A back pressure machine switching system

Abstract

The present invention discloses a back pressure machine switching system, comprising a plant power system and a back pressure machine system; wherein, the present invention provides a "one-to-two" system in which one back pressure machine supplies power to two main plant loads at the same time, and realizes flexible switching of the back pressure machine with three-section and four-section plant bus loads through a quick-cut device, and provides switching methods under various working conditions, thereby avoiding duplicate construction, effectively absorbing the power generation of the back pressure machine, and giving full play to the energy-saving effect of the back pressure machine; the present invention is a back pressure machine switching system, which can greatly reduce investment, further reduce energy consumption and plant power consumption rate, and has good economy and engineering practice value.

Description

Technical Field

[0001] The present invention relates to a back pressure machine, in particular to a back pressure machine switching system. Background Art

[0002] Currently, cogeneration units within power plants use reheated steam directly for external heat supply, resulting in a "high-quality, low-use" scenario. This approach fails to achieve cascaded steam utilization, increasing energy losses. To address this issue, many thermal power plants are retrofitting their heating systems with small backpressure units, which are used to drive generators to fully utilize steam. These backpressure units utilize steam extracted from the corresponding generators to generate power, with the exhaust used for heat supply. The generated electricity is then fed into the plant's power system, reducing the energy loss associated with using steam from larger units for heat supply after desuperheating and pressure reduction. This can also further reduce plant power consumption, resulting in significant energy savings and widespread adoption. In domestic thermal power plant heating retrofits, the capacity of the backpressure unit selected varies depending on the heating load, with common capacities ranging from 2,000 kW to 25,000 kW. Generally, these units are initially designed with a small capacity, employing either a "one-to-one" power supply system (where a single unit supplies power to a single main plant), or a "multiple-to-one" power supply system (where multiple units supply power to a single main plant). When the power generation of the back pressure machine is no more than the power consumption of a single main engine plant, it can operate safely, stably and economically.

[0003] However, with economic development, the heat load of many thermal power plant users has gradually increased, and the power generation of backpressure units has gradually increased. This has led to situations where the backpressure unit's power generation capacity exceeds the plant power consumption of a single main unit, resulting in a negative plant power consumption rate. Currently, the profitability of these backpressure unit power supply projects is achieved by significantly reducing the plant power consumption rate within the current grid generation dispatch model, thereby obtaining more grid-connected power. Once the plant power consumption rate of a unit becomes negative, the dispatcher will likely prohibit the unit from generating power. Therefore, the original design upper limit of the backpressure unit's power generation capacity is the plant power consumption rate. To maximize the energy-saving benefits of backpressure units and absorb their power generation, research is underway to develop a "one-to-two" system in which one backpressure unit simultaneously supplies power to two main units' plant loads. This system, coupled with a quick-cut device to flexibly switch between the plant power sections it supplies, can further reduce energy consumption and plant power consumption rates, significantly reduce investment, and avoid redundant construction, offering excellent economic and practical engineering value. Summary of the Invention

[0004] The purpose of the present invention is to address the current situation where the thermal load of thermal power plants gradually increases, the power generation power of the back pressure machine exceeds the power consumption of a single main machine, the energy is not fully utilized, and the power consumption rate of the main machine is "negative". A back pressure machine switching system method is provided with clear wiring, simple logic, and flexible switching, which fully utilizes the energy-saving effect of the back pressure machine, effectively reduces energy consumption and power consumption rate, greatly reduces investment, and avoids duplicate construction.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A back pressure machine switching system includes a plant power system and a back pressure machine system; wherein the back pressure machine system is connected to the 6kV plant 3A section bus, 6kV plant 3B section bus, 6kV plant 4A section bus and 6kV plant 4B section bus of the plant power system through a ninth circuit breaker, a tenth circuit breaker, an eleventh circuit breaker and a twelfth circuit breaker respectively.

[0007] A further improvement of the present invention is that: the auxiliary power system includes a No. 3 main transformer, a No. 3 generator, a No. 3 high-voltage auxiliary transformer, a first circuit breaker, a second circuit breaker, a 6kV auxiliary busbar 3A, a starting standby transformer, a third circuit breaker, a fourth circuit breaker, a fifth circuit breaker, a sixth circuit breaker, a 6kV auxiliary busbar 3B, a 6kV auxiliary busbar 4A, a No. 4 main transformer, a No. 4 generator, a No. 4 high-voltage auxiliary transformer, a seventh circuit breaker, an eighth circuit breaker and a 6kV auxiliary busbar 4B; wherein,

[0008] The No. 3 generator is connected to the power grid through the No. 3 main transformer, and the high-voltage side of the No. 3 high-voltage plant transformer is connected to the No. 3 generator terminal, and its two low-voltage sides are connected to the 6kV plant 3A section bus and the 6kV plant 3B section bus through the first circuit breaker and the second circuit breaker respectively; the high-voltage side of the starting standby transformer is connected to the power grid, one of its low-voltage sides is connected to the 6kV plant 3A section bus and the 6kV plant 4A section bus through the third circuit breaker and the fourth circuit breaker respectively, and the other low-voltage side is connected to the 6kV plant 3B section bus and the 6kV plant 4B section bus through the fifth circuit breaker and the sixth circuit breaker respectively; the No. 4 generator is connected to the power grid through the No. 4 main transformer, and the high-voltage side of the No. 4 high-voltage plant transformer is connected to the No. 4 generator terminal, and its two low-voltage sides are connected to the 6kV plant 4A section bus and the 6kV plant 4B section bus through the seventh circuit breaker and the eighth circuit breaker respectively.

