Drive system and control method

Abstract

The present invention provides a drive system and control method that can increase the amount of work obtained from a steam turbine relative to the amount of heat injected into a steam engine. [Solution] The drive system comprises a superheated steam generator, a compressor, and a steam turbine, and is configured to utilize the rotational force of the steam turbine to drive the load. The superheated steam generator generates superheated steam. The compressor pressurizes the superheated steam using a first power supply. The steam turbine rotates by receiving the supply of the pressurized superheated steam or a driving force around its shaft based on a second power supply, and is capable of supplying rotational force to the load.

Description

[Technical Field]

[0001] Embodiments of the present invention relate to a drive system and a control method. [Background technology]

[0002] A drive system uses the rotational force of a shaft to drive and rotate a load. Some drive systems utilize the rotational force generated by a steam turbine in a steam engine. To increase the amount of work produced by a steam turbine, it was necessary to increase the amount of heat injected into the steam engine. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 58-5411 [Overview of the project] [Problems that the invention aims to solve]

[0004] The object of the present invention is to provide a drive system and control method that can increase the amount of work obtained from a steam turbine relative to the amount of heat injected into a steam engine. [Means for solving the problem]

[0005] The drive system of this embodiment comprises a superheated steam generator, a compressor, and a steam turbine, and is configured to utilize the rotational force of the steam turbine to drive the load. The superheated steam generator generates superheated steam. The compressor pressurizes the superheated steam using a first power supply. The steam turbine rotates by receiving the supply of the pressurized superheated steam or a driving force around its shaft based on a second power supply, and is capable of supplying rotational force to the load. [Brief explanation of the drawing]

[0006] [Figure 1] A diagram illustrating the configuration of a drive system according to an embodiment. [Figure 2] Configuration diagram of a compressor according to an embodiment. [Figure 3] Configuration diagram of a steam engine according to an embodiment. [Figure 4] Diagram for explaining the operating principle of the drive system of an embodiment. [Figure 5] Timing chart for explaining the functions of the drive system of an embodiment.

Mode for Carrying Out the Invention

[0007] Hereinafter, the drive system and control method of the embodiment will be described with reference to the drawings. In the following description, components having the same or similar functions are denoted by the same reference numerals, and redundant descriptions of those components may be omitted. Note that being electrically connected may simply be referred to as "connected".

[0008] FIG. 1 is a configuration diagram of a drive system 1 according to an embodiment. FIG. 2 is a configuration diagram of a compressor 22 in the drive system 1 according to an embodiment. Note that the same reference numerals are given to the same parts, redundant descriptions are appropriately omitted, and mainly different parts will be described.

[0009] The drive system 1 includes a steam engine 2. The steam engine 2 includes a superheated steam generation unit 21, a compressor 22, a steam turbine 23, etc., as shown in FIG. 1. The drive system 1 may further include an electric motor 3, a power converter 4, a power supply unit 5, a storage battery 6, and a control unit 10.

[0010] First, a more specific example of the steam engine 2 of the embodiment will be shown, and its configuration will be described in order. FIG. 3 is a configuration diagram of a steam engine according to an embodiment. FIG. 3(a) shows a configuration example of the steam engine 2 according to the drive system 1 of the embodiment, and FIG. 3(b) shows a configuration example of a general steam engine which is a comparative example of the embodiment.

[0011] The steam engine 2 of the drive system 1 includes a superheated steam generation unit 21, a compressor 22, a steam turbine 23, a condenser 24, a pump 25, and a valve 26. The steam engine of the comparative example does not have a compressor 22. The superheated steam generation unit 21, valve 26, compressor 22, steam turbine 23, condenser 24, and pump 25 of the embodiment are provided in the pipeline 29 for circulating the fluid in the described order. The valve 26 is an example of a main steam stop valve that blocks the circulation of the fluid and stops the supply of steam from the superheated steam generation unit 21 to the subsequent components after the compressor 22. The fluid of the embodiment is, for example, a single-phase flow or a two-phase flow of steam and water. The phase of the fluid is determined by the section through which it flows.

