Active Damping Technique Research Articles

Interferometric phase stability from Gaussian and space–time light sheets

The incredible phase sensitivity of Michelson interferometry has made it useful for a variety of metrology and sensing applications with the trade-off that it is also vulnerable to unwanted fluctuations in the sensing environment. Here, we demonstrate that Michelson interferometry using either Gaussian or space–time (ST) light sheets results in enhanced passive phase stability. Our experiments are absent of any active damping techniques. When using the ST light sheet, the interferometer exhibits 23% higher phase stability compared to the Gaussian light sheet (GLS), and 80% higher stability when compared to the Gaussian beam (GB). We find that while both ST light sheet and GLS exhibit significantly higher phase stability than the GB, ST light sheets have the added advantage of being resistant to speckle generation when a thin diffuser is inserted in the interferometer. Additionally, we show that interferometry using the ST light sheet results in approximately 11× more accurate measure of an oxide thickness on the substrate than the Gaussian beam. Our findings provide a simple approach to improving the stability of optical interferometry for applications, such as high-precision length measurements, enhanced sensing, and quantum optical experiments.

Optimization of LCL Filter Grid-Connected Inverters

The increasing use of grid-connected inverters in power systems, driven by renewable energy growth and high-voltage, high-power open-loop devices, poses challenges due to PWM modulation generating harmful high-frequency harmonic currents. Optimizing parameter selection becomes crucial.LCL grid-connected inverters, as third-order systems, suffer from insufficient damping, leading to oscillations. Active and passive damping techniques are employed for effective control. The optimization process involves analyzing the fundamental principles of LCL filters, selecting space vector modulation for PWM. Design focuses on controlling current ripple within limits by considering LCL filter parameter constraints.A comparison of passive and active damping methods favors a current dual-loop control system. Simulation models evaluate system performance, confirming successful implementation of the optimized design.

Improved Voltage Regulation of PV System With Current-Sensorless Active Damping Technique

Due to changing environmental conditions, mainly irradiance, photovoltaic (PV)-interfaced converters inevitably switch between continuous conduction mode and discontinuous conduction mode. Two modes present significantly different characteristics. Moreover, the dynamics in each mode is also dependent on the operating point. This article focuses on the system dynamics and proposes a new control scheme in the voltage-mode framework that enables the mixed conduction mode operation with consistently fast and null overshoot performance. A single control law is made possible for the entire operating range without complex adaptive mechanisms owning to the PV voltage feedback active damping technique. The controller tuning is designed to meet the desired settling time specified by the MPPT requirement. The advantages are validated with numeral simulations and experimental results in comparison to various available control proposals.

Multi-input multi-output sliding-mode control of LCL-based grid-connected modified Y-source inverter for power conditioning of photovoltaic generation

A multi-input-multi-output (MIMO) sliding mode controller has been proposed in this paper in order to control a grid-connected photovoltaic (PV) power conditioning system with an LCL filter. In the proposed control approach, nonlinear-control method is used and simultaneous control of both the AC and DC inverter sides is done. Therefore, all the state variables are controlled simultaneously. The proposed sliding mode control (SMC) method provides several advantages, including zero grid current error, easy implementation, and robustness against parameter uncertainties of the investigated system. Hence, the resonance in the inverter output resulting from the LCL filter can be eliminated using SMC with no need for active damping techniques. Applying this approach can bring about maximum power point tracking (MPPT), control of the DC side, and injection of high-quality current into the grid at the AC side of the inverter. Various simulations have been conducted in MATLAB/Simulink for the proposed system.

