Voltage Feedback Control Research Articles

Feedforward-Double Feedback Control System of Dual-Switch Boost DC/DC Converters for Fuel Cell Vehicles

DC/DC converters for fuel cell electric vehicles need not only high boost ratio and high efficiency, but also strong anti-jamming capability. Therefore, it is especially important to devise a control method with strong robustness under the premise of an appropriate topology. In this paper, a simple dual-switch boost converter topology is adopted. We use the state space averaging method to build a small signal model, and based on this model, we propose a feedforward-double feedback control system for continuous conduction mode (CCM) mode. Simulation and experimental results show that the proposed feedforward-double feedback control system improves the robustness of the system while ensuring a high boost ratio and efficiency, and solves the problem of weak output characteristics of fuel cells. The control effect is similar to the sliding mode control, which is known for its robustness, while the rise time of step response is only 1/10 of that of the voltage feedback control system. When the output voltage of the DC/DC converter is 55 V, the DC/DC converter using feedforward-double feedback control system is more robust than the voltage feedback control system under sudden change of load.

Three-loop Control Strategy of High Power Harmonic Voltage Generator Based on FFT

Voltage feedback control of the inverter, such as dual-loop control with voltage outer loop and current inner loop, the deadbeat control, RMS control and so on, can’t eliminate the steady-state error of the harmonic. In order to solve the above problems, this paper proposes a three-loop control strategy based on FFT. On the basis of the dual-loop control system with good dynamic performance, the FFT outer loop is added, which controls the real part and the imaginary part of each harmonic respectively in spectrum to eliminate the static error. The simulation results and experimental results show that the control algorithm not only has high dynamic performance, but also can eliminate the harmonic tracking error.

Imbalanced Load Regulation Based on Virtual Resistance of A Three-Phase Four-Wire Inverter for EV Vehicle-to-Home Applications

As a new application area of electric vehicles, vehicle to home (V2H) recently becomes one of the most attractive research areas. In this paper, a three-phase four-wire inverter using four half-bridge legs is adopted to realize the V2H functionality. Such three-phase inverter acts as the grid-side ac/dc part of the battery charger. In order to deal with the imbalanced load, an independently controlled neutral module has been adopted to form the neutral line and provide the path for the zero-sequence current, together with split dc-bus capacitors. Each phase employs the independent sinusoidal pulse width modulation control with the virtual resistor paralleled with the load, namely, notch-filter-incorporated capacitor voltage feedback control, which damps harmonics around the resonant frequency at various load conditions. In addition, this paper quantifies the load imbalance versus the dc-link voltage oscillation and provides the guidance for the selection of the dc-link capacitance. Finally, a 10-kW three-phase four-wire inverter working at the V2H mode is built and tested, with the three-phase imbalanced load imposed to validate the proposed design and control strategy.

Stability and Small-Signal Analyses of the Dual Series-Resonant DC–DC Converter

The stability and small-signal analyses of the dual series-resonant dc–dc converter are investigated in this paper. The small-signal model of the converter is derived from the extended describing function analysis. Frequency-domain analysis is then employed to derive the small-signal transfer functions of the converter. This procedure establishes an insightful understanding about the effects of the converter parameters and operating conditions on the stability and transient behavior of the converter. The results are used to illustrate the development of the single-loop, voltage-feedback control scheme for the dual series-resonant dc–dc converter. It is demonstrated that the proposed control method enables the converter to regulate its output voltage in the case of abrupt changes in input voltage and output load, and it provides improvement in the transient response. An experimental prototype of the dual series-resonant dc–dc converter is built and the performance of the control scheme is experimentally evaluated by applying abrupt changes in the operating condition of the converter. Based on the experimental results, it is shown that the single-loop, voltage-feedback control scheme is effective in regulating the output voltage of the converter.

Optimized Use of PV Distributed Generation in Voltage Regulation: A Probabilistic Formulation

This paper proposes a probabilistic optimiz-ation strategy for optimized use of Photovoltaic (PV) generators in distribution networks voltage regulation. Probabilistic PV output scenarios are incorporated in a constrained optimal load flow planning analysis for a given distribution network to minimize a voltage deviation index indicative of the quality of voltage regulation. The proposed strategy utilizes the PV generators as capacitors and inductors, whose reactive power compensation is monthly scheduled in coordination with the high-voltage/medium-voltage (HV/MV) substation on-load tap changer setting. The proposed strategy does not rely on a communication infrastructure nor does it comprise feedback voltage control. Physical solar irradiance and ambient temperature measurements are used to demonstrate the effectiveness of the proposed strategy on two detailed North-American MV distribution networks (25 kV and 12.66 kV). The results are validated by two distribution load flow calculation algorithms: backward/forward sweep in a MATLAB script; and the harmonic load flow solver in OpenDSS.

