Power Topology Research Articles

Calculating ‘climate migrants’: An emerging topology of power

On what basis can it be said that climate change contributes to human migration? What are we to make of new statistical models used to construct the relationship between these two epochal phenomena? This article proposes Collier’s conception of topology to characterize the novel politics of gravity modelling, a technique increasingly used to calculate numeric estimates of ‘climate migrants’. These models do not simply signify a revival or repetition of political sovereignty, nor an affirmation of biopower, but a novel recalibration of power arising in response to the climate crisis. This recalibration signals the early stages of a new topology of power organized around intuitive calculation. To make this claim, the article draws on recent discussions in geography on the relationship between calculation, number and the political to first situate the models within contemporary critical scholarship on climate change and migration. It then examines the models’ statistical logics, in particular how intuition, inference and the incalculable shape three facets of this emerging topology: the correlation of Earth science data with population-level economic data; the calculation of mobile populations; and the unique spatiality at stake in gravity modelling.

Series partial power converter with half bridge LLC series resonant converter for PV application

Abstract This study proposes a series partial power converter with a half-bridge LLC series resonant converter for photovoltaic (PV) applications. The main advantage of the implementation of a partial power converter with LLC series resonant converter is zero voltage switching (ZVS) operation of primary side enables the converter to work at a higher switching frequency. The partial power topology used in the proposed converter enables low power rating switches in the primary, which in other terms reduces the primary current. The proposed converter achieves excellent efficiency due to its ZVS and partial power operating capabilities. The valuation of the proposed converter is done in MATLAB Simulink with a 300 W PV module, which is made to operate in varying irradiance and module temperature of 25 °C. The operational waveforms and the power outputs obtained when the proposed converter is implemented by using perturbation and observation (P&O) maximum power point tracking (MPPT) control algorithm are discussed in this paper.

Demystifying the Chinese local state: Planning and contesting urban growth at Hexi New Town, Nanjing

Taking note of the limitations of previously dominant political economy perspectives on China’s urban transformation, and inspired by recent works calling for “beyond-growth” and “micro-level” studies of the Chinese state, as well as ethnographic approaches to the state, this paper aims to explore the often-untold everyday politics of decision-making processes in China’s state-led urban development. Using an urban design project at Hexi New Town in Nanjing, China, as an empirical lens, the article makes three main contributions. Firstly, it reveals how the Chinese local state is constitutive of and lived through intense negotiations and contestations over urban visions, subjectivities, and rules of practices in everyday life. Secondly, building upon existing ethnographic approaches to the state, which focus primarily on state-society dynamics, this paper develops a framework to re-conceptualize the power topology within the Chinese local state as a field of relational modalities (ruling power relations (re)enacted in everyday practices) and relational embeddedness (situated positionalities and subjectivities of state actors). Thirdly, it further shows how the power modalities (the interplay of political-economy power vs technical-power, territorial power vs trans-territorial power) of the Chinese local state are constantly reworked, sometimes re-enacted, sometimes challenged, through both formal and tacit rules in the state’s everyday life. As such, the article provides a new set of entry points to open the black-box of the Chinese local state and to explore the relational nature and an ethnographic perspective of the local state and urban politics in China and beyond.

Feasibility Study of Three-Phase Modular Converter for Dual-Purpose Application in DC and AC Microgrids

The modern concept of a universal converter is intended as a power converter suitable for application in both dc or ac grids using the same external connectors. This novel family was recently proposed to allow an easier integration of renewable energy sources and energy storage systems, interfacing with dc/ac grids and/or loads with a minimum redundancy of power switches and passive elements. This kind of solution and applications are expected to be a reality in the nearest decade, as ac and dc low voltage distribution networks will coexist. Nevertheless, the initial solutions proposed as universal converter were focused on ac single-phase power conversion systems. In this sense, this article proposes and describes a new member of the universal converter family suitable for dc to dc and dc to ac power conversion (both in three-phase three-wire and in three-phase four-wire). The proposed power topology is derived as a modular extension from the single buck-boost bidirectional cell. Its main operation modes (buck and boost) are discussed, and a pulse-width-modulation technique is developed to generate the corresponding switching patterns. The proposed solution is successfully validated in open-loop mode both in simulation and experimentally with a laboratory prototype. The measured efficiency of the power converter was above 97% in the dc to ac mode and around 99% in the dc to dc mode.