Speed/Torque Ripple Reduction of High-Speed Permanent Magnet Starters/Generators With Low Inductance for More Electric Aircraft Applications

With the electrification trend of future aircraft, high-speed permanent magnet starters/generators (PMSs/Gs) will potentially be widely used in onboard generation systems due to their high power density and high efficiency. However, the per-unit reactance of such high-speed machines is normally designed to be very low due to limited onboard power supply voltage and large electrical power demand, which can result in large current ripples in the machine and thus large torque ripples especially when the machine is fed with a semiconductor-based inverter of a lower switching frequency. The torque ripples may further lead to speed oscillation and generate severe vibrations and noises that are harmful to the mechanical system and human beings around. In this article, a speed/torque ripple reduction method for high-speed PMS/Gs with a low inductance is proposed to improve their performance within a wide speed range. An active damping technique is applied to the speed loop to increase the anti-disturbance capability and generate a smoother reference for the current loop, whereas an adaptive output voltage saturation limit is utilized for the current loop to limit the peak value of current to prevent overcurrent and torque spikes. The parameter tuning criteria are derived through a thorough analysis. Finally, the proposed method is validated on a high-speed PMS/G with an inductance of 99 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{H}$ </tex-math></inline-formula> . The results show that the speed ripples and torque ripples are reduced by over 50% within a speed range of 2–14 krpm.

Analytical approach to suppress the vibration of spur gear pair using particle damping technique

Vibration and noise have annihilated effect on the mechanical systems. These two are main adverse parameters leading to many undesirable effects lead to fatigue and failure of the machine decreased reliability, energy losses and degraded performance. Vibration damping is reactive vibration control method. Passive and active damping techniques are used to reduce the resonant vibrations. Theory of energy dissipation mechanism is followed by particle damping and is one of the passive vibration control technology. Particle damping, an impact mass is attached contains number of particles. The dissipation of loss of vibrational energy will occur due to impact, friction and change of energy. Damping is an effect of reducing, preventing its oscillations. Particle impact dampers are used to decrease the undesirable vibration in automobile industries, robots aerospace industries, gear box, etc. like engineering applications. This paper focused on the particle damping technology to reduce the vibrations generated in transmission spur gear. The model is developed which have cavity or holes in which particle dampers are present; it decide the relation between friction coefficient of the particles at constant rotational speed, various particle size. In present research damping particle of different sizes are selected to study the effect on damping using modal analysis. We found that, at the low or minimum speed, small and edgeless particles have good damping impact and at fast speed, more unpleasant and irregular particles are even better. It is observed that, the particle size and damping effect are directly proportional. This reduces the noise and harshness in system and ultimately improves the quality performance and life of the gearbox.

Multi-Sampled Grid-Connected VSCs: A Path Toward Inherent Admittance Passivity

This article investigates the capability of multi-sampled pulsewidth modulator (MS-PWM) control to improve the input admittance properties of voltage source converters (VSCs). Due to delays found in digital control systems, the VSC admittance features a negative real part above a certain frequency, which may result in lowly damped or even unstable grid dynamics. To prevent the occurrence of harmonic instability, recent standards require the admittance of every grid-connected VSC to behave as a passive network. In this article, it is shown that the MS-PWM control significantly improves passivity measures by reducing the overall system delay. The passive behavior is achieved effortlessly, using a single-stage control loop. This avoids the need for passive or active damping techniques, which are associated with increased losses and number of sensors, sensitivity to noisy measurements, ambiguity of damping filter design, and overall system complexity. The experimental verification, performed on a two-level single-phase VSC, shows a very good match between admittance measurements and analytic modeling even above the switching frequency. Grid-connected operation is tested to demonstrate the improvement of resonance damping obtained with MS-PWM control.

