Download Hybrid Railway Power Quality Conditioner (HPQC)

ANALYSIS OF DC LINK OPERATION VOLTAGE OF A HYBRID RAILWAY POWER
QUALITY CONDITIONER AND ITS PQ COMPENSATION CAPABILITY IN HIGH
SPEED CO-PHASE TRACTION POWER SUPPLY
ABSTRACT:
Hybrid Railway Power Quality Conditioner (HPQC) is newly proposed for its effective
reduction in DC link operation voltage while providing similar power quality compensation in
co-phase traction power supply compared to conventional railway power quality conditioner
(RPC). However, reduction in HPQC operation voltage limits its power quality compensation
capability. For instance, the previously proposed HPQC design based on minimum operation
voltage under fixed rated load has minimum power quality compensation capability. Under
practical conditions when load varies, the required HPQC active and reactive compensation
power also changes. The DC link operation voltage of HPQC may therefore need to be enhanced
to increase its power quality compensation capability. Therefore in this paper, the relationship
between DC link voltage of HPQC and its power quality compensation capability, as well as its
limitations, are being analyzed. Simulation and experimental results are also presented to verify
the mentioned relationship via investigations of system performance under different loading
conditions. The research can provide a guideline for determination of HPQC operation voltage
when load varies.
INTRODUCTION:
With rapid country and city development around the world, electric railway transportation has
played an essential role in economics and daily lives. This causes high and increasing
transportation demand.
It is therefore important that traction power supply is stable and can provide power with high
power quality to locomotives. However, traction power supply usually suffers from various
power quality problems such as reactive power, system unbalance and harmonics, etc. Various
power quality compensation techniques, which are discussed in later sections, are therefore
proposed.
The key concept of the capacitive current balancing methods is the use of blocking capacitor,. A
series connected blocking capacitor in the secondary side of the transformer balances the current
of two LED strings. By the charge conservation, the average current flows through the two LED
strings (Avg(iLED1) and Avg(iLED2) are naturally balanced without the active components.
The capacitive method is very cost-effective in that it uses small number of components. In the
primary side of the passive current balancing drivers, a current source type inverter is required in
order to use the charge balance of the blocking capacitor. LLC converter is widely used because
of its zero voltage switching characteristics.
However, the LLC converter requires two main switches and the additional resonant inductor to
obtain wide output voltage range. Therefore, the passive current balancing drivers that use the
LLC converter have a limitation in their system volume and cost.
EXISTING SYSTEM:
In traditional AC traction power supply, the power in three phase grid is transformed into two
single phase outputs through substation and supply power to locomotives. Since the two single
phase power is of different phase, neutral sections (without power supply) are required to avoid
risk of phase mixing. As locomotives run through neutral sections, they lose power and velocity.
Traditional AC power structure is therefore not suitable for high-speed railway. It is basically
composed of a back to back converter with a common DC link. One converter, or instance, the
Vac phase converter is connected to the locomotive phase through inductive coupled impedance;
and another phase, Vbc phase converter, is connected to the unloaded phase through inductive
coupled impedance. In order to control the power flow so as to achieve power quality
compensation, the energy of the DC link must be higher than the point of common coupling
(PCC) point. In other words, the DC link voltage must be higher than the peak of Vac voltage.
BLOCK DIAGRAM:
INDUCTIVE
LOAD
FILTER
CONVERTER 2
12V
DC
5V DC
FILTER
ENERGY
STORAGE
DRIVER
CIRUIT
PIC CONTROLLER
WITH BUFFER
CONVERTER 1
PROPOSED SYSTEM:
In co-phase traction power locomotive loadings are connected across one single phase output of
substation transformer only, leaving another phase unloaded. This proposed structure is
beneficial for effective reduction of neutral sections and higher transformer utilization ratio. The
co-phase structure is thus more suitable for application in high-speed railway. Hybrid railway
power quality conditioner (HPQC) is thus proposed and developed. Different from traditional
RPC, the Vac phase converter in HPQC is connected to the PCC through capacitive coupled
impedance
ADVANTAGES:

The capacitive coupled capacitance can help to provide support voltage during reactive
power compensation so that the DC link voltage can be decreased.

The device rating and cost of HPQC can thus be reduced
TOOLS AND SOFTWARE USED:

MPLAB – microcontroller programming.

ORCAD – circuit layout.

MATLAB/Simulink – Simulation
APPLICATIONS:

Electric railway transportation
CONCLUSION:
In this paper, the relationship between HPQC DC link voltage and its power quality
compensation capability in co-phase traction power is being analyzed and discussed. Co-phase
traction power has high potential to be power supply system. However, the operation voltage
requirement of conventional inductive coupled RPC within the system is high due to its high
power requirement to control power flow. This leads to higher cost and device ratings. The
capacitive coupled HPQC is therefore newly proposed for reduction of operation voltage while
providing similar performance at rated load. Nevertheless, reduction in HPQC operation voltage
limits its power quality compensation capability. Therefore, it is essential to determine the
relationship between HPQC DC operation voltage and the corresponding power quality
compensation capability so as to provide a guideline for the design of HPQC.
REFERENCES:
[1] Amrutha Paul, P. ; Anju, U.D. ; Anoop, M.P. ; RajanPallan, M. ; Roshna, N.K. ; Sunny, A.,
“Effects of two phase traction loading on a three phase power transformer”, in Annual
International Conference on Emerging Research Areas: Magnetics, Machines and Drives,
AICERA/iCMMD, 2014, pp. 1-5.
[2] Joseph, V.P. ; Thomas, J., “Power quality improvement of AC railway traction using railway
static power conditioner a comparative study”, in International Conference on Power Signals
Control and Computations , EPSCICON, 2014, pp. 1-6.
[3] Gunavardhini, N. ; Chandrasekaran, M. ; Sharmeela, C. ; Manohar, K., “A case study on
Power Quality issues in the Indian Railway traction sub-station” in 7th International Conference
onIntelligent Systems and Control, ISCO, 2013, pp. 7-12