The original publication’s Fig. 5 image lacks some of its labels. On the top right, the label for the solid black line is BCF^ while the label of the broken blue line is BCF^. The correct label for the solid black line should be BCfmin^ while the broken blue line should be BCF = 1^. Figure 5 image with the wrong label (top image) and with the correct label (bottom image) is shown here. The original publication was corrected.(Figure Presented.).

In this paper, a coupled-inductor-based LCC resonant converter with the primary-parallel-secondary-series (PPSS) configuration is proposed to achieve output-voltage sharing ability for HV generator applications. The PPSS configuration of the LCC resonant converter with the voltage multipliers is introduced to achieve high output-voltage and increase the output-power level. However, the variations of the magnetizing inductance, leakage inductance, and winding capacitance of the HV transformer and voltage multiplier impact on the output-voltage sharing performance. Subsequently, the resonant inductors in the primary side of the conventional LCC resonant converters with the PPSS configuration are coupled to achieve the output-voltage sharing without any additional circuits and control efforts. Furthermore, an analytical equivalent circuit model considering the magnetizing inductor of the HV transformer is derived to analyze the output-voltage sharing ability. Moreover, the design method for the coupled inductors considering the output-voltage sharing performance affected by the leakage inductance of the coupled inductors is presented. Finally, the output-voltage sharing performance of the proposed coupled-inductor-based LCC resonant converter with the PPSS configuration is validated by the experimental results of a 50-V input, 5-kV output 100-W prototype. The prototype experimental results show that the unbalance voltage degree decreases from 67.7% to 8.5% with the utilization of the coupled inductor.

Off-grid solar home systems (SHSs) currently constitute a major source of providing basic electricity needs in un(der)-electrified regions of the world, with around 73 million households having benefited from off-grid solar solutions by 2017. However, in and of itself, state-of-the-art SHSs can only provide electricity access with adequate power supply availability up to tier 2, and to some extent, tier 3 levels of the Multi-tier Framework (MTF) for measuring household electricity access. When considering system metrics of loss of load probability (LLP) and battery size, meeting the electricity needs of tiers 4 and 5 is untenable through SHSs alone. Alternatively, a bottom-up microgrid composed of interconnected SHSs is proposed. Such an approach can enable the so-called climb up the rural electrification ladder. The impact of the microgrid size on the system metrics like LLP and energy deficit is evaluated. Finally, it is found that the interconnected SHS-based microgrid can provide more than 40% and 30% gains in battery sizing for the same LLP level as compared to the standalone SHSs sizes for tiers 4 and 5 of the MTF, respectively, thus quantifying the definite gains of an SHS-based microgrid over standalone SHSs. This study paves the way for visualizing SHS-based rural DC microgrids that can not only enable electricity access to the higher tiers of the MTF with lower battery storage needs but also make use of existing SHS infrastructure, thus enabling a technologically easy climb up the rural electrification ladder.

With almost 1.1 billion people lacking access to electricity, solar-based off-grid products like Solar Home Systems (SHS) have become a promising solution to provide basic electricity needs in un(der)-electrified regions. Therefore, optimal system sizing is a vital task as both oversizing and undersizing a system can be detrimental to system cost and power availability, respectively. This paper presents an optimal SHS sizing methodology that minimizes the loss of load probability (LLP), excess energy dump, and battery size while maximizing the battery lifetime. A genetic algorithm-based multi-objective optimization approach is utilized to evaluate the optimal SHS sizes. The potential for SHS to cater to every tier of the Multi-tier framework (MTF) for measuring household electricity access is examined. The optimal system sizes for standalone SHS are found for different LLP thresholds. Results show that beyond tier 2, the present day SHS sizing needs to be expanded significantly to meet the load demand. Additionally, it is deemed untenable to meet the electricity needs of the higher tiers of MTF purely through standalone SHS without compromising one or more of the system metrics. A way forward is proposed to take the SHS concept all the way up the energy ladder such that load demand can also be satisfied at tier 4 and 5 levels.

This paper investigates the diode reverse recovery process and reduction of a half-wave (HW) series Cockcroft-Walton (CW) voltage multiplier based on the steady-state analysis for high-frequency high-voltage (HV) generator applications. The diode reverse recovery process for a multistage voltage multiplier is analyzed after the introduction of steady-state operation. The diode reverse recovery problem is the bottleneck to further increase the circuit operation switching frequency for achieving high power density and short HV pulse rise and decay times. The diode reverse recovery problem is mainly caused by the diodes in the first-stage voltage multiplier. It is suggested that the most effective and economic way to alleviate the diode reverse recovery problem is by employing diodes without reverse recovery such as silicon carbide Schottky diodes in the first stage only. The silicon carbide Schottky diode without reverse recovery needs to be used only in the first stage of the voltage multiplier to effectively mitigate the reverse recovery problems at high frequency. The 300 kHz switching frequency three-stage voltage multiplier circuit hardware prototype experimental results finally validate the analysis. A technology demonstrator of a 300 kHz 8 kW 160 kV HV generator based on the proposed hybrid silicon carbide and silicon diode solution for the HW series CW voltage multiplier is provided finally.

