A flywheel energy storage braking energy recovery system and method

Abstract

The present disclosure provides a flywheel energy storage braking energy recovery system and method. The system includes a main transformer incoming line unit, a prefabricated cabin unit, a flywheel energy storage system unit, and an energy recovery unit. The main transformer incoming line unit is used to realize the conversion of the bus voltage and the voltage of the prefabricated cabin unit. The prefabricated cabin unit is used to control the charging and discharging of the flywheel energy storage system unit based on the received charging and discharging instructions, and is also used to control the flywheel energy storage system unit to enter the braking state when the flywheel speed does not meet the requirements. The flywheel energy storage system unit includes a flywheel, and the flywheel is used for energy storage. The energy recovery unit includes a supercapacitor, and the supercapacitor is used to store the energy released by the flywheel energy storage system unit when the flywheel energy storage system unit is in the braking state. Based on the system of the present disclosure, the problem of energy waste during the braking of the flywheel energy storage system in the prior art is solved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of flywheel energy storage, and in particular, to a flywheel energy storage braking energy recovery system and method. Background Art

[0002] With the increase in the proportion of new energy power generation, the stability of the power grid frequency has been severely challenged, and higher requirements are put forward for the frequency modulation ability of thermal power units in the power grid. However, traditional thermal power units have a slow response to power regulation and are difficult to meet the rapid demand for primary frequency modulation. Moreover, frequent disturbances will also cause serious wear to thermal power units, reducing the safety and economy of unit operation. Among them, energy storage has received increasing attention and will be an indispensable part of the power system.

[0003] In recent years, large-scale energy storage has assisted the power system in frequency modulation. Among them, flywheel energy storage stores energy or momentum in a high-speed rotating flywheel rotor and realizes the conversion of electrical energy to mechanical kinetic energy and then to electrical energy through an electric motor. Flywheel energy storage is an advanced physical energy storage technology with the characteristics of high safety, high power density, fast response speed, long life, maintenance-free, good scalability, pollution-free, small floor area for underground layout, and no need for special fire protection systems and ventilation systems. With these advantages, it provides a new idea for solving the frequency modulation problem of thermal power units. Its cycle times can reach up to millions of times, and the response time is within ten milliseconds, which well matches the requirements of frequent power fluctuations and small time scales for primary frequency modulation.

[0004] Existing flywheel energy storage systems mainly include transformers, machine-side PCS (converters), grid-side PCS, control cabinets, flywheel energy storage systems, and braking resistors. Among them, the braking system of flywheel energy storage consists of a grid-side PCS and a braking resistor. When the flywheel speed exceeds the limit value in flywheel energy storage, the inverter reports an overspeed fault, and when a fault occurs during flywheel operation, the main control gives an emergency stop command, the inverter and PCS trip in series, disconnect the connection with the transformer, and at the same time start the braking resistor to brake the flywheel. In this process, the mechanical energy stored in the flywheel is converted into electrical energy and wasted in the braking resistor in the form of heat. Therefore, the existing flywheel energy storage system absorbs the energy stored in the flywheel with a braking resistor during braking and then dissipates it in the form of heat, resulting in energy waste. Summary of the Invention

[0005] The present disclosure aims to solve at least one of the technical problems in the related art to some extent.

[0006] To this end, the first object of the present disclosure is to propose a flywheel energy storage braking energy recovery system to solve the problem of energy waste in the existing flywheel energy storage system during braking.

[0007] The second object of the present disclosure is to propose a flywheel energy storage braking energy recovery method.

[0008] To achieve the above object, an embodiment of the first aspect of the present disclosure provides a flywheel energy storage braking energy recovery system, including a main transformer incoming line unit, a prefabricated cabin unit, a flywheel energy storage system unit, and a recovered energy unit;

[0009] The main transformer incoming line unit is used to realize the conversion between the bus voltage and the voltage of the prefabricated cabin unit;

[0010] The prefabricated cabin unit is used to control the charging and discharging of the flywheel energy storage system unit based on the received charging and discharging instructions, and is also used to control the flywheel energy storage system unit to enter the braking state when the flywheel speed does not meet the requirements;

[0011] The flywheel energy storage system unit includes a flywheel, and the flywheel is used for energy storage;

[0012] The recovered energy unit includes a super capacitor, and the super capacitor is used to store the energy released by the flywheel energy storage system unit when the flywheel energy storage system unit is in the braking state.

[0013] In the flywheel energy storage braking energy recovery system according to the embodiment of the present disclosure, the main transformer incoming line unit is used to realize the conversion between the bus voltage and the voltage of the prefabricated cabin unit; the prefabricated cabin unit is used to control the charging and discharging of the flywheel energy storage system unit based on the received charging and discharging instructions, and is also used to control the flywheel energy storage system unit to enter the braking state when the flywheel speed does not meet the requirements; the flywheel energy storage system unit includes a flywheel, and the flywheel is used for energy storage; the recovered energy unit includes a super capacitor, and the super capacitor is used to store the energy released by the flywheel energy storage system unit when the flywheel energy storage system unit is in the braking state. In this case, the electric energy generated during the braking process is transmitted to the super capacitor, and the flywheel braking energy is recovered, solving the problem of energy waste in the prior art when the flywheel energy storage system brakes.

