A power balance device and operation method based on mechatronic planetary speed regulation

Abstract

The present invention relates to the field of high-power speed regulation, and specifically to a power balance device and an operation method based on mechatronic planetary speed regulation. The device includes a main motor, a sub-motor, a main drive end gear, a differential planetary mechanism, an A speed regulation end idler gear, an A speed regulation end gear, an A clutch, an A clutch output end gear, an A clutch output end idler gear, an A speed regulation motor, an A frequency converter, an A soft start device, a main motor bypass switch, a B speed regulation end idler gear, a B speed regulation end gear, a B clutch, a B clutch output end gear, a B clutch output end idler gear, a B speed regulation motor, a B frequency converter, a B soft start device, a sub-motor bypass switch, an A speed regulation motor incoming line switch, a B speed regulation motor incoming line switch, a main motor incoming line switch, a sub-motor incoming line switch, and a plant power system. The present invention can be used both in the power balance operation mode and in direct drive, can improve the operation efficiency, and can meet the requirements of all starting and operating conditions of the driven equipment system.

Description

Technical Field

[0001] The present invention relates to the field of high-power speed regulation, and specifically to a power balance device and an operation method based on mechatronic planetary speed regulation, which are applicable to the field of industrial speed regulation drives, such as equipment like boiler feed pumps in power plants, steam-driven compressors in the petrochemical and natural gas industries, etc. It can be used both in the power balance operation mode and for direct drive. Background Art

[0002] Large-capacity thermal power units play a significant role in China's energy supply guarantee. At present and for a quite long period in the future, thermal power remains the ballast of China's power supply. Based on China's energy endowment, to ensure energy security, a number of advanced coal-fired power units will still be built in China. Under the current constraints of the dual-carbon goal, new units should adopt as many advanced technologies as possible to maximize efficiency and reliability.

[0003] Domestic relevant research institutions have studied the efficiency problem of small steam turbines driving auxiliary machines in thermal power plants and proposed solutions. East China Electric Power Design Institute publicly disclosed "Back-pressure small steam turbine-driven feed pump system and method with variable-frequency generator speed regulation" and "Pure condensing small steam turbine-driven feed pump system and method with power-frequency generator speed regulation" in 2013, proposing to control the speed of the small steam turbine by controlling the output of the power-frequency or variable-frequency generator, partially or completely replacing the regulating valve method, so as to control the speed of the feed pump group, and the generator can be used for power generation, thus making full use of the output of the small steam turbine. The opening of the regulating valve of the small steam turbine remains at 70% - 100% for a long time, greatly reducing the throttling loss and improving the operation efficiency of the small steam turbine. The limitations of the above solutions are that the power of the small steam turbine must always be greater than the power of the feed pump to keep the generator in a normal power generation state, and the small steam turbine still needs to be selected according to the "Design Code for Large and Medium-sized Thermal Power Plants" (GB50660 - 2011), and the capacity of the small steam turbine cannot be flexibly selected; the power-frequency generator scheme requires a speed-regulating gearbox, and the speed-regulating gearbox has a hydraulic coupling with a gearbox or a speed-regulating planetary gearbox with a hydraulic torque converter, which can only perform single-direction power transmission. For the former, due to the slip of the hydraulic coupling, the efficiency loss is still very large, and for the latter, it is an imported equipment with a high price; the variable-frequency generator scheme changes the output of the generator by adjusting the excitation system of the variable-frequency generator. On the one hand, the auxiliary system using a synchronous generator with excitation makes the system too complex and the reliability relatively reduced. In addition, the method of controlling the output of the generator through excitation will make the power angle of the synchronous generator work at 90°, at the critical point between the stable and unstable regions, and the control difficulty is very high.

[0004] Datong Coal Mine Group applied for the utility model patents of "An energy-saving boiler feed water pump drive system for thermal power plants" and "An electric motor - small steam turbine variable speed dual drive system" in 2014 and 2018 respectively, which can realize the full-open operation of the small steam turbine valves. However, the limitation of the former is that the selected capacity of the small steam turbine needs to reach about twice the shaft power of the boiler feed water pump, resulting in an overly large selected capacity and being no longer suitable for the current situation. The planetary gear speed regulation device used in the shafting is still the above-mentioned speed regulation planetary gearbox with a hydraulic torque converter, and the boiler feed water pump adopts full-capacity speed regulation, so the selected capacity of the speed regulation equipment is large; the latter involves a wound permanent magnet speed regulation device, and its degree of miniaturization is not enough, making the overall volume of the planetary gear speed regulation device relatively large.

[0005] Datong Coal Mine Group applied for the utility model patents of "An energy-saving induced draft fan drive system for thermal power plants" and "The shafting structure of a steam-electric dual drive for large axial flow fans in utility boilers" in 2014 and 2015 respectively, and implemented the transformation on the 2×660MW units of Shanxi Tonghua Power Generation in 2015, realizing the first case of steam-electric dual drive for induced draft fans in China. This case belongs to a power balance method with a fixed shaft speed and cannot achieve variable speed.

[0006] Lianfeng Energy Technology (Beijing) Co., Ltd. and Yang Derong etc. disclosed "A multi-speed steam-electric dual drive system for axial flow fans" in 2018, which already belongs to the category of power balance with variable shaft speed, but the device is not yet perfect.

[0007] The second phase of the 2×1000MW units of Huaneng Ruijin Power Plant was put into operation at the end of 2021. Its main boiler feed water pump 8 is driven by a extraction condensing steam turbine (hereinafter referred to as: extraction condensing steam turbine 46), as specifically shown in Figure 1 the figure, and a synchronous generator 47 is set to balance the surplus power of the shafting and feed it back to the plant power system, realizing the power balance scheme for the main boiler feed water pump 8 for the first time. The power balance motor uses a synchronous generator 47. Due to the existence of a coaxial exciter 48 and an excitation system, the system is relatively complex, and the critical speed avoidance rate is also relatively insufficient. The motor selection needs to meet both the maximum torque condition and the maximum power condition at the same time, so the selected power is relatively large. The power balance motor is driven by a full-capacity converter (frequency converter), and the selected capacity of the converter is large. The fore pump 34 is decelerated by the main boiler feed water pump 8 through a gearbox 45 and driven by a long shaft 44, running at variable speed, and the shafting is very long.

[0008] Currently, most 1000MW units tend to be configured with 1×100% capacity steam-driven boiler feed water pumps. This is because the reliability levels of the small steam turbines and boiler feed water pumps are already comparable to those of the main engines. The 1×100% capacity configuration is beneficial in terms of both efficiency and cost compared to the 2×50% capacity configuration. However, all 1000MW units are ultra-supercritical once-through boilers. The tripping of a 100% capacity boiler feed water pump will cause the unit to trip, so the 1×100% capacity configuration cannot be adopted in occasions with higher reliability requirements. Summary of the Invention

[0009] The present invention provides a power balance device and an operation method based on mechatronic planetary speed regulation, which are applicable to the field of industrial speed regulation drives, such as equipment like boiler feed pumps in power plants, steam-driven compressors in the petrochemical and natural gas industries, etc. It can be used both in power balance operation modes and for direct drive, can improve the operation efficiency, and meet the requirements of all starting and operating conditions of the driven equipment system. Shanxi Rongsheng Zhida Technology Co., Ltd. has publicly disclosed a utility model patent of "A Mechatronic Planetary Speed Regulation Device with Full Range Speed Regulation". On this basis, the present invention has improved some electrical and mechanical devices and systems, and proposed a power balance device based on mechatronic planetary speed regulation.

