Sinusoidal Current Source Research Articles

A Champernowne Adaptive Filter-Based Control of Grid Interactive Solar PV with Power Quality Enrichment

This work presents a variable step Champernowne Adaptive Filter (VS-CAF) based control architecture for a grid-integrated solar photovoltaic system. The control structure is implemented to successfully synchronize the two-stage solar photovoltaic at the point of common coupling where the source and domestic loads are connected. The control architecture ensures solar power injection and improvised power quality at the unity power factor. Moreover, the control structure provides only the balanced positive sequence fundamental sinusoidal source currents at solar irradiation alteration and load disturbances. The VS-CAF is exploited to estimate the peak of the fundamental component out of the harmonics-rich domestic load currents. To examine the efficacy of the suggested control technique, a 40 kW solar photovoltaic is simulated using MATLAB/Simulink. The performance assessment of the grid-tied solar generation system is carried out at solar irradiation alteration, zero solar irradiation, and detachment of one phase of the three-phase load. Various simulation results are carried out to verify the successful integration of solar photovoltaics into the three-phase grid following the IEEE-519 standard and satisfactory performance during various working conditions. Moreover, the simulation results are also verified with real-time results taken from the Opal-RT simulator.

Alleviation of Power Quality Issues in MVF-DEANF-PLL Based Solar PV Systems under Polluted Grid Conditions

Solar energy is a sustainable and environmentally safe power source due to its widespread availability and cleanliness. Nowadays, the grid-integrated solar photovoltaic system (SPVS) has to work with a polluted grid, an imbalanced load, and changing solar irradiation. When the grid is polluted, it is also crucial to enhance power quality (PQ) at a common coupling point (CCP) while supplying significantly distorted and unreliable loads. For effective synchronization and the production of unit templates, it is necessary to retrieve positive sequence components (PSCs) from distorted/imbalanced grid voltages. In this study, a control algorithm for a grid-integrated SPVS is developed using a multi-variable filter dual-enhanced adaptive notch filter phase-locked loop (MVF-DEANF-PLL) which offers seamless grid synchronization and PQ issue alleviation. In a polluted grid environment, the proposed control approach aids in the reduction in current/voltage harmonics, DC offset, unity power factor (UPF) operation, and rapid estimation of sequence components. Even in unbalanced grid conditions, the proposed control approach efficiently extracts PSCs of both unbalanced load current and polluted CCP grid voltages. These PSCs are utilized to generate unit templates and reference source currents. By using a flexible step-size incremental conductance (FSSINC) maximum power point tracking (MPPT) technique, the highest available power of SPVS is gathered. MATLAB/Simulink is utilized for modelling a 7.22 kW SPV system, and results from simulations which depict that the proposed algorithm efficiently resolves PQ concerns in distribution networks with a polluted grid. Test observations of a 1 kW laboratory-developed SPVS prototype were recorded in compliance with the IEEE-519 standard. The suggested control technique complies with the aforementioned standards by providing a sinusoidal balanced source current that has a THD of 2.5%. Comparisons between the proposed control’s performance and that of a conventional SRF-PLL-based control technique were also performed.

Analysis and Power Quality Improvement in Hybrid Distributed Generation System with Utilization of Unified Power Quality Conditioner

This paper presents a comprehensive study that includes the sizing and power flow by series and parallel inverters in a distributed generation system (DGs) that integrates the system of hybrid wind photovoltaic with a unified power quality conditioner (UPQC). In addition to supplying active power to the utility grid, the system of hybrid wind photovoltaic functions as a UPQC, compensating reactive power and suppressing the harmonic load currents. Additionally, the load is supplied with harmonic-free, balanced and regulated output voltages. Since PVWind-UPQC is established on a dual compensation scheme, the series inverter works like a sinusoidal current source, while the parallel inverter works like a sinusoidal voltage source. Consequently, a smooth alteration from interconnected operating modes to island operating modes and vice versa can be achieved without load voltage transients. Since PV-Wind-UPQC inverters handle the energy generated through the hybrid wind photovoltaic system and the energy demanded through the load, the converters should be sized cautiously. A detailed study of the flow of power via the PV-Wind-UPQC is imperative to gain a complete understanding of the system operation and the proper design of the converters. Thus, curves that allow the sizing of the power converters according to the power flow via the converters are presented and discussed. Simulation results are presented to assess both steady state and dynamic performances of the grid connected hybrid system of PV-Wind-UPQC. This investigation is verified by simulating and analyzing the results with Matlab/Simulink.

