Flexible DC ring network power supply system for hydrogen-powered ships and working method thereof

Abstract

The present invention discloses a flexible DC ring network power supply system for hydrogen-powered ships, comprising a DC ring network main system, a first hydrogen fuel cell power supply system (1), a first composite energy storage system (2), a second hydrogen fuel cell power supply system (3), a second composite energy storage system (4), a first regional load system (5), a second regional load system (6), a monitoring system (7), an energy management system (8), a daily AC distribution network system (14), a first auxiliary load (15), and a second auxiliary load (16), a first hydrogen fuel cell power supply system (1), and a first composite energy storage system (2). The DC ring network main system comprises a first DC bus (10), a second DC bus (11), a third DC bus (12), and a fourth DC bus (13). The present invention can solve the technical problem that the existing radial power supply system is prone to overload of the transmission line due to load concentration.

Description

Technical Field

[0001] The present invention belongs to the technical field of ship power systems and power supply systems, and more specifically, relates to a flexible DC ring network power supply system for a hydrogen-powered ship and a working method thereof. Background Art

[0002] Hydrogen-powered ships are a new type of green ship with high energy utilization efficiency, which can reduce fossil fuel consumption and pollutant emissions during navigation. Traditional mechanical propulsion systems have problems such as high noise, small speed regulation range, poor flexibility and economy. Hydrogen fuel cells, as a new type of green power device, have the characteristics of zero emission, no pollution, and renewable. They can replace internal combustion engines and realize the transformation and upgrading of ship power systems. Hydrogen fuel cells have high energy density, high conversion efficiency, and strong environmental adaptability. They are ideal power sources for ship electric propulsion systems.

[0003] Ships that use hydrogen fuel cells as their main power source currently widely use radial power supply systems as DC power supply systems. The hydrogen fuel cells and energy storage systems are respectively connected to two DC bus bars, and power is distributed through the two DC bus bars. The two DC bus bars are connected by a bus tie switch. The left and right thrusters, thrusters, auxiliary loads, daily loads, etc. are respectively connected to the two DC bus bars through inverters. Its main advantages are simple structure and low investment cost.

[0004] However, the existing radial power supply system has some defects that cannot be ignored:

[0005] First, the power supply and load can only be connected to two DC buses, which requires thicker cables to obtain higher transmission capacity. Transmission through only two buses makes the load more concentrated, which can easily cause overload problems of the transmission line and increase the risk of system operation.

[0006] Second, the system has the disadvantages of poor power supply reliability and flexibility. Therefore, when the bus fails or is under maintenance, all loads connected to the bus will be powered off, thus affecting all connected power supplies and loads.

[0007] Third, the system uses lithium batteries as the power source of the energy storage system. During long-term use, components may need to be replaced frequently, increasing maintenance costs. In addition, the control mode is single and the scheduling operation is not flexible enough, which limits the ability to adapt to changes in power flow and makes it difficult to take into account multiple performance requirements. Summary of the invention

[0008] In view of the above defects or improvement needs of the prior art, the present invention provides a flexible DC ring network power supply system for hydrogen-powered ships and a working method thereof, which aims to solve the technical problems of the existing radial power supply system, which is prone to overload of transmission lines due to concentrated load, as well as the technical problems of poor fault isolation capability, long fault recovery time and low power supply reliability, as well as the technical problems of single control mode, inflexible scheduling operation, difficulty in adapting to changes in tides and difficulty in taking into account various performance requirements.

[0009] To achieve the above-mentioned object, according to one aspect of the present invention, a flexible DC ring network power supply system for hydrogen-powered ships is provided, comprising a DC ring network main system, a first hydrogen fuel cell power supply system (1), a first composite energy storage system (2), a second hydrogen fuel cell power supply system (3), a second composite energy storage system (4), a first regional load system (5), a second regional load system (6), a monitoring system (7), an energy management system (8), a daily AC distribution network system (14), a first auxiliary load (15), and a second auxiliary load (16), the first hydrogen fuel cell power supply system (1), the first composite energy storage system (2), the DC ring network main system comprising a first DC bus (10), a second DC bus (11), a third DC bus (12), and a fourth DC bus (13), wherein the four DC buses are electrically connected end to end via four solid-state switches (9);

[0010] The first hydrogen fuel cell power supply system (1) and the first composite energy storage system (2) are electrically connected to the first DC bus, and the second hydrogen fuel cell power supply system (3) and the second composite energy storage system (4) are electrically connected to the second DC bus (11);

[0011] The first regional load system (5) is electrically connected to the first DC bus (10) and the third DC bus (12), respectively, and the second regional load system (6) is electrically connected to the second DC bus (11) and the fourth DC bus (13), respectively;

[0012] The monitoring system (7) is electrically connected to the first hydrogen fuel cell power supply system (1), the second hydrogen fuel cell power supply system (3), the first composite energy storage system (2), the second composite energy storage system (4), the first regional load system (5), and the second regional load system (6) through weak current signal lines, and is electrically connected to the first DC bus (10), the second DC bus (11), the third DC bus (12), and the fourth DC bus (13) to monitor the real-time status of each system and the DC bus in real time;

[0013] The energy management system (8) is electrically connected to the monitoring system (7), the first hydrogen fuel cell power supply system (1), the second hydrogen fuel cell power supply system (3), the first composite energy storage system (2), and the second composite energy storage system (4);

[0014] The daily AC power distribution network system (14) is electrically connected to the third DC bus (12) and the fourth DC bus (13) respectively;

[0015] The first auxiliary load (15) is electrically connected to the third DC bus (12), and the second auxiliary load (16) is electrically connected to the fourth DC bus (13).

[0016] Preferably, the first regional load system (5) and the first auxiliary load (15) are arranged in the port side area of ​​the hydrogen-powered ship, and the second hydrogen fuel cell power supply system (3), the second composite energy storage system (4), the second regional load system (6) and the second auxiliary load (16) are arranged in the starboard side area of ​​the hydrogen-powered ship;

[0017] The first hydrogen fuel cell power supply system (1) and the second hydrogen fuel cell power supply system (3) are completely identical, and the first composite energy storage system (2) and the second composite energy storage system (4) are completely identical;

[0018] The first hydrogen fuel cell power supply system (1) comprises a hydrogen fuel cell (1-1), a boost DC converter (1-2), a DC circuit breaker (1-3), and a protection module (1-4); the hydrogen fuel cell (1-1) is electrically connected to a first DC bus (10) via the boost DC converter (1-2), the DC circuit breaker (1-3), and the protection module (1-4) in sequence;

[0019] The first composite energy storage system (2) comprises a lithium battery (2-1), a first bidirectional DC converter (2-3), a super capacitor (2-2), a second bidirectional DC converter (2-4), a DC circuit breaker (2-5), and a protection module (2-6); the lithium battery (2-1) is electrically connected to a first DC bus (10) via the first bidirectional DC converter (2-3), the DC circuit breaker (2-5), and the protection module (2-6); and the super capacitor (2-2) is electrically connected to the first DC bus (10) via the second bidirectional DC converter (2-4), the DC circuit breaker (2-5), and the protection module 2-6.

[0020] Preferably, the first regional load system (5) and the second regional load system (6) are completely identical, and the first auxiliary load (15) and the second auxiliary load (16) are completely identical;

[0021] The first regional load system (5) comprises a propulsion motor (5-1), a thruster (5-2), an impact load (5-3), a DC / AC inverter (5-4), a first regional distribution board (5-5), a protection module (5-6) and a DC circuit breaker (5-7); the propulsion motor (5-1), the thruster (5-2) and the impact load (5-3) are all electrically connected to the first regional distribution board (5-5) through the DC / AC inverter (5-4) and the DC circuit breaker (5-7); and the first regional distribution board (5-5) is electrically connected to the first DC bus (10) and the second DC bus 12 respectively through the protection module (5-6);

[0022] The first auxiliary load (15) includes a protection module 15-1, a DC circuit breaker (15-2), a DC / AC inverter (15-3), an isolation transformer (15-4), and an auxiliary device (15-5), wherein the auxiliary device (15-5) is connected to the third DC bus (12) via the isolation transformer (15-4), the DC / AC inverter (15-3), the DC circuit breaker (15-2), and the protection module (15-1).

[0023] Preferably, the daily AC distribution network system (14) comprises a protection module (14-1), a DC circuit breaker (14-2), a DC / AC inverter (14-3), an isolation transformer (14-4), an AC circuit breaker (14-5), a pair of AC distribution boards (14-6), a bus tie switch 14-7, and a pair of daily loads (14-8);

[0024] The third DC bus (12) and the fourth DC bus (13) are respectively connected to an AC distribution board (14-6) via a protection module (14-1), a DC circuit breaker (14-2), a DC / AC inverter (14-3), an isolation transformer (14-4), an AC circuit breaker (14-5), and the protection module (14-1);

[0025] The two AC distribution boards (14-6) are connected to each other via a busbar switch (14-7), and supply power to a corresponding daily load (14-8) via an AC circuit breaker (14-5).

[0026] According to another aspect of the present invention, there is provided a working method of a flexible DC ring network power supply system for a hydrogen-powered ship, comprising the following steps:

[0027] (1) The first hydrogen fuel cell power supply system and the second hydrogen fuel cell power supply system generate electric energy and boost the electric energy to 500V and output it to the first DC bus and the second DC bus respectively. The third and fourth DC buses are electrically connected to the first DC bus and the second DC bus through solid-state switches to obtain a DC voltage of 500V. At the same time, the monitoring system determines whether the operating status of the first hydrogen fuel cell power supply system and the second hydrogen fuel cell power supply system is normal, overloaded, or faulty according to the output voltage and output current of the first hydrogen fuel cell power supply system and the second hydrogen fuel cell power supply system. If both are in a normal state, the process proceeds to step (5). If one of them is in a faulty state and the other is in a normal state or an overloaded state, the process proceeds to step (2). If both are in an overloaded state, the process proceeds to step (3). If both are in a faulty state, the energy management system sends a fault alarm signal and proceeds to step (12);

[0028] (2) The energy management system sends out a fault alarm signal and automatically cuts off the connection between the hydrogen fuel cell power supply system with the fault and the DC ring network main system. At the same time, the monitoring system determines whether the operating state of the hydrogen fuel cell in another hydrogen fuel cell power supply system is normal or overloaded. If it is in a normal state, it proceeds to step (5); if it is in an overloaded state, it proceeds to step (3);

[0029] (3) The energy management system sends out an overload alarm signal and automatically reduces the output power of the hydrogen fuel cell in the overload state to the rated output power, and determines whether the voltage of the first DC bus and the second DC bus drops seriously at this time. If so, the process proceeds to step (4), otherwise, the process proceeds to step (5);

[0030] (4) The energy management system selectively cuts off the first regional load system, the second regional load system, the first auxiliary load, the second auxiliary load, and the daily load according to their importance until the hydrogen fuel cell power supply system in the overload state is restored to a normal state and the voltages of the first DC bus and the second DC bus remain stable, and then enters step (5);

