A gas heat pump system with a DC generator and a control method

Abstract

The application discloses a gas heat pump system with a direct-current generator and a control method, and the system comprises a gas engine, a compressor, a main heat exchanger, an oil-gas separator, a four-way valve, an outdoor unit refrigerant heat exchanger, an indoor unit refrigerant heat exchanger, a gas-liquid separator and a waste heat recovery system, the compressor is connected with the gas engine, the main heat exchanger is connected with the compressor, and the main heat exchanger is connected with the compressor through the oil-gas separator, the four-way valve, the outdoor unit refrigerant heat exchanger, the indoor unit refrigerant heat exchanger, the four-way valve and the gas-liquid separator connected in sequence in series. The application is aimed at the existing air conditioning system which is in a low-efficiency small load or shutdown idle scene for a long time due to design redundancy, and a direct-current generator system is coupled compared with a single air conditioning system. The generator can adjust the power output of the generator according to the running state of the engine at different speeds to change the external characteristic curve of the engine, so as to improve the efficiency of the engine.

Description

TECHNICAL FIELD

[0001] The application discloses a heat pump system, in particular, a gas heat pump system with a direct-current generator and a control method. BACKGROUND

[0002] The gas heat pump (Gas Engine Driven Heat Pump, hereinafter referred to as GHP) system is an air conditioning system that uses gas (including natural gas, liquefied petroleum gas, biogas, etc.) as a high-grade driving energy source, directly drives an open-type compressor to work through the work of a gas engine, and then completes a vapor compression refrigeration cycle to achieve the purpose of refrigeration or heating. Compared with the electric heat pump (EHP) using electricity as a high-grade driving energy source, the gas heat pump has no difference in heat pump theory. The high-efficiency gas engine replaces the electric motor of the electric heat pump. Due to the change of the driving source, a large amount of engine cylinder sleeve heat and exhaust heat can be recovered to construct a distributed energy system for energy cascade utilization, thereby significantly improving the primary energy utilization rate.

[0003] The gas heat pump uses a gas engine as a power source. Due to the characteristics of the engine, different torques and powers are output at different speeds, driving the compressor to compress the refrigerant to circulate and work. However, the total load of the heat pump is affected by the ambient temperature and the load demand of the indoor unit. The engine needs to adjust the speed to control the output power to match the different load requirements. This results in that the engine is not working in the best efficiency range in most cases, and the engine efficiency is relatively low. SUMMARY

[0004] In view of the relatively low efficiency of the gas heat pump in the prior art mentioned above, the application provides a gas heat pump system with a direct-current generator and a control method. The engine system, heat pump system, generator system, waste heat recovery system and control system are integrated together. The power output of the generator can be adjusted according to the running state of the engine at different speeds to change the external characteristic curve of the engine, so as to improve the efficiency of the engine.

[0005] The technical solution adopted by the application to solve the technical problem is: a gas heat pump system with a direct-current generator, the system comprising a gas engine, a compressor, a main heat exchanger, an oil-gas separator, a four-way valve, an outdoor unit refrigerant heat exchanger, an indoor unit refrigerant heat exchanger, a gas-liquid separator and a waste heat recovery system, the compressor being connected with the gas engine, the main heat exchanger being connected with the compressor, and the main heat exchanger being connected with the compressor through the oil-gas separator, the four-way valve, the outdoor unit refrigerant heat exchanger, the indoor unit refrigerant heat exchanger, the four-way valve and the gas-liquid separator connected in series.

