Stable transient state analysis method and system of submarine observation network power supply system

Abstract

The invention relates to a steady transient analysis method and system for a submarine observation network power supply system, and belongs to the technical field of submarine observation networks. The method comprises the following steps: establishing a junction box converter system equivalent model, and carrying out cathode constant-voltage submarine observation network power supply system modeling by using the junction box converter system equivalent model so as to carry out stable and transient analysis on the submarine observation network power supply system; the junction box current transformation system equivalent model is an improved junction box current transformation system equivalent model, and the improvement is that an input side positive electrode of the junction box current transformation system is grounded, and an input side negative electrode is connected to a negative electrode constant-voltage seabed observation network submarine cable. The input side positive electrode of the junction box conversion system is grounded, and the input side negative electrode is connected to the negative electrode constant-voltage submarine observation network submarine cable, so that the loop impedance between the shore-based power supply output polarity and the junction box electric energy conversion system is calculated, and the influence on the overall stable transient analysis of the constant-voltage submarine observation network power supply system is further reduced; and the stable transient analysis requirement in the modeling of the power supply system is met.

Description

Technical Field

[0001] This invention relates to a steady-state and transient analysis method and system for a power supply system of a submarine observation network, belonging to the technical field of submarine observation networks. Background Technology

[0002] Regarding the research on the converter model of the junction box in the negative pole constant voltage power supply system of the seabed observation network, existing literature, based on the characteristics of poor failure risk and poor heat dissipation of seabed equipment, proposes a high-redundancy high-voltage DC / DC junction box converter topology model based on a combination of high-frequency PWM low-voltage DC / DC converters. This converter topology has strong fault tolerance and high power density, making it suitable for operation in the deep-sea environment. Furthermore, based on the input / output dynamic characteristics of a single PWM control power module, existing literature proposes a high-voltage DC / DC junction box converter topology model based on multi-module series-parallel stacking with common duty cycle synchronous rectification. In addition, existing literature has established a small-signal mathematical model of the junction box converter with a full-bridge buck converter topology to further analyze the static and transient stability of the negative pole constant voltage power supply system of the seabed observation network.

[0003] The aforementioned existing technical solutions mainly suffer from the following technical defects: Existing literature has established small-signal mathematical models of junction box converters with a full-bridge step-down converter topology. However, these studies do not consider the disconnection characteristics of the junction box converter under abnormal input voltage ranges, thus affecting the overall transient fault characteristic analysis of the constant-voltage seabed observation network power supply system before and after the fault transient. Furthermore, existing junction box converter models do not consider the loop impedance between the anode and cathode of the shore-based power supply / junction box current converter system, nor the output polarity of the shore-based power supply for the constant-voltage seabed observation network. This results in incorrect input-side loop impedance settings for the junction box converter, thereby affecting the overall steady-state and transient analysis of the constant-voltage seabed observation network power supply system. Summary of the Invention

[0004] The purpose of this invention is to provide a method and system for steady-state and transient analysis of the power supply system of a submarine observation network, in order to solve the problem that the current model of the junction box converter does not take into account the circuit impedance between the output polarity of the shore power source and the power conversion system of the junction box, which affects the overall steady-state and transient analysis of the constant voltage submarine observation network power supply system.

[0005] To achieve the above objectives, the present invention includes: The present invention provides a steady-state and transient analysis method for a power supply system of a submarine observation network, the method comprising: 1) Establish an equivalent model of the junction box converter system; 2) The equivalent model of the junction box converter system is used to model the power supply system of the negative pole constant voltage submarine observation network, so as to carry out steady-state and transient analysis of the power supply system of the submarine observation network. The equivalent model of the junction box converter system adopts an improved equivalent model of the junction box converter system, and its improvement includes: the positive terminal of the input side of the junction box converter system is grounded, and the negative terminal of the input side is connected to the negative terminal constant voltage submarine observation network cable.

