An aircraft multi-source heterogeneous power supply system and a regulation method thereof
The system architecture, which combines gas turbine generators and battery packs for power supply, solves the problem of large-scale power requirements for space-to-ground reciprocating spacecraft, achieves efficient and reliable power supply, reduces system weight and size, and improves power supply safety under extreme operating conditions.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHANGSHA AEROSPACE TECHNOLOGY INNOVATION RESEARCH INSTITUTE
- Filing Date
- 2026-06-23
- Publication Date
- 2026-07-21
AI Technical Summary
Existing technologies cannot effectively adapt to the large power requirements of space-to-ground reciprocating vehicles, resulting in a sharp increase in system size and weight. This makes it impossible to meet the stringent weight constraints of the vehicles and also fails to resolve the contradiction between system redundancy and energy efficiency caused by the extremely high peak-to-average power ratio.
The system architecture adopts a combination of gas turbine generator and battery pack for power supply. Through automatic switching of generator controller and gas switching valve, it realizes multi-source heterogeneous power supply. Combined with ground power supply and distribution equipment, it constructs a closed-loop power matching and control logic to adapt to the power characteristics of different flight stages.
It improves system energy density, reduces system size and weight, ensures power supply reliability and efficient use of primary energy, adapts to the load requirements of the entire flight profile, extends the life of core components, and improves power supply safety under extreme conditions.
Smart Images
Figure CN122437168A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of aircraft electrical design technology, specifically to a multi-source heterogeneous power supply system for aircraft and its control method. Background Technology
[0002] For aircraft capable of round-trip air transport, a typical flight mission consists of five phases: takeoff, air-breathing acceleration climb, rocket-assisted acceleration climb, reentry energy management, and approach / landing. The power modes and flight environments of such aircraft vary greatly across different mission phases, resulting in orders-of-magnitude differences in the types of electrical loads, power consumption, and load characteristics. For example, the takeoff and air-breathing acceleration climb phases require the simultaneous operation of high-voltage, high-power electromechanical loads such as air servo motors, power intake and exhaust actuators, circulation pumps, and landing gear, as well as pipeline solenoid valves and low-voltage, low-power electronic loads, with peak power requirements reaching hundreds of kilowatts. The rocket-assisted acceleration climb and reentry energy management phases only require the operation of low-power valves and electronic loads, and low-power servo mechanisms, significantly reducing power consumption. The approach / landing phase, however, again presents a concentrated power supply requirement for high-power electromechanical loads. Meanwhile, during the takeoff and acceleration climb phases when peak power demand is highest, the engine of this type of aircraft cannot provide shaft power output and can only provide gas flow for power generation. After the acceleration climb phase ends, the gas flow supply capacity disappears completely, and subsequent flight phases cannot rely on the gas flow to continuously generate electricity.
[0003] In existing power supply technologies in similar fields, traditional launch vehicles only have a single flight mission during the ascent phase, resulting in a simple flight profile, small and uniform electrical load power across the entire rocket. They generally use chemical battery packs to directly power the entire rocket load. This approach cannot meet the wide-ranging power demands of spacecraft operating between Earth and space. When facing peak power demands of hundreds of kilowatts, pure chemical battery power supply leads to a sharp increase in system size and weight, failing to meet the stringent weight constraints of the spacecraft. Conventional aircraft generally employ a three-tiered power supply architecture: a main power source from an engine turbine shaft-driven generator, a backup power source from an air turbine, and an emergency power source from chemical batteries. This architecture relies on the continuous shaft power provided by the engine for continuous power generation, which is completely unsuitable for the unique dynamic characteristics of spacecraft operating between Earth and space without shaft power output and only able to provide gas flow for short periods. Furthermore, it cannot resolve the contradiction between system redundancy and energy efficiency caused by the extremely high peak-to-average power ratio. Summary of the Invention
[0004] To address the shortcomings of the existing technology, this invention provides a multi-source heterogeneous power supply system for aircraft and its control method, which can achieve efficient and highly reliable power supply for the entire flight profile and the entire load of the aircraft under the strict weight constraints of a spacecraft traveling between Earth and space.