A Nonlinear Adaptive Backstepping Controller for Stabilizing the DC Bus Voltage of an Islanded Hybrid Microgrid

A bidirectional interlinking converter (BIC) interconnects the ac and dc buses of a hybrid microgrid (HMG). Under certain operating conditions, the BIC may appear as constant power load to the dc bus causing low-frequency oscillations in it. This instability is observed during the power flow from dc to ac buses and is attributed to an interaction between the input and output impedances seen at the point of interface. In this article, an active damping scheme based on an adaptive backstepping controller (ABC) is proposed for the BIC of an islanded HMG to address the voltage instability in the dc bus. The proposed scheme can be easily integrated with a conventional backstepping controller and an attractive feature is its ability to disengage itself from the ac voltage controller of the BIC as soon as voltage oscillations in the dc bus die out. Thus, the active damper does not deteriorate the ac voltage quality at steady state. The proposed method uses fewer current sensors as compared with a recently reported active damping technique based on predictive control. Typical of a backstepping controller, large signal stability is ensured while deriving the control and adaptation laws. Experimental validation is included.

Passivity-Based Design of a Fractional-Order Virtual Capacitor for Active Damping of Multiparalleled Grid-Connected Current-Source Inverters

Current-source inverters (CSIs) have advantages, such as voltage boosting capability and direct current controllability, in high-power conversion applications with low switching frequency. However, inadequate damping of the passive <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$CL$</tex-math></inline-formula> filter gives rise to low-order harmonic resonance. The recent research regarding active damping techniques generally focuses on resonance mitigation of single grid-connected inverters. However, multiple resonances that arise from dynamic interactions among paralleled grid-connected inverters compromise system stability and power quality. This article presents the delay-dependent passivity-based analysis and design of a lossless fractional-order virtual capacitor for resonance damping of multiparalleled grid-connected CSI-based systems. Fractional-order capacitors provide a higher degree of freedom that enhances the frequency behavior and robustness of the control. Simulation and experimental results demonstrate the effectiveness of the proposed active damping control even with variations in the grid impedance and the number of paralleled CSIs.

Active power decoupling for differential boost inverter with linear and nonlinear loads using inverse model approach

In this paper, a novel control system structure is introduced for generating a sinusoidal wave on the differential boost inverter terminals using inverse model approach. To address the high-frequency resonance issues, an active damping technique is proposed. Proportional-resonant controllers are designed for tracking and harmonic rejection. Pulling direct and constant current from photovoltaic panels as the DC source is essential in maximum power point tracking. Therefore, a decoupling controller is utilised to suppress current oscillations. An innovative combination of tracking controller, harmonic rejector, and decoupling controller is proposed in order to provide a sinusoidal voltage output for linear and nonlinear loads with low total harmonic distortion. The proposed method reduces the number of controllers by half compare to conventional methods. In addition to simulation, experimental results show the effectiveness of the proposed method.

Nonlinear damping of auxetic sandwich plates with functionally graded magneto-electro-elastic facings under multiphysics loads and electromagnetic circuits

This work addresses the damped transient response of smart sandwich plates subjected to coupled/multiphysics loads. The plate is made of an auxetic core with magneto-electro-elastic functionally graded (MEEFG) facesheets. The well known active constrained layer damping (ACLD) technique making use of the piezoelectric (PE) patch also known as1-3 PZC layer embedded on the viscoelastic (VE) layer is adopted to attenuate the vibrations. A finite element (FE) based approach has been adopted in order to derive the governing equations. Further, the solutions to the considered problem are obtained by adopting the direct iterative method. The primary focus of this work is to evaluate the effects of the auxetic core's rib-length ratio, inclination angle on the damped structural response, which has been carried out for the first time in the literature. Also, parametric studies on the geometric and material properties such as thickness configuration of core and facesheets, ACLD patch positions, PE fiber orientation angle, control gain, functional gradation pattern, and gradient index have been carried out. Emphasize has been made to understand the impact of applying open and closed circuits associated with the rest of the parameters, on the controlled nonlinear behaviour of smart sandwich plates. The numerical results of this work make some major revelation about the implementation of auxetic cores in the smart structures, which make this work interesting.

