Compressor unit

Abstract

This compressor unit comprises: a compressor body; a variable-speed drive; a variable value acquisition means that acquires a variable value varying in relation to a gas generation amount in a water electrolysis device; a storage unit that stores information indicating an addition amount for a control amount of the variable-speed drive that is to be changed in accordance with the variable value; a determination unit that refers to a relationship indicated by the information and determines the addition amount for the control amount of the variable-speed drive, on the basis of the variable value acquired from the variable value acquisition means; and a variable-speed drive control unit that controls the variable-speed drive on the basis of a corrected control amount obtained by adding a predetermined reference amount to the determined addition amount. The relationship includes a discontinuous relationship in which the addition amount changes discontinuously with respect to the variable value so that the motor rotation speed increases discontinuously when the variable value varies with an increase in the gas generation amount.

Description

Compressor unit

[0001] The present invention relates to a compressor unit.

[0002] In recent years, in consideration of the environment, the use of hydrogen as a fuel for power generation, automobiles and the like has been considered, and the demand for hydrogen is increasing. A compressor unit that compresses hydrogen gas is disclosed, for example, in Patent Document 1 below. Patent Document 1 discloses that a stable discharge pressure of compressed hydrogen gas generated from water electrolysis is achieved at the outlet of a multi-stage compression system.

[0003] Incidentally, when a water electrolysis apparatus generates hydrogen gas using renewable energy, the generation amount of hydrogen gas tends to fluctuate. If the generation amount of hydrogen gas increases abruptly, there is a risk that the compressor that compresses hydrogen gas from the water electrolysis apparatus cannot follow the fluctuation of the hydrogen gas flow rate. A similar problem can also occur in a compressor that sucks boil-off gas of liquefied gas.

[0004] United States Patent Application Publication No. 2022 / 0397118

[0005] An object of the present invention is to provide a compressor unit capable of following a sudden increase in gas generation amount.

[0006] A compressor unit according to one aspect of the present invention is a compressor unit that compresses gas generated from a gas source and supplies it to a customer facility, and comprises a motor, a compressor body driven by the motor, a variable speed drive configured to control the rotational speed of the motor, a fluctuation value acquisition means configured to acquire or store a fluctuation value that fluctuates in relation to the amount of gas generated at the gas source, a storage unit configured to store in advance information representing the relationship between the fluctuation value and an add amount for the control amount of the variable speed drive that should be changed according to the fluctuation value, a determination unit configured to determine an add amount for the control amount of the variable speed drive based on the fluctuation value acquired from the fluctuation value acquisition means by referring to the relationship represented by the information stored in the storage unit, and a variable speed drive control unit configured to control the variable speed drive based on a corrected control amount obtained by adding a predetermined reference amount to the add amount determined by the determination unit. The relationship includes a discontinuous relationship in which the add amount changes discontinuously in response to fluctuations in the fluctuation value, such that the rotational speed of the motor increases discontinuously when the fluctuation value fluctuates with an increase in the amount of gas generated.

[0007] A compressor unit according to another aspect of the present invention is a compressor unit that compresses hydrogen gas generated from a water electrolysis device that uses renewable energy-derived electricity as input power and supplies it to a customer facility, comprising: a motor; a compressor body driven by the motor; a variable speed drive configured to control the rotational speed of the motor; a fluctuation value acquisition means configured to acquire fluctuation values ​​of the amount of electricity input to the water electrolysis device or the amount of hydrogen gas generated; a storage unit configured to store in advance information representing the relationship between the fluctuation value and a control amount of the variable speed drive to be changed according to the fluctuation value; a determination unit configured to refer to the relationship represented by the information stored in the storage unit and determine the control amount of the variable speed drive based on the fluctuation value acquired from the fluctuation value acquisition means; and a variable speed drive control unit configured to control the variable speed drive based on the control amount determined by the determination unit. The relationship includes a discontinuous relationship in which the control amount changes discontinuously in response to fluctuations in the fluctuation value, such that the rotational speed of the motor increases discontinuously when the fluctuation value changes due to an increase in the amount of electricity input or the amount of hydrogen gas generated.

[0008] Figure 1 is a schematic diagram showing the configuration of the compressor unit according to the first embodiment. Figure 2 is a diagram for explaining the relationships contained in the information stored in the memory unit. Figure 3 is a diagram for explaining the control operation of the bypass valve control unit. Figure 4 is a diagram for explaining the control operation when acquiring fluctuation values ​​in the bypass valve control unit. Figure 5 is a diagram for explaining the control operation when controlling the output frequency of the variable speed drive. Figure 6 is a diagram for explaining the control operation when determining the addition amount in the determination unit. Figure 7 is a schematic diagram showing the configuration of the compressor unit according to the second embodiment. Figure 8 is a diagram for explaining the relationships contained in the information stored in the memory unit. Figure 9 is a diagram for explaining the control operation when controlling the output frequency of the variable speed drive. Figure 10 is a diagram for explaining the control operation when determining the addition amount in the determination unit. Figure 11 is a schematic diagram showing the configuration of the compressor unit according to the third embodiment. Figure 12 is a diagram for explaining the relationships contained in the information stored in the memory unit. Figure 13 is a diagram for explaining the control operation when determining the addition amount in the determination unit. Figure 14 is a schematic diagram showing the configuration of the compressor unit according to the fourth embodiment. Figure 15 is a diagram illustrating the relationships contained in the information stored in the memory unit. Figure 16 is a diagram illustrating the control operation when controlling the output frequency of the variable speed drive. Figure 17 is a diagram illustrating the relationships contained in the information stored in the memory unit according to a modified example of the first embodiment. Figure 18 is a diagram illustrating the relationships contained in the information stored in the memory unit according to a modified example of the first embodiment.

[0009] Embodiments of the present invention will be described below with reference to the attached drawings. Note that the following embodiments are merely examples of the present invention and do not limit the technical scope of the present invention.