[0014] In a flywheel energy storage braking energy recovery system according to an embodiment of the first aspect of the present disclosure, the recovered energy unit further includes a capacitor energy storage converter, the super capacitor is connected to the flywheel energy storage system unit through the capacitor energy storage converter, and the prefabricated cabin unit is further used to control the capacitor energy storage converter not to conduct when the flywheel speed meets the requirements, and to control the capacitor energy storage converter to conduct when the flywheel speed does not meet the requirements.

[0015] In a flywheel energy storage braking energy recovery system according to an embodiment of the first aspect of the present disclosure, the prefabricated cabin unit includes a grid-side converter and a machine-side converter, and the main transformer incoming line unit is connected to the flywheel energy storage system unit through the grid-side converter and the machine-side converter.

[0016] In a flywheel energy storage braking energy recovery system according to an embodiment of the first aspect of the present disclosure, the prefabricated cabin unit further includes a grid-side control cabinet and a machine-side control cabinet. The grid-side control cabinet is configured to control the working mode of the grid-side converter based on a first control instruction, and the machine-side control cabinet is configured to control the working mode of the machine-side converter based on a second control instruction.

[0017] In a flywheel energy storage braking energy recovery system according to an embodiment of the first aspect of the present disclosure, the prefabricated cabin unit further includes a main control cabinet. The main control cabinet is respectively connected to the grid-side control cabinet and the machine-side control cabinet. The main control cabinet is configured to generate a first control instruction and a second control instruction based on the received charge-discharge instruction, and the main control cabinet is further configured to generate a third control instruction based on the received flywheel speed and send the third control instruction to the capacitor energy storage converter.

[0018] In a flywheel energy storage braking energy recovery system according to an embodiment of the first aspect of the present disclosure, the flywheel energy storage braking energy recovery system further includes a resistive braking unit, and the resistive braking unit is connected to the flywheel energy storage system unit.

[0019] In a flywheel energy storage braking energy recovery system according to an embodiment of the first aspect of the present disclosure, the resistive braking unit includes a braking resistor and a braking resistor switch, and the braking resistor is connected to the flywheel energy storage system unit through the braking resistor switch.

[0020] In a flywheel energy storage braking energy recovery system according to an embodiment of the first aspect of the present disclosure, the main transformer incoming line unit includes an incoming line circuit breaker, an incoming line transformer, and an outgoing line circuit breaker connected in sequence. The incoming line circuit breaker is connected to the bus, and the incoming line circuit breaker is connected to the grid-side converter of the prefabricated cabin unit.

[0021] To achieve the above object, an embodiment of the second aspect of the present disclosure provides a braking energy recovery method based on the flywheel energy storage braking energy recovery system according to the embodiment of the first aspect of the present disclosure, including:

[0022] Receiving a charge-discharge instruction and controlling the flywheel energy storage system unit to perform charge and discharge;

[0023] During the charge and discharge process, obtaining the flywheel speed of the flywheel energy storage system unit and determining whether the flywheel speed meets the requirements;

[0024] If not, controlling the flywheel energy storage system unit to be in a braking state and controlling the energy recovery unit to work to store the energy released by the flywheel energy storage system unit.

[0025] The flywheel energy storage braking energy recovery method according to the embodiments of the present disclosure receives charge and discharge commands and controls the flywheel energy storage system unit to charge and discharge; during the charge and discharge process, the flywheel speed of the flywheel energy storage system unit is obtained, and it is judged whether the flywheel speed meets the requirements; if not, the flywheel energy storage system unit is controlled to be in a braking state, and the energy recovery unit is controlled to work to store the energy released by the flywheel energy storage system unit. In this case, the electric energy generated during the braking process is transmitted to the energy recovery unit, and the flywheel braking energy is recovered, solving the problem of energy waste during braking of the flywheel energy storage system in the prior art.

[0026] In a flywheel energy storage braking energy recovery method according to the second aspect embodiment of the present disclosure, it further includes: when the flywheel energy storage system unit is in a braking state, if the flywheel speed meets the requirements, controlling the energy recovery unit to release energy to the flywheel energy storage system unit; after the energy of the energy recovery unit is completely released, using the bus voltage to charge the flywheel energy storage system unit through the main transformer incoming line unit and the prefabricated cabin unit so that the flywheel speed maintains the rated speed.