[0012] As shown in FIGS. 1 and 3, as an example, a configuration applying a simple Rankine cycle as the steam engine 2 is illustrated, but it is not limited to this, and other types of heat cycles may be applied to the steam engine 2. As described above, the steam engine 2 of the drive system 1 in the embodiment includes a compressor 22. The same applies when applying other types of heat cycles.

[0013] The superheated steam generation unit 21 receives the supply of electric power or recycled heat (waste heat) from the outside and vaporizes the water inside it by heat, mechanical, or electromagnetic methods. For example, the superheated steam generation unit 21 includes a feed water tank 211, a boiler 212 that generates high-pressure heated steam, and a superheater 213 that generates superheated steam. The feed water tank 211 stores the water supplied from the pump 25 inside and makes it available for steam generation by the boiler 212. The boiler 212 uses heat from combustion, waste heat supplied from the outside, etc. to vaporize the water inside the boiler 212 and separate the gas and liquid. The superheater 213 generates superheated steam from the steam vaporized in the boiler 212. This superheater 213 may be provided attached to the boiler 212 and utilize the waste heat of the boiler 212 for superheating, or may be provided separately from the boiler 212.

[0014] As shown in Figure 2, the compressor 22 includes, for example, a motor 221, a rotor 222 that pumps superheated steam by the operation of the motor 221, and a gear unit 223 that converts the rotational speed of the motor 221 at a predetermined ratio. The compressor 22 may also be of the axial flow type. The compressor 22 uses electricity (first power) to drive the motor 221 and further pressurizes the superheated steam. The superheated steam generated by the superheated steam generation unit 21 is further pressurized by this compressor 22. The compressor 22 supplies the generated superheated steam to the downstream steam turbine 23. It is preferable to use electricity pre-stored in the storage battery 6 for the electricity (first power) to drive the compressor 22.

[0015] When the steam turbine 23 receives a supply of high-pressure steam, it gradually expands the steam inside. The rotor of the steam turbine 23 rotates in accordance with the flow of the steam, and this rotational force is supplied to the load. The rotor and shaft of the steam turbine 23 rotate in response to a supply of at least compressed pressurized steam. For example, the rotor of the steam turbine 23 may be configured to rotate by receiving a driving force around its shaft based on the supply of superheated steam pressurized by the compressor 22 or a second power supply. The rotational force from the supply of superheated steam is supplied to the load.

[0016] As shown in Figure 1, the shaft of the compressor 22 and the shaft of the rotor of the steam turbine 23 are independent. The compressor 22 is preferably used to compress the steam supplied from the boiler 212 of the superheated steam generation unit 21 via the superheater 213 using power from the first power converter 41 (first power).

[0017] The condenser 24 is located on the output side of the steam turbine 23 and cools the steam discharged by the steam turbine 23 back into water, which is then retained inside the container of the condenser 24. This water is then circulated by the pump 25.

[0018] Next, we will show an example of an electrical system configuration and explain its configuration step by step. The shaft of the electric motor 3 is directly or indirectly connected to the shaft of the rotor of the steam turbine 23 and the main shaft that supplies power to the load. The electric motor 3 receives power (second power) from the second power converter 42, which will be described later, and supplies power to the shaft of the rotor of the steam turbine 23 and the load, causing them to rotate. In this case, the electric motor 3 functions as a so-called AC electric motor. Furthermore, the electric motor 3 is driven by the rotational force of the rotor of the steam turbine 23, etc. In this case, the electric motor 3 can function as a generator.

[0019] The power converter 4 comprises a first power converter 41, a second power converter 42, and a third power converter 43. Each of the first power converter 41, the second power converter 42, and the third power converter 43 is an inverter that converts DC power to AC power.

[0020] The first power converter 41 supplies power (first power) to the motor 221 of the compressor 22 to power the compressor 22. The second power converter 42 converts the power regenerated from the motor 221 of the compressor 22 to charge, for example, the storage battery 6. The second power converter 42 supplies power (second power) to the electric motor 3 to drive the electric motor 3. The second power converter 42 converts the power regenerated from the electric motor 3 to charge, for example, the storage battery 6. The third power converter 43 supplies power (third power) to the superheater 213 of the superheated steam generation unit 21 to generate superheated steam.

