JP7603527B2 - Control device, control method and power supply system - Google Patents

Description

The present disclosure relates to a control device, a control method, and a power supply system.

Patent Document 1 discloses a ship equipped with a main generator and a power system that assists the main generator. The power system described in Patent Document 1 includes a first power storage device consisting of a storage battery and a second power storage device consisting of a capacitor. The ship described in Patent Document 1 can achieve zero emissions at the port by operating the power system as the only power source supplying power to the ship while anchored or traveling at low speed near the port.

JP 2017-136894 A

However, the power system described in Patent Document 1 has the problem that it can be difficult to miniaturize the storage battery in order to operate the power system as the sole power source.

The present disclosure has been made to solve the above problems, and aims to provide a control device, a control method, and a power supply system that can reduce the size of storage batteries.

To solve the above problem, the control device disclosed herein is a control device for a power supply system including a power generation device that generates electricity using a rotating electric machine, a power storage device that charges and discharges electricity, and an electrical load that is driven by the power supplied from the power generation device and the power storage device, and the control device controls the output power of the power generation device based on the average load power of the electrical load.

The control method disclosed herein is a control method for a power supply system that includes a power generation device that generates electricity using a rotating electric machine, a power storage device that charges and discharges electricity, and an electrical load that is driven by the power generation device and the power storage device, and the control device controls the output power of the power generation device based on the average load power of the electrical load.

The power supply system according to the present disclosure includes a power generation device that generates electricity using a rotating electric machine, a power storage device that charges and discharges electricity, an electrical load that is driven by the power generation device and the power storage device, and a control device that controls the output power of the power generation device based on the average power of the electrical load.

The control device, control method, and power supply system disclosed herein allow the storage battery to be made smaller.

1 is a diagram illustrating a configuration example of a power supply system according to a first embodiment of the present disclosure. FIG. 2 is a schematic diagram showing an operation example of the power supply system according to the first embodiment of the present disclosure. 3 is a block diagram showing an example configuration of a power supply optimization unit according to the first embodiment of the present disclosure. FIG. 5 is a schematic diagram for explaining an example of the operation of a power supply optimization unit according to the first embodiment of the present disclosure. FIG. 5 is a schematic diagram for explaining an example of the operation of a power supply optimization unit according to the first embodiment of the present disclosure. FIG. 5 is a schematic diagram for explaining an example of the operation of a power supply optimization unit according to the first embodiment of the present disclosure. FIG. 5 is a schematic diagram for explaining an example of the operation of a power supply optimization unit according to the first embodiment of the present disclosure. FIG. 5 is a schematic diagram for explaining an example of the operation of a power supply optimization unit according to the first embodiment of the present disclosure. FIG. 5 is a schematic diagram for explaining an example of the operation of a power supply optimization unit according to the first embodiment of the present disclosure. FIG. 5 is a schematic diagram for explaining an example of the operation of a power supply optimization unit according to the first embodiment of the present disclosure. FIG. 6 is a flowchart for explaining an example of the operation of a power supply optimization unit according to the first embodiment of the present disclosure. 6 is a flowchart for explaining an example of the operation of a power supply optimization unit according to the first embodiment of the present disclosure. FIG. 11 is a diagram illustrating a configuration example of a power supply system according to a second embodiment of the present disclosure. FIG. 11 is a block diagram showing an example configuration of a power supply optimization unit according to a second embodiment of the present disclosure. FIG. 11 is a block diagram showing an example configuration of a power supply optimization unit according to a second embodiment of the present disclosure. FIG. 11 is a schematic diagram for explaining an example of the operation of a power supply optimization unit according to the second embodiment of the present disclosure. FIG. 11 is a schematic diagram for explaining an example of the operation of a power supply optimization unit according to the second embodiment of the present disclosure. FIG. 11 is a schematic diagram for explaining an example of the operation of a power supply optimization unit according to the second embodiment of the present disclosure. FIG. 11 is a schematic diagram for explaining an example of the operation of a power supply optimization unit according to the second embodiment of the present disclosure. FIG. 11 is a schematic diagram for explaining a configuration example of a power supply optimization unit according to a second embodiment of the present disclosure. FIG. 11 is a schematic diagram for explaining a configuration example of a power supply optimization unit according to a second embodiment of the present disclosure. FIG. 11 is a schematic diagram for explaining a configuration example of a power supply system according to a second embodiment of the present disclosure. FIG. 11 is a schematic diagram for explaining a configuration example of a power supply system according to a second embodiment of the present disclosure. FIG. 1 is a schematic block diagram illustrating a configuration of a computer according to at least one embodiment.

First Embodiment
(Power supply system configuration)
Hereinafter, a control device, a control method, and a power supply system according to a first embodiment of the present disclosure will be described with reference to FIGS. 1 to 12. FIG. 1 is a diagram showing a configuration example of a power supply system according to a first embodiment of the present disclosure. FIG. 2 is a schematic diagram showing an operation example of the power supply system according to a first embodiment of the present disclosure. FIG. 3 is a block diagram showing a configuration example of a power supply optimization unit according to a first embodiment of the present disclosure. FIGS. 4 to 10 are schematic diagrams for explaining an operation example of the power supply optimization unit according to a first embodiment of the present disclosure. FIGS. 11 and 12 are flowcharts for explaining an operation example of the power supply optimization unit according to a first embodiment of the present disclosure. Note that the same or corresponding configurations in each drawing are designated by the same reference numerals, and the description thereof will be omitted as appropriate.

The power supply system 100 according to the first embodiment of the present disclosure shown in FIG. 1 is configured as an on-board power supply system mounted on a parallel hybrid system vehicle, as an example. The power supply system 100 shown in FIG. 1 includes a power supply optimization unit 1 as an example of a control device according to the present disclosure, an engine generator 2 as an example of a power generation device, an electricity storage device 3, a load 4 such as a large auxiliary machine as an example of a load device, a voltage sensor 61, and a current sensor 62.

