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DC microgrids, along with existing AC grids, are a future trend in energy distribution systems. At the same time, many related issues are still undefined and unsolved. In particular, uncertainty prevails in isolation requirements between AC grids and novel microgrids as well as in the grounding approaches. This paper presents a critical technical analysis and an overview of possible grounding approaches in DC systems and the feasibility of avoiding isolation between AC and DC grids. [ABSTRACT FROM AUTHOR]

The article presents an induction generator connected to the power grid using the AC/DC/AC converter and LCL coupling filter. Three-level inverters were used in the converter, both from the generator side and the power grid side. The algorithm realizing Pulse Width Modulation (PWM) in inverters has been simplified to the maximum. Control of the induction generator was based on the Direct Field-Oriented Control (DFOC) method. At the same time, voltage control has been used for this solution. The MPPT algorithm has been extended to include the variable pitch range of wind turbine blades. The active voltage balancing circuit has been used in the inverter DC voltage circuit. In the control system of the grid converter with an LCL filter, the number of measurements was limited to the measurement of power grid currents and voltages. Synchronization of control from the power grid side is ensured by the use of a PLL loop with the system of preliminary suppression of undesired harmonics. [ABSTRACT FROM AUTHOR]

Energy routers act as an interface between the distribution network and electrical facilities, which meet the requirements of clean energy substitution and achieve the energy sharing and information transmission in the energy network. However, the protection of the dc load side of residential energy routers including interruption and isolation of short-circuit fault currents is vital for discussion. Since the traditional mechanical and hybrid circuit breakers for dc fault protection have the drawback of slow operation, a solid-state circuit breaker (SSCB) is an optimal solution for fast dc fault interruption. In this paper, a dc SSCB is proposed that uses an RCD + MOV snubber circuit, which is considered the best and most complete circuit used in common SSCBs. There are two main contributions in this paper: First, a dc SSCB is designed, which isolates both positive and negative terminals of a circuit and its working principle and operating modes along with the formulas for calculation of crucial time intervals, voltages, and currents along with the design procedure are provided. Second, a soft turn-on auxiliary is designed to prevent a high current surge caused by the capacitance difference between the source and the load. The experimental results demonstrate the proper performance of the topology and the validity of the findings. [ABSTRACT FROM AUTHOR]

There is a growing interest in solar energy systems with storage battery assistance. There is a corresponding growing interest in hybrid converters. This paper provides a comprehensive review of hybrid converter topologies. The concept of a hybrid inverter is introduced and then classified into isolated and non-isolated structures based on using a galvanic transformer. The classification and description of each type are presented based on the features and applications. Furthermore, the most popular commercial solutions are investigated in terms of their simplicity, flexibility, efficiency, and battery technology. The summarizing features are presented through tables, and future trends for researchers to follow to develop efficient hybrid converters are discussed. This review paper is intended as a convenient reference for hybrid converter users. [ABSTRACT FROM AUTHOR]

The focus is on the maximum power point tracking implementation for the buck-boost voltage mode control of a single-phase multilevel inverter based on a three-level neutral point clamped quasi-Z-source topology. To utilize shoot-through states only when boost function is needed and avoid it in the buck mode, two different control approaches are required. This article proposes merged control system which provides switching between different control algorithms in the buck and boost modes. In particular, a hysteresis band between the buck and boost modes is proposed which provides smooth and stable performance. It also includes features of the implementation of the global maximum power point tracking, which can scan the entire input voltage range in up to 10 s. Experimental results showed that proposed control system provides high and stable maximum power point tracking efficiency in different operation points. Finally, the key features are verified, the advantages, drawbacks, and an eventual potential for other applications are presented in conclusions. [ABSTRACT FROM AUTHOR]

New emerging power inverter topologies are aiming at high-power density and efficiency with reliable performance. The recently proposed family of single-phase single-stage buck–boost inverters with output unfolding circuits have promising features for application in different fields. Nevertheless, the incapacity of injecting reactive power by the classical unfolding inverters has been assumed as its main drawback. Thus, our focus is on the reactive power injection capability of the single-stage buck–boost inverters with unfolding circuits. This attribute enables the converter to provide some extra ancillary services for friendly integration of the renewable energy resources and energy storage systems, providing support to the smart grid/microgrid, thus contributing to its power quality welfare. By means of a comprehensive analysis and implementation of proper closed-loop model predictive control, together with an adequate selection of the output capacitor, the single-inductor unfolding buck–boost inverter is capable of delivering reactive power to the utility grid. We used the simulation and experimental tests to validate the theoretical aspects. [ABSTRACT FROM AUTHOR]

