Resonant capacitor compensation method for LLC converter with half-wave variable resonant capacitor in submarine DC power supply system

Abstract

The present invention discloses a resonant capacitor compensation method for an LLC converter containing a half-wave variable resonant capacitor in a submarine DC power supply system, comprising: locally monitoring and adaptively compensating the LLC converter according to a preset period by a local microcontroller: controlling the LLC converter to form a first sub-loop, comprising a resonant capacitor, a resonant inductor, a transformer excitation inductor and a power device group; the resonant capacitor comprises a half-wave variable resonant capacitor; the power device group comprises a first device group or a second device group; sampling the resonant current of the first sub-loop to obtain a resonant current sampling value; obtaining a resonant capacitor estimation value according to the resonant current sampling value; obtaining a resonant capacitor attenuation rate according to the resonant capacitor rated value and the resonant capacitor estimation value; when the resonant capacitor attenuation rate reaches a preset threshold, changing the duty cycle of the half-wave variable resonant capacitor according to the resonant capacitor estimation value to achieve local adaptive compensation of the resonant capacitor.

Description

Technical Field

[0001] The present invention relates to the technical field of aging compensation of direct current converters, and in particular to a resonant capacitor compensation method for a half-wave variable resonant capacitor LLC converter in a submarine direct current power supply system. Background Art

[0002] LLC resonant converters have become the preferred solution for DC-DC conversion in many industrial applications due to their high efficiency, high power density, easy implementation of ZVS (Zero Voltage Switch) and electrical isolation. In practical applications, the resonant capacitor of LLC converters often changes parameters due to factors such as manufacturing tolerances and natural aging, resulting in resonant frequency shifts and affecting the operating efficiency of LLC converters.

[0003] During the service life of the LLC converter, it is necessary to introduce capacitor status monitoring to obtain the degree of degradation of the resonant capacitor, that is, to obtain the deviation of the resonant frequency. Most capacitor status monitoring methods in existing literature are mainly aimed at DC capacitors, such as input and output capacitors, and are not suitable for online monitoring of AC resonant capacitors, that is, existing capacitor status monitoring methods are difficult to apply to DC power supply systems with AC resonant capacitors. After obtaining the monitoring degradation information, even if the parameters of the circuit elements are different from their design values, the required performance can be restored by actively compensating the capacitor. However, existing resonant capacitor compensation methods often require manual removal of aging resonant capacitors and replacement with new resonant capacitors. In DC power supply systems in special environments such as the seabed, the high operating difficulty and cost make it difficult to manually operate and maintain LLC converters.

[0004] Therefore, there is an urgent need for a local resonant capacitor compensation method based on state monitoring and aging compensation to solve the technical problem of how to compensate for the aging resonant capacitor of the LLC converter in a DC power supply system in special environments such as the seabed. Summary of the invention

[0005] The present invention provides a resonant capacitor compensation method for an LLC converter containing a half-wave variable resonant capacitor in a submarine DC power supply system, so as to solve the technical problem of how to compensate for the aging resonant capacitor of the LLC converter in a DC power supply system in special environments such as the seabed.

[0006] To achieve the above object, the present invention provides a resonant capacitor compensation method for a half-wave variable resonant capacitor LLC converter in a submarine DC power supply system, comprising:

[0007] Local monitoring and local adaptive compensation of LLC converter by local microcontroller according to preset cycle:

[0008] The LLC converter is controlled to form a first sub-loop; the first sub-loop includes a resonant capacitor, a resonant inductor, a transformer excitation inductor and a power device group; the resonant capacitor includes a half-wave variable resonant capacitor.

[0009] The power device group includes the first device group or the second device group; the first device group includes the second power device and the fourth power device; the second device group includes the first power device and the third power device.

[0010] The resonant current of the first sub-loop is sampled to obtain a resonant current sampling value; an estimated resonant capacitance value is obtained according to the resonant current sampling value; and a resonant capacitance attenuation rate is obtained according to the resonant capacitance rated value and the resonant capacitance estimated value.

[0011] When the attenuation rate of the resonant capacitor reaches a preset threshold, the duty cycle of the half-wave variable resonant capacitor is changed according to the estimated value of the resonant capacitor to achieve local adaptive compensation of the resonant capacitor.

[0012] Preferably, controlling the LLC converter to form a first sub-loop comprises:

[0013] The four power devices of the full-bridge part in the LLC converter are controlled by a local microcontroller, so that the four power devices enter a preset level combination state and maintain a preset time; the preset level combination state includes:

[0014] Case 1: the second power device and the fourth power device maintain a high level, that is, the second power device and the fourth power device are turned on to form a power device group; the first power device and the third power device maintain a low level, that is, the second power device and the fourth power device are turned off.