[0010] (First Embodiment) The compressor unit according to this embodiment is a compressor unit for compressing gas generated from a gas source and supplying it to a customer facility. As shown in Figure 1, hydrogen gas is introduced into the compressor unit 10 from a water electrolysis device WE, which is a gas source. The water electrolysis device WE is configured to generate hydrogen gas using electricity generated using renewable energy, for example. Examples of renewable energy include solar power, wind power, hydropower, wave power, tidal power, geothermal energy, solar heat, heat in the atmosphere, other heat present in nature, or biomass. Note that the water electrolysis device WE is not limited to one that generates hydrogen gas using electricity derived from renewable energy.

[0011] The compressor unit 10 includes a motor 11, a compressor body 12 driven by the motor 11, a variable speed drive 13 (also called a VFD (Variable Frequency Drive)) that controls the rotational speed of the motor 11, and a controller 15. The compressor body 12 is composed of a centrifugal or positive displacement compressor.

[0012] The compressor unit 10 is connected to the water electrolysis device WE through the suction passage 21. Therefore, the compressor body 12 is driven by the motor 11 to draw in hydrogen gas sent from the water electrolysis device WE and compress the drawn-in hydrogen gas. The water electrolysis device WE may include a tank (not shown) for storing the generated hydrogen gas, in which case the hydrogen gas stored in the storage tank may be supplied to the compressor body 12.

[0013] A discharge channel 22 is connected to the compressor body 12, and the gas compressed by the compressor body 12 is supplied to the customer equipment (not shown) through this discharge channel 22. The process in which the compressor unit 10 is used is a non-refrigeration process. That is, the compressor unit 10 is used in a process that is not a refrigeration cycle that circulates refrigerant gas using evaporators and condensers. The customer equipment can be various, such as high-pressure gas storage tanks, turbines, engines, and boilers. Therefore, hydrogen gas can be used as fuel.

[0014] The compressor unit 10 is equipped with a bypass section 23 that can adjust the suction pressure to the compressor body 12. The bypass section 23 has a bypass passage 23a that bypasses the compressor body 12 and a bypass valve 23b provided in the bypass passage 23a. The bypass passage 23a returns a portion of the gas flowing through the discharge passage 22 to the suction passage 21. By adjusting the opening of the bypass valve 23b, the suction pressure of the compressor body 12 can be adjusted without changing the rotational speed of the motor 11.

[0015] The suction passage 21 is equipped with a suction pressure sensor 25 for acquiring the gas suction pressure. The suction pressure sensor 25 is configured to detect the gas pressure in the suction passage 21 and outputs a signal indicating the acquired value, which is the detected gas pressure. This signal is input to the controller 15.

[0016] The controller 15 is a computer that controls various operations of the compressor unit 10. The functions of the controller 15, which are executed by the central processing unit (CPU) of this computer, include a storage unit 31, a bypass valve control unit 32, a determination unit 33, and a variable speed drive control unit 34.

[0017] The memory unit 31 stores information representing the relationship between the fluctuation value ΔPs (MPa) of the suction pressure and the amount added to the control amount of the variable speed drive 13. The relationship shown by this information is, for example, as shown in Figure 2. The vertical axis of Figure 2 has a predetermined set value "s" as the origin and shows the fluctuation value ΔPs (MPa) of the suction pressure, which is the difference between the suction pressure obtained from the suction pressure sensor 25 and the set value. For example, it is assumed that a first set range of s to +a (MPa), a second set range of +a to +b (MPa), and a third set range of +b to +c (MPa) are set as the range of the fluctuation value ΔPs. When the fluctuation value ΔPs is included in the first set range, the amount added is 0%. When the fluctuation value ΔPs is included in the second set range, the amount added is α%. When the fluctuation value ΔPs is included in the third set range, the amount added is β%, which is greater than α%. The relationship of the amount added is β > α > 0. In other words, if the fluctuation value ΔPs of the suction pressure is within one of the set ranges, the amount added remains constant even if the fluctuation value ΔPs increases. On the other hand, if the fluctuation value ΔPs increases beyond the set range, the amount added increases discontinuously rather than continuously. Thus, the amount added (%) for the control amount of the variable speed drive 13 is set according to the fluctuation value ΔPs (MPa) of the suction pressure.

[0018] Furthermore, the amount of addition may be set so that it increases continuously when the fluctuation value ΔPs of the suction pressure is within any of the set ranges. That is, in each set range shown in Figure 2, the amount of addition may not be constant, but may have a constant slope so that it gradually increases. However, even in that case, if the fluctuation value ΔPs increases beyond the set range, the amount of addition will be set so that it increases discontinuously.

[0019] The signal sent from the suction pressure sensor 25 is input to the bypass valve control unit 32. The bypass valve control unit 32 refers to the value obtained from the suction pressure sensor 25 indicated by this signal and controls the bypass valve 23b so that the measurement value from the suction pressure sensor 25 falls within a predetermined range.

[0020] The pressure of the gas flowing through the suction channel 21 fluctuates in accordance with fluctuations in the flow rate of the gas supplied from the water electrolysis device WE. Furthermore, the flow rate of the gas supplied from the water electrolysis device WE fluctuates in accordance with the amount of gas generated in the water electrolysis device WE. Therefore, the value acquired by the suction pressure sensor 25 fluctuates sequentially in accordance with the amount of gas generated in the water electrolysis device WE. The bypass valve control unit 32 sequentially records the value acquired by the suction pressure sensor 25, as indicated by the received signal. The bypass valve control unit 32 obtains the deviation of the acquired value from these sequentially recorded acquired values. This deviation is the fluctuation value ΔPs (MPa) of the suction pressure. In other words, the bypass valve control unit 32 is a fluctuation value acquisition means 28 that acquires or stores fluctuation values ​​that fluctuate in relation to the amount of gas generated in the water electrolysis device WE.

[0021] The determination unit 33 refers to the relationship indicated by the information stored in the memory unit 31 (for example, the relationship shown in Figure 2) and determines the amount to add to the control amount of the variable speed drive 13 based on the fluctuation value ΔPs derived from the suction pressure acquired by the bypass valve control unit 32. For example, if the fluctuation value ΔPs is within the first setting range, the determination unit 33 determines the amount to add to 0%; if the fluctuation value ΔPs is within the second setting range, the amount to add to α%; and if the fluctuation value ΔPs is within the third setting range, the amount to add to β%. Since the determination unit 33 periodically acquires the fluctuation value ΔPs from the bypass valve control unit 32, the determination unit 33 determines the amount to add each time it acquires the fluctuation value ΔPs.