[0006] Furthermore, the control unit in the junction box converter system is used to implement any or any combination of the following controls: ① During the operation of the junction box converter in the junction box converter system, when the input side voltage on the input side of the junction box converter system is less than or equal to the preset exit threshold, the control unit disconnects the DC switch used to put the junction box converter into operation. ② After the DC switch used to put the junction box converter into operation is closed, the control unit starts the control of each power unit of the junction box converter; ③ After receiving the pre-charge start command to put the junction box converter into operation, the control unit closes the soft start switch in the soft start module used for slow start of the junction box converter. When the input side voltage on the input side of the junction box converter system is not lower than the preset soft start voltage threshold, the control unit closes the DC switch and opens the soft start switch; when the input side voltage is lower than the soft start voltage threshold, the control unit opens the soft start switch.

[0007] Furthermore, in ②, each power unit of the junction box converter adopts the same control strategy, which uses peak current control to quickly respond to changes in the input voltage and the load connected to the output side of the junction box converter.

[0008] Furthermore, a soft-start module for slow-start converters is connected in series on the input side of the junction box converter system.

[0009] Furthermore, the soft-start module includes a DC switch, a soft-start switch, and a soft-start resistor for limiting the starting current. The soft-start switch, which is connected in series, is connected in parallel with the soft-start resistor and the DC switch so that when starting the converter, the soft-start switch is closed first, and then the DC switch is closed.

[0010] Furthermore, the junction box converter system is also equipped with a sampling module to collect the input voltage and input current on the input side of the junction box converter system, as well as the output voltage on the output side of the junction box converter system.

[0011] Furthermore, the input side of the junction box converter system is also equipped with an LC filter circuit.

[0012] Furthermore, the junction box converter in the junction box converter system adopts an ISOP modular stacking structure converter.

[0013] Furthermore, in ①, the exit threshold is the absolute value of the rated voltage of the input voltage of the junction box converter, which is 60% of the rated voltage.

[0014] The present invention provides a steady-state and transient analysis system for a power supply system of a seabed observation network, comprising a processor for executing a computer program to implement the steps of the steady-state and transient analysis method for a power supply system of a seabed observation network as described above.

[0015] The beneficial effects of this invention are: This invention is an improved invention, providing a method for steady-state and transient analysis of a power supply system for a submarine observation network. It adopts an improved equivalent model of the junction box converter system. Specifically, the positive input terminal of the junction box converter system is grounded, and the negative input terminal is connected to the negative terminal of the constant voltage submarine observation network cable. This takes into account the output polarity of the shore-based power supply and the loop impedance between the junction box power converter system, thereby reducing the impact on the overall steady-state and transient analysis of the constant voltage submarine observation network power supply system and enabling it to meet the steady-state and transient analysis requirements in the modeling of the constant voltage submarine observation network power supply system. Attached Figure Description

[0016] Figure 1 This is a topology diagram of the equivalent junction box converter in the junction box power conversion system; Figure 2 This is a topology diagram of the low-voltage, low-power unit in the junction box converter. Detailed Implementation

[0017] To address the problems in the background art, this invention reduces the impact on the overall steady-state and transient analysis of the constant-pressure seabed observation network power supply system by taking into account the output polarity of the shore-based power supply and the loop impedance between the junction box power converter system and the constant-pressure seabed observation network power supply system. This enables the equivalent model of the junction box power converter system to meet the steady-state and transient analysis requirements in the modeling of the constant-pressure seabed observation network power supply system.

[0018] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0019] Implementation method of a steady-transient analysis method for a power supply system of a submarine observation network: A method for steady-state and transient analysis of a power supply system for a submarine observation network is provided. The method includes: 1) establishing an equivalent model of the junction box converter system; 2) using the equivalent model of the junction box converter system to model the negative pole constant voltage submarine observation network power supply system, so as to perform steady-state and transient analysis of the submarine observation network power supply system.

[0020] The equivalent model of the junction box converter system adopts an improved equivalent model, and its improvement includes: the positive terminal of the input side of the junction box converter system is grounded, and the negative terminal of the input side is connected to the negative terminal of the constant voltage submarine observation network cable, so as to take into account the output polarity of the shore power supply and the loop impedance between the junction box power converter system, thereby reducing the impact on the overall steady and transient analysis of the constant voltage submarine observation network power supply system, so as to meet the steady and transient analysis requirements in the modeling of the constant voltage submarine observation network power supply system.

