Modelling a Variable Displacement Axial Piston Pump in a Multibody Simulation Environment

An irregular performance of a mechanical-type constant power regulator is considered. In order to find the cause of an irregular discharge flow at the cut-off pressure area, modeling and numerical simulations are performed to observe dynamic behavior of internal parts of the constant power regulator system for a swashplate-type axial piston pump. The commercial numerical simulation software AMESim is applied to model the mechanical-type regulator with hydraulic pump and simulate the performance of it. The validity of the simulation model of the constant power regulator system is verified by comparing simulation results with experiments. In order to find the cause of the irregular performance of the mechanical-type constant power regulator system, the behavior of main components such as the spool, sleeve, and counterbalance piston is investigated using computer simulation. The shape modification of the counterbalance piston is proposed to improve the undesirable performance of the mechanical-type constant power regulator. The performance improvement is verified by computer simulation using AMESim software.

An improvement on a method for nonlinear pressure control of self-supplied variable displacement axial piston pumps

Low noise axial piston pumps become the rapid increasing demand in modern hydraulic fluid power systems. This paper proposes a systematic approach to simulate the vibroacoustic characteristics of an axial piston pump using a hybrid lumped parameters/finite element/boundary element (LP/FE/BE) model, and large amount of experimental work was performed to validate the model. The LP model was developed to calculate the excitation forces and was validated by a comparison of outlet flow ripples. The FE model was developed to calculate the vibration of the pump, in which the modeling of main friction pairs using different spring elements was presented in detail, and the FE model was validated using experimental modal analysis and measured vibrations. The BE model was used to calculate the noise emitted from the pump, and a measurement of sound pressure level at representative field points in a hemianechoic chamber was conducted to validate the BE model. Comparisons between the simulated and measured results show that the developed LP/FE/BE model is effective in capturing the vibroacoustic characteristics of the pump. The presented approach can be extended to other types of fluid power components and contributes to the development of quieter fluid power systems.

Starting from previous papers [1], where hydrostatic transmissions automotive controls functionalities were investigated, an embedded electronic control system was designed. It is based on a low cost electronic control unit, controlling a hydrostatic transmission with a variable displacement axial piston pump and an axial piston dual displacement motor. The pump displacement control strategy, which depends on diesel engine working point and delivery pressure, is based on a fully customisable engine performance map. Special control strategies superimposed on this strategy and depending on autorecognized working mode, that allowed excellent performance in the vehicle field test phase to be reached. Special diagnostic strategies were introduced, based on functional and congruence controls, relying on fault recovery systems, to maintain the system in a high safety condition and to modify automatically the system working mode in case of fault occurrence. This approach allows reductionof overall risks for the operator and the environment.

The paper reports upon numerical simulation tests carried out on a variable displacement axial piston pump equipped with multiple automatic controls. The swashplate control circuit includes three 3-way valves: the pressure compensator, the flow compensator and the torque limiter. The dynamic response of the system is evaluated for both separate and combined control functions. The effect of changes in the design parameters is discussed in terms of both sensitivity analysis and conventional discrete search.

As the power sources in hydraulic systems, variable displacement axial piston pumps generate flow fluctuation. Unfortunately, it results in pressure pulsation which excites the system vibration and emitted noise. The majority of studies try to eliminate the pulsation via a passive technique and the active control methodology has not been discussed in detail. In this research, the feasibility of reducing the pressure ripple by properly controlling the proportional valve has been investigated, which also supports the miniaturization of the active control system. A mathematical model of the self-supplied variable displacement pump including the control system has been developed. The filtered-X least mean square algorithm with time-delay compensation is utilized to calculate the active control signal. Simulation results show the effectiveness of the active control technique. The effect of the active control signal on the flow rate from different chambers of the pump has been analyzed. It demonstrates that the variation of the pressure pulsation should be ascribed to the comprehensive reaction of different flow rates. The major reason is that the flow of the actuator piston neutralizes the peak value of the flow ripple, generated by the nine pistons.

