Showing papers on "Damping torque published in 2020"

Deep Reinforcement Learning-Based Approach for Proportional Resonance Power System Stabilizer to Prevent Ultra-Low-Frequency Oscillations

Abstract: Recent studies have shown that due to the hammer effect of the governor, hydropower units are easily creating negative damping torque at the common mode frequency (below 0.1 Hz). Therefore, there is a risk of ultra low frequency oscillations (ULFO) in hydropower-dominated systems. ULFO is a small-signal frequency oscillation problem, which is quite different from low frequency oscillations (LFO). A conventional power system stabilizer (CPSS) has less effect on suppressing ULFO. To solve this problem, this paper proposes a high-order polynomial structure to replace the CPSS, and combine it with a proportional resonance controller to form a novel PR-PSS. In order to ensure the robustness of PR-PSS, based on the characteristic analysis results of the PR-PSS, a deep reinforcement learning (DRL) algorithm asynchronous advantage actor-critic (A3C) is introduced to train an agent. After training, the proposed agent can provide optimal parameter settings for PR-PSS under various operating conditions. Simulation results verify the effectiveness of the proposed method.

Modal Shift Evaluation and Optimization for Resonance Mechanism Investigation and Mitigation of Power Systems Integrated With FCWG

Abstract: The integration of full converter-based wind power generation (FCWG, e.g., permanent magnet synchronous generator (PMSG)) not only introduces the PMSG oscillation modes (POMs) but also might excite severe resonances with electromechanical oscillation modes (EOMs) of the power system. In this paper, a two-open-loop-subsystem dynamic model is firstly established to investigate the interactions between the PMSG and the rest of the power system. On this basis, a modal shift evaluation (MSE) method by using bilateral damping torque analysis is proposed to accurately quantify the interaction effect of POMs and EOMs on each other and effectively explain their complex interaction process. Then two important concepts, i.e., modal shift sensitivity (MSS) with respect to various PMSG controller parameters and resonance excitation index (REI) according to a per unit open-loop modal distance indicating the intensity of modal interactions, are derived to dig the essential modal resonance mechanisms. Furthermore, by using MSS and REI as two tools, the modal interaction optimization (MIO) is conducted through POM tuning in order to prevent potential system modal resonance and enhance resonance mode damping for the first time. The optimized modal interaction is validated to be beneficial and effective for the improvement of power system resonance stability.

Damping Torque Analysis of DC Voltage Stability of an MTDC Network for the Wind Power Delivery

Abstract: Conventional damping torque analysis (DTA) is a well-known and widely used method to examine the low-frequency electromechanical oscillation stability of an AC power system. This article expands the conventional DTA for studying the DC voltage stability of an MTDC network. In the article, analysis is carried out to prove that the DTA can be applied to examine the DC voltage stability of MTDC network. Application of DTA can not only reveal the insight about why growing DC voltage oscillations may occur, but also to guide the parameters tuning of control systems of voltage source converters (VSCs). The parameters tuning is to avoid that the damping contributions from the VSCs in the MTDC network are very much varied such that DC voltage instability may occur after some of VSCs are withdrawn from operation. In addition, DTA can also be applied to guide the parameters setting of a current flow controller (CFC) in order to ensure the DC voltage stability of the MTDC network after the CFC is installed. An example MTDC network is used to demonstrate and evaluate the applications of DTA in the article.