[0010] The present invention is implemented by the following technical solutions: A power balance device based on mechatronic planetary speed regulation (hereinafter referred to as: the device), including a main motor, a sub-motor, a main drive end gear, a differential planetary mechanism, an A speed regulation end idler gear, an A speed regulation end gear, an A clutch, an A clutch output end gear, an A clutch output end idler gear, an A speed regulation motor, an A frequency converter, an A soft start device, a main motor bypass switch, a B speed regulation end idler gear, a B speed regulation end gear, a B clutch, a B clutch output end gear, a B clutch output end idler gear, a B speed regulation motor, a B frequency converter, a B soft start device, a sub-motor bypass switch, an A speed regulation motor incoming line switch, a B speed regulation motor incoming line switch, a main motor incoming line switch, a sub-motor incoming line switch and a plant power system. The inner gear ring input shaft of the differential planetary mechanism is connected to the main drive end gear. The main drive end gear is connected to the A clutch output end gear through the A clutch output end idler gear, and the main drive end gear is also connected to the B clutch output end gear through the B clutch output end idler gear. The A clutch output end gear is connected to the output shaft of the A clutch, and the B clutch output end gear is connected to the output shaft of the B clutch. The main motor is connected to the main drive end gear, and the sub-motor is connected to the main motor through a coupling. The sun gear of the differential planetary mechanism is connected to an external device, and the sub-motor is also connected to another external device. The planet carrier of the differential planetary mechanism is connected to the A speed regulation end idler gear. The A speed regulation end idler gear meshes with the A speed regulation end gear, and the A speed regulation end gear is connected to the A speed regulation motor. The A speed regulation end idler gear is connected to the input shaft of the A clutch. The planet carrier of the differential planetary mechanism is also connected to the B speed regulation end idler gear. The B speed regulation end idler gear meshes with the B speed regulation end gear, and the B speed regulation end gear is connected to the B speed regulation motor. The B speed regulation end idler gear is connected to the input shaft of the B clutch. The inverter end of the A frequency converter is connected to the A speed regulation motor, and the rectifier end is connected to the plant power system through an A transformer and the A speed regulation motor incoming line switch. The inverter end of the B frequency converter is connected to the B speed regulation motor, and the rectifier end is connected to the plant power system through a B transformer and the B speed regulation motor incoming line switch. The output end of the A soft start device is connected to the main motor, and the input end is connected to the plant power system through the main motor incoming line switch. One end of the main motor bypass switch is connected to the main motor incoming line switch, and the other end is connected to the main motor. The output end of the B soft start device is connected to the sub-motor, and the input end is connected to the plant power system through the sub-motor incoming line switch. One end of the sub-motor bypass switch is connected to the sub-motor incoming line switch, and the other end is connected to the sub-motor.

[0011] Operating method of the device: When the device is normally started, the A frequency converter drives the A speed-regulating motor for variable-frequency speed-regulating startup, thereby driving the A speed-regulating end gear, A speed-regulating end idle gear and the planet carrier to speed up. The B frequency converter drives the B speed-regulating motor for variable-frequency speed-regulating startup, thereby driving the B speed-regulating end gear, B speed-regulating end idle gear and the planet carrier to speed up. The speed increase of the A speed-regulating end idle gear causes the A clutch to engage and drive the A clutch output end gear, A clutch output end idle gear and the main drive end gear to speed up (at this time, the B clutch does not engage), thereby driving the main motor, auxiliary motor and internal gear ring to speed up. In this way, the sun gear drives the external connection device to speed up. When the outputs of the A frequency converter and B frequency converter reach the reverse maximum frequency, the main motor and auxiliary motor reach the synchronous speed corresponding to the power frequency. At this time, the speed of the external connection device reaches the upper limit of the low-speed range speed regulation speed. Then, the main motor and auxiliary motor are started respectively through the A soft start device and B soft start device (soft grid connection). After reaching the rated voltage, the main motor bypass switch and auxiliary motor bypass switch are closed, and the A soft start device and B soft start device are withdrawn from operation. The main motor and auxiliary motor start to work, and then gradually reduce the output frequencies of the A frequency converter and B frequency converter. As the speeds of the A speed-regulating motor and B speed-regulating motor decrease, the A clutch disengages, and the speed of the sun gear increases, driving the external connection device to continue to speed up and enter the high-speed range speed regulation working condition.

[0012] When the external connection device transfers to normal operation, that is, when shaft power can be input to the device (sun gear), the power flow is reversed. The power input from the main motor and auxiliary motor and the power output from the sun gear are changed to the power input from the sun gear and the power output from the main motor and auxiliary motor.

[0013] When the main motor, auxiliary motor, A speed-regulating motor or A frequency converter, B speed-regulating motor or B frequency converter are partially or completely faulty and power cannot be output externally through the electrical circuit, the B clutch engages, and the differential planetary mechanism becomes a fixed-ratio gearbox, and mechanical power can still be output externally through the main motor and auxiliary motor shaft systems connected by the internal gear ring.

[0014] When both the A speed-regulating motor and B speed-regulating motor lose power, the A clutch engages. At this time, the differential planetary mechanism is a fixed-ratio gearbox, and it is possible to input shaft power from the internal gear ring and output shaft power from the sun gear.

[0015] When both the A speed-regulating motor and B speed-regulating motor lose power, the B clutch engages. At this time, the differential planetary mechanism is a fixed-ratio gearbox, and it is possible to input shaft power from the sun gear and output shaft power from the internal gear ring.

[0016] When both the A speed-regulating motor and B speed-regulating motor lose power, neither the A clutch nor the B clutch engages, and the internal gear ring and the sun gear are in a decoupled state, each being in a free driven state. The main motor or auxiliary motor connected to the internal gear ring drives the external device at the other end at a fixed speed, or the main motor and auxiliary motor jointly drive the external device at the other end at a fixed speed, and the external device connected to the sun gear can operate independently.

[0017] When both the main motor and the auxiliary motor lose power and the power of the input shaft of the sun gear runs with speed change, by adjusting the speed of the speed-regulating motor A or the speed-regulating motor B, the constant-speed output shaft power of the internal gear ring can be achieved, and the variable-speed output shaft power can also be achieved.

[0018] The main motor and the auxiliary motor can be used as spares for each other, and the auxiliary motor can also carry peak load to improve the overall operation efficiency of the equipment.

[0019] In the above solution, the auxiliary motor and the supporting soft start device, the speed-regulating motor B and its supporting B frequency converter can be cancelled. The above solution can be used not only for power balance speed regulation of the shafting, but also for direct speed regulation drive.

