Additional Compensator Research Articles

Evaluation of wind-induced response of high-rise structure with TMD system by real-time hybrid simulation test with motor-driven shaking table

Due to the difficulty in constructing the small-scaled model of tuned mass damper (TMD) system to meet the requirement of dynamic similarity law, it is hard to evaluate the vibration control effect of passive TMD system on the wind-induced response of high-rise structure by wind tunnel test. The Real-Time Hybrid Simulation (RTHS) test could provide a suitable solution to this problem by increasing the size of the scaled TMD model to overcome the limitation in dynamic similarity law. A RTHS test system with a linear electric motor-driven shaking table was developed by the interface with model interface toolkit in general real time system operating environment. Taking the Guangzhou New TV Tower with a passive TMD system as an example, the Finite Element (FE) model of Guangzhou New TV Tower was selected as the numerical substructure and TMD system was selected as the experimental substructure, the RTHS test was conducted at a sampling frequency of 250 Hz to estimate the wind-induced response of this high-rise structure with a TMD system in various dynamic wind loading cases. To reduce the time delay effect generated by the nonlinear interaction between motion control system and experimental substructure, the adaptive time series (ATS) compensator for time delay compensation was proposed in the RTHS test. The RTHS results were also compared with the numerical simulation results using the FE model of the investigated object. The RTHS test with additional ATS time delay compensator can obtain more accurate experimental results. The effectiveness of the proposed RTHS test system was testified to be powerful test system to evaluate the wind-induced response of high-rise structures with complex passive TMD system.

Site-selective time resolved laser spectroscopy and DFT studies of Nd3+ optical centers in BaF2 doped crystals

Site-selective time-resolved laser spectroscopy techniques, which provide high spectral resolution at low temperatures (4.2 K and 6.5 K), were used to clarify the formation mechanism, spectral and kinetic properties of the Nd3+ ion single-site optical centers formed in the fluorite-type BaF2 single crystals doped with Nd3+. This formation occurs by heterovalent substitution of Ba2+ host cations with additional charge compensation by F− anions. To determine the lifetimes of the Stark 4F3/2(1) levels of the Nd3+ impurity centers, the fluorescence decay kinetics was measured using the gated photon counting technique. The data from spectroscopic experiments were combined with density functional theory (DFT) calculations to identify and analyze the local structure of Nd3+ cations in the Nd3+ ions doped BaF2 crystal. Our studies have shown that several types of single-site Nd3+ optical centers can be distinguished in BaF2:Nd3+. We confirmed the existence of an optical center with high C4v site symmetry and a long radiative lifetime of the 4F3/2(1) state τ = 14.3 ms. We also describe two other configurations of centers with local structure characterized by low site symmetry of Cs, which were identified and described for the first time. The decrease in the tetragonal site symmetry from C4v to Cs was explained by the fact that the Nd3+ dopants, distributed over the equivalent cationic positions of the fluorite-type crystal lattice, coordinate to anionic motifs that essentially differ in the position of the additional charge compensator F−. This structural variability induced in the local coordination environment of the optical center affects its spectroscopic properties through a shift in the energy of the 4F3/2(1) Stark level of the Nd3+ ion and results in a different radiative lifetime τ.

Input data to match model and prototype states of WWER NPP

The paper considers some possible input data of NPP power unit model for solving the problem of model state matching with prototype state. In the course of work on matching the state of NPP model with the prototype, a numerical experiment using full-scale modeling complex PROSTOR was conducted. Its essence was to obtain steady states of the model with capacity from 94% to 104% with a step of 0,05%. For modeling we used data of Kalinin NPP unit 3 loading 4 on 248 effective days. When analyzing the results of the numerical experiment, two effects were found. One of them, expressed in the bend of the derivative of the obtained graph, is connected with reaching the upper limit of the possibility to regulate the pressure in the main steam collector. The regulating valves on the turbine generator are the executing mechanism of pressure regulator in main steam collector. At the break of the graph they open at 100%, which causes further inability to regulate pressure. The pressure in the main steam collector starts to increase. This effect corresponds to the real processes occurring at the NPP. In this case, as one of the model tuning parameters, it is proposed to use the adaptive coefficient to the concentration of boric acid in the reactor, for the control of which, it is proposed to use a mathematical boric regulator. It was also shown that it is impossible to accurately control the pressure in the reactor due to the peculiarities of operation of the volume compensator electric heaters automatics. In this regard, it was proposed to use an additional mathematical volume compensator electric heaters regulator to match the state of the model with the prototype. These regulators have been successfully tested as part of the PROSTOR software package to match the states of the model and the prototype.