[0022] The variable speed drive control unit 34 has a reference value (or set value) set for the output frequency of the variable speed drive 13, and the variable speed drive control unit 34 controls the variable speed drive 13 so that the output frequency of the variable speed drive 13 becomes the reference value. If the suction pressure differs from the preset pressure, the output frequency is adjusted to a frequency that differs from the reference value, as will be described later.

[0023] The reference amount (or set value) of the variable speed drive control unit 34 is set so that the rotational speed of the motor 11 reaches a predetermined value (for example, the minimum rotational speed).

[0024] Furthermore, the variable speed drive control unit 34 derives a corrected control amount by adding the reference amount determined by the determination unit 33, and controls the variable speed drive 13 with this derived corrected control amount. In other words, since the output frequency of the variable speed drive 13 is adjusted to the corrected control amount, the motor 11 is driven at a rotational speed corresponding to this output frequency. The variable speed drive control unit 34 periodically acquires the addition amount determined by the determination unit 33, and derives the corrected control amount each time the addition amount is acquired.

[0025] Since the output frequency of the variable speed drive 13 (or the rotational speed of the motor 11) is controlled to become a reference value, if the output frequency of the variable speed drive 13 (or the rotational speed of the motor 11) is changed to a corrected control value and deviates from the reference value, the variable speed drive control unit 34 performs feedback control (PI control or PID control) according to the difference between the corrected control value and the reference value, so that the output frequency of the variable speed drive 13 becomes the reference value. In this feedback control, the manipulated variable is set so that the output frequency returns to the reference value over a period of time longer than the cycle in which the variable speed drive control unit 34 takes the added amount from the determination unit 33.

[0026] Here, the operation of the compressor unit 10 will be explained with reference to Figures 3 to 5.

[0027] As shown in Figure 3, the bypass valve control unit 32 first acquires the suction pressure Ps (MPa), which is the value obtained from the suction pressure sensor 25 (step S11). Next, the bypass valve control unit 32 calculates the difference between the acquired suction pressure Ps and a predetermined value, and calculates the amount to change the opening degree of the bypass valve 23b according to this calculated difference (step S12). At this time, the opening degree of the bypass valve 23b is derived so that the value detected by the suction pressure sensor 25 approaches the predetermined value. Then, the bypass valve control unit 32 controls the bypass valve 23b so that the opening degree is changed by the derived amount (step S13). By repeating steps S11 to S13, the gas pressure in the suction passage 21 is periodically adjusted.

[0028] In step S12, feedback control is performed according to the difference between the suction pressure Ps (MPa), which is the value obtained from the suction pressure sensor 25, and a predetermined value. However, instead of this, feedforward control, which opens to a predetermined degree, may be performed.

[0029] Furthermore, as shown in Figure 4, the bypass valve control unit 32 derives a fluctuation value ΔPs, which is a deviation, from the suction pressure Ps that is repeatedly acquired at regular intervals (step S15).

[0030] Meanwhile, the variable speed drive control unit 34 periodically adjusts the control amount of the variable speed drive 13. As shown in Figure 5, when adjusting the control amount of the variable speed drive 13, the variable speed drive control unit 34 first acquires the current value of the output frequency or the rotational speed (current value) of the motor 11 (step S21), and performs PI control on the output frequency of the variable speed drive 13 (step S22). At this time, the variable speed drive control unit 34 adds the amount determined by the determination unit 33 to the current value of the output frequency (step S23) to determine the corrected control amount, which is the output frequency (step S24). Then, in step S22, PI control is performed on the output frequency based on the difference between this determined output frequency and the reference amount. Note that PID control may be performed instead of PI control.

[0031] If the current value is the same as the reference quantity and the addition amount is 0%, the corrected control quantity will be the output frequency (or rotational speed of motor 11) maintained at the reference quantity. On the other hand, even if the current value is the same as the reference quantity, if the addition amount is, for example, α%, the corrected control quantity will be the output frequency (or rotational speed of motor 11) increased by α% relative to the reference quantity. Steps S21 to S24 are performed repeatedly at regular intervals.

[0032] The variable speed drive control unit 34 is configured to perform feedback control so that the output frequency of the variable speed drive 13 (or the rotational speed of the motor 11) becomes a reference value. Therefore, when the corrected control amount deviates from the reference value as a result of executing steps S21 to S24, the variable speed drive control unit 34 performs feedback control to return the output frequency (or rotational speed of the motor 11) to the reference value. However, this feedback control is set so that the output frequency (or rotational speed of the motor 11) returns to the reference value over a period of time required to repeatedly execute steps S21 to S24. Therefore, even if the corrected control amount deviates from the reference value, the output frequency (or rotational speed of the motor 11) does not immediately return to the reference value.

[0033] The variable speed drive 13 is controlled by the variable speed drive control unit 34, with the control amount of the variable speed drive 13 being adjusted periodically. The motor 11 of the compressor body 12 is driven at a rotational speed corresponding to this determined output frequency (corrected control amount).

[0034] The determination amount by the determination unit 33 is also determined periodically (at predetermined intervals). Specifically, as shown in Figure 6, the determination unit 33 obtains a fluctuation value ΔPs from the bypass valve control unit 32 (step S31). The determination unit 33 first determines whether the obtained fluctuation value ΔPs is within the first set range (step S32). If the fluctuation value ΔPs is within the first set range, it maintains the addition amount at 0% (step S33) and returns to step S31. After a predetermined time, the determination unit 33 again obtains the fluctuation value ΔPs from the bypass valve control unit 32, and as long as the fluctuation value ΔPs is within the first set range, the addition amount is maintained at 0% (step S33).

