Output Current Control Research Articles

Improving Inverter Output Current Controller Under Unbalanced Conditions by Using Virtual Impedance

Improving Inverter Output Current Controller Under Unbalanced Conditions by Using Virtual Impedance

A Minimum-Voltage Driving Amplifier with Adaptive Three-Stage Open-Loop Gain and Folded Cascade Class-AB Output Current Control

A driving amplifier capable of operating at a minimum voltage is proposed, aiming to subdue the distortion effect caused by large amplitude driving at the hearing aid loudspeaker. Since the linearity of a cascode amplifier usually degrades with the reduced supply voltage, a three-stage cascade amplifier having a parallel cascade second stage, and a folded cascade Class-AB output current control in place are designed. With such an arrangement, the open loop gain should still be maintained at a sufficiently high level even in the presence of increased output amplitude. Also, the minimum supply voltage required can then be reduced to merely [Formula: see text]. Fabricated on a 0.18[Formula: see text][Formula: see text]m complementary metal oxide semiconductor (CMOS) process, the proposed amplifier achieves [Formula: see text][Formula: see text]dB total harmonic distortion [Formula: see text] with a loudspeaker load of 100[Formula: see text]ohm while operating from a 1.2[Formula: see text]V supply and being subject to a 1[Formula: see text]kHz sinusoidal input.

A Constant Current Digital Control Method for Primary-Side Regulation Active-Clamp Flyback Converter

Constant current controlled flyback converter is widely used in low power applications for its simple structure and low cost. In order to further improve the output power and the efficiency, active-clamp flyback converter with soft-switching technique is always used. To avoid the nonlinearity and temperature drift of opto-coupler in the feedback circuit, a constant current digital control method is proposed for a primary-side regulation active-clamp (PSRAC) flyback converter in this article. Soft-switching technique is realized in discontinuous conduction modulation mode with a modified active-clamp technique. To compensate the nonlinearity of the secondary diode current with primary-side regulation, a new output current estimation algorithm is put forward based on the charge balance principle. The output current is predicted from primary current and the auxiliary winding voltage, and constant output current control is realized with primary peak current control method. The cost is low as only one low speed digital-to-analog converter, three comparators and a digital controller are required. The proposed control scheme was verified by a field-programmable gate array controlled 5.4-10.8 V/1.80 A PSRAC flyback converter. The output current accuracy is within in 1.2% in different input and output condition and the peak efficiency is improved by 3.6% after active-clamp technique is used.

A path-tracking algorithm using predictive Stanley lateral controller

Path tracking is one of the most important aspects of autonomous vehicles. The current research focuses on designing path-tracking controllers taking into account the stability of the yaw and the nonholonomic constraints of the vehicle. In most cases, the lateral controller design relies on identifying a path reference point, the one with the shortest distance to the vehicle giving the current state of the vehicle. That restricts the controller’s ability to handle sudden changes of the trajectory heading angle. The present article proposes a new approach that imitates human behavior while driving. It is based on a discrete prediction model that anticipates the future states of the vehicle, allowing the use of the control algorithm in future predicted states augmented with the current controller output. The performance of the proposed approach is verified through several simulations on V-REP simulator with different types of maneuvers (double lane change, hook road, S road, and curved road) and a wide range of velocities. Predictive Stanley controller was used compared to the original Stanley controller. The obtained results of the proposed control approach show the advantage and the performance of the technique in terms of minimizing the lateral error and ensuring yaw stability by an average of 53% and 22%, respectively.

Comprehensive Compensation Strategy on the Power Quality of Micro-grid Integration Based on the Multifunctional Energy Storage Converter

In order to improve the utilization rate of the energy storage system as well as the power quality of micro-grid and grid under parallel operations, this paper proposed an integrated compensation strategy of power quality based on the composite controlling principle of frequency division and hysteresis loops. On the premise of not changing the operation state of the power conversion system (PCS), combined with the current generation principle of multi-objective compensation, use the residual capacity of PCS to compensate harmonic, reactive and unbalanced currents quickly, accurately and selectively, so as to realize the current control on the compensation component of the grid-connected current under the disturbance of the distorted voltage. At the same time, aiming at the dwarf-signal dynamic models of the converter, use the designed output current control loop based on H ∞ resonance control theories to provide the tuning basis of the controller parameters, and thus the anti-disturbance ability of the system is improved, and the sudden change of the frequency is reduced. Finally, construct a micro-grid system with energy storage devices, and carry out experiments on the proposed control strategies. The results show that it has well governance abilities on the power quality.

