Zhongdian Xiaodu Tianjin Zhongdian Boyuan Technology Co., Ltd. http://
Abstract: The rotor variable frequency speed control system is a relatively advanced speed control system used in the field of energy saving and speed regulation of high voltage and large capacity asynchronous motors. This article describes the technical and economic analysis of the condensate pump application rotor frequency control system.
Key words: Rotary frequency conversion speed control Condensate pump energy-saving speed control Foreword: The fan and the water pump have applied in the various departments of national economy numerous, the distribution area is extremely wide, the power consumption is enormous. According to the statistics of related departments, the total installed capacity of fans and pumps in the country is about 35,000 MW, and the power consumption accounts for about 40% of the total electricity consumption in the country. At present, there are still great potentials for energy conservation in the operation of fans and pumps. The potential for excavation is to improve the operational efficiency of fans and pumps. It is estimated that the energy-saving potential for improving the operational efficiency of wind turbines and water pump systems can reach 300-500 million kW•h/year, which is equivalent to the total annual power generation of 6 to 10 large-scale thermal power plants with installed capacity of 1,000 MW.
Usti Power Generation Co., Ltd. is located in Wuhai City, Inner Mongolia. Fans and pumps are the most important power-consuming equipment in our plant. These equipments are continuously operated for a long period of time and are often under low-load and variable-load operation. The potential for energy saving is huge. . The economic operation of the auxiliary motor of a power plant is directly related to the utilization rate of the plant. With the continuous deepening of the reform of the power industry, the gradual implementation of the separation of factories and networks, and the bidding for access to the Internet, the reduction of the electricity consumption rate of the plant, the reduction of the cost of power generation and the improvement of the competitiveness of electricity prices have become the economic goals pursued by various power plants.
Usti Power Generation Co., Ltd. has applied a number of rotor variable frequency speed control systems. After a long period of practical operation, product reliability and performance have been tested, and significant energy saving and economic benefits have been received.
First, the principle and technical characteristics of the rotor frequency control system
1) The principle of rotor frequency conversion speed regulation system SAVER series rotor frequency conversion speed control system is based on the theory of traditional cascade speed regulation of Hebei Taida Energy Saving Equipment Technology Co., Ltd., and contemporary advanced power electronic technology, AC speed regulation technology, and computer control technology. The latest results of development. Its unique technology of controlling the stator with a rotor, controlling a high voltage with a low voltage, and controlling the total power with a partial slip power makes it unique in many wind turbines and water pumps with high-voltage, medium- and high-power motors, and has other speed adjustment solutions. Irreplaceable superiority. The rotor block diagram of the variable frequency speed control system is shown below.
Rotor frequency conversion speed control system block diagram
SAVER series rotor variable frequency speed control system is an energy-saving speed control method that changes the motor speed by changing the size of the rotor circuit in series with the equivalent potential, and feedbacks the rotor slip power back to the motor power supply. The inner feedback winding and the inverter with a fixed inverter angle form a fixed potential source to absorb the slip power. The IGBT chopper is controlled by a PWM signal to form a variable rotor circuit equivalent potential.
2) SAVER series rotor frequency conversion speed control system is composed of high voltage switch cabinet, internal feedback speed control motor, rotor variable frequency speed control device and remote control system. The rotor variable frequency speed control device consists of a starter cabinet and a frequency converter cabinet.
The rotor frequency conversion speed regulating device is mainly composed of the following parts: The internal description of the starter cabinet The interior of the starter cabinet mainly includes the starter, rectifier (ZP1-6), control, operation part and display.
