Load Disturbance Research Articles

Analytically derived disturbance rejection‐based PID controller tuning for second‐order plus dead time plants

AbstractThis letter proposes a proportional‐integral‐derivative (PID) design method for second‐order plus dead time models based on a desired closed‐loop transfer function for load disturbance changes. Also, tuning rules for single integrating first‐order plus dead time models are provided. Using a two‐degree‐of‐freedom control scheme, the design problem considers load disturbance rejection, robustness to model uncertainties, and setpoint tracking. Three examples are used to assess the performance of the proposed method. Finally, the results are compared to two popular PID control design methodologies, skogestad internal model control or skogestad IMC (SIMC) and improved SIMC (iSIMC).

An all-position type control strategy of the haptic interactive virtual training system based on cable-driven

The virtual microgravity training system based on cable drive usually uses a force-position hybrid control strategy which has following problems: the force control method is sensitive to load disturbances, variable stiffness characteristics of cables reduce the control accuracy of PID controllers, and the expected tension fluctuations are large. These will affect the control accuracy, and further affect the tactile sensation and training effectiveness of astronauts. For the above problems, an all-position type control strategy is proposed to improve the system control accuracy. This strategy uses a compliant control method. In this method, elastic elements are connected in cables, the conversion model of tension and displacement is established, and the tension control is realized by the displacement control which has characteristics of high control accuracy and strong resistance to load disturbance. The PID controller is replaced by the active disturbance rejection controller. In this controller, the tracking differentiator is used to reduce high frequency noises of the input signal, and the extended state observer is used to estimate and compensate the error caused by the change of the cable stiffness. A tension distribution method is designed to make expected cable tensions approach the average tension to reduce the tension fluctuation. The experimental results show that compared with the force-position hybrid control strategy, the all-position type control strategy reduces the tension error and speed error by about 51% and 33% respectively.

A Control Strategy for Solid-State Transformers With Coupled Load Disturbance Attenuation Ability

A Control Strategy for Solid-State Transformers With Coupled Load Disturbance Attenuation Ability

Performance Analysis of Thirty-one Level Multilevel Inverter for Electric Vehicle Application

This research provides a new architecture for reduced component count 31-level multilevel inverter (MLI). The suggested design uses four unequal DC sources and an H-bridge to provide a maximum 31-level output voltage. For applications using renewable energy, the topology designed for the 31-level can be employed. This lowers the system's total cost, number of components, and size. Higher level counts for lower total harmonic distortion (THD), however, dependability concerns are more significant than MLIs' many benefits. Total standing voltage (TSV), cost function (CF), and power loss are the various metrics that are examined for 31-level MLI. Experiments with different combinational loads and dynamic load fluctuations with sudden load disturbances are performed to assess the inverter's performance. The cost-effectiveness of the suggested MLI is demonstrated while comparing its TSV with the cost function against other topologies that have been recently published.

Distributed sliding mode control for reactive power sharing in an islanded microgrid

This paper presents a novel microgrid secondary control method based on distributed sliding mode control, addressing the issue of reactive power sharing in islanded microgrids. Acknowledging the complications posed by feeder impedance mismatch, the traditional droop control mechanism fails to facilitate efficient reactive power sharing. Utilizing a distributed framework, this paper initially introduces a reactive power ratio observer, enabling the observation of global average reactive power without the need for precise reactive power calculation as required in a conventional centralized control setup. Subsequently, employing the devised reactive power ratio observer, sliding mode control is integrated to achieve effective reactive power sharing. Furthermore, this paper broadens its scope to encompass both reactive power sharing and voltage restoration, resulting in the design of a comprehensive controller. Notably, the proposed distributed sliding mode controller not only achieves accurate reactive power sharing but also exhibits significant resilience in the face of load disturbances. The simulation results conducted under various scenarios effectively validate the efficacy of the proposed distributed sliding mode control strategy.

