Electrically-driven five-stage cascade large-temperature-difference high-power high-temperature heat pump system of heat supply pipe network

Abstract

The invention discloses an electrically-driven five-stage cascade large-temperature-difference high-power high-temperature heat pump system of a heat supply pipe network, and relates to the technical field of heat supply devices. Comprising a plate heat exchanger, a first-stage heat pump, a second-stage heat pump, a third-stage heat pump, a fourth-stage heat pump and a fifth-stage heat pump, a primary pipe network side water inlet of the plate heat exchanger is connected with a primary pipe network water supply pipe, and a primary pipe network side water outlet of the fifth-stage heat pump is connected with a primary pipe network water return pipe; a primary pipe network side water outlet of the plate heat exchanger is connected with a primary pipe network side water inlet pipeline of the first-stage heat pump; a secondary pipe network side water inlet of the plate heat exchanger and a secondary pipe network side water inlet of the first-stage heat pump are respectively connected with a secondary pipe network water return pipe, a secondary pipe network side water outlet of the plate heat exchanger is connected with a secondary pipe network water supply pipe, and a secondary pipe network side water outlet of the fifth-stage heat pump is connected with the secondary pipe network water supply pipe. The technical problems that in the prior art, the heat extraction temperature difference is small, the unit capacity is small, and the energy utilization rate is low are solved.

Description

Technical Field

[0001] This invention belongs to the technical field of heating devices, specifically relating to a five-stage cascaded high-temperature heat pump system with large temperature difference and high power for heating pipe networks. Background Technology

[0002] Currently, building energy consumption accounts for a quarter of my country's total social energy consumption, and winter heating in northern cities accounts for about 40% of building energy consumption. With urban development and improved living standards, the scale of centralized urban heating is expanding, exacerbating energy shortages and environmental pollution. In response, the Chinese government has introduced a series of policies and measures in recent years to promote clean energy heating.

[0003] Clean heating refers to a heating method that utilizes clean energy sources such as natural gas, electricity, industrial waste heat, clean coal, and nuclear energy, and achieves low emissions and low energy consumption through a high-efficiency energy system. It encompasses the entire heating process with the goal of reducing pollutant emissions and energy consumption.

[0004] Currently, urban centralized heating in northern my country is dominated by combined heat and power (CHP), supplemented by other forms of clean energy such as natural gas and electricity. CHP technology adheres to the energy utilization principle of "high-energy, high-use; low-energy, low-use," offering unparalleled advantages in energy conservation and efficiency compared to other heat sources. Furthermore, due to the generally large scale of CHP plants and the relatively sophisticated flue gas treatment of power plant boilers, environmental pollution is relatively low. Therefore, urban centralized heating using CHP as the heat source is the most economical and environmentally friendly method of clean heating.

[0005] Traditional combined heat and power (CHP) systems can be divided into two types based on the generator unit: back-pressure turbine units and extraction-condensing turbine units. In a back-pressure turbine, the exhaust gas, with a pressure higher than atmospheric pressure and a temperature exceeding 100°C, still possesses a certain capacity to generate electricity. This exhaust gas is entirely fed into a steam-water heat exchanger located in the primary heat exchange station, transferring its heat to the circulating heat medium of the heating system. Therefore, theoretically, the thermal efficiency of a back-pressure CHP system can reach 100%. However, due to the mutual constraints between heat and electricity loads, it is only used to handle the basic heat load throughout the year or during the heating season, and is therefore rarely used in actual CHP systems. Extraction-condensing units, on the other hand, use a portion of the extracted steam from the turbine, which has already performed some work, as the heat source for centralized heating, directly heating the circulating heat medium in the heating network. The remaining steam expands in the turbine to perform work until it becomes exhaust steam. This system is widely used in centralized heating systems within CHP systems because the electrical and thermal loads can be independently adjusted. However, the large amount of latent heat of vaporization contained in the exhaust steam is emitted into the atmosphere as a cold-end loss through the circulating cooling system, resulting in a significant waste of low-grade heat energy. This phenomenon runs counter to my country's current energy conservation and emission reduction policies and the strategic concept of sustainable development, making the recovery of this energy an urgent matter.

[0006] Meanwhile, with the continuous development of urban construction and the continuous improvement of people's living standards in my country, the heat load of centralized heating systems is also constantly increasing, and the service area is constantly expanding, leading to a serious shortage of the transmission capacity of the original pipeline network. Re-laying the heating pipeline network would not only increase investment, causing duplication and waste of investment, and placing a heavy economic burden on enterprises and society, but would also adversely affect normal life and social order. Therefore, without fundamentally changing the original pipeline network structure, increasing the supply and return temperature difference of the circulating heat medium in the heating system as a technical measure to significantly improve its heat transmission capacity is feasible both theoretically and practically.

[0007] In view of the above two issues, it is essential to develop and research a centralized heating system with a large temperature difference that can make full use of the energy of the heating network.

[0008] Currently, the most commonly used technology is the absorption heat pump unit with a large temperature difference. This unit adds an absorption heat pump to a plate heat exchanger, using the primary return water as the heat source and a small amount of high-temperature hot water from the primary heating network as the driving heat source. By lowering the primary network return water temperature, the temperature difference between the primary and return water is increased, thereby increasing the heat input to the primary network. For centralized heating systems, absorption heat pump units can be centrally installed in power plants or energy stations, or distributed across user-side heating stations.

[0009] See the schematic diagram of the centralized absorption heat exchanger unit. Figure 4The basic principle of a centralized absorption heat exchanger with a large temperature difference is as follows: It utilizes 120°C water supplied from a thermal power plant or long-distance heating network (primary side) as the driving energy. The water temperature is reduced to 100°C in the absorption heat pump generator, then further reduced to 60°C in a plate heat exchanger, and finally further cooled to 45°C in the absorption heat pump evaporator. Part of the 55°C return water from the primary network enters the absorption heat pump and is heated to 75°C, while the other part enters the plate heat exchanger and is heated to 95°C. The two portions of hot water are mixed and output as 85°C hot water. When driven solely by a heat source, the primary side supply water temperature of the centralized absorption heat exchanger with a large temperature difference is too low to meet the heating needs of residents during periods of severe cold.

[0010] See the schematic diagram of the distributed absorption large temperature difference unit. Figure 5 The basic principle of a distributed absorption heat pump unit with a large temperature difference is as follows: The 110°C high-temperature hot water from the primary heating network first acts as a heat source for absorption circulation in the generator. After cooling to 90°C, it enters a plate heat exchanger to heat the secondary network return water. Subsequently, it enters the evaporator of the hot water absorption heat pump as a low-temperature heat source, further reducing the return water temperature to 25°C. Part of the secondary network return water enters the plate heat exchanger to exchange heat with the primary network supply water that has released heat from the hot water absorption heat pump generator. The other part passes through the absorber and condenser of the hot water absorption heat pump to raise its temperature. After the two secondary network return waters are heated, they are mixed and supplied to users as secondary network supply water.

[0011] Existing technologies have the following shortcomings: small temperature difference between supply and return water in the primary pipeline network, small heating temperature difference, small unit capacity, and low energy utilization rate; large size and weight of absorption heat pump units, requiring high floor height and foundation bearing capacity; high retrofitting cost of absorption heat pump units, and large-scale implementation of absorption heat pump unit retrofitting across the entire network is expected to result in a large total investment cost; some key components of absorption heat pumps, such as vacuum pumps, solution pumps, and heat exchangers, have high spare parts prices, and due to the relatively small market share of absorption heat pumps, the supply of some spare parts may not be timely, requiring advance stockpiling, which also increases maintenance costs; the structure and principle of absorption heat pumps are relatively complex, requiring professional technicians for maintenance and upkeep, resulting in high labor costs. Summary of the Invention

[0012] The technical problem to be solved by the present invention is to provide a five-stage cascaded high-temperature heat pump system with large temperature difference and high power for heating pipe networks, so as to at least solve some of the above-mentioned technical problems.

[0013] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A five-stage cascaded high-temperature heat pump system with large temperature difference and high power for heating network electric drive includes a plate heat exchanger, a first-stage heat pump, a second-stage heat pump, a third-stage heat pump, a fourth-stage heat pump, a fifth-stage heat pump, a primary network water supply pipe, a primary network return pipe, a secondary network return pipe, and a secondary network water supply pipe. The inlet of the plate heat exchanger on the primary network side is connected to the primary network water supply pipe, and the outlet of the fifth-stage heat pump on the primary network side is connected to the primary network return pipe. The plate heat exchanger is connected by pipes between the primary network outlet and the primary network inlet of the first-stage heat pump, between the primary network outlet of the first-stage heat pump and the primary network inlet of the second-stage heat pump, between the primary network outlet of the second-stage heat pump and the primary network inlet of the third-stage heat pump, between the primary network outlet of the third-stage heat pump and the primary network inlet of the fourth-stage heat pump, and between the primary network outlet of the fourth-stage heat pump and the primary network inlet of the fifth-stage heat pump.

[0014] Furthermore, the secondary network inlet of the plate heat exchanger and the secondary network inlet of the first-stage heat pump are respectively connected to the secondary network return pipe, the secondary network outlet of the plate heat exchanger is connected to the secondary network supply pipe, and the secondary network outlet of the fifth-stage heat pump is connected to the secondary network supply pipe. Pipelines are connected between the outlet of the first-stage heat pump secondary network and the inlet of the second-stage heat pump secondary network, between the outlet of the second-stage heat pump secondary network and the inlet of the third-stage heat pump secondary network, between the outlet of the third-stage heat pump secondary network and the inlet of the fourth-stage heat pump secondary network, and between the outlet of the fourth-stage heat pump secondary network and the inlet of the fifth-stage heat pump secondary network.

[0015] Furthermore, the first-stage heat pump includes a first-stage evaporator, a first-stage compressor, a first-stage economizer, a first-stage exhaust check valve, a first-stage condenser, a first-stage throttling device C1, and a second-stage throttling device D1; the first-stage compressor is a two-stage centrifugal compressor, including a first-stage impeller A1 and a second-stage impeller B1, with a first intermediate chamber provided between the outlet of the first-stage impeller A1 and the inlet of the second-stage impeller B1; The inlet of the first-stage condenser is connected to the return water pipe of the secondary pipeline, and the outlet of the first-stage condenser is connected to the inlet pipe of the secondary pipeline of the second-stage heat pump; the inlet of the first-stage evaporator is connected to the outlet pipe of the primary pipeline of the plate heat exchanger, and the outlet of the first-stage evaporator is connected to the inlet pipe of the primary pipeline of the second-stage heat pump.

[0016] Furthermore, the refrigerant outlet of the first-stage evaporator is connected to the inlet pipe of the first-stage impeller A1; the outlet of the second-stage impeller B1, the first-stage exhaust check valve, and the refrigerant inlet of the first-stage condenser are connected in sequence; the refrigerant outlet of the first-stage condenser, the first-stage throttling device C1, and the high-pressure side inlet of the first-stage economizer are connected in sequence; the high-pressure side outlet of the first-stage economizer, the second-stage throttling device D1, and the refrigerant inlet of the first-stage evaporator are connected in sequence; and the low-pressure side outlet of the first-stage economizer is connected to the first intermediate chamber through a make-up gas pipe.