[0031] (5) The energy management system sends a control instruction to the first composite energy storage system and the second composite energy storage system, so that the first composite energy storage system and the second composite energy storage system all enter the voltage fluctuation smoothing mode, and then proceeds to step (6);

[0032] (6) The energy management system obtains the voltage and current signals of the first regional load system, the second regional load system, the first auxiliary load, and the second auxiliary load collected by the monitoring system, and generates corresponding power signals according to the respective voltage and current signals, and decomposes the power signals using a second-order filtering control strategy to obtain a reference power of the first lithium battery in the first composite energy storage system, a reference power of the second lithium battery in the second composite energy storage system, a reference power of the first supercapacitor in the first composite energy storage system, and a reference power of the second supercapacitor in the second composite energy storage system, and then proceeds to step (7);

[0033] (7) determining whether the reference power of the first lithium battery in the first composite energy storage system is greater than its maximum power; if so, the energy management system adjusts the reference power of the first lithium battery to its maximum power and then proceeds to step (8); otherwise, directly proceeds to step (8);

[0034] (8) determining whether the reference power of the first supercapacitor in the first composite energy storage system is greater than its maximum power; if so, the energy management system adjusts the reference power of the first supercapacitor to its maximum power and then proceeds to step (9); otherwise, directly proceeds to step (9);

[0035] (9) determining whether the reference power of the second lithium battery in the second composite energy storage system is greater than its maximum power; if so, the energy management system adjusts the reference power of the second lithium battery to its maximum power and then proceeds to step (10); otherwise, directly proceeds to step (10);

[0036] (10) Determine whether the reference power of the second supercapacitor in the second composite energy storage system is greater than its maximum power. If so, the energy management system adjusts the reference power of the second supercapacitor to its maximum power and then proceeds to step (11). Otherwise, directly proceeds to step (11).

[0037] (11) The bidirectional DC converter in the first composite energy storage system adopts a power tracking control method to keep the power of the first lithium battery and the first super capacitor near their reference power, and the bidirectional DC converter in the second composite energy storage system adopts a power tracking control strategy to keep the power of the second lithium battery and the second super capacitor near their reference power, and then enters step (20);

[0038] (12) The bidirectional DC converter of the first lithium battery in the first composite energy storage system is switched to a voltage constant value control mode, and the bidirectional DC converter of the second lithium battery in the second composite energy storage system is switched to a voltage constant value control mode, and then the process proceeds to step (13);

[0039] (13) The monitoring system monitors whether the power of the first lithium battery in the first composite energy storage system exceeds its maximum power. If so, it is determined that the first lithium battery is in an overload state. The energy management system controls the bidirectional DC converter of the first lithium battery in the first composite energy storage system to send an overload alarm signal and automatically reduce the power of the first lithium battery to the maximum power of 120 kW, and then proceeds to step (14). If not, it directly proceeds to step (14);

[0040] (14) The monitoring system monitors whether the power of the second lithium battery in the second composite energy storage system exceeds its maximum power. If it exceeds, it is determined that the second lithium battery is in an overload state, and the energy management system controls the bidirectional DC converter of the second lithium battery in the second composite energy storage system to send an overload alarm signal and automatically reduce the power of the second lithium battery to the maximum power, and then proceed to step (15); if it does not exceed, directly proceed to step (15);

[0041] (15) The monitoring system monitors the voltage values ​​of the first DC bus and the second DC bus, and determines whether the voltage of the first DC bus and the second DC bus drops seriously at this time. If so, the energy management system selectively cuts off the first regional load system, the second regional load system, the first auxiliary load, the second auxiliary load, and the daily load according to the load importance until the voltage of the first DC bus and the second DC bus remains stable, and then enters step (16); otherwise, directly transfers to step (16);

[0042] (16) The energy management system obtains the voltage and current signals of the first regional load system, the second regional load system, the first auxiliary load, and the second auxiliary load collected by the monitoring system, and generates corresponding power signals according to the respective voltage and current signals, and decomposes the power signals using a first-order filtering strategy to obtain a power reference value of the first supercapacitor in the first composite energy storage system and a power reference value of the second supercapacitor in the second composite energy storage system, and then enters step (17);

[0043] (17) determining whether the reference power of the first supercapacitor in the first composite energy storage system is greater than its maximum power; if so, the energy management system adjusts the reference power of the first supercapacitor to its maximum power and proceeds to step (18); otherwise, the system directly proceeds to step (18);

[0044] (18) Determine whether the reference power of the second supercapacitor in the second composite energy storage system is greater than its maximum power. If so, the energy management system adjusts the reference power of the second supercapacitor to its maximum power and proceeds to step (19); otherwise, directly proceeds to step (19);

[0045] (19) The bidirectional DC converter of the first supercapacitor in the first composite energy storage system adopts a power tracking control mode to keep the power of the first supercapacitor near its reference power, and the bidirectional DC converter of the second supercapacitor in the second composite energy storage system adopts a power tracking control mode to keep the power of the second supercapacitor near its reference power, and then enters step (20);

[0046] (20) The monitoring system monitors the differential currents of the first DC bus, the second DC bus, the third DC bus, and the fourth DC bus, and determines whether any one of the four differential currents exceeds a set threshold value. If so, it is determined that a short circuit fault occurs in the area of ​​the DC bus where the differential current is located, and then the process goes to step (21); otherwise, the process goes to step (29);

[0047] (21) The monitoring system generates a protection signal and determines whether the short-circuited DC bus is connected to a hydrogen fuel cell power supply system and a composite energy storage system. If so, the system proceeds to step (22); otherwise, the system proceeds to step (27);

[0048] (22) The monitoring system sends a protection signal to the solid-state switch that is electrically connected to the short-circuited DC bus and is closest to it, as well as the protection modules in the hydrogen fuel cell power supply system, the composite energy storage system, and the regional load system that are electrically connected to the short-circuited DC bus; the protection module isolates the short-circuited DC bus from the hydrogen fuel cell power supply system, the composite energy storage system, and the regional load system; the solid-state switch is disconnected to isolate the short-circuited DC bus from other DC buses electrically connected to it, and then enters step (23);

[0049] (23) The regional load system connected to the short-circuited DC bus supplies power to the regional load system electrically connected to the short-circuited DC bus relative to the DC bus on the other side of the short-circuited DC bus; the DC ring network main system is switched from being powered by the dual fuel cell power supply system and the dual composite energy storage system to being powered by a single hydrogen fuel cell power supply system and a single composite energy storage system, and at the same time, the monitoring system determines whether the operating state of the single hydrogen fuel cell power supply system is in a normal state, an overload state, or a fault state. If it is in a normal state, it proceeds to step (26); if it is in an overload state, it proceeds to step (24); if it is in a fault state, it proceeds to step (25);

[0050] (24) The energy management system sends out an overload alarm signal and automatically reduces the output power of the single hydrogen fuel cell power supply system to the rated output power, and determines whether the voltage of the first DC bus and the second DC bus drops seriously at this time. If so, proceed to step (26), otherwise proceed to step (27);

[0051] (25) The energy management system sends out a fault alarm signal and switches the bidirectional DC converter of the lithium battery in the single composite energy storage system to a voltage constant value control mode. At the same time, the monitoring system determines whether the power of the lithium battery in the single composite energy storage system exceeds its maximum power. If so, it indicates that the lithium battery is in an overload state. The energy management system controls the bidirectional DC converter of the lithium battery in the single composite energy storage system to send out an overload alarm signal and automatically reduces the power of the lithium battery in the single composite energy storage system to the maximum power, and then proceeds to step (26). Otherwise, proceeds to step (28);

[0052] (26) The energy management system selectively cuts off the first regional load system, the second regional load system, the first auxiliary load, the second auxiliary load, and the daily load according to their importance until the voltages of the first DC bus and the second DC bus remain stable, and then enters step (28).

[0053] (27) The monitoring system sends a protection signal to the solid-state switch that is electrically connected to the short-circuited DC bus and is closest to it, and to a protection module in the regional load system that is electrically connected to the short-circuited DC bus, and the protection module isolates the short-circuited DC bus from the regional load system; the solid-state switch is disconnected to isolate the short-circuited DC bus from other DC buses that are electrically connected to it, and the regional load system that is connected to the short-circuited DC bus supplies power to the regional load system that is electrically connected to the short-circuited DC bus relative to the DC bus on the other side of the short-circuited DC bus, and then proceeds to step (28);

[0054] (28) The DC ring network main system switches to open-loop operation and handles the short-circuited DC bus fault, and then enters step (29);

[0055] (29) The DC ring network main system maintains closed-loop operation and the process ends.

[0056] Preferably, in step (1), the monitoring system calculates the output power based on the output voltage and output current of the first hydrogen fuel cell power supply system and the second hydrogen fuel cell power supply system. When the first hydrogen fuel cell power supply system and the second hydrogen fuel cell power supply system start normally and the output power does not exceed 120 kW, the hydrogen fuel cell is in a normal state; when the first hydrogen fuel cell power supply system and the second hydrogen fuel cell power supply system start normally, but the output power exceeds 120 kW, the hydrogen fuel cell power supply system is in an overload state; when the first hydrogen fuel cell power supply system and the second hydrogen fuel cell power supply system cannot start or the output power is 0 kW, the hydrogen fuel cell power supply system is in a fault state;

[0057] In step (4), the first area load system, the second area load system, the first auxiliary load, the second auxiliary load, and the daily load are classified into Class I load, Class II load, and Class III load according to their respective importance; Class I load is a load that is critical to the safety and basic operation of the hydrogen-powered ship and must always be powered, Class II load is a load that is critical to the operation and comfort of the hydrogen-powered ship but can be shut down for a short time in an emergency, and Class III load is a load that is helpful for the daily operation of the hydrogen-powered ship but can be shut down for a long time in an emergency.

[0058] Preferably, step (6) is specifically as follows: the monitoring system collects the voltage and current signals of the first regional load system, the voltage and current signals of the first auxiliary load, the voltage and current signals of the second regional load system, and the voltage and current signals of the second auxiliary load, and multiplies the voltage and current signals of the first regional load system to convert into the power signal of the first regional load system, multiplies the voltage and current signals of the first auxiliary load to convert into the power signal of the first auxiliary load, multiplies the voltage and current signals of the second regional load system to convert into the power signal of the second regional load system, and multiplies the voltage and current signals of the second auxiliary load to convert into the power signal of the second auxiliary load, and then adds the power signal of the first regional load system to the power signal of the first auxiliary load to obtain a first total power signal, and adds the power signal of the second regional load system to the power signal of the second auxiliary load to obtain a second total power signal; wherein Afterwards, the first total power signal and the second total power signal are sent to the energy management system, and the energy management system uses a second-order filtering strategy to decompose the first total power signal to obtain a first low-frequency power, a first intermediate frequency power and a first high-frequency power, and decomposes the second total power signal to obtain a second low-frequency power, a second intermediate frequency power and a second high-frequency power; thereafter, the first and second low-frequency powers are added to obtain a total reference output power of the first hydrogen fuel cell power supply system and the second hydrogen fuel cell power supply system, and the power is evenly shared by the first and second hydrogen fuel cell power supply systems, and the first intermediate frequency power is used as a reference power of the first lithium battery in the first composite energy storage system, the first high frequency power is used as a reference power of the first supercapacitor in the first composite energy storage system, the second intermediate frequency power is used as a reference power of the second lithium battery in the second composite energy storage system, and the second high frequency power is used as a reference power of the second supercapacitor in the second composite energy storage system.