[0035] On the other hand, if the acquired fluctuation value ΔPs exceeds the first setting range (NO in step S32), the process proceeds to step S34, where the setting range is changed according to the fluctuation value ΔPs. Then, according to this changed setting range, the determination unit 33 changes the addition amount while referring to the relationship stored in the storage unit 31 (step S35). For example, if the fluctuation value ΔPs is within the second setting range, the determination unit 33 changes the addition amount from 0% to α%, and if the fluctuation value ΔPs is within the third setting range, the determination unit 33 changes the addition amount from 0% to β%. Steps S31 to S35 are also executed repeatedly. The addition amount determined by the determination unit 33 is then used in step S23.

[0036] As shown in Figure 2, the relationship between the fluctuation value ΔPs of the suction pressure and the amount added to the control variable of the variable speed drive 13 includes a discontinuous relationship in which the amount added changes discontinuously with respect to the fluctuation value ΔPs. This discontinuous relationship is such that when the fluctuation value ΔPs increases with increasing gas generation, the frequency of the variable speed drive 13 (i.e., the rotational speed of the motor 11) increases discontinuously. When the variable speed drive control unit 34 adjusts the control variable of the variable speed drive 13, the variable speed drive 13 is controlled so that the output frequency (or rotational speed of the motor 11) is determined by referring to this relationship. Therefore, when the fluctuation value ΔPs of the suction pressure increases rapidly, the rotational speed of the compressor body 12 can be increased discontinuously, thus suppressing overshoot in the control of the variable speed drive 13.

[0037] In other words, if a rapid fluctuation in suction pressure occurs, attempting to control the variable speed drive 13 based on the suction pressure using feedback control (such as PI control or PID control) may result in an overshoot of the output frequency set value or unstable behavior of the control circuit inside the variable speed drive 13. For example, consider a case where increasing the rotational speed of the motor 11 by a few percent when the suction pressure rises by several MPa returns it to the original suction pressure. In this case, even if the output frequency could be controlled to exactly a few percent using feedback control when the rate of increase of several MPa is several tens of seconds, the gain becomes large when the rate of increase of suction pressure is short, such as several seconds, causing the output frequency to overshoot before returning to the aforementioned few percent. This increases the likelihood of hunting occurring. However, in this embodiment, since the rotational speed of the compressor body 12 is increased discontinuously, hunting can be suppressed. If there is a risk of overshoot even when the rate of increase of several MPa is several tens of seconds or longer, a control method using a corrected control amount may be adopted.

[0038] As described above, according to this embodiment, when fluctuations in suction pressure occur due to an increase in the amount of gas generated, it is possible to control the variable speed drive 13 so that the rotational speed of the motor 11 increases discontinuously. Therefore, even when there is a rapid fluctuation in the amount of gas generated that would cause an overshoot in the controlled amount (speed of the VFD) of the variable speed drive 13 if controlled by feedback control alone, the control of the variable speed drive 13 can be stabilized. Thus, it contributes to a stable supply of hydrogen gas.

[0039] Furthermore, in this embodiment, the opening value of the bypass valve 23b is controlled by the bypass valve control unit 32 so that the suction pressure of the compressor body 12 reaches a predetermined value. Therefore, the gas suction pressure to the compressor body 12 can be made more stable.

[0040] Furthermore, in this embodiment, the fluctuation value acquisition means 28, which acquires fluctuation values ​​that fluctuate in relation to the amount of gas generated, is the bypass valve control unit 32. Therefore, the equipment within the compressor unit 10 for controlling the bypass valve 23b can be used to implement control that suppresses overshoot of the control amount of the variable speed drive 13.

[0041] Furthermore, in this embodiment, when the current value of the corrected control amount deviates from the reference amount, the variable speed drive control unit 34 performs feedback control to return the output frequency to the reference amount. However, since the feedback control is not such that the output frequency immediately returns to the reference amount even when the corrected control amount deviates from the reference amount, it is possible to suppress disturbances in the control of the variable speed drive 13.

[0042] In the first embodiment, in step S31 of Figure 6, the difference ΔPs (MPa) between the suction pressure Ps1 obtained in the previous step (control one loop prior in the loop control shown in Figure 6) and the suction pressure Ps2 obtained in the current step may be used as the fluctuation value. This ΔPs (MPa) is obtained from the bypass valve control unit 32. In this case as well, as shown in Figure 17, the relationship between the fluctuation value ΔPs of the suction pressure and the amount added to the control amount of the variable speed drive 13 includes a discontinuous relationship in which the amount added changes discontinuously with respect to the fluctuation value ΔPs. Note that the origin is set to 0 on the vertical axis of Figure 17. This makes it possible to control the variable speed drive 13 so that the rotation speed of the motor 11 increases discontinuously when the fluctuation value changes due to an increase in the amount of gas generated.

[0043] Furthermore, in step S31 of FIG. 6, a fluctuation value ΔPs / Δt (MPa / sec), which is the deviation of the suction pressure Ps per predetermined time, may be used as a fluctuation value that fluctuates in association with the gas generation amount. The bypass valve control unit 32 derives the fluctuation value ΔPs / Δt, which is a deviation, from the suction pressure Ps repeatedly acquired periodically in step S15 of FIG. 4. Even in this case, as shown in FIG. 18, the relationship between the fluctuation value ΔPs / Δt of the suction pressure and the addition amount for the controlled variable of the variable speed drive 13 includes a discontinuous relationship in which the addition amount changes discontinuously with respect to the fluctuation value ΔPs / Δt. Instead of the bypass valve control unit 32 deriving the fluctuation value ΔPs / Δt (MPa / sec), a fluctuation value acquisition means for deriving the aforementioned fluctuation value ΔPs / Δt based on the suction pressure Ps sent from the bypass valve control unit 32 may be separately provided.

[0044] (Second Embodiment) In the first embodiment, the determination unit 33 determines the addition amount for the controlled variable of the variable speed drive 13 based on the fluctuation value ΔPs of the suction pressure acquired from the bypass valve control unit 32. In contrast, in the second embodiment, as shown in FIG. 7, a valve opening fluctuation value acquisition unit 36 is included as a function of the controller 15, and the determination unit 33 determines the addition amount based on the fluctuation value (% / sec) of the valve opening per predetermined time output from the valve opening fluctuation value acquisition unit 36. Here, the same constituent elements as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

[0045] The bypass valve control unit 32 holds an opening value (current value) of the bypass valve 23b. The valve opening value, which is the opening value of the bypass valve 23b, is periodically sent to the valve opening fluctuation value acquisition unit 36.