An Applicable Method to Improve Transient and Dynamic Performance of Power System Equipped With DFIG-Based Wind Turbines

Abstract: The improvement of synchronous generators (SGs) stability is one of the most important issues in power systems. To this aim, doubly fed induction generator (DFIG) can be helpful. The main purpose of this paper is to improve both transient and dynamic performance of SG by using local DFIG-based wind turbines. Firstly, a transient controller (TC) is designed in controlling block of DFIG which changes its operating mode from generator to motor regime. Secondly, two damping controllers which are named electromagnetic torque band damping controller (ETBDC) and reactive power band damping controller (RPBDC) are suggested to improve dynamic stability of SG. Each damping controller includes three feedbacks namely, SG speed changes, SG electromagnetic torque and DFIG electromagnetic torque. Moreover, genetic algorithm (GA) is used to adjust these controlling parameters. The performance of TC is examined by comparison of system transient indexes such as critical clearing time (CCT), SG accelerating energy and DFIG inertia energy with and without using the proposed TC in a two-area test network. Similarly, system dynamic performance indexes such as overshoot, settling time, eigenvalue and damping torque of SG are compared with and without using two dynamic controllers. The obtained results show the effectiveness of proposed controllers.

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

Abstract: 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.

Small-Signal Stability Analysis of Photovoltaic-Hydro Integrated Systems on Ultra-Low Frequency Oscillation

Abstract: In recent years, ultralow-frequency oscillation has repeatedly occurred in asynchronously connected regional power systems and brought serious threats to the operation of power grids. This phenomenon is mainly caused by hydropower units because of the water hammer effect of turbines and the inappropriate Proportional-Integral-Derivative (PID) parameters of governors. In practice, hydropower and solar power are often combined to form an integrated photovoltaic (PV)-hydro system to realize complementary renewable power generation. This paper studies ultralow-frequency oscillations in integrated PV-hydro systems and analyzes the impacts of PV generation on ultralow-frequency oscillation modes. Firstly, the negative damping problem of hydro turbines and governors in the ultralow-frequency band was analyzed through the damping torque analysis. Subsequently, in order to analyze the impact of PV generation, a small-signal dynamic model of the integrated PV-hydro system was established, considering a detailed dynamic model of PV generation. Based on the small-signal dynamic model, a two-zone and four-machine system and an actual integrated PV-hydro system were selected to analyze the influence of PV generation on ultralow-frequency oscillation modes under different scenarios of PV output powers and locations. The analysis results showed that PV dynamics do not participate in ultralow-frequency oscillation modes and the changes of PV generation to power flows do not cause obvious changes in ultralow-frequency oscillation mode. Ultra-low frequency oscillations are mainly affected by sources participating in the frequency adjustment of systems.

Damping Torque Analysis of VSC-HVDC Supplementary Damping Controller for Small-Signal Stability

Abstract: In order to improve the small-signal stability of AC/DC hybrid systems containing voltage-source converter based high-voltage direct current (VSC-HVDC), this article extends damping torque analysis (DTA) theory to VSC-HVDC supplementary damping controller to analyze its dynamic impacts and inhibit oscillations. Firstly, this article presents the mechanism and procedure of VSC supplementary damping controller and establishes the linearized model of AC/DC system with damping controllers. On this basis, the DTA theory of VSC supplementary damping controller and the equation of damping torque index (DTI) are derived. The theory can be applied to the design of the damping controller including the selection of installation location and channel as well as the parameter tuning. Finally, case studies are carried out in two AC/DC hybrid systems containing VSC-HVDC. The simulation results verify the correctness and feasibility of DTI analysis. VSC damping controllers designed by the proposed method can effectively suppress oscillations and improve the dynamic stability of the AC/DC system.

Analytical Approach of a Pure Flow Mode Serpentine Path Rotary Magnetorheological Damper

Abstract: This paper has two main goals in the development of a novel flow-mode magnetorheological brake (MRB): (1) produce a mathematical model of a flow-mode MRB and (2) predict the torque density of the proposed MRB compared to the other type of MRB. In this design, the flow mode MRB is made by screw pump to make the Magnetorheological Fluid (MRF) flow through the radial and annular channel. The serpentine path flux is developed in the proposed MRB to make the annular channel an active region as well. With the proposed design concept, the work of a pure flow-mode serpentine path MRB can be accomplished. In this study, Finite Element Method Magnetics (FEMM) is used to calculate the magnetic field applied to the active regions and analytical approach used to obtain the output damping torque. The simulation results show that the magnetic fluxes flow through the radial channel and annular channel as well. The radial and annular channel is activated, which led to higher output damping torque. The mathematical modelling shows that the helical angle of the screw pump significantly affects the damping torque. The results show that the output damping torque density can be adjusted from 42.18 N/mm2 in the off-state with 0 rpm to around 40,518.96 N/mm2 at 20 rpm. The torque density of the proposed MRB is higher than the shear mode MRB.