[0059] Preferably, the power tracking control process of the first composite energy storage system in step (11) is specifically as follows: first, the bidirectional DC converter in the first composite energy storage system obtains the actual output voltage V of the first lithium battery collected by the monitoring system. B and the actual output voltage V of the first supercapacitor SC , the reference power P of the first lithium battery ref_bDivide by the actual output voltage V of the first lithium battery B , get the reference output current I of the first lithium battery ref_b , and the reference power P of the first supercapacitor ref_sc Divide by the actual output voltage V of the first supercapacitor SC , get the reference output current I of the first supercapacitor ref_sc ; Then, the reference output current I of the first lithium battery ref_b The actual output current I of the first lithium battery b Subtract and get the current error ΔI b , the reference current I ref_sc and the actual output current I of the first supercapacitor sc Subtract and get the current error ΔI sc ; Afterwards, the current error ΔI b , ΔI sc The duty cycle signal D is obtained by respectively passing through the PI controller to control the bidirectional DC converter of the first lithium battery in the first composite energy storage system. b The duty cycle signal D of the bidirectional DC converter of the first supercapacitor in the first composite energy storage system sc , then the duty cycle signal D b , D sc The bidirectional DC converter of the first lithium battery in the first composite energy storage system and the bidirectional DC converter of the first super capacitor in the first composite energy storage system are controlled by pulse width modulation PWM, thereby adjusting the power of the first lithium battery and the first super capacitor, thereby smoothing the power output of the ring network power supply system;

[0060] In step (12), the bidirectional DC converter of the first lithium battery is switched to the voltage constant value control mode. The specific process is as follows: first, the first DC bus voltage setting value V ref The bidirectional DC converter output voltage V b Subtracting each other to obtain a voltage difference ΔV; subsequently, the voltage difference ΔV passes through a PI controller to obtain a duty cycle signal D, and the duty cycle signal D is modulated by PWM to control the bidirectional DC converter of the first lithium battery in the first composite energy storage system, thereby maintaining the stability of the first DC bus voltage.

[0061] Preferably, step (16) is specifically as follows: the monitoring system collects the voltage and current signals of the first regional load system, the voltage and current signals of the first auxiliary load, the voltage and current signals of the second regional load system, and the voltage and current signals of the second auxiliary load, and multiplies the voltage and current signals of the first regional load system to convert them into the power signal of the first regional load system, multiplies the voltage and current signals of the first auxiliary load to convert them into the power signal of the first auxiliary load, multiplies the voltage and current signals of the second regional load system to convert them into the power signal of the second regional load system, and multiplies the voltage and current signals of the second auxiliary load to convert them into the power signal of the second auxiliary load, and then adds the power signal of the first regional load system to the power signal of the first auxiliary load to obtain a first total power signal, and converts The power signal of the second regional load system is added to the power signal of the second auxiliary load to obtain a second total power signal; then, the first total power signal and the second total power signal are sent to the energy management system, and the energy management system uses a first-order filtering strategy to decompose the first total power signal to obtain a first low-frequency power and a first high-frequency power, and decomposes the second total power signal to obtain a second low-frequency power and a second high-frequency power; then, the first low-frequency power and the second low-frequency power are added to obtain the total low-frequency power, which is evenly shared by the first lithium battery and the second lithium battery in the first composite energy storage system and the second composite energy storage system, and the first high-frequency power is used as a reference power of the first supercapacitor in the first composite energy storage system, and the second high-frequency power is used as a reference power of the second supercapacitor in the second composite energy storage system.

[0062] Preferably, in step (23), when the first DC bus is short-circuited, the first hydrogen fuel cell power supply system and the first composite energy storage system are disconnected from the DC ring network main system, and the first regional load system is powered by the third DC bus; when the second DC bus is short-circuited, the second hydrogen fuel cell power supply system and the second composite energy storage system are disconnected from the DC ring network main system, and the second regional load system is powered by the fourth DC bus;

[0063] In step (27), when the third DC bus is short-circuited, the first area load system is powered by the first DC bus; when the fourth DC bus is short-circuited, the second area load system is powered by the fourth DC bus.

[0064] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0065] (1) The flexible DC ring network power system of the present invention effectively disperses the load and reduces the current density of a single path by constructing a ship microgrid composed of multiple distributed power sources and loads, thereby improving the power supply capacity and power supply stability of the entire system. Therefore, it can solve the technical problem that the existing radial power supply system is prone to overload of the transmission line due to load concentration;

[0066] (2) The working method of the flexible DC ring network power system of the present invention adopts steps (20)-(28). When a certain section of the bus fails, it can use corresponding control means to quickly isolate the faulty bus, and other normal buses supply power to the loads connected to the faulty bus, thereby avoiding the expansion of the impact of the accident, thereby improving the reliability of the system operation. Therefore, it can solve the technical problems of poor fault isolation capability, long fault recovery time and low power supply reliability existing in the existing radial power supply system;

[0067] (3) The working method of the flexible DC ring network power system of the present invention adopts steps (6)-(19), and realizes the functions of voltage fluctuation smoothing and providing electric energy support through different control methods. In the voltage fluctuation smoothing mode, the lithium battery and the super capacitor can bear power of different frequencies, so that the system has a flexible bus current control mode, which can quickly transfer the fluctuation of load power and significantly reduce the voltage fluctuation of the DC bus; in the electric energy support mode, the lithium battery control mode is converted into a voltage constant value control mode to support the bus voltage, ensuring the power supply continuity of the system when the hydrogen fuel cell power supply system fails. At the same time, the first-order filtering strategy for the super capacitor can also ensure a certain voltage fluctuation smoothing effect, optimize energy utilization, and realize efficient, safe and reliable operation. Therefore, it can solve the technical problems of the existing radial power supply system such as single control mode, inflexible scheduling operation, difficulty in adapting to power flow changes, and difficulty in taking into account various performance requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 It is a schematic diagram of the overall layout structure of the present invention;

[0069] Figure 2 is a structural schematic diagram of a first hydrogen fuel cell power supply system in the present invention;

[0070] Figure 3 is a schematic structural diagram of the first composite energy storage system in the present invention;

[0071] Figure 4 is a schematic structural diagram of the first regional load system in the present invention;

[0072] Figure 5 It is a structural schematic diagram of the daily AC power distribution network system of the present invention;

[0073] Figure 6 is a schematic structural diagram of the first auxiliary load in the present invention;

[0074] Figure 7 It is a single line diagram of the ring network power supply system of the present invention;

[0075] Figure 8It is a second-order filtering control strategy diagram of the composite energy storage system in the fluctuation smoothing mode in the present invention;

[0076] Fig. 9 It is a power tracking control logic block diagram of the composite energy storage system in the present invention;

[0077] Fig.10 It is a DC bus voltage diagram when the composite energy storage system does not participate in regulation under the simulated typical working conditions of the present invention;

[0078] Fig.11 It is a DC bus voltage diagram when the composite energy storage system participates in regulation under the simulated typical working conditions of the present invention;

[0079] Fig.12 It is a logic block diagram of the voltage constant value control method of the lithium battery in the island power supply mode of the present invention;

[0080] Fig.13 This is a first-order filtering control strategy diagram of the supercapacitor in the island power supply mode of the present invention. DETAILED DESCRIPTION

[0081] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0082] In view of the problems of insufficient fully selective protection, high cost and low system control stability of existing ship DC electric propulsion systems, the present invention provides a hydrogen-driven ship multi-source flexible DC ring network power system, which uses a DC ring network to transmit and distribute electric energy, and integrates power conversion and power supply functions of multiple groups of hydrogen fuel cells and composite energy storage systems to directly supply power to loads in the area. The system adopts compact functional and structural design, has multi-terminal redundant power supply and multiple power supply protection functions, and can provide high-density, safe and reliable power supply for ship power.

[0083] like Figure 1As shown, the present invention provides a flexible DC ring network power supply system for a hydrogen-powered ship, comprising a DC ring network main system, a first hydrogen fuel cell power supply system 1, a first composite energy storage system 2, a second hydrogen fuel cell power supply system 3, a second composite energy storage system 4, a first regional load system 5, a second regional load system 6, a monitoring system 7, an energy management system 8, a daily AC distribution network system 14, a first auxiliary load 15, and a second auxiliary load 16, wherein the first hydrogen fuel cell power supply system 1, the first composite energy storage system 2, the first regional load system 5 and the first auxiliary load 15 are arranged in the port side area of ​​the hydrogen-powered ship, and the second hydrogen fuel cell power supply system 3, the second composite energy storage system 4, the second regional load system 6 and the second auxiliary load 16 are arranged in the starboard side area of ​​the hydrogen-powered ship.

[0084] The DC ring network main system includes a first DC bus 10 , a second DC bus 11 , a third DC bus 12 , and a fourth DC bus 13 . The four DC buses are electrically connected end to end via four solid-state switches 9 .

[0085] The first hydrogen fuel cell power supply system 1 and the first composite energy storage system 2 are electrically connected to the first DC bus, and the second hydrogen fuel cell power supply system 3 and the second composite energy storage system 4 are electrically connected to the second DC bus 11 .

[0086] The first regional load system 5 is electrically connected to the first DC bus 10 and the third DC bus 12 , respectively. The second regional load system 6 is electrically connected to the second DC bus 11 and the fourth DC bus 13 , respectively.

[0087] The monitoring system 7 is electrically connected to the first hydrogen fuel cell power supply system 1, the second hydrogen fuel cell power supply system 3, the first composite energy storage system 2, the second composite energy storage system 4, the first regional load system 5, and the second regional load system 6 through weak current signal lines, and is also electrically connected to the first DC bus 10, the second DC bus 11, the third DC bus 12, and the fourth DC bus 13 to monitor the real-time status of each system and the DC bus in real time.

[0088] The energy management system 8 is electrically connected to the monitoring system 7 , the first hydrogen fuel cell power supply system 1 , the second hydrogen fuel cell power supply system 3 , the first composite energy storage system 2 , and the second composite energy storage system 4 .

[0089] The daily AC power distribution network system 14 is electrically connected to the third DC bus 12 and the fourth DC bus 13 respectively.

[0090] The first auxiliary load 15 is electrically connected to the third DC bus 12 , and the second auxiliary load 16 is electrically connected to the fourth DC bus 13 .

[0091] Since the port and starboard areas of the ship are arranged symmetrically, the specific configuration of each system is discussed taking the port area as an example.

[0092] like Figure 2 As shown, the first hydrogen fuel cell power supply system 1 includes a hydrogen fuel cell 1-1, a boost DC converter 1-2, a DC circuit breaker 1-3, and a protection module 1-4. The hydrogen fuel cell 1-1 is electrically connected to the first DC bus 10 through the boost DC converter 1-2, the DC circuit breaker 1-3, and the protection module 1-4 in sequence.