[0017] Furthermore, the second-stage heat pump includes a second-stage evaporator, a second-stage compressor, a second-stage economizer, a second-stage exhaust check valve, a second-stage condenser, a first-stage throttling device C2, and a second-stage throttling device D2; the second-stage compressor is a two-stage centrifugal compressor, including a first-stage impeller A2 and a second-stage impeller B2, with a second intermediate chamber between the outlet of the first-stage impeller A2 and the inlet of the second-stage impeller B2; the inlet of the second-stage condenser is connected to the outlet pipe of the first-stage condenser, and the outlet of the second-stage condenser is connected to the inlet pipe of the secondary network side of the third-stage heat pump; the inlet of the second-stage evaporator is connected to the outlet pipe of the first-stage evaporator, and the outlet of the second-stage evaporator is connected to the inlet pipe of the primary network side of the third-stage heat pump.

[0018] Furthermore, the refrigerant outlet of the second-stage evaporator is connected to the inlet pipe of the first-stage impeller A2; the outlet of the second-stage impeller B2, the second-stage exhaust check valve, and the refrigerant inlet of the second-stage condenser are connected in sequence; the refrigerant outlet of the second-stage condenser, the first-stage throttling device C2, and the high-pressure side inlet of the second-stage economizer are connected in sequence; the high-pressure side outlet of the second-stage economizer, the second-stage throttling device D2, and the refrigerant inlet of the second-stage evaporator are connected in sequence; and the low-pressure side outlet of the second-stage economizer is connected to the second intermediate chamber through a make-up gas pipe.

[0019] Furthermore, the third-stage heat pump includes a third-stage evaporator, a third-stage compressor, a third-stage economizer, a third-stage exhaust check valve, a third-stage condenser, a first-stage throttling device C3, and a second-stage throttling device D3; the third-stage compressor is a two-stage centrifugal compressor, including a first-stage impeller A3 and a second-stage impeller B3, with a third intermediate chamber between the outlet of the first-stage impeller A3 and the inlet of the second-stage impeller B3; the inlet of the third-stage condenser is connected to the outlet pipe of the second-stage condenser, and the outlet of the third-stage condenser is connected to the secondary network side pipe of the fourth-stage heat pump; the inlet of the third-stage evaporator is connected to the outlet pipe of the second-stage evaporator, and the outlet of the third-stage evaporator is connected to the primary network side pipe of the fourth-stage heat pump; The refrigerant outlet of the third-stage evaporator is connected to the inlet pipe of the first-stage impeller A3; the outlet of the second-stage impeller B3, the third-stage exhaust check valve, and the refrigerant inlet of the third-stage condenser are connected in sequence; the refrigerant outlet of the third-stage condenser, the first-stage throttling device C3, and the high-pressure side inlet of the third-stage economizer are connected in sequence; the high-pressure side outlet of the third-stage economizer, the second-stage throttling device D3, and the refrigerant inlet of the third-stage evaporator are connected in sequence; the low-pressure side outlet of the third-stage economizer is connected to the third intermediate chamber through a make-up gas pipe.

[0020] Furthermore, the fourth-stage heat pump includes a fourth-stage evaporator, a fourth-stage compressor, a fourth-stage economizer, a fourth-stage exhaust check valve, a fourth-stage condenser, a first-stage throttling device C4, and a second-stage throttling device D4; the fourth-stage compressor is a two-stage centrifugal compressor, including a first-stage impeller A4 and a second-stage impeller B4, and a fourth intermediate chamber is provided between the outlet of the first-stage impeller A4 and the inlet of the second-stage impeller B4; The inlet of the fourth-stage condenser is connected to the outlet pipe of the third-stage condenser, and the outlet of the fourth-stage condenser is connected to the secondary network side pipe of the fifth-stage heat pump; the inlet of the fourth-stage evaporator is connected to the outlet pipe of the third-stage evaporator, and the outlet of the fourth-stage evaporator is connected to the primary network side pipe of the fifth-stage heat pump. The refrigerant outlet of the fourth-stage evaporator is connected to the inlet pipe of the first-stage impeller A4; the outlet of the second-stage impeller B4, the fourth-stage exhaust check valve, and the refrigerant inlet of the fourth-stage condenser are connected in sequence; the refrigerant outlet of the fourth-stage condenser, the first-stage throttling device C4, and the high-pressure side inlet of the fourth-stage economizer are connected in sequence; the high-pressure side outlet of the fourth-stage economizer, the second-stage throttling device D4, and the refrigerant inlet of the fourth-stage evaporator are connected in sequence; the low-pressure side outlet of the fourth-stage economizer is connected to the fourth intermediate chamber through a make-up gas pipe.

[0021] Furthermore, the fifth-stage heat pump includes a fifth-stage evaporator, a fifth-stage compressor, a fifth-stage economizer, a fifth-stage exhaust check valve, a fifth-stage condenser, a first-stage throttling device C5, and a second-stage throttling device D5; the fifth-stage compressor is a two-stage centrifugal compressor, including a first-stage impeller A5 and a second-stage impeller B5, with a fifth intermediate chamber located between the outlet of the first-stage impeller A5 and the inlet of the second-stage impeller B5; The inlet of the fifth-stage condenser is connected to the outlet pipe of the fourth-stage condenser, and the outlet of the fifth-stage condenser is connected to the secondary water supply pipe; the inlet of the fifth-stage evaporator is connected to the outlet pipe of the fourth-stage evaporator, and the outlet of the fifth-stage evaporator is connected to the return water pipe of the primary water supply network.

[0022] Furthermore, the refrigerant outlet of the fifth-stage evaporator is connected to the inlet pipe of the first-stage impeller A5; the outlet of the second-stage impeller B5, the fifth-stage exhaust check valve, and the refrigerant inlet of the fifth-stage condenser are connected in sequence; the refrigerant outlet of the fifth-stage condenser, the first-stage throttling device C5, and the high-pressure side inlet of the fifth-stage economizer are connected in sequence; the high-pressure side outlet of the fifth-stage economizer, the second-stage throttling device D5, and the refrigerant inlet of the fifth-stage evaporator are connected in sequence; and the low-pressure side outlet of the fifth-stage economizer is connected to the fifth intermediate chamber through a make-up gas pipe.

[0023] Compared with the prior art, the present invention has the following beneficial effects: Primary water supply at temperature T1 enters the plate heat exchanger through the primary water supply pipe. Secondary return water at temperature H1 is divided into two parts after passing through the secondary return pipe. The first part of the secondary return water enters the plate heat exchanger, and the second part enters the first-stage heat pump. The first part of the secondary return water at temperature H1 and the primary water supply at temperature T1 exchange heat in the plate heat exchanger. The temperature of the primary water supply drops to T2, which is a decrease of ΔT1, where ΔT1 = T1 - T2. The temperature of the first part of the secondary return water rises to H2, where H2 = H1 + ΔT1. The primary water supply at temperature T2 then flows through the pipe... After heat exchange between the primary water supply (temperature H1) and the return water from the secondary network (temperature H1), the primary water supply temperature drops to T3, a decrease of ΔT2 (ΔT2 = T2 - T3). The return water temperature rises to H3 (H3 = H1 + ΔT2). The primary water supply (temperature T3) and the return water from the secondary network (temperature H3) then enter the second-stage heat pump through pipes for heat exchange. After the heat exchange, the primary water supply temperature drops to T4, a decrease of ΔT3 (ΔT3 = T3 - T4). The return water temperature rises to H4 (H4 = H3 + ΔT3). The primary water supply and the return water from the secondary network at temperature H4 are respectively piped into the third-stage heat pump for heat exchange. After heat exchange, the primary water supply temperature drops to T5, a decrease of ΔT4, where ΔT4 = T4 - T5. The return water temperature from the second secondary network then rises to H5, where H5 = H4 + ΔT4. The primary water supply at temperature T5 and the return water from the second secondary network at temperature H5 are respectively piped into the fourth-stage heat pump for heat exchange. After heat exchange, the primary water supply temperature drops to T6, a decrease of ΔT5, where ΔT5 = T5 - T6. The return water temperature from the second secondary network then rises to H6, where H6 = ... H5+ΔT5; The primary network supply water at temperature T6 and the secondary network return water at temperature H6 respectively enter the fifth-stage heat pump for heat exchange. After heat exchange, the temperature of the primary network supply water drops to T7, a decrease of ΔT6, where ΔT6 = T6 - T7. The temperature of the secondary network return water rises to H7, where H7 = H6 + ΔT6. Finally, the primary network supply water at temperature T7 is output as the primary network return water through the primary network return pipe. The first part of the secondary network return water at temperature H2 and the second part of the secondary network return water at temperature H7 converge in the secondary network supply pipe and are transported to the user end for heating. Compared with the prior art, this invention, by combining a plate heat exchanger with a five-stage heat pump in series, increases the temperature difference between the primary network supply and return water, increases the transmission capacity of the heating network without changing the pipe diameter, and improves energy utilization. Attached Figure Description

[0024] Figure 1This is a system block diagram of the present invention.

[0025] Figure 2 This is a schematic diagram of the structure of the present invention.

[0026] Figure 3 This is a schematic diagram of the structure of a single compressor in this invention.

[0027] Figure 4 This is a schematic diagram of a centralized absorption heat exchanger with a large temperature difference.

[0028] Figure 5 This is a schematic diagram of a distributed absorption heat exchanger with a large temperature difference.

