Sinusoidal Current Injection Research Articles

Control Approach of Grid-Connected PV Inverter under Unbalanced Grid Conditions

In grid-connected photovoltaic (PV) systems, power quality and voltage control are necessary, particularly under unbalanced grid conditions. These conditions frequently lead to double-line frequency power oscillations, which worsen Direct Current (DC)-link voltage ripples and stress DC-link capacitors. The well-known dq frame vector control technique, which is effective under normal conditions, struggles with oscillatory component management in unbalanced grid conditions. To address this issue, this paper presents an advanced control approach designed for grid-connected PV inverters. The proposed approach is effective at reducing oscillations in the DC-link voltage at double the grid frequency, thereby enhancing system stability and component longevity. This method introduces a feedback control method designed to regulate oscillatory components that appeared within the dq frame and suppress the DC-link voltage oscillations under imbalance conditions, including single line-to-ground (SLG) faults. Additionally, the control scheme incorporates a maximum power point tracking (MPPT) controller to optimize PV efficiency. Comprehensive simulations demonstrate the effectiveness of this method in maintaining sinusoidal current injections and stabilizing DC-link voltage during unbalanced grid conditions. Simulation results show that the control scheme effectively stabilizes DC-link voltage, maintains balanced grid current, and ensures constant active power under various conditions, including SLG faults and solar irradiance changes.

Power quality optimization using a novel backstepping control of a three-phase grid-connected photovoltaic systems

<span lang="EN-US">A novel nonlinear backstepping controller based on direct current (DC) link voltage control is proposed in three-phase grid-connected solar photovoltaic (PV) systems to control the active and reactive power flow between the PV system and the grid with improved power quality in terms of pure sinusoidal current injection with lower total harmonic distortion (THD), as well as to ensure unity power factor, or to compensate for reactive power required by the load, i.e., the electrical grid. The output power of the PV array is supplied to the grid through a boost converter with maximum power point tracking (MPPT) control and an inverter. Simulation results of the proposed controller show good robustness under nominal conditions, parameter variations, and load disturbances, which presents the main advantage of this controller as compared to an existing controller. The performance of this work was evaluated using a MATLAB/Simulink environment.</span>

Switched-capacitor-based five-level inverter with closed-loop control for grid-connected PV application

Multilevel inverters (MLIs) have received a lot of attention in the power sector. The use of MLI to improve the power quality and performance of photovoltaic (PV) systems has increased significantly. The layout, expense, and voltage stress of an MLI connecting PV device are the main MLI constraints that must be optimized. This paper describes a five-level (5-L) inverter interfacing a single-stage tied to the grid to a PV system with a feedback control technique and a lower component count. The inverter will generate a higher voltage at the inverter output, indicating that it can raise the voltage. To prove the supremacy of the 5-L switched capacitor (SC) inverter, a comparative analysis is performed. A 3.424 kW PV system is used to test the feasibility of the 5-L SC inverter. The feedback control approach ensures that appropriate power monitoring, voltage balancing, proper SC inverter functioning, and the injection of clean sinusoidal grid current are maintained regardless of the dynamic changes that may occur. A 5-L SC inverter structure is used to do a thorough MATLAB/Simulation and experimental study.

A control strategy for DFIG-based systems operating under unbalanced grid voltage conditions

An integral control strategy for DFIG-based systems operating under unbalanced grid-voltage conditions is presented in this article. First, dynamic models of the DFIG and the back-to-back converter needed to design the system’s current control-loops are presented. Then, a strategy to control the generator’s electromagnetic torque and reactive power is introduced. The strategy is implemented by using a stator-flux aligned reference frame, where the stator-flux signals are obtained from an observer. Next, a control strategy for sinusoidal current injection under unbalanced voltage conditions is presented. This strategy generates the current references for the grid side converter from the desired mean values of the output active and reactive powers and the positive-sequence component of the grid voltage. Also, a DC-Link voltage control that works in combination with the sinusoidal current injection strategy is proposed. The design of a non-linear passivity-based controller to track the rotor- and grid-side converters current reference signals is presented. The controller allows the implementation of the integral control strategy without negative-sequence detectors which increases robustness and simplicity. Finally, simulation results are presented to validate the proposal and a stability analysis is performed.