[0015] Situation 2: the second power device and the fourth power device maintain a low level, that is, the second power device and the fourth power device are turned off; the first power device and the third power device maintain a high level, that is, the second power device and the fourth power device are turned on, forming a power device group.

[0016] The power device group, the resonant capacitor, the resonant inductor and the transformer excitation inductor form a first sub-loop.

[0017] Preferably, sampling the resonant current of the first sub-loop includes:

[0018] A resonant current sensor in the DC power supply system is controlled by a local microcontroller to sense the resonant current in the first sub-loop; the resonant current is returned to the local microcontroller by the resonant current sensor to obtain a resonant current sampling value.

[0019] Preferably, obtaining the estimated value of the resonant capacitance according to the resonant current sampling value includes:

[0020] In the LLC converter, the energy consumption of the resonant cavity is in the first sub-loop, which includes:

[0021] ;

[0022] in, represents loop inductance; represents the resonant capacitance; Indicates loop resistance; Represents the resonant current; variable is the time differential of the resonant current.

[0023] In LLC converter, loop inductance The size is microhenry level, the resonant capacitor The size is nanofarad level, the loop resistance The size of is in the milliohm range, so the circuit is in an underdamped state, and the corresponding transient process is characterized by oscillatory discharge of resistance, inductance and capacitance.

[0024] The resonant current The analytical expression of can be expressed by the following relationship:

[0025] ;

[0026] Among them, the variable Indicates discharge time; constant Indicates the resonant current amplitude at the initial moment of discharge; constant represents the attenuation coefficient; constant represents the resonant frequency, constant Indicates the resonant current phase at the initial moment of discharge.

[0027] Resonant frequency The analytical expression of can be expressed by the following relationship:

[0028] ;

[0029] By combining the analytical formula of the resonant current and the resonant frequency, we can get the resonant capacitance at this time. The actual value of the resonant capacitance is obtained.

[0030] Preferably, obtaining the resonant capacitance attenuation rate according to the resonant capacitance rated value and the resonant capacitance estimated value comprises:

[0031] Compare the estimated resonant capacitance with the rated resonant capacitance to get the resonant capacitance degradation ratio , which can be expressed by the following relationship:

[0032] ;

[0033] in, represents the estimated value of the resonant capacitance; Indicates the resonant capacitor rating.

[0034] Preferably, changing the duty cycle of the half-wave variable resonant capacitor according to the estimated value of the resonant capacitor to achieve local adaptive compensation of the resonant capacitor includes:

[0035] When the LLC converter is in a normal state, the resonance condition of the LLC converter can be expressed by the following relationship:

[0036] ;

[0037] in, represents the resonant angular frequency of the LLC converter; and They represent the resonant inductance and the resonant capacitance respectively.

[0038] The resonant capacitor includes a half-wave variable resonant capacitor and an equivalent capacitor of a half-wave variable resonant capacitor. The estimated value of the resonant capacitance is , which can be expressed by the following relationship:

[0039] ;

[0040] in, Indicates the duty cycle of the half-wave variable resonant capacitor; and Represents the two capacitors inside the half-wave variable resonant capacitor.

[0041] When the attenuation rate of the resonant capacitor reaches a preset threshold, the duty cycle of the half-wave variable resonant capacitor is changed. , that is, the equivalent capacitance of the half-wave variable resonant capacitor To compensate, the equivalent capacitance The value of the resonant capacitor Rated value.

[0042] Preferably, local monitoring also includes:

[0043] The load condition of the LLC converter is determined by a local microcontroller; the load condition includes a normal load condition and a light load condition; in the normal load condition, the first power device, the second power device, the third power device and the fourth power device continuously operate at a preset duty cycle; in the light load condition, the operation of the first power device, the second power device, the third power device and the fourth power device includes a working phase and a stopping phase.

[0044] When the LLC converter is in a normal load condition, the local microcontroller sends a first control wave to the LLC converter; the first control wave is used to control the power device group to maintain a high level for a preset time period, and locally monitor the LLC converter within the preset time period.

[0045] When the LLC converter is in a light load condition, the local microcontroller sends a second control wave to the LLC converter; the second control wave is used to control the power device group to maintain a high level for a preset period of time during the stop phase of the light load condition, and locally monitor the LLC converter within the preset period of time.

