Frequency Conversion Improvement of Condensate Pump of 300MW Unit Hao Mei, Kang Xinping (Shanxi Sunshine Power Co., Ltd., Pingding 045200, Shanxi, China) Application of the operation mode, energy saving effect and social benefits of condensate pumps after conversion to frequency conversion With the rapid development of electric power and electronic technology, and the increasing importance of energy conservation and consumption reduction by enterprises, the frequency conversion control technology has basically matured. In many thermal power plants, a surge of frequency conversion reforms has emerged. Some thermal power units have been installed with frequency conversion devices. Conversion of large auxiliary equipment such as condensate pumps and blower induced draft fans In October 2003, Sunny Power Co., Ltd. successfully completed the frequency conversion transformation of No. 1 unit A condensate pump and achieved good results. 1 Condition before the transformation Sunlight Power Limited Liability The total installed capacity of the company is 4 Condensate system diagram The pressure of the desuperheating water supply to the shaft seal during low load operation is relatively high, resulting in a low control range of the low temperature cylinder shaft seal temperature adjustment door opening, resulting in a large fluctuation in the temperature of the low pressure cylinder shaft seal. Oxygen water level adjustment in the low load section of the unit adopts single impulse adjustment at high load The use of three impulses (water flow, condensate flow deaerator water level) adjustment, can not adapt to the changing operating conditions of the unit, the adjustment quality can not meet the operational requirements of the condensate recirculation valve control for the follow-up system, according to the main condensate The opening of the regulating valve and the pressure of the outlet of the condensate pump are adjusted to ensure the safe operation of the condensate pump in the work and the capacity of the deaerator to feed water.
Adjusting the throttling mode of operation by adjusting the condensate water not only wastes a lot of electric energy, but also increases the maintenance cost and the workload of the personnel.
In order to reduce the unit consumption of the condensate pump and reduce the cost of power generation, it is necessary to carry out technological transformation of the condensate pump. Use the frequency conversion condensate pump to adjust the water level configuration diagram of the deaerator. Table 1 Comparison of the data of the unit under the typical operating conditions Condensate pumping out of the main condensate main condensation Condensate pump number load speed port pressure control valve opening degree of water flow current / MW/rpm/MPa/%/tDh-1/A11809471.0490.449125.9522010741. 3 problem solution 3.1 transformation mode using frequency conversion technology to reduce the speed of the condensate pump, Changing the QH characteristic curve of the condensate pump, the pressure is reduced when the flow of the condensate pump is constant, so that the main condensate control valve C22-1 is basically in the fully open position, eliminating the throttling loss of the main condensate control valve.
3.2 Inverter Mode Selection There are many ways to install the condensate pump. If two condensate pumps are all installed with frequency converters, the operating modes are unified and the design control logic is simple, but the cost is high and the area is large. It is more difficult to transform the units that have already been put into operation. The operation mode of the condensate pumps is one operation. 1 In order to reduce the cost of retrofitting, only one of the two condensing pumps, which are mutually standby, is converted to frequency conversion. After transformation, the variable frequency pump can be bypassed after the failure of the frequency conversion device, and switched to the power frequency operation mode. 3.3 System Operation Mode The condensate system operation mode after the transformation: A pump frequency conversion mode operation, deaerator water level through the change of the frequency conversion pump speed control, The main condensate adjustment door C22-1 is in the fully open position, and the condensate recirculation door automatic mode is changed to adjust the condensate pump outlet pressure to prevent the pump outlet pressure from overpressure; under the condition of the A pump inverter device, the bypass switch can be used to switch to work. Frequency operation mode, deaerator water level is automatically adjusted by the main condensate adjustment gate C22-1; A pump standby, B pump operation deaerator water level automatically through the main condensate adjustment gate C22-1 adjustment 3.4 frequency conversion modification logic to modify two sets of condensation The control method of the water pump is different. Therefore, when designing the control logic of the condensate system, the two main control valves of the main condensate water valve C22-1 and the variable frequency speed condensate pump must be taken into consideration. The next two rapid adjustment of the adjustment method, and secondly, how to reduce the impact on the deaerator and the condensate pipe in the dynamic process of switching, ensure the design Prepare and operate the system safely.
