Hybrid power supply system of ultra-low frequency variable frequency pulse load and capacity configuration and power control method thereof

Abstract

The application discloses a hybrid power supply system of an ultra-low frequency variable frequency pulse load and a capacity configuration and power control method thereof, and the hybrid power supply system comprises a battery, a capacitor, a DC / DC converter and the ultra-low frequency variable frequency pulse load. The ultra-low frequency variable frequency pulse load is directly connected to a battery output end, and the capacitor is connected in parallel to the battery output end after passing through the DC / DC converter, and the battery and the capacitor supply power to the ultra-low frequency variable frequency pulse load together. The application establishes the relationship between the system volume and the proportion of the pulse power borne by the battery and the capacitor, and gives a capacity optimization matching design method of the battery and the capacitor, so that the total volume of the hybrid power supply system can be guaranteed to be minimum; and the power control method of the hybrid power supply system is proposed on the basis, so that the output current i o is rapidly and well tracked oref , and the purpose of providing the required low-frequency pulse power by the capacitor is achieved, and the good power supply capability of the hybrid power supply system to the low-frequency pulse load is further guaranteed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pulse load power supply, hybrid power supply and special power supply, in particular to a capacity optimization configuration and control method of a hybrid power supply system suitable for a pulse load with ultra-low frequency variable frequency. BACKGROUND

[0002] With the increasing application of multi-source hybrid power supply technology to large vehicles, such as aircraft, ships, rockets and other fields, there are many low-frequency pulse loads in these systems, such as solid-state radars, electromagnetic guns, etc., and the power characteristics required by these loads will seriously affect the power supply quality and reliability of the system. How to reliably power the variable frequency low-frequency high-power pulse load and reduce its impact on the power supply system is a key problem to ensure the reliable operation of the power supply system.

[0003] Increasing the power supply capacity of the system and adding energy storage units with fast response characteristics are widely used in power supply systems with pulse loads, so that the drop of the bus voltage of the hybrid power supply system under the impact of the pulse load is within the allowable range. Since increasing the power supply capacity of the system will significantly increase the overall volume of the power supply system, this method is usually applied to ground systems, such as radar stations. In large electrified vehicles, energy storage units are usually used to absorb pulse power to reduce the system volume, such as using batteries, capacitors, flywheel energy storage, etc. For high-power pulse loads, if only batteries are used to absorb pulse power, the battery life will be significantly reduced due to long-time high-current discharge, and the capacity of the battery will increase significantly with the increase of the discharge current. If a capacitor is directly connected to the bus, since the allowable drop range of the bus voltage is small, in order to cope with the impact of the high-power pulse load on the bus voltage, the capacity of the capacitor is usually large. In order to reduce the volume of the pulse power absorption module, some people have proposed using a converter to increase the fluctuation range of the capacitor voltage, so that more energy is released under the same capacity, thereby reducing the volume of the capacitor and minimizing the overall volume of the power supply system. This is of great significance to micro-grid systems with pulse loads that have strict requirements on system volume and weight, such as aircraft and rockets.

[0004] Currently, in order to solve the miniaturization problem of pulse load power supply systems, many academic papers and patents have been studied and corresponding solutions have been proposed, such as:

[0005] 1、Xinze. Huang et al. published "A Pulsed Power Supply Adopting Active Capacitor Converter for Low-Voltage and Low-Frequency Pulsed Loads" in IEEE Transactions on Power Electronics, 2018: 9219-9230, which significantly increases the variation range of the capacitor voltage by introducing an active capacitor converter, so that the capacitor capacity is significantly reduced under the condition of absorbing the same pulse power, and the power density of the power supply system is significantly improved. The control method increases the feedforward control on the basis of the traditional double-closed-loop control, so that the drop of the bus voltage is further reduced. However, the bidirectional Buck-Boost converter used in it needs to ensure that the capacitor voltage is always higher than the bus voltage to work normally, and the control method needs to use a filter to generate a control reference. For ultra-low frequency wide frequency (such as 0.5Hz-200Hz) and variable frequency pulse load, this method is not applicable. It will cause the low-pass filter to be difficult to design, the distortion is large, and the response speed is slow.