An Improved Dynamic Control and Resonance Damping for Voltage Source Inverters in Microgrids Through a Novel Active Damping Technique

Microgrids have the potential to provide customers with improved power quality and reliability. However, there are technical challenges related to the operation and control of microgrids and the distributed energy source (DERs) that constitute them. Resonance caused by the low-pass filters connected to the voltage source inverters of the DERs is one of those issues in the operation of microgrids. This paper proposes a novel technique of Active Damping Algorithm (ADA) for resonance damping and improving the dynamic stability of a microgrid composed of multiple converter-interfaced DERs. The paper considers two cases; one is where the resistor and the filter capacitor are connected in parallel, and the other is where they are connected in series. The proposed active damping method is based on output current feedback with automatically calculated and adjusted damping coefficients to suppress resonance. The proposed method was verified through simulation and experimental tests carried out using PSCAD/EMTDS and an operational microgrid in Beijing, China. The results from both the experiment and simulation analysis showed that the devised method was able to achieve the intended target; where the filter resonance is effectively surpassed and the voltage and frequency dynamic responses are quite stable and within the acceptable range during large power changes in the microgrid system.

Vector Modulation-Based Model Predictive Current Control with Filter Resonance Suppression and Zero-Current Switching Sequence for Two-Stage Matrix Converter

This paper proposes a novel model predictive current control scheme for two-stage matrix converter. The switching frequency is kept constant by fixing the switching instant. The control strategy achieves to control source reactive power in the input side and output currents in the output side. In addition, the advantage of the proposed strategy compared with conventional model predictive control is firstly proved using the principle of vector synthesis and the law of sines in the vector distribution area. Moreover, a zero-current switching sequence is proposed and implemented to insure zero-current switching operations and reduce the switching losses. Furthermore, in order to suppress the input filter resonance, which is easier to be inspired by the model predictive control, compared with traditional control strategies, an innovative active damping technique is proposed and implemented. Finally, both simulation and experiment are implemented to verify the performance of the proposed strategy. The results demonstrate that the control system features both good steady and transient performance.

A Novel Predictive Control Method with Optimal Switching Sequence and Filter Resonance Suppression for Two-Stage Matrix Converter

This paper proposes a vector modulation-based model predictive current control strategy for a two-stage matrix converter. The switching frequency is kept constant by fixing the switching instantly. The control scheme controls the source reactive power on the input side and output currents on the output side. Besides, the advantage of the proposed strategy compared with conventional model predictive control is firstly proved using the principle of vector synthesis and the law of sines in the vector distribution area. Moreover, to ensure zero-current switching operations and reduce the switching losses, an optimal switching sequence is proposed and implemented. Furthermore, considering that the input filter resonance is easier to be inspired by the model predictive control, compared with conventional linear control strategies, an innovative active damping technique is proposed to suppress the input filter resonance. To assess the performance of the proposed method, simulation and experimental results are demonstrated, showing that the control system features both good steady-state and transient performance.

An Active Damping Technique for PI and Predictive Controllers of an Interlinking Converter in an Islanded Hybrid Microgrid

This article highlights a voltage instability when the bidirectional interlinking converter (BIC) of a hybrid ac-dc microgrid operates as a constant power load (CPL). The instability is attributed to the impedance interactions seen at the dc port of the BIC. The BIC is operated with two different controllers, viz., a PI controller and a model predictive controller (MPC). In order to avert the instability, prohibiting impedance interactions is proposed as a design objective while determining the bandwidth of the PI controller. However, since a flexible control over bandwidth is not available with MPC, an active damping technique is proposed to address the instability. The proposed technique works equally well for the PI controllers with fixed or predetermined bandwidths. An important feature of the proposed technique is that it does not interfere with the original objectives of the controllers, once the instability is addressed. The technique comprises only one tuning factor, which does not depend on the BIC's internal parameters. As a result, it can easily be implemented as a general stabilizing scheme in any BIC. The efficacy of the proposed technique is verified through simulations, frequency-domain impedance analyses as well as experiments on a laboratory prototype of the BIC.