3.5 Intermittent Control In order to improve the adjustment quality of the deaerator water level, condenser water level automatic adjustment system, and improve the control level of the condensate water system, we grafted on the latest research results of the control valve in the field—discontinuous control theory. In the control scheme of the frequency conversion condensate pump, this is the first time in the deaerator water level adjustment system that the control scheme introduces some advanced control ideas (incomplete static estimation), the main idea is to convert the frequency conversion condensate pump speed signal Introduced into the control system, balanced with the water level deviation to ensure the relative stability of the water level (control in a certain range), and to introduce the main steam flow signal of the unit to improve the system's load adaptability and to compensate the frequency conversion condensation pump speed signal signal! During the process of changing the partial load and during the process of spontaneous disturbance of the water level, the speed signal of the frequency conversion condensate pump is balanced with the above-mentioned disturbance variation, and the system is in a waiting state to adapt to the lag and various uncertainties of the thermal system. Factors (see) 4 Comparison of economic effects after retrofit In order to determine the economics of condensate pump conversion to variable frequency control, frequency conversion regulation power consumption test of Unit 1 Condensate Pump under a load of 300MW~150MW is used to calculate the electrical power using a carousel dial Obtained, the condensate flow, pressure, speed and other main parameters using the running meter from the data in Table 1 shows that the use of variable speed adjustment can greatly reduce the power consumption of the condenser pump, especially the low load is more obvious (power savings of 631.5kW at 150MW Saving power consumption is 470.7kW at 300MW. After the condensate pump adopts variable frequency regulation, the average load rate of 68.09% (204.27MW) of power production plan in 2003 is 7047h, the annual energy saving is 4306.4217MWh, and the on-grid electricity price is calculated at 0.32 yuan. Saving RMB 13.78 million, by calculating the single plant power consumption rate can be reduced by 0.3%. 5 conclusions only in the unit negative, 1.1 running Throttling loss, condensate pump current drop, play an energy-saving role, the condensate pump is equipped with a frequency conversion device, and the condensate pump is transformed from the original constant speed operation to the variable frequency stepless operation pump, on the one hand, the condensate pump is reduced on the other hand. The drop in outlet water pressure has greatly improved the working conditions of low-pressure heaters, reduced the leakage of low-pressure heaters, reduced the amount of maintenance work, and achieved relatively clear safety and economic effects. After the minor repair of Unit 1, after the trial run under different load conditions, the deaerator water level adopts an intermittent control scheme, and the frequency conversion control of the condensate pump has achieved good results, effectively solving the lag of the condensate system. , coupling with each other seriously control the problem of uncertainty in the characteristics of the object (continued from page 33). The line method and the two-point method calculate the heat transfer signal and the main steam pressure. The transfer function corresponding to the amount of fuel needs to be repeated several times to complete the test. The unit heat signal changes through an inertial link of 1/(1+15S). The main steam pressure changes through the second-order inertia link. 3.3 Coordinated controller parameters are set. The fuel master sub-adjusts the proportional coefficient. The static gain of the sum of the 16 average rotational speeds is determined, and the number of automatic operations for the layer operations is different, and the proportional coefficients are also different. Variable gain control is used. The secondary tuning integration time is 30s. The fuel master scaling factor is determined based on the sum of the 16 average speeds and the static gain of the heat signal. The main integration time is 30s3.4. Feedforward setting In the coordinated control mode, the load is raised and lowered at a certain rate, and the differential feedforward and load command feedforward of the energy command are adjusted to observe the main steam pressure curve to fit the main steam pressure target as far as possible. Value, the test principle is to ensure that the dynamic process is matched to ensure the stability of the static energy instruction. Differential feedforward is (8/PTKPX 27.6) X Load instruction Feedforward The upper and lower limit of the saturation link can control the feedforward strength, differential link The differential time is 3.5 system commissioning methods. The coordinated control system includes manual, machine following, furnace following, and coordination 4 ways. The main control output of the turbine control system controls the total valve signal in the DEH, ie the ESC is used as When an implementing agency controls and puts into coordination, it needs to first request “CCS, ESC to remotely control the CCS, and ESC to get out of the power regulation loop. The follow-up mode of the turbine main control controller is only used when the boiler is in manual or RB condition. The follow-up method is generally not used frequently, because the coordinated control system of Unit 9 of Taiyuan No. 2 Thermal Power Plant adopts boiler following as the basis, adding the energy balance letter No. 1 direct energy balance coordination control scheme, so under the normal circumstances of the unit directly into the coordinated control mode 4 summed up the characteristics of this type of unit combined with the original design ideas, from the program design and adjustment, the test took some effective measures and methods Therefore, the coordinated control system of Unit 9 of Taiyuan No. 2 Thermal Power Plant has achieved good results.
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