Inductor Current Research Articles

Optimization of Minimum Negative Current BCM Synchronous Buck Converter

Non-isolated DC-DC converters are widely used in renewable energy applications, such as the hybrid energy storage system (HESS), charging and discharging system of batteries and supercapacitors and the photovoltaic power generation. With the advantages of achieving zero-voltage-switching (ZVS), high efficiency and power density, low cost, and fast dynamic response, the converters operating in boundary current mode (BCM) have caught researchers' eyes recently. Taking the synchronous buck converters as an example, this paper briefly introduces the working principle and advantages of BCM converter realize soft switching. Firstly, it is pointed out that the phenomenon of circulating energy exists in the BCM converter. Then, the relationship between circulating energy and negative current is analyzed, and an optimal control strategy of negative current minimization is proposed to reduce the circulating energy. In the condition of realizing ZVS, negative current minimization not only improves the efficiency of the converter, but also reduces the ripple of inductor current to a certain extent. Finally, the experimental platform of 100 W synchronous buck converter is built. Experimental results validate that the optimal control of minimum negative current has good effect on improving efficiency of converter and reducing the ripple of inductor current.

Modeling and analysis of the LC filter-integrated quasi Z-source indirect matrix converter for the wind energy conversion system

A Quasi Z-Source Indirect Matrix Converter (QZSIMC) is proposed in this paper for Permanent Magnet Generator (PMG) based Direct Drive Wind Energy Conversion Systems (DDWECS) to enhance the voltage transfer ratio and also to control the output voltage under various loading conditions. The QZSIMC comprises three Quasi Z-Source (QZS) networks connected between PMG and load through a three-phase Indirect Matrix Converter (IMC). Two different PWM control techniques such as Carrier Based Pulse Width Modulation Technique and Modified Space Vector Pulse Width Modulation Technique are proposed to analyze the performance of QZSIMC. By changing the shoot through time period, the duty ratio of quasi Z-Source network can be increased which in turn increases the boost factor of both QZSIMC without affecting the efficiency of the converter. A closed-loop control system has also been designed to sustain constant parameters at the output. The proposed QZSIMC for PMG based DDWECS along with two different PWM Control Schemes are to be modeled using MATLAB/SIMULINK environment. To validate the simulation results, a 1 kW, 415 V, 50 Hz experimental setup with an FPGA SPARTAN-6 processor has been developed in the laboratory for QZSIMC and the results are investigated based on the parameters such as output voltage, output current, Switching Stress, Boost Factor, inductor current, capacitor voltage, Total Harmonic Distortion.

Energy efficient half-flux-quantum circuit aiming at milli-kelvin stage operation

Half-flux-quantum (HFQ) circuits are based on 0–π superconducting quantum interference devices (SQUIDs) and is one of the energy-efficient superconductor digital circuits. The bit energy is determined by the critical current I cn of 0–π SQUID, which can be easily tuned with the loop inductance and junction critical current. In this work, an alternative π–π–π SQUID is adopted to demonstrate HFQ circuits to simplify the fabrication process and enhance circuit energy efficiency. The properties of superconductor/ferromagnet/insulator/superconductor Josephson junctions (π-JJs) are measured with temperature dependence from 4.2 K down to 10 mK. HFQ toggle flip-flops (TFFs) are successfully demonstrated at frequencies of up to 6.7 GHz and 44.5 GHz at temperatures of 4.2 K and 10 mK, respectively. Comparing the HFQ TFF with its rapid single-flux quantum counterpart under the same fabrication process, it is anticipated that the HFQ TFF will exhibit approximately 70% reduction in both static and dynamic energy dissipation. This research establishes the foundation for developing cryogenic interface control and readout circuits for large-scale quantum computing in the future.

33kV cable connector failures due to shunt reactor switching by means of vacuum circuit breaker – A thorough investigation & mitigation analysis

Switching of (small) inductive currents by means of vacuum circuit breakers may lead to multiple re-ignitions. This is the result of the ability of the interrupter's quenching capability, which generates steep overvoltages that can stress the equipment insulation. Should no mitigation measures be applied, the equipment is exposed to a high risk of failure. In this paper, the findings and conclusions of a such a failure investigation and mitigation analysis are presented, referring to multiple cable connector failures in 33kV shunt reactor installations in the Netherlands.

