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One of the most serious issues that requires special attention is the protection of distribution networks. Using the proper protective equipment improves the safety of the power distribution network during fault conditions. Fault current limiter (FCL) is a type of modern preservation system used to protect power networks and equipment. The voltage restoration of buses during faulty conditions is one of the main concerns of power networks. A group of coordinated DC reactor type fault current limiters are designed and tested in this study to protect the network and restore its bus voltage during the fault period. The proposed FCLs coordination strategy is modelled and simulated in the MATLAB platform, and the results are validated.

In this article, a cooperative resilient control method for DC MG is proposed to dispel the adverse influences of both communication delays and DoS attacks. To avoid that the sampling period is captured by intelligent attackers, a new time-varying sampling period and an improved communication mechanism are firstly introduced under the sampling control framework. Based on the designed sampling period and communication mechanism, a resilient secondary controller is designed based on the sampling and communication mechanism. It is theoretically shown that the developed method can achieve the goals of bus voltage restoration and current sharing even in the presence of both DoS attacks and heterogeneous communication delays. Finally, a DC MG test system is built in a controller-hardware-in-the-loop testing platform to illustrate and verify the effectiveness of our developed method against both communication delays and DoS attacks.

In this article, a half-bridge class-D audio amplifier (HB-CDAA) system with embedded bidirectional buck–boost converter is proposed. The proposed HB-CDAA system consists of a front-end symmetric bipolar output converter, a bidirectional buck–boost converter, and an HB-CDAA. With the help of the embedded bidirectional buck–boost converter, bus voltage pumping on the output of the front-end symmetric bipolar output converter of HB-CDAA can be suppressed. Thus, small ceramic capacitors can be used as bus capacitors to increase power density and to improve audio output quality. Furthermore, ZVS of the embedded bidirectional buck–boost converter can be achieved. The operating principle of the proposed circuit is analyzed and an experimental prototype is built. Experimental results show that ZVS of the embedded bidirectional buck–boost converter is achieved, and bus voltage pumping is successfully suppressed with small bus capacitors.

Though the merits of matrix-based dual-activebridge (MB-DAB) AC-DC converter as a submodule for gridconnected multilevel medium-voltage AC (MVAC) - low-voltage DC (LVDC) conversion have been presented in recent literature, its operational challenges in the cascaded configuration have not been explored. The objective of this paper is to present the inevitable challenge of unequal power routing through the submodules of cascaded matrix-based dual-active-bridge (CMBDAB) and its mitigation. The detailed and simplified small-signal model of the CMB-DAB converter along with the proposed power balance control (PBC) strategy required to eliminate the power imbalance issue are explained comprehensively. The simulation results for a 3-cell 52.65 kVA CMB-DAB converter along with scaled-down 5.85 kVA experimental results are presented, to demonstrate the unavoidable power imbalance issue and the proposed PBC strategy as a mitigation technique. The proposed scheme is observed to perform seamlessly with the conventional LVDC bus voltage control and remediate power routing imbalances during the steady-state and load-change operations.

This paper proposes a novel distributed event-triggered secondary control method to overcome the drawbacks of primary control for DC microgrids. With event-triggered distributed communication, the proposed control method can achieve system-wide control of parallel operating DGs with two main control objectives: a) estimate the average bus voltage and regulate it at the nominal value; b) achieve accurate current sharing among the DGs in proportion to their power output ratings. Furthermore, the proposed control strategy can be implemented in a distributed way that sharing the required tasks between the DGs. Thus, it shows the advantages of flexible and scalable. Furthermore, this paper also proposes a simple event-triggered condition that does not need extra state estimator. Thus, limited communication among neighbors is required only when the event-triggered condition is satisfied, which significantly reduce communication burden in the cyber layer.

