Converters In Microgrids Research Articles

A New Wide Range and High Voltage Conversion Bidirectional DC/DC Converter for DC Microgrid

ABSTRACTBidirectional DC/DC converters (BDCs) are crucial in energy storage integration with DC microgrid. In this article, a new wide‐range and high voltage conversion (VC) nonisolated BDC with simple structure having reasonable components (total 13) is proposed. The proposed BDC with symmetrical VC ratio delivers high conversion of voltage within the vicinity of 0.5 duty ratio in both boost and buck modes of operation. In addition, the proposed BDC has features of continuous currents at low and high voltage stages and reduced switch voltage stress. This article presents the proposed BDC with circuit configuration and its detailed steady‐state boost and buck mode analyses to verify achievable VC ratio and design consideration. With the designed practical model of the proposed BDC, loss analysis is exhibited to verify the conversion efficiency in boost and buck modes of operation. In real time, experimental prototype of the proposed BDC is operated with LAUNCHXL‐F28379D kit to realize switching pulse generation. The experimental response of the entire proposed BDC operation is captured at 200 W loading. The attained experimental results and discussions validate the proposed BDC operation with the mentioned features. Finally, a comparative analysis with existing BDCs is performed to prove the competence of the proposed BDC for DC microgrid.

Real-time monitoring and control of a PV-fed enhanced cubic voltage gain converter for DC microgrid

In this manuscript, a novel high-gain DC-DC converter with an ultra-step-up voltage gain value of 22.2 is introduced along with a custom-developed web application for remotely monitoring and controlling the power converter. The proposed converter is synthesized using two stages – stage 1 yields a cubic voltage gain and stage employs a diode-capacitor gain cell (DCGC) to reduce the voltage stress on the switch. The proposed gain extension hypothesis is experimentally validated through an 18 V to 400 V, 175 W prototype converter which delivers 175 W to the load at a 93.5% efficiency. The proposed converter exhibits excellent dynamic response when regulating the output voltage to 400 V over a wide range of input voltage and load current variations; the overshoots and undershoots are also negligible. Further, the maximum voltage stress on the switch is only 37.5% of the output voltage. For remotely controlling and monitoring the converter under real-time conditions with a high sampling rate, a web application is developed using React.js. The STM32 microcontroller is programmed to transmit data serially to the server, which then interacts with the web application using hypertext transfer protocol (HTTP) and WebSockets. The effectiveness of the developed interface is also practically verified by controlling the proposed converter in various modes viz., open-loop, soft-start, constant voltage, constant current, soft-stop, load regulation and overvoltage protection modes. Based on the comparison with several converters the proposed converter possesses unique advantages. Additionally, its web-based remote monitoring and control features are preferable for DC microgrid application.

GRFO Optimization Based Multi-port Hybrid Converter for Micro Grid

GRFO Optimization Based Multi-port Hybrid Converter for Micro Grid

A model predictive control based MPPT technique for novel DC-DC converter and voltage regulation in DC microgrid

A model predictive control based MPPT technique for novel DC-DC converter and voltage regulation in DC microgrid

On the optimal game control in the DC microgrid systems

AbstractThis paper introduces static and dynamic competitive optimal control of DC/DC converters in DC microgrids based on game theory considering mutual effects. Using static and dynamic game theories, the conditions for competitive optimal control of DC/DC converters in Nash equilibrium with static and dynamic states are determined. Also, to reduce the complexity in the design of competitive optimal control of DC/DC converters due to the bilinear dynamic model of the system, generalized objective functions are considered. The competitive optimal controls using the Lyapunov and Riccati equations are determined to track the system trajectory to Nash equilibrium. Also, the numerical and experimental results are presented and compared in several cases. The results show that the competitive optimal control of the DC/DC converters in the DC microgrids can effectively improve the performance of the system.