Analysis of a DC converter working on a plasma arc

Introduction. The article is devoted to the analysis of a stabilized direct current converter operating on a plasma arc. Electroplasma technologies of the new generation cause the need to design workable systems that provide control of technological processes and their dynamic optimization in real time. The improvement of any electroplasma technology begins with the improvement of the operating parameters of the main element of plasma installations - the power source. Goal is to build and study a continuous model of a pulsed source of secondary power supply, which works on an electric welding and plasma arc. Methodology. In the work, a mathematical description of the converter was performed. The continuous model of the system is substantiated, taking into account its features, namely, the load (gas-discharge gap) is a source of voltage and dynamic resistance. The parameters of the constant part during circuit synthesis are determined: the components of the gain of the constant part, the relative signal coefficient of the current sensor and the PWM gain. Studies of the open system «power source - arc» have been carried out. Results. MATLAB objects were created - continuous mathematical models of the object in the form of transfer functions. The obtained transient characteristics for different options: «arc current - control signal» and « inductor current - control signal» showed that open systems are unstable. It was found that in the case of instability, the filling frequency of self-oscillations occurring in the linear mode is close to the frequency of natural oscillations of the circuit. The dependence of the module and the argument of the input resistance of the power part of the pulsed power supply with parallel capacitance to the electric arc and without it, which have matching frequency characteristics, is established. The circuit considered with the initial data adopted in this article has a frequency transfer coefficient of the same type as the first-order non-minimum-phase (phase-shifting) link. Frequency response graphs for the output impedance of the power unit show that this power unit is a broadband frequency-selective system with a bandwidth of B0.707 = 100 kHz. Originality. Expressions for the frequency transfer function, input and output resistance of the pulse voltage converter operating on an arc load were obtained by the method of averaging and linearization. The frequency amplitude and phase characteristics for the pulse voltage converter with an LC filter and the output according to the arc current and the choke current were studied. The transfer functions of the continuous model in terms of arc current and choke current at the specified parameters are the same, which must be taken into account when designing regulators. Practical significance. The frequency characteristics of the input and output resistances and transfer functions can be used when forming a technical task for designing a power source to assess the stability of the «pulse converter - arc» system and rational calculation of input filters.

A maximum power point tracking of a photovoltaic system connected to a three-phase grid using a variable step size perturb and observe algorithm

Purpose. The production of electricity from solar energy is necessary because of the global consumption of this energy. This article’s study is based on increased energy extraction by improving maximum power point tracking (MPPT). From different MPPT techniques proposed, the perturb and observe (P&O) technique is developed because of its low implementation cost and ease of implementation. Methods. A modified variable step-size P&O MPPT algorithm is investigated which uses fuzzy logic to automatically adjust step-size to better track maximum power point, compared with the conventional fixed step-size method. The variable step P&O improves the speed and the tracking accuracy. This controller is implemented on a boost DC-DC power converter to track the maximum power point. The suggested controlled solar energy system includes a boost converter, a voltage-source inverter, and a grid filter. The control scheme of a three-phase current-controlled pulse-width modulation inverter in rotating synchronous coordinate d-q with the proposed MPPT algorithm and feed-forward compensation is studied. Results. The photovoltaic grid-connected system controller employs multi-loop control with the filter inductor current of the inverter in the inner loop to achieve a fast dynamic response and the outer loop to control bus voltage for MPPT, the modeling, and control of three phase grid connected to photovoltaic generator is implemented in the MATLAB/Simulink environment and validated by simulation results.