This article presents a power converter topology with integrated driving and charging capability of switched reluctance motor (SRM) drive for electric vehicle (EV) application. In the driving mode, the bus voltage can be adjusted flexibly by the front-end buck converter, which meets the requirements of the speed open-loop and closed-loop control. Besides, higher voltage demagnetization can be achieved by connecting the upper freewheeling diodes of the asymmetric half-bridge converter to the battery bank, thus can accelerate the demagnetization process, extend the dwell angle, and enhance the output of the motor. In battery charging mode, a bridgeless rectifier converter is constructed by utilizing two-phase windings of the SRM and the existing power devices of integrated power converter, without additional inductors and charging units. The battery charging and power factor correction control can be realized by closed-loop control of charging current. Detailed analysis and experiments on a 1 kW 12/8 structure prototype SRM validate the effectiveness of the proposed technologies.

The purpose of this paper is to research the effect of interconnection a photovoltaic power system PVPS with a power system on a bus voltage. This work is accomplished by using a modified Gauss-Seidel method. The modification presents PVPS as a negative load which means when a PVPS is connected – to a generator bus. And the real power generated from it must be added to the generated power. On the other hand if PVPS is connected to a load bus. The power generated from it is subtracted from the real power of this load. The study of this integration is programmed for various sites of PVPS on a power system. And for different sizes of PVPS. The results of this study show that the insertion of PVPS on a power system has a pronounced effect on the active and reactive components of bus voltages. Besides, it has an effect on the absolute value of the buses voltages.

This article presents a single-stage ac–dc light-emitting diode (LED) driver to achieve current regulation of red, green, and blue (RGB)-LED strings and ac–dc rectification with high power factor. The advantages of single-stage topology include single inductor, lower component counts, and smaller form factor. To adaptively and accurately regulate RGB-LED strings a switching capacitor control scheme is adopted with the properties of dynamic voltage difference detection and fast bus voltage hopping. The dynamic voltage difference detection precisely detects the voltage difference between the R- and GB-LED strings while the fast bus voltage hopping can immediately adjust the bus voltage level. The experimental results are shown to verify the theoretical analysis of the proposed LED driver, and the transient response time is less than 0.3 μ s, which is at least three orders faster than the previous work. The peak efficiency of the proposed LED driver is up to 88.6%.

This article presents the design and evaluation of robust controllers, based on linear programming, Kharitonov's theorem and Chebyshev's theorem, in order to enhance the performance of a typical structure of multistage converters present in direct current (dc) systems. In such electric power distribution systems, point-of-load converters act as a constant power load (CPL), which introduces a destabilizing nonlinear effects to their supply bus voltage. The multistage converter system uses a simplified scheme based on a cascaded converter, which is comprised of two dc–dc buck converters in a series connection. The robust controllers evaluated overcome the negative incremental impedance instability problem due to CPL, which causes a high risk of instability in interconnected converters. Thereby, the robust controllers evaluated ensure robust control performance and stability with a minor performance degradation compared to a conventional controller when the cascaded converter system is subjected to parametric uncertainties. The control methodologies evaluated are applied in both dc–dc buck converters. Assessments on the performance of the control methodologies evaluated are conducted. Experimental validations on a 160-W dc–dc cascaded converter system test board are carried out to verify the theoretical claims.

In the literature, many studies on stability analysis of dc microgrids have been conducted. However, most of them mainly focus on small-signal stability. On the other hand, few works analyze large-signal stability, but the major part of these works is based on a single unit or a simple cascaded system as a case study. Different from those, this article aims to address the large-signal stability analysis of a dc microgrid from a system-level perspective. First, the equivalent model of a droop-controlled dc microgrid is developed. Subsequently, the Lyapunov-based large-signal stability analysis and the stability criterion are derived, and mixed potential theory is used to make comparisons to verify the effectiveness of the derived criterion. The equilibrium point stability for different operation stages was obtained by means of theoretical calculation. Furthermore, the instabilities principle as well as their physical interpretation is revealed. In this article, the bus voltage is used as the only index to assess the microgrid power balance. Hence, the power load limit can be obtained by taking into consideration the stability and voltage deviation constraints. Finally, simulation and experimental results from a four-converter dc microgrid system verify the feasibility of the proposed theoretical analysis.

