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This paper proposes a new senseless start-up method by using a terminal voltage/current without position sensor. A flux estimator consisting of field flux model, P controller and flux voltage model is proposed and rotor angle/speed is estimated by using a phase locked loop. Furthermore, initial rotor angle is estimated rapidly and accurately by using the same flux voltage model during the initial...
Passive damping is proven as a robust stabilizing technique for LCL-filtered voltage source converters. However, conventional design methods of passive dampers are based on the passive components only, while the inherent damping effect of time delay in the digital control system is overlooked. In this paper, a frequency-domain passivity-based design approach is proposed, where the passive dampers...
The concept of Double-Delta Sourced Transformer (DDST) had been proposed to eliminate passive filters in large-scale power conversion systems. For the grid connection, active and reactive powers in DDST must be under control. In this paper, the power modulation method is proposed for DDST through the current regulation. And, it is also considered when one of converters is disconnected from the transformer...
Photovoltaic power plants (PV) are equipped with anti-islanding algorithms, embedded in the converters controller, to avoid the island operation. However, the current trends in the development of the future electrical networks evidence that it is technically feasible and economically advantageous to keep feeding islanded systems under these situations, without cutting the power supply to the loads...
With power converters integrated to the weak power grid, the influences of the voltage feed-forward and the current decoupling on the stability of the current control loop become obvious and need to be considered. Complex transfer functions are applied to analyze the effects of the feed-forward and cross decoupling compensation on the stability of the current control loop. Negative influences of the...
Generated harmonic current as a consequence of employing power electronics converter is known as an important power quality issue in distribution networks. From industry point of view complying with international standards is mandatory, however cost and efficiency are two other important features, which need to be considered in order to be competitive in the market. Therefore, having a flexibility...
Analytical design and adaptation of voltage regulation loop for flux-weakening control of Interior Permanent Magnet Synchronous Motor drives are addressed in this paper. Theoretical analysis of the overall dynamics of the loop has been carried out in recent papers, also taking into account non-linear effects and discrete-time implementation issues. A proper gain adaptation technique was proposed to...
Modular multilevel converters with storage devices integrated in the submodules are emerging topologies for traction drives. This paper proposes a new state-of-charge control technique to optimally utilise supercapacitor cells that are connected to the sub-module capacitors by means of boost DC/DC converters. The proposed strategy ensures that the charging/discharging trajectory of all the supercapacitor...
This paper presents the comparison of three different fully digital, oversampled, large bandwidth inverter current controllers: a proportional integral controller, a predictive controller, and a non-linear hysteresis controller. The purpose is to determine which one allows to achieve the highest final performance when adopted as the inner current control loop in a microgrid utility interface converter...
The following two types of resonant controllers are mainly employed in stationary reference frame to obtain high performance in voltage-source converters: 1) proportional + resonant (PR) and 2) complex vector proportional + integral (cVPI). The performance analysis and parameter design of these two controllers has been researched in many papers. In this paper, these two groups of resonant controllers...
Predictive current control (PCC) methods have been widely implemented for grid-connected voltage source inverters (VSIs) recently to achieve better output performance, however, facing the challenge of high sensitivity to uncertain system disturbances and inevitable time delay. In this paper, a new PCC scheme has been proposed for a single-phase VSI to improve the quality of the current fed to the...
Active damping of LCL-filter resonance based on single-state feedback control is widely used with voltage source converters. Its robustness against grid impedance variation has always been a major concern with its controller design. To deal with this issue, this paper begins by developing a generalized impedance-based model of grid current control with feedback-type active damping. Then, a controller...
The DC transmission system provides a cost effective solution for long distance power transmission compared to the AC transmission system. Hence, this has increased the emphasis on the development of the DC transmission system. Development of power converter with modular structure has now made it possible to achieve higher voltage and power level. This opens the possibility for further development...
Zero-Voltage Transition (ZVT) DC-DC converters with active snubber can be used in photovoltaic applications requiring high efficiency and high-frequency isolation transformer. In order to improve the dynamic response of ZVT converters, two different current control strategies, namely Feed Forward and Dead-Beat, are proposed. The Feed Forward and Dead-Beat control, both based on the converter electrical...
This paper investigates the stability regions of current control for LCL-filtered grid-connected converters, where no active or passive damping is required to stabilize the closed-loop control system. It is already identified in the literature that if the LCL resonance frequency is placed within 1/6 to 1/2 of the system sampling frequency, the grid current control can be directly used without damping...
The combination of deadbeat controller and open-end winding topology is effective for improving the response of current control of induction motor drive system. A deadbeat current controller achieves high gain by compensating the delay element of digital controller with current prediction and excluding it from the control loop. The response of a deadbeat current controller depends on the duration...
The development of distributed generation (DG) systems has led to the increasing use of voltage source inverters. However, step-changes in the modulated voltage can produce dangerous peak common-mode currents (CMCs), which can interfere with the power system ground and cause detrimental effects on other equipment. In this paper, the root cause of CMCs is explored and analyzed. After this, a new method...
Distribution STATic synchronous COMpensators (DSTATCOMs) have been proved an effective approach to correct power quality in distribution network. With reactive component and harmonic component of load current detected independently, selective compensation mode can be realized. To improve the reactive compensation ability and harmonic suppression performance of a cascaded DSTATCOM, the fast-transient...
This paper proposes a novel LCL-filter design method and its current control for grid-connected converters. With the proposed design method, it is possible to set the resonance frequency of the LCL-filter to be higher than the Nyquist frequency, i.e. half of the system sampling frequency, and this observation is so far not discussed in the literature. In this case, very cost-effective LCL-filter design...
High-speed regimes allow to increase the power density of electrical drives, which is a necessary characteristic in aeronautical applications. In such a context, together with the typical non-linearity of low speed drives, such as core saturation, phenomena related to high fundamental to sampling frequency ratios appear increasingly significant. This paper applies methodologies based on modern robust...
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