[0009] A further improvement of the present invention is that: the back pressure machine system includes a back pressure machine, a back pressure asynchronous generator outlet circuit breaker, a current limiter, a ninth circuit breaker, a tenth circuit breaker, an eleventh circuit breaker and a twelfth circuit breaker; wherein,

[0010] After passing through the backpressure asynchronous generator outlet circuit breaker and current limiter, the backpressure machine is connected to the 6kV plant 3A section bus, 6kV plant 3B section bus, 6kV plant 4A section bus and 6kV plant 4B section bus of the plant power system through the ninth circuit breaker, the tenth circuit breaker, the eleventh circuit breaker and the twelfth circuit breaker respectively.

[0011] A further improvement of the present invention is that: when the twelfth circuit breaker is in a closed state, the back pressure machine is connected to the 6kV plant 4B section bus, and the electric energy generated by the back pressure machine supplies the plant power of the 6kV plant 4B section bus and the 6kV plant 4A section bus; when the electric energy generated by the back pressure machine increases, so that it can still supply power to the 6kV plant 3B section bus after meeting all the plant power needs of generator No. 4, the tenth circuit breaker is closed under the premise of disconnecting the second circuit breaker, so as to achieve the purpose of the back pressure machine carrying the load of three bus sections, namely the 6kV plant 3B section bus, the 6kV plant 4A section bus and the 6kV plant 4B section bus.

[0012] A further improvement of the present invention is that: on the basis of the back pressure machine carrying a total of three busbar loads, namely, the 6kV plant 3B segment bus, the 6kV plant 4A segment bus and the 6kV plant 4B segment bus, if the electric energy generated by the back pressure machine continues to increase, so that it can still supply power to the 6kV plant 3A segment bus after meeting the plant power demand of the No. 4 generator and the 6kV plant 3B segment bus, under the premise of disconnecting the first circuit breaker, the ninth circuit breaker is closed, so as to achieve the purpose of the back pressure machine carrying a total of four busbar loads, namely, the 6kV plant 3A segment bus, the 6kV plant 3B segment bus, the 6kV plant 4A segment bus and the 6kV plant 4B segment bus.

[0013] A further improvement of the present invention is to enable the back pressure machine to operate with a total of three bus sections: 6kV plant 3B bus section, 6kV plant 4A bus section and 6kV plant 4B bus section.

[0014] Switching method under normal working conditions

[0015] Step 1: During the rated operation of the No. 3 and No. 4 generators, when the phase sequence, frequency, phase and output voltage of the back pressure generators are the same as those of the auxiliary power system, the back pressure generators are connected to the 6kV auxiliary power bus section 4B by closing the twelfth circuit breaker;

[0016] Step 2: Increase the power of the back pressure generator so that the plant load of generator No. 4 is fully supplied by the back pressure generator. At this time, the high-voltage side power of the No. 4 high-voltage plant transformer is close to 0MW.

[0017] Step 3: Switch the 6kV auxiliary bus section 3B load to the back pressure generator through parallel switching, i.e., first close the tenth circuit breaker and then open the second circuit breaker;

[0018] Step 4: Further increase the power generation of the back pressure generator to make the high-voltage side power of the No. 4 high-voltage auxiliary transformer close to 0MW again, and prevent the auxiliary power from being fed back to the grid;

[0019] (2) Switching method under abnormal working conditions

[0020] 1) When the No. 3 generator trips and stops, the back pressure machine's operating mode remains unchanged, so the 6kV plant bus section 3B power supply is not affected. By closing the third circuit breaker, the 6kV plant bus section 3A is switched to the start-up standby transformer;

[0021] 2) When the No. 4 generator trips and shuts down, the back pressure unit trips in conjunction with the 4th, 5th, and 6th circuit breakers, and the 6kV plant busbar 4A, 3B, and 4B are switched to the starting standby transformer by closing the 4th, 5th, and 6th circuit breakers;

[0022] 3) When the back pressure machine trips and stops, there are two switching methods:

[0023] The first method is to switch the 6kV auxiliary bus 3B section to the starting standby transformer by closing the fifth circuit breaker while disconnecting the back pressure asynchronous generator outlet circuit breaker, the ninth circuit breaker, the tenth circuit breaker, the eleventh circuit breaker and the twelfth circuit breaker;

[0024] The second method is to only disconnect the back-pressure asynchronous generator output circuit breaker. When the capacity of the No. 4 high-voltage plant transformer meets the load requirements, the No. 4 high-voltage plant transformer is operated with the 6kV plant 3B section bus, the 6kV plant 4A section bus and the 6kV plant 4B section bus.

[0025] A further improvement of the present invention is to enable the back pressure machine to operate with a total of four bus sections, namely, a 6kV plant 3A bus section, a 6kV plant 3B bus section, a 6kV plant 4A bus section, and a 6kV plant 4B bus section.