Simulating Elliptic Low-pass Filter based on MOCCCII

Multiple output current-control current conveyer (MOCCCII) based Elliptic low-pass filter by using a simulating of RLC ladder prototype is presented in this work. The good performances of RLC ladder as well as low-sensitivity are inherited. Signal flow graph (SFG) method is applied to convert the RLC Elliptic ladder low-pass filter prototype to be the different function blocks. These function blocks can be realized by integrator and differentiator. Lossy integrator, lossless integrator and lossless differentiator realized from MOCCCII are straightforward replaced in SFG. Due to the tuning ability of MOCCCII, the proposed Elliptic low-pass filter can be tuned by adjusting the bias current (IB ). In addition, the frequency responses can be varied from 50kHz to 1MHz by tuning IB from 1μA to 100 μA to prove the electronic tuning performance of the proposed filter. The simulation results are carried out by PSpice that the performances are totally agreed with the theory.

Control strategies for seamless transfer between the grid-connected and islanded modes of a microgrid system

Design of control strategies for Distributed generation systems is very important to achieve smoother transition between the grid connected and islanding modes of operation. The transition between these two modes of operation should be seamless, without any severe transients during the changeover. In this paper, two different control strategies namely inverter output current control and indirect grid current control for the seamless transfer between the modes of operation has been explored for the suitability. The design and analysis of the cascaded control loops based on Proportional Integral (PI) controller has been dealt in detail for both inverter output current control and indirect grid current control strategy. Control parameters are designed using the control system toolbox in MATLAB. A 10kW grid connected microgrid system has been designed and simulated in MATLAB/Simulink and the results are presented under grid connected operation, islanding operation and the transition between the modes considering fault condition in the grid side. The simulation studies are carried out using both the control strategies and the results are presented to validate the design methodology.

Uncertainty and disturbance estimator with improved steady‐state performance for grid‐connected power converters

The study suggests a method aimed to improve the performance of practical grid-connected converters connected to distorted mains, utilising total uncertainty and disturbance estimator (TUDE) based control structures with time-delay filter. Such a TUDE filter enhances disturbance rejection performance by possessing near-unity magnitude and near-zero phase at integer multiples of the base frequency, imposing repetitive-control-alike behaviour. However, it is well-known that in repetitive control, disturbance rejection at mid-frequencies, were non-periodic disturbances and noise may exist, is deteriorated. This study presents an enhancement, allowing to retain good disturbance rejection at mid-frequencies within the low-frequency portion of control bandwidth (relevant in practical systems) while trading-off the performance in the high-frequency control bandwidth part. The proposed methodology is verified by application to output current control of LCL-filter based inverter feeding distorted AC mains. The validity and performance of the proposed methodology are well-supported by simulations and experiments.

Recent Advancements in Submodule Topologies and Applications of MMC

Modular multilevel converter (MMC) is a promising topology for medium- and high-power conversion systems. In recent years, it has been prominent over other power converters because of its exceptional features, including modularity and flexibility to adapt any voltage level, remarkable harmonic performance, no dc-link capacitors, transformerless operation, absence of ac-side filters, and capacitive nature of phase legs. However, there are some challenges, for instance, submodule (SM) capacitor voltage balancing, output current control, circulating current control, minimization of SM capacitor voltage ripple, dc-side faults, and efficient SM topologies that have been addressed by the research studies over time. In this article, we focus on the recent advancements in SM structures and their capability to overcome the faults, reduction in switching losses, decrease in voltage sensor count, and minimization of SM capacitor voltage ripple and provide the quick restoration of SM capacitor voltages after the removal of faults. Finally, the applications and development prospects of MMC are discussed in detail.

DC-link loop bandwidth selection strategy for grid-connected inverters considering power quality requirements

DC-link voltage and output current control loops are two cascaded loops in the control structure of grid-connected inverters. A high DC-link voltage loop bandwidth (DCL-BW) provides more disturbance rejection capability for the control loop and is preferred from control system perspective. However, for stability issues, this BW is limited and must be sufficiently less than that of the current control loop. Among the different control schemes, instantaneous active reactive control (IARC) method provides the highest possible DCL-BW (i.e., 0.02 × switching frequency). Having this degree of freedom in the controller design, a proper methodology should be defined for selection of DCL-BW. In this paper, different factors including the output current harmonic distortion, low-order harmonics on DC link voltage, and the inverter nominal rating are introduced as affecting parameters for DCL-BW selection. Accordingly, a DCL-BW selection strategy based on output current harmonic distortion is proposed. The proposed method enhances the power quality indices of the grid-connected inverters, which especially is useful for few kVA power inverters. Finally, to validate the conducted analysis, experimental and simulation results are provided.