In this paper, a unified equivalent circuit model which can simplify the design and analysis of a family of high-voltage (HV) generation architectures based on the series-parallel (LCC) resonant converter is proposed. First, four HV generation architectures are reviewed in terms of the modularization level of HV transformers and rectifiers. Next, the steady-state, unified equivalent resistor and capacitor (RC) model that can be easily embedded into the resonant tank to replace the complex HV transformers and rectifiers is derived. The generic model can be applied to the HV generators with different architectures, different voltage multiplier topologies, stage, and polarities number. Further analysis of the power factor of the resonant tank, the voltage gain of HV generators, and electrical stresses of power components is achieved with the derived equivalent circuit model. The analysis reveals the inherent circuit properties among HV generators with different configurations. Subsequently, a comprehensive design methodology considering the power factor, conduction angle, and quality factor is presented, which leads to low electrical stresses on the components and high efficiency. Furthermore, the parameter selection constraint based on the power factor, conduction angle, and quality factor is derived, which can ensure the effective design outputs. Finally, the proposed unified equivalent model and comprehensive design methodology are validated by the experimental results of a 250 V input, 20 kV output 500 W HV generator hardware prototype with distributed transformers and voltage multipliers.

The past few years have seen strong growth of solar-based off-grid energy solutions such as Solar Home Systems (SHS) as a means to ameliorate the grave problem of energy poverty. Battery storage is an essential component of SHS. An accurate battery model can play a vital role in SHS design. Knowing the dynamic behaviour of the battery is important for the battery sizing and estimating the battery behaviour for the chosen application at the system design stage. In this paper, an accurate cell level dynamic battery model based on the electrical equivalent circuit is constructed for two battery technologies: the valve regulated lead-acid (VRLA) battery and the LiFePO₄ (LFP) battery. Series of experiments were performed to obtain the relevant model parameters. This model is built for low C-rate applications (lower than 0.5 C-rate) as expected in SHS. The model considers the non-linear relation between the state of charge (SOC) and open circuit voltage (V_OC) for both technologies. Additionally, the equivalent electrical circuit model for the VRLA battery was improved by including a 2nd order RC pair. The simulated model differs from the experimentally obtained result by less than 2%. This cell level battery model can be potentially scaled to battery pack level with flexible capacity, making the dynamic battery model a useful tool in SHS design.

Solar Home Systems (SHS) have recently gained prominence as the most promising solution for increasing energy access in remote, off-grid communities. However, the higher than standard testing conditions (STC) temperatures have a significant impact on the SHS components like PhotoVoltaic (PV) module and battery. A modeling methodology is described in this study for quantifying the temperature impact on SHS. For a particular location with high irradiation and temperatures and a given load profile, an SHS model was simulated, and the temperature-impact was analyzed on the performance and lifetime of the SHS components. Different PV module temperature estimation models were applied, and the corresponding dynamic PV outputs were compared. The nominal operating cell temperature (NOCT) model was found inadequate for estimating PV module temperatures under high irradiance conditions. The PV yield was found to be affected by almost 10% due to thermally induced losses. When different levels of temperature variations were considered, the battery lifetime was seen to be up to 33% less than that at 25 ° C. The modeling methodology presented in this paper can be used to include the thermal losses in SHS for rural electrification, which can further help accordingly in system sizing.

The rapid increase in the adoption of Solar Home Systems (SHS) in recent times hopes to ameliorate the global problem of energy poverty. The battery is a vital but usually the most expensive part of an SHS; owing to the least lifetime among other SHS components, it is also the first to fail. Estimating battery lifetime is a critical task for SHS design. However, it is also a complex task due to the reliance on experimental data or modelling cell level electrochemical phenomena for specific battery technologies and application use-case. Another challenge is that the existing electrochemical models are not application-specific to Solar Home Systems. This paper presents a practical, non-empirical battery lifetime estimation methodology specific to the application and the available candidate battery choices. An application-specific SHS simulation is carried out, and the battery activity is analyzed. A practical dynamic battery lifetime estimation method is introduced, which captures the fading capacity of the battery dynamically through every micro-cycle. This method was compared with an overall non-empirical battery lifetime estimation method, and the dynamic lifetime estimation method was found to be more conservative but practical. Cyclic ageing of the battery was thus quantified and the relative lifetimes of 4 battery technologies are compared, viz. Lead-acid gel, Flooded lead-acid, Nickel-Cadmium (NiCd), and Lithium Iron Phosphate (LiFePO₄) battery. For the same SHS use-case, State-of-Health (SOH) estimations from an empirical model for LiFePO₄ is compared with those obtained from the described methodology, and the results are found to be within 2.8%. The relevance of this work in an SHS application is demonstrated through a delicate balance between battery sizing and lifetime. Based on the intended application and battery manufacturer's data, the practical methodology described in this paper can potentially help SHS designers in estimating battery lifetimes and therefore making optimal SHS design choices.