This article presents a novel concept of a universal solar converter suitable for application in both in the dc or single-phase ac grids using the same terminals. The idea lies in the utilization of the same semiconductors in the dc–dc and in the dc–ac configuration, resulting in minimal redundancy. Possible semiconductor stages are considered. The particular attention is focused on the output filter design along with proper protection circuit selection for dc and ac grids. The design example and comparative analysis between dc–dc, dc–ac, and universal solutions are given. The experimental prototype of the universal solar converter that is rated for 3.6 kVA power in the ac mode and 5 kW in the dc mode is presented. The experimental results demonstrate the ability of operation in ac or dc grids with main correspondent modes. Possible fields of application along with main benefits are addressed in conclusions. [ABSTRACT FROM AUTHOR]

This article studies the model predictive control (MPC) for a twisted buck–boost inverter based on unfolding circuit. The focus is on the practical implementation of the MPC algorithm for the microcontroller designed for application in power electronics. Selection of proper cost function parameters along with a continuous control set reduced prediction horizon, at the same time keeping good quality of the grid current. The results showed that simplified differential equations and a multicore microcontroller contribute to the sample time reduction, which in turn increases the sampling frequency with the corresponding increase in the output current quality. The simulation and experimental results confirmed theoretical predictions. In conclusion, the MPC technique suits for reducing zero-crossing distortion and in applications based on unfolding circuit. [ABSTRACT FROM AUTHOR]

This article describes an example of a solar inverter design based on the quasi-Z-source network taking into account multi-objective optimization. An overview of the solar inverter market is provided. Based on this overview, the specification of the most important parameters of commercial solutions is derived. The target efficiency profile and operation range are selected as the main criteria for the design of a competitive solution. The theoretical losses model is designed for preliminary estimation of efficiency profile at any operation point. Optimal switching frequency range is defined. Active and passive components are selected according to the defined efficiency profile and the switching frequency range. The experimental setup including a pre-industrial prototype is built and tested. Experimental results demonstrate the performance of the solar inverter with different photovoltaic string profiles. Finally, the results and feasibility in the commercial application are discussed, and conclusions are drawn. [ABSTRACT FROM AUTHOR]

This study proposes an example of a wireless charging station design for a small-scale vehicle available on the market. The article analyzes basic transmitter inverter topologies and their compensation methods in terms of flexibility of control, tolerance to uncertainty in positioning, and the possibility of decreasing the integration price. Our comprehensive analysis focuses on the battery voltage range, energy capacity, cost, and travel distance. We evaluate the constraints of efficiency, transmitted power, amount of used material, and size of the energy delivery system based on our design example. The aim is to increase the penetration of wireless technology in terms of convenience and integration capabilities. [ABSTRACT FROM AUTHOR]

This paper describes the tuning process of the proportional-resonant controller, taking into account the significant computational delay from the digital control system. Different structures of the controller and related contradicting results are discussed. Particular attention is paid to the stability domain and its dependence on different parameters of the proportional-resonant controller. The main outcome of this paper consists in the tuning approach guidelines for selection of controller parameters in case of significant digital system delay. An optimal controller structure and start-up current optimization are proposed. All results are confirmed by simulation and experimental setup. [ABSTRACT FROM AUTHOR]

This paper describes a novel family of single-phase single-stage buck–boost inverters using output unfolding circuits. Operation principles and component design guidelines along with modulation techniques are presented and discussed. The simulation results confirm all theoretical statements. Experimental setup of the most promising solution is assembled and tested, where the efficiency for different operation modes is analyzed. Finally, the pros and cons along with applications of the proposed solutions are discussed in the conclusions. [ABSTRACT FROM AUTHOR]