Novel adaptive stability enhancement strategy for power systems based on deep reinforcement learning

As the access rate of wind energy in a power system has significantly increased, stabilizing the power system has become challenging. Among these challenges, low-frequency oscillation is one of the most harmful problems, effectively resolved by adding a damping controller according to the relevant properties of the low-frequency oscillation. However, the controller often fails to adapt to the constantly changing wind energy system owing to the lack of a targeted dynamic change strategy. Thus, to address this issue, an adaptive stabilization strategy that uses a static var compensator with an additional damping controller structure is proposed. Specifically, the entire power system is equivalently represented as a generalized regression neural network, with a deep reinforcement learning algorithm called soft actor-critic introduced to train the agent based on the generalized regression neural network model. After the training process, the agent can provide additional efficient static var compensator damping controller parameters under different operating conditions, vastly improving the system stability. Simulation results verify the improved performance using the proposed strategy compared to other optimization methods, regardless of whether the low-frequency oscillations were suppressed in the time or frequency domains.

Balancing a Stick With Eyes Shut: Inverted Pendulum on a Cart Without Angle Measurement

Abstract We consider linear time-invariant dynamic systems in the single-input, single-output (SISO) framework. In particular, we consider stabilization of an inverted pendulum on a cart using a force on the cart. This system is easy to stabilize with pendulum angle feedback. However, with cart position feedback it cannot be stabilized with stable and proper compensators. Here, we demonstrate that with an additional compensator in a parallel feedforward loop, stabilization is possible with such compensators. Sensitivity to noise seems to be about three times worse than for the situation with angle feedback. For completeness, discussion is presented of compensator parameter choices, robustness, fragility, and comparison with another control approach.

Performance Improvement of Weak Grid-Connected Wind Energy System Using FLSRF-Controlled DSTATCOM

Wind energy (WE) is emerging as a green and clean energy source. The power quality (PQ) significantly deteriorates when WE sources are connected to the weak ac grid. This is due to the variable wind speed, the impedance of weak grids, and nonlinear loads. This article proposes a methodology to improve the PQ in the weak grid with WE penetration using additional distribution static compensator (DSTATCOM). Fuzzy logic (FL) controller is implemented in the conventional synchronous reference frame (SRF) scheme to minimize the oscillations in the voltage signals. Also, a feedforward block of the WE source is incorporated in the FLSRF control scheme for adapting changes associated with the wind speed. The proposed control scheme accommodates the changes related to the grid’s strength, wind speed, load currents, and dc-link voltage dynamics to estimate the switching signals for the DSTATCOM. The MATLAB simulation and experimental studies established the effectiveness of the proposed method for enhancing the PQ performance of weak grid-connected WE sources in the presence of nonlinear loads.

MIMO Coded Generalized Reduced Dimension Fourier Algorithm for 3-D Microwave Imaging

In this paper, to accelerate data acquisition and image reconstruction procedures in a multistatic short-range microwave imaging scenario, an orthogonal coding approach with Fourier domain processing is presented. First, a special two-dimensional (2D) multiple-input multiple-output (MIMO) structure is introduced to fully electronically synthesize the 2D aperture. Then, the model of the transmitted and received signals by a MIMO stepped-frequency-modulated radar is presented, with special considerations about orthogonal, balanced and optimal sequences. On the receiver side, the backscatter frequency response extraction process is formulated with the aim of obtaining individual information of all channels. Finally, based on the introduced model, a fast Fourier-based algorithm with reduced dimensions, named MIMO coded generalized reduced dimension Fourier (CGRDF), is mathematically derived. It includes extracting phase and amplitude compensators with the aim of mapping 4D to 2D spatial data, transferring the backscatter transfer function from the spatial domain to the wavenumber domain, extracting the smoothing filter, compensating the curvature of the wavefront of all scatterers, extracting the reflectivity function and an additional range compensator. The results of numerical simulations show the satisfactory and reliable performance of the proposed approach in terms of the information retrieval process and processing speed.