An Improved Current Ripples Minimization Technique for Cascaded DC–DC Converter in DC Microgrid

An Improved Current Ripples Minimization Technique for Cascaded DC–DC Converter in DC Microgrid

An Adaptive Extended Kalman Filter With Passivity-Based Control for DC-DC Converter in DC Microgrids Supplying Constant Power Loads

This paper proposes an adaptive nonlinear control strategy to eliminate the instability problem of buck converters in DC microgrids (DCMG) considering constant power load (CPL). The strategy includes an Adaptive Passivity-Based Controller (PBC) and an Adaptive Extended Kalman Filter (AEKF). The proposed AEKF performs faster and more accurately than the conventional EKF and adjusts the covariance matrices adaptively. Furthermore, this AEKF directly estimates the unknown CPL power supplied by the converter and prevents the number of measurement sensors from increasing. Hence, PBC ensures system stability alongside AEKF. The controller guarantees Lyapunov stability and fast dynamic response in the presence of uncertainties and perturbations compared to other nonlinear methods. MATLAB simulations and laboratory implementation are provided to confirm the performance and robustness of the proposed control strategy and validate the analysis.

Control of Power Converters in Micro Grids

Owing to several operational drawbacks in the existing power management schemes for interlinked AC-DC micro grids which are either concerned about only on sharing power or regulation of voltage but not on both, so as to overcome these issues this paper is proposed. This proposed autonomous power management scheme will consider the specific loading condition of the DC micro grid before importing power from the interlinked AC microgrid. This strategy not only enables voltage regulation in the DC micro grid but also reduces the number of converters in operation which will in turn reduces the power transfer losses. Theproposed scheme is fully self governed as it holds on the plug-nplay features for generators and tie-converters. The performance of the proposed control scheme has been validated under different operating scenarios. The results reveal the usefulness of the proposed scheme in managing the shortcoming of power in the DC microgrid efficiently and autonomously, on the other hand maintaining the better voltage regulation in the DC micro grid. In this project a DG interfacing network and its control also to be simulated to analyze the system stability The results are verified through MATLAB/SIMULINK environment.

Current-Limiting-Type Fault Ride-Through Control Scheme for Converters in DC Microgrid

Current-Limiting-Type Fault Ride-Through Control Scheme for Converters in DC Microgrid

A comprehensive overview of DC‐DC converters control methods and topologies in DC microgrids

AbstractMicrogrids with large‐scale photovoltaic systems constitute a large part of distributed renewable generation in many grids around the world. Managing the performance of such microgrids and especially their interaction with the main power grid is a challenging task, because it requires the control of renewable resources. This paper presents a comprehensive overview of DC‐DC converter structures used in microgrids and presents a new classification for converters. This paper also provides an overview of the control techniques of DC‐DC converters in DC microgrids and the advantages and disadvantages of the control methods are discussed. In connection with the increasing penetration of distributed generation sources (DGS) and renewable sources in power systems and their power management has been raised as a major concern and methods for power management have been investigated in this paper. Finally, a DC microgrid system, which includes a solar system, wind turbine, and battery, is simulated in MATLAB/Simulink software and its performance is analyzed.

Convolutional Neural Network With Reinforcement Learning for Trajectories Boundedness of Fault Ride-Through Transients of Grid-Feeding Converters in Microgrids

Convolutional Neural Network With Reinforcement Learning for Trajectories Boundedness of Fault Ride-Through Transients of Grid-Feeding Converters in Microgrids

A coordination control strategy for parallel-connected boost converters in dc microgrid

Due to the constant power loads (CPLs), the system damping of the DC microgrid is reduced, which will lead to the collapse of bus voltage. In addition, the errors of current sharing amplify due to different line impedances. To address these issues, a hybrid coordination control strategy is proposed for parallel-connected boost converters, which realizes stable control and maintains the accuracy of the current distribution. Firstly, a passivity-based control (PBC) with a proportional-integral (PI) regulator is developed. The virtual damping-based PBC enhances the system damping and the PI regulator eliminates errors. On this basis, a secondary voltage control (SVC) featuring simplicity and weak dependence on communication is introduced to remove the errors of current distribution. Finally, the hybrid coordination control strategy is verified by RT-LAB-based hardware in the loop (HIL) experiment.