[0006] A control method of a gas heat pump with a direct-current generator, the method comprising the following steps:

[0007] Step S1, the controller collects the suction pressure, the exhaust pressure and the current ambient temperature parameter through the corresponding sensor;

[0008] Step S2, judge whether the air conditioner compressor has the need requirement When the air conditioner starts, it is the control method of the whole system when the air conditioner system runs, jump to step S3, when the air conditioner does not start, it is the control method of the whole system when the air conditioner system does not run, jump to step S31;

[0009] Step S3, calculate the current compressor demand W according to the relationship in the controller;

[0010] Step S4, the controller calculates the current compressor demand speed S0 according to the built-in relationship S=f(W);

[0011] Step S5, based on the inherent transmission ratio of the engine and the compressor, the demand speed R0 of the engine is obtained S0*D2 / D1;

[0012] Step S6, start the engine and control the engine to run at the demand speed S0;

[0013] Step S7, the controller calculates the current value C0 and the minimum value C1 of specific fuel consumption at the current speed;

[0014] Step S8, compare whether the current fuel consumption is in the economic zone, if it is in the economic zone, turn to step S9, if it is not in the economic zone, turn to step S12;

[0015] Step S9, the engine maintains the speed operation, and the generator system does not put into operation;

[0016] Step S10, detect whether the compressor demand changes, if yes, jump to step S1, repeat the above steps, if not, execute step S11 according to step S11;

[0017] Step S11, keep the engine running at the current speed;

[0018] Step S12, the controller retrieves the torque T1 at the best specific fuel consumption at the current speed;

[0019] Step S13, the controller retrieves the power P1 corresponding to the best specific fuel consumption at the current speed;

[0020] Step S14, the controller retrieves the torque Tm of the compressor at the current speed;

[0021] Step S15, the controller calculates the torque lifting capacity AT=T1-Tm;

[0022] Step S16, the controller calculates the speed of the generator according to the inherent transmission relationship of the engine and the generator M=S*D3 / D1;

[0023] Step S17, the controller calculates the torque Tsp=9550*sP / M corresponding to the increase of the minimum adjustment unit sP of the generator power;

[0024] Step S18, it is judged whether Tsp is greater than △T, if yes, step S19 is executed, if not, step S20 is executed;

[0025] Step S19, the output power of the generator is kept as 0;

[0026] Step S20, the controller calculates the sum P0 of the current generator power sP and the compressor power W when the generator increases the power sP and Tsp is less than △T;

[0027] Step S21, it is judged whether P0 is greater than P1, if yes, step S19 is returned to execute, if not, step S22 is executed;

[0028] Step S22, the generator adjusts the duty cycle output power to increase sP;

[0029] Step S23, the controller calculates the current output power Pm0 and the output torque Tm0 of the engine;

[0030] Step S24, the controller calculates the output torque Tm1 of the engine when the generator increases the power sP;

[0031] Step S25, it is judged whether Tm1 exceeds T1, if yes, step S28 is executed, if not, step S26 is executed;

[0032] Step S26, the controller calculates the output power Pm1 of the engine when the engine power output increases sP;

[0033] Step S27, it is judged whether Pm1 exceeds P1, if yes, step S28 is executed, if not, step S22 is executed;

[0034] Step S28, the current generator output power is maintained;

[0035] Step S29, it is judged whether the compressor needs to change, if yes, step S30 is executed, if not, step S28 is executed;

[0036] Step S30, the generator stops outputting and returns to step S1 to execute;

[0037] Step S31, the optimal economic point of the engine is searched, at this time, the speed of the engine is S1, the total torque output Te and the power output Pe of the engine are relatively maximum;

[0038] Step S32, the generator output power increases the minimum adjustment precision sP;

[0039] Step S33, the controller calculates the engine current output power Pme0 and output torque Tme0;

[0040] Step S34, the controller calculates the engine output torque Tme1 after the generator output power increases sP;

[0041] Step S35, judge whether the engine output torque Tme1 exceeds the rated torque Te of the best economic point engine, if yes, execute step S38, if not, execute step S36;

[0042] Step S36, the controller calculates the engine output power Pme1 after the generator power output increases sP;

[0043] Step S37, judge whether Pme1 exceeds Pe, if yes, execute step S38, if not, return to execute step S32;

[0044] Step S38, the generator maintains the current power output, and then returns to step S2 for initial judgment.