Phase-Locked Loop Research of Grid-Connected Inverter Based on Impedance Analysis

In order to improve the phenomenon that a traditional phase-locked loop based on a double second-order generalized integrator (DSOGI-PLL) cannot track signal amplitude and phase accurately when the input signal contains DC components and high-order harmonics, the structure of a second-order generalized integrator-quadrature signals generator (SOGI-QSG) is modified. The paper establishes the impedance model considering the DSOGI-PLL structure of the inductor-capacitor-inductor-type (LCL-type) inverter grid-connected system adopting current control measured from the grid terminal in alternating current side, introducing voltage feedback control to enhance the stability of the system. Meanwhile, analyzing the influence of parameters on impedance according to the impedance model established preferable design parameters. The improvement in SOGI-QSG structure is good for PLL to lock the grid voltage phase more accurately and the retrofitting in control strategy based on the impedance is able to uplift the inverter output impedance phase which is conducive to system stability by increasing the phase margin of the system. The simulation in Matlab/Simulink is carried out to verify the effectiveness of the proposed control strategy.

Current Sharing in Multiterminal DC Grids—The Analytical Approach

This paper presents a new analytical approach for dc voltage control in dc grids. The control approach aims at improving the dc voltage droop control by generalized feedback which combines the local voltage signal available at the converter terminals with remote voltage signals at different locations in the dc system by means of communication. The main contribution is an analytical approach to derive the generalized feedback gain allowing to differentiating the system response for different converter outages. The goal of the system response is to share the power, in the event of disconnection of a converter, between the remaining converters according to a predetermined scheme. The local voltage feedback control is used for fast and reliable system response, and remote signals to achieve the goal. The analysis of the feasibility space the power shares is also presented, which is a direct function of the grid layout. Simulation results show the validity of the proposed control scheme.

Damping Optimum-Based Design of Control Strategy Suitable for Battery/Ultracapacitor Electric Vehicles

This contribution outlines the design of electric vehicle direct-current (DC) bus control system supplied by a battery/ultracapacitor hybrid energy storage system, and its coordination with the fully electrified vehicle driveline control system. The control strategy features an upper-level DC bus voltage feedback controller and a direct load compensator for stiff tracking of variable (speed-dependent) voltage target. The inner control level, comprising dedicated battery and ultracapacitor current controllers, is commanded by an intermediate-level control scheme which dynamically distributes the upper-level current command between the ultracapacitor and the battery energy storage systems. The feedback control system is designed and analytical expressions for feedback controller parameters are obtained by using the damping optimum criterion. The proposed methodology is verified by means of simulations and experimentally for different realistic operating regimes, including electric vehicle DC bus load step change, hybrid energy storage system charging/discharging, and electric vehicle driveline subject to New European Driving Cycle (NEDC), Urban Driving Dynamometer Schedule (UDDS), New York Certification Cycle (NYCC) and California Unified Cycle (LA92), as well as for abrupt acceleration/deceleration regimes.

Baseband simulation model of the vector rf voltage control system for the J-PARC RCS

Vector rf voltage feedback control for the wideband magnetic alloy cavity of the J-PARC RCS is considered to be employed to compensate the heavy beam loading caused by high intensity proton beams. A prototype system of multiharmonic rf vector voltage control has been developed and is under testing. To characterize the system performance, full rf simulations could be performed by software like Simulink, while the software is proprietary and expensive. Also, it requires much computing power and time. We performed the simplified baseband simulations of the system in z-domain by using free software, the Python control library. It seems to be beneficial for searching the parameters that the baseband simulation can be performed quickly. In this presentation, we present the setup and results of the simulations. The simulations well reproduce the open and closed loop responses of the prototype system.

Implementation of an Excitation Controller for an Impulse Motor-Generator

Three flywheel energy-stored impulse motor-generators (MGs) are used in the power supply system of HL-2A tokamak to produce short high-voltage or high-current pulse of desired parameters that are usually used for magnetic field coils and auxiliary heating equipment loads. The operation changing of these loads will cause disturbances in generator’s terminal voltage and the remarkable drop in MG’s rotating speed. This paper describes the implementation of an excitation controller using LabVIEW and CompactRIO for a 125-MVA impulse MG in power supply system of HL-2A/2M. Both a staged control strategy and digital PID algorithm built in LabVIEW are applied to the excitation controller that runs preciously in a 1-ms cycle to achieve voltage feedback control. The excitation controller, composed mainly of host computer and CompactRIO embedded reconfigurable system, is available to restore and stabilize terminal voltage in accordance with the desired voltage curves set by operators when pulsed loads and motor speed change quickly. It also implements real-time monitoring of the working condition and some electrical parameters of excitation system and communicates with central control system via Ethernet to either download discharge control files at time interval between two impulse discharges or upload waveform data generated in control process after a pulsed discharge. Engineering experiment results show that the use of excitation controller improves the voltage stiffness of the power supply system and provides the effective control of generator’s terminal voltage under the management of central control system.