[0093] Specifically, the rated power of the hydrogen fuel cell 1-1 is 120kW and the rated output voltage is 210V; the rated power of the boost DC converter 1-2 is 120kW, the voltage input range of the low-voltage side is 10-400V, the output range of the high-voltage side is 60-550V, the maximum working voltage of the DC circuit breaker 1-3 is 600V, the maximum working current is 250A, the rated voltage of the protection module 1-4 is 500V, the circuit breaking capacity is 20kA, the response time is less than 10ms, and it has overvoltage protection, overcurrent protection, undervoltage protection, and circuit breaking protection functions.

[0094] like Figure 3 As shown, the first composite energy storage system 2 includes a lithium battery 2-1, a first bidirectional DC converter 2-3, a super capacitor 2-2, a second bidirectional DC converter 2-4, a DC circuit breaker 2-5, and a protection module 2-6. The lithium battery 2-1 is electrically connected to the first DC bus 10 through the first bidirectional DC converter 2-3, the DC circuit breaker 2-5, and the protection module 2-6, and the super capacitor 2-2 is electrically connected to the first DC bus 10 through the second bidirectional DC converter 2-4, the DC circuit breaker 2-5, and the protection module 2-6.

[0095] Specifically, the capacity of the lithium battery 2-1 is 30kWh and the rated voltage is 250V, the capacity of the supercapacitor 2-2 is 1kWh and the rated voltage is 230V, the rated power of the first bidirectional DC converter 2-3 is 30kW, the rated power of the second bidirectional DC converter 2-4 is 50kW, the maximum operating voltage of the DC circuit breaker 2-5 is 600V, and the maximum operating current is 100A. The rated voltage of the protection module 2-6 is 500V, and the circuit breaking capacity is 20kA. It has overvoltage protection, overcurrent protection, undervoltage protection, and circuit breaking protection functions.

[0096] like Figure 4As shown, the first area load system 5 includes a propulsion motor 5-1, a thruster 5-2, an impact load 5-3, a DC / AC inverter 5-4, a first area distribution board 5-5, a protection module 5-6 and a DC circuit breaker 5-7. The propulsion motor 5-1, the thruster 5-2 and the impact load 5-3 are electrically connected to the first area distribution board 5-5 through the DC / AC inverter 5-4 and the DC circuit breaker 5-7. The first area distribution board 5-5 is electrically connected to the first DC bus 10 and the second DC bus 12 respectively through the protection module 5-6.

[0097] Specifically, the rated power of the propulsion motor 5-1 is 90kW, the rated power of the thruster 5-2 is 20kW, the impact load 5-3 refers to loads such as radars and steering gears that generate high peak current or power in a short period of time, and the total power of such loads is less than 20kW, the DC / AC inverter 5-4 outputs 380V AC three-phase power, the maximum working voltage of the DC circuit breaker 5-7 is 600V, and the maximum working current is 200A, the rated voltage of the protection module 5-6 is 500V, and the circuit breaking capacity is 20kA, and it has overvoltage protection, overcurrent protection, undervoltage protection, and circuit breaking protection functions.

[0098] like Figure 5 As shown, the daily AC distribution network system 14 includes a protection module 14-1, a DC circuit breaker 14-2, a DC / AC inverter 14-3, an isolation transformer 14-4, an AC circuit breaker 14-5, a pair of AC distribution boards 14-6, a bus tie switch 14-7 and a pair of daily loads 14-8. The third DC bus 12 and the fourth DC bus 13 are respectively connected to an AC distribution board 14-6 via the protection module 14-1, the DC circuit breaker 14-2, the DC / AC inverter 14-3, the isolation transformer 14-4, the AC circuit breaker 14-5 and the protection module 14-1. The two AC distribution boards 14-6 are connected to each other through the bus tie switch 14-7, and power is supplied to each corresponding daily load 14-8 through the AC circuit breaker 14-5.

[0099] Specifically, the rated voltage of the protection module 14-1 is 500V, and the breaking capacity is 20kA. The maximum operating voltage of the DC circuit breaker 14-2 is 600V, and the maximum operating current is 50A. The rated power of the DC / AC inverter 14-3 is 25kW, and the output is 380V / 50Hz AC three-phase electricity. The rated capacity of the isolation transformer 14-4 is 30kVA, the input voltage is 380V, and the output voltage is 400V. The rated operating voltage of the AC circuit breaker 14-5 is 400V, and the maximum rated current is 75A.

[0100] like Figure 6As shown, the first auxiliary load 15 includes a protection module 15-1, a DC circuit breaker 15-2, a DC / AC inverter 15-3, an isolation transformer 15-4, and an auxiliary device 15-5. The auxiliary device 15-5 is connected to the third DC bus 12 through the isolation transformer 15-4, the DC / AC inverter 15-3, the DC circuit breaker 15-2, and the protection module 15-1.

[0101] Specifically, the rated voltage of the protection module 15-1 is 500V, and the breaking capacity is 20kA. The maximum working voltage of the DC circuit breaker 15-2 is 600V, and the maximum working current is 30A. The rated power of the DC / AC inverter 15-3 is 15kW, and the output is 380V / 50Hz AC three-phase electricity. The rated capacity of the isolation transformer 15-4 is 20kVA, the input voltage is 380V, and the output voltage is 400V. The auxiliary equipment 15-5 refers to navigation equipment, communication equipment, emergency equipment, fire-fighting equipment, marine pumps, anchor machines, mooring equipment, etc., and its maximum power is less than 15kW.

[0102] The working principle of the present invention is as follows:

[0103] Firstly, the first hydrogen fuel cell power supply system 1 and the second hydrogen fuel cell power supply system 3 generate electric energy and modulate and boost the voltage to 500V, and are connected to the first DC bus 10 and the second DC bus 11 respectively. The first composite energy storage system 2 and the second composite energy storage system 4 are connected to the first DC bus 10 and the second DC bus 11 respectively; the energy management system 8 determines the working status of each system through the output voltage and output current of each hydrogen fuel cell power supply system and each composite energy storage system, the voltage and current of each DC bus, and the voltage and current values ​​of each regional load collected by the monitoring system 7, and implements corresponding control strategies; when the first hydrogen fuel cell power supply system 1 and the second hydrogen fuel cell power supply system 3 are working normally, the first composite energy storage system 2 and the second composite energy storage system 4 are in the voltage fluctuation smoothing mode, and the bus voltage fluctuation is smoothed by the second-order filtering control strategy; when the first hydrogen fuel cell power supply system 1 and the second fuel cell power supply system 3 fail, the first composite energy storage system 2 and the second composite energy storage system 4 switch to the island power supply mode, and adopt the voltage constant value control method to maintain the stability of the voltage of the first DC bus, the second DC bus, the third DC bus, and the fourth DC bus.

[0104] During the operation of the entire system, the energy management system 8 will determine whether the first hydrogen fuel cell power supply system 1, the second hydrogen fuel cell power supply system 3 and the first composite energy storage system 2, the second composite energy storage system 4 are in an abnormal overload state based on the signal collected by the monitoring system 7. When the first hydrogen fuel cell power supply system 1 and the second hydrogen fuel cell power supply system 3 are detected to be overloaded, the energy management system 8 will send out an alarm signal and automatically adjust the output power of the first hydrogen fuel cell power supply system 1 and the second hydrogen fuel cell power supply system 3 to prevent the internal current of the hydrogen fuel cell 1-1 and the hydrogen fuel cell 3-1 from being too large, causing irreversible damage; when the first composite energy storage system 2 and the second composite energy storage system 4 are detected to be overloaded, the energy management system 8 can also automatically adjust the charging and discharging power of the first composite energy storage system 2 and the second composite energy storage system 4 to avoid overload operation.

[0105] In addition, when the monitoring system 7 detects that the differential current of a certain section of the DC bus in the ring network is greater than the preset differential signal threshold, it can be determined that a short circuit fault has occurred in this section of the DC bus, and a corresponding protection signal is generated and sent to the solid-state switch that is electrically connected to and closest to this section of the DC bus, so that the solid-state switch is disconnected, and at the same time, the electrical connection between this section of the DC bus and the hydrogen fuel cell power supply system, the composite energy storage system, and the load system is cut off. At this time, the load system is powered by another section of the DC bus that is electrically connected to the load system. In this way, when any section of the DC bus fails, it can be quickly isolated and operated in an open loop to ensure the continuity of the load power supply.

[0106] The present invention also provides a working method of a flexible DC ring network power supply system for a hydrogen-powered ship, comprising the following steps:

[0107] (1) The first hydrogen fuel cell power supply system and the second hydrogen fuel cell power supply system generate electric energy and boost the electric energy to 500V and output it to the first DC bus and the second DC bus respectively. The third and fourth DC buses are electrically connected to the first DC bus and the second DC bus through solid-state switches to obtain a DC voltage of 500V. At the same time, the monitoring system determines whether the operating status of the first hydrogen fuel cell power supply system and the second hydrogen fuel cell power supply system is normal, overloaded, or faulty based on the output voltage and output current of the first hydrogen fuel cell power supply system and the second hydrogen fuel cell power supply system. If both are in normal status, the system proceeds to step (5). If one of them is in fault status and the other is in normal status or overload status, the system proceeds to step (2). If both are in overload status, the system proceeds to step (3). If both are in fault status, the energy management system sends a fault alarm signal and proceeds to step (12).

[0108] Specifically, the monitoring system calculates the output power based on the output voltage and output current of the first hydrogen fuel cell power system and the second hydrogen fuel cell power system. When the first hydrogen fuel cell power system and the second hydrogen fuel cell power system start normally and the output power does not exceed 120kW, the hydrogen fuel cell is in a normal state; when the first hydrogen fuel cell power system and the second hydrogen fuel cell power system start normally but the output power exceeds 120kW, the hydrogen fuel cell power system is in an overload state; when the first hydrogen fuel cell power system and the second hydrogen fuel cell power system cannot start or the output power is 0kW, the hydrogen fuel cell power system is in a fault state.

[0109] (2) The energy management system sends out a fault alarm signal and automatically cuts off the connection between the hydrogen fuel cell power supply system with the fault and the DC ring network main system. At the same time, the monitoring system determines whether the operating state of the hydrogen fuel cell in another hydrogen fuel cell power supply system is normal or overloaded. If it is in a normal state, it proceeds to step (5); if it is in an overloaded state, it proceeds to step (3);

[0110] (3) The energy management system sends out an overload alarm signal and automatically reduces the output power of the hydrogen fuel cell in the overload state to the rated output power (120kW in this example), and determines whether the voltage of the first DC bus and the second DC bus has a serious drop (that is, the drop value exceeds 15% of the rated bus voltage). If so, go to step (4), otherwise go to step (5).

[0111] (4) The energy management system selectively cuts off the first area load system, the second area load system, the first auxiliary load, the second auxiliary load, and the daily load according to their importance until the hydrogen fuel cell power supply system in the overloaded state recovers to the normal state and the voltage of the first DC bus and the second DC bus remains stable, and then enters step (5).

