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Bipolar DC–DC converter plays an important role in data center and distributed renewable energy unit with the advantages of high efficiency and low cost. In order to improve the power density of bipolar DC–DC converter, a high frequency and high power density bipolar DC–DC converter based on Gallium Nitride High Electron Mobility Transistor (GaN HEMT) is proposed under the development trend of miniaturization, lightweight and high power density of power electronic converter. By using gallium nitride (GaN) switch device, the switching frequency of the converter is increased to 1 MHz, which effectively reduces the volume and weight of the device. In addition, through the design of high frequency driver circuit, two separate pull-up/pull-down outputs are provided for the control signal, and the rising and falling rates of the switch signal are controlled by adjusting the resistance to obtain good performance and driving stability. The experimental results show that the total weight of the converter with radiator is only 121.6 g, the power density is 35.23 W/in3, and the maximum efficiency can reach 92.7%. Compared with the same type of converter, the volume and weight of the converter are greatly reduced, effectively realizing the goals of miniaturization, lightweight and high power density of the converter.

A high-reliability SEPIC converter with reconfigurable voltage conversion gain is proposed, which is composed of a basic SEPIC converter and n extended units. Adopting an interleaved parallel structure on the input side of the converter not only achieves leg-level hardware redundancy but also reduces the input current ripple. When one branch of the converter suddenly changes or fails, due to the redundancy between branches, the converter can still to work, and the duty cycle of the other branches can be readjusted by using PI control without changing output voltage and power of the converter. This feature undoubtedly presents the reliability of the converter. On the contrary, when the converter works in normal operation, it can also actively control operation mode of each branch to achieve reconfigurable voltage conversion gain function. In addition, since the duty cycles of the switches are not limited, voltage conversion gain of the converter is widely, which makes it more suitable for the occasions where the input side fluctuates greatly. Section 2 details the working principle of the proposed converter and the voltage and current stress on components. Then, the reconfigurable voltage conversion gain of the converter and its high reliability characteristics are analyzed in Section 3. Finally, the correctness of the theoretical analysis is verified by experiments.

In order to address the energy imbalance issue of a series-connected lithium-iron battery pack, this paper proposes an active equalization method based on a reduced-order solving strategy for the Hanoi Tower problem. The proposed scheme utilizes a combined structure of a switching-network circuit and a bidirectional Cuk converter and leverages an ultracapacitor cell as the energy-transfer carrier. Simulation and comparison demonstrate that the exchange of unbalanced energy within the battery pack can be achieved. The proposed approach can effectively achieve various balancing modes such as cell-to-cell, cell-to-string, string-to-cell, and string-to-string with a relatively fast balancing speed.

Abstract This paper proposes an intelligent Deep Learning (DL) based approach for Data‐Driven Security‐Constrained Unit Commitment (DD‐SCUC) decision‐making. The proposed approach includes data pre‐processing and a two‐stage decision‐making process. Firstly, historical data is accumulated and pre‐processed. Then, the DD‐SCUC model is created based on the Gated Recurrent Unit‐Neural Network (GRU‐NN). The mapping model between system daily load and decision results is created by training the DL model with historical data and then is utilized to make SCUC decisions. The two‐stage decision‐making process outputs the decision results based on various applications and scenarios. This approach has self‐learning capabilities because the accumulation of historical data sets can revise the mapping model and therefore improve its accuracy. Simulation results from the IEEE 118‐bus test system and a real power system from China showed that compared with deterministic Physical‐Model‐Driven (PMD)‐SCUC methods, the approach has higher accuracy, better efficiency in the practical use case, and better adaptability to different types of SCUC problems.

Security-constrained unit commitment (SCUC) has been extensively studied as a key decision-making tool to determine optimal power generation schedules in the operation of electricity market. With the development of emerging power grids, fruitful research results on SCUC have been obtained. Therefore, it is essential to review current work and propose future directions for SCUC to meet the needs of developing power systems. In this paper, the basic mathematical model of the standard SCUC is summarized, and the characteristics and application scopes of common solution algorithms are presented. Customized models focusing on diverse mathematical properties are then categorized and the corresponding solving methodologies are discussed. Finally, research trends in the field are prospected based on a summary of the state-of-the-art and latest studies. It is hoped that this paper can be a useful reference to support theoretical research and practical applications of SCUC in the future.

