LCL Topology Research Articles

An Economical DWPT System With Mutual Compensation of Segmented Power Supply Rails Based on LCL Topology

For high-power, long-mileage dynamic wireless power transfer (DWPT) system, its economy and adaptability to complex working conditions are the main factors limiting its popularization and application. In this paper, the compensation and power supply of segmented rails are studied, and a DWPT system with mutual compensation of segmented power supply rails based on LCL topology is constructed. By multiplexing components, the number, cost and volume of devices are reduced, and the economy of the system is improved. The power supply topology is optimized to achieve constant-current characteristics over a wide load range to generate a stable high-frequency magnetic field in space and avoid short-circuit current induced by mutual coupling of adjacent rail. The resonant control conditions of the system are derived, and a phase shift control method based on the three-leg inverter is proposed to realize the full range regulation of transmitter current and output power, and improve the adaptability of the system. The characteristics of the proposed DWPT system have been verified by an experimental prototype.

A Magnetic Field Containment Method for an IPT System with Multiple Transmitting Coils Based on Reflective Properties

Inductive power transfer (IPT) systems with multiple transmitting coils are mainly used in specific scenarios, such as IPT sharing platforms and dynamic wireless charging of electric vehicles, etc. However, it faces problems of electromagnetic field leakage and low efficiency. A new magnetic field containment method based on reflective properties is proposed to solve the above shortcomings. Firstly, the reflective properties and performance figures of the IPT system with a unified passive compensation network are described and derived. Then, an S−LCL topology appropriate for the time−varying coupling IPT system is presented, where the IPT system’s transmitter consists of multiple coils that are compatible with one or more moving receivers and is powered by an inverter. Then, magnetic field focusing, power transfer and overall efficiency are analyzed and simulated. Finally, an experimental prototype is built to validate the feasibility of the proposed system. The experimental results show that the proposed method can increase the power transfer of the coupled transmitting coil and reduce the magnetic field leakage of the standby transmitting coils without complex shielding measures, switch, position detection and communication circuits.

Research on strong anti-misalignmemt methods of double-coupled LCL topology ICPT system

Research on strong anti-misalignmemt methods of double-coupled LCL topology ICPT system

Design and Implementation of Double‐Sided LCL Variable Compensation Topology of MCR‐WPT System

Aiming at the constant current charging and the constant voltage charging mode of the power battery pack in an electric vehicle, this paper proposes a double‐sided LCL variable compensation topology in a magnetically coupled resonance wireless power transfer system. With the proposed topology, the complexity of the circuit design and control will be simplified. The mathematical model for the double‐sided LCL topology is established using a two‐port network, and the output characteristics of constant current mode and constant voltage mode are studied on. By compensation analysis, the double‐sided LCL topology is improved and designed. The specific parameter configuration method and compensation conversion circuit are developed. Load characteristics analysis of variable compensation topology is given. A MATLAB Simulink simulation model and a prototype were built. Both the simulation results and the experiment results show the validity of the proposed variable compensation topology and parameter configuration method. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

The Design and Optimization of a Wireless Power Transfer System Allowing Random Access for Multiple Loads

As is common in multi-load wireless power transfer (WPT) systems based on series–series compensation topology, the power received by loads and the efficiency of the process are highly sensitive to changes in the number of loads. To guarantee that the power supplied to a load remains stable when other loads access or leave the system, we propose an improved multi-load system for WPT. The new system uses an LCC/S topology (based on inductor–capacitor–inductor or LCL topology) to keep the power received by the loads stable. By comparing two scenarios (ideal and real models based on LCC/S topology), we aim to eliminate cross-coupling between receiving coils by connecting compensating capacitors in series on the receiving side. In this way, the stability of the power received by loads is further improved. Moreover, a method of optimizing control over the efficiency is proposed based on the effect on the overall efficiency of impedance and number of loads. This allows us to optimize the overall efficiency of the system. Finally, a system to verify our theoretical analysis is established and used to show the validity and effectiveness of the proposed system.

High‐gain LCL architecture based IPT system for wireless charging of EV

In this study, a high-gain LCL topology based inductive power transfer (IPT) system is proposed for wireless charging of electric vehicle (EV). The hybrid resonance topology is modified to achieve high gain in the proposed system. The duty ratio of semiconductor switches is adjusted to control the primary power flow in the IPT system. A detailed mathematical model of the proposed system is obtained and performances are analysed under contingency in misalignment of the inductive coil. The developed prototype of IPT system is tested and the experimental studies substantiate the results of numerical simulation.