[0112] Specifically, the present invention classifies all loads into Class I loads, Class II loads and Class III loads according to their importance. Class I loads refer to propulsion motors in the first area load system and the second area load system, thrusters and radar loads in impact loads, steering gear loads, etc., as well as navigation equipment, communication equipment, fire-fighting equipment, and emergency equipment in the first auxiliary loads and the second auxiliary loads. Class I loads are crucial to the safety and basic operation of the ship and must always be powered on; Class II loads refer to air-conditioning loads, lighting loads, crew accommodation area power loads, etc. in daily loads. Class II loads are very important to the operation and comfort of the ship, but the power supply can be stopped for a short time in an emergency; Class III loads refer to entertainment equipment loads, non-critical office equipment loads, etc. in daily loads. This type of load is helpful for the daily operation of the ship, but the power supply can be stopped for a longer time in an emergency.

[0113] (5) The energy management system sends a control instruction to the first composite energy storage system and the second composite energy storage system, so that the first composite energy storage system and the second composite energy storage system all enter the voltage fluctuation smoothing mode, and then proceeds to step (6).

[0114] (6) The energy management system obtains the voltage and current signals of the first regional load system, the second regional load system, the first auxiliary load, and the second auxiliary load collected by the monitoring system, and generates corresponding power signals according to the respective voltage and current signals, and decomposes the power signals using a second-order filtering control strategy to obtain the reference power of the first lithium battery in the first composite energy storage system, the reference power of the second lithium battery in the second composite energy storage system, the reference power of the first supercapacitor in the first composite energy storage system, and the reference power of the second supercapacitor in the second composite energy storage system, and then enters step (7).

[0115] Specifically, the monitoring system collects the voltage and current signals of the first regional load system, the voltage and current signals of the first auxiliary load, the voltage and current signals of the second regional load system, and the voltage and current signals of the second auxiliary load, and multiplies the voltage and current signals of the first regional load system to convert them into the power signal of the first regional load system, multiplies the voltage and current signals of the first auxiliary load to convert them into the power signal of the first auxiliary load, multiplies the voltage and current signals of the second regional load system to convert them into the power signal of the second regional load system, and multiplies the voltage and current signals of the second auxiliary load to convert them into the power signal of the second auxiliary load, then adds the power signal of the first regional load system to the power signal of the first auxiliary load to obtain a first total power signal, and adds the power signal of the second regional load system to the power signal of the second auxiliary load to obtain a second total power signal; thereafter, A total power signal and a second total power signal are sent to the energy management system. The energy management system uses a second-order filtering strategy to decompose the first total power signal to obtain a first low-frequency power, a first intermediate frequency power and a first high-frequency power, and decomposes the second total power signal to obtain a second low-frequency power, a second intermediate frequency power and a second high-frequency power; thereafter, the first and second low-frequency powers are added to obtain a total reference output power of the first hydrogen fuel cell power supply system and the second hydrogen fuel cell power supply system, which power is evenly shared by the first and second hydrogen fuel cell power supply systems, and the first intermediate frequency power is used as a reference power of the first lithium battery in the first composite energy storage system, the first high frequency power is used as a reference power of the first supercapacitor in the first composite energy storage system, the second intermediate frequency power is used as a reference power of the second lithium battery in the second composite energy storage system, and the second high frequency power is used as a reference power of the second supercapacitor in the second composite energy storage system.

[0116] More specifically, if Figure 8As shown in the figure, the principle of the second-order filtering strategy is: the total power signal is divided into medium-low frequency mixed power and high frequency power after passing through the first-order filter, and then the medium-low frequency mixed power is passed through the first-order filter again to obtain low frequency power and medium frequency power; taking the first total power signal as an example, the reference power expression obtained after the total power signal is decomposed by the second-order filtering is:

[0117]

[0118]

[0119]

[0120] Among them, s is a complex variable, P load is the first total power signal, P ref_fc / 2 is the reference power of the first hydrogen fuel cell power supply system, which is equal to the reference power of the second hydrogen fuel cell power supply system, P ref_b is the reference power of the first lithium battery in the first composite energy storage system, P ref_sc is the reference power of the supercapacitor in the first composite energy storage system, T1 and T2 are second-order filter time constants, and different smoothing effects can be achieved by adjusting the sizes of T1 and T2. The decomposition process of the second total power signal is the same as above.

[0121] (7) determining whether the reference power of the first lithium battery in the first composite energy storage system is greater than its maximum power; if so, the energy management system adjusts the reference power of the first lithium battery to its maximum power and then proceeds to step (8); otherwise, directly proceeds to step (8);

[0122] Specifically, the maximum power of the first lithium battery in the first composite energy storage system and the second lithium battery in the second composite energy storage system is 30kW in the fluctuation smoothing mode, and the maximum power of the first supercapacitor in the first composite energy storage system and the second supercapacitor in the second composite energy storage system is 60kW.

[0123] (8) determining whether the reference power of the first supercapacitor in the first composite energy storage system is greater than its maximum power; if so, the energy management system adjusts the reference power of the first supercapacitor to its maximum power and then proceeds to step (9); otherwise, directly proceeds to step (9);

[0124] (9) determining whether the reference power of the second lithium battery in the second composite energy storage system is greater than its maximum power; if so, the energy management system adjusts the reference power of the second lithium battery to its maximum power and then proceeds to step (10); otherwise, directly proceeds to step (10);

[0125] (10) Determine whether the reference power of the second supercapacitor in the second composite energy storage system is greater than its maximum power. If so, the energy management system adjusts the reference power of the second supercapacitor to its maximum power and then proceeds to step (11). Otherwise, directly proceeds to step (11).

[0126] (11) The bidirectional DC converter in the first composite energy storage system adopts a power tracking control method to keep the power of the first lithium battery and the first super capacitor near their reference power, and at the same time, the bidirectional DC converter in the second composite energy storage system adopts a power tracking control strategy to keep the power of the second lithium battery and the second super capacitor near their reference power, and then enters step (20).

[0127] Specifically, if Fig. 9 As shown, taking the first composite energy storage system as an example, P ref_b / sc is the reference power of the first supercapacitor, V b / sc is the actual output voltage of the first supercapacitor, I ref_b / sc is the reference output current of the first supercapacitor, I b / sc is the actual output current of the first supercapacitor, and D is the duty cycle. The specific process is as follows: first, the bidirectional DC converter in the first composite energy storage system obtains the actual output voltage V of the first lithium battery collected by the monitoring system. B and the actual output voltage V of the first supercapacitor SC , the reference power P of the first lithium battery ref_b Divide by the actual output voltage V of the first lithium battery B , get the reference output current I of the first lithium battery ref_b , and the reference power P of the first supercapacitor ref_sc Divide by the actual output voltage V of the first supercapacitor SC , get the reference output current I of the first supercapacitor ref_sc ; Then, the reference output current I of the first lithium battery ref_b The actual output current I of the first lithium battery b Subtract and get the current error ΔI b , the reference current I ref_sc and the actual output current I of the first supercapacitor sc Subtract and get the current error ΔI sc ; Afterwards, the current error ΔI b , ΔI sc The duty cycle signal D is obtained by respectively passing through the PI controller to control the bidirectional DC converter of the first lithium battery in the first composite energy storage system. b The duty cycle signal D of the bidirectional DC converter of the first supercapacitor in the first composite energy storage system sc , then the duty cycle signal Db , D sc The bidirectional DC converter of the first lithium battery in the first composite energy storage system and the bidirectional DC converter of the first super capacitor in the first composite energy storage system are controlled by pulse width modulation (PWM), thereby adjusting the power of the first lithium battery and the first super capacitor, thereby smoothing the power output of the ring network power supply system; the power tracking control of the second composite energy storage system is the same as above.

[0128] More specifically, if Fig.10 , Fig.11 As shown, when the first composite energy storage system and the second composite energy storage system do not participate in voltage regulation, under typical operating conditions, the voltage of the first DC bus 10 has a maximum peak value of 611.074V and a minimum valley value of 442.324V, with a peak-to-valley difference of 168.75V, accounting for 33.75% of the rated voltage; when the first composite energy storage system and the second composite energy storage system participate in voltage regulation, under typical operating conditions, the voltage of the first DC bus 10 has a maximum peak value of 510.428V and a minimum valley value of 484.124V, with a peak-to-valley difference of 26.304V, accounting for 5.26% of the rated voltage, which is 28.49% lower than when the energy storage system does not participate in voltage regulation.

[0129] The advantages of the above steps (1) to (11) are that, through real-time monitoring and status judgment, the system can quickly identify the operating status of the first hydrogen fuel cell power supply system and the second hydrogen fuel cell power supply system to ensure the normal operation of the equipment; secondly, the energy management system performs secondary control under overload conditions, automatically reduces power and sends out an alarm signal to protect the equipment from damage. At the same time, the system prioritizes the removal of secondary loads based on the importance of the load, thereby ensuring the normal operation of key equipment. The first composite energy storage system and the second composite energy storage system use a second-order filtering control strategy to decompose the power signal, so that the hydrogen fuel cell, lithium battery and supercapacitor respectively assume power output in different frequency bands, optimize energy utilization, significantly reduce the voltage fluctuation of the DC bus, greatly improve the stability of the system, and achieve efficient, safe and reliable operation.

[0130] (12) The bidirectional DC converter of the first lithium battery in the first composite energy storage system is switched to a voltage constant value control mode (which is used to support the first DC bus voltage), and the bidirectional DC converter of the second lithium battery in the second composite energy storage system is switched to a voltage constant value control mode (which is used to support the second DC bus voltage), and then enters step (13).

[0131] Specifically, if Fig.12 As shown, taking the first composite energy storage system as an example, the voltage constant value control method principle is as follows: the first DC bus voltage setting value V refThe bidirectional DC converter output voltage V b Subtracting each other obtains a voltage difference ΔV; subsequently, the voltage difference ΔV passes through a PI controller to obtain a duty cycle signal D, and the duty cycle signal D is modulated by PWM to control the bidirectional DC converter of the first lithium battery in the first composite energy storage system, thereby maintaining the stability of the first DC bus voltage; the second composite energy storage system is also similar to the above.

[0132] (13) The monitoring system monitors whether the power of the first lithium battery in the first composite energy storage system exceeds its maximum power. If so, it is determined that the first lithium battery is in an overload state. The energy management system controls the bidirectional DC converter of the first lithium battery in the first composite energy storage system to send an overload alarm signal and automatically reduce the power of the first lithium battery to the maximum power of 120 kW, and then proceeds to step (14). If not, it directly proceeds to step (14).

[0133] Specifically, the maximum power of the first lithium battery and the second lithium battery in the first composite energy storage system and the second composite energy storage system is set to 120kW in the island power supply mode.

[0134] (14) The monitoring system monitors whether the power of the second lithium battery in the second composite energy storage system exceeds its maximum power. If so, it is determined that the second lithium battery is in an overload state. The energy management system controls the bidirectional DC converter of the second lithium battery in the second composite energy storage system to send an overload alarm signal and automatically reduce the power of the second lithium battery to the maximum power (120 kW in this example), and then proceeds to step (15); if not, directly proceeds to step (15).