Methods of the Strength Computation for the Covers, Bottoms, Assemblies and Elements of the Structure of Steam Generators Used by the Two-Loop Nuclear Power Plants with BBEP-1000 Reactors

This scientific paper gives a review of the available methods and approaches used for the strength computation of the covers, bottoms, assemblies and elements of the structures of steam generators of the two-loop NPPs with BBEP-1000 reactors. For most assemblies and elements of the structures of steam generators of NPPs, the main strains arising in them are the consequences of the uniform internal and external pressures. However, in many cases the assemblies and elements of the structures of steam generators of NPPs can also be exposed to additional loads (weight loads, efforts and moments that result from nonhomogeneous thermal expansion of different parts of steam generator, etc.). The values of the strains caused by additional loads can sometimes exceed the value of the main strain. These can be decreased by the arrangement of additional supports or compensators or by changing the structure configuration. Sometimes, it is reasonable to increase the wall thickness of the calculated elements of the structures in order to reduce the strains caused by additional loads. Before getting to the strength computations for the assemblies and elements of the structures of steam generators we need to define first the character of the external loads on them (constant or cyclic load) and the deformability of their structural materials (ductile material, brittle material or limited plasticity material) and then to select the method for their strength computation. To provide a reliable operation of the steam generators of NPPs it is important to provide appropriate strength characteristics for all its assemblies and elements. These elements include process pipelines that are connected to the steam generator structure. These represent a spatially branched pipeline systems of a different technological purpose whose structures are supported by special fastening elements (the supports of different types, spring suspenders, etc.). The strength computations done for such systems include static and cyclic strength computations, seismic action computations, etc.

Optimal Intelligent Control for Doubly Fed Induction Generators

For the first time, a novel concept of merging computational intelligence (the type-2 fuzzy system) and control theory (optimal control) for regulator and reference tracking in doubly fed induction generators (DFIGs) is proposed in this study. The goal of the control system is the reference tracking of torque and stator reactive power. In this case, the type-2 fuzzy controller is activated to enhance the performance of the optimum control. For instance, in abrupt changes of the reference signal or uncertainty in the parameters, the type-2 fuzzy system performs a complementary function. Both parametric uncertainty and a perturbation signal are used to challenge the control system in the simulation. The findings demonstrate that the presence of a type-2 fuzzy system as an additional controller or compensator significantly enhances the control system. The root mean square error of the suggested method’s threshold was 0.012, quite acceptable for a control system.

Solar PV Integration to E-Rickshaw With Regenerative Braking and Sensorless Control

This article proposes a novel drivetrain design of a solar-powered e-rickshaw with the controller. Hall-Effect position sensorless brushless dc (BLDC) motor drive often suffers from delayed commutation at high speed and even at low speed, conventional control does not work well due to low magnitude of back EMF. Here, the proposed sensorless control with commutation error compensation is implemented, which drives the motor over the entire range. A simple commutation error compensation algorithm is designed to detect the freewheeling pulses, reducing the control complexity for low-cost EV application and eliminating low pass filter requirement. Moreover, a zero-crossing detection (ZCD) algorithm is suggested, which inherently compensates the delay and removes the need of any additional phase compensator. A fixed delay digital filter is used to eliminate any unwanted spikes in ZCD circuit. For effective MPPT control, a modified Landsman converter is used, which provides ripple-free current at output and reduces the requirement of ripple filter at front end. The BLDC motor drive is capable of energy regeneration, which reduces the range anxiety for EV. The solar energy and the battery ensure that the vehicle never runs out of power irrespective of the climate conditions. The average distance covered by the vehicle on a single charge is improved <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">.</i>

An improved PGC demodulation algorithm for optical fiber interferometers with insensitive to carrier phase delay and modulation depth

Phase generated carrier (PGC) demodulation is widely used in optical fiber interferometers due to its high sensitivity, large dynamic range and high signal fidelity. Based on the traditional PGC DCM demodulation scheme, we propose a algorithm to eliminate the carrier phase delay and compensate the modulation depth of PGC phase demodulation. The proposed algorithm provides real-time compensation for carrier phase delay and modulation depth without additional compensators. Through theoretical analysis and simulation, the performance of the improved demodulation scheme is compared with the traditional PGC-DCM demodulation algorithm. A complete demodulation system hardware is built, and the improved algorithm, the traditional PGC-DCM scheme and the traditional PGC-Arctan algorithm are tested respectively based on the Michelson interferometer. Experimental results show that the proposed algorithm is insensitive to carrier phase delay and modulation depth, its signal-to-noise ratio and distortion rate can reach 56.15 dB, and the total harmonic distortion rate is 0.13 %.

