LCL Filter Design Research Articles

LCL filter design and experimental response analysis for a SiC inverter

In this paper, an LCL filter for a 20-kW SiC power inverter with a 25 kHz switching frequency is proposed and assessed. The transfer function without neglecting the network effect is considered. The optimal value of the damping resistor is evaluated to minimize losses while maintaining power quality and device stability. Finally, the harmonic content produced by the SiC inverter is experimentally measured to verify the effectiveness of the LCL filter.

Optimal passive LCL filter design for grid-connected converters in weak grids

In an era characterized by the increasing integration of renewable energy sources into the power grid, the stability and resilience of the grid have become paramount, especially in areas with weak grid infrastructure. One effective approach to mitigate the adverse effects of grid disturbances and harmonics is passive LCL (inductor-capacitor-inductor) filters. However, designing these filters for optimal performance under varying conditions remains challenging. This research paper presents an effective approach to addressing this challenge by utilizing the power of evolutionary algorithms, specifically Multi-Objective Particle Swarm Optimization (MOPSO) and Multi-Objective Genetic Algorithm (MOGA), to design optimal passive LCL filters for weak grid environments. The proposed method aims to enhance grid resilience by optimizing the filter parameters to consider a weak grid's unique characteristics and uncertainties. Minimizing the resonance frequency has succeeded in achieving power quality and stability improvements related to changes in grid impedance. The proposed approach achieves power quality and stability improvements related to changes in grid impedance and dealing with fragile conditions, which is the main scope of this paper.© 2017 Elsevier Inc. All rights reserved.

Optimal fractional PI controller-based VSC-HVDC system with LCL filter design

For decades, high voltage direct current (HVDC) has been an essential means in designing smart microgrids. Though, a control approach for Voltage Source Converter (VSC)-based HVDC, like dampening oscillations, must be established for improved operational execution, as these oscillations can cause stability issues. Considering its versatility, the Fractional order Proportional Integral (FPI) controller is used in this study's control approach instead of the PI controller. With frequency domain analysis, comprehensive modelling and design of LCL filters for harmonic reduction to improve power quality are presented. The dynamic characteristics of VSC-HVDC are comprehensively presented based on dq axis synchronous frame of reference. The VSC-HVDC improved control outcome is validated by the result analysis using PI and FPI controller using ITLBO. It is found in both frequency and time-domain simulations and analysis that the AFPI-VSC-HVDC system is capable of effectively dampening oscillations to enhance the small-signal stability.

A New LCL Filter Design Method for Single-Phase Photovoltaic Systems Connected to the Grid via Micro-Inverters

A New LCL Filter Design Method for Single-Phase Photovoltaic Systems Connected to the Grid via Micro-Inverters

Simple Control Schme of Three-Level PWM Converter Connecting Wind Turbine with Grid.

This paper proposes a simple direct power control using space vector modulation (DPC-SVM) for three-phase three level neutral point clamped (3L-NPC) PWM converter connecting a wind turbine generator with grid. The active and reactive power are used as the control variables instead of the currents applied in conventional control method. Moreover, grid voltage sensors are replaced by a virtual flux (VF) estimator. The theoretical principle of this method as well as the synthesis of the active and reactive power controllers are discussed. It is shown that the proposed method exhibits several features as: simple and robust algorithm as well as simple tuning procedure of PI power controllers. Furthermore the paper presents a LCL-filter design, which fulfils IEEE-SCR 20-50 recommendation. Simulation results have proven an excellent performance and verified the validity of the proposed system.

LCL Filter Design of STATCOM using Genetic Algorithm Scheme for SCIG Based Microgrid Operation

In a microgrid static Compensator (STATCOM) is the most prominent inverter circuit for stabilizing the bidirectional power flow requirements of the system. This inverter circuit is the primary source of harmonics when the supply current feeds from the microgrid to the main grid. Improved control strategy and proper filter design may give solution to these issues and so, there is a huge scope of research in the field of the converter control techniques and filter designing for such microgrid based power system. The key objectives of this paper are (i) to develop an adequate current control scheme for adjusting real and reactive power fluctuations produced by load time to time, and (ii) to reduce the harmonic level of output characteristics in terms of real and reactive power flow and current frequency. For this, an approach is presented to estimate the filter design parameters for current controlled STATCOM connected to squirrel cage induction generator (SCIG) based microgrid. A nature-inspired optimization namely, genetic algorithm (GA), is implemented to estimate the most suitable parameters for the LCL filter. Results obtained through GA are validated with a conventional mathematical method in terms of real and reactive power flow through microgrid along with harmonic-based studies.