[0029] The names corresponding to the reference numerals in the attached figures are as follows: 1-Plate heat exchanger, 2-First-stage heat pump, 3-Second-stage heat pump, 4-Third-stage heat pump, 5-Fourth-stage heat pump, 6-Fifth-stage heat pump, 7-Primary network supply pipe, 8-Primary network return pipe, 9-Secondary network return pipe, 10-Secondary network supply pipe, 11-First-stage evaporator, 12-First-stage compressor, 13-First-stage economizer, 14-First-stage exhaust check valve, 15-First-stage condenser, 16-First-stage throttling device C1, 17- Secondary throttling device D1, 18-First stage impeller A1, 19-Second stage impeller B1, 21-Second stage evaporator, 22-Second stage compressor, 23-Second stage economizer, 24-Second stage exhaust check valve, 25-Second stage condenser, 26-First stage throttling device C2, 27-Second stage throttling device D2, 28-First stage impeller A2, 29-Second stage impeller B2, 31-Third stage evaporator, 32-Third stage compressor, 33-Third stage economizer, 3 4-Third-stage exhaust check valve, 35-Third-stage condenser, 36-First-stage throttling device C3, 37-Second-stage throttling device D3, 38-First-stage impeller A3, 39-Second-stage impeller B3, 41-Fourth-stage evaporator, 42-Fourth-stage compressor, 43-Fourth-stage economizer, 44-Fourth-stage exhaust check valve, 45-Fourth-stage condenser, 46-First-stage throttling device C4, 47-Second-stage throttling device D4, 48-First-stage impeller A4, 49-Second-stage throttling device C4 Impeller B4, 51-Fifth stage evaporator, 52-Fifth stage compressor, 53-Fifth stage economizer, 54-Fifth stage exhaust check valve, 55-Fifth stage condenser, 56-First stage throttling device C5, 57-Second stage throttling device D5, 58-First stage impeller A5, 59-Second stage impeller B5, 100-First intermediate chamber, 101-Second intermediate chamber, 102-Third intermediate chamber, 103-Fourth intermediate chamber, 104-Fifth intermediate chamber. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0031] In the description of this invention, it should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0032] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; of course, they can also refer to a mechanical connection or an electrical connection; furthermore, they can refer to a direct connection, an indirect connection through an intermediate medium, or a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0033] Example 1, such as Figures 1-3 As shown, a five-stage cascaded high-temperature heat pump system with large temperature difference and high power for heating network electric drive includes a plate heat exchanger 1, a first-stage heat pump 2, a second-stage heat pump 3, a third-stage heat pump 4, a fourth-stage heat pump 5, a fifth-stage heat pump 6, a primary network water supply pipe 7, a primary network water return pipe 8, a secondary network water return pipe 9, and a secondary network water supply pipe 10. The inlet of the plate heat exchanger 1 on the primary network side is connected to the primary network water supply pipe 7, and the outlet of the fifth-stage heat pump 6 on the primary network side is connected to the primary network return pipe 8. The plate heat exchanger 1 is connected to the primary network outlet and the primary network inlet of the first-stage heat pump 2, the primary network outlet of the first-stage heat pump 2 is connected to the primary network inlet of the second-stage heat pump 3, the primary network outlet of the second-stage heat pump 3 is connected to the primary network inlet of the third-stage heat pump 4, the primary network outlet of the third-stage heat pump 4 is connected to the primary network inlet of the fourth-stage heat pump 5, and the primary network outlet of the fourth-stage heat pump 5 is connected to the primary network inlet of the fifth-stage heat pump 6 via pipelines.

[0034] The secondary network inlet of plate heat exchanger 1 and the secondary network inlet of first-stage heat pump 2 are respectively connected to the secondary network return pipe 9. The secondary network outlet of plate heat exchanger 1 is connected to the secondary network supply pipe 10. The secondary network outlet of fifth-stage heat pump 6 is connected to the secondary network supply pipe 10. Pipelines are connected between the outlet of the secondary network side of the first-stage heat pump 2 and the inlet of the secondary network side of the second-stage heat pump 3, between the outlet of the secondary network side of the second-stage heat pump 3 and the inlet of the secondary network side of the third-stage heat pump 4, between the outlet of the secondary network side of the third-stage heat pump 4 and the inlet of the secondary network side of the fourth-stage heat pump 5, and between the outlet of the secondary network side of the fourth-stage heat pump 5 and the inlet of the secondary network side of the fifth-stage heat pump 6.

[0035] Working principle: Primary network water at temperature T1 enters the plate heat exchanger through the primary network supply pipe. Secondary network return water at temperature H1 is divided into two parts after passing through the secondary network return pipe. The first part of the secondary network return water enters the plate heat exchanger, and the second part enters the first-stage heat pump. The first part of the secondary network return water at temperature H1 and the primary network supply water at temperature T1 exchange heat in the plate heat exchanger. The temperature of the primary network supply water drops to T2, which is a decrease of ΔT1, where ΔT1 = T1 - T2. The temperature of the first part of the secondary network return water rises to H2, where H2 = H1 + ΔT1. The primary network supply water at temperature T2 then... After the primary water supply (temperature H1) enters the first-stage heat pump through pipes and exchanges heat with the return water of the second-stage secondary network, the primary water supply temperature drops to T3, a decrease of ΔT2, where ΔT2 = T2 - T3. The return water temperature of the second-stage secondary network then rises to H3, where H3 = H1 + ΔT2. The primary water supply (temperature T3) and the return water of the second-stage secondary network (temperature H3) then enter the second-stage heat pump through pipes for heat exchange. After the heat exchange, the primary water supply temperature drops to T4, a decrease of ΔT3, where ΔT3 = T3 - T4. The return water temperature of the second-stage secondary network then rises to H4, where H4 = H3 + ΔT3. The primary water supply and the return water from the secondary network (temperature H4) both enter the third-stage heat pump for heat exchange. After heat exchange, the primary water supply temperature drops to T5, a decrease of ΔT4, where ΔT4 = T4 - T5. The return water temperature rises to H5, where H5 = H4 + ΔT4. Similarly, the primary water supply at temperature T5 and the return water from the secondary network at temperature H5 both enter the fourth-stage heat pump for heat exchange. After heat exchange, the primary water supply temperature drops to T6, a decrease of ΔT5, where ΔT5 = T5 - T6. The return water temperature rises to H6, where H6... =H5+ΔT5; The primary network supply water at temperature T6 and the secondary network return water at temperature H6 are respectively introduced into the fifth-stage heat pump for heat exchange. After heat exchange, the temperature of the primary network supply water drops to T7, a decrease of ΔT6, where ΔT6=T6-T7. The temperature of the secondary network return water rises to H7, where H7=H6+ΔT6. Finally, the primary network supply water at temperature T7 is output as the primary network return water through the primary network return water pipe. The first part of the secondary network return water at temperature H2 and the second part of the secondary network return water at temperature H7 are combined and transported to the user end in the secondary network supply water pipe to provide heating for the user. Compared with the prior art, this invention, by combining a plate heat exchanger with a five-stage heat pump in series, increases the temperature difference between the primary network supply and return water, increases the transmission capacity of the heating network without changing the pipe diameter, and improves energy utilization.

[0036] Example 2, as Figures 1-3As shown, a five-stage cascaded high-temperature heat pump system with large temperature difference and high power for heating network electric drive includes a plate heat exchanger 1, a first-stage heat pump 2, a second-stage heat pump 3, a third-stage heat pump 4, a fourth-stage heat pump 5, a fifth-stage heat pump 6, a primary network water supply pipe 7, a primary network water return pipe 8, a secondary network water return pipe 9, and a secondary network water supply pipe 10. The inlet of the plate heat exchanger 1 on the primary network side is connected to the primary network water supply pipe 7, and the outlet of the fifth-stage heat pump 6 on the primary network side is connected to the primary network return pipe 8. The plate heat exchanger 1 is connected to the primary network outlet and the primary network inlet of the first-stage heat pump 2, the primary network outlet of the first-stage heat pump 2 is connected to the primary network inlet of the second-stage heat pump 3, the primary network outlet of the second-stage heat pump 3 is connected to the primary network inlet of the third-stage heat pump 4, the primary network outlet of the third-stage heat pump 4 is connected to the primary network inlet of the fourth-stage heat pump 5, and the primary network outlet of the fourth-stage heat pump 5 is connected to the primary network inlet of the fifth-stage heat pump 6 via pipelines.

[0037] The secondary network inlet of plate heat exchanger 1 and the secondary network inlet of first-stage heat pump 2 are respectively connected to the secondary network return pipe 9. The secondary network outlet of plate heat exchanger 1 is connected to the secondary network supply pipe 10. The secondary network outlet of fifth-stage heat pump 6 is connected to the secondary network supply pipe 10. Pipelines are connected between the outlet of the secondary network side of the first-stage heat pump 2 and the inlet of the secondary network side of the second-stage heat pump 3, between the outlet of the secondary network side of the second-stage heat pump 3 and the inlet of the secondary network side of the third-stage heat pump 4, between the outlet of the secondary network side of the third-stage heat pump 4 and the inlet of the secondary network side of the fourth-stage heat pump 5, and between the outlet of the secondary network side of the fourth-stage heat pump 5 and the inlet of the secondary network side of the fifth-stage heat pump 6.

[0038] The first-stage heat pump 2 includes a first-stage evaporator 11, a first-stage compressor 12, a first-stage economizer 13, a first-stage exhaust check valve 14, a first-stage condenser 15, a first-stage throttling device C116, and a second-stage throttling device D117; the first-stage compressor 12 is a two-stage centrifugal compressor, including a first-stage impeller A118 and a second-stage impeller B119, and a first intermediate chamber 100 is provided between the outlet of the first-stage impeller A118 and the inlet of the second-stage impeller B119; The inlet of the first-stage condenser 15 is connected to the return water pipe 9 of the secondary pipeline network, and the outlet of the first-stage condenser 15 is connected to the inlet pipe of the secondary pipeline network of the second-stage heat pump 3; the inlet of the first-stage evaporator 11 is connected to the outlet pipe of the primary pipeline network of the plate heat exchanger 1, and the outlet of the first-stage evaporator 11 is connected to the inlet pipe of the primary pipeline network of the second-stage heat pump 3.

[0039] The refrigerant outlet of the first-stage evaporator 11 is connected to the inlet pipe of the first-stage impeller A118; the outlet of the second-stage impeller B119, the first-stage exhaust check valve 14, and the refrigerant inlet of the first-stage condenser 15 are connected in sequence; the refrigerant outlet of the first-stage condenser 15, the first-stage throttling device C116, and the high-pressure side inlet of the first-stage economizer 13 are connected in sequence; the high-pressure side outlet of the first-stage economizer 13, the second-stage throttling device D117, and the refrigerant inlet of the first-stage evaporator 11 are connected in sequence; the low-pressure side outlet of the first-stage economizer 13 is connected to the first intermediate chamber 100 through a make-up gas pipe.

[0040] This embodiment 2 provides a more preferred structure for the first-stage heat pump based on embodiment 1. The working principle of the first-stage heat pump is as follows: Primary network water at temperature T2 is supplied from the plate heat exchanger and transported through pipes to the first-stage evaporator. The low-temperature, low-pressure liquid refrigerant in the evaporator absorbs heat from the primary network water and evaporates into low-temperature, low-pressure vapor refrigerant, while the temperature of the primary network water decreases. The low-temperature, low-pressure vapor refrigerant enters the first-stage impeller A1 and is compressed. It then mixes with makeup gas drawn from the low-pressure side outlet of the first-stage economizer in the first intermediate chamber and enters the second-stage impeller B1, where it is compressed into a high-temperature, high-pressure refrigerant. The high-temperature, high-pressure refrigerant gas enters the first-stage condenser and releases heat to the second-stage secondary network return water at temperature H1 flowing through the first-stage condenser. The temperature of the second-stage secondary network return water increases, and the high-temperature, high-pressure refrigerant gas condenses into a high-pressure liquid. The high-pressure liquid... The refrigerant first passes through a first-stage throttling device C1 to reduce its pressure before entering the first-stage economizer. The separated flash vapor is used as makeup gas and is returned to the first intermediate chamber through the low-pressure side outlet of the first-stage economizer. The remaining liquid is subcooled and discharged from the high-pressure side outlet of the first-stage economizer to a second-stage throttling device D1. After passing through the second-stage throttling device D1, the pressure is reduced to the evaporation pressure, and the refrigerant is injected back into the first-stage evaporator as a low-temperature, low-pressure liquid refrigerant. During this process, if the temperature of the primary network supply water in the first-stage evaporator drops to T3 and the temperature of the secondary network return water in the second part of the first-stage condenser rises to H3, the primary network supply water in the first-stage evaporator is piped to the primary network side of the second-stage heat pump, and the secondary network return water in the first-stage condenser is piped to the secondary network side of the second-stage heat pump for heat exchange. Otherwise, the current cycle is maintained, allowing the refrigerant to continue circulating in the predetermined process. The function of the first-stage exhaust check valve is to prevent high-pressure gas from flowing back into the first-stage compressor from the first-stage condenser side, ensuring the safe operation of the system.

