Filter Inductor Research Articles

An inductor design method based on multi-objective optimized algorithm for LCL-type shunt active power filter

The application of pulse width modulation (PWM) technology will produce a high-frequency switching ripple. Generally, it is considered to filter it with an LCL filter to ensure the compensation performance of the shunt active power filter. According to the system requirements for ripple current suppression and maximum current tracking capability, this paper first optimizes the design of the filter inductance in the LCL. Then, aiming at the shortcomings of the traditional inductor design process that is complicated and cumbersome, with repetitiveness and difficulty to obtain reliable analytical solutions, a 4-dimensional visualization based multi-objective optimized algorithm is proposed, and the ternary function expression between each design goal and known independent variables is first derived and established. And then, through the visual programming of the 4-dimensional data field, the optimal solution set that meets the multi-objective design requirements is directly given, which is intuitive, clear, simple, and practical. Finally, according to the algorithm results, the corresponding inductance was wound and applied to a 50kVA three-phase four-wire active power filter prototype. The experimental results verified the feasibility and effectiveness of the proposed design method.

A Single-Phase Compact-Sized Matrix Converter with Symmetrical Bipolar Buck and Boost Output Voltage Control

The development of single-phase symmetrical bipolar voltage gain matrix converters (MC) is growing rapidly as they find their application in power systems for dynamic restoration of line voltages, high voltage AC–DC converters, and variable frequency controllers for many industrial processes. However, the existing trend in matrix converter technology is a buck–boost operation that has inherently serious issues of high voltage and current surges or stresses. This is a big source of the high voltage and current rating of semiconductor switching devices. There is also a problem of high ripples both for voltage as well for current, requiring large size of filtering capacitors and inductors. The non-symmetrical control of the voltage gain increases the control complication. A large count of operating transistors is critical regarding their cost, size, and power conversion losses, as the space and cost required by their gate control circuits are much larger than the size and cost of the switching transistors. Thus, in this research work, a new single-phase MC is introduced only employing six fully controlled switching devices, ensuring similar operation or outputs as is obtained from the existing topologies that require the use of eight or more fully controlled switching devices, and the reduction by two or more switching transistors helps to compact the overall size and lower the overall cost. The separation in its voltage buck and boost operation enables smooth control of the voltage gain through duty cycle control. The low values of the voltage and current surges reduce the power rating and losses of the switching devices. The flow of the current in the filtering inductor is kept unidirectional to avoid the current interruption and reversal problem once the operation of the converter is abruptly switched from inverting to non-inverting and vice versa. All these factors are comprehensively detailed through the circuit’s description and comparative analysis. Simulation and practical results are presented to confirm the effectiveness of the developed circuit topology.

Adaptive Neuro-Fuzzy Voltage Control for LCL-Filter Grid-Connected Converter

Inductance – Capacitance – Inductance (LCL) filter is a very attractive candidate for renewable energy system applications due to its high efficiency. High attenuation of the switching frequency harmonics, small size, low fee, and improving the overall harmonic distortion (THD). This paper presents how voltage is affected by increased loads or voltage sag. Therefore it is necessary to control it with certain controllers. The Adaptive Neuro-Fuzzy Inference System (ANFIS) is used as an intelligent controller, the voltage constraint as training data for ANFIS obtained from PI. The filter works in a good connection between the inverter and the grid and rewords unwanted harmonics from using the inverter. The mathematical models for the LCL filter are investigated. The proposed approach shows more effective results than previous performance for voltage controlling and harmonic reduction. It gives overshoot (0.5%), steady state error (0.005), settling time (0.03 sec), rise time (0.005 sec), and improving THD 8.67% to 2.33% by comparing these results of ANFIS respectively with the results of PI which gave(3%),(0.01),(0.2sec)and( 0.02sec).

DC-Link Voltage Constraint Strategy for DC Power Supply Film-Capacitor Drive System Based on Improved Model Predictive Control

DC-link voltage oscillation is a common problem that needs special attention in dc power supply film-capacitor drive systems. For this problem, an improved model predictive control method is presented in this article, which achieves system stability control by adding voltage stability constraint of dc-link in the cost function. First, the discrete predictive equations of motor current and LC filter voltage for permanent magnet synchronous motor are derived in this article. The system stability is proved by analyzing the system damping with voltage constraint in the meantime. The weight factor of the cost function based on exponential function is designed to accelerate the suppression of dc-link voltage oscillation in the dynamic process. Second, a full-order observer is designed for observing the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> filter inductor current, which is designed to reduce hardware costs. Third, an improved control set method is proposed to improve the steady-state performance of each control item in the cost function. Finally, a hardware platform based on DSP is built to verify the validity of the stability constraint scheme proposed in this article.