[0027] Additional aspects and advantages of the present disclosure will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present disclosure. Brief Description of the Drawings

[0028] The above-mentioned and / or additional aspects and advantages of the present disclosure will become apparent and be easily understood from the following description of the embodiments in conjunction with the drawings, where:

[0029] Figure 1 is a block diagram of a flywheel energy storage braking energy recovery system provided by an embodiment of the present disclosure;

[0030] Figure 2 is a block diagram of another flywheel energy storage braking energy recovery system provided by an embodiment of the present disclosure;

[0031] Figure 3 is a structural schematic diagram of a flywheel energy storage braking energy recovery system provided by an embodiment of the present disclosure;

[0032] Figure 4 is a flow schematic diagram of a flywheel energy storage braking energy recovery method provided by an embodiment of the present disclosure;

[0033] Description of the Reference Numerals:

[0034] 1 - Main transformer incoming line unit; 2 - Prefabricated cabin unit; 3 - Flywheel energy storage system unit; 4 - Recovered energy unit; 5 - Resistive braking unit; 1-1 - Incoming line circuit breaker; 1-2 - Incoming line transformer; 1-3 - Outgoing line circuit breaker; 2-1 - Grid-side converter; 2-2 - Machine-side converter; 2-3 - Main control cabinet; 2-4 - Grid-side control cabinet; 2-5 - Machine-side control cabinet; 4-1 - Capacitor energy storage converter; 4-2 - Super capacitor; 5-1 - Braking resistor switch; 5-2 - Braking resistor. Specific embodiments

[0035] Here, the exemplary embodiments will be described in detail, and the examples are shown in the drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the embodiments of the present disclosure. On the contrary, they are merely examples of devices and methods consistent with some aspects of the embodiments of the present disclosure as detailed in the appended claims.

[0036] In the description of this specification, the description referring to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0037] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" can explicitly or implicitly include at least one of the features. In the description of the present disclosure, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined. It should also be understood that the term "and / or" used in the present disclosure refers to and includes any or all possible combinations of one or more of the associated listed items.

[0038] The embodiments of the present disclosure will be described in detail below. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are intended to explain the present disclosure and should not be construed as a limitation of the present disclosure.

[0039] The present disclosure will be described in detail below with reference to specific embodiments.

[0040] The present disclosure provides a flywheel energy storage braking energy recovery system and method to solve the problem of energy waste during braking in existing flywheel energy storage systems.

[0041] Figure 1 It is a block diagram of a flywheel energy storage braking energy recovery system provided by an embodiment of the present disclosure. Figure 2 It is a block diagram of another flywheel energy storage braking energy recovery system provided by an embodiment of the present disclosure. Figure 3 It is a schematic structural diagram of a flywheel energy storage braking energy recovery system provided by an embodiment of the present disclosure.

[0042] As Figure 1 shown, the flywheel energy storage braking energy recovery system provided by the embodiment of the present disclosure includes a main transformer incoming line unit 1, a prefabricated cabin unit 2, a flywheel energy storage system unit 3, and a recovered energy unit 4.

[0043] In this embodiment, the main transformer incoming line unit 1 is used to realize the conversion between the bus voltage and the voltage of the prefabricated cabin unit 2.

[0044] Specifically, the incoming line end of the main transformer incoming line unit 1 is connected to the bus of the power grid, and the outgoing line end of the main transformer incoming line unit 1 is connected to the prefabricated cabin unit 2. When the flywheel energy storage system unit 3 is in the charging state, the main transformer incoming line unit 1 converts the voltage of the bus into the voltage required by the prefabricated cabin unit 2; when the flywheel energy storage system unit 3 is in the discharging state, the main transformer incoming line unit 1 converts the voltage output by the prefabricated cabin unit 2 into the voltage required by the bus.

[0045] In some embodiments, as Figure 3 shown, the main transformer incoming line unit 1 includes an incoming line circuit breaker 1-1, an incoming line transformer 1-2, and an outgoing line circuit breaker 1-3 connected in sequence. The incoming line circuit breaker 1-1 is connected to the bus, and the incoming line circuit breaker 1-1 is connected to the prefabricated cabin unit 2. The bus is, for example, the 10 kV common A section bus of the power plant auxiliary power system. The voltage of the prefabricated cabin unit 2 is, for example, 400 V. That is, the high-voltage side of the incoming line transformer 1-2 is connected to the 10 kV common A section bus of the power plant auxiliary power system through the incoming line circuit breaker 1-1, and the low-voltage side of the incoming line transformer 1-2 is connected to the 400 V prefabricated cabin unit 2 through the outgoing line circuit breaker 1-3.

[0046] The incoming line circuit breaker 1-1 is used to cut off or connect the incoming line transformer 1-2 and the bus. The incoming line circuit breaker 1-1 is connected to the main control cabinet 2-3 (described later), and the closing or opening of the incoming line circuit breaker 1-1 is controlled by the main control cabinet 2-3.

[0047] The incoming transformer 1-2 is used to convert the voltage of the bus into the voltage required by the prefabricated cabin unit 2 when the flywheel energy storage system unit 3 is in the charging state; when the flywheel energy storage system unit 3 is in the discharging state, it converts the voltage output by the prefabricated cabin unit 2 into the voltage required by the bus.