[0026] Switching method under normal working conditions

[0027] Step 1: During the rated operation of the No. 3 and No. 4 generators, when the phase sequence, frequency, phase and output voltage of the back pressure generators are the same as those of the auxiliary power system, the back pressure generators are connected to the 6kV auxiliary power bus section 4B by closing the twelfth circuit breaker;

[0028] Step 2: Increase the power of the back pressure generator so that the plant load of generator No. 4 is fully supplied by the back pressure generator. At this time, the high-voltage side power of the No. 4 high-voltage plant transformer is close to 0MW.

[0029] Step 3: Switch the loads of the 6kV plant service busbar section 3A and the 6kV plant service busbar section 3B to the back pressure machine through parallel switching, i.e., first close the ninth and tenth circuit breakers, and then open the first and second circuit breakers;

[0030] Step 4: Further increase the power generation of the back pressure generator to make the high-voltage side power of the No. 4 high-voltage auxiliary transformer close to 0MW again, and prevent the auxiliary power from being fed back to the grid;

[0031] (2) Switching method under abnormal working conditions

[0032] 1) When the No. 3 generator trips and stops, the power supply of the 6kV plant 3A section bus and the 6kV plant 3B section bus is not affected because the back pressure machine's operating mode remains unchanged;

[0033] 2) When the No. 4 generator trips and shuts down, the back pressure unit trips in conjunction with the tripping of the generator. By closing the third, fourth, fifth, and sixth circuit breakers, the 6kV plant busbars for 3A, 4A, 3B, and 4B are switched to the starting standby transformer.

[0034] 3) When the back pressure machine trips and stops, there are two switching methods:

[0035] The first method is to switch the 6kV plant 3A section bus and the 6kV plant 3B section bus to the starting standby transformer by closing the third circuit breaker and the fifth circuit breaker while disconnecting the back pressure asynchronous generator outlet circuit breaker, the ninth circuit breaker, the tenth circuit breaker, the eleventh circuit breaker and the twelfth circuit breaker;

[0036] The second method is to disconnect only the back-pressure asynchronous generator output circuit breaker, and when the capacity of the No. 4 high-voltage plant transformer meets the load requirements, make the No. 4 high-voltage plant transformer operate with 6kV plant 3A section bus, 6kV plant 3B section bus, 6kV plant 4A section bus and 6kV plant 4B section bus.

[0037] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0038] 1. The system structure of the present invention is clear and the wiring is simple. Through simple wiring, a "one-to-two" system can be realized in which one back pressure machine supplies power to two main engine plant loads at the same time, thus avoiding duplicate construction and reducing investment costs.

[0039] 2. The present invention can give full play to the energy-saving effect of the back pressure machine, absorb the power generation of the back pressure machine, greatly reduce energy consumption and plant power consumption rate, and improve the economic efficiency of the unit operation;

[0040] 3. The present invention can realize flexible switching of the power supply section of the back pressure machine through the quick-cut device, thereby improving the flexibility of system operation;

[0041] 4. The switch switching logic of the present invention is simple and clear under normal working conditions and various accident situations, thereby improving the safety and reliability of the switching system operation.

[0042] In summary, the present invention avoids duplicate construction, reduces investment, is highly practical, and is easy to promote and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is the principle wiring diagram of the back pressure machine switching system.

[0044] Figure 2 This is the switch switching diagram during normal operation of the load on three bus sections, namely the 6kV plant 3B bus section, the 6kV plant 4A bus section and the 6kV plant 4B bus section.

[0045] Figure 3 This is the switch switching diagram when the #3 machine trips and stops during load operation with 6kV plant 3B section bus, 6kV plant 4A section bus and 6kV plant 4B section bus.

[0046] Figure 4 This is the switch switching diagram when the #4 machine trips and stops during load operation with 6kV plant 3B section bus, 6kV plant 4A section bus and 6kV plant 4B section bus.

[0047] Figure 5 This is the switch switching diagram when the back pressure machine trips and stops during load operation with 6kV plant 3B busbar, 6kV plant 4A busbar and 6kV plant 4B busbar ( Figure 5 (a) represents the first switching method, Figure 5 (b) represents the second switching method).

[0048] Figure 6 This is the switch switching diagram when the 6kV plant 3A section bus, 6kV plant 3B section bus, 6kV plant 4A section bus, and 6kV plant 4B section bus are in normal load operation / the switch switching diagram when the #3 machine trips and stops during the load operation of the 6kV plant 3A section bus, 6kV plant 3B section bus, 6kV plant 4A section bus, and 6kV plant 4B section bus.

[0049] Figure 7 This is the switch switching diagram when the #4 machine trips and stops during load operation with 6kV plant 3A section busbar, 6kV plant 3B section busbar, 6kV plant 4A section busbar, and 6kV plant 4B section busbar.

[0050] Figure 8This is the switch switching diagram when the back pressure machine trips and stops during load operation with 6kV plant 3A busbar, 6kV plant 3B busbar, 6kV plant 4A busbar, and 6kV plant 4B busbar ( Figure 8 (a) represents the first switching method, Figure 8 (b) represents the second switching method).