How to obtain the optimal decision-making scheme based on the investment behavior of various stakeholders is an important issue that needs to be solved urgently in incremental distribution network planning. To this end, this article introduces the virtual player “Nature” to realize the combination of the game theory and robust optimization and proposes an incremental distribution network source–load–storage collaborate planning method with a multi-agent game. First, the planning and decision-making models of a DG investment operator, a distribution network (DN) company, power consumers, and a distributed energy storage (DES) investment operator are constructed, respectively. Then the static game behaviors between the DG investment operator and distribution network company, as well as the DG investment operator and the DES investment operator, are analyzed based on the transfer relations between these four participants. At the same time, robust optimization is used to deal with the uncertainty of the DG output, and the virtual player “Nature” is introduced to study the dynamic game behavior between the DG investment operator and the distribution company. Finally, a dynamic–static joint game planning model is proposed. The simulation results verify the correctness and effectiveness of the proposed method.

An interleaved zero-voltage zero-current switching (ZVZCS) high step-up DC-DC converter is proposed for modern photovoltaic power generation systems. The proposed converter can achieve high voltage conversion gain without operating under extreme duty cycles. The voltage conversion gain can be readily adjusted by selecting different numbers of the diode-capacitor multiplier (DCM) cells in the circuit at the design stage. Moreover, with the passive snubber circuit in the proposed converter, all power switches and diodes in the DCMs can achieve zero-voltage turn-off and zero-current turn-on, which effectively reduces switching losses and increases the overall converter efficiency. The operational principles and analysis of the performance analysis with two DCMs are presented for demonstrative purpose. The effectiveness of the proposed ZVZCS DC-DC converter is validated using an 800W experimental prototype.

The rapid drop of frequency under the disturbance is a major threat to the safe and stable operation of a microgrid (MG) system. Emergency load shedding is the main measure to prevent continuous frequency drop and power outage. The existing load shedding strategies have poor adaptability to deal with the problem of MG load shedding under different disturbance situations, and it is difficult to ensure the safe and stable operation of an MG in different operating environments. To address this problem, this paper proposes a data-driven load shedding strategy. First, considering the importance of the load and the frequency recovery time of the system, a load shedding contribution indicator is designed that takes into account the load frequency adjustment effect and the load shedding priority. This contribution indicator is introduced as a load shedding criterion into the reward value function of dueling deep Q learning. Second, considering the suddenness and uncertainty of emergency load shedding, a MG emergency load shedding strategy (ELSS) based on dueling deep Q-learning is proposed. On this basis, the dueling deep Q learning algorithm is used to obtain the load shedding decision with the maximum cumulative reward. Finally, taking the MG load shedding cases in two different scenarios as examples, a simulation study is carried out on a modified IEEE-25 bus MG. The simulation results show that, compared with the model-driven implicit enumeration strategy (IES), the proposed ELSS has superiority in maintaining stable power supply for important loads and reducing load shedding decision-making time and frequency fluctuations.

By the negative influence of parasitic parameters from the components, the voltage step-up capacity of basic dc-dc converters is limited at extremely high duty cycle. Which makes the traditional dc-dc converters are difficult to be applied to renewable energy generation systems such as fuel cell and photovoltaic (PV) systems. In this study, a single-switch high step-up Zeta converter is proposed based on the basic Zeta converter and corresponding coat circuit. By using the coat circuit, the proposed converter not only can achieve higher voltage gain, but also acquire lower voltage stress on the semiconductor devices. Therefore, the devices with lower conduction resistances can be used to improve the efficiency. Furthermore, the coat circuit is composed of passive components, which does not change the continuous output current characteristic of the basic Zeta converter. And the proposed converter has only one active switch, the drive and control circuits are simple. The operation principle and the performance analysis of the proposed Zeta converter are described in detail, and a 300 W closed-loop experimental prototype has been developed for verification.

The fault of power systems introduces a severe challenge in terms of fault recording analysis, and the traditional Prony method cannot perform satisfactorily in the process of signal recordings fitting caused by faults. Therefore, an improved adaptive Prony algorithm is proposed in this article to study the characteristics of fault recordings. Specifically, the search step size is taken as an adaptive variable, and the mean square relative fitting error (MSRFE) is set as the criterion. Then, a large step is employed to rapidly determine an approximate segmentation point in the initial stage of the searching process, and its horizon is gradually reduced to establish an accurate subsegment point. Finally, the Prony algorithm is deployed to analyze the subsegment fitting original signal. The proposed approach has been simulated on an assumed fault signal, and the results validate the accuracy and efficiency of the method.

The conventional buck-boost converter has the advantages of simple structure, low cost, and the capability to achieve both voltage step-up and down. However, due to the negative impacts of the parasitic parameters of the device, the voltage conversion gain of the conventional buck-boost converter is greatly limited. A low-voltage stress buck-boost converter with a high voltage conversion gain based on a coat circuit is proposed in this paper to address the problem. Similar to a coat that can enhance human's resistance to cold weather, by adding the proposed coat circuit to the conventional buck-boost converter, not only the range for the voltage conversion can be extended, but also the voltage stresses of the semiconductor components are effectively reduced. In this work, comprehensive analysis on the working principles and performance characteristics of the coat converter are provided. Experimental results are obtained and analyzed to validate of the theoretical analysis based on a 300W closed-loop prototype platform.