Design optimization and experimental characterization of a rotary magneto-rheological fluid damper to control torsional vibration

Abstract: This paper aims at optimum design formulation of a rotary disk-type magneto-rheological (MR) fluid damper to increase its torsional vibration control performance. The objective is to maximize the torsional damping torque for a given volume, geometric and inertia constraints. The damping torque has been derived based on Bingham plastic model for a commercial MR fluid provided by Lord corporation. As MR fluid's yield strength directly depends on the applied magnetic field intensity, an analytical magnetic circuit analysis has been conducted to approximately evaluate the magnetic field intensity in the MR fluid gap. A finite element model of the rotary MR damper has also been developed to evaluate the magnetic field distribution. A formal design optimization problem has then been formulated to maximize the dynamic range for a given volume under geometric, inertia and torque ratio constraints. Genetic Algorithm (GA) combined with Sequential Quadratic Programming (SQP) method has been utilized to accurately capture the global optimum solution. Finally, a proof-of-concept of the optimal design has been manufactured and then tested experimentally to investigate the generated damping torque under different current excitation and also to validate the model and optimization strategy.

Current-driven transverse domain wall oscillations in perpendicular spin-valve structures

Abstract: Spin-transfer-driven oscillations of a transverse domain wall confined to a perpendicular spin-valve structure are investigated using a one-dimensional model. The stack consists of a polarizer, nonmagnetic spacer, soft free layer, and pinned magnetic layer. It is found that the domain-wall oscillation frequency is a nonmonotonic, highly asymmetrical function of applied electric current, showing a strong dependence on the current direction and the relative strengths of the interfacial and bulk spin-transfer torques. Micromagnetic analysis reveals that the surprising and atypical oscillator response is due to an interplay between the interfacial spin-transfer torque, the bulk spin-transfer torque, the exchange torque, and the damping torque. The underlying physical and material responses are examined, including the important role of the domain-wall twist. The competitions between the involved torques under different operating conditions suggest that the oscillator could serve as a model system to investigate magnetic and spintronic phenomena at the nanoscale. The observed current-dependent twisting of the free-layer magnetization about the axis of precession may further be found interesting for investigations of the interaction between spin-polarized current and chiral spin structures.

Mode-based damping torque analysis method in power system low-frequency oscillations

Abstract: The mode-based damping torque analysis (M-DTA) method for studying the effect of an external controller on power system low-frequency oscillations is proposed in this paper. Firstly, based on the interconnection model between the system and the controller in the frequency domain, the oscillation loop corresponding to the electromechanical oscillation mode is built, and the mode-based damping torque of the controller can be calculated. Then, the application of the M-DTA method in the power system is illustrated. The derivation shows that in the single-machine infinite-bus power system, the M-DTA method is completely equivalent to the classical damping torque analysis (C-DTA) method. In the multi-machine power system, the mode-based damping torque reflects the effect of the controller on the oscillation mode directly, overcoming the shortcomings of the C-DTA method in which there is no direct correspondence between damping torque and the oscillation mode. By deriving the relationship with the residue index, the M-DTA method shows higher accuracy than the residue method in applications such as controller parameter adjustment. Finally, two example power systems are presented to demonstrate the application of the proposed M-DTA method.