Inductor-Volume Comparison for 3Φ3W LCL Converter With Direct Digital Control and Different Filter-Inductance Drop-Rates

Magnetic powder cores have soft-saturation properties and high temperature stability compared with other materials, which are widely used in LCL filter design. Conventionally, when designing a filter for a 3Φ3W LCL converter controlled with abc-to dq frame transformation, a low drop-rate inductor is selected to stabilize the system and improve the current THD; however, it results in high inductor volume. With the proposed direct digital control (DDC) operating in nature frame, the filter is allowed to have a wide inductance drop-rate (75%) which can reduce core size significantly. The DDC is first addressed and the filter design is correspondingly presented. Comparison of filter volume, loss, and temperature rise for the converters with DDC and different drop-rates is presented, and it is the primary contribution. Simulated and experimental results from a 33 kW 3Φ3W LCL converter with different inductance drop-rates have been used to verify the analyses and discussions.

Optimal LCL-filter design for a single-phase grid-connected inverter using metaheuristic algorithms

The inductor-capacitor-inductor (LCL) filter is used to lower the high-frequency switching noise of a grid-connected inverter (GCI). However, a robust design of the LCL filter is a challenge due to its complex model, variations in the operating conditions of the grid, and its stability gain margin. Therefore, this paper designs an optimal LCL filter for GCI and considers the changing grid conditions. This paper utilized four metaheuristic optimization algorithms, including the Whale Optimization Algorithm, the Circle Search Algorithm, the Particle Swarm Optimization, and the gray Wolf Optimization. These algorithms are applied to minimize the total harmonic distortion (THD) and the error between the reference and real grid current. The robustness of the optimal LCL filter is investigated under transient and steady states of the grid by using MATLAB/SIMULINK and real-time simulations. The obtained results revealed that the optimal LCL filter is capable of reducing the THD under different grid variations.

LCL-filter design and analysis for PWM recuperating system used in DC traction power substation

Voltage source inverter (VSI) had been used in dc traction power substation to deliver the trains braking energy back to the utility grid. To mitigate low order harmonics components, pulse-width-modulation (PWM) technique is commonly used in VSI controlled. As a result, the ac voltage and current waveforms may contain high frequency ripples. This paper proposes to mitigate the high frequency harmonics using LCL-filter with series <em>R</em>-damper. This filter offers good attenuation on harmonics with smaller size compare to other passive filter topologies. Theoretical analysis and simulation verification are conducted in designing the proposed filter. System level simulation had also been carried out. Sinusoidal grid current and voltage waveforms are recorded (THD<2%). This paper also includes damping losses analysis in conjunction with resonance peak suppression in designing the <em>R</em>-damper.

An Improvement of Holistic Control Tuning for Reducing Energy Consumption in Seamless Transitions for a BESS Grid-Connected Converter

This paper presents an improvement of the tuning process of the holistic control published by the authors in previous research to achieve a seamless transition among three operation mode changes and load transients. The proposed tuning approach reveals an improvement in the energy consumption of the Battery Energy Storage System (BESS) during all operation mode transients compared to the holistic control. For this aim, the system addressed is a BESS with the capability to ride through three operation modes of interest: the grid-connected mode as an inverter, the grid-connected mode as a rectifier, and the islanded operation mode. The LCL filter design by using the Butterworth polynomial approach is presented in more detail, and its smooth inherent transient response is preserved when the tuning of the controller gains is carried out by using the same polynomial approach but now including the integral action within the Butterworth polynomial. To reveal the reduction in energy consumption, the closed-loop transfer functions of each mode were used to compare the previous holistic control and this new one named by the authors as the “improved holistic control”. The closed-loop system fulfills the frequency and voltage thresholds of the IEEE 1547-2018 standard seamlessly. The simulation runs were conducted on the PSCAD/EMTDC to evaluate the seamless transition among the operation mode changes and load steps. The experimental results in a 617 W, 120 VL−L three-phase converter prototype are included to demonstrate the validity of the improved holistic control.