Primary frequency control optimization of coal-fired power plants with high-low position shafts: Employing a revised strategy with power-decoupling and feedforward-compensating

Coal-fired units play a critical role in peak-shaving and frequency regulation with high penetration of renewable energy. The coal-fired unit arranged by high-low position shafts applied in power stations will participate in these regulation processes. In this study, the dynamic model of the 1100 MW supercritical coal-fired unit is built and verified, dynamic characteristics of the primary frequency regulation process are analyzed and a poor control effect of the original control strategy is illustrated. Then, the dynamic coupling relationship between high and low-level units is obtained, and there is a 14-s time delay between the two power outputs, and a revised regulation strategy that employs load distribution factor and flow-rate feedforward-compensating is proposed. Compared with the original control strategy, the revised control strategy can effectively lower fluctuations of the steam parameters by approximately 50%, and the corrective regulation time decreases from 25.1 s and 15.8 s to 6.9 s and 12.1 s under positive and negative load disturbance, respectively. Moreover, it can improve the control effect of low-level unit, whose regulation time under positive and negative load disturbance decreases from 45.7 s and 27.7 s to 9.4 and 20.6 s, respectively. This research can provide technical guidance for the operation of coal-fired units.

Adaptive Virtual Inertial Control and Virtual Droop Control Coordinated Control Strategy for Hybrid Energy Storage Taking into Account State of Charge Optimization

For energy-storage-assisting conventional units to participate in the primary frequency regulation of a power system, firstly, based on the frequency regulation mechanism of virtual inertial control (VIC) and virtual droop control (VDC) of energy storage, we analyze the effect of the action timing of energy storage on the frequency deviation of the grid under two control methods and put forward a reasonable combination of the two control methods; on this basis, we also put forward hybrid energy storage adaptive VIC and VDC based on the demand of VIC and VDC on the power and capacity of energy storage. On this basis, based on the demand of VIC and VDC on the power and capacity of energy storage, a hybrid energy storage adaptive VIC and VDC coordinated control strategy based on supercapacitor–lithium batteries is proposed, whereby a high-power storage supercapacitor responds to inertial control signals to rapidly suppress a drop in frequency, and the high-capacity lithium battery responds to droop control signals to perform long-time droop control. The high-capacity lithium battery responds to the sagging control signal and is used to perform a long-time sagging power response; finally, in order to avoid the state of charge (SOC) of energy storage falling into a low/high working condition and losing the subsequent frequency regulation ability, an adaptive power control strategy of energy storage based on the improved logistic function is proposed. The simulation results show that under typical load disturbance, the SOC level of the proposed strategy increases by 19.17% and 30.16%, respectively, compared with that of the single-lithium strategy and no energy storage, and the SOC level of the supercapacitor and lithium battery increases by 29.4% and 2.1%, respectively, compared with that of logistic optimization.

Model Predictive Current Control of Permanent Magnet Synchronous Motor Based on Sliding‐Mode Disturbance Observer

A nonlinear multivariable highly coupled system that is susceptible to both internal and external perturbations is the permanent magnet synchronous motor. A new reaching law‐based control approach that combines a sliding‐mode disturbance observer and an enhanced two‐vector model predictive current control is suggested in order to enhance the dynamic performance of the permanent magnet synchronous motor and its robustness to system disturbances. First, a new reaching law is developed in this paper to resolve the conflict between the traditional reaching law's chattering of the system and the reaching time of the sliding‐mode surface. This new reaching law not only makes the system's response more rapid but also reduces chattering; second, taking into account the possibility of systems with internal parameter uptake and external load disturbance, a sliding‐mode disturbance observer based on t is developed. Finally, the q‐axis current obtained from the speed sliding‐mode control rate is added to the model predictive current control, and an optimal duty cycle model predictive current control based on space vector modulation is designed because the traditional two‐vector model predictive current control is to optimize the duty cycle and voltage vectors separately, and the switching frequency is not fixed. The method suggested in this research may successfully suppress the sliding‐mode control system chattering and increase the resilience and dynamic response performance of the speed control system, according to simulation findings compared to the traditional reaching law and traditional duty cycle. © 2024 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Disturbance observer-based fixed time control for bidirectional DC-DC converter with input voltage and load uncertainty

The bidirectional DC-DC converter serves a vital role in the energy recovery system of new energy vehicles. However, external interference and parameter uncertainty can easily affect its dynamic performance. A disturbance observer-based fixed time control strategy for bidirectional DC-DC is proposed to address the impact of input voltage and load uncertainty on bidirectional converters. Firstly, the bidirectional converter model undergoes coordinate transformation, and disturbance observers are designed to compensate for input voltage and load disturbances. Secondly, based on the fixed time control theory, a fixed-time controller is devised for the bidirectional DC-DC converter to facilitate fast tracking and adjustment of output voltage without requiring measurement of input voltage and load current. Finally, simulation and experiment evaluations are conducted to assess the proposed scheme’s effectiveness in output voltage regulation.