[0005] To achieve the above object, the present invention provides a multi-source heterogeneous power supply system for an aircraft, including a power supply bus, an electrical load, a ground power supply, a ground control device, and a distributor. The ground power supply is electrically connected to the power supply bus, and the distributor is electrically connected to the power supply bus, the electrical load, and the ground control device respectively; The power supply system further includes a battery pack, a first gas turbine generator, a first generator controller, a first gas switch valve, a second gas turbine generator, a second generator controller, and a second gas switch valve; The battery pack, the first generator controller, and the second generator controller are electrically connected to the power supply bus respectively. The first gas turbine generator and the second gas turbine generator are electrically connected to the first generator controller and the second generator controller respectively. The first gas switch valve and the second gas switch valve are respectively arranged on the gas pipelines of the first gas turbine generator and the second gas turbine generator; The first generator controller and the second generator controller are communicatively connected to the first gas switch valve and the second gas switch valve respectively, and are used to control the opening and closing of the first gas switch valve and the second gas switch valve, and the power supply state of the battery pack connected to the power supply bus according to the comparison result of the real-time power of the electrical load, the rated power of the first generator controller, and the rated power of the second generator controller.
[0006] In one embodiment, when P L > P1 + P2, the first generator controller and the second generator controller respectively control the first gas switch valve and the second gas switch valve to open, and the battery pack, the first gas turbine generator, and the second gas turbine generator jointly supply power to the power supply bus; Where, P L is the real-time power of the electrical load, P1 is the rated power of the first generator controller, and P2 is the rated power of the second generator controller.
[0007] In one embodiment, when P L < P1 + P2, the second generator controller controls the second gas switch valve to disconnect, and enters the single generator power supply mode; In the single generator power supply mode: When P L > P1, the battery pack and the first gas turbine generator jointly supply power to the power supply bus; When P L < P1, the first generator controller controls the first gas switch valve to disconnect, and the battery pack supplies power to the power supply bus alone; Among them, P L P1 is the real-time power of the electrical load, P2 is the rated power of the first generator controller, and P2 is the rated power of the second generator controller.
[0008] In one embodiment, when the battery pack supplies power to the power bus alone, the real-time power of the electrical load is continuously collected and the average power P within a first set time window is calculated. L1 : When P L1 When P1 is less than or equal to 1, the battery pack supplies power to the power supply bus independently. When P L1 When P1 is reached, the first generator controller controls the first gas switch valve to open.
[0009] In one embodiment, after the first generator controller controls the first gas switch valve to open, the real-time power of the electrical load is continuously collected and the average power P within a second set time window is calculated. L2 When P L2 When P1+P2, the second generator controller controls the second gas switch valve to open.
[0010] In one embodiment, the window lengths of both the first set time window and the second set time window are 5s to 10s.