[0048] The outgoing line circuit breaker 1-3 is used to cut off or connect the incoming transformer 1-2 and the prefabricated cabin unit 2. The outgoing line circuit breaker 1-3 is connected to the main control cabinet 2-3, and the closing or opening of the outgoing line circuit breaker 1-3 is controlled by the main control cabinet 2-3.

[0049] In this embodiment, the prefabricated cabin unit 2 (also called the PCS prefabricated cabin unit 2) is used to control the flywheel energy storage system unit 3 to charge and discharge based on the received charge and discharge instructions, and is also used to control the flywheel energy storage system unit 3 to enter the braking state when the flywheel speed does not meet the requirements. The incoming line end of the prefabricated cabin unit 2 is connected to the outgoing line end of the main transformer incoming line unit 1, and the outgoing line end of the prefabricated cabin unit 2 is connected to the flywheel energy storage system unit 3.

[0050] In some embodiments, as Figure 3 shown, the prefabricated cabin unit 2 includes a grid-side converter 2-1 (which can be called the grid-side PCS) and a machine-side converter 2-2 (which can be called the machine-side PCS). The grid-side converter 2-1 is connected to the machine-side converter 2-2. The incoming line circuit breaker 1-1 is connected to the grid-side converter 2-1, and the machine-side converter 2-2 is connected to the flywheel energy storage system unit 3. That is, the main transformer incoming line unit 1 is connected to the flywheel energy storage system unit 3 via the grid-side converter 2-1 and the machine-side converter 2-2. Among them, the working mode of the grid-side converter 2-1 includes the rectifier mode or the inverter mode. The working mode of the machine-side converter 2-2 includes the rectifier mode or the inverter mode.

[0051] When the grid-side converter 2-1 works in the rectifier mode, it sends the electric energy of the main transformer incoming line unit 1 to the machine-side converter 2-2; when it works in the inverter mode, it sends the electric energy output by the machine-side converter 2-2 to the main transformer incoming line unit 1.

[0052] When the machine-side converter 2-2 works in the inverter mode, it sends the electric energy output by the grid-side converter 2-1 to the flywheel energy storage system unit 3; when it works in the rectifier mode, it sends the electric energy of the flywheel energy storage system unit 3 to the flywheel energy storage system unit 3.

[0053] In some embodiments, as Figure 3 shown, the prefabricated cabin unit 2 further includes a main control cabinet 2-3, a grid-side control cabinet 2-4, and a machine-side control cabinet 2-5. The main control cabinet 2-3 is respectively connected to the grid-side control cabinet 2-4 and the machine-side control cabinet 2-5. The grid-side control cabinet 2-4 is connected to the grid-side converter 2-1, and the machine-side control cabinet 2-5 is connected to the machine-side converter 2-2.

[0054] The main control cabinet 2-3 is used to generate a first control instruction and a second control instruction based on the received charge and discharge instructions, and send the first control instruction to the grid-side control cabinet 2-4 and the second control instruction to the machine-side control cabinet 2-5. Among them, the charge and discharge instructions come from the power grid or the dispatching center. The first control instruction includes a first rectification instruction and a first inversion instruction, and the second control instruction includes a second rectification instruction and a second inversion instruction.

[0055] The main control cabinet 2-3 is also used to generate a third control instruction based on the received flywheel speed and send the third control instruction to the capacitor energy storage converter 4-1. The third control instruction includes a third conduction instruction and a third turn-off instruction.

[0056] The grid-side control cabinet 2-4 is used to control the working mode of the grid-side converter 2-1 based on the first control instruction. That is, the main control cabinet 2-3 communicates with the grid-side PCS through the grid-side control cabinet 2-4; the main control cabinet 2-3 controls the working mode of the grid-side PCS through the grid-side control cabinet 2-4 according to the superior dispatching instruction (i.e., the charge and discharge instruction) to perform flywheel energy storage or energy release (i.e., charging or discharging). If the first rectification instruction is received, the grid-side control cabinet 2-4 controls the grid-side converter 2-1 to be in the rectifier mode, and if the first inversion instruction is received, the grid-side control cabinet 2-4 controls the grid-side converter 2-1 to be in the inverter mode.

[0057] The machine-side control cabinet 2-5 is used to control the working mode of the machine-side converter 2-2 based on the second control instruction. That is, the main control cabinet 2-3 communicates with the machine-side PCS through the machine-side control cabinet 2-5; the main control cabinet 2-3 controls the working mode of the machine-side PCS through the machine-side control cabinet 2-5 according to the superior dispatching instruction (i.e., the charge and discharge instruction) to perform flywheel energy storage or energy release (i.e., charging or discharging). If the second rectification instruction is received, the machine-side control cabinet 2-5 controls the machine-side converter 2-2 to be in the rectifier mode, and if the second inversion instruction is received, the machine-side control cabinet 2-5 controls the machine-side converter 2-2 to be in the inverter mode.