Open-winding permanent magnet synchronous machine (OW-PMSM) could obtain the higher bus voltage utilization and more robustness against the component damage and faults. However, the additional torque ripples and total harmonic distortion (THD) caused by zero-sequence current would limit the further applications of OW-PMSM. In this article, a novel model predictive two-target current control (MPTCC) scheme is presented to deal with such problem through model predictive control concept. First, a basic model predictive current control is proposed to deal with the torque production in fundamental components. Then, another modified cost function is proposed to provide more precise voltage vectors in torque production. After that, the deadbeat predictive control concept is proposed to calculate the required voltage vectors in zero-sequence loop. This zero-sequence voltage is injected in the voltage vectors, which are responsible for torque production. It needs to be mentioned that the limitation of inverter is analyzed. And the real-time judgment is proposed to assess the performance of MPTCC in some work conditions. Finally, both simulation and experiments have been both applied to assess the performances of the proposed control scheme. Comparing with those existing q -axis current injection methods and modified space vector pulse width modulation (SVPWM) technologies, the proposed control scheme could eliminate the torque ripple and THD at the same time and thus possess the better performances.

In this article, a high-efficiency and power-density unregulated inductor-inductor-capacitor (LLC) converter (DCX) is proposed for a first-stage converter in a two-stage 48-V voltage regulator module (VRM) for data center applications. The intermediate bus voltage in the two-stage architecture is evaluated by designing two LLC-DCX converters with fixed transformation ratios of (4:1) and (8:1). The overall efficiency of the two-stage architecture is evaluated, and the optimal bus voltage is selected. The LLC-DCX is designed using gallium nitride (GaN) devices and an optimized integrated magnetic structure. An enhanced primary and secondary termination method, as well as a printed circuit board (PCB) winding structure for equal current sharing among all transformer layers, is proposed, A significant reduction in the total conduction loss for the high-frequency transformer is achieved. The designed LLC-DCX can provide a continuous output power of 900 W with maximum efficiencies of 98.4% for the (4:1) conversion, and 98.0% for the (8:1) conversion, with high-power densities of 1600 and 1200 W/in3, respectively. The overall efficiency of the two-stage VRM was evaluated, and the results show a superior performance when using a lower bus voltage of 6 V.

The optimal placement of Distributed Generation (DG) units in radial distribution system is one of the important ways for techno-economic improvements. The maximum technical benefits can be extracted by minimizing the distribution power loss as well as bus voltage deviation, whereas the maximum economical benefits can be procured by minimizing the total yearly economic loss which includes installation, operation and maintenance cost. So for the maximum techno-economic benefits, all three objectives should be simultaneously minimized by considering a multiobjective optimization technique. For optimal results, a Pareto optimal concept-based novel multiobjective quasi-oppositional grey wolf optimizer (MQOGWO) algorithm has been proposed. The performance of the proposed algorithm has been tested on IEEE-33 bus radial distribution system. In this analysis, various voltage-dependent load models such as constant power, constant current, constant impedance, residential, industrial and commercial load models have been considered at different loading conditions like light load, full load and heavy load. The effects of DG type on the system performance have also been analyzed to find the best optimal solution.

The lack of a load power prediction function in conventional multi-wheel electric drive vehicles leads to lags in control action. To address this issue, we developed a real-time energy management strategy with improved load power prediction accuracy. Based on an assessment of the overall vehicle structure, a mathematical model for each power source was established using theoretical analysis and data fitting. A method for the joint prediction of non-stationary load power combining Kalman filter and Markov chain forecasting methods was established, and a multi-objective optimization function was constructed under the nonlinear model predictive control framework. To enable real-time optimal control command, a sequential quadratic programming method in the finite time domain was applied. Finally, the multi-power source was optimized and coordinated. Multi-road driving experiments were carried out using a hardware-in-the-loop simulation platform. Comparisons of energy management control strategies with and without power prediction revealed that applying the former enhances the predictability of future load power, significantly optimizes the coordinated control of multiple power sources, improves vehicle fuel economy, and stabilizes bus voltage and battery state of charge. Moreover, it has specific reference significance in engineering application scenarios under conventional model predictive control.