Torsional subsynchronous oscillations caused by grid-connected wind farms in a complex multi-machine power system under the condition of near strong modal resonance

In this paper, we propose a novel approach for 1D and CFD co-simulation basing on general purpose simulation software. The shared memory inter-process communication method is selected and the implementing procedure is given. For code reuse the functions are compiled and linked into a static linking library. The approach has been successfully applied to a problem of underwater torpedo launching system simulation. The results of this application show that the proposed approach is effective in simulating complex fluid power systems and need much less computational resources than conventional full domain CFD simulations.

ON-LINE FAULT DIAGNOSIS IN THE LARGE POWER SYSTEM

Harmonics in large systems

A fault recognition method for transmission systems based on independent component analysis and convolutional neural networks

The article is devoted to increasing the stability of synchronous generators of factory power plants by improving the automatic excitation control system. The team of authors has proposed a method that provides significant damping of transient oscillatory processes in a complex electrical power system with the participation of several synchronous gener-ators caused by disturbing and control influences, including short circuits. The invention “Device for controlling the exci-tation of a synchronous generator in an alternating current distribution network” has been developed and registered, which allows to significantly increase the efficiency of stabilization channels. Software has also been obtained for as-sessing electromechanical transient processes of a synchronous generator during voltage dips in the network, taking into account the action of stabilization channels. Calculations of transient processes were carried out to confirm the effec-tiveness of the resulting method. The proposed solution ensures the aperiodic or close to it nature of electromechanical transient processes.

This paper addresses applications of modern technology, advanced feedback control schemes using wide area measurements, and wide-area visualization techniques to improve grid reliability in complex and multifaceted power system conditions. Reliability aspects of P&C systems such as methods to identify and correct hidden failures and methodologies for optimal testing are also described. As new technologies offer significant improvements, large numbers of legacy P&C systems are still in operation. Upgrading aging P&C systems with modern counterparts not only reduces possibilities for failure, but offers unprecedented capabilities for reliable and high quality data and flexibility in operations which are presently largely untapped. Possibility to monitor equipment performance and to identify failed parts or components helps with equipment life projections and replacement decisions. Integration of P&C systems into Enterprise Systems for improved Asset Management, including value of standardization, is also assessed. The goal of this paper is to provide a comprehensive and systematic approach to meeting the P&C challenges of the 21st century

In recent years, the introduction of the dual carbon strategy has made the development of new power systems more and more crucial. The accurate and efficient prediction of household load has become a hot topic in this field. This paper proposes a hybrid model based on improved complete ensemble empirical mode decomposition with adaptive noise (ICEEMDAN), integrating convolutional neural networks (CNN), bidirectional long short-term memory (BiLSTM), and self-attention (SA) techniques, and incorporating the wavelet domain denoising (WDD) algorithm to enhance data smoothness. The spatial feature extraction capability of CNN and the bidirectional time series extraction capability of BiLSTM are fully utilized, and the ability of SA to highlight the key historical time node information is combined to reduce the loss of historical information. To validate the effectiveness of this method, real household load data is used for verification. Through comprehensive experimental results comparison from multiple perspectives, it is found that both prediction accuracy and error have been significantly improved, demonstrating great potential for this model in addressing increasingly complex new power systems in electrical engineering applications.

In shipboard DC grids, tightly controlled load converters can impair the system stability, thus provoking the ship blackout. Conversely, load converters regulated by low control bandwidths are capable of inducing a stabilizing action. This compensation is verifiable if the loads are few. On the contrary, the balancing of control dynamics is hardly evaluated if the bus feeds multiple (i.e., hundreds or more) DC controlled loads. In this paper, the weighted bandwidth method (WBM) is presented to assess the small-signal stability of a complex shipboard power system by aggregating the multiple converters into two sets of controlled loads. Once the validity of the aggregation is proven, a stability study is performed on the two-loads system. As the last system is more inclined to instability than the initial multiple-loads system, the verification of the two-loads stability criterion guarantees that the shipboard DC grid also remains stable. Finally, emulations on HIL verify the proposed stability assessment thus providing the first unique verification of WBM.