Low-temperature waste heat variable-frequency starting asynchronous power generation grid-connected system

Abstract

The utility model discloses a low-temperature waste heat frequency conversion starting asynchronous power generation grid-connected system which comprises a waste heat recovery unit, an asynchronous generator and a grid-connected unit. The grid-connected unit comprises a frequency conversion output contactor, a power frequency contactor, a frequency converter, a circuit breaker and a user bus; the waste heat recovery unit is connected with the asynchronous generator, the asynchronous generator is connected with the frequency conversion output contactor and the power frequency contactor, the frequency conversion output contactor is connected with the frequency converter, the power frequency contactor and the frequency converter are both connected with the circuit breaker, and the circuit breaker is connected with the user bus. The frequency conversion starting grid-connected asynchronous generator has the advantages that the frequency conversion starting grid-connected asynchronous generator is adopted, the problem of current impact is solved, meanwhile, the number of parts is small, occupied space is small, only a small-capacity frequency converter is needed, and the influence on cost is small.

Description

TECHNICAL FIELD

[0001] The utility model relates to low temperature power generation technical field especially relates to a low temperature waste heat variable frequency starting asynchronous power generation grid-connected system. BACKGROUND

[0002] In some energy-saving reconstruction occasions of organic Rankine cycle power generation, small generators are suitable to be connected to the power grid through the existing power transformer of the user. However, when the capacity of the transformer is small, the generator is not allowed to cause impact on the system during grid connection and thus lower the system voltage, affecting the normal work of other electrical equipment. Compared with the asynchronous generator directly connected to the grid, the synchronous generator has smaller impact on the power system, but its cost is higher, the components are more, and the electric control system is more complex, which is not suitable for small power generation projects. SUMMARY

[0003] The utility model discloses a low temperature waste heat variable frequency starting asynchronous power generation grid-connected system, thereby solve the preceding problems existing in prior art.

[0004] In order to realize the above-mentioned purpose, the utility model adopts the following technical scheme:

[0005] A low temperature waste heat variable frequency starting asynchronous power generation grid-connected system, comprising a waste heat recovery unit, an asynchronous generator and a grid-connected unit; the grid-connected unit comprises a frequency conversion output contactor, a power frequency contactor, a frequency converter, a circuit breaker and a user bus; the waste heat recovery unit is connected with the asynchronous generator, the asynchronous generator is connected with the frequency conversion output contactor and the power frequency contactor, the frequency conversion output contactor is connected with the frequency converter, and the power frequency contactor and the frequency converter are connected with the circuit breaker, and the circuit breaker is connected with the user bus.

[0006] Preferably, the waste heat recovery unit comprises a turbine, a heat exchange assembly, a condenser and a working medium pump; the asynchronous generator is connected with the turbine, the turbine is connected with the condenser through a first working medium pipeline, the condenser is connected with the heat exchange assembly through a second working medium pipeline, and the heat exchange assembly is connected with the turbine through a third working medium pipeline; a working medium pump is arranged on the second working medium pipeline, and the heat exchange assembly is connected with the condenser through a fourth working medium pipeline.

[0007] Preferably, an exhaust valve is arranged on the first working medium pipeline.

[0008] Preferably, an air inlet valve is arranged on the third working medium pipeline.

[0009] Preferably, a bypass valve connected with the controller is arranged on the fourth working medium pipeline.

[0010] Preferably, the heat exchange assembly comprises a preheater and an evaporator, the preheater is connected with the evaporator through a fifth working medium pipeline; the preheater is connected with the second working medium pipeline, and the evaporator is connected with the third working medium pipeline and the fourth working medium pipeline.

[0011] The grid-connected system provided by the utility model can recover waste heat to generate power, avoids energy waste, has smooth grid connection process, less components, low cost, and is more conducive to user energy-saving reconstruction implementation. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a structural schematic view of the grid-connected system in the utility model embodiment.

[0013] In the figure: 1, evaporator; 2, preheater; 3, working medium pump; 4, condenser; 5, bypass valve; 6, inlet valve; 7, turbine; 8, asynchronous generator; 9, exhaust valve; 10, frequency conversion output contactor; 11, power frequency contactor; 12, frequency converter; 13, circuit breaker; 14, user bus. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical scheme and advantages of the utility model more clear and obvious, the utility model is further described in detail below in combination with the drawings. It should be understood that the specific embodiments described herein are only used to explain the utility model, and are not used to limit the utility model.