[0041] Example 3, as Figures 1-3As shown, a five-stage cascaded high-temperature heat pump system with large temperature difference and high power for heating network electric drive includes a plate heat exchanger 1, a first-stage heat pump 2, a second-stage heat pump 3, a third-stage heat pump 4, a fourth-stage heat pump 5, a fifth-stage heat pump 6, a primary network water supply pipe 7, a primary network water return pipe 8, a secondary network water return pipe 9, and a secondary network water supply pipe 10. The inlet of the plate heat exchanger 1 on the primary network side is connected to the primary network water supply pipe 7, and the outlet of the fifth-stage heat pump 6 on the primary network side is connected to the primary network return pipe 8. The plate heat exchanger 1 is connected to the primary network outlet and the primary network inlet of the first-stage heat pump 2, the primary network outlet of the first-stage heat pump 2 is connected to the primary network inlet of the second-stage heat pump 3, the primary network outlet of the second-stage heat pump 3 is connected to the primary network inlet of the third-stage heat pump 4, the primary network outlet of the third-stage heat pump 4 is connected to the primary network inlet of the fourth-stage heat pump 5, and the primary network outlet of the fourth-stage heat pump 5 is connected to the primary network inlet of the fifth-stage heat pump 6 via pipelines.

[0042] The secondary network inlet of plate heat exchanger 1 and the secondary network inlet of first-stage heat pump 2 are respectively connected to the secondary network return pipe 9. The secondary network outlet of plate heat exchanger 1 is connected to the secondary network supply pipe 10. The secondary network outlet of fifth-stage heat pump 6 is connected to the secondary network supply pipe 10. Pipelines are connected between the outlet of the secondary network side of the first-stage heat pump 2 and the inlet of the secondary network side of the second-stage heat pump 3, between the outlet of the secondary network side of the second-stage heat pump 3 and the inlet of the secondary network side of the third-stage heat pump 4, between the outlet of the secondary network side of the third-stage heat pump 4 and the inlet of the secondary network side of the fourth-stage heat pump 5, and between the outlet of the secondary network side of the fourth-stage heat pump 5 and the inlet of the secondary network side of the fifth-stage heat pump 6.

[0043] The first-stage heat pump 2 includes a first-stage evaporator 11, a first-stage compressor 12, a first-stage economizer 13, a first-stage exhaust check valve 14, a first-stage condenser 15, a first-stage throttling device C116, and a second-stage throttling device D117; the first-stage compressor 12 is a two-stage centrifugal compressor, including a first-stage impeller A118 and a second-stage impeller B119, and a first intermediate chamber 100 is provided between the outlet of the first-stage impeller A118 and the inlet of the second-stage impeller B119; The inlet of the first-stage condenser 15 is connected to the return water pipe 9 of the secondary pipeline network, and the outlet of the first-stage condenser 15 is connected to the inlet pipe of the secondary pipeline network of the second-stage heat pump 3; the inlet of the first-stage evaporator 11 is connected to the outlet pipe of the primary pipeline network of the plate heat exchanger 1, and the outlet of the first-stage evaporator 11 is connected to the inlet pipe of the primary pipeline network of the second-stage heat pump 3.

[0044] The refrigerant outlet of the first-stage evaporator 11 is connected to the inlet pipe of the first-stage impeller A118; the outlet of the second-stage impeller B119, the first-stage exhaust check valve 14, and the refrigerant inlet of the first-stage condenser 15 are connected in sequence; the refrigerant outlet of the first-stage condenser 15, the first-stage throttling device C116, and the high-pressure side inlet of the first-stage economizer 13 are connected in sequence; the high-pressure side outlet of the first-stage economizer 13, the second-stage throttling device D117, and the refrigerant inlet of the first-stage evaporator 11 are connected in sequence; the low-pressure side outlet of the first-stage economizer 13 is connected to the first intermediate chamber 100 through a make-up gas pipe.

[0045] The second-stage heat pump 3 includes a second-stage evaporator 21, a second-stage compressor 22, a second-stage economizer 23, a second-stage exhaust check valve 24, a second-stage condenser 25, a first-stage throttling device C226, and a second-stage throttling device D227. The second-stage compressor 22 is a two-stage centrifugal compressor, including a first-stage impeller A228 and a second-stage impeller B229. A second intermediate chamber 101 is provided between the outlet of the first-stage impeller A228 and the inlet of the second-stage impeller B229. The inlet of the second-stage condenser 25 is connected to the outlet pipe of the first-stage condenser 15, and the outlet of the second-stage condenser 25 is connected to the secondary network inlet pipe of the third-stage heat pump 4. The inlet of the second-stage evaporator 21 is connected to the outlet pipe of the first-stage evaporator 11, and the outlet of the second-stage evaporator 21 is connected to the primary network inlet pipe of the third-stage heat pump 4.

[0046] The refrigerant outlet of the second-stage evaporator 21 is connected to the inlet pipe of the first-stage impeller A228; the outlet of the second-stage impeller B229, the second-stage exhaust check valve 24, and the refrigerant inlet of the second-stage condenser 25 are connected in sequence; the refrigerant outlet of the second-stage condenser 25, the first-stage throttling device C226, and the high-pressure side inlet of the second-stage economizer 23 are connected in sequence; the high-pressure side outlet of the second-stage economizer 23, the second-stage throttling device D227, and the refrigerant inlet of the second-stage evaporator 21 are connected in sequence; the low-pressure side outlet of the second-stage economizer 23 is connected to the second intermediate chamber 101 through a make-up gas pipe.

[0047] This embodiment 3 provides a more preferred structure for the second-stage heat pump based on embodiment 2. The working principle of the second-stage heat pump is as follows: Primary network water at temperature T3 is supplied from the first-stage evaporator through a pipeline to the second-stage evaporator, where the low-temperature, low-pressure liquid refrigerant absorbs heat from the primary network water and evaporates into low-temperature, low-pressure vapor refrigerant. Simultaneously, the temperature of the primary network water decreases. The low-temperature, low-pressure vapor refrigerant enters the first-stage impeller A2 and is compressed. It then mixes with makeup gas drawn from the low-pressure side outlet of the second-stage economizer in the second intermediate chamber, and then enters the second-stage impeller B2 where it is compressed into a high-temperature, high-pressure refrigerant. The high-temperature, high-pressure refrigerant gas enters the second-stage condenser and releases heat to the second-part secondary network return water at temperature H3 flowing through the second-stage condenser. The temperature of the second-part secondary network return water increases, and simultaneously, the high-temperature, high-pressure refrigerant gas condenses into a high-pressure liquid. The refrigerant first undergoes pressure reduction via the primary throttling device C2 before entering the second-stage economizer. The separated flash vapor is used as makeup gas and returned to the second intermediate chamber through the low-pressure outlet of the second-stage economizer. The remaining liquid is subcooled and discharged from the high-pressure outlet of the second-stage economizer to the secondary throttling device D2. After passing through D2, the pressure is reduced to the evaporation pressure, and the refrigerant is re-injected into the second-stage evaporator as a low-temperature, low-pressure liquid. During this process, if the primary water supply temperature in the second-stage evaporator drops to T4 and the secondary water return temperature in the second part of the second-stage condenser rises to H4, the primary water supply in the second-stage evaporator is piped to the primary network side of the third-stage heat pump, and the secondary water return temperature in the second-stage condenser is piped to the secondary network side of the third-stage heat pump for heat exchange. Otherwise, the current cycle is maintained, allowing the refrigerant to continue circulating within the predetermined process. The function of the second-stage exhaust check valve is to prevent high-pressure gas from flowing back into the second-stage compressor from the second-stage condenser side, ensuring safe system operation.

[0048] Example 4, as Figures 1-3 As shown, a five-stage cascaded high-temperature heat pump system with large temperature difference and high power for heating network electric drive includes a plate heat exchanger 1, a first-stage heat pump 2, a second-stage heat pump 3, a third-stage heat pump 4, a fourth-stage heat pump 5, a fifth-stage heat pump 6, a primary network water supply pipe 7, a primary network water return pipe 8, a secondary network water return pipe 9, and a secondary network water supply pipe 10. The inlet of the plate heat exchanger 1 on the primary network side is connected to the primary network water supply pipe 7, and the outlet of the fifth-stage heat pump 6 on the primary network side is connected to the primary network return pipe 8. The plate heat exchanger 1 is connected to the primary network outlet and the primary network inlet of the first-stage heat pump 2, the primary network outlet of the first-stage heat pump 2 is connected to the primary network inlet of the second-stage heat pump 3, the primary network outlet of the second-stage heat pump 3 is connected to the primary network inlet of the third-stage heat pump 4, the primary network outlet of the third-stage heat pump 4 is connected to the primary network inlet of the fourth-stage heat pump 5, and the primary network outlet of the fourth-stage heat pump 5 is connected to the primary network inlet of the fifth-stage heat pump 6 via pipelines.

[0049] The secondary network inlet of plate heat exchanger 1 and the secondary network inlet of first-stage heat pump 2 are respectively connected to the secondary network return pipe 9. The secondary network outlet of plate heat exchanger 1 is connected to the secondary network supply pipe 10. The secondary network outlet of fifth-stage heat pump 6 is connected to the secondary network supply pipe 10. Pipelines are connected between the outlet of the secondary network side of the first-stage heat pump 2 and the inlet of the secondary network side of the second-stage heat pump 3, between the outlet of the secondary network side of the second-stage heat pump 3 and the inlet of the secondary network side of the third-stage heat pump 4, between the outlet of the secondary network side of the third-stage heat pump 4 and the inlet of the secondary network side of the fourth-stage heat pump 5, and between the outlet of the secondary network side of the fourth-stage heat pump 5 and the inlet of the secondary network side of the fifth-stage heat pump 6.

