3 similar situation exists where fault occurs the side the system, and the system design must such that this fault
cannot propagate the side the system. Many
of the technologies and practices detailed in
Section are relatively undeveloped: industry is
still cautious about the availability and reliability
of MVDC power converters and circuit breakers.
5.2 System economics
The economics MVDC systems are not yet clear. To
provide fault ride through capability, tripping must
be avoided, which complicates MVDC converter
design, and particularly challenging with long
MVDC lines (as the length increases the inductance
of the lines). the same time, MVDC might offer
other, less direct, economic advantages such as
reduced social rejection (due the lower ffootprint
required from MVDC systems), sustainability
advantages and, over the long term, reduced
cost and improved efficiency the installation
of additional DC-based generation and storage. MVDC technology matures, is
expected such devices will become less expensive.3 Standards
Given the myriad devices and complexity of
system operation, reliable and economic design
and operation MVDC grids will depend heavily
on standardization.4 fault ride through
Power system operators often require power
electronics devices with fault ride through
capability, where the converter must stay
connected the grid during grid fault and
attempt support the grid voltage and stability
during and after the transient event.47
Barriers the uptake MVDC grids
approaches MVDC applications include shunt
resistors, Hall effect sensors, and Rogowski coils.
For MVDC system, the requirement for fault
ride through typically obliges the MVDC converter
controls balance the energy the and the
AC side the converter, with the converter acting
as energy buffer. can seen below, a
significant energy imbalance between the and
DC sides the converter accumulates, causing a
significant voltage increase across the converter,
which can lead overvoltage and tripping.
. There currently lack
of standards and guidelines for MVDC grid
technologies and operational practices, and is
this critical issue which Section devoted.
A more general economic concern about
deploying MVDC technology power systems
is its immaturity and operational practices.3
5. The future cost MVDC
technology will depend heavily semiconductor
devices.1.
Currently, MVDC technology typically has higher
up-front cost than MVAC system similar
capacity.
Annex contains case studies one aspect the
economics MVDC versus MVAC deployment.
Other indirect economic advantages come with
the greater control and flexibility power system
operation provided MVDC infrastructure.
Similar reservations exist regarding both the cost
of repairing these components and the availability
of spare parts [48]. Achieving such functionality
can challenge. Figure 5-15-1 depicts an
example grid fault the MVDC converter
station, where the active power delivered the AC
grid suddenly reduces.
One major reason for the greater initial expense is
the cost semiconductor components MVDC
power converters.
5