[0021] The power supply unit 5 receives AC power from the grid or other sources and converts it into DC power. For example, the power supply unit 5 is a converter that converts AC power to DC power. A battery 6 and a DC bus are connected to the power supply unit 5. The power supply unit 5 charges the battery 6 using a portion of the DC power generated by the conversion. The power supply unit 5 supplies the DC bus with the remaining portion of the DC power converted from AC power, or power from the battery 6. Note that this power supply unit 5 does not need to have a regenerative function for the grid. Other power supply equipment such as a transformer may be connected to the AC side of the power supply unit 5.

[0022] The storage battery 6 includes a secondary battery that holds power to supplement a portion of the power used by the drive system 1. The storage battery 6 is connected to the power supply unit 5, and charging and discharging are performed via the power supply unit 5.

[0023] The control unit 10 may include, for example, a processor such as a CPU, and the processor may implement some or all of the functional parts of the drive system 1 by executing a predetermined program, or it may implement the above by a combination of electrical circuits. The control unit 10 may use the storage area of ​​an internally provided storage unit to perform data transfer processing and calculation processing for analysis by having the processor execute a predetermined program. For example, the control unit 10 controls the first power converter 41 to control the rotational speed or torque of the motor 221 of the compressor 22. The control unit 10 controls the second power converter 42 to control the rotational speed or torque of the electric motor 3. The control unit 10 controls either the first power converter 41 or the second power converter 42 to switch between enabling and disabling the regenerative function. In such a control unit 10, it is preferable to adjust the first power supplied to the motor 221 of the compressor 22 by controlling the first power converter 41. The control unit 10 acquires the detected or estimated rotational speed of the motor 221 of the compressor 22, the detected or estimated rotational speed of the electric motor 3, the voltage of the DC bus, etc., and uses them for the control described above.

[0024] The operating principle of the drive system 1 configured as described above will be explained with reference to Figures 3 and 4. Figure 4 is a diagram illustrating the operating principle of the drive system 1 of the embodiment.

[0025] Figure 4(a) shows the steam state in each part of the steam engine 2 of the drive system 1 of the embodiment. Figure 4(b) shows the steam state in each part of the steam engine of the comparative example drive system 1Z. The graphs shown in Figure 4 are hs diagrams showing the relationship between entropy s and enthalpy h. A saturated steam line is drawn in each graph.

[0026] First, we will describe a comparative example to which the general Rankine cycle shown in Figure 4(b) is applied. In this comparative example, the Rankine cycle transitions the fluid state at points X1, X2, X3, and X4. Points X1, X2, X3, and X4 are examples of change points and correspond to the points in Figure 3(b).

[0027] For example, X1 to X2 in Figure 4(b) corresponds to the process of circulating water by the pump 25. This process is considered adiabatic compression. X2 to X3 corresponds to the process of heating water by the superheated steam generator 21 to produce superpressurized steam. This process is considered an isobaric change. X3 to X4 corresponds to the process of expanding the superheated steam passing through the steam turbine 23 by reducing the output side of the steam turbine 23 by cooling and condensing the exhaust from the steam turbine 23 by the condenser 24. If this process is in an ideal state, it can be considered adiabatic expansion. X4 to X1 corresponds to the process of changing the water stored in the condenser 24. This process is considered an isobaric change.

[0028] The difference between X3 and X4 above, multiplied by the efficiency, gives the work done by the steam turbine 23 (Wt Z This corresponds to the fact that the higher the enthalpy of X3 and the lower the enthalpy of X4, the greater the work that can be output from the steam turbine 23. To increase the enthalpy of X3, it was necessary to increase the vapor pressure in the process from X2 to X3. If this was achieved, the amount of heat injected would increase, and the amount of heat recovered in the condenser 24 would increase. However, the heat recovered in the condenser 24 would have a lower absolute temperature, making it difficult to utilize and sometimes resulting in ineffective use.

