior and provide fast prototyping.</p