The engine generator 2 includes an internal combustion engine 21, a motor/generator (hereinafter, motor generator) 22 as an example of a rotating electric machine, and an inverter 23. The engine 21 drives the motor generator 22 to generate electric power, and drives a running load 8 consisting of drive wheels and the like via a transmission 7. The motor generator 22 is an AC rotating electric machine that is driven by the engine 21 and operates as a generator to generate electric power, or operates as an electric motor using electric power supplied from the power storage device 3 to drive the running load 8. The inverter 23 converts the AC power generated by the motor generator 22 into DC power and outputs it to the bus 5, or converts the DC power supplied from the power storage device 3 via the bus 5 into AC power and supplies it to the motor generator 22, thereby rotating and driving the motor generator 22. The inverter 23 also controls the output power of the motor generator 22 during power generation based on the engine generator output command value output by the power supply optimization unit 1.

The power storage device 3 includes a battery (storage battery) 31, a DC/DC converter (DC-DC conversion device) 32, and a status monitoring circuit 33. The battery 31 is a secondary battery that charges and discharges, for example, a lithium ion battery. The DC/DC converter 32 converts the DC power supplied from the engine generator 2 via the bus 5 to a predetermined voltage to charge the battery 31, and converts the discharge power of the battery 31 to a predetermined voltage to output to the bus 5. The DC/DC converter 32 also controls the DC current output to the bus 5 (= the discharge current from the battery 31) and the DC current input from the bus 5 (= the charging current to the battery 31) based on the DC/DC converter command current value output by the power supply optimization unit 1. The state monitoring circuit 33 monitors the charge/discharge current, charge/discharge voltage, temperature, etc. of the battery 31, calculates the SOC (State of Charge; charging state or charging rate) of the battery 31, and outputs the result as the battery SOC (signal or information) to the power supply optimization unit 1.

The load 4 is an electrical load whose power consumption changes relatively sharply, such as a large auxiliary machine, a high-output actuator, or a mobile machine tool. A relatively sharp change in power consumption means, for example, that the capacity of the battery 31 selected to correspond to the peak power consumption of the load 4 is greater than the capacity of the battery 31 selected to correspond to the average power consumption of the load 4. The load 4 may be one electrical load or multiple electrical loads.

The voltage sensor 61 measures the voltage of the bus 5 near the load 4 and outputs the measurement result to the power supply optimization unit 1. The current sensor 62 measures the current supplied from the bus 5 to the load 4 and outputs the measurement result to the power supply optimization unit 1.

The power supply system 100 according to the first embodiment of the present disclosure shown in FIG. 1 controls the output power of the engine generator 2 so that the output power of the engine generator 2 is equal to the average load power consumed by the load 4, as shown in FIG. 2, by the control of the power supply optimization unit 1 described later. The power supply system 100 also controls the output power of the power storage device 3 so that the fluctuation from the average load power consumed by the load 4 is equal to the charge/discharge power from the power storage device 3. With this configuration, the engine generator 2 bears part of the power consumption of the load 4, so that the output power of the power storage device 3 can be suppressed and the battery 31 can be easily made smaller.

(Configuration of power supply optimization unit 1)
As shown in Fig. 3, the power supply optimization unit 1 includes, as a functional configuration formed by a combination of hardware and software, a load power average P load calculation unit 11, a correction amount ΔPbatt calculation unit 12, an engine generator output command value Pinv* calculation unit 13, and a DC/DC converter command current value calculation unit 14. Here, "" corresponds to an overline. In addition, in the specification, for ease of reading, the subscripts of each variable are written as full-width characters without changing the character size.

In this embodiment, the following power flow is considered for load power with abrupt fluctuations, with the aim of suppressing the output of the battery 31 and miniaturizing the storage device 3 in mind. As shown in FIG. 2, the load power is considered to be the sum of a fluctuation portion corresponding to a fluctuation faster than the response speed of the engine generator 2 and an average portion corresponding to the average power, and a situation is considered in which the engine generator 2 outputs the average amount of power. In this situation, the DC/DC converter 32 operates such that when the output of the engine generator 2 is larger than the load power, power is passed to the battery 31, and when the output is smaller, power is supplied from the battery 31 to the load 4, so that the battery 31 bears just the fluctuation amount of power. Therefore, if the DC/DC converter 32 operates as described above, the engine generator 2 is supplying power, and the output of the battery 31 is suppressed. To realize such a situation, a controller that determines the operation of the DC/DC converter 32 and the engine generator 2 is required. In this embodiment, this controller is the power supply optimization unit 1.

In the power supply system 100 of FIG. 1, the power supply optimization unit 1 calculates the command current value of the DC/DC converter and the output command value of the engine generator from the received bus voltage, load current, mode signal, and battery SOC, and transmits them to the DC/DC converter 32 and inverter 23 to control these devices. To obtain the bus voltage, load current, and mode signal, a voltage sensor 61 is installed on the bus 5, a current sensor 62 is installed between the bus and the auxiliary load, and a control device (not shown) is installed on the load 4. In addition, the SOC signal of the battery 31 is received from a status monitoring circuit 33 (which monitors the current, voltage, temperature, etc.) associated with the battery.

Here, the mode signal is a signal that indicates the state of the load 4, and takes one of four types: (ST1) stopped, (ST2) waiting, (ST3) standby, or (ST4) operating (Figure 7 explains each state using an example waveform of the auxiliary load power). For example, as summarized in Figure 8, stopped is a state in which the auxiliary equipment is completely stopped and no load power is generated. Waiting is a state in which load power is generated by auxiliary equipment excluding the cooling system. Standby is a state in which load power is generated by auxiliary equipment including the cooling system. Operating is a state in which the main auxiliary equipment is operating and load power with sudden fluctuations may be generated.