Analysis and design of a multi‐channel constant current LED driver based on DC current bus distributed power system structure

The colourful light emitting diode (LED) strings require the corresponding driver to achieve independent control of each output current in the applications of RGB mixed colour LED lighting, LED projection etc. For this purpose, a multi-channel constant current LED driver based on DC current bus distributed power system structure is proposed and analysed here, which is composed of a source converter and several load converters as needed. The source converter adopts the flyback converter to realise power factor correction, electrical isolation, and the load converter adopts the current-type buck converter to realise independent control of the corresponding output current. A 60 W experimental prototype for 42.8 V/0.35 A, 40 V/0.5 A, 35.7 V/0.7 A three outputs with the universal input voltages 90–264 V is designed and implemented, and the experimental results are presented to verify the correctness of the theory analysis.

Redução da capacitância de barramento em driver para alimentação de LEDS

This paper presents the performance evaluation of control techniques for the reduction of capacitors in drivers for actuation LED.Through the active control of the driver output current, the ripple from the PFC stage of the current can be controlled, keeping itat levels appropriate to the technical standards, being IEC 61000-3-2 Class C and IEEE 1789. This control allows the outputvoltage ripple to vary at higher amplitude levels, allowing the use of a lower capacitance bus capacitor, therefore longer life usefuland reliability.The analyzed electronic system consists of the Buck-Boost converter was performed at the power control stagefor different bus voltages and output power. Different controller structures were analizes, in order to obtain an analysis of theinfluence of these controllers in the reduction of bus capacitance. Thus obtaining a greater ripple in the bus voltage, maintainingagreement with IEEE 1789 standard regarding current ripple limits on LEDs.

Simplified Input Voltage Sensorless Vector Control for PWM Rectifiers

A conventional input-voltage sensor-based vector-controlled PWM rectifier is used in wide range of applications due to its well-known control structure, simple design, and good dynamic performance. Many existing input voltage sensorless methods have a control structure significantly different from that of conventional vector control, involving additional computational and design efforts. This article proposes a simplified input voltage sensorless control which has the same control structure as that of vector control and can utilize similar controller design procedure. The input voltage required for a phase-locked loop (PLL) is estimated from the current controller output using a simple algebraic equation. The sensorless PLL, so obtained, is mathematically modeled, and its frequency response is shown to be similar to that of a sensor-based PLL. The performance of the proposed method is compared with those of existing methods in terms of input power factor, response to distorted input voltage, sensitivity to system parameter, and computation time requirement through simulations and experiments. Apart from having the lowest computation requirement, the proposed method is shown to achieve the sensorless operation without any performance degradation, compared to the sensor-based operation, and with robustness to parameter variation. The proposed method includes a start-up procedure, which ensures low starting transient current.

Artificial Neural Network based SVPWM for Five Level Cascaded H-bridge Inverter fed Grid connected PV System

An Artificial Neural Network (ANN) based Space Vector Pulse Width Modulation (SVPWM) for five level cascaded H-bridge inverter (CHBI) fed grid connected photovoltaic (PV) system. The multilevel inverter topologies are offers better performance compare conventional two level inverter like reduced total harmonic distortion, less electromagnetic interferences and voltage stresses across switches are low. The ANN based SVPWM generates the switching pulses for cascaded H-bridge inverter; it improves the accuracy in reference vectors tuning and identification, which leads to improve the inverter output voltage, better utilization of dc-link voltage and controlled output current. The ANN control makes the implementation of SVPWM becomes simple and minimizes the intricacy in tracking reference vector and calculation of switching time; it is suitable for any type of non-linear systems. This proposed system is energized using PV system and it is boosted using dc-dc boost converter, and the output of CHBI is synchronized with grid connected system using coupled inductor. The simulation and experimental results of ANN based SVPWM for CHBI is verified using simulink-matlab and DSP processor.

Power balanced control of rectifier permanent magnet generator sets

With the wide application of electric drive equipment and variable frequency load, the power supply system based on the DC grid has attracted much attention because of its high energy density and simple control, and the operation mode of rectifier AC synchronous generators operating in parallel is often adopted. The available topology structures of the rectifier permanent magnet (PM) generator sets are analyzed in this paper, the parallel operation principle of uncontrolled rectifier PM generator sets is analyzed in theory. The parallel operation characteristics of the generator sets are summarized when the voltage-stabilizing and power balanced measures are not taken, and the influence factors of power balancing among parallel operation generators are analyzed. The power-balanced method of rectifier generator sets operating in parallel based on a master-slave control strategy is proposed, which can realize power balanced with the closed-loop control of the DC side output current. The simulation and experiment results show that the proposed method can realize the power balanced control of rectifier generator sets operating in parallel well. The output power of each generator set can be distributed according to capacity. The rationalization proposal of how to matching generators’ parameters in the power supply system of rectifier PM generator sets operating in parallel is given.

