JP7579078B2 - Marine Power Systems - Google Patents

Description

This disclosure relates to a marine power supply system.

The use of fuel cells as a power source for ships is being considered. Generally, fuel cells have issues with their load-following performance, and in particular, operation that causes load fluctuations on the fuel cell accelerates damage to the fuel cell's electrodes, which leads to performance degradation. In order to suppress such performance degradation of fuel cells, a power supply system has been proposed that combines a fuel cell with a storage battery and has the storage battery bear the load of the load fluctuations (see, for example, Patent Document 1).

JP 2013-243009 A

However, conventional power supply systems such as those described above have room for improvement when used as power supplies for ships, which can experience more complex load fluctuations specific to ships.

This disclosure has been made to solve these problems, and aims to provide a marine power supply system that can appropriately suppress the deterioration of fuel cell performance caused by load fluctuations that may occur on the ship.

A marine power supply system according to one aspect of the present disclosure is a marine power supply system including an onboard wiring section to which a load is connected, a power conversion device connected to the onboard wiring section, a power source that supplies power to the onboard wiring section via the power conversion device, and a controller that controls the power conversion device, wherein the power source includes a first power storage device, a second power storage device, and a fuel cell, the first power storage device being configured to have an output density higher than the output density of the second power storage device, and the second power storage device being configured to have an energy density higher than the energy density of the first power storage device, and the power conversion device includes a first power conversion device provided between the first power storage device and the onboard wiring section, a second power conversion device provided between the second power storage device and the onboard wiring section, and a controller that controls the power conversion device between the fuel cell and the onboard wiring section. and a third power conversion device connected between the fuel cell and the controller. The controller generates a first power command signal including a first frequency band component that is included in a first frequency or higher of the power value required by the onboard wiring section, and generates a second power command signal including a second frequency band that is included in a second frequency or lower of the power value required by the onboard wiring section. The first power conversion device charges and discharges the first power storage device based on the first power command signal, and the second power conversion device charges and discharges the second power storage device based on the second power command signal. The controller controls the third power conversion device so that a power value obtained by subtracting the power values supplied from the first and second power storage devices from the power value required by the onboard wiring section is supplied from the fuel cell.

Alternatively, the controller may control the third power conversion device so that the SOC (State Of Charge) of the second power storage device becomes a predetermined value. In this case, the third power conversion device may be configured to be capable of charging the second power storage device via the onboard wiring section.

The power command signal generating unit may include a first filter that passes the first frequency band that is equal to or greater than the first frequency of the power value required by the onboard wiring unit, and a second filter that passes the second frequency band that is equal to or less than the second frequency of the power value required by the onboard wiring unit.

The power command signal generating unit may include a first filter that generates the first power command signal by passing the first frequency band that is equal to or higher than the first frequency of the power value required by the onboard wiring unit, and a subtractor that generates the second power command signal by subtracting the first power command signal from a variable power signal that includes an AC component of the power value required by the onboard wiring unit.

The controller may include a variable power signal generating unit that extracts an AC component from the power value required by the onboard wiring unit to generate a variable power signal, and the power command signal generating unit may generate the first power command signal and the second power command signal based on the variable power signal.

This disclosure makes it possible to appropriately suppress the deterioration of fuel cell performance due to load fluctuations that may occur on a ship.

FIG. 1 is a block diagram showing a schematic configuration of a marine power supply system according to a first embodiment of the present disclosure. FIG. 2 is a graph showing an example of a change over time in load fluctuation in a ship. FIG. 3 is a graph showing another example of the change over time in load fluctuation in a ship. FIG. 4 is a diagram showing another example of the power command signal generating unit applied in the marine power supply system according to the first embodiment. FIG. 5 is a block diagram showing a schematic configuration of a marine power supply system according to a second embodiment of the present disclosure. FIG. 6 is a graph showing changes over time in the load current and the SOC in the second power storage device.

