The Application Of WIN-HV Inverter In The Thermal Power Plant Of Shandong Linglong Group


The application of WIN-HV inverter in the thermal power plant of Shandong Linglong Group


I Prolegomena

The application of the medium voltage inverter in the large-sized asynchronous motor is just at the initial stage in China, which, however, has been pretty popular in the developed countries. As the development of the electronic components, types of the medium voltage inverter become very diverse. By the topological structure, the medium voltage inverter can be classified as IGBT module serial-connection type, tri-level type and multiple power unit serial-connection type with voltage superposition.

II Introduction of Shandong Linglong Group

Shandong Linglong Group is one of China’s top 3, and the world’s top 20 tyre producers. Besides the tyre industry, it also sets foot in other fields like cement, electronic mechanism and power through its subsidiaries. Its power plant has two generators with an annual production capacity of 15MW respectively and also a 30MW generator. The plant can provide power not only for the company’s normal operation but also to support local living electricity consumption. The two 15MW generators totally have three boilers whose water supply pumps are driven by three high voltage motors (355kW/kV), with one standby for emergency. Previously, the power plant realized constant voltage water supply by the valve, which wasted a lot of power but with poor accuracy. To respond to the government’s call to save energy, Shandong Linglong Group is determined to enhance its production level, and finally selected WIN-HV inverter manufactured by Shenzhen Winner after repeated investigation and comparison. WIN-HV inverter can realize medium voltage input --medium voltage output through serial connection of power units, with perfect input/output waveform, prominent reliability and lower price. Meanwhile, when one power unit has fault, WIN-HV inverter can automatically bypass this unit and continue running with lower frequency. That is a great advantage due to characteristics of pumps and blowers.

WIN-HV inverter main circuit diagram

III reformation blue print

a) Considering that there will be just a little pressure change, Shandong Linglong Group decided to only reconstruct the 2# water supply pump with the inverter.

  • Adopt the mode of one inverter to controll one pump, and no need to add power frequency bypass system
  • Take 4~20mA current of the pressure transmitter from the pumping main as the feedback signal, and obtain the given frequency from the DCS system
  • Run signal and stop signal are given by the DCS system
  • The condition signal of the medium voltage inverter is sent from the control cabinet to the DCS system for the purpose of instantaneous detection
  • The pressure value of the pumping main can reach or overrun the requested 6.8MPa after reconstruction
  • Shut down the by-pass valve of each pump, and the appropriate flux can be produced by adjusting the speed of the motor through the medium voltage inverter

b) Close-loop control

Shut down the by-pass valve of each pump, and realize close-loop control by the inverter’s PID function, and the DCS system will provide the given 4~20mA corresponding to 0~10MP. And the press transformer on the pumping main will feed back the 0~10MP press signal to the inverter, and to control output torque by PID, so as to adjust the water flux.

IV Efficiency

According to the characteristics of the pump, it can be found that the flux varies due to different motor speed. On condition that less water is needed in operation, we can decrease the motor speed through the inverter rather than the valve, thus we can save a lot of electricity. You can see the economic benefits from the following diagram

Item

PowerkW

Power fare RMB

Press at the output ternimal (MPa) 

Average daily power consumption (kW.h)

Average yearly power consumption(kW.h)

Average Power saving (kW.h)

Average yearly saved cost RMB

Before

355

0.52

8.0

7647

2523510

 

 

Current

355

0.52

7.0

5739

1893870

629640

327412.80

From the diagram above, we can find WIN-HV inverter can help Shandong Linglong Group save as much as RMB0.33 million per year.

V Conclusion

In recent years, the Chinese government has been shifting focuses on energy saving and environmental protection, issuing a series of preferential policies to encourage its enterprises to save energy. Chinese enterprises, pretty active to respond to the government’s appeal, are endeavoring to enhance their management level on energy use, reduce production cost and strenghten their competitiveness, which indirectly promotes the expansion of the inverter.