Search

LCL-type grid-connected inverters have been widely used in renewable power generation due to their size and cost advantages. However, the LCL filter has a problem of insufficient damping, which may lead to power system instability. Two common methods are used to address this problem: passive damping (PD) and active damping (AD). PD methods suppress resonance by adding resistors to the LCL filter, but this approach increases system losses. AD methods enhance damping through control to suppress resonance. Existing AD methods are often significantly affected by grid-side inductance perturbation, resulting in insufficient robustness. To address this issue, this article proposes a novel robust active damping (RAD) control strategy based on H∞ loop shaping. Simulation analysis and experimental research show that the RAD control method exhibits superior robustness compared with the traditional capacitor current active damping control.

Abstract Satellite electrical power supply system requires higher redundancy and reliability. The failure of the secondary power supply of the power distribution unit will directly lead to the unavailability of the load. The matrix switch can connect multiple secondary power supplies to multiple loads to improve the fault tolerance of the distribution unit. As the number of redundant switches increases, the process of fault reconstruction becomes more complex. In this paper, a matrix switch fault reconstruction method based on 0–1 integer programming is proposed. This method can reconstruct the matrix switch for different fault modes to meet the electrical power supply and protection requirements of the load. Compared with the general fault countermeasure, this method has independent decision‐making ability, can be expanded by modifying a few parameters, and can be integrated into the management of the whole satellite power supply system. A 500‐W satellite power supply system experimental platform was built, and a matrix distribution switch unit prototype meeting the requirements of integration and low volume was manufactured. The experimental results verify the effectiveness of the reconstruction strategy when dealing with multiple faults in different locations.

This article presents a DOD-SOH equalization method for a DRB system based on the Deep DQN algorithm. The proposed method utilizes DQN to learn the operational processes of the system. By integrating the advantages of DRB with SOH equalization theory and the DQN algorithm from the perspective of DOD, our method significantly improve battery performance and ensure cell balancing. To begin with, we present a dynamic reconfigurable battery system with a simple topological structure and outline its switching control process. Additionly, we provide an analysis of the SOH balancing principle and elaborate on the control process of DQN algorithm. Finally, subsequent simulations are carried out, and the simulation results demonstrate outstanding performances in reducing the variance of SOHs, which indicates an enhancement in the level of SOH balancing as well.

The research domain about the selection and design methodology of battery topology structures for energy storage systems, grounded in practical application scenarios, remains significantly underexplored. Furthermore, a substantial gap exists in the current state of research, where the majority of studies lack a comprehensive analysis of losses and reliability associated with reconfigurable battery topology structures. This paper quantitatively analyzes existing MOSFET-based topologies from three key dimensions: losses, costs, and reliability. The study aims to discern the impact of different topology structures and energy storage systems with redundant units on these three dimensions. Subsequently, while ensuring the adaptability of the topology structure, we propose a novel reconfigurable battery system topology suitable for DC microgrids, accompanied by its corresponding control strategy. Through comparative analysis with three typical topology structures, this topology structure has been validated to exhibit certain advantages in terms of losses, reliability, and costs. Lastly, the feasibility of the introduced topology structure is demonstrated through simulation using MATLAB/Simulink. Simulation results indicate that the proposed topology structure not only provides precise control of charge and discharge currents but also demonstrates excellent battery balancing capabilities.

Abstract A carbon responsibility allocation method based on the complex structure carbon emission flow theory is proposed to address the problem posed by the unclear carbon responsibility allocation of each link in the low-carbon development of electric power. First, the calculation method, distribution characteristics, and mechanism of carbon emission flow were analyzed. The “carbon potential of complex structure” concept was introduced to track “carbon trajectory” and “green trajectory” by harnessing the ability of complex structures to retain two-dimensional information. Subsequently, the carbon responsibility allocation methods for network loss and users’ electricity consumption behavior were developed to realize the accurate carbon responsibility allocation of each system link. Finally, the effectiveness and advancement of the proposed carbon responsibility allocation method were verified using the improved IEEE 6-bus and 30-bus test systems. The application of the proposed complex structure carbon potential in the carbon emission flow theory expands the research dimension of electric power carbon emission for low-carbon development from the “carbon perspective,” provides a novel optimization space for the operation of the distribution network and realizes the carbon emission flow theory, which serves as a bridge from calculation evaluation to optimization decision.

