MVDC for enhanced utility scale distribution power delivery and control

IEEE Trans. Power Delivery

Egea‐Àlvarez

et al. 2021

1 -This paper presents a new fast-acting backup protection strategy for future hybrid ac-dc distribution networks. By examining the impedance measured by a distance protection relay measuring from the "ac-side" of the network, a unique characteristic is established for faults occurring on the "dc-side" of an embedded medium-voltage dc (MVDC) link, interconnecting two 33 kV distribution network sections. Based on the identified impedance characteristic, appropriate settings are developed and deployed on a verified software model of a commercially available distance protection relay. To remain stable for ac-side faults, it is found that the tripping logic of the device must be altered to provide correct time grading between standard, ac, protection zones and the fast-acting dc region, which can identify faults on the dc system within 40 ms. An additional confirmatory check is also employed to reduce the likelihood of mal-operation. Trials on a test system derived from an actual distribution network, which employs distance protection, are shown to provide stable operation for both ac-side and dc-side pole-pole and pole-pole-ground faults.

“…The network section modelled is based upon an area of the 33 kV network in the south of Scotland where the benefits of introducing embedded MVDC links has been shown via simulation [33].…”

Section: A Network Modellingmentioning

confidence: 99%

A New Fast-Acting Backup Protection Strategy for Embedded MVDC Links in Future Distribution Networks

IEEE Trans. Power Delivery

Egea‐Àlvarez

et al. 2021

“…Network modelling is undertaken using SimPowerSystems components within Simulink. The network section being modelled is based upon small section of 33 kV network found in the south of Scotland where the introduction of embedded MVDC links has been shown to be promising through simulation [14]. Lines are modelled as lumped element R-L impedances and neglect negative sequence components.…”

Section: Network Modellingmentioning

confidence: 99%

The impact of MVDC upon conventional distance protection schemes in hybrid ac-dc distribution networks

15th IET International Conference on AC and DC Power Transmission (ACDC 2019)

Finney

et al. 2019

This paper looks at the protection implications of introducing fully controllable, embedded, medium voltage dc (MVDC) power electronic links into power distribution networks. Studies have indicated, protection notwithstanding, that embedded MVDC can be used to provide economically attractive, enhanced capacity and control of power flows. Through a series of simulation studies, the impact on distance protection schemes (in terms of reach and response time) resulting from the introduction of a controlled MVDC link have been examined for symmetrical faults. The paper also considers under what conditions a dc side fault can be observed from the ac grid.

“…Modelling is carried out using DIgSILENT PowerFactory 15.2. Similar studies have looked at the role that single embedded MVDC links could play in distribution networks to create additional export capacity [8] - [10]. Figure 2 and Table I outline a simplified network topology and device ratings to help contextualise the modelling.…”

Section: Study Overviewmentioning

confidence: 99%

“…According to the Angle-DC funding proposal, the uptake of embedded MVDC depends largely on the cost of power electronics, which SP Energy Networks estimate will drop by up to 55% between now and 2040 [8]. With the cost per installed watt presently being 0.42 £/W there is a clear challenge to reduce these down to 0.19 £/W.…”

Section: ) Costsmentioning

confidence: 99%

MVDC Network Balancing for Increased Penetration of Low Carbon Technologies

2018 IEEE PES Innovative Smart Grid Technologies Conference Europe (ISGT-Europe)

Finney

et al. 2018

Self Cite

This paper outlines the case for using Medium Voltage Direct Current (MVDC) (5-50 kV) elements in distribution systems as a means to accelerate the deployment of low carbon technologies. The approach uses existing cable and overhead assets, originally designed into the ac system for security purposes. By selective conversion to dc, an inter GSP (grid supply point) balancing network can be created with modifications only required at substations. This approach allows for increased network transfer capability without increasing fault level as would be the case with conventional interconnection. Using data from a real-world Scottish suburban distribution network, the benefits and barriers to such an approach are examined. Power flows for the existing network are benchmarked under various present day and future loading scenarios. Controllable MVDC links are introduced to the network and power flow studies used to assess the value of such an approach to network reinforcement. Cost estimates for such a scheme are projected using data from industrial trials.