ABSTRACT
Power Quality (PQ) improvement in distribution
level is an increasing concern in modern electrical power systems. One of
the main problems in LV networks is related to load voltage stabilization
close to the nominal value. Usually this problem is solved by Smart Distribution Transformers, Hybrid
Transformers and Solid-state Transformers, but also Dynamic Voltage Conditioner (DVC) can be an innovative and a cost effective
solution. The paper introduces a new control method of a single-phase DVC
system able to compensate these long duration
voltage drifts. For these events, it is mandatory
to avoid active power exchanges
so, the controller is designed to work with non-active power
only. Operation limits for quadrature voltage injection control is formulated and reference voltage update
procedure is proposed to guarantee
its continuous operating. DVC performance for main
voltage and load variation is examined.
Proposed solution is validated with
simulation study and experimental laboratory tests. Some simulation and experimental results are illustrated to show
the prototype device’s performance.
KEYWORDS:
Power Quality
Power conditioning
Power electronics
Dynamic Voltage Conditioner DVC
DVR
LV Distribution System
Smart Grid
SOFTWARE:
MATLAB/SIMULINK
BLOCK
DIAGRAM:
EXPECTED
SIMULATION RESULTS:
Fig. 2. Simulation - DVC
operation limit update procedure under voltage - limits due to : Case 2.b) –
(a) grid and minimum grid voltage, (b) PCC and PCC reference voltage, (c) load
power factor.
Fig. 3. Experimental - DVC
response to load variation, adding and removing the load – (a),(d) PCC voltage,
(b),(e) DVC injected voltage, (c),(f) load current.
CONCLUSION
A new device concept, which goes beyond typical DVR
functionalities, is presented. The
proposed device is named DVC (Dynamic Voltage
Conditioner), it is an active
voltage conditioner able to cover both short- and fast-events, as a typical
DVR, and long-events (in the grid voltage range from 0.9-1.1 p.u.). So it can perfectly satisfy modern power
system DSO requirements. In particular the paper presents only the control
strategy that can be adapted during steady state condition (long-events) for a
single-phase DVC. Indeed, the steady state condition is not reported in literature
and the single phase configuration seems to be the best
economic solution for smart grid LV
distribution system. The device
controller, here introduced for first time, has been designed to operate with non-active power during steady state condition. So, to
guarantee DVC continuous working, the paper describes a control method to
generate DVC reference voltage considering its limits. Moreover, single-phase
design can decrease device initial cost and it
is also more compatible with
LV distribution and mostly single-phase domestic loads.
Designed control method is verified by MATLAB based simulation and laboratory
experimental test bed. Results show that, the device has good performance and it can improve PQ level of the installed distribution Smart Grid network effectively (mainly in the grid voltage range from 0.9-1.1
p.u.). This is essential for
nowadays modern network because the proposed DVC can give flexibility to the
system operator in order to move all problematic single-phase loads on
a specific phase (where the DVC is installed).
Even if the paper analyzed a single-phase system, all
the theoretical analysis on device limits can be extended for three phase
system and it will be addressed in future works. It should be noted that, this
solution since it injects the compensation voltage in quadrature to line
current, creates phase shifting on installed phase voltage so, it can impose
voltage unbalance issues to the
supplied
three-phase loads. Therefore this device can be used effectively in LV
distribution network with single phase loads only.
REFERENCES:
[1]
“IEEE recommended practice for monitoring electric
power quality,” IEEE Std 1159-2009
(Revision of IEEE Std 1159-1995), pp. c1–81, June 2009.
[2]
C. Sankaran, Power quality.
CRC press, 2001.
[3]
“IEEE application guide for IEEE std 1547(TM), IEEE
standard for interconnecting distributed resources with electric power
systems,” IEEE Std 1547.2-2008, pp.
1–217, April 2009.
[4]
E. Standard, “50160,” Voltage
characteristics of public distribution systems, 2010.
[5]
H. Farhangi, “The path of the smart grid,” IEEE Power and Energy Magazine, vol. 8,
no. 1, pp. 18–28, January 2010.