The large number of distributed generations connected to the power grid brings the problems of reverse power flow and voltage rise. Due to the existence of “negative regulating voltage effect”, traditional on-load tap changer (OLTC) needs reactive power compensation device to make good voltage regulation. In this paper, the flexible OLTC with back-to-back voltage source converter (BTB-VSC) technology can generate a certain reactive power without a reactive power compensation device, which can achieve a better voltage regulation effect. Meanwhile, based on the principle of voltage sensitivity partition, we propose a coordinated voltage control strategy of flexible OLTC and distributed generators (DG), and coordinate the action of flexible OLTC and DG. The simulation model of the system operation is built in the Simulink software, and the research results show that a good voltage regulation effect can be achieved through the coordination of flexible OLTC and DG.

In order to solve the problem of difficult coordination of traditional overcurrent relay protection caused by short supply radius and little difference of fault current along urban distribution network, a coordinated relay protection strategy based on economical fault current limiter (FCL) is proposed. The FCL device is configured at the export of the main transformer, by using quick fault identification method, setting different protection current value and relay protection delay time, once the fault occurs, the FCL can quickly limit the fault current first then cooperate with the circuit break and switches on the feeder line to achieved the coordinated relay protection. Combining with faults occurring at different locations along the feeder line, the composition and basic working principle of the FCL are discussed, the theory of fast fault identification method and the setting method of the coordinated relay protection parameters are emphatically discussed. The simulation results show that the proposed current limiting coordinated relay protection strategy can effectively reduce the short-circuit current level and bus voltage drop during the fault handle processing, thus reduce the damage to the distribution system and influence range of the fault, greatly improve the selectivity of the relay protection finally.

The high proportion of renewable energy access and randomness of load side has resulted in several operational challenges for conventional power systems. Firstly, this paper proposes the concept of a flexible energy storage power station (FESPS) on the basis of an energy-sharing concept, which offers the dual functions of power flow regulation and energy storage. Moreover, the real-time application scenarios, operation, and implementation process for the FESPS have been analyzed herein. Subsequently, a method involving a bilevel optimization model was adopted: by replacing the original energy storage capacity at each end of the source, grid, and load with the FESPS, the energy storage capacity was fully released. Finally, a case study was performed to verify that the proposed FESPS based on the energy-sharing concept can effectively promote the on-site consumption of renewable energy, reduce the configuration capacity of energy storage equipment, and realize the function of energy storage/reuse. Notably, the application of FESPS in different application scenarios of the power grid is conducive to promoting the construction of new power systems. Configuration capacity of FESPS is only 70% of that of conventional power stations featuring shared energy storage.

The multiport hybrid dc circuit breaker (M-HCB) is a cost-effective choice for fault blocking in meshed HVDC system. Various M-HCB topologies have been proposed in recent years. However, the topology derivation has randomness and uncertainty. Whether the topology can be improved and how to derive new topology from existing topology has less discussion. In this paper, a topology optimization and evaluation method based on graph theory is proposed to deduce more M-HCB topologies from existing topologies. A series of new topologies is quickly derived from the proposed method, and the performance can be evaluated based on the feasible path calculation. Compared with the existing topology, the derived topologies have the advantages of cost and loss in specific application scenarios. Simulation and experiment results are given to verify the topologies. The comparison between the existing topologies proves the superiority of the deduced topologies and the feasibility of the proposed method.

Traditional on-load tap changer (OLTC) has problems such as easy oscillation and low regulation precision in the voltage regulation control of the power system. In order to seek a speedy and stable voltage control strategy, a flexible on-load voltage regulator is studied in this paper. A stepless energy take-off winding is set on the high-voltage side to connect the back-to-back converter, and the winding side of the converter is used to realize reactive power compensation. The grid side of the converter can realize continuous voltage regulation. A coordinated voltage regulation control strategy between flexible on-load voltage regulator and static synchronous compensator (STATCOM) is proposed. The tap positions of the flexible on-load voltage regulator and the reactive power sent by the STATCOM are used as reference signals to ensure sufficient capacity of the compensator and reduce the number of tap actions. The strategy proposed in this paper is compared with the voltage regulation method based on the traditional voltage regulation devices, the effectiveness of the strategy is demonstrated by some simulations based on Matlab/Simulink.

Due to the significant advantages of low cost, integrated multi-port hybrid DC circuit breakers (M-HCBs) with a reduced number of devices have attracted extensive attention for fault blocking in multi-terminal VSC-HVDC system. However, the current topology exploration by researchers is random, uncertain, and time-consuming. In order to provide more new cost-effective topologies, this paper innovatively proposes a topology searching algorithm for the IGBT-type M-HCB and uses the concept of ‘roadblock’ to simplify the adjacency matrix. It can be used to significantly save time spent on proposing a new M-HCB topology because viable topologies can be quickly and rigorously carried out from a large number of directed graphs using computers. Performance characteristics of all derived topologies are simultaneously obtained, and a comparison can be easily conducted to meet the needs of actual application scenarios. A three-port M-HCB example-specific application is given, along with some detailed output topologies that prove the validity and feasibility of the proposed method.