Embodiments of the present disclosure will be described in detail below with reference to the drawings. Note that, in the following, identical or corresponding elements are given the same reference symbols throughout all the drawings, and duplicate descriptions will be omitted.

(Embodiment 1)
The configuration of a marine power supply system according to a first embodiment of the present disclosure will be described. Fig. 1 is a block diagram showing a schematic configuration of the marine power supply system according to the first embodiment of the present disclosure. As shown in Fig. 1, the marine power supply system 1 according to the present embodiment includes an onboard wiring section 2, a power conversion device 3, a power source 4, and a controller 5.

A load 6 is connected to the onboard wiring section 2. The load 6 includes, for example, a ship's propulsion motor 6a. The propulsion motor 6a has a screw 7 connected to its output shaft. The propulsion motor 6a is connected to the onboard wiring section 2 via an inverter 8. The onboard wiring section 2 may be an AC system or a DC system. Multiple propulsion motors 6a may be connected to one onboard wiring section 2. Furthermore, the load 6 connected to the onboard wiring section 2 may include equipment other than the propulsion motor 6a, such as propulsion accessories and onboard electrical equipment.

The power source 4 is connected to the power conversion device 3 and supplies power to the onboard wiring section 2 via the power conversion device 3. The power conversion device 3 is provided between the onboard wiring section 2 and the power source 4, and outputs the power output by the power source 4 to the onboard wiring section 2.

The controller 5 controls the power conversion device 3. This controls the power output (discharging) or input (charging) from the power source 4. The controller 5 includes a computer such as a microcontroller or a personal computer. The controller 5 also includes a storage unit (not shown) that stores a control program and various data. In addition to the computer, the controller 5 may also include peripheral devices such as electronic circuits that perform predetermined calculations, etc.

The power source 4 includes a first storage device 4a, a second storage device 4b, and a fuel cell 4c. The fuel cell 4c generates electricity by reacting hydrogen gas supplied from the hydrogen gas supply device 12 with oxygen.

The power conversion device 3 includes a first power conversion device 3a connected to a first storage device 4a, a second power conversion device 3b connected to a second storage device 4b, and a third power conversion device 3c connected to a fuel cell 4c.

The controller 5 is configured to generate a first power command signal P1o including a first frequency band component that is equal to or higher than a first frequency of the power value P required by the onboard wiring section 2, and to generate a second power command signal P2o including a second frequency band that is equal to or lower than a second frequency of the power value P required by the onboard wiring section 2. For this purpose, the power supply system 1 is provided with a power detector 9 that measures the power value P in the onboard wiring section 2 and a voltage detector 10 that measures the voltage (power supply voltage) V in the onboard wiring section 2.

The controller 5 includes a variable power signal generator 5a and a power command signal generator 11. The variable power signal generator 5a extracts an AC component from the power value P required by the onboard wiring section 2 to generate a variable power signal ΔP. The variable power signal generator 5a has a first controller C ₁ (s) for maintaining the power supply voltage V of the onboard wiring section 2 at a set voltage Vref. The first controller C ₁ (s) calculates a base load power signal Po (a signal indicating a change over time in the base load power value) from the deviation ΔV (=Vref-V) between the power supply voltage V of the onboard wiring section 2 detected by the voltage detector 10 and a predetermined set voltage Vref for the onboard wiring section 2. The base load power signal Po includes the power of a planned load change (change due to an output change, etc.).

The variable power signal generator 5a generates a variable power signal (signal indicating the change over time in the variable power command value) ΔP (=P-Po) based on the load fluctuation, which is the deviation between the power value (power value required by the onboard wiring section 2) P detected by the power detector 9 and the base load power value (each value of the base load power signal Po). In this way, the variable power signal ΔP is a command value signal generated based on the power oscillation component obtained by extracting the power component based on external load fluctuation from the total power value P in the onboard wiring section 2, which includes a DC component (base load power).

The variable power signal ΔP is the basis for a first power command signal P1o for controlling the first power conversion device 3a corresponding to the first storage device 4a and a second power command signal P2o for controlling the second power conversion device 3b corresponding to the second storage device 4b.

