Digital Current Control Research Articles

A hybrid inductor‐current sensor with fast response and high accuracy using online calibration for high‐frequency BUCK DC‐DC converters

AbstractThis paper introduces a hybrid inductor‐current sensor with fast response and high accuracy using online calibration for 25 MHz BUCK DC‐DC converter. The proposed inductor‐current sensor combines the high accuracy of the senseFET sensing method with the lossless and real‐time response characteristics of the RC filter technique. Comparing to exist techniques, the proposed calibration scheme can make filter coefficient converge even in unsteady state, which improve its effectiveness in practical application. Moreover, the proposed inductor‐current sensor utilizes sample‐based senseFET‐based current sensing to offer calibration reference, which avoid the use of high bandwidth amplifier. Digital current balance control is seamlessly integrated into the 25 MHz 2‐phase digital adaptive time‐controlled (AOT) BUCK DC‐DC converter through the utilization of the proposed hybrid inductor‐current sensor. The 2‐phase BUCK DC‐DC converter is implemented in a standard 0.18‐µm CMOS process. After online calibration, proposed hybrid inductor‐current sensor outputs a full‐wave waveform with high accuracy and low propagation delay of only 9 ns in post‐layout simulation.

Constant On/Off-Time Digital Current Control and Design Methods in Three-Level Flying-Capacitor Boost Converters for Fast Transient and Voltage Balancing

Constant On/Off-Time Digital Current Control and Design Methods in Three-Level Flying-Capacitor Boost Converters for Fast Transient and Voltage Balancing

A Deadbeat Digital Current Controller Based on Parallel Disturbance Rejection Structure for SPMSM

A Deadbeat Digital Current Controller Based on Parallel Disturbance Rejection Structure for SPMSM

Implementation of a Digitally Controlled MOS based Tuned Reconfigurable Filter for High Frequency Applications

ith the advent of recent standard of high data rate communication standards, the systems need to meet the requirement of multi-frequency processing. Moreover to achieve backward and forward compatibility across communication standards, reconfigurable and tunable designs are preferred. This paper proposes a fully digital reconfigurable all pass filter (APF) with a tunable passband to meet such requirements. The reconfigurable APF is capable of band tuning using a digital current control source (DCCS) which uses a digital word count making it most effective and simple reconfigurable design than the already reported designs. This can be widely used in different systems, e.g., 5G receivers, radar communication, cyber security, sensor interfaces, etc. This APF is also connected to Schmitt trigger inverter for smooth communication. Moreover, the circuit is designed to be inductor less thus making the design area efficient and suitable for wide range of applications and systems. The proposed design is simulated using 65 nm GPDK CMOS technology that achieves a wideband range of 0.1-15 GHz and achieves a bandwidth of 12.6 GHz with a gain of 15.5dB with a time delay of 1.62ps. The static power consumption of the circuit is only 2.52mW.

Predictive deadbeat average model control for phase‐shifted full‐bridge DC/DC converter

Digital current control method is the mainstream method for high-power DC/DC converters. However, digital controllers require additional filters for noise suppression to ensure their proper operation in the complicated electromagnetic environment. The filtering processes coupled with the inherent time delays of digital systems significantly degrade dynamic performance. Thus, steady-state performance is improved at cost of dynamic performance in conventional current control. To solve the problems, this paper establishes a deadbeat average control model based on application of the oversampling technique for phase-shifted full-bridge (PS-FB) DC/DC converter and proposes a predictive deadbeat average model control method by incorporating predictive control into the proposed control model. Simulation and experimental results verify the effectiveness of the proposed control method in mitigating the contradiction between steady-state performance and dynamic performance in the digital system.

A Digital Current Controller Based on Active Resistance Term Feedback for SPMSM Drives

Improving the control performance of surfaced-mounted permanent magnet synchronous machine (SPMSM) drives, digital current controllers with active resistance term feedback (ARTF) based on an exact zero-order hold (ZOH) equivalent discrete SPMSM model have been developing. Derived from the ARTF structure, few approaches are developed to suppress the ARTF delay effect on the digital current controller. To fill this gap, an improved digital current controller with the proposed digital internal mode control current estimator is designed. In the proposed structure, the predicted current can be effectively utilized as the ARTF delay compensation and feedback of the current controller at the same time. Compared with other state-of-the-art digital current controllers with ARTF, the performance evaluation of dynamic response, disturbance rejection, and parameter robustness is originally carried out based on the exact ZOH equivalent discrete SPMSM model. Furthermore, the experimental results are able to fully verify the correctness of the proposed method.