[0020] Another solution adopted by the present invention is as follows: A power balance device based on mechatronic planetary speed regulation, comprising a main motor, a main drive end gear, a differential planetary mechanism, an A speed regulation end idler gear, an A speed regulation end gear, an A clutch, an A clutch output end gear, an A clutch output end idler gear, an A speed regulation motor, an A frequency converter, a B speed regulation end idler gear, a B speed regulation end gear, a B clutch, a B clutch output end gear, a B clutch output end idler gear, a B speed regulation motor, a B frequency converter, an A speed regulation motor incoming line switch, an A soft start device, a main motor bypass switch, a B speed regulation motor incoming line switch, a main motor incoming line switch, a plant power system, a step-down power supply, a reactor, a main motor incoming line step-down switch, and a main motor bypass step-down switch. The inner gear ring input shaft of the differential planetary mechanism is connected to the main drive end gear. The main drive end gear is connected to the A clutch output end gear through the A clutch output end idler gear, and the main drive end gear is also connected to the B clutch output end gear through the B clutch output end idler gear. The A clutch output end gear is connected to the output shaft of the A clutch, and the B clutch output end gear is connected to the output shaft of the B clutch. The main motor is connected to the main drive end gear. The sun gear of the differential planetary mechanism is connected to an external device, and the main motor is also connected to another external device. The planet carrier of the differential planetary mechanism is connected to the A speed regulation end idler gear. The A speed regulation end idler gear meshes with the A speed regulation end gear, and the A speed regulation end gear is connected to the A speed regulation motor. The A speed regulation end idler gear is connected to the input shaft of the A clutch. The planet carrier of the differential planetary mechanism is also connected to the B speed regulation end idler gear. The B speed regulation end idler gear meshes with the B speed regulation end gear, and the B speed regulation end gear is connected to the B speed regulation motor. The B speed regulation end idler gear is connected to the input shaft of the B clutch. The inverter end of the A frequency converter is connected to the A speed regulation motor, and the rectifier end is connected to the plant power system through an A transformer and the A speed regulation motor incoming line switch. The inverter end of the B frequency converter is connected to the B speed regulation motor, and the rectifier end is connected to the plant power system through a B transformer and the B speed regulation motor incoming line switch. The output end of the A soft start device is connected to the main motor, and the input end is connected to the step-down power supply through the main motor incoming line step-down switch. One end of the main motor bypass step-down switch is connected to the main motor incoming line step-down switch, and the other end is connected to the main motor. One end of the reactor is connected to the main motor, and the other end is connected to the plant power system through the main motor incoming line switch. One end of the main motor bypass switch is connected to the main motor incoming line switch, and the other end is connected to the main motor.

[0021] For the above-mentioned power balance device based on mechatronic planetary speed regulation, the A speed regulation motor and the B speed regulation motor are respectively driven by the A frequency converter and the B frequency converter in a master-slave control mode.

[0022] For the above-mentioned power balance device based on mechatronic planetary speed regulation, the A transformer and the B transformer can be phase-shifting transformers.

[0023] The above-mentioned power balance device based on mechatronic planetary speed regulation, the idler gear at the output end of the A clutch is a two-stage idler gear at the output end of the A clutch, and the idler gear at the output end of the B clutch is a single-stage idler gear at the output end of the B clutch. Other numbers of stages may be adopted to match the center distance or rotation direction of the gears, and idler gears may be arranged at other positions, but the rotation directions of the gears at the output ends of the two clutches are opposite.

[0024] In the above-mentioned power balance device based on mechatronic planetary speed regulation, when the external equipment connected to the sun gear of the differential planetary mechanism includes a main feed water pump, the main feed water pipe switching system of the main feed water pump is composed of a quick closing feed water valve, a main feed water valve, and a bypass regulating feed water valve in parallel. The sum of the flow capacities of the quick closing feed water valve and the main feed water valve is 100%.

[0025] The beneficial effects of the present invention are as follows:

[0026] 1) The power flow of the power balance device based on mechatronic planetary speed regulation of the present invention can achieve bidirectional flow, that is, power can be input or output to the externally connected equipment through the sun gear, and correspondingly, electric power can be transmitted to the electrical system or taken from the electrical system through the power balance motor connected to the internal gear ring.

[0027] 2) The present invention can achieve that in the case of all electrical equipment failures of the power balance device based on mechatronic planetary speed regulation, the differential planetary mechanism is used as a fixed ratio gearbox.

[0028] 3) The present invention is applied to the steam-driven feed water pump of a power station boiler, and can achieve operating modes of steam drive, electric drive, and combined steam-electric drive, which can improve the efficiency, reliability, and flexibility of the pump set, and is beneficial to energy conservation, emission reduction, and deep peak shaving of thermal power units.

[0029] 4) The present invention is applied to the steam-driven feed water pump of a power station boiler. In the combined steam-electric drive operating mode, the valves of the small steam turbine can be fully opened without regulation, and the regulating stage can be cancelled in the design to further improve the efficiency.

[0030] 5) The present invention is applied to the steam-driven feed water pump of a power station boiler, and the capacity of the small steam turbine can be flexibly selected, and thus the selection can be optimized with the highest unit efficiency as the goal.

[0031] 6) The present invention is applied to the steam-driven feed water pump of a power station boiler. When the small steam turbine of the unit configured with a 1×100% capacity steam pump (especially a once-through boiler unit) trips, the RB function can be realized through the characteristics of the device itself, and the unit does not have to trip, and it can be applied to occasions with higher reliability requirements and configured with a 1×100% capacity steam-driven feed water pump.

[0032] 7) The present invention is applied to the steam-driven feed water pump of a power station boiler. Since it has the starting function in the electric mode, the starting pump in the conventional configuration can be cancelled.

[0033] 8) The present invention is applied to the steam-driven feed water pump of a power station boiler. The power balance motor can be an asynchronous motor, and it is a 4-pole motor. Compared with a 2-pole high-power motor, the 4-pole motor is a rigid rotor, which is more mature, stable and reliable. It has higher efficiency than a multi-pole motor, and its technical economy has more obvious advantages than that of a synchronous motor.

[0034] 9) The present invention is applied to the steam-driven feed water pump of a power station boiler, and most of the balance power can be transmitted by an asynchronous motor operating at a fixed power frequency speed, while a small part is transmitted by a speed-regulating motor. The capacity of the frequency converter can be matched with the speed-regulating motor.

[0035] 10) The present invention is applied to the steam-driven feed water pump of a power station boiler, and the booster pump can be directly driven at a fixed speed by the power balance motor, and there is no need to set up a speed reducer and a long shaft. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the shafting structure of the feed water pump set driven by a extraction-condensing small steam turbine of a 1000MW ultra-supercritical double reheat double-machine regenerative unit based on the existing power balance principle.

[0037] Figure 2 It is Schematic Diagram A of the shafting structure of a power balance device based on mechatronic planetary speed regulation for a steam-driven feed water pump set of a power station boiler.

[0038] Figure 3 It is a schematic diagram of the electrical system of a power balance device based on mechatronic planetary speed regulation.

[0039] Figure 4 It is a schematic diagram of the power flow in the starting condition of a power balance device based on mechatronic planetary speed regulation (electric).

[0040] Figure 5 It is a schematic diagram of the power flow in the operating condition (reverse rotation of the planet carrier) of a power balance device based on mechatronic planetary speed regulation, a for electric, b for power feeding.

[0041] Figure 6 It is a schematic diagram of the power flow in the operating condition (forward rotation of the planet carrier) of a power balance device based on mechatronic planetary speed regulation, a for electric, b for power feeding.

[0042] Figure 7 It is a system diagram of the valve switching of the feed water pipeline of a power balance device based on mechatronic planetary speed regulation for a steam-driven feed water pump set of a power station boiler.

[0043] Figure 8 It is Schematic Diagram B of the shafting structure of a power balance device based on mechatronic planetary speed regulation for a steam-driven feed water pump set of a power station boiler.

[0044] Figure 9 It is a system diagram of the full-voltage / step-down switching of the main motor of a power balance device based on mechatronic planetary speed regulation.