[0046] The valve opening fluctuation value acquisition unit 36 acquires the fluctuation value (% / sec) of the valve opening value per predetermined time based on the valve opening values periodically sent from the bypass valve control unit 32. This fluctuation value (% / sec) fluctuates in association with the gas generation amount in the water electrolysis apparatus WE. In other words, the valve opening fluctuation value acquisition unit 36 is fluctuation value acquisition means 28 that acquires or holds a fluctuation value that fluctuates in association with the gas generation amount in the water electrolysis apparatus WE.

[0047] The determining unit 33 refers to the relationship represented by the information stored in the storage unit 31 (for example, the relationship shown in FIG. 8), and determines the addition amount for the control amount of the variable speed drive 13 based on the fluctuation value (% / sec) of the valve opening degree acquired or held by the valve opening fluctuation value acquiring unit 36. For example, the determining unit 33 determines the addition amount to be 0% if the fluctuation value of the valve opening value per predetermined time falls within the first setting range, determines the addition amount to be α% if the fluctuation value of the valve opening value per predetermined time falls within the second setting range, and determines the addition amount to be β% if the fluctuation value of the valve opening value per predetermined time falls within the third setting range, where β>α>0. Since the determining unit 33 periodically acquires the fluctuation value of the valve opening value from the bypass valve control unit 32, the determining unit 33 determines the addition amount every time it acquires the fluctuation value of the valve opening value per predetermined time.

[0048] Here, the control operation of the output frequency of the variable speed drive 13 in the compressor unit 10 according to the second embodiment will be described with reference to FIG. 9 and FIG. 10.

[0049] The variable speed drive control unit 34 periodically adjusts the control amount of the variable speed drive 13. When adjusting the control amount of the variable speed drive 13, as shown in FIG. 9, the variable speed drive control unit 34 first acquires the valve opening value (current value) of the bypass valve 23b (step S41), and performs PI control based on the deviation between the valve opening value and the set value (step S42).

[0050] In this PI control, the addition amount determined by the determining unit 33 is added to the output frequency (or the rotation speed of the motor 11) (step S43), and the output frequency (or the rotation speed of the motor 11) which is the corrected control amount is determined (step S44). Then, in step S42, PI control is performed on the output frequency based on the deviation between the valve opening value and the set value. Note that PID control may be performed instead of PI control.

[0051] If the current output frequency is the same as the reference quantity and the addition amount is 0%, the corrected control quantity will be the output frequency maintained at the reference quantity. On the other hand, even if the current output frequency is the same as the reference quantity, if the addition amount is, for example, α%, the corrected control quantity will be an output frequency increased by α% relative to the reference quantity, and the variable speed drive 13 will be controlled with this corrected output frequency. Steps S41 to S44 are performed repeatedly at regular intervals.

[0052] The motor 11 of the compressor body 12 is then driven at a rotational speed corresponding to the output frequency (corrected control amount) output by the variable speed drive control unit 34.

[0053] The determination unit 33 also periodically determines the amount to be added. Specifically, the valve opening degree fluctuation value acquisition unit 36 ​​acquires the fluctuation value (% / sec) of the valve opening degree value per predetermined time from the valve opening degree value acquired from the bypass valve control unit 32. Then, as shown in Figure 10, the determination unit 33 acquires the fluctuation value (% / sec) of the opening degree value of the bypass valve 23b per predetermined time from the valve opening degree fluctuation value acquisition unit 36 ​​(step S51). The determination unit 33 first determines whether this acquired fluctuation value is within the first set range (step S52). If the acquired fluctuation value is within the first set range, the amount to be added is maintained at 0% (step S53), and the process returns to step S51. After a predetermined time, the determination unit 33 again acquires the fluctuation value from the bypass valve control unit 32, and as long as the acquired fluctuation value is within the first set range, the amount to be added is maintained at 0% (step S53).

[0054] On the other hand, if the acquired fluctuation value exceeds the first setting range (NO in step S52), the process proceeds to step S54, where the setting range is changed according to the fluctuation value. Then, according to this changed setting range, the addition amount is changed (step S55) while referring to the relationship stored in the storage unit 31. For example, if the fluctuation value per predetermined time is within the second setting range, the determination unit 33 changes the addition amount from 0% to α%, and if the fluctuation value per predetermined time is within the third setting range, the determination unit 33 changes the addition amount from 0% to β%. Steps S51 to S55 are also executed repeatedly. The addition amount determined by the determination unit 33 is then used in step S43.

[0055] Therefore, according to this embodiment, the control of the variable speed drive 13 to deal with sudden fluctuations in the amount of gas generated can be achieved using the equipment within the compressor unit 10.

[0056] The other configurations, functions, and effects will not be described here, but the description of the first embodiment can be applied to the second embodiment.

[0057] (Third Embodiment) In the second embodiment, the determination unit 33 obtains the valve opening degree fluctuation value from the valve opening degree fluctuation value acquisition unit 36, whereas in the third embodiment, as shown in Figure 11, the determination unit 33 obtains the opening degree value (more precisely, the opening degree command value) of the bypass valve 23b from the bypass valve control unit 32, which is different from the second embodiment. Here, the same reference numerals are used for the same components as in the first and second embodiments, and their detailed descriptions are omitted.

[0058] The bypass valve control unit 32 controls the bypass valve 23b based on the value obtained from the suction pressure sensor 25, and at this time stores the opening degree (%) of the bypass valve 23b. The opening degree of the bypass valve 23b fluctuates according to the gas pressure in the suction passage 21, and is therefore also a fluctuating value that fluctuates in relation to the amount of gas generated in the water electrolysis device WE. In other words, the bypass valve control unit 32 holds an opening degree value that is a fluctuating value related to the amount of gas generated. Thus, the bypass valve control unit 32 is a fluctuating value acquisition means 28 that acquires or holds a fluctuating value that fluctuates in relation to the amount of gas generated in the water electrolysis device WE.