[0021] Specifically, the control unit in the junction box converter system is used to implement any or any combination of the following controls: ① During the operation of the junction box converter in the junction box converter system, when the input voltage on the input side of the junction box converter system is less than or equal to the preset exit threshold, the control unit disconnects the DC switch used to put the junction box converter into operation. This takes into account the exit characteristics of the junction box converter under abnormal normal operating input voltage range, thereby reducing the impact on the overall transient fault characteristic analysis of the constant voltage seabed observation network power supply system before and after the fault transient, so as to meet the steady and transient analysis requirements in the modeling of the constant voltage seabed observation network power supply system.

[0022] ② After the DC switch used to put the junction box converter into operation is closed, the control unit starts the control of each power unit of the junction box converter.

[0023] ③ After receiving the pre-charge start command to put the junction box converter into operation, the control unit first closes the soft start switch in the soft start module used for slow start of the junction box converter. Then, when the input voltage on the input side of the junction box converter system is not lower than the preset soft start voltage threshold, it closes the DC switch and opens the soft start switch; when the input voltage is lower than the soft start voltage threshold, it opens the soft start switch. The DC switch is connected in parallel across the branch where the soft start switch is located. When the DC switch is closed, the branch where the DC switch is located bypasses the branch where the soft start switch is located.

[0024] The following is combined Figure 1 and Figure 2 The equivalent model of the junction box converter system used in the steady-state analysis method of the power supply system of the submarine observation network is further explained in detail.

[0025] The improvement of the equivalent model of the junction box power converter system relates to the field of power electronic conversion technology, specifically to an equivalent model of a power converter system under a DC distribution network. To address the problems in existing technical solutions where the equivalent model of the junction box power converter system in a constant-voltage seabed observation network does not consider low-voltage exit control characteristics or input-side loop impedance, this invention proposes an equivalent model of the junction box power converter system for a constant-voltage seabed observation network, also known as an equivalent model of a power converter system under a DC distribution network. Specifically, the junction box power conversion system (junction box power converter system) is equivalent to a typical high-voltage DC / DC converter model for the junction box. This equivalent model simplifies the structure of the junction box power conversion system in a constant-voltage seabed observation network while ensuring that the external characteristics of the input side of the junction box power conversion system remain unchanged.

[0026] The equivalent model topology of the power conversion system is as follows: Figure 1 As shown, it includes: a DC soft start circuit ( Figure 1The branch containing the soft-start resistor R has a soft-start switch and the soft-start resistor R connected in series, and a DC switch ( Figure 1 The circuit connected in parallel with the DC soft starter circuit is a DC switch, and the input-side LC filter circuit is also connected in parallel. Figure 1 The input-side LC filter includes the filter inductor. L in and filter capacitor C in The system includes components such as low-voltage, low-power units, control circuits, and grounding circuits. The equivalent model control circuit of this power converter system includes: input voltage sampling (…). Figure 1 Input side voltage sampling U JBCn ), output voltage sampling ( Figure 1 Output side voltage sampling U out_JBCn Input current sampling () Figure 1 Input-side current sampling i JBCn The equivalent model is applicable to the modeling of the power supply system of the constant-pressure seabed observation network, taking into account the loop impedance between the shore-based power supply and the junction box power converter system, as well as the low-voltage exit control characteristics, thereby meeting the steady-state and transient analysis requirements in the modeling of the power supply system of the constant-pressure seabed observation network.

[0027] The specific scheme of the equivalent model of the power conversion system is as follows: 1) The topology of the constant pressure seabed observation network junction box power converter system is as follows: like Figure 1 As shown, the equivalent model of the junction box converter includes a DC soft-start circuit, a DC switch, an LC filter circuit, and the converter on the input side. The converter as a whole adopts an ISOP modular stacked structure, that is, the junction box converter is composed of several low-voltage, low-power units sharing the same input filter circuit, connected in series at the input and in parallel at the output. The low-voltage, low-power units are as follows: Figure 2 The two corresponding forward converters with identical component parameters shown are connected in series on the input side and in parallel on the output side. The negative terminal of the converter input side is connected to the submarine cable of the constant voltage submarine observation network, and the positive terminal of the input side is grounded.