[0006] Yang Ping et al. published "A High-Power Pulsed Load Power Supply for Suppressing Bus Current Spikes" patent, which increases two structurally identical first inductance branches and second inductance branches in reverse parallel, solves the problem of bus current spikes caused by different inductance current directions and inability to mutate when the pulse load power supply is lightly loaded / heavily loaded, and can adapt to arbitrary changes in pulse power and frequency. The control method proposed in it also uses a filter to generate a control reference, which is not suitable for ultra-low frequency variable frequency pulse load. SUMMARY

[0007] Therefore, the purpose of the present application is to provide a hybrid power supply system capacity configuration and control method suitable for ultra-low frequency variable frequency pulse load, to solve the technical problems of reliable power supply for variable frequency low frequency high power pulse load, reducing the impact of ultra-low frequency variable frequency pulse load on the power supply system, ensuring the reliable operation of the power supply system and reducing the size of the hybrid power supply system.

[0008] The hybrid power supply system for ultra-low frequency variable frequency pulse load of the present application comprises a battery and an ultra-low frequency variable frequency pulse load connected to the output end of the battery.

[0009] The hybrid power supply system for ultra-low frequency variable frequency pulse load of the present application further comprises a capacitor, which is connected in parallel to the output end of the battery through a DC / DC converter.

[0010] The hybrid power supply system for ultra-low frequency variable frequency pulse load of the present application further comprises a current reference generating unit, which is used to detect the current of the ultra-low frequency variable frequency pulse load iload and the voltage of the capacitor V C After combining the power flow requirements and the proportion of pulse power that the capacitor should bear, the output current reference signal of the DC / DC converter is generated. i oref ;

[0011] The hybrid power supply system for ultra-low frequency variable pulse load of the present invention also includes a PI regulator, which is used to adjust the output current reference signal of the DC / DC converter. i oref With DC / DC converter output current i o difference;

[0012] The hybrid power supply system for ultra-low frequency variable frequency pulse load of the present invention further includes a PWM and a drive circuit. The PWM and drive circuit is used to generate a drive signal to control the DC / DC converter based on the output signal of the PI regulator, so as to ensure the output current of the DC / DC converter. i o For the output current reference signal i oref To enable fast and efficient tracking.

[0013] This invention relates to a capacity configuration method for a hybrid power supply system based on an ultra-low frequency variable frequency pulse load, comprising:

[0014] Let the power distribution ratio of the pulse power between the capacitor and the battery be respectively. λ CC and λ BAT Both satisfy λ BAT + λ CC =1, λ BAT (0, 1), λ CC (0, 1), when the energy absorbed by the ultra-low frequency inverter pulse load from the hybrid power supply system within one pulse cycle is W At that time, the minimum capacitance of the capacitor is determined as follows:

[0015]

[0016] in V Cmax This is the upper limit of the capacitor's voltage. V Cmin The lower limit of the capacitor's voltage is the voltage limit when the upper limit of the capacitor's voltage is... V CmaxAfter determination, the volume of the capacitor Vol CC With the capacitance Q C Satisfy Vol CC = k CC Q C Wherein k CC Is a constant coefficient, related to the model of the capacitor;

[0017] Let the energy consumed by the hybrid power supply system throughout the working time period be W total The rated current when the load is pulseless is i n Then the minimum capacity of the battery is determined as:

[0018]

[0019] Wherein Q BAT1min Satisfy:

[0020]

[0021] Wherein V BAT Is the platform voltage of the battery, that is Q BAT1min Can guarantee to provide the energy consumed throughout the working time period;

[0022] Q BAT2min Satisfy:

[0023]

[0024] Wherein k r Is a constant related to the internal resistance of the battery, Δ V max Is the maximum allowable drop value of the bus voltage, Q BAT2min Can guarantee that the output voltage is not lower than i n Under the condition of the rated current V bus - Δ V max Wherein V bus Is the bus voltage, that is i n r BAT ≤ Δ Vmax , r BAT is the internal resistance of the battery; k r with r BAT , the capacity Q BAT , the output voltage V BAT satisfies the following relationship:

[0025]

[0026] Q BAT3min satisfies:

[0027]

[0028] wherein t p is the pulse width, Q BAT3min ensures that the battery provides λ BAT times the pulse current, i.e. i p V bus t p = Wλ BAT = W (1- λ CC ), wherein i p is the output current of the battery at this time, and ensures that the output voltage is not lower than λ BAT times the pulse current V bus - Δ V max , i.e. i p r BAT ≤ Δ V max ;

[0029] Q BAT4min satisfies:

[0030]