[0059] The determination unit 33 refers to the relationship indicated by the information stored in the memory unit 31 (for example, the relationship shown in Figure 12) and determines the amount to be added to the control amount of the variable speed drive 13 based on the valve opening value held by the bypass valve control unit 32. Specifically, the relationship indicated by the information stored in the memory unit 31 is as shown in Figure 12, with a first setting range as the range of valve opening values ​​and a second setting range which is a range of valve opening values ​​larger than the first setting range. The first setting range is the point where the valve opening value is 0% (however, it is also possible to consider an extremely small range including 0% as the first setting range). The second setting range is the range of valve opening values ​​greater than 0%. If the valve opening value is within the second setting range, the amount to be added to the control amount of the variable speed drive 13 is 0%, and if the valve opening value is within the first setting range, the amount to be added is α%. In other words, the relationship stored in the memory unit 31 is such that the amount to be added is 0% unless the valve opening value is 0%, but when the valve opening value is 0%, the amount to be added is α%. Note that the valve opening value corresponding to the first setting range may be a value other than 0%.

[0060] Therefore, the determination unit 33 determines the addition amount to α% if the valve opening value is within the first set range, and determines the addition amount to 0% if the valve opening value is within the second set range. Specifically, as shown in Figure 13, the determination unit 33 obtains the valve opening value from the bypass valve control unit 32 (step S61). The determination unit 33 determines whether the obtained valve opening value is a predetermined value (0%), that is, within the first set range (step S62). If the obtained valve opening value is not the predetermined value, the determination unit 33 maintains the addition amount at 0% (step S63) and returns to step S61. On the other hand, if the obtained valve opening value is the predetermined value (0%), the determination unit 33 changes the addition amount to α% (step S64) and returns to step S61. Thereafter, this cycle is repeated at predetermined time intervals.

[0061] The variable speed drive control unit 34 derives a corrected control amount by adding a reference amount to the addition amount determined by the determination unit 33, and controls the variable speed drive 13 with this derived corrected control amount. Even after the addition amount α% is added to the reference amount, if the valve opening value is within the first setting range in the step shown in Figure 13, the determination unit 33 maintains the addition amount at α% (step S63), so a corrected control amount with an additional α% added is derived.

[0062] Therefore, according to this embodiment, the control of the variable speed drive 13 to deal with sudden fluctuations in the amount of gas generated can be achieved using the equipment within the compressor unit 10.

[0063] In this embodiment, one additional amount (α%) is provided to be added to the base amount, but a setting range of three or more may be set so that two or more additional amounts greater than zero are available. In this case, the additional amount may be set to increase as the valve opening value decreases.

[0064] In this embodiment, the determination unit 33 may be configured to directly obtain the opening value from the bypass valve 23b. In this case, the bypass valve 23b plays the role of the fluctuation value acquisition means 28.

[0065] The other configurations, functions, and effects will not be described here, but the descriptions of the first and second embodiments can be applied to the third embodiment.

[0066] (Fourth Embodiment) In the first to third embodiments, the determination unit 33 determines the amount to be added to the control amount of the variable speed drive 13, whereas in the fourth embodiment, the determination unit 33 determines the control amount of the variable speed drive 13. Here, the same reference numerals are used for the same components as in the first to third embodiments, and their detailed descriptions are omitted.

[0067] As shown in Figure 14, the controller 15 includes an input power acquisition unit 38 that periodically receives information about the amount of power input to the water electrolysis device WE and acquires the fluctuation value of the input power per predetermined time.

[0068] The input power acquisition unit 38 sequentially records the input power (kWh) indicated by the received information. In other words, the sequentially recorded input power (kWh) is a fluctuating value that changes in relation to the amount of gas generated in the water electrolysis device WE. To put it another way, the input power acquisition unit 38 is a fluctuation value acquisition means 28 that acquires a fluctuating value that changes in relation to the amount of gas generated in the water electrolysis device WE.

[0069] The input power acquisition unit 38 may receive information about the amount of hydrogen gas generated instead of information about the amount of power input. In this case, the input power acquisition unit 38 will sequentially record the amount of hydrogen gas generated as indicated by the received information, and based on this recorded information, it will acquire a fluctuation value of the amount of hydrogen gas generated per predetermined time. This fluctuation value is also a fluctuation value that fluctuates in relation to the amount of gas generated in the water electrolysis device WE.

[0070] The determination unit 33 refers to the relationship indicated by the information stored in the memory unit 31 (for example, the relationship shown in Figure 15) and determines the control amount of the variable speed drive 13 based on the input energy amount (kWh) acquired by the input energy amount acquisition unit 38. For example, if the input energy amount (kWh) is in the range of 0 to +a, the determination unit 33 determines the control amount of the variable speed drive 13 to 0%; if the fluctuation value of the input energy is in the range of +a to +b, the determination unit 33 determines the control amount of the variable speed drive 13 to α2%; and if the fluctuation value of the input energy is in the range of +b to +c, the determination unit 33 determines the control amount of the variable speed drive 13 to β2%, which is greater than α2%. The relationship of the added amounts is β2 > α2 > 0. Furthermore, if the fluctuation value is even larger, the control amount will also be larger. Note that the determination unit 33 periodically acquires the fluctuation value of the input energy from the input energy amount acquisition unit 38, so the determination unit 33 determines the control amount of the variable speed drive 13 each time it acquires the fluctuation value.

[0071] The variable speed drive control unit 34 controls the variable speed drive 13 based on the control amount of the variable speed drive 13 determined by the determination unit 33.

[0072] In this embodiment, as shown in Figure 16, when the input power acquisition unit 38 receives information about the amount of power input to the water electrolysis device WE, it records the amount of power input indicated by the received information. This recording is performed periodically, and the input power acquisition unit 38 acquires the input power (kWh) based on the recorded information (step S71). Then, the determination unit 33 determines the control amount of the variable speed drive 13 based on the input power (kWh) (step S72). The variable speed drive control unit 34 controls the variable speed drive 13 based on this control amount of the variable speed drive 13.