When the mode signal is "(ST4) in operation", the load 4 generates load power with abrupt fluctuations. In this situation, the power supply optimization unit 1 calculates a power value equivalent to the average of the load power from the bus voltage and load current signals, and transmits it to the inverter 23 as an output command value for the engine generator 2 (a specific calculation method for the engine generator output command value will be described later). In addition, a command current value is transmitted to the DC/DC converter 32 so that the bus voltage is discharged when it is below a certain reference voltage value, and charged when it is above it (for example, the characteristics in FIG. 4 can be used to generate such a command current). This means that when the engine generator 2 is larger than the load power, the bus voltage rises, so the battery 31 is charged, and when it is smaller, the bus voltage drops, so the battery 31 is discharged. Therefore, the DC/DC converter 32 appropriately controls the flow of power, so that the battery 31 bears the fluctuation of the load power and the engine generator 2 bears the average of the load power, that is, the DC/DC converter 32 realizes the expected operation of the two power sources, the battery 31 and the engine generator 2.

In addition, since the DC/DC converter 32 needs to operate to follow sudden load fluctuations, the DC/DC converter command current value calculation unit 14 in the power supply optimization unit 1 may be included in the (local) controller of the DC/DC converter 32. In that case, a voltage sensor is added to send the bus voltage to the local controller.

In this embodiment, the configuration that introduces the power supply optimization unit 1 allows the DC/DC converter 32 to control the flow of power for a load that fluctuates faster than the response speed of the engine generator 2, and allows the battery 31 and the engine generator 2 to perform the expected power supply operation. At the same time, since the engine generator 2 bears part of the load power, the battery output can be suppressed, leading to a reduction in the size of the storage device 3.

The DC/DC converter command current value calculation unit 14 calculates the DC/DC converter command current value, which is the command value of the output current when controlling the output power (charge/discharge power) of the DC/DC converter 32 based on the bus voltage, and outputs the calculated DC/DC converter command current value to the DC/DC converter 32. FIG. 4 shows an example of the correspondence between the bus voltage VBUS and the output current of the DC/DC converter 32. In the example shown in FIG. 4, discharging starts when the bus voltage is 620V or less, the discharge current increases as the voltage decreases, and the limit current during discharging is constant when the bus voltage is 600V or less. Charging starts when the bus voltage is 670V or more, the charge current increases as the voltage increases, and the limit current during charging is constant when the bus voltage is 700V or more.

When the output power of the engine generator 2 is controlled to match the average power consumption of the load 4 as shown in FIG. 2, the bus voltage changes according to the fluctuation in the power consumption of the load 4. Therefore, for example, as shown in FIG. 4, the DC/DC converter command current value calculation unit 14 controls the DC/DC converter command current value based on the bus voltage, so that the output power of the storage device 3 can be set to a value according to the fluctuation in the load power. Note that the output control of the DC/DC converter based on the bus voltage is described, for example, in Patent No. 3886940.

The load power average component P￣load calculation unit 11 calculates the average component of the load power as follows. That is, the load power average component P￣load calculation unit 11 calculates the average component of the load power as the time average of the product of the bus voltage and the load current acquired by the sensor, as shown in formula (1), with the intention of using the average component of the load power as the engine generator output command value.

Here, P load is the average load power (moving average value). VBUS is the bus voltage measured by the voltage sensor 61, and Iload is the load current measured by the current sensor 62.

When calculating the time average, the time length T is set to be sufficiently long with respect to the period of the (anticipated) load fluctuation so that if equation (1) is used directly as the output command value for the engine generator, the fluctuation in the output command value will be slower than the response speed of the engine generator.

Note that while equation (1) calculates the load power directly using the sensor value of the load current, as an alternative, the average of the supplied power may be calculated using the output current value (sensor value) of the inverter 23 or the DC/DC converter 32 to the bus 5, and this may be used as the average of the load power.

Here, Pinv is the output power of the inverter 23, and P_DCDC is the average output power of the DC/DC converter 32. Iinv is the inverter current, a value measured by a current sensor (not shown) in the inverter 23. IDCDC is the DC/DC converter current, a value measured by a current sensor (not shown) in the DC/DC converter 32.

The outputs of the inverter 23 and the DC/DC converter 32 may also be calculated using the following formula, which uses not only the sensor values but also command values and internal parameters of the controller.

ηmot is the motor efficiency (controller internal parameter), ηinv is the inverter efficiency (controller internal parameter), ω is the motor rotation speed (sensor value), and τ is the motor torque (command value). ηDCDC is the DC/DC converter efficiency, Vbatt is the battery voltage (sensor value), Kbatt is the conversion coefficient from SOC to power, and SOCbatt is the battery SOC (sensor value).

The sensor values, command values, and controller internal parameters used to calculate the various average outputs are summarized in Figure 5.

The correction amount ΔPbatt calculation unit 12 calculates the correction amount ΔPbatt for the error that occurs in the load power average portion calculated by the load power average portion P￣load calculation unit 11 as follows:

As described above, the load power average portion P load calculation unit 11 estimates the load power average portion using formula (1) (or formulas (2) to (4)), but due to the influence of sensor errors and delays in time averaging, deviations from the actual value may occur. Figure 6 shows, as an example, the behavior of the load power at the start of the load and the state in which deviations occur between the actual value and the estimated value due to delays in time averaging. In Figure 6, the actual value of the load power is shown by a solid line, the estimated value (calculated average load power) is shown by a thin dashed line, and the average power calculated for each state is shown by a thick dashed line as the actual average load power. In such a situation, the SOC of the battery 31 may fluctuate and deviate from the specified value. Therefore, when calculating the output command value of the engine generator, the engine generator output command value Pinv* calculation unit 13, which will be described later, adds a correction amount to the average load power as shown in formula (5).

Here, Pinv* is the engine generator output command value, and ΔPbatt is the correction amount.