A massive number of DC circuit breaker is usually necessary to be installed to protect HVDC grids from DC faults, this will lead to high capital costs because large number of expensive IGBT-in-series are used. In this paper, an interline hybrid circuit breaker is proposed by the combination of SCR string and a small number of H-bridge modules (SCR-IHCB). The proposed SCR-IHCB has the capacity of blocking DC fault of two adjacent lines respectively by sharing only one main breaker branch (MB) mainly composed of low-cost SCR string and H-bridge module instead of IGBT-in-series string. The interline current flow control function is also integrated. Hence it has advantages of simple and compact topology, economical design compared with typical IGBT based HCB solutions. The operation process of the proposed SCR-IHCB is discussed in detail, and the performance is verified by MATLAB Simulink simulation and scale-down prototype experiment.

With the high-proportion accession of renewable energy and randomness of the load side in the new energy power system, unbalanced feeder power and heavy overload of the transformer caused by massive access of highly uncertain source loads become more and more serious. In order to solve the aforementioned problems, a honeycomb topology of the multi-station integrated system is proposed. The soft open point (SOP) is used as the key integrated equipment of the internal unit of a multi-station integrated system. The honeycomb grid structure is composed of flexible nodes, and the multi-station integrated system is composed of multi-network flexible interconnection. Based on the characteristics of the regional resource endowment, hydrogen energy flow is deeply coupled in parts of honeycomb grids. In order to improve the reliability and flexibility of the multi-station integrated unit, the structure of the new multi-station integrated unit, the power balance constraints on the unit, and the switching process of SOP control mode are studied. At the same time, the hydrogen electricity coupling structure and the coordinated control strategy of hydrogen electricity conversion are proposed to solve the problem of deep application of hydrogen energy. Finally, the effectiveness of the proposed multi-station integrated system is verified by using three simulation models.

Except for pumped storage, other existing electric energy storage technologies are difficult to achieve large-capacity energy storage and not easy to simultaneously meet the requirements in terms of site selection, cost, efficiency, and response. For this end, this paper combines the advantages of maglev technology and vacuum technology, proposes a new type of mechanical large-capacity energy storage technology which is vacuum pipeline maglev energy storage. Based on the idea of vacuum pipeline maglev energy storage technology, we have constructed a case system of vacuum pipeline magnetic maglev energy storage technology. The key technical parameters of the energy storage system, such as the maglev train's weight ratio and speed per hour, the mode of levitation and guidance, the car-track structure, the type and size of the vacuum pipeline, the type of the motor, the process of charging with acceleration, the process of no-load with uniform-speed and the process of generating electricity with deceleration were studied. On this basis, the energy storage capacity and cost of the vacuum pipeline maglev energy storage system were obtained through analysis. By comparing the energy storage capacity and cost of Fengning Pumped Storage Power Station in China, the advantages of vacuum pipeline maglev energy storage technology in economy and technology were verified. Finally, based on the technical characteristics of the vacuum pipeline maglev energy storage system, we analyzed its broad applications in renewable energy power consumption, optimization and upgrade of distribution network structure, urban emergency power supply and pulse power supply.

The modular multilevel converter (MMC) is now the most attractive topology for medium and high voltage power conversion applications with several advantages over the traditional voltage source converter (VSC). However, due to a large number of sub-modules (SMs) in the MMC, system reliability is a big challenge in its practical application, where each SM may be considered as a potential point of failure. In this paper, a reliability evaluation based on the Markov model is proposed for the MMC. The failure rates of the power electronic devices and SMs are firstly analyzed. Then, the Markov model and the state transition equation of the system are built in detail. A general reliability evaluation function is established, in which the mean time to failure and reliability evaluation of the MMC with redundant SMs are also discussed. Finally, a practical direct current (DC) distribution example for reliability evaluation is analyzed, and the results verify that the reliability evaluation based on the Markov model could provide a useful reference for project design.