An adjustable machine learning gradient boosting-based controller for PV applications

Traditional Proportional, Integral, and Derivative (PID) controllers are employed in most industrial control applications because they are simple and easy to implement. However, they are fallible and exhibit poor performance in complicated, non-linear, time-delayed systems, and noisy feedback loops. In photovoltaic systems applications such as maximum power point (MPP) tracking, PI controller performance in low irradiance levels, varying load conditions, and partial shading scenarios is considerably inefficient in tracking the corresponding reference current, which generates MPP and causes considerable steady-state error. Machine learning can be used with selective input/output data from the PI controller to build a model that has the ability to adjust in case of steady-state error. Thus, an adjustable Machine Learning Gradient Boosting-based (MLGB) controller with a PV module and a DC-DC boost converter is proposed in this work. To create the raw dataset, a PI controller was simulated, and the input/output signals were recorded. Data preprocessing, utilizing feature engineering and Shapley Additive Explanations (SHAP) values, was used to explain the dynamic behavior of each feature, the inter-feature dependability, and their significance with reference to the model output. Hyperparameters were tuned with cross-validation while the model was being created using the CatBoost method. To assess the adjustment of each feature to minimize the error, particularly for lower irradiance values, varying load conditions, and partial shading, a regression model was built. Using the MATLAB Simulink Environment, a complete system controlled by both the PI and the MLGB controller was developed and tested. A random irradiance level fluctuation profile, along with varying load and partial shading scenarios, was used to compare three controllers, namely the PI, conventional MLGB, and adjusted MLGB controllers, to see how they respond to rapidly changing environmental conditions. It has been proven through a thorough simulation analysis that the novel adjustable MLGB controller exhibits good tracking performance to follow the DC-DC boost converter's inductor current. When compared to the traditional PI controller, the new controller exhibits better results in terms of steady-state behavior and transient responsiveness in general, with a much lower mean (3.059E-03), median (1.908E-03), and RMS value (2.168E-02) of the signal error under various conditions.

Sequence-Admittance Measurement Method of Grid-Connected Inverter With Its Control System Disturbance

The impedance or admittance characteristics of the grid-connected inverter play an important role in its stability analysis. The traditional sequence-admittance measurement methods of the grid-connected inverter mostly rely on special admittance measurement equipment or adjacent grid-connected inverters for disturbance injection. Because of high hardware cost or inconvenience, the above methods are not suitable for price-conscious testers to some extent. To address the above issues, this paper proposes a sequence-admittance measurement method of the grid-connected inverter with its control system disturbance. Firstly, the sequence-admittance model of the measured grid-connected inverter when small-disturbance signal is superimposed on its modulation signal is deduced and the system equivalent circuit model is built. Then, the flow chart of the proposed sequence-admittance measurement method is designed. According to the injected small-disturbance signal, the output voltage and inductor current of the grid-connected inverter, the sequence-admittance characteristics in sub/super-synchronous frequency area can be obtained. The measurement process does not need the cooperation of external disturbance source, which saves costs and improves the measurement convenience. Finally, experiments verify the effectiveness of the proposed sequence-admittance measurement method.

New Control Method for Receiver-Side DC–DC Converter With Large Stability Margin and Fluctuation Suppression Toward DWPT System

Dynamic wireless power transfer (DWPT) system is applied to electric vehicles, medical treatment, communication and many other fields. Usually, a DC-DC converter is cascaded at the receiver side to suppress output fluctuation caused by mutual inductance change in the moving process. However, there occurs instability in some conditions in the system under conventional topology and control method. This work proposes a new control method based on dual buck-boost converter to handle the above two problems at the same time. It can, in theory, reduce the peak-peak and average values of DC inductor current, meanwhile, increase the converter efficiency. Also, it can improve the stability margin of the whole system. In this paper, we use a simulator to replace the actual DWPT system. Through the simulator, the WPT system can produce the same fluctuating output voltage as that under dynamic conditions to support experiment. The stability of the system is explored by constructing the small signal model of the system. Then, the effectiveness of the method is proved by simulation and experiment results.