[0058] In this embodiment, the flywheel energy storage system unit 3 includes a flywheel, and the flywheel is used for energy storage.

[0059] In this embodiment, the flywheel energy storage system unit 3 further includes a flywheel unit. Specifically, when the flywheel energy storage system unit 3 stores energy (or charges), the flywheel unit drives the flywheel to convert the electric energy output by the prefabricated cabin unit 2 into mechanical energy and store it in the flywheel. When the flywheel energy storage system unit 3 discharges, the flywheel unit acts as a generator to convert the mechanical energy stored in the flywheel into electric energy and send it to the prefabricated cabin unit 2.

[0060] In some embodiments, such as Figure 3As shown, the flywheel energy storage system unit 3 is connected to the machine side converter 2-2 of the prefabricated cabin unit 2. When the flywheel energy storage system unit 3 is in the charging state, the flywheel energy storage system unit 3 receives the electric energy output by the machine side converter 2-2 and converts the electric energy into mechanical energy for storage; when the flywheel energy storage system unit 3 is in the discharging state, the flywheel energy storage system unit 3 converts the mechanical energy into electric energy and sends it to the side converter 2-2.

[0061] In this embodiment, the flywheel energy storage system unit 3 is connected to the main control cabinet 2-3. The flywheel energy storage system unit 3 sends the flywheel speed to the main control cabinet 2-3 for detection. If the main control cabinet 2-3 determines that the flywheel speed does not meet the requirements, the main control cabinet 2-3 controls the flywheel energy storage system unit 3 to enter the braking state. At this time, the flywheel unit is in the generator state. Among them, the flywheel speed not meeting the requirements can be, for example, that the flywheel speed exceeds the set speed or the ratio of the flywheel speed to the set speed exceeds the set ratio. The flywheel speed not meeting the requirements means abnormal charging and discharging of the flywheel, and the flywheel speed meeting the requirements means normal charging and discharging of the flywheel.

[0062] In this embodiment, the energy recovery unit 4 includes a super capacitor, which is used to store the energy released by the flywheel energy storage system unit 3 when the flywheel energy storage system unit 3 is in the braking state.

[0063] In some embodiments, as Figure 3 shown, the energy recovery unit 4 includes a capacitor energy storage converter 4-1 (which can be called a capacitor energy storage PCS) and a super capacitor 4-2. The super capacitor 4-2 is connected to the flywheel energy storage system unit 3 through the capacitor energy storage converter 4-1. In this case, the energy recovery unit is also called a super capacitor energy storage recovery unit.

[0064] The capacitor energy storage converter 4-1 is used to cut off or connect the super capacitor 4-2 and the flywheel energy storage system unit 3. The on-off of the flywheel energy storage system unit 3 is controlled by the prefabricated cabin unit 2.

[0065] The super capacitor 4-2 is used to store the energy released by the flywheel energy storage system unit 3 when the flywheel energy storage system unit 3 is in the braking state.

[0066] Specifically, the capacitor energy storage converter 4-1 is connected to the main control cabinet 2-3 of the prefabricated cabin unit 2. The main control cabinet 2-3 of the prefabricated cabin unit 2 is also used to generate a third turn-off command to control the non-conduction of the capacitor energy storage converter 4-1 when the flywheel speed meets the requirements. At this time, the flywheel is normally charged and discharged, and the supercapacitor 4-2 and the capacitor energy storage converter 4-1 do not work. When the flywheel speed does not meet the requirements, a third turn-on command is generated to control the conduction of the capacitor energy storage converter 4-1. At this time, the flywheel charge and discharge are abnormal, the capacitor energy storage converter 4-1 connects the supercapacitor 4-2, and the flywheel unit operates in the generator state. The braking torque formed by the power generation of the flywheel unit will directly act on the flywheel drive wheel through the transmission system to decelerate or stop the flywheel. The electric energy generated during this braking process is stored in the supercapacitor 4-2 through the capacitor energy storage converter 4-1. Among them, the supercapacitor has good large-current charge and discharge capabilities, and the linearly stable voltage change trend is conducive to monitoring the SOC of the supercapacitor. Therefore, the supercapacitor is suitable as an energy storage element for storing energy in the flywheel braking energy feedback and can quickly recover energy to achieve the braking effect. Since the supercapacitor absorbs energy faster than the resistance braking process, using the supercapacitor to recover the flywheel braking energy can improve the flywheel braking rate.

[0067] In some embodiments, as Figure 2 shown, the flywheel energy storage braking energy recovery system further includes a resistance braking unit 5, and the resistance braking unit 5 is connected to the flywheel energy storage system unit 3.

[0068] In some embodiments, as Figure 3 shown, the resistance braking unit 5 includes a braking resistor 5-2 and a braking resistor switch 5-1, and the braking resistor 5-2 is connected to the flywheel energy storage system unit 3 through the braking resistor switch 5-1.