Intelligent control based on single-input interval type-2 fuzzy iPI and super twisting nonlinear sliding mode compensator for regulating PEMFC output voltage

The control of Proton Exchange Membrane Fuel Cell (PEMFC) is exceptionally challenging due to its complex nonlinearity, slow dynamics and load disturbance. In this paper, an Adaptive Model Free Control (AMFC) approach is introduced for regulating the PEMFC output voltage under load perturbation and measurement noise conditions. The proposed method consists of four sub-elements. Firstly, an Extended State Observer (ESO) based on a Single-Input Interval Type-2 Fuzzy intelligent PI (SI-IT-2-FLC-iPI) scheme is designed to enhance the performance of PEMFC. Secondly, a Nonlinear Sliding Mode Control-based Super Twisting Algorithm (NSMC-STA) is used as an auxiliary control approach to reduce the estimation error and ameliorate the system robustness. Thirdly, a Forgotten Recursive Least Square Error (FRLSE) is applied for adjusting the physical parameter of MFC and further ameliorating the control response. Finally, all these elements are merged together within what it is called Ultra Local Model (ULM).Through extensive simulation, the efficacy of the proposed regulator in accurately tracking the output signal is showcased, outperforming conventional controllers with remarkable improvements. The system achieves 0.001 steady-state error, 0% overshoot and settling time of approximately 8.9 s, which is good enough in the context of standalone fuel cell applications.

Analysis of the evolution characteristics of infrared energy of coal samples under composite disturbance of dynamic and static loads

Analysis of the evolution characteristics of infrared energy of coal samples under composite disturbance of dynamic and static loads

Optimization of hydraulic parameters for pipeline system of hydropower station with super long headrace tunnel based on mayfly algorithm considering operational scenarios

AbstractThis paper studies the optimization of hydraulic parameters for pipeline system of hydropower station with super long headrace tunnel (HSSLHT) based on mayfly algorithm considering operational scenarios. Firstly, the state equation of HSSLHT under load disturbance is derived. The optimization design of hydraulic parameters for pipeline system based on mayfly algorithm is proposed. Then, the optimization of hydraulic parameters is conducted and analyzed. Finally, the effects of pipeline diameters and transfer coefficients of turbines on the optimization of hydraulic parameters for pipeline systems are revealed. The results show that the optimization of hydraulic parameters for pipeline system is a multiobjective problem, and the several objective functions exhibit significant conflicts. Compared to the firefly algorithm and genetic algorithm, the objective function under mayfly algorithm is improved by 14.7% and 5.1%, respectively. The mayfly algorithm can make the hydraulic parameters for the pipeline system reach the Pareto optimal solution under both load decrease condition and load increase condition. The diameter of penstock has an obvious influence on the robustness of dynamic performance of HSSLHT. When the diameter of penstock increases by 30%, the robustness of HSSLHT becomes worse and the robustness index deteriorates by 57%. The reason is that the flow inertia of penstock becomes smaller with the increase of diameter, and the flow inertia of penstock is favorable for resisting disturbance of HSSLHT. The coefficient of throttled orifice head loss and the lengths and head losses of headrace tunnel and penstock are the key hydraulic parameters for matching the operation of HSSLHT.

Performance Analysis of Positive Output (P/O) Push-Pull Switched Capacitor Converter for High Power Density Applications

The micro-power-consumption technique requires high power density DC/ DC converters and power supply sources. In this research, a PI and Fuzzy Logic Controllers for an elementary circuit of positive output (P/O) push-pull switched capacitor converter has developed for high power density applications with high sustainability under enormous line and load disturbances. The voltage lift technique is a popular application in electronic circuit design. The power converter performs DC-DC step-up voltage conversion with high efficiency, high power density and cheap topology in a simple structure. The proposed converter combines both switched-capacitor and voltage lift techniques. Referable to the time varying and switching nature of the power electronic converter their dynamic behavior becomes highly nonlinear. Conventional controllers are incapable of providing excellent dynamic performance and hence the fuzzy logic controller can be used as a feed forward controller for controlling power electronic converters. The control algorithm is developed to ensure tracking of the reference voltage and rejection of system disturbances by successive measurements of the converter output voltage at certain time instants within a conduction period. The simulation of PI and Fuzzy logic controls have been carried out using MATLAB/Simulink software to evaluate the controller’s performances. Keywords: Luo converter, DCDC converter, PI Controller, Fuzzy Controller.