[0011] To achieve the above objectives, the present invention also provides a control method for the above-mentioned multi-source heterogeneous power supply system of an aircraft, comprising the following steps: Step 1: Connect the ground power supply to the power supply bus and send a power-on command to the power distributor through the ground control equipment to complete the ground power-on of each electrical load; Step 2: Send start commands to the first generator controller and the second generator controller through the ground control equipment, and simultaneously control the opening of the first gas switch valve and the second gas switch valve. The first gas turbine generator and the second gas turbine generator start and generate electricity. At the same time, the power supply path of the ground power supply is automatically shut off, completing the power transfer from the generator to the ground. Step 3: Collect the real-time power P of the electrical load. L Comparison P L Based on the numerical relationship between the rated power P1 of the first generator controller and the rated power P2 of the second generator controller, the corresponding control strategy is executed: If P L >P1+P2 controls the battery pack to connect to the power supply bus, and jointly supplies power with the first gas turbine generator and the second gas turbine generator; If P L =P1+P2, maintaining the current state of dual-generator power supply; If P L <P1 + P2, control to turn off the second gas switch valve and enter the single generator power supply mode; Step 4, in the single generator power supply mode, compare P L with the rated power P1 of the first generator controller, and execute the corresponding control strategy: If P L > P1, control the battery pack to be connected to the power supply bus and supply power jointly with the first gas turbine generator; If P L = P1, maintain the current state of single generator power supply; If P L < P1, control to turn off the first gas switch valve and enter the battery pack single power supply mode; Step 5, in the battery pack single power supply mode, continuously collect the real-time power of the electrical load and calculate the power average value P within the first set time window L1 and the power average value P within the second set time window L2 , compare P L1 , P L2 with the rated power P1 of the first generator controller and the rated power P2 of the second generator controller, and execute the corresponding control strategy: When P L1 ≤ P1, maintain the battery pack single power supply mode; When P L1 > P1, control the first gas switch valve to open, and when P L2 ≤ P1 + P2, return to Step 4, and when P L2 > P1 + P2, control the second gas switch valve to open and then return to Step 3.
[0012] Compared with the prior art, the present invention has the following beneficial technical effects: 1. The power supply system in the present invention adopts a system architecture of combined power supply of gas turbine power generation and battery pack, effectively improving the energy density of the system and reducing the volume and weight of the system; 2. The regulation method in the present invention can effectively achieve automatic and reliable switching among ground power supply, redundant gas turbine power generation and battery pack, ensuring both the power supply reliability of the system and the efficient utilization of primary energy. Brief Description of the Drawings
[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.
[0014] Figure 1 This is a schematic diagram of the structure of the multi-source heterogeneous power supply system for an aircraft in an embodiment of the present invention; Figure 2 This is a flowchart of the control method in an embodiment of the present invention.
[0015] Reference numerals: 1. Power supply busbar; 2. Electrical load; 3. Ground power supply; 4. Ground control equipment; 5. Power distributor; 6. Battery pack; 7. First gas turbine generator; 8. First generator controller; 9. First gas switch valve; 10. Second gas turbine generator; 11. Second generator controller; 12. Second gas switch valve.
[0016] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation
[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0018] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.
[0019] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.
[0020] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection, an electrical connection, a physical connection, or a wireless communication connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two elements or the interaction between two elements, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.
[0021] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.
[0022] like Figure 1 The diagram illustrates a multi-source heterogeneous power supply system for an aircraft disclosed in this embodiment. It mainly includes a power supply bus 1, an electrical load 2, a ground power source 3, ground control equipment 4, a power distributor 5, a battery pack 6, a first gas turbine generator 7, a first generator controller 8, a first gas switching valve 9, a second gas turbine generator 10, a second generator controller 11, and a second gas switching valve 12. The ground power source 3, battery pack 6, first generator controller 8, and second generator controller 11 are electrically connected to the power supply bus 1. The power distributor 5 is electrically connected to the power supply bus 1, the electrical load 2, and the ground control equipment 4. The ground control equipment 4 is electrically connected to the first generator controller 8 and the second generator controller 11. By employing a system architecture that combines gas turbine power generation and battery pack 6 for power supply, the system's energy density is effectively improved, while its size and weight are reduced.
[0023] The first gas turbine generator 7 is electrically connected to the first generator controller 8, and the second gas turbine generator 10 is electrically connected to the second generator controller 11. A first gas switching valve 9 is located on the gas pipeline of the first gas turbine generator 7 and is used to control whether the first gas turbine generator 7 generates electricity; a second gas switching valve 12 is located on the gas pipeline of the second gas turbine generator 10 and is used to control whether the second gas turbine generator 10 generates electricity. Preferably, both the first gas switching valve 9 and the second gas switching valve 12 are located on the gas outlet pipeline to improve their service life. The first generator controller 8 is communicatively connected to the first gas switching valve 9 to control its on / off state; the second generator controller 11 is communicatively connected to the second gas switching valve 12 to control its on / off state.