[0050] The first-stage heat pump 2 includes a first-stage evaporator 11, a first-stage compressor 12, a first-stage economizer 13, a first-stage exhaust check valve 14, a first-stage condenser 15, a first-stage throttling device C116, and a second-stage throttling device D117; the first-stage compressor 12 is a two-stage centrifugal compressor, including a first-stage impeller A118 and a second-stage impeller B119, and a first intermediate chamber 100 is provided between the outlet of the first-stage impeller A118 and the inlet of the second-stage impeller B119; The inlet of the first-stage condenser 15 is connected to the return water pipe 9 of the secondary pipeline network, and the outlet of the first-stage condenser 15 is connected to the inlet pipe of the secondary pipeline network of the second-stage heat pump 3; the inlet of the first-stage evaporator 11 is connected to the outlet pipe of the primary pipeline network of the plate heat exchanger 1, and the outlet of the first-stage evaporator 11 is connected to the inlet pipe of the primary pipeline network of the second-stage heat pump 3.

[0051] The refrigerant outlet of the first-stage evaporator 11 is connected to the inlet pipe of the first-stage impeller A118; the outlet of the second-stage impeller B119, the first-stage exhaust check valve 14, and the refrigerant inlet of the first-stage condenser 15 are connected in sequence; the refrigerant outlet of the first-stage condenser 15, the first-stage throttling device C116, and the high-pressure side inlet of the first-stage economizer 13 are connected in sequence; the high-pressure side outlet of the first-stage economizer 13, the second-stage throttling device D117, and the refrigerant inlet of the first-stage evaporator 11 are connected in sequence; the low-pressure side outlet of the first-stage economizer 13 is connected to the first intermediate chamber 100 through a make-up gas pipe.

[0052] The second-stage heat pump 3 includes a second-stage evaporator 21, a second-stage compressor 22, a second-stage economizer 23, a second-stage exhaust check valve 24, a second-stage condenser 25, a first-stage throttling device C226, and a second-stage throttling device D227. The second-stage compressor 22 is a two-stage centrifugal compressor, including a first-stage impeller A228 and a second-stage impeller B229. A second intermediate chamber 101 is provided between the outlet of the first-stage impeller A228 and the inlet of the second-stage impeller B229. The inlet of the second-stage condenser 25 is connected to the outlet pipe of the first-stage condenser 15, and the outlet of the second-stage condenser 25 is connected to the secondary network inlet pipe of the third-stage heat pump 4. The inlet of the second-stage evaporator 21 is connected to the outlet pipe of the first-stage evaporator 11, and the outlet of the second-stage evaporator 21 is connected to the primary network inlet pipe of the third-stage heat pump 4.

[0053] The refrigerant outlet of the second-stage evaporator 21 is connected to the inlet pipe of the first-stage impeller A228; the outlet of the second-stage impeller B229, the second-stage exhaust check valve 24, and the refrigerant inlet of the second-stage condenser 25 are connected in sequence; the refrigerant outlet of the second-stage condenser 25, the first-stage throttling device C226, and the high-pressure side inlet of the second-stage economizer 23 are connected in sequence; the high-pressure side outlet of the second-stage economizer 23, the second-stage throttling device D227, and the refrigerant inlet of the second-stage evaporator 21 are connected in sequence; the low-pressure side outlet of the second-stage economizer 23 is connected to the second intermediate chamber 101 through a make-up gas pipe.

[0054] The third-stage heat pump 4 includes a third-stage evaporator 31, a third-stage compressor 32, a third-stage economizer 33, a third-stage exhaust check valve 34, a third-stage condenser 35, a first-stage throttling device C336, and a second-stage throttling device D337. The third-stage compressor 32 is a two-stage centrifugal compressor, including a first-stage impeller A338 and a second-stage impeller B339. A third intermediate chamber 102 is provided between the outlet of the first-stage impeller A338 and the inlet of the second-stage impeller B339. The inlet of the third-stage condenser 35 is connected to the outlet of the second-stage condenser 25, and the outlet of the third-stage condenser 35 is connected to the secondary network side pipe of the fourth-stage heat pump 5. The inlet of the third-stage evaporator 31 is connected to the outlet of the second-stage evaporator 21, and the outlet of the third-stage evaporator 31 is connected to the primary network side pipe of the fourth-stage heat pump 5. The refrigerant outlet of the third-stage evaporator 31 is connected to the inlet pipe of the first-stage impeller A338; the outlet of the second-stage impeller B339, the third-stage exhaust check valve 34, and the refrigerant inlet of the third-stage condenser 35 are connected in sequence; the refrigerant outlet of the third-stage condenser 35, the first-stage throttling device C336, and the high-pressure side inlet of the third-stage economizer 33 are connected in sequence; the high-pressure side outlet of the third-stage economizer 33, the second-stage throttling device D337, and the refrigerant inlet of the third-stage evaporator 31 are connected in sequence; the low-pressure side outlet of the third-stage economizer 33 is connected to the third intermediate chamber 102 through a make-up gas pipe.

[0055] This embodiment 4 provides a more preferred structure for the third-stage heat pump based on embodiment 3. The working principle of the third-stage heat pump is as follows: Water supplied from the primary network at temperature T4 in the second-stage evaporator is piped to the third-stage evaporator, where the low-temperature, low-pressure liquid refrigerant absorbs heat from the primary network water and evaporates into low-temperature, low-pressure vapor refrigerant. Simultaneously, the temperature of the primary network water decreases. The low-temperature, low-pressure vapor refrigerant enters the first-stage impeller A3 and is compressed. It then mixes with makeup gas drawn from the low-pressure side outlet of the third-stage economizer in the third intermediate chamber, and then enters the second-stage impeller B3 where it is compressed into a high-temperature, high-pressure refrigerant. The high-temperature, high-pressure refrigerant gas enters the third-stage condenser and releases heat to the second-part secondary network return water at temperature H4 flowing through the third-stage condenser. The temperature of the second-part secondary network return water increases, and simultaneously, the high-temperature, high-pressure refrigerant gas condenses into a high-pressure liquid. The refrigerant first undergoes a pressure reduction process via the primary throttling device C3 before entering the third-stage economizer. The separated flash vapor is used as makeup gas and returned to the third intermediate chamber through the low-pressure side outlet of the third-stage economizer. The remaining liquid is subcooled and discharged from the high-pressure side outlet of the third-stage economizer to the secondary throttling device D3. After passing through D3, the pressure is reduced to the evaporation pressure, and the refrigerant is re-injected into the third-stage evaporator as a low-temperature, low-pressure liquid. During this process, if the primary water supply temperature in the third-stage evaporator drops to T5 and the secondary water return temperature in the second part of the third-stage condenser rises to H5, the primary water supply from the third-stage evaporator is piped to the primary network side of the fourth-stage heat pump, and the secondary water return temperature from the third-stage condenser is piped to the secondary network side of the fourth-stage heat pump for heat exchange. Otherwise, the current cycle is maintained, allowing the refrigerant to continue circulating within the predetermined process. The third-stage exhaust check valve prevents high-pressure gas from flowing back into the third-stage compressor from the third-stage condenser side, ensuring safe system operation.

[0056] Example 5, as Figures 1-3As shown, a five-stage cascaded high-temperature heat pump system with large temperature difference and high power for heating network electric drive includes a plate heat exchanger 1, a first-stage heat pump 2, a second-stage heat pump 3, a third-stage heat pump 4, a fourth-stage heat pump 5, a fifth-stage heat pump 6, a primary network water supply pipe 7, a primary network water return pipe 8, a secondary network water return pipe 9, and a secondary network water supply pipe 10. The inlet of the plate heat exchanger 1 on the primary network side is connected to the primary network water supply pipe 7, and the outlet of the fifth-stage heat pump 6 on the primary network side is connected to the primary network return pipe 8. The plate heat exchanger 1 is connected to the primary network outlet and the primary network inlet of the first-stage heat pump 2, the primary network outlet of the first-stage heat pump 2 is connected to the primary network inlet of the second-stage heat pump 3, the primary network outlet of the second-stage heat pump 3 is connected to the primary network inlet of the third-stage heat pump 4, the primary network outlet of the third-stage heat pump 4 is connected to the primary network inlet of the fourth-stage heat pump 5, and the primary network outlet of the fourth-stage heat pump 5 is connected to the primary network inlet of the fifth-stage heat pump 6 via pipelines.

[0057] The secondary network inlet of plate heat exchanger 1 and the secondary network inlet of first-stage heat pump 2 are respectively connected to the secondary network return pipe 9. The secondary network outlet of plate heat exchanger 1 is connected to the secondary network supply pipe 10. The secondary network outlet of fifth-stage heat pump 6 is connected to the secondary network supply pipe 10. Pipelines are connected between the outlet of the secondary network side of the first-stage heat pump 2 and the inlet of the secondary network side of the second-stage heat pump 3, between the outlet of the secondary network side of the second-stage heat pump 3 and the inlet of the secondary network side of the third-stage heat pump 4, between the outlet of the secondary network side of the third-stage heat pump 4 and the inlet of the secondary network side of the fourth-stage heat pump 5, and between the outlet of the secondary network side of the fourth-stage heat pump 5 and the inlet of the secondary network side of the fifth-stage heat pump 6.

[0058] The first-stage heat pump 2 includes a first-stage evaporator 11, a first-stage compressor 12, a first-stage economizer 13, a first-stage exhaust check valve 14, a first-stage condenser 15, a first-stage throttling device C116, and a second-stage throttling device D117; the first-stage compressor 12 is a two-stage centrifugal compressor, including a first-stage impeller A118 and a second-stage impeller B119, and a first intermediate chamber 100 is provided between the outlet of the first-stage impeller A118 and the inlet of the second-stage impeller B119; The inlet of the first-stage condenser 15 is connected to the return water pipe 9 of the secondary pipeline network, and the outlet of the first-stage condenser 15 is connected to the inlet pipe of the secondary pipeline network of the second-stage heat pump 3; the inlet of the first-stage evaporator 11 is connected to the outlet pipe of the primary pipeline network of the plate heat exchanger 1, and the outlet of the first-stage evaporator 11 is connected to the inlet pipe of the primary pipeline network of the second-stage heat pump 3.

[0059] The refrigerant outlet of the first-stage evaporator 11 is connected to the inlet pipe of the first-stage impeller A118; the outlet of the second-stage impeller B119, the first-stage exhaust check valve 14, and the refrigerant inlet of the first-stage condenser 15 are connected in sequence; the refrigerant outlet of the first-stage condenser 15, the first-stage throttling device C116, and the high-pressure side inlet of the first-stage economizer 13 are connected in sequence; the high-pressure side outlet of the first-stage economizer 13, the second-stage throttling device D117, and the refrigerant inlet of the first-stage evaporator 11 are connected in sequence; the low-pressure side outlet of the first-stage economizer 13 is connected to the first intermediate chamber 100 through a make-up gas pipe.