Here, the first storage device 4a is configured to be a high-output storage device with a higher output density than the second storage device 4b, and the second storage device 4b is configured to be a large-capacity storage device with a higher energy density than the first storage device 4a. For example, the output density of the first storage device 4a is 3000 W/Kg or more, and the output density of the second storage device 4b is less than that. Also, the energy density of the first storage device 4a is about several tens of Wh/Kg, and the storage capacity of the second storage device 4b is greater than that. Also, the first storage device 4a and the second storage device 4b are configured to be capable of charging and discharging between the onboard wiring section 2.

The first storage device 4a is preferably a capacitor that has the capacity to store electric charge in advance, such as a lithium ion capacitor. The second storage device 4b is preferably a secondary battery, such as a lithium ion battery (LIB), a nickel metal hydride battery, or a lead storage battery.

In this embodiment, the power command signal generating unit 11 generates a first power command signal P1o including a first frequency band that is equal to or greater than a first frequency of the fluctuating power signal ΔP generated by the fluctuating power signal generating unit 5a, and generates a second power command signal P2o by passing a second frequency band that is equal to or less than a second frequency of the fluctuating power signal ΔP. The power command signal generating unit 11 includes a first filter 11a that generates the first power command signal P1o and a second filter 11b that generates the second power command signal P2o.

The first filter 11a generates the first power command signal P1o by passing a first frequency band that is equal to or higher than a first frequency of the fluctuating power signal ΔP. For example, the first filter 11a is configured by a high-pass filter (HPF).

In this embodiment, the fluctuating power signal ΔP is input to the first filter 11a, but the power value P required by the onboard wiring section 2 may be input directly to the first filter 11a.

The second filter 11b generates the second power command signal P2o by passing a second frequency band included in the fluctuating power signal ΔP that is less than the second frequency. For example, the second filter 11b is configured with a low-pass filter (LPF). The second frequency band may be set with only an upper limit value, or with an upper limit value and a lower limit value. That is, the first filter 11a may be configured with a band-pass filter (BPF) instead of an LPF. The first frequency and the second frequency may be the same value or different values. When the first frequency and the second frequency are different values, the second frequency may be greater than the first frequency, or the second frequency may be greater than the first frequency.

The first power conversion device 3a charges and discharges the first storage device 4a based on the first power command signal P1o output from the power command signal generation unit 11 (first filter 11a). The second power conversion device 3b charges and discharges the second storage device 4b based on the second power command signal P2o output from the power command signal generation unit 11 (second filter 11b).

More specifically, the difference between the first power command signal P1o and the first power P1 output by the first storage device 4a through the first power conversion device 3a is input to the first power conversion device 3a. Similarly, the difference between the second power command signal P2o and the second power P2 output by the second storage device 4b through the second power conversion device 3b is input to the second power conversion device 3b.

The controller 5 controls the third power conversion device 3c to supply the onboard wiring section 2 with a power value P3 (=P-P1-P2) obtained by subtracting the total value (P1+P2) of the power output from the first storage device 4a and the second storage device 4b from the power value P required by the onboard wiring section 2. More specifically, the third power conversion device 3c controls the output of the fuel cell 4c based on the base load power signal Po output from the controller 5. More specifically, the difference between the base load power signal Po and the third power P3 output by the fuel cell 4c through the third power conversion device 3c is input to the third power conversion device 3c.

Figure 2 is a graph showing an example of the change over time in load fluctuations on a ship. Figure 2 shows a state in which there is no output fluctuation in the load 6 itself (a state in which the output of the propulsion motor 6a is controlled to a constant value). The top graph in Figure 2 is a graph showing the change over time in the power value P in the onboard wiring section 2. The other graphs in Figure 2 are graphs that show the power value P divided into three components.