A Simple Three-Degree-of-Freedom Digital Current Controller With Dead Beat Response for AC Machines

Since current controllers are implemented digitally, digital current controllers need to be established for pursuing high performance alternating current (AC) machine drives. Considering to enhance the dynamic response, disturbance rejection and stability both, this paper proposes a simple three-degree-of-freedom (3DOF) digital current controller. In the proposed structure, three needed coefficients have been theoretically designed, which stand for the dynamic response ability, disturbance rejection and rejection of the instability caused by machine parameters mismatch, respectively. In addition, the proposed 3DOF current controller can own dead beat response characteristic with one-step delay compensation. Experimental results validate the effectiveness of the proposed digital current controller in a AC machine drive test rig.

Digital Current Controller Design for SPMSM With Low Switching-to-Fundamental Frequency Ratios

High speed becomes an important development direction of permanent magnet synchronous machines (PMSM) for higher power density. However, with the reduction of the switching-to-fundamental frequency ratios (SFRs), the dynamic performance and robustness of the current controller deteriorate and even lead to instability. To address this issue, this article proposes a distinctive current controller designed directly in the discrete-time domain for PMSM, which combines two-degree-of-freedom internal model control (TDOF-IMC) with active damping. The salient feature of this controller is that from the point of directly assigning or optimizing the pole and zero coordinates, a distinctive current controller is designed. Specifically, the TDOF-IMC realizes the ability to arbitrarily arrange the pole–zero placement of the closed-loop transfer function, and, therefore, the current tracking response can be improved. The addition of active damping enhances the antidisturbance ability, and as a result, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> -axis current oscillations effectively at low SFR are getting weakened. On this basis, current control can achieve better dynamic response and robustness at the same time. Finally, simulation and experimental results validate the effectiveness of the proposed controller.

Digital Current Controller With a Novel Active Damping Design for IPMSM

Internal model control gets wide attentions in electric drives for its outstanding robustness. Underdamped oscillations however, always can be seen in the synchronous <i>d</i>- and <i>q</i>- axis components of the stator currents if without proper extra damping elements included, especially under the low sampling to fundamental frequency ratios. The reasons for these oscillations are analyzed in the discrete-time domain other than as usually done in the continuous-time domain. Following that, a distinctive active damping matrix is proposed for the current closed-loop control of interior permanent magnet synchronous motors (IPMSMs). As a result, the anti-disturbance capability is enhanced, allowing the oscillations, often seen in the <i>d</i>- and <i>q</i>-axis current components, suppressed very well. Compared with other damping methods, the typical PI structure is still retained, which is desired on the point of engineering view. At last, the analysis as well as the damping effectiveness is validated through experiments.

ВПЛИВ ПУЛЬСАЦІЙ НАПРУГИ ЖИВЛЕННЯ ЛІНІЙНОГО ЕЛЕКТРОДВИГУНА НА ПАРАМЕТРИ ПЕРЕХІДНОЇ ХАРАКТЕРИСТИКИ КОНТУРУ СТРУМУ БОРТОВОЇ АВІАЦІЙНОЇ СИСТЕМИ ПОЗИЦІОНУВАННЯ

A comparison of the parameters of the transient characteristics of the module-optimized closed-loop transfer current of the positioning system without taking into account and taking into account the deep pulse-width modulation of the supply voltage of the linear motor. Their essential difference on speed, overregulation, static error is established. A method of optimization according to the criterion of current circuit speed is proposed, which allows to realize its transient characteristic during a finite number of switching intervals of the pulse-width converter. The synthesis of a digital current loop controller is performed, it allows to realize its transient characteristic without over-regulation during a finite number of switching intervals. The results obtained are based on the transfer function of a pulse-width converter, which is a link in the current loop. It is obtained for the case of deep pulse-width modulation based on the statistical linearization of piecewise-linear modulation characteristics of the channels of the pulse-width converter model. The modulation characteristics are obtained as a result of the expansion of the latitude-modular voltage for multiple values of the control coordinate in the Walsh-Fourier series. The number of Walsh functions taken into account depends on the approximation error and the cutoff frequency of the system. References 11, figures 3.