[0045] The technical scheme further comprises:

[0046] The waste heat recovery system comprises a cylinder sleeve, a heat recovery device and a flue gas waste heat recovery device, the cylinder sleeve is connected with the gas engine, the heat recovery device is connected with the cylinder sleeve through a pipeline, and the flue gas waste heat recovery device is connected with the heat recovery device through a pipeline.

[0047] The compressor is provided with two sets, the gas engine drives the two sets of compressors to operate simultaneously through a belt, and whether the compressor operates or not is controlled through a clutch; when the clutch works, the compressor starts to operate under load, and the air conditioning system starts to operate; when the clutch is disconnected, the compressor is separated from the load, and the air conditioning system stops operating.

[0048] The outdoor unit refrigerant heat exchanger is connected with an outdoor unit cooling water heat exchanger, and the outdoor unit cooling water heat exchanger is connected with a third heat exchanger.

[0049] The system further comprises a second heat exchanger, and the second heat exchanger is connected with the first heat exchanger through a pipeline.

[0050] The beneficial effects of the present application are: the present application is aimed at the existing air conditioning system which is in a low-efficiency small load or shutdown idle scene for a long time due to design redundancy, compared with a single air conditioning system, a set of direct current generator system is coupled, the generator can adjust the power output of the generator according to the different rotating speed operation state of the engine to change the external characteristic curve of the engine, so as to improve the efficiency of the engine. The single air conditioning system can only adjust the efficiency by adjusting the frequency of the compressor, but the adjustable frequency of the compressor is relatively narrow, and it cannot solve the low efficiency in low load from the principle. The gas heat pump system with direct current generator can improve the overall efficiency of the engine by controlling the output power of the generator in the low load interval, and comprehensively improve the system efficiency. At the same time, the cooling and heating regulation of the air conditioning system can also perfectly solve the heat dissipation problem of the generator system, avoid the decrease of the power generation efficiency due to the temperature rise, complementary advantages, and the comprehensive energy efficiency is greatly improved.

[0051] The present application will be further described below in combination with the drawings and specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0052] Figure 1 It is a gas heat pump system diagram in the present application.

[0053] Figure 2 It is a connection mode schematic diagram of an engine, double compressors and a direct current generator in the present application.

[0054] Figure 3 It is a gas heat pump pure power generation mode, heating mode system diagram in the present application.

[0055] Figure 4 It is a gas heat pump refrigeration mode system diagram in the present application.

[0056] Figure 5 It is an engine external characteristic diagram in the present application.

[0057] Figure 6 It is a direct current generator control flow chart when the air conditioning system is running in the present application.

[0058] Figure 7 It is a direct current generator control flow chart when the air conditioning system is not running in the present application. DETAILED DESCRIPTION

[0059] The present embodiment is a preferred embodiment of the present application, and other embodiments having the same or similar principles and basic structures as the present embodiment are within the protection scope of the present application.

[0060] The application mainly protects a gas heat pump system with a direct current generator, which mainly comprises a gas engine, a compressor, a main heat exchanger, an oil-gas separator, a four-way valve, an outdoor machine refrigerant heat exchanger, an indoor machine refrigerant heat exchanger, a gas-liquid separator and a waste heat recovery system. The compressor is connected with the gas engine, the main heat exchanger is connected with the compressor, the main heat exchanger is connected with the compressor through the oil-gas separator, the four-way valve, the outdoor machine refrigerant heat exchanger, the indoor machine refrigerant heat exchanger, the four-way valve and the gas-liquid separator connected in series, forming a cycle, and the waste heat recovery system is connected with the main heat exchanger. After the gas (including natural gas, liquefied petroleum gas, coal gas or biogas and other gaseous fuels) is burned by the gas engine (internal combustion engine), the heat energy released by the burning pushes the piston in the engine cylinder to reciprocate, and the mechanical driving device transmits the kinetic energy to drive the compressor to compress the refrigerant to absorb energy from the air (reverse Carnot cycle). Part of the heat energy released directly by the engine is converted into mechanical energy to drive the compressor of the heat pump system, and the rest of the heat energy exists in the form of waste heat (including flue gas waste heat, cylinder cooling water, oil heat, mechanical loss heat) and the proportion of waste heat is higher than that of converted mechanical energy. The waste heat can be recovered by the waste heat recovery system, which can greatly improve the overall thermal efficiency of the engine system.