Wind Power Determination for Maximum Power Point Tracking in Lab-scale Multi-MW Wind Energy Systems

The low voltage ride through (LVRT) grid code requirements are pushing the new era of multi MW wind energy conversion systems (WECS) to full power topologies. Lab scale emulation of such multi MW systems usually substitutes the wind energy conversion by a torque producing emulator (e.g. DC machine). Nevertheless, the complete study of the wind energy system is more insightful and allows a better analysis of the WECS. This work focuses on the design of the blades and the wind power calculation for lab scale emulation of multi MW wind energy systems. Theoretical analysis for the design of the lab scale system is presented and experimental results show the wind power characteristic curves for maximum power point tracking of variable speed generators.

Power factor correction using an ESP32 embedded in an interleaved boost converter

This paper addresses a power factor correction (PFC) approach, employing an ESP32 microcontroller and utilizing an interleaved boost converter as the primary power topology. The issue of low power factor in systems is a critical concern, as it results in increased energy consumption, reduced efficiency, and potential power quality issues. Such problems can be observed in various applications, including industrial machinery, renewable energy systems, and consumer electronics, all of which stand to benefit from an effective power factor correction solution. The proposed system offers several unique advantages and characteristics that set it apart from traditional techniques. First and foremost, the utilization of an ESP32 microcontroller enables increased computational capabilities and flexibility, allowing for advanced control algorithms and real-time monitoring of the system's performance. Secondly, the interleaved boost converter topology enhances efficiency by distributing power among multiple converters, thereby reducing the stress on individual components and minimizing losses. The key aspect of the system's design is the autonomous control of the two converters within the interleaved boost converter, achieved through the implementation of a sliding mode (SM) control strategy that mimics resistive behavior. To enhance the system's stability and performance, a dual feedback loop architecture is incorporated: a swift internal current loop and a slower external loop responsible for regulating output voltage. Promising simulation results validate the effectiveness and robustness of the presented PFC approach. This solution not only addresses the challenges associated with low power factors but also demonstrates the potential for further advancements in the field of power electronics and control systems.

Energy management strategy of fuel cell vehicles with hybrid energy sources: A novel framework via deep reinforcement learning and transfer learning

This study presents a multicriteria energy management strategy (EMS) for hybrid energy sources (HES) composed of fuel cell/battery/supercapacitor hybrid power system for logistics trucks, which uses a model-free deep reinforcement learning (DRL) algorithm, namely deterministic strategy gradient (DDPG), to improve the portability and reusability of the system. The proposed EMS is capable of reducing the hydrogen consumption cost, the degradation of fuel cell and battery, as well as sustaining the state of charge (SOC) of battery and supercapacitor. The results of the study found that the total cost was reduced by 9.5% compared to equivalence consumption minimization strategy (ECMS) based EMS under the WLTP driving cycle. A novel deep transfer learning (DTL) based framework for DRL-based EMS is further elaborated and evaluated by four metrics. Two DTL techniques including policy transfer and experience transfer are leveraged to transfer the EMS from original logistic truck to a B-class passenger car powered by fuel cell and battery. The results indicate that the proposed DTL framework is an appropriate approach to transfer EMSs from different vehicle model with various power topology. The convergence speed of DTL-based EMS is apparently accelerated over 50% in comparison to DRL-based EMS. Besides, the fuel optimality, robustness, convergence, and generalization stability for DTL-based EMS is also improved.

A Novel Current Harmonic Suppression Method for HSPMSG Based on the Hybrid Rectifier

This paper presents a novel current harmonic suppression scheme for the high-speed permanent magnet synchronous generator (HSPMSG). Aiming to effectively reduce current harmonics for the HSPMSG, this paper focuses on two areas: improving the rectifier power topology and developing a current loop controller. Firstly, a hybrid rectifier based on Silicon-Carbide/Silicon (SiC/Si) is designed to equivalently increase the switching frequency of the HSPMSG to address the problem of low carrier frequency ratio. In addition, an improved space-vector-modulation (ISVM) strategy based on the hybrid rectifier is proposed. However, the harmonic distortion caused by rectifier nonlinearity will deteriorate as the switching frequency is increased. For further suppressing harmonic disturbances caused by rectifier nonlinearity, a resonant-super-twisting (R-STW) controller is designed by combining the resonant controller and the super-twisting (STW) controller in this paper. The stability of the STW is demonstrated by Lyapunov stability theory and the resonant controller is discretized. Finally, a number of simulations and experiments based on a high-speed permanent magnet synchronous generator are carried out to verify the effectiveness of the control method proposed in this paper.