IPMSM Sensorless Control for Zero- and Low-Speed Regions Under Low Switching Frequency Condition Based on Fundamental Model

In the high-power traction system, such as rail transit, the switching frequency is relatively low. The bandwidth of the current controller and the frequency of the injected signal are both limited under low switching frequency, which hinders the sensorless control of interior permanent magnet synchronous motor (IPMSM) in the zero- and low-speed regions. This article presents an IPMSM sensorless control for zero- and low-speed regions under low switching frequency conditions based on the fundamental model. The position can be estimated from the estimated virtual back electromotive force (EMF) with sinusoidal current injection. An internal model control (IMC) and a vector PI (VPI) control are designed to solve the problem of current controller bandwidth limitation. The multiple adaptive filters (AFs) based on the second-order second-order generalized integrator (SO-SOGI) are designed to eliminate the harmonics related to the injection frequency and the fundamental frequency in the stationary frame (SF) to improve the control performance. Meanwhile, the proposed sensorless control strategy is extended from the SF to the rotating frame (RF), which is easier to implement. The rotor position and speed are estimated by a third-order supertwisting extended state observer. The effectiveness of both proposed strategies is verified by experiments.

A grid-connected single-stage closed-loop controlled five-level boosting inverter for solar PV systems

ABSTRACT Multilevel inverters (MLIs) have gotten a lot of attention recently in the power industry because of their efficiency. The application of MLI in photovoltaic (PV) systems to improve power quality and performance has grown dramatically. An innovative, low-component-count 5-L boosting inverter interfaces a single-stage grid-tied PV system with a closed-loop control method in this research. The proposed MLI is put to the test using a 2.1 kW PV system. This technique guarantees optimum power monitoring, DC link voltage balancing, appropriate MLI operation and injection of clean sinusoidal grid current. The suggested system’s outcome is tested by Matlab/Simulink.

A Fast Estimation of Initial Rotor Position for Low-Speed Free-Running IPMSM

Fast and reliable initial rotor position detection is essential for restarting sensorless permanent magnet synchronous motors (PMSMs) in free-running condition. In this article, a fast initial rotor position estimation method for low-speed free-running motor is proposed, which utilizes a combined sinusoidal current and square-wave voltage injection method. The sinusoidal current is imposed into the estimated d-axis to magnify the magnetic saturation effect. The amplitudes of the d-axis current caused by injected square-wave voltage are then accumulated. The large difference of the two integrated signals for positive and negative d-axis currents can be reliably used to identify the rotor polarity. Meanwhile, in low-speed free-running stage, the change of saturation degrees introduced by the injected sinusoidal signal does not affect the position estimation accuracy. Moreover, even if the sinusoidal current signal is injected in the incorrect d-axis, the resultant torque is small and unexpected rotation of the rotor is prevented. Its influence on the free-running motor is negligible, due to the combined injection with continuously online updated estimated rotor position by high-frequency square-wave voltage injection during the polarity identification process. Finally, the effectiveness of the proposed method is investigated on a 1.5 kW interior PMSM test platform.

An Efficient Chaotic Optical signal generation scheme using Gain Lever Effect in bi-section laser diodes

Chaotic optical communication is a promising technique to improve both privacy and security in communication network. This research work reports numerical investigation on optical bistability based chaos in 1.3 μm bisection, Multiple Quantum Well (MQW) laser diode. The device has longer (gain section) and shorter active regions (absorber section) with the length ratio as 97:3. In contrast to the conventional scheme of sinusoidal current injection in the gain section with unpumped absorber, this paper evaluates chaos under absorber section excitation leading to gain lever effect. The generated chaotic optical carrier at the transmitter is used to mask a 10 Gbps optical data which can be extracted by synchronizing the transmitter and receiver. Operating with a threshold current of 0.245 mA, absorber section based chaotic generation, requires only 0.51 μW of input RF power for operation. Further, it also provides an improvement in RF to optical conversion ratio by 31.02 dB making it more efficient compared to gain section-based chaos generation.

Design and experimental implementation of a wind energy conversion platform with education and research capabilities

Today, pitch-controlled variable speed wind turbines (WTs) are the most installed Wind Energy Conversion (WEC) systems. They mainly use two types of generators: the permanent magnet synchronous generator (PMSG) and the double-fed induction generator (DFIG). In this paper, the overall configuration of DFIG-based WEC systems is reviewed and its control strategy is experimentally implemented using dSPACE DS1104 controller board. In this context, emphasis is placed on active power transfer management, reactive power compensation, and sinusoidal current injection into the main grid to improve power quality. The built lab-scale prototype allows validating different subsystems operation and demonstrating DFIG-based WEC capabilities.This paper specifically provides a thorough and consistent step-by-step modeling and control design methodology for a DFIG-based WEC simulation and experimentation platform that could be used for education and research addressing the wind energy conversion timely topic.