[0015] For some small energy utilization occasions, low-temperature waste heat resources are rich, but the power system capacity is insufficient, the reconstruction space is small, the cost is required to be low, the operation is required to be simple and reliable, the impact on the system is small. In the embodiment, a low-temperature waste heat frequency conversion starting asynchronous power grid-connected system is provided, as shown in the figure, the grid-connected system is composed of a waste heat recovery unit, an asynchronous generator 8 and a grid-connected unit. The waste heat recovery unit is responsible for converting the heat energy in the factory waste heat into mechanical energy, the asynchronous generator 8 is responsible for converting the mechanical energy into electrical energy, and the grid-connected unit is responsible for connecting the electrical energy into the user power system. Figure 1

[0016] ​The waste heat recovery unit includes a turbine 7, a heat exchange assembly, a condenser 4, and a working fluid pump 3. The asynchronous generator 8 is connected to the turbine 7. The turbine 7 is connected to the condenser 4 via a first working fluid pipeline. The condenser 4 is connected to the heat exchange assembly via a second working fluid pipeline. The heat exchange assembly is connected to the turbine 7 via a third working fluid pipeline. A working fluid pump 3 is installed on the second working fluid pipeline. The heat exchange assembly is connected to the condenser 4 via a fourth working fluid pipeline. An exhaust valve 9 is installed on the first working fluid pipeline. An intake valve 6 is installed on the third working fluid pipeline. A bypass valve 5 connected to the controller is installed on the fourth working fluid pipeline. The heat exchange assembly includes a preheater 2 and an evaporator 1. The preheater 2 is connected to the evaporator 1 via a fifth working fluid pipeline. The preheater 2 is connected to the second working fluid pipeline, and the evaporator 1 is connected to both the third and fourth working fluid pipelines.

[0017] The liquid organic working fluid in condenser 4 is pressurized by working fluid pump 3 and transported to preheater 2 and evaporator 1, where it exchanges heat with the heat source. After being heated in evaporator 1, the working fluid turns into vapor, which enters turbine 7 through inlet valve 6, driving turbine 7 to rotate and completing the conversion of thermal energy into mechanical energy. The working fluid vapor, having performed its work, returns to condenser 4 through exhaust valve 9, is cooled to a liquid state, and begins the next cycle.

[0018] The asynchronous generator 8 is connected to the turbine 7. After the turbine 7 is driven to rotate, it drives the generator to rotate as well.

[0019] The grid connection unit is responsible for connecting the generator to the power grid, and includes a variable frequency output contactor 10, a power frequency contactor 11, a frequency converter 12, a circuit breaker 13, and a user bus 14. The waste heat recovery unit is connected to the asynchronous generator 8, the asynchronous generator 8 is connected to the variable frequency output contactor 10 and the power frequency contactor 11, the variable frequency output contactor 10 is connected to the frequency converter 12, the power frequency contactor 11 and the frequency converter 12 are both connected to the circuit breaker 13, and the circuit breaker 13 is connected to the user bus 14. Before starting the generator set, circuit breaker 13 is closed to connect the grid-connected unit to the user bus 14. After entering the start-up process, heat source is gradually introduced to evaporator 1. Once the evaporation pressure is sufficient, turbine 7 intake valve 6 is opened to a minimum to warm up turbine 7. After warm-up, the control system issues a command to start inverter 12 and inverter output contactor 10, driving the generator and turbine 7 to rotate. When the rated speed is reached, inverter 12 uses a special control algorithm to lock the output voltage in frequency and phase. After stabilization, inverter 12 is disconnected and a closing command is issued to power frequency contactor 11, starting power frequency contactor 11, and the generator switches to power frequency operation. Then, intake valve 6 is opened again and bypass valve 5 is closed. After the generator speed is driven to exceed the synchronous speed, the generator supplies power to the bus.

[0020] In the embodiment, the working principle of the grid-connected system is as follows: the liquid organic working medium is stored in the condenser 4, is pumped to the preheater 2 and the evaporator 1 by the working medium pump 3, exchanges heat with the factory heat source flowing through the preheater 2 and the evaporator 1, and the working medium heated into steam returns to the condenser 4 through the bypass valve 5, is cooled into liquid working medium, and continues the next cycle, and the process is an internal circulation process.

