Interface Converter Research Articles

Fault Detection and Identification Strategy Based on Luenberger Observer for Bidirectional Interleaved Switched—Capacitor DC–DC Converter Interfaced Microgrids

Fault Detection and Identification Strategy Based on Luenberger Observer for Bidirectional Interleaved Switched—Capacitor DC–DC Converter Interfaced Microgrids

Adaptive Neuro Sliding Mode Control of Superconducting Magnetic Energy Storage System

ABSTRACT In this paper, an adaptive RBF neural network-based sliding mode controller is developed for superconducting magnetic energy storage (SMES) installed in a wind–diesel power system. Due to sudden load and wind power variations in a wind–diesel power system, power imbalances may force the system frequency to deviate from its nominal value and drive the system to operate in an unstable mode. Therefore, in a wind–diesel power system using a converter interface, a fast-acting and high power density SMES device is interconnected to carry the required power exchange whenever power imbalances occur. Based on switching manifold design, a sliding mode controller is developed to control the charging and discharging operations of SMES coil as per the power requirements, and the same is achieved by controlling the converter. A neural network using a radial basis function (RBF) is developed to estimate the unknown function of the system. Lyapunov stability analysis is conducted to guarantee the asymptotic stability of the system. MATLAB simulations are carried out and are presented to show the improved performance with the system exposed to disturbances in load and wind power.

A two-level power management strategy in a DC-coupled hybrid microgrid powered by fuel cell and energy storage systems with model predictive controlled interface converter

This paper intends to present a DC-coupled hybrid microgrid, including proton exchange membrane fuel cell (PEMFC), battery bank, and supercapacitor, which is suitable for applications such as distributed power generation and the power system of vessels. In the proposed configuration, the PEMFC serves as the main energy source, and supercapacitor and battery bank are as energy storage systems. A comprehensive model of the 6 kW PEMFC, including the dynamic model along with the electrical model, is presented. Three DC-DC converters, consisting of an inter-leaved boost with voltage multiplier converter (IBVM) connected to the fuel cell and two bi-directional converters connected to the storage devices are employed. Additionally, an AC-DC converter is utilized to ensure stable AC voltage supply, proper power flow, and DC-link voltage control. Moreover, this paper provides a two-level power management strategy (PMS) to control and optimally distribute power between the components of the hybrid microgrid. The proposed strategy is divided into device-level and system-level controls. At the device-level control, a decentral-ized model predictive control strategy (MPC) without using any proportional-integral-derivative (PID) controllers is proposed to control the different modules of the hybrid microgrid. Also, at the system-level control, a rule-based strategy is developed to optimally distribute power between power sources and ensure stable operation under different operation modes. The simulation results in Matlab/Simulink environment are given to verify the effectiveness of the PEMFC model, the chosen converters, the proposed control methods, and the proposed hybrid microgrid.

A Generic User-Defined Modeling Method in PSS/E and Its Application in an MMC-HVDC System

This paper studies the user-defined modeling (UDM) method in PSS/E and applies it to a modular multilevel converter high-voltage direct current (MMC-HVDC) system. First, the mechanism of PSS/E UDM is discussed, including the requirements of the model call, storage space allocation, and flows of dynamic simulation. Then, a generic UDM method applicable to various objects is proposed in PSS/E, considering both the internal structures of models and their interfaces with the PSS/E main program. Next, the design of multiple time scales of UDM is presented for hybrid step size simulation. Accordingly, a user-defined MMC-HVDC system model is built in PSS/E considering the converter, DC-line, control system, and system interface. Finally, the model is compared with a PSCAD electromagnetic transient MMC-HVDC model in a modified two-area-four-generator system. The simulation results demonstrate the proposed UDM method.