Tek Fazlı Şebekeye Bağlı Evirici Tasarımı ve Kontrolü

The energy demand has been increasing over the last decade. With the integration of renewable energy sources, grid-connected inverters play a key role in a power system. The main objective of the paper is to discuss a grid-connected inverter with single-phase structure in particular. The design and working principle of a basic grid-connected inverter are presented together with the cycle-by-cycle average (CCA) model. The LCL filter design is also introduced to decrease the current harmonics. To attain unity power factor operation, the closed loop control is essential for the grid-connected inverters. For this reason, a current controller in dq-frame is performed by utilizing MATLAB/Simulink environment. The results indicate that the suggested current controller presents good performance during the variations. This study is anticipated to draw the attention of grid-connected inverter designers and serve as a reference for them.

Design of Three Level Neutral Point clamped inverter with Fuzzy logic based MPPT for PV applications.

In this paper a solar photovoltaic (PV) system with maximum power point tracking (MPPT) for domestic low power applications. The proposed system contains a PV array which provides electrical power, while a DC/DC converter is incorporated to regulate the power derived from PV panels. Fuzzy logic control (FLC) based MPPT has been proposed. To convert the DC voltages and currents obtained from Solar panels to AC voltages and currents, a Neutral point clamped multilevel inverter is included. Furthermore, harmonics are removed by using the LCL filter. The PV system working, design of the DC/DC Boost converter, Novel MPPT techniques, Multilevel inverter topologies and LCL filter design are explained. Results reveal that the FLC based MPPT has much lesser total harmonic distortion (THD) in the PV system. With this property, FLC possesses faster convergence than the perturb & observe (P&O) and other MPPT techniques.

Integrated Renewable Smart Grid System Using Fuzzy Based Intelligent Controller

In high power medium voltage applications, the utilization of 5-H Bridge Multi-Level Inverter (MLI) has grown vastly in recent years. The 5-H Bridge MLI can effectively control link voltage as well as power factor. However, the inverter imparts harmonics owing to the high switching frequency. Hence Inductance Capacitance Inductance (LCL) filter is implemented at its output to mitigate harmonics in presence of non-linear load. It’s of highly important to choose LCL parameters wisely in order to attain good filtering effect. This work investigates the application of 5-H Bridge MLI with LCL filter at the output for efficient integration of renewable energy sources on to the grid. A modified fuzzy heuristic approach is used to solve LCL power filter optimization problem at output of 5-H Bridge Multi-Level Inverter. Subject to the constraint’s harmonic distortion and losses of the inverter, multi objective optimization problem is solved to obtain LCL filter optimal values. The optimized LCL filter design was applied to a grid connected cascaded H-bridge MLI of rating 4.5 MW, 11 kV. MATLAB-Simulink is utilized for modelling and simulating the system. The results showed that the system is more efficient and generic. dSPACE Hardware in Loop (HIL) test system was used to verify the efficacy of the prototype system.

Magnetic integrated LCL filter design for a 2.5 kW three-phase grid-connected inverter with double closed-loop control

Magnetic integrated LCL filter design for a 2.5 kW three-phase grid-connected inverter with double closed-loop control

LCL filter design for grid-connected single-phase flyback microinverter: a step by step guide

<span lang="EN-US">Recently, <em>LCL</em> has become amongst the most attractive filter used for grid-connected flyback inverters. Nonetheless, the switching of power devices in the inverter configuration creates harmonics that affect the end application behavior and might shorten its lifetime. Furthermore, the resonance frequencies produced by the <em>LCL</em> network contribute to the system instability. This paper proposes a step-by-step guide to designing an <em>LCL</em> filter by considering several key aspects such as the resonance frequency and maximum current ripple. A single-phase grid-connected flyback microinverter with an <em>LCL</em> filter was designed then constructed in the MATLAB/Simulink environment. Several different parameter variations and damping solutions were used to analyze the performance of the circuit. The simulation result shows a promising total harmonic distortion (THD) value below 5% and harmonic suppression up to 14%.</span>

LCL-Filter Design Based on Modulation Index for Grid-Connected Three-Level Hybrid ANPC Inverters

This paper proposes an LCL-filter design based on the modulation index for grid-connected hybrid active neutral point clamped (ANPC) inverters. The three-level hybrid ANPC inverter consists of silicon insulated gate bipolar transistors and silicon carbide metal oxide semiconductor field effect transistors to reduce the switching losses. LCL-filter parameters for the three-level hybrid ANPC inverter are calculated using the current ripple factor. The current ripple factor is affected by phase voltage, which varies according to the modulation index, and therefore the inductance on the inverter side must be considered with the modulation index. To design inductance on the inverter side, the output phase voltage and grid voltage are used to analyze the current ripple factor. The filter capacitor and the inductance on the grid side are designed based on the reactive power absorption and current ripple attenuation. The effectiveness of the proposed LCL-filter design method is validated via simulation and experimental results.