Explicit Solution of Parameter Estimate using Multiparametric Programming for Boost Converter

This work proposes an approach to estimate the parameters of capacitance and inductance in a boost converter using an explicit solution. A multiparametric programming (MPP) algorithm is fundamental to the suggested methodology, which aims to develop parameters as explicit functions of measurements. In this method, the generalised mathematical model of the boost converter is discretised into an algebraic equation. The parameter estimation problem is then formulated and solved using Karush-Kuhn-Tucker. Finally, an explicit solution of estimate parameters such as capacitor and inductor is formulated as an explicit function of the inductor currents and capacitor voltage. Finally, the state variables of the boost converter are numerically obtained and used to test the capability of the proposed work. The results presented in this work prove the MPP algorithm can estimate the boost converter’s parameters, which can be extended to other power converters and filters.

Graph Theory-Based Sneak Circuit Analysis and Trigger of Semi-DAB With Parasitic Parameters

Parasitic parameters and dynamic sneak paths would lead to unexpected phenomena, exerting negative impacts on the reliability and safety of Semi-dual active bridge (S-DAB) DC-DC converter. Therefore, a graph theory-based sneak circuit characteristics analysis, trigger mechanism, and suppression method of S-DAB are proposed in this paper. The complete current-based sneak path modeling is obtained, combining both bridges via high frequency link inductor current. Then, the accurate sneak modalities are proposed and detailed, including high-order and first-order sneak operating modalities. Thus, the possible sneak circuit phenomena are detailed to explain the negative impact on operating characteristics, depicting the chaotic phenomenon caused by the dynamic characteristics of bus capacitance. Then, the trigger mechanism and timing are proposed and indicated in time series. Moreover, the suppression conditions are derived by optimizing modulation parameters and parasitic parameters. Compared with the previous researches, the modeling, analysis, and suppression of sneak operation are more detailed and general in this paper to improve the stability and reliability of S-DAB. Finally, experimental results verify the theoretical analysis. The variation range of converter output with proposed suppression method is reduced by 65.4%, and the bifurcation chaos can be suppressed effectively.

Second Harmonic Current Suppression and Dynamic Response Improvement for V2G System

Electric vehicles interconnect and interact with the grid bidirectionally through a vehicle-to-grid (V2G) system. In V2G, the output power on the AC side pulsates at twice the grid frequency 2 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> , which leads to the presence of a second harmonic current (SHC) on the DC side and reduces the reliability of the system. A bandstop filter (BSF) with a center frequency of 2 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> is introduced in the voltage sampling loop to suppress the SHC. A digital implementation of the BSF is proposed to apply at arbitrary frequencies, which avoids the cost increase and provides high simplicity and flexibility. An adaptive PI control method is further proposed to improve the dynamic performance, which adjusts the PI parameters in real-time according to the inductor current. A 3.5 kW V2G experimental prototype is built and tested to verify the feasibility and stability of the proposed strategies. The prototype offers an excellent dynamic and steady-state response in stand-alone and grid-tie modes.

A step-by-step full-order sliding mode controller design for standalone inverter-interfaced cleaner renewable energy sources

Power electronic inverters are one of the most significant components for the integration of clean energy systems and the proper control of these power electronic interfaces helps to enhance power quality. This paper presents a robust step-by-step full-order sliding mode voltage control strategy for standalone single-phase inverters that can be interfaced with cleaner renewable energy sources. The proposed controller employs a cascaded method through outer- and inner-loops to facilitate tracking of the desired load voltage. In contrast to the most commonly used sliding mode techniques for interfacing these cleaner energy sources, which usually utilize the canonical-form of the system’s state-space model, the designed controller uses a block-controllable model that mitigates unwanted noises. To design the controller, the capacitor voltage and the inductor current of the LC filter are measured to be employed in the outer second-order sliding mode voltage control loop and the inner first-order sliding mode current control loop, respectively. The utilization of such full-order sliding surfaces in each step effectively reduces the chattering in the control signals as well as facilitates the transient and steady-state responses with less harmonic distortion and thereby, promoting the effective integration of renewable energy sources. To verify the performance of the proposed controller under various loading conditions as external disturbances, a 2.2 kW standalone single-phase inverter is simulated using MATLAB/Simulink platform along with a microcontroller-based processor-in-loop through the digital signal processing. In terms of internal disturbances, the proposed controller is also tested under different filter parameters’ variations over a wider range. The results indicate a better alignment for coupling with clean energy sources and the comparisons with other control techniques show better performance of the proposed controller.