[0029] Therefore, in this embodiment, as shown in Figure 4(a), the position of X3 shown in Figure 4(b) above is shifted to change it to X3b. As a result, the enthalpy of X3b becomes a larger value than the enthalpy of X3. Furthermore, a control target point X3a is added to the isobar line connecting X2 to X3 shown in Figure 4(b) above. The location of X3a is included in the superheated steam region. In this case, the enthalpy of X3a becomes smaller than the enthalpy of X3, which reduces the amount of heat injected into the steam engine 2. In Figure 4(a), the position of X4b is the same as that of X4 mentioned earlier, for the sake of simplicity in the explanation. The position between X1 and X4b, when adiabatic change occurs from X3a, is called X4a.

[0030] The superpressurized steam, which is pressurized by the heat of the superheated steam generation unit 21 between X2 and X3a, is further overpressurized using the compressor 22 of the drive system 1. If we assume this compression is adiabatic, then X3b would be located above X3a. In reality, due to compression losses, X3b will be located on an upward-sloping line. Even with these compression losses, the enthalpy of X3b can be made higher than that of X3 and X3a. Since the difference between X3b and X4b corresponds to the work done by the steam turbine 23, if the conversion rate is the same as in the comparative example, it becomes possible to generate more work than in the comparative example.

[0031] The thermal efficiency η of this embodiment will be described. Using the signs of the points shown in Figures 3 and 4, the formula for calculating the thermal efficiency η is given by equation (1) below. The thermal efficiency η is the ratio of the total work obtained to the total amount of heat input into the system during one cycle.

[0032] η = (Σ work) / (Σ heat) =-(Wt+Wp+Wc) / (Qin+Qout) ···(1)

[0033] The variables in equation (1) above are as follows: Heat quantity of boiler 212 and superheater 213: Qin=h 3a -h2 Turbine work: Wt = h 4b -h 3b Heat quantity of the condenser 24: Qout = h1 - h 4b Work of the pump 25: Wp = h2 - h1 Work of the compressor 22: Wc = h 3b - h 3a

[0034] The variable h in the above formula 1、 h 2、 h 3a、 h 3b、 h 4a、 h 4b is the enthalpy at each point of X1, X2, X3a, X3b, X4a, X4b. The calculation result of (Wt + Wp + Wc) in the above formula becomes the work W. Substituting each variable, the following formula (2) is obtained.

[0035] W = (Wt + Wp + Wc) = (h 4b - h 3b ) + (h2 - h1) + (h 3b - h 3a ) = (h 4b - h 3a ) + (h2 - h1) ···(2)

[0036] In contrast, the comparative example has a configuration without the work of the compressor 22, and its work W Z becomes the following formula (3).

[0037] W Z = (Wt Z + Wp) = (h4 - h3) + (h2 - h1) ···(3)

[0038] As described above, when comparing the work W of the embodiment and the work W of the comparative example approximated to the ideal state, it can be seen that there is no significant difference. Z

[0039] The thermal efficiency η in the case of the embodiment can be approximated as shown in the following formula (4).

[0040] η = -(Wt + Wp + Wc) / (Qin) = (h 3a - h4b ) / (h 3a -h2) ···(4) Furthermore, the work Wp of pump 25 is considered to be negligible and can be ignored.

[0041] According to this analysis, in the comparative example, between X2 and X3, the heat from the boiler 212 and superheater 213 was used exclusively to increase the fluid's entropy s and enthalpy h. Of this heat, the amount that could be effectively utilized was limited, and a large amount of heat was wasted and discharged. In contrast, in this embodiment, in addition to the heat from the boiler 212 and superheater 213, the work done by the compressor 22 is utilized to increase the entropy s and enthalpy h of the fluid before it is supplied to the steam turbine 23. Although there is not much difference in thermal efficiency compared to the comparative example, as shown in X3b, the enthalpy h value on the inlet side of the steam turbine 23 is significantly different in the embodiment. In this way, the enthalpy h of the superheated steam supplied to the steam turbine 23 can be increased, and the amount of work that can be extracted from the steam turbine 23 using this superheated steam can be increased.