[0069] The braking resistor switch 5-1 is used to connect or disconnect the connection between the braking resistor 5-2 and the flywheel energy storage system unit 3. The on-off of the braking resistor switch 5-1 is controlled by the main control cabinet 2-3. When the flywheel speed is less than or equal to one-third of the initial flywheel speed, the main control cabinet 2-3 controls the braking resistor switch 5-1 to close.

[0070] The braking resistor 5-2 is used to consume the electric energy generated by the flywheel energy storage system unit 3 when the braking resistor switch 5-1 is closed. In this case, considering that when the flywheel speed drops to a certain extent, the output power drops, which will cause the charging speed of the supercapacitor to decrease. Open the braking resistor switch 5-1, and the braking resistor 5-2 absorbs the residual energy of the flywheel, so that the flywheel speed drops to 0 and is in a shutdown state.

[0071] Combined with Figure 3 , the normal charge and discharge process of the flywheel energy storage system unit 3 is as follows:

[0072] When the flywheel energy storage system unit 3 is charging, the main transformer incoming line unit 1 is switched on and controlled by the main control cabinet 2-3 of the prefabricated cabin unit 2. Among them, the grid-side PCS operates in the rectifier state, and the machine-side PCS operates in the inverter state; the flywheel rotor rotates at an accelerated speed, and electrical energy is stored in the flywheel of the flywheel energy storage system unit 3 that rotates at an accelerated speed in the form of kinetic energy;

[0073] When the flywheel energy storage system unit 3 discharges, the rotor of the flywheel rotates at a decelerated speed to drive the flywheel unit to release energy. The flywheel unit operates in the generator mode, the machine-side PCS operates in the rectification state, and the grid-side PCS operates in the inverter state. The kinetic energy stored in the flywheel rotor is supplied to the power grid through the main transformer incoming line unit 1 via the 10kV common section A bus of the plant through the prefabricated cabin unit 2.

[0074] Combined with Figure 3 , the braking energy recovery method of the flywheel energy storage braking energy recovery system is as follows:

[0075] a. Braking process when the flywheel energy storage system unit 3 is abnormal:

[0076] If the flywheel speed of the flywheel energy storage system unit 3 exceeds the set speed, the main control cabinet 2-3 reports an overspeed fault and a flywheel operation fault. The main control cabinet 2-3 gives corresponding instructions to control the grid-side PCS and the machine-side PCS to trip in series, control the incoming line circuit breaker 1-1 and the outgoing line circuit breaker 1-3 to disconnect, thereby cutting off the connection with the incoming line transformer 1-2. At the same time, control the capacitor energy storage converter 4-1 to conduct to start the super capacitor energy storage recovery energy unit. The mechanical energy stored in the flywheel is converted into electrical energy and charged to the super capacitor 4-2 in the constant current mode of the capacitor energy storage converter 4-1. Since the super capacitor has the characteristic of large current charging, it can quickly absorb the energy stored in the flywheel and quickly brake the flywheel to a low-speed state; when the flywheel speed drops to a certain extent (for example, one-third of the initial flywheel speed), the output power of the flywheel energy storage system unit 3 decreases, resulting in a decrease in the charging speed of the super capacitor. At this time, the main control cabinet 2-3 closes the capacitor energy storage converter 4-1 and turns on the braking resistor switch 5-1. The braking resistor 5-2 absorbs the residual energy of the flywheel, and the flywheel speed drops to 0 and is in a shutdown state;

[0077] b. Process of the flywheel energy storage system unit 3 returning to normal:

[0078] After troubleshooting the flywheel system (i.e., after the flywheel speed of the flywheel energy storage system unit 3 is restored), first, the main control cabinet 2-3 controls the conduction of the capacitor energy storage converter 4-1, and the electric energy stored in the supercapacitor 4-2 drives the flywheel to rotate, feeding back the energy recovered by the supercapacitor during the braking process to the flywheel energy storage system unit 3. Considering that there will be energy dissipation during the recovery and feedback process, after all the electric energy of the supercapacitor 4-2 is fed back to the flywheel energy storage system unit 3, the incoming line breaker 1-1 and the outgoing line breaker 1-3 are connected through the main control cabinet 2-3, so that the incoming line transformer 1-2 is connected to the 10 kV common section A of the plant service bus; the main control cabinet 2-3, the grid-side control cabinet 2-4, and the machine-side control cabinet 2-5 control the working modes of the grid-side PCS and the machine-side PCS to charge the flywheel, so that the flywheel speed reaches the rated speed, the flywheel is fully charged, the charging power is set to 0, and the flywheel operates in a rated state.

