Summary:

This tutorial provides a comprehensive overview of the challenges and solutions for protection in DC microgrids. DC microgrids present unique protection requirements that differ fundamentally from traditional AC systems, including non-standardized fault characteristics, fast fault currents, and the absence of natural zero-crossings for conventional protection coordination. Key topics include the short-circuit behavior of power electronic converters, grounding schemes, the application of solid-state circuit breakers, and measurements from short-circuit tests, providing participants with both theoretical understanding and practical industrial insights.

Summary:

This report is presented from four aspects. Firstly, it introduces the demand for new energy development driven by the dual-carbon and new-type power system strategies, analyzes the challenges brought by the integration of distributed photovoltaic power to distribution networks, and puts forward the significance of AC/DC flexible distribution networks in accommodating massive distributed new energy sources and constructing new-type power systems. Secondly, it describes the typical networking forms of AC/DC flexible distribution networks and relevant engineering cases. The third part introduces a series of core equipment involved in AC/DC networking. The fourth part prospects the future technology development trends.

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As large-capacity power electronic interface, HVDC systems are increasingly expected to act as active parts of the power grid, rather than just passive connections for transmitting electricity. This presentation aims to offer a way to improve and make use of the ability of HVDC systems to support the power grid. The focus will be on new converter designs, control methods, and ways to integrate these systems so that HVDC can actively help keep the power grid stable and resilient.

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With the rapid development of new power systems, the integration of large-scale renewable energy and MMC-HVC transmission into receiving-end power grids has become a defining trend in China. This presentation investigates the active frequency support control methods for large-scale renewable energy MMC-HVDC systems. It systematically analyzes the factors limiting frequency support capabilities, focusing on both the energy sources available (such as sending-end power, energy storage, and submodule capacitance) and the energy transmission pathways (overload capability of DC converters). The efficacy of frequency support is quantified considering technical constraints, such as inertia emulation duration and power margin. A comparative study of phase-locked loop (PLL) and virtual synchronous control strategies is presented, revealing that while virtual synchronous control offers quicker frequency response, the robustness of PLL makes it more adaptable to practical grid conditions. Furthermore, two main frequency signal transmission strategies (communication based and DC voltage based) are evaluated. Results indicate that communication based approaches provide greater flexibility and stability, with minimal frequency support degradation due to communication delays, which can be compensated by energy management measures. The proposed control and transmission strategies have been validated through simulation, demonstrating their effectiveness in enhancing the frequency stability of receiving-end power grids dominated by renewable energy and MMC-HVDC systems.

Summary:

Presentation summary will be announced soon.

Summary:

Switched-capacitor Converter (SC) belongs to a branch of power electronics converters, which comprises capacitors and switches without the participation of inductors. In the first part, a family of switched capacitors is introduced, featuring simple circuit, interleaved operation, continuous input current, and systematic expandability, suitable for renewable power conversion from low voltage to high voltage, for connecting battery to high-voltage DC to perform charging and discharging, and also for micro-grid operation with distributed DC sources, batteries, and loads. The circuit can be implemented in the form of discrete circuit for high-power applications or in the form of integrated circuit for low-power applications. In the second part, a new family of Hybrid Boost Converter (HBC) is introduced on top of the first part, which features in symmetrical configuration, low component voltage rating, small output voltage ripple, and expendable structure. The topology integrates inductive switching cores of various functionalities and control strategies with Bipolar Voltage Multiplier (BVM) to form the new HBC including the Basic, Symmetrical, Isolated, and Tapped-inductor collections. Additionally, all of the collections can be extended for bidirectional power delivery, 3D structure for high power delivery, and half-bridge micro-inverter configuration for DC/AC applications. The proposed HBC family is suitable in DC Micro-grid system such as fossil fuel cell energy conversion, front-end photovoltaic energy system, and energy storage systems.

Summary:

The rapid development of Solid-State Transformers (SST) enables a future for microgrids that features the connection of various sources, loads, and storage elements to a common MVDC bus. The simulation of such systems presents various challenges due to their growing complexity caused by the large number of connected power converters and the diversification of sources and loads. Quick benchmarking in booming MVDC areas requires simulation models that feature superior speed with a dynamic response that fits real hardware. This tutorial provides an accessible overview of MVDC distribution grids and the system-level modelling approach used to simulate them. Starting from DC grid fundamentals and emerging standards, it introduces the concept of average models for elementary SST cells built with controlled current/voltage sources embodying the dynamic behaviour of real SST systems. Modular configurations and their implications on the DC bus are discussed, and representative simulation examples illustrate the approach in practical MVDC scenarios. The presentation is supported by industrial experience and academic insight. Outline: 1) Introduction to MVDC grids: DC grid fundamentals: topology, strengths, and typical disturbances, Overview of emerging DC standards; 2) System-level modelling of SST for MVDC: Average model of an elementary SST cell, Paralleling and modularity of SSTs, Modelling of the DC bus and peripheral elements (sources, loads, storage); 3) Simulation examples: Walkthrough of a representative MVDC grid model for renewable energy systems, Discussion of dynamic responses and failure scenarios; 4) Conclusions and outlook: Prospects for MVDC grids and open discussion.

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Summary:

Presentation summary will be announced soon.