[0060] The second-stage heat pump 3 includes a second-stage evaporator 21, a second-stage compressor 22, a second-stage economizer 23, a second-stage exhaust check valve 24, a second-stage condenser 25, a first-stage throttling device C226, and a second-stage throttling device D227. The second-stage compressor 22 is a two-stage centrifugal compressor, including a first-stage impeller A228 and a second-stage impeller B229. A second intermediate chamber 101 is provided between the outlet of the first-stage impeller A228 and the inlet of the second-stage impeller B229. The inlet of the second-stage condenser 25 is connected to the outlet pipe of the first-stage condenser 15, and the outlet of the second-stage condenser 25 is connected to the secondary network inlet pipe of the third-stage heat pump 4. The inlet of the second-stage evaporator 21 is connected to the outlet pipe of the first-stage evaporator 11, and the outlet of the second-stage evaporator 21 is connected to the primary network inlet pipe of the third-stage heat pump 4.

[0061] The refrigerant outlet of the second-stage evaporator 21 is connected to the inlet pipe of the first-stage impeller A228; the outlet of the second-stage impeller B229, the second-stage exhaust check valve 24, and the refrigerant inlet of the second-stage condenser 25 are connected in sequence; the refrigerant outlet of the second-stage condenser 25, the first-stage throttling device C226, and the high-pressure side inlet of the second-stage economizer 23 are connected in sequence; the high-pressure side outlet of the second-stage economizer 23, the second-stage throttling device D227, and the refrigerant inlet of the second-stage evaporator 21 are connected in sequence; the low-pressure side outlet of the second-stage economizer 23 is connected to the second intermediate chamber 101 through a make-up gas pipe.

[0062] The third-stage heat pump 4 includes a third-stage evaporator 31, a third-stage compressor 32, a third-stage economizer 33, a third-stage exhaust check valve 34, a third-stage condenser 35, a first-stage throttling device C336, and a second-stage throttling device D337. The third-stage compressor 32 is a two-stage centrifugal compressor, including a first-stage impeller A338 and a second-stage impeller B339. A third intermediate chamber 102 is provided between the outlet of the first-stage impeller A338 and the inlet of the second-stage impeller B339. The inlet of the third-stage condenser 35 is connected to the outlet of the second-stage condenser 25, and the outlet of the third-stage condenser 35 is connected to the secondary network side pipe of the fourth-stage heat pump 5. The inlet of the third-stage evaporator 31 is connected to the outlet of the second-stage evaporator 21, and the outlet of the third-stage evaporator 31 is connected to the primary network side pipe of the fourth-stage heat pump 5. The refrigerant outlet of the third-stage evaporator 31 is connected to the inlet pipe of the first-stage impeller A338; the outlet of the second-stage impeller B339, the third-stage exhaust check valve 34, and the refrigerant inlet of the third-stage condenser 35 are connected in sequence; the refrigerant outlet of the third-stage condenser 35, the first-stage throttling device C336, and the high-pressure side inlet of the third-stage economizer 33 are connected in sequence; the high-pressure side outlet of the third-stage economizer 33, the second-stage throttling device D337, and the refrigerant inlet of the third-stage evaporator 31 are connected in sequence; the low-pressure side outlet of the third-stage economizer 33 is connected to the third intermediate chamber 102 through a make-up gas pipe.

[0063] The fourth-stage heat pump 5 includes a fourth-stage evaporator 41, a fourth-stage compressor 42, a fourth-stage economizer 43, a fourth-stage exhaust check valve 44, a fourth-stage condenser 45, a first-stage throttling device C446, and a second-stage throttling device D447; the fourth-stage compressor 42 is a two-stage centrifugal compressor, including a first-stage impeller A448 and a second-stage impeller B449, and a fourth intermediate chamber 103 is provided between the outlet of the first-stage impeller A448 and the inlet of the second-stage impeller B449; The inlet of the fourth-stage condenser 45 is connected to the outlet pipe of the third-stage condenser 35, and the outlet of the fourth-stage condenser 45 is connected to the secondary network side pipe of the fifth-stage heat pump 6; the inlet of the fourth-stage evaporator 41 is connected to the outlet pipe of the third-stage evaporator 31, and the outlet of the fourth-stage evaporator 41 is connected to the primary network side pipe of the fifth-stage heat pump 6. The refrigerant outlet of the fourth-stage evaporator 41 is connected to the inlet pipe of the first-stage impeller A448; the outlet of the second-stage impeller B449, the fourth-stage exhaust check valve 44, and the refrigerant inlet of the fourth-stage condenser 45 are connected in sequence; the refrigerant outlet of the fourth-stage condenser 45, the first-stage throttling device C446, and the high-pressure side inlet of the fourth-stage economizer 43 are connected in sequence; the high-pressure side outlet of the fourth-stage economizer 43, the second-stage throttling device D447, and the refrigerant inlet of the fourth-stage evaporator 41 are connected in sequence; the low-pressure side outlet of the fourth-stage economizer 43 is connected to the fourth intermediate chamber 103 through a make-up gas pipe.

[0064] This embodiment 5, based on embodiment 4, provides a more preferred structure for the fourth-stage heat pump. The working principle of the fourth-stage heat pump is as follows: Primary network water at temperature T5 is supplied from the third-stage evaporator through a pipeline to the fourth-stage evaporator, where the low-temperature, low-pressure liquid refrigerant absorbs heat from the primary network water and evaporates into low-temperature, low-pressure vapor refrigerant. Simultaneously, the temperature of the primary network water decreases. The low-temperature, low-pressure vapor refrigerant enters the first-stage impeller A4 and is compressed. It then mixes with makeup gas drawn from the low-pressure side outlet of the fourth-stage economizer in the fourth intermediate chamber, and then enters the second-stage impeller B4 where it is compressed into a high-temperature, high-pressure refrigerant. The high-temperature, high-pressure refrigerant gas enters the fourth-stage condenser and releases heat to the second-part secondary network return water at temperature H5 flowing through the fourth-stage condenser. The temperature of the second-part secondary network return water increases, and simultaneously, the high-temperature, high-pressure refrigerant gas condenses into a high-pressure liquid. The refrigerant first undergoes pressure reduction via the primary throttling device C4 before entering the fourth-stage economizer. The separated flash vapor is used as makeup gas and returned to the fourth intermediate chamber via the low-pressure side outlet of the fourth-stage economizer. The remaining liquid is subcooled and discharged from the high-pressure side outlet of the fourth-stage economizer to the secondary throttling device D4. After passing through D4, the pressure is reduced to the evaporation pressure, and the refrigerant is injected back into the fourth-stage evaporator as a low-temperature, low-pressure liquid. During this process, if the primary network supply water temperature in the fourth-stage evaporator drops to T6 and the secondary network return water temperature in the second part of the fourth-stage condenser rises to H6, the primary network supply water in the fourth-stage evaporator is piped to the primary network side of the fifth-stage heat pump, and the secondary network return water in the fourth-stage condenser is piped to the secondary network side of the fifth-stage heat pump for heat exchange. Otherwise, the current cycle is maintained, allowing the refrigerant to continue circulating within the predetermined process. The fourth-stage exhaust check valve prevents high-pressure gas from flowing back into the fourth-stage compressor from the fourth-stage condenser side, ensuring safe system operation.

[0065] Example 6, as Figures 1-3As shown, a five-stage cascaded high-temperature heat pump system with large temperature difference and high power for heating network electric drive includes a plate heat exchanger 1, a first-stage heat pump 2, a second-stage heat pump 3, a third-stage heat pump 4, a fourth-stage heat pump 5, a fifth-stage heat pump 6, a primary network water supply pipe 7, a primary network water return pipe 8, a secondary network water return pipe 9, and a secondary network water supply pipe 10. The inlet of the plate heat exchanger 1 on the primary network side is connected to the primary network water supply pipe 7, and the outlet of the fifth-stage heat pump 6 on the primary network side is connected to the primary network return pipe 8. The plate heat exchanger 1 is connected to the primary network outlet and the primary network inlet of the first-stage heat pump 2, the primary network outlet of the first-stage heat pump 2 is connected to the primary network inlet of the second-stage heat pump 3, the primary network outlet of the second-stage heat pump 3 is connected to the primary network inlet of the third-stage heat pump 4, the primary network outlet of the third-stage heat pump 4 is connected to the primary network inlet of the fourth-stage heat pump 5, and the primary network outlet of the fourth-stage heat pump 5 is connected to the primary network inlet of the fifth-stage heat pump 6 via pipelines.

[0066] The secondary network inlet of plate heat exchanger 1 and the secondary network inlet of first-stage heat pump 2 are respectively connected to the secondary network return pipe 9. The secondary network outlet of plate heat exchanger 1 is connected to the secondary network supply pipe 10. The secondary network outlet of fifth-stage heat pump 6 is connected to the secondary network supply pipe 10. Pipelines are connected between the outlet of the secondary network side of the first-stage heat pump 2 and the inlet of the secondary network side of the second-stage heat pump 3, between the outlet of the secondary network side of the second-stage heat pump 3 and the inlet of the secondary network side of the third-stage heat pump 4, between the outlet of the secondary network side of the third-stage heat pump 4 and the inlet of the secondary network side of the fourth-stage heat pump 5, and between the outlet of the secondary network side of the fourth-stage heat pump 5 and the inlet of the secondary network side of the fifth-stage heat pump 6.

[0067] The first-stage heat pump 2 includes a first-stage evaporator 11, a first-stage compressor 12, a first-stage economizer 13, a first-stage exhaust check valve 14, a first-stage condenser 15, a first-stage throttling device C116, and a second-stage throttling device D117; the first-stage compressor 12 is a two-stage centrifugal compressor, including a first-stage impeller A118 and a second-stage impeller B119, and a first intermediate chamber 100 is provided between the outlet of the first-stage impeller A118 and the inlet of the second-stage impeller B119; The inlet of the first-stage condenser 15 is connected to the return water pipe 9 of the secondary pipeline network, and the outlet of the first-stage condenser 15 is connected to the inlet pipe of the secondary pipeline network of the second-stage heat pump 3; the inlet of the first-stage evaporator 11 is connected to the outlet pipe of the primary pipeline network of the plate heat exchanger 1, and the outlet of the first-stage evaporator 11 is connected to the inlet pipe of the primary pipeline network of the second-stage heat pump 3.

[0068] The refrigerant outlet of the first-stage evaporator 11 is connected to the inlet pipe of the first-stage impeller A118; the outlet of the second-stage impeller B119, the first-stage exhaust check valve 14, and the refrigerant inlet of the first-stage condenser 15 are connected in sequence; the refrigerant outlet of the first-stage condenser 15, the first-stage throttling device C116, and the high-pressure side inlet of the first-stage economizer 13 are connected in sequence; the high-pressure side outlet of the first-stage economizer 13, the second-stage throttling device D117, and the refrigerant inlet of the first-stage evaporator 11 are connected in sequence; the low-pressure side outlet of the first-stage economizer 13 is connected to the first intermediate chamber 100 through a make-up gas pipe.

