Nancal 6kV/7.2KV 8000KW MV AC drives used as starter of large gas turbine generator

Input voltage: 6kV
Output voltage: 7.2kV
Rated capacity: 8000kW
Function: Soft start & Soft stop


Gas turbine generator has the characteristics of compact structure, small size, advanced design concept and so on. As an efficient and environmentally friendly power generation device, it is developing vigorously in the world in recent years. When the system starts at rest, the starter rotates with it. When it is accelerated enough to run independently, the starter disconnects, and the subsequent rotational energy comes from the burning hot gas. Medium voltage AC drive is adopted as the starting equipment of gas turbine, which requires high performance, including meeting various operating conditions of gas turbine starting, running at low speed, no limit of starting times, and adaptive load parameters.
The NC HVVF series medium voltage AC drives developed by Shanghai Nancal Electric co., ltd. has accumulated years of practical application experience. It adopts high-performance speed sensorless vector control algorithm, with high control accuracy and reliable operation, and can drive asynchronous motor, synchronous motor (generator) and permanent magnet motor.
This article mainly introduces the application of NC HVVF series medium voltage AC drives in a gas turbine soft starting project in Shenyang. The frequency converter adopts 1 drive 1 solution. The model is NC HVVF 6/7.2-8000.
2-On site situation
In this project, the HVVF drives accelerate the gas turbine to the self-sustaining speed or slightly higher than the self-sustaining speed within the specified time. In addition to being used as a starter, it also serves as a driving device for the cold running of the gas turbine & cleaning of the compressor.
 Shanghai Nancal Electric Co., Ltd. provides a reliable solution. On the basis of the conventional MV VFD scheme, the optimal configuration is not only to meet the commissioning start function of the gas turbine plant (in the gas turbine plant commissioning process, by driving the asynchronous motor to start the gas turbine), but also to meet the gas turbine power plant startup function, and drive the power generation. Machine, start the gas turbine. The primary system diagram is as follows:

Figure 1: System diagram


The project is equipped with an asynchronous motor of 5000kW-6kV used for testing in the factory and a generator load of 177MVA-15.75kV. The grid voltage is 6kV. The VFD is equipped with power of 8000kW and output voltage of 7.2kV, mainly including pre-charging cabinet, transformer cabinet, power cell cabinet, control cabinet, output reactor cabinet etc.

Figure 2: Starting system of gas turbine generator

The main functions of NANCAL HVVF drives in this project:
• Gas turbine commissioning start function, starting gas turbine by driving asynchronous motor during commissioning in gas turbine plant
• Gas turbine start function in power plant, starting the gas turbine by driving the generator
• During the startup in power plant, the excitation device is controlled by the output excitation current setting value to complete the start and speed control of the generator.
• During the start-up process of the power plant, the generator output side step-up transformer and the factory transformer can be disconnected, and the converter can be equipped with a transformer to complete the start and speed regulation of the generator.
• Configure the touch screen to implement system parameter setting, monitoring operation, status display, data storage and query functions.


The application of NC HVVF series medium voltage AC drives in the gas turbine generator soft starting project in Shenyang has various advantages, which not only provides sufficient power for the start of the gas turbine, but also ensures the smooth operation of the start-up process, reduces the impact on the generator, and prolongs the use. The life, at the same time, the dynamic adjustable performance and the precise control advantages of the frequency converter also meet the requirements of various working conditions when the gas turbine is started, which ensures the normal starting of the gas turbine, optimizes the running process, improves the starting efficiency, and further promotes The development level of gas turbines.