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Operation of two-coil inductive power transfer (IPX) system is affected by bifurcation phenomenon. In this paper, bifurcation in dependency on resonance frequency is examined. At first, voltage equations are analyzed, and impedance and transfer function derived. In next step, condition for resonance frequency is stated, which is followed by bifurcation analysis. Resulting bifurcation map is analytically...
The capacitor voltage of an LC-filtered voltage source inverter is fed back for output-voltage regulation, which includes twin aspects of command tracking and output impedance control. The same feedback can also be used for active damping of filter resonance. Compared with the existing active damping techniques using filter inductor or capacitor current feedback, this technique saves a current sensor...
A method for hybrid active damping in power converters connected to a weak grid using an LCL filter is proposed. It uses feedback of the grid current and capacitor voltage and is derived as an equivalent to the capacitor current feedback active damping method. A co-design procedure for the grid current controller with the proposed hybrid active damping method is presented. The robustness, system bandwidth...
This contribution propose a design procedure applicable to many kinds of wireless or contactless energy transfer systems. The design procedure is limited to near field wireless energy transfer systems in resonant operation. Therefore it is well applicable to systems with a primary side power oscillator or systems with a control strategy that forces an equal system behavior compared to a primary side...
LCL-filter is commonly used as an output-side filter in a grid-connected converter due to its good attenuation capability at the switching harmonic frequencies. LCL-filter creates several resonances in the converter dynamics which shall be damped for ensuring robust performance of the converter. The resonant behavior introduced by the LCL-filter can be attenuated with active damping (AD) instead of...
Grid-connected Voltage Source Inverter (VSI) with LCL filters, controlled by proportional-resonant compensator in αβ frame, is very popular in utility application for its better power quality feature, while the inherent LCL resonance characteristic limits the control loop bandwidth and threatens the system stability. The active damping is essential to dampen the LCL resonance. This paper investigates...
This paper discusses the emulation of an active RLC load by means of an inverter. To this purpose, a suitable current control strategy is analyzed and developed. The limitations of this approach are explored, highlighting the requirements of the adopted regulator in order to avoid instability issues. The proposed analysis and model of the controlled system are verified by means of simulations and...
Weak grid is commonly seen as a voltage source which contains the gird impedance and background harmonics. The grid current closed-loop control and the grid voltage feed forward control are coupled with each other because of the grid impedance. The proportion feed forward control strategy introduces a positive feedback loop, which affects the grid current quality and the system stability. This paper...
The operation features of induction generator are revealed in the paper. Parametric resonance as a cause of induction generator excitation is investigated. The study was performed by the mathematical description and modeling in the block diagram environment Simulink pack of MatLab software applications. It was confirmed on the basis of studies that residual magnetization is not a mandatory factor...
A simple design procedure for multiband waveguide filters using multiband reactance function mapping is presented. The technique directly expands the transformation function into a coupled-resonator form with equal resonator impedances, without any optimisation or transformations. A tri-band X-band rectangular waveguide filter is designed using this approach.
Widespread deployment of Voltage Source Inverters (VSI-s) in high penetration applications like distributed generation, UPS and stand-alone renewable energy conditioning imposes stringent demands on reliability and output voltage regulation. Reported literature offers numerous solutions for output voltage regulation, which includes twin aspects of command tracking and output impedance control. Most...
The combination of coupled inductors (CIs) and LCL filters can be a filter configuration to achieve high power density for high current applications. Frequency characteristics (i.e., resonance phenomenon) are changed according to the filter configuration and feedback currents (i.e., inverter-side or grid-side current) for current control loops. Therefore, stability analysis should be performed to...
In this paper, the combinations of coupled inductors (CIs) and LCL filters are comparatively investigated for grid-connected interleaved three-phase voltage source inverters (VSIs) in terms of the resonance phenomenon. In current-controlled direct parallel VSIs, two current controllers are required for the power flow and the circulating currents. Therefore, the stability of both current controllers...
For cascaded systems, interactions among individually designed power subsystems may cause the instability of the whole system. Regulating the input impedance of the load converter is an effectively way to solve this problem, however, one big challenge of this method is how to consider the stability of cascaded system and the dynamic performance of load converter together. In light of this, this paper...
This paper presents a simplified envelope model to study the dynamics of a phase-controlled resonant converter suitable to drive light emitting diode (LED) lamps. The approximate closed form of the transfer function is obtained from the proposed reduced-order model. The fast dynamics of the resonant converter allows us implementing a pulsed current source with active control of the on-time-current...
This paper establishes the model of multiple paralleled grid-connected inverters with LCL filter and analysis its resonant characteristics and influencing factors. The analysis results show that multiple paralleled grid-connected inverters have more than one resonant frequency, and the resonant frequency are closely related to the number, type and composition ratio of parallel inverters. Meanwhile...
In order to improve the input impedance of stacked boost converter (SBC) that processes only a part of the total power delivery, the traditional three-capacitor structure is optimized as single-capacitor structure in this paper. Then small signal models of push-pull SBC based on these two capacitor structures are set up, the loop gain and input impedance are analyzed and compared. Finally, the effectiveness...
Small-signal stability in balanced three-phase systems can be analyzed using Generalized Nyquist stability Criterion (GNC), which is based on source and load impedances in synchronous rotating (d-q) frame. The derivation of d-q input impedance of controlled power electronics converters is relatively easy in the case that current controller is implemented in d-q reference frame, while the analysis...
Track Circuits (TCs) are the most diffused and popular train detection system and they are in close relationship to the concept of track integrity, in terms of robustness with respect to and monitoring of track defects (such as broken rails, component disconnection, etc.). In this paper the general modeling of TC transfer functions is presented, together with an analysis of the sensitivity to TC parameters...
This paper analyzes the stability problem of the grid-connected voltage source inverter (VSI) with LC filters, which demonstrates that the possible grid-impedance variations have a significant influence on the system stability when conventional proportional-integrator (PI) controller is used for grid current control. As the grid inductive impedance increasing, the low-frequency gain and bandwidth...
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