[0069] The second-stage heat pump 3 includes a second-stage evaporator 21, a second-stage compressor 22, a second-stage economizer 23, a second-stage exhaust check valve 24, a second-stage condenser 25, a first-stage throttling device C226, and a second-stage throttling device D227. The second-stage compressor 22 is a two-stage centrifugal compressor, including a first-stage impeller A228 and a second-stage impeller B229. A second intermediate chamber 101 is provided between the outlet of the first-stage impeller A228 and the inlet of the second-stage impeller B229. The inlet of the second-stage condenser 25 is connected to the outlet pipe of the first-stage condenser 15, and the outlet of the second-stage condenser 25 is connected to the secondary network inlet pipe of the third-stage heat pump 4. The inlet of the second-stage evaporator 21 is connected to the outlet pipe of the first-stage evaporator 11, and the outlet of the second-stage evaporator 21 is connected to the primary network inlet pipe of the third-stage heat pump 4.

[0070] The refrigerant outlet of the second-stage evaporator 21 is connected to the inlet pipe of the first-stage impeller A228; the outlet of the second-stage impeller B229, the second-stage exhaust check valve 24, and the refrigerant inlet of the second-stage condenser 25 are connected in sequence; the refrigerant outlet of the second-stage condenser 25, the first-stage throttling device C226, and the high-pressure side inlet of the second-stage economizer 23 are connected in sequence; the high-pressure side outlet of the second-stage economizer 23, the second-stage throttling device D227, and the refrigerant inlet of the second-stage evaporator 21 are connected in sequence; the low-pressure side outlet of the second-stage economizer 23 is connected to the second intermediate chamber 101 through a make-up gas pipe.

[0071] The third-stage heat pump 4 includes a third-stage evaporator 31, a third-stage compressor 32, a third-stage economizer 33, a third-stage exhaust check valve 34, a third-stage condenser 35, a first-stage throttling device C336, and a second-stage throttling device D337. The third-stage compressor 32 is a two-stage centrifugal compressor, including a first-stage impeller A338 and a second-stage impeller B339. A third intermediate chamber 102 is provided between the outlet of the first-stage impeller A338 and the inlet of the second-stage impeller B339. The inlet of the third-stage condenser 35 is connected to the outlet of the second-stage condenser 25, and the outlet of the third-stage condenser 35 is connected to the secondary network side pipe of the fourth-stage heat pump 5. The inlet of the third-stage evaporator 31 is connected to the outlet of the second-stage evaporator 21, and the outlet of the third-stage evaporator 31 is connected to the primary network side pipe of the fourth-stage heat pump 5. The refrigerant outlet of the third-stage evaporator 31 is connected to the inlet pipe of the first-stage impeller A338; the outlet of the second-stage impeller B339, the third-stage exhaust check valve 34, and the refrigerant inlet of the third-stage condenser 35 are connected in sequence; the refrigerant outlet of the third-stage condenser 35, the first-stage throttling device C336, and the high-pressure side inlet of the third-stage economizer 33 are connected in sequence; the high-pressure side outlet of the third-stage economizer 33, the second-stage throttling device D337, and the refrigerant inlet of the third-stage evaporator 31 are connected in sequence; the low-pressure side outlet of the third-stage economizer 33 is connected to the third intermediate chamber 102 through a make-up gas pipe.

[0072] The fourth-stage heat pump 5 includes a fourth-stage evaporator 41, a fourth-stage compressor 42, a fourth-stage economizer 43, a fourth-stage exhaust check valve 44, a fourth-stage condenser 45, a first-stage throttling device C446, and a second-stage throttling device D447; the fourth-stage compressor 42 is a two-stage centrifugal compressor, including a first-stage impeller A448 and a second-stage impeller B449, and a fourth intermediate chamber 103 is provided between the outlet of the first-stage impeller A448 and the inlet of the second-stage impeller B449; The inlet of the fourth-stage condenser 45 is connected to the outlet pipe of the third-stage condenser 35, and the outlet of the fourth-stage condenser 45 is connected to the secondary network side pipe of the fifth-stage heat pump 6; the inlet of the fourth-stage evaporator 41 is connected to the outlet pipe of the third-stage evaporator 31, and the outlet of the fourth-stage evaporator 41 is connected to the primary network side pipe of the fifth-stage heat pump 6. The refrigerant outlet of the fourth-stage evaporator 41 is connected to the inlet pipe of the first-stage impeller A448; the outlet of the second-stage impeller B449, the fourth-stage exhaust check valve 44, and the refrigerant inlet of the fourth-stage condenser 45 are connected in sequence; the refrigerant outlet of the fourth-stage condenser 45, the first-stage throttling device C446, and the high-pressure side inlet of the fourth-stage economizer 43 are connected in sequence; the high-pressure side outlet of the fourth-stage economizer 43, the second-stage throttling device D447, and the refrigerant inlet of the fourth-stage evaporator 41 are connected in sequence; the low-pressure side outlet of the fourth-stage economizer 43 is connected to the fourth intermediate chamber 103 through a make-up gas pipe.

[0073] The fifth-stage heat pump 6 includes a fifth-stage evaporator 51, a fifth-stage compressor 52, a fifth-stage economizer 53, a fifth-stage exhaust check valve 54, a fifth-stage condenser 55, a first-stage throttling device C556, and a second-stage throttling device D557; the fifth-stage compressor 52 is a two-stage centrifugal compressor, including a first-stage impeller A558 and a second-stage impeller B559, and a fifth intermediate chamber 104 is provided between the outlet of the first-stage impeller A558 and the inlet of the second-stage impeller B559; The inlet of the fifth-stage condenser 55 is connected to the outlet pipe of the fourth-stage condenser 45, and the outlet of the fifth-stage condenser 55 is connected to the secondary water supply pipe 10; the inlet of the fifth-stage evaporator 51 is connected to the outlet pipe of the fourth-stage evaporator 41, and the outlet of the fifth-stage evaporator 51 is connected to the primary water return pipe 8.

[0074] The refrigerant outlet of the fifth-stage evaporator 51 is connected to the inlet pipe of the first-stage impeller A558; the outlet of the second-stage impeller B559, the fifth-stage exhaust check valve 54, and the refrigerant inlet of the fifth-stage condenser 55 are connected in sequence; the refrigerant outlet of the fifth-stage condenser 55, the first-stage throttling device C556, and the high-pressure side inlet of the fifth-stage economizer 53 are connected in sequence; the high-pressure side outlet of the fifth-stage economizer 53, the second-stage throttling device D557, and the refrigerant inlet of the fifth-stage evaporator 51 are connected in sequence; the low-pressure side outlet of the fifth-stage economizer 53 is connected to the fifth intermediate chamber 104 through a make-up gas pipe.

[0075] This embodiment 6 provides a more preferred structure for the fifth-stage heat pump based on embodiment 5. The working principle of the fifth-stage heat pump is as follows: Primary network water at temperature T6 is supplied from the fourth-stage evaporator through a pipeline to the fifth-stage evaporator, where the low-temperature, low-pressure liquid refrigerant absorbs heat from the primary network water and evaporates into low-temperature, low-pressure vapor refrigerant. Simultaneously, the temperature of the primary network water decreases. The low-temperature, low-pressure vapor refrigerant enters the first-stage impeller A5 and is compressed. It then mixes with makeup gas drawn from the low-pressure side outlet of the fifth-stage economizer in the fifth intermediate chamber, and then enters the second-stage impeller B5 where it is compressed into a high-temperature, high-pressure refrigerant. The high-temperature, high-pressure refrigerant gas enters the fifth-stage condenser and releases heat to the second-stage secondary network return water at temperature H6 flowing through the fifth-stage condenser. The temperature of the second-stage secondary network return water increases, and simultaneously, the high-temperature, high-pressure refrigerant gas condenses into a high-pressure liquid refrigerant. The high-pressure liquid first undergoes pressure reduction via the first-stage throttling device C5 before entering the fifth-stage economizer. The separated flash vapor is used as makeup gas and is returned to the fifth intermediate chamber through the low-pressure side outlet of the fifth-stage economizer. The remaining liquid is subcooled and discharged from the high-pressure side outlet of the fifth-stage economizer to the second-stage throttling device D5. After passing through the second-stage throttling device D5, the pressure is reduced to the evaporation pressure, and the refrigerant is injected back into the fifth-stage evaporator as a low-temperature, low-pressure liquid. During this process, if the primary network supply water temperature in the fifth-stage evaporator drops to T7 and the secondary network return water temperature in the second part of the fifth-stage condenser rises to H7, the primary network supply water in the fifth-stage evaporator is used as primary network return water and output through the primary network return water pipe, while the second part of the secondary network return water in the fifth-stage condenser is transported to the secondary network supply water pipe. Otherwise, the current cycle is maintained, allowing the refrigerant to continue circulating in the predetermined process. The function of the fifth-stage exhaust check valve is to prevent high-pressure gas from flowing back into the fifth-stage compressor from the fifth-stage condenser side, ensuring safe system operation.

[0076] The plate heat exchanger, evaporator, compressor, economizer, exhaust check valve, condenser, primary throttling device, and secondary throttling device used in this invention are all existing known electrical devices and can be directly purchased and used on the market. The structure, circuit, and control principle of the plate heat exchanger, evaporator, compressor, economizer, exhaust check valve, condenser, primary throttling device, and secondary throttling device are all existing known technologies. Therefore, the structure, circuit, and control principle of the plate heat exchanger, evaporator, compressor, economizer, exhaust check valve, condenser, primary throttling device, and secondary throttling device will not be described in detail here.

[0077] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention used to illustrate the technical solutions of the present invention, and are not intended to limit the invention, nor are they intended to limit the patent scope of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. That is to say, any changes or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but whose technical problems are still consistent with the present invention, should be included within the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields are similarly included within the patent protection scope of the present invention.

Claims

1. A five-stage cascade high-temperature heat pump system with large temperature difference and high power, electrically driven, for heating pipe networks, characterized in that: It includes a plate heat exchanger (1), a first-stage heat pump (2), a second-stage heat pump (3), a third-stage heat pump (4), a fourth-stage heat pump (5), a fifth-stage heat pump (6), a primary network water supply pipe (7), a primary network water return pipe (8), a secondary network water return pipe (9), and a secondary network water supply pipe (10). The inlet of the plate heat exchanger (1) on the primary network side is connected to the primary network water supply pipe (7), and the outlet of the fifth-stage heat pump (6) on the primary network side is connected to the primary network return pipe (8). The plate heat exchanger (1) is connected to the outlet of the primary pipeline and the inlet of the first-stage heat pump (2) on the primary pipeline, the outlet of the first-stage heat pump (2) on the primary pipeline and the inlet of the second-stage heat pump (3) on the primary pipeline, the outlet of the second-stage heat pump (3) on the primary pipeline and the inlet of the third-stage heat pump (4) on the primary pipeline, the outlet of the third-stage heat pump (4) on the primary pipeline and the inlet of the fourth-stage heat pump (5) on the primary pipeline, and the outlet of the fourth-stage heat pump (5) on the primary pipeline and the inlet of the fifth-stage heat pump (6) on the primary pipeline respectively.