Closed-Loop Control and Performance Evaluation of Reduced Part Count Multilevel Inverter Interfacing Grid-Connected PV System

Multilevel inverters (MLIs) have drawn tremendous attention in the power sector. Application of MLI has grown extensively to improve the power quality and efficiency of the photovoltaic (PV) system. For an MLI interfacing PV system, the size, cost and voltage stress are the key constraints of the MLI that need to be minimized. This paper presents a novel reduced part count MLI interfacing single-stage grid-tied PV system along with a closed-loop control strategy. The proposed MLI consists of n repeating units and a level boosting circuit (LBC) that assists in generating 4n + 7 voltage levels instead of 2n + 3 levels. Three different algorithms are proposed for a proper selection of dc-link voltages to enhance the levels further. A comparative analysis is carried out to confirm the superiority of the developed MLI. The workability of the proposed MLI is investigated with a 1.3 kW PV system. The closed-loop control strategy ensures the maximum power tracking, dc-link voltage balancing, satisfactory operation of the MLI and injection of clean sinusoidal grid current under any dynamic changes. Comprehensive simulation analysis is carried out considering a 15-level MLI structure. Experimental tests further confirm the practicality of the topological advancement for a PV system under different dynamic conditions.

Development of a Control Scheme for Grid Connected Solar Inverter

Now-a-days the renewable energy sources (RES) are going under development, research and implementation to serve the civilization. Solar energy is the most easily available RES. A solar grid connected scheme, consists of the photovoltaic (PV) module, voltage step up converter, and DC to AC converter is discussed in this work. The control technologies like (i) maximum power point tracking (MPPT), (ii) grid synchronization and (iii) sinusoidal current injection into the grid are considered in this work. The Incremental Conductance (IC) technique is used here to attain the MPPT of the PV arrangement. A Second Order Generalized Integrator (SOGI) based PLL is developed to collect the grid voltage phase angle for synchronizing with the inverter. A Proportional-Resonant (PR) based controller is developed for regulating the exchange of power with the single phase grid as well as to reduce harmonic distortions in injected current

An integrated interlinking converter with DC-link voltage balancing capability for bipolar hybrid microgrid

The bipolar hybrid microgrid is a newly emerged structure which has gained increasing attention during the last decades. The heart of this structure is the interlinking converter that plays a crucial role in this system and has three main functionalities: (1) bidirectional connection between AC and DC subsystems, (2) sinusoidal current injection with desired power factor to AC side and (3) providing two buses with equal voltages in DC side. This paper applies a recently proposed ten-switch inverter as an interlinking converter in the bipolar hybrid microgrid that can increase efficiency, reliability and power quality on AC and DC sides in such systems. Ten-switch converter has lower cost, volume and size compared to the conventional interlinking converters. A new modulation and control strategy is proposed for ten-switch converter in the bipolar hybrid microgrid which, unlike conventional systems, does not need any extra hardware as a voltage balancer converter to balance DC-link pole voltages. The effectiveness of the proposed modulation and control strategy of ten-switch converter is evaluated and compared with conventional structures in a simulation study. Adaptive power loss calculations and cost analysis are conducted and then compared with three interlinking converters candidates to show the superiority of the proposed interlinking converter.

Fuzzy SVPWM‐based inverter control realisation of grid integrated photovoltaic‐wind system with fuzzy particle swarm optimisation maximum power point tracking algorithm for a grid‐connected PV/wind power generation system: hardware implementation

This research study presents the fuzzy space vector pulse width modulation (FSVPWM) method of current control for three-phase voltage source inverter. The hybrid fuzzy particle swarm optimisation-based maximum power point (MPP) tracking algorithm has been employed to obtain high tracking efficiency as well as optimal MPP under adverse operating states. The FSVPWM technique provides less current harmonic content, fixed switching pattern, protection from over current, low switching losses and able to handle the non-linearities and uncertainties of the photovoltaic-wind grid integrated system. Grid synchronisation with sinusoidal current injection is achieved using the inverter controller. Fuzzy logic controller-based SVPWM controller compensates current error and provides DC-link utilisation with high efficiency. The experimental responses have been validated using MATLAB/Simulink interfaced real-time dSPACE DS 1104 controller. Irrespective of solar irradiance and wind velocity, the proposed hybrid system obeys MPP accurately with high performance.