Target Voltage Hysteresis Behavior and Control Point in the Preparation of Aluminum Oxide Thin Films by Medium Frequency Reactive Magnetron Sputtering

Aluminum oxide thin films were prepared by medium frequency reactive magnetron sputtering. The target voltage hysteresis behavior under different argon partial pressure and target power conditions were studied. The results indicate that the target voltage hysteresis loop of aluminum oxide thin film preparation has typical behavior of that for reactive sputtering deposition of compound films. The target voltage feedback control approach was applied to circumvent the hysteresis problem. The microstructure and chemical composition of the aluminum oxide thin films prepared at different target voltage control points were investigated by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and Auger electron spectroscopy. The results indicated that the prepared aluminum oxide thin films, which are compact and mostly amorphous, can be obtained with target voltage control point in the range of 25~35%.

Sensorless Control of Dual-Active-Bridge Converter with Reduced-Order Proportional-Integral Observer

When controlling a Dual-Active-Bridge (DAB) DC/DC converter, the high frequency terminal current is usually measured for use in the current feedback controller. In order to measure that current, a wide bandwidth sensor accompanied with high-speed amplifiers are required. Furthermore, a high Analog-to-Digital sampling rate is also necessary for sampling and processing the measured data. To avoid those expensive requirements, this paper proposes an alternative control method for the DAB converter. In the proposed method, the terminal current is estimated by a reduced-order proportional integral observer. A technique is also proposed to reduce the phase drift effect when the voltages at two terminals are not matched. Afterwards, a combined current feedforward—voltage feedback control system is developed to enhance the system dynamics and to regulate the output voltage. This control system needs only the information of the terminal voltages and no current sensor is required. Experimental results show that the observer can estimate the terminal current very quickly with the accuracy of more than 98 % . In addition, the output voltage is well regulated with a fluctuation of less than ± 2.6 % and a settling time of less than 6.5 ms in the presence of a 30 % load change.

A Novel Power-Voltage Control Strategy for the Grid-Tied Inverter to Raise the Rated Power Injection Level in a Weak Grid

The conventional power-current controlled grid-tied inverter suffers from interactive stability issues, including harmonic oscillations when connected to a weak ac grid, which limits the integrated power rating of distributed generators. To overcome preceding drawbacks, a novel power-voltage control strategy, based on the voltage feedback control of the inverter LCL filter capacitor, is proposed in this paper. A dynamic model of the inverter output impedance is developed in the rotating d–q frame. This model includes main circuit parameters, phase-locked loop (PLL) dynamics, and regulator parameters. Frequency characteristics of the output impedance, contrastive analysis between the conventional power-current strategy and proposed power-voltage strategy based on generalized Nyquist criterion are presented to show superiority of the latter in a weak grid. The impedance analysis proves the power-voltage controlled inverter can stably operate in a weak grid. The stability of the grid-tied inverter system remains unchanged with increasing PLL bandwidth and delivered power, thereby effectively raising the rated power injection level of the inverter in a weak grid. A low-power inverter prototype is built and tested in the laboratory. The simulation and experimental results verify the effectiveness of the proposed control strategy.

Modular Design and Analysis of Plasma-Driven System With Integrated Resonant Circuit and Capacity Expansion Mechanism

The study proposes a modular design of plasma-driven system with an integrated resonant circuit and regulation mechanism. This design is developed to increase the expansion capability of plasma-driven systems. In the study, step-up transformers are combined with resonant circuits as a hybrid resonant tank, which is then augmented with plasma loads as a module to provide expandable capacities for a system. Analysis of resonant circuit and connected modules is performed to find design parameters. Feedback voltage control and asymmetric pulse width modulation are meanwhile applied to stabilize the system and regulate the plasma generation. To validate this proposed method, the circuit hardware realization has been completed under different scenarios. Test results indicate that this proposed system produces a higher concentration of plasma with an expanded capacity, supporting the feasibility and practicality for plasma industry applications.

A Comparison between Voltage and Reactive Power Feedback Schemes of DFIGs for Inter-Area Oscillation Damping Control

Reactive power modulation of wind power plants is an effective way to damp inter-area oscillation in wind power penetrated power systems. For doubly fed induction generator (DFIG) based wind farms, there are two different ways to achieve reactive power modulation: one is via reactive power feedback control, and the other method is via voltage feedback control. While both of the control schemes are feasible, their effectiveness may differ, and there has not been a systematic comparison between them. This paper investigates the differences between these two feedback schemes for inter-area oscillation damping control. The principles of utilizing DFIG for damping control is introduced at first. Then, analytical techniques including the frequency domain analysis, μ -analysis and time domain analysis are used to systematically study the performance of the two control schemes against inter-area oscillation. The robustness of the control schemes with respect to the variety of system operation points is also studied. The results from this paper can provide an insight into the understatement of DFIG reactive modulation against oscillation and guidance for controller design.