[0045] In the figure: 1 - Main motor, 2 - Coupling A, 3 - Main drive end gear, 4 - Internal gear ring, 5 - Planet carrier, 6 - Sun gear, 7 - Coupling B, 8 - Main feed water pump, 9 - Idler gear at the A speed regulation end, 10 - Gear at the A speed regulation end, 11 - Synchronous automatic clutch A, 12 - Gear at the output end of clutch A, 13 - Two-stage idler gear at the output end of clutch A, 14 - Coupling C, 15 - Speed regulation motor A, 16 - Inverter A, 17 - Inverter B, 18 - Bypass switch of the main motor, 19 - Plant power system, 20 - Incoming line switch of speed regulation motor A, 21 - Incoming line switch of the main motor, 22 - Soft start device A, 23 - Idler gear at the B speed regulation end, 24 - Gear at the B speed regulation end, 25 - Synchronous automatic clutch B, 26 - Gear at the output end of clutch B, 27 - First-stage idler gear at the output end of clutch B, 28 - Coupling D, 29 - Speed regulation motor B, 30 - Auxiliary motor, 31 - Coupling E, 32 - Extraction condensing turbine, 33 - Coupling G, 34 - Booster pump, 35 - Coupling H, 36 - Incoming line switch of speed regulation motor B, 37 - Incoming line switch of the auxiliary motor, 38 - Bypass switch of the auxiliary motor, 39 - Soft start device B, 40 - Synchronous automatic clutch C, 41 - Coupling F, 42 - Coupling I, 43 - Coupling J, 44 - Long shaft, 45 - Gearbox, 46 - Extraction condensing turbine, 47 - Synchronous generator, 48 - Exciter, 49 - Reactor, 50 - Step-down of the incoming line of the main motor, 51 - Step-down switch of the bypass of the main motor, 52 - Step-down power supply, 53 - Quick closing valve for feed water, 54 - Main valve for feed water, 55 - Bypass regulating valve for feed water, 56 - Transformer A, 57 - Transformer B. Specific implementation mode

[0046] Implementation mode of the feed water pump set driven by the extraction condensing turbine of the 1000MW ultra-supercritical double reheat double-machine regenerative unit with the existing power balance principle: It includes the extraction condensing turbine 46, synchronous generator 47, exciter 48, coupling E 31, coupling B 7, main feed water pump 8, coupling G 33, booster pump 34, coupling H 35, coupling I 42, coupling J 43, long shaft 44, gearbox 45, and the above equipment is connected as Figure 1 shown. During the operation of the unit, the valve of the extraction condensing turbine 46 is fully open, and the synchronous generator 47 is driven by a high-power converter to run at a variable speed, so that the main feed water pump 8 connected coaxially runs at a variable speed. The power difference between the extraction condensing turbine 46 and the main feed water pump 8 is borne by the synchronous generator 47, and power exchange is carried out with the plant power system through the high-power converter.

[0047] Embodiment 1: A power balance device based on mechatronic planetary speed regulation, taking the application to the steam-driven feed water pump of a power station boiler as an example, includes a main motor 1 (specifically a main power balance motor), a coupling A 2, a main drive end gear 3, an internal gear ring 4, a planet carrier 5, a sun gear 6, a coupling B 7, a main feed water pump 8, an A speed regulation end idler gear 9, an A speed regulation end gear 10, an A clutch 11 (specifically an A synchronous automatic clutch), an A clutch output end gear 12, an A clutch output end two-stage idler gear 13, a coupling C 14, an A speed regulation motor 15, a B speed regulation end idler gear 23, a B speed regulation end gear 24, a B clutch 25 (specifically a B synchronous automatic clutch), a B clutch output end gear 26, a B clutch output end first-stage idler gear 27, a coupling D 28, a B speed regulation motor 29, a sub-motor 30 (specifically a sub power balance motor), a coupling E 31, a small steam turbine 32, a coupling F 33, a booster pump 34, a coupling G 35, and the connection mode is as Figure 2 shown. Among them, the internal gear ring 4, the planet carrier 5, and the sun gear 6 form a differential planetary mechanism. The A speed regulation end idler gear 9, the A speed regulation end gear 10, and the planet carrier 5 form a differential planetary A branch speed regulation mechanism. The A speed regulation end idler gear 9, the A clutch 11, the A clutch output end gear 12, the clutch output end two-stage idler gear 13, and the main drive end gear 3 form an A branch speed regulation / constant speed clutch mechanism, which is used for the starting condition of the device and the overspeed protection of the A speed regulation motor 15 and the B speed regulation motor 29 in the state of sun gear output power; the B speed regulation end idler gear 23, the B speed regulation end gear 24, and the planet carrier 5 form a differential planetary B branch speed regulation mechanism, which can jointly regulate speed with the A branch speed regulation mechanism; the B speed regulation end idler gear 23, the B clutch 25, the B clutch output end gear 26, the B clutch output end first-stage idler gear 27, and the main drive end gear 3 form a B branch speed regulation / constant speed clutch mechanism, which is used for the state where the entire electrical circuit of the device trips, and the differential planetary mechanism becomes a constant speed ratio gearbox working state, and the overspeed protection of the A speed regulation motor 15 and the B speed regulation motor 29 in the state of sun gear input power. The main feed water pump 8, the small steam turbine 32, and the booster pump 34 are external devices. The booster pump 34 is connected to the sub-motor 30 through the coupling G 35. The small steam turbine 32 is connected to the sun gear 6 through the coupling B 7. The main feed water pump 8 is connected to the small steam turbine 32 through the coupling F 33. The connection mode is as Figure 2 shown. It also includes an A frequency converter 16 (specifically an A four-quadrant frequency converter), a main motor bypass switch 18, a plant power system 19, an A speed regulation motor incoming line switch 20, a main motor incoming line switch 21, an A soft start device 22 (specifically an A solid-state soft start device), a B frequency converter 17 (specifically a B four-quadrant frequency converter), a B speed regulation motor incoming line switch 36, a sub-motor incoming line switch 37, a sub-motor bypass switch 38, a B soft start device 39 (specifically a B solid-state soft start device), an A transformer 56, a B transformer 57, and the connection mode is as Figure 3 shown.

[0048] In the present invention, the speed-regulating end gear 24 of B, the coupling 28 of D, and the speed-regulating motor 29 of B may not be provided, and correspondingly, the frequency converter 17 of B, the transformer 57 of B, and the incoming line switch 36 of the speed-regulating motor 29 of B supporting the speed-regulating motor 29 of B are not provided either.

[0049] Taking a 1000MW unit as an example, the capacity of the small steam turbine is designed to just meet the shaft power requirement of the feed water pump set under the THA condition of the unit, that is, the balance power is zero. Without considering the full cut-off condition of the high-pressure heaters, the maximum balance power appears near about 50% THA condition, about 9000kW. During the normal operation of the unit, the device is always in the state of feeding power to the plant power system. Under the TRL (full load in summer) condition, the device is in the electric state to make up for the insufficient power of the small steam turbine. The design speed of the planetary carrier commutation point is preferably selected, such as 63.6% of the rated speed, to make the weighted efficiency of all operating conditions the highest. The powers of the main motor 1 and the auxiliary motor 30 can be preferably selected. For example, the main motor is selected according to the unit to meet all other conditions except the full cut-off condition of the high-pressure heaters, and the auxiliary motor is selected according to the condition that after the small steam turbine trips, the main motor and the auxiliary motor jointly meet a certain load condition of the unit, such as 75% of the rated load.