2. The heating network electrically driven five-stage cascade high-temperature heat pump system with large temperature difference and high power according to claim 1, characterized in that, The secondary network inlet of the plate heat exchanger (1) and the secondary network inlet of the first-stage heat pump (2) are connected to the secondary network return pipe (9) respectively. The secondary network outlet of the plate heat exchanger (1) is connected to the secondary network supply pipe (10). The secondary network outlet of the fifth-stage heat pump (6) is connected to the secondary network supply pipe (10). The outlet of the first-stage heat pump (2) on the secondary network side and the inlet of the second-stage heat pump (3) on the secondary network side are connected by pipes, as are the outlet of the second-stage heat pump (3) on the secondary network side and the inlet of the third-stage heat pump (4) on the secondary network side, the outlet of the third-stage heat pump (4) on the secondary network side and the inlet of the fourth-stage heat pump (5) on the secondary network side, and the outlet of the fourth-stage heat pump (5) on the secondary network side and the inlet of the fifth-stage heat pump (6) on the secondary network side.

3. A five-stage cascade high-temperature heat pump system with large temperature difference and high power for heating pipe networks according to claim 2, characterized in that, The first-stage heat pump (2) includes a first-stage evaporator (11), a first-stage compressor (12), a first-stage economizer (13), a first-stage exhaust check valve (14), a first-stage condenser (15), a first-stage throttling device C1 (16), and a second-stage throttling device D1 (17); the first-stage compressor (12) is a two-stage centrifugal compressor, including a first-stage impeller A1 (18) and a second-stage impeller B1 (19), and a first intermediate chamber (100) is provided between the outlet of the first-stage impeller A1 (18) and the inlet of the second-stage impeller B1 (19). The inlet of the first-stage condenser (15) is connected to the return water pipe (9) of the secondary pipeline network, and the outlet of the first-stage condenser (15) is connected to the inlet pipe of the secondary pipeline network of the second-stage heat pump (3); the inlet of the first-stage evaporator (11) is connected to the outlet pipe of the primary pipeline network of the plate heat exchanger (1), and the outlet of the first-stage evaporator (11) is connected to the inlet pipe of the primary pipeline network of the second-stage heat pump (3).

4. A five-stage cascade high-temperature heat pump system with large temperature difference and high power for heating pipe networks according to claim 3, characterized in that, The refrigerant outlet of the first-stage evaporator (11) is connected to the inlet pipe of the first-stage impeller A1 (18); the outlet of the second-stage impeller B1 (19), the first-stage exhaust check valve (14), and the refrigerant inlet of the first-stage condenser (15) are connected in sequence; the refrigerant outlet of the first-stage condenser (15), the first-stage throttling device C1 (16), and the high-pressure side inlet of the first-stage economizer (13) are connected in sequence; the high-pressure side outlet of the first-stage economizer (13), the second-stage throttling device D1 (17), and the refrigerant inlet of the first-stage evaporator (11) are connected in sequence; the low-pressure side outlet of the first-stage economizer (13) is connected to the first intermediate chamber (100) through a gas replenishment pipe.

5. A five-stage cascade high-temperature heat pump system with large temperature difference and high power for heating pipe networks according to claim 4, characterized in that, The second-stage heat pump (3) includes a second-stage evaporator (21), a second-stage compressor (22), a second-stage economizer (23), a second-stage exhaust check valve (24), a second-stage condenser (25), a first-stage throttling device C2 (26), and a second-stage throttling device D2 (27); the second-stage compressor (22) is a two-stage centrifugal compressor, including a first-stage impeller A2 (28) and a second-stage impeller B2 (29), the outlet of the first-stage impeller A2 (28) and the outlet of the second-stage impeller B2 (29) are connected. A second intermediate chamber (101) is provided between the air inlets; the water inlet of the second-stage condenser (25) is connected to the water outlet pipe of the first-stage condenser (15), and the water outlet of the second-stage condenser (25) is connected to the water inlet pipe of the secondary network side of the third-stage heat pump (4); the water inlet of the second-stage evaporator (21) is connected to the water outlet pipe of the first-stage evaporator (11), and the water outlet of the second-stage evaporator (21) is connected to the water inlet pipe of the primary network side of the third-stage heat pump (4).

6. A five-stage cascade high-temperature heat pump system with large temperature difference and high power for heating pipe networks according to claim 5, characterized in that, The refrigerant outlet of the second-stage evaporator (21) is connected to the inlet pipe of the first-stage impeller A2 (28); the outlet of the second-stage impeller B2 (29), the second-stage exhaust check valve (24), and the refrigerant inlet of the second-stage condenser (25) are connected in sequence by pipes. The refrigerant outlet of the second-stage condenser (25), the first-stage throttling device C2 (26), and the high-pressure side inlet of the second-stage economizer (23) are connected in sequence via pipelines; the high-pressure side outlet of the second-stage economizer (23), the second-stage throttling device D2 (27), and the refrigerant inlet of the second-stage evaporator (21) are connected in sequence via pipelines; the low-pressure side outlet of the second-stage economizer (23) is connected to the second intermediate chamber (101) via a gas replenishment pipeline.

7. A five-stage cascade high-temperature heat pump system with large temperature difference and high power for heating pipe networks according to claim 6, characterized in that, The third-stage heat pump (4) includes a third-stage evaporator (31), a third-stage compressor (32), a third-stage economizer (33), a third-stage exhaust check valve (34), a third-stage condenser (35), a first-stage throttling device C3 (36), and a second-stage throttling device D3 (37); the third-stage compressor (32) is a two-stage centrifugal compressor, including a first-stage impeller A3 (38) and a second-stage impeller B3 (39), the outlet of the first-stage impeller A3 (38) and the outlet of the second-stage impeller B3 (39) are connected. A third intermediate chamber (102) is provided between the air inlets of the third stage condenser (39); the water inlet of the third stage condenser (35) is connected to the water outlet pipe of the second stage condenser (25), and the water outlet of the third stage condenser (35) is connected to the secondary network side pipe of the fourth stage heat pump (5); the water inlet of the third stage evaporator (31) is connected to the water outlet pipe of the second stage evaporator (21), and the water outlet of the third stage evaporator (31) is connected to the primary network side pipe of the fourth stage heat pump (5); The refrigerant outlet of the third-stage evaporator (31) is connected to the inlet pipe of the first-stage impeller A3 (38); the outlet of the second-stage impeller B3 (39), the third-stage exhaust check valve (34), and the refrigerant inlet of the third-stage condenser (35) are connected in sequence; the refrigerant outlet of the third-stage condenser (35), the first-stage throttling device C3 (36), and the high-pressure side inlet of the third-stage economizer (33) are connected in sequence; the high-pressure side outlet of the third-stage economizer (33), the second-stage throttling device D3 (37), and the refrigerant inlet of the third-stage evaporator (31) are connected in sequence; the low-pressure side outlet of the third-stage economizer (33) is connected to the third intermediate chamber (102) through a gas replenishment pipe.

8. A five-stage cascade high-temperature heat pump system with large temperature difference and high power for heating pipe networks according to claim 7, characterized in that, The fourth-stage heat pump (5) includes a fourth-stage evaporator (41), a fourth-stage compressor (42), a fourth-stage economizer (43), a fourth-stage exhaust check valve (44), a fourth-stage condenser (45), a first-stage throttling device C4 (46), and a second-stage throttling device D4 (47); the fourth-stage compressor (42) is a two-stage centrifugal compressor, including a first-stage impeller A4 (48) and a second-stage impeller B4 (49), and a fourth intermediate chamber (103) is provided between the outlet of the first-stage impeller A4 (48) and the inlet of the second-stage impeller B4 (49). The inlet of the fourth-stage condenser (45) is connected to the outlet pipe of the third-stage condenser (35), and the outlet of the fourth-stage condenser (45) is connected to the secondary network side pipe of the fifth-stage heat pump (6); the inlet of the fourth-stage evaporator (41) is connected to the outlet pipe of the third-stage evaporator (31), and the outlet of the fourth-stage evaporator (41) is connected to the primary network side pipe of the fifth-stage heat pump (6). The refrigerant outlet of the fourth-stage evaporator (41) is connected to the inlet pipe of the first-stage impeller A4 (48); the outlet of the second-stage impeller B4 (49), the fourth-stage exhaust check valve (44), and the refrigerant inlet of the fourth-stage condenser (45) are connected in sequence; the refrigerant outlet of the fourth-stage condenser (45), the first-stage throttling device C4 (46), and the high-pressure side inlet of the fourth-stage economizer (43) are connected in sequence; the high-pressure side outlet of the fourth-stage economizer (43), the second-stage throttling device D4 (47), and the refrigerant inlet of the fourth-stage evaporator (41) are connected in sequence; the low-pressure side outlet of the fourth-stage economizer (43) is connected to the fourth intermediate chamber (103) through a gas replenishment pipe.

9. A five-stage cascade high-temperature heat pump system with large temperature difference and high power for heating pipe networks according to claim 8, characterized in that, The fifth-stage heat pump (6) includes a fifth-stage evaporator (51), a fifth-stage compressor (52), a fifth-stage economizer (53), a fifth-stage exhaust check valve (54), a fifth-stage condenser (55), a first-stage throttling device C5 (56), and a second-stage throttling device D5 (57); the fifth-stage compressor (52) is a two-stage centrifugal compressor, including a first-stage impeller A5 (58) and a second-stage impeller B5 (59), and a fifth intermediate chamber (104) is provided between the outlet of the first-stage impeller A5 (58) and the inlet of the second-stage impeller B5 (59); The inlet of the fifth-stage condenser (55) is connected to the outlet pipe of the fourth-stage condenser (45), and the outlet of the fifth-stage condenser (55) is connected to the secondary water supply pipe (10); the inlet of the fifth-stage evaporator (51) is connected to the outlet pipe of the fourth-stage evaporator (41), and the outlet of the fifth-stage evaporator (51) is connected to the primary water return pipe (8).

10. A five-stage cascade high-temperature heat pump system with large temperature difference and high power for heating pipe networks according to claim 9, characterized in that, The refrigerant outlet of the fifth-stage evaporator (51) is connected to the inlet pipe of the first-stage impeller A5 (58); the outlet of the second-stage impeller B5 (59), the fifth-stage exhaust check valve (54), and the refrigerant inlet of the fifth-stage condenser (55) are connected in sequence. The refrigerant outlet of the fifth-stage condenser (55), the first-stage throttling device C5 (56), and the high-pressure side inlet of the fifth-stage economizer (53) are connected in sequence by pipelines. The high-pressure side outlet of the fifth-stage economizer (53), the second-stage throttling device D5 (57), and the refrigerant inlet of the fifth-stage evaporator (51) are connected in sequence by pipelines; the low-pressure side outlet of the fifth-stage economizer (53) is connected to the fifth intermediate chamber (104) through a gas replenishment pipeline.

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