Predictive Algorithm for Control of Common Mode Voltage and Switching Frequency in Direct Matrix Converter Fed System

Multiobjective model predictive control (Mo-MPC), owing to its simplicity and adaptability to comply with diverse constraints, has gained popularity in the control of direct matrix converters (DMCs). However, the MPC strategy makes the converter operate at an uncontrolled and variable switching frequency, which may inhibit high power density applications due to increased power losses. This article proposes a method for controlling the switching frequency of the converter and simultaneously regulating the common mode voltage in the DMC fed system while maintaining sinusoidal load and source currents at near unity input power factor. Furthermore, in order to streamline the control while simultaneously dealing with these objectives, a suitable normalization technique is implemented for scaling the errors in each objective. This method is validated through simulation and experimental results.

Performance Analysis of Grid-Connected Distributed Generation System Integrating a Hybrid Wind-PV Farm Using UPQC

This work presents a distributed generation system (DG) that combines system of a wind turbine (WT) and photovoltaic (PV) using a unified power quality conditioner (UPQC). Along with providing active power (AP) to the utility grid, Wind-PV-UPQC improves PQ indicators, for example, voltage drops/surges, harmonics of grid voltages, and PF. Since Wind-PV-UPQC depends on dual compensation scheme, the parallel converter works as a sinusoidal voltage source, while the series converter works as a sinusoidal current source. In this way, a smooth transition from grid operation to island operation and vice versa can be achieved without load voltage transitions. In addition, in order to overcome the problems through abrupt solar radiation or wind speed variations, a faster power balance is achieved between the wind turbines, the PV array, and the grid, as FFCL pursue the production of the current references of series converter. Consequently, the dynamic reactions of the converter currents and the voltage of dc bus are enhanced. A comprehensive analysis of flow of the AP through the converters is done to ensure a proper understanding of how Wind-PV-UPQC works. Finally, the simulation results are shown to estimate the dynamic and static performance of Wind-PV-UPQC in conjunction with the power distribution system.

Power decoupling control of single‐phase or three‐phase input high‐frequency single‐phase output matrix converters

AbstractThis study proposes a matrix converter (MC) control method capable of power decoupling (PD) for a single‐phase input isolated AC‐DC converter. The proposed converter can also be fed by a three‐phase source without any additional components. The PD circuit shares its capacitors with the input filters and its switches with the MC, and absorbs the source power ripple to supply a constant DC voltage for the load. Moreover, the MC control method achieves a sinusoidal source current, a high output frequency, and soft switching. Additionally, the feedback control to compensate for the DC output voltage error is applied. The proposed method is evaluated experimentally.

Reactive Power Control and Neutral Current Elimination of Four Wire Five Level NPC Inverter based STATCOM using 3D-SVPWM Technique

In this paper, three phase four wire five level Neutral Point Clamped Inverter (NPCI) based Static synchronous Compensator (STATCOM) is implemented for reactive power control and neutral current elimination. Three dimensional Space Vector Pulse Width Modulation (3D-SVPWM) control strategy is developed to control this 5-level NPC inverter. The behaviour of static synchronous compensator is analyzed and reactive power control is done using constant DC voltage. The objective of this compensating method is to provide balanced and sinusoidal source currents under unbalanced and nonlinear load conditions and reactive power control. The 3D-SVPWM technique provides reduced harmonic content in output voltage and current, controlled source current, minimized common mode voltage and improved output voltage. In 3D-SVPWM, switching pulses are generated with non-redundant switching states, which lead to reduce the complexity in switching time calculation and computational time is less. The highlights of the paper includes the neutral current is reduced to 0.25A, source current harmonics is minimized and it provides balanced and sinusoidal source currents with help of STATCOM compensation. The simulation and experimental results demonstrates the sinusoidal and harmonics free source current and minimized neutral current for four wire five level NPCI based STATCOM.

PV integrated universal active power filter for power quality enhancement and effective power management

This paper presents a new control scheme for solar photo-voltaic (PV) integrated universal active power filter (PV-UAPF). Here, the instantaneous power balance theory (IPBT) is proposed to extract the reference signals for shunt active filter (ShAPF) and series active power filters (SeAPF). Thereby, ShAPF will act as a pure sinusoidal voltage source and SeAPF will act as a pure sinusoidal current source. In the IPBT control scheme, the frequency locked loop (FLL) based modified reduced order generalized integrator (MROGI) is proposed to extract positive and negative sequence components (PNSC) and phase angle during adverse grid conditions. Also, the PV integration at the DC link will reduce demand on the supply system thereby reduces the burden on the utility grid. Hence, the proposed system combines both the benefits of clean energy generation along with power quality improvement. To validate the performance of the proposed system, simulation is developed in MATLAB, and results are verified. Also, the system performance is then verified in the hardware setup under various disturbances such as voltage sag/swell, load distortion, and change in PV power.