Prediction of Utility Tunnel Performance in a Soft Foundation during an Operation Period Based on Deep Learning

The underground utility tunnel in a soft foundation is generally affected by the serious disturbance of the vehicle load during the operation period. Therefore, in this study, for the typical utility tunnel engineering in Suqian City of Jiangsu Province, China, field tests were conducted to monitor the performance of the utility tunnel structure in a soft foundation affected by the ground traffic loads during the operation period. Based on the test results, the datasets whose number is 15,376, composed of the five main disturbance factors (four vehicle operating load parameters and one operating time parameter), and the corresponding two main structure responses (displacement and stress) have been constructed. Based on the obtained datasets, using the proposed new deep learning model called WO-DBN, in which the seven hyperparameters of a deep belief network (DBN) are determined by the whale optimization algorithm (WOA), the safety responses of the utility tunnel structure have been predicted. The results show that for the prediction results, the average absolute error for the displacement is 0.1604, and for the stress, it is 12.3726, which are not significant and can meet the requirement of the real engineering. Therefore, the deep learning model can accurately predict the performance of the utility tunnel structure under a vehicle load and other disturbances, and the model has good applicability.

Harmonic suppression of active disturbance rejection control for virtual synchronous generators

SummaryVirtual synchronous generators (VSGs) are comprised of an outer power loop and inner cascaded control loops. The dynamic performance of the output interface is severely degraded when microgrid loads exhibit variability and nonlinearity. Therefore, robustness against load disturbances must be possessed by any voltage control scheme. In this paper, a proportional resonance‐linear active disturbance rejection control (PR‐LADRC) scheme based on an improved linear extended state observer (ILESO) is proposed for VSG voltage control. In comparison with the traditional linear extended state observer (LESO), the differential state variable of the output voltage is utilized to increase the observation bandwidth; consequently, the proposed ILESO can effectively overcome the disadvantage of phase lag when tracking disturbances. Additionally, a proportional resonance controller is incorporated into the LESO feedforward channel to suppress voltage harmonics. The proposed scheme enhances the disturbance observation bandwidth compared to traditional strategies, resulting in a substantial improvement in both the disturbance observation capability of LADRC and the harmonic suppression ability of the VSG system. Theoretical analysis and simulations are conducted to validate the effectiveness of the proposed PR‐LADRC approach.

Source-Storage-Load Coordinated Master-Slave Control Strategy for Islanded Microgrid Considering Load Disturbance and Communication Interruption.

When there is a sudden load disturbance in an islanded microgrid, the peer-to-peer control model requires the energy resource to maintain a margin of generation, resulting in a relatively limited regulation range, that is, voltage/frequency sometimes requires additional control to maintain stability. A "source-storage-load" coordinated master-slave control strategy is proposed in this study to address the aforementioned issues. The system voltage and frequency will be stable as long as the output frequency and voltage of the master resource are stable. Furthermore, it can fully utilize the power supply capacity of resources to support the supply-demand balance. The following tasks are included in the proposed strategy: 1) to improve the operational security in the face of load disruption, a source-storage-load coordinated control method based on the "ramping speed" ratio is proposed, which can quickly restore the balance of supply and demand; 2) to improve the communication reliability in the face of interruption, a channel planning method is proposed, which can address the communication interruption problem by constructing an internal network among source-storage-load; and 3) to improve the mode switching stability of resources subjected to external disturbance, the external disturbance suppression and stability analysis involved in the regulation process are completed using sliding-mode control and small signal model methods. Related case studies are carried out to verify the effectiveness of the proposed strategies.

Super capacitor and SSSC-based coordinated strategy for performance improvement of diverse source interconnected power system

In this work, the dynamical behavior of the dual area thermal-hydro-wind (DATHW) model of the interconnected power system (IPS) is investigated. For analysis, the area-1 of the DATHW system is laid with a disturbance in step load (SLD) of 10%. The investigation is carried out on the DATHW system under the supervision of the fractional order proportional-integral-derivative-filter (FOPIDN) controller optimized with the water cycle algorithm (WCA). However, the dominance of FOPIDN in regulating the DATHW system performance deviations is validated by other regulators. To get the research near practicality, the DATHW system is deliberated with communication time delays (CTDs). The CTDs is the inherit nature of the communication peripherals that are employed in the IPS network for providing the data exchange among various devices. Further, the supplementary control approach of super capacitors (SC) and static synchronous series compensators (SSSC) is adopted with the DATHW system for performance improvement. The supplementary control is implemented by integrating the SC in the control areas and the SSSC with the tie-line. Finally, we conducted the sensitivity test to reveal the efficacy of the suggested controller mechanism in this work.