[0046] The present invention has the following beneficial effects:

[0047] The resonant capacitor compensation method for the LLC converter containing a half-wave variable resonant capacitor in the submarine DC power supply system of the present invention triggers local monitoring and local adaptive compensation according to a preset period by a local microcontroller, so that the method of the present invention can be applied to special environments such as the seabed, without manual operation, avoiding problems such as high operation difficulty and cost. By controlling the LLC converter to form a sub-circuit including a resonant capacitor, a resonant inductor, a transformer excitation inductor and a power device, the energy consumption of the resonant cavity is in an independent circuit, so that the method can monitor the resonance information of the LLC converter simply and conveniently. By collecting the resonant current in the sub-circuit and calculating the estimated value of the resonant capacitor according to the resonant current, the aging data basis of the resonant capacitor is passed for subsequent calculations. By judging whether the attenuation rate of the resonant capacitor reaches a preset threshold, the method of the present invention can independently judge whether local compensation is required. The duty cycle of the half-wave variable resonant capacitor is changed according to the estimated value of the resonant capacitor, so that the equivalent capacitance of the half-wave variable resonant capacitor changes, thereby realizing the local adaptive compensation of the resonant capacitor.

[0048] In addition to the above-described purposes, features and advantages, the present invention has other purposes, features and advantages. The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0050] Figure 1 Schematic diagram of an LLC converter including a half-wave variable resonant capacitor according to a preferred embodiment of the present invention.

[0051] Figure 2 It is a flow chart of a preferred embodiment of the present invention.

[0052] Figure 3This is a schematic diagram of controlling the LLC converter to form a first sub-loop in scenario 1 of a preferred embodiment of the present invention.

[0053] Figure 4 It is a schematic diagram of the first sub-loop of a preferred embodiment of the present invention.

[0054] Figure 5 It is a schematic diagram of the first control wave control method of the preferred embodiment of the present invention.

[0055] Figure 6 It is a schematic diagram of the second control wave control method of the preferred embodiment of the present invention.

[0056] Figure 7 Schematic diagram of variable capacitance compensation according to a preferred embodiment of the present invention.

[0057] Figure 8 is the duty cycle of the preferred embodiment of the present invention Schematic diagram of the change in equivalent capacitance value when changing in the range of 0-1. DETAILED DESCRIPTION

[0058] The embodiments of the present invention are described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0059] See also Figure 1 The LLC converter containing a half-wave variable resonant capacitor of the present invention specifically comprises:

[0060] First power device , the second power device 、Third power device , the fourth power device , DC power supply , Input Capacitance , resonant network part, rectifier bridge part, output capacitor and load .

[0061] Among them, the input capacitance Connect the positive and negative poles of the DC power supply to both ends respectively; Drain connected to DC power supply The positive electrode, The source is connected to the middle point of the bridge arm ; The drain is connected to the middle point of the bridge arm , The source is connected to a DC power supply The negative electrode; Drain connected to DC power supply The positive electrode, The source is connected to the middle point of the bridge arm ; The drain is connected to the middle point of the bridge arm , The source is connected to a DC power supply of the negative electrode.

[0062] The resonant network includes a half-wave variable resonant capacitor , resonant inductor and transformer magnetizing inductance ; Half-wave variable resonant capacitor Connect the midpoint of the bridge arm at both ends and resonant inductor The first end of the transformer excitation inductance The two ends are connected to the midpoint of the bridge arm and resonant inductor The second end of the half-wave variable resonant capacitor , resonant inductor and transformer magnetizing inductance Constitute a resonant cavity.

[0063] The rectifier bridge includes diodes and ; Cathode connected to load The positive electrode, Anode to cathode; Anode connected to load The negative electrode; Cathode connected to load The positive electrode, Anode to cathode; Anode connected to load In addition, the output capacitor The two ends are connected to the positive and negative poles of the output bus, that is, to the load Both ends are connected.

[0064] Half-wave variable resonant capacitor In the internal capacitor and Series, switch tubes in parallel Both ends.

[0065] The submarine DC power supply system of the present invention comprises a local microcontroller and a resonant current sensor connected to the LLC converter containing a half-wave variable resonant capacitor of the present invention.