The load fluctuations of a ship include low-frequency load fluctuations where the load changes relatively small over time due to maneuvering (the load changes at a slow rate), and high-frequency load fluctuations where the load changes relatively large over time due to waves (the load changes at a fast rate). In other words, the power value P in the onboard wiring section 2 is the control value (base load power value) of the load 6 plus the low-frequency load fluctuation component and the high-frequency load fluctuation component.

Therefore, according to the above configuration, the power command signal generating unit 11 separates the fluctuating component power (fluctuating power signal ΔPo) in the onboard wiring unit 2 into a high-frequency frequency component (first power command signal P1o) and a low-frequency frequency component (second power command signal P2o). Of the fluctuating component power separated in this way, the high-frequency fluctuating component that fluctuates quickly and changes over a short period of time is borne by the first storage device 4a, which is a high-output storage device with a higher output density, and the low-frequency fluctuating component that fluctuates slowly and changes over a relatively long period of time is borne by the second storage device 4b, which is a large-capacity storage device with a higher energy density.

The first power command signal P1o and the second power command signal P2o both have oscillatory waveforms centered around 0. In FIG. 2, when the first power command signal P1o and the second power command signal P2o have positive values, they are discharge commands to discharge the charge stored in the corresponding power storage devices 4a, 4b. When the first power command signal P1o and the second power command signal P2o have negative values, they are charge commands to charge the corresponding power storage devices 4a, 4b from the onboard wiring section 2.

As a result, the fuel cell 4c does not need to bear these load fluctuations and only needs to bear the base load power. Therefore, there is no need to operate the fuel cell 4c in a way that causes abrupt load fluctuations. In other words, according to the above configuration, the DC component of the power value P required by the onboard wiring section 2 is the base load power signal Po, the high frequency AC component of the power value P is the first power command signal P1o, and the low frequency AC component of the power value P is the second power command signal P2o, so that the fuel cell 4c, the first storage device 4a, and the second storage device 4b share and bear the power value P required by the onboard wiring section 2.

In this way, by using two types of storage batteries 4a, 4b with different characteristics and charging and discharging each of the storage batteries 4a, 4b to cover the load fluctuations in the frequency bands according to their respective characteristics, it is possible to reduce the impact on the fuel cell 4c of the two types of load fluctuations specific to ships. This makes it possible to extend the electrode life of the fuel cell 4c and appropriately suppress performance degradation of the fuel cell 4c due to load fluctuations that may occur on the ship.

The base load power may change due to a change in the output of the load 6, etc., at the set voltage Vref. Figure 3 is a graph showing another example of the load fluctuation over time on a ship. As shown in Figure 3, the relatively gradual change (DC change) in the base load power is borne by the fuel cell 4c. Such DC changes in the base load power are tolerated because they have a small effect on the performance degradation of the fuel cell 4c.

(Modification)
Fig. 4 is a diagram showing another example of a power command signal generating section applied in the marine power supply system in embodiment 1. In the marine power supply system 1 in Fig. 1, a power command signal generating section 11B shown in Fig. 4 can be applied in place of the power command signal generating section 11 shown in Fig. 1.

The power command signal generating unit 11B shown in FIG. 4 includes a first filter 11a and a subtractor 11c. The first filter 11a has the same configuration (e.g., a high-pass filter) as the first filter 11a shown in FIG. 1. That is, the first filter 11a generates the first power command signal P1o by passing a first frequency band that is included in the fluctuating power signal ΔP and above a first frequency. The subtractor 11c generates the second power command signal P2o by subtracting the first power command signal P1o from the fluctuating power signal ΔP.

By configuring the power command signal generating unit 11B in this way, it is possible to generate power command signals P1o, P2o for the two power conversion devices 3a, 3b with one filter (first filter 11a). In other words, the second filter 11b can be eliminated. Furthermore, with this configuration, it is possible to have the second storage device 4b bear the load fluctuation components other than the power borne by the first storage device 4a. This allows the two storage devices 4a, 4b to appropriately share the load fluctuation components.