Design Method of LCL Filter for Grid-Connected Inverter Based on Particle Swarm Optimization and Screening Method

The trial and error method is the conventional method for LCL parameter design. Its efficiency is low and it is difficult to obtain the optimal parameter. Furthermore, due to the lack of detailed analysis of the high-frequency harmonics in the inverter output voltage, the designed LCL filter cannot effectively filter them, resulting that the quality of the grid-connected current cannot fully meet IEEE 519 standard. Based on the above-mentioned problems, the high-frequency harmonics of inverter output voltage is analyzed in detail in this article, and the multiobjective optimization function, including five optimization objectives, is constructed. Combined with the particle swarm optimization, a screening method is proposed to realize the multiobjective optimization process. Under the proposed method, the LCL parameter, which happens to meet the requirement of IEEE 519 for the high-frequency harmonic distortion rate of the grid-connected current, can be obtained, and the greatest tradeoff of LCL filtering performance and filter cost is achieved. In addition, the proposed method considers the problem of weak grid and provides a complete engineering solution for LCL parameter design in different degrees of weak grid. Finally, the effectiveness and accuracy of the proposed design method are verified by contrast simulation and experiment.

A compound control strategy for LCL-based three phase four leg shunt active power filter

Conventional single inductor filter which is applied to three-phase four-leg shunt active power filter hardly meet the requirements for high frequency harmonic suppression. LCL filter has advantage both in high dynamic response and high frequency harmonic suppression. Repetitive control can realize accurate tracking of multi-harmonics signal. However, the design of corrector for repetitive control is mostly complicated. This paper proposes a topology of three-phase four-leg shunt active power filter based on LCL filter and improve its stability through capacitive current feedback. Compound control strategy which includes PI control and repetitive control is adopted to improve the compensation effect of harmonic current. Corrector for repetitive control has simple structure and is easy to design. The conventional PI control and compound control are compared and analyzed in detail. Moreover, the difference of property between LCL filter and single inductor filter is compared and analyzed. Simulation results show the correctness and effectiveness of the designed LCL filter and the proposed compound control strategy. The proposed method provides a reference for making three-phase four-leg shunt active power filter more practical.

Design Space Optimization of a Three-Phase LCL Filter for Electric Vehicle Ultra-Fast Battery Charging

State-of-the-art ultra-fast battery chargers for electric vehicles simultaneously require high efficiency and high power density, leading to a challenging power converter design. In particular, the grid-side filter, which ensures sinusoidal current absorption with low pulse-width modulation (PWM) harmonic content, can be a major contributor to the overall converter size and losses. Therefore, this paper proposes a complete analysis, design and optimization procedure of a three-phase LCL filter for a modular DC fast charger. First, an overview of the basic LCL filter modeling is provided and the most significant system transfer functions are identified. Then, the optimal ratio between grid-side and converter-side inductance is discussed, aiming for the maximum filtering performance. A novel design methodology, based on a graphical representation of the filter design space, is thus proposed. Specifically, several constraints on the LCL filtering elements are enforced, such that all feasible design parameter combinations are identified. Therefore, since in low-voltage high-power applications the inductive components typically dominate the overall filter volume, loss and cost, the viable LCL filter design that minimizes the total required inductance is selected. The proposed design procedure is applied to a 30 kW, 20 kHz 3-level unidirectional rectifier, employed in a modular DC fast charger. The performance of the selected optimal design, featuring equal grid-side and converter-side 175 μμH inductors and 15 μμF capacitors, is verified experimentally on an active front-end prototype, both in terms of harmonic attenuation capability and current control dynamics. A current total harmonic distortion (THD) of 1.2% is achieved at full load and all generated current harmonics comply with the applicable harmonic standard. Moreover, separate tests are performed with different values of grid inner impedance, verifying the converter control stability in various operating conditions and supporting the general validity of the proposed design methodology.

The LCL filter design for three phase DC-AC voltage converter

This paper discusses LCL filter design to apply for a three phase DC-AC converter from a DC source of distributed generator to a three phase power system. System is transformer less, using H-bridge switching with 6 IGBTs, modelled by using PSIM to deliver 20 kW 400V source to a three phase 380 V 50 Hz system. the LCL filter requires inductors 518,564 μH and 311.13 μH, capacitor of 65.74μF. The loss resistance is 0.573 Ohm. The LCL filter is able to smooth DC-AC converter output starts from 0.005 s.