A New Robust Digital Non-Linear Control for Power Factor Correction—Arc Welding Applications

A welding power source is commonly assimilated to a non-linear load. Arc welding market being in full growth, the resulting harmonic pollution is becoming an increasingly difficult problem to ignore. Therefore, the main purpose of this work is to define and implement the most suitable solution for power factor correction in a welding power source. Due to the high non-linearity of the electric arc, the current controller used to control grid current need to show high robustness. Consequently, this paper focuses on the digitization of a very robust Phase-Shift Self-Oscillating Current Controller (PSSOCC), which only exists in its analog version until then, to carry out this task. After quick descriptions of the entire energy conversion chain and the PSSOCC operation principle, a model of the digital PSSOCC is proposed. Then, the quality and the accuracy of the aforementioned model are evaluated and its operating limits are identified. Afterwards, the behavior of the digital controller is studied within a Power Factor Correction (PFC) regulation for several specific arc welding operating modes. Finally, excellent robustness of this new FPGA-based digital current controller, named DPSSOCC, is confirmed on a three-phase Vienna converter test bench.

One-Cycle Zero-Integral-Error Current Control for Shunt Active Power Filters

Current control has, for decades, been one of the more challenging research fields in the development of power converters. Simple and robust nonlinear methods like hysteresis or sigma-delta controllers have been commonly used, while sophisticated linear controllers based on classical control theory have been developed for PWM-based converters. The one-cycle current control technique is a nonlinear technique based on cycle-by-cycle calculation of the ON time of the converter switches for the next switching period. This kind of controller requires accurate measurement of voltages and currents in order achieve a precise current tracking. These techniques have been frequently used in the control of power converters generating low-frequency currents, where the reference varies slowly compared with the switching frequency. Its application is not so common in active power filter current controllers due to the fast variation of the references that demands not only accurate measurements but also high-speed computing. This paper proposes a novel one-cycle digital current controller based on the minimization of the integral error of the current. Its application in a three-leg four-wire shunt active power filter is presented, including a stability analysis considering the switching pattern selection. Furthermore, simulated and experimental results are presented to validate the proposed controller.

Robust Control of a Variable-Speed BLDC Motor Drive

This article deals with the design of a digital current control applied to a variable-speed low inductance brushless dc (BLdc) motor drive. A robust static full-state feedback control law is determined by means of a convex optimization problem, subject to linear-matrix-inequality constraints. The optimization is used to achieve a fast time response with reduced overshoot under the parametric variation. Results from a 5 kW/48 V BLdc motor prototype is used to validate the proposed approach with a superior performance when compared to two other control strategies.

ADC Quantization Effects in Two-Loop Digital Current Controlled DC-DC Power Converters: Analysis and Design Guidelines

This paper analyzes the presence of undesired quantization-induced perturbations (QIP) in a dc-dc buck-boost converter using a two-loop digital current control. This work introduces design conditions regarding control laws gains and signal quantization to avoid the quantization effects due to the addition of the outer voltage loop in a digital current controlled converter. The two-loop controller is composed of a multisampled average current control (MACC) in the inner current-programmed loop and a proportional-integrator compensator at the external loop. QIP conditions have been evaluated through simulations and experiments using a digitally controlled pulse width modulation (DPWM) buck-boost converter. A 400 V 1.6 kW proof-of-concept converter has been used to illustrate the presence of QIP and verify the design conditions. The controller is programmed in a digital signal controller (DSC) TMS320F28377S with a DPWM with 8.96-bit equivalent resolution, a 12-bit ADC for current sampling, and a 12-bit ADC for voltage sampling or a 16-bit ADC for voltage error sampling.

Highly Accurate Digital Current Controllers for Single-Phase LCL-Filtered Grid-Connected Inverters

Photovoltaic (PV) systems are the most promising technology for residential installation as an alternative source of energy. To interface the primary source of PV to the electrical grid, an LCL-filtered inverter is being broadly adopted due to its low volume compared to the L-filtered one and the superior ability to filter high-frequency harmonics. In this context, this paper proposes highly accurate digital current controllers for single-phase LCL-filtered grid-connected inverters. The proposed controllers are: Integral-single-lead, integral double-lead, integral double-lead taking into account the effect of pulse width modulation (PWM) delay and the proportional-resonant (PR). These controllers are different from the traditional Proportional-Integral (PI), Proportional-Derivative (PD), and Proportional-Integral-Derivative (PID). One of the novelties of this paper is the detailed, step-by-step procedure for tuning each parameter of the proposed digital controllers considering the dynamic behavior of the LCL filter. The proposed PR has a different and more straightforward tuning methodology than those procedures commonly found in the literature. Therefore, this paper is an attractive tool for a fast, accurate, and reliable way to tune digital current controllers for a single-phase LCL-filtered grid-connected inverter. The controllers were verified in the digital signal controller (DSC) TMS320F28335 while the power structure runs in a hardware-in-loop (HIL device). Results show the efficacy of the proposed controllers.