[0073] Therefore, according to this embodiment, since the fluctuation amount of the input power is directly acquired, the control amount of the variable speed drive 13 can be determined more accurately. Furthermore, it is possible to control the variable speed drive 13 so that the rotational speed of the motor 11 increases discontinuously. For this reason, even when there is a sudden increase in the input power that would cause an overshoot of the control amount of the variable speed drive 13 if controlled by feedback control alone, it is possible to suppress the overshoot of the control amount of the variable speed drive 13 and stabilize the behavior of the control circuit inside the variable speed drive 13.

[0074] In this embodiment 4, a flow sensor for measuring the flow rate of hydrogen gas may be provided in the flow path (suction flow path 21) from the water electrolyzer WE to the compressor body 12. In this case, the input power acquisition unit 38 (fluctuation value acquisition means 28) may acquire the deviation of the measurement value from the flow sensor as the fluctuation value, rather than the amount of power input to the water electrolyzer WE.

[0075] The other configurations, functions, and effects will not be described here, but the descriptions of the first to third embodiments can be applied to the fourth embodiment.

[0076] (Other Embodiments) It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The present invention is not limited to the embodiments described above, and various modifications and improvements are possible without departing from the spirit of the invention.

[0077] For example, in the above embodiment, a water electrolysis device WE is exemplified as a gas source, but it is not limited to this. For example, the gas source may be a liquefied gas tank storing LNG (liquefied natural gas), LH2 (liquid hydrogen), LNH3 (liquefied ammonia), etc. These gases may also be boil-off gases. Furthermore, equipment such as a tank may be interposed between the gas source and the compressor body 12.

[0078] The specific embodiments described above mainly include inventions having the following configurations.

[0079] (1) The compressor unit according to the above embodiment is a compressor unit that compresses gas generated from a gas source and supplies it to a customer facility, and comprises a motor, a compressor body driven by the motor, a variable speed drive configured to control the rotational speed of the motor, a fluctuation value acquisition means configured to acquire or store a fluctuation value that fluctuates in relation to the amount of gas generated at the gas source, a storage unit configured to store in advance information representing the relationship between the fluctuation value and an add amount for the control amount of the variable speed drive that should be changed according to the fluctuation value, a determination unit configured to refer to the relationship represented by the information stored in the storage unit and determine an add amount for the control amount of the variable speed drive based on the fluctuation value acquired from the fluctuation value acquisition means, and a variable speed drive control unit configured to control the variable speed drive based on a corrected control amount obtained by adding a predetermined reference amount to the add amount determined by the determination unit. The relationship includes a discontinuous relationship in which the add amount changes discontinuously in response to fluctuations in the fluctuation value, such that the rotational speed of the motor increases discontinuously when the fluctuation value fluctuates with an increase in the amount of gas generated.

[0080] In the aforementioned compressor unit, it is possible to control the variable speed drive so that the motor speed increases discontinuously when the fluctuation value changes due to an increase in the amount of gas generated. Therefore, even in cases where there is a rapid fluctuation in the amount of gas generated that would cause an overshoot in the control amount of the variable speed drive (VFD speed) if controlled only by general feedback control such as PID control, it is possible to suppress the overshoot in the control amount of the variable speed drive and stabilize the variable drive control.

[0081] (2) The compressor unit may further include a bypass section having a suction pressure sensor provided in a suction passage connected to the compressor body, a bypass passage that bypasses the compressor body, and a bypass valve provided in the bypass passage. In this case, the fluctuation value acquisition means is a bypass valve control unit configured to acquire the deviation of the gas suction pressure as the fluctuation value based on the measurement value from the suction pressure sensor, and the bypass valve control unit may be configured to control the bypass valve by referring to the measurement value from the suction pressure sensor. In this embodiment, control can be achieved by the equipment within the compressor unit.

[0082] (3) The compressor unit may further include a bypass section having a suction pressure sensor provided in a suction passage connected to the compressor body, a bypass passage that bypasses the compressor body, and a bypass valve provided in the bypass passage. In this case, the fluctuation value acquisition means is a bypass valve control unit configured to acquire the deviation of the gas suction pressure per predetermined time as the fluctuation value based on the measurement value from the suction pressure sensor, and the bypass valve control unit may be configured to control the bypass valve by referring to the measurement value from the suction pressure sensor. In this embodiment, control can be achieved by the equipment within the compressor unit.

[0083] (4) The compressor unit may further include a bypass section having a suction pressure sensor provided in a suction passage connected to the compressor body, a bypass passage that bypasses the compressor body, and a bypass valve provided in the bypass passage, and a bypass valve control unit configured to adjust the opening value of the bypass valve so that the measurement value from the suction pressure sensor becomes a predetermined value. In this case, the fluctuation value acquisition means may be a valve opening fluctuation value acquisition unit configured to acquire the fluctuation value of the opening value per predetermined time based on the opening value of the bypass valve sent from the bypass valve control unit. In this embodiment, control can be achieved by the equipment within the compressor unit.

[0084] (5) The compressor unit may further include a bypass section having a suction pressure sensor provided in a suction passage connected to the compressor body, a bypass passage that bypasses the compressor body, and a bypass valve provided in the bypass passage. In this case, the fluctuation value acquisition means is a bypass valve control unit configured to hold the opening value of the bypass valve, which is the fluctuation value, and the bypass valve control unit may be configured to control the bypass valve by referring to the measurement value from the suction pressure sensor. In this embodiment, control can be achieved by the equipment within the compressor unit.

[0085] (6) In the compressor unit, the gas source may be a water electrolysis device, and the gas may be hydrogen gas supplied from the water electrolysis device.