[0021] After the internal circulation establishes the evaporation pressure, the exhaust valve 9 is opened, and the intake valve 6 is opened to a small opening degree, so that the working medium vapor enters the turbine 7 to be warmed up.

[0022] After the warming up is completed, the frequency converter 12 is started, the generator is connected to the user bus 14, the alternating magnetic field is established in the air gap of the generator stator, the generator is dragged to the rated speed, the frequency converter 12 starts the frequency locking and phase locking function, the voltage is stabilized, the frequency converter 12 is cut off, and the power frequency contactor 11 is closed, so that the generator is operated at the power frequency in the form of a motor.

[0023] The intake valve 6 is continuously opened, and the bypass valve 5 is gradually closed, so that the generator speed gradually exceeds the synchronous speed, and after the intake valve 6 is fully opened, the generator reaches the optimal power generation state.

[0024] In the embodiment, the generator set adopts a programmable logic controller to realize automatic control, and control instructions of the related components are issued by the controller.

[0025] In the embodiment, the grid-connected system utilizes an existing small-capacity transformer to save investment cost. Meanwhile, the asynchronous power generation scheme is adopted, the grid-connected device has few components, is simple and reliable to operate, saves the land occupation space and the operation and maintenance personnel cost. The frequency starting grid-connected scheme can smoothly connect the generator to the power grid, provide sufficient starting torque, and shorten the current impact time and impact amplitude.

[0026] By adopting the above technical scheme of the utility model, the following beneficial effects are obtained:

[0027] The low-temperature waste heat frequency starting asynchronous power generation grid-connected system can recover waste heat to generate power, avoids energy waste, has a smooth grid connection process, has few components, has low cost, and is more conducive to user energy-saving reconstruction implementation.

[0028] The preferred embodiments of the utility model are described above, and it should be noted that, for ordinary skilled persons in the technical field, some improvements and refinements can be made without departing from the principle of the utility model, and these improvements and refinements should be regarded as the protection scope of the utility model.

Claims

1. A low-temperature waste heat variable frequency starting asynchronous power generation grid-connected system, characterized in that: The waste heat recovery unit, the asynchronous generator and the grid-connected unit are included; the grid-connected unit includes a variable frequency output contactor, a power frequency contactor, a frequency converter, a circuit breaker and a user bus; the waste heat recovery unit is connected with the asynchronous generator; the asynchronous generator is connected with the variable frequency output contactor and the power frequency contactor; the variable frequency output contactor is connected with the frequency converter; the power frequency contactor and the frequency converter are connected with the circuit breaker; the circuit breaker is connected with the user bus.

2. The low-temperature waste heat variable frequency starting asynchronous power generation grid-connected system according to claim 1, characterized in that: The waste heat recovery unit includes a turbine, a heat exchange assembly, a condenser and a working medium pump; the asynchronous generator is connected with the turbine; the turbine is connected with the condenser through a first working medium pipeline; the condenser is connected with the heat exchange assembly through a second working medium pipeline; the heat exchange assembly is connected with the turbine through a third working medium pipeline; the working medium pump is arranged on the second working medium pipeline; the heat exchange assembly is connected with the condenser through a fourth working medium pipeline.

3. The low-temperature waste-heat variable-frequency starting asynchronous power generation grid-connected system according to claim 2, characterized in that: An exhaust valve is arranged on the first working medium pipeline.

4. The low temperature waste heat variable frequency starting asynchronous power generation grid-connected system according to claim 2, characterized in that: An air inlet valve is arranged on the third working medium pipeline.

5. The low temperature waste heat variable frequency starting asynchronous power generation grid-connected system according to claim 2, characterized in that: A bypass valve connected with a controller is arranged on the fourth working medium pipeline.

6. The low temperature waste heat variable frequency starting asynchronous power generation grid-connected system according to claim 2, characterized in that: The heat exchange assembly includes a preheater and an evaporator; the preheater is connected with the evaporator through a fifth working medium pipeline; the preheater is connected with the second working medium pipeline; the evaporator is connected with the third working medium pipeline and the fourth working medium pipeline.

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