[0061] In the embodiment, the waste heat recovery system comprises a cylinder sleeve, a heat recovery device and a flue gas waste heat recovery device. The cylinder sleeve is connected with the gas engine, the heat recovery device is connected with the cylinder sleeve through a pipeline, and the flue gas waste heat recovery device is connected with the heat recovery device through a pipeline. The cooling liquid takes away the preheating generated by the gas engine through the cylinder sleeve, exchanges heat with cold water in the heat recovery device to preliminarily heat the cold water, discharges the cooled liquid for the next cycle, and the preliminarily heated cold water enters the flue gas waste heat recovery device to be heated again by the flue gas discharged by the gas engine. The heated water is discharged as hot water or enters the main heat exchanger for final heating.

[0062] The gas heat pump system with a direct current generator comprises an engine system, a heat pump system, a generator system, a waste heat recovery system and a control system. The direct current generator can dynamically adjust the output power size through the control system. The engine system is composed of a gas engine and an engine control part, and provides a power source for the whole system. The heat pump system is composed of a condenser, an evaporator, a throttling device, various temperature and pressure sensors, a compressor and the like. The generator system is composed of a motor part, a transmission part, a control part and the like. The waste heat recovery system is composed of an engine waste gas recovery device. The control system collects all running data, drives the engine or the actuator according to the built-in logic processing response mechanism to maintain the normal operation of the system.

[0063] Please refer to the attached drawings for a better understanding of the application Figure 2, the gas engine drives two compressors through belt transmission, the operation of the compressors is controlled by the clutch, when the clutch works, the compressors start to run under load, and the air conditioning system starts to run; when the clutch is disconnected, the compressors are disconnected from the load, and the air conditioning system stops running. For the heat pump system, the low-temperature and low-pressure gaseous refrigerant in the system pipeline is compressed by the compressor to form high-temperature and high-pressure gaseous refrigerant, which flows through the condenser to condense, the high-pressure liquid refrigerant after condensation flows through the throttling device to be throttled and decompressed, the low-temperature and low-pressure gaseous and liquid two-phase refrigerant after throttling evaporates into low-temperature and low-pressure gaseous refrigerant through the evaporator, and then the low-temperature and low-pressure gaseous refrigerant returns to the compressor to continue to be compressed into high-temperature and high-pressure gaseous refrigerant and is discharged to the condenser, thereby forming a complete heat pump system circulation.

[0064] In this embodiment, the gas engine also drives the DC generator to run through belt transmission, the operation of the DC generator is controlled by the clutch, when the clutch works, the DC generator starts to generate electricity and runs, and outputs power load to the outside, the generator outputs different electric power at different engine speeds, and the output voltage remains unchanged.

[0065] Please refer to the attached drawings Figure 3 In this embodiment, an outdoor unit cooling water heat exchanger is arranged in connection with the outdoor unit refrigerant heat exchanger, and a third heat exchanger is connected with the outdoor unit cooling water heat exchanger. As shown in Figure 3 is the system diagram in the heating mode and the pure power generation mode in the transition season, in the heating mode, there are two circuits for generating hot water, circuit one: the gas engine runs to drive the compressor to compress the refrigerant, and the heat of the air is absorbed from the outdoor unit refrigerant heat exchanger through the phase change of the refrigerant, and the main heat exchanger is used for heat exchange again to generate part of the hot water for heating; circuit two: the gas engine burns to generate a large amount of waste heat, and the waste heat of the gas engine is recovered through the cylinder sleeve and the heat recovery device to generate another part of the hot water for heating. The cooling liquid of the DC generator is cooled through the outdoor cooling water heat exchanger through the fan rotation to ensure the efficient operation of the generator and avoid power attenuation caused by high temperature. In the pure power generation mode in the transition season, the clutch does not run, the compressor is disconnected from the belt transmission, and the air conditioning system does not run. There is one circuit for generating hot water, the gas engine burns to generate a large amount of waste heat, and the waste heat of the engine is recovered through the cylinder sleeve and the heat recovery device to generate hot water for heating. At this time, the cooling liquid of the DC generator is cooled through the outdoor cooling water heat exchanger through the fan rotation to the control target temperature, to ensure the efficient operation of the generator.

