Sheng Wang

Cardiff University | CU · Institute of Energy

Silicon-controlled rectifier-based dc solid-state circuit breakers (SCR-SSCBs) have received an increased attention for their ease of control and high efficiency, but their considerable conduction losses remain a major disadvantage. This paper presents a new bidirectional SCR-SSCB topology which reduces the conduction losses by ∼50%, with the loss...

High-voltage direct-current (HVDC) rated at 270 Vdc is one of the main power supply technologies expected for future more electric aircraft (MEA). However, dc protection is still one major challenge preventing the wide deployment of HVDC. To overcome this, Z-source solid-state circuit breakers (Z-SSCBs) could be employed due to their simple structu...

Abstract A transformer‐less unified power flow controller (UPFC) is a power electronic device consisting of series and shunt voltage source converters (VSCs) that are not connected to a common DC bus. It can control power flow in medium voltage (MV) distribution networks without the need for interfacing transformers. Hence there is a significant re...

DC technologies will be essential building blocks for future DC distribution networks. As in any DC system, these networks will face crucial threats imposed by short-circuit DC faults. Protection is thus of great interest, and it will likely rely on DC circuit breakers (DCCBs). Among available configurations, Z-source solid-state circuit breakers (...

Decentralized control with multiple droop characteristics can significantly improve the accuracy of power flow in medium-voltage direct-current (MVdc) networks. However, multiple crossovers caused by different control characteristics can lead to the drifts of power and voltage and instability issues. When this type of control is implemented in the...

On 29 June 2022, the IEEE Power Electronics Society (PELS) United Kingdom and Ireland (UK&I) Section Chapter hosted a series of online talks on professional developments with IEEE in honor of PELS Day. Chapter Chair Bing Ji began the event with an opening speech and presentation of the vision and mission of the Chapter. Dr. Ji also explained the im...

This letter proves that a grid-following converter can stably connect to a weak grid even short-circuit ratio (SCR) is 1. Root instability causes of this grid-following control are identified including fast control response, insufficient damping, and slow voltage support. A simple and effective tuning method is proposed to stabilize this connection...

The design of single-phase differential buck inverters has two important considerations, including reducing second-order ripple power using decoupling capacitors and increasing inverter performances. Using larger decoupling capacitors will improve the performance of ripple power reduction and efficiency while reducing power density. Such trade-off...

Although the control of modular multi-level converters (MMCs) in high-voltage direct-current (HVDC) networks has become a mature subject these days, the potential for adverse interactions between different converter controls remains an under-researched challenge attracting the attention from both academia and industry. Even for point-to-point HVDC...

Design methodology of power electronics converters is critical to fully explore the potential of wide-bandgap power semiconductors at the converter level. However, existing design methods largely rely on complex mathematical models which significantly increases the computational time, complexity and further leads to problems including poor constrai...

The cascaded three-level neutral-point-clamped (3L-NPC) converter and the modular multi-level converter (MMC) are attractive solutions for medium-voltage direct-current (MVDC) applications. Due to their low cost compared to MMCs, cascaded 3L-NPC converters have been adopted in ANGLE-DCa 30 MVA MVDC link demonstration project in North Wales, UK. DC...

In this paper, it is identified that unstable weak grid connection of voltage source inverters (VSIs) is dominantly caused by the current control. In particular, it is found the proportional gain $ k_p$ of conventional PI controller cannot balance the grid voltage impact and damping capability especially when a very weak grid with short circuit r...

The HTSConductor on Round Core (CORC) Cables have been widely recognized as the proper candidate for superconducting applications such as the high-field magnets and power transmission cables. This article presents the modeling of HTS CORC cables using the FEM H -formulation model merged into the package COMSOL Multi-physics. The 2D and 3D H -fo...

This paper presents the loss analysis on the saturated iron-core superconducting fault current limiter (SISFCL) for a VSC-HVDC transmission system. The numerical model of SISFCL as well as its loss calculation on superconducting parts were carried out by the finite-element method (FEM) using the H -formulation merged into the commercial package C...

The superconducting fault current limiter (SFCL) has been regarded as one of most popular superconducting applications. This article reviews the modern energy system with two major issues (the power stability and fault-current), and introduces corresponding approaches to mitigate these issues, including the importance of using SFCL. Then the articl...

Hybrid dc circuit breakers (HCBs) are recognized as suitable devices for protecting high-voltage direct-current (HVDC) systems, along with other dc circuit breakers (DCCB). However, compared to mechanical circuit breakers, HCBs exhibit higher conduction losses. Such losses are inevitable under no-fault conditions as current may flow through some of...

Deployment of dc circuit breakers (DCCBs) will help to isolate dc faults in dc systems. Conversely, current flow controllers (CFCs) will be employed in dc grids to balance currents among transmission lines. However, the inclusion of these devices may incur significant capital investment. A way to reduce costs is by integrating current control capab...

