International Journal of Advanced Research in Electrical, Electronics and Instrumentation Engineering
MenuISSN ONLINE(2278-8875) PRINT (2320-3765)
ISSN ONLINE(2278-8875) PRINT (2320-3765)
Ajal.A.J1, Chikku Jose2 and Manu Jacob3
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A short dip in supply voltage, unnoticed by the majority of electricity consumers, can still stop an entire production line in highly sensitive industries such as computer chip manufacturing, oil refining ..etc.We have to develop and successfully introduce systems to overcome these obstacles by means of advanced power electronics. In this paper , a noval approach on active series & shunt power line conditioner upqc (unified power quality conditioner ) has been described. It is a combination of a STATCOM as well as DVR .a series compensating stage connected before the load in series with the mains using a matching transformer. UPQC can mitigate voltage sag, swell, voltage transient & voltage unbalance. UPQC can supply VAR to the load. DSP based controller is connected to UPQC in order to increase the system performance
Why is Power Quality Important? |
| In a nut shell we can brief it as [1 ] |
| • Cost |
| • Competitiveness |
| • Down time |
| • Losses |
| • Loss of life |
| • Metering error |
| • EMC |
| • Proper service to the load |
CUSTOM POWER DEVICES |
| Concept introduced hingorani. Custom power devices enhance the quality and reliability of power delivered to the customer .Custom power devices are designed to improve the quality of power at their point of installation of power distribution systems. They are not primarly designed to improve power quality of the entire system.With a custom power device ,a customer will be able to receive a prespecified quality of electric power with a combination of specifications including bt not limited to small phase imbalance, Low flicker in supply vtg, Control of power interruptions, Control of supply vtg freq, Low harmonic distortion in supply, load voltage and current. |
| UPQC_UPQC stands for Unified Power Quality Conditioner. UPQC is an active series & shunt power line conditioner. It is a combination of STATCOM as well as DVR - a series compensating stage connected before the load in series with the mains using a matching transformer. UPQC is the ideal power electronic device to solve the power quality problems. UPQC can mitigate voltage sag, swell, voltage transients and voltage unbalance. UPQC can supply VAR to the load |
| The major components present in UPQC includes Series converter, Shunt converter, Mid point –to –ground DC capacitor bank, Low pass filter, High pass filter, Series and shunt transformers |
How STATCOM work in the UPQC? |
| Shunt Active Series STATCOMS has the capability to generate and absorb variable reactive power by switching the IGBT based voltage source converter (VSC). STATCOM belongs to a synchronous link converter (SLC). The supply voltage ad PWM voltage generated by the converter are isolated by a Boost reactor. Using DQ Theory the change in fundamental component of the PWM voltage allow the converter to draw either Leading or lagging supply current form the mains. The converter is capable of generating capacitive or inductive current based on the feedback taken from the load current.The IGBT based voltage source converter (VSC) generates an AC voltage which is in phase with the mains voltage. This voltage determines the direction of the current flowing through the reactor lag/lead. When the voltage generated by the VSC greater than the mains voltage a leading reactive currents is drawn from the mains and the STATCOM acts like a capacitor. In the case when the mains voltage is greater than the voltage developed by the VSC, a lagging current is drawn from the mains and the STATCOM acts like a reactor. |
How DVR work the UPQC ? |
| A DVR (Dynamic Voltage Restorer)-is a solid state electronic Power Conditioner DVR provides a constant output voltage which gives a clean sinusoidal waveform free from spikes, transients, voltage sags, voltage dips, under voltage and over voltage. |
| The DVR maintains the applied to the connected load during sags and swells by injecting a compensating voltage of proper magnitude and phase angle through a series transformer. It is capable of injecting up 35% of line-to-ground voltage on all three phases of the feeder, for up to 20 cycles. It can corrects for up to 20 cycles. It can thus corrects for the vase majority of sags and swells originating on the distribution system including under voltage and over voltage. |
Key features: [3 ] |
| DVR response time < 1 ms, Power ratings, Available for indoor installation or in weatherproof containers, Efficiency better than 95.5 %. |
| The inverter in the DVR can boost & buck the line voltage by 20-30% of the mains voltage to provide a constant voltage to the connected load. The DVR is having excellent dynamics with a correction speed of less 1 millisecond which is far superior to a servo stabilizer. |
BENEFITS OF DVR |
| Reducers losses from process shut down and product degradation, Protects expensive and sensitive production equipment from voltage anomalies, Minimizes the potentials for production shut downs due to faults elsewhere on the distribution systems including those caused by the lightning strikes. |
UPQC is a total of STATCOM and DVR |
Equivalent circuit of UPQC [ 4 ] |
Simulink model of UPQC |
FUNCTION |
| Load Voltage Regulation by series Voltage Injection. & Dynamic Current injection for reactive power compensation . UPQC issued to compensate voltage and current harmonics, control input power factor to near unity as well as regulate the load voltage. It can be installed by the electric utilities to damp out harmonic propagation caused by resonance with line impedance and passive shunt compensators.Power Factor correction system ensures optimum power for the running loads, thereby: a) Avoidance of Power Factor penalty b) Reduction in Maximum Demand (KVA) c) Reduction in Energy (KWH) Consumption d) Claim higher Power Factor Incentives |
DSP BASED CONTROLLERS IN UPQC |
TMS 320 C5X nomenclature |
| • TMX : Experimental device |
| • TMP : Prototype |
| • TMS : Qualified device |
| • C: CMOS Tech with on – chip non- volatile memory as ROM |
| • E: CMOS tech with on-chip non – volatile memory as EPROM |
| • nothing : NMOS tech with on-chip non – volatile mem as ROM |
| • 5 : Generation |
| • X : Version number- 0,1,2,3,4x,5,6,7 |
| F28x denotes all the Flash devices We have gone for an industrial training at Hykon industries pvt ltd in kerala . Below shown is the snap shot of UPQC manufactured there. |
FUTURE SCOPE |
| The economics for the capacity enhancement of UPQC should also be analyzed.the flexibility of UPQC to increase its capacity in future and to cope up with the increase load demand in low voltage distribution level has not been achieved.simulations to be carried out by the PSCAD®/ EMTDC™ - ElectroMagnetic Transients including DC |
CONCLUSION |
| The effects of power quality problems on the loads and other components depend on the type of components and the type of quality problems. The sensitivity of loads to power quality is variable even with a specific category of loads. This paper mention UPQC and simulation model using simulink has been carried out. Detail on TMS 320 C5X DSP processors has been carried out successfully. |
References |
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