Power network operations are increasingly becoming complex due to upsurge in power transactions, following the ongoing power system deregulation and restructuring. The alteration in dynamics of power operations based on this upsurge, usually results into contingency because power facilities are made to operate in region of their limits. In this regards, high voltage direct current (HVDC) based voltage source converter (VSC) and other flexible alternating current transmission systems (FACTS) imbedded with VSC have established competence for noticeable diverse power network characteristics improvements. Therefore, this study applies optimized VSC-HVDC transmission system for mitigation of bus voltage and line thermal limit violation as a result of n-1-line outage contingency during bilateral, simultaneous and multilateral transactions. Line contingency evaluation through real power performance index (RPPI) is adopted for severe contingency identification purposes. Optimization of VSC-HVDC system is achieved through statically developed sensitivity-based analysis of VSC control parameters, while its performance for both steady state and contingency conditions are verified with IEEE 6 and 30 bus networks. An improvement in power flow, voltage deviation minimization and automatic alleviation of violated thermal and voltage limits during contingency present optimized VSC-HVDC system as a solution for network performance optimization especially during various transactions occasioned by unbundling power processes. Besides, the superiority of the proposed optimization techniques is established through performance comparison with other sensitivity methods involving reactive power (RPSM), active power (APSM) and performance index (PISM), where the proposed sensitivity method (PSM) outperformed these other methods.

Power loss is a bottleneck in every power system and it has been in focus of majority of the researchers and industry. This paper proposes a new method for determining the power loss in wind-solar power system based on deep learning. The main idea of the proposed scheme is to freeze the feature extraction layer of the deep Boltzmann network and deploy deep learning training model as the source model. The sample data with closer distribution with the data under consideration is selected by defining the maximum mean discrepancy contribution coefficient. The power loss calculation model is developed by configuring the deep neural network through the sample data. The deep learning model is deployed to simulate the non-linear mapping relationship between the load data, power supply data, bus voltage data and the grid loss rate during power grid operation. The proposed algorithm is applied to an actual power grid to evaluate its effectiveness. Simulation results show that the proposed algorithm effectively improved the system performance in terms of accuracy, fault tolerance, nonlinear fitting and timeliness as compared with existing schemes.

Simultaneous deployment of the electric vehicle charging stations (EVCSs) and distributed photovoltaic stations (DPVSs) in the distribution systems is an effective way to reduce greenhouse gas emissions, promote renewable power adoption, and achieve sustainable development in energy utilization. In this context, how to deploy the EVCSs and DPVSs in the distribution systems with a reasonable scheme is of great importance. In this article, a joint planning model is developed to optimize locations and capacities of the EVCSs and DPVSs simultaneously to reduce energy losses in the distribution systems. In the joint planning model, constraints on bus voltage deviations and line currents are both formulated as chance constraints to ensure that the distribution systems are in reasonable operating statues. To quantify these two chance constraints, a scenario-based method is developed to calculate the probabilistic power flow of the distribution systems during a typical planning day, in which random characters of the DPVS generations and the EVCS charging loads are both considered. The joint planning model of the EVCSs and DPVSs developed in this article is difficult to be solved by mathematical optimization methods. Therefore, genetic algorithm (GA) is customized and utilized to solve the joint planning model of the EVCSs and DPVSs. Finally, a case study based on IEEE 33-bus distribution systems validates the joint planning model and its solving algorithm.