Analysis of Induction Based Wireless Power Transfer Scheme

Abstract: Wireless power transfer scheme has become quite popular in recent times and used in various applications including consumer electronics, and electrical vehicle chargers. Although the power transfer scheme based on magnetic induction is knowledge, the relationship between efficiency of power transfer scheme with the ferrite core cross sectional area is not well understood. Surfaces with symmetrical ferrite core cross section area, will have good magnetic coupling while unsymmetrical cross-sectional surfaces with smaller overlap of magnetic flux, will suffer from high leakage inductance and excessive losses. Since majority of the wireless charging applications use non-uniform magnetic surfaces, the efficiency of real power transfer across primary and secondary windings tends to be lower and will require additional compensating circuitry or complex control algorithm. Unless a thorough understanding of leakage inductance is performed, wireless power topology will suffer from excessive resonant power circulation and output regulation will become unstable. Compensating circuit added at the secondary output can decrease overall reliability and increase BOM (Bill of material) cost. In this paper, wireless power transfer scheme is reviewed, and a theoretical model is provided. Analysis will be presented for various leakage inductances including the impact of operating frequency and line/load conditions

Probabilistic machine learning aided transformer lifetime prediction framework for wind energy systems

Accurate lifetime prediction of transformers operated in power grids with renewable energy systems is a challenging task because it requires a large amount of data that is not usually available. In the case of wind energy, this complexity is intensified with the stochastic ageing process influenced by the intermittency of the wind and weather conditions. Existing models make use of detailed power topologies to evaluate transformer stress profiles and associated degradation. However, this modelling approach requires high computational resources and long simulation times. In this context, this paper presents a lifetime prediction model for transformers designed through probabilistic machine learning, thermal modelling and ageing analysis. The proposed model is compared with synthetic wind-to-power detailed simulations of a wind farm and validated with real data. The lifetime prediction is evaluated with different mission profile estimates and results show that the accuracy of the probabilistic machine learning model is very high, with an error of 0.47% for the median value and 80% prediction interval errors within 6%–7% with respect to observations. Moreover, there is a substantial reduction in the simulation time and memory requirements when compared to the synthetic model. A detailed sensitivity analysis demonstrates the influence on transformer ageing of different overloading strategies, thermal constants and the geographic location of the wind farm.

Design Consideration of ZVS Single-Ended Parallel Resonant DC-DC Converter, Based on Application of Optimization Techniques

The paper presents the design of a single-ended transistor zero-voltage switch (ZVS) parallel resonant DC-DC converter. Due to the use of a resonant inverter in the structure of the DC-DC converter, it is characterized by high efficiency and improved performance. On the other hand, due to the specifics of the power circuit operation, in the work, it is proposed to find the values of some of the elements of the circuit of the electronic converter to be carried out based on the application of optimization. To solve this task, various tools available in Matlab/Simulink have been applied, as well as author’s programs specially developed for the purpose. The use of a hybrid method for the design of power electronic converters, which combines analytical and optimization approaches, is justified in cases where there is no adequate design procedure. With the increase in the complexity of the power topologies and their possible modes of operation, difficulties arise related to their design such as: assumptions and limitations in conducting the analysis and the corresponding methodologies based on this analysis; high order of the differential equations composing the mathematical models; need for highly qualified specialists in the field of design. The proposed approach does not negate the classical design methods based only on analytical ratios determined by analysis of power circuits, but complements and develops them with innovative ones based on the application of computational mathematics and information and communication technologies.