Resonance Analysis as a Tool for Characterizing Functional Division of Layer 5 Pyramidal Neurons.

Evidence suggests that layer 5 pyramidal neurons can be divided into functional zones with unique afferent connectivity and membrane characteristics that allow for post-synaptic integration of feedforward and feedback inputs. To assess the existence of these zones and their interaction, we characterized the resonance properties of a biophysically-realistic compartmental model of a neocortical layer 5 pyramidal neuron. Consistent with recently published theoretical and empirical findings, our model was configured to have a “hot zone” in distal apical dendrite and apical tuft where both high- and low-threshold Ca2+ ionic conductances had densities 1–2 orders of magnitude higher than anywhere else in the apical dendrite. We simulated injection of broad spectrum sinusoidal currents with linearly increasing frequency to calculate the input impedance of individual compartments, the transfer impedance between the soma and key compartments within the dendritic tree, and a dimensionless term we introduce called resonance quality. We show that input resonance analysis distinguished at least four distinct zones within the model based on properties of their frequency preferences: basal dendrite which displayed little resonance; soma/proximal apical dendrite which displayed resonance at 5–23 Hz, strongest at 5–10 Hz and hyperpolarized/resting membrane potentials; distal apical dendrite which displayed resonance at 8–19 Hz, strongest at 10 Hz and depolarized membrane potentials; and apical tuft which displayed a weak resonance largely between 8 and 10 Hz across a wide range of membrane potentials. Transfer resonance analysis revealed that changes in subthreshold electrical coupling were found to modulate the transfer resonant frequency of signals transmitted from distal apical dendrite and apical tuft to the soma, which would impact the frequencies that individual neurons are expected to respond to and reinforce. Furthermore, eliminating the hot zone was found to reduce amplification of resonance within the model, which contributes to reduced excitability when perisomatic and distal apical regions receive coincident stimulating current injections. These results indicate that the interactions between different functional zones should be considered in a more complete understanding of neuronal integration. Resonance analysis may therefore be a useful tool for assessing the integration of inputs across the entire neuronal membrane.

Ih interacts with somato-dendritic structure to determine frequency response to weak alternating electric field stimulation.

Transcranial current stimulation (tCS) modulates brain dynamics using weak electric fields. Given the pathological changes in brain network oscillations in neurological and psychiatric illnesses, using alternating electric field waveforms that engage rhythmic activity has been proposed as a targeted, network-level treatment approach. Previous studies have investigated the effects of electric fields at the neuronal level. However, the biophysical basis of the cellular response to electric fields has remained limited. Here, we characterized the frequency-dependent response of different compartments in a layer V pyramidal neuron to exogenous electric fields to dissect the relative contributions of voltage-gated ion channels and neuronal morphology. Hyperpolarization-activated cation current (Ih) in the distal dendrites was the primary ionic mechanism shaping the model's response to electric field stimulation and caused subthreshold resonance in the tuft at 20 ± 4 Hz. In contrast, subthreshold Ih-mediated resonance in response to local sinusoidal current injection was present in all model compartments at 11 ± 2 Hz. The frequencies of both resonance responses were modulated by Ih conductance density. We found that the difference in resonance frequency between the two stimulation types can be explained by the fact that exogenous electric fields simultaneously polarize the membrane potentials at the distal ends of the neuron (relative to field direction) in opposite directions. Our results highlight the role of Ih in shaping the cellular response to electric field stimulation and suggest that the common model of tCS as a weak somatic current injection fails to capture the cellular effects of electric field stimulation. NEW & NOTEWORTHY Modulation of cortical oscillation by brain stimulation serves as a tool to understand the causal role of network oscillations in behavior and is a potential treatment modality that engages impaired network oscillations in disorders of the central nervous system. To develop targeted stimulation paradigms, cellular-level effects must be understood. We demonstrate that hyperpolarization-activated cation current (Ih) and cell morphology cooperatively shape the response to applied alternating electric fields.