The correction amount ΔPbatt is set according to the following concept. Now, assume that the system design requires that the amount of battery SOC to be restored per unit time when the SOC of battery 31 is "low" or "high." In this case, the design value of the correction amount is determined using the relationship between the change in SOC and the battery's input (output) power, shown in equation (6) (the voltage of battery 31 is assumed to be constant).

Here, ΔSOC is the change in SOC, Vbatt is the battery voltage, Abatt is the current capacity of battery 31, and t is time.

For example, if the battery voltage is 300 [V] and the battery current capacity is 80 [Ah], and you want to increase or decrease the SOC by 0.025% in one second, the correction amount will be the following value.

The correction amount calculated above is applied when the battery SOC is in a "low" or "high" state, and if the correction is doubled when the battery SOC deviates from this range, the correction amount can be taken as shown in FIG. 10. FIG. 10 shows a table 121 that defines the correspondence between the SOC of the battery 31 and the correction amount ΔPbatt. The correction amount ΔPbatt calculation unit 12 calculates the correction amount ΔPbatt using, for example, the table 121 shown in FIG. 10.

The engine generator output command value Pinv* calculation unit 13 calculates the engine generator output command value Pinv* using the above-mentioned formula (5) based on the load power average portion P￣load calculated by the load power average portion P￣load calculation unit 11 and the positive amount ΔPbatt calculated by the correction amount ΔPbatt calculation unit 12, and outputs the calculated value to the inverter 23.

However, if we try to deal with this using equation (5), there is a possibility that the power supply to the load will be momentarily insufficient in the following situation. Consider a situation in which a large load fluctuation occurs immediately after switching from standby state to large auxiliary operation state, as shown in Figure 6. In this case, since the average power calculated by time averaging is small, the output of the engine generator 2 also becomes small, and the power borne by the battery 31 exceeds the maximum allowable output, which may result in an insufficient power supply to the load.

To avoid this situation, the engine generator output command value Pinv* calculation unit 13 secures the power supply to the load as follows. For example, immediately after the transition from the standby state to the large auxiliary operation state, the output command value Pinv* of the engine generator 2 is given by a value (fixed value) Pinv_const that can sufficiently handle instantaneous high load power when added to the output of the battery 31 as shown in FIG. 9, instead of by equation (5). At the same time, the load power average P￣load calculation unit 11 performs the calculation of equation (1), and when the value becomes equal to or greater than Pinv_const, the command value of the engine generator is given by equation (5). As described above, when the transition is made to the large auxiliary operation state, the power supply to the load is secured by giving a fixed value without using equation (5) from the beginning. Note that, for example, even when changing from the standby state to the standby state, the engine generator output command value Pinv* may be set to the fixed value Pinv_const. By introducing this fixed value Pinv_const, large changes in charging and discharging current can be suppressed, which allows for the miniaturization of the battery.

When the battery SOC is high and the average load power is small, the engine generator output command value Pinv* calculation unit 13 may cause the engine generator to operate in a powered manner, with the command power for the engine generator being negative. To avoid this situation, a limit is set on the engine generator output command value so that the engine generator output is a value equal to or greater than 0.

The flow of the engine generator output command value Pinv* calculation unit 13's determination of the engine generator output command value is shown in Figure 11.

Figure 11 shows the flow of processing by the engine generator output command value Pinv* calculation unit 13. The processing shown in Figure 11 is executed repeatedly at a predetermined cycle. In the processing shown in Figure 11, first, when a predetermined condition is satisfied, for example, when the mode signal first indicates a change in state, the engine generator output command value Pinv* calculation unit 13 sets the engine generator output command value Pinv* to a predetermined fixed value Pinv_const (step S21). Next, the engine generator output command value Pinv* calculation unit 13 determines whether P ￣ load + ΔPbatt is equal to or greater than the fixed value Pinv_const (or whether P ￣ load + ΔPbatt is within a predetermined range from the fixed value Pinv_const) (step S22). If P load + ΔPbatt is equal to or greater than the fixed value Pinv_const (or if P load + ΔPbatt is within a predetermined range from the fixed value Pinv_const) (step S22: YES), the engine generator output command value Pinv* calculation unit 13 sets the engine generator output command value Pinv* to P load + ΔPbatt (step S23). Next, the engine generator output command value Pinv* calculation unit 13 determines whether P load + ΔPbatt is smaller than 0 (step S24). If P load + ΔPbatt is smaller than 0 (step S24: YES), the engine generator output command value Pinv* calculation unit 13 sets the engine generator output command value Pinv* to 0 (step S25). If step S22 is "No", if step S24 is "No", or if step S25 is executed, the engine generator output command value Pinv* calculation unit 13 ends the process shown in FIG. 11.

(Operation of power supply optimization unit 1)
Fig. 12 shows an example of the operation of the power supply optimization unit 1. The process shown in Fig. 12 is repeatedly executed at a predetermined cycle. In the process shown in Fig. 12, first, the power supply optimization unit 1 acquires various information such as the bus voltage, the load current, the mode signal, the battery SOC, etc. (step S1). Next, the power supply optimization unit 1 determines an output command value for the engine generator (step S2). The power supply optimization unit 1 determines a command current value for the DC/DC converter (step S3). Next, the power supply optimization unit 1 outputs the determined values (step S4) and ends the process shown in Fig. 12.

(Actions and Effects of the First Embodiment)
According to this embodiment, the engine generator covers part of the load power that is accompanied by abrupt load fluctuations, thereby suppressing the output of the battery and leading to a reduction in the size of the battery.

Second Embodiment
(Power supply system configuration)
Hereinafter, a control device, a control method, and a power supply system according to a second embodiment of the present disclosure will be described with reference to Figs. 13 to 23. Fig. 13 is a diagram showing a configuration example of a power supply system according to a second embodiment of the present disclosure. Fig. 14 is a block diagram showing a configuration example of a power supply optimization unit according to a second embodiment of the present disclosure. Fig. 15 is a block diagram showing a configuration example of a power supply optimization unit according to a second embodiment of the present disclosure. Figs. 16 to 23 are schematic diagrams for explaining an operation example of the power supply optimization unit according to the second embodiment of the present disclosure. Note that the same reference numerals are used to designate the same configuration as in the first embodiment, and the description will be omitted as appropriate.