A Marx generator based on thyristors triggered in a shock ionization wave mode

Recently, a new trigger mode of thyristor which is called shock ionization wave mode is researched. Compared with the conventional trigger mode, this trigger mode can turn on the thyristor rather fast. In this mode, a trigger voltage with a high amplitude and fast rising speed is applied at both ends of the thyristor. Many single-tube conduction experiments are reported while the conduction threshold of shock ionization wave mode has not been investigated. Besides, the application of this trigger mode in some pulse power topology remains blank which is useful for this mode. In this paper, to explore the impact ionization wave mode conduction threshold of commercial thyristor, fast front high voltage nanosecond pulses are generated by avalanche tube Marx circuit. Pulse signals of different amplitudes are realized through the voltage division resistor. The impact ionization wave mode trigger threshold for commercial thyristors is about 2500 V in amplitude and 250 V/ns in voltage rising speed and the higher the rated parameter of the thyristor, the higher the threshold. To broaden the application of this mode, a novel Marx generator based on thyristors is proposed. A four-stage Marx generator is constructed and the amplitude of the output voltage can reach 1869 V.

Research on the development and intelligent application of power environmental protection platform based on big data

Abstract In order to improve the practical effect of the power environmental protection platform, this paper combines the big data technology to develop and design the power environmental protection platform. In this paper, a power factor correction (PFC) and resonant half-bridge joint controller is used to combine the traditional two-level topology into one-level topology. Moreover, this paper adopts a fixed frequency half-bridge LLC resonant converter with a simple control circuit to obtain a stable resonant half-bridge controller with a fixed output voltage. The choice of this overall power topology architecture can not only meet the design requirements, save costs and simplify the control of the circuit, but also improve the efficiency of the whole machine and the performance of the power environmental protection platform. The experimental research shows that the power environmental protection platform based on big data proposed in this paper can effectively improve the effectiveness of power environmental protection strategies.

Open-Circuit Fault-Tolerant Vector Control for Five-Phase SPMSM Based on Five-Phase Six-Leg Inverter

Five-phase permanent-magnet synchronous motor (PMSM) has the ability of fault-tolerant operation, which is beneficial for high reliability occasions. A fault-tolerant current vector control strategy based on five-phase six-leg inverter is proposed for open-circuit fault in this article. It deals with single-, double-, and triple-phase fault conditions. First, the overall control scheme is established based on the mathematical model of five-phase surface-mounted PMSM. To release more control degrees of freedom, the constraint for the sum of fault-tolerant phase currents is removed, and the control variates method is used to calculate the optimal fault-tolerant currents. Furthermore, to achieve the current tracking, the corresponding reduced-order current transformation matrices are derived, and the corresponding main power topology, the five-phase six-leg voltage source inverter (VSI), is established. The unbalanced operation of the topology is investigated, the equivalence to the full-bridge VSI is proved, and the voltage utilization and voltage unbalance of five phase half-bridge, full-bridge, and six-leg inverter are compared. Then, the corresponding carrier-based PWM control strategy based on zero-sequence injection has been proposed, which is equivalent with the three-dimensional space vector PWM algorithm and is computationally efficient. The experimental results confirm the effectiveness of the proposed fault-tolerant control strategy.

A Comprehensive Review of Power Converters for E-Mobility

The penetration of electric vehicles is becoming more and more widespread and recently electric buses and trains are fetching the attention of researchers and developers. In this review, we examine the charging systems applied to the fast charging of electric vehicles and buses as well as the charging strategies, mainly applied to electric buses. We also briefly delve into power topologies for a more electrified railway system where we discuss their different supply systems as well as their motor drive systems. Problems and charge challenges for electric buses and trains are discussed too.

Analysis and Design of Resonant DC/AC Converters with Energy Dosing for Induction Heating

This article presents an analysis and methodology for designing resonant inverters with energy dosing for induction heating applications. These power topologies are characterized by the fact that the power consumption of the DC power source does not depend on the magnitude and changes of the load but is a function of the operating frequency, the value of the resonant capacitor and the DC supply voltage. Based on a description of the electromagnetic processes in the power circuit, analytical dependencies have been determined that describe the behavior of the studied power electronic devices. The expressions for the current of the AC circuit in the various stages of the converter’s operation are obtained, and on this basis an engineering methodology for design and prototyping is presented. The proposed methodology is verified through two specific numerical examples, simulation and experimental studies. In this way, the possibilities of these power electronic devices for self-adaptation to the needs and changes of the load, which is very important in the implementation of induction technologies, are demonstrated. Furthermore, the creation and testing of engineering methodologies for the design of power electronic devices are very useful for improving power electronics education.