[0050] Zero starting speed of the device (unit starting condition): The bypass switch 18 of the main motor and the incoming line switch 21 of the main motor are in the off state, the A soft start device 22 is not started, the bypass switch 38 of the auxiliary motor and the incoming line switch 37 of the main motor are in the off state, the B soft start device 39 is not started, the incoming line switch 20 of the A speed-regulating motor is closed, the transformer 56 of A is energized, the A frequency converter 16 is started, and the output frequency of the A frequency converter 16 is gradually increased to drive the A speed-regulating motor 15 to increase speed, thereby driving the speed-regulating end gear 10 of A and the speed-regulating end idle gear 9 of A to increase speed. The increase in speed of the speed-regulating end idle gear 9 of A causes the A clutch 11 to engage and drive the gear 12 at the output end of the A clutch, the two-stage idle gears 13 at the output end of the A clutch, and the main drive end gear 3 to increase speed, thereby driving the main motor 1 and the internal gear ring 4 to increase speed. In this way, the planetary carrier 5, the sun gear 6, and the main feed water pump 8 are also driven to increase speed. Among them, the planetary carrier 5 also transmits power to the speed-regulating end idle gear 9 of A, forming a closed mechanical power cycle. At this time, the entire differential planetary speed-regulating mechanism forms a whole and becomes a constant speed ratio gearbox. The A speed-regulating motor 15 reaches the maximum reverse speed. At this time, the main feed water pump 8 reaches the lower limit of the speed in the working speed-regulating range (27.2% speed, corresponding to the frequency of the A frequency converter 16 being -100Hz). The above is the operation of the A branch speed-regulating mechanism and the A branch speed-regulating / constant speed clutch mechanism. The operation of the B branch speed-regulating mechanism is the same as that of the A branch speed-regulating mechanism. The A frequency converter 16 and the B frequency converter 17 are in a master-slave control relationship. The power flow during the starting process is as Figure 4As shown. When the outputs of Inverter A 16 and Inverter B 17 reach the reverse maximum frequency (-100 Hz), the main motor 1 and the auxiliary motor 30 reach the synchronous speed corresponding to the power frequency. At this time, the speed of the main feed water pump 8 reaches the upper limit of the speed regulation in the low-speed range, and the speed of the booster pump 34 also reaches the fixed-speed operating speed. Then, the incoming line switch 21 of the main motor is closed. The soft starter A 22 starts in the thyristor ramp voltage mode (soft grid connection). After reaching the rated voltage, the bypass switch 18 of the main motor is closed, and the soft starter A 22 stops operating. The main motor 1 is connected to the plant power system 19. The incoming line switch 37 of the auxiliary motor is closed. The soft starter B 39 starts in the thyristor ramp voltage mode (soft grid connection). After reaching the rated voltage, the bypass switch 38 of the main motor is closed, and the soft starter B 39 stops operating. The auxiliary motor 30 is connected to the plant power system 19. The device completes the startup process, and the lower limit speed of the working speed regulation range can be optimized according to the working conditions.

[0051] Speed regulation of the working speed range of the feed water pump: After the device completes startup, the device is at the lower limit of the speed regulation range (the planet carrier and the internal gear ring rotate in the same direction. According to the planetary differential principle, when the internal gear ring rotates at a fixed speed and the planet carrier rotates in the same direction as the internal gear ring, the speed of the planet carrier increases, and the speed of the sun gear decreases. That is, when the speed regulation motor is at the upper limit of the speed range, the feed water pump is at the lower limit of the speed regulation range). The speed regulation motors A 15 and B 29 are at the maximum speed of their speed regulation ranges, and the clutch A 11 is still in the engaged state. When it is necessary to increase the speed of the main feed water pump 8, the output frequencies of Inverter A 16 and Inverter B 17 are reduced. The speed of the input end of the clutch A 11 decreases, while the speed of the output end remains unchanged. Therefore, the clutch A 11 disengages, and the speed of the main feed water pump 8 increases. When the speeds of the speed regulation motors A 15 and B 29 are in the range from the reverse maximum speed to zero speed, the speed range of the main feed water pump 8 is 27.2% - 63.6%. The power flow is as Figure 5 shown in Fig. a (when the output of the small steam turbine is greater than the output of the feed water pump during normal operation of the unit, the power flow is as Figure 5As shown in Figure b, at this time, the small steam turbine 32 has not yet generated power. The main motor 1 and the auxiliary electric drive 30 input power to the internal gear ring 4, and the sun gear 6 outputs power to the small steam turbine 32 and the main feed water pump 8. During the startup process of the unit, since the small steam turbine 32 has no steam source yet, the device drives the feed water pump group to work at this time, which is equivalent to the existing motor-driven feed water pump. The small steam turbine is in the state of sending shaft seal and evacuating vacuum. Due to the low speed, the blowing effect of the small steam turbine is not obvious. As the load of the unit increases, the small steam turbine has the condition of admitting steam. After taking on the power output, the device gradually transitions from the electric state to the power feeding state and outputs power to the plant power system 19. When the A speed regulating motor 15 and the B speed regulating motor 29 are commutated to rotate forward until the maximum forward rotation speed (corresponding to the frequencies of the A frequency converter 16 and the B frequency converter 17 being 73.3 Hz, the reverse rotation state of the planet carrier and the internal gear ring. According to the planetary differential principle, when the internal gear ring rotates at a constant speed and the planet carrier rotates in the opposite direction to the internal gear ring, the speed of the planet carrier increases, and the speed of the sun gear increases. That is, when the speed regulating motor is at the upper limit of the speed range, the main feed water pump 8 is at the upper limit of the speed range of the speed regulation), the speed range of the main feed water pump 8 is 63.6% - 100%. The power flow of the device in the electric state is as Figure 6 As shown in Figure a, the small steam turbine 32 operates normally with all valves fully open, delivering power to the main feed water pump 8 and the sun gear 6. The internal gear ring 4 outputs power to the main motor 1 and the auxiliary motor 30, and the planet carrier 5 outputs power to the A speed regulating motor 15 and the B speed regulating motor 29. The power flow is as Figure 6 shown in Figure b.

[0052] Device shutdown: As the output of the unit decreases, the inlet steam pressure of the small steam turbine 32 gradually decreases. The small steam turbine 32 trips. The A frequency converter 16 controls the speed of the A speed regulating motor 15 and the B frequency converter 17 controls the speed of the B speed regulating motor 29 (reverse rotation) to reach the upper limit of the speed regulation range. The A clutch 11 engages, disconnecting the main motor bypass switch 18 and the main motor incoming line switch 21. The main motor 1 enters the passive driving state. The auxiliary motor bypass switch 38 and the auxiliary motor incoming line switch 37 are disconnected, and the auxiliary motor 30 enters the passive driving state. Then, the output frequencies of the A frequency converter 16 and the B frequency converter 17 are gradually reduced. The speeds of the A speed regulating motor 15 and the B speed regulating motor 29 decrease, and the speed of the main feed water pump 8 also synchronously decreases to a certain speed. Then, the A frequency converter 16 and the B frequency converter 17 are stopped, and the B speed regulating motor incoming line switch 36 and the A speed regulating motor incoming line switch 20 are disconnected. The shafting of the pump group coasts to a stop, and the speed gradually reaches zero.

[0053] Energy-saving optimized operation: Under different load conditions of the unit, the balancing power borne by the sun gear 6 is different, so the power of the internal gear ring 4 will also be different. According to the power of the internal gear ring 4, the operating modes of the main motor 1 and the auxiliary motor 30 are determined. There can be three modes: the main motor and the auxiliary motor work simultaneously, the main motor works, and the auxiliary motor works. However, in all three modes, the main motor and the auxiliary motor are in a rotating state. Whether they work depends on whether the motor is connected to the plant power system. The motor is put into operation through a soft start device and can be withdrawn by disconnecting the motor bypass switch. This can increase the load rate of the motor, thereby improving the operating efficiency of the motor. The motor can be equipped with an external cooling fan, which is only put into operation when the motor is working to further reduce losses.

[0054] High load condition in summer: Due to the insufficient output of the small steam turbine 32 under the summer back pressure, the device enters the electric working state to supplement the output of the small steam turbine 32. If the main motor 1 is not sufficient to provide the input power required by the internal gear ring 4 at this time, start the B soft start device 39, and then close the auxiliary motor bypass switch 38. The auxiliary motor 30 completes the start and continuously supplements the output.

