Power Reference Research Articles

Bioequivalence of zolpidem hemitartrate: new formulations of 5 mg SL, 10 mg and 12.5 mg XR and comparison of their bioavailabilities

Objective: To evaluate pharmaceutical bioequivalence between two formulations of 5 mg zolpidem hemitartrate sublingual and, 10 and 12.5 mg extended-release formulations tablets in healthy subjects under fasting and fed conditions. Methods: An open label, monocentric, randomized, 2 x 2 crossover study in 40 healthy adults under fasting conditions comparing two formulations of zolpidem 5mg sublingual tablets. Analyte concentrations in human plasma were determined using a validated liquid chromatography with a tandem mass spectrometer detector method (LC-MS/MS). The same design was utilized to evaluate the other formulations.
 Results: Statistical analysis has determined geometric mean of test / reference ratio, confidence intervals, and power of the test to the pharmacokinetic parameters Cmax, AUC0-t, and AUC0-∞. The geometric mean ratio (90%CI) of the test drug/reference drug for zolpidem 5mg were 99.89 to 113.57% for Cmax, 97.15% to 108.40% for AUC0-t, and 97.22% to 108.13% for AUC0-∞. Power of the test was 99.35% for Cmax and 100% AUC0-t, and AUC0-∞. Conclusion: Both test and reference are bioequivalent for all formulations and, therefore, they are interchangeable, according to the Brazilian criteria (Anvisa resolution RE nº 1170/2006), since confidence intervals for Cmax and AUC0-t ratios were within 80% and 125%.

VSG Frequency Regulation Strategy for Adaptive Model Predictive Control

When the active power of a Virtual Synchronous Generator (VSG) is unbalanced, the frequency will fluctuate significantly. Based on this, this article proposes an adaptive model predictive control method. By introducing a hyperbolic tangent function to construct an adaptive moment of inertia that includes frequency change and frequency change rate to provide the inertia for the island microgrid system, and the predicted model is updated in real-time; At the same time, model predictive control is used to calculate the optimal power reference value of VSG, strengthening the power support of VSG. The results indicate that under joint control improves the frequency regulation capability of VSG units and further enhances the system frequency performance, and the frequency deviation reduces from 0.15Hz to 0.05Hz, and the frequency change rate reduces from 0.58Hz/s to 0.5Hz/s. It is proved that the proposed control strategy can effectively suppress the maximum frequency offset and maximum frequency change rate during power fluctuations.

Design and evaluation of a municipal solid waste incineration power plant integrating with absorption heat pump

The absorption heat pump can consume a small amount of high temperature heat source instead of electricity to realize the waste heat recovery. It has a potential to be applied in the energy efficiency improvement of municipal solid waste incineration power plant. In this study, a proposed integrated system has been designed, where the sludge heat pump drying system and dump pit heating system are coupled with the absorption heat pumps. The power generation improvement is evaluated through simulation calculation by EBSILON Professional and Aspen Plus. The results show that the power generation of proposed integrated system is 1.21 MW higher than that of reference power plant in winter operating condition. This is mainly due to the reductions of energy loss and exergy loss in incinerator and boiler system according to the energy flow and exergy flow analysis. The extracted steam from turbine is more suitable than the flue gas out of bag filter as the high temperature heat source of heat pump. In addition, the variable operating condition analysis is carried out for the proposed integrated system.

An emergency control considering current limitation and transient stability of virtual synchronous generator

AbstractWith the increasing application of renewable energy sources (RESs), more and more grid‐connected voltage‐source converters (VSCs) in the grid need to operate in a “grid‐forming” manner. However, when large disturbances occur in the grid, grid‐connected converters may lose synchronization and cause the current to exceed set limits. To ensure the stable and safe operation of VSC during large disturbances and to improve the power supply capacity during voltage dips of RES, this paper proposes an emergency control method that takes into account the virtual synchronous generator (VSG) current limit and transient stability based on a large‐signal mathematical model of the VSG during fault and normal states. The method divides the operation area of the VSG into non‐emergency area and emergency area. If the operating point is in the non‐emergency region after a fault, only the active power reference value is changed to avoid current exceeding the limit and transient instability; if the operating point is in the emergency region, the current exceeding the limit and transient instability are avoided by changing the active power reference value and adding in the virtual impedance. Finally, the effectiveness of the proposed control strategy is verified by simulation.