As shown in FIG. 13, the power supply system 100a of the second embodiment is the power supply system 100 of the first embodiment shown in FIG. 1, in which the power storage device 3 is replaced with a power storage device 3a in which a battery 31 and a capacitor 34 are connected in parallel. Note that the power supply optimization unit 1a outputs a battery DC/DC converter command current value to the DC/DC converter 32 instead of the DC/DC converter command current value.

The power supply system 100a according to the second embodiment of the present disclosure shown in FIG. 13 is configured as an on-board power supply system mounted on a parallel hybrid system vehicle, similar to the first embodiment. The power supply system 100a shown in FIG. 13 includes a power supply optimization unit 1a as an example of a configuration of a control device according to the present disclosure, an engine generator 2, a power storage device 3a, a load 4, a voltage sensor 61, and a current sensor 62.

The power storage device 3a includes a battery 31, a DC/DC converter 32, a status monitoring circuit 33, a capacitor 34, a DC/DC converter 35, and a status monitoring circuit 36.

The capacitor 34 is a storage device such as an electric double layer capacitor. The DC/DC converter 35 converts the DC power supplied from the engine generator 2 via the bus 5 to a predetermined voltage to charge the capacitor 34, and converts the discharge power of the capacitor 34 to a predetermined voltage to output to the bus 5. The DC/DC converter 35 also controls the DC current (= discharge current from the capacitor 34) output to the bus 5 and the DC current (= charge current to the capacitor 34) input from the bus 5 based on the capacitor DC/DC converter command current value output by the power supply optimization unit 1a. The state monitoring circuit 36 monitors the charge/discharge current, charge/discharge voltage, temperature, etc. of the capacitor 34, calculates the SOC of the capacitor 34, and outputs the calculated result to the power supply optimization unit 1a as the capacitor SOC (signal or information).

(Configuration of power supply optimization unit 1a)
As shown in FIG. 14 , the power supply optimization unit 1a has, as its functional configuration, a load power average portion P_load calculation unit 11, a correction amount ΔPbatt calculation unit 12a, an engine generator output command value Pinv* calculation unit 13, a battery DC/DC converter command current value calculation unit 15, a capacitor DC/DC converter command current value calculation unit 16, and a correction amount Δk calculation unit 17.

The power supply system 100a in FIG. 13 has three types of power supplies: the engine generator 2, the battery 31, and the capacitor 34. The expected operation of each power supply will be described. First, the engine generator 2 outputs power equivalent to the average load power, as in the first embodiment. Next, the battery 31 and the capacitor 34 are charged and discharged so that the sum of the outputs of the battery 31 and the capacitor 34 corresponds to the fluctuation in the load power, since the engine generator 2 outputs the average load power. In addition, in order to miniaturize the power storage device 3a, the output ratio of the capacitor 34 to the fluctuation in the load power is increased (within the output possible range of the capacitor).

To realize the operation of each of the above power sources, a controller called the power supply optimization unit 1a is introduced, as in the first embodiment (see FIG. 13). The difference from the first embodiment is that a command current is added to the capacitor DC/DC converter to control the capacitor DC/DC converter. In addition, the capacitor SOC signal used to calculate the output command value of the engine generator 2 is sent from a state monitoring circuit 36 associated with the capacitor (which monitors the current, voltage, temperature, etc.).

Now, assume that the engine generator 2 is given an output command value of a power value equivalent to the average load power, and that the engine generator 2 is supplying power equivalent to the average load power. At this time, the battery 31 and capacitor 34 should be able to operate to cover the fluctuating power, but unless the input and output power of both are appropriately controlled, the power covered by the battery 31 cannot be reduced, and this does not lead to a reduction in the size of the power storage device 3a. For this reason, the power supply optimization unit 1a has the control logic of FIG. 15 to adjust the output power ratio between the battery 31 and the capacitor 34 and reduce the power covered by the battery.

Figure 15 shows an example of the configuration of the battery DC/DC converter command current value calculation unit 15, the capacitor DC/DC converter command current value calculation unit 16, and the correction amount Δk calculation unit 17. The correction amount Δk calculation unit 17 receives the battery SOC, the capacitor SOC, the bus voltage, and the output power of the power storage device 3a as input, calculates the correction amount Δk using a correction amount Δk map 171, and outputs it.

The battery DC/DC converter command current value calculation unit 15 includes a command current generation map 151, a multiplier 152, a k1 characteristic map 153, an adder 154, and a multiplier 155. The command current generation map 151 is a map that converts the bus voltage into a battery DC/DC converter command current value (output current of the power storage device 3a) with the characteristics shown in FIG. 2, for example. The multiplier 152 multiplies the output current of the power storage device 3a by the bus voltage to calculate the output power of the power storage device 3a. The k1 characteristic map 153 outputs a coefficient k1 based on the output power. The adder 154 adds the coefficient k1 and a correction amount Δk and outputs the result. The multiplier 155 multiplies the output current of the power storage device 3a by a value obtained by adding the coefficient k1 and the correction amount Δk, and calculates and outputs the battery DC/DC converter command current value.

On the other hand, the capacitor DC/DC converter command current value calculation unit 16 includes a command current generation map 161, a multiplier 162, a k2 characteristic map 163, an adder 164, and a multiplier 165. The command current generation map 161 is a map with the same characteristics as the command current generation map 151, and is a map that converts the bus voltage into a capacitor DC/DC converter command current value (output current of the power storage device 3a) with the characteristics shown in FIG. 2, for example. The multiplier 162 multiplies the output current of the power storage device 3a by the bus voltage to calculate the output power of the power storage device 3a. The k2 characteristic map 163 outputs a coefficient k2 based on the output power. The adder 164 subtracts a correction amount Δk from the coefficient k2 and outputs it. The multiplier 165 multiplies the output current of the power storage device 3a by a value obtained by subtracting the correction amount Δk from the coefficient k2, and calculates and outputs the capacitor DC/DC converter command current value.