[0051] Description of reference numerals:

[0052] 1—Auxiliary power system; 2—Back pressure system; 1-1—Main transformer No. 3; 1-2—Generator No. 3; 1-3—High-voltage auxiliary transformer No. 3; 1-4—First circuit breaker; 1-5—Second circuit breaker; 1-6—6kV auxiliary busbar 3A; 1-7—Starting standby transformer; 1-8—Third circuit breaker; 1-9—Fourth circuit breaker; 1-10—Fifth circuit breaker; 1-11—Sixth circuit breaker; 1-12—6kV auxiliary busbar 3B; 1-13— 6kV plant busbar section 4A; 1-14—Main transformer No. 4; 1-15—Generator No. 4; 1-16—High-voltage plant transformer No. 4; 1-17—Seventh circuit breaker; 1-18—Eighth circuit breaker; 1-19—6kV plant busbar section 4B; 2-1—Back pressure machine; 2-2—Back pressure asynchronous generator output circuit breaker; 2-3—Current limiter; 2-4—Ninth circuit breaker; 2-5—Tenth circuit breaker; 2-6—Eleventh circuit breaker; 2-7—Twelfth circuit breaker. DETAILED DESCRIPTION

[0053] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments.

[0054] like Figure 1As shown, the present invention provides a back pressure machine switching system, including a plant power system 1 and a back pressure machine system 2; wherein, the back pressure machine system 2 is connected to the 6kV plant 3A segment bus 1-6, 6kV plant 3B segment bus 1-12, 6kV plant 4A segment bus 1-13 and 6kV plant 4B segment bus 1-19 of the plant power system 1 through the ninth circuit breaker 2-4, the tenth circuit breaker 2-5, the eleventh circuit breaker 2-6 and the twelfth circuit breaker 2-7 respectively. The auxiliary power system 1 includes a No. 3 main transformer 1-1 (the auxiliary power system generally includes a main transformer and a generator), a No. 3 generator 1-2, a No. 3 high-voltage auxiliary power transformer 1-3, a first circuit breaker 1-4, a second circuit breaker 1-5, a 6kV auxiliary power 3A section bus 1-6, a starting standby transformer 1-7, a third circuit breaker 1-8, a fourth circuit breaker 1-9, a fifth circuit breaker 1-10, a sixth circuit breaker 1-11, a 6kV auxiliary power 3B section bus 1- 12, 6kV plant 4A section bus 1-13, No. 4 main transformer 1-14, No. 4 generator 1-15, No. 4 high-voltage plant transformer 1-16, the seventh circuit breaker 1-17, the eighth circuit breaker 1-18, 6kV plant 4B section bus 1-19; wherein, the No. 3 generator 1-2 is connected to the power grid through the No. 3 main transformer 1-1, the high-voltage side of the No. 3 high-voltage plant transformer 1-3 is connected to the No. 3 generator 1-2 machine end, and its two low-voltage sides are respectively The 6kV plant 3A busbar 1-6 and the 6kV plant 3B busbar 1-12 are connected through the first circuit breaker 1-4 and the second circuit breaker 1-5; the high-voltage side of the starting standby transformer 1-7 is connected to the power grid, and one of the low-voltage sides is connected to the 6kV plant 3A busbar 1-6 and the 6kV plant 4A busbar 1-13 through the third circuit breaker 1-8 and the fourth circuit breaker 1-9, respectively, and the other low-voltage side is connected to the 6kV plant 3A busbar 1-6 and the 6kV plant 4A busbar 1-13 through the fifth circuit breaker 1-10 and the sixth circuit breaker 1 -11 is connected to the 6kV plant 3B section bus 1-12 and the 6kV plant 4B section bus 1-19; the No. 4 generator 1-15 is connected to the power grid through the No. 4 main transformer 1-14, and the high-voltage side of the No. 4 high-voltage plant transformer 1-16 is connected to the machine end of the No. 4 generator 1-15, and its two low-voltage sides are connected to the 6kV plant 4A section bus 1-13 and the 6kV plant 4B section bus 1-19 through the seventh circuit breaker 1-17 and the eighth circuit breaker 1-18 respectively.The back pressure machine system 2 includes a back pressure machine 2-1, a back pressure asynchronous generator output circuit breaker 2-2, a current limiter 2-3, a ninth circuit breaker 2-4, a tenth circuit breaker 2-5, an eleventh circuit breaker 2-6 and a twelfth circuit breaker 2-7; wherein, the back pressure machine 2-1 is connected to the 6kV plant 3A segment bus 1-6, the 6kV plant 3B segment bus 1-12, the 6kV plant 4A segment bus 1-13 and the 6kV plant 4B segment bus 1-19 of the plant power system 1 through the ninth circuit breaker 2-4, the tenth circuit breaker 2-5, the eleventh circuit breaker 2-6 and the twelfth circuit breaker 2-7 after passing through the back pressure asynchronous generator output circuit breaker 2-2 and the current limiter 2-3. When the twelfth circuit breaker 2-7 is in a closed state, the back pressure machine 2-1 is connected to the 6kV plant 4B section bus 1-19, and the electric energy generated by the back pressure machine 2-1 can supply the plant power of the 6kV plant 4B section bus 1-19 and the 6kV plant 4A section bus 1-13; when the electric energy generated by the back pressure machine 2-1 increases, so that it can still supply power to the 6kV plant 3B section bus 1-12 after meeting all the plant power needs of the No. 4 generator 1-15, the tenth circuit breaker 2-5 can be closed on the premise of disconnecting the second circuit breaker 1-5, so as to achieve the purpose of the back pressure machine 2-1 carrying the load of three bus sections, namely the 6kV plant 3B section bus 1-12, the 6kV plant 4A section bus 1-13 and the 6kV plant 4B section bus 1-19. On the basis of the back pressure machine 2-1 carrying three busbar loads, namely, the 6kV plant 3B segment bus 1-12, the 6kV plant 4A segment bus 1-13 and the 6kV plant 4B segment bus 1-19, if the electric energy generated by the back pressure machine continues to increase, so that it can still supply power to the 6kV plant 3A segment bus 1-6 after meeting the plant power demand of the No. 4 generator 1-15 and the 6kV plant 3B segment bus 1-12, the ninth circuit breaker 2-4 can be closed on the premise of disconnecting the first circuit breaker 1-4, so as to achieve the purpose of the back pressure machine 2-1 carrying four busbar loads, namely, the 6kV plant 3A segment bus 1-6, the 6kV plant 3B segment bus 1-12, the 6kV plant 4A segment bus 1-13 and the 6kV plant 4B segment bus 1-19.