This paper presents new space vector pulsewidth modulation (PWM) strategies for a single-phase three-level buck-boost neutral point clamped inverter coupled with impedance-source (IS) network. These strategies can be implemented for systems with any IS network with neutral point. The case study system is based on the quasi-Z-source inverter with continuous input current. To demonstrate an improved performance, the strategies are compared with a traditional PWM strategy. The advantages lie in reduced switching number, without output voltage quality distortion. The simulation and experimental results confirm the theoretical predictions. [ABSTRACT FROM AUTHOR]

This paper proposes a new photovoltaic panel maximum-power-point optimizer based on a buck converter. It can be connected to the DC-link distributed energy harvesting system that should perform the true maximum-power-point tracking algorithm based on maintaining a constant DC link voltage. The algorithm is based on the sensorless hysteresis control and ensures high efficiency. Three different realizations of proposed hysteresis optimizers have been analyzed in the paper, including operation principle and adjustment of hysteresis intervals. An experimental study has been performed for a portable low-power photovoltaic system in case of different loads and irradiance levels. The efficiency of maximum power point tracking has been calculated analytically for different hysteresis intervals and validated by experiment, which proved a 97-98 % efficiency of tracking for different PV panel temperatures. The proposed solution is recommended to be used in small- and medium-sized power systems where the price of the conventional maximum power point tracking converter is very high and is comparable to the cost of the individual panel. [ABSTRACT FROM AUTHOR]

This paper presents a novel power conditioning unit (PCU) for variable-speed micro wind turbine applications. It contains a simple generator-side rectifier, galvanic isolation with a simple dc–dc converter, and a single-phase full-bridge inverter at the grid side. Variable-speed micro wind turbines based on a permanent magnet synchronous generator (PMSG) are increasingly used in residential and small commercial buildings, despite their relatively low output voltage. Therefore, they can be used easily for battery charging, while their grid integration requires a PCU with galvanic isolation. Most of available PCUs provide no galvanic isolation, or use relatively complicated topologies or four stage energy conversion for that purpose. The dc–dc converter proposed allows reducing the complexity of the PCU. Steady-state analysis shows that the converter is capable of regulating voltage in a wide range suitable for micro wind turbines, which is supported by experimental results within the input voltage range of 40–400 V. The prototype built for integration of a 1.3-kW PMSG-based micro wind turbine shows good performance over the entire 1:5 range of the given wind turbine output voltage. A study of efficiency and power losses was conducted according to the wind turbine power profile. [ABSTRACT FROM PUBLISHER]

Impedance-source networks are an increasingly popular solution in power converter applications, especially in single-stage buck–boost power conversion to avoid additional front-end dc–dc power converters. In the survey papers published, no analytical comparisons of different topologies have been described, which makes it difficult to choose the best option. Thus, the aim of this paper is to present a comprehensive analytical comparison of the impedance-source-based buck–boost inverters in terms of passive component count and semiconductor stress. Based on the waveform of the input current, i.e., with or without a transformer, and with or without inductor coupling, the impedance-source converters are classified. The main criterion in our comprehensive comparison is the energy stored in the passive elements, which is considered both under constant and predefined high frequency current ripple in the inductors and the voltage ripple across the capacitors. Two-level and multilevel solutions are described. The conclusions provide a “one-stop” information source and a selection guide of impedance-source-based buck–boost inverters for different applications. [ABSTRACT FROM PUBLISHER]

This paper describes novel single-phase solutions with increased inverter voltage levels derived by means of a nonstandard inverter configuration and impedance source networks. Operation principles based on special modulation techniques are presented. Detailed component design guidelines along with simulation and experimental verification are also provided. Possible application fields are discussed, as well as advantages and disadvantages. Finally, future studies are addressed for the new solutions. [ABSTRACT FROM PUBLISHER]

This paper presents a hysteresis current control technique with shoot-through states distribution. This control algorithm could be applied to three-level and multi-level inverters with any impedance source network where reference current control signal along with shoot-through states are required. Possible modifications of the presented algorithm are discussed. The steady-state analysis was made to explain the operation principle of the algorithm. As a result, the link between the band ratio of the hysteresis current controller, the input voltage, and the desired DC-link voltage was obtained. All theoretical predictions were proved by simulation and experimental results. Future applications are discussed.Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper presents a three-phase three-level neutral-point-clamped quasi-Z-source inverter as a novel solution for photovoltaic applications. The topology was derived by combining properties of the quasi-Z-source networks with those of three-level neutral-point-clamped inverters. A case study system, a steady state analysis and a novel special modulation technique for shoot-through states distribution during the whole operation period are described. Component design guidelines for a three-phase system are presented. All theoretical findings have been confirmed by simulation and experimental results. A “full SiC” experimental prototype was developed. A comprehensive study of the converter's efficiency is provided. [ABSTRACT FROM AUTHOR]