[0135] (15) The monitoring system monitors the voltage values ​​of the first DC bus and the second DC bus, and determines whether the voltage of the first DC bus and the second DC bus drops seriously (the drop value exceeds 15% of the rated bus voltage). If so, the energy management system selectively cuts off the first area load system, the second area load system, the first auxiliary load, the second auxiliary load, and the daily load according to the importance of the load until the voltage of the first DC bus and the second DC bus remains stable, and then enters step (16); otherwise, it directly goes to step (16).

[0136] (16) The energy management system obtains the voltage and current signals of the first regional load system, the second regional load system, the first auxiliary load, and the second auxiliary load collected by the monitoring system, and generates corresponding power signals according to the respective voltage and current signals, and decomposes the power signals using a first-order filtering strategy to obtain a power reference value of the first supercapacitor in the first composite energy storage system and a power reference value of the second supercapacitor in the second composite energy storage system, and then enters step (17).

[0137] Specifically, the monitoring system collects the voltage and current signals of the first regional load system, the voltage and current signals of the first auxiliary load, the voltage and current signals of the second regional load system, and the voltage and current signals of the second auxiliary load, and multiplies the voltage and current signals of the first regional load system to convert them into the power signal of the first regional load system, multiplies the voltage and current signals of the first auxiliary load to convert them into the power signal of the first auxiliary load, multiplies the voltage and current signals of the second regional load system to convert them into the power signal of the second regional load system, and multiplies the voltage and current signals of the second auxiliary load to convert them into the power signal of the second auxiliary load, and then adds the power signal of the first regional load system to the power signal of the first auxiliary load to obtain a first total power signal, and multiplies the voltage and current signals of the second regional load system to obtain a first total power signal. The power signal of the load system is added to the power signal of the second auxiliary load to obtain a second total power signal; then, the first total power signal and the second total power signal are sent to the energy management system, and the energy management system uses a first-order filtering strategy to decompose the first total power signal to obtain a first low-frequency power and a first high-frequency power, and decomposes the second total power signal to obtain a second low-frequency power and a second high-frequency power; then, the first low-frequency power and the second low-frequency power are added to obtain the total low-frequency power, which is evenly shared by the first lithium battery and the second lithium battery in the first composite energy storage system and the second composite energy storage system, and the first high-frequency power is used as the reference power of the first supercapacitor in the first composite energy storage system, and the second high-frequency power is used as the reference power of the second supercapacitor in the second composite energy storage system.

[0138] More specifically, if Fig.13 As shown, the total power signal is divided into low-frequency power and high-frequency power after passing through a first-order filter; taking the first total power signal as an example, the reference power expression obtained after the signal is decomposed by first-order filtering is:

[0139]

[0140]

[0141] Among them, s is a complex variable, P load is the first total power signal, P ref_b / 2 is the reference power of the first lithium battery in the first composite energy storage system and the second composite energy storage system, which is equal to the reference power of the second lithium battery in the second composite energy storage system, P ref_sc is the reference power of the first supercapacitor in the first composite energy storage system, T1 is the first-order filter time constant, and different smoothing effects can be achieved by adjusting the size of T1. The decomposition process of the second total power signal is the same as above.

[0142] (17) Determine whether the reference power of the first supercapacitor in the first composite energy storage system is greater than its maximum power. If so, the energy management system adjusts the reference power of the first supercapacitor to its maximum power and proceeds to step (18); otherwise, directly proceeds to step (18).

[0143] (18) Determine whether the reference power of the second supercapacitor in the second composite energy storage system is greater than its maximum power. If so, the energy management system adjusts the reference power of the second supercapacitor to its maximum power and proceeds to step (19); otherwise, directly proceeds to step (19).

[0144] (19) The bidirectional DC converter of the first supercapacitor in the first composite energy storage system adopts a power tracking control method to keep the power of the first supercapacitor near its reference power. At the same time, the bidirectional DC converter of the second supercapacitor in the second composite energy storage system adopts a power tracking control method to keep the power of the second supercapacitor near its reference power, and then enters step (20).

[0145] The advantage of the above steps (12) to (19) is that when the hydrogen fuel cell power supply system fails, the lithium battery control mode is switched to a voltage constant control mode to support the bus voltage, thereby ensuring the power supply continuity of the system when the hydrogen fuel cell power supply system fails. At the same time, the use of a first-order filtering strategy for the supercapacitor can also ensure a certain voltage fluctuation smoothing effect, thereby optimizing energy utilization and achieving stable system operation.

[0146] (20) The monitoring system monitors the differential current of the first DC bus, the second DC bus, the third DC bus, and the fourth DC bus (which is equal to the difference between the total inflow current and the total outflow current of the DC bus), and determines whether any of the four differential currents exceeds a set threshold value. If so, it is determined that a short circuit fault occurs in the area of ​​the DC bus where the differential current is located, and then the process goes to step (21); otherwise, the process goes to step (29).

[0147] Specifically, the differential current threshold is set to 25A.

[0148] (21) The monitoring system generates a protection signal and determines whether the short-circuited DC bus is connected to a hydrogen fuel cell power supply system and a composite energy storage system. If so, it indicates that the hydrogen fuel cell power supply system and the composite energy storage system connected to the short-circuited DC bus need to be processed, and then enters step (22); otherwise, enters step (27).

[0149] (22) The monitoring system sends a protection signal to the solid-state switch that is electrically connected to the short-circuited DC bus and is closest to it, as well as to the protection modules in the hydrogen fuel cell power supply system, the composite energy storage system, and the regional load system that are electrically connected to the short-circuited DC bus; the protection module isolates the short-circuited DC bus from these hydrogen fuel cell power supply systems, the composite energy storage system, and the regional load system; the solid-state switch is disconnected to isolate the short-circuited DC bus from other DC buses electrically connected to it, and then enters step (23).

[0150] (23) The regional load system connected to the short-circuited DC bus supplies power to the regional load system electrically connected to the short-circuited DC bus relative to the DC bus on the other side of the short-circuited DC bus; the DC ring network main system is switched from being powered by the dual fuel cell power supply system and the dual composite energy storage system to being powered by a single hydrogen fuel cell power supply system and a single composite energy storage system, and at the same time, the monitoring system determines whether the operating state of the single hydrogen fuel cell power supply system is in a normal state, an overload state or a fault state. If it is in a normal state, it proceeds to step (26); if it is in an overload state, it proceeds to step (24); if it is in a fault state, it proceeds to step (25).

[0151] Specifically, when the first DC bus is short-circuited, the first hydrogen fuel cell power supply system and the first composite energy storage system are disconnected from the DC ring network main system, and the first regional load system is powered by the third DC bus; when the second DC bus is short-circuited, the second hydrogen fuel cell power supply system and the second composite energy storage system are disconnected from the DC ring network main system, and the second regional load system is powered by the fourth DC bus.

[0152] (24) The energy management system sends out an overload alarm signal and automatically reduces the output power of the single hydrogen fuel cell power supply system to the rated output power (120 kW in this example), and determines whether the voltage of the first DC bus and the second DC bus drops seriously (i.e., the drop value exceeds 15% of the rated bus voltage). If so, the process proceeds to step (26); otherwise, the process proceeds to step (27).

[0153] (25) The energy management system sends out a fault alarm signal and switches the bidirectional DC converter of the lithium battery in the single composite energy storage system to a voltage constant control mode. At the same time, the monitoring system determines whether the power of the lithium battery in the single composite energy storage system exceeds its maximum power. If so, it indicates that the lithium battery is in an overload state. The energy management system controls the bidirectional DC converter of the lithium battery in the single composite energy storage system to send out an overload alarm signal and automatically reduces the power of the lithium battery in the single composite energy storage system to the maximum power (120 kW in this example), and then proceeds to step (26). Otherwise, it proceeds to step (28).

[0154] (26) The energy management system selectively cuts off the first regional load system, the second regional load system, the first auxiliary load, the second auxiliary load, and the daily load according to their importance until the voltages of the first DC bus and the second DC bus remain stable, and then enters step (28).

[0155] (27) The monitoring system sends a protection signal to the solid-state switch that is electrically connected to the short-circuited DC bus and is closest to it, and to a protection module in the regional load system that is electrically connected to the short-circuited DC bus, and the protection module isolates the short-circuited DC bus from the regional load system; the solid-state switch is disconnected to isolate the short-circuited DC bus from other DC buses that are electrically connected to it, and the regional load system connected to the short-circuited DC bus supplies power to the regional load system that is electrically connected to the short-circuited DC bus relative to the DC bus on the other side of the short-circuited DC bus, and then enters step (28).

[0156] Specifically, when the third DC bus is short-circuited, the first area load system is powered by the first DC bus; when the fourth DC bus is short-circuited, the second area load system is powered by the fourth DC bus.

[0157] (28) The DC ring network main system switches to open-loop operation and handles the fault of the short-circuited DC bus, and then enters step (29).

[0158] The advantage of the above steps (20) to (28) is that the DC ring network main system implements a complete short-circuit fault monitoring and processing mechanism. Once the monitoring system detects a short-circuit fault, it can respond quickly and generate a corresponding protection signal to quickly, accurately and effectively isolate the faulty DC bus, thereby minimizing the impact of the fault on the system operation, ensuring the normal operation of the branch, and improving the reliability and stability of the system.

[0159] (29) The DC ring network main system maintains closed-loop operation and the process ends.