[0055] Motor-driven feed pump mode: The device drives the feed pump group to operate, and the small steam turbine is in the state of supplying shaft seal and evacuating air and keeps idling.

[0056] Motor-driven condensate pump mode with the condensate pump driven by the main motor 1 or the auxiliary motor 30: The main motor 1 or the auxiliary motor 30 drives the condensate pump 34 to operate. The A frequency converter 16 does not work, the A speed regulating motor 15 is not powered and is driven by the device to idle. The B frequency converter 17 does not work, the B speed regulating motor 29 is not powered and is driven by the device to idle. The steam admission regulating valve of the small steam turbine is in the regulating state to control the speeds of the small steam turbine 32 and the main feed pump 8.

[0057] Motor-driven condensate pump mode with the condensate pump driven by the small steam turbine at variable speed coaxially: All the electrical equipment of the whole device does not work with power. The B clutch 25 is engaged. The steam admission regulating valve of the small steam turbine is in the regulating state. The small steam turbine 32 drives the main feed pump 8 and drives the condensate pump 34 to operate at variable speed through the device (at this time, the differential planetary mechanism is a fixed-ratio gearbox).

[0058] Fault condition: Refers to the situation where an electrical fault occurs and the mechanical part is normal, without affecting the rotation of the faulty equipment.

[0059] Fault of a set of speed regulating motor or the frequency converter used: When the unit load > about 75%THA, the power of a set of speed regulating motors can meet the device requirements, and the unit can maintain a high load. When the unit load < about 75%THA, the power of a set of speed regulating motors cannot meet the device requirements. Quickly close the steam admission regulating valve of the small steam turbine 32 to reduce the balancing power of the device and control it in a condition where a set of speed regulating motors can meet the requirements, and the unit operation is not affected.

[0060] Failure of two sets of speed-regulating motors or frequency converters: Quickly close the steam inlet regulating valve of the small steam turbine 32 to balance the power of the small steam turbine 32 and the main feed water pump 8. The small steam turbine changes from the fully open valve state to the speed control state. Disconnect the bypass switch 18 of the main motor and keep the auxiliary motor 30 running to drive the booster pump 34. The operation of the unit is not affected.

[0061] When the feed water pump set is in operation and before the failure of two sets of speed-regulating motors or frequency converters, when the power flow is from the sun gear 6 to the small steam turbine 32 (i.e., the device is in the electric state), after the speed-regulating mechanisms of both branch A and branch B trip, the speed of the main feed water pump 8 will decrease to a state balanced with the output of the small steam turbine 32. The A clutch can also prevent the speed of the speed-regulating motors of branch A and branch B from exceeding the limit. If the speeds of the speed-regulating motors of branch A and branch B have a dynamic overshoot and reach their maximum speeds, the A clutch will engage. At this time, the speed of the main feed water pump 8 will decrease and be maintained at 27.2% of the rated speed. When the power flow is from the small steam turbine 32 to the sun gear 6 (i.e., the device is in the power feeding state), after the speed-regulating mechanisms of both branch A and branch B trip, the B clutch can also prevent the speed of the speed-regulating motors of branch A and branch B from exceeding the limit. If the small steam turbine 32 and the speed-regulating motors of branch A and branch B have a dynamic overshoot and reach the engagement speed, the B clutch will engage. The differential planetary mechanism becomes a fixed ratio gearbox and runs synchronously with the main feed water pump 8. At this time, the small steam turbine 32 changes from the fully open valve state to the speed control state.

[0062] Failure of one power balance motor: Quickly close the steam inlet regulating valve of the small steam turbine 32 to reduce the balance power of the device and control it within the rated power of the non-failed power balance motor. The operation of the unit is not affected. If only one power balance motor is running when the power balance motor fails and trips, it will be processed according to the failure mode of two power balance motors. After the shafting working condition is stable, the non-failed power balance motor will be put into operation in a soft grid connection manner.

[0063] Failure of two power balance motors (except in the high-load condition in summer): Quickly close the steam inlet regulating valve of the small steam turbine 32 to keep the power of the small steam turbine 32 and the main feed water pump 8 roughly balanced. The small steam turbine 32 changes from the fully open valve state to the speed control state. The speed-regulating motors of branch A and branch B and the frequency converters of branch A and branch B keep running. The output frequency of the frequency converter tracks the speed of the small steam turbine to keep the internal gear ring 4 running at a fixed speed of about 1500 rpm to drive the booster pump 34. The operation of the unit is not affected.

[0064] Both sets of speed-regulating motors or the frequency converters and two power-balancing motors are faulty (except under high-load conditions in summer): All electrical circuits trip and disconnect. The steam inlet regulating valve of the small steam turbine 32 is quickly closed slightly to balance the power of the small steam turbine 32 with that of the main feed pump 8 and the pre-pump 34. The small steam turbine 32 changes from the fully open valve state to the speed control state. At this time, under the action of torque, the B-speed-regulating end idler gear 23 has a tendency to increase in speed, and the B-clutch output end gear 26 has a tendency to decrease in speed. At a certain speed ratio, the B-clutch engages, and the differential planetary mechanism becomes a fixed-speed ratio gearbox. At this time, the entire pump set shafting becomes the existing steam-driven feed pump set mode driven coaxially by the pre-pump. The pre-pump 34 operates variably. The speed ratio of the sun gear and the internal gear ring when the B-clutch engages should be optimized so that the pre-pump designed for fixed-speed operation can match the variable-speed operation conditions, and the unit operation is not affected.

[0065] Small steam turbine trip condition: The device changes from outputting power to the plant power system 19 to inputting power. The power of the feed pump set changes to be borne by the device, but the device is not sufficient to bear the power of the feed pump set of the unit under high load. If the device can bear the shaft power of the feed pump set of the unit at about 75% of the rated load (if only the main motor 1 is running at this time, the standby auxiliary motor 30 in the interlock start state directly closes the auxiliary motor bypass switch 38 without passing through the B soft start device 39, and the auxiliary motor 30 completes the full-voltage direct start and takes on the output. The relay protection setting should include this method). If the unit operates below this load, the device quickly changes from the power supply state to the electric state. Among them, the main and auxiliary motors adaptively complete the state conversion, and the state conversion of the speed-regulating motor is completed through the frequency converter, and the unit operation is not affected.

[0066] If the unit operates above this load, the RB of the unit control system acts, quickly cuts and grinds to reduce the fuel input to the furnace to reduce the boiler heat load, and quickly reduces the unit load to the allowable level. Due to the existence of thermal storage, this process will last for about several minutes. At the same time as the small steam turbine trip triggers the RB of the unit, such as Figure 7As shown in the figure, the feed water quick closing valve 53 is quickly closed according to the closing rate curve (to prevent the occurrence of water hammer or reduce the impact), and the main feed water valve 54 is kept fully open (the sum of the flow capacities of the feed water quick closing valve and the main feed water valve is 100% capacity, and the existing unit is set with a 100% capacity main feed water valve and a 30% capacity feed water bypass regulating valve). The feed water bypass regulating valve 55 is in the fully closed state (30% capacity, used during unit startup), so that the boiler feed water flow rate is quickly reduced to a reasonable level, enabling the main feed water pump 8 to maintain a relatively high head while keeping a relatively high rotational speed without overloading the device. During the above dynamic process, the feed water control system will increase the output command in the automatic state, and the frequency converter control system will quickly reduce the output frequency of the frequency converter through the current loop limit value in the case of overcurrent (an open-loop mode can also be adopted, directly setting the frequency reduction target value and the frequency reduction rate, and when the load is normal, re-engaging the automatic mode), which plays a role in limiting the device overload, that is, quickly reducing the rotational speed of the main feed water pump 8 to the allowable value, so that the power of the feed water pump group is reduced within the rated power of the device. During the deceleration process of the main feed water pump 8, the rotational inertia of the shafting of the feed water pump group will also play a certain power compensation role. After the feed water quick closing valve 53 is closed, the device load will return to the normal state. At this time, the rotational speed of the main feed water pump 8 can be increased again to meet the dynamic demand for feed water flow during the RB process of the unit. As the main steam pressure of the unit decreases and the feed water system pressure decreases, the feed water quick closing valve is gradually opened, and the rotational speed of the main feed water pump 8 is gradually reduced. While meeting the feed water flow, the device is not overloaded, and the working condition is gradually stabilized.