Optimal Power Quality Compensation of Energy Storage System in Distribution Networks Based on Unified Multi-Phase OPF Model

Energy Storage System (ESS) is a promising solution to suppress the peak-valley difference of residential distribution networks (RDN) with high penetration of distributed photovoltaic generations. Meanwhile, it can also provide certain power quality compensations to RDN due to the flexible adjusting ability of its converter interface. To make full use of this feature, this paper investigates the optimal power quality compensation of the ESS. This is achieved by formulating and solving an optimal power flow (OPF) problem, the objectives of which are to minimize the power loss, harmonic distortion, and voltage unbalance of the network. Noticeably, the established model includes the neutral line and inter-phase loads; thus, it is unified and can be easily extended to networks with different structures. However, the coupling between different phases and the inclusion of harmonic variables significantly increase the complexity of the OPF problem. To address this issue, the optimization model is further transformed into a convex quadratic constrained quadratic program (QCQP) by replacing power flow equations with current injection equations. As a result, the problem can be solved by the primal-dual interior-point method (PDIPM) with guaranteed convergence and computational efficiency. An iterative solution method is further proposed to improve the accuracy of the solution. Finally, the proposed method is verified using a three-phase three-wire 25-node distribution network and a three-phase four-wire 162-node distribution network in North America.

Concept of an efficient self-startup voltage converter with dynamic maximum power point tracking for microscale thermoelectric generators

Microscale Thermoelectric Generators (microTEGs) have a high application potential for energy harvesting for autonomous microsystems. In contrast to conventional thermoelectric generators, microTEGs can only supply small output-voltages. Therefore, voltage converters are required to provide supply-voltages that are sufficiently high to power microelectronics. However, for high conversion efficiency, voltage converters need to be optimized for the limited input voltage range and the typically high internal resistance of microTEGs. To overcome the limitations of conventional voltage converters we present an optimized self-startup voltage converter with dynamic maximum power point tracking. The performance potential of our concept is theoretically and experimentally analyzed. The voltage conversion interface demonstrates energy harvesting from open-circuit voltages as low as 30.7 mV, and enables independent and full start-up from 131 mV. No additional external power supply is required at any time during operation. It can be operated with a wide range of internal resistances from 20.6 to − 4 kΩ with a conversation efficiency between η = 68–79%.

An intelligent capacity management system for interface converter in AC-DC hybrid microgrids

An interface converter (IC) is used in an AC-DC hybrid microgrid (HMG) and its main tasks are frequency regulation in the AC side, adjusting the DC voltage, and controlling the power flow between AC/DC sides based on the droop control method. The IC should be capable of providing ancillary services such as reactive power supply and compensation of unbalanced and harmonic components in the AC side. However, the use of the IC to provide ancillary services occupies its capacity, which may interfere with the main tasks of the IC. In addition, it is shown in this paper that in unbalanced conditions, the effective power capacity of the IC is reduced by considering the current limit of the converter. In this case, the converter may not be able to perform the main task and provide all the necessary ancillary services at the same time, otherwise, it may be exposed to an overcurrent condition. Therefore, an efficient strategy is needed to manage the IC converter capacity to facilitate optimal use of the entire IC capacity even in unbalanced conditions. Given this challenge, this paper proposes an intelligent strategy for managing the IC capacity, which prioritizes the realization of the main task and the provision of ancillary services. The proposed strategy is evaluated, and its effectiveness is proven by simulation results in Matlab/Simulink.

AUTOMATIC SAFETY EVALUATION AND VISUALIZATION OF SUBWAY STATION EXCAVATION BASED ON BIM-FEM/FDM INTEGRATED TECHNOLOGY

With the progressive promotion of BIM technology in collaborative design and engineering data management, there are large amounts of project information available for intelligent construction, engineering computation and design optimization. In the construction of subway station, BIM technology is still not mature and the engineering design is generally separate from the engineering safety evaluation. Thus, this paper proposed a technology that integrates BIM and numerical simulation (BIM-FEM/FDM integrated technology) to solve the problem of separation between engineering design and computation. A three-dimensional parametric modeling of subway station excavation was first carried out using the Revit® modeling software. Afterward, a FEM/FDM-process oriented data conversion interface was developed to extract and process the critical information from the parametric BIM model for numerical simulation. Then, under the impetus of an auto-simulation interface, the safety evaluation of subway station excavation was realized automatically and visualized graphically. The research of the BIM-FEM/FDM integrated technology presented in this paper has established a supporting platform to achieve the integration of BIM-based design and safety evaluation for subway station excavation.