Enhancing voltage profile in islanded microgrids through hierarchical control strategies

This paper presents a novel approach aimed at enhancing the voltage profile of an islanded microgrid (MG) through the utilization of Phasor Measurement Units (PMUs) and a hierarchical control system for Distributed Generators (DGs). Recognizing the criticality of maintaining an optimal voltage profile for essential loads within an MG, we assume that PMUs are strategically placed across the MG based on existing placement methodologies to ensure the observability of load buses. The synchrophasor measurements captured by these PMUs are leveraged within an offline-designed tertiary control layer of the hierarchical framework, which in turn sets the voltage reference for the secondary control layer of DGs across the MG. This approach effectively enhances the voltage profile of vital load buses within the MG. The proposed hierarchical strategy encompasses primary, secondary, and tertiary levels of control, responsible for stabilizing voltage and frequency, computing power references, and managing power flow, respectively. PMU measurements play a crucial role in the secondary control level by continuously monitoring deviations. By ensuring the effective placement of PMUs, the proposed framework enables efficient control, leading to notable improvements in the voltage profile and power management. To evaluate the effectiveness of our approach, five test networks were used: 14-bus, 30-bus, 39-bus, 57-bus, and 118-bus test networks. Simulation results demonstrate an impressive over 80 % enhancement in the MG's voltage profile achieved by our proposed method. Additionally, our heuristic strategy efficiently assigns the closest load bus to each DG while aggregating equidistant bus deviations. Collectively, our research underscores the significant impact of PMU measurements and a well-structured hierarchical voltage control system in substantially improving the voltage profile of MGs.

Analysis and Control of Cascaded Energy Storage System for Energy Efficiency and Power Quality Improvement in Electrified Railways

Energy-efficient and grid-friendly railway power system is critical for the sustainable development of electrified railways. In this paper, a cascaded energy storage system (CESS) is investigated for energy efficiency and power quality improvement of the railway power system. First, the detailed operation principles of the CESS for multiple control objectives, including regenerative braking energy (RBE) utilization, reactive power compensation, and negative sequence current suppression, are analyzed. On this basis, a hierarchical power flow control strategy is developed for achieving the power flow management and control of multiple objectives for CESS. Specifically, a multi-objective power flow management strategy is designed in the system layer to allocate the power references for the CESS under sufficient and insufficient capacity scenarios. In the sufficient capacity scenario, the power references are directly obtained by the operation principles. In the insufficient capacity scenario, the power references are allocated through a three-stage optimization method considering the power shaving rate, grid power factor, and grid imbalance degree. Subsequently, the power references from the system layer are tracked in the converter layer to achieve power flow control. Finally, the effectiveness of the proposed hierarchical power flow control strategy is verified through experimental results. The results show that the proposed CESS can achieve superior performance on RBE utilization and power quality improvement under complex operating conditions in electrified railways.

AI-Based Technique to Enhance Transient Response and Resiliency of Power Electronic Dominated Grids via Grid-Following Inverters

