Output Load Research Articles

Multi-Time Interval Dynamic Optimization Model of New Energy Output Based on Multi-Energy Storage Coordination

In response to the problem of mismatch between new energy output and multi-energy load requirement in multi-energy power systems, this article proposes a dynamic optimization model for new energy output in multiple time intervals based on multi-energy storage coordination. First, considering the energy conversion characteristics of multi-energy storage, the dynamic optimization method of new energy output based on the discrete division of subinterval of scheduling time is studied. Then, considering the cost of adjusting various resources comprehensively, the optimization objective of new energy output is studied, and a model-solving method based on a directed graph topology distributed algorithm is proposed. Finally, simulation verification was conducted, and the simulation results showed that the method proposed in this paper can effectively suppress the new energy fluctuation and reduce peak-shaving costs.

A 180 nA Quiescent Current Digital Control Dual-Mode Buck Converter With a Pulse-Skipping Load Detector for Long-Range Applications

A digitally controlled dual-mode buck converter using low quiescent current is proposed in this work. In particular, the proposed dual pulse-skipping mode adopts a pulse-skipping adaptive on-time (PSAOT) mode for heavy load; and a pulse-skipping asynchronous mode (PSAM) for light and ultra-light loads to achieve a 100,000X wide load range for the Long-range (LoRa) application. Specifically, the pulse-skipping mode selector adopts a digital logic circuit to realize the 180nA low quiescent current. In addition, a low-power dynamic comparator with an adjustable offset is used to accelerate the transient response. The proposed converter is fabricated in a TSMC 350 nm CMOS process and results in an output voltage of 3.3 V from 5V to 4.2 V input voltage range. These results show that the overall system achieves 92.9 % peak eficiency at 8 mA output load and a figure of merit (FoM) of 2.29.

Hybrid physical and data driven modeling for dynamic operation characteristic simulation of wind turbine

Accurate simulation of wind turbines is the key to achieve efficient control of wind turbines and optimal scheduling of wind power systems. Most of the existing methods are physical simulation models, which have heavy computational burden, especially for large-scale wind turbines, and the simulation accuracy is poor under complex dynamic operating conditions. In response, this paper proposes a hybrid physical and data driven model for dynamic operation characteristic simulation of wind turbines. Firstly, a database of dynamic characteristics of wind turbine operation under various wind conditions is constructed, and then the sequence learning (Seq2Seq) model is used to mine the time series characteristics of wind turbine operation parameters. Combining with long short-term memory (LSTM) network, the mapping relationship between various operating parameter time series to establish. On this basis, an attention mechanism is added to the model to learn the dynamic response characteristics of rotor inertia to natural wind process. Through numerical example analysis, the method proposed in this paper can accurately excavate and learn the time sequence dynamic characteristics of wind turbine operating conditions and parameters under various wind conditions, thereby improving the simulation accuracy and calculation efficiency of wind turbine output power and load dynamic characteristics. Taking the actual wind turbine operation data as an example, the simulation accuracy of wind turbine output power reaches 99.8%. Compared with traditional methods, and the simulation accuracy of tower root load reaches 88.5%.

An efficient energy management framework for residential communities based on demand pattern clustering

Intelligently managing energy production and consumption on community basis can enhance the demand side energy efficiency. The fact that the number of energy resources (especially controllable appliances) could be large imposes non-trivial computational burden to community-scale energy management. This paper proposes a community energy management framework that coordinately manages the operations of different kinds of energy resources in a community (i.e., photovoltaic solar power sources, battery energy storage systems (BESSs), and controllable appliances from different households) to minimize the community’s energy cost while sufficiently considering the peak-to-average ratio (PAR) of the community’s load and the occupants’ satisfaction. The proposed framework is with a two-stage design: in the day-ahead stage, multiple “virtual appliances” are formed, where each virtual appliance represents a group of appliances that have similar operational patterns. Based on this, a day-ahead scheduling model is formulated to determine the optimal operation plans of the virtual appliances and other energy resources. The virtual appliances’ schedules are then mapped to actual individual appliances through the developed mapping algorithms. In the real-time operation stage, a receding horizon-based energy management model is developed for correcting the BESS’s operation subjected to the day-ahead plan and real-time solar power output and uncontrollable load. Extensive simulation is conducted to validate the proposed framework based on a real-world dataset.