The command current calculation units 15 and 16 of the DC/DC converters for the battery and capacitor both have common command current generation characteristics (command current generation maps 151 and 161) (for example, a map as shown in FIG. 2), and the command current, which is the output signal, is multiplied by coefficients k1 and k2 in multipliers 155 and 165. Since the same bus voltage is referenced when generating the command current, these DC/DC converters charge and discharge so that the output power ratio is exactly k1:k2. k1 and k2 are functions of the sum of the output power of the battery 31 and the capacitor 34 (hereinafter referred to as P_bc), and when P_bc is equal to or less than the maximum allowable output value of the capacitor 34, k2 is set to be sufficiently larger than k1 (for example, k1=0.1, k2=0.9) so that the capacitor 34 bears almost all of the charge and discharge power.

Also, if P_bc is equal to or greater than the maximum allowable output of capacitor 34, k1 and k2 are set to gradually increase the burden on battery 31 so that the output of capacitor 34 becomes exactly the maximum allowable output value (this will be described later, but the rough shape of the graph will be as shown in Figure 16).

The logic shown in FIG. 15 is provided in the power supply optimization unit 1a, but in order to increase the response speed to follow sudden load fluctuations, the command current calculation unit for the DC/DC converters of the capacitor 34 and the battery 31 may be provided in the (local) controllers of the capacitor 34 and the battery 31. In that case, a voltage sensor for transmitting the bus voltage is added to each local controller.

Here, in the above k1 and k2 settings, the charging and discharging of the capacitor is prioritized, but in this situation, the SOC of the capacitor is sacrificed. For example, if the output command value of the engine generator becomes lower than the average of the actual load power due to the influence of the sensor error or the inherent nature of the calculation algorithm, the battery 31 and the capacitor 34 are charged and discharged, but the discharge rate is large. In addition, since the output power ratio of the capacitor 34 to the battery 31 is large, the discharge amount of the capacitor 34 increases and the SOC decreases. In order to avoid such a situation in which the SOC of the capacitor 34 is sacrificed, the correction amount Δk calculated by the correction amount Δk calculation unit 17 according to the SOC of the battery 31 and the capacitor 34 is added to or subtracted from the values of k1 and k2 to change the output power ratio. The power supply system 100a in FIG. 13 basically operates to prioritize the charging and discharging of the capacitor 34, but in the following situations (1) and (2), it is desired to prioritize the charging and discharging of the battery 31.

(1) When charging (bus voltage is equal to or higher than the reference voltage value), the SOC of capacitor 34 is high and the SOC of battery 31 is low.

(2) When discharging (bus voltage is below the reference voltage value), the SOC of capacitor 34 is low and the SOC 31 of the battery is high.

Therefore, the bus voltage, battery SOC, and capacitor SOC are referenced, and if the situation corresponds to (1) or (2), the coefficients k1 and k2 are changed to k1+Δk and k2-Δk by adding or subtracting a correction amount Δk. Since charging and discharging of the battery 31 is prioritized, the value of the correction amount Δk is set so that k1+Δk is sufficiently large compared to k2-Δk (for example, k1+Δk=0.9, k2-Δk=0.1). To calculate this correction amount Δk, information on the SOC of the battery 31 and capacitor 34 is required, and these signals are sent from status monitoring circuits 33 and 36 (which monitor the current, voltage, temperature, etc.) associated with the battery 31 and capacitor 34, respectively.

The specific method of taking the coefficients k1, k2 and the correction amount Δk can be, for example, as follows. Now, consider the allocation of the load power to various power sources (engine generator, battery, capacitor) as shown in FIG. 16. FIG. 16 includes the output of the engine generator, and in order to focus on the allocation of the battery 31 and the capacitor 34, the power allocation obtained by subtracting the output of the engine generator from FIG. 16 is shown in FIG. 17. FIG. 17 means that when the load power is below a certain value, the load power is almost entirely borne by the capacitor 34, and when the load power exceeds that value, the load power is also supplied from the battery 31. By allocating the load power in this way, the output of the battery 31 is reduced. The vertical axis of FIG. 17 is the total output of the battery 31 and the capacitor 34, and the output of each is expressed as a ratio to the total output as shown in FIG. 16. In other words, since it is desired to operate the output power of the battery 31 and the capacitor 35 to be at this ratio, k1 and k2 can be given in the form of a graph in FIG. 18. The k1 characteristic map 153 and the k2 characteristic map 163 in FIG. 15 can be defined as the characteristics in FIG. 18.

In FIG. 17, the battery output power is not set to 0 over the entire range of the total output power of the power storage device because keeping the DC/DC converter 32 in operation at all times when the power storage device 3a is in operation makes it easier to suppress abrupt changes in current from (to) the battery 31 when the DC/DC converter 32 is started up.

Next, a specific method for setting the correction amount Δk will be described. In the second embodiment, it is desirable to prioritize charging and discharging the battery 31 in the following situations (1) and (2).

(1) When charging (bus voltage is above the reference voltage value), the capacitor SOC is high and the battery SOC is low.

(2) When discharging (bus voltage is below the reference voltage value), the capacitor SOC is low and the battery SOC is high.

The above is a qualitative expression, and the reference voltage value and the battery capacitor SOC threshold value for the situations (1) and (2) are summarized in Figure 20. Figure 20 shows an example of the configuration of map 171 of the correction amount Δk shown in Figure 15. Figure 20 shows an example of setting the correction amount Δk when the reference voltage value at which the battery charging and discharging operations are switched from Figure 4 is set to 645 [V]. Map 171 of the correction amount Δk shown in Figure 20 includes map 172 during charging and map 173 during discharging. The coefficients (k1, k2) indicate that no correction is made using the correction amount Δk when they are (0, 0), and that correction is made using the correction amount Δk when they are (Δk, -Δk).