Multi‐input multi‐output converter for simultaneous buck and boost voltage conversion

SummaryInternet of Things (IoT) devices, portable electronics, and electric vehicle (EV) accessories have increased the need for DC power distribution with various outputs. Multiport converters (MPCs) handle numerous inputs and loads with fewer components, low power losses, and less cost. Most multi‐input converters are time‐shared and restrict the duty cycle's working range, limiting energy sources and output voltage. Single‐input multi‐output (SIMO) converters have inductor current and duty cycle limits. In this study, a dual‐input dual‐output (DIDO) converter is proposed to overcome the limitations mentioned above. It can operate multiple loads without restrictions on charging inductor currents and cross‐regulation problems. Any variations will not influence the proposed converter's output voltage VO1 (VO2) by the load current iO2 (iO1). To verify the feasibility of the proposed configuration, a 250 W laboratory prototype has been developed, and experimental results are validated.

Design and Analysis of Interleaved High-Gain Bi-Directional DC–DC Converter for Microgrid Application Integrated with Photovoltaic Systems

Solar photovoltaic (PV) connection with the grid becomes more prevalent in distributed generation, and the DC grid contributes a significantly to the distributing system. The current study focuses on combining rooftop solar with the DC microgrid. A high-gain DC–DC converter for photovoltaic systems (HGBC-PVS) is proposed in this article to link two lower-voltage photovoltaic panels to a higher-voltage network. The designed converter with low-rating switches generates improved values of voltage gain and efficiency. To gain the most power out of solar modules, Maximum Power Point Tracking (MPPT) is used, which employs the Adaptive Incremental Conductance approach. It extracts the maximum power, thereby facilitating efficient converter operation and generating optimal outputs. The simulation outcomes in terms of voltage, inductor current, output efficiency, and voltage gain are computed, and the outcomes show the significance of the introduced topology. The efficacy of the introduced work is proved by the comparison of measured outputs with the computed outputs for various parameters.

An Improved Asymmetric Modulation of Current-Source Rectifier With CM Filter for Low Voltage Stress on Switching Devices

Common mode (CM) filters are usually utilized in high power density three-phase current source rectifier (3ph-CSR) to suppress the CM noise in the input currents. However, when CM filters are utilized, the inductor currents at the positive and the negative ends of the DC side of 3ph-CSR are unequal, which brings high voltage stress on switching devices. To reduce the voltage stress on the switching devices, an improved asymmetric modulation is proposed in this letter. In the proposed asymmetric modulation, two switching devices are always turned on in each sector, which clamps the voltage of the switching devices to the peak of the input line voltages. A 1kW experimental prototype of the 3ph-CSR is built to verify the analysis results.

Minimizing Input Current Ripple for Four-Phase Input-Parallel Output-Series DC–DC Converter With Phase-Shift Modulation

This paper proposes a PWM scheme based on phase-shift modulation (PSM) for the four-phase input-parallel output-series (4P-IPOS) converter. And operation with dual-output configuration is investigated. The natural output voltages and inductor currents balancing can be achieved even without any extra components or dedicated control. In addition, compared with the conventional PWM scheme, performance improves. The input current ripple is reduced significantly at high voltage gain. An 800-W prototype of the 4P-IPOS converter was built and tested to verify the performance of the suggested scheme.

Analysis and Suppression of Rectifier Diode Voltage Oscillation Mechanism in IPOS High-Power PSFB Converters