[0055] like Figure 2 As shown in the example, the back pressure machine 2-1 with the 6kV plant 3B segment bus 1-12, the 6kV plant 4A segment bus 1-13 and the 6kV plant 4B segment bus 1-19 are operating normally, and the switching can be achieved through the following steps:

[0056] Step 1: During rated operation of the No. 3 generator 1-2 and the No. 4 generator 1-15, when the phase sequence, frequency, phase, and output voltage of the back pressure generator 2-1 are the same as those of the auxiliary power system 1, the back pressure generator 2-1 can be connected to the 6kV auxiliary power section 4B bus 1-19 by closing the twelfth circuit breaker 2-7;

[0057] Step 2: Increase the power of the back pressure generator 2-1 so that the plant load of the No. 4 generator 1-15 is fully supplied by the back pressure generator 2-1. At this time, the high-voltage side power of the No. 4 high-voltage plant transformer 1-16 is close to 0MW.

[0058] Step 3: Switch the load of the 6kV auxiliary bus 3B section 1-12 to the back pressure unit 2-1 by parallel switching, i.e., first close the tenth circuit breaker 2-5 and then open the second circuit breaker 1-5;

[0059] Step 4: Further increase the power generation of the back pressure machine 2-1, so that the high-voltage side power of the No. 4 high-voltage plant transformer 1-16 is close to 0MW again, and the plant power is not fed back to the grid.

[0060] like Figure 3 As shown, in this embodiment, during the operation of the back pressure machine 2-1 with the 6kV plant 3B segment bus 1-12, the 6kV plant 4A segment bus 1-13 and the 6kV plant 4B segment bus 1-19, the No. 3 generator 1-2 trips and stops. Since the operation mode of the back pressure machine 2-1 remains unchanged, the power supply of the 6kV plant 3B segment bus 1-12 is not affected. By closing the third circuit breaker 1-8, the 6kV plant 3A segment bus 1-6 can be switched to the starting standby transformer 1-7.

[0061] like Figure 4 As shown, in this embodiment, during the operation of the back pressure machine 2-1 with the 6kV plant 3B segment bus 1-12, the 6kV plant 4A segment bus 1-13 and the 6kV plant 4B segment bus 1-19, the No. 4 generator 1-15 trips and stops. At this time, the back pressure machine 2-1 trips together. The 6kV plant 4A segment bus 1-13, the 6kV plant 3B segment bus 1-12 and the 6kV plant 4B segment bus 1-19 can be switched to the starting standby transformer 1-7 by closing the fourth circuit breaker 1-9, the fifth circuit breaker 1-10 and the sixth circuit breaker 1-11.

[0062] like Figure 5 As shown, in this embodiment, during the operation of the back pressure machine 2-1 with 6kV plant 3B segment bus 1-12, 6kV plant 4A segment bus 1-13 and 6kV plant 4B segment bus 1-19, the back pressure machine 2-1 trips and stops. There are two switching methods: the first is as follows: Figure 5 The method shown in (a) is that when the back pressure asynchronous generator output circuit breaker 2-2, the ninth circuit breaker 2-4, the tenth circuit breaker 2-5, the eleventh circuit breaker 2-6 and the twelfth circuit breaker 2-7 are disconnected, the 6kV plant 3B section bus 1-12 can be switched to the starting standby transformer 1-7 by closing the fifth circuit breaker 1-10; the second method is as follows Figure 5The method shown in (b) is that when only the back-pressure asynchronous generator output circuit breaker 2-2 is disconnected, when the capacity of the No. 4 high-voltage plant transformer 1-16 meets the load requirement, the No. 4 high-voltage plant transformer 1-16 is operated with the 6kV plant 3B segment bus 1-12, the 6kV plant 4A segment bus 1-13 and the 6kV plant 4B segment bus 1-19.