The correction amount Δk is calculated as shown in Figure 19 according to the load power when the battery 31 is to bear almost all of the charge and discharge load in a situation where a correction amount is added (Figure 19 shows an example where k1+Δ:k2-Δ=0.9:0.1).

The SOC of the battery 31 or the capacitor 34 is controlled so as not to deviate from the "low" or "high" range in Figure 20.

By using the correction amount Δk, it is possible to control the output power of the battery and the capacitor at an expected ratio. This makes the power storage device smaller than a single battery.

In addition, in the second embodiment, the correction amount ΔPbatt calculation unit 12a calculates the correction amount ΔPbatt as follows. Below, we will explain how to obtain the correction amount ΔPbatt when the capacitor 34 is also used as the storage device 3a.

When the capacitor 34 is also used as in this embodiment, the correction amount ΔPbatt is determined by referring to the SOC of both the battery 31 and the capacitor 34. Specifically, it is set as shown in map 121a in FIG. 21. The idea behind setting it as shown in FIG. 21 will be explained below.

When considering setting the correction amount ΔPbatt, consider the following four situations:

(1) When the battery SOC is high and the capacitor SOC is medium.
(2) When the battery SOC is low and the capacitor SOC is medium.
(3) When the capacitor SOC is high regardless of the battery SOC state.
(4) When the capacitor SOC is low, regardless of the battery SOC state.

In the situation (1), a negative value is set as the correction amount ΔPbatt to reduce the output of the engine generator 2 in order to lower the SOC of the battery 31. At this time, the output of the engine generator 2 is smaller than the average load power, and the bus voltage is equal to or lower than the reference voltage. In this case, the coefficients k1 and k2 introduced in this embodiment are corrected (see FIG. 20), and charging and discharging of the battery 31 are prioritized. As a result, the discharge of the battery 31 progresses, and the SOC of the battery 31 becomes medium. Therefore, the SOC of both the battery 31 and the capacitor 34 becomes medium (no correction is required). In the situation (2), if a positive value is set as the correction amount Δk based on the same concept, the output of the engine generator 2 increases, charging of the battery 31 progresses, and the SOC of the battery 31 becomes medium.

In the situation (3), a negative value is set as the correction amount ΔPbatt to reduce the output of the engine generator 2 in order to lower the SOC of the capacitor 34. At this time, the output of the engine generator 2 is smaller than the average load power, and the bus voltage is equal to or lower than the reference voltage. In this case, the coefficients k1 and k2 introduced in this embodiment are not corrected (see FIG. 20), and the charging and discharging of the capacitor are prioritized. Therefore, the discharging of the capacitor 34 progresses, and the SOC of the capacitor 34 becomes medium. In the situation (4), if a positive value is set as the correction amount Δk based on the same idea, the output of the engine generator 2 increases, so that the charging of the capacitor 34 progresses, and the SOC of the capacitor 34 becomes medium. Thus, when the correction amount ΔPbatt is added as described above in the situations (3) and (4), the SOC of (1) and (2) or both the battery and the capacitor becomes medium. When transitioning to situations (1) and (2), the SOC of both the battery and the capacitor will be at a medium level (no correction required) by adding the correction amount ΔPbatt as described above.

From the above, by adding a correction amount ΔPbatt according to the state of the SOC of the battery and capacitor, as shown in Figure 21, it is possible to restore the SOC of the battery and capacitor to a moderate level.

In the case of situations (3) and (4), since the purpose is to increase or decrease the SOC of the capacitor, the specific correction amount ΔPbatt value may be calculated by replacing the battery voltage and current capacity in equation (6) with the capacitor voltage and current capacity.

(Actions and Effects of the Second Embodiment)
With the above-mentioned configuration, the engine generator 2 outputs power to cover the average load power, while the battery 31 and the capacitor 34 output power to cover the fluctuating power. In addition, the DC/DC converter operation of the battery 31 and the capacitor 34 allows the output of the battery 31 to be suppressed, since the power shared by the capacitor 34 is increased while following steep load fluctuations.

In this embodiment, the power storage device is configured not only with a battery, but also with a high output density power storage device (for example, an EDLC (electric double layer capacitor)) to reduce the power burden on the battery. Figure 22 is a diagram comparing the electrical characteristics of a battery and a capacitor. Compared to a battery, a capacitor has a lower energy density but a higher output density, so using a capacitor leads to smaller size. On the other hand, as shown in Figure 23, a certain degree of continuity of power supply to the load is required, which cannot be achieved by a capacitor alone, and a battery with a high energy density is required with a certain capacity. In this embodiment, the capacity of the power storage device is reduced by using a battery and a capacitor in combination.

According to this embodiment, it is possible to control the output power of the battery and the capacitor at an expected ratio. This also allows the power storage device to be made smaller than a single battery.

(Action and Effect)
According to the control device, control method, and power supply system of the present disclosure, the storage battery can be made smaller.

Other Embodiments
Although the embodiments of the present disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like that do not depart from the gist of the present disclosure are also included.

Computer Configuration
FIG. 24 is a schematic block diagram illustrating a configuration of a computer according to at least one embodiment.
The computer 90 comprises a processor 91 , a main memory 92 , a storage 93 , and an interface 94 .
The above-mentioned power supply optimization units 1 and 1a are implemented in a computer 90. The operations of the above-mentioned processing units are stored in the form of a program in a storage 93. The processor 91 reads the program from the storage 93, loads it in the main memory 92, and executes the above-mentioned processing in accordance with the program. The processor 91 also secures storage areas in the main memory 92 corresponding to the above-mentioned storage units in accordance with the program.