Parasitic oscillations in the rectifier diode voltage of phase-shifted-full-bridge (PSFB) converters limit their application in high-voltage and high-power situations. The conventional analysis method for parasitic oscillation in rectifier diode voltage in PSFB converters treats the filter inductor as a constant current source and fails to consider the impact of changes in filter inductor current on the rectifier diode’s parasitic oscillation. Consequently, this approach does not apply when analyzing the rectifier diode voltage’s parasitic oscillations in high-power PSFB converters employing an input-parallel output-series (IPOS) configuration with interleaved drive. This research paper introduces an innovative equivalent circuit model for analyzing the parasitic oscillations of rectifier diode voltage in IPOS high-power PSFB converters. The model takes into account the mutual influence of rectifier diode voltage oscillations between submodules under interleaved control, considering the influence of changes in filter inductor current on rectifier diode parasitic oscillation. Based on the circuit model, we explain the mechanism of multiple oscillations of the rectifier diode voltage and the reason for the high peak of the first oscillation. Consequently, the interplay of rectifier diode voltage oscillations in IPOS high-power k-module PSFB converters under interleaved control is analyzed. To mitigate the adverse effects of rectifier diode voltage parasitic oscillation, a buffering strategy involving the connection of a resistor capacitor diode (RCD) circuit in parallel after the rectifier bridge is adopted, considering the structure of the IPOS high-power PSFB converter. The study provides a detailed analysis of the circuit’s operation mechanism upon incorporating the RCD buffer circuit and establishes the relationship between buffer capacitance, resistance, and spike voltage. Furthermore, a design method for buffer capacitors and discharge resistors in buffer circuits is presented. Finally, a 100 kW prototype is tested to verify the rectifier diode voltage oscillation mechanism of the IPOS high-power PSFB converter and the rationality of the buffer capacitor and discharge resistor design method under the interleaved drive approach.

A Current-Fed ZVS High Step-Up Boost Converter Integrated with Isolated SEPIC Converter

In this paper, the combination of a high step-up boost converter with extended voltage multiplier cell and isolated SEPIC converter with a series output module is presented. Since these converters use the same current source in their inputs, they can share the common parts, so the structure of the proposed converter is simple. In this converter, the high frequency transformer used in the SEPIC converter and the inductor of the extended voltage multiplier cell are coupled, so the volume of the magnetic parts is reduced. In addition, an active-clamp circuit is used to solve the problem of leakage inductor and achieve to Zero Voltage Switching (ZVS) turn on/off for switches and ZCS for diodes. Compared to its high step-up counterpart, the proposed converter has the following: (1) distributed voltage stress on the diodes and voltage of the output capacitors are fair. (2) Higher voltage gain. (3) Voltage stresses on the diodes are lower and the reverse-recovery problem of the diodes is eliminated. (4) Minimum root mean square (RMS) leakage inductor current. The operational principle and characteristics of the proposed converter are presented, and in order to verify the proposed converter, a 200 W, 20–400 V prototype converter is implemented and experimental results are provided.

Influence of Induction Heat Treatment Conditions on the Properties of Coatings Formed by Electroplasma Spraying

Porous titanium coatings were formed on titanium samples by electroplasma spraying, followed by induction heat modification in an air atmosphere at a processing temperature of 650–1250°C and a duration of 120 and 300 s. The layers formed by electroplasma spraying consisted of grains 9.9±0.5 µm in size. The coating composition included TiO, Ti2O3, and TiO2 (anatase) oxides formed as a result of interaction between titanium and gaseous medium (residual air atmosphere) in the installation working volume. After low-temperature thermal modification, the size of structural elements increased to 12.5±0.4 µm. The pore size decreased from 12.9±0.2 to 7.5±0.3&nbsp;µm at an inductor current of 7.6 kA, whereas the surface porosity remained at the level of 56–58%. The induction treatment of the coatings has led to an increase in the oxygen content in the coatings from 49.6±9.2 to 71.7±1.1 at % and the formation of an oxide layer on the surface, consisting of prismatic nanosized anatase and rutile crystals. High-temperature thermal modification has led to intensive growth and subsequent exfoliation of scale. Induction heat treatment has led to an increase in the microhardness of the coatings from 1530±55 to 1825±191&nbsp;HV0.98. The hardness of plasma-sprayed and low-temperature modified coatings was 82–88&nbsp;HRF. The highest value of this parameter was observed during high-temperature treatment, which amounted to 108–115&nbsp;HRF; in this case, the coating cracked during indentation, which is associated with the formation of a rather thick scale layer. As a result of static processing, regression models have been determined that describe the effect of temperature and time of modification of electroplasma coatings on the size of structural elements (grains, pores) and coating hardness.