Reconstructed rheometer for direct monitoring of dewatering performance and torque in tailings thickening process

Abstract: To further clarify the dewatering performance and torque evolution during the tailings thickening process, a self-made rake was connected to a rheometer to monitor the shear stress and torque. The dewatering performance of the total tailings was greatly improved to a solid mass fraction of 75.33% in 240 min. The dewatering process could be divided into three stages: the rapid torque growth period, damping torque growth period, and constant torque thickening zone. The machine restart was found to have a significant effect on the rake torque; it could result in rake blockage. Furthermore, the simultaneous evolution of the torque and solid mass fraction of thickened tailings was analyzed. A relationship between the torque and the solid mass fraction was established, which followed a power function. Both the experimental and theoretical results provide a reference for the deep cone thickener design and operation to enhance the dewatering performance.

Influence of Rotor Damping Structures on Damping Torque Coefficient of Turbo-Generator During Low-Frequency Oscillation Caused by Large Disturbance

Abstract: The damping structures of turbo-generators, such as rotor damping bars, core, and slot wedges, can provide positive damping effect for the low-frequency oscillation of power system. However, the magnetic saturation, distortion, and skin effect of generators make nonlinear damping effects during the low-frequency oscillation caused by large disturbance. In order to quantitatively describe the damping effect of the three damping structures, the damping torque coefficient (DTC) during the low-frequency oscillation is calculated by coupling time-stepping finite element method with the polynomial approximation method. The DTCs of turbo-generator with different rotor damping structures are obtained by comparing the individual and combined effect of the three damping components. Since there are several material options for the rotor slot wedges and damping bars, the influence of these materials on DTC is studied. A rotor damping structure that can not only improve the symmetry of rotor damping structure, but also enhance the DTC of turbo-generator is proposed. The results provide theoretical basis for power system stability enhancement by improving the rotor damping structures of turbo-generator.

An Effective Control Scheme for Multimodal SSR Suppression via VSC-Based Controller

Abstract: Multimodal sub-synchronous resonance (SSR) induced by the interactions between the generator shafts and the fixed series capacitors has become a serious threat for the power system. To overcome this, a voltage source converter (VSC) based controller for multimodal SSR suppression, named sub-synchronous resonance dynamic suppressor (SSRDS), is presented and analyzed in this paper. The controller is placed at the point of common coupling (PCC) of the power plant for multi-generator SSR suppression purpose so that the investment costs can be minimized while making sure the requirements of the SSR damping. To quantify the contribution of SSRDS to the SSR damping, the damping torque analysis is carried out, which can reveal the influences of the operating conditions and the correlated control parameters on the damping performance. Furthermore, to avoid the negative affects between the different TMs in close range as well as maximize the damping ability of SSRDS, the parameters tuning method of the mode filters and the gain and phase shifters are proposed. A detailed nonlinear simulation model is established in PSCAD/EMTDC based on the Jinjie series compensated transmission system located in China. The damping torque analysis, the eigenvalues analysis and the simulation results have fully demonstrated the effectiveness and the robustness of the proposed SSRDS for multi-generator and multimodal SSR suppression under both small and large disturbances in various operating conditions.

Design of a Motorcycle Steering Damper for a Safer Ride

Abstract: Powered-two-wheelers (PTWs) are increasingly popular because of their lower cost compared to cars, and therefore the riders’ exposure risk is increasing. Due to their complex dynamics characterized by high non-linearity and inherent instability, PTWs are more difficult to control compared to four-wheeled vehicles. Wobble is a high-frequency instability mode affecting the steering assembly of the PTW, and which often causes the rider to lose control and crash when it occurs. In this paper, we present the design of a new motorcycle semi-active steering damper integrated into the steering column and utilizing a magnetorheological fluid (MRF) for variable damping torque. An analytical model of the concept was first used to perform the preliminary sizing, followed by concept validation using a 3D FE multiphysics magnetic-fluid analysis. The final innovative design offers several advantages compared to traditional steering dampers: (i) a wide range of adjustable damping torque values, with a multiplication factor up to 10 with a maximum electrical current of 2 A; (ii) total integration into the motorcycle steering column enabled by its axial design and limited radius; (iii) a simple chamber geometry that allows for easy manufacture; (iv) longer seal life due to the absence of direct contact between seals and the MRF.