[0067] Unit load rejection condition: When the unit experiences load rejection at high load (i.e., the generator is disconnected from the grid, and the steam turbine enters the 3000 rpm speed control to maintain the unit at a constant speed and idling), at this time, the working steam source of the small steam turbine is lost. Even if the standby steam source is normally put into operation, if the rotational speed (output) of the main feed water pump 8 cannot be quickly reduced, the device will still be overloaded, and the degree of overload will be relatively serious. It is necessary for the device control to quickly reduce the rotational speed of the main feed water pump 8. Moreover, at this time, the unit itself also needs to quickly reduce the output of the main feed water pump 8. Through debugging, the target frequency and the frequency change rate of the frequency converter can be determined, so that the rotational speed of the main feed water pump 8 is quickly reduced to the target rotational speed (the frequency of the frequency converter quickly decreases from the positive frequency to the frequency hopping point near zero frequency, and then quickly increases after switching to the negative frequency), reducing the power of the main feed water pump 8 within the rated output of the device, and then re-switching to the feed water target control.

[0068] Example 2: A power balance device based on mechatronic planetary speed regulation, taking the application to the steam-driven feed water pump of a power plant boiler as an example, as Figure 8As shown, the difference from Embodiment 1 lies in the different connection method of the booster pump 34. Specifically, the booster pump 34, H coupling 35, long shaft 44, J coupling 43, gearbox 45, G coupling 42, and main feed water pump 8 are connected in sequence. The difference also lies in that a C synchronous automatic clutch 40 is provided between the main motor 1 and the auxiliary motor 30. Specifically, the main motor 1, E coupling 31, C synchronous automatic clutch 40, F coupling 41, and auxiliary motor 30 are connected in sequence. The difference also lies in that the booster pump 34 is designed with variable speed and operates synchronously with the main feed water pump 8 at a fixed speed ratio, and the auxiliary motor 30 can only operate in the electric working condition.

[0069] Embodiment 3: A power balance device based on mechatronic planetary speed regulation, taking the application to the steam-driven feed water pump of a power station boiler as an example. The difference from Embodiment 1 and Embodiment 2 lies in that the auxiliary motor 30 is not provided, and the main motor 1 is increased with a path of step-down power supply 52 (for example, the voltage can be 8 kV. Preferably, the main motor 1 is designed according to the plant use voltage level of 10 kV, and the nameplate power is 15 MW, which is the sum of the powers of the main motor and the auxiliary motor in Embodiment 1 and Embodiment 2). A reactor 49, main motor incoming line step-down switch 50, and main motor bypass step-down switch 51 are added, and the connection method is as Figure 9 shown. When the unit is operating normally, the main motor incoming line step-down switch 50 and the main motor bypass step-down switch 51 are closed, and the main motor 1 operates with reduced capacity at a voltage level of 8 kV, equivalent to a nameplate power of about 11 MW, so that the main motor 1 maintains a high load rate and power factor, improving the operating efficiency. The main motor incoming line switch 21 and the main motor bypass switch 18 are in the open state; when the main motor 1 encounters a condition of insufficient output, such as when the small steam turbine 32 trips, the main motor incoming line switch 21 is quickly closed, the voltage of the step-down power supply 52 and the plant use power system 19 is matched through the reactor 49, then the main motor bypass step-down switch 51 is opened, and then the main motor bypass switch 18 is closed to bypass the reactor 49, so that the main motor 1 operates at a voltage of 10 kV and restores the nameplate power of 15 MW to meet the power requirement, and the above operations are completed interlocked.

Claims

1. A power balance device based on mechatronic planetary speed regulation, characterized in that: It includes a main motor (1), a sub-motor (30), a main drive end gear (3), a differential planetary mechanism, an A speed regulation end idler gear (9), an A speed regulation end gear (10), an A clutch (11), an A clutch output end gear (12), an A clutch output end idler gear, an A speed regulation motor (15), an A frequency converter (16), an A soft start device (22), a main motor bypass switch (18), a B speed regulation end idler gear (23), a B speed regulation end gear (24), a B clutch (25), a B clutch output end gear (26), a B clutch output end idler gear, a B speed regulation motor (29), a B frequency converter (17), a B soft start device (39), a sub-motor bypass switch (38), an A speed regulation motor incoming line switch (20), a B speed regulation motor incoming line switch (36), a main motor incoming line switch (21), a sub-motor incoming line switch (37) and a plant power system (19). The inner gear ring input shaft of the differential planetary mechanism is connected to the main drive end gear (3). The main drive end gear (3) is connected to the A clutch output end gear (12) through the A clutch output end idler gear. The main drive end gear (3) is also connected to the B clutch output end gear (26) through the B clutch output end idler gear. The A clutch output end gear (12) is connected to the output shaft of the A clutch (11). The B clutch output end gear (26) is connected to the output shaft of the B clutch (25). The main motor (1) is connected to the main drive end gear (3). The sub-motor (30) is connected to the main motor (1) through a coupling. The sun gear (6) of the differential planetary mechanism is connected to an external device. The sub-motor (30) is also connected to an external device. The planet carrier (5) of the differential planetary mechanism is connected to the A speed regulation end idler gear (9). The A speed regulation end idler gear (9) meshes with the A speed regulation end gear (10). The A speed regulation end gear (10) is connected to the A speed regulation motor (15). The A speed regulation end idler gear (9) is connected to the input shaft of the A clutch (11). The planet carrier (5) of the differential planetary mechanism is also connected to the B speed regulation end idler gear (23). The B speed regulation end idler gear (23) meshes with the B speed regulation end gear (24). The B speed regulation end gear (24) is connected to the B speed regulation motor (29). The B speed regulation end idler gear (23) is connected to the input shaft of the B clutch (25). The inverter end of the A frequency converter (16) is connected to the A speed regulation motor (15). The rectifier end is connected to the plant power system (19) through an A transformer (56) and the A speed regulation motor incoming line switch (20). The inverter end of the B frequency converter (17) is connected to the B speed regulation motor (29). The rectifier end is connected to the plant power system (19) through a B transformer (57) and the B speed regulation motor incoming line switch (36). The output end of the A soft start device (22) is connected to the main motor (1). The input end is connected to the plant power system (19) through the main motor incoming line switch (21). One end of the main motor bypass switch (18) is connected to the main motor incoming line switch (21), and the other end is connected to the main motor (1). The output end of the B soft start device (39) is connected to the sub-motor (30). The input end is connected to the plant power system (19) through the sub-motor incoming line switch (37).The by-pass switch (38) of the auxiliary motor is connected to the incoming line switch (37) of the auxiliary motor at one end and to the auxiliary motor (30) at the other end. The idler pulley at the output end of the A clutch is the two-stage idler pulley (13) at the output end of the A clutch, and the idler pulley at the output end of the B clutch is the single-stage idler pulley (27) at the output end of the B clutch.

