Active Compensation Technique Research Articles

The Active Compensation Technique for Large Reflector Antennas Based on Quadratic Curve Fitting

Active reflectors are often used to compensate the surface distortion caused by environmental factors that degrade the electromagnetic performance of large high-frequency reflector antennas. This is crucial for maintaining high gain operation in antennas. A distortion compensation method for the active reflector of a large dual-reflector antenna is proposed. A relationship is established between the surface deformation and the optical path difference for the primary reflector by geometric optics. Subsequently, employing finite element analysis, a polynomial fitting approach is used to describe the impact of adjusting points on the reflector surface based on the coordinates of each node. By standardizing the positions of various panels on the reflector, the fitting ns can be applied to the reflector panels of similar shapes. Then, based on the distribution characteristics of the primary reflector panels, the adjustment equation for the actuators is derived by the influence matrix method. It can be used to determine the adjustment amount of actuators to reduce the rms of the optical path difference. And, the least squares method is employed to resolve the matrix equation. The example of a 110 m aperture dual-reflector antenna is carried out by finite element analysis and the proposed method. The results show that the optical path difference is reduced significantly at various elevation cases, which indicates that the proposed method is effective.

Active Compensation Technology for the Target Measurement Error of Two-Axis Electro-Optical Measurement Equipment.

For two-axis electro-optical measurement equipment, there are many error sources in parts manufacturing, assembly, sensors, calibration, and so on, which cause some random errors in the final measurement results of the target. In order to eliminate the random measurement error as much as possible and improve the measurement accuracy, an active compensation technique for target measurement error is proposed in this paper. Firstly, the error formation mechanism and error transfer model establishment of the two-axis electro-optical measurement equipment were studied, and based on that, three error compensation and correction methods were proposed: the least square (LS)-based error compensation method, adaptive Kalman filter(AKF)-based error correction method, and radial basis function neural network (RBFNN)-based error compensation method. According to the theoretical analysis and numerical simulation comparison, the proposed RBFNN-based error compensation method was identified as the optimal error compensation method, which can approximate the random error space surface more precisely, so that a more accurate error compensation value can be obtained, and in order to improve the measurement accuracy with higher precision. Finally, the experimental results proved that the proposed active compensation technology was valid in engineering applicability and could efficiently enhance the measurement accuracy of the two-axis electro-optical measurement equipment.

Frequency-Based Active Ripple Compensation Technique to Reduce Bulk Capacitance in Integrated Offline LED Drivers

In order to increase the power density and the lifespan of LED drivers, several studies have proposed Active Ripple Compensation (ARC) techniques for minimizing the converter bulk capacitance. However, a common side-effect of the ARC method is the increase in the Total Harmonic Distortion (THD) of the converter input current. In this context, a frequency-based ARC technique is proposed as an alternative to the conventional ARC methodology, in which the duty-cycle is modulated. The analyses presented in this paper show that the frequency-based ARC approach applied to resonant converters has a better performance than the one used in hard-switching converters, since it allows for a huge capacitance reduction with a small THD increase. Furthermore, this paper presents a generalized analysis of ARC techniques applied to integrated off-line LED drivers, which reduce the number of components and the overall LED driver cost. The input current harmonic content and the output ripple reduction have been theoretically predicted for several converters. Experimental results gathered from a 96-W laboratory prototype supplied from a 127-V 60-Hz grid attested the superior performance of the frequency-based active ripple compensation, since a capacitance reduction of 66.6% has been obtained with an increase of only 0.9% in the THD.