Parameter design method of grid-connected inverter microgrid system

LCL filter is widely used in three-phase voltage converters due to its superior high-frequency harmonic suppression ability. In this paper, aiming at the instability problem caused by the resonance peak of the impedance characteristics of the LCL filter third-order system, the relationship between the parameters of the filter inductance, damping resistance, and the harmonic suppression ability is deduced. The impedance analysis method is used to obtain the constraint conditions of the grid stability on the LCL parameters. Based on the stability criterion, a parameter design scheme of passive damping LCL filter is proposed. Finally, experiments are conducted on filters that conform to the proposed design method, and the simulation results verify the rationality and effectiveness of the design method.

Research on the Voltage Spike Suppression Strategy for Three-Phase High Frequency Link Matrix-Type Inverter

The problem of high-voltage spikes on the secondary side of a high-frequency transformer (HFT) in the commutation process of a three-phase high-frequency link matrix-type inverter (HFLMI) is studied. Considering the parasitic capacitance of MOSFETs, the mechanism of voltage spikes during HFLMI commutation is revealed. According to the characteristics of the topology, the later stage matrix converter (MC) is decoupled into two groups of conventional three-phase voltage type inverters by the de-re-coupling idea, and the space vector pulsewidth modulation (SVPWM) is carried out, respectively. The zero vector is inserted between two nonzero voltage vectors to accomplish smooth commutation for addressing the problem of voltage overshoot on the secondary side of HFT due to the switching of HFT leakage inductance and filter inductance to the same path. Due to the existence of parasitic capacitance, the voltage spikes caused by its resonance with the system’s stray inductance cannot be solved by optimizing modulation strategies. In order to further suppress voltage spikes, a flyback clamp circuit is proposed to absorb the leakage inductance energy. Ultimately, a prototype with a rated power of 200 W is developed for experimental verification. The results show that the peak efficiency of three-phase HFLMI with the flyback clamp circuit is 92.6% in the full power range, the voltage spikes on the secondary side of HFT are clamped to about 1.2 times the rated voltage, and all switches realize soft-switching.

Correction: Khowja et al. Integrated Motor Drive: Mass and Volume Optimization of the Motor with an Integrated Filter Inductor. Energies 2021, 14, 4564

The authors would like to replace [...]

A Contemporary Design Process for Single-Phase Voltage Source Inverter Control Systems.

This paper presents an overview of contemporary voltage source inverter control system design. Design begins with the theoretical considerations that lead to the creation of the system’s differential control law. This stage does not include scaling coefficients for the output voltage, output current, and filter inductor current. Following this, the inverter is modelled in MATLAB’s Simulink environment with an appropriate load and control system. If the resultant simulation provides satisfactory results, a hybrid system consisting of MATLAB’s Simulink and dSpace libraries with the MicroLabBox device is used to interface the simulation with an experimental hardware model in real-time. This allows the hardware plant and measuring traces to be validated. ControlDesk is used to scale the relevant coefficients. During the final stage of the design process, a microprocessor is programmed to control the inverter according to the dSpace simulation results. This requires new scaling values. Throughout every stage of the design process, too high a value of the modulation index disables the reduction of output voltage distortions. This paper details the entire design process for both single-input and multi-input control systems, explaining the scaling process and the required software. Such a modern design process ensures the shortest time between conceptualization and the final product.