[0042] Referring to Figure 5, the functions of the drive system 1 configured as described above will be explained in order. Figure 5 is a timing chart illustrating the function of the drive system 1 of the embodiment. From the top of Figure 5, (a) the operating mode of the electric motor 3, (b) the operating mode of the compressor 22, (c) the output torque related to the shaft of the steam turbine 23, and (d) the output rotational speed related to the shaft of the steam turbine 23 are shown. As shown in Figure 5, the operating modes of the electric motor 3 and the compressor 22 include a power mode and a regenerative mode. When the output torque value related to the shaft of the steam turbine 23 is positive, it indicates a state in which torque is applied from the shaft to the load, and when it is negative, it indicates a state in which the kinetic energy of the load and the steam turbine 23 can be recovered (regeneration). The output rotational speed of the steam turbine 23 shaft changes according to the control state of the drive system 1 and the load state.

[0043] The control of drive system 1 will be explained by dividing it into several states as shown below, and describing the control in each state.

[0044] • Drive system 1 is stopped (initial stage) • When starting drive system 1 • During operation after startup of drive system 1 • The end stage after the operation of drive system 1 has finished.

[0045] (1) Initial stage when drive system 1 is stopped: The control unit 10 stops the power conversion of each inverter, thereby stopping both the compressor 22 and the motor 3. The control unit 10 also stops the power supply to the superheater 213 of the superheated steam generation unit 21. The boiler 212 is supplied with waste heat from an external device, and the water temperature is preferably maintained at approximately 100°C.

[0046] (2) When drive system 1 is started (within period T1): The period corresponding to the startup of drive system 1 is called period T1. Its starting point is time t0. When period T1 begins, the control unit 10 controls the first power converter 41 to use the power from the storage battery 6 to drive the motor 221 of the compressor 22. The control unit 10 starts heating the steam using the superheater 213. For example, it heats it to about 100°C to 150°C. Furthermore, the control unit 10 opens the valve 26 and controls the second power converter 42 to drive the electric motor 3 using the power from the storage battery 6.

[0047] Furthermore, at the start of heating when drive system 1 is activated, the steam temperature of the superheated steam is low, and sufficient steam pressure cannot be obtained. In such cases, the control unit 10 should operate the compressor 22 after a predetermined time has elapsed from time t0 and sufficient steam has been generated. The control unit 10 may determine the start time of the compressor 22 according to the water temperature in the boiler 212 or the steam temperature on the input side of the compressor 22 when the drive system 1 is started. For example, if the compressor 22 is controlled according to the water temperature in the boiler 212, the control unit 10 should start the rotation of the compressor 22's motor 221 only after the water temperature reaches a predetermined temperature (compression start temperature) of at least 100°C. Furthermore, when controlling the compressor 22 according to the steam temperature, the control unit 10 should start the rotation of the compressor 22's motor 221 only after the steam temperature on the input side of the compressor 22 reaches a predetermined temperature (compression start temperature) of 100°C or higher. It is also preferable to stop the compressor 22's motor 221 and close the valve 26 before the steam temperature on the input side of the compressor 22 falls below 100°C. This helps to suppress an excessive drop in the water temperature in the boiler 212 or the steam temperature on the input side of the compressor 22.

[0048] Until the start-up phase of the drive system 1 is complete, the steam turbine 23 is rotated by the torque of the electric motor 3. However, the heat output of the boiler 212 and superheater 213 and the rotational speed of the compressor 22 should be adjusted so as not to disrupt the state in which the steam turbine 23 is rotating with the torque of the electric motor 3. Specifically, to prevent an excessive supply of superheated steam, the rotation of the steam turbine 23 should be controlled so as not to exceed the rotational speed at which it rotates with the torque of the electric motor 3. The control unit 10 should use a map that defines the control conditions to control the system so that the ratio of the rotational speed of the electric motor 3 to the rotational speed of the compressor 22 (rotational speed of the motor 221) is within a predetermined range.