Sequential switching shunt regulators (S3Rs) are widely used in the satellites owing to their simple structure and high reliability. The high-power communication satellites require a power supply with a high bus voltage and large solar array section current. However, a large solar array capacitance and new time-division multiple access operations complicate the design of a lightweight and cost-effective power supply by increasing the difficulty in dissipation and thermal control. On the basis of passive current limitation, in this article, we propose a novel shunt regulator with only one output diode and a protection strategy to achieve high efficiency, appropriate shunt current limitation, and low turn- off delay. In addition, to reduce the dissipation of an S3R cell when feeding the solar array current to the main bus and to satisfy the single point failure-free requirement, an innovative self-retriggerable diode short-circuit fault detector circuit is proposed, which includes a protection switch for a safe thermal or electrical operation. Finally, simulation and experimental results are presented to validate the proposed shunt regulator and the corresponding control method or protection strategy.

This article introduces a new energy management control method for energy storage systems used in dc microgrids. The proposed control method is based on an adaptive droop control algorithm that maintains the dc-bus voltage in the desired range. In the islanded mode of operation, tightly regulating the bus voltage is very challenging. The proposed control technique is based on a nonlinear droop profile with four adaptive parameters. These parameters are determined using the optimization algorithms to achieve reliable and efficient operation. The adaptive parameters enable the proposed nonlinear droop controller to tightly regulate the bus voltage during various changes in loads/sources within a dc MG. The stability of the proposed system for a very wide range of operating conditions is proved. Simulation and experimental results verify the feasibility of the proposed approach and demonstrate its superior performance compared to the conventional controllers.

The interleave boost converter (IBC) has been used as the interface converter between the low-voltage electrical energy sources, such as lithium-ion battery banks, solar panels, and fuel cells, and the dc bus of dc microgrids. With increasing penetration of tightly regulated power electronic loads, which behave as constant power loads, the stability of microgrid dc-bus voltage that is fed by the IBC is threatened by the loads’ negative incremental impedance feature. To ensure the stability of the bus voltage, this article proposes a nonlinear disturbance observer (NDO)-based sliding-mode control algorithm. The proposed algorithm has excellent robustness, low computational burden, and no extra hardware cost. A generalized average state-space model is proposed to facilitate the control design. In addition, an NDO is employed to estimate the output power of IBC rapidly and accurately. To verify the effectiveness of the proposed algorithm, simulation and experimental results are presented.

A power factor correction (PFC) charge-pump (CP) bridgeless converter for LEDs is presented. In the input stage, coupled inductors, together with CP capacitors, are integrated into a half-bridge inverter, thus characterising the single stage. This topology even being bridgeless due to the positioning of the load operates with a bus voltage below the bending voltage. The CP configuration is used to reduce the LED's current ripple. The prototype achieves an output power of 60 W with high power factor, achieving the efficiency of up to 94%, 127 Vac input, total harmonic distortion of input current, with harmonic magnitudes within the IEC 61000-3-2 standard class C the device limits and flicker in conformed with the recommendation of IEEE 1789.

This article introduces the notion of minimum distortion point tracking (MDPT) : a control strategy where switching waveforms are optimally phase shifted to minimize aggregate ripple power for networks of dc–dc converters that are connected in series or parallel at the input or output. In a sense, MDPT generalizes the ubiquitous concept of interleaving in balanced systems to a broad class of asymmetric series- or parallel-connected dc–dc converters. For networks of up to one hundred interconnected power converters, MDPT demonstrates a one to two order of magnitude reduction (−14 to −22 dB) in distortion power. We present and experimentally verify three algorithms that can dynamically solve the MDPT optimization problem on a network of three input-parallel connected dc–dc buck converters handling 1.8 kW. The experimental results illustrate an up to $\text{3.06}\times$ reduction in the peak-to-peak ripple of the parallel-side bus voltage and convergence close to an optimal steady-state solution in 5 ms.