The protection and current flow regulation of high-voltage direct-current (HVDC) grids requires the deployment of additional semiconductor-based equipment including dc circuit breakers (DCCBs) and current flow controllers (CFCs). However, the inclusion of multiple devices could significantly increase the total cost of an HVDC system. To potentially...

The inclusion of a large number of controllable semiconductor devices in conventional hybrid dc circuit breakers (HCBs) may significantly increase the cost of an HVDC grid protection scheme. In an attempt to reduce this cost, this paper proposes the use of two novel topologies of bridge-type integrated HCBs (BT-ICBs). The two configurations are exa...

“Open Grid” protection strategy is proposed for protecting DC networks with converters that cannot block fault current and rely on DC circuit breakers. With this method, each DC circuit breaker (DC-CB), based on its own, local measurements (e.g. overcurrent, undervoltage) trips without discrimination. Using the same local measurements, the DCCBs, d...

A high-voltage direct-current (HVDC) grid protection strategy to suppress dc fault currents and prevent overcurrent in the arms of modular multi-level converters (MMCs) is proposed in this paper. The strategy is based on the coordination of half-bridge (HB) MMCs and hybrid dc circuit breakers (DCCBs). This is achieved by allowing MMC submodules (SM...

To protect HVDC grids from DC faults, the concept of a hybrid DC circuit breaker is widely accepted due to its low conduction losses and fast interruption speed. For a well-built DC grid, a massive number of hybrid DC circuit breakers have to be installed. This will lead to high capital costs. An interlink DC circuit breaker based on an idea of sha...

Voltage source converter (VSC) based HVDC links have been deployed to increase crosscountry exchange capabilities and to transmit power from remote offshore wind farms. The delivery of smooth and reliable power to onshore AC grids may be further facilitated by connecting additional VSCs to form a multi-terminal HVDC (MTDC) grid. It is expected that...

Recently, DC current reduction control for commutation failure mitigation is executed through point-to-point LCC-HVDC's rectifier. For an interconnected LCC-HVDC system through MMC-based DC-DC converter (MDC), MDC can be used to reduce the DC current toward inverter instead of rectifier, which will achieve better commutation failure mitigation perf...

In this paper, a new control strategy for Thyristor Controlled Series Compensator (TCSC) to mitigate Sub-Synchronous Resonance (SSR) problems is introduced. Different from conventional sub-synchronous damping controller, this scheme involves using only local measurements which can be effectively obtained at the TCSC side. The structure of the contr...

Decarbonisation of the European electricity system can become dauntingly costly due to transmission and distribution network issues arising from the integration of intermittent renewable generation sources. It is expected that wind energy will be the principal renewable source by 2050 and, as such, a number of initiatives in the academia and in the...

A universal analysis calculation method is presented for DC grid with DC power flow controllers (DCPFC). The impact of DCPFC and the control of converter station are taken into account in the algorithm. Theoretical calculations are carried out to analyze the sensitivity of DCPFC to the power flow controlling. The impact of DCPFC on power flow of DC...

This chapter presents an overview of DC power flow control devices (DCPFCs) and the effects of DCPFCs on DC grids. There are mainly three types of DCPFCs to realize the flexible power flow control: DC transformers, variable series resistors (VSR), and series voltage sources (SVS). DC transformers are shunt connected devices, while VSR and SVS are s...

The generation of offshore wind power is less predictable. This can cause the overload of offshore DC transmission system and thus requires the curtailment of wind power. To reduce the amount of wind power curtailment, a method of optimising DC power flow using DC power flow controller (DC-PFC) is proposed. The analytical expression of coordinating...

HVDC grids have been made practical with the introduction of Voltage Source Converters (VSC). The development of VSC technology has, and continues to be rapid, with new converter topologies and new manufacturers entering the market. For the power transmission industry to fully exploit the benefits of this rapidly developing field of engineering a "...

HVDC grids have been made practical with the introduction of the voltage source converter (VSC). The development of VSC technology has been, and continues to be rapid, with new converter topologies and new manufacturers entering the market. For the power transmission industry to fully exploit the benefits a 'multi-vendor' supply chain is considered...

This Paper presents the modeling and control of two-terminal Voltage Source Converter Based High Voltage Direct Current (VSC-HVDC) transmission system which are achieved using the software of PSCAD/EMTDC. There are two control designs for VSC-HVDC system in this project: 1. Phase and magnitude control design, 2. Control design under d-q frame. The...

Due to low load factors of wind power generation, it is possible to reduce transmission capacity to minimize the cost of transmission system construction. Two VSC-HVDC schemes for offshore wind farm, called the point to point (PTP) and DC mesh connections are compared in terms of the utilization of transmission system and its cost. A Weibull distri...

This paper presents an economical and technological comparison between a conventional point to point (PTP) VSC-HVDC system and a DC mesh grid. A case study based on Dogger Bank Creyke Beck is used for this investigation. In the economic comparison, three main components are considered- VSC converter, DC cable and DC circuit breaker. The cost of los...