Universal Continuous Model of Active Power Factor Correctors

The purpose of the work is to develop continuous mathematical models of power factor correctors for switch-mode power supplies. The models are designed to solve optimization problems aimed at increasing the energy efficiency of these devices. This goal was achieved by developing a universal continuous averaged model of switch-mode voltage converters, which are an integral part of any active power factor corrector. State-space averaging method was proposed for constructing such a universal model. It has been shown that such a model adequately reproduces the processes in any of the main types of DC-DC voltage converters. The possibility of constructing a mathematical model of an active power factor corrector based on the proposed universal model of a DC-DC voltage converter is substantiated. The features of the structures of active power factor correctors for switching power supplies are considered and the problems that arise when studying their energy efficiency are shown. By simulation in the time domain with using the constructed model, diagrams of transients of the power factor corrector during load and primary network voltage disturbances are obtained. The most important result is the creation of a universal continuous mathematical model of switching voltage regulators. This model, unlike previously proposed models, is suitable for use in the analysis, modeling and design of any power factor correctors without the need to modify it in each specific case. The significance of the results obtained lies in accelerating the design process of active power factor correctors built on the basis of any type of pulsed DC-DC voltage converters. The developed model is intended for use in the Micro-Cap electronic circuit analysis program. However, since it is ultimately a software module in the SPICE language, this model can be used in many circuit analysis programs that support this language.

Cyber-Physical Attack Launched From EVSE Botnet

With the development of electric vehicles, millions of electric vehicle service equipment (EVSE) are integrated into the power grid. These EVSEs are weakly protected from cyber-attacks. By exploiting vulnerabilities, attackers could establish a botnet integrating hundred-MW-level EVSE loads from the Internet. Dynamic load-altering attack (DLAA) is powerful to amplify the load disturbance to destabilize the power grid. However, different from large-scale loads controlled by existing DLAA, the EVSE botnet is formulated by tens of thousands of bots widely distributed on various power grid nodes, rendering it challenging to be coordinated. In this paper, we analyze the approach to launching a DLAA from the distributed EVSE botnet. Firstly, we adopt a time-division model to evaluate the impact of communication limitations on the attack vectors of the botnet. Then we develop an analytical model to calculate the coordinated effect of attack vectors from different nodes and with varying phase angles; thus, we provide a foundation for the optimal coordination of distributed bots. Subsequently, considering the power grid has adopted defense measures to eliminate or suppress the attack, we formulate an optimization algorithm to make the attack robust against these potential defense measures. Numerical simulations validate the effectiveness of the proposed approach.

SSA-based Fractional Order PI-PD Cascade Controller Design for DC Motor Speed Control

Bu çalışmada doğru akım (DA) motoru hız kontrolünü sağlamak için eklemeli ve kesir dereceli (FOPI-FOPD) denetleyici tasarımı önerilmiştir. Önerilen denetleyici parametreleri son yıllarda geliştirilen Serçe Arama Algoritması (SAA) ile optimize edilmiştir. Denetleyici parametrelerinin aranması için çeşitli amaç fonksiyonları kullanılmıştır. Bu amaç fonksiyonları zamanla çarpılan mutlak hatanın integrali (ITAE), mutlak hatanın integrali (IAE), zamanla çarpılan hatanın karesinin integrali (ITSE), hatanın karesinin integrali (ISE) ve Zwe-Lee Gaing (ZLG) fonksiyonudur. Zaman bölgesinde aşma (M_p), oturma süresi (t_s) ve yükselme süresi (t_r) bakımından kullanılan amaç fonksiyonlarından elde edilen sonuçlar karşılaştırılmıştır. Ayrıca elde edilen sonuçlar frekans bölgesinde kazanç marjı, faz marjı ve bant genişliği açısından incelenmiştir. Zaman ve frekans bölgesinde farklı amaç fonksiyonlarından elde edilen en iyi sonuç literatürdeki çalışmalarla karşılaştırılmıştır. Ayrıca önerilen denetleyicide elde edilen en iyi sonuç için gürbüzlük, bozucu yük ve referans hız değişimi analizleri incelenmiştir.