Thermo-economic analysis for a novel grid-scale pumped thermal electricity storage system coupled with a coal-fired power plant

Combining pumped thermal electricity storage with existing thermal power plants can be a promising technical route for developing large-scale grid energy storage technologies for stably consuming renewable power. In this paper, a novel pumped thermal electricity storage system coupled with a supercritical coal-fired power plant is designed based on cascade heat storage. The thermodynamic analysis shows that the round-trip efficiency of the integrated system can reach 0.53–0.56 under 60–100% output load, for a practical design with a recuperation temperature of 280 °C and compressor outlet temperature of 500 °C. An economic analysis is performed and indicates this design can achieve a payback period of around 4 years considering a moderate charging electricity price of 3 ¢/kWh and a long storage period of 12 h. Further decreasing the recuperation temperature and increasing the compressor outlet temperature can reduce the system investment cost and LCOE, while it requires technological advancement of molten salts working at a wider temperature range and more robust compressors. In comparison to the integrated system with conventional two-tank storage, as well as other storage systems like vanadium redox flow batteries, the current design has a more attractive cost and can be scaled up in future multi-energy applications.

The influence of yaw misalignment on turbine power output fluctuations and unsteady aerodynamic loads within wind farms

Systematic wind tunnel experiments were performed to quantify the power output fluctuations and unsteady aerodynamic loads of modeled wind farms with 3 rows and 3 columns across various yaw angles. Time-resolved particle image velocimetry (PIV) was applied to characterize the flow statistics, while the power output and aerodynamic loads on the turbine tower were measured by a data logger and force cell at high temporal resolution. Results showed that the growth of the yaw misalignment angle mitigates the turbine power output fluctuation. However, this can increase the power fluctuations of downstream turbines. Measurements of the aerodynamic loads on the turbine tower revealed that the growth of the yaw angle significantly increased the fatigue loading in the side-force direction across all frequency components. At the same time, such impact was less distinctive for the thrust force. The dominating unsteady aerodynamic loads are always in the direction perpendicular to the rotor surface. Flow statistics demonstrated that yaw misalignment could effectively increase mean wake velocity, and integral time scale and reduce the turbulence intensity. Finally, theoretical models based on the coupling between turbine properties and local incoming flow statistics were derived to reveal the evolution of turbine power fluctuations and unsteady aerodynamic loads in the wake flow across various yaw misalignment.

Boost power factor correction converter with adaptive harmonic compensation control

AbstractIn low‐voltage distribution systems, the increased penetration of power electronic devices leads to the decentralization of harmonic sources, which puts the sensitive loads or communication systems in the risk status. The conventional methods of point‐to‐point harmonic control are not applicable. In order to solve this problem without increasing additional investments, this paper focuses on mitigating the harmonic interference through the power factor correction (PFC) converter. Hence, a critical conduction mode (CRM) single‐phase boost PFC converter with adaptive harmonic compensation (AHC) control is proposed to reduce the harmonic interference at user side. Firstly, the feed‐forward control loop of a PFC converter is decoupled into the fundamental branch and harmonic branch to trace the harmonic interference and generate the compensation current. Then the compensation gain is designed by the compensation loop gain and compensation capacity of PFC converter. Meanwhile, the characteristics of the PFC converter are analyzed to study the effect of the AHC control on the active power transmission and output load, which can provide important support for the proposed method in application. Finally, a 160‐W experimental prototype is built to verify the effectiveness of the proposed AHC control.

A Bionic Type Piezoelectric Actuator Based on Walking Motion and Asymmetrical L-Shaped Flexure Mechanisms