[0079] The flywheel energy storage braking energy recovery system proposed in the embodiments of the present disclosure, the main transformer incoming line unit is used to realize the conversion of the bus voltage and the voltage of the prefabricated cabin unit; the prefabricated cabin unit is used to control the charging and discharging of the flywheel energy storage system unit based on the received charging and discharging instructions, and is also used to control the flywheel energy storage system unit to enter the braking state when the flywheel speed does not meet the requirements; the flywheel energy storage system unit includes a flywheel, and the flywheel is used for energy storage; the energy recovery unit includes a supercapacitor, and the supercapacitor is used to store the energy released by the flywheel energy storage system unit when the flywheel energy storage system unit is in the braking state. In this case, the electric energy generated during the braking process is transmitted to the supercapacitor, and the flywheel braking energy is recovered, solving the problem of energy waste during the braking of the flywheel energy storage system in the prior art. In addition, when the system of the present disclosure stores the electric energy generated during the braking process into the supercapacitor, the braking torque formed when the flywheel unit generates electricity directly acts on the flywheel drive wheel through the transmission system, so that the flywheel decelerates or stops, which not only has a braking effect, but also enables the recovery of the flywheel braking energy. The system of the present disclosure adds an energy recovery unit, reduces the waste of the braking energy of the braking flywheel through the braking resistor; improves the efficiency of the plant service power, such as the power consumption of the flywheel energy storage system, improves the energy utilization rate of the flywheel energy storage system, reduces the braking heat dissipation, and has good economic effects; adopts a large-capacity supercapacitor bank, which can provide a storage path for the recovery of the braking energy of multiple flywheels; the energy recovery units can be used as backups for each other to form an energy recovery energy storage unit group, improving the reliability of the flywheel braking energy recovery; has good environmental protection and energy-saving effects, improves the flywheel energy storage efficiency, can reduce the plant service power rate, is highly practical, and is convenient for application in large flywheel energy storage frequency modulation power plants; reduces the flywheel energy storage braking loss, improves the working efficiency of the flywheel energy storage, has good energy-saving performance, and is convenient for popularization and use; the system structure is simple, reduces the plant service power loss, and can be popularized and used in various flywheel energy storage systems. The system of the present disclosure is applicable to the braking energy recovery of the flywheel energy storage frequency modulation system, and solves the problem of energy waste existing in the flywheel energy storage frequency modulation braking of the existing power plant.

[0080] Based on the flywheel energy storage braking energy recovery system proposed in the above embodiments, the present disclosure also proposes a flywheel energy storage braking energy recovery method.

[0081] Figure 4 It is a flowchart of a flywheel energy storage braking energy recovery method provided by an embodiment of the present disclosure. As Figure 4 shown, the flywheel energy storage braking energy recovery method includes the following steps:

[0082] Step S11: Receive a charge-discharge instruction and control the flywheel energy storage system unit to perform charge and discharge;

[0083] Step S12: During the charge and discharge process, obtain the flywheel speed of the flywheel energy storage system unit and determine whether the flywheel speed meets the requirements;

[0084] Step S13: If not, control the flywheel energy storage system unit to be in a braking state and control the energy recovery unit to work to store the energy released by the flywheel energy storage system unit.

[0085] Optionally, the flywheel energy storage braking energy recovery method further includes: when the flywheel energy storage system unit is in a braking state, if the flywheel speed meets the requirements, control the energy recovery unit to release energy to the flywheel energy storage system unit; after the energy of the energy recovery unit is completely released, use the bus voltage to charge the flywheel energy storage system unit through the main transformer incoming line unit and the prefabricated cabin unit so that the flywheel speed maintains the rated speed.

[0086] It should be noted that the foregoing explanation of the embodiments of the flywheel energy storage braking energy recovery system also applies to the flywheel energy storage braking energy recovery method of this embodiment, and will not be elaborated here.

[0087] The flywheel energy storage braking energy recovery method proposed by the embodiments of the present disclosure receives charge-discharge instructions and controls the flywheel energy storage system unit to charge and discharge; during the charge-discharge process, the flywheel speed of the flywheel energy storage system unit is obtained, and it is judged whether the flywheel speed meets the requirements; if not, the flywheel energy storage system unit is controlled to be in a braking state, and the energy recovery unit is controlled to work to store the energy released by the flywheel energy storage system unit. In this case, the electric energy generated during the braking process is transmitted to the energy recovery unit, and the flywheel braking energy is recovered, solving the problem of energy waste during the braking of the flywheel energy storage system in the prior art. In addition, when the electric energy generated during the braking process is stored in the supercapacitor by the method of the present disclosure, the braking torque formed when the flywheel unit generates electricity directly acts on the flywheel drive wheel through the transmission system, causing the flywheel to decelerate or stop. It not only has a braking effect, but also enables the recovery of the flywheel braking energy. The method of the present disclosure adds an energy recovery unit, reduces the waste of braking energy of the braking flywheel through the braking resistor; improves the efficiency of auxiliary power, such as the power consumption of the flywheel energy storage system, improves the energy utilization rate of the flywheel energy storage system, reduces the braking heat dissipation, and has good economic effects; adopts a large-capacity supercapacitor bank, which can provide a storage path for the recovery of the braking energy of multiple flywheels; the energy recovery units can be used as backups for each other to form an energy recovery energy storage unit group, improving the reliability of the flywheel braking energy recovery; has good environmental protection and energy-saving effects, improves the flywheel energy storage efficiency, can reduce the auxiliary power rate, has strong practicability, and is convenient to be applied in large flywheel energy storage frequency modulation power plants; reduces the flywheel energy storage braking loss, improves the working efficiency of the flywheel energy storage, has good energy-saving performance, and is convenient to be popularized and used; the system structure is simple, reduces the auxiliary power loss, and can be popularized and used in various flywheel energy storage systems. The method of the present disclosure is applicable to the braking energy recovery of the flywheel energy storage frequency modulation system, solving the problem of energy waste existing in the flywheel energy storage frequency modulation braking of the existing power plants.

