15,384 research outputs found
Small Signal Stability Analysis of Distribution Networks with Electric Springs
This paper presents small signal stability analysis of distribution networks with electric springs (ESs) installed at the customer supply points. The focus is on ESs with reactive compensation only. Vector control of ES with reactive compensation is reported for the first time to ensure compatibility with the standard stability models of other components such as the interface inverter of distributed generators (DGs). A linearized state-space model of the distribution network with multiple ESs is developed which is extendible to include inverter-interfaced DGs, energy storage, active loads etc. The impact of distance of an ES from the substation, proximity between adjacent ESs and the R/X ratio of the network on the small signal stability of the system is analyzed and compared against the case with equivalent DG inverters. The collective operation of ESs is validated through simulation study on a standard distribution network
Impact Assessment of Hypothesized Cyberattacks on Interconnected Bulk Power Systems
The first-ever Ukraine cyberattack on power grid has proven its devastation
by hacking into their critical cyber assets. With administrative privileges
accessing substation networks/local control centers, one intelligent way of
coordinated cyberattacks is to execute a series of disruptive switching
executions on multiple substations using compromised supervisory control and
data acquisition (SCADA) systems. These actions can cause significant impacts
to an interconnected power grid. Unlike the previous power blackouts, such
high-impact initiating events can aggravate operating conditions, initiating
instability that may lead to system-wide cascading failure. A systemic
evaluation of "nightmare" scenarios is highly desirable for asset owners to
manage and prioritize the maintenance and investment in protecting their
cyberinfrastructure. This survey paper is a conceptual expansion of real-time
monitoring, anomaly detection, impact analyses, and mitigation (RAIM) framework
that emphasizes on the resulting impacts, both on steady-state and dynamic
aspects of power system stability. Hypothetically, we associate the
combinatorial analyses of steady state on substations/components outages and
dynamics of the sequential switching orders as part of the permutation. The
expanded framework includes (1) critical/noncritical combination verification,
(2) cascade confirmation, and (3) combination re-evaluation. This paper ends
with a discussion of the open issues for metrics and future design pertaining
the impact quantification of cyber-related contingencies
Electric spring and smart load: technology, system-level impact and opportunities
Increasing use of renewable energy sources to combat climate change comes with the challenge of power imbalance and instability issues in emerging power grids. To mitigate power fluctuation arising from the intermittent nature of renewables, electric spring has been proposed as a fast demand-side management technology. Since its original conceptualization in 2011, many versions and variants of electric springs have emerged and industrial evaluations have begun. This paper provides an update of existing electric spring topologies, their associated control methodologies, and studies from the device level to the power system level. Future trends of electric springs in large-scale infrastructures are also addressed
Distributed voltage-driven demand response: flexibility, stability and value assessment
The need for operating reserve from energy storage, demand reduction (DR) etc. is expected
to increase signifcantly in future low-carbon Great Britain (GB) power system with high
penetration of non-synchronous renewable generation. One way to provide the reserve is to
use power electronic compensators (PECs) for point-of-load voltage control (PVC) to exploit
the voltage dependence of loads.
This thesis focuses on the quantifcation of DR capability from PVC in the domestic sector
using high-resolution stochastic demand models and generic distribution networks in GB.
The effectiveness of utilising PVC in contributing to frequency regulation is analysed and
demonstrated through time domain simulations. The techno-economic feasibility of such
technology is evaluated considering the investment cost of the PEC deployment as well as
the economic and environmental benefts of using PVC. The payback period varies between
0.3 to 6.7 years for different future scenarios considering a range of converter price. It is
demonstrated that PVC could effectively complement battery energy storage system towards enhanced frequency response provision in future GB power system.
For practical application of PVC for flexible demand and voltage regulation in future distribution networks/microgrids, it is important to investigate the overall small signal stability of
the system. In this thesis, the linearised state space model of a distribution network/isolated
microgrid with converter-interfaced distributed generators (CDGs) working in grid following
mode along with loads with PVC is developed. The stability performance is revealed through
both modal analysis and time domain simulations. It is shown that multiple loads with PVC for voltage regulation in distribution networks are not likely to threaten the small signal stability of the system. In the case of a microgrid, the introduction of PVC is shown to have marginal impact on the low frequency modes associated with the droop control of the CDGs. However, there is a trade-off when choosing the droop gain of the loads with PVC. Lower droop gains could ensure better frequency regulation in face of intermittent renewables but at the expense of a lower stability margin for an oscillation mode at a frequency slightly higher
than 20Hz.Open Acces
Kytketyt MEMS-resonaattoriverkot
Micromechanical resonance frequencies are in a standard manner a few tens of MHz and can even cover the requency range up to a few GHz. When using high quality material such as quartz of silicon, also internal losses are very low.
By physical coupling of resonators into a network, one can realize various mechanical signal processing, filtering or for example neural network type behavior. Since coupling between resonators are realized by some kind of bridge, which can be either rather linear or alternatively intentionally very nonlinear, the overall behavior of the whole network is very complex.
Of general interest are effects that originate from multiple inputs and outputs and which could lead to a rather unexpected spectral or transient behavior of the signals, which can be found by computer modelling.Mikromekaaniset resonanssitaajuudet ovat tyypillisesti muutamia kymmeniä megahertsejä mutta voivat kattaa taajuuskaistan aina muutamiin gigahertseihin asti. Käytettäessä korkealaatuisia materiaaleja kuten kvartsia tai piitä myös signaalin häviöt ovat erittäin pieniä.
Kytkemällä resonaattoreita fyysiseksi verkoksi voidaan mekaanisilla rakenteilla suorittaa signaalinkäsittelyä, realisoida suodattimia ja jopa neuroverkkoja. Koska yksittäisten resonaattorien välinen kytkentä on jonkinlainen silta, joka voi olla joko melko lineaarinen tai vaihtoehtoisesti tarkoituksellisesti erittäin epälineaarinen, on koko verkon käyttäytyminen erittäin monimutkaista.
Yleisesti kiinnostavia ovat useista sisäänmenoista ja ulostuloista johtuvat ilmiöt, jotka voivat johtaa signaalien spektrin tai transienttivasteen melko odottamattomaan tai epäintuitiiviseen käyttäytymiseen, jonka voi löytää ja tulkita tietokonesimulaatioilla
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