Small-Signal Model of Voltage Source Inverter (VSI) and Voltage Source Converter (VSC) Considering the DeadTime Effect and Space Vector Modulation Types

This paper presents a modified small-signal model of a voltage source inverter (VSI) and a voltage source converter (VSC) that captures model nonlinearities such as deadtime and modulation effects that were not presented in the literature. Previous research has concentrated on developing compensation methods for these types of phenomena in a switching model, but very little on predicting them. In this paper, the small-signal model of the VSI in literature is used, and the different phenomena are then incorporated into the model to get a complete one. In addition, the effect of voltage and current feedback control is also analyzed. The output impedance of the VSI is derived with the modified small-signal model, compared to the conventional one and validated with switching model and experimental results.

Powering IoTs with a feedforward quasi universal boost converter energy harvester

This paper proposes a feedforward quasi universal converter for energy harvesters, and uses it to power IoTs (Internet of Things). A typical DC/DC converter uses voltage feedback control or current feedback control. It is difficult to meet its output voltage and power targets and have its input impedance stay as close to the output impedance of the energy source as possible. The proposed feedforward quasi universal converter allows the input/output parameters of the DC to DC converter in the energy harvester to loosely follow the variation of the energy source output parameters. It controls the DC to DC converter input impedance and output voltage/power to vary within a range that meets the design targets by either adaptively or manually adjusting the circuit parameters. It also allows a system designer to trade off precision for flexibility/simplicity in each unit of the harvester to achieve an optimum design. This paper uses a boost converter to present the feedforward quasi universal converter concept, discusses the cases that may cause overvoltage/overcurrent conditions, and provides the analysis for choosing proper design parameters to avoid them.

Voltage Stabilization in Microgrids via Quadratic Droop Control

We consider the problem of voltage stability and reactive power balancing in islanded small-scale electrical networks outfitted with DC/AC inverters ("microgrids"). A droop-like voltage feedback controller is proposed which is quadratic in the local voltage magnitude, allowing for the application of circuit-theoretic analysis techniques to the closed-loop system. The operating points of the closed-loop microgrid are in exact correspondence with the solutions of a reduced power flow equation, and we provide explicit solutions and small-signal stability analyses under several static and dynamic load models. Controller optimality is characterized as follows: we show a one-to-one correspondence between the high-voltage equilibrium of the microgrid under quadratic droop control, and the solution of an optimization problem which minimizes a trade-off between reactive power dissipation and voltage deviations. Power sharing performance of the controller is characterized as a function of the controller gains, network topology, and parameters. Perhaps surprisingly, proportional sharing of the total load between inverters is achieved in the low-gain limit, independent of the circuit topology or reactances. All results hold for arbitrary grid topologies, with arbitrary numbers of inverters and loads. Numerical results confirm the robustness of the controller to unmodeled dynamics.

Design of Solar Inverter Based on CPLD

In this paper, the design and implementation of complex programmable logic device (CPLD) based solar inverter which generates power of AC 110 volts is proposed. In this framework, the former adopt DC to DC boost convert circuit and the latter adopt bipolar full-bridge inverter, and then complex programmable logic device to control system is used. The system uses four solar photovoltaic modules with connection and then can generate 50∼80 volt of DC. The former DC to DC boost converter voltage and transfers circuit, we adopt pulse-width modulation (PWM) technology and the voltage feedback control to stabilize voltage at the value of 200 volt. The latter converter adopts bipolar sinusoidal pulse width modulation (SPWM) technology such that power cord arrives to 110 volt of alternating current output.

Single-Atom Switches and Single-Atom Gaps Using Stretched Metal Nanowires.

Utilizing individual atoms or molecules as functional units in electronic circuits meets the increasing technical demands for the miniaturization of traditional semiconductor devices. To be of technological interest, these functional devices should be high-yield, consume low amounts of energy, and operate at room temperature. In this study, we developed nanodevices called quantized conductance atomic switches (QCAS) that satisfy these requirements. The QCAS operates by applying a feedback-controlled voltage to a nanoconstriction within a stretched nanowire. We demonstrated that individual metal atoms could be removed from the nanoconstriction and that the removed metal atoms could be refilled into the nanoconstriction, thus yielding a reversible quantized conductance switch. We determined the key parameters for the QCAS between the "on" and "off" states at room temperature under a small operating voltage. By controlling the applied bias voltage, the atoms can be further completely removed from the constriction to break the nanowire, generating single-atom nanogaps. These atomic nanogaps are quite stable under a sweeping voltage and can be readjusted with subangstrom accuracy, thus fulfilling the requirement of both reliability and flexibility for the high-yield fabrication of molecular devices.