[0024] The power supply system in this embodiment is built-in with a control strategy module communicatively connected to the first generator controller 8, the second generator controller 11, and the battery pack 6, and is used to control the on / off of the first gas switch valve 9 and the second gas switch valve 12, as well as the power supply state of the battery pack 6 connected to the power supply bus 1, according to the comparison result of the real-time power of the electrical load 2, the rated power of the first generator controller 8, and the rated power of the second generator controller 11.
[0025] In this embodiment, let the real-time power of the electrical load 2 be P L , the rated power of the first generator controller 8 be P1, the rated power of the second generator controller 11 be P2, the power supply voltage of the power supply bus 1 be U0, the power supply voltage of the ground power supply 3 be U1, the rated output voltage of the first generator controller 8 and the second generator controller 11 be U2, the output voltage of the battery pack 6 be U3, and the initial voltage of the battery pack 6 be U 30 . Among them, U2 > U1 > U 30 .
[0026] In this embodiment, according to the comparison result of the real-time power of the electrical load 2, the rated power of the first generator controller 8, and the rated power of the second generator controller 11, the process of controlling the on / off of the first gas switch valve 9 and the second gas switch valve 12, as well as the power supply state of the battery pack 6 connected to the power supply bus 1, specifically includes: When P L < P1 + P2, the second generator controller 11 controls the second gas switch valve 12 to disconnect, and enters the single generator power supply mode. In the single generator power supply mode: When P L > P1, the battery pack 6 and the first gas turbine generator 7 jointly supply power to the power supply bus 1; When P L < P1, the first generator controller 8 controls the first gas switch valve 9 to disconnect, and the battery pack 6 supplies power to the power supply bus 1 alone.
[0027] In the mode where the battery pack 6 supplies power to the power supply bus 1 alone, continuously collect the real-time power of the electrical load 2 and calculate the power average value P L1 within the first set time window: When P L1 ≤ P1, keep the battery pack 6 supplying power to the power supply bus 1 alone; when P L1 > P1, the first generator controller 8 controls the first gas switch valve 9 to open. After the first generator controller 8 controls the first gas switch valve 9 to open, continuously collect the real-time power of the electrical load 2 and calculate the power average value P L2 within the second set time window. When P L2When P1 + P2, the second generator controller 11 controls the second gas switch valve 12 to open. Among them, the window lengths of the first set time window and the second set time window are both 5s to 10s, preferably 5s.
[0028] Based on the above control strategy, this embodiment also discloses a regulation method for the above-mentioned multi-source heterogeneous power supply system of the aircraft. Refer to Figure 2 , and this regulation method mainly includes the following steps: Step 1: Connect the ground power supply 3 to the power supply bus 1. At this time, the power supply voltage U0 of the power supply bus 1 is equal to the output voltage U1 of the ground power supply 3. Subsequently, send a power-on command to the distributor 5 through the ground control device 4 to complete the ground power-on of each electrical load 2. Step 2: Send a start command to the first generator controller 8 and the second generator controller 11 through the ground control device 4 to synchronously control the opening of the first gas switch valve 9 and the second gas switch valve 12. The first gas turbine generator 7 and the second gas turbine generator 10 start and generate electricity. The rated output voltage U2 of the first generator controller 8 and the second generator controller 11 is higher than the output voltage U1 of the ground power supply 3, and the power supply path of the ground power supply 3 is automatically turned off to complete the transfer of power from the ground to the aircraft. At the same time, the ground control device 4 disconnects the electrical connection with the first generator controller 8 and the second generator controller 11. Step 3: Collect the real-time power P of the electrical load 2 L , and compare the value relationship between P L and the rated power P1 of the first generator controller 8 and the rated power P2 of the second generator controller 11, and execute the corresponding control strategy: If P L > P1 + P2, control the battery pack 6 to be connected to the power supply bus 1 to jointly supply power with the first gas turbine generator 7 and the second gas turbine generator 10; If P L = P1 + P2, maintain the current state of dual-generator power supply; If P L < P1 + P2, control