In this modified example, the power command signal generating unit 11B is configured with the first filter 11a and the subtractor 11c. Alternatively, the power command signal generating unit 11B may be configured with the second filter 11b (e.g., a low-pass filter) and the subtractor 11c. In this case, the subtractor 11c subtracts the second power command signal P2o (the output of the second filter 11b) from the fluctuating power signal ΔP to generate the first power command signal P1o.

(Embodiment 2)
Next, a configuration of a marine power supply system according to a second embodiment of the present disclosure will be described. Fig. 5 is a block diagram showing a schematic configuration of the marine power supply system according to the second embodiment of the present disclosure. In Fig. 5, components similar to those in the marine power supply system 1 according to the first embodiment shown in Fig. 1 are given the same reference numerals, and descriptions thereof will be omitted.

The marine vessel power supply system 1B in this embodiment differs from the marine vessel power supply system 1 in the first embodiment in that the connection mode of the third power conversion device 3c corresponding to the fuel cell 4c and the control mode therefor by the controller 5B are different from those in the first embodiment.

In this embodiment, the power value P required by the onboard wiring section 2 is shared by the first power storage device 4a and the second power storage device 4b, and the fuel cell 4c does not directly bear the power value P required by the onboard wiring section 2. Instead, the fuel cell 4c charges the second power storage device 4b so that the SOC of the second power storage device 4b is maintained at a predetermined value.

The third power conversion device 3c is connected to the onboard wiring section 2. Therefore, the fuel cell 4c can supply charging power to the second storage device 4b via the onboard wiring section 2 to set the SOC of the second storage device 4b to a predetermined value. The controller 5B controls the discharge of the fuel cell 4c using the third power conversion device 3c so that the SOC of the second storage device 4b becomes the predetermined value. The marine power supply system 1B is equipped with an SOC meter 13 that measures the SOC of the second storage device 4b.

The controller 5B includes an SOC control unit 5b that generates a third power command signal P3o that includes a control command value for the third power conversion device 3c. The SOC control unit 5b calculates the charge power to the second storage device 4b to maintain the SOC of the second storage device 4b at the SOC set value SOCref from the deviation ΔS (=SOCref-SOC) between the SOC of the second storage device 4b measured by the SOC meter 13 and a predetermined SOC set value SOCref. The controller 5B outputs a third power command signal P3o that sets the charge power to the second storage device 4b calculated by the SOC control unit 5b as the control command value for the third power conversion device 3c.

The power command signal generating unit 11B includes a first filter 11a and a second filter 11b, as in the first embodiment. Furthermore, the power command signal generating unit 11B includes an adder 11d that adds a base load power signal Po to the output signal P2a of the second filter 11b. The power command signal generating unit 11B outputs the output of the first filter 11a as a first power command signal P1o, and outputs the output of the adder 11d as a second power command signal P2o (=Po+P1a).

According to the above configuration, the power command signal generating unit 11B separates the power value P in the onboard wiring unit 2 into a high-frequency frequency component (first power command signal P1o) and a component including a low-frequency frequency component and a DC component (second power command signal P2o). Of the power of the fluctuating components separated in this way, the high-frequency fluctuating component that fluctuates quickly and changes over a short period of time is borne by the first storage device 4a, which is a high-output storage device with a higher output density, and the low-frequency fluctuating component that fluctuates slowly and changes over a relatively long period of time and the DC component are borne by the second storage device 4b, which is a large-capacity storage device with a higher energy density.

That is, the first power command signal P1o has an oscillating waveform centered on 0, similar to the graphs of P1o shown in Figures 2 and 3. On the other hand, the second power command signal P2o has a waveform that is the sum of the graphs of P2o and Po shown in Figures 2 and 3. The second power command signal P2o can also take a negative value depending on the load fluctuation, but since the second storage device 4b bears the base load power, the average discharge amount in the second storage device 4b is greater than the average charge amount in the second storage device 4b.

Therefore, the SOC of the second storage device 4b may fluctuate (tend to decrease). The power supply system 1B in this embodiment monitors the fluctuations in the SOC of the second storage device 4b that occur in this way, and charges the second storage device 4b with the power output by the fuel cell 4c.

