Load Compensation Research Articles

Dual-Band Three-Way Doherty Power Amplifier Employing Dual-Mode Gate Bias and Load Compensation Network

This article presents a new method to design dual-band three-way Doherty power amplifiers (DPAs). A novel modified load modulation network (LMN) is constructed for enabling dual-mode Doherty operation with three-way configuration, providing enhanced high efficiency range in both modes. Moreover, a parallel load compensation network (LCN) is employed in the proposed three-way DPA to provide wideband performance in each operation band. A three-way dual-mode DPA using commercial gallium nitride high electron mobility transistors (GaN HEMTs) is then designed and manufactured to verify the proposed architecture. Frequency bands of 1.45–1.9 GHz in Mode I and 0.75–1.0 GHz in Mode II are achieved by the DPA, respectively. The fabricated DPA has a 9-dB output back-off (OBO) efficiency of 42.8%–57.7% and a saturated efficiency of 55.4%–70.1%. When driven by a 20-MHz long term evolution (LTE) modulated signal with 8-dB peak-to-average ratio (PAPR), the adjacent channel power ratio (ACPR) of the fabricated DPA is better than −49.9 dBc after digital predistortion at 0.9 and 1.7 GHz with average efficiency of 45.7% and 54.6%.

Global identification and compensation of nonlinear variable load for an electrohydraulic system

In an electrohydraulic system, the load is an external factor that cannot obtain similar results by repetitive experiments compared with other internal factors. It can work a great change in an extremely short time determined by the characteristics of the loaded object, which is more difficult to be identified timely and compensated precisely. This paper first built the mathematic model of the electrohydraulic system containing load characteristics and illustrated most kinds of basic loads that possibly occur in it. Then, a practice nonlinear variable load composed of these basic loads is presented, and the corresponding effect to the electrohydraulic system is analyzed. Based on the summary of load, a nonlinear variable load compensation controller (NVLCC) with neural networks is proposed to identify the mathematic model of the electrohydraulic system. The nonlinear variable load is considered as a part of the model to be globally identified, and an adaptive sliding mode control method is combined to quickly converge the errors of system state variables. The compensation effectiveness is demonstrated by both rigid step response and dynamic sine response in the simulations, and the actual improvements are verified with the experiments using three different typical linear loaded objects and a representative nonlinear loaded object.

Sea trial investigation for dynamic load compensation effect evaluation on novel soft hang-off system

ABSTRACT Offshore drilling activities have been significantly impacted by extreme storm conditions as oil and gas development has moved into deeper water. Under the situation of the imminent arrival of a typhoon, retrieval of the whole drilling riser is time-consuming and tedious. A novel soft hang-off system under hang-off and transit operations is proposed and developed to solve the low-efficiency and time limitation for risers' retrieval. The hang-off joint system suspends the drilling riser and the hydraulic system is designed for dynamic load compensation. Sea trial for enhanced hang-off mode with hang-off joint, non-differential control dynamic load compensation mode at hang-off operation and passive compensation mode at transit operation are conducted to evaluate the load compensation effect equipped with novel soft hang-off system compared with conventional hard hang-off mode. Results on dynamic load compensation effect are discussed. The novel soft hang-off system is of high application value for deepwater drilling engineering.

Enhancement of Power Quality in Power Distribution Systems Using FC- TCR Based Compensation Systems

The development of modern electronic systems and increasing number of application areas (computers, office equipment, rectifiers, converters, speed control devices, uninterruptible power supplies, switched power supplies) has led to harmonic generation and reduced energy efficiency. The majority of loads are inductive in nature and the draw of reactive power has increased in networks and transmission lines resulting in problems with power quality. In addition to efficient power flow in transmission systems, there is also a need to compensate for the reactive power flow in order the meet the requirements of the load and system. As an alternative to traditional solutions, FACTS (Flexible Alternating Current Transmission Systems) has been developed in order to operate electrical systems efficiently and improve stability and power quality. Technological applications such as SVC, STATCOM, SSSC and active harmonic filter are becoming widespread in order to improve power quality. In this study, applications within the scope of FACTS systems are explained and analysis of a fixed capacitor-thyristor controlled reactor (FC-TCR) to improve power factor is discussed. A circuit model of the FC-TCR is developed as a simulation and used to investigate how power factor may be kept within desired limits by adjusting the firing angle of the thyristors under different load conditions. A comparative evaluation has been carried out to determine the effect of FC-TCR by presenting results before and after the load compensation process is applied. From the simulation it is observed that reactive power compensation can be achieved even for varying linear loads.