[0066] See also Figure 2In a preferred embodiment of the present invention, based on the above-mentioned LLC converter containing a half-wave variable resonant capacitor, a resonant capacitor compensation method for a LLC converter containing a half-wave variable resonant capacitor in a submarine DC power supply system is provided, comprising:

[0067] The LLC converter is locally monitored and adaptively compensated by the local microcontroller according to a preset period, including:

[0068] S1: Control the LLC converter to form a first sub-loop. The first sub-loop includes a resonant capacitor, a resonant inductor, a transformer excitation inductor and a power device group; the resonant capacitor includes a half-wave variable resonant capacitor.

[0069] The power device group includes the first device group or the second device group; the first device group includes the second power device and the fourth power device; the second device group includes the first power device and the third power device.

[0070] See also Figure 3 to Figure 4 In a preferred embodiment of the present invention, controlling the LLC converter to form the first sub-loop specifically includes:

[0071] The four power devices of the full-bridge part in the LLC converter are controlled by a local microcontroller, so that the four power devices enter a preset level combination state and maintain a preset time; the preset level combination state includes:

[0072] Case 1: the second power device and the fourth power device maintain a high level, that is, the second power device and the fourth power device are turned on to form a power device group; the first power device and the third power device maintain a low level, that is, the second power device and the fourth power device are turned off.

[0073] Situation 2: the second power device and the fourth power device maintain a low level, that is, the second power device and the fourth power device are turned off; the first power device and the third power device maintain a high level, that is, the second power device and the fourth power device are turned on, forming a power device group.

[0074] The power device group, the resonant capacitor, the resonant inductor and the transformer excitation inductor form a first sub-loop.

[0075] In a preferred embodiment of the present invention, local monitoring further includes:

[0076] The load condition of the LLC converter is determined by a local microcontroller; the load condition includes a normal load condition and a light load condition; in the normal load condition, the first power device, the second power device, the third power device and the fourth power device continuously operate at a preset duty cycle; in the light load condition, the operation of the first power device, the second power device, the third power device and the fourth power device includes a working phase and a stopping phase.

[0077] See also Figure 5 When the LLC converter is in a normal load condition, the local microcontroller sends a first control wave to the LLC converter; the first control wave is used to control the power device group to maintain a high level for a preset time period, and locally monitor the LLC converter within the preset time period.

[0078] exist Figure 5 middle, and Respectively represent the levels of the first power device, the second power device, the third power device and the fourth power device; Indicates time; and Represent the resonant current and output voltage respectively; and In the section, the red waveform indicates , the blue waveform indicates ; and In the section, the red waveform indicates , the blue waveform indicates .

[0079] See also Figure 6 When the LLC converter is in a light load condition, the local microcontroller sends a second control wave to the LLC converter; the second control wave is used to control the power device group to maintain a high level for a preset period of time during the stop phase of the light load condition, and locally monitor the LLC converter within the preset period of time.

[0080] exist Figure 6 middle, and Respectively represent the levels of the first power device, the second power device, the third power device and the fourth power device; Indicates time; and Represent the resonant current and output voltage respectively; and In the section, the red waveform indicates , the blue waveform indicates ; and In the section, the red waveform indicates , the blue waveform indicates .

[0081] S2: Sampling the resonant current of the first sub-loop to obtain a resonant current sampling value. Specifically including:

[0082] A resonant current sensor in the DC power supply system is controlled by a local microcontroller to sense the resonant current in the first sub-loop; the resonant current is returned to the local microcontroller by the resonant current sensor to obtain a resonant current sampling value.

[0083] S3: Obtain the estimated value of the resonant capacitance based on the resonant current sampling value. Specifically including:

[0084] In the LLC converter, the energy consumption of the resonant cavity is in the first sub-loop, which includes:

[0085] ;

[0086] in, represents loop inductance; represents the resonant capacitance; Indicates loop resistance; Represents the resonant current; variable is the time derivative of the resonant current.

[0087] In the LLC converter containing a half-wave variable resonant capacitor of the present invention, the loop inductance The size is designed to be microhenry level, the resonant capacitor The size is designed to be nanofarad level, the loop resistance The size of is designed to be in the milliohm level, so the circuit is in an underdamped state, and the corresponding transient process is characterized by oscillatory discharge of resistance, inductance and capacitance.

[0088] The resonant current The analytical expression of can be expressed by the following relationship:

[0089] ;

[0090] Among them, the variable Indicates discharge time; constant Indicates the resonant current amplitude at the initial moment of discharge; constant represents the attenuation coefficient; constant represents the resonant frequency, constant Indicates the resonant current phase at the initial moment of discharge.

[0091] Resonant frequency The analytical expression of can be expressed by the following relationship:

[0092] ;

[0093] By combining the analytical formula of the resonant current and the resonant frequency, we can get the resonant capacitance at this time. The actual value of the resonant capacitance is obtained.