This brief uses a double-quadrant state-of-charge (SoC) consistent adaptive droop control method for extending the service life of distributed energy storage units (DESUs). During charging, the power absorbed by DESU is inversely proportional to its SoC. On the other hand, during discharging, the power emitted by DESU is proportional to its SoC. The SoC of DESUs and the power absorbed or emitted by the DESUs tend to be consistent under charging and discharging conditions. To compensate for the direct-current (DC) bus voltage change caused by droop control during charging and discharging of DESUs, this brief proposes a novel double-quadrant SoC consistent adaptive droop control method which is based on multi-agent approach and considers the real-time capacities of DESUs. The reliability of the proposed novel control design method is confirmed by simulations.

Flexible Alternating Current Transmission Systems (FACTS) devices have been suggested as an efficient solution for regulating bus voltage and controlling in power flow in electrical power networks, which leads to improve stability and reduce the loss of electrical power. Suitable location and the appropriate size of these devices can lead to control line flow and maintain the voltage at each bus at the desired level and so recover system security. This paper shows comparison study between two techniques from artificial intelligent techniques to determine location and optimal size of FACTS devices based on power losses, voltage division and system over load. Also, in this paper a comparison between multi- and single objective function to find the optimal location and optimal size of SVC has been carried out. The proposed algorithms are simulated annealing and particle swarm optimization and are tested on modified IEEE 30-bus power system for optimal allocation of Static VAR Compensator (SVC) as a kind of FACTS devices and results are presented. تم اقتراح أجهزة تعويض القدرة غير الفعالة کحل فعال لتنظيم جهد الناقل والتحکم في تدفق الطاقة في شبکات القدرة الکهربائية ، مما يؤدي ذلک إلى تحسين الاستقرار وتقليل فقدان الطاقة الکهربائية. يمکن أن يؤدي الموقع المناسب والسعة المناسبه لهذه النبائط إلى التحکم في تدفق سريان القدرة والحفاظ على الجهد عند کل ناقل في المستوى المطلوب وبالتالي استعادة أمان المنظومة الکهربية. تم في هذا البحث عرض دراسة مقارنة بين خوارزمية محاکاة التلدين وتحسين سرب الجسيمات لتحديد موقع وسعة أجهزة تعويض القدرة غيرالفعالة على أساس فقدان الطاقة وتقليل الفقد في الجهد وخفض حمولة المنظومة الکهربية . أيضا ، يقارن هذا البحث بين مشکلة التحسين متعددة الأهداف ومشکلة التحسين ذات الهدف الواحد للعثورعلى الموقع والسعة المثلي لـمعوض القدرة غير الفعالة. وقد تم اختبار الخوارزمية المقترحة على منظومة المعدل للبحث عن الموقع والسعة المثلي لمعوض القدرة غير الفعالة کنوع من أجهزة تعويض القدرة غير الفعالة وقد تم عرض نتائج هذا الإختبار.

The multilevel boost converter (MBC) has been widely adopted in the dc microgrid systems due to its high voltage gain and simple structure. In recent years, the power electronic loads, which usually behave as constant power loads (CPLs), are penetrating in microgrids. The incremental negative impedance of CPLs degrades the stability of microgrid systems. To ensure effective power flow and guarantee system stability, eliminating the undesired effects of CPLs is a necessity. In this article, a novel assorted nonlinear stabilizer, which is integrated with an extended nonlinear disturbance observer (NDO) and an adaptive backstepping controller, is proposed for stabilizing the MBC-fed microgrid system with CPLs. First, the reduced-order MBC model is transformed into the Brunovsky's canonical form using the exact feedback linearization technique. Second, owing to the NDO, fast system dynamic responses are achieved. Using the estimations of NDO, an adaptive backstepping controller is developed to strictly guarantee the microgrid bus voltage stability in the sense of a large signal. Simulation and experiment results are presented to verify the effectiveness and feasibility of the proposed stabilizer.