Figure 6 is a graph showing the load current and SOC over time in the second storage device. Note that Figure 6 shows the change over time in the SOC of the second storage device 4b when the fuel cell 4c is not charging the second storage device 4b. As described above, the second storage device 4b outputs the second power P2 to the onboard wiring section 2 based on the second power command signal P2o. Since the oscillatory component P2a in the second power command signal P2o corresponds to P2o in the graphs of Figures 2 and 3, the current I2 input to the second storage device 4b oscillates around 0. Note that in Figure 6, the current during charging is a positive value, and the current during discharging is a negative value.

In contrast, the SOC of the second storage device 4b changes relatively slowly compared to the changes in current I2. Figure 6 shows the tendency for the SOC of the second storage device 4b to decrease gradually as the second storage device 4b supplies power to the onboard wiring section 2. In this embodiment, the fuel cell is controlled to respond to changes in the SOC of the second storage device 4b, which change relatively slowly compared to power fluctuations in the load 6. This eliminates the need to operate the fuel cell 4c in a way that causes abrupt load fluctuations.

In this way, by having the fuel cell 4c generate only the power to charge the second power storage device 4b, the impact on the fuel cell 4c of two types of load fluctuations specific to ships can be reduced. This extends the electrode life of the fuel cell 4c and appropriately suppresses performance degradation of the fuel cell 4c due to load fluctuations that may occur on the ship.

In the present embodiment, the output signal P2a obtained by passing the fluctuating power signal ΔP through the second filter 11b is added to the base load power signal Po to generate the second power command signal P2o, but this is not limited to the above. For example, the power value P required by the onboard wiring section 2 may be directly input to the second filter 11b configured as a low-pass filter. Even in this case, the second filter 11b may output a signal obtained by adding the low-frequency component P2a to the base load power signal Po, which is a DC component, as the second power command signal P2o.

In this embodiment, as in the first embodiment, the power value P required by the onboard wiring section 2 is input directly to the first filter 11a, and a first power command signal P1o can be generated in which the high-frequency components in the power value P are extracted.

Also, in this embodiment, as in embodiment 1, the power command signal generating unit 11B may be configured using the first filter 11a or the second filter 11b and the subtractor 11c instead of the first filter 11a and the second filter 11b.

The above describes an embodiment of the present invention, but the present invention is not limited to the above embodiment, and various improvements, changes, and modifications are possible without departing from the spirit of the invention.

The power supply system disclosed herein is useful for appropriately suppressing the deterioration of fuel cell performance due to load fluctuations that may occur on a ship.

REFERENCE SIGNS LIST 1, 1B Marine power supply system 2 Shipboard wiring section 3 Power conversion device 3a First power conversion device 3b Second power conversion device 3c Third power conversion device 4 Power source 4a First power storage device 4b Second power storage device 4c Fuel cell 5, 5B Controller 5a Fluctuating power signal generating section 6 Load 11, 11B Power command signal generating section 11a First filter 11b Second filter 11c Subtractor

Claims (4)