[0066] Please refer to the attached drawings Figure 4 In this embodiment, a second heat exchanger is further included, as shown in Figure 4The refrigeration mode system diagram is shown, the gas engine runs to drive the compressor to compress the refrigerant, and the heat is exchanged through the phase change of the refrigerant from the outdoor unit refrigerant heat exchanger, and the refrigeration water is generated through the main heat exchanger to supply cold, and at the same time, the gas engine combustion does work to generate a large amount of waste heat, and the waste heat of the engine is recovered through the cylinder sleeve and the heat recovery device to generate hot water for heating. At this time, the cooling liquid of the DC generator passes through the second heat exchanger, and the temperature of the cooling liquid of the DC generator is reduced to the control target temperature through the processing of the opening degree of the second regulating valve, to ensure the efficient operation of the generator.

[0067] As shown in Figure 5 The universal characteristic curve of the gas engine is shown, the X axis is the engine speed, and the Y axis is the torque. The solid line is the specific fuel consumption (gas consumption), which can also be called the fuel consumption rate. It represents the mass of fuel consumed by the engine in 1 hour for every 1 kW of effective power output. The area with the lowest specific fuel consumption (gas consumption) is the highest efficiency working interval of the engine, which is the economic speed interval. The dashed line part is the engine's constant power curve. By controlling the output power of the generator, the engine's efficiency can be improved and the gas consumption can be reduced under the premise of meeting the power of the air conditioning system. In the non-economic interval of the engine, the specific fuel consumption (gas consumption) can also be reduced by adjusting the output power to improve the efficiency of the engine.

[0068] For Figure 2 The connection mode of a gas engine with a double compressor and a generator is shown. At this time, the flywheel diameter of the gas engine is D1, the pulley diameter of the compressor is D2, and the pulley diameter of the generator is D3. The transmission ratio between the compressor and the engine is n1=D1 / D2, and the transmission ratio between the generator and the engine is n2=D1 / D3. The minimum speed in the economic interval of the gas engine is R1, and the maximum speed is R2. The minimum speed for reliable operation of the compressor is Rmin, and the maximum speed is Rmax. Usually, Rmin < R1 < R2 < Rmax, and the speed range of the compressor is within the speed range of the engine.

[0069] The system can calculate the compressor required capacity W according to the data such as suction and discharge pressure and ambient temperature collected by sensors, and can arrange the relationship between the compressor required capacity W and the compressor speed S as S=f(W) according to the compressor characteristics, and set the relationship as control logic automatic calculation. According to the transmission ratio characteristics, the gas engine speed R=S*D2 / D1, and the corresponding relationship between the output torque T and the output power Pm of the gas engine and the gas engine speed R can be retrieved from the universal characteristic curve of the gas engine at this speed as Pm=f(R,T), and the output torque of the gas engine at each speed in the design stage meets the real-time demand torque Tm of the compressor, and the surplus output torque can drive the generator to generate power. The controller retrieves the minimum specific fuel consumption C1 of the gas engine at the current speed and the measured real-time specific fuel consumption C0, and if the gas engine is not in the minimum specific fuel consumption operating interval, the generator starts to start. The initial power generation capacity is 0, the power generation power Pg, the speed M and the torque Tg of the generator meet the relationship Pg=Tg*M / 9550, and the speed of the generator and the transmission ratio are related M=S*D3 / D1, so Pg=Tg*S*D3 / D1 / 9550. The minimum power regulation accuracy of the generator per unit time is sP, and before each power output is increased, the controller calculates whether the total torque of the compressor and the generator will exceed the total torque T1 of the gas engine at the speed after the power output of the generator is increased by sP, if not, whether the output power of the generator will exceed the total power P1 of the gas engine at the current speed after the output power of the generator is increased by sP, if both the torque and the power are within the range, the output power of the generator is increased by sP. Until the torque or power output limit of the gas engine at the speed is approached, and the earlier one is used as the criterion, at this time, the economy of the engine is the best, and the efficiency of the system is the highest.