A distributed rule‐based power management strategy in a photovoltaic/hybrid energy storage based on an active compensation filtering technique

This paper proposes a distributed rule-based power management strategy for dynamic power balancing and power smoothing in a photovoltaic (PV)/battery-supercapacitor hybrid energy storage system. The system contains a PV system, a battery-supercapacitor hybrid energy storage system (HESS), and a group of loads. Firstly, an active compensation technique is proposed which improves the efficiency of the power smoothing filter. Then, a distributed supervisory control technique is employed that prevents the BESS and SC from SOC violation while maintaining the balance between generation and load. To this end, the system components are divided into three different reactive agents including an HESS agent, a PV agent, and a load agent. These agents react to the system changes by switching their operational mode upon satisfying a predefined rule. To analyse the hybrid dynamical behaviour of the agents and design the supervisory controllers, the agents are modelled in hybrid automata frameworks. It is shown that the proposed distributed approach reduces the complexity of the supervisory control system and increases its scalability compared to its equivalent centralized method. Finally, the performance of the proposed approach is validated using a test system simulated in MATLAB/Simulink.

Solar Powered Unmanned Aerial Vehicle With Active Output Filter Under Non-Linear Load Conditions

This paper presents a new electric powertrain for solar powered unmanned aerial vehicle (UAV). The proposed system structure is based on the development of the power supply system for both the Solong and Zyphyr aircraft models. The proposed UAV model incorporates the Zyphry UAV use of an AC line feeder instead of DC power lines to power the propellers. The proposed powertrain includes solar panels, an energy management system based on lithium sulfide battery, inverter, AC bus-line and active output filter (AOF). AOF topology is composed of a high switching frequency H-bridge inverter with a reduced size LC filter. The utilization of AOF system reduces the size and weight of the power transmission system and significantly improves its conversion efficiency by introducing an emulated series resistance with the H-bridge stage to ensure high quality pure sinusoidal waveform of the line voltage. This emulated series resistance produces an injected voltage across it to diminish unwanted harmonics created from the non-linear load. A simulation model and experimental setup are created to simulate the proposed system and the system is tested under non-linear load condition with closed-loop feed-back control strategy. The obtained simulation and experimental results demonstrate that high-quality sinusoidal line voltage waveforms can be obtained using the active resistance compensation technique with total harmonic distortion factor less than 3%. Moreover, power losses analysis and conversion efficiency calculation of the proposed system are performed and compared with that of the conventional three-phase PWM inverter, which proved that the power losses are reduced by 31%.

Optimized capacitive active ripple compensation topology for a 3.7 kW single-phase high power density on-board charger of electric vehicles

In this paper, a comprehensive investigation of the capacitive active ripple compensation (ARC) techniques is made to conclude which one is optimal to be used in on-board chargers of electric vehicles. Crucial aspects in such an application are: lifetime, volumetric and specific power density (including components’ size and the needed cooling solution), and overall efficiency of the charger. As presented in this paper, all capacitive ARC topologies (buck, boost, and buck–boost) have successfully diverted the low-frequency ripple from the dc side with a maximized power density. The ARC circuit consists of two additional switches, a smoothing auxiliary inductor, and a storage auxiliary capacitor. Finally, the buck capacitive ARC topology proves to be the optimal ARC technique for on-board chargers because of its maximal power density, minimal loss behavior and voltage stress, and long lifetime capability as it requires a downsized capacitance to the extent, where film capacitors or ceramic capacitors can replace the normally used bulky electrolytic capacitors. The performance of the three capacitive ARC techniques is proved by simulation results.

A Fully Integrated Low-Dropout Regulator With Differentiator-Based Active Zero Compensation

An area-efficient low-power fully integrated output-capacitorless low-dropout regulator (OCL-LDO) is presented in this paper. The three-stage OCL-LDO utilizes an embedded differentiator-based active zero compensation technique together with adaptive biasing. The proposed active zero compensation helps enhance the unity-gain bandwidth (UGB) of the regulator with very small silicon area and almost no extra current consumption. The UGB is therefore able to be maintained above 2.5 MHz even at a measured quiescent current of mere $1.6~\mu \text{A}$ . Adaptive bias is employed to further stabilize the circuit and extend the bandwidth extension as well as enhance the transient response. The chip area is 0.0021 mm2 with maximum load capability of 25 mA, which leads to a maximum current density of 11.9 A/mm2. The measured voltage spikes are below 40 mV for full-load transient responses, and the response time is about 1.2 ns. The voltage spikes of line transient responses are only 4 mV at full load. The measured full-load power-supply rejection is better than −44 dB up to 100 kHz.

Investigation of the Active Ripple Compensation Technique to Reduce Bulk Capacitance in Offline Flyback-Based LED Drivers

This paper presents the study of an offline flyback-based light-emitting diode (LED) driver with reduced storage capacitance. An approach called active ripple compensation was used for minimizing the converter bulk capacitance. This technique is oriented to voltage-controlled pulse width modulation converters and is based on the modulation of the duty cycle, which allows for the reduction of the filtering capacitance by increasing the harmonic content of the input current up to the limits established by the standards. By means of the design procedure presented in this paper, the amount of capacitance reduction and input current distortion can be fully controlled and theoretically predicted. In addition, no extra sensors are required to implement the proposed technique, apart from the LED current sensor already available in most LED drivers. Experimental results from a 50-W laboratory prototype supplied from a 220-V 60-Hz grid were carried out. The results were compared with the conventional approach, attesting the superior performance of the proposed methodology.

Stability improvement of microgrids in the presence of constant power loads

Renewable energy sources, the most reasonable fuel-shift taken over the naturally limited conventional fuels, necessarily deal with the self-sustainable microgrid system rather than the traditional grid distribution system. In practice, the microgrid system experiences the challenge of instability due to the Constant Power Load (CPL) from many electronic devices. In this paper, AC microgrid stability, besides the stability analysis and pole zero movement, is thoroughly investigated for each and every considerable parameter of the system in order to improve the stability scenario. After demonstrating all cases regarding the instability problem, the storage based virtual impedance power compensation method is introduced to retain the system stability and extend the loading limit of the microgrid system. Here, in this proposed method, both the active and reactive power compensation techniques are suggested for a potential solution. Besides this, a PID controller is implemented to maintain the constant terminal voltage of CPL via current injection method from storage. All the cases and results are rigorously scrutinized in the virtual platform such as MATLAB/Simulink with appreciable aftermaths. Hardware implementation of the proposed method is also conducted to find out its effectiveness.

Active phase compensation technique for buried target extraction

A novel method for buried target extraction, the active phase compensation technique is proposed. The range migration algorithm (RMA) is the conventional method for synthetic aperture radar (SAR) image reconstruction, but if targets exist in different media, identification of the target can be difficult because of losses and the significant reflection from the boundary face. In this regard, the matrix pencil method is utilised to actively find the boundary point and buried target responses. Then, the reflection effect can be eliminated, and range cells corresponding to estimated target responses can be compensated by applying newly created compensation functions. It improves the detection accuracy of buried targets. Finally, experimental results demonstrated that the proposed technique performs better than the classic RMA.

Active compensation of nonlinear distortion in balanced armature receivers

Balanced armature receivers have been widely used in hearing aids due to their higher efficiency and more discrete size comparing to moving coil loudspeakers. For the application of hearing aids, it may require a very high output sound pressure level (up to 110 dB in an opened ear canal) and, yet, minimum nonlinear distortions. This requirement often results in a larger receiver in size, which is less comfortable for wearing. It is highly desired if the linear range of a smaller receiver can be broaden without increasing its physical size. Active compensation of nonlinearity for moving coil loudspeakers through signal processing means have been well studied. However, similar research for balanced armature receivers is rarely seen in the literature. Although the two types of transducers differ in many aspects, they share commonalities in the nonlinearity mechanism. The current study surveys the active compensation techniques developed for moving coil loudspeakers and explores the possibility of adopting them to reduce the nonlinearity of balanced armature receivers.

Effect of magnetic field fluctuation on ultra-low field MRI measurements in the unshielded laboratory environment

Magnetic field fluctuations in our unshielded urban laboratory can reach hundreds of nT in the noisy daytime and is only a few nT in the quiet midnight. The field fluctuation causes the Larmor frequency fL to drift randomly for several Hz during the unshielded ultra-low field (ULF) nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) measurements, thus seriously spoiling the averaging effect and causing imaging artifacts. By using an active compensation (AC) technique based on the spatial correlation of the low-frequency magnetic field fluctuation, the field fluctuation can be suppressed to tens of nT, which is a moderate situation between the noisy daytime and the quiet midnight. In this paper, the effect of the field fluctuation on ULF MRI measurements was investigated. The 1D and 2D MRI signals of a water phantom were measured using a second-order low-Tc superconducting quantum interference device (SQUID) in three fluctuation cases: severe fluctuation (noisy daytime), moderate fluctuation (daytime with AC) and minute fluctuation (quiet midnight) when different gradient fields were applied. When the active compensation is applied or when the frequency encoding gradient field Gx reaches a sufficiently strong value in our measurements, the image artifacts become invisible in all three fluctuation cases. Therefore it is feasible to perform ULF-MRI measurements in unshielded urban environment without imaging artifacts originating from magnetic fluctuations by using the active compensation technique and/or strong gradient fields.

A novel ±0.8 V high-performance voltage-tunable CDTA with enhanced bandwidth

In this article, we propose a novel high-performance complementary metal oxide semiconductor (CMOS) current differencing transconductance amplifier (CDTA) with a transconductance gain (GM) that can be linearly tuned by a voltage. By using a high-speed, low-voltage, cascaded current mirror active resistance compensation technique, the proposed CDTA circuit exhibits wide frequency bandwidths, high current tracking precisions as well as large output impedances. The linear-tunable GM of the CDTA is designed with the use of linear composite metal oxide semiconductor field-effect transistor as basic cells in the circuit. Combining these two approaches, several design concerns are studied, including: impedance characteristic, tracking errors, offset and linearity and noise. The prototype chip with a 0.25 mm2 area is fabricated in a GlobalFoundries’0.18 μm CMOS process. The simulated results and measured results with ±0.8 V DC supply voltages are presented, and show extremely wide bandwidths and wide linear tuning range. In addition, a fully differential band-pass filter for a high-speed system is also given as an example to confirm the high performance of the proposed circuit.

Performance Evaluation of Adaptive Tabu Search Algorithm Optimized Sinusoidal Fryze Voltage Control based Hybrid Series Active Power Filter

A novel hybrid series active power filter to eliminate harmonics and compensate reactive power is presented and analyzed. The proposed active compensation technique is based in a hybrid series active filter using adaptive tabu search algorithm in the conventional Sinusoidal Fryze voltage control technique. The paper analyzes the proposed hybrid series active power filter when connected with load of 3-phase diode bridge rectifier with R-L branch directly. This paper intends to show the improvement between the performance of conventional scheme and ATS-optimized scheme. Simulation results obtained using MATLAB/Simulink confirm the viability of the proposed compensation technique.

New machine tool motorized spindle integrated with one electromagnetic ring balancer driven by optimal square wave

Machine tool motorized spindle usually encounters mass imbalance in the operational process. In order to enhance the machining efficiency and precision, on-line active unbalance compensation technique is becoming the first choice of vibration suppression for machine tool spindle. This paper proposes a new motorized spindle integrated with one electromagnetic ring balancer. Firstly, the three-dimension structural design of the integrated spindle is described in detail. Then, the balancing principle of electromagnetic ring balancer is set forth. In order to disclose the structural characteristic and determine the reasonable square wave drive parameters, the finite element calculations are carried out to obtain the relationship between the torque and rotational angle of counterweight disk when coil is not electrified, and the movement curve when coil is applied different currents. Based on the steady-state and transient electromagnetic field simulations, a specific spindle prototype with one electromagnetic ring balancer is developed. For the prototype, vibration test rig is built to verify the balancer design correctness, fabrication quality and vibration reduction effectiveness. The experimental results show that the proposed balancer has a smooth movement process under square wave drive, a desired unbalance response and the spindle vibration can be effectively reduced in a semiautomatic balance way, which is very beneficial to the improvement of operational precision and service life of machine tool motorized spindle.

Application of Adaptive Tabu Search Algorithm in Sinusoidal Fryze Voltage Control based Hybrid Series Active Power Filter

A novel hybrid series active power filter to eliminate harmonics and compensate reactive power is presented and analyzed. The proposed active compensation technique is based in a hybrid series active filter using adaptive Tabu search (ATS) algorithm in the conventional Sinusoidal Fryze voltage (SFV) control technique. Optimization of the conventional Sinusoidal Fryze voltage control technique has been done using adaptive tabu search algorithm. This paper discusses about the comparative performances of conventional Sinusoidal Fryze voltage control strategy and ATS-optimized controllers. ATS algorithm has been used to obtain the optimum value of Kp and Ki. Analysis of the hybrid series active power filter system under non linear load condition and its impact on the performance of the controllers is evaluated. Effectiveness of the hybrid series active power filter to provide harmonic damping is demonstrated by MATLAB/Simulink results. Total harmonic distortion (THD) demonstrates the practical viability of the controller for hybrid series active power filter to provide harmonic isolation of non-linear loads and to comply with IEEE 519 recommended harmonic standards.

Stabilization of Medium-Frequency Modes in Isolated Microgrids Supplying Direct Online Induction Motor Loads

Driven by the economical and environmental concerns, the importance of distributed generation-based microgrids is increasing. However, the presence of induction motor (IM) loads in converter-based microgrids might induce source-load admittance mismatch between the IM load and microgrid converters leading to medium-frequency instabilities, particularly in isolated microgrids. To overcome this issue, this paper presents detailed small-signal admittance models, analysis, and stabilization of a voltage-source inverter (VSI)-based microgrid with direct online IM load. The resultant source (VSI) and load (IM) admittances form a multi-input-multi-output (MIMO) system. Using the generalized Nyquist stability criterion, it is shown that the interactions between the lightly-damped dynamics of IMs and isolated VSI-based microgrid have significant destabilizing effect. Active compensation techniques are proposed to maintain the system stability. Time-domain simulations and experimental results are presented to validate the theoretical analysis.

Decoupled Reference-Voltage-Based Active DC-Link Stabilization for PMSM Drives With Tight-Speed Regulation

Reference-current-based active compensation techniques are widely used to actively damp the negative admittance effect associated with constant power loads in power electronic systems. These methods, however, yield strong coupling among the active compensator, speed, and current control dynamics when applied to motor drives. To overcome these difficulties, a new reference-voltage-based active compensator (RVC) is proposed to mitigate the negative admittance effect in permanent-magnet synchronous motor drives with tight-speed regulation. The proposed RVC suppresses the interaction dynamics between the compensator and motor drive dynamics in the low- and medium-frequency regions and maintains stability and effective damping performance along the whole loading trajectory of the motor drive. In addition, the proposed compensator has a very simple structure, and it can easily be augmented to existing motor drives with minimal interactions with existing drive control strategy and parameters. A theoretical comparative analysis and test results are provided to demonstrate the validity and effectiveness of the proposed technique.

Design of optimum actively compensated networks

This paper describes an active compensation technique which is readily applicable to all active-RC networks, independently of the circuit topology. This procedure considers the network in its totality and derives general active compensation conditions for a generic active-RC network employing 2 or 3 operational amplifiers. Furthermore, the remaining degrees of freedom of the circuits are used to optimize the performance of the actively compensated circuits to further extend its operating frequency range. Simulation and experimental results are also reported.

Modeling, Analysis, and Stabilization of Converter-Fed AC Microgrids With High Penetration of Converter-Interfaced Loads

This paper addresses ac microgrid stability under high penetration of converter-interfaced loads (CILs). According to the Nyquist admittance ratio criterion, destabilizing interaction dynamics are yielded among the interfacing voltage-source inverter (VSI) of the ac microgrid and CILs. Active stabilization techniques are proposed to maintain the overall system stability from the VSI side using admittance-based small signal analysis. Sensitivity and robustness analyses are presented to assess the dynamic coupling among active damping and voltage tracking controllers of the interfacing VSI. A complete Matlab/Simulink model of an ac microgrid with multiple CILs is used to demonstrate the effectiveness of the proposed active compensation techniques.