Power Quality Improvement for Grid-connected PV System Based on Distribution Static Compensator with Fuzzy Logic Controller and UVT/ADALINE-based Least Mean Square Controller

This paper presents a novel method of power quality enrichment in a grid-connected photovoltaic (PV) system using a distribution static compensator (DSTATCOM). The paper consists of two-step control processes. In the primary step, a fuzzy logic controller (FLC) is employed in the DC-DC converter to extract the peak power point from the PV panel, where the FLC produces a switching signal for the DC-DC converter. In the secondary step, a unit vector template (UVT)/adaptive linear neuron (ADALINE)-based least mean square (LMS) controller is adopted in the DC-AC converter, i.e., voltage source converter (VSC). The input to this VSC is the boosted DC voltage, which originates from the PV panel as a result of DC-DC conversion. The VSC shunted with the power grid is known as a DSTATCOM, which can maintain the power quality in the distribution system. The UVT controller generates reference source currents from the grid voltages and DC-link voltages. The ADALINE-based LMS controller calculates the online weight according to the previous weights by the sensed load current. The UVT/ADALINE-based LMS controller of a DSTAT-COM performs several tasks such as maintaining the sinusoidal source current, achieving a unity power factor, and performing reactive power compensation. The reference current extracted from the UVT/ADALINE-based LMS controller is fed to the hysteresis current controller to obtain the desired switching signal for the VSC. A 100 kW solar PV system integrated into a three-phase four-wire distribution system through a four-leg VSC is designed in MATLAB/Simulink. The performances of the FLC and UVT/ADALINE-based LMS controllers are demonstrated under various irradiances as well as constant temperature and nonlinear loading conditions.

Design and implementation of ANN-based SAPF approach for current harmonics mitigation in industrial power systems

This article describes with Shunt Active Power Filter (SAPF) for compensation of reactive Power (P), current harmonics. An ADALINE based neural network current estimator can control the SAPF to maintain sinusoidal source currents and unity Power Factor (PF). The three-phase (III-Phase) load currents are sensed and measured by Least Mean Square(LMS) algorithm based on ADALINE, the weights obtained with the help of online calculation, and then these weights are multiplied with the help of unit vector, which gives the fundamental frequency of Load Currents (LC). The DC link voltage (V) of the V Source Converter, maintained at a constant value, and it can work as the SAPF, and various simulation results are presented under the steady-state conditions using the PI controller. The switching action of VSC is performed using Hysteresis Current Control based on pulse width modulation, which makes the source currents should follow the reference source currents. The MATLAB based simulation results and implementation results are obtained to determine the efficacy of the SAPF with ADALINE based neural network control for load compensation. SAPF system meets IEEE Standard 519 recommended harmonic standards for different rated nonlinear loads under balanced supply conditions.

Simple Power Quality Compensation with Bidirectional Battery Charger for Electric Vehicles in Single-Phase Three-Wire Distribution Feeders

This paper deals with power quality compensation in single-phase three-wire distribution feeders using a constant DC-capacitor voltage-control (CDCVC)-based strategy of the previously proposed bidirectional battery charger (BBC) for electric vehicles under the distorted source-voltage and load-current conditions. Instantaneous active power flowing into the three-leg pulse-width-modulated (PWM) rectifier in the BBC is discussed. The instantaneous power flowing into the three-leg PWM rectifier demonstrates that the CDCVC-based strategy obtains balanced and sinusoidal source currents at a unity power factor, where the source-side active power is balanced with the load-side active power. Simulation and experimental results demonstrate that balanced and sinusoidal source currents at a unity power factor are attained in single-phase three-wire distribution feeders with both battery-charging and -discharging operations for electric vehicles even though both source voltage and load currents are distorted.