Digital Implementation of Harmonic and Unbalanced Load Compensation for Voltage Source Inverter to Operate in Grid Forming Microgrid

Voltage source inverter (VSI) is a good candidate for grid forming microgrid because it provides constant amplitude, frequency, and sinusoidal shape voltage at point of common coupling (PCC). As the microgrid is separated from utility grid, voltage quality of the PCC is easily affected by the type of load. To ensure power quality in grid operation, a three-phase VSI providing automatic voltage compensation for unbalanced or nonlinear load is presented in this paper. To maintain voltage quality at a certain level, the Fast Fourier Transform (FFT) algorithm is embedded in a proportional-resonant (PR) controller to mitigate the total harmonic distortion (THD) at PCC. In the meantime, any change of voltage magnitude that is caused by the unbalanced load could be reduced as well. To further enhance the transient response with the change of load, a predictive current (PC) controller is integrated into the PR controller. All the control strategies are implemented by digital approach. The effectiveness of proposed controls is verified through experiments on a testbed of the three-phase stand-alone system.

Multi-Functional UPS for Commercial Use

This paper proposes a line-interactive static UPS system with a simple control strategy for the operation of three-leg IGBT based AC/DC converter. Min-Max algorithm based PWM technique is used as switching logic for AC/DC converter. The developed control strategy addresses the applications like reactive power compensation of load, unbalanced currents compensation, active power compensation during peak load time on the grid and Seamless power transfer operation from grid-connected mode to islanding mode. LCL filter is designed to meet the THD limits specified in IEEE Std 519-2014.

CERN’s Super Proton Synchrotron 200 MHz cavity regulation upgrade: Modeling, design optimization, and performance estimation

CERN's Super Proton Synchrotron (SPS) accelerates protons to $450\text{ }\text{ }\mathrm{GeV}/c$ and transfers them into the Large Hadron Collider (LHC). It is currently one of the limiting factors in increasing the beam intensity and thus the luminosity of the LHC. As part of the LHC injectors upgrade project, the SPS 200 MHz rf system has been modified during the CERN long shutdown 2 (January 2019--April 2021), resulting in a new layout containing two additional cavities. The goal is to improve longitudinal stability required for the planned doubling of the beam intensity for the high luminosity LHC. In parallel with the upgrade of the high-power rf, a new low-level rf (LLRF) system has been designed, including a new cavity field regulation system. This work presents a model of the beam-rf interaction which includes a detailed representation of the LLRF controlling the cavity. This model is used to determine the optimal LLRF design for maximum loop stability and beam loading compensation. Finally, the performance of the upgraded LLRF is estimated.

Feedforward-Feedback Based Adaptive Control Algorithm for Power Quality Improvement of Grid Integrated Photovoltaic System

Integration of renewable energy systems such as wind and solar energy with the regular grid via inverters has shown to be a dependable approach for delivering end customers with consistent and high-quality power. Controlling and synchronizing generated power with the grid requires integrating the control algorithm in a Grid Integrated Photovoltaic (GIPV) system. A feedforward-feedback (FFFB) based adaptive control technique for the 3-stage dual-stage GIPV system is proposed in this research. The fuzzy logic controller is employed for DC-link voltage feedback control in the proposed feedforward-feedback adaptive control algorithm, and an additional feedforward loop is introduced to improve the GIPV system's performance. The efficiency of the suggested control algorithm in managing inverter operation while maintaining power quality is demonstrated. Furthermore, the system response of providing reactive power compensation, harmonic compensation, and load balancing for varied loads is explored using MATLAB and the Simulink tools.

Adaptive Fuzzy Logic Controller for Harmonics Mitigation Using Particle Swarm Optimization

An excessive use of non-linear devices in industry results in current harmonics that degrades the power quality with an unfavorable effect on power system performance. In this research, a novel control technique-based Hybrid-Active Power-Filter (HAPF) is implemented for reactive power compensation and harmonic current component for balanced load by improving the Power-Factor (PF) and Total–Hormonic Distortion (THD) and the performance of a system. This work proposed a soft-computing technique based on Particle Swarm-Optimization (PSO) and Adaptive Fuzzy technique to avoid the phase delays caused by conventional control methods. Moreover, the control algorithms are implemented for an instantaneous reactive and active current (I_d-I_q) and power theory (Pq0) in SIMULINK. To prevent the degradation effect of disturbances on the system's performance, PS0-PI is applied in the inner loop which generate a required dc link-voltage. Additionally, a comparative analysis of both techniques has been presented to evaluate and validate the performance under balanced load conditions. The presented result concludes that the Adaptive Fuzzy PI controller performs better due to the non-linearity and robustness of the system. Therefore, the gains taken from a tuning of the PSO based PI controller optimized with Fuzzy Logic Controller (FLC) are optimal that will detect reactive power and harmonics much faster and accurately. The proposed hybrid technique minimizes distortion by selecting appropriate switching pulses for VSI (Voltage Source Inverter), and thus the simulation has been taken in SIMULINK/MATLAB. The proposed technique gives better tracking performance and robustness for reactive power compensation and harmonics mitigation. As a result of the comparison, it can be concluded that the PSO-based Adaptive Fuzzy PI system produces accurate results with the lower THD and a power factor closer to unity than other techniques.