Mitigation of severe false data injection attacks (FDIAs) in marine current turbine (MCT) type 4 synchronous generator renewable energy using promoted backstepping method

False data injection attack (FDIA) is kind of the most important and prevalent cyber attacks, influencing in power systems and renewable energy resources in microgrids (MGs). The destructive effects caused by FDIAs in the voltage components of synchronous generator with full converter in AC microgrid (ACMG) renewable energy production would seriously damage the DC link voltage, network frequency and also, the active power. The extracted voltage components in the d and q axes to control the grid side converter (GSC) as the main control section, are the important signals for power control process of the synchronous generator with wind or marine current turbine (MCT). In this regards and due to the nonlinear behavior caused by cyber attacks in the generator control process, the robust performance of modified nonlinear backstepping method would be an appropriate alternative, instead of the conventional linear control including PI controllers. Thus, a remedial action against various FDIAs caused in the voltage control commands of the GSC is proposed. Moreover, promotion of the backstepping control by combining with the switching terms, adopted from the higher order super twisting sliding mode control (HOSTSMC), the performance of the proposed method would be precisely robust. To verify the proposed method, severe FDIAs by injecting various constant values, periodic and also, noisy signals are our case studies which are simulated via MATLAB software in the weak grid connect and standalone operation modes.

Reduced-Order Model for Wind-Solar Multi-Microgrids Considering Time-Scale Coupling

A computationally efficient and accurate reduced-order model (ROM) that characterizes the time-scale coupling caused by the high penetration of power-electronic converters in microgrids (MGs) is crucial to system stability analysis. When such MGs are interconnected into multi-microgrids (MMGs), the coupling between fast and slow dynamics will be more complicated due to the interactions among each MG. The traditional ROM without concerning dynamic coupling may lead to low accuracy and even misjudgment of system stability. In this paper, by considering primary energy dynamics of renewable energy sources, e.g., doubly-fed induction generator (DFIG) and photovoltaic (PV), a small-signal model that characterizes the practical multi-timescale of MMGs is firstly presented. Then with the division of the entire MMGs into fast and slow dynamic subsystems based on the assumption of time-scale separating, the coupling dynamics are identified via the residues-based method. Finally, a ROM considering coupling dynamics and preserving physical meaning is proposed by reconfiguring the fast and slow dynamic subsystems based on singular perturbation. The accuracy of the proposed ROM is verified by comparing it with the detailed model under different control parameters, wind speeds and irradiance conditions. The time-domain simulation is employed to validate the dynamic response of the proposed ROM.

Ancillary Service Provision via Primal-Dual Based Coordination of Distributed Power Electronic Converters in Three-Phase Microgrids

Ancillary Service Provision via Primal-Dual Based Coordination of Distributed Power Electronic Converters in Three-Phase Microgrids

An adaptive voltage control compensator for converters in DC microgrids under fault conditions

This paper proposes a voltage compensator for converters in multi-converter DC microgrids (MG), which enhances the DC-MG behavior under fault conditions. Among the four existing categories in the classification of the faults, this paper focuses on those faults that affect voltage generation of converter-based distributed generation units (DGUs). Such faults conceptually occur from the terminal voltage reference to actual voltage generated by DGUs. To compensate the adverse effects of the faults, an adaptive scheme is proposed, which considers the most general case of the faults by using the time-varying multiplicative and additive fault models. The proposed scheme benefits from an integrated structure, which does not require separate fault detection, isolation, and identification blocks. As an advantage of the proposed approach, it is designed independent of the primary and secondary controllers of DGUs, and hence its performance is not affected by using different primary and secondary controllers. The effectiveness of the proposed scheme is verified under various fault conditions and uncertainty in the system parameters. Using the proposed scheme, the results show that the performance of system under the fault condition is similar to that of the normal operation.