Measurements of magnetic characteristics of laminated Fe-Si steel filter inductors in grid interface converters

The knowledge of the magnetic characteristic of an inductor is a key factor for the design of filters of power converter systems for electric grid interfaces. The accurate and reliable definition and measurement of the parameters such as the differential inductance, the saturation level and the linearity range is a difficult task, in particular for high current inductors. In this paper a comparison between different methods of measure of the magnetic characteristic of a gapped filtering inductor versus current, in the range from zero magnetization to the saturation, is presented and discussed. It is shown that the different measurement methods provide appreciable differences in the evaluation of the magnetic characteristic of a benchmark inductor. The differences found are also analyzed by suitable numerical simulations.

Modelling and controlling A new PV/FC/battery DC–DC converter suitable for DC motor

Here, a new hybrid DC–DC converter is presented to enable controlling a DC motor. Since renewable energy sources, including PV, FC, and batteries, are projected to be used extensively in the future, using interface converters becomes essential. Firstly, these converters must have a suitable voltage gain because PV and FC have a low voltage at the output. Secondly, such converters must be controlled correctly because PV and FC do not provide a constant voltage, they have different characteristics, and they may work in any operating point instead of the maximum power point. Therefore, a suitable controller is essential for extracting maximum power values from these energy sources. In this paper, the decentralized control method, as a multivariable control technique, has been used to control a PV/FC/battery DC–DC converter.

Model predictive control of solar photovoltaic‐based microgrid with composite energy storage

SummaryThe renewable energy (e.g., solar photovoltaic)‐based grid‐connected microgrid (MG) with composite energy storage system (CESS) is feasible to ensure sustainable and quality power to the commercial and domestic load demands. Effective control systems provide the dynamic performance of such deployed MGs. This paper investigates the application of the finite control‐set model predictive controller (FCS‐MPC) for solar photovoltaic‐based grid‐connected MGs with composite energy storage. FCS‐MPC considers the discrete nature of interfacing (DC–AC and DC–DC) converters into the control algorithm to predict the optimal control command for reference current tracking. Compared to classical control approaches, FCS‐MPC provides a fast‐dynamic response, discards the modulation stage, and effectively handles the effects of dynamic source and load variations and nonlinear loads. The control system encapsulates a proportional–integral (PI) controller, low‐pass filter (LPF), power management algorithm (PMA) unit, and followed by the FCS‐MPC approach. The CESS unit consists of a battery and supercapacitor storage system. The efficacy of the FCS‐MPC approach is verified through the MATLAB/Simulink results. Solar photovoltaic variation due to irradiance, utility grid availability, electricity pricing, and dynamic load variations are considered in the implementation. Furthermore, real‐time simulation of the proposed method is validated using OPAL‐RT OP4510 real‐time simulator.

Optimal Load Distribution in DG Sources Using Model Predictive Control and the State Feedback Controller for Switching Control

The distributed energy management of interconnected microgrids, which is based on model predictive control (MPC), relies on the cooperation of all the agents (i.e., microgrids). Model predictive control or MPC is widely used in industrial applications as an effective tool for dealing with multivariable limited control problems. MPC uses an explicit system model to predict the future horizon of the system and its outputs. This predictability allows calculating the optimal order of inputs to minimize output errors over a limited horizon, which is effected by the limitations of the system. This study presents a distributed economic model predictive control method using the new state feedback controller to control the switching of interface converters and compensate for the unbalanced and nonlinear loads. In this model, the islanding mode and the reconnection of the grid are considered to improve the transient behavior of the system to achieve steady-state power distribution. It has been proposed that it could obtain better results in predictive control, utilizing similarity transform in the state matrix and its modification. First, this model is simulated on distributed generation sources with power-sharing and local loads using the state feedback controller in MATLAB Simpower. Then, the performance of the proposed method is evaluated, confirming that it is more reliable than the FS-MPC and DSVM-MPC methods.

Simultaneous frequency up/down converting interface based on a single hardware incorporating two phase-correlated photonic mixers.