Design and implementation of a current controlled grid connected inverter for thermoelectric generator sources

This paper presents the digital implementation of a current controlled grid connected inverter for Thermoelectric Generator (TEG) sources. Considering the electrical characteristics of a TEG source, several important aspects that a designer has to consider in selecting the rating of power converters for the grid connected operation of TEG source are discussed. The closed loop control of a TEG fed grid connected voltage source inverter (VSI) requires line current control to regulate the power pumped into the grid. Considering the inverter, current sensor and line inductor models, a simplified method is espoused to determine the parameters of the digital current controller. An Altera Cyclone II FPGA board is used to implement the current control strategy in VSI fed with TEG power source. The proposed design approach is validated using simulations and experiments and verified with the time domain specifications.

Chaos in the switched reluctance motor drive employing digital speed and current control

Adjustable speed motor drives are among the most representative types of non-linear systems which can exhibit rich varieties of complex dynamic behaviours. This study presents the investigation of chaotic phenomena in the switched reluctance (SR) motor drive employing digital speed regulator and hysteresis current controller. For conducting stability analysis, a small signal discrete-time model of the SR drive has been derived and analysed for a range of control parameters. The simulation results of time-domain and frequency-domain analysis and phase portraits of the SR drive system are also demonstrated and discussed. Two influencing factors for chaotic behaviour in the SR drive system are identified and examined in detail: the feedback delay of the speed regulator and measurement imperfection from a rotary incremental encoder. For verification, an 8/6 pole 2.3 kW SR drive is employed in experimental tests. The bifurcation diagrams of the reference signal, waveforms of phase current, and the corresponding frequency spectra are recorded and illustrated for both normal and chaotic operations, which reveal the pattern of chaos exhibited from this type of electric drive system.

Design of Digital Control System for DC/DC Converter of On-Board Charger

Vehicle charging power supply is widely used because of its small size and portability. Aiming at the problems of slow dynamic response, subharmonic, oscillation and limited soft-switching range of phase-shifted full-bridge DC/DC converter, the paper proposed a modified PSFB converter by introducing clamp diodes at the primary side of the transformer to suppress voltage oscillation of the transformer’s secondary side. Also, digital peak current phase-shifting control and slope compensation are introduced to avoid subharmonic oscillation. Dynamic dead-time control technology introduced adjust the dead-time in different load ranges through the dead-time adjustment subroutine. Finally, an experimental platform of on-board charging phase-shifted full-bridge DC/DC converter is established. The experimental results show that the power supply eliminates subharmonic oscillation, achieves a wide range of soft-switching, improves the dynamic performance and antiinterference ability of the system, and optimizes the power efficiency.

A Single-Phase Transformer-Less Grid-Tied Inverter Based on Switched Capacitor for PV Application

In this paper, a transformer-less grid-tied single-phase inverter is proposed which is directly connected to the topology. The voltage across the leakage capacitor has the base frequency, which decreases the leakage current under the defined value in the standards. This inverter’s active switches are high- and low-frequency types. High-frequency switches control the inductor’s current. In addition, the low-frequency switches are synchronous with the grid and operate in the base frequency. Since no power electrolytic decoupled capacitor is utilized between the high- and low-frequency switches, the system’s total efficiency and lifespan are improved. The proposed inverter has the capability of stepping up/down the output voltage, making it suitable for operating in a wide range of voltages and also providing large range of powers to the grid. This topology is directly connected to the grid, without any output filter, leading to elimination of the losses caused by the filter and increased efficiency. In the proposed inverter, a digital current controller is employed to control the injected current to the grid. Furthermore, P&O algorithm is adapted to extract the maximum power from the input source. For proving the proposed converter’s performance, a 770-W prototype has been implemented and comprehensive experimental results are presented.

Multi-Resonant Indirect Digital Current Control Technique for Single-Phase Shunt Active Power Filters

This article proposes multi-resonant indirect digital current control technique for single-phase shunt active power filters. The main advantages of the suggested technique are simplicity, fast dynamics, low computational burden, and low current ripple. A straightforward design technique in the frequency domain is proposed to properly decide the controller gains and study its performance. Then, the digital implementation of the proposed control algorithm is presented, which lets implement it on a mid-range digital signal controller. Simulation and experimental results on a prototype system are reported to demonstrate the effectiveness of the proposed control system.