[0088] It should be understood that the components, the connections and relationships of the components, and the functions of the components shown in the present disclosure are only examples and are not intended to limit the implementation of the present disclosure described and / or claimed in the present disclosure. Various forms of processes shown above can be used, with steps reordered, added or deleted. For example, the steps recorded in the present disclosure can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solutions disclosed in the present disclosure can be achieved, and the present disclosure does not limit this here.

[0089] The above specific embodiments do not constitute a limitation to the protection scope of the present disclosure. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present disclosure shall be included within the protection scope of the present disclosure.

Claims

1. A flywheel energy storage braking energy recovery system, characterized in that, It includes a main transformer incoming line unit, a prefabricated cabin unit, a flywheel energy storage system unit, and a recovered energy unit; The main transformer incoming line unit is used to realize the conversion of the bus voltage and the voltage of the prefabricated cabin unit; The prefabricated cabin unit is used to control the charging and discharging of the flywheel energy storage system unit based on the received charging and discharging instructions, and is also used to control the flywheel energy storage system unit to enter the braking state when the flywheel speed does not meet the requirements; The flywheel energy storage system unit includes a flywheel, and the flywheel is used for energy storage; The recovered energy unit includes a super capacitor, and the super capacitor is used to store the energy released by the flywheel energy storage system unit when the flywheel energy storage system unit is in the braking state; The main transformer incoming line unit includes an incoming line circuit breaker, an incoming line transformer, and an outgoing line circuit breaker connected in sequence. The incoming line circuit breaker is connected to the bus, and the outgoing line circuit breaker is connected to the grid-side converter of the prefabricated cabin unit; The prefabricated cabin unit includes a grid-side converter and a machine-side converter. The main transformer incoming line unit is connected to the flywheel energy storage system unit via the grid-side converter and the machine-side converter; The recovered energy unit further includes a capacitor energy storage converter. The super capacitor is connected to the flywheel energy storage system unit via the capacitor energy storage converter. The prefabricated cabin unit is also used to control the capacitor energy storage converter not to conduct when the flywheel speed meets the requirements, and to control the capacitor energy storage converter to conduct when the flywheel speed does not meet the requirements; The flywheel energy storage braking energy recovery system further includes a resistive braking unit, and the resistive braking unit is connected to the flywheel energy storage system unit; Among them, receive the charging and discharging instructions and control the flywheel energy storage system unit to charge and discharge; During the charging and discharging process, obtain the flywheel speed of the flywheel energy storage system unit and judge whether the flywheel speed meets the requirements; If not, control the flywheel energy storage system unit to be in the braking state, and control the recovered energy unit to work to store the energy released by the flywheel energy storage system unit.

2. The flywheel energy storage braking energy recovery system according to claim 1, wherein The prefabricated cabin unit further includes a grid-side control cabinet and a machine-side control cabinet. The grid-side control cabinet is used to control the working mode of the grid-side converter based on the first control instruction, and the machine-side control cabinet is used to control the working mode of the machine-side converter based on the second control instruction.

3. The flywheel energy storage braking energy recovery system according to claim 2, wherein The prefabricated cabin unit further includes a main control cabinet. The main control cabinet is respectively connected to the grid-side control cabinet and the machine-side control cabinet. The main control cabinet is used to generate the first control instruction and the second control instruction based on the received charging and discharging instructions. The main control cabinet is also used to generate a third control instruction based on the received flywheel speed and send the third control instruction to the capacitor energy storage converter.

4. The flywheel energy storage braking energy recovery system according to claim 1, wherein The resistive braking unit includes a braking resistor and a braking resistor switch. The braking resistor is connected to the flywheel energy storage system unit via the braking resistor switch.

5. The flywheel energy storage braking energy recovery system according to claim 1, characterized in that, It further includes: When the flywheel energy storage system unit is in the braking state, if the flywheel speed meets the requirements, control the recovered energy unit to release energy to the flywheel energy storage system unit; After the energy of the energy recovery unit is completely released, the bus voltage is used to charge the flywheel energy storage system unit through the main transformer incoming line unit and the prefabricated cabin unit, so as to keep the flywheel speed at the rated speed.

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