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An expanded sequence-to-sequence (E- Seq2Seq) based data-driven security-constrained unit commitment (SCUC) expert system for dynamic multiple-sequence mapping samples is proposed in this paper. First,the dynamic multiple-sequence mapping samples of SCUC are reconstructed by analyzing the input-output sequence characteristics. Then,an E-Seq2Seq approach with a multiple-encoder-decoder architecture and a fully connected extension layer is proposed. On this basis,the simple recurrent unit is introduced as a neuron of the E-Seq2Seq approach to construct the deep learning model,and an intelligent data-driven expert system for SCUC is further developed. The proposed approach has been simulated on a typical IEEE 118-bus system and a practical system from Hunan province in China. The results indicate that the proposed approach possesses strong generality,high solution accuracy,and efficiency over traditional methods.

In this paper, a buck based active-clamp circuit for current-fed isolated DC-DC converters is proposed. The proposed active-clamp circuit can not only suppress the voltage spikes caused by the current difference between the current-fed inductor and leakage inductor of the transformer, but also transfer the energy of the above process to the input voltage source. Different from the traditional active-clamp circuit, the proposed active-clamp circuit needs only one switch regardless of the number of input phases in the main circuit. Moreover, the control of the proposed active-clamp circuit is decoupled with the main circuit, which makes the design and implementation of the system controller easier. A 400W experimental prototype has been built to verify the effectiveness of the proposed circuit.

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.

Dual-stage cascaded dc systems are some of the most widely applied power interfaces in dc distributed power systems. However, in some practical situations, these systems might be unstable, especially if they incorporate tightly regulated load converters that operate as constant power loads (CPLs), whose power fluctuations could exert a cascading impact on the operation of the systems. Existing studies tend to describe the instability phenomena using bifurcation diagram analysis and the loci of eigenvalue analysis. However, it is usually difficult to derive the explicit expressions of the stability criterion. This paper addresses the large-signal stability issue of the dual-stage cascaded dc systems from a standpoint of load power and obtains the explicit form large-signal stability boundary in terms of load power by using Lyapunov-type mixed potential theory. Moreover, the prototype dual-stage cascaded dc system, in which the control strategies for the feeder converter and the load converter are different, is used as an example in this study. According to the results, the system remains stable when the load power is in [5.8, 23.2] W. When load power is less than 5.8 W or increased to [23.2, 32.8] W, the system is in a period-2 subharmonic oscillation state. Moreover, when the load power exceeds 32.8 W, the system falls into a chaotic state. The deduced boundary is highly consistent with the analysis results of both a bifurcation diagram and Jacobian matrix based analysis. Finally, both circuit-level simulation and experimental results validate the effectiveness of the load power stability boundary.

Voltage multipliers (VMs) are widely used in applications with the high-voltage-gain rectifiers and dc/dc converters with the capability of increasing voltage conversion ratio. Currently, all the existing VM circuits are designed with two input terminals, while the optimal design on the voltage conversion ratio and voltage stress on the semiconductor devices of the converters with VMs can be achieved by varying the number of basic VM units. However, as the number of its input terminals is fixed and, thus, the current stress on the semiconductor devices are not adjustable at the design stage, such circuits have limited applications in today's high-power energy conversion systems. In order to address such drawbacks of the conventional VMs, a multiple input-terminal VM (MIVM) circuit is proposed in this article. The analysis of the operation principles and the performance characteristics of the proposed MIVM circuit are presented in detail. As an example, the application of the MIVM with the traditional boost converters is presented and discussed, and the efficacy of the theoretical analysis is validated experimentally.

The voltage conversion ratio of basic dc/dc converters is limited due to the influence of parasitic elements of circuits and components. In this article, a family of passive circuits termed as “coat circuits” are proposed for conventional dc/dc converters. Not only voltage step-up capacity can be improved but also the voltage stress of components can be decreased by adding coat circuits to basic dc/dc converters. Moreover, no additional active switches are needed in the coat circuits, that means the control and driver circuits of the converters are not changed. The Cuk converter with the coat circuit has been analyzed as an example, and a 200 W experimental prototype has been built to verify the validity of the theoretical analysis.

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 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.

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.

A dual-input high step-up DC/DC converter with zero voltage turn-off (ZVT) auxiliary circuit is presented in this paper. The cost of whole photovoltaic (PV) power could be decreased significantly by the proposed converter because it allows two PV panels to be connected at the same time. ZVT auxiliary circuit provides soft switching in a wide range of load variations with six passive components. Turn-off switching losses could be decreased and the efficiency of the whole converter could be improved. In Section II , the operation principle and performance characteristics of the proposed converter have been analyzed and an 800 W experimental prototype has been built to validate the analytical results in Section III . In Section IV , a dual-input maximum power point tracking (DMPPT) control algorithm has been designed for the proposed converter. Experimental results show that two PV panels can achieve the maximum power output state separately by the proposed DMPPT control algorithm.

Studying the faster and more efficient method of solving the uncertain security-constrained unit commitment (SCUC) problem is an urgent need for the development of power systems under the background of large-scale wind power access and power dispatching. This study proposes an improved constrained order optimization (COO) algorithm to solve the uncertain SCUC problem. First, the data-driven discrete variable identification strategy is incorporated into the COO rough model, and then, the invalid security constraints identification strategy is incorporated into the COO accurate model. Finally, the improved COO algorithm combines the discrete variable identification with the invalid security constraint identification to make the uncertain SCUC decision. The results of the IEEE 118-bus test system showed that, compared with the traditional COO algorithm, the improved COO algorithm proposed has higher accuracy and better efficiency.

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.

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.

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 500 W experimental prototype with two VMCs has been developed to validate the effectiveness of the theoretical analysis, and the highest efficiency is 93.8%.

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.

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.

A kind of interleaved non-isolated high step-up DC/DC converter is presented in this study. The converter consists of two basic Boost cells and some diode-capacitor multiplier (DCM) cells as needed. Because of the DCM cells, the voltage conversion ratio is enlarged and the extreme large duty ratio can be avoided in the high step-up applications. Moreover, the voltage stress of all the power devices is greatly lower than the output voltage. As a result, lower-voltage-rated power devices can be employed, and higher efficiency can be expected. Since the two basic Boost cells are controlled by the interleaving method, which means the phase difference between the two pulse width moderlation (PWM) signals is 180° and the input current is the sums of the two inductor currents, the input current ripple is decreased and the size of the input filter could be reduced, which make it a suitable choice in the photovoltaic power generation system and hybrid electric vehicles, etc. Finally, the experimental results from a 300 W, 30-400 V laboratory prototype are presented to validate the effectiveness of the proposed converter.

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.

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 channels. 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.

In this paper, a multiple-input high step-up boost converter is presented for grid-connected photovoltaic power generation system. Firstly, the derivation of the converter with dual input is presented and its operation principle and steady state performance arc analyzed in detail. Secondly, the n-input high step-up boost converter made up of n boost cells is deduced. Its high step-up ratio and the relationship among the input currents are analyzed. Finally, an experimental prototype rated 100 W is built and the experimental results are given.