The application of on-load tap-charger (OLTC) transformer technology has become the most direct and effective way to solve the voltage fluctuation of power grid. With the development of active distribution technology, the research focus of on-load voltage regulation technology has gradually turned to the development direction of arc free, fast and intelligent. This paper presents a flexible on-load voltage regulation topology based on power electronic technology. The flexible on-load voltage regulation (flexible OLVR) transformer is a combination of power electronic technology and traditional on-load tap-charger transformer, which can realize fast arcless switching, voltage step-less regulation, power regulation and other functions. In this paper, a new type of flexible on-load voltage regulation transformer is proposed. The OLTC switches of the device adopts the power electronic switch of anti-parallel thyristors, which can realize step, fast and arcless voltage regulation; the power electronic converter (PEC) module is connected to the primary side of the main transformer. At the same time, it proposed a new reactive power compensation control strategy, which could realize the functions of step-less voltage regulation and reactive power compensation. In the end, the rationality and validity of the proposed topology is tested and verified by simulations and experimental tests.

Voltage stability has always been a hot topic in power system research. Traditional On-Load Tap-Charger (OLTC) transformer is considered to play a very important role in the system voltage stability. However, in the heavy load of distribution network, the tap adjustment of OLTC transformer will lead to the shift of critical stable operating point, which bring the “negative voltage regulating effect” of voltage adjustment, and even cause the instability of system voltage. This paper presents a Flexible On-Load Voltage Regulation (OLVR) transformer based on power electronic technology. The Flexible On-Load Voltage Regulation (OLVR) transformer is a combination of Power Electronic Converter (PEC) and OLTC transformer, which can realize voltage step-less regulation and reactive power regulation. Meanwhile, the paper presents the equivalent models of distribution network with Flexible OLVR transformer and analyzes the critical operating point. Through the step-less voltage regulation control of the Flexible OLVR transformer, the negative voltage regulation effect of the transformer in on-load voltage regulation is avoided, and the voltage stability of the distribution network is improved.

The current large-scale access to distributed power and the rapid growth of electric vehicles are seriously affecting the reliability of distribution networks. The new multi-station fusion technology based on the flexible interconnection of the distribution network can effectively solve this problem. In this study, we design a multi-purpose station and a multi-function device using a soft normally open point (SOP). A new multi-station integration topology and a coordinated control strategy are developed using an active power signal (APS) and an energy management system (EMS). The coordinated control strategy involves sending out the corresponding operation mode command after the EMS receives the superior instruction or the APS of the local system and coordinating the operation mode of the SOP, energy storage DC/DC converter, and photovoltaic DC/DC converter, thereby ensuring stable and efficient operation of the multi-station fusion system. Finally, two typical cases are simulated to verify the feasibility and effectiveness of the proposed topology and control strategy.

Since each branch of the multiterminal DC circuit system relies on the DC circuit breaker for breaking and fault isolation, the prohibitive cost and huge volume of the Hybrid DC Circuit Breaker (HCB) limit its development and broad application in multiterminal flexible DC systems. Multiport hybrid DC circuit breaker (MP-HDCCB) based on device and branch sharing reduces the configuration cost of the circuit breaker to a certain extent. In order to further reduce the cost of MP-HDCCB, a novel MP-HDCCB topology based on hybrid switching devices is proposed, adopting full controlled switching devices to achieve rapidity of breaking fault current, and using semi-controlled switching devices in series to withstand the transient interruption voltage (TIV), so as to reduce the construction cost and technical difficulty. In this paper, the working principle and fault breaking strategy of the topology are introduced in detail, then the parameters of the major circuit are analyzed theoretically, and the parameter design of each branch is given. In the end, the rationality and validity of the proposed topology is tested and verified by simulations and experimental tests.

In order to realize the cyclic utilization for the regenerative braking energy of a metro, a high-speed flywheel array based on high power density and long life is adopted. First, a regenerative energy braking system with a flywheel array is constructed. In order to achieve stable operation and high dynamic response of the flywheel, a control strategy based on voltage threshold is proposed. At the same time, a simulation model of starting and braking of the metro with a high-speed flywheel array is built in MATLAB/Simulink, and the relevant simulation verification is completed. Finally, in order to further verify the effectiveness of the proposed strategy, a GTR flywheel array with a total capacity of 1 MW was installed in a domestic traction station, and field application tests were carried out. The results show that the proposed control strategy can effectively realize the cyclic utilization for regenerative braking energy.