[0049] This allows the compressor rotation speed, the amount of superheated steam supplied, the rotation speed of the steam turbine 23, or the rotation speed of the electric motor to be gradually increased. For example, when the rotational speed of the turbine or the rotational speed of the electric motor reaches a predetermined rotational speed, the control unit 10 may determine that "startup is complete". Upon completion of this startup, the control unit 10 stops the operation of the electric motor 3 and switches to a state where it rotates in accordance with the rotation of the steam turbine 23.

[0050] (3) During normal operation of drive system 1 (period T3): The period corresponding to the normal operation of drive system 1 is called period T3. Its starting point is time t1. When period T3 begins, the control unit 10 uses the superheated steam generator 21 and the compressor 22 to supply superheated steam and operate the steam turbine 23 to obtain rotational force for the shaft. In this case, the control unit 10 may control the first power converter 41 to control the compressor 22 to the powered state. The first power converter 41 operates the motor 221 of the compressor 22. In response to this, the electric motor 3 is essentially put into a free-running state by opening each semiconductor switch of the second power converter 42.

[0051] In addition, under normal operating conditions, there may be excess power (rotational force) in the steam turbine 23. In such cases, the control unit 10 may use the electric motor 3, which is driven by the operation of the steam turbine 23, to regenerate surplus power according to the amount of excess power and charge the storage battery 6. The second power converter 42 regenerates surplus power generated while driving the electric motor 3 through control and charges the storage battery 6.

[0052] After the drive system 1 has finished starting up due to the above control, it switches to the normal operating state. For example, in this normal operating state, the control rotates the steam turbine 23 at a predetermined speed. More specifically, without basically using the torque of the electric motor 3, the desired rotational speed of the steam turbine 23 and the rotational force of the shaft are obtained by adjusting the heat generated by the boiler 212 and superheater 213 and the rotational speed of the compressor 22 to predetermined values. In this way, the rotational force of the shaft of the steam turbine 23 is mainly used, but if the rotational speed of the steam turbine 23 is insufficient, the torque of the compressor 22 can be supplemented with a correction amount corresponding to the amount of the rotational speed deficiency.

[0053] (4) Termination phase (period T4) for ending the operation of drive system 1: The period required to terminate the normal operation of drive system 1 is called period T4. Its starting point is time t4. When period T4 begins, drive system 1 is transitioned from the operating state to the stopped state.

[0054] For example, the control unit 10 uses the second power converter 42 to regenerate surplus power generated in the motor 3 and charge the storage battery 6. The control unit 10 also uses the first power converter 41 to regenerate surplus power generated in the motor 221 of the compressor 22 and charge the storage battery 6. For example, when the motor 221 of the compressor 22 and the electric motor 3 have stopped, the control unit 10 ends the period T4 and shuts down the drive system 1.

[0055] (5) The idle phase of drive system 1 (period T5): As described above, when period T5 begins, drive system 1 enters a dormant state. This state corresponds to the initial stage when drive system 1 is stopped.

[0056] The control unit 10 may repeat the above series of controls as appropriate based on commands from a higher-level device or the like. In the example above, the output torque from drive system 1 is configured to remain constant during period T3. During this period, if the load's required torque fluctuates, the output rotational speed may fluctuate. However, if the effect is minor, control that maintains a constant output torque can be used.

[0057] According to the above embodiment, the drive system 1 comprises a superheated steam generator 21, a compressor 22, and a steam turbine 23, and is configured to utilize the rotational force of the steam turbine 23 to drive the load. The superheated steam generator 21 generates superheated steam. The compressor 22 pressurizes the superheated steam using a first power. The steam turbine 23 rotates by receiving the superheated steam pressurized by the compressor 22 or a driving force around its shaft based on a second power, and supplies rotational force to the load. In this drive system 1, for example, at startup the steam turbine 23 is rotated using a driving force around its shaft based on a second power, and after startup it rotates by receiving the superheated steam pressurized by the compressor 22, and supplies rotational force to the load. This makes it possible to increase the amount of work obtained from the steam turbine for a given amount of heat injected into the steam engine.

[0058] (Variations concerning special cases in control) The following are examples of special cases that may arise at each of the above stages.