Deep Reinforcement Learning Based Optimization Strategy for Hydro-Governor PID Parameters to Suppress ULFO

Abstract: In this paper, the mechanism of ultra-low frequency oscillation (ULFO) is studied according to the damping torque theory and the influence of proportional, integral and differential parts (PID) parameter settings of hydro-governor on ULFO is investigated. After that, a deep Q network (DQN) based method is proposed for the hydro-governor PID parameter settings self-tuning, which considering the uncertainty of the hydraulic turbine operating conditions. Simulation results show that the proposed DQN-based method can provide the optimal parameters for the hydro-governor PID under all operating conditions, which achieves better performance in preventing ULFO in comparison with other methods.

Power System Stabilizers

Abstract: This chapter discusses the process of improving damping on the local mode by adding a supplementary input signal to the voltage regulator. To facilitate the Power System Stabilizers (PSS) design, it deals with a small‐signal analysis approach to build the concepts of synchronizing and damping torques. The Single‐Machine Infinite‐Bus system is used to discuss the synchronizing and damping torque concept which is useful in understanding the impact of excitation systems on the swing‐mode damping and in developing the intuitions for damping control design. The chapter also discusses the use of other signals for PSS design, including a dual‐input‐signal design. The purpose of a PSS is to restore or add damping torque to the swing modes. There are three components to a control system: an input signal, a compensator, and an actuator. The chapter discusses two of which using linearized models. These are: phase compensation method; and root‐locus method.

Magnetic eddy current damping device, frequency modulation mass magnetic eddy current damper and method for restraining vibration

Abstract: The invention discloses a magnetic eddy current damping device, a frequency modulation mass magnetic eddy current damper and a method for restraining vibration. The magnetic eddy current damping device comprises a supporting framework, a stator assembly, a rotor assembly and a gear and rack mechanism. The stator assembly and the rotor assembly are disc-shaped or cylinder-shaped parts made by utilizing a conductor material/a permanent magnet material and a permanent magnet material/a conductor material. The gear and rack mechanism converts linear motion of a mass block into rotating motion of the rotor assembly. When the permanent magnet material and the conductor material move relatively, the stator assembly generates damping torque to the rotor assembly through non-contact magnetic force,thus the system vibration frequency is changed, and amplitude is restrained. The magnetic eddy current damping device has the characteristics of making no contact, avoiding friction abrasion, and being adjustable in damping coefficient, high in reliability and long in service life. The magnetic eddy current damper comprises a swing rod, a balancing weight, a frequency modulation spring and the magnetic eddy current damping device. The method for restraining vibration is achieved by installing the frequency modulation mass magnetic eddy current damper on an object with vibration to be restrained.

Nonlinear negative damping caused August 10, 1996-WECC blackout

Abstract: This paper shows that the August 10, 1996-WECC blackout originated from negative damping arising from sin6 nonlinearity. The proof is based on keeping the nonlinearity in the dynamic equation of a turbine-generator swinging against an infinite bus. Small signal perturbation linearization can predict the occurrence of negative damping. But the linear approach cannot produce the negatively damped waveform of the WECC blackout. Therefore, the graphical Phase Plane method is resorted to. As MatLab, MATHEMATICA, Wolfram MathWorld, etc. offer software plotters, the phase plane method is not difficult to use. Phase portraits show that the “Swing Equation” has stable and unstable regions. The WECC blackout happened because the initial states fell in the unstable region. Although dismissed as being limited to two-dimensions, the paper makes a contribution by showing that phase plane can be used to study the impact of 3 independent controllers. A worked-example shows when the independent controllers (turbine torque, the generator counter-torque and the damping torque) cannot meet the Transient Stability Limit after a line short circuit fault, local blackout occurs. The global WECC blackout is considered to be a scaled up local blackout. Instead of a turbine-generator swinging against an infinite bus, the last stage of the August 10, 1996-WECC blackout is assumed to be the Seattle-area swinging against the California-area. A phase portrait is found in the unstable region whose trajectory unravels in several cycles. Time-domain simulation shows a waveform oscillating with same number of cycles, which qualitatively matches the waveform of the August 10, 1996-WECC blackout.