DC-Link voltage control of a multifunctional PV-GCVSI to reduce VSI switching losses

ABSTRACT The reference input dc voltage of grid connected voltage source inverter (GCVSI) is altered in this article based on power (both active and reactive) injection from GCVSI for minimising inverter switching losses, and total harmonic distortion (THD) of grid current. If the GCVSI is exclusively used for actual power injection from the photo-voltaic (PV) system to the utility grid, the needed input dc voltage of GCVSI is twice the utility grid phase peak voltage. According to the literature, GCVSI is also used to compensate for power quality issues, and in these circumstances, the dc-link voltage value is determined by the maximum power injection of GCVSI. Under reduced load, and reduced power generation from the PV system, keeping maximum GCVSI input dc voltage reference causes extra voltage stress at GCVSI switches, and the grid current THD is worse due to high ripple current in filter inductance. Therefore, to reduce the inverter switching losses and to improve the grid current THD, the relationship between the GCVSI input dc voltage reference and the power flow from GCVSI has been formulated. The proposed work is verified using simulation studies, as well as hardware studies, and the results are compared with existing methods for validation.

Direct Charge Control Method for Inverters in Discontinuous Conduction Mode

The discontinuous conduction mode (DCM) of the inductor current is an effective way to achieve high efficiency and high power density of inverters because it has the advantages of zero-current switching and small inductance of the filter inductor. Although the DCM can operate at a fixed switching frequency, there has been no linear model for realizing high-performance digital control. This paper provides a solution for this problem. Firstly, a linear first-order charge quantity model (CQM) for a DCM inverter with a fixed switching frequency is established, which uses charge quantities output by the inverter bridge as a control variable. Secondly, a direct charge control (DCC) method is proposed, and the design process is significantly simplified. Finally, the performance of the proposed control method is verified by the experiments using a 1 kW prototype, and a high-quality output voltage waveform with a peak efficiency of above 98% was achieved. The proposed method outperforms existing works because the CQM is a first-order linear model that realizes the high-performance digital control and significantly simplifies the design of controller.

More Enhanced Swing Colpitts Oscillators: A Circuit Analysis

In this paper, we show that an additional inductor–capacitor–inductor filter can increase the oscillation amplitude of the enhanced swing Colpitts oscillator (ESCO), and call this topology the more enhanced swing Colpitts oscillator (mESCO). When it is connected with a rectifier, the DC–DC boost conversion ratio can be increased, especially for low-voltage sensor ICs or energy harvesting. This paper focuses on the electrical characteristics of mESCO. The oscillation frequency was modeled as a function of the circuit parameters of mESCO. The common gate voltage gain (ACG), defined by the ratio of the drain voltage amplitude to the source voltage amplitude of the switching MOSFET of mESCO, was also modeled under the assumption that all the circuit elements are ideal. The model was validated with a SPICE simulation. For ACG &lt; 1.5, the model was in good agreement with the SPICE results within 10%. In addition, the drain voltage amplitude vda was modeled by assuming that the average transconductance of the MOSFET in a half cycle is null when the long-channel Shockley model is used. vda needs to be sufficiently high to have a large DC–DC boost conversion ratio. The model can predict the tendency that vda increases as ACG approaches unity. We found that the voltage difference of the drain voltage amplitude to the source voltage amplitude is a constant even when the circuit parameters, and thereby ACG are varied.

Minimum-Output-Current-Ripple Control of Current-Fed Three-Level Phase-Shift Full-Bridge Converter

Electrified ports using medium-voltage DC (MVDC) renewable energy microgrids require current-fed dc/dc converters in application scenarios such as battery or ultracapacitor charging units and hydrogen production systems. This paper designs a three-level phase-shift full-bridge (TL-PSFB) converter that interfaces with the MVDC microgrid. Its operation in the current source mode requires a wide output voltage range and small output current ripple. Firstly, the dual-output TL-PSFB topology is introduced, and the principle of phase-shift pulse width modulation (PS-PWM) is presented. Secondly, the principle of the traditional constant-conduction-duty-cycle (CCDC) strategy is analyzed. Then, a minimum-output-current-ripple (MOCR) strategy is proposed by analyzing the relationship between output current ripple, conducting-duty cycle, and phase-shift duty cycle, and a constant current control combined with the MOCR strategy is designed. The output current ripple of the MOCR strategy is smaller than that of the CCDC strategy in a full range of operating conditions. Under the same output current ripple design index, the value and loss of the filter inductor can be reduced with the MOCR strategy. In addition, the MOCR strategy can widen the output voltage regulation range and increase the bus voltage utilization without causing significant changes to the total harmonic distortion (THD) of primary voltage. Finally, experimental results verify the correctness of the theoretical analysis.