The analysis and calculation of the short-circuit fault current in the DC grid is of great significance to the design and configuration of the converter station and DC circuit breaker parameters. The existing flexible DC system not only includes the modular multilevel converter (MMC) converter, but also needs power equipment such as the fault current limiter and DC circuit breaker. Therefore, the system modeling and short circuit calculation of the multi-terminal DC system after adding the DC circuit breaker are also of great significance for the design of DC power system parameters and the grid troubleshooting ability. In this paper, firstly, the parameters of the four-terminal DC system of the modular multilevel converter (MMC) are simplified, and the analytical solution of the short circuit fault current of the multi-terminal DC system is given. Then, the external characteristics of the cascaded hybrid DC circuit breaker are modeled. Based on the equivalent circuit of the fault current in different stages, the short circuit calculation method of four-terminal MMC system with DC circuit breaker is obtained. This method can effectively describe the overall trend of fault current and provide the basis for the configuration of DC line protection settings and DC circuit breaker related parameters.

The widely used flywheel energy storage (FES) system has such advantages as high power density, no environment pollution, a long service life, a wide operating temperature range, and unlimited charging−discharging times. The flywheel array energy storage system (FAESS), which includes the multiple standardized flywheel energy storage unit (FESU), is an effective solution for obtaining large capacity and high-power energy storage. In this paper, the strategy for coordinating and controlling the charging−discharging of the FAESS is studied in depth. Firstly, a deep analysis is conducted on the loss generated during the charging−discharging process of the FESU. The results indicate that the loss is related to the charging−discharging of power. To solve the problems of over-charging, over-discharging, and overcurrent caused by traditional charging−discharging control strategies, this paper proposes a charging−discharging coordination control strategy based on the equal incremental principle (EIP). This strategy aims to minimize the total loss and establish a mathematical model of optimal coordination control with the constraints of total charging−discharging power, rated power limit, over-charging, over-discharging, and overcurrent. Based on the EIP, the optimal distribution scheme of power charging−discharging is determined. Secondly, this paper gives the specific implementation scheme of the optimal coordinated control strategy. Lastly, the charging−discharging coordinated control strategy is verified by examples. The results show that the coordinated control strategy can effectively reduce the loss during the charging−discharging process and can prevent over-charging, over-discharging, and overcurrent of the system. Overall, it has a better control effect than the existing charging−discharging control strategies.

CHB is a suitable type of topology for synchronous rectifier application which has two or more independent DC loads. Focusing on the individual DC-link capacitor voltage balancing problems caused by asymmetric parameters of independent DC loads, this paper developed a new dual modulation signals based phase disposition pulse width modulation (PD-PWM) strategy using dynamic carrier bias allocation method. Its main idea is to allocate the bias of the carrier wave dynamically according to the balance situation of the system. Compared with the traditional modulation strategies, this method is more easily to be realized and has much stronger dynamic regulation ability. This modulation strategy is widely applicable to various types of CHB structures. A detailed analysis of the DC-link capacitor charge-discharge profile is performed, and an operation condition based dynamic bias allocation method is described using the cascaded H-bridge rectifier (CHBR) structure of five sub-modules as an example. A simulation model and an experiment platform are developed, and the feasibility and effectiveness of the modulation strategy are verified by simulation and experiment results.

Voltage source converter-based high-voltage direct current transmission system (VSC-HVDC) technology has been widely used. However, traditional half-bridge sub module (HBSM)-based module multilevel converter (MMC) cannot block a DC fault current. This paper proposes that a full-bridge director switches based multi-level converter can offer features such as DC side fault blocking capability and is more compact and lower cost than other existing MMC topologies. A suitable predictive control strategy is proposed to minimize the error of the output AC current and the capacitor voltage of the sub-module while the director switches are operated in low-frequency mode. The validity of the proposed topology and control method is demonstrated based on simulation and experimental studies.

Resent studies have identified Pygopus as a core component of the β-catenin/T-cell factor (TCF)/lymphoid-enhancing factor 1 (LEF) transcriptional activation complex required for the expression of canonical Wg/Wnt target genes in Drosophila. However, the biochemical involvement of mammalian Pygopus proteins in β-catenin/TCF/LEF gene activation remains controversial. In this study, we perform a series of molecular/biochemical experiments to demonstrate that Pygo2 associates with histone-modifying enzymatic complexes, specifically the MLL2 histone methyltransferase (HMT) and STAGA histone acetyltransferase (HAT) complexes, to facilitate their interaction with β-catenin and to augment Wnt1-induced, TCF/LEF-dependent transcriptional activation in breast cancer cells. We identify a critical domain in Pygo2 encompassing the first 47 amino acids that mediates its HMT/HAT interaction. We further demonstrate the importance of this domain in Pygo2's ability to transcriptionally activate both artificial and endogenous Wnt target genes and to expand breast cancer stem-like cells in culture. This work now links mechanistically Pygo2's role in histone modification to its enhancement of the Wnt-dependent transcriptional program and cancer stem-like cell expansion. [ABSTRACT FROM AUTHOR]