A step-by-step modelling approach for SiC half-bridge modules considering temperature characteristics

In this paper, a detailed step-by-step modellingapproach is proposed for Silicon Carbide (SiC) MOSFET half-bridge power modules. The drain-to-source current, anti-paralleldiode and parasitic capacitors are accurately modelled consider-ing temperature dependency. A step-by-step parameter extractionmethod based on datasheet is introduced. A SPICE model is builtbased on the proposed modelling approach for a commercialpower module. The model is verified by comparing experimentand PSpice simulation results of the same double pulse tester(DPT), which proves the effectiveness of the modelling approachfor analysing switching losses and converter design. The proposedmodelling approach can help the converter designers quickly andaccurately develop their own models for SiC MOSFET powermodules

Power Electronic Converters for Microgrids

Power electronic converters are indispensable building blocks of microgrids. They are the enabling technology for many applications of microgrids, e.g., renewable energy integration, transportation electrification, energy storage, and power supplies for computing. In this chapter, the requirements, functions, and operation of power electronic converters are introduced. Then, different topologies of the converters used in microgrids are discussed, including DC/DC converters, single-phase DC/AC converters, three-phase three-wire, and four-wire DC/AC converters. The remaining parts of this chapter focus on how to optimally design and control these converters with the emerging wide-bandgap semiconductors. Correlated tradeoffs of converter efficiency, power density, and cost are analyzed using Artificial Neural Networks to find the optimal design of the converters

Unlocking the flexibility of combined heat and power for frequency response by coordinative control with batteries

Owners of combined heat and power (CHP), e.g., industrial manufacturers, are motivated to provide frequency response to power grids due to clear financial benefits. Yet, the slow response speed of CHP limits its capability in providing such services. Moreover, frequent adjustments would cause a faster lifetime reduction of CHP and rapid pressure fluctuation in the gas network. To further unlock the flexibility of CHP, this paper integrates a battery unit with CHP via a power electronic interface. A filter-based coordinative controller is designed for smoothing short-term fluctuations in CHP outputs. Based on the filter parameters and frequency response requirements, the minimum required capacity of the battery is identified. The results show that the proposed system enhances the capability of CHP for frequency response and mitigates the associated adverse effects on the gas network. The required capacity of the battery is economically feasible considering the benefit it brings to the CHP

A four-leg buck inverter for three-phase four-wire systems with the function of reducing DC-bus ripples

Three-phase four-wire inverters are usually used to feed unbalanced three-phase loads with neutral currents. The unbalanced three-phase loads also bring to second-order ripples in the DC bus, which should be mitigated by bulky DC-bus capacitors to improve the system performance. In this case, the DC capacitance is designed for the second-order ripple frequency instead of the switching frequency, so it can not be reduced even when SiC MOSFETs are adopted to achieve high switching frequency. Although various topologies of three-phase four-wire inverters has been proposed to provide the path for neutral currents, they cannot handle the second-order ripples. Also, some active power decoupling solutions can be adopted, but they require additional active swithes and components, which increases the cost of the system. In this paper, a four-leg buck inverter is proposed, which consists of four DC-DC buck converters. Each buck converter is independently controlled. This topology can not only provide neutral currents, but also reduce the second-order ripples in the DC bus with active power decoupling control. The proposed topology doesn't require any additional active switches comparing to the conventional topologies with neutral legs. The effectiveness of proposed topology is verified by the simulation in MATLAB/Simulink

State-of-the-art analysis and perspectives for peer-to-peer energy trading

As a promising solution to address the “energy trilemma” confronting human society, peer-to-peer (P2P) energy trading has emerged and rapidly developed in recent years. When carrying out P2P energy trading, customers with distributed energy resources (DERs) are able to directly trade and share energy with each other. This paper summarizes and analyzes the global development of P2P energy trading based on a comprehensive review of related academic papers, research projects, and industrial practice. Key aspects in P2P energy trading are identified and discussed, including market design, trading platforms, physical infrastructure and information and communication technology (ICT) infrastructure, social science perspectives, and policy. For each key aspect, existing research and practice are critically reviewed and insights for future development are presented. Comprehensive concluding remarks are provided at the end, summarizing the major findings and perspectives of this paper. P2P energy trading is a growing field with great potential and opportunities for both academia and industry across the world