[0160] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for operating a flexible DC ring network power supply system for a hydrogen-powered ship, the flexible DC ring network power supply system for a hydrogen-powered ship comprising a DC ring network main system, a first hydrogen fuel cell power supply system (1), a first composite energy storage system (2), a second hydrogen fuel cell power supply system (3), a second composite energy storage system (4), a first regional load system (5), a second regional load system (6), a monitoring system (7), an energy management system (8), a daily AC distribution network system (14), a first auxiliary load (15), and a second auxiliary load (16), wherein the first hydrogen fuel cell A power supply system (1), a first composite energy storage system (2), a DC ring network main system comprising a first DC bus (10), a second DC bus (11), a third DC bus (12), and a fourth DC bus (13), wherein the four DC buses are electrically connected end to end via four solid-state switches (9); the first hydrogen fuel cell power supply system (1) and the first composite energy storage system (2) are electrically connected to the first DC bus, and the second hydrogen fuel cell power supply system (3) and the second composite energy storage system (4) are electrically connected to the second DC bus (11); the first regional load system (5) is electrically connected to the first DC bus (10) and the second composite energy storage system (4) are electrically connected to the second DC bus (11); the first regional load system (5) is electrically connected to the first DC bus (10) and the second composite energy storage system (4) are electrically connected to the second composite energy storage system (4); the first regional load system (5) is electrically connected to the first DC bus (10) and the second composite energy storage system (4) are electrically connected to the second composite energy storage system (4) and the first ... and the third DC bus (12), the second regional load system (6) is respectively electrically connected to the second DC bus (11) and the fourth DC bus (13); the monitoring system (7) is respectively electrically connected to the first hydrogen fuel cell power supply system (1), the second hydrogen fuel cell power supply system (3), the first composite energy storage system (2), the second composite energy storage system (4), the first regional load system (5), and the second regional load system (6) through weak current signal lines, and is respectively electrically connected to the first DC bus (10), the second DC bus (11), the third DC bus (12), and the fourth DC bus (13). 3) is electrically connected to monitor the real-time status of each system and the DC bus in real time; the energy management system (8) is electrically connected to the monitoring system (7), the first hydrogen fuel cell power supply system (1), the second hydrogen fuel cell power supply system (3), the first composite energy storage system (2), and the second composite energy storage system (4); the daily AC distribution network system (14) is electrically connected to the third DC bus (12) and the fourth DC bus (13) respectively; the first auxiliary load (15) is electrically connected to the third DC bus (12), and the second auxiliary load (16) is electrically connected to the fourth DC bus (13), characterized in that: The method comprises the following steps: (1) The first hydrogen fuel cell power supply system and the second hydrogen fuel cell power supply system generate electric energy and boost the electric energy to 500V and output it to the first DC bus and the second DC bus respectively. The third and fourth DC buses are electrically connected to the first DC bus and the second DC bus through solid-state switches to obtain a DC voltage of 500V. At the same time, the monitoring system determines whether the operating status of the first hydrogen fuel cell power supply system and the second hydrogen fuel cell power supply system is normal, overloaded, or faulty according to the output voltage and output current of the first hydrogen fuel cell power supply system and the second hydrogen fuel cell power supply system. If both are in a normal state, the process proceeds to step (5). If one of them is in a faulty state and the other is in a normal state or an overloaded state, the process proceeds to step (2). If both are in an overloaded state, the process proceeds to step (3). If both are in a faulty state, the energy management system sends a fault alarm signal and proceeds to step (12); (2) The energy management system sends out a fault alarm signal and automatically cuts off the connection between the hydrogen fuel cell power supply system with the fault and the DC ring network main system. At the same time, the monitoring system determines whether the operating state of the hydrogen fuel cell in another hydrogen fuel cell power supply system is normal or overloaded. If it is in a normal state, it proceeds to step (5); if it is in an overloaded state, it proceeds to step (3); (3) The energy management system sends out an overload alarm signal and automatically reduces the output power of the hydrogen fuel cell in the overload state to the rated output power, and determines whether the voltage of the first DC bus and the second DC bus drops seriously at this time. If so, the process proceeds to step (4), otherwise, the process proceeds to step (5); (4) The energy management system selectively cuts off the first regional load system, the second regional load system, the first auxiliary load, the second auxiliary load, and the daily load according to their importance until the hydrogen fuel cell power supply system in the overload state is restored to a normal state and the voltages of the first DC bus and the second DC bus remain stable, and then enters step (5); (5) The energy management system sends a control instruction to the first composite energy storage system and the second composite energy storage system, so that the first composite energy storage system and the second composite energy storage system all enter the voltage fluctuation smoothing mode, and then proceeds to step (6); (6) The energy management system obtains the voltage and current signals of the first regional load system, the second regional load system, the first auxiliary load, and the second auxiliary load collected by the monitoring system, and generates corresponding power signals according to the respective voltage and current signals, and decomposes the power signals using a second-order filtering control strategy to obtain a reference power of the first lithium battery in the first composite energy storage system, a reference power of the second lithium battery in the second composite energy storage system, a reference power of the first supercapacitor in the first composite energy storage system, and a reference power of the second supercapacitor in the second composite energy storage system, and then proceeds to step (7); (7) determining whether the reference power of the first lithium battery in the first composite energy storage system is greater than its maximum power; if so, the energy management system adjusts the reference power of the first lithium battery to its maximum power and then proceeds to step (8); otherwise, directly proceeds to step (8); (8) determining whether the reference power of the first supercapacitor in the first composite energy storage system is greater than its maximum power; if so, the energy management system adjusts the reference power of the first supercapacitor to its maximum power and then proceeds to step (9); otherwise, directly proceeds to step (9); (9) determining whether the reference power of the second lithium battery in the second composite energy storage system is greater than its maximum power; if so, the energy management system adjusts the reference power of the second lithium battery to its maximum power and then proceeds to step (10); otherwise, directly proceeds to step (10); (10) Determine whether the reference power of the second supercapacitor in the second composite energy storage system is greater than its maximum power. If so, the energy management system adjusts the reference power of the second supercapacitor to its maximum power and then proceeds to step (11). Otherwise, directly proceeds to step (11). (11) The bidirectional DC converter in the first composite energy storage system adopts a power tracking control method to keep the power of the first lithium battery and the first super capacitor near their reference power, and the bidirectional DC converter in the second composite energy storage system adopts a power tracking control strategy to keep the power of the second lithium battery and the second super capacitor near their reference power, and then enters step (20); (12) The bidirectional DC converter of the first lithium battery in the first composite energy storage system is switched to a voltage constant value control mode, and the bidirectional DC converter of the second lithium battery in the second composite energy storage system is switched to a voltage constant value control mode, and then the process proceeds to step (13); (13) The monitoring system monitors whether the power of the first lithium battery in the first composite energy storage system exceeds its maximum power. If so, it is determined that the first lithium battery is in an overload state. The energy management system controls the bidirectional DC converter of the first lithium battery in the first composite energy storage system to send an overload alarm signal and automatically reduce the power of the first lithium battery to the maximum power of 120 kW, and then proceeds to step (14). If not, it directly proceeds to step (14); (14) The monitoring system monitors whether the power of the second lithium battery in the second composite energy storage system exceeds its maximum power. If it exceeds, it is determined that the second lithium battery is in an overload state, and the energy management system controls the bidirectional DC converter of the second lithium battery in the second composite energy storage system to send an overload alarm signal and automatically reduce the power of the second lithium battery to the maximum power, and then proceed to step (15); if it does not exceed, directly proceed to step (15); (15) The monitoring system monitors the voltage values ​​of the first DC bus and the second DC bus, and determines whether the voltage of the first DC bus and the second DC bus drops seriously at this time. If so, the energy management system selectively cuts off the first regional load system, the second regional load system, the first auxiliary load, the second auxiliary load, and the daily load according to the load importance until the voltage of the first DC bus and the second DC bus remains stable, and then enters step (16); otherwise, directly transfers to step (16); (16) The energy management system obtains the voltage and current signals of the first regional load system, the second regional load system, the first auxiliary load, and the second auxiliary load collected by the monitoring system, and generates corresponding power signals according to the respective voltage and current signals, and decomposes the power signals using a first-order filtering strategy to obtain a power reference value of the first supercapacitor in the first composite energy storage system and a power reference value of the second supercapacitor in the second composite energy storage system, and then enters step (17); (17) determining whether the reference power of the first supercapacitor in the first composite energy storage system is greater than its maximum power; if so, the energy management system adjusts the reference power of the first supercapacitor to its maximum power and proceeds to step (18); otherwise, the system directly proceeds to step (18); (18) Determine whether the reference power of the second supercapacitor in the second composite energy storage system is greater than its maximum power. If so, the energy management system adjusts the reference power of the second supercapacitor to its maximum power and proceeds to step (19); otherwise, directly proceeds to step (19); (19) The bidirectional DC converter of the first supercapacitor in the first composite energy storage system adopts a power tracking control mode to keep the power of the first supercapacitor near its reference power, and the bidirectional DC converter of the second supercapacitor in the second composite energy storage system adopts a power tracking control mode to keep the power of the second supercapacitor near its reference power, and then enters step (20); (20) The monitoring system monitors the differential currents of the first DC bus, the second DC bus, the third DC bus, and the fourth DC bus, and determines whether any one of the four differential currents exceeds a set threshold value. If so, it is determined that a short circuit fault occurs in the area of ​​the DC bus where the differential current is located, and then the process goes to step (21); otherwise, the process goes to step (29); (21) The monitoring system generates a protection signal and determines whether the short-circuited DC bus is connected to a hydrogen fuel cell power supply system and a composite energy storage system. If so, the process proceeds to step (22); otherwise, the process proceeds to step (27); (22) The monitoring system sends a protection signal to the solid-state switch that is electrically connected to the short-circuited DC bus and is closest to it, as well as the protection modules in the hydrogen fuel cell power supply system, the composite energy storage system, and the regional load system that are electrically connected to the short-circuited DC bus; the protection module isolates the short-circuited DC bus from the hydrogen fuel cell power supply system, the composite energy storage system, and the regional load system; the solid-state switch is disconnected to isolate the short-circuited DC bus from other DC buses electrically connected to it, and then enters step (23); (23) The regional load system connected to the short-circuited DC bus supplies power to the regional load system electrically connected to the short-circuited DC bus relative to the DC bus on the other side of the short-circuited DC bus; the DC ring network main system is switched from being powered by the dual fuel cell power supply system and the dual composite energy storage system to being powered by a single hydrogen fuel cell power supply system and a single composite energy storage system, and at the same time, the monitoring system determines whether the operating state of the single hydrogen fuel cell power supply system is in a normal state, an overload state, or a fault state. If it is in a normal state, it proceeds to step (26); if it is in an overload state, it proceeds to step (24); if it is in a fault state, it proceeds to step (25); (24) The energy management system sends out an overload alarm signal and automatically reduces the output power of the single hydrogen fuel cell power supply system to the rated output power, and determines whether the voltage of the first DC bus and the second DC bus drops seriously at this time. If so, proceed to step (26), otherwise proceed to step (27); (25) The energy management system sends out a fault alarm signal and switches the bidirectional DC converter of the lithium battery in the single composite energy storage system to a voltage constant value control mode. At the same time, the monitoring system determines whether the power of the lithium battery in the single composite energy storage system exceeds its maximum power. If so, it indicates that the lithium battery is in an overload state. The energy management system controls the bidirectional DC converter of the lithium battery in the single composite energy storage system to send out an overload alarm signal and automatically reduces the power of the lithium battery in the single composite energy storage system to the maximum power, and then proceeds to step (26); otherwise, proceeds to step (28); (26) The energy management system selectively cuts off the first regional load system, the second regional load system, the first auxiliary load, the second auxiliary load, and the daily load according to their importance until the voltages of the first DC bus and the second DC bus remain stable, and then enters step (28). (27) The monitoring system sends a protection signal to the solid-state switch that is electrically connected to the short-circuited DC bus and is closest to it, and to a protection module in the regional load system that is electrically connected to the short-circuited DC bus, and the protection module isolates the short-circuited DC bus from the regional load system; the solid-state switch is disconnected to isolate the short-circuited DC bus from other DC buses that are electrically connected to it, and the regional load system that is connected to the short-circuited DC bus supplies power to the regional load system that is electrically connected to the short-circuited DC bus relative to the DC bus on the other side of the short-circuited DC bus, and then proceeds to step (28); (28) The DC ring network main system switches to open-loop operation and handles the short-circuited DC bus fault, and then enters step (29); (29) The DC ring network main system maintains closed-loop operation and the process ends.