[0063] like Figure 6 As shown in this embodiment, the back pressure machine 2-1 with 6kV plant 3A bus 1-6, 6kV plant 3B bus 1-12, 6kV plant 4A bus 1-13, and 6kV plant 4B bus 1-19 are operating normally. Switching can be achieved through the following steps:

[0064] Step 1: During rated operation of the No. 3 generator 1-2 and the No. 4 generator 1-15, when the phase sequence, frequency, phase, and output voltage of the back pressure generator 2-1 are the same as those of the auxiliary power system 1, the back pressure generator 2-1 can be connected to the 6kV auxiliary power section 4B bus 1-19 by closing the twelfth circuit breaker 2-7;

[0065] Step 2: Increase the power of the back pressure generator 2-1 so that the plant load of the No. 4 generator 1-15 is fully supplied by the back pressure generator 2-1. At this time, the high-voltage side power of the No. 4 high-voltage plant transformer 1-16 is close to 0MW.

[0066] Step 3: Switch the loads of the 6kV plant 3A busbar 1-6 and the 6kV plant 3B busbar 1-12 to the back pressure unit 2-1 through parallel switching, i.e., first close the ninth circuit breaker 2-4 and the tenth circuit breaker 2-5, and then open the first circuit breaker 1-4 and the second circuit breaker 1-5;

[0067] Step 4: Further increase the power generation of the back pressure machine 2-1, so that the high-voltage side power of the No. 4 high-voltage plant transformer 1-16 is close to 0MW again, and the plant power is not fed back to the grid.

[0068] At the same time, if Figure 6 As shown, in this embodiment, when the back pressure machine 2-1 is operating with the 6kV plant 3A segment bus 1-6, the 6kV plant 3B segment bus 1-12, the 6kV plant 4A segment bus 1-13, and the 6kV plant 4B segment bus 1-19, the No. 3 generator 1-2 trips and stops. Since the operating mode of the back pressure machine 2-1 remains unchanged, the power supply of the 6kV plant 3A segment bus 1-6 and the 6kV plant 3B segment bus 1-12 is not affected.

[0069] like Figure 7As shown, in this embodiment, during the operation of the back pressure machine 2-1 with the 6kV plant 3A segment bus 1-6, 6kV plant 3B segment bus 1-12, 6kV plant 4A segment bus 1-13, and 6kV plant 4B segment bus 1-19, the No. 4 generator 1-15 trips and stops. At this time, the back pressure machine 2-1 trips together. The 6kV plant 3A segment bus 1-6, 6kV plant 4A segment bus 1-13, 6kV plant 3B segment bus 1-12, and 6kV plant 4B segment bus 1-19 can be switched to the starting standby transformer 1-7 by closing the third circuit breaker 1-8, the fourth circuit breaker 1-9, the fifth circuit breaker 1-10, and the sixth circuit breaker 1-11.

[0070] like Figure 8 As shown, in this embodiment, during the operation of the back pressure machine 2-1 with 6kV plant 3A bus 1-6, 6kV plant 3B bus 1-12, 6kV plant 4A bus 1-13, and 6kV plant 4B bus 1-19, the back pressure machine 2-1 trips and stops. There are two switching methods: the first is as follows: Figure 8 The method shown in (a) is that when the back-pressure asynchronous generator output circuit breaker 2-2, the ninth circuit breaker 2-4, the tenth circuit breaker 2-5, the eleventh circuit breaker 2-6 and the twelfth circuit breaker 2-7 are disconnected, the 6kV plant 3A section bus 1-6 and the 6kV plant 3B section bus 1-12 can be switched to the starting standby transformer 1-7 by closing the third circuit breaker 1-8 and the fifth circuit breaker 1-10; the second method is as follows Figure 8 The method shown in (b) is that when only the back-pressure asynchronous generator output circuit breaker 2-2 is disconnected, when the capacity of the No. 4 high-voltage plant transformer 1-16 meets the load requirement, the No. 4 high-voltage plant transformer 1-16 is operated with the 6kV plant 3A segment bus 1-6, the 6kV plant 3B segment bus 1-12, the 6kV plant 4A segment bus 1-13 and the 6kV plant 4B segment bus 1-19.