Técnicas de controle e métodos de sincronização para sistemas de energia renovável ligados à rede elétrica - Uma revisão

Os Sistemas de Energia Renovável (SER) tornaram-se uma alternativa atrativa frente às fontes de energia convencional, devido à necessidade de diversificar a matriz energética e assim garantir o abastecimento da demanda futura de eletricidade de uma forma sustentável. As fontes renováveis precisam de equipamentos de conversão de energia com um controle adequado para conseguir operar ligados à rede elétrica de maneira satisfatória. O controle deve garantir a sincronização com a rede e o fornecimento de corrente senoidal para cumprir com as normas internacionais de qualidade de energia. Este trabalho apresenta de forma geral as principais técnicas de controle de corrente para os SER e os métodos de sincronização com a rede elétrica, apresentados na literatura. Técnicas de controle linear e não linear são abordadas, considerando diferentes sistemas de referência, assim como métodos de sincronização monofásicos e trifásicos.

Ion channel mechanisms underlying frequency-firing patterns of the avian nucleus magnocellularis: A computational model

ABSTRACTWe have previously shown that late-developing avian nucleus magnocellularis (NM) neurons (embryonic [E] days 19–21) fire action potentials (APs) that resembles a band-pass filter in response to sinusoidal current injections of varying frequencies. NM neurons located in the mid- to high-frequency regions of the nucleus fire preferentially at 75 Hz, but only fire a single onset AP to frequency inputs greater than 200 Hz. Surprisingly, NM neurons do not fire APs to sinusoidal inputs less than 20 Hz regardless of the strength of the current injection. In the present study we evaluated intrinsic mechanisms that prevent AP generation to low frequency inputs. We constructed a computational model to simulate the frequency-firing patterns of NM neurons based on experimental data at both room and near physiologic temperatures. The results from our model confirm that the interaction among low- and high-voltage activated potassium channels (KLVA and KHVA, respectively) and voltage dependent sodium channels (NaV) give rise to the frequency-firing patterns observed in vitro. In particular, we evaluated the regulatory role of KLVA during low frequency sinusoidal stimulation. The model shows that, in response to low frequency stimuli, activation of large KLVA current counterbalances the slow-depolarizing current injection, likely permitting NaV closed-state inactivation and preventing the generation of APs. When the KLVA current density was reduced, the model neuron fired multiple APs per sinusoidal cycle, indicating that KLVA channels regulate low frequency AP firing of NM neurons. This intrinsic property of NM neurons may assist in optimizing response to different rates of synaptic inputs.

Inhibition of spikes in an array of coupled FitzHugh–Nagumo oscillators by external periodic forcing

Damping of spikes in an array of coupled oscillators by injection of sinusoidal current is studied both electronically and numerically. The effect is investigated using an array consisting of thirty mean-field coupled FitzHugh–Nagumo-type oscillators. The results are considered as a possible mechanism of the deep brain stimulation used to avoid the symptoms of the Parkinson's disease.

Intrinsic frequency response patterns in mechano-sensory neurons of the leech.

ABSTRACTAnimals employ mechano-sensory systems to detect and explore their environment. Mechano-sensation encompasses stimuli such as constant pressure, surface movement or vibrations at various intensities that need to be segregated in the central nervous system. Besides different receptor structures, sensory filtering via intrinsic response properties could provide a convenient way to solve this problem. In leech, three major mechano-sensory cell types can be distinguished, according to their stimulus sensitivity, as nociceptive, pressure and touch cells. Using intracellular recordings, we show that the different mechano-sensory neuron classes in Hirudo medicinalis differentially respond supra-threshold to distinct frequencies of sinusoidal current injections between 0.2 and 20 Hz. Nociceptive cells responded with a low-pass filter characteristic, pressure cells as high-pass filters and touch cells as an intermediate band-pass filter. Each class of mechano-sensory neurons is thus intrinsically tuned to a specific frequency range of voltage oscillation that could help segregate mechano-sensory information centrally.

IZDPWM-Based Feedforward Controller for Grid-Connected Inverters Under Unbalanced and Distorted Conditions

In grid-connected inverters, a feedforward controller accurately compensates for a large number of the harmonic components of the injected current. This controller is fast and directly tackles the grid dynamic voltage disturbances without doing any further harmonic analysis. A feedforward controller was introduced to a three-phase grid connection with a wye configuration; however, for the widespread delta connections, such a scheme is less established. Moreover, the nonsinusoidal profile of the grid voltage waveform makes the online conversion of line-to-line values into phase values impossible. In this paper, implicit zero-sequence discontinuous pulse width modulation (IZDPWM) based feedforward control is implemented on the two-level grid-connected inverter. Regardless of the grid topology, the IZDPWM-based controller ensures sinusoidal current injection to the grid under balanced, unbalanced, and distorted conditions.