This paper presents a frequency restoration method to enhance power electronic dominated grid (PEDG) resiliency and transient response via re-defining grid following inverters (GFLIs) role at the grid-edge. An artificial intelligence-based power reference correction (AI-PRC) module is developed for GFLIs to autonomously adjust their power setpoints during transient disturbances. A detailed analytical validation is provided that shows control rules in PEDG intrinsically follow the underlying dynamic of the swing-based machines to extend its stability boundary. Considering this fact, comprehensive transient and steady state-based mathematical models are used for constructing the learning database of the proposed AI-PRC. The proposed training approach can deal with grid's characteristics alterations and uncertainties. Thus, this approach incorporates PEDG's effective variables that shapes its dynamic response during transient disturbances. Subsequently, a neural network is trained by Bayesian regularization algorithm (BRA) to realize the proposed AI-PRC scheme for frequency support via GFLIs. Several simulation and experimental case studies results validate the functionality of the proposed AI-PRC towards enhancing the PEDG's transient response and resiliency via GFLIs. The provided case studies demonstrate significant improvement in frequency restoration in response to transient disturbances.

Data-Driven Emergency Frequency Control for Multi-Infeed Hybrid AC-DC System

With the continuous development of large-scale complex hybrid AC-DC grids, the fast adjustability of HVDC systems is required by the grid to provide frequency regulation services. This paper develops a fully data-driven linear quadratic regulator (LQR) for the HVDC to provide temporal frequency support. The main technical challenge is the complexity and the nonlinearity of multi-infeed hybrid AC-DC (MIDC) systems dynamics that make the LQR intractable. Based on Koopman operator (KO) theory, a Koopman eigenpairs construction method is developed to fit a global linear dynamic model of MIDC systems. Once globally linear representation of uncontrolled system dynamics is obtained offline, the control term is constituted by the gradient of the identified eigenfunctions and the control matrix <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{B}$</tex-math></inline-formula> . In case that <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{B}$</tex-math></inline-formula> is unknown, we propose a method to identify it based on the verified Koopman eigenfunctions. The active power reference is optimized online for LCC-HVDC in a moving horizon fashion to provide frequency support, with only locally measurable frequency and transmission power. The robustness of the proposed control method against approximation errors of the linear representation in eigenfunction coordinates is analyzed. Simulation results show the effectiveness, robustness and adaptability of the proposed emergency control strategy.

Power Advance Prediction to Improve the Energy Utilization Efficiency of Motor-Driven System Considering Multilink Time-Delay

In the motor-driven system, the utilization of a supercapacitor energy storage unit contributes to energy saving. However, the multi-link time-delay in the system makes the supercapacitor unable to immediately track and respond to the sharp change of motor power. This will cause the large DC bus voltage fluctuation, the peak current at the power grid side, and unnecessary energy loss. In this paper, a power advance prediction control strategy considering multi-link time-delay is proposed. The multi-link time-delay mechanism in the system is analyzed, in particular for the different conditions of motor power change. Afterward, with the motor speed, torque, and the inverter acceleration/deceleration rate obtained in advance, the motor steady power and power change rate are predicted. In the dynamic process, by adjusting the tracking rate in real time, the motor reference power function is derived. The reference current of the supercapacitor is given online, so as to match the power between the motor and the energy storage unit. Both simulation and experimental results verify the rationality and validity of the proposed control strategy. In the dynamic process, the system stability and energy utilization are successfully improved in comparison with multi-parameter collaborative power prediction control and double closed-loop control.

From theory to practice: Monitoring mechanical power output during wheelchair field and court sports using inertial measurement units

An important performance determinant in wheelchair sports is the power exchanged between the athlete-wheelchair combination and the environment, in short, mechanical power. Inertial measurement units (IMUs) might be used to estimate the exchanged mechanical power during wheelchair sports practice. However, to validly apply IMUs for mechanical power assessment in wheelchair sports, a well-founded and unambiguous theoretical framework is required that follows the dynamics of manual wheelchair propulsion. Therefore, this research has two goals. First, to present a theoretical framework that supports the use of IMUs to estimate power output via power balance equations. Second, to demonstrate the use of the IMU-based power estimates during wheelchair propulsion based on experimental data. Mechanical power during straight-line wheelchair propulsion on a treadmill was estimated using a wheel mounted IMU and was subsequently compared to optical motion capture data serving as a reference. IMU-based power was calculated from rolling resistance (estimated from drag tests) and change in kinetic energy (estimated using wheelchair velocity and wheelchair acceleration). The results reveal no significant difference between reference power values and the proposed IMU-based power (1.8% mean difference, N.S.). As the estimated rolling resistance shows a 0.9–1.7% underestimation, over time, IMU-based power will be slightly underestimated as well. To conclude, the theoretical framework and the resulting IMU model seems to provide acceptable estimates of mechanical power during straight-line wheelchair propulsion in wheelchair (sports) practice, and it is an important first step towards feasible power estimations in all wheelchair sports situations.