This paper focuses on the galvanically isolated quasi-Z-source dc–dc converter with a novel zero voltage and zero current switching technique. The unique feature of the impedance network lies in combining the buck–boost operation capability with the short- and open-circuit immunity of transistors; at the same time, it can perform zero voltage and zero current switching on the primary side. The boundary conduction mode of the current in the second inductor of the quasi-Z-source network was used along with snubber capacitors in the two out of four transistors and a special control algorithm to achieve full zero-switching operation of the inverter. Simulation and experimental results prove the discussed ideas. Possible modifications of the algorithm and future applications are also described. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel voltage distortion approach for output filter design based on the voltage transfer function for both off-grid and grid-connected Pulse Width Modulation (PWM) Inverters. The method explained in detail is compared to conventional methods. A comparative analysis is performed on an example of L and LCL-filter design. Simulation and experimental results for the off-grid and the grid-connected single phase inverter prove our theoretical predictions. It was found that conventional methods define redundant values of the output filter elements. Assumptions and limitations of the proposed approach are also discussed. [ABSTRACT FROM AUTHOR]

Single-stage buck–boost inverters have attracted the attention of many researchers, due to their ability to increase/decrease the output voltage in one power conversion stage. One of the most important uses of these inverters is in photovoltaic applications, where the voltage of the solar panels varies in a wide range. In recent years, many new inverters have been proposed to improve the performance of existing structures. In this paper, the state of the art of these single-stage buck–boost inverters is discussed. The advantages and disadvantages of each structure are examined from different perspectives, such as the number of components, losses, and performance. Finally, in a general comparison, the properties of all structures are discussed and summarized in a table. [ABSTRACT FROM AUTHOR]

This paper is focused on the control issues of the quasi-Z-source derived push-pull converter with integrated magnetic elements. The proposed converter is intended for applications that require a high gain of the input voltage and galvanic isolation, i.e. power conditioning systems for renewable energy sources, such as variable speed wind turbines with direct driven permanent magnet synchronous generators. Magnitude and frequency of the output voltage of such turbines are variable due to intermittent nature of the wind power. Despite number of advantages converter has complicated dynamic behavior. Simulations showed change of stability margin depending on current operation point of the wind turbine and output load. Closed loop control system should provide fast response and stable operation in the wide range of wind speeds. Simulations showed that the conventional PI-controller with saturation cannot satisfy those requirements. Nonlinear PI-controller was derived by adding adjustment block to the conventional PI-controller. Adjustment block is drastically changing proportional and integral gains of the controller according to sign of the output voltage error. Proposed controller is compared with conventional one by means of simulation in PSIM. Simulation results prove that proposed nonlinear control system has improved regulator performance. [ABSTRACT FROM AUTHOR]

The focus of this study is on the grid-forming operation of the Energy Router (ER) based on Model Predictive Control (MPC). ER is regarded as a key component of microgrids. It is a converter that interfaces the microgrid (s) with the utility grid. The ER has a multiport structure and bidirectional energy flow control. The ER concept can be implemented in Nearly Zero-Energy Buildings (NZEB) to provide flexible energy control. A concept is proposed where the ER works as a single grid-forming converter. The challenge is to keep the predefined reference voltage and frequency inside the NZEB in all possible modes, including the idle operation mode, current sources, and nonlinear load control. To gain stability and output voltage quality, the MPC is proposed. The design of the modified MPC algorithm with improved dynamics performance is explained. PLECS software is utilized to verify the proposed algorithm. The results demonstrate the suitable performance of the proposed control method in terms of total harmonic distortion of the output voltage. The influence of weighting coefficiencies is evaluated, showing the higher impact of the capacitor filter voltage on lowering the total harmonics distortion of the output voltage. Finally, the capability of the control system toward step change in the reference value is evaluated. [ABSTRACT FROM AUTHOR]