Virtual State Damping for Resonance Suppression and Robustness Improvement in LCL-Type Distributed Generation Inverters

This article proposes a Virtual State Damping (VSD) plugin to output current controllers of distributed generation (DG) inverters. The VSD is designed to suppress the resonance usually present in LCL-type grid-connected DG systems, providing robustness to the control system against grid impedance uncertainties or variations. Typical active damping techniques apply an equivalence impedance model to design their structures. The proposed VSD has the advantage of not needing to take such analysis into account for its design, i.e., it is not dependent on the LCL filter's physical model. The VSD structure applies the model reference theory, and it does not require additional sensors for its implementation. The paper also presents the VSD design methodology and stability analysis. Real-time domain emulation (RTDE) results and 5kW lab-prototype experimental results demonstrate the effectiveness of the proposed technique.

Impedance-Based Stability Analysis and Design of a Fractional-Order Active Damper for Grid-Connected Current-Source Inverters

Due to its voltage boosting capability and current controllability, the current-source inverter (CSI) is a strong candidate for interfacing high-power photovoltaic (PV) systems with the utility grid. However, low-order harmonics from semiconductor switching or grid voltage give rise to resonance and render the converter unstable. Active damping techniques can modify the control algorithm to mitigate the resonance. However, digital control delays and grid-impedance variations complicate the active damping design and result in poor robustness. Notwithstanding recent research advancements, the technology of the CSI-based PV systems is still in its infancy, needing more attention to the control aspects. This paper proposes a fractional-order active damping control with a more tuning parameter for grid-connected CSI-based PV systems. A sound design strategy further has been presented for the fractional-order damper taking into account the digital control delay. The proposed active damper robustly mitigates the passive filter resonance and guarantees the power quality despite the grid-impedance variations. Simulation and experimental results demonstrate that the fractional-order active damper offers a superior response in comparison with a standard active damper.

Stability of Grid-Connected Inverter with LCL Filter

&lt;p&gt;The paper analyses oscillations in a single-phase grid connected inverter with the LCL output filter. Passive and active damping techniques are designed and compared by simulations. The inverter is controlled by a proportional resonant controller.&lt;/p&gt;

Active damping technique based on H ∞ controller for VSC under parallel compensation grid

Aimed at damping the high-frequency resonance (HFR) which exists in the voltage-source converter (VSC) system connected to the parallel compensation grid, an active damping method based on the H ∞ theory is proposed. Compared to the existing HFR damping methods, the H ∞ damping controller has the advantage of strong robustness, which means that the damping effect can be maintained when parameters of VSC system change. For obtaining the H ∞ damping controller, the design procedure of weight functions for the synthesis of H ∞ controller based on the requirements of HFR damping is investigated. Theoretical analysis and experimental results are given to verify the effectiveness and availability of the proposed active damping technique.

Experimental Validation of an Active Wideband SSR Damping Scheme for Series-Compensated Networks

Transmission network reinforcements are being undertaken to meet renewable energy targets toward a low carbon transition. High-voltage direct-current (HVDC) links and series-compensated ac lines are frontrunners in these developments. Although series capacitor installations can lead to subsynchronous resonance (SSR), HVDC links based on voltage source converters (VSCs) can be used to effectively damp SSR upon occurrence. An active damping technique to mitigate torsional interactions (TIs), a form of SSR, is presented. The damping scheme considers an active wideband filter to ensure positive damping in a wide range of subsynchronous frequencies. A state-space representation of the system has been formulated and eigenanalyses have been performed to assess the impact of the HVDC link on the TIs. A damping torque study for SSR screening is carried out, with results complemented with time-domain simulations to assess the accuracy of the small-signal models. The test system is implemented in a real-time digital simulator and connected to a VSC-HVDC scaled-down test rig to validate the damping scheme through hardware-in-the-loop experiments. The presented damping method exhibits a satisfactory performance, with time-domain simulations and laboratory experiments showing a good correlation.