59 research outputs found
HVDC Loss Factors in the Nordic Power Market
In the Nordic countries (Sweden, Norway, Finland and Denmark), many
interconnectors are formed by long High-Voltage Direct-Current (HVDC) lines.
Every year, the operation of such interconnectors costs millions of Euros to
Transmission System Operators (TSOs) due to the high amount of losses that are
not considered while clearing the market. To counteract this problem, Nordic
TSOs (Svenska kraftn\"at - Sweden, Statnett - Norway, Fingrid - Finland,
Energinet - Denmark) have proposed to introduce linear HVDC loss factors in the
market clearing algorithm. The assessment of such a measure requires a detailed
model of the system under investigation. In this paper we develop and introduce
a detailed market model of the Nordic countries and we analyze the impact of
different loss factor formulations. We show that linear loss factors penalize
one HVDC line over the other, and this can jeopardize revenues of merchant HVDC
lines. In this regard, we propose piecewise-linear loss factors: a simple to
implement but highly effective solution. Moreover, we demonstrate how the
introduction of only HVDC loss factors is a partial solution, since it
disproportionately increases the AC losses. Our results show that the inclusion
of AC loss factors can eliminate this problem.Comment: Submitted to "XXI Power Systems Computation Conference" on October 4,
2019 - Revised on April 19, 2020 - Accepted on May 13, 202
Market Integration of HVDC Lines
Moving towards regional Supergrids, an increasing number of interconnections
are formed by High Voltage Direct Current (HVDC) lines. Currently, in most
regions, HVDC losses are not considered in market operations, resulting in
additional costs for Transmission System Operators (TSOs). Nordic TSOs have
proposed the introduction of HVDC loss factors in market clearing, to account
for the cost of losses and avoid HVDC flows between zones with zero price
difference. In this paper, we introduce a rigorous framework to assess the
introduction of HVDC loss factors in flow-based market coupling. Our results
apply to nodal and peer-to-peer markets as well. First, we focus on the
identification of an appropriate loss factor. We propose and compare three
different models: fixed, linear, and piecewise linear. Second, we introduce
formulations to include HVDC losses in market clearing algorithms. Carrying
numerical tests for a whole year, we find that accounting only for HVDC losses
may lead to lower social welfare for a non-negligible amount of time. To
counter this, this paper introduces a framework for including both AC and HVDC
losses in a zonal or nodal pricing environment. We show both theoretically and
through simulations that such a framework is guaranteed to increase social
welfare.Comment: Submitted to "IEEE Transactions on Power Systems" on December 3, 201
Loss Allocation in Joint Transmission and Distribution Peer-to-Peer Markets
Large deployment of distribute energy resources and the increasing awareness
of end-users towards their energy procurement are challenging current practices
of electricity markets. A change of paradigm, from a top-down hierarchical
approach to a more decentralized framework, has been recently researched, with
market structures relying on multi-bilateral trades among market participants.
In order to guarantee feasibility in power system operation, it is crucial to
rethink the interaction with system operators and the way operational costs are
shared in such decentralized markets. We propose here to include system
operators, both at transmission and distribution level, as active actors of the
market, accounting for power grid constraints and line losses. Moreover, to
avoid market outcomes that discriminate agents for their geographical location,
we analyze loss allocation policies and their impact on market outcomes and
prices.Comment: Submitted to "IEEE Transactions on Power Systems" on January 15, 2020
- Revised on May 6, 2020 and on August 6, 2020 - Accepted on September 13,
202
Zero-inertia Offshore Grids: N-1 Security and Active Power Sharing
With Denmark dedicated to maintaining its leading position in the integration
of massive shares of wind energy, the construction of new offshore energy
islands has been recently approved by the Danish government. These new islands
will be zero-inertia systems, meaning that no synchronous generation will be
installed in the island and that power imbalances will be shared only among
converters. To this end, this paper proposes a methodology to calculate and
update the frequency droops gains of the offshore converters in compliance with
the N-1 security criterion in case of converter outage. The frequency droop
gains are calculated solving an optimization problem which takes into
consideration the power limitations of the converters as well as the stability
of the system. As a consequence, the proposed controller ensures safe operation
of off-shore systems in the event of any power imbalance and allows for greater
loadability at pre-fault state, as confirmed by the simulation results.Comment: Submitted to "IEEE Transactions on Power Systems" on February 19,
202
Sharing Reserves through HVDC: Potential Cost Savings in the Nordic Countries
During summer 2018, the Nordic system's kinetic energy dropped below a
critical level. As a consequence, Svenska kraftn\"{a}t, the Swedish
transmission system operator (TSO), requested the largest production unit to
reduce its power output to guarantee system's security. This action resulted in
a deviation from the generation dispatch determined by the market and in high
costs for the Nordic TSOs. In this regard, this paper presents a tool for
comparing mitigation strategies from an economic point of view and evaluates
potential economic benefits of utilizing the Emergency Power Control (EPC)
functionality of HVDC lines for the provision of fast reserves as a compliment
to Frequency Containment Reserves (FCR). Moreover, the analysis is extended to
the years 2020 and 2025 using inertia estimations from the Nordic TSOs. The
findings of the paper suggest that the frequency of redispatching actions will
increase in the future and that the cost of security for Nordic TSOs could be
reduced by 70\% if HVDC links are used for frequency support.Comment: Submitted to "IET Generation, Transmission & Distribution" on June
12, 2020 - Revised on September 6, 2020 - Accepted on September 16, 202
Market Integration of HVDC Lines: Cost Savings from Loss Allocation and Redispatching
In the Nordic region, many interconnectors are formed by HVDC links, as
Scandinavia, Continental Europe and the Baltic region are non-synchronous AC
systems. This paper presents two cost benefit analyses on the utilization of
HVDC interconnectors in the Nordic countries: in the first we investigate the
utilization of HVDC interconnectors for reserve procurement and, in the second,
we assess the implementation of implicit grid losses on HVDC interconnectors in
the day-ahead market.
