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SUPERCAPACITORS ENERGY STORAGE SYSTEM
FOR POWER QUALITY IMPROVEMENT: AN
OVERVIEW
INTRODUCTION
 The reason behind overview of supercapacitors energy storage system is that
supercapacitors are less weighty than that of battery of the same energy storage capacity,
 A fast access to the stored energy,
 Charging very fast than battery, Charge/discharge cycle is 106 time,
storage capacity independent of number of charging/discharging cycles,
energy density for Supercapacitor is 10 to 100 times larger than of traditional
capacitors(typical 20-70 MJ/m3),
capacities up to 5F/cm2, life cycles 25-30 years,
high efficiency (95%),
power density 10 times greater than batteries,
Charge and discharge time very less,
rated capacitance value ranging from 0.043-2700F,
nominal voltage ranging from 2.3 to 400V,
rated current ranging from 3-600 A,
operating temperature ranging -40°C to 85°C,
Maintenance free,
very low leakage current, also non polar.
Power Quality Issues
 Voltage sags
Voltage flicker
 Sustained Interruptions
Voltage regulation
Harmonics
ENERGY STORAGE SYSTEMS
Existing Storage Systems
 Pumped Hydro
Storage of Compressed Air
Electrochemical Storage
Hydrogen Storage
Heat Storage
Mechanical Storage
Oncoming energy storage systems
Superconducting Magnetic Energy Storage (SMES)
Redox Flow Batteries
Available Supercapacitors in market
Supercapacitors cost trend
Models of Supercapacitors
The RC series model of Supercapacitor
The two branches model of Bonert and Zubieta for a Supercapacitor
RC model of Supercapacitor
Supercapacitors model reduced to the mainline (generator convention)
Measurement Methods of Supercapacitor Parameters
Constant Current Charge Method
General schema used for constant current charge method
The work stages according to this method are:
•a constant current charge is applied at the
supercapacitors terminals;
•during the charge process, the voltage across
supercapacitors terminals is measured;
•data is processed to obtain the experimental
response: curves Isc(t), Usc(t);
•Model parameters are extracted from the
experimental response Usc (t); are identified: the
internal resistance and the equivalent capacity of
the pack.
Capacitance Time-Domain Conversion Method
The work stages according to this method are:
a constant current charge is applied;
a potential difference is created, preselected as
function of supercapacitor’s working voltage;
measurement of time period needed to create the
voltage variation;
Data processing and computing in order to obtain
the supercapacitor capacity.
a) at Uc = V1 , the output of comparator U1 is ‘1’ and the output
Q of flip flop U3 switches to ‘high’ state (logical ‘1’);
b) at Uc = V2, the output of comparator U2 is ‘1’ and the output
Q of flip-flop U3 switches to ‘low’ value(logical ‘0’). At the output
Q of circuit U3 a time pulse τ will be obtained, that is directly
proportional to the capacitance Cx, according to relation (3);
c) turning off the switch S1 (stopping the charging process);
d) turning on the switch S2 (discharging the capacitor);
e) watching the value Uc < V1 , after which the measuring
process can be restarted;
f) Determining the time value τ, that will give the size of
capacitance Cx.
Supercapacitors Parameters Determination: Case Study
Using Constant Current Charge Method
The pack of supercapacitors used is BOSTCAP BMOD0050
E015 B1 (5.8 F, 150 V, 10 modules × 10 cells in series).
The working test bench to determinate the
supercapacitors parameters contain:
the pack of batteries, 23 cells in series, 12 V/100 Ah each;
the bidirectional current converter, that allows current with
values between 10 and 400 A. Reference current of converter by a low-pass filter strategy of a DC bus current;
resistances (Load);
 voltage/current sensors;
280 V DC bus.
supercapacitors pack BPAK0058 E015 B1 parameters
Experimental characteristics obtained by the constant current (50A) charge method for BPAK0058 E015 B1 module
Simulations characteristics obtained by the constant current (50A) charge method for BPAK0058 E015 B1 module
Circuit diagram of SCESS
SCESS CONTROL
Control concept for boost mode
Control concept for Buck mode
Vdc link control Design
Current control Design
Control of STSTCOM plus SCESS (MODE 2)
Controlof STSTCOM plus SCESS (MODE 3)
Experimental Results
Vdc link, Vsc, Va, and Ia during STSTCOM plus SCESS inject real power to grid
Vdc link, Vsc, and Isc during STSTCOM plus SCESS inject and absorb real power
Various Approaches for Power
Quality Improvement by SCES
Through a critical survey of the literature for the energy
storage system especially for the Supercapacitors energy
storage system for improvement of power quality of the
different systems; an overview has been presented. Various
aspects of the problem, such as to provide ride through,
stabilization of power system, to make undispatchable power
into dispatchable, to improve power quality of weak
transportation system, of aircraft distribution system UPS,
elevator and PDS adopting PI control technique, dynamic
voltage restorer in the island mode, switching transients mode,
grid connected mode, in stand alone for the short term outage.
Therefore it would prove a good energy storage option and
power quality maintenance purpose with power conditioning
system as the cost falls down being the life and its efficiency is
very high.