Wireless Power Transfer for Battery Powering System

The LCL topology (formed by an LC tank with a transmitting coil) is extensively utilized in wireless power transfer (WPT) systems with the features of a constant resonant current and ability to disconnect load abruptly. However, it requires high input voltage, which limits its utilization in battery powering scenarios (12~24 V). A current-fed inverter (CFI) is applied to the LCL-S (a compensation capacitor in series with the receiving coil) WPT systems to boost the input voltage, thereby getting a higher resonant current in the transmitting side (Tx). To facilitate the voltage regulation in the receiving side (Rx), a semi-active bridge (SAB) is introduced into the system, which further boosts the output voltage by a lower frequency switching at different duty ratios. Rigorous mathematical analysis of the proposed system is carried out and design guidelines are subsequently derived. Moreover, a power loss reduction is realized by zero voltage switch (ZVS) of the four switches in the Tx which are deduced and presented. Simulations and experiments are added to verify the proposed system. Consequently, a 93.3% system efficiency (DC-to-DC efficiency) is obtained using the proposed topology. Optimization techniques for a higher efficiency are included in this study.

A 60-kW 3-kW/kg Five-Level T-Type SiC PV Inverter With 99.2% Peak Efficiency

A silicon carbide (SiC) T-type LCL inverter can achieve smaller device loss than two-level topology, however, its improvement on power density is limited by current ripple loss on magnetic components as switching frequency increases. This paper presents a five-level T-type (5LT2) photovoltaic (PV) inverter that achieves better utilization of SiC devices than the traditional three-level T-type LCL topology at higher switching frequency. The operation principle of the SiC 5LT2 PV inverter has been presented. The key design aspects including magnetic balancing, short-circuit protection, and digital controller computation time have been discussed and methods are developed. A 60-kW PV converter including boost stage and inverter stage has been built in the laboratory, which achieves a power density of 27 W/in3 and 3 kW/kg, and measured peak efficiency of 99.2%.

An LCC-Compensated Resonant Converter Optimized for Robust Reaction to Large Coupling Variation in Dynamic Wireless Power Transfer

In this paper, a reformed compensation network based on traditional LCL topology is proposed to realize robust reaction to large coupling variation that is common in dynamic wireless charging application. From the perspective of smoothing, the power characteristic against coupling factor and to achieve high efficiency simultaneously, extra reactive element is inserted into the resonant tank to provide higher degree of design freedom, forming the improved LCC type compensated inductive power transfer (IPT) system that features with distinct parameter design approach. Comparing to existing compensation topologies, the optimized LCC compensation topology shows more robust power characteristic against variation of coupling factor and, thus, minimizes the need for complex control which is usually undesired in dynamic charging scheme, thereby helping maintain effective power transfer in dynamic charging application and largely enhancing the systematic controllability. Finally, the effectiveness of the proposed method is experimentally verified. The power transfer profile is smooth against coupling factor to realize high tolerance to position as the power drop is no more than 20% within almost 200% of coupling factor variation.

An Inductance Voltage Vector Control Strategy and Stability Study Based on Proportional Resonant Regulators under the Stationary αβ Frame for PWM Converters

The mathematical model of a three phase PWM converter under the stationary αβ reference frame is deduced and constructed based on a Proportional-Resonant (PR) regulator, which can replace trigonometric function calculation, Park transformation, real-time detection of a Phase Locked Loop and feed-forward decoupling with the proposed accurate calculation of the inductance voltage vector. To avoid the parallel resonance of the LCL topology, the active damping method of the proportional capacitor-current feedback is employed. As to current vector error elimination, an optimized PR controller of the inner current loop is proposed with the zero-pole matching (ZPM) and cancellation method to configure the regulator. The impacts on system's characteristics and stability margin caused by the PR controller and control parameter variations in the inner-current loop are analyzed, and the correlations among active damping feedback coefficient, sampling and transport delay, and system robustness have been established. An equivalent model of the inner current loop is studied via the pole-zero locus along with the pole placement method and frequency response characteristics. Then, the parameter values of the control system are chosen according to their decisive roles and performance indicators. Finally, simulation and experimental results obtained while adopting the proposed method illustrated its feasibility and effectiveness, and the inner current loop achieved zero static error tracking with a good dynamic response and steady-state performance.

Analysis of the resonant LCL circuit operation: the case of discontinuous current

The article is focused on the analysis of the LCL resonant circuit, which operates under discontinuous input current condition. This condition leads to the LCL topology variability phenomenon what drastically changes Inverter-LCL system properties. The LCL topology variability phenomenon is precisely described. The analytical analysis presents formulae that express VSI-LCL converter features. The theoretical results are compared with laboratory tests. The concept of Controlled Variable Frequency Resonant Converter is presented and illustrated by simulation tests. The principle of CVFRC operation is based on the LCL topology variability phenomenon.