[0031] wherein t i is the minimum interval time of the pulse load, Q BAT4min ensures that the battery can providet i The capacitor is charged to V Cmax , i.e. i ch t i ≥ Q C ( V Cmax -V Cmin ), wherein i ch is the charging current of the capacitor, while ensuring that the output voltage is not lower than V bus - Δ V max , i.e. i ch r BAT ≤ Δ V max ;

[0032] Since Q BAT1min is greater than Q BAT2min , the minimum capacity of the battery is determined as:

[0033]

[0034] The volume of the battery Vol BAT and the capacity of the battery Q BAT and the output voltage V BAT satisfy Vol BAT = k BAT Q BAT V BAT , wherein k BAT is a constant coefficient related to the model of the battery; when Q BAT = Q BAT1min , the minimum total volume of the hybrid power supply system is determined as:

[0035]

[0036] , wherein V CTRL is the volume of the DC / DC converter, which is considered as a constant in the hybrid power supply system; when QBAT = Q BAT3min The minimum total volume of the hybrid power supply system is determined as:

[0037]

[0038] When Q BAT = Q BAT4min The minimum total volume of the hybrid power supply system is determined as:

[0039]

[0040] In combination with the above three cases, the relationship between the minimum total volume of the hybrid power supply system and λ CC is:

[0041]

[0042] Wherein K = 2 V BAT / ( V Cmax + V Cmin ) is a constant, and δ = t p / ( t p + t i ) is the duty cycle of the pulse load.

[0043] The power control method of the capacity configuration method of the ultra-low frequency variable frequency pulse load hybrid power supply system is based on the power control method, which comprises determining the output current reference signal of the DC / DC converter i oref , first detecting the ultra-low frequency variable frequency pulse load current i load , then comparing the ultra-low frequency variable frequency pulse load current i load with the threshold current i th , i th = ( i n +i pulse ) / 2, wherein i n is the rated current when there is no pulse load, i pulse is the pulse current, and if:

[0044] 1)i load ≥ i th

[0045] indicates that there is a pulse power demand, at this time, the voltage of the capacitor is further detected V C , if the voltage of the capacitor is lower than V Cmax , it indicates that the capacitor is not fully charged, and it is continuously judged whether the charging voltage is lower than V Cmin , if not lower than V Cmin , the load is still supplied by the battery and the capacitor together, and i oref is set to i load - i BATmax , wherein i BATmax is the maximum discharge current of the battery to ensure that the output voltage is greater than V bus - Δ V max , if the bus voltage is lower than V bus - Δ V max , the pulse load is immediately cut off, and the load is reconnected when the capacitor voltage is charged to V Cmax ; if the voltage of the capacitor is lower than V Cmin , the pulse load should be immediately cut off, and the pulse load is reconnected when the capacitor voltage is charged to V Cmax ; if the voltage of the capacitor is higher than V Cmax , then i oref is set to i load times of the λ CC of the ultra-low frequency variable frequency pulse load current

[0046] 2) i load < i th

[0047] it is judged whether i load is less than zero, that is, whether there is feedback energy, if i loadLess than zero, indicating that there is feedback energy, the voltage of the detection capacitor, if the capacitor voltage has reached V Cmax , then set i oref to 0, if the capacitor voltage has not reached V Cmax , then set i oref to i load , the capacitor absorbs all the feedback energy; if i load greater than zero, the voltage of the detection capacitor, if the capacitor voltage has not reached V Cmax , set i oref to I ch , I ch In order to ensure that the minimum current that can guarantee the capacitor full of electricity before the next pulse load, meet I ch t p ≥ Q C ( V Cmax - V Cmin ), if the capacitor voltage has reached V Cmax , set i oref to 0.

[0048] The beneficial effects of the present application:

[0049] 1、The capacity configuration method of the hybrid power supply system of the ultra-low frequency variable frequency pulse load proposed in the present application can ensure that the total volume of the hybrid power supply system is minimum by establishing the relationship between the system volume and the proportion of the battery and the capacitor to bear the pulse power.

[0050] 2. The power control method based on the capacity configuration method of the super-low-frequency variable-frequency pulse load hybrid power supply system, by detecting the super-low-frequency variable-frequency pulse load current, extracting the pulse component and processing it according to the optimized design proportion as the DC / DC converter output current reference signal, the capacitor converter output current can quickly track the reference current through the current loop control, so as to realize the purpose of providing the required low-frequency pulse power by the capacitor, the variable-frequency low-frequency high-power pulse load can be reliably powered, the impact of the super-low-frequency variable-frequency pulse load on the power supply system is reduced, the power density of the hybrid power supply system is improved, the reliable operation of the hybrid power supply system is ensured, and the application occasion with the super-low-frequency variable-frequency pulse load and strict volume requirement is suitable.