A SiC-based neutral leg for the three-phase four-wire inverter

SiC-based inverters can operate at high switching frequency with high efficiency, which can reduce the size of passive components and heat sinks to achieve high power density. However, in three-phase four-wire inverters supplying unblanced loads, the second-order ripples in the DC bus need to be mitigated by large DC capacitance, which increases the size of the converter. The conventional neutral leg is widely used in three-phase four-wire inverters to provide neutral currents for the unbalanced loads. In this paper, an improved neutral leg is proposed, which can provide neutral currents and reduce the second-order ripples in the DC bus simultaneously. The DC bus ripples can be reduced without adding any hardware components. Furthermore, the proposed neutral leg can save 50% DC capacitance comparing to the conventional neutral leg. The proposed neutral leg was built with SiC MOSFETs and tested with a three-phase four-wire inverter in the laboratory. The experimental results verified the effectiveness of the proposed neutral leg

Dual-buck arbitrary voltage divider with one output having reduced ripples

In this paper, a dual-buck voltage divider is further studied to provide two arbitrary, instead of balanced, voltage outputs. The two voltage outputs can be the same or different and are robust against parameter drift. The low-frequency ripples in one output are significantly reduced by actively diverting low-frequency ripple currents away from the corresponding output. Note that these are achieved by designing an advanced controller, without changing the topology. The controller consists of a PI controller to split the voltage, a repetitive controller and a resonant controller to deal with the low-frequency ripples at different frequencies. Experimental results are presented to validate the effectiveness of the proposed strategy

Reduction of DC-link ripples for SiC-based three-phase four-wire inverters with unbalanced loads

Three-phase inverters are widely used in the smart grid to integrate renewable energy resources. When the inverters are used to feed the unbalanced three-phase loads, the threephase four-wire inverters are usually required to provide the current path for neutral currents. However, unbalanced loads will cause undesirable second-order ripples on DC bus. Conventional three-phase four-wire inverters with neutral legs can not address this challenge. Bulky capacitors or extra active circuits are still required to reduce the ripples. This inevitably leads to increased size and cost of the system. Although SiC-based converters have the advantage of achieving high power density, the DCbus capacitance can not be reduced by simply replacing Si IGBTs with SiC MOSFETs. In this paper, a new topology of SiC-based three-phase four-wire inverters is proposed to reduce the DC-bus ripples without adding any additional hardware components. With the reduction of DC-bus ripples, the DC-bus capacitance can be reduced to achieve high power density. The equivalent circuit is analyzed and the control strategy for the proposed topology is designed. The proposed topology is built in Matlab/Simulink and simulation results are presented to verify the proposed topology

SEAL: A Framework for Systematic Evaluation of Real-World Super-Resolution

Real-world Super-Resolution (real-SR) methods focus on dealing with diverse real-world images and have attracted increasing attention in recent years. The key idea is to use a complex and high-order degradation model to mimic real-world degradations. Although they have achieved impressive results in various scenarios, they are faced with the obstacle of evaluation. Currently, these methods are only assessed by their average performance on a small set of degradation cases randomly selected from a large space, which fails to provide a comprehensive understanding of their overall performance and often yields biased results. To overcome the limitation in evaluation, we propose SEAL, a framework for systematic evaluation of real-SR. In particular, we cluster the extensive degradation space to create a set of representative degradation cases, which serves as a comprehensive test set. Next, we propose a coarse-to-fine evaluation protocol to measure the distributed and relative performance of real-SR methods on the test set. The protocol incorporates two new metrics: acceptance rate (AR) and relative performance ratio (RPR), derived from an acceptance line and an excellence line. Under SEAL, we benchmark existing real-SR methods, obtain new observations and insights into their performance, and develop a new strong baseline. We consider SEAL as the first step towards creating an unbiased and comprehensive evaluation platform, which can promote the development of real-SR.Comment: The source code is available at https://github.com/XPixelGroup/SEA

DQ impedance stability analysis for the power-controlled grid-connected inverter

For a grid-connected inverter requiring the ac volt- age magnitude and the active power control, both vector control and power synchronization control can be applied. The stability comparison based on the dq impedance stability analysis between both control are carried out via three factors including the grid impedance, the inner current loop and the virtual impedance. The dq impedances of the inverter based on both control are derived. The determinant of the impedance ratio is used for the stability analysis. The bode plot of the grid impedance and the inverter impedance are present to assist the stability analysis and explain their interactions. It is found that increasing the grid impedance and the cut-off frequency of the current loop stabilize the inverter with the power synchronization control, which is converse to the vector control. Furthermore, the inverter with the power synchronization control may suffer the instabilities when connecting to a strong grid. The virtual inductor and resistor are proposed to enhance the stability for the vector control and the power synchronization control respectively. The simulation validation using Matlab/Simulink is performed