Description
hardware flow control. It is an ideal choice in the field of industrial automation.
Guoxin Yangdian ABB excitation regulator technology upgrade
1 Overview
The 2×630Mw coal-fired units (units #3 and #4) of Jiangsu Guoxin Yangzhou Power Generation Co., Ltd. were put into commercial
operation in September 2006 and January 2007 respectively. The generator excitation system is a complete set of excitation
system equipment imported from Switzerland provided by Shanghai ABB Engineering Co., Ltd. The supporting excitation system is
ABBUnitrol5000
. For more than 10 years of operation, jumper Hall elements have been disturbed and tripped, and ARCnet communication
faults have tripped. and other problems, and as the use time increases, the failure rate increases significantly,
and the stability of the excitation system gradually
decreases. According to the needs of unit capacity increase, efficiency improvement and upgrading, the company has
simultaneously upgraded the excitation system, upgraded the original Unitrol5000 to the latest Unitrol6800 system, and also
adjusted the original components
such as resistance-capacitance absorbers and jumpers. Make sure the parameters match.
2 Advantages of the modified excitation system
2.1 The reliability of the three-channel input power supply redundancy mode in the control part is improved
The power supply of the control part adopts three input power supplies with AC or DC redundancy mode, thus
improving the reliability of the system. Each control module is equipped with two independent power supplies for power supply,
which significantly improves the redundancy of the power supply. In this way, the power supply of the control module can be disconnected separately to
facilitate online replacement of faulty components. Secondly, since the boards are installed independently and each board is
powered by dual power supplies, the power supply has an independent switch, making online maintenance work safer.
2.2 Fiber optic redundant internal communications
Unitrol6800 uses optical fiber redundancy for internal communication, which avoids the problem of downtime caused by
ARCnet serial communication in the Unitrol5000 system. The controller can independently transmit the trigger pulse of the
thyristor to the rectifier bridge. In conjunction with optical fiber transmission, the trigger pulse can be generated in each rectifier bridge, making the
internal communication more resistant to interference.
2.3 Eliminate the security risks brought by the public PSl board in the original system to the system
Unitrol6800 uses a rectifier cabinet to separately collect the synchronization voltage, excitation voltage and excitation current,
which reduces the safety hazards caused by the public PsI board. In the rectifier bridge of Unitrol6800, the AC side phase sequence
detection function is added. The fan power supply uses the independent power distribution method of each rectifier cabinet. The fan power supply
loop control system of all rectifier cabinets is inside the rectifier cabinet, ensuring that each rectifier cabinet is It can independently
control the fan in the cabinet, thereby solving the problem of power loss in the fan circuit of Unitrol5000 due to relay failure and avoiding non-stop
accidents.
In the rectifier bridge of the Unitrol5000 system, a Hall element is installed on the rectifier side to measure the excitation current
of the rectifier bridge. The current sharing of the excitation current by the system must be carried out through a current sharing test.
However, the characteristics of the Hall element itself prevent it from being based on the load. changes in dynamic current sharing. To this end,
in the Unitrol6800 system, a CT is installed on the AC incoming line side of the rectifier cabinet to sample and calculate the
excitation current. The linearity of the CT is very high, which ensures that the excitation system can perform dynamic current sharing according to the
load changes of the working conditions, allowing Each rectifier cabinet of the system can be more balanced.
In the rotor overvoltage protection of the Unitrol6800 system, a current relay is used to detect the current. Since the anti-interference
ability of the current relay is stronger than the Hall element of the Unitrol5000, it can avoid false alarms of the rotor
overvoltage in the excitation system caused by external interference and avoid power generation. The occurrence of unit non-stop accidents.
3 Renovation Plan
The steam turbine generator unit has been modified to increase capacity and improve efficiency. The rated output of the steam
turbine unit has been increased from 630Mw to 650Mw, the self-set rated current of the generator has been increased from
17495A to 19245A, and the rated voltage of the excitation rotor
has also been increased from 400.1V to 428V. The excitation current increases from 4387.4A to 4697A. In this transformation
, the cabinet structure of the excitation system remains unchanged. The system upgrade is achieved by upgrading boards, updating equipment and
upgrading the control system. During the transformation process, it is necessary to ensure that the generator capacity is
increased, and the excitation system needs to provide more excitation current and voltage to ensure the stable operation of the unit by increasing the
deexcitation capacity.
3.1 Adjustment of demagnetization and AC side voltage absorption module
Since the generator is upgraded from 630Mw to 650Mw, the demagnetization and AC side overvoltage
absorption modules need to be adjusted. For the adjustment of the capacity of the excitation de-excitation
resistor, the capacity calculation of the de-excitation resistor needs to be calculated based on the most serious
de-excitation state of the generator. The demagnetizing resistor is a siC nonlinear resistor
. The number of resistors is changed from 5 to 6. The capacity of the demagnetizing resistor is 6MJ, which
meets the needs of the excitation system for demagnetizing. In the modification of the demagnetization circuit
jumper, the voltage resistance level of the thyristor was improved by replacing the jumper and BoD board. Regarding
the transformation of the overvoltage absorption module on the AC side of the rectifier bridge, according to the design
of the rectifier bridge of the ABB excitation system, the overvoltage absorption modules on the AC side of the rectifier bridge were changed to five groups in parallel.
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