Automatic Dependent Surveillance-Broadcast Deceptive Jamming Detection Method Based on Track Data

The characteristics of automatic dependent surveillance-broadcast (ADS-B) technology, such as unencrypted channels and open data protocols, make it extremely vulnerable to various intentional or unintentional spoofing and jamming, which seriously threatens air traffic safety. Traditional approaches do not update their high-bit data for a long time, which causes the situations of the same encoding results to have different aircraft positions and it is difficult to determine the real position of the aircraft and effectively detect ADS-B jamming. Therefore, it is urgent to propose more effective detection methods for ADS-B spoofing and jamming. First, the methods and principles of frequency shift calculation and automatic monitoring algorithm are introduced. Then, signal consistency detection and error robustness are analyzed, and a track-data-based detection model for abnormal ADS-B data are proposed. The track-data-based detection methods can use multi-point sampling judgment algorithm to realize the reception and processing of data bits. This method makes full use of the information of multiple sampling values of each data bit and the reference power value obtained in the preamble detection, and determines the data value and confidence value through the relationship between the two. The detection methods for ADS-B spoofing and jamming distinguishes the true and false signals and the authenticity of target positions by comparing the arrival time difference of each signal at the ground station. Finally, the research results show that, with the increase of signal to noise ratio, no matter the estimation based on virtual array translation or the estimation based on circular stationary signal, their estimation accuracies are improved with gradually increasing trends.

Design of Z source converter with the genetic-based chicken swarm algorithm for closed loop control of PV integrated grid

A single-phase grid coupled PV system with a switched Z-source boost converter is analysed on the basis of closed-loop control using a novel hybrid algorithm. As PV results in low-voltage DC, it is vital to step up this low-voltage DC and so a suitable DC-DC converter is needed. A switched Z-source boost converter is utilized for the step-up process as this converter uses minimum passive components, thereby reducing the cost with improved power density. Control of the converter is carried out by a closed loop control using a PI controller tuned with a novel genetic-based chicken swarm (GBCS) algorithm which combines the merits of both genetic and chicken swarm able to deal with complex problems, simple with fast convergence. The output of the converter is then given to the grid through a single-phase VSI in which DC–AC conversion takes place. While connecting PV to the grid, another factor to be taken care of is grid synchronization which is accomplished by a PI controller in which the actual and reference power are analogized. The proposed control scheme is simulated in a MATLAB environment and the outcomes are observed. The grid current THD of 1.6% and reactive power compensation is accomplished.

Passivity-based Rieman Liouville fractional order sliding mode control of three phase inverter in a grid-connected photovoltaic system.