Supply and demand balance is required to assure the normal operation of microgrids. When unintentional islanding occurs in a microgrid, a load shedding (LS) control scheme is necessary to achieve the power balance and frequency stability of an islanded microgrid due to its limited power generation. However, the LS control of a microgrid faces two key challenges, i.e., how to determine the appropriate LS amount and LS objects in an islanded microgrid. To solve these problems, this paper proposes a coordinated LS control scheme based on Double-Q learning for an islanded microgrid. In the proposed coordinated LS control scheme, aiming at the LS amount problem in the process of unintentional islanding, this paper considers the relationship between the active power and frequency deviation of each distributed energy resource (DER) and uses the frequency deviation measured locally to calculate the LS amount and guide LS actions. Aiming at the problem of LS object selection in the process of unintentional islanding, this paper describes the LS control problem as a Markov decision process (MDP). The load priority is considered in a reward value function to ensure the uninterrupted power supply of critical loads in a microgrid. The two value functions of Double-Q learning are used to make the two Q value tables measure each other, which can reduce the overestimation of Q values and improve the accuracy of decision-making. The performance of the proposed coordinated LS control scheme is verified by a microgrid model based on a modified IEEE 13-bus system. The test results verify the feasibility and effectiveness of the proposed coordinated LS control scheme.

A multi-input-port bidirectional DC/DC converter is proposed in this paper for the energy storage systems in DC microgrid. The converter can connect various energy storage batteries to the DC bus at the same time. The proposed converter also has the advantages of low switch voltage stress and high voltage conversion gain. The working principle and performance characteristics of the converter were analyzed in detail, and a 200 W, two-input-port experimental prototype was built. The experimental results are consistent with the theoretical analysis.

The modeling and control system design of high step-up DC/DC converters based on voltage multipliers (VMs) are difficult, due to the various circuit topologies and the presence of large number of capacitors in VMs. This paper proposes a generic approach to reduce the model order of such converters by replacing the VM capacitors with voltage sources controlled by the output voltage of the converter. Theoretical analysis and simulation results show that the derived models can accurately represent the low frequency response of the converter which is valuable for obtaining a small-signal AC model for control system design. The detailed modeling and controller design process are demonstrated for the converter, and the obtained simulation results are verified experimentally on a 400 W prototype.

The vulnerability patch R&D has become an important part of information security governance. An effective collaboration with software vendors in patch R&D is of great significance to reduce the existence time of information security risks. This works aims to explore the relationship between vulnerability information disclosure and patch R&D of software vendors. The data regarding the vulnerability and software vendors is gathered from third-party vulnerability sharing platforms, including (China's national information security vulnerability database, CNNVD) and Tianyacha.com. Based on the theory of organizational information processing, linear regression model and Cox proportional risk regression model are built for appropriately addressing the research questions. The results show that the vulnerability disclosure of the third-party sharing platform can improve the patch R&D probability of software vendors. The information processing requirements, such as vulnerability information attention, vulnerability score and whether vulnerabilities are disclosed in advance accelerate the vulnerability patch R&D. The enterprise information processing capability indicators, including the industry dependence of software product customers and the staff size of software vendors accelerate the patch R&D. The number of products affected by the vulnerabilities and the number of software copyrights of software vendors have no significant impact on patch R&D. [ABSTRACT FROM AUTHOR]

Amid the pandemic of COVID-19, the collaborative innovation network of enterprises is conducive to the sharing of innovation resources, knowledge transfer, and technology diffusion, which is closely related to the improvement of corporate technological innovation performance. Based on the patent application data of listed enterprises in Jiangsu, Zhejiang, and Shanghai in China, this study constructs a cooperation matrix, describes the characteristics of collaborative innovation network from two dimensions of network structure and network relationship, introduces the breadth of the knowledge base as a moderating variable, and analyzes the nexus between characteristics of a collaborative innovation network and technological innovation performance. Based on the panel data of 193 listed companies in Jiangsu, Zhejiang, and Shanghai, this study uses a multiple linear regression model for empirical analysis. The results show a U-shaped relationship between clustering coefficient and technological innovation performance. The breadth of knowledge base strengthens the positive relationship between the structural hole and technological innovation performance. In contrast, the breadth of knowledge base weakens the positive relationship between network relationships strength and technological innovation performance. The study findings will enhance enterprises' participation in a suitable collaborative innovation according to their knowledge-based characteristics and improve the technological innovation performance. [ABSTRACT FROM AUTHOR]