Active and Passive Reset Circuits for Multistage Magnetic Pulse Compression (MPC) Circuits Used in Gas Laser Applications

Magnetic pulse compression (MPC) circuits are commonly used in pulsed power circuits for powering gas lasers to shorten the duration of the pulse. If the core of every magnetic switch in the MPC is biased to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-\Delta B_{r}$ </tex-math></inline-formula> by a reset circuit, then the voltage hold-off time is doubled, and the cross-sectional area required is halved. Reset circuits must be isolated from the high-voltage pulses appearing in the pulsed power circuit using filters. The required filter (inductor) size becomes too large if the reset circuit is connected directly in parallel to the magnetic switches, especially if the volt-sec product across the filter inductor is large. The most common, existing reset circuits available in the literature directly connect in parallel to the magnetic switch ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$s$ </tex-math></inline-formula> ) and, therefore, require larger filter sizes to protect the reset circuitry. In addition, reset circuits cannot always be wound on the magnetic core to create a step-down transformation of the pulsed power voltages (lack of physical space or the use of a single primary winding). This article proposes a new reset circuit topology which resolves these problems by enabling the use of the smallest possible filter size (inductance value). In addition, only a single reset circuit is needed to reset multiple magnetic switches in the MPC network. An active reset circuit is also proposed which is more suitable for resetting magnetic cores that are relatively harder, i.e., requiring higher H values to saturate (equivalent currents greater than a few amperes). The reset circuits discussed in this article can in general be applied to many pulsed power applications employing MPC networks.

PWM Inverter with 4-Phase Carrier for Grid Connection Via Combined LCL Filter

A PWM power conversion system connected to a grid through parallel-combined LCL filter is proposed in this paper. The system has four inverters paralleled and operates with PWM using 4-phase carrier for powering up and performance improvement. Four LCL filters have four separate filter inductors connected to individual inverters and one common LC filter which is composed of a filter capacitor and a grid inductor. The differential mode current circulates only through four inverters and four filter inductors. The differential mode current is completely eliminated from the filter capacitor and the connected power grid. Accordingly, performance improvement can be achieved since the current in the filter capacitor is reduced and the harmonic current into a grid is reduced. An 1.3kW single phase prototype system has been constructed and tested, and the proposed system has been verified.

Novel Wind Power Grid-connection System Using Inductive Filtering Technology

Herein, a novel wind power grid-connection system based on inductive filtering is proposed to improve grid-connection compatibility, and is implemented in a 50-MW real system. First, the topology and wiring configuration of the proposed system are discussed. Thereafter, an equivalent circuit and mathematical model are established to reveal the filtering characteristics and resonance damping mechanism of the proposed system. Finally, a 50-MW wind farm-based experimental study, which is conducted to validate the effectiveness and availability of the system is discussed. The experimental results show that the main harmonics, power factor, voltage fluctuation, and flicker satisfy national standards.

Injected power control for grid-connected converter based on particle swarm optimization

Inductance–capacitance–inductance (LCL) filters are very attractive candidates for renewable energy system applications due to their high efficiency, high harmonic reduction, small bulk, and improved harmonic distortion (THD). These papers take advantage of the capabilities of renewable energy sources and inject them into the network by using an inverter when it enters work at high loads at certain times. Therefore, it is necessary to control power with certain controllers. The proportional-integral controller (PI) is used; conventional methods for tuning the controller parameters cannot give satisfactory performance due to the high instability of the closed-loop system. This paper presents the particle swarm optimization (PSO) method for tuning the controller's parameters to achieve optimum performance associated with sufficient stability margin. The mathematical models for the LCL filter and the frequency response were investigated by using the bode-plot. The proposed approach shows effective results for both power control and harmonic reduction. The proposed PI-PSO controller gives overshoot (1.08%), settling time (0.03 sec), rise time (0.00035 sec) and improved THD from 10.29% to 1.67% with compared to using the trial and error method, which gives (1.035%), (0.015) and (0.003) and THD from 10.23% to 1.575%, respectively.

