IEEE Power Electronics Magazine - March 2016 - 36

Based on these talks, note-taker Marcelo L. Heldwein
presented his views on what some of the major challenges
posed by the emerging integrated grid are. According to
Heldwein, power converters need a more integrated design
approach, including system-level control that is reliable
and low cost. Power electronic and power system engineers
must communicate effectively. Although the integration of
distributed renewable resources is accelerated with low
cost, it will bring challenges to distribution network operation. For example, the networks must be rated for thermal
overloads and be capable of handling bidirectional power
flow. Volt-var control and distributed energy-storage integration must also be considered, and excess intermittent
resources might lead to system-wide stability problems.
In addition, stated Heldwein, widespread use of multiple
power electronics in the transmission and distribution grid
leads to system resonances, and grid protection needs to
be redesigned with power electronics in mind. With an integrated grid, better utilization of distribution network capacity is also going to be challenging.
Other challenges highlighted by Heldwein include cyber- and physical security risk with power-electronicsrich networks; underutilized advanced metering infrastructure by the power electronics community; modeling
of large numbers of converters, grid impedances, energy
resources, and loads; and energy-storage optimization
and applications. Furthermore, he added that there is a
need for better interaction between filters and systems
of converters at high populations and for developing optimum value propositions using power electronics in distribution networks.

Regarding the solutions offered in this session, Heldwein
indicated that power electronics is well positioned to mitigate intermittent sources at the LV grid edge as well as manage power flow, increase capacity utilization, and provide
ancillary services, such as demand response and regulation.
Similarly, distributed intelligence with communication and
supervisory control can optimize distribution network operation through converters. While improving ac grids with
distributed power converters, it can provide an intermediary step to future dc grids. Furthermore, to gradually improve the overall system, dc systems could be built on top of
ac systems, and power electronics could play a more dominant role in integrating thermal and electric networks. With
this growing integration, protection methodology and solidstate protection at all levels (ac and dc) are needed in the
power electronics strategy. With respect to cost, Heldwein
concluded that the power electronics community is close to
the breakeven point between solid-state and conventional
(copper and iron) 50-/60-Hz distribution systems.

converter networks/systems
Before starting the session "Converter Networks/Systems,"
session Chair Prof. Braham Ferreira quickly highlighted the
challenges confronting power electronics converters in the
emerging power systems. According to Prof. Ferreira,
power converters increasingly have to work together in systems while walking a tightrope to balance and control the
interaction they have with each other. Concurrently, these
power converters have to collectively provide the desired
system performance. As a result, there are new challenges
in control and communications, he noted.
230 V
Regulated

Series Reactive Power
Compensator as
ES
Vs

Original
ac Bus

E
N
ac/dc
ES

0 V+Vdc
Adaptive dc
Power Supply

1-Phase
ES

LAdapt N
Adaptive ac
Power Supply
(With Earth)

LAdaptN
Adaptive ac
Power Supply

180 V-268 V

PWM
Power
Inverter

Active
Power
Flow

L N
Standard ac
Power Supply

+
Vs_ref

Load

Not Well
Regulated

Other
Load

180-265 V

230 V

ES-Embedded
Power Supplies
FIG 4 Two ESs embedded in a power supply infrastructure provide regulated output despite fluctuations in the input.
(Figure courtesy of The University of Hong Kong/Imperial College London.)

IEEE PowEr ElEctronIcs MagazInE

z March 2016

Table of Contents for the Digital Edition of IEEE Power Electronics Magazine - March 2016