the second gas switch valve 12 to be turned off and enter the single-generator power supply mode; Step 4: In the single-generator power supply mode, compare the value relationship between P L and the rated power P1 of the first generator controller 8, and execute the corresponding control strategy: If P L > P1, control the battery pack 6 to be connected to the power supply bus 1 to jointly supply power with the first gas turbine generator 7; If P L = P1, maintain the current state of single-generator power supply; If P L<P1, control to turn off the first gas switch valve 9 and enter the mode of independent power supply by the battery pack 6; Step 5, in the mode of independent power supply by the battery pack 6, continuously collect the real-time power of the electrical load 2 and calculate the average power P within the first set time window L1 and the average power P within the second set time window L2 , and compare P L1 , P L2 with the rated power P1 of the first generator controller 8 and the rated power P2 of the second generator controller 11, and execute the corresponding control strategy: When P L1 ≤P1, maintain the mode of independent power supply by the battery pack 6; When P L1 >P1, control to open the first gas switch valve 9, and when P L2 ≤P1+P2, return to Step 4, and when P L2 >P1+P2, control to open the second gas switch valve 12 and then return to Step 3.
[0029] The regulation method in this embodiment constructs a closed-loop power matching regulation logic, which can adaptively complete the switching of working modes of combined power supply by two gas turbine generators, single gas turbine generator power supply, independent power supply by the battery pack 6, and multi-source combined energy supplement power supply according to the real-time power of the electrical load 2, so as to effectively adapt to the dynamic characteristics and energy supply conditions of the whole mission segment of the space shuttle. At the same time, through the design of the judgment threshold of the average power, the problem of frequent switching caused by the instantaneous fluctuation of the load power is avoided, the action frequency of the gas switch valve and the generator is greatly reduced, the service life of the core components is extended, and the reliability of the system in long-term operation is further improved. In addition, the hierarchical switching design of the two gas turbine generators realizes the redundant fault tolerance ability of mutual backup. Under the condition of a single generator failure, the other generator can quickly take over the basic power demand and cooperate with the battery pack 6 to supplement the power gap to ensure the uninterrupted power supply of all loads on the spacecraft, and greatly improve the power supply safety under extreme conditions.
[0030] The above are only the preferred embodiments of the present invention, and do not limit the protection scope of the present invention. Any equivalent structural transformation made under the inventive concept of the present invention by using the content of the specification and drawings of the present invention, or directly / indirectly applied in other related technical fields, is included in the protection scope of the present invention.
Claims
1. A multi-source heterogeneous power supply system for an aircraft, comprising a power supply bus, an electrical load, a ground power supply, ground control equipment, and a power distribution unit, wherein the ground power supply is electrically connected to the power supply bus, and the power distribution unit is electrically connected to the power supply bus, the electrical load, and the ground control equipment, respectively; Its features are, It also includes a battery pack, a first gas turbine generator, a first generator controller, a first gas switching valve, a second gas turbine generator, a second generator controller, and a second gas switching valve; The battery pack, the first generator controller, and the second generator controller are electrically connected to the power supply bus, the first gas turbine generator and the second gas turbine generator are electrically connected to the first generator controller and the second generator controller, respectively, and the first gas switch valve and the second gas switch valve are respectively installed on the gas pipelines of the first gas turbine generator and the second gas turbine generator. The first generator controller and the second generator controller are respectively communicatively connected to the first gas switch valve and the second gas switch valve, and are used to control the opening and closing of the first gas switch valve and the second gas switch valve, as well as the power supply status of the battery pack connected to the power supply bus, based on the comparison result of the real-time power of the electrical load, the rated power of the first generator controller, and the rated power of the second generator controller.