A single-switch high step-up boost converter based on a novel voltage multiplier (VM) has been proposed in this study. Compared to traditional boost converter, not only the voltage conversion ratio has been increased, but also voltage stress across semiconductor devices has been decreased. Moreover, the voltage conversion ratio and voltage stress of switch of the proposed converter can be adjusted by the number of the VM cells. The control and drive circuits for the proposed converter is as simple as boost converter as there are no additional switches. Working principles and performance characteristics of the proposed converter have been analysed in detail. A 200 W experimental prototype with three VMs has been built to validate the theoretical analysis. [ABSTRACT FROM AUTHOR]

This study presents a high step-up scalable voltage multiple cell (SVMC)-based DC/DC converters, which have the features of high gain, low and adjustable components stresses and automatic input-current sharing in each input phase. In virtue of the above features, the converter is applicable for the DC collection grids for offshore wind farms. In this study, the converter in terms of working principle and property characteristics are analysed with four input phases and three SVMCs. The converter has also been evaluated in terms of the component stress and voltage conversion ratio against some other converters for high-power occasions. Moreover, a 2.5 MW simulation model and a 1.2 kW prototype were constructed for verification. [ABSTRACT FROM AUTHOR]

A non-isolated high-voltage gain dual-input DC/DC converter with a zero voltage turn-off (ZVT) auxiliary circuit has been presented. Two photovoltaic (PV) modules can be connected to the proposed converter with separate maximum power point tracking (MPPT). The cost of whole PV power generation system can be decreased significantly as a single converter is employed instead of two converters. All switches can achieve ZVT by an auxiliary circuit, and turn-off switching losses can be decreased and the efficiency of the converter can be improved. Working principle and performance characteristics of the proposed converter are analysed in detail, a dual-input maximum power point tracking control algorithm has been designed for the proposed converter. An 800 W experimental prototype has been built to verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

This study presents a non-isolated high step-up DC/DC converter based on a high degree of freedom voltage gain cell (HDF-VGC). Both voltage stress of components and conversion ratio of the proposed converter could be adjusted by the number of the HDF-VGC, the current stress of the semiconductor devices can also be adjusted by the input phase numbers of the converter. Moreover, the input current of each phase are automatically balanced. These characteristics make the proposed converter very suitable for high-power and high-voltage applications, such as offshore wind power high-voltage DC transmission system. In this study, the topology construction of the proposed converter has been discussed. The operation principle and performance characteristics of the converter are analysed with four input phases and five HDF-VGCs, then the converter is simulated and a 400 W experimental prototype has been built to verify the correctness of the theoretical analysis. [ABSTRACT FROM AUTHOR]

A zero voltage turn-off high step-up DC/DC converter is presented. The conversion efficiency and power density are improved significantly by using a novel passive snubber cell, which only consists of two diodes and a snubber capacitor. The converter also provides high-voltage conversion ratio as well as low-voltage stress on switches and diodes, which make it suitable for some special industrial applications as electric-vehicle, uninterruptible power supply system or photovoltaic power generation system. The topology, operation principles and performance characteristics are analysed in detail. Moreover, a maximum 800 W experimental prototype has been developed to validate the effectiveness of the theoretical analysis, and 96.2% efficiency has been achieved. [ABSTRACT FROM AUTHOR]

This study proposes a kind of high step-up dc/dc converter with a novel voltage multiplier cell (VMC). The proposed VMC sharply reduces voltage stress on switches and diodes. Therefore, the conversion efficiency can be improved significantly. The converter also provides a wide range of voltage conversion ratios including fractional as well as VMC numbers and switch duty cycle. The topologies, operation principles, working characteristics and voltage conversion ratio are analysed in detail. A 500W experimental prototype with two VMCs has been developed to validate the effectiveness of the theoretical analysis, and the highest efficiency is 93.8%. [ABSTRACT FROM AUTHOR]

A high step-down multiple-output LED. driver is proposed in this paper. Firstly, the derivation of the driver with dual-output is presented and its operation principle and steady state performance are analyzed in detail. Secondly, a high step-down N-channel LED driver is proposed and its current auto-balance characteristic and step-down ratio are analyzed. Finally, an experimental prototype is built and the experimental results are given. The theoretical analysis and experimental results show that the proposed driver has the following virtues: First, if load balancing is achieved, the voltage gain is 1/N that of a Buck driver, where N is the number of chamiels. Second, each output automatically has an equal output current, without requiring more current close-loop control circuits than a Buck driver. Last, the voltage stresses of the switches and diodes are lower than those of a Buck driver, meaning that lower voltage switches and diodes can be used, and a higher efficiency can be expected. [ABSTRACT FROM AUTHOR]