[0070] When the air conditioner in the transition season is idle, the compressor required capacity W is 0. At this time, the gas engine only drives the generator to operate to generate power, the speed of the gas engine is controlled to run in the economic interval, and according to the relationship Pg=Tg*M / 9550 between the power generation power Pg, the speed M and the torque Tg of the generator, when the product of Tg and M is maximum, the output power is maximum, the efficiency of the gas engine is the highest, and the economy is the best, and the waste heat of the engine is recovered through the waste heat recovery system to produce hot water for heating or hot water supply.

[0071] Please refer to the accompanying drawings Figure 6 and the accompanying drawings Figure 7 , the application also protects a control method of a gas heat pump with a direct-current generator, which comprises the following steps:

[0072] Step S1, the controller collects relevant parameters such as suction pressure, discharge pressure and current ambient temperature through corresponding sensors;

[0073] Step S2, judge whether the air conditioning compressor has a demand, that is, whether the air conditioning system is started, when the air conditioning is started, the control method of the whole system when the air conditioning system runs, jump to step S3, when the air conditioning is not started, the control method of the whole system when the air conditioning system does not run, jump to step S31;

[0074] Step S3, the current compressor demand W is calculated according to the relationship in the controller;

[0075] Step S4, the controller calculates the current compressor demand speed S0 according to the built-in relationship S=f(W);

[0076] Step S5, based on the inherent transmission ratio of the engine and the compressor, the demand speed R0 of the engine is obtained S0*D2 / D1;

[0077] Step S6, start the engine and control the engine to run at the demand speed S0;

[0078] Step S7, the controller calculates the current value C0 and the minimum value C1 of specific fuel consumption at the current speed;

[0079] Step S8, compare whether the current fuel consumption is in the economic zone, if it is in the economic zone, go to step S9, if it is not in the economic zone, go to step S12;

[0080] Step S9, the engine maintains the speed and the generator system does not run;

[0081] Step S10, detect whether the compressor demand changes, if yes (that is, change), jump to step S1, repeat the above steps, if no (that is, no change), execute step 11, according to step 11 processing;

[0082] Step S11, keep the engine running at the current speed;

[0083] Step S12, the controller retrieves the torque T1 at the best specific fuel consumption at the current speed;

[0084] Step S13, the controller retrieves the power P1 corresponding to the best specific fuel consumption at the current speed;

[0085] Step S14, the controller retrieves the torque Tm of the compressor at the current speed;

[0086] Step S15, the controller calculates the torque lifting capacity △T=T1-Tm;

[0087] Step S16, the controller calculates the speed of the generator according to the inherent transmission relationship M=S*D3 / D1 of the engine and the generator;

[0088] Step S17, the controller calculates the corresponding increased torque Tsp=9550*sP / M when the generator power increases by the minimum adjustment unit sP (i.e. the generator power adjustment precision ΔT=T1-Tm);

[0089] Step S18, judge whether Tsp is greater than ΔT, if yes, execute step S19, if not, execute step S20;

[0090] Step S19, keep the output power of the generator as 0;

[0091] Step S20, the controller calculates the sum P0 of the current generator power sP and the compressor power W when the generator increases the power sP and Tsp is less than ΔT;

[0092] Step S21, judge whether P0 is greater than P1, if yes, return to execute step 19, if not, execute step 22;

[0093] Step S22, the generator adjusts the duty cycle output power to increase sP;