Investigation of the Stochastic Harmonic Distortion Caused by Multiple Converters in Micro-Grid

Investigation of the Stochastic Harmonic Distortion Caused by Multiple Converters in Micro-Grid

Distributed Control Scheme for Clusters of Power Quality Compensators in Grid-Tied AC Microgrids

Modern electrical systems are required to provide increasing standards of power quality, so converters in microgrids need to cooperate to accomplish the requirements efficiently in terms of costs and energy. Currently, power quality compensators (PQCs) are deployed individually, with no capacity to support distant nodes. Motivated by this, this paper proposes a consensus-based scheme, augmented by the conservative power theory (CPT), for controlling clusters of PQCs aiming to improve the imbalance, harmonics and the power factor at multiple nodes of a grid-tied AC microgrid. The CPT calculates the current components that need to be compensated at the point of common coupling (PCC) and local nodes; then, compensations are implemented by using each grid-following converter’s remaining volt-ampere capacity, converting them in PQCs and improving the system’s efficiency. The proposal yields the non-active power balancing among PQCs compounding a cluster. Constraints of cumulative non-active contribution and maximum disposable power are included in each controller. Also, grid-support components are calculated locally based on shared information from the PCC. Extensive simulations show a seamless compensation (even with time delays) of unbalanced and harmonics current (below 20% each) at selected buses, with control convergences of 0.5–1.5 [s] within clusters and 1.0–3.0 [s] for multi-cluster cooperation.

Enhancing Performance of Andronov-Hopf Oscillator-Based Grid-Forming Converters in Microgrids With Non-Invasive Online Impedance Estimation

The Andronov-Hopf based Virtual Oscillator Control (AHO) is an emerging control strategy for grid-forming converters (GFC) to ensure the stability of the future power system with high level of penetration of renewable energies. AHO allows converters to operate in either grid-connected and islanded operating modes. However, the application of this control strategy is limited due to the inherent problem in simultaneous controlling active and reactive power output of GFCs. This paper presents a modification in AHO control structure, and adopts a wide-band grid impedance estimation to improve the dispatchability of AHO in grid-connected mode. The impedance estimation algorithm is embedded into the control loop of AHO, and requires only the measurement of the voltages and currents at the point of common coupling. Thus it is cost-effective and practical. The performance of the proposed method is validated in both simplestructure, and large low-voltage benchmark distribution systems, using MATLAB/Simulink software and the real-time Opal-RT platform. The simulation results confirm the high-accuracy of the estimation and the capability of AHO in simultaneously controlling active and reactive power with zero steady-state errors. Additionally, this paper discusses the small-signal stability and Lyapunov large signal stability of the proposed AHO and compares it to existing methods.

Fuzzy logic-based controller of the bidirectional direct current to direct current converter in microgrid

Microgrids are small-scale power networks that include renewable energy sources, load, energy storage systems, and energy management systems (EMS). Lithium-ion batteries are the most used battery for energy storage in microgrids due to their advantages over other types of batteries. However, to protect the battery from the explosion and to manage to charge and discharge based on state-of-charge (SoC) value, this type of battery requires the use of an energy management system. The main objective of this paper is to propose an intelligent control strategy for energy management in the microgrid to control the charge and discharge of Li-ion batteries to stabilize the system and reduce the cost of electricity due to the high cost of grid electricity. The proposed technique is based on a fuzzy logic controller (FLC) for voltage control. The FLC is based on the measured voltage of the direct current (DC) bus and the fixed reference voltage to generate buck/boost converter signal control. The proposed technique has been simulated and tested using MATLAB/Simulink software which illustrates the tracking of desired power and DC bus voltage regulation. The simulation results confirm that the proposed systems can diminish the deviations of the system's voltage.