Small‐signal modelling considering internal perturbations for modular multilevel converters

Small-signal modelling of modular multilevel converters (MMC) has drawn lots of attention recently. Existing research mainly studies MMC terminal impedances by injecting corresponding AC-side and DC-side external small-signal perturbations. This paper focuses on the MMC internal small-signal perturbations, that is, perturbations in control signal and their effect. There are two kinds, that is, differential-mode and common-mode, of internal small-signal perturbations, which influence MMC external and internal state variables, respectively. Then, the existing MMC small-signal model is improved. With its help, accurate MMC control-signal to state-variables transfer functions are established, which can aid precise MMC controller analysis and performance optimization. In this paper, an analysis of MMC phase capacitor voltage regulation control is demonstrated as an example. The stability can be precisely ascertained based on the obtained transfer function. The effect of parameter variation of the proportional-integral controller is also studied. Moreover, an additional compensator is introduced in the existing control loop to attenuate resonance peaks in the transfer function, which mitigates the large voltage overshoot and makes the transient state much smoother. Simulation and experimental results support and well confirm the analysis of this paper.

A Novel Method for Accuracy Improvement of Variable Reluctance Linear Resolvers

A novel technique for accuracy improvement of the variable reluctance linear resolvers (VR-L resolvers) is investigated in this article. A well-known structure and a calculation correcting factor are applied to propose a VR-L resolvers model with higher accuracy. A periodic finite-element analysis (FEA) is employed with a shorter processing time. The modeling is also performed for conventional and proposed improved structures by the mentioned FEA, where the extra teeth suppress the end effect in the model. The main reasons for the position error in linear actuators/sensors are the windings’ end effect and nonequal magnetic circuit. Two additional compensator teeth (CT)/slots with different heights are considered at both entrance and front parts of the mover, which introduces an improved structure. Furthermore, a new correction factor is employed to amend the demodulation process resulting in better performance. Compared to the conventional type, the proposed resolver is evaluated in healthy and faulty cases with asymmetric air-gap conditions. It is shown that the position error is significantly reduced in the improved structure. Finally, the effectiveness of the proposed design is proved by experimental results.

Modeling and Extended State Observer-Based Backstepping Control of Underwater Electro Hydrostatic Actuator with Pressure Compensator and External Load

Electro hydrostatic actuator (EHA) has been successfully developed for flight control applications to replace the cumbersome centralized hydraulic system. It also has excellent potential for ocean applications due to its advantages on miniaturization and energy-savings. One of the special technologies for EHA’s underwater application is pressure compensation, which is used to equalize the return pressure of the hydraulic system and the seawater pressure. This paper investigates the modeling and control design of underwater EHA to improve performance, especially considering the effect of additional pressure compensator and uncertain external load. The nonlinear hydraulic model is extended by the dynamic characteristics of the pressure compensator. Two low-order extended state observers were constructed to cope with the external load fore and the effect of the pressure compensator, respectively. The backstepping methods were designed to guarantee the robust stability of the entire high-order nonlinear hydraulic system. Finally, the theoretical proving and simulation on Matlab/Simulink are conducted to demonstrate the high tracking performance of the proposed control strategy.

Reactive power compensation using derated power generation mode of modified P&O algorithm in grid-interfaced PV system

A local load connected with the grid-interfaced photovoltaic (GIPV) system demands reactive power compensation at the distribution level. The compensation either fulfilled by the PV inverter or grid side arrangements such as capacitor bank, static VAR compensator or tap-changing transformers. Amongst both, the inverter has merit to compensate reactive power without using an additional compensator or oversizing the inverter rating. However, it always depends upon the availability of irradiance and especially when the inverter transfers power with full capacity has no margin to generate the reactive power. Therefore, to make the system flexible according to the demand of the local loads and to create a margin to generate the reactive power at any time instant, a GIPV system with modified perturb & observe (MP&O) maximum power point tracking (MPPT) technique has been proposed. This proposed technique with an intermediate boost converter extracts maximum power more efficiently as compared to the traditional MPPT technique. On the other hand, it curtails the generated active power and provides margin for the PV inverter to generate the reactive power. Further, the PV inverter generates active and reactive power to the local loads as well as transfer power to the grid using inverter control. The inverter control comprises of decoupled instantaneous active and reactive power control. In this control scheme, it maintains the DC-link voltage and power flow between the GIPV system and the grid under all available irradiance conditions. In this respect, a 30 kW GIPV system is simulated and performance of the system is validated using real-time OP4510 hardware-in-loop (HIL) setup.