High-energy-consumption-density torsional eddy current damping device and damping system

Abstract: The invention belongs to the field of vibration control, and particularly relates to a high-energy-consumption-density torsional eddy current damping device and damping system. The eddy current damping device comprises at least one stage of speed increasing gear set, conducting tubes which are in running fit with each other, and magnets which are arranged in a staggered manner along the annular direction. The output end of the speed increasing gear set is connected with the conducting tubes; and the speed increasing gear set can drive the conducting tubes to rotate relative to the magnets arranged in the staggered manner along the annular direction. According to the high-energy-consumption-density torsional eddy current damping device provided by the invention, the energy consumption density can be greatly improved, the needed damping torque is generated, the damping torque acts on an external structure so as to meet the requirement for the high energy consumption density, and the purpose of restraining structural vibration is achieved.

Rotating electric machine control device

Abstract: Provided is a technique for appropriately embedding, in a rotating electric machine control device for controlling a rotating electric machine, a damping function for reducing a transfer torque vibration transferred to the rotating electric machine. The rotating electric machine control device (10) for drive-controlling a rotating electric machine (80) in a dq-axes vector coordinate system is provided with a feedback controller (1) which calculates a voltage command (V*) for the rotating electric machine (80) in each of a d-axis and a q-axis, and which feedback-controls the rotating electric machine (80), wherein the gain of the feedback controller (1) for the q-axis is set so that a voltage command (V*) for outputting a damping torque for attenuating a transfer torque vibration (Tn) is calculated on the basis of a back electromotive force of the rotating electric machine (80) caused by the transfer torque vibration (Tn).

Isolation device with two or more springs in series

Abstract: In one aspect, there is provided an isolation device, which includes a hub, a pulley and at least one isolation spring arrangement including first and second springs in series. The first spring rate is higher than the second spring rate. Initially during torque transfer from the first one to a second one of the hub and the pulley, the entire first isolation spring is slid along a friction surface towards the second one of the hub and the pulley during compression of the second isolation spring thereby generating a first frictional damping torque. During torque transfer the other way, at least a portion of the first isolation spring remains stationary relative to the friction surface, such that the first frictional damping torque is greater than the second frictional damping torque.

A single axis solar tracker with a torsional vibration damping device

Abstract: The solar tracker includes a pivoting assembly (2) having solar panels (3) fixed to a rotating shaft (1), a fixed structure with support elements (4, 5, 6) rotationally supporting the rotating shaft (1), a motor-reducer assembly (7) having an irreversible reducer (24) connected to the rotating shaft (1) at a motor connection point (12), and a torsional vibration damping device (8) having a moving member (9) rigidly connected to the rotating shaft (1) at a damper connection point (13) spaced apart from the motor connection point (12) and a stationary member (10) rigidly attached to the fixed structure. One member selected between the moving member (9) and the stationary member (10) comprises magnetic field-generating elements (11) and the other member comprises a section made of an electrically conductive, non-ferromagnetic material. Relative movement between the two members close to one another without contact produces a damping torque by Foucault currents effect.