[0086] (7) The compressor unit according to the above embodiment is a compressor unit that compresses hydrogen gas generated from a water electrolysis device that uses electricity derived from renewable energy as input power and supplies it to a customer facility, and comprises a motor, a compressor body driven by the motor, a variable speed drive configured to control the rotational speed of the motor, a fluctuation value acquisition means configured to acquire fluctuation values ​​of the amount of electricity input to the water electrolysis device or the amount of hydrogen gas generated, a storage unit configured to store in advance information representing the relationship between the fluctuation value and a control amount of the variable speed drive that should be changed according to the fluctuation value, a determination unit configured to refer to the relationship represented by the information stored in the storage unit and determine the control amount of the variable speed drive based on the fluctuation value acquired from the fluctuation value acquisition means, and a variable speed drive control unit configured to control the variable speed drive based on the control amount determined by the determination unit. The relationship includes a discontinuous relationship in which the control amount changes discontinuously in response to fluctuations in the fluctuation value, such that the rotational speed of the motor increases discontinuously when the fluctuation value changes due to an increase in the amount of electricity input or the amount of hydrogen gas generated.

[0087] In the aforementioned compressor unit, the control amount of the variable speed drive can be determined more accurately by directly acquiring the fluctuation amount of the input power. Furthermore, it is possible to control the variable speed drive so that the motor rotation speed increases discontinuously. Therefore, even when there is a sudden fluctuation in the input power that would cause an overshoot in the control amount of the variable speed drive (VFD speed) with control using only general feedback control such as PID control, it is possible to suppress the overshoot in the control amount of the variable speed drive.

[0088] As described above, the compressor unit according to the embodiment can keep up with a sudden increase in the amount of gas generated.

[0089] This application is based on Japanese Patent Application No. 2025-040359, filed with the Japan Patent Office on 13 March 2025, the contents of which are incorporated herein by reference.

[0090] To illustrate the present invention, the embodiments have been adequately and fully described above with reference to the drawings. However, those skilled in the art should recognize that it is easy to modify and / or improve upon the embodiments described above. Therefore, unless such modifications or improvements implemented by those skilled in the art fall outside the scope of the claims, such modifications or improvements shall be considered to be included within the scope of the claims.

Claims

1. A compressor unit for compressing gas generated from a gas source and supplying it to a customer's facility, comprising: a motor; a compressor body driven by the motor; a variable speed drive configured to control the rotational speed of the motor; a fluctuation value acquisition means configured to acquire or store a fluctuation value that fluctuates in relation to the amount of gas generated at the gas source; a storage unit configured to store information in advance representing the relationship between the fluctuation value and an add amount for the control amount of the variable speed drive that should be changed according to the fluctuation value; a determination unit configured to refer to the relationship represented by the information stored in the storage unit and determine an add amount for the control amount of the variable speed drive based on the fluctuation value acquired from the fluctuation value acquisition means; and a variable speed drive control unit configured to control the variable speed drive based on a corrected control amount obtained by adding a predetermined reference amount to the add amount determined by the determination unit, wherein the relationship includes a discontinuous relationship in which the add amount changes discontinuously in response to fluctuations in the fluctuation value, such that the rotational speed of the motor increases discontinuously when the fluctuation value fluctuates as the amount of gas generated increases.

2. The compressor unit according to claim 1, further comprising: a suction pressure sensor provided in a suction passage connected to the compressor body; a bypass section having a bypass passage that bypasses the compressor body and a bypass valve provided in the bypass passage, wherein the fluctuation value acquisition means is a bypass valve control unit configured to acquire the deviation of the gas suction pressure as the fluctuation value based on the measurement value from the suction pressure sensor, and the bypass valve control unit is configured to control the bypass valve by referring to the measurement value from the suction pressure sensor.

3. The compressor unit according to claim 1, further comprising: a suction pressure sensor provided in a suction passage connected to the compressor body; a bypass section having a bypass passage that bypasses the compressor body and a bypass valve provided in the bypass passage, wherein the fluctuation value acquisition means is a bypass valve control unit configured to acquire the deviation of the gas suction pressure per predetermined time as the fluctuation value based on the measurement value from the suction pressure sensor, and the bypass valve control unit is configured to control the bypass valve by referring to the measurement value from the suction pressure sensor.

4. The compressor unit according to claim 1, further comprising: a suction pressure sensor provided in a suction passage connected to the compressor body; a bypass section having a bypass passage that bypasses the compressor body and a bypass valve provided in the bypass passage; and a bypass valve control unit configured to adjust the opening value of the bypass valve so that the measurement value obtained by the suction pressure sensor becomes a predetermined value, wherein the fluctuation value acquisition means is a valve opening fluctuation value acquisition unit configured to acquire the fluctuation value of the opening value per predetermined time based on the opening value of the bypass valve sent from the bypass valve control unit.

5. The compressor unit according to claim 1, further comprising: a suction pressure sensor provided in a suction passage connected to the compressor body; a bypass section having a bypass passage that bypasses the compressor body and a bypass valve provided in the bypass passage, wherein the fluctuation value acquisition means is a bypass valve control unit configured to hold the opening degree value of the bypass valve which is the fluctuation value, and the bypass valve control unit is configured to control the bypass valve by referring to a measurement value from the suction pressure sensor.

6. The compressor unit according to any one of claims 1 to 5, wherein the gas source is a water electrolysis device, and the gas is hydrogen gas supplied from the water electrolysis device.

7. A compressor unit for compressing hydrogen gas generated from a water electrolysis apparatus that uses renewable energy-derived electricity as input power and supplying it to a customer's facility, comprising: a motor; a compressor body driven by the motor; a variable speed drive configured to control the rotational speed of the motor; a fluctuation value acquisition means configured to acquire fluctuation values ​​of the amount of electricity input to the water electrolysis apparatus or the amount of hydrogen gas generated; a storage unit configured to store information in advance representing the relationship between the fluctuation value and a control amount of the variable speed drive to be changed according to the fluctuation value; a determination unit configured to refer to the relationship represented by the information stored in the storage unit and determine the control amount of the variable speed drive based on the fluctuation value acquired from the fluctuation value acquisition means; and a variable speed drive control unit configured to control the variable speed drive based on the control amount determined by the determination unit, wherein the relationship includes a discontinuous relationship in which the control amount changes discontinuously in response to fluctuations in the fluctuation value such that the rotational speed of the motor increases discontinuously when the fluctuation value changes due to an increase in the amount of electricity input or the amount of hydrogen gas generated.

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