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The growing development of distributed generation and storage devices has allowed the growth of micro-grids in low voltage and medium voltage grids. This caused the increase of voltage harmonics with high frequency in LV and MV grids. This aspect is most important to right operations of the VSI-current controlled. This paper investigated the effect of the voltage high frequency ripple in the point...
A complete control system of smart microgrid is proposed in this paper, in order to realize the smooth mode transfer of the grid-connected mode (GTM) and islanding mode (ILM). In the system, every DG unit will work as the voltage source and use the same control method of output voltage, whatever in GTM or ILM. The only difference of GTM and ILM is how to regulate of the reference voltage of the voltage...
Unbalanced grid voltage causes a large second-order harmonic current in the dc-link capacitors as well as dc-voltage fluctuation, which potentially will degrade the lifespan and reliability of the capacitors in voltage source converters. This paper proposes a novel dc-capacitor current control method for a grid-side converter (GSC) to eliminate the negative impact of unbalanced grid voltage on the...
Effects of lower order harmonic grid voltage on the stator current of the Doubly Fed Induction Generator (DFIG) are investigated. A stator harmonic current control method for DFIG wind power system is presented to suppress the effects of the lower order harmonic grid voltage on the stator current. The proposed control scheme is analyzed using transfer function. The performance of the proposed control...
Critical Conduction Mode (CRM) Flyback APFCs is widely used in High Brightness Light Emitting Diodes (HB-LEDs) driver. But with high input voltage or light load, its line current distortion deteriorates because of the peak distortion. In this paper, an improved control strategy is introduced to solve this problem. It is realized by the injection of sin2θ component to primary reference current. Nonetheless,...
Droop control method is the fundamental theory in wireless parallel operation. In droop method, the output active power and reactive power need to be calculated accurately for adjusting angular frequency and amplitude of inverter output voltage. So the accuracy and speed of power calculation is very important for the performance of parallel operation. Traditional calculation methods in single-phase...
With high input voltage or light load, the peak of AC line current for critical conduction mode (CRM) flyback power factor Correctors (PFCs) appears notably distorted. In this paper, the reasons of line current distortion are investigated. Moreover, the relationship between line current peak distortion and high input voltage or light load is presented. Based on theoretical analysis, a simple improved...
Droop control method is widely used in wireless parallel inverters control strategy. In this application, inverters output active power and reactive power need to be calculated accurately for control of the angular frequency and amplitude of output voltage. Traditional calculation methods have a slow and oscillating transient response and could be easily impacted by disturbance and variation of load...
Proportional Resonant (PR) controller with harmonic compensators has extremely higher gain at the desired frequencies to reduce the harmonic distortions in the alternative voltage or current waves. However, the harmonic compensators of the PR controller are limited to several low-order current harmonics, due to the system instability when the compensated frequency is out of the bandwidth of the system...
This paper presents an improved controller for parallel connected single-phase UPS inverters in distributed generation application areas. The proposed control strategy needs only locally measurable feedback signals with communicationless between each inverter. It also shows how the improved adaptive droop method can be easily adapted to account for the operation of parallel inverters, providing good...
Active power filter (APF) with digital control is widely used to solve harmonic problems. But inherent delay time introduced by digital control significantly affects the performance of APF. Here, we introduce an improved harmonic detection method by using phase-shifting. In order to shorten the computation time of harmonics reference, we use the data calculated in the last sample period. So the delay...
Aimed at solving the harmonic distortion problem of the DSB (Double Side Band) method which is employed in audio directional loudspeaker, an improved amplitude modulation (AM) method is investigated. According to the parametric acoustic array principle and self-demodulation theory, the theoretical self-demodulation model of the improved AM method is established, and a conclusion that the variational...
A directional audible sound could be generated from the nonlinear interaction of ultrasound in the propagation medium. The demodulated audible signal is proportional to the second time derivative of the square of the ultrasound envelope, described in Berktaypsilas Far-field solution, which is nonlinear to the process of sound reproduction. Double side-band modulation (DSB) is proposed to amplitude-modulate...
The design and implementation of multi-modular shunt active power filter (APF) system is presented. System configuration and N+1 redundancy design, load current sensing scheme, modeling and stability analysis have been investigated. Finally, simulation and experiment results of multi-modular shunt active power filter system are given to verify the control strategy.
This paper proposed an accurate analytical method to calculate the current harmonic components of uncontrolled rectifiers. These analyses are greatly simplified through superposition method. All the calculations are purely algebraic, with high accuracy. The validity of the proposed method is demonstrated by comparison with the results of time-domain simulation. Therefore, choice of power compensation...
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