A bionic type piezoelectric actuator based on the walking motion of L-shaped flexure mechanisms has been proposed. By mimicking the walking motion of “human legs,” the proposed actuator is able to not only eliminate the backward motion to improve the motion efficiency, but also achieve the large working stroke with high output load easily. The special L-shaped flexure mechanism is employed as the “leg,” and the bionic walking motion is realized by applying two L-shaped flexure mechanisms alternately. The driving principle of the proposed piezoelectric actuator is discussed in detail, and the simulation is carried out to study the feasibility. An experimental system has been set up to investigate the actual working performance. According to the experimental results, the suitable phase difference between the two L-shaped flexure mechanisms to eliminate the backward motion is around <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">θ</i> = 5°, the maximum speed is <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> = 1887.3 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m/s, the minimum stepping distance is 0.084 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m, and the maximum load is more than <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F_v</i> = 1100 g. The motion speed and the maximum load under the proposed bionic walking motion (two flexure mechanisms work together as “legs”) could be improved greatly for almost 3.7 and 1.7 times, respectively, compared with that of the traditional friction–inertial motion (only one flexure mechanism works). By eliminating the backward motion, the motion efficiency is improved about 52.9% under the condition of 120 V and 1 Hz. This article shows the feasibility of applying the bionic motion to improve the performance of piezoelectric actuators, which may be instructive for the design of piezoelectric actuators with large working stroke. In the future, it may be helpful for the real application of piezoelectric actuators in the fields of ultraprecision machining, optical engineering, and aerospace technology.

An Output-Capacitor-Free Synthesizable Digital LDO Using CMP-Triggered Oscillator and Droop Detector

This article presents a synthesizable digital low-dropout regulator (DLDO) that precludes the use of an output load capacitor. For efficient regulation, the DLDO consists of fine and coarse loops that have different load conditions to operate. The dual loops are made of typical standard cells to improve the synthesizability. In the coarse loop, a comparator (CMP)-triggered oscillator is employed to generate a high-frequency clock signal without concerning the metastability in the CMP. In order to achieve a fast response to a voltage droop caused by load–current variation, a droop detector and latch-based drivers are exploited that are capable of compensating for a voltage droop asynchronously. The prototype of the DLDO was fabricated in 28-nm CMOS technology. A range of supply voltage is from 0.5 to 1.0 V with a 50-mV dropout voltage. Depending on a supply voltage, a maximum load current and a quiescent current are measured as 160-to-480 mA and 7.7-to-241 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> A, respectively. While a load current is increased from 20 to 450 mA with a 2-ns edge time, a 112-mV voltage droop and a 1.4-ns response time are achieved. Thanks to the synthesizability and the output-capacitor-free design, the DLDO occupies an 0.049-mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^2$</tex-math> </inline-formula> total area and offers 9.8-A/mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^2$</tex-math> </inline-formula> current density.

Design of a reliable and coordinated protection strategy for zonal shipboard power systems

AbstractThe reliable performance of the shipboard power system (SPS) is essential for the safe and efficient operation of marine vessels. SPSs are subject to various types of electrical faults that can cause equipment failure, system downtime, and even catastrophic events. One effective way to provide redundancy and fault tolerance in the event of a fault or failure is through the use of zonal configuration. However, the protection of such systems is a challenging task due to their complex topology and the potential for multiple sources of fault. Therefore, it is imperative to protect the SPS with zonal configuration from various types of fault to ensure its continuous operation. This article presents a comprehensive coordinated protection strategy for a hybrid AC/DC SPS with the zonal configuration by using the available protective equipment. The proposed strategy consists of fault current limiting, grounding, fault detection, and faulty section isolation, and provides both primary and backup protections for all SPS equipment, including generator, busbar, line, input and output feeders, loads, propulsion motors, and DC system. Also, it does not require a comprehensive communication infrastructure and training dataset. The selective and reliable performance of the proposed protection strategy is verified through several case studies under various fault scenarios in the ETAP environment. The article provides valuable insights into the selection and implementation of appropriate protection measures for the SPS with ring configuration which are useful for the designers, operators, and maintenance personnel, improving the reliability and safety of these critical and autonomous systems.

A higher-order sliding mode controller’s super twisting technique for a DC–DC converter in photovoltaic applications

Electricity can be produced using solar photo.voltaic (SPV) modules. Variable solar energy operational characteristics including irradiance, ambient temperature, wind speed, etc. considerably affect the output voltage and load power of SPV-based systems. DC–DC power converters create extra challenges for the robust design of power converters since they provide a constant voltage to the power line. A more robust control design for the power converter is required due to the characteristics and load patterns of a nonlinear system. This paper explains how to effectively regulate high-order sliding mode (HOSM) in solar photovoltaic isolated flyback converters. Compare the suggested HOSM approach with the usual PI control technique. The proposed HOSM control strategy outperforms conventional PI control techniques in uncertain and perturbed environments. This research also offers a unique technique for avoiding chattering in flyback converters (FCs) through the use of super-twisting sliding modes.