A novel photonic frequency up/down-converting interface (FCI) with the capability of up-converting an intermediate frequency (IF) signal to a radio frequency (RF) signal and simultaneously down-converting a RF signal to a low IF signal is proposed, and a new application scenario, where both up and down frequency conversion stages of a deramp-on-receive linearly frequency modulated (LFM) continuous wave (CW) radar system are replaced by the FCI, is demonstrated. The five-port photonic FCI can be seen as two ultra-wideband phase-correlated photonic RF mixers incorporated in a single hardware, and the working frequency range of the FCI is up to Ka-band. The FCI is tested by an LFM waveform with 1GHz bandwidth in a deramp-on-receive LFM CW imaging radar system. In the test, the LFM signal can be transmitted and received correctly, and deramp output signals are able to coherently combine among multiple pulses, which generates a clear image of two point-targets with a 3dB range resolution of 15cm.

Fault control and line protection strategy for LVDC microgrids based on modified high-frequency-link DC solid state transformer

Fault current with high amplitude and rate of change, together with the vulnerability of electronic devices, poses a great challenge to the line protection in low voltage DC (LVDC) microgrids. A fast fault control and protection method are proposed for LVDC microgrids, based on the modified topology of the high-frequency-link DC solid state transformer (DCSST). By installing two bidirectional antiparallel thyristors in the DCSST and isolation devices at the interface converter side, the freewheeling diodes are protected and current zero-crossings occur due to the submodule capacitor discharge during the fault. Then the line protection could be realized by improved current differential protection, and the mechanical circuit breaker can be tripped around current zero-crossings. It alleviates the high requirement for fast tripping devices (such as solid-state circuit breakers) and fault identification within several milliseconds. The scheme combines the converter fault control with line protection to ensure slow but more economic and reliable fault identification for LVDC grid protection. The proposed strategy is verified by PSCAD/EMTDC simulations and the results show that the fault-tripping-recovery process only takes few tens of milliseconds.

Dynamic performance improvement of wind-diesel power system through robust sliding mode control of hybrid energy storage system

Off-grid users can be provided with electricity via a hybrid integration of wind power generators and a diesel system functioning as a backup supply. However, due to wind power fluctuations and rapid load changes, system voltage and frequency variances may exceed permitted limits, resulting in aberrant system behavior. Therefore, to improve the dynamic performance of the wind-diesel power system, a hybrid energy storage system (HESS) made of battery and superconducting magnetic energy storage is installed with the system via a converter interface. Based on the switching manifold design, a sliding mode controller with the super-twisting feature is developed over the hybrid energy storage system (HESS) to carry out the required amount of power exchanges with the system accomplished through the control of converter operation. Lyapunov stability analysis is conducted to guarantee the asymptotic stability of the system. MATLAB simulations are performed to validate the improved performance of the system with the proposed scheme.

The main types of wind turbines-generators in the power supply system

PURPOSE. Conduct a detailed analysis of existing wind turbines. Analyze the role, place and features of the functioning of wind power plants. Provide various options for generators and schemes for converting wind energy into electricity. Provide recommendations for improving the reliability of wind turbines in smart grids.METHODS. The article was prepared using analytical methods, statistical, theoretical, factorial and technical methods.RESULTS. A fixed speed asynchronous generator used in a wind power conversion system (WECS) without a power converter interface draws a significant portion of the reactive power from the grid. This configuration features simple, reliable operation. Wind turbine asynchronous generator with dual power supply. can improve overall power conversion efficiency by performing maximum power point tracking (MPPT), and an increase in speed of about 30% can improve dynamic performance and increase resilience to system disturbances that are not available for turbine types 1 and 2. The use of full-scale 100% power converters will significantly increase the productivity of SPEV wind energy conversion systems, but will slightly increase the cost of the power converter, up to 7% - 12% of the total equipment cost. By using a large number of pole pairs for all types of permanent magnet synchronous generator (PMG), the turbine gearbox can be removed. This type of wind energy conversion system is more resilient to grid disruptions compared to type 1, 2 and 3 wind systems. The review shows that types 3 and 4 technologies are used to most efficiently sell and recycle wind turbines in electricity markets.CONCLUSION. The article analyzes the features of the functioning of wind power plants operating on the grid. Various options for generators and schemes for converting wind energy into electricity are presented. A detailed analysis of existing wind turbines is provided. Recommendations are given for improving the reliability and efficiency of wind power plants in smart grids.