[0094] Step S23, the controller calculates the current output power Pm0 and the output torque Tm0 of the engine;

[0095] Step S24, the controller calculates the output torque Tm1 of the engine when the generator increases the power sP;

[0096] Step S25, judge whether Tm1 exceeds T1, if yes, execute step 28, if not, execute step 26;

[0097] Step S26, the controller calculates the output power Pm1 of the engine when the engine power output increases sP;

[0098] Step S27, judge whether Pm1 exceeds P1, if yes, execute step 28, if not, execute step 22;

[0099] Step S28, maintain the current generator output power;

[0100] Step S29, judge whether the compressor needs to change, if yes, execute step 30, if not, execute step 28;

[0101] Step S30, the generator stops outputting and returns to step S1 for execution;

[0102] Step S31, search for the best economic point of the engine, at this time the engine speed is S1, the total torque output Te and the power output Pe of the engine are relatively maximum;

[0103] Step S32, the generator output power increases by the minimum adjustment precision sP;

[0104] Step S33, the controller calculates the current engine output power Pme0 and the output torque Tme0 of the engine;

[0105] Step S34, the controller calculates the output torque Tme1 of the engine after the generator output power is increased by sP;

[0106] Step S35, it is judged whether the output torque Tme1 of the engine exceeds the rated torque Te of the engine at the best economic point, if yes, step S38 is executed, and if no, step S36 is executed;

[0107] Step S36, the controller calculates the engine output power Pme1 after the generator power output is increased by sP;

[0108] Step S37, it is judged whether Pme1 exceeds Pe, if yes, step S38 is executed, and if no, step S32 is executed;

[0109] Step S38, the generator maintains the current power output, and then returns to step S2 for initial judgment.

[0110] The present application aims at the existing air conditioning system which is in a low-efficiency small load or idle state for a long time due to design redundancy. Compared with a single air conditioning system, a direct-current generator system is coupled, the generator can adjust the power output of the generator according to the engine operating state at different speeds to change the external characteristic curve of the engine, thereby improving the efficiency of the engine. The single air conditioning system can only adjust the efficiency by adjusting the frequency of the compressor, but the adjustable frequency of the compressor is relatively narrow, and it cannot solve the low efficiency at low load in principle. The gas heat pump system with a direct-current generator can improve the overall efficiency of the engine by controlling the output power of the generator at low load, thereby improving the overall system efficiency. At the same time, the cooling and heating regulation of the air conditioning system can also perfectly solve the heat dissipation problem of the generator system, avoid the decrease of the power generation efficiency due to the temperature rise, complementary advantages, and greatly improve the overall energy efficiency.

[0111] Most of the existing building design air conditioning loads have design redundancy, and in actual use, most of the time, the air conditioner is running in the partial load range or some air conditioners are in an idle state for a long time. In the transition seasons such as spring and autumn, the air conditioner is basically in an idle state.

[0112] The gas heat pump system with DC generator can not only maintain the engine in the gas economic interval by adjusting the power size to improve the engine efficiency, but also can drive the generator to generate electricity when the air conditioning is in part load or idle in the transition season, improving the utilization rate of the equipment. Since the gas heat pump uses natural gas as energy input, the gas heat pump system with DC generator can not only reduce the load impact of air conditioning equipment on the power grid during peak electricity consumption, but also effectively alleviate the peak pressure of the power grid. At the same time, it balances the redundant gas pipeline load and tight power load demand in summer.