[0071] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural change made to the above embodiment based on the technical essence of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A back pressure machine switching system, characterized by: It includes a plant power system (1) and a back pressure machine system (2); wherein, The back pressure machine system (2) is connected to the 6kV plant 3A section busbar (1-6), the 6kV plant 3B section busbar (1-12), the 6kV plant 4A section busbar (1-13) and the 6kV plant 4B section busbar (1-19) of the plant power system (1) through the ninth circuit breaker (2-4), the tenth circuit breaker (2-5), the eleventh circuit breaker (2-6) and the twelfth circuit breaker (2-7) respectively; The plant power system (1) comprises a No. 3 main transformer (1-1), a No. 3 generator (1-2), a No. 3 high-voltage plant transformer (1-3), a first circuit breaker (1-4), a second circuit breaker (1-5), a 6kV plant 3A section busbar (1-6), a starting standby transformer (1-7), a third circuit breaker (1-8), a fourth circuit breaker (1-9), a fifth circuit breaker (1-10), a sixth circuit breaker (1-11), a 6kV plant 3B section busbar (1-12), a 6kV plant 4A section busbar (1-13), a No. 4 main transformer (1-14), a No. 4 generator (1-15), a No. 4 high-voltage plant transformer (1-16), a seventh circuit breaker (1-17), an eighth circuit breaker (1-18) and a 6kV plant 4B section busbar (1-19); wherein, The No. 3 generator (1-2) is connected to the power grid via the No. 3 main transformer (1-1); the No. 3 high-voltage plant transformer (1-3) is connected to the No. 3 generator (1-2) at its high-voltage side, and its two low-voltage sides are connected to the 6kV plant 3A busbar (1-6) and the 6kV plant 3B busbar (1-12) via the first circuit breaker (1-4) and the second circuit breaker (1-5) respectively; the starting standby transformer (1-7) is connected to the power grid at its high-voltage side, and one of its low-voltage sides is connected to the 6kV plant 3A busbar (1-6) and the 6kV plant 4A busbar via the third circuit breaker (1-8) and the fourth circuit breaker (1-9) respectively. Line (1-13), the other low-voltage side is connected to the 6kV plant 3B section bus (1-12) and the 6kV plant 4B section bus (1-19) through the fifth circuit breaker (1-10) and the sixth circuit breaker (1-11); the No. 4 generator (1-15) is connected to the power grid through the No. 4 main transformer (1-14), the high-voltage side of the No. 4 high-voltage plant transformer (1-16) is connected to the machine end of the No. 4 generator (1-15), and its two low-voltage sides are connected to the 6kV plant 4A section bus (1-13) and the 6kV plant 4B section bus (1-19) through the seventh circuit breaker (1-17) and the eighth circuit breaker (1-18); The back pressure machine system (2) comprises a back pressure machine (2-1), a back pressure asynchronous generator outlet circuit breaker (2-2), a current limiter (2-3), a ninth circuit breaker (2-4), a tenth circuit breaker (2-5), an eleventh circuit breaker (2-6) and a twelfth circuit breaker (2-7); wherein, The back pressure machine (2-1) is connected to the 6kV plant 3A section busbar (1-6), the 6kV plant 3B section busbar (1-12), the 6kV plant 4A section busbar (1-13) and the 6kV plant 4B section busbar (1-19) of the plant power system (1) through the back pressure asynchronous generator outlet circuit breaker (2-2) and the current limiter (2-3) respectively through the ninth circuit breaker (2-4), the tenth circuit breaker (2-5), the eleventh circuit breaker (2-6) and the twelfth circuit breaker (2-7); The back pressure machine (2-1) is operated with the load of three bus sections, namely, the 6kV plant 3B bus section (1-12), the 6kV plant 4A bus section (1-13), and the 6kV plant 4B bus section (1-19): Switching method under normal working conditions Step 1: During the rated operation of the No. 3 generator (1-2) and the No. 4 generator (1-15), when the phase sequence, frequency, phase and output voltage of the back pressure machine (2-1) are the same as those of the plant power system (1), the back pressure machine (2-1) is connected to the 6kV plant 4B section bus (1-19) by closing the twelfth circuit breaker (2-7); Step 2: Increase the power of the back pressure machine (2-1) so that the plant load of generator No. 4 (1-15) is fully supplied by the back pressure machine (2-1). At this time, the high-voltage side power of the No. 4 high-voltage plant transformer (1-16) is close to 0MW. Step 3: Switch the load of the 6kV plant 3B busbar (1-12) to the back pressure machine (2-1) by parallel switching, i.e., first close the tenth circuit breaker (2-5) and then open the second circuit breaker (1-5); Step 4: Further increase the power generation of the back pressure machine (2-1) to make the high-voltage side power of the No. 4 high-voltage plant transformer (1-16) close to 0MW again, and prevent the plant power from being fed back to the grid; (2) Switching method under abnormal working conditions 1) When the No. 3 generator (1-2) trips and stops, the power supply of the 6kV plant 3B section bus (1-12) is not affected because the operation mode of the back pressure machine (2-1) remains unchanged. By closing the third circuit breaker (1-8), the 6kV plant 3A section bus (1-6) is switched to the start-up standby transformer (1-7); 2) When the No. 4 generator (1-15) trips and stops, the back pressure machine (2-1) trips in conjunction with the 4th circuit breaker (1-9), the 5th circuit breaker (1-10) and the 6th circuit breaker (1-11) are closed to switch the 6kV plant 4A section bus (1-13), the 6kV plant 3B section bus (1-12) and the 6kV plant 4B section bus (1-19) to the starting standby transformer (1-7); 3) When the back pressure machine (2-1) trips and stops, there are two switching methods: The first method is to switch the 6kV plant 3B section busbar (1-12) to the starting standby transformer (1-7) by closing the fifth circuit breaker (1-10) while disconnecting the back-pressure asynchronous generator outlet circuit breaker (2-2), the ninth circuit breaker (2-4), the tenth circuit breaker (2-5), the eleventh circuit breaker (2-6) and the twelfth circuit breaker (2-7); The second method is to disconnect only the back-pressure asynchronous generator output circuit breaker (2-2), and when the capacity of the No. 4 high-voltage plant transformer (1-16) meets the load requirement, operate the No. 4 high-voltage plant transformer (1-16) with the 6kV plant 3B section bus (1-12), the 6kV plant 4A section bus (1-13) and the 6kV plant 4B section bus (1-19).