Comparative Performance Analysis Involving a Three-Phase UPQC Operating With Conventional and Dual/Inverted Power-Line Conditioning Strategies

This article deals with a complete evaluating and comparative analysis involving static and dynamic performances of a three-phase unified power quality conditioner (UPQC) controlled to operate using conventional and dual/inverted compensation strategies for performing active power-line conditioning. In the conventional strategy, the series converter of the UPQC operates as a nonsinusoidal voltage source, while the parallel converter operates as a nonsinusoidal current source. Differently, when the UPQC operates with a dual/inverted strategy, the series converter operates as a sinusoidal current source, while the parallel converter is controlled to act as a sinusoidal voltage source. Although, in theory, the results achieved using the mentioned strategies looks similar, in practical applications there are considerable differences in both static and dynamic performances that must be considered for choosing the best compensation strategy to be adopted. Thus, this article addresses aspects related to the mathematical modeling, control and generation of the control references applied to the UPQC, which are implemented using two three-level neutral-point clamped inverters. Furthermore, the performance of the UPQC operating under static disturbances (grid voltage harmonics/unbalances and load current harmonics), as well as dynamic disturbances (voltage sags/swells and load changes) are extensively tested by means of an experimental setup.

Study of Excitation Characteristics of Traction Machine/Drive Systems

In order to accurately evaluate the performance of a traction machine/drive system, it is necessary to have an accurate excitation source which considers current harmonics. In this paper, four machine/drive systems with different excitation sources have been modeled, simulated, and studied to evaluate the effects on permanent magnet synchronous machines (PMSMs) from different perspectives. In Model I, the excitation is an ideal sinusoidal current source with no harmonics. Model II is excited by an ideal sinusoidal voltage source regardless of the pulse width modification’s (PWM’s) influence. Model III takes into account the influence of current harmonics under space vector pulse width modulation (SVPWM) control. Model IV is based on the equivalent circuit extraction (ECE) model (a look-up table motor model). We simulate these four models and study the characteristics of the excitation sources, based on the observations of current harmonics, torque, electromagnetic force, computation time, and efficiency. Experiments are also conducted to show that Model III allows the most precise study of the considered system. Model IV is a good substitution, providing similar results with a shorter running time.

Control shunt active filter based on dq frame using current model prediction

The nonlinear loads present more in the power systems in the practice today by developing of electronic technology and using the small distributed power sources (solar power, wind power etc.), this causes the increasing the high frequency switch devices etc. in the power network. Nonlinear loads cause non-sinusoidal currents and voltages with harmonic components, increasing the reactive power, overload of power lines and electrical devices, low power factor and affecting badly to the networks. Shunt active filters (SAF) with current controlled voltage source inverters (CCVSI) are used effectively to reduce the harmonics and to balance the phases sinusoidal source currents by generating the currents to compensate the harmonic currents caused by the nonlinear loads. In this paper we suppose a control strategy to generate the compensation currents of SAF by using the current model predictive engineering. This method is better than the control strategy using PI controller in term of transient time. The desired compensation currents can track exactly the reference compensation currents on the dq frame. The simulation results implemented on the nonlinear load, a full bridge rectifier and 3 phase unbalance load, show that the transient period decrease from 0.1s to 0.02s in comparing with PI controller. The experimental results proof that the THD of source currents decrease from 24.8% to 5.4% when using the proposed method.

A Hybrid Predictive Control for a Current Source Converter in an Aircraft DC Microgrid

A current source converter (CSC) is a promising topology for interfacing aircraft generators with the onboard DC microgrid. In this paper, a hybrid predictive control is proposed for the CSC with an output LC filter in such application. Deadbeat predictive control with larger sampling time is applied to the output circuit, generating reference source currents. Finite-set model predictive control with smaller sampling time is applied to the input circuit to achieve sinusoidal source currents, which is simplified by saving the source current predictions. The proposed scheme eliminates both the proportional-integral controller and the weighting factor, which are required in the existing studies. Besides, it has lower control complexity. A SiC-MOSFET-based prototype is used to verify the validity of the proposed scheme. Experimental results under 150 V/350–800 Hz AC input and 270 V DC output demonstrate the superior control performance.

Functioning ability of multilevel Vienna converter as new parallel active filtering configuration: simulation and experimental evaluation

This paper presents a modern solution based on power electronics, recommended to solve the problems posed by harmonic pollution of the electrical network. This pollution is generated mainly by nonlinear loads such as rectifiers with diodes and thyristors, recognized as the principal source of harmonic currents injection. As such, a curative solution was provided by a new three-phase parallel active filter based on the multilevel Vienna converter. The novel task assigned to the Vienna converter is to compensate the reactive power and to eliminate the harmonic currents caused by the nonlinear polluting loads. A simple and effective control approach has been developed guaranteeing sinusoidal shape source currents and unity power factor of the electrical network. In addition, the multilevel Vienna converter-based parallel active filter operates with convincing performances identified through the admitted DC output voltage undulations and the balance between the two partial outputs voltages. Satisfactory results have been obtained when the proposed algorithm has been subjected to simulation using the MATLAB/Simulink software and confirmed in real-time implementation via a dSPACE 1104 card.