2. The multi-source heterogeneous power supply system for aircraft according to claim 1, characterized in that, When P L When P1+P2, the first generator controller and the second generator controller respectively control the first gas switch valve and the second gas switch valve to open, and the battery pack, the first gas turbine generator and the second gas turbine generator jointly supply power to the power supply bus. Among them, P L P1 is the real-time power of the electrical load, P2 is the rated power of the first generator controller, and P2 is the rated power of the second generator controller.
3. The multi-source heterogeneous power supply system for aircraft according to claim 1 or 2, characterized in that, When P L When P1 + P2, the second generator controller controls the second gas switch valve to disconnect, and enters the single generator power supply mode; In the single generator power supply mode: When P L >At time P1, the battery pack and the first gas turbine generator jointly supply power to the power supply bus; When P L <is less than P1, the first generator controller controls the first gas switch valve to disconnect, and the battery pack supplies power to the power supply bus alone; Among them, P L P1 is the real-time power of the electrical load, P2 is the rated power of the first generator controller, and P2 is the rated power of the second generator controller.
4. The aircraft multi-source heterogeneous power supply system according to claim 3, characterized in that, In the mode where the battery pack supplies power to the power bus alone, the real-time power of the electrical load is continuously collected and the average power P within a first set time window is calculated. L1 : When P L1 When P1 is less than or equal to 1, the battery pack supplies power to the power supply bus independently. When P L1 When P1 is reached, the first generator controller controls the first gas switch valve to open.
5. The multi-source heterogeneous power supply system for aircraft according to claim 4, characterized in that, After the first generator controller controls the first gas switch valve to open, it continuously collects the real-time power of the electrical load and calculates the average power P within the second set time window. L2 When P L2 When P1+P2, the second generator controller controls the second gas switch valve to open.
6. The multi-source heterogeneous power supply system for aircraft according to claim 5, characterized in that, The window lengths of both the first and second set time windows are 5s to 10s.
7. A method for controlling a multi-source heterogeneous power supply system for an aircraft as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Step 1: Connect the ground power supply to the power supply bus and send a power-on command to the power distributor through the ground control equipment to complete the ground power-on of each electrical load; Step 2: Send start commands to the first generator controller and the second generator controller through the ground control equipment, and simultaneously control the opening of the first gas switch valve and the second gas switch valve. The first gas turbine generator and the second gas turbine generator start and generate electricity. At the same time, the power supply path of the ground power supply is automatically shut off, completing the power transfer from the generator to the ground. Step 3: Collect the real-time power P of the electrical load. L Comparison P L Based on the numerical relationship between the rated power P1 of the first generator controller and the rated power P2 of the second generator controller, the corresponding control strategy is executed: If P L >P1+P2 controls the battery pack to connect to the power supply bus, and jointly supplies power with the first gas turbine generator and the second gas turbine generator; If P L =P1+P2, maintaining the current state of dual-generator power supply; If P L <P1 + P2, control to turn off the second gas switch valve and enter the single generator power supply mode; Step 4, in single generator power supply mode, compare P L The numerical relationship between the rated power P1 of the first generator controller and the actual power is used to execute the corresponding control strategy: If P L >P1 controls the battery pack to connect to the power supply bus and supply power together with the first gas turbine generator; If P L =P1, maintain the current state of single generator power supply; If P L <P1, control to turn off the first gas switch valve and enter the mode of single power supply by the battery pack; Step 5: In the battery pack-only power supply mode, continuously collect the real-time power of the electrical load and calculate the average power P within the first set time window. L1 and the average power P within the second set time window L2 Comparison P L1 P L2 Based on the numerical relationship between the rated power P1 of the first generator controller and the rated power P2 of the second generator controller, the corresponding control strategy is executed: When P L1 When P1 is ≤, maintain the battery pack's independent power supply mode; When P L1 >At P1, the first gas switch valve is opened, and at P L2 If P ≤ P1 + P2, return to step 4. L2 After controlling the second gas switch valve to open when P1+P2, return to step 3.