This paper describes a bidirectional twisted single-phase single-stage buck-boost dc-ac converter based on an output unfolding circuit. This solution is derived by the combination of an inverting buck-boost dc-dc converter and an unfolding circuit. The operation principle, component design guidelines, along with the control approach are presented. The zero-crossing distortion problem is discussed and solved by a simple approach. The simulation and experimental results confirm all theoretical statements. Loss distribution and achievable efficiency are analyzed. Finally, the pros and cons of the proposed solution, along with the most promising application field, are analyzed and discussed in the conclusion. [ABSTRACT FROM AUTHOR]

A high step-up dc–dc converter with multiple magnetic devices and switched-capacitor voltage multiplier cell (SC VMC) is proposed in this article. By simultaneous implementation of a coupled inductor (CI) and a built-in transformer (BIT), the voltage gain is flexibly increased with an additional degree of freedom in comparison with the converters with only BIT or CI. To further increase the voltage gain, the secondary winding of the CI is inserted in series with the primary winding of the BIT. This new architecture leads to multiplication of the turns ratios of the CI and BIT in the voltage gain expression, as well. The SC VMC not only extends the voltage gain but also reduces the voltage stress across the MOSFETs. To have a better device utilization, the blocking capacitor is participated in voltage gain improvement. Moreover, through active clamp circuit, the leakage energy of the magnetic devices is recycled and zero voltage switching (ZVS) performance is obtained for the main and auxiliary MOSFETs. In such a case, the switching frequency can be increased to reduce the volume of the converter. Finally, a 400-W laboratory prototype with 25– 400 V voltage conversion is fabricated to demonstrate the effectiveness of the proposed converter. [ABSTRACT FROM AUTHOR]

The paper presents a comparative study of two solar string inverters based on the Quasi-Z-Source (QZS) network. The first solution comprises a full-SiC two-level QZS inverter, while the second design was built based on a three-level neutral-point-clamped QZS inverter with Silicon based Metal–Oxide–Semiconductor Field-Effect Transistors (Si MOSFETs). Several criteria were taken into consideration: the size of passive elements, thermal design and size of heatsinks, voltage stress across semiconductors, and efficiency investigation. The Photovoltaic (PV)-string rated at 1.8 kW power was selected as a case study system. The advantages and drawbacks of both solutions are presented along with conclusions. [ABSTRACT FROM AUTHOR]

The focus of this paper is to provide a comparative analysis of various common-ground converters that serve as dual-purpose power electronic interfaces. These interfaces are designed to be used in both DC and single-phase AC grids, utilizing the same terminals for both modes of operation. The idea lies in the utilization of the same semiconductors in the DC-DC and DC-AC configurations, resulting in minimal redundancy. Particular attention is focused on the comparative evaluation approach. A novel Flying Inductor (FI)-based converter was selected for experimental verification. The design example and experimental prototype of a dual-purpose DC-DC/AC power electronic converter is capable of providing 2 kVA of power in AC mode and 4 kW in DC mode. The experimental results indicate that the converter can operate in both AC and DC grids according to their respective modes. The conclusion of the study highlights the potential applications and main benefits of this technology. [ABSTRACT FROM AUTHOR]

As the use of photovoltaics becomes more widespread, new technologies for more efficient energy generation, transmission, and distribution based on power electronics converters are being developed. The most common applications are grid-on, energy storage, hybrid, and high voltage gain applications. These applications impose several additional requirements in the design of power converters associated with the solar battery's maximum power tracking and operation in a wide range of input currents and voltages. The practical realization of such solutions can be implemented on the basis of various topologies, which requires a preliminary application of criteria for assessing their effectiveness. The paper conducts a comparison of different topologies on power converters based on two parameters that describe their cost and power loss for various PV applications. For a straightforward study, these parameters are represented using the gain factor, which allows for an accurate comparison of the efficiency of various types of converters. [ABSTRACT FROM AUTHOR]