The program may be for realizing some of the functions to be performed by the computer 90. For example, the program may be for realizing the functions by combining with other programs already stored in the storage, or by combining with other programs implemented in other devices. In other embodiments, the computer may include a custom LSI (Large Scale Integrated Circuit) such as a PLD (Programmable Logic Device) in addition to or instead of the above configuration. Examples of PLDs include PAL (Programmable Array Logic), GAL (Generic Array Logic), CPLD (Complex Programmable Logic Device), FPGA (Field Programmable Gate Array), etc. In this case, some or all of the functions realized by the processor may be realized by the integrated circuit.

Examples of storage 93 include HDD (Hard Disk Drive), SSD (Solid State Drive), magnetic disk, magneto-optical disk, CD-ROM (Compact Disc Read Only Memory), DVD-ROM (Digital Versatile Disc Read Only Memory), semiconductor memory, etc. Storage 93 may be an internal medium directly connected to the bus of computer 90, or an external medium connected to computer 90 via interface 94 or a communication line. In addition, when this program is distributed to computer 90 via a communication line, computer 90 that receives the program may expand the program in main memory 92 and execute the above-mentioned processing. In at least one embodiment, storage 93 is a non-transitory tangible storage medium.

<Additional Notes>
The power supply optimization units 1 and 1a described in each embodiment can be understood, for example, as follows.

(1) The power supply optimization units 1 and 1a (control devices) according to the first aspect are control devices for power supply systems 100, 100a that include a power generation device (engine generator 2) that generates electricity using a rotating electric machine, a power storage device 3, 3a that charges and discharges electricity, and an electric load 4 that is driven by the power supplied from the power generation device and the power storage device, and the control device controls the output power of the power generation device based on the average portion of the load power of the electric load. According to this aspect and each of the following aspects, the average portion can be covered by the output of the power generation device, and therefore the power storage device can be easily miniaturized.

(2) The power supply optimization units 1 and 1a (control devices) according to the second aspect are the power supply optimization units 1 and 1a (control devices) of (1), and the control devices correct the control of the output power of the power generation device according to the state of charge (SOC) of the power storage device. According to this aspect, it becomes easy to maintain the state of charge within a certain range.

(3) The power supply optimization units 1 and 1a (control devices) according to a third aspect are the power supply optimization units 1 and 1a (control devices) according to (1) or (2), in which the electrical load operates in at least two different predetermined states, and when the state changes, the control device controls the output power of the power generation device to a predetermined power, and then controls the output power of the power generation device based on the average portion. According to this aspect, it is possible to prevent abrupt changes in charging and discharging current from occurring when the operating state changes.

(4) The power supply optimization unit 1a (control device) according to the fourth aspect is the power supply optimization unit 1a (control device) of (1) or (2), in which the power storage device 3a has a storage battery 31 and a capacitor 34, and the control device controls the ratio of the charge/discharge current of the storage battery to the charge/discharge current of the capacitor so that the charge/discharge current of the capacitor exceeds the charge/discharge current of the storage battery when the charge/discharge current of the capacitor has a margin relative to the allowable charge/discharge current.

(5) The power supply optimization unit 1a (control device) according to the fifth aspect is the power supply optimization unit 1a (control device) of (4), and the control device corrects the ratio according to the charging state of the storage battery and the charging state of the capacitor.

100, 100a... Power supply system 1, 1a... Power supply optimization unit 2... Engine generator (power generation device)
3, 3a...electric storage device 4...load (electric load)
31...Battery (storage battery)
34...Capacitor

Claims (6)

A control device for a power supply system including a power generation device that generates electricity using a rotating electric machine, a power storage device that charges and discharges electricity, and an electric load that is driven by electric power supplied from the power generation device and the power storage device,
the control device controls the output power of the power generation device based on an average portion of the load power of the electric load;
the electrical load operates under at least two different predetermined conditions;
When the state changes, the control device controls the output power of the power generation device so that the output power becomes a predetermined fixed value corresponding to the state, and then, from a point in time when the average portion of the load power becomes equal to or greater than the predetermined fixed value, controls the output power of the power generation device to the average portion of the load power.
Control device. The control device according to claim 1 , wherein the control device corrects control of the output power of the power generation device in accordance with a state of charge of the power storage device. the power storage device includes a storage battery and a capacitor,
When the charge/discharge current of the capacitor has a margin relative to an allowable charge/discharge current, the control device controls a ratio of the charge/discharge current of the storage battery to the charge/discharge current of the capacitor so that the charge/discharge current of the capacitor exceeds the charge/discharge current of the storage battery.
The control device according to claim 1 or 2 . The control device corrects the ratio according to a charging state of the storage battery and a charging state of the capacitor.
The control device according to claim 3 . A control method for a power supply system including a power generation device that generates electricity using a rotating electric machine, a power storage device that charges and discharges electricity, and an electric load that is driven by electric power supplied from the power generation device and the power storage device, comprising:
controlling the output power of the power generation device based on an average portion of the load power of the electrical load;
the electrical load operates under at least two different predetermined conditions;
In the step of controlling the output power of the power generation device, when the state changes, the output power of the power generation device is controlled so as to become a predetermined fixed value of power corresponding to the state, and then, from a point in time when the average portion of the load power becomes equal to or greater than the predetermined fixed value, the output power of the power generation device is controlled at the average portion of the load power.
Control methods. A power generation device that generates power using a rotating electric machine;
A storage device that charges and discharges electricity;
an electric load driven by electric power supplied from the power generation device and the power storage device;
a control device that controls the output power of the power generation device based on an average load power of the electric load;
the electrical load operates under at least two different predetermined conditions;
When the state changes, the control device controls the output power of the power generation device so that the output power becomes a predetermined fixed value corresponding to the state, and then, from a point in time when the average portion of the load power becomes equal to or greater than the predetermined fixed value, controls the output power of the power generation device to the average portion of the load power.
Power supply system.

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