[0051] 3. The capacitor absorbs the feedback energy on the bus, avoids the frequent charging and discharging of the battery, and reduces the influence of the feedback energy on the battery life. BRIEF DESCRIPTION OF DRAWINGS

[0052] Figure 1 It is the structure block diagram of the hybrid power supply system in the embodiment.

[0053] Figure 2 It is the load characteristic diagram in the embodiment.

[0054] Figure 3 It is the current reference generation logic block diagram in the embodiment.

[0055] Figure 4 It is the time domain simulation waveform when the load frequency is 2Hz in the embodiment, Figure 4 From top to bottom, it is the simulation waveform of the bus voltage, the converter output current, the battery output current and the capacitor voltage.

[0056] Figure 5 It is the time domain simulation waveform when the load frequency is changed from 2Hz to 1Hz and there is energy feedback in the embodiment, Figure 5 From top to bottom, it is the simulation waveform of the bus voltage, the converter output current, the battery output current and the capacitor voltage. DETAILED DESCRIPTION

[0057] The application will be further described below in combination with the drawings and embodiments.

[0058] As Figure 1 shown, the hybrid power supply system of the super-low-frequency variable-frequency pulse load in the embodiment includes a battery and a super-low-frequency variable-frequency pulse load connected with the output end of the battery; further includes a capacitor C, the capacitor C is connected in parallel to the output end of the battery through a DC / DC converter; further includes a current reference generation unit, the current reference generation unit is used for detecting the current i load and the voltage of the capacitorV C and the capacitor should bear, to generate the output current reference signal of the DC / DC converter i oref ; also includes a PI regulator for regulating the output current reference signal of the DC / DC converter i oref and the DC / DC converter output current i o ; also includes a PWM and driving circuit for generating a driving signal of the DC / DC converter according to the output signal of the PI regulator, to ensure that the DC / DC converter output current i o tracks the output current reference signal i oref well and quickly.

[0059] The hybrid power supply system of the super-low frequency variable frequency pulse load in the embodiment, during the interval of the pulse power load, the battery charges the capacitor, and the battery and the DC / DC converter jointly supply power for the super-low frequency variable frequency pulse load. By detecting the super-low frequency variable frequency pulse load current i load , extracting the pulse component, considering the voltage C V C limit of the capacitor C and the pulse power proportion that the capacitor should bear, the output current reference signal of the DC / DC converter is obtained i oref . The output current reference signal i oref is subtracted from the actual output current i o , and the error is regulated by the PI regulator, and the driving signal of the DC / DC converter is generated by the PWM and driving circuit.

[0060] The capacity configuration method of the hybrid power supply system of the super-low frequency variable frequency pulse load in the embodiment includes:

[0061] The power distribution ratios of the pulse power between the capacitor and the battery are respectively λ CC and λ BAT , both of which satisfy λ BAT + λ CC =1, λ BAT (0, 1),​λ CC When the ultra-low frequency variable frequency pulse load absorbs energy from the hybrid power supply system in a pulse period W , the minimum capacity of the capacitor is determined as:

[0062]

[0063] Wherein V Cmax is the upper limit of the voltage of the capacitor, V Cmin is the lower limit of the voltage of the capacitor, when the upper limit of the voltage of the capacitor V Cmax is determined, the volume of the capacitor Vol CC and the capacity of the capacitor Q C satisfy Vol CC = k CC Q C Wherein k CC is a constant coefficient related to the model of the capacitor;

[0064] Let the energy consumed by the hybrid power supply system in the entire working time period be W total , the rated current without pulse load is i n , then the minimum capacity of the battery is determined as:

[0065]

[0066] Wherein Q BAT1min satisfy:

[0067]

[0068] Wherein V BAT is the platform voltage of the battery, that is Q BAT1min can guarantee to provide the energy consumed in the entire working time period;

[0069] Q BAT2min satisfy:

[0070]