A Comparative Study of Power Supply Architectures in Wireless EV Charging Systems

This paper examines two of the primary power supply architectures being predominantly used for wireless electric vehicle (EV) charging, namely the series LC (SLC) resonant and the hybrid series-parallel (LCL) resonant full-bridge inverter topologies. The study of both of these topologies is presented in the context of designing a 3-kW primary-side controlled stationary wireless EV charger with nominal operating parameters of 30-kHz center frequency, a range of coupling in the neighborhood of 0.18-0.26, and a parallel secondary pick-up with partial series coil compensation. A comparison of both architectures is made in terms of their design methodology, physical size, cost, complexity, and efficiency. It is found that the SLC architecture is 2.45% less costly than the LCL topology. On the other hand, it is observed that the LCL architecture achieves almost 10% higher peak efficiency at rated load and minimum coupling. The study also showed that the SLC topology suffers from poor light load efficiency, while the LCL topology maintains very high efficiency over its full range of coupling and loading. The study also revealed that the capacitor voltage stress is significantly higher in the SLC topology. Finally, it is also shown that the control complexity of the SLC architecture is higher than that of the LCL architecture because of its sensitivity to changes in the reflected secondary impedance, which result in loss of constant current source and ZVS operation unless a suitable combination of parameters are modulated by the closed-loop controller.

LCL Filter Design and Inductor Current Ripple Analysis for a Three-Level NPC Grid Interface Converter

The harmonic filter for a three-level neutral-point-clamped (NPC) grid interface converter is designed in this paper with good filtering performance and small component size. LCL topology is selected because of the attenuation and size tradeoff. The design of the inverter-side inductor L 1 is emphasized due to its cost. A detailed inductor current ripple analysis is given based on the space vector modulation. The analysis derives the inductor volt-second and the maximum current ripple equation in line cycle. It also reveals the switching cycle current ripple distribution over a line cycle, with the consideration of power factor. The total system loss is calculated with different ripple current. Inductor L 1 is determined by the loss and size tradeoff. Also the capacitor- and grid-side inductor L 2 is designed based on attenuation requirement. Different damping circuits for LCL filter are compared and investigated in detail. The filter design is verified by both simulation and 200-kVA three-level NPC converter hardware.

Current controller for a bidirectional boost input stage equipped with an LCL (inductance–capacitance–inductance) filter

A control strategy for a low resonance frequency LCL (inductance–capacitance–inductance) filter used in the input stage of dc–dc bidirectional boost converters is proposed. When compared with the classical L filter, an LCL filter allows to obtain a cheaper topology. However, with an LCL topology, damping is needed for guaranteeing the system stability. In this paper an active damping strategy is designed. The needed damping is achieved via a dynamic controller. The controller consists of a simple PI (proportional-integral) controller plus a linear filter added in series with the PI integrator term. The modified PI controller achieves the active damping of the LCL filter and allows to arbitrarily place the system closed-loop poles. The proposed strategy only requires measurement of the variable to be controlled, the source current. Simulation and experimental results validate the proposed controller and show its effectiveness.

Investigation of fuzzy control based LCL resonant converter in RTOS environment

This paper presents a comparative evaluation of Fuzzy Logic FLC Controller and Open loop Controller for a modified LCL Resonant Converter has been simulated and the performance is analyzed. A three element LCL Resonant converter working under load independent operation is presented in this paper. In this work, the applicability of the ARM Advanced RISC Machine processor LPC 2148 is to be investigated as the controller for resonant converter. The simulation study indicates the superiority of Fuzzy Logic control over the conventional control method. The evaluation version of MATLAB was used to model the LCL topology for varied loads and LCL configurations. A LCL Resonant Inverter is proposed for applications in high frequency distributed AC power systems and Resonant Converter is proposed for applications in many space and radar power supplies. The advantages of the LCL topology are low total harmonic distortion THD high efficiency and the ability to handle varying loads.

Investigation of closed-loop performance for an LCL resonant converter in a real-time operating system environment

This study presents a comparative evaluation of proportional integral (PI) controller and fuzzy logic controller (FLC) for a modified Inductance-Capacitance-Inductance resonant converter. It has been simulated and the performance is analysed. A three-element LCL resonant converter working under load-independent operation is presented in this study. In this study, the applicability of the Philips Advanced RISC Machine (ARM) processor LPC 2148 is also investigated as the controller for resonant converter. The comparison study indicates the superiority of fuzzy control over the conventional control methods and these results are presented. MATLAB was used to model the LCL topology for varied loads and LCL configurations. The LCL resonant inverter is proposed for applications in high-frequency distributed AC power systems and resonant converter is proposed for applications in many space and radar power supplies. This study presents the design, simulation and experimental results for a 133-W, 50-KHz LCL resonant converter having efficiencies >89% down to resistive loads of 50%. Efficiencies >80% were obtained at significantly reduced loads (11%).

Harmonic Investigation and Simulation of Full Bridge LCL Resonant Inverter

This paper presents 250W, 20 KHz LCL resonant inverter having Efficiencies greater than 95% were obtained down to resistive loads of 50%. Efficiencies greater than 80% were obtained at significantly reduced loads (11%). Operation above resonance was utilized to increase the efficiency and maintain zero voltage switching (ZVS) for varied loads. Total harmonic distortion (THD) of less than 8% was achieved for all resistive loads. The above results were obtained from evaluation version of PSIM also used to model the LCL topology for varied loads and LCL configurations. A LCL Resonant Inverter is proposed for applications in high frequency distributed AC power systems.