Application of a Tuned Inductor in a DC Power Supply with an Active Compensation Function

This work focuses on the use of a one-phase direct current (DC) power supply equipped with a shunt active filter feature, which enabled the possibility of compensation (minimisation) of reactive and distortion power, generated by a group of loads, that was connected to the same power grid node as the power supply. A tuned inductor, which was included at the input of the controlled current source (constituting the main part of the power supply) allowed for an improvement in the quality of the compensation process, compared to a device with a fixed inductive filter This resulted in a visible reduction of the nonlinear distortions of the grid current. The improvement was made possible by extending the frequency response of the current source, which allowed to increase the dynamics of the current changes at the input of the power supply. This solution represents a new approach to such power devices. This work describes the principle of operation of the proposed converter solution and presents selected test results for a laboratory model of an electric system with this device.

A 380 V/50 kVar SiC-SVG Achieving a Power Density of 1.652 kVar/L With the Optimization of Heatsink and Output Filter Volume

With the rapid development of new energy vehicles, 5G facilities, electric aircraft, and new energy power generation, the high-power-density inverters are developed rapidly. A comprehensive optimization method combining heatsink and inductance filter was proposed in this article. Based on accurate thermal modeling and magnetic modeling, the method proposed chose an optimized switching frequency to minimize the volume of the inverters by compromising the design of the heatsink and inductor volume. Among them, a model of multichip forced air-cooling heatsink was proposed to reduce the size of the heatsink, and the comprehensive thermal resistance error of the proposed model is within 2%. The structure of the grid-connected filter and the inductor model is analyzed showing that the single inductor L-filter has a smaller size and more stability than the LCL-filter at a high switching frequency. The comprehensive optimization method proposed was implemented by 380-V/50-kVar SiC-static var generator (SVG) with the 50-kHz switching frequency, and its topology is a two-level inverter with a single inductor filter. This SiC-SVG reached a volume of 30.2 L (including all components required for mainstream products), which is 50% lower than insulated gate bipolar translator (IGBT)-SVGs. Its efficiency is 98.5% at full load, which is 1.5% higher than IGBT-SVGs. The experiments and temperature rising tests at full load proved the feasibility of the comprehensive optimization method.

A Voltage Spike Suppression Strategy Based on De-Re-Coupling Idea for the Three-Phase High-Frequency Isolated Matrix-Type Inverter

In order to solve the problem of high voltage spikes on the secondary side of the high-frequency transformer when the three-phase high-frequency isolated matrix inverter (HFIMI) operates under the conventional modulation strategies, a new modulation strategy is proposed without introducing an auxiliary circuit. In the proposed scheme, the H-bridge inverter adopts phase-shift control. The matrix converter (MC) adopts the voltage-type de- and recoupling idea, and the decoupled positive and negative group inverters are, respectively, applied with a modified Space vector pulse width modulation (SVPWM) strategy to operate synchronously with the H-bridge inverter. When the H-bridge inverter is in dead-zone mode, the switching tubes of MC are all turned <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> to provide continuous flow paths for leakage inductance and output filter inductance current and suppress high voltage spikes. The operating mode of the three-phase HFIMI under the proposed modulation strategy is analyzed in detail, the realization conditions for soft switching are designed, and the soft-switching ranges are also discussed. The feasibility and validity of the voltage spike suppression strategy are verified by building a 3-kW principle prototype. The experimental results show that the voltage spikes are effectively suppressed, all switches achieve zero-voltage soft-switching, and the peak efficiency of the three-phase HFIMI can reach 95.2%.

Simple and Seamless PWM Scheme of Isolated Bidirectional AC–DC Converter for Reducing Voltage Spike

This article proposes an improved modulation scheme based on unipolar sinusoidal pulsewidth modulation for a single-phase single-stage isolated bidirectional ac&#x2013;dc converter. A direct ac&#x2013;ac conversion system connected with a high-frequency transformer typically suffers from high-voltage spikes because of the leakage inductors of the high-frequency transformer and the grid filter inductors, resulting in reduced reliability and large power losses. The proposed modulation scheme can eliminate the high-voltage spikes in bidirectional power flow without the use of additional circuits while realizing zero-voltage switching. In addition, because the proposed method does not require individual gate control of the bidirectional power switches, the generation of gate signals can be simplified using the proposed modulation scheme. A simulation model and a 1.2 kW grid-connected ac&#x2013;dc converter based on silicon-carbide metal&#x2013;oxide&#x2013;semiconductor field-effect transistors are implemented to validate the effectiveness of the proposed modulation scheme.