2. A back pressure machine switching system according to claim 1, characterized in that: When the twelfth circuit breaker (2-7) is in a closed state, the back pressure machine (2-1) is connected to the 6kV plant 4B section bus (1-19), and the electric energy generated by the back pressure machine (2-1) supplies the plant power of the 6kV plant 4B section bus (1-19) and the 6kV plant 4A section bus (1-13); when the electric energy generated by the back pressure machine (2-1) increases so that it can still supply power to the 6kV plant 3B section bus (1-12) after meeting all the plant power requirements of the No. 4 generator (1-15), the tenth circuit breaker (2-5) is closed under the premise of disconnecting the second circuit breaker (1-5), so as to achieve the purpose of the back pressure machine (2-1) carrying the load of three bus sections, namely the 6kV plant 3B section bus (1-12), the 6kV plant 4A section bus (1-13) and the 6kV plant 4B section bus (1-19).

3. The back pressure machine switching system according to claim 1, characterized in that: On the basis of the back pressure machine (2-1) being operated with a total of three busbar loads, namely, a 6kV plant-use 3B segment busbar (1-12), a 6kV plant-use 4A segment busbar (1-13), and a 6kV plant-use 4B segment busbar (1-19), if the electric energy generated by the back pressure machine continues to increase so that it can still supply power to the 6kV plant-use 3A segment busbar (1-6) after meeting the plant power demand of the No. 4 generator (1-15) and the 6kV plant-use 3B segment busbar (1-12), the ninth circuit breaker (2-4) is closed under the premise of disconnecting the first circuit breaker (1-4), thereby achieving the purpose of the back pressure machine (2-1) being operated with a total of four busbar loads, namely, a 6kV plant-use 3A segment busbar (1-6), a 6kV plant-use 3B segment busbar (1-12), a 6kV plant-use 4A segment busbar (1-13), and a 6kV plant-use 4B segment busbar (1-19).

4. The back pressure machine switching system according to claim 1, characterized in that: The back pressure machine (2-1) is operated with loads of four busbars, namely, the 6kV plant 3A busbar (1-6), the 6kV plant 3B busbar (1-12), the 6kV plant 4A busbar (1-13), and the 6kV plant 4B busbar (1-19). Switching method under normal working conditions Step 1: During the rated operation of the No. 3 generator (1-2) and the No. 4 generator (1-15), when the phase sequence, frequency, phase and output voltage of the back pressure machine (2-1) are the same as those of the plant power system (1), the back pressure machine (2-1) is connected to the 6kV plant 4B section bus (1-19) by closing the twelfth circuit breaker (2-7); Step 2: Increase the power of the back pressure machine (2-1) so that the plant load of generator No. 4 (1-15) is fully supplied by the back pressure machine (2-1). At this time, the high-voltage side power of the No. 4 high-voltage plant transformer (1-16) is close to 0MW. Step 3: Switch the loads of the 6kV plant 3A busbar (1-6) and the 6kV plant 3B busbar (1-12) to the back pressure machine (2-1) by parallel switching, i.e., first closing the ninth circuit breaker (2-4) and the tenth circuit breaker (2-5), and then opening the first circuit breaker (1-4) and the second circuit breaker (1-5); Step 4: Further increase the power generation of the back pressure generator (2-1) so that the high-voltage side power of the No. 4 high-voltage plant transformer (1-16) is close to 0MW again, and the plant power is not fed back to the grid; (2) Switching method under abnormal working conditions 1) When the No. 3 generator (1-2) trips and stops, the power supply of the 6kV plant 3A section bus (1-6) and the 6kV plant 3B section bus (1-12) is not affected because the operation mode of the back pressure machine (2-1) remains unchanged; 2) When the No. 4 generator (1-15) trips and stops, the back pressure machine (2-1) trips in conjunction with the back pressure machine (2-1), and the 6kV plant 3A busbar (1-6), 6kV plant 4A busbar (1-13), 6kV plant 3B busbar (1-12), and 6kV plant 4B busbar (1-19) are switched to the starting standby transformer (1-7) by closing the third circuit breaker (1-8), the fourth circuit breaker (1-9), the fifth circuit breaker (1-10), and the sixth circuit breaker (1-11); 3) When the back pressure machine (2-1) trips and stops, there are two switching methods: The first method is to switch the 6kV plant 3A section busbar (1-6) and the 6kV plant 3B section busbar (1-12) to the starting standby transformer (1-7) by closing the third circuit breaker (1-8) and the fifth circuit breaker (1-10) while disconnecting the back-pressure asynchronous generator outlet circuit breaker (2-2), the ninth circuit breaker (2-4), the tenth circuit breaker (2-5), the eleventh circuit breaker (2-6) and the twelfth circuit breaker (2-7); The second method is to disconnect only the back-pressure asynchronous generator output circuit breaker (2-2), and when the capacity of the No. 4 high-voltage plant transformer (1-16) meets the load requirement, operate the No. 4 high-voltage plant transformer (1-16) with the 6kV plant 3A section bus (1-6), the 6kV plant 3B section bus (1-12), the 6kV plant 4A section bus (1-13) and the 6kV plant 4B section bus (1-19).

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