[0071] Wherein k r is a constant related to the internal resistance of the battery, ΔV max the maximum allowable drop value of bus voltage, Q BAT2min can ensure that the output voltage is not lower than i n under the condition of rated current V bus - Δ V max , wherein V bus is the bus voltage, i.e. i n r BAT ≤ Δ V max , r BAT is the internal resistance of the battery; k r and r BAT , the capacity Q BAT , the output voltage V BAT satisfy the following relationship:

[0072]

[0073] Q BAT3min satisfy:

[0074]

[0075] wherein t p is the pulse width, Q BAT3min can ensure that the battery provides λ BAT times the pulse current, i.e. i p V bus t p = Wλ BAT = W (1- λ CC ), wherein i p is the output current of the battery at this time, and can ensure that the output voltage is not lower than λ BAT times the pulse current, i.e. V bus - Δ V max , i.e. ip r BAT ≤ Δ V max ;

[0076] Q BAT4min satisfies:

[0077]

[0078] wherein t i is the minimum interval time of the pulse load, Q BAT4min to ensure that the battery can charge the capacitor to t i within the time V Cmax , i.e. i ch t i ≥ Δ Q C ( V Cmax -V Cmin ), wherein i ch is the charging current of the capacitor, while the output voltage is ensured to be not lower than V bus - Δ V max , i.e. i ch r BAT ≤ Δ V max ;

[0079] Since Q BAT1min is greater than Q BAT2min , the minimum capacity of the battery is determined as:

[0080]

[0081] The volume of the battery Vol BAT is proportional to the capacity of the battery Q BAT and the output voltage V BAT satisfies Vol BAT = k BAT Q BAT VBAT wherein k BAT is a constant related to the model of the battery; when Q BAT = Q BAT1min The minimum total volume of the hybrid power supply system is determined as:

[0082]

[0083] wherein V CTRL is the volume of the DC / DC converter, which is considered as a constant in the hybrid power supply system; when Q BAT = Q BAT3min The minimum total volume of the hybrid power supply system is determined as:

[0084]

[0085] when Q BAT = Q BAT4min The minimum total volume of the hybrid power supply system is determined as:

[0086]

[0087] Combining the above three cases, the relationship between the minimum total volume of the hybrid power supply system and λ CC is:

[0088]

[0089] wherein K = 2 V BAT / ( V Cmax + V Cmin ) is a constant, and t p / ( t p + t i ) is the duty cycle of the pulse load.

[0090] The nominal voltage of the battery in this embodiment is 270 V. According to Figure 2The load characteristics shown, the pulse load frequency varies between 1 Hz to 2 Hz, the pulse width is 20 ms, the pulse load current is 150 A, the minimum pulse interval is 500 ms, and the rated current is 10 A. When the pulse load is over, there is feedback energy immediately, the feedback energy is less than 50% of the energy absorbed by the pulse load, the whole working time is 600 s, and the pulse number is less than 600.

[0091] According to the load characteristics, it can be known that the energy consumed in the whole working time period is about:

[0092]

[0093] That is, Q BAT1min = 1.88 Ah, Q BAT2min , Q BAT3min , Q BAT4min respectively,

[0094]

[0095]

[0096]

[0097] That is, Q BAT4min ≤ Q BAT1min ≤ Q BAT3min , satisfying Q BAT = Q BAT1min . The four-switch DC / DC converter is further used to increase the capacitor voltage variation range, so that the overall volume of the system is further reduced, and V Cmax = 400 V, V Cmin = 140 V, combined with the conclusion obtained by the foregoing optimization method, the power supply proportion of the capacitor to the pulse load should be:

[0098]

[0099] At this time, the total volume of the hybrid power supply system is:

[0100]

[0101] The power control method of the embodiment based on the capacity configuration method of the ultra-low frequency variable frequency pulse load hybrid power supply system includes determining the output current reference signal of the DC / DC converteri oref First, the ultra-low frequency variable frequency pulse load current is detected i load Then, the ultra-low frequency variable frequency pulse load current is compared with threshold current i load i th , i th = ( i n +i pulse ) / 2, wherein i n is the rated current when there is no pulse load, i pulse is the pulse current, and if:

[0102] 1) i load ≥ i th

[0103] It indicates that there is a pulse power demand, at this time, the voltage of the capacitor is further detected V C If the voltage of the capacitor is lower than V Cmax , it indicates that the capacitor is not fully charged, and it is continuously determined whether the charging voltage is lower than V Cmin If it is not lower than V Cmin , the load is still supplied by the battery and the capacitor together, and i oref is set to i load - i BATmax , wherein i BATmax is the maximum discharge current of the battery when the output voltage is greater than V bus - Δ V max If the bus voltage is lower than V bus - Δ V max during the process, the pulse load is immediately cut off, and the load is connected again when the capacitor voltage is charged to V Cmax If the voltage of the capacitor is lower than V Cmin , the pulse load should be immediately cut off, and the load is connected again when the capacitor voltage is charged to V Cmax ​Re-Accessing pulse load; if the voltage of the capacitor is higher than V Cmax , then set i oref to the ultra-low frequency variable frequency pulse load current i load of λ CC times;

[0104] 2) i load i th

[0105] Determine i load if it is less than zero, that is, determine whether there is feedback energy, if i load is less than zero, indicating that there is feedback energy, detect the voltage of the capacitor, if the voltage of the capacitor has reached V Cmax , then set i oref to 0, if the voltage of the capacitor has not reached V Cmax , then set i oref to i load , the capacitor absorbs all the feedback energy; if i load is greater than zero, detect the voltage of the capacitor, if the voltage of the capacitor has not reached V Cmax , set i oref to I ch , I ch In order to ensure that the capacitor is fully charged before the next pulse load arrives, the minimum current that meets I ch t p ≥ Q C ( V Cmax - V Cmin ), in which Q C is the capacitance of the capacitor, if the voltage of the capacitor has reached V Cmax , set i oref to 0.

[0106] As​Figure 3 The current reference generating unit logic block diagram shown, when detecting the load current, if the load current is greater than 80A, indicating that there is a pulse power demand, detecting capacitor voltage, if the capacitor voltage is less than 400V, indicating that the capacitor is not fully charged, not enough to provide pulse power completely, cut off the load. If the capacitor voltage is greater than or equal to 400V, the reference current is set to 86% of the load current. If the load current is less than 20A, determine whether the load current is less than zero, that is, to determine whether there is feedback energy. If the load current is less than zero, indicating that there is feedback energy, detecting capacitor voltage, if the capacitor voltage has reached 400V, the reference current is set to 0A, if the capacitor voltage has not reached 400V, the load current is set to the reference current, the capacitor absorbs all the feedback energy; if the load current is greater than zero, detecting capacitor voltage, if the capacitor voltage has not reached 400V, the reference current is set to -10A, if the capacitor voltage has reached 400V, the reference current is set to 0A.

[0107] Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present application and not to limit it. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application, and they should be covered in the scope of the claims of the present application.