[0094] S4: Obtain the resonant capacitance attenuation rate based on the resonant capacitance rated value and the resonant capacitance estimated value. Specifically including:

[0095] Compare the estimated resonant capacitance with the rated resonant capacitance to get the resonant capacitance degradation ratio , which can be expressed by the following relationship:

[0096] ;

[0097] in, represents the estimated value of the resonant capacitance; Indicates the resonant capacitor rating.

[0098] S5: When the attenuation rate of the resonant capacitor reaches a preset threshold, the duty cycle of the half-wave variable resonant capacitor is changed according to the estimated value of the resonant capacitor to achieve local adaptive compensation of the resonant capacitor. Specifically including:

[0099] When the LLC converter is in a normal state, the resonance condition of the LLC converter can be expressed by the following relationship:

[0100] ;

[0101] in, represents the resonant angular frequency of the LLC converter; and Respectively represent the resonant inductance and the resonant capacitance;

[0102] The resonant capacitor includes a half-wave variable resonant capacitor and an equivalent capacitor of a half-wave variable resonant capacitor. The estimated value of the resonant capacitance is , which can be expressed by the following relationship:

[0103] ;

[0104] in, Indicates the duty cycle of the half-wave variable resonant capacitor; and Represents the two capacitors inside the half-wave variable resonant capacitor;

[0105] See also Figure 7 When the attenuation rate of the resonant capacitor reaches the preset threshold, the duty cycle of the half-wave variable resonant capacitor is changed. , that is, the equivalent capacitance of the half-wave variable resonant capacitor To compensate, the equivalent capacitance The value of the resonant capacitor Rated value.

[0106] See also Figure 8 , duty cycle C1 (60nF) and C2 (280nF) form the equivalent capacitance of the variable capacitor when varying in the range of 0-1 .

[0107] In summary, the resonant capacitor compensation method for the LLC converter containing a half-wave variable resonant capacitor in the submarine DC power supply system of the present invention triggers local monitoring and local adaptive compensation according to a preset period by a local microcontroller, so that the method of the present invention can be applied to special environments such as the seabed, without manual operation, avoiding problems such as high operation difficulty and cost. By controlling the LLC converter to form a sub-circuit including a resonant capacitor, a resonant inductor, a transformer excitation inductor and a power device, the energy consumption of the resonant cavity is in an independent circuit, so that the method can monitor the resonance information of the LLC converter simply and conveniently. By collecting the resonant current in the sub-circuit and calculating the estimated value of the resonant capacitor according to the resonant current, the aging data basis of the resonant capacitor is passed for subsequent calculations. By judging whether the attenuation rate of the resonant capacitor reaches a preset threshold, the method of the present invention can independently judge whether local compensation is required. According to the estimated value of the resonant capacitor, the duty cycle of the half-wave variable resonant capacitor is changed, so that the equivalent capacitance of the half-wave variable resonant capacitor changes, thereby realizing the local adaptive compensation of the resonant capacitor.

[0108] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A resonant capacitor compensation method for a half-wave variable resonant capacitor LLC converter in a submarine DC power supply system, characterized in that: include: The LLC converter is locally monitored and locally adaptively compensated by a local microcontroller according to a preset period: Controlling the LLC converter to form a first sub-loop; the first sub-loop includes a resonant capacitor, a resonant inductor, a transformer excitation inductor and a power device group; the resonant capacitor includes a half-wave variable resonant capacitor; The power device group includes a first device group or a second device group; the first device group includes a second power device and a fourth power device; the second device group includes a first power device and a third power device; Sampling the resonant current of the first sub-loop to obtain a resonant current sampling value; and obtaining a resonant capacitance estimation value according to the resonant current sampling value; The resonant capacitance attenuation rate is obtained based on the resonant capacitance rated value and the resonant capacitance estimated value. , which can be expressed as: ； in, represents the estimated value of the resonant capacitance; Indicates the rated value of the resonant capacitor; When the attenuation rate of the resonant capacitor reaches a preset threshold, the duty cycle of the half-wave variable resonant capacitor is changed according to the estimated value of the resonant capacitor to achieve local adaptive compensation of the resonant capacitor.