The sequential power flow in complex plane for solving the VSC-MTDC hybrid AC/DC transmission grids

This paper presents new methodologies and modeling aimed at studying interwoven AC and DC subsystems of a power system in the complex plane. It is well known that the development of any former power flow application in real domain addressed to embedding FACTS devices is preceded by an arduous algebra task. To overcome this difficulty, a novel power flow solution method is proposed in this work. Thanks to the Wirtinger calculus, a Newton–Raphson method based on Taylor series expansions of nonlinear functions of complex variables and their complex conjugates is developed. Thus, the voltage-source-converter multi-terminal direct current is formulated in complex plane without any loss of accurateness and is termed as VSC-MTDC. Its performance is assessed through IEEE-test systems interconnected across a DC network prone to several scenarios, e.g., topology, loading magnitude and interchanging of active power.

Topologies of power in China's grid-style social management during the COVID-19 pandemic.

This article analyses the organization of Chinese grassroots social management during the COVID-19 pandemic. Drawing on a range of local cases researched through policy documents, media coverage and interviews, we scrutinize the appropriation of emergency measures and the utilization of grid-style social management since the outbreak of COVID-19. Grid-style social management - a new grassroots administrative division aiming to mobilize neighbourhood control and services - is a core element in China's pursuit of economic growth without sacrificing political stability. Conceptualizing grids as confined spaces of power, we show how the Chinese party-state is able to flexibly redeploy diverse forms of power depending on the particular purpose of social management. During non-crisis times, grid-style social management primarily uses security power, casting a net over the population that remains open for population elements to contribute their share to the national economy. Once a crisis has been called, sovereign power swiftly closes the net to prevent further circulation while disciplinary power works towards a speedy return to a pre-crisis routine.

Self-Balanced Clamp-Double Submodule for Modular Multilevel Converter

The modular multilevel converter (MMC) has been widely used in the field of high-voltage direct current (HVDC) transmission and motor drivers due to its many advantages. As voltage sensors and sorting algorithm are often used to depress the voltage fluctuation of submodules (SMs), it suffers from the algorithm complexity and hardware cost, especially for a large number of output levels. In this article, a new clamp-double-SM (CDSM) composed of two capacitors and five transistors is proposed. The symmetrical operation of the two capacitors enables the CDSM to output three levels and their voltages are self-balanced. Moreover, the capacitor voltages among different SMs of a CDSM-based MMC are also self-balanced by adding two auxiliary balance branches between adjacent CDSMs. It means that the new MMC can operate normally without using complex balancing algorithms based on capacitor voltage sorting. Compared with existing self-balanced MMCs, the new MMC uses fewer components in both the main power topology and auxiliary balancing circuits. In addition to topology, modulation, parameter design, and power loss are analyzed in detail. Finally, the feasibility of the CDSM-based MMC is verified by simulation and experimental results.

Nonisolated DC–DC Power Converter Synthesis Using Low-Entropy Equations

There is a growing demand for novel nonisolated dc–dc power converters with the deployment of dc power distribution systems integrating renewable sources and energy storing elements. The load and source of these applications have different input and output voltage levels, and it is vital to avoid operating the interfacing power converters at extreme duty ratios. Therefore, engineers and researchers explore the power converter synthesizing techniques since the mid-1970s, fulfilling the above requirement besides the nonpulsating input and output current. Among them, the analytical synthesis method has gained popularity, although it gives rise to high-entropy equations. This article shows a simple yet powerful topology synthesis method based on the low-entropy equations that reveal the connection between the energy storing elements and switches. To this end, a set of design rules have been introduced in this article to realize the voltage-second balance equations obtained by decomposing the voltage gain polynomial using design-oriented analysis. Moreover, different decomposition levels of the gain polynomial have been discussed to embed inductors at either input or output or both ports. Furthermore, the synthesis of multitopology converters using low-entropy equations has been demonstrated. The applicability of the proposed method is validated using motivational examples and using experimental results of the selected converters.