Steady-State Error Suppression and Simplified Implementation of Direct Source Current Control for Matrix Converter With Model Predictive Control

A matrix converter (MC) with model predictive control based on the source reactive power control usually fails to show sinusoidal source currents. The analysis presented in this paper shows that this common combination of a converter and control has the inherent inability to suppress some harmonics in the source currents, even with additional passive or active damping control. Direct source current control can be implemented to give sinusoidal source currents and intrinsic active damping. However, the issue of steady-state error in output currents then arises, as the MC topology does not allow of the independent control of source and output currents. Therefore, feedback control of load active power is proposed to address this issue without degrading the fast dynamic performance. Benefiting from the direct source current control, a simplified implementation is also proposed to decrease the number of candidate switching states from 27 to 5, which significantly reduces the computational burden. Experimental results have verified the theoretical analysis and the effectiveness of the proposed control scheme.

Simple Harmonics Compensation Method for Smart Charger with Constant DC-Capacitor Voltage-Control for Electric Vehicles in Single-Phase Three-Wire Distribution Feeders

This paper discusses harmonic current compensation of the constant dc-capacitor voltage-control (CDCVC)-based strategy for smart charger for electric vehicles (EVs) in single-phase three-wire distribution feeders (SPTWDFs) under distorted load current conditions. The basic principle of the CDCVC-based harmonics compensation strategy under distorted load current conditions is discussed in detail. The instantaneous power flowing into the three-leg pulse-width modulated (PWM) rectifier, which acts as a smart charger, shows that the CDCVC-based strategy achieves balanced and sinusoidal source currents with a unity power factor (PF). The CDCVC-based harmonics compensation strategy does not require any calculation blocks of fundamental reactive, unbalanced active, and harmonic currents. Thus, the authors propose a simplified algorithm to compensate for reactive, unbalanced active, and harmonic currents. Simulation and experimental results demonstrate that balanced and sinusoidal source currents with a unity PF in SPTWDFs are obtained on the secondary side of the pole-mounted distribution transformer during both the battery-charging and battery-discharging operations in EVs, compensating the reactive, unbalanced active, and harmonic currents.

A Cost-Effective and Low-Complexity Predictive Control for Matrix Converters Under Unbalanced Grid Voltage Conditions

Due to no dc-link energy storage element in the matrix converter (MC), its input and output performances are highly sensitive to the unbalanced grid conditions. In order to mitigate the adverse effects of the unbalanced grid voltages, this paper proposes a simple and effective control strategy based on the finite-control set model predictive control (FCS-MPC). In this case, an extended instantaneous power theory is adapted to generate the source current references. As a result, both sinusoidal source currents and balanced output currents are ensured. Besides, complicated positive and negative sequence decomposition is avoided. Furthermore, an extended state observer (ESO) is designed to eliminate the grid voltages sensors, which not only estimates the grid voltages but also provides the delayed grid voltage information required for the source current reference calculation. The effectiveness of the proposed method is verified by the simulation and experimental results.

A Wide-Range Frequency Model for Dielectric Barrier Discharge Type Ozone Generators Powered by Series Resonant Inverters

Dielectric Barrier Discharge (DBD) type ozone generators (OGs) are widely used for industrial ozone generation. As OGs are typical non-linear load, different models are presented to analyze the characteristic of OGs and the models of OGs have proven to be an effective tool to design power supplies for OGs. However, most of the models are only applicable to nominal conditions and not suitable for a wide working range at present. Considering that almost all of the series resonant inverters use resonant tanks operating in resonance or near of it, the current through OGs can be substituted by a sinusoidal current source with variable amplitude and frequency. According to the concept, a wide-range frequency model composed of an equivalent resistance in series of an equivalent capacitance for OGs is proposed. Because the equivalent resistance and the equivalent capacitance are closely related to switching frequency of inverter and the current through OGs, the model can be used in the wide working range. Based on the model, the characteristic of OGs is analyzed and a methodology for power supplies is developed. Through a combination of the proposed model and the four limit parameters of ozone generators and power supplies in the methodology, the main circuit parameters of the power supply for maximizing the ability of OGs are obtained. To validate the wide-range frequency model and the design methodology, an ozone generation system powered by a 14-kW series resonant inverter is built. The differences between the experimental results and the analytical results show that the proposed model has satisfying accuracy in a wide working range. Compare to the conventional methodology for power supplies, the main circuit parameters of the power supply can be obtained conveniently regardless of the heavy-load condition and light-load condition of OGs.