Photovoltaic (PV) system parameters are always non-linear due to variable environmental conditions. The Maximum power point tracking (MPPT) is difficult under multiple uncertainties, disruptions and the occurrence of time-varying stochastic conditions. Therefore, Passivity based Fractional order Sliding-Mode controller (PBSMC) is proposed to examine and develop a storage function in error tracking for PV power and direct voltage in this research work. A unique sliding surface for Fractional Order Sliding Mode Control (FOSMC) framework is proposed and its stability and finite time convergence is proved by implementing Lyapunov stability method. An additional input of sliding mode control (SMC) is also added to a passive system to boost the controller performance by removing the rapid uncertainties and disturbances. Therefore, PBSMC, along with globally consistent control efficiency under varying operating conditions is implemented with enhanced system damping and substantial robustness. The novelty of the proposed technique lies in a unique sliding surface for FOSMC framework based on Riemann Liouville (R-L) fractional calculus. Results have shown that the proposed control technique reduces the tracking error in PV output power, under variable irradiance conditions, by 81%, compared to fractional order proportional integral derivative (FOPID) controller. It is reduced by 39%, when compared to passivity based control (PBC) and 28%, when compared to passivity based FOPID (EPBFOPID). The proposed technique led to the least total harmonic distortion in the grid side voltage and current. The tracking time of PV output power is 0.025 seconds in PBSMC under varying solar irradiance, however FOPID, PBC, EPBFOPID, have failed to converge fully. Similarly the dc link voltage has tracked the reference voltage in 0.05 seconds however the rest of the methods either could not converge, or converged after significant amount of time. During solar irradiance and temperature change, the photovoltaic output power has converged in 0.018 seconds using PBSMC, however remaining methods failed to converge or track fully and the dc link voltage has minimum tracking error due to PBSMC as compared to the other methods. Furthermore, the photovoltaic output power converges to the reference power in 0.1 seconds in power grid voltage drop, whereas other methods failed to converge fully. In addition power is also injected from the PV inverter into the grid at unity power factor.

Distributed ADMM power optimal control for standalone hybrid generation systems

With the rapid development and increased demand for renewable energy sources, standalone hybrid generation systems have become an essential energy solution. Power optimization control is thus critical to achieving the efficient operation and stability of this system. The distributed ADMM (alternating direction method of multipliers)-based approach has the full potential to deal with the power optimization problem of standalone hybrid generation systems. This study uses an optimization algorithm with a Gaussian penalty function, ADMM-ρ, to alternately optimize the power reference values of wind, light, and battery-containing power generation subsystems. The local controller regulates the output power of the converter according to this reference value. This ensures that the wind and photovoltaic power generation subsystem work in load-tracking or maximum power-tracking modes so that the optimal operation of hybrid power generation meets the balance of supply and demand while prolonging the service life of the batteries. Simulation experiments show that the distributed ADMM algorithm can reliably address the power optimization challenge of hybrid power generation systems.

Constant Power Load Stabilization With Fast Transient Boundary Control for DAB-Converters-Based Electric Drive Systems

Due to the negative incremental impedance of constant power loads (CPLs), many undesirable issues such as the oscillations or even possible collapse of the main dc bus voltage may occur, which may significantly degrade the system stability of Electrical Vehicles (EVs). This paper presents a natural-switching-surface (NSS) fast-transient-boundary-control (FTBC) based stabilization solution for EVs with dual-active-bridge (DAB) converters as the main power interface. Based on the mathematical models of multiple natural switching surfaces (NSS) and characteristics of CPL, the proposed FTBC control can achieve stable operation of DAB converters feeding CPLs and fast dynamic response irrespective operating stages such as the startup, sudden voltage and power reference changing conditions. Compared with other strategies such as load shedding, the proposed FTBC has no additional requirements for hardware, which is cost-effective. The analytical derivation of the proposed algorithm under the CPL condition is presented together with simulation and experimental evaluations, which validate that the proposed FTBC is capable of achieving 2 times faster start-up process and at least 33% dynamic response improvement compared with proportional integrator (PI) closed-loop control while eliminating the dc-bias current and guaranteeing the CPL stability by regulating the dynamic trajectories of DAB converters in the geometric domain.

