Constant-voltage output electric ship photovoltaic power supply system based on disturbance observation method

Abstract

According to the constant-voltage output electric ship photovoltaic power supply system based on the perturbation observation method, a photovoltaic input system comprises a photovoltaic cell module, a power converter module and a power control module; the DC boost system comprises a boost converter module and a boost control module. The energy storage system comprises an energy storage bin, a bidirectional direct-current converter module and a circuit breaker module. The power control module controls the power converter module through a maximum power point search algorithm, so that the output power of the photovoltaic cell module is maximum, and meanwhile, stable voltage output exists; the boost converter module controls the turn-on time and the turn-off time of a switch tube by changing the duty ratio of a PWM modulation signal, so that the input voltage is boosted to a higher output voltage level. According to the system, the maximum power point tracking algorithm based on the perturbation observation method is adopted to ensure that the photovoltaic cell is in the maximum power output state, and meanwhile, the output voltage is adjusted through the DC-DC converter to keep stable constant voltage output, so that the requirement of the electric ship for power stability is met.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic power supply for electric ships, and in particular to a photovoltaic power supply system for electric ships with constant voltage output based on a disturbance observation method. Background Art

[0002] In recent years, with the increasing awareness of environmental protection, electric ships have become an important direction for green shipping. Using solar energy as a power source for ships, combined with efficient photovoltaic power generation and maximum power point tracking technology (MPPT), can effectively utilize natural energy and reduce energy consumption. Existing photovoltaic systems often face the problem of output voltage fluctuations, especially when the light conditions change, the output power of photovoltaic cells is unstable. For example, in existing literature,

[0003] Reference [1]: Yu Shuguang. Research on power system dispatching methods to smooth out photovoltaic power generation power fluctuations [J]. China New Technologies and New Products, 2025, (02): 13-15. DOI: 10.13612 / j.cnki.cntp.2025.02.044. It points out that during the photovoltaic power generation process, factors such as temperature changes and solar radiation intensity will affect the power generation efficiency and stability of photovoltaic power stations, resulting in unpredictable fluctuations in distributed photovoltaic power generation power.

[0004] Reference [2]: Fu Baochuan, Zhu Jianye, Wei Liangjiang. A review of methods for dealing with uncertainty in photovoltaic microgrid output [J]. Journal of Suzhou University of Science and Technology (Natural Science Edition), 2024, 41(04): 51-59. The output model of the relationship between photovoltaic power generation and solar radiation is given, which shows that the stronger the solar radiation, the greater the output of photovoltaic power generation, and the intensity of solar radiation is related to weather, season, time, location, etc.

[0005] Therefore, how to achieve stable output of photovoltaic systems under complex lighting environments is a technical problem that needs to be solved urgently.

[0006] The perturbation and observation method is a commonly used maximum power point tracking (MPPT) algorithm for optimizing the power output of photovoltaic systems. The algorithm periodically perturbs the operating voltage of the photovoltaic module and observes the change in power after the perturbation. If the power increases, the system will continue to adjust the voltage in that direction; if the power decreases, the adjustment direction will be changed to find the maximum power point. This method is simple and easy to implement, and can effectively track the maximum power output of the photovoltaic module under different light and temperature conditions. Therefore, it is widely used in photovoltaic power generation systems. Summary of the invention

[0007] Aiming at the problems of short endurance of large ships, insufficient utilization of distributed energy, and unstable output of photovoltaic cells, etc., the present invention provides a constant-voltage output photovoltaic power supply system for electric ships based on the perturbation observation method. This system ensures that the photovoltaic cells are in the maximum power output state by adopting the maximum power point tracking algorithm based on the perturbation observation method. At the same time, the output voltage is adjusted through a DC-DC converter to maintain a stable constant-voltage output, so as to meet the stable power demand of electric ships.

[0008] The technical solution adopted by the present invention is as follows:

[0009] A constant-voltage output photovoltaic power supply system for electric ships based on the perturbation observation method, which system includes: a photovoltaic input system, a DC boost system, and an energy storage system;

[0010] The photovoltaic input system includes a photovoltaic cell module, a power converter module, and a power control module; the photovoltaic cell module is respectively connected to the power converter module and the power control module, and the power converter module is connected to the power control module; the power control module is used to collect the voltage and current information of the photovoltaic cell module and process it to generate a control signal and transmit it to the power converter module to control the power output;

[0011] The DC boost system includes a boost converter module and a boost control module. The boost converter module and the boost control module are both connected to the power converter module, and the boost converter module is connected to the shipboard DC bus; the boost control module collects the output voltage and current of the power converter module, and generates a control signal through PI control and outputs it to the boost converter module to ensure a stable DC voltage output;

[0012] The energy storage system includes an energy storage bin, a bidirectional DC converter module, and a circuit breaker module; the energy storage bin is connected to the bidirectional DC converter module, the bidirectional DC converter module is connected to the circuit breaker module, and the circuit breaker module is connected to the shipboard DC bus.

[0013] The photovoltaic input system adopts the maximum power point search algorithm to ensure that the photovoltaic array always outputs the maximum power under different light and temperature conditions. The power control module collects the output voltage and current of the photovoltaic cell module, and controls the power converter module through the maximum power point search algorithm to make the output power of the photovoltaic cell module the largest and have a stable voltage output, specifically as follows:

[0014] Taking the voltage of the photovoltaic cell as the output variable y(t) = v pv (t), where v pv (t) represents the input voltage at the terminal of the capacitor C pv , and it can be obtained that:

[0015]

[0016] In formula (1), represents the output voltage of the photovoltaic cell, C pv represents the filter capacitor, i L (t) represents the current of the inductor L, and u(t) represents the control signal; i pv (t) represents the output current of the photovoltaic cell;

[0017] Since the control signal u(t) appears in the first derivative of y(t), the relative degree ρ of the photovoltaic input system in three-dimensional Euclidean space is 1. It means that the two internal states of the photovoltaic input system are unobservable for control actions. However, internal stability can be guaranteed under various load conditions.

[0018] Assume that the state i L (t) can be used for feedback, then the linearized control law is defined as follows:

[0019]

[0020] where γ(t) represents the auxiliary control law; substituting the control signal u(t) into Equation (1), we can obtain:

[0021] C pv y(t) = γ(t) + i pv (t) (3)

[0022] It is necessary to ensure that the components of the buck converter and its switching frequency are reasonably selected to maintain the continuous conduction mode and ensure i L (t) > 0,

[0023] Define the tracking error as e(t) = y * (t) - y(t), y * (t) = v * pv(t), e(t) represents the voltage tracking error; y * (t) represