Active Damping Methods Research Articles

A Current Controller Design for Current Source Inverter-Fed AC Machine Drive System

A current source inverter (CSI) requires a capacitor filter for the commutation of switching device as well as for attenuating switching harmonics. Hence, the CSI-fed ac machine has a second-order system in the continuous time domain. This paper presents a design methodology for the closed-loop current controller of the CSI-fed ac machine drive system. A multiloop current controller design using a pole/zero cancellation method is employed with a transfer function matrix. To decouple the cross-coupling terms which cause mutual interferences between the d- and q-axes in the synchronous reference frame, two types of controller are proposed and implemented using different decoupling method. Additionally, active damping methods are incorporated to enhance the stability of the system. A stability analysis in discrete-time domain is investigated to verify the feasibility of the proposed closed-loop current controller. To evaluate the effectiveness of the proposed current controller, computer simulations and experimental tests were performed and the results are discussed.

추가적인 센서가 필요 없는 3상 PWM 인버터의 LCL 필터 능동댐핑

In this paper, a new active damping method of LCL filter without capacitor voltage sensors is proposed for 3 phase PWM Inverter. Normally, L filter or LCL filter is used as an output filter of grid connected PWM inverter. An LCL filter has more excellent performance than L filter to reduce harmonic current, so the small inductance value can be used. However, the resonance problem in LCL filter is happen due to the zero impedance by the addition of LC branch. To solve the resonance problem, the various active damping method has been proposed so far. Generally, the virtual resistor active damping methods is required to additional hardware sensors for measurement of capacitor voltage and current. In this paper, the new active damping method is proposed without any capacitor voltage or current sensors. In the proposed method, the resonance component of the capacitor voltage of LCL filter can be observed by a simple MRAS(Model Reference Adaptive System) observer without additional hardware sensors, and this component is suppressed by feedforward compensation. The validity of the proposed method is proven by simulation and experiment on the 3-phase PWM inverter system.

Investigation and Active Damping of Multiple Resonances in a Parallel-Inverter-Based Microgrid

This paper addresses the resonance problem in a parallel-inverter-based grid-interactive microgrid. Unlike the single grid-connected inverter system where the resonance frequency is mainly fixed by the inverter output LCL filter parameters, the parallel-inverter-based grid-interactive microgrid system presents a more challenging picture where inverter interactions will excite complex resonances at various frequencies. As a result, line currents of inverters can be severely distorted even when the control schemes and filter circuits are properly designed based on the single-inverter model. This paper first develops a microgrid model using discrete time-domain closed-loop Norton's equivalent circuit. Multiple resonances can then be evaluated with the developed model. To improve the microgrid power quality, this paper also designs a virtual-harmonic-resistance-based active damping method. The proposed damping method can be seamlessly incorporated into the conventional deadbeat control scheme through the direct control reference modification. Therefore, the active damping method is able to address both the transient and steady-state resonances within the deadbeat current control bandwidth. Simulation and experimental results are provided to validate the correctness of the developed resonance modeling and active damping methods.

Linear Active Stabilization of Converter-Dominated DC Microgrids

DC microgrids are gaining high momentum under the smart grid environment. DC microgrid stability can be an issue under high penetration of tightly regulated power converters used to interface distributed resources and loads. This paper addresses dc microgrid stability under high penetration of tightly regulated power electronic converters; and proposes three simple and computationally efficient active damping solutions that can be implemented to stabilize a controlled voltage-source converter (VSC) interfacing a dc- microgrid to an ac system. The proposed active damping methods depend on reshaping the VSC impedance by injecting internal-model-based active damping signal at the outer, intermediate and inner control loops of the voltage-oriented VSC interface. Small signal analysis is conducted to assess the system stability under different compensation schemes. Moreover, the reshaped source impedance of the VSC interface and the modified voltage-tracking dynamics are derived under different compensation schemes. Sensitivity and robustness analyses are provided to assess the dynamic coupling among active damping and voltage tracking controllers. Evaluation results, based on a detailed model of a dc microgrid with multiple tightly regulated converter-interfaced loads, are provided to validate the developed models and demonstrate the effectiveness and robustness of proposed techniques.

Filter-Based Active Damping of Voltage Source Converters With $LCL$ Filter

Pulsewidth modulation (PWM) voltage source converters are becoming a popular interface to the power grid for many applications. Hence, issues related to the reduction of PWM harmonics injection in the power grid are becoming more relevant. The use of high-order filters like <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> filters is a standard solution to provide the proper attenuation of PWM carrier and sideband voltage harmonics. However, those grid filters introduce potentially unstable dynamics that should be properly damped either passively or actively. The second solution suffers from control and system complexity (a high number of sensors and a high-order controller), even if it is more attractive due to the absence of losses in the damping resistors and due to its flexibility. An interesting and straightforward active damping solution consists in plugging in, in cascade to the main controller, a filter that should damp the unstable dynamics. No more sensors are needed, but there are open issues such as preserving the bandwidth, robustness, and limited complexity. This paper provides a systematic approach to the design of filter-based active damping methods. The tuning procedures, performance, robustness, and limitations of the different solutions are discussed with theoretical analysis, selected simulation, and experimental results.

Analysis of Multi-Converter System’s Stability Using the Active Damping Method

In Multi-converter power electronic systems, load converters exhibit constant power load (CPL) behavior for the feeder converters and tend to destabilize the system. In this paper, Buck DC-DC converters are taken as an example, and the implementation of active-damping techniques has been shown to analyze the stability of multi-converter power electronic systems. Moreover, active damping is generally implemented by a feedback loop, which produces the effect of a virtual resistor and damps the oscillations, the proposed active-damping method can overcome the negative impedance instability problem caused by the CPLs. The effectiveness of the proposed approach has been verified by Matlab/Simulink simulations.

Control Law Design Based on the Polynomial Method for Active Damping of Oscillatory Modes -The Application of the Delta Operator to the Polynomial Method-

The polynomial or algebraic method based on the transfer function can achieve simultaneously pole and zero placement. Since the method has clear physical interpretation, it is easy to introduce many different constraints such as vibration modes and the operation limit of the actuator. However, when the controlled plant is high-order, numerical problems arise in the solution of a Diophantine equation or a Sylvester matrix. In order to make the conventional polynomial method practicable, this paper presents an improved polynomial method based on the modified delta operator δ for the microprocessor control. The modified delta form can significantly improve numerical conditioning of a Sylvester matrix on pole and zero assignment in controller design. As an example of a controlled plant, a 10th-order plant is considered. Then, the numerical sensitivity of a Sylvester matrix reduces at one millionth of the conventional one obtained on the z-plane. The simulated results show that the proposed method can be applied to a high-order plant and a robust controller can be developed. Therefore, the proposed method would be useful for the computer controlled plants in industry.

Systems and methods for active vibration damping

An active vibration damping system having a supporting spring for addressing a static force from a payload, and an independent actively isolated damper positioned in parallel between a payload and a source of vibration for damping dynamic force from the payload to an actively isolated point. The actively isolated damper includes a small intermediate mass, distinct and decoupled from the payload mass, and a passive isolator element for dynamic coupling of the isolated platform to the small intermediate mass. The small intermediate mass provides a point to which dynamic forces from the payload may be dampened. The active damper also includes at least one actuator coupled at one surface to the small intermediate mass and coupled at a second surface to the vibrating base platform. A motion sensor may also be provided on the small intermediate mass so as to generate a feedback signal as a function of the movement of the small intermediate mass. The motion sensor together with a compensation/amplifier module and the actuator act as part of a feedback compensation loop for minimizing vibration.

4B15 Control Law Design Based on The Polynomial Method for Active Damping of Oscillatory Modes : The Application of The Delta Operator to The Polynomial Method

The polynomial or algebraic method based on the transfer function can achieve simultaneously pole and zero placement. Since the method has clear physical interpretation, it is easy to introduce many different constraints such as vibration modes and the operation limit of the actuator. However, if the controlled plant is high-order, numerical problems arise in the solution of a Diophantine equation. This paper presents a new polynomial design method on the modified delta δ^^--plane instead of the s-plane and the z-plane for the microprocessor control. As an illustration, active damping of second-order system is considered. The numerical sensitivity of a Diophantine equation becomes about one thousandth of that based on the conventional design. The simulated results show that the proposed method is applicable to the high-order systems.

Active Damping in DC/DC Power Electronic Converters: A Novel Method to Overcome the Problems of Constant Power Loads

Multi-converter power electronic systems exist in land, sea, air, and space vehicles. In these systems, load converters exhibit constant power load (CPL) behavior for the feeder converters and tend to destabilize the system. In this paper, the implementation of novel active-damping techniques on dc/dc converters has been shown. Moreover, the proposed active-damping method is used to overcome the negative impedance instability problem caused by the CPLs. The effectiveness of the new proposed approach has been verified by PSpice simulations and experimental results.

Vibration Reduction and Power Generation with Piezoceramic Sheets Mounted to a Flexible Shaft

A flexible shaft with surface-mounted piezoceramic sheets and strain sensors is considered which suffers from resonance and self-excited vibration. Frequency domain models, time domain simulations, and control experiments are used to analyze active modal damping and active modal balancing methods. The generation of electric power from cyclic straining of rotor-fixed piezoelectric material is studied and several self-powering devices for condition monitoring and vibration control are proposed.

Active Damping of Driveline Oscillation

This controller approach describes a method for active damping of torsional vibrations in a vehicle driveline during clutch engagement. The problem of oscillations appears in a wide range of drivelines equipped with an automated clutch capacity controller, e.g. continuously variable automatic transmission (CVT), automated manual transmission (AMT) or classical automatic transmission with torque converter. It does not depend on the clutch type. Drivelines equipped with both wet and dry clutches can cause this bad behavior. Here, active damping of the driveline oscillation by a wet clutch in a dual clutch gearbox using an electro hydraulic actuator is discussed. This kind of gearbox is called Direct Shift Gearbox (DSG).

Genetic Algorithm-Based Design of the Active Damping for an LCL-Filter Three-Phase Active Rectifier

Active rectifiers/inverters are becoming used more and more often in regenerative systems and distributed power systems. Typically, the interface between the grid and rectifier is either an inductor or an LCL-filter. The use of an LCL-filter mitigates the switching ripple injected in the grid by a three-phase active rectifier. However, stability problems can arise in the current control loop. In order to overcome them, a damping resistor can be inserted, at the price of a reduction of efficiency. The use of active damping by means of control may seem attractive but it is often limited by the use of more sensors compared to the standard control and also by a complex tuning procedure of the controllers. This paper introduces a new active damping method that does not require the use of more sensors. It consists of adding a filter on the reference voltage for the modulator. The tuning process of this filter is easily done, for a wide range of sampling frequencies, with the use of genetic algorithms. This method is used only for the optimum choice of the parameters in the filter and an on-line implementation is not needed. Thus the resulting active damping solution does not need new sensors or complex calculations. Moreover, in the paper particular attention is devoted to the susceptibility of the system in a high polluting environment.

Panel discussion on the application of HDM

In the panel discussion, various applications for damping of materials, both by passive and active damping methods, are presented by the panelists. Then, comments on high damping materials and their applications are presented by three commentators.

Non-contact suspension techniques for pellets in laser fusion experiments

A Ni-coated plastic micro balloon (Ni-PMB) suspended in non-contact fashion is reported to achieve uniform irradiation of a laser fusion target. The first section presents the development of magnetic suspension system ‘MINO-2’ for laser fusion experiment; MINO-2 demonstrates magnetic suspension of a 1 mm diameter, Ni-PMB at <1.0×10 −3 Pa with the vertical oscillation amplitude <5 μm; We successfully demonstrated a laser shot experiment in MINO-2. The second section describes the method of active damping of horizontal oscillation using optical forces, in which the initial vibration 27.3 μm became 1.8 μm in 3.7 s. In the third section, a pulsed current method for laser physical deposition is proposed where we find the droplets decrease. Finally, another method of non-contact technique is proposed where an electrodynamic suspension is used as one of non-contact suspension methods. The minimum vibrating amplitude less than observable resolution is attained experimentally at three voltages and at the precise position of the ring electrode in the air.

Grinding Chatter – Origin and Suppression

Grinding chatter is one of the most critical errors in grinding operations and one that has a strong impact on the ultimate geometrical workpiece accuracy. In the paper the origin of chatter that is particularly due to regenerative effects during inner and outer diameter as well as surface grinding is explained. After the discussion on its influence on surface quality, the possibilities related to process monitoring for the detection of chatter during grinding are presented. Special attention is paid to the suppression of chatter e.g. by employing active or passive damping methods. Furthermore, information on a suitable procedure to conduct a stability assessment for grinding machines is provided.

On the Significance of Reference System for Active Damping of Vibration Isolators in Gravitational Wave Detection

Several active damping methods corresponding to various reference systems are discussed. The theoretical analyses show that a quasi-fixed reference system can be used to improve the high-frequency performance of a multi-stage active damping system because its high-frequency performance is equivalent to that of a low-pass electronic filter with a very low cut-off frequency.

A unified analysis of both active and passive damping for a plate with piezoelectric transducers

The complete set of equations for describing the mechanical and electrical behavior of a piezoelectric medium is given. From these equations, the electromechanical equations describing the dynamical behavior of discrete PZTs and their mounting plate are derived. The electromechanical equations are used to explain active damping with the PZTs as actuators and an accelerometer as the sensor. The active damping model is applied to a more realistic case. The transverse displacement and the plate vibration damping are calculated using the electromechanical equations and compared with the experimental results. A comparison of the open loop transverse displacement of the plate as a function of the applied PZT voltage with the corresponding experimental case shows good agreement. The damping of the plate vibration is found to be approximately 20 dB for both the calculation and the corresponding experiment when the plate is driven at the lowest modal plate frequency. A sensor equation describing the output of a PZT used as a sensor is derived with the PZT terminated with an arbitrary impedance. Using the sensor equation, a concise and unified approach is developed for constructing both active and passive damping methods. Two limiting active damping cases (the terminal impedance zero or infinity) and one passive damping case are considered using the sensor equation. A useful design guide for the corresponding active and passive damping methods is determined.

Device and method for active vibration damping

A device and method for active vibration damping of an object which comprises a beam with two free ends comprises a vibration sensor, a control circuit, and an actuator. The sensor is located near the first end of the beam and the actuator is located near the second end of the beam. The control circuit converts input signals from said vibration sensor into control signals for controlling the actuator. The damping device is particularly useful where it forms part of a precision coordinate measuring machine which has a beam of varying length. In this instance, the sensor is located on a sliding spindle of the measuring machine.

Damping of Vibration by Actively Controlled Initial Distortions

A concept for the artificial damping of free vibration by means of actively controlled initial distortions imposed on the structure is presented. Two formulations for active control are presented: The first simulates the natural damping properties of structures, while the second uses a more sophisticated modal strategy of control (but with a faster damping process). The general idea of damping by actively forced distortions is explained and followed by a simple example for a one‐degree‐of‐freedom system. Then, the simulation of natural damping (which is a particular case of active control) and the possibility of accelerating the damping process by the modal optimal strategy are discussed and demonstrated with some examples for a two‐degree‐of‐freedom system. Finally, the vibration control of a four‐degree‐of‐freedom system is presented to demonstrate the efficiency of the proposed method. The method of active damping is described for truss structures, but it can be easily generalized to include frame stru...