Power matching based current limitation method for grid forming converter under large disturbances

Grid forming (GFM) converter mimics the operational characteristics of the synchronous generator, serves as a voltage source that provides voltage and frequency support to the power system. However, due to its voltage source nature, the current of the GFM converter is highly determined by the external system, increasing the risk of overcurrent under large disturbances and potential damage to the converter. The conventional current reference limitation suffers from synchronization instability, which causes the converter to lose synchronization. To address this issue, this paper proposes a novel power matching based current limitation method, which maintains the synchronization of the GFM converter and also avoids overcurrent issues. Specifically, when a large disturbance occurs, considering the maximum output power of the GFM converter, the reference power of the converter is corrected using the frequency to match the output power in real time. Therefore, the output power of the converter is always its maximum value, with the current constrained to the maximum level allowed, avoiding overcurrent and instability. Finally, the superiority of the proposed method is verified by experiment and simulation.

Grid manager design using Battery Energy Storage Systems in weak power systems with high penetration of wind energy

The increasing penetration of renewable energies is becoming a problem for the stability of the grid and the planning of electricity generation. The use of batteries in parallel to wind farms can be a very interesting issue in order to assure controlled power delivery of renewable energy sources. In this way wind energy can become in a predictable and even controllable energy resource. This article presents a proposition to design a grid manager for weak power systems with high penetration of wind energy using Battery Energy Storage Systems (BESS). Using power demand and wind predictions this system manager will send reference power to BESS and controllable generators. In this way the primary power reserve can be reduced and wind deviations will not affect to the performance of generators.

Short-Term Forecasting of Pork Price Based on The ARIMA Model

China's large population requires a large and diverse amount of food, of which pork is one of the important agricultural products related to the national economy and people's livelihood. Based on the pork price data from 2010 to July 2023, this paper adopts the ARIMA time series model to forecast the pork price in the short term from August 2023 to February 2024 in order to provide a powerful reference for the macroeconomic management of the country. After testing, the ARIMA model has a certain guiding and reference value for predicting the high and low pork prices in the short term, which can provide a decision-making basis for the macroeconomic management of the country.

Yaw misalignment in powertrain degradation modeling for wind farm control in curtailed conditions

A framework characterizing the degradation of wind turbines for use in multiple-input damage-aware farm control is suggested. The focus is on the fatigue damage of the powertrain (drivetrain + generator) system, but the methodology may be extended to other components. A database of steady-state damage analyses for different operating conditions (average wind speeds, turbulence levels, power demands, and yaw misalignment angles) using aero-hydro-servo-elastic simulations is first generated. Then, a weighted damage index based on probabilistic long-term fatigue damage analysis of the powertrain system components is suggested and used to represent degradation at the farm level for control purposes. The focus is on curtailed conditions where the farm controller dispatches power commands to individual turbines in order to track a demanded power reference (rather than seeking to maximize power) at the farm level. As a secondary objective, the controller seeks to mitigate degradation through a smart combination of power commands and yaw offset angles, making use of the weighted degradation index. The potential of the proposed approach is demonstrated through a case study on the TotalControl Reference Wind Power Plant in a FLORIS-based simulation framework. The proposed farm controller is compared with the conventional one without damage mitigation feature and with damage mitigation but without yaw angle as the control input. It is found that combining yawing and downregulation effectively slows down degradation on the main bearing and powertrain as a whole.

Analyzing the Automatic Power Level Control Effect of a Signal Generator in RF Power Sensor Calibration by a Direct Comparison Transfer Method and a Millimeter Wave Application.

Most calibration laboratories prefer the Direct Comparison Transfer Method (DCTM) for a reliable and accurate calibration of power sensors in the radio frequency (RF) scope. Most studies suggest using this calibration method, with its automatic power level control (APLC) of RF signal generators. The APLC is preferred to keep the output power level of the signal generator the same, while the power sensor is calibrated and the reference power sensor is connected to the measurement system. The known APLC mechanisms are also explained for the DCTM, and a comparison of the calibration factor values carried out with and without the automatic power level control process in the DCTM is also given in this study. RF power sensor calibrations with coaxial and waveguide connector types are examined with DCTM in this study as well. This study shows that the DCTM, unless with APLC, should be applied for the waveguide power sensor's calibration at millimeter wave frequencies.