[0028] The ISOP modular stacking structure ensures that the junction box converter maintains high reliability and power density while also achieving high power conversion efficiency and low heat loss. A DC soft-start circuit and DC switch are used for slow-starting the converter and connecting the submarine fiber optic cable. The input-side LC filter circuit includes a filter inductor. L in and filter capacitor C inIt is mainly used to filter out high-frequency harmonics. The low-voltage, low-power unit is used for modular power conversion and output of the junction box converter.

[0029] The negative input terminal of the converter in the junction box is connected to the submarine cable because constant-voltage submarine observation networks generally use unipolar DC transmission, and the onshore power supply's unipolar output voltage is negative due to the rapid loss of power at the submarine electrodes. The positive input terminal of the converter in the junction box is grounded because the positive terminal of the onshore power supply is the submarine electrode (anode), while the negative terminal of the converter in the junction box is the submarine electrode (cathode). The loop loss between the positive terminal of the onshore power supply and the negative terminal of the converter in the junction box includes contact resistance (contact resistance between the electrode and seawater) and the resistance of the seawater conductor. Research shows that the contact resistance value is mainly related to three factors: the contact area between the seawater and the electrode, the grounding method of the onshore base station anode, and the potential of the submarine electrode. Under the current actual operational observation network conditions of the submarine electrode surface area and the onshore power supply output voltage level, the contact resistance is approximately zero, and the resistance of the seawater conductor is negligible. Therefore, the resistance of the seawater-submarine electrode positive voltage return loop in the constant-voltage power supply system of the submarine observation network is approximately zero.

[0030] 2) The control circuit of the power conversion system of the junction box of the constant pressure seabed observation network includes: input voltage sampling, output voltage sampling, input current sampling, control unit, etc.

[0031] 3) The working process of the equivalent model of the power conversion system applied under DC distribution network is as follows: ① After receiving the pre-charge start command to put the junction box converter into operation, the control unit closes the soft start switch in the input side DC soft start circuit. When the collected input side voltage is not lower than the soft start voltage threshold, the control unit closes the input side DC switch and then opens the soft start switch in the input side DC soft start circuit after the input side DC switch is closed. When the collected input side voltage is lower than the soft start voltage threshold, the control unit opens the soft start switch in the DC soft start circuit and exits the start-up process.

[0032] ② Close the input-side DC switch and the control unit activates the control loop of each power unit of the junction box converter.

[0033] ③ All power units, i.e., all low-voltage small-power units, of the junction box converter adopt the same control strategy. Each low-voltage small-power unit of the junction box converter uses peak current control capable of quickly responding to changes in input voltage and the load connected to the output side. They are controlled by the same peak current controller, and all low-voltage small-power units operate under the same duty cycle PWM, such as... Figure 2 As shown, in the low-voltage low-power unit, switching transistors S1 and S2 are driven by the same turn-on and turn-off signals, and switching transistors S3 and S4 are driven by the same turn-on and turn-off signals.

[0034] In this system, the peak current control of each low-voltage, low-power unit of the junction box converter is achieved by real-time monitoring of the inductor current peak value, comparing it with a reference signal, and then adjusting the switching transistors cycle by cycle to achieve rapid dynamic response and overcurrent protection. Its core is a dual closed-loop control: the outer voltage loop stabilizes the DC bus voltage, while the inner current loop tracks the sinusoidal reference current to ensure unity power factor and harmonic suppression.

[0035] ④ Due to factors such as submarine load switching and changes in shore-based power transmission, the input voltage of the junction box converter may fluctuate significantly. Limited by the DC / DC gain range, the junction box converter will shut down when the input voltage falls below the minimum operating threshold. When the input voltage (input-side voltage) of the junction box converter is less than or equal to the shutdown threshold (minimum operating threshold), the relay switch at the junction box input terminal is opened (i.e., the input-side DC switch is opened, with an opening delay of 0.1ms), and the junction box converter shuts down. Based on the typical conversion characteristics of junction box converters, the shutdown voltage threshold (shutdown threshold) is taken as the absolute value of 60% of the rated voltage of the junction box converter's input voltage.