2. The resonant capacitor compensation method for a half-wave variable resonant capacitor LLC converter in a submarine DC power supply system according to claim 1, characterized in that: Controlling the LLC converter to form a first sub-loop includes: The four power devices of the full-bridge part in the LLC converter are controlled by a local microcontroller, so that the four power devices enter a preset level combination state and maintain a preset time; the preset level combination state includes: Scenario 1: the second power device and the fourth power device maintain a high level, that is, the second power device and the fourth power device are turned on to form the power device group; the first power device and the third power device maintain a low level, that is, the second power device and the fourth power device are turned off; Scenario 2: the second power device and the fourth power device maintain a low level, that is, the second power device and the fourth power device are turned off; the first power device and the third power device maintain a high level, that is, the second power device and the fourth power device are turned on, forming the power device group; The power device group, the resonant capacitor, the resonant inductor and the transformer excitation inductor form the first sub-loop.

3. The resonant capacitor compensation method for a half-wave variable resonant capacitor LLC converter in a submarine DC power supply system according to claim 2, characterized in that: Sampling the resonant current of the first sub-loop includes: A resonant current sensor in the DC power supply system is controlled by a local microcontroller to sense the resonant current in the first sub-loop; the resonant current sensor returns the resonant current to the local microcontroller to obtain the resonant current sampling value.

4. The resonant capacitor compensation method for a half-wave variable resonant capacitor LLC converter in a submarine DC power supply system according to claim 3, characterized in that: Obtaining an estimated value of the resonant capacitance according to the resonant current sampling value includes: In the LLC converter, the energy of the resonant cavity is consumed in the first sub-loop, which includes: ； in, represents loop inductance; represents the resonant capacitance; Indicates loop resistance; Represents the resonant current; variable is the differential of the resonant current with respect to time; In the LLC converter, the loop inductance The size is microhenry level, the resonant capacitor The size is nanofarad level, the loop resistance The magnitude of is in the milliohm range, so the circuit is underdamped, and the corresponding transient process is characterized by oscillatory discharges of resistance, inductance, and capacitance; Then the resonant current The analytical expression of can be expressed by the following relationship: ； Among them, the variable Indicates discharge time; constant Indicates the resonant current amplitude at the initial moment of discharge; constant represents the attenuation coefficient; constant represents the resonant frequency, constant Indicates the resonant current phase at the initial moment of discharge; Resonant frequency The analytical expression of can be expressed by the following relationship: ； By combining the analytical formula of the resonant current and the resonant frequency, we can get the resonant capacitance at this time. The actual value of the resonant capacitance is obtained, that is, the estimated value of the resonant capacitance is obtained.

5. The resonant capacitor compensation method for a half-wave variable resonant capacitor LLC converter in a submarine DC power supply system according to claim 4, characterized in that: Changing the duty cycle of the half-wave variable resonant capacitor according to the estimated value of the resonant capacitor to achieve local adaptive compensation of the resonant capacitor includes: When the LLC converter is in a normal state, the resonance condition of the LLC converter can be expressed by the following relationship: ； in, represents the resonant angular frequency of the LLC converter; and Respectively represent the resonant inductance and the resonant capacitance; The resonant capacitor comprises a half-wave variable resonant capacitor, and the equivalent capacitance of the half-wave variable resonant capacitor is This is the estimated value of the resonant capacitance , which can be expressed by the following relationship: ； in, represents the duty cycle of the half-wave variable resonant capacitor; and Represents two capacitors inside the half-wave variable resonant capacitor; When the attenuation rate of the resonant capacitor reaches a preset threshold, the duty cycle of the half-wave variable resonant capacitor is changed. , that is, the equivalent capacitance of the half-wave variable resonant capacitor To compensate, the equivalent capacitance The value of the resonant capacitor Rated value.

6. The resonant capacitor compensation method for a half-wave variable resonant capacitor LLC converter in a submarine DC power supply system according to claim 5, characterized in that: The local monitoring also includes: Determining the load condition of the LLC converter by a local microcontroller; the load condition includes a normal load condition and a light load condition; in the normal load condition, the first power device, the second power device, the third power device and the fourth power device continuously operate according to a preset duty cycle; in the light load condition, the operation of the first power device, the second power device, the third power device and the fourth power device includes an operating phase and a stop phase; When the LLC converter is in a normal load condition, the local microcontroller sends a first control wave to the LLC converter; the first control wave is used to control the power device group to maintain a high level for a preset time period, and to perform local monitoring on the LLC converter within the preset time period; When the LLC converter is in a light load condition, the local microcontroller sends a second control wave to the LLC converter; the second control wave is used to control the power device group to maintain a high level for a preset period of time during the stop phase of the light load condition, and locally monitor the LLC converter within the preset period of time.

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