Basic information of users
The key domestic sewage treatment of a wastewater treatment company, the switching power supply part of the wastewater treatment line uses DC variable frequency drive motors, with 1000KVA2, 630KVA transformers. The power supply system diagram is as follows:
Actual operating data
The output power of the 1000KVA transformer soft starter is 860KVA, the average power factor is PF=0.83, the working current is 1250A, the working current is 630KVA, the power factor is PF=0.87, and the working current is 770A. So the total power factor can only be 0.84.
Power System Situation Analysis
The main load of the converter ballast is 6 single-pulse ballasts. The ballast equipment produces a large amount of pulse current in the work of converting AC to DC. It is a typical pulse current source and is input into the power grid. Harmonic currents cause pulsed current working voltage to the characteristic impedance of the power grid, resulting in frame loss of working voltage and current, endangering the quality and operation safety of switching power supplies, increasing line loss and working voltage deviation, and causing negative effects on the power grid and power plants themselves Influence.
The program controller computer interface (PLC) is sensitive to the harmonic distortion of the working voltage of the switching power supply. It is generally stipulated that the total pulse current working voltage frame loss (THD) is less than 5%, and the individual pulse current working voltage If the frame rate is too high, the operation error of the control system may lead to the interruption of production or operation, resulting in a large production liability accident. Therefore, a low-voltage reactive power compensation filter with a pulse current suppression function should be used to suppress the pulse current of the system, compensate the reactive load, and improve the power factor.
Filter reactive power compensation treatment plan
Governance goals
The design of filter compensation equipment meets the requirements of harmonic suppression and reactive power suppression management.
Under the 0.4KV system operating mode, after the filter compensation equipment is put into operation, the pulse current is suppressed, and the monthly average power factor is around 0.92.
High-order harmonic resonance, resonance overvoltage, and overcurrent caused by connecting to the filter compensation branch circuit will not occur.
Design Follows Standards
Power quality Public grid harmonics GB/T14519-1993
Power quality Voltage fluctuation and flicker GB12326-2000
General technical conditions of low-voltage reactive power compensation device GB/T 15576-1995
Low-voltage reactive power compensation device JB/T 7115-1993
Reactive power compensation technical conditions JB/T9663-1999 “Low-voltage reactive power automatic compensation controller” from the high-order harmonic current limit value of low-voltage power and electronic equipment GB/T17625.7-1998
Electrotechnical terms Power capacitors GB/T 2900.16-1996
Low voltage shunt capacitor GB/T 3983.1-1989
Reactor GB10229-88
Reactor IEC 289-88
Low-voltage reactive power compensation controller order technical conditions DL/T597-1996
Low-voltage electrical enclosure protection grade GB5013.1-1997
Low-voltage complete switchgear and control equipment GB7251.1-1997
Design ideas
According to the specific situation of the company, a set of reactive power compensation plan for the inverter power filter that fully considers the load power factor and pulse current suppression is designed, and a set of filter low voltage is installed on the 0.4kV bottom voltage side of the company’s transformer Reactive power compensation to suppress pulse current, compensate reactive load, and improve power factor.
The ballast generates 6K-1 order pulse current during the operation of the converter, and uses the leaf code sequence around 5250Hz and 7350Hz to carry out the dissolution conversion. Therefore, the reactive power compensation design of the intermediate frequency induction furnace filter should take 250Hz, 350Hz and the frequency design as the target, so as to ensure that the compensation branch of the filter can effectively suppress the pulse current compensation, and at the same time suppress the reactive load and improve the Power Factor.
design assignment
The comprehensive power factor of the 1000KVA transformer production line is compensated from 0.8 to about 0.95. The filter compensation equipment needs to be installed with a volume of 380KVar, which is divided into four groups, each of which is automatically closed and disconnected, compensates for the winding resistance of the bottom voltage side of the transformer, and has a step adjustment volume of 45KVAR, which can be integrated into the output power requirements of the production line. The comprehensive power factor is compensated from 0.8 to 0.95. The filter compensation equipment needs to be installed with a volume of 310KVar, and four groups are automatically disconnected to compensate the low-side winding of the transformer, and the volume is adjusted to 26KVAR to meet the working voltage requirements of the production line.
Effect analysis after installation of filter compensation
In August 2010, the inverter filtering reactive power compensation device was installed and put into operation. The device automatically tracks the load change of the inverter, suppresses high-order harmonics in real time, compensates reactive power, and improves the power factor. details as following:
After the filter compensation device is put into use, the power factor change curve after the filter compensation device is put into use is about 0.97 (the raised part is about 0.8 when the filter compensation device is removed)
Load operation
The current used by the 1000KVA transformer is reduced from 1250A to 1060A, a drop of 15%; the current used by a 630KVA transformer is reduced from 770A to 620A, a drop of 19%. After compensation, the power loss reduction value is WT=△Pd*(S1/S2)2*τ*[1-(cosφ1/cosφ2)2]=24×{(0.85×2000)/2000}2×0.4≈16(kw h) In the formula, Pd is the short-circuit loss of the transformer, which is 24KW, and the annual saving of electricity expenses is 16*20*30*10*0.7=67,000 yuan (based on working 20 hours a day, 30 days a month, 10 months a year, 0.7 yuan per kWh).
Load operation
The current used by the 1000KVA transformer is reduced from 1250A to 1060A, a drop of 15%; the current used by a 630KVA transformer is reduced from 770A to 620A, a drop of 19%. After compensation, the power loss reduction value is WT=△Pd*(S1/S2)2*τ*[1-(cosφ1/cosφ2)2]=24×{(0.85×2000)/2000}2×0.4≈16(kw h) In the formula, Pd is the short-circuit loss of the transformer, which is 24KW, and the annual saving of electricity expenses is 16*20*30*10*0.7=67,000 yuan (based on working 20 hours a day, 30 days a month, 10 months a year, 0.7 yuan per kWh).
Post time: Apr-14-2023