High resolution sequence stratigraphic analysis of Qingyi section in Hei-258 area

In order to solve the problems of unclear division of the delta front pre delta facies belt of the first member of Qing Dynasty in Hei-258 area of Daqingzijing in the south of Songliao Basin and the lack of a unified fine isochronous stratigraphic framework in the whole region, the types and genesis of the cycle interface of the first member of Qing Dynasty are summarized by using the core data of a coring well and the logging data of more than 70 wells, combined with the theory of high-resolution sequence stratigraphy and sedimentology, Establish a high-resolution sequence stratigraphic framework and summarize the control of base level cycle on sedimentary evolution. The results show that the delta front subfacies are the main subfacies in the first member of Qinghe formation in Hei-258 area, and a small amount of pre delta deposits are developed in the northeast of the study area in some periods. The types of cycle interfaces are mainly Lake flooding surface of different levels, conversion interface from progradation to retrogradation or retrogradation to progradation, lithologic catastrophe interface, etc., and the short-term cycles are classified into three categories according to the structural style. The above understanding can provide a theoretical basis for the distribution range of sedimentary facies belt and the establishment of high-resolution sequence stratigraphic framework in Daqingzijing area.

ПРОГРАММНЫЕ И АППАРАТНЫЕ СРЕДСТВА ДЛЯ ОПРЕДЕЛЕНИЯ ТЯГОВОГО СОПРОТИВЛЕНИЯ РАБОЧИХ ОРГАНОВ МАШИН ДЛЯ ОСНОВНОЙ ОБРАБОТКИ ПОЧВЫ

The efficiency of the use of agricultural machinery depends on various factors, one of which is the rational acquisition of machines with energy resources based on the calculation of traction resistance. The purpose of the study is to describe an experimental setup for measuring, accumulating and analyzing data on the traction resistance of working bodies of machines for basic tillage and the results of research based on it. The main method of research is conducting an experiment using software and hardware; methods of mathematical statistics were also used. The authors consider the features of the software and hardware used to measure the traction resistance of working bodies for basic tillage. The hardware of the experimental installation consists of a personal computer, an acid GP-1223 battery, a 3.5 mm Jack microcontroller power cable, a panel, an RS-485 – USB-B Aries AC4 interface converter, a microcontroller, a 15-pin COM port, Type DEE 500 kg load cells. The software allows you to get interactive graphs of the traction resistance of the working body, change settings, in particular, scaling, the limits of measurement of the ordinate scale, the displacement of the abscissa axis. Studies of tag resistance are given on the example of the paws of a cultivator for stubble after buckwheat (at a processing depth of 14, 18 cm, an operating speed of 5, 10, 15 km/h), and an experimental setup is proposed. Cultivator racks were used for experiments: vertical rigid and spring-loaded with replaceable paws and tips. The measurement results confirm that an increase in the speed of movement significantly affects the growth of the traction resistance of the studied working organ for cultivation.

Stability Analysis of Photovoltaic Interface Converter Taking Dynamic Model of Photovoltaic Cells into Account

Stability Analysis of Photovoltaic Interface Converter Taking Dynamic Model of Photovoltaic Cells into Account

Solar Power Generation System With Power Smoothing Function

The output power from a solar power generation system (SPGS) changes significantly because of environmental factors, which affects the stability and reliability of a power distribution system. This study proposes a SPGS with the power smoothing function. The proposed SPGS consists of a solar cell array, a battery set, a dual-input buck-boost DC-AC inverter (DIBBDAI) and a boost power converter (BPC). The DIBBDAI combines the functions of voltage boost, voltage buck and DC-AC power conversion. The BPC acts as a battery charger between the solar cell array and the battery set. For the proposed SPGS, the DC power that is provided by the solar cell array or the battery set is converted into AC power through only one power stage. The solar cell array also charges the battery set through only one power stage. This increases the power conversion efficiency for the solar cell array, the battery set and the utility. The battery set is charged/discharged when the output power of the solar cell array changes drastically, in order to smooth the output power from the SPGS. In addition, the DIBBDAI can suppress the leakage current that is induced by the parasitic capacitance of the solar cell array. The proposed power conversion interface increases power efficiency, smooths power fluctuation and decreases leakage current for a SPGS. A hardware prototype is completed to verify the performance of the proposed SPGS.