The first analysis is motivated by real events in 2018 where the inertia of
the Nordic system dropped below a critical level and the most critical
generating unit, a nuclear power plant in Sweden, was redispatched to guarantee
the security of the system. In order to guarantee system security while
reducing the costs of preventive actions, in summer 2020 new frequency products
were introduced in the Nordic system: the Fast Frequency Reserves (FFR). HVDC
lines, however, can perform similar tasks at lower costs. In our analysis, we
are, thus, investigating the cost savings of using HVDC lines for frequency
support using their Emergency Power Control (EPC) functionality, instead of
redispatching or FFR.
The second analysis is based on the proposition of Nordic Transmission System
Operators (TSOs) to introduce linear HVDC loss factors in the market clearing.
With our analysis, we show that linear loss factors can unfairly penalize one
HVDC line over the other, and this can reduce social benefits and jeopardize
revenues of merchant HVDC lines. In this regard, we propose piecewise-linear
loss factors: a simple-to-implement but highly-effective solution. Moreover, we
demonstrate how the introduction of HVDC loss factors is a partial solution,
since it disproportionally increases the AC losses. Our results show that the
additional inclusion of AC loss factors can eliminate this problem.Comment: Submitted to "CIGRE Centennial Exhibition 2021" on December 15, 2020.
arXiv admin note: text overlap with arXiv:1910.05607, arXiv:2001.0066
Huntingtin-mediated axonal transport requires arginine methylation by PRMT6
The huntingtin (HTT) protein transports various organelles, including vesicles containing neurotrophic factors, from embryonic development throughout life. To better understand how HTT mediates axonal transport and why this function is disrupted in Huntington's disease (HD), we study vesicle-associated HTT and find that it is dimethylated at a highly conserved arginine residue (R118) by the protein arginine methyltransferase 6 (PRMT6). Without R118 methylation, HTT associates less with vesicles, anterograde trafficking is diminished, and neuronal death ensues—very similar to what occurs in HD. Inhibiting PRMT6 in HD cells and neurons exacerbates mutant HTT (mHTT) toxicity and impairs axonal trafficking, whereas overexpressing PRMT6 restores axonal transport and neuronal viability, except in the presence of a methylation-defective variant of mHTT. In HD flies, overexpressing PRMT6 rescues axonal defects and eclosion. Arginine methylation thus regulates HTT-mediated vesicular transport along the axon, and increasing HTT methylation could be of therapeutic interest for HD.Telethon-Italy and Autonomous Province of Trento (TCP12013 to M.P.); Association Française contre les Myopathies (AFM-22221 to M.P. and M.B.); PRIN-MUR (2017F2A2C5 to M.P.); National Institutes of Health (1R21NS111768-01 to M.P. and U.B.P.); PROGRAM RARE DISEASES CNCCS-Scarl-Pomezia (M.P.); FONDAZIONE AIRC-Italy (24423 to M.P.); Alzheimer Trento Onlus with the legato Baldrachi (M.B.); the Agence Nationale de la Recherche (ANR-15-JPWG-0003-05 JPND CIRCPROT and ANR-18-CE16-0009-01 AXYON to F.S.) and the Spanish Ministry of Science, Innovation and Universities (RTI2018-096322-B-I00 MCIU/AEI/FEDER-UE to J.J.L.
- …