2. The operating method of a power balance device based on mechatronic planetary speed regulation according to claim 1, characterized in that: The steps include: When the device starts up normally, the A frequency converter (16) drives the A speed-regulating motor (15) to start with variable-frequency speed regulation, thereby driving the A speed-regulating end gear (10), the A speed-regulating end idler gear (9) and the planet carrier (5) to increase speed. The B frequency converter (17) drives the B speed-regulating motor (29) to start with variable-frequency speed regulation, thereby driving the B speed-regulating end gear (24), the B speed-regulating end idler gear (23) and the planet carrier (5) to increase speed. The increase in speed of the A speed-regulating end idler gear (9) causes the A clutch to engage and drive the A clutch output end gear (12), the A clutch output end idler gear and the main drive end gear (3) to increase speed, thereby driving the main motor (1), the auxiliary motor (30) and the internal gear ring (4) to increase speed. In this way, the sun gear (6) drives the external connected device to increase speed. When the outputs of the A frequency converter (16) and the B frequency converter (17) reach the reverse maximum frequency, the main motor (1) and the auxiliary motor (30) reach the synchronous speed corresponding to the power frequency. At this time, the speed of the external connected device reaches the upper limit of the speed regulation in the low-speed range; Then, the main motor (1) and the auxiliary motor (30) are started respectively through the A soft start device (22) and the B soft start device (39). After reaching the rated voltage, the main motor bypass switch (18) and the auxiliary motor bypass switch (38) are closed, and the A soft start device (22) and the B soft start device (39) are withdrawn from operation. The output frequencies of the A frequency converter (16) and the B frequency converter (17) are gradually reduced. As the speeds of the A speed-regulating motor (15) and the B speed-regulating motor (29) decrease, the A clutch (11) disengages, and the speed of the sun gear (6) increases, driving the external connected device to continue to increase speed and enter the high-speed range speed regulation working condition. When the external connected device transfers to normal operation and can input shaft power to the sun gear (6), the power flow reverses. The main motor (1) and the auxiliary motor (30) input power, and the sun gear (6) outputs power, changing to the sun gear input power and the main motor (1) and the auxiliary motor (30) output power; When both the A speed-regulating motor (15) and the B speed-regulating motor (29) lose power, the A clutch (11) engages. At this time, the differential planetary mechanism is a fixed-ratio gearbox, which can realize input shaft power from the internal gear ring and output shaft power from the sun gear; When both the A speed-regulating motor (15) and the B speed-regulating motor (29) lose power, the B clutch (25) engages. At this time, the differential planetary mechanism is a fixed-ratio gearbox, which can realize input shaft power from the sun gear and output shaft power from the internal gear ring; When both the A speed-regulating motor (15) and the B speed-regulating motor (29) lose power, neither the A clutch (11) nor the B clutch (25) engages. The internal gear ring (4) and the sun gear (6) are in a decoupled state, each being in a free driven state. The main motor (1) or the auxiliary motor (30) connected to the internal gear ring (4) drives the external device at the other end at a fixed speed, or the main motor (1) and the auxiliary motor (30) jointly drive the external device at the other end at a fixed speed. The external device connected to the sun gear (6) can operate independently; When both the main motor (1) and the auxiliary motor (30) lose power and the power of the input shaft of the sun gear runs with speed change, by adjusting the speed of the A speed-regulating motor (15) or the B speed-regulating motor (29), a constant-speed output shaft power of the internal gear ring can be achieved, or a variable-speed output shaft power can also be achieved.

3. A power balance device based on mechatronic planetary speed regulation, characterized in that: It includes a main motor (1), a main drive end gear (3), a differential planetary mechanism, an A speed regulation end idler gear (9), an A speed regulation end gear (10), an A clutch (11), an A clutch output end gear (12), an A clutch output end idler gear, an A speed regulation motor (15), an A frequency converter (16), a B speed regulation end idler gear (23), a B speed regulation end gear (24), a B clutch (25), a B clutch output end gear (26), a B clutch output end idler gear, a B speed regulation motor (29), a B frequency converter (17), an A speed regulation motor incoming line switch (20), an A soft start device (22), a main motor bypass switch (18), a B speed regulation motor incoming line switch (36), a main motor incoming line switch (21), a plant power system (19), a step-down power supply (52), a reactor (49), a main motor incoming line step-down switch (50) and a main motor bypass step-down switch (51). The inner gear ring input shaft of the differential planetary mechanism is connected to the main drive end gear (3). The main drive end gear (3) is connected to the A clutch output end gear (12) through the A clutch output end idler gear. The main drive end gear (3) is also connected to the B clutch output end gear (26) through the B clutch output end idler gear. The A clutch output end gear (12) is connected to the output shaft of the A clutch (11). The B clutch output end gear (26) is connected to the output shaft of the B clutch (25). The main motor (1) is connected to the main drive end gear (3). The sun gear (6) of the differential planetary mechanism is connected to an external device. The main motor (1) is also connected to the external device. The planet carrier (5) of the differential planetary mechanism is connected to the A speed regulation end idler gear (9). The A speed regulation end idler gear (9) meshes with the A speed regulation end gear (10). The A speed regulation end gear (10) is connected to the A speed regulation motor (15). The A speed regulation end idler gear (9) is connected to the input shaft of the A clutch (11). The planet carrier (5) of the differential planetary mechanism is also connected to the B speed regulation end idler gear (23). The B speed regulation end idler gear (23) meshes with the B speed regulation end gear (24). The B speed regulation end gear (24) is connected to the B speed regulation motor (29). The B speed regulation end idler gear (23) is connected to the input shaft of the B clutch (25). The inverter end of the A frequency converter (16) is connected to the A speed regulation motor (15). The rectifier end is connected to the plant power system (19) through an A transformer (56) and the A speed regulation motor incoming line switch (20). The inverter end of the B frequency converter (17) is connected to the B speed regulation motor (29). The rectifier end is connected to the plant power system (19) through a B transformer (57) and the B speed regulation motor incoming line switch (36). The output end of the A soft start device (22) is connected to the main motor (1). The input end is connected to the step-down power supply (52) through the main motor incoming line step-down switch (50). One end of the main motor bypass step-down switch (51) is connected to the main motor incoming line step-down switch (50), and the other end is connected to the main motor (1). One end of the reactor (49) is connected to the main motor (1), and the other end is connected to the plant power system (19) through the main motor incoming line switch (21). One end of the main motor bypass switch (18) is connected to the main motor incoming line switch (21), and the other end is connected to the main motor (1).The idler pulley at the output end of Clutch A is the two-stage idler pulley (13) at the output end of Clutch A, and the idler pulley at the output end of Clutch B is the single-stage idler pulley (27) at the output end of Clutch B., 4. A power balance device based on mechatronic planetary speed regulation according to claim 1 or 3, characterized in that: The A speed-regulating motor (15) and the B speed-regulating motor (29) are respectively driven by the A frequency converter (16) and the B frequency converter (17) in a master-slave control mode.

5. A power balance device based on mechatronic planetary speed regulation according to claim 1 or 3, characterized in that: The A transformer (56) and the B transformer (57) are phase-shifting transformers.

6. The power balance device based on mechatronic planetary speed regulation according to claim 1 or 3, characterized in that: When the external equipment connected to the sun gear (6) of the differential planetary mechanism includes a main feed water pump, the main feed water pipe switching system of the main feed water pump is composed of a feed water quick closing valve (53), a feed water main valve (54), and a feed water bypass regulating valve (55) in parallel, and the sum of the flow capacities of the feed water quick closing valve (53) and the feed water main valve (54) is 100%.

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