an onboard wiring section to which a load is connected;
a power conversion device connected to the onboard wiring section;
a power source for supplying power to the onboard wiring section via the power conversion device;
A marine power supply system comprising:
the power supply includes a first power storage device, a second power storage device, and a fuel cell;
the first power storage device is configured to have a higher output density than the output density of the second power storage device, and the second power storage device is configured to have a higher energy density than the energy density of the first power storage device;
The power conversion device is
a first power conversion device provided between the first power storage device and the onboard wiring section;
a second power conversion device provided between the second power storage device and the onboard wiring section;
a third power conversion device connected between the fuel cell and the onboard wiring section,
the controller includes a power command signal generating unit that generates a first power command signal, the command value of which is a power value included in a first frequency band among the power values required by the onboard wiring unit, and generates a second power command signal, the command value of which is a power value included in a second frequency band including a frequency range lower than the first frequency band among the power values required by the onboard wiring unit,
the first power conversion device charges and discharges the first power storage device based on the first power command signal;
the second power conversion device charges and discharges the second power storage device based on the second power command signal;
the controller controls the third power conversion device so that a power value obtained by subtracting the power values supplied from the first power storage device and the second power storage device from a power value required by the onboard wiring section is supplied from the fuel cell, or controls the third power conversion device so that an SOC of the second power storage device becomes a predetermined value ;
The power command signal generating unit
a first filter that passes the first frequency band of the power required by the onboard wiring unit;
a second filter that passes the second frequency band of the power value required by the onboard wiring section . an onboard wiring section to which a load is connected;
a power conversion device connected to the onboard wiring section;
a power source for supplying power to the onboard wiring section via the power conversion device;
A marine power supply system comprising:
the power supply includes a first power storage device, a second power storage device, and a fuel cell;
the first power storage device is configured to have a higher output density than the output density of the second power storage device, and the second power storage device is configured to have a higher energy density than the energy density of the first power storage device;
The power conversion device is
a first power conversion device provided between the first power storage device and the onboard wiring section;
a second power conversion device provided between the second power storage device and the onboard wiring section;
a third power conversion device connected between the fuel cell and the onboard wiring section,
the controller includes a power command signal generating unit that generates a first power command signal, the command value of which is a power value included in a first frequency band among the power values required by the onboard wiring unit, and generates a second power command signal, the command value of which is a power value included in a second frequency band including a frequency range lower than the first frequency band among the power values required by the onboard wiring unit,
the first power conversion device charges and discharges the first power storage device based on the first power command signal;
the second power conversion device charges and discharges the second power storage device based on the second power command signal;
the controller controls the third power conversion device so that a power value obtained by subtracting the power values supplied from the first power storage device and the second power storage device from a power value required by the onboard wiring section is supplied from the fuel cell, or controls the third power conversion device so that an SOC of the second power storage device becomes a predetermined value;
The power command signal generating unit
a first filter that generates the first power command signal by passing the first frequency band of a power value required by the onboard wiring unit;
a subtractor that generates the second power command signal by subtracting the first power command signal from a fluctuating power signal that includes an AC component of a power value required by the onboard wiring section. an onboard wiring section to which a load is connected;
a power conversion device connected to the onboard wiring section;
a power source for supplying power to the onboard wiring section via the power conversion device;
A marine power supply system comprising:
the power supply includes a first power storage device, a second power storage device, and a fuel cell;
the first power storage device is configured to have a higher output density than the output density of the second power storage device, and the second power storage device is configured to have a higher energy density than the energy density of the first power storage device;
The power conversion device is
a first power conversion device provided between the first power storage device and the onboard wiring section;
a second power conversion device provided between the second power storage device and the onboard wiring section;
a third power conversion device connected between the fuel cell and the onboard wiring section,
The controller includes:
a power command signal generating unit that generates a first power command signal, the command value of which is a power value included in a first frequency band among the power values required by the onboard wiring unit, and generates a second power command signal, the command value of which is a power value included in a second frequency band including a frequency range lower than the first frequency band among the power values required by the onboard wiring unit;
a variable power signal generating unit that extracts an AC component from a power value required by the onboard wiring unit and generates a variable power signal,
the first power conversion device charges and discharges the first power storage device based on the first power command signal;
the second power conversion device charges and discharges the second power storage device based on the second power command signal;
the controller controls the third power conversion device so that a power value obtained by subtracting the power values supplied from the first power storage device and the second power storage device from a power value required by the onboard wiring section is supplied from the fuel cell, or controls the third power conversion device so that an SOC of the second power storage device becomes a predetermined value;
The power command signal generating unit generates the first power command signal and the second power command signal based on the fluctuating power signal . the third power conversion device is configured to be capable of charging the second power storage device via the onboard wiring section,
4. The marine power supply system according to claim 1, wherein the controller controls the third power conversion device so that an SOC of the second power storage device becomes a predetermined value.

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