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The correct initial data are very important for model adequacy, especially for load curves. Probabilistic evaluations and statistical analysis produce for determination of the conditions stochastic process of change loads. Basic properties of stochastic function are mathematical expectation, dispersion, correlation function, probability density. Loads of most current-using equipment are changing with...
The Compact Fluorescent Lamps (CFLs) are widely adopted in residential and commercial sector. This adoption is proposed following the energy conservation and environmental protection efforts. Despite, the CFLs consume low power, many users using these loads can cause a harmonic impact depending of the Attenuation-Amplification Effect. For instance, if this Effect is neglected (e.g., using Harmonic...
Models for active devices operating in a nonlinear regime are an indispensable tool for modern RF-circuit design. A popular class of large signal models are X-parameters which offer an accurate description of nonlinear devices. However, they require a specialized measurement setup. Typically nonlinear vector network analyzers (NVNA), are used to conduct the measurements required for an X-parameter...
Conventional Hybrid Power Quality Conditioner (HPQC) adopts LC coupling branch and L coupling branch in the back-to-back converters to reduce the converter compensation capacity as well as the DC voltage. However, HPQC could only achieve the minimum compensation capacity under certain special load condition. To maintain the converter compensation capacity at a low level under all load conditions,...
Solid state transformers (SSTs) include dc subsystems to enable plug-and-play support of dc loads, generation sources, and energy storage. Dual active bridge (DAB) converters are a suitable topology for both the primary energy conversion and load interface applications in an SST. This study considers an SST that uses DAB converters for both applications, and describes a method of generating a full...
This paper presents a unified selective harmonic compensation strategy using DG-interfacing inverter with LCL filter in the presence of nonlinear local loads for both grid-connected and islanded microgrid. Compared with the existing harmonic compensation methods in the literature, the proposed strategy consists of a triple-control-loop in the grid-connected mode to compensate the grid current harmonics...
Active power filters (APF) are used to improve power quality and are commonly connected in parallel with the load at the point of common coupling (PCC). They are used to compensate for harmonics from nonlinear loads, for reactive power compensation and/or balancing mains currents. This paper will investigate the effect of using an APF to improve the output power quality of a simplified synchronous...
The impacts of distributed generation (DG) units on the unbalanced three-phase power systems are analyzed. Line loss mathematic model caused by harmonic with unbalanced three-phase loads is proposed through theoretical derivation. The corresponding simulation model based on typical 10kV medium voltage microgrid is established with Matlab/Simulink. The simulation results show that an optimal grid connection...
Aim of this paper is to check a feasibility of utilization of Recursive Least Square (RLS) and Goertzel algorithms for harmonic component calculation. These methods are utilized within Active Power Filters (APF) which compensate higher harmonics present in the power grid. This paper is not focused on describing methods for generating the harmonic compensation current. Our goal is only to consider...
This paper presents a flexible harmonic domain (FHD) model of a three-phase photovoltaic (PV) system aimed at steady-state analysis. The proposed FHD model involves a PV array Thévenin equivalent, a DC-link capacitor, a boost converter, a three-phase inverter, an LC low-pass filter-bank, a PI-shaped distribution line, and a nonlinear load. The FHD PV model is able to include an arbitrary number of...
The X-parameter model is designed for modeling weakly nonlinear devices in an approximately impedance-matched environment. Load dependent X-parameter models were proposed to overcome this, practically very relevant, limitation and model a nonlinear device in a highly mismatched environment. However, the applicability of load dependent X-parameter models for DUTs operating in deep saturation like in...
Torsional resonances may incur in induction drives due to large harmonic torques produced by the inverter. The torsion can affect the rotor-load system, but more sneaky resonances may arise in the rotor end-rings of fabricated-cage induction motors. Abnormal cage torsions may lead to bar breakage due to high-cycle fatigue. Since the high-frequency speed oscillations are difficult to detect, torsional...
Harmonics identification in distribution systems has always been a difficult task, due to the variety of the loads, more and more often nonlinear and unbalanced, and the spread of the harmonics along the grid. Typically, few real measurements are available in distribution systems, commonly in the HV-MV substations, whereas monitoring of power quality phenomena requires specific methodologies and measurement...
A strategy for voltage harmonics suppression is proposed to upgrade existing grid-connected inverters. It utilizes the already available measurement of the voltage at the point of common connection and the inverter output current. As a result, on top of conventional power injection, the inverter is equipped with an additional feature for harmonics compensation. Model analysis, simulation and experiments...
The paper presents the results of the analysis of voltage and current distortions of the power system containing nonlinear load at changing location. The calculations are done for the power system consisted of overhead line 110kV, transformer station 110/15kV, overhead line 15kV and transformer station 15/0.4kV. Simulations were performed in the Microcap environment.
Shunt active power filters (SAPF) generally compensate harmonic current of centralized non-linear loads, which may cause undesired economical burden for networks with distributed harmonic sources. This paper proposed an SAPF predictive control method based on online impedance measurement which can suppress the network-wide harmonics systematically in an optimized way.
The Quito Metropolitan District is committed to solve its existing traffic congestion problems in the city. One of the solutions is the construction of a Massive Transportation System called “Metro de Quito”, making it the backbone that integrates all means of existing public transportation such as Trole, Ecovia, Corredores Suroriental, Central Norte and Suroccidental. In this work, a detailed model...
In this paper we propose a new optimal power flow scheme that takes into account the harmonics generated by power electronics interfaced distributed generation (DG). The objective is to minimize the cost of generation under constraints on the total harmonic distortion (THD) of voltage. The frequency coupling matrix (FCM) is used to model the harmonic current injected by a converter. Network current...
For high power rectifiers, due to the limit restriction of the switching loss, operating at low switching frequency is necessary. In this paper, an effective approach is proposed to restrain grid harmonic current and DC-link pulsating voltage. A discrete-time domain of the complex vector current regulator combined with a synchronized PWM modulation strategies at low switching frequency are employed...
The efficiency of motor can be increased by optimizing stator, rotor slot design and using more materials, but there is limit within the narrow space of motor frame. Because of limited dimension, high quality material can be adapted, such as copper bar instead of aluminum bar, or low core loss Si-steel. However, adapting low core loss electrical steel does not always mean reduction of core loss. Because...
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