This paper is focused on a single-phase three-level neutral-point-clamped quasi-z-source inverter when it is operating being connected to the electrical grid. A control strategy for injecting current synchronized in phase with the voltage at the point of common coupling has been proposed and studied. It is achieved by means of controlling the output voltage between branches adjusting the output current by using a d-q frame and the analysis of the output filter. The control strategy generates the reference to be used in the modulation technique and it has been validated with and without shoot-through switching states. A method to calculate the minimum value of the shoot-through duty cycle is also explained in order to assure the proper control of the injected current when the input voltage is less than peak value of the grid voltage. It is an important feature because 3L-NPC qZSI due to its possibility of boosting input voltage in a single stage would operate better than a traditional inverter, for instance in photovoltaic applications when the value of irradiance is decreased. The presented results have been obtained using PSCAD/EMTDC as a simulation tool. [ABSTRACT FROM AUTHOR]

Deployment of photovoltaic (PV) systems in nearly zero energy buildings is rapidly increasing, negatively affecting grid stability and power quality. Therefore, many utilities favour policies that limit the power injection to the grid and increase PV self-consumption. A battery energy storage system (BESS) could constitute a possible solution. However, BESS optimal scheduling to increase PV self-consumption and minimize potential purchased energy from the grid in the situation of non-supported demand by PV is a non-linear multi-variable decision-making problem. Previous works have used optimization algorithms to overcome this problem. Due to these algorithms' nature, instead of global optimum scheduling, just near-optimal results are achieved and the consistency of the results, which is essential especially for sensitivity analysis is not guaranteed. The main goal of this paper is to present an analytical approach to maximize the PV self-consumption and optimize BESS scheduling to minimize electricity costs for a two-level electricity tariff energy system. The effectiveness of the proposed analytical scheduling of the BESS-PV energy system is demonstrated through simulation on real data of a Nearly Zero Energy Building (nZEB) in the Baltic region, Estonia, as the case study. Compared with alternative optimization algorithms, the proposed approach leads to a significant reduction in the purchased energy from the grid, while maximizing PV self-consumption and also noticeably reducing computation complexity and time for reaching the global solution. • Proposing an analytical approach to determine the global optimal scheduling of BESS in nZEBs. • Maximizing PV self-consumption and minimizing the cost of purchase energy from the grid. • Reducing the complexity of computations. • Possibility to implement accurate sensitivity analysis of BESS scheduling. [ABSTRACT FROM AUTHOR]

Increasing converter power density is a problem of topical interest. This paper discusses an interleaved approach of the efficiency increase in the buck-boost stage of an inverter with unfolding circuit in terms of losses in semiconductors, output voltage ripples and power density. Main trends in the power converter development are reviewed. A losses model was designed and used for the proposed solution to find an optimal number of interleaved cells. It describes static and dynamic losses in semiconductor switches for buck and boost mode. The presented calculation results demonstrate the efficiency of the interleaved approach for photovoltaic system. 1 kW power converter prototype was designed with two parallel dc-dc cells for experimental verification of obtained theoretical results. The experimental results confirm theoretical statements. [ABSTRACT FROM AUTHOR]

The paper is devoted to the comparison of different types and different values of coils for inductive power transfer in the classical circuit. This topic is relevant with the growing demand and interest in wireless chargers and the diversity of inductance coils for wireless power transfer. The main geometric parameters affecting the coil efficiency are determined. For experimental verification the classical scheme for wireless power transfer is used based on a full-bridge inverter. Different coils at different distance between them, lateral misalignment and load resistance changed are tested. It is determined that single-layer coils have better transmit-receive efficiency than double-layer ones, especially with series-series compensation topology. The application of two-layer coils is recommended in case of high input current. The investigated samples have efficiency at the level of industrial standards. The design approach can be used for any level of power and application, including wireless charging of electric vehicle batteries. [ABSTRACT FROM AUTHOR]

A promising solution for inductive power transfer and wireless charging is presented on the basis of a single-phase three-level T-type Neutral Point Clamped GaN-based inverter with two coupled transmitting coils. The article focuses on the feasibility study of GaN transistor application in the wireless power transfer system based on the T-type inverter on the primary side. An analysis of power losses in the main components of the system is performed: semiconductors and magnetic elements. System modeling was performed using Power Electronics Simulation Software (PSIM). It is shown that the main losses of the system are static losses in the filter inductor and rectifier diodes on the secondary side, while GaN transistors can be successfully used for the wireless power transfer system. The main features of the Printed Circuit Board (PCB) design of GaN transistors are considered in advance. [ABSTRACT FROM AUTHOR]