2. The working method of the flexible DC ring network power supply system for hydrogen-powered ships according to claim 1 is characterized in that: In step (1), the monitoring system calculates the output power based on the output voltage and output current of the first hydrogen fuel cell power supply system and the second hydrogen fuel cell power supply system. When the first hydrogen fuel cell power supply system and the second hydrogen fuel cell power supply system start normally and the output power does not exceed 120kW, the hydrogen fuel cell is in a normal state; when the first hydrogen fuel cell power supply system and the second hydrogen fuel cell power supply system start normally, but the output power exceeds 120kW, the hydrogen fuel cell power supply system is in an overload state; when the first hydrogen fuel cell power supply system and the second hydrogen fuel cell power supply system cannot start or the output power is 0kW, the hydrogen fuel cell power supply system is in a fault state; In step (4), the first area load system, the second area load system, the first auxiliary load, the second auxiliary load, and the daily load are classified into Class I load, Class II load, and Class III load according to their respective importance; Class I load is a load that is critical to the safety and basic operation of the hydrogen-powered ship and must always be powered, Class II load is a load that is critical to the operation and comfort of the hydrogen-powered ship but can be shut down for a short time in an emergency, and Class III load is a load that is helpful for the daily operation of the hydrogen-powered ship but can be shut down for a long time in an emergency.

3. The working method of the flexible DC ring network power supply system for hydrogen-powered ships according to claim 2 is characterized in that: Step (6) is specifically as follows: the monitoring system collects the voltage and current signals of the first regional load system, the voltage and current signals of the first auxiliary load, the voltage and current signals of the second regional load system, and the voltage and current signals of the second auxiliary load, and multiplies the voltage and current signals of the first regional load system to convert into the power signal of the first regional load system, multiplies the voltage and current signals of the first auxiliary load to convert into the power signal of the first auxiliary load, multiplies the voltage and current signals of the second regional load system to convert into the power signal of the second regional load system, and multiplies the voltage and current signals of the second auxiliary load to convert into the power signal of the second auxiliary load, then adds the power signal of the first regional load system to the power signal of the first auxiliary load to obtain a first total power signal, and adds the power signal of the second regional load system to the power signal of the second auxiliary load to obtain a second total power signal; thereafter, The first total power signal and the second total power signal are sent to the energy management system, and the energy management system uses a second-order filtering strategy to decompose the first total power signal to obtain a first low-frequency power, a first intermediate frequency power and a first high-frequency power, and decomposes the second total power signal to obtain a second low-frequency power, a second intermediate frequency power and a second high-frequency power; thereafter, the first and second low-frequency powers are added to obtain a total reference output power of the first hydrogen fuel cell power supply system and the second hydrogen fuel cell power supply system, and the power is evenly shared by the first and second hydrogen fuel cell power supply systems, and the first intermediate frequency power is used as a reference power of the first lithium battery in the first composite energy storage system, the first high frequency power is used as a reference power of the first supercapacitor in the first composite energy storage system, the second intermediate frequency power is used as a reference power of the second lithium battery in the second composite energy storage system, and the second high frequency power is used as a reference power of the second supercapacitor in the second composite energy storage system.

4. The working method of the flexible DC ring network power supply system for hydrogen-powered ships according to claim 3 is characterized in that: The power tracking control process of the first composite energy storage system in step (11) is specifically as follows: first, the bidirectional DC converter in the first composite energy storage system obtains the actual output voltage V of the first lithium battery collected by the monitoring system. B and the actual output voltage V of the first supercapacitor SC , the reference power P of the first lithium battery ref_b Divide by the actual output voltage V of the first lithium battery B , get the reference output current I of the first lithium battery ref_b , and the reference power P of the first supercapacitor ref_sc Divide by the actual output voltage V of the first supercapacitor SC , get the reference output current I of the first supercapacitor ref_sc ; Then, the reference output current I of the first lithium battery ref_b The actual output current I of the first lithium battery b Subtract and get the current error ΔI b , the reference current I ref_sc and the actual output current I of the first supercapacitor sc Subtract and get the current error ΔI sc ; Afterwards, the current error ΔI b , ΔI sc The duty cycle signal D is obtained by respectively passing through the PI controller to control the bidirectional DC converter of the first lithium battery in the first composite energy storage system. b The duty cycle signal D of the bidirectional DC converter of the first supercapacitor in the first composite energy storage system sc , then the duty cycle signal D b , D sc The bidirectional DC converter of the first lithium battery in the first composite energy storage system and the bidirectional DC converter of the first super capacitor in the first composite energy storage system are controlled by pulse width modulation PWM, thereby adjusting the power of the first lithium battery and the first super capacitor, thereby smoothing the power output of the ring network power supply system; In step (12), the bidirectional DC converter of the first lithium battery is switched to the voltage constant value control mode. The specific process is as follows: first, the first DC bus voltage setting value V ref The bidirectional DC converter output voltage V b Subtracting each other to obtain a voltage difference ΔV; subsequently, the voltage difference ΔV passes through a PI controller to obtain a duty cycle signal D, and the duty cycle signal D is modulated by PWM to control the bidirectional DC converter of the first lithium battery in the first composite energy storage system, thereby maintaining the stability of the first DC bus voltage.

5. The working method of the flexible DC ring network power supply system for hydrogen-powered ships according to claim 4 is characterized in that: Step (16) is specifically as follows: the monitoring system collects the voltage and current signals of the first regional load system, the voltage and current signals of the first auxiliary load, the voltage and current signals of the second regional load system, and the voltage and current signals of the second auxiliary load, and multiplies the voltage and current signals of the first regional load system to convert them into the power signal of the first regional load system, multiplies the voltage and current signals of the first auxiliary load to convert them into the power signal of the first auxiliary load, multiplies the voltage and current signals of the second regional load system to convert them into the power signal of the second regional load system, and multiplies the voltage and current signals of the second auxiliary load to convert them into the power signal of the second auxiliary load, and then adds the power signal of the first regional load system to the power signal of the first auxiliary load to obtain a first total power signal, and converts the second auxiliary load into the power signal of the second auxiliary load. The power signal of the regional load system is added to the power signal of the second auxiliary load to obtain a second total power signal; then, the first total power signal and the second total power signal are sent to the energy management system, and the energy management system uses a first-order filtering strategy to decompose the first total power signal to obtain a first low-frequency power and a first high-frequency power, and decomposes the second total power signal to obtain a second low-frequency power and a second high-frequency power; then, the first low-frequency power and the second low-frequency power are added to obtain the total low-frequency power, which is evenly shared by the first lithium battery and the second lithium battery in the first composite energy storage system and the second composite energy storage system, and the first high-frequency power is used as the reference power of the first supercapacitor in the first composite energy storage system, and the second high-frequency power is used as the reference power of the second supercapacitor in the second composite energy storage system.

6. The working method of the flexible DC ring network power supply system for hydrogen-powered ships according to claim 5, characterized in that: In step (23), when the first DC bus is short-circuited, the first hydrogen fuel cell power supply system and the first composite energy storage system are disconnected from the DC ring network main system, and the first regional load system is powered by the third DC bus; when the second DC bus is short-circuited, the second hydrogen fuel cell power supply system and the second composite energy storage system are disconnected from the DC ring network main system, and the second regional load system is powered by the fourth DC bus; In step (27), when the third DC bus is short-circuited, the first area load system is powered by the first DC bus; when the fourth DC bus is short-circuited, the second area load system is powered by the fourth DC bus.

7. The working method of the flexible DC ring network power supply system for hydrogen-powered ships according to claim 6, characterized in that: The first regional load system (5) and the first auxiliary load (15) are arranged in the port side area of ​​the hydrogen-powered ship, and the second hydrogen fuel cell power supply system (3), the second composite energy storage system (4), the second regional load system (6) and the second auxiliary load (16) are arranged in the starboard side area of ​​the hydrogen-powered ship; The first hydrogen fuel cell power supply system (1) and the second hydrogen fuel cell power supply system (3) are completely identical, and the first composite energy storage system (2) and the second composite energy storage system (4) are completely identical; The first hydrogen fuel cell power supply system (1) comprises a hydrogen fuel cell (1-1), a boost DC converter (1-2), a DC circuit breaker (1-3), and a protection module (1-4); the hydrogen fuel cell (1-1) is electrically connected to a first DC bus (10) via the boost DC converter (1-2), the DC circuit breaker (1-3), and the protection module (1-4) in sequence; The first composite energy storage system (2) comprises a lithium battery (2-1), a first bidirectional DC converter (2-3), a super capacitor (2-2), a second bidirectional DC converter (2-4), a DC circuit breaker (2-5), and a protection module (2-6); the lithium battery (2-1) is electrically connected to a first DC bus (10) via the first bidirectional DC converter (2-3), the DC circuit breaker (2-5), and the protection module (2-6); and the super capacitor (2-2) is electrically connected to the first DC bus (10) via the second bidirectional DC converter (2-4), the DC circuit breaker (2-5), and the protection module 2-6.

8. The working method of the flexible DC ring network power supply system for hydrogen-powered ships according to claim 7, characterized in that: The first regional load system (5) and the second regional load system (6) are completely identical, and the first auxiliary load (15) and the second auxiliary load (16) are completely identical; The first regional load system (5) comprises a propulsion motor (5-1), a thruster (5-2), an impact load (5-3), a DC / AC inverter (5-4), a first regional distribution board (5-5), a protection module (5-6) and a DC circuit breaker (5-7); the propulsion motor (5-1), the thruster (5-2) and the impact load (5-3) are all electrically connected to the first regional distribution board (5-5) through the DC / AC inverter (5-4) and the DC circuit breaker (5-7); and the first regional distribution board (5-5) is electrically connected to the first DC bus (10) and the second DC bus 12 respectively through the protection module (5-6); The first auxiliary load (15) includes a protection module 15-1, a DC circuit breaker (15-2), a DC / AC inverter (15-3), an isolation transformer (15-4), and an auxiliary device (15-5), wherein the auxiliary device (15-5) is connected to the third DC bus (12) via the isolation transformer (15-4), the DC / AC inverter (15-3), the DC circuit breaker (15-2), and the protection module (15-1).

9. The working method of the flexible DC ring network power supply system for hydrogen-powered ships according to claim 8, characterized in that: The daily AC power distribution network system (14) comprises a protection module (14-1), a DC circuit breaker (14-2), a DC / AC inverter (14-3), an isolation transformer (14-4), an AC circuit breaker (14-5), a pair of AC distribution boards (14-6), a bus tie switch 14-7, and a pair of daily loads (14-8); The third DC bus (12) and the fourth DC bus (13) are respectively connected to an AC distribution board (14-6) via a protection module (14-1), a DC circuit breaker (14-2), a DC / AC inverter (14-3), an isolation transformer (14-4), an AC circuit breaker (14-5), and the protection module (14-1); The two AC distribution boards (14-6) are connected to each other via a busbar switch (14-7), and supply power to a corresponding daily load (14-8) via an AC circuit breaker (14-5).

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