[0059] (Special case 1) If an overload condition occurs during "(3) Normal operation (period T3)" as described above: As described above, the steam turbine 23 is basically driven using the steam pressure obtained from the operation of the compressor 22, and the load is driven by that power. If the output torque is insufficient to meet the load's required torque and the steam turbine 23 becomes overloaded, the control unit 10 may increase the torque by increasing the supply of superheated steam from the compressor 22 to alleviate the overload condition. The control unit 10 may detect the overload condition of the steam turbine 23 due to fluctuations in the load's required torque in this case based on the rotational speed of the electric motor 3, the load current, etc.

[0060] (Special case #2) If an overload condition occurs during "(3) Normal operation (period T3)" as described above: This is the same situation as described above (Part 1), but the method of dealing with it is different. If the output torque is insufficient to meet the load's torque requirements and the steam turbine 23 becomes overloaded, the control unit 10 may increase the amount of superheated steam supplied by the compressor 22 to increase the torque, keep the motor 3 operating at a light load throughout period T3, and adjust the torque at the light load in accordance with fluctuations in the load's torque requirements. The control unit 10 may detect these fluctuations in the load's torque requirements based on the rotational speed of the motor 3, the load current, etc. The average torque of the electric motor 3 is determined so that it becomes the load of the steam turbine 23. For example, by setting the average torque to an appropriate value that does not overload the steam turbine 23 and operating the electric motor 3, fluctuations in the load's required torque can be absorbed. The heat generated in the electric motor 3 as a result may be reused to raise the water temperature of the water recirculated to the boiler 212 or to generate steam.

[0061] (Special case #3) When the superheated steam temperature is insufficient in the above "(3) During normal operation (period T3)": When starting the drive system 1 from a dormant state, if the pressure or temperature of the superheated steam is insufficient, the overpressurized steam, which has been pressurized by the heat of the superheated steam generation unit 21 between X2 and X3a, may be further overpressurized using the compressor 22 of the drive system 1.

[0062] (Special case #4) When the temperature or pressure of the superheated steam is high: As described above, the control unit 10 operates the steam turbine 23 using the compressor 22. However, when the superheated steam temperature is high, or when the superheated steam pressure is high, the control unit 10 may reduce the efficiency of the superheated steam supply by the compressor 22 or limit the operation of the compressor 22. For example, to reduce the efficiency of the compressor 22, the control unit 10 may reduce the required torque of the motor 221 of the compressor 22, or reduce the required rotational speed. To limit the operation of the compressor 22, the control unit 10 may close the valve 26 to cut off the supply of steam to the compressor 22. In the former case, a compressor 22 that is stopped or rotating at a relatively low speed will be present in the flow path. With such a compressor 22, the flow resistance of the superheated steam will be greater than when there is no compressor 22, and the pressure inside the steam turbine 23 will decrease.

[0063] (Special case #5) When increasing the charge level of battery 6 before entering a sleep state: In this case, the control unit 10 enables speed control (deceleration control) by the compressor 22 and the electric motor 3, and continues to supply superheated steam by the compressor 22. This state is maintained to gradually reduce the exhaust pressure from the boiler 212. During this process, the use of steam from the boiler 212 continues until the rotational speed of the compressor 22 (rotational speed of the motor 221) drops to a predetermined value. Once the rotational speed of the compressor 22 (rotational speed of the motor 221) drops to a predetermined value, the control unit 10 closes the valve 26 to stop the supply of superheated steam to the compressor 22. The control unit 10 may also replace the above-mentioned speed control (deceleration control) with the regenerative function of the power converter 4 (inverter).

[0064] According to at least one of the above embodiments, the drive system comprises a superheated steam generator, a compressor, and a steam turbine, and is configured to utilize the rotational force of the steam turbine to drive a load. The superheated steam generator generates superheated steam. The compressor pressurizes the superheated steam using a first power. The steam turbine rotates by receiving the supply of the pressurized superheated steam or a driving force around its shaft based on a second power, and can supply rotational force to the load. This makes it possible to increase the amount of work obtained from the steam turbine for a given amount of heat injected into the steam engine.