A novel high frequency high voltage (HV) generator circuit with air-core transformer is proposed in this paper to achieve high power density packaging structure and compact size advantages. Planar multi-layer printed circuit board(PCB) winding and litz wire wound winding structure are investigated for air-core HV transformer. The electrical design of air-core HV transformer with HV multiplier circuit based on 1.2kV SiC Schottky diode are introduced. A with 450 kHz switching frequency HV generator prototype with 310W output power and 1kV output voltage is built in lab. The litz wire air-core HV transformer prototype is built to compare the efficiency, thermal performance and size with planar air-core HV transformer. The planar PCB air-core transformer based on HV generator can achieve 80.5% efficiency and 1.09kW/L power density. The litz wire wounded transformer based HV generator provide 89.0% efficiency and around 0.53kW/L power density. The design with planar PCB air-core transformer enable high voltage generation circuit system compact planar packaging. The design with litz wire air-core HV transformer behaves higher efficiency and thermal performance with low high frequency AC winding loss.

This paper introduces the high voltage generation architectures derivation methodology and comparative evaluation of high voltage power generation architectures based on the key performance items such as efficiency, power density, high voltage pulse speed, high voltage pulse ripple, HV insulation and scalability for different output voltage and output power ratings. Based on comparative evaluation of high voltage generation architectures with single inverter configuration, high voltage generation architecture with single inverter, multiple high voltage transformers and multiple stage voltage multiplication circuits overall outperforms other high voltage generation architectures based on architecture performance comparative analysis and evaluation at 100kV/10kW output rating as case study.

Power packaging technology plays an important role to achieve high performance for high voltage (HV) generator. The HV generator packaging techniques are systematically classified according to different component level packaging and system assembly technology. Both component level packaging and system assembly technology are included in the review and their advantages and disadvantages are discussed. Planar air-core multi-layer printed circuit board (PCB) winding transformer is introduced for HV generator with planar structure. A 450kHz switching frequency HV generator prototype with 310W output power and 1kV output voltage is built in lab. The high frequency HV generator prototype can achieve 1.09kW/L power density at rated 1kV output voltage and 310W full power. The litz wire air-core HV transformer prototype is built to compare the efficiency, thermal performance and size with planar air-core HV transformer. The planar PCB air-core transformer enables high voltage generation circuit system compact planar packaging. The litz wire air-core HV transformer behaves higher efficiency and thermal performance with low high frequency AC winding loss.

This paper introduces the unified equivalent circuit model for modular high voltage(HV) power generation architectures. The HV generation architectures are introduced considering the modularity of key HV components such as transformers or rectifier circuits firstly. An equivalent resister and capacitor circuit network is adopted to model the HV transformer and multi-stage voltage multiplier circuit for HV generation architectures to simplifies the analysis, design and optimization for HV generation architectures. The expressions of equivalent resister and capacitor network in modular HV generation architectures are deduced. Based on the proposed equivalent circuit model, a 400kHz switching frequency 500W 20kV output HV generator prototype based on modular HV architecture is built to validate the equivalent circuit model. The experimental results of HV generator prototype are given finally.

The state-of-the-art architectures of high frequency high voltage (HFHV) generators are surveyed and classified according to their applications to achieve compact size, high energy efficiency and high power density. HFHV generation architectures and derivation methodology are concluded systematically based on the level of distributedness of the main sub-components. The characteristics for each HFHV generation architecture are described in details. Comparative qualitative evaluation of HV generation architectures are performed considering different output voltage and output power ratings in various industrial applications. The HV generation architecture with distributed HV transformer and distributed multiplier overall outperforms compared with other HV generation architectures. The recommendations for the HV generation architecture selections would be provided to identify the promising architectures for different output voltage and power applications with optimal performance finally.

Increased proliferation of the renewable energy sources (RES) brings more power electronic devices to the power distribution. Modularity on the converter level is one of the key concepts enabling flexibility, scalability and high availability of the new solutions for the distribution networks(e.g. for low voltage DC). To understand the trends and performance trade-offs it is important to describe and classify different aspects of the modularity concept. This paper presents a comprehensive literature review, classification of modular power electronics and outlook on future research. Different aspects of modularity are identified and described from the perspective of a converter designer, manufacturer and a user. It is illustrated that depending on a combination of different aspects, different modules are selected resulting in different technical challenges. These aspect can be considered as a mapping tool for the functional description and physical realization of the power converter.

Cockcroft-Walton voltage multiplier circuit is widely used for high voltage generation circuit. The diode reverse recovery effect of Cockcroft-Walton voltage multiplier circuit is investigated by analysis and circuit simulation. According to the analysis and circuit simulation study, it can be concluded that the multiplier diode reverse recovery problem is mainly caused by the diodes in the first stage voltage multiplier. The most effective and economic way to alleviate the diode reverse recovery problem is employing diodes with good reverse recovery performance such as silicon carbide Schottky diodes only in the first stage for good system performance. The experimental results of 3 stages Cockcroft-Walton voltage multiplier circuit hardware prototype operating at 300kHz switching frequency validate the concept based on analysis and simulation study. The silicon carbide diode without reverse recovery needs to be used only in the first stage of voltage multiplier circuit to effectively mitigate the reverse recovery problems in high frequency operations with good circuit performance.