Observer-Based Quadrature Signal Generator for UPQC in a Single-Phase Distribution System

This paper presents a control algorithm for generation of reference voltage and current based on Observerbased QSG (Quadrature Signal Generator) for UPQC (Unified Power Quality Conditioner) in a Single-Phase Distribution System. The proposed UPQC is a combination of DSTATCOM and DVR used for load and source compensation such as voltage sag and swell, voltage and current harmonics etc. The proposed control algorithm is capable of generating reference signals from the distorted voltages and currents. In this paper, an improved OQSGbased PLL (Phase-Locked Loop) is utilized over OQSG to enable and operate with increased bandwidths that will improve the dynamic response, tracking accuracy and faster detection of reference signal under all varying load and grid conditions. The control algorithm is tested and evaluated using MATLAB / Simulink.

Elastic energy aggregation and distribution method in load compensation mechanism using linear spring

Elastic energy aggregation and distribution method in load compensation mechanism using linear spring

Development and sea trial investigation for deepwater drilling riser specialized soft hang-off system during transit

Offshore drilling activates have been significantly impacted by severe weather conditions as oil and gas development has moved into deep and ultra-deep water. Under the situation of imminent arrival of a typhoon, emergency retrieval of the whole drilling riser is time consuming and tedious. A novel specialized soft hang-off system to improve the adaptability of the drilling riser system under hang-off or transit operations is developed to solve the low-efficiency and time limitation for retrieval all drilling riser joints during extreme storm environment. The specialized soft hang-off system improves its bending capacity and reduce the risk of interference with diverter housing and moonpool and partially compensate the heave motion of drilling platform, to ensure the drilling riser keep lower tension and not compression during hang-off or transit mode. A numerical solution with mechanical model, boundary condition, results validation is conducted and transit operation window is obtained. Sea trial investigation on the novel specialized soft hang-off system during transit operation are conducted to evaluate the performance on global strength and dynamic load compensation effect. The research can be a significant basis and of valuable reference for deepwater engineering and the manufactured novel specialized soft hang-off system is an important emergency equipment.

Statistical Multimode Accounting in the Problem of Optimal Reactive Load Compensation when Constructing Smart Grids

The article deals with the development prospects for smart grids. An approach to optimizing the modes of electric power systems in terms of reactive power is presented in detail. The solution of this problem considers the multimodality, determination of the integral characteristics of the modes, etc. Analytical modeling of load changes by means of the method of factor analysis allows to reduce the amount of information drastically without a significant loss of the accuracy of the obtained solutions. For this purpose, the actually correlated electrical loads of various nodes of electric power systems are represented in the form of a linear combination of independent random variables, namely, generalized load graphs. It is shown that the inclusion of multimode by orthogonal graphs results in a significant simplification of the solution of multimode problems. The choice of the dependent and independent variables composition when solving the optimization problem with the power consumption modes has a fundamental effect both on the modeling of constraints, the formation of the reduced gradient and the main calculation expressions, and on the speed of the optimization search as a whole

Modeling, Controller Design and Simulation Groundwork on Multirotor Unmanned Aerial Vehicle Hybrid Power Unit

This paper presents the results of modeling, control system design and simulation verification of a hybrid-electric drive topology suitable for power flow control within unmanned aerial vehicles (UAVs). The hybrid power system is based on the internal combustion engine (ICE) driving a brushless DC (BLDC) generator supplying the common DC bus used for power distribution within the aircraft. The overall control system features proportional-integral-derivative (PID) feedback control of the ICE rotational speed using a Luenberger estimator for engine-generator set rotational speed estimation. The BLDC generator active rectifier voltage and current are controlled by proportional-integral (PI) feedback controllers, augmented by estimator-based feed-forward load compensators. The overall control system design has been based on damping optimum criterion, which yields straightforward analytical expressions for controller and estimator parameters. The robustness to key process parameters variations is investigated by means of root-locus methodology, and the effectiveness of the proposed hybrid power unit control system is verified by means of comprehensive computer simulations.