The starting device mainly includes frequency sensitive rheostat (PBR) and vacuum contactor (KM1-3). Large motors, especially wire-wound motors, cause a large impact on the power grid when the motor is started, resulting in a large starting current. In order to reduce the starting current and enable the motor to start smoothly, an automatic switching starter is added to the speed controller. When the motor is started, KM1 is closed, KM2 is opened, and the motor rotor is connected in series with the frequency sensitive rheostat PBR. The resistance of the frequency sensitive rheostat is proportional to the frequency of the current flowing through it. When the motor is started, the speed of the motor is zero and the frequency of the rotor current is the highest, which is the frequency of the power frequency. At this time, the resistance of the frequency sensitive rheostat is also high, thus limiting the Starting current. As the motor speed increases, the rotor current frequency gradually decreases, and the frequency sensitive rheostat resistance gradually decreases. When the motor speed reaches the set value, the device automatically closes KM2, removes the frequency sensitive rheostat, and the motor enters the full speed working state or the speed regulation working state (according to the touch screen setting), and completes the starting process.
Rectifier The rectifier unit is a three-phase bridge rectifier that converts the rotor current into a direct current.
Inverter Inverter is a three-phase full-bridge active inverter. When the device operates in the speed regulation state, the chopper-controlled slip power is inverted to the internal feedback winding or the inverter transformer. The inverter trigger angle is the minimum fixed value, which overcomes the shortcomings of phase shift triggering such as strict requirements on trigger pulse and commutation, large pulse movement range, poor anti-interference ability, easy subversion, and low power factor.
Control, operation part and display Mainly includes touch screen, ordinary button, display instrument, programmable controller, miniature circuit breaker, power supply, key switch and external terminal block. The starter cabinet has two operations, a display section, which is not a touch screen and an ordinary button and a display meter section. Both operations are independent of each other. The touch screen can perform logic switching, speeds up and down, system settings and other operations (see Chapter 5 for details). The internal normal button can be switched logically. The display meter can display primary current, rotor voltage (DC), rotor current (DC), rotation speed, feedback voltage, and feedback current. The programmable controller is used for automatic control. The miniature circuit breaker is divided into three-phase AC and DC, and it supplies power to the power supply at the same time. The key switch controls all the control power in the cabinet, including DC and AC power. It is strictly prohibited to disconnect during operation.
The internal description of the frequency conversion cabinet The frequency conversion cabinet mainly includes a chopper, a driver board, and a control board.
When the circuit is working, the inverter's inverter angle is constant at the minimum βmin, and the rotor circuit's additional potential adjustment is accomplished by the chopper switch. The chopper switch works in a constant-frequency widening mode, that is, the operating frequency is constant, and the switch-on time is adjustable. In this way, by adjusting the ratio of the on time and the chopping cycle of the chopping switch (ie, duty cycle or PWM modulation pulse width), the magnitude of the equivalent potential of the series-into-rotor circuit is changed to change the rotor current to achieve the adjustment of the motor. The purpose of the speed.
3) Main features of SAVER series variable frequency speed control system 平滑 Smooth stepless speed control performance: Smooth stepless speed regulation within the speed range.
调速 High efficiency of speed regulation: As the speed control device only controls part of the capacity of the motor, its loss is smaller, the speed regulation efficiency is higher, and the power saving effect is better.
良好 Good start performance: With the frequency sensitive rheostat starting method, the starting torque is large, the starting current is small, the starting is rapid, and the whole starting process is switched automatically.
çµæ´» Flexible and convenient speed control mode: It can realize conversion between speed control and full speed operation, open loop operation and closed loop operation conversion (or manual operation and automatic operation conversion), and local control and remote control conversion. Can be easily connected to a DCS system or other computer network.
充分 Sufficient overload capacity: The maximum torque multiple of the motor is not less than 1.8 times that of the national standard.
ç†æƒ³ Ideal static accuracy: The static accuracy of the rotor variable frequency speed control system is ≥99.8%, which fully meets the requirements of fan and pump load.
ç†æƒ³ Ideal dynamic accuracy: Double closed-loop control of the speed and current, which not only ensures the dynamic accuracy of the speed but also effectively suppresses the overload current.
完善 Perfect protection measures: In addition to conventional overvoltage, overcurrent and other protection measures, when the system fails, the system's fault detection device can turn the motor into the user's optional full-speed operation or stop, and provide text or light alarms.
 The main chopper circuit uses a large power device IGBT system that can be turned off automatically, which is simpler and more reliable.