[0036] The beneficial effects of this plan are: The equivalent model of the power conversion system under the DC distribution network has a simple topology and the power conversion control is easy to implement. This equivalent model is suitable for modeling the power supply system of the constant voltage seabed observation network, and takes into account the loop impedance between the shore power source and the junction box power conversion system, as well as the low voltage exit control characteristics, thus meeting the steady-state and transient analysis requirements in the modeling of the power supply system of the constant voltage seabed observation network.

[0037] An implementation method for a steady-state and transient analysis system for a power supply system of a submarine observation network: A steady-state transient analysis system for a power supply system of a seabed observation network includes a processor. The processor executes a computer program to implement the steps of a steady-state transient analysis method for a power supply system of a seabed observation network. The specific steps and effects of the steady-state transient analysis method for a power supply system of a seabed observation network have been described in detail in an implementation method for the steady-state transient analysis method of a seabed observation network, and will not be repeated here.

Claims

1. A steady-state and transient analysis method for a power supply system of a submarine observation network, characterized in that, The method includes: 1) Establish an equivalent model of the junction box converter system; 2) The equivalent model of the junction box converter system is used to model the power supply system of the negative pole constant voltage submarine observation network, so as to carry out steady-state and transient analysis of the power supply system of the submarine observation network. The equivalent model of the junction box converter system adopts an improved equivalent model of the junction box converter system, and its improvement includes: the positive terminal of the input side of the junction box converter system is grounded, and the negative terminal of the input side is connected to the negative terminal constant voltage submarine observation network cable.

2. The steady-state and transient analysis method for the power supply system of the submarine observation network according to claim 1, characterized in that, The control unit in the junction box converter system is used to implement any or any combination of the following controls: ① During the operation of the junction box converter in the junction box converter system, when the input side voltage on the input side of the junction box converter system is less than or equal to the preset exit threshold, the control unit disconnects the DC switch used to put the junction box converter into operation. ② After the DC switch used to put the junction box converter into operation is closed, the control unit starts the control of each power unit of the junction box converter; ③ After receiving the pre-charge start command to put the junction box converter into operation, the control unit closes the soft start switch in the soft start module used for slow start of the junction box converter. When the input side voltage on the input side of the junction box converter system is not lower than the preset soft start voltage threshold, the control unit closes the DC switch and opens the soft start switch; when the input side voltage is lower than the soft start voltage threshold, the control unit opens the soft start switch.

3. The steady-state and transient analysis method for the power supply system of the submarine observation network according to claim 2, characterized in that, ② Each power unit of the junction box converter adopts the same control strategy, which uses peak current control to quickly respond to changes in the input voltage and the load connected to the output side of the junction box converter.

4. The steady-state and transient analysis method for the power supply system of the submarine observation network according to claim 1, characterized in that, The input side of the junction box converter system is connected in series with a soft-start module for slow-start converter.

5. The steady-state and transient analysis method for the power supply system of the submarine observation network according to claim 4, characterized in that, The soft-start module includes a DC switch, a soft-start switch, and a soft-start resistor for limiting the starting current. The soft-start switch, which is connected in series, is connected in parallel with the soft-start resistor and the DC switch so that when starting the converter, the soft-start switch is closed first, and then the DC switch is closed.

6. The steady-state and transient analysis method for the power supply system of the submarine observation network according to claim 1, characterized in that, The junction box converter system is also equipped with a sampling module to collect the input voltage and input current on the input side of the junction box converter system, as well as the output voltage on the output side of the junction box converter system.

7. The steady-state and transient analysis method for the power supply system of the submarine observation network according to claim 1, characterized in that, The input side of the junction box converter system is also equipped with an LC filter circuit.

8. The steady-state and transient analysis method for the power supply system of the submarine observation network according to claim 1, characterized in that, The junction box converter in the junction box converter system adopts an ISOP modular stacking structure converter.

9. The steady-state and transient analysis method for the power supply system of the submarine observation network according to claim 2, characterized in that, The exit threshold mentioned in ① is the absolute value of the rated voltage of the input voltage of the junction box converter at 60%.

10. A steady-state and transient analysis system for a power supply system of a submarine observation network, comprising a processor, characterized in that, The processor is used to execute a computer program to implement the steps of the steady-state and transient analysis method for the power supply system of the submarine observation network as described in any one of claims 1 to 9.

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