[0065] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. Furthermore, the embodiments described above can be implemented in combination with each other.

[0066] For example, the drive system 1 described above is just one example of an embodiment and can be applied to more specific systems. For instance, it can be applied to all kinds of drive systems, including general industrial drive systems, plant drive equipment, and vehicle drive systems.

[0067] The superheated steam generation unit 21 generates superheated steam from the steam produced by the boiler 212, utilizing the heat from the superheater 213. Alternatively, superheated steam may be generated using steam produced by other methods.

[0068] (Note) It can be applied to any of the following drive systems. [1] The drive system of the embodiment is a drive system that can utilize the rotational force of a steam turbine to drive a load, A superheated steam generating unit that generates superheated steam, A compressor that pressurizes the superheated steam using a first power supply, A steam turbine that rotates by receiving a driving force around its shaft based on the supply of pressurized superheated steam or a second power supply, and is capable of supplying rotational force to a load, It is a drive system equipped with [a specific feature]. [2] The drive system described in [1] above is A first power converter that supplies the first power to a motor 221 that drives the rotor of the compressor, A control unit that adjusts the first power supplied to the motor 221 of the compressor by controlling the first power converter 41, and It would be good to have that. [3] The first power converter 41 in the drive system described in [2] above is: It is preferable to convert the first regenerated power recovered from the motor of the compressor and charge the storage battery 6. [4] The drive systems described in [2] or [3] above are: An electric motor 3 that is driven by the rotational force of the rotor of the steam turbine, A second power converter 42 that supplies power to the aforementioned electric motor 3, Equipped with, The control unit, The operating state of the electric motor 3 can be adjusted by controlling the second power converter. [5] In any of the drive systems described in [4] above, The second power converter is It is preferable to convert the second regenerative power recovered from the aforementioned electric motor 3 and use it to charge the storage battery 6. [6] In the drive system described in [2] or [3] above, The shaft of the compressor and the shaft of the rotor of the steam turbine are independent of each other. The compressor may compress the steam supplied from the superheated steam generator using the power from the first power converter 41. [Explanation of Symbols]

[0069] 1 Drive System 2 Steam engine 3 Electric motor 4 Power Converters 5 Power supply section 6. Storage Battery 10 Control Unit 21 Superheated steam generation unit 22 Compressor 23 Steam Turbine 24 Condenser 25 pumps 26 valves 41. First power converter 42. Second power converter 221 Motor 222 Rotary Wing 223 Gear section

Claims

1. A drive system that can utilize the rotational force of a steam turbine to drive a load, A superheated steam generating unit that generates superheated steam, A compressor that pressurizes the superheated steam using a first power supply, A steam turbine that rotates by receiving a driving force around its shaft based on the supply of pressurized superheated steam or a second power supply, and is capable of supplying rotational force to a load, A drive system equipped with the following features.

2. A first power converter that supplies the first power to a motor that drives the rotor of the compressor, A control unit that adjusts the first power supplied to the motor of the compressor by controlling the first power conversion device, and The drive system according to claim 1, comprising:

3. The first power converter is The first regenerated power recovered from the motor of the compressor is converted to charge the storage battery 6. The drive system according to claim 2.

4. An electric motor driven by the rotational force of the rotor of the steam turbine, A second power converter that supplies power to the aforementioned electric motor 3, Equipped with, The control unit, The operating state of the electric motor is adjusted by controlling the second power converter. The drive system according to claim 2.

5. The second power converter is The second regenerative power recovered from the aforementioned electric motor 3 is converted to charge the storage battery. The drive system according to claim 4.

6. The shaft of the compressor and the shaft of the rotor of the steam turbine are separate from each other. The compressor compresses the steam supplied from the superheated steam generating unit using the first power from the first power conversion device. The drive system according to claim 2.

7. A control method for a drive system that can utilize the rotational force of a steam turbine to drive a load, By generating superheated steam, The superheated steam is pressurized using the first power supply. The supply of the aforementioned pressurized superheated steam or the rotational force of a steam turbine that rotates by receiving a driving force around its shaft based on a second power supply, is supplied to the load. A control method including

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