Claims

1. A capacity configuration method of a hybrid power supply system of an ultra-low frequency variable frequency pulse load, the hybrid power supply system of the ultra-low frequency variable frequency pulse load comprising a battery and an ultra-low frequency variable frequency pulse load connected to an output end of the battery; further comprising a capacitor, the capacitor being connected in parallel to the output end of the battery through a DC / DC converter. The current reference generating unit is used for detecting the current of the ultra-low frequency variable frequency pulse load i load and the voltage of the capacitor V C and generates an output current reference signal of the DC / DC converter according to the power flow demand and the proportion of the pulse power that the capacitor should bear i oref The PI regulator is used for adjusting the output current reference signal of the DC / DC converter i oref and the difference between the output current of the DC / DC converter i o The PWM and driving circuit is used for generating a driving signal of the DC / DC converter according to the output signal of the PI regulator, so as to ensure that the output current of the DC / DC converter i o tracks the output current reference signal i oref quickly and well; characterized in that: Let the power distribution ratio of the pulse power between the capacitor and the battery be λ CC and λ BAT , both satisfy λ BAT + λ CC =1, λ BAT (0, 1), λ CC (0, 1), when the energy absorbed by the ultra-low frequency variable frequency pulse load from the hybrid power supply system in a pulse period is W , the minimum capacity of the capacitor is determined as: wherein V Cmax is an upper voltage limit for the capacitor, V Cmin is a lower voltage limit for the capacitor, when the upper voltage limit for the capacitor V Cmax is determined, the volume of the capacitor Vol CC is related to the capacity of the capacitor Q C satisfies Vol CC = k CC Q C wherein k CC is a constant coefficient related to the model of the capacitor; Let the energy consumed by the hybrid power supply system during the entire working time period be W total The rated current when the load is not pulsed is i n The minimum capacity of the battery is determined as wherein Q BAT1min satisfies: wherein V BAT is the platform voltage of the battery, i.e. Q BAT1min guarantees that the energy consumed over the entire working time period is provided; Q BAT2min satisfies: wherein k r is a constant related to the internal resistance of the battery, Δ V max is the maximum allowable drop value of the bus voltage, Q BAT2min guarantees that the output voltage is not lower than i n in the case of a rated current V bus - Δ V max wherein V bus is the bus voltage, i.e. i n r BAT ≤ Δ V max , r BAT is the internal resistance of the battery; k r and r BAT , the capacity Q BAT , the output voltage V BAT satisfy the following relationship: Q BAT3min satisfies: wherein t p is the pulse width, Q BAT3min ensures that the battery provides λ BAT a pulse current of i p V bus t p = Wλ BAT = W (1- λ CC ), wherein i p is the battery output current at this time, and ensures that the output voltage is not lower than λ BAT when providing a pulse current of V bus - Δ V max , i.e. i p r BAT ≤ Δ V max ; Q BAT4min satisfies: wherein t i is the minimum interval time for the pulse load, Q BAT4min ensures that the battery can charge the capacitor to t i within the time V Cmax , i.e. i ch t i ≥ Q C ( V Cmax -V Cmin ), wherein i ch is the charging current of the capacitor, while ensuring that the output voltage is not lower than V bus - Δ V max , i.e. i ch r BAT ≤ Δ V max ; Because Q BAT1min greater than Q BAT2min The minimum capacity of the battery is thus determined as: Volume of the battery Vol BAT Capacity of the battery Q BAT and output voltage V BAT satisfies Vol BAT = k BAT Q BAT V BAT wherein k BAT is a constant factor related to the model of the battery; when Q BAT = Q BAT1min the minimum total volume of the hybrid power supply system is determined as wherein V CTRL The volume of the DC / DC converter, in the hybrid power supply system, is considered constant; when Q BAT = Q BAT3min The minimum overall volume of the hybrid power supply system is determined as: When Q BAT = Q BAT4min the minimum total volume of the hybrid power supply system is determined as: Combining the above three cases, the minimum total volume of the hybrid power supply system is determined in relation to λ CC is: wherein K = 2 V BAT / ( V Cmax + V Cmin ) is a constant, δ = t p / ( t p + t i ) is the duty cycle of the pulsed load.

2. A power control method based on the capacity configuration method of the ultra-low frequency variable frequency pulse load hybrid power supply system of claim 1, characterized in that: Determining an output current reference signal of a DC / DC converter i oref first detecting an ultra-low frequency variable frequency pulse load current i load then comparing the ultra-low frequency variable frequency pulse load current i load to a threshold current i th , i th =( i n +i pulse ) / 2, where i n is a rated current without pulse load, i pulse is a pulse current, if: 1） i load ≥ i th It indicates that there is pulse power demand, at this time, further detect the voltage of the capacitor V C If the voltage of the capacitor is lower than V Cmax , it indicates that the capacitor is not fully charged, continue to determine whether the charging voltage is lower than V Cmin , if not lower than V Cmin , still supply power to the load by the battery and the capacitor together, set i oref to i load - i BATmax , wherein i BATmax is the maximum discharge current of the battery to ensure that the output voltage is greater than V bus - Δ V max , if the bus voltage is lower than V bus - Δ V max , immediately cut off the pulse load, and then connect the load again when the capacitor voltage is charged to V Cmax ; if the voltage of the capacitor is lower than V Cmin , the pulse load should be immediately cut off, and then connect the pulse load again when the capacitor voltage is charged to V Cmax ; if the voltage of the capacitor is higher than V Cmax , set i oref to i load times of the λ CC of the ultra-low frequency variable frequency pulse load current 2) i load < i th determining i load whether it is less than zero, i.e. determining whether there is feedback energy, and if i load less than zero, indicating that there is feedback energy, the voltage of the capacitor is detected, and if the voltage of the capacitor has reached V Cmax , the value i oref is set to 0, and if the voltage of the capacitor has not reached V Cmax , the value i oref is set to i load , the capacitor absorbing the entire feedback energy; like i load If the voltage is greater than zero, check the capacitor voltage; if the capacitor voltage is less than zero... V Cmax ,Will i oref Set as I ch , I ch To ensure the minimum current required to fully charge the capacitor before the next pulse load arrives, and to satisfy... I ch t p ≥ Q C ( V Cmax - V Cmin If the voltage of the capacitor has reached V Cmax Then i oref Set to 0.

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