æ•£çƒ The heat dissipation of all power electronic power devices adopts the combination of heat pipe heat dissipation and forced air cooling, resulting in better heat dissipation and more reliable systems.
 The electronic circuit adopts microcomputer control and phase-locked loop pulse control, which has a high degree of automation and strong anti-interference ability.
å¤šé‡ Multiple isolation and anti-jamming design, the device has strong anti-interference ability.
高 High reliability working power supply with AC and DC dual power supply.
4) Main performance index of SAVER series rotor frequency conversion speed control system Rated motor voltage: 3KV, 6KV, 10KV
ï¬ Rated motor power: 200～5600KW
ï¬ Speed ​​range: Normal (50～98)%ne +100%ne
ï¬ Motor pole number: 4～24 poles ï¬ Rated frequency: 50HZ±2%
ï¬ Average speed regulation efficiency: η>98.9%
Rated power factor: >0.85
ï¬ Rated DC current: 315-3000A
ï¬ Rated DC voltage: 125～2500V
ï¬ Starting current: 2.5 to 3 times rated current ï¬ Harmonic content: ≤3%
ï¬ Overload capacity: 1.8 times rated load ï¬ Speed ​​regulation accuracy: ≥99.8%
Second, the application situation USI too power limited liability company 2X300MW unit project four condensate pump motor uses a rotor frequency conversion speed control system, put into operation on March 23, 2007, to April 30, 2005, Ushita power generation The limited liability company conducted tracking and monitoring of the system and conducted some key tests on some of the data.
The following are the test data for the #1 condensate pump motor and #1 condensate pump for the 2X300MW unit of Usti Power Generation Co., Ltd.
(1) 1# Condensate Pump Motor Motor Specifications Motor Model: YRLKKNT560-4 Voltage: 6.3KV Rated Current: 135A
Power: 1250KW Rated Speed: 900-1488 RPM (b) Test Results
(III) Analysis of test results
1) Full speed status:
At full speed, it passes inspection: the vibration of the motor is 16.3um, which conforms to the national standard; the motor temperature is between 44-56°C, within the normal range.
2) Speed ​​regulation status:
1. Electricity Saving Rate Table 4 Electricity Saving Rate Statistics
2. Speed ​​adjustment range and accuracy Speed ​​measurement: 984r/min to 1450 r/min is measured under speed regulation. Since the system load is a centrifugal pump, when the speed is less than 984 r/min, the pump cannot work normally. Failed to perform lower speed test.
Speed ​​control static accuracy up to 1 turn (99%).
3, speed state motor speed and the relationship between the motor and the pump vibration Motor vibration in line with national standards, and can be seen that the motor vibration, with the decrease in speed decreases.
4, speed and duty cycle It can be seen that the speed decreases with the reduction of the duty cycle, and basically a linear change.
5, the motor temperature and speed and duty cycle can be seen, the motor temperature decreases as the speed decreases.
Third, the conclusion
1. The rotor frequency conversion speed control system has reliable operation and obvious energy-saving effect, and has achieved the project implementation objective.
2. Energy-saving rate: The energy-saving rate increases with the decrease of the rotation speed. The lower the rotation speed, the more obvious the energy-saving effect.
3, speed stability and continuity:
The motor adopts a frequency sensitive rheostat to start the system, and the starting current is small, and the impact of the motor starting is small. When the motor is switched from full speed to speed, the motor speed is smoothly reduced from the maximum speed to the set speed, and the motor speed change is continuous and stable. At the same time, the temperature rise of the speed control system is not high and the operation is stable and reliable.
4, motor vibration and temperature rise motor vibration between 16-12.3um, in line with national standards, and can be seen that motor vibration, with the decrease in speed (see Table 2); motor temperature between 64-68 °C, in Within the normal range. This shows that the motor is stable and reliable.
IV. Concluding remarks Since the rotor frequency conversion speed control system has been successfully put into production in our factory, the operation has been relatively stable and reliable, and the energy saving effect is very obvious. Practice has proved that the system has high speed regulation efficiency, simple equipment structure, and short investment recovery period. It is indeed a good method of speed control, with strong practicality and economy.