Intelligent Control Method of Power Supply for Tundish Electromagnetic Induction Heating System

An intelligent control method is proposed to improve the performance of power supply for tundish electromagnetic induction heating, which can adequately regulate the tundish temperature. The topology structure of power supply for tundish electromagnetic induction heating is presented, and its working principle is analyzed. The power supply consists of six power units, and each of them consists of a fore-stage three-phase rectifier and back-stage single-phase inverter. The feedforward control DC voltage is used by three-phase rectifier to obtain the stable DC voltage supplied to the inverter. The cloud controller based intelligent temperature control algorithm is combined with the power feed-forward algorithm to obtain accurate tracking of the output current and constant temperature control of the tundish steel in the back-stage inverter. The simulation and experiment are performed to verify the accuracy and effectiveness of the proposed method.

Model Predictive Control of a Nine-Level Internal Parallel Multilevel Converter With Phase-Shifted Pulsewidth Modulation

Among various multilevel converter topologies, the nine-level internal parallel multilevel converter (9L-IPMC) stands out due to its capability to incorporate the advantages of both parallel modularity and active neutral point clamped converter. However, suppressing the circulating current and balancing the neutral-point voltage and six flying capacitor voltages while providing fast output current control is always a challenging task in 9L-IPMC. This is particularly true when the flying capacitor is small. This article proposes a model predictive control (MPC) scheme for the 9L-IPMC with phase-shifted pulsewidth-modulation (PS-PWM) to achieve these goals. By considering the high-frequency cell in 9L-IPMC as a whole, PS-PWM can be integrated into MPC scheme, and no parameter tuning process is required for the output current control. The internal circulating current suppression and flying capacitor voltage balancing are achieved by the flexibility of the inherent redundancy in 9L-IPMC. A thorough experimental evaluation of the proposed method has been conducted to validate the effectiveness of the proposed MPC scheme.

Stability analysis of modular multilevel converter based on harmonic state‐space theory

Modular multilevel converter (MMC) is regarded as one of the most potential topologies for high-voltage direct current transmission system. However, the multi-frequency behaviour and complex control structure of MMC bright great challenges to the stability analysis, identification of factors affecting stability, and controller design. To address this problem, the harmonic state-space (HSS) theory is applied to MMC in this study. First, the small-signal HSS model is established to describe the multi-frequency behaviour of MMC. Capacitor voltage control, circulating current control, and output current control are also taken into account in the modelling. On this basis, the stability analysis is performed by evaluating the eigenvalues of the HSS model, and participation factor is introduced to identify the factors affecting stability. In addition, the proposed approach reveals the influence of different controllers on the system stability, providing guidance for the tuning of multiple controller parameters. Finally, the effectiveness and accuracy of the proposed approach are verified by simulation and experiment results.

A fully-adjustable picosecond resolution arbitrary timing generator based on multi-stage time interpolation.

We report a fully adjustable arbitrary timing generator (ATG) that is based on a multistage time interpolation method. A 3 ps timing adjustment resolution is achieved using a three-stage time interpolation module. The output signal amplitude of the ATG is adjustable, as a current controlled output module is designed to adjust the output voltage of driver circuits. A field programmable gate array is used to realize the main logic of the ATG. A 3.2 ps short term jitter, a pulse width dynamic range from 6.25 ns to 5 s, and an output voltage range between -1 and +5 V are obtained. The arbitrary timing generator can be used in the applications that require high precision timing control and adjustable output capacity.

Control of Output and Circulating Current of Modular Multilevel Converter Using a Sliding Mode Approach

The modular multilevel converter (MMC) has been prominently used in medium- and high-power applications. This paper presents the control of output and circulating current of MMC using sliding mode control (SMC). The design of the proposed controller and the relation between control parameters and validity condition are based on the system dynamics. The proposed designed controller enables the system to track its reference values. The controller is designed to control both output current and circulating current along with suppression of second harmonics contents in circulating current. Furthermore, the capacitor voltage and energy of the converter are also regulated. The control of output current is carried out in d q -axis as well as in α β − a x i s with first-order switching law. However, a second-order switching law-based super twisting algorithm is used for controlling circulating current and suppression of its second harmonics contents. The stability of the controlled system is numerically calculated and verified by Lyapunov stability conditions. Moreover, the simulation results of the proposed controller are critically compared with the conventional proportional resonant (PR) controller to verify the effectiveness of the proposed control strategy. The proposed controller attains faster dynamic response and minimizes steady-state error comparatively. The simulation of the MMC model is carried out in MATLAB/Simulink.