Claims

1. A control method for a gas heat pump with a DC generator, characterized by: The method comprises the following steps: Step S1, the controller collects the suction pressure, exhaust pressure and current ambient temperature parameters through corresponding sensors; Step S2, it is judged whether the air conditioner compressor has a demand, when the air conditioner is started, it is the control method of the whole system when the air conditioner system runs, jump to step S3, when the air conditioner is not started, it is the control method of the whole system when the air conditioner system does not run, jump to step S31; Step S3, the current compressor demand W is calculated according to the relationship in the controller; Step S4, the controller calculates the current compressor demand speed S0 according to the built-in relationship S=f(W); W is the compressor demand, and S is the compressor speed; Step S5, based on the inherent transmission ratio of the engine and the compressor, the demand speed R0 of the engine is obtained, R0=S0*D2 / D1; D1 is the flywheel disc diameter of the gas engine, D2 is the belt pulley diameter of the compressor, and S0 is the compressor demand speed; Step S6, the engine is started, and the engine is controlled to run at the demand speed S0; Step S7, the controller calculates the current value C0 and the minimum value C1 of the specific fuel consumption at the current speed; Step S8, it is compared whether the current fuel consumption is in the economic zone, if it is in the economic zone, it is turned to step S9, if it is not in the economic zone, it is turned to step S12; Step S9, the engine maintains the speed running, and the generator system is not put into operation; Step S10, it is detected whether the compressor demand changes, if yes, it is jumped to step S1, and the above steps are repeatedly executed, if not, step S11 is executed according to step S11; Step S11, the engine is kept running at the current speed; Step S12, the controller retrieves the torque T1 at the best specific fuel consumption at the current speed; Step S13, the controller retrieves the corresponding power P1 at the best specific fuel consumption at the current speed; Step S14, the controller retrieves the torque Tm of the compressor at the current speed; Step S15, the controller calculates the torque lifting capacity △T=T1-Tm; Step S16, the controller calculates the speed M of the generator according to the inherent transmission relationship of the engine and the generator, M=S*D3 / D1; D1 is the flywheel disc diameter of the gas engine, D3 is the belt pulley diameter of the generator, and S is the compressor speed; Step S17, the controller calculates the torque Tsp=9550*sP / M corresponding to the increase of the minimum adjustment unit sP of the generator power; M is the speed of the generator; Step S18, it is judged whether Tsp is greater than △T, if yes, step S19 is executed, if not, step S20 is executed; Step S19, the output power of the generator is kept as 0; Step S20, when Tsp is less than △T, the controller calculates the minimum adjustment unit sP of the generator, and P0 is the sum of the current generator power and the compressor power; Step S21, it is judged whether P0 is greater than P1, if yes, step S19 is returned to execute, if not, step S22 is executed; Step S22, the generator adjusts the duty cycle output power to increase the minimum adjustment unit sP; Step S23, the controller calculates the current engine output power Pm0 and output torque Tm0; Step S24, the controller calculates the engine output torque Tm1 after the generator power is increased by the minimum adjustment unit sP; Step S25, it is judged whether Tm1 exceeds T1, if yes, step S28 is executed, if not, step S26 is executed; Step S26, the controller calculates the engine output power Pm1 after the engine power output is increased by the minimum adjustment unit sP; Step S27, it is judged whether Pm1 exceeds P1, if yes, step S28 is executed, if not, step S22 is executed; Step S28, the current generator output power is maintained; Step S29, it is judged whether the compressor needs to be changed, if yes, step S30 is executed, if not, step S28 is executed; Step S30, the generator stops outputting and returns to step S1 for execution; Step S31, the optimal economic point of the engine is searched, at this time, the engine speed is S1, and the total torque output Te and power output Pe of the engine are relatively maximum; Step S32, the generator output power is increased by the minimum adjustment unit sP; Step S33, the controller calculates the current engine output power Pme0 and output torque Tme0; Step S34, the controller calculates the engine output torque Tme1 after the generator output power is increased by the minimum adjustment unit sP; Step S35, it is judged whether the engine output torque Tme1 exceeds the rated torque Te of the optimal economic point engine, if yes, step S38 is executed, if not, step S36 is executed; Step S36, the controller calculates the engine output power Pme1 after the generator power output is increased by the minimum adjustment unit sP; Step S37, it is judged whether Pme1 exceeds Pe, if yes, step S38 is executed, if not, step S32 is returned for execution; Step S38, the generator maintains the current power output, and then returns to step S2 for initial judgment.

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