유도전동기에서 부하 변동시 역률 보상 장치 적용 여부에 따른 특성 해석

Induction motors are most widely used for driving rotating loads in the industrial applications. This induction motor may be operated at the rated output load in some cases, but it is often operated at lower load than the rated load. Induction motor has a low power factor due to its inductive load. A device such as a capacitor is used to compensate for a low power factor, but it is difficult to maintain a constant power factor in response to load fluctuations. Therefore, reactive power compensators such as Statcom are also used to keep constant the power factor that varies depending on load fluctuations.BRIn this study, when the load of the induction motor changes, the changes in active power, reactive power, and apparent power were confirmed for cases where no capacitor was installed, only capacitors installed, and only Statcom installed. In addition, based on this, the efficiency and power factor fluctuations at the power source side were also analyzed.

Optimization of Integrated Hybrid Systems Using Model Predictive Controller

In recent times, the research in sustainable energy resources was integrated with the control approaches of various hybrid renewable energy systems for balancing the electricity generation. The accelerated hybrid energy storage systems and steadily growing energy consumption make the variability and the predictable behavior occur in the renewable energy sources, which requires an energy management system. This paper aims to control hybrid renewable energy systems for power management. The systems consist of photovoltaic (PV) arrays, diesel generators, wind systems with boost converter DC-DC, and inverters. The optimum of the real-time process is less due to prediction errors of multiple renewable sources, which track the output voltage and load current. Model predictive control (MPC) is proposed for problem-solving time operation to address this issue and compensate for the prediction error. The major impact factors, such as optimal split power, stability, reliability of energy, and desired dynamic responses, have been identified by applying the MPC technique. A simulation model has been constructed using MATLAB/Simulink environment to confirm the effectiveness of the MPC technique model.

Ternary Full Adder Designs Employing Unary Operators and Ternary Multiplexers.

The design of the Ternary Full Adders (TFA) employing Carbon Nanotube Field-Effect Transistors (CNFET) has been widely presented in the literature. To obtain the optimal design of these ternary adders, we propose two new different designs, TFA1 with 59 CNFETs and TFA2 with 55 CNFETs, that use unary operator gates with two voltage supplies (Vdd and Vdd/2) to reduce the transistor count and energy consumption. In addition, this paper proposes two 4-trit Ripple Carry Adders (RCA) based on the two proposed TFA1 and TFA2; we use the HSPICE simulator and 32 nm CNFET to simulate the proposed circuits under different voltages, temperatures, and output loads. The simulation results show the improvements of the designs in a reduction of over 41% in energy consumption (PDP), and over 64% in Energy Delay Product (EDP) compared to the best recent works in the literature.

Analysis of the impact of traction power supply system containing new energy on the power quality of the power system

The access of new energy in the traction power supply system (TPSS) can not only realize low-carbon operation of electrified railroads in the western region, but also promote elimination on the spot of new energy. However, it also brings a series of power quality problems to the power system. The objective of this study was to analyze the impact of TPSS containing new energy on the power quality of the power system. Firstly, a probabilistic model of TPSS containing new energy is established by means of the randomness of locomotive and new energy output power; Secondly, it is analyzed theoretically that the impact of new energy access to the TPSS on the voltage imbalance, power factor and voltage deviation of power system; Finally, Monte Carlo simulation is applied to calculate the probabilistic load flow to obtain the evaluation index, which is used to quantify the impact of new energy access on the power system quality. The results show that the matching degree of new energy output power and load power has a significant impact on the voltage imbalance, power factor and voltage deviation of the power system, while the access location has a smaller impact on the above indicators.

Super twisting approach of a higher order sliding mode controller for a flyback DC–DC converter in photovoltaic applications

SummarySolar photovoltaic (SPV) modules are frequently utilised to produce electricity. The output voltage and load power in SPV‐based applications are variable and strongly reliant on the operating conditions of solar energy, such as irradiance and ambient temperature. They offer additional challenges for the robust design of power converters, and DC–DC power converters provide the power bus with a constant voltage. Properties of a nonlinear system and load patterns necessitate a more robust control design for the power converter. This paper gives robust control of high‐order sliding mode (HOSM) control in isolated flyback converters for solar photovoltaic applications. The proposed HOSM technique is contrasted with the conventional PI control technique. The proposed HOSM control approach outperforms traditional PI control strategies under uncertainty and disturbance settings. This paper also presents a method for preventing chattering in flyback converters (FCs) using modified super twisting sliding modes.