The Baltic countries have good potential for solar photovoltaic (PV) energy generation, as on average 15 hours of sunlight is available in summer. Another potential option is to encourage the construction of nearly zero-energy buildings (NZEBs) according to the EU framework. This study focuses on solar irradiance and energy generation potential in different regions of Estonia as a case study. Techno-economic analysis of possible solutions to use differently rated domestic and commercial PV systems' feasibility and payback periods are presented. The results illustrate that all PV systems studied in the research are self-sufficient while selling excess energy to the grid with a nominal payback period. Furthermore, for short-term energy management, we developed an efficient deep learning-based forecasting algorithm. Apart from the inherent non-linear nature of solar energy data, what makes forecasting particularly challenging is to efficiently cope with the issue of data regression and random noise. The RNN-LSTM algorithm is chosen for the prediction of solar energy. This is the first comprehensive report that can encourage potential Estonian users to invest in solar PV systems and gain economic benefits. The results presented in this study cover a broader perspective and are more useful keeping in mind the real market situation of the Baltic countries. • Compared initial investment and payback period of multiple rated PV systems. • Design and development of deep learning based short-term forecasting algorithm for solar PV generation. • ROI and payback period has been calculated for different rated PV systems in different regions. • Economic impact on Estonian's national grid due to on-grid distributed PV systems. [ABSTRACT FROM AUTHOR]

This study proposed an approach to dynamic wireless charging that uses a rotating receiver coil. Our simulation study focused on the verification of a novel way of increasing the coupling coefficient and power transfer stability by following the flux of the transmitting coils. To obtain the highest possible coupling by means of the FEM analysis, we studied the optimization of the trajectory of the angular velocity of the rotating receiver. The coupling coefficient trajectories that were obtained were simulated by means of the state space model with three transmitters. Our comprehensive analysis showed that the proposed approach of wireless power transmission enabled a 40% increase in the usage of track space. [ABSTRACT FROM AUTHOR]

Power system planning in numerous electric utilities merely relies on the conventional statistical methodologies, such as ARIMA for short-term electrical load forecasting, which is incapable of determining the non-linearities induced by the non-linear seasonal data, which affect the electrical load. This research work presents a comprehensive overview of modern linear and non-linear parametric modeling techniques for short-term electrical load forecasting to ensure stable and reliable power system operations by mitigating non-linearities in electrical load data. Based on the findings of exploratory data analysis, the temporal and climatic factors are identified as the potential input features in these modeling techniques. The real-time electrical load and meteorological data of the city of Lahore in Pakistan are considered to analyze the reliability of different state-of-the-art linear and non-linear parametric methodologies. Based on performance indices, such as Root Mean Square Error (RMSE), Mean Absolute Percentage Error (MAPE) and Mean Absolute Error (MAE), the qualitative and quantitative comparisons have been conferred among these scientific rationales. The experimental results reveal that the ANN–LM with a single hidden layer performs relatively better in terms of performance indices compared to OE, ARX, ARMAX, SVM, ANN–PSO, KNN, ANN–LM with two hidden layers and bootstrap aggregation models. [ABSTRACT FROM AUTHOR]

This paper presents an inductive power transfer system on the basis of a double single-phase three-level T-type inverter and two split transmitting coils for constant current and constant voltage wireless charging of low-voltage light electric vehicle batteries with closed-loop control, considering time-delay communication constraints. An optimal control structure and a modified control strategy were chosen and implemented to the wireless power transfer system as a result of a review and analysis of existing solutions. The control system analysis and adjustment of the coefficients of the regulator using Laplace transform were performed. Our study addressed the behavior of the control system with different time delays as well as the dynamic response of the system. The detecting algorithm of a secondary coil was proposed, which ensured efficient system operation and increased the functionality, safety and usability of the device. The efficiency of energy transfer of 90% was reached at the transmitted power of 110 W, which is at the level of existing solutions considered in the article and opens the way to the commercialization of the proposed solution. Therefore, the feasibility of using a nonclassical multilevel inverter, together with split transmitting coils for wireless charging was confirmed. [ABSTRACT FROM AUTHOR]