Rotary type electromagnetic damper with bidirectional torsion spring

Abstract: The invention relates to the field of space robot research and engineering, in particular to a rotary motion type electromagnetic damper. The damper comprises an electromagnetic damping assembly, a bidirectional torsion spring assembly and a main shaft, and the electromagnetic damping assembly and the bidirectional torsion spring assembly are connected with the main shaft. When rotary impact actson a rotary impact input end, the main shaft rotates to enable a rotor of the electromagnetic damping assembly to rotate, the bidirectional torsion spring assembly generates damping force of oppositedirection by different rotation directions of the main shaft, the electromagnetic damping assembly generates electromagnetic damping torque to the main shaft, the bidirectional torsion spring assemblygenerates rotating resistance torque to the main shaft, and the electromagnetic damping torque and the rotating resistance torque jointly form rotating electromagnetic damping torque.

Operation stability analysis method for AC-DC power distribution and utilization system

Abstract: The invention provides an operation stability analysis method for an AC-DC power distribution and utilization system. The method comprises the steps of: 1, building a first transfer function between aDC bus voltage and the DC side voltage of an AC/DC interconnection converter station according to the equivalent circuit of an AC/DC power distribution system; 2, establishing a mathematical expression between the DC side voltage change and active power change of the AC/DC interconnected converter station according to the equivalent circuit of the AC/DC power distribution system, and establishinga second transfer function between the DC bus voltage and the active power on the basis of the first transfer function output in the step 1; 3, establishing a third transfer function between the active power and AC according to the structures of the power controller and current controller of the AC/DC interconnected converter station, and establishing a fourth transfer function between the DC busvoltage and the AC on the basis of the second transfer function output in the step 2; and 4, complex torque decomposition is performed on the fourth transfer function output in the step 3 to obtain the amplitude-frequency gains of a synchronous torque and a damping torque.

Adrc Additional Damping for Flexible DC Transmission Control

Abstract: According to the advantages of flexible dc system with abundant control methods and flexible and reliable regulation means, an adrc based on ac system decoupling control based on ac-dc power decoupling control is proposed to provide damping support for ac system. Firstly, the mechanism of damping torque provided by additional damping controller is analyzed. Then design the excellent robustness since immunity damping controller for the system to provide the damping support and stabilize voltage, a typical 4 machine 2 area system by PSCAD/EMTDC platform building, and has carried on the simulation results under different controller scheme, the results show that the additional damping controller based on the immunity control better suppress the system oscillation and improve the system stability.

Performance test device for mechanical seal of manned spaceflight water treatment system

Abstract: The invention discloses a performance test device for mechanical seal of a manned spaceflight water treatment system. The performance test device comprises a power output and torque measurement assembly and a mechanical seal test accommodating cavity assembly, the power output and torque measurement assembly comprises a servo motor, a torque sensor, a fixing bracket and a coupler; the mechanical seal test accommodating cavity assembly comprises a transmission shaft, a framework oil seal, a bearing, a suspension assembly and an O-shaped sealing ring; the power output and torque measurement assembly is used for providing rotating power, so that a moving ring of the mechanical seal can rotate relative to a static ring, and damping torque of the mechanical seal is measured; and the mechanicalseal test accommodating cavity assembly is used for providing a certain pressure space for a tested mechanical seal, and the suspension assembly thereof is used for preventing the tested mechanical seal from being stressed by mechanical pressure generated due to the fact that the coaxiality cannot be precisely controlled, thereby ensuring that the tested mechanical seal cannot be damaged by external mechanical pressure in the test process.

Damping torsional oscillations in a drive system

Abstract: A drive system (10) comprises at least one electrical machine (12) and a plurality of rotating components (14), which are interconnected via shafts (18, 20, 22). A method for damping torsional oscillations in the drive system (10) comprises: determining angular speeds ([theta]i) for at least one of the shafts (18) based on measurements in the drive system (10); determining a damping torque (Tdamp)from the angular speeds ([theta]i) with a function that models at least some of the electrical machine (12), the rotating components (14) and the shafts (18, 20, 22); adapting a reference torque (Tref) for the at least one electrical machine (12) by adding the damping torque; and controlling the at least one electrical machine (12) with the adapted reference torques (T).