A New Intrinsic Power Balancing Control Method for Boosting Grid-Connected PV System Power Stability

Photovoltaic sources have recently become economical electrical generation resources with high potential power generation systems. The increasing rate of PV system penetration and grid integration has raised serious concerns about the stability and reliability of energy networks. The grid-connected inverter and its operations are taken into consideration in the architecture to provide grid failure robustness. As a result, the capacity of the Low Voltage Ride-Through photovoltaic grid-connected power production system to inject more reactive power into the grid when the voltage disturbance is large has become the most critical issue correlated to the grid. The proposed IPBC controller circuit automatically adjusts the duty cycle value, a desired constant output voltage value, and the load output. To achieve this objective, a suitable feedback controller is necessary to regulate the output voltage to a reference value by automatically controlling the system’s duty cycle, quick response and output load, minimum overshoot zero steady-state error. The effectiveness and reliability of the proposed IPBC controller-based grid-connected solar power generation are developed and verified MATLAB 2017 b software environment. Several simulation programs are based on the operation and performance under different operating conditions evaluated for each of different parameters like steady-state error, THD, and system efficiency.

Distributed robust operation of integrated energy system considering gas inertia and biogas–wind renewables

Multiple uncertainties caused by renewable energy and loads bring challenges to the secure operation of integrated energy system (IES). Concurrently, the centralized control methods based on global information of IES cannot preserve the data privacy of each individual subsystem. To deal with these issues, this paper proposes a distributed two-stage robust optimization (TRO) scheduling strategy for IES considering gas inertia and biogas–wind renewables. To address the uncertainties of wind turbines output and electricity loads in IES, a TRO model is first established, and the column and constraint generation (C&CG) algorithm is employed to handle the min–max–min problem of TRO model. On this basis, a distributed cooperative scheduling framework based on the consensus-based alternating direction method of multipliers (C-ADMM) for IES is developed, which requires no overall system information but only local information. Additionally, natural gas pipelines that consider gas inertia are used as gas storage facilities, which provides IES with additional scheduling resources and flexibility. Furthermore, an adaptive step-size strategy is proposed to adjust the step-size of ADMM in real time, which reduces the dependence of ADMM performance on the initial parameters selection and improves its convergence performance. The simulation results in a three-subsystem joint IES are presented to demonstrate the effectiveness of the proposed distributed TRO scheduling strategy.

Fixed‐time prescribed performance optimization control for the speed and tension system of the cold strip rolling mill with output constraints

SummaryFor the speed and tension system of the reversible cold strip rolling mill with output constraints, parameter perturbations and load disturbance, a fixed‐time prescribed performance optimization control method is proposed based on disturbance observers in this article. First, the disturbance observers are constructed to estimate the system's unmatched uncertainties, and the observer errors can converge in fixed time. Second, a time‐varying logarithmic barrier Lyapunov function (TLBLF) is given and combined with the command filtered backstepping approach, the fixed‐time control and the prescribed performance control to complete the controller designs for the speed and tension system of the cold strip rolling mill, which make the system states converge in fixed time and are always constrained within predefined ranges. Third, particle swarm optimization‐gray wolf optimization (PSO_GWO) hybrid intelligent algorithm is used to optimize the main control parameters of the designed controllers, which further improves the convergence speed and steady‐state accuracy of the rolling mill system. Theoretical analysis proves that the proposed control method can ensure the closed‐loop system is stable in fixed time. Finally, the simulation comparison study is carried out by using the field actual data of a reversible cold strip mill system, and the simulation results verify the effectiveness of the proposed control method.

Integrated Energy Microgrid Economic Dispatch Optimization Model Based on Information-Gap Decision Theory

To address the problems of “difficult to consume” renewable energy and the randomness of power output, we propose the CHP unit joint-operation model with power to gas (P2G) and carbon capture system (CCS) technologies and analyze the operation cost, carbon emission, and “electric-heat coupling” characteristics of this model. A dispatch optimization model is constructed based on the information-gap decision theory under the strategy to further consider the interval uncertainty of renewable energy unit output and load forecast. The optimized-dispatching model effectively solves the fate of renewable unit output and electric-thermal load and provides dispatching strategies for decision-makers to balance risk and capital management.