Mid-Infrared Ultra-Short Pulse Generation in a Gas-Filled Hollow-Core Photonic Crystal Fiber Pumped by Two-Color Pulses

We show numerically that ultra-short pulses can be generated in the mid-infrared when a gas filled hollow-core fiber is pumped by a fundamental pulse and its second harmonic. The generation process originates from a cascaded nonlinear phenomenon starting from a spectral broadening of the two pulses followed by an induced phase-matched four wave-mixing lying in the mid-infrared combined with a dispersive wave. By selecting this mid-infrared band with a spectral filter, we demonstrate the generation of ultra-short 60 fs pulses at a 3–4 µm band and a pulse duration of 20 fs can be reached with an additional phase compensator.

LCL resonant current depression control strategy against pulse width modulated harmonic voltage under low switching frequency

The LCL filter is widely used in grid connected converters for good harmonic mitigation performance. With pulse width modulation strategy, converter terminal voltage contains various sideband harmonic components together with expected components corresponding to the modulation wave, especially under a low switching frequency. Considerable resonant current can be generated if the undesired sideband harmonic voltage is located around the LCL resonant frequency. With the background of a medium voltage three-level wind power converter, where the switching frequency is as low as 1.5 kHz, a resonant current depression strategy is proposed against undesired sideband harmonic voltage under low switching frequency. Additional compensators are adopted in the converter current loop. Depending on the system mathematical model, two solutions, a Butterworth low pass filter and a notch filter, based on phase compensation and amplitude compensation, are proposed in this paper. It is shown that the Butterworth low pass filter exhibits better resonant current depression performance, while the notch filter performance is better in terms of system stability. Simulation and experimental results validated the proposed control method.

The Multivariable Control of Carbon Dioxide Absorption System using the Proportional Integral Plus (PIP) Controller

The present article investigates the implementation of non-minimal state space (NMSS) representation with proportional-integral-plus (PIP) controller for the carbon dioxide absorption process of Shiraz petrochemical ammonia unit. The PIP controller is a logical extension of conventional PI/PID controllers with additional dynamic feedback and input compensators. PIP controller is used for multivariable control without limitation on the number of controlled variables. A Multi Input - Multi Output (MIMO) square model was extracted from step response test. In this way, input water flow rate to carbon dioxide absorption system, the heat duty of input absorbent cooler to tray (1) of absorption tower and re-boiler heat duty of stripping tower are chosen as manipulated variables (inputs), while carbon dioxide mole fraction in absorption tower vapor product, the water mole fraction in absorption tower liquid product and tray temperature No. 36 of stripping tower are determined as controlled ones (outputs). The system identification is performed with three input and three output variables using step response test. As a result, continuous and discrete time transfer function matrices and suitable NMSS model for PIP controller are reported. Finally, in order to evaluate the PIP control performance, the feed flow rate increases by 2%. The results show the proper performance of designed PIP controller for both disturbance rejection and set point tracking.

Optimal Disturbance Observer Design for High Tracking Performance in Motion Control Systems

In this paper, a stability-driven optimal disturbance observer (DO) is proposed. The proposed method does not require any plant inverse dynamics to detect introduced disturbances or a stabilizing Q filter. It does not require additional compensators to resolve causality problems, due to the relative degree, or filters to solve instability problems of non-minimum phase plants. Using this method enables wideband and narrowband disturbances to be attenuated by simply multiplying the corresponding peak filters by the baseline weight function. Furthermore, the proposed DO guarantees the stability of closed-loop systems because the already designed outer-loop systems are considered as a target plant to be stabilized and because of the Lyapunov stability-based H∞ control. In the application example, it was confirmed that the proposed method is effective, and the position error signals were improved by 20.9% in commercial hard disk drives and 36.6% in optical image stabilization systems.

A Novel Direct Power Control for DFIG With Parallel Compensator Under Unbalanced Grid Condition

This article presents a voltage-modulated direct power control (VM-DPC) with an additional parallel compensator for the doubly fed induction generator under unbalanced grid conditions. The proposed method not only guarantees a satisfying steady-state performance but provides also a regulating property of the negative-sequence output currents through designed negative-sequence parallel compensator. It can provide symmetrical stator currents and suppress the ripples in both active and reactive powers under unbalanced grid conditions. The performance of the proposed method are verified by comparing it with three different control strategies in simulations carried out in MATLAB/Simulink SimScape Power System. Finally, the effectiveness of the proposed method is evaluated in an experimental prototype, which proves the proposed VM-DPC with the additional compensator has a satisfactory steady-state performance and a fast power transient response under unbalanced grid conditions.