An Effective Reactive Power Compensation Method and a Modern Metaheuristic Algorithm for Loss Reduction in Distribution Power Networks

In this paper, a new method of reactive power compensation is proposed for reducing power loss of distribution power networks. The new method is the combination of local compensation at each load and distribution line compensation. In the method, local capacitors at each load are determined to increase power factor of load to an expected value first and then a number of capacitors are placed in distribution lines with two factors, location and capacity by using the three applied methods. Particle swarm optimization (PSO), parasitism predation algorithm (PPA), and tunicate swarm algorithm (TSA) are applied for the proposed method on four distribution systems with 15, 33, 69, and 85 buses. The comparisons of results with previous methods indicate that the three applied methods can reach higher loss reduction for all study cases. TSA can reach loss reduction more effectively than others by 19.4%, 0.5%, 7.9%, and 10.76% for the four distribution systems, respectively. The most important emphasis is that PSO, which was considered to be of low effectiveness in previous studies, can reach much better loss than approximately all previous methods thank to the proposed compensation method. PSO also reached better loss reduction than others by 18.97%, 0.4%, 7.73%, and 10.21%, respectively. Consequently, it is recommended that the proposed compensation method is useful for distribution systems in minimizing total power loss and TSA can be selected a new and powerful method for the problem.

Exo-Muscle: A Semi-Rigid Assistive Device for the Knee

In this work, we introduce the principle, design and mechatronics of Exo-Muscle, a novel assistive device for the knee joint. Different from the existing systems based on rigid exoskeleton structures or soft-tendon driven approaches, the proposed device leverages a new semi-rigid principle that explores the benefits of both rigid and soft systems. The use of a novel semi-rigid chain mechanism around the knee joint eliminates the presence of misalignment between the device and the knee joint center of rotation, while at the same time, it forms a well-defined route for the tendon. This results in more deterministic load compensation functionality compared to the fully soft systems. The proposed device can provide up to 38Nm assistive torque to the knee joint. In the experiment section, the device was successfully validated through a series of experiments demonstrating the capacity of the device to provide the target assistive functionality in the knee joint.

Optimal actuator placement and static load compensation for a class of distributed parameter systems

Abstract Adaptive structures where actuators are incorporated into a building structure have the potential to reduce resource consumption in construction industry drastically. However, the performance of static load compensation depends to a large extend on the actuator placement. This paper presents optimal actuator placement for systems with distributed parameters based on the Gramian compensability matrix. To provide a general framework for different kind of loads, static loads are discretized as Dirac impacts. The resulting optimal actuator placement is robust against unknown load amplitudes, as load profiles are only considered qualitatively in the cost function. Further, the optimal control input for a given load results directly from the optimization problem. The procedure is illustrated for a Kirchhoff-Love plate and integrated fluidic actuators.

Design and study of new riser dynamic load compensation device test system

To ensure the safety of the riser, a kind of new riser dynamic load compensation device is used in this paper, which can effectively reduce the dynamic load of the riser. At the same time, according to a certain similarity criterion, the riser dynamic load compensation test system was designed, including heave simulation system, load simulation system and compensation system. The co-simulation model of the system was established by using ADAMS and Simulink, and the effects of accumulator volume, precharge pressure, piston rod area of compensating hydraulic cylinder and throttle time constant on the system performance were analyzed. The simulation results show that the dynamic load compensation device has a certain compensation effect.

Nonlinear Loads Compensation Using a Shunt Active Power Filter Controlled by Feedforward Neural Networks

The shunt active power filter (SAPF) is a widely used tool for compensation of disturbances in three-phase electric power systems. A high number of control methods have been successfully developed, including strategies based on artificial neural networks. However, the typical feedforward neural network, the multilayer perceptron, which has provided effective solutions to many nonlinear problems, has not yet been employed with satisfactory performance in the implementation of the SAPF control for obtaining the reference currents. In order to prove the capabilities of this simple neural topology, this work describes a suitable strategy of use, based on the accurate estimation of the Fourier coefficients corresponding to the fundamental harmonic of any distorted voltage or current. An effective training method has been developed, consisting of the use of many distorted patterns. The new generation procedure uses random combinations of multiple harmonics, including the possible nominal frequency deviations occurring in real power systems. The design of the generation of reference signals through computations based on the Fourier coefficients is presented. The objectives were the harmonic mitigation and power factor correction. Practical cases were tested through simulation and also by using an experimental platform, showing the feasibility of the proposal.

Modelling and Performance Analysis of a DSTATCOM using ISCT Control Technique

This paper chiefly deals with the performance of DSTATCOM as a load compensator. For enhancing the power quality and so as to mitigate harmonics it is employed on the load side. The reactive power is absorbed or generated by DSTATCOM by regulating the bus voltage. The most reason for occurring of the power quality issues is because of the non-liner loads that were employed by the consumers. DSTATCOM works as inductive or capacitive modes basing on the system voltage. The analysis is performed on the issues in the distribution side by employing the DSTATCOM compensation in this paper. In this paper,we had adopted Instantaneous Symmetrical Compound Theory (ISCT) controller to mitigate harmonics on the source side. The harmonics are due to the increase in the usage of non-linear loads by the consumers. The DSTATCOM regulates the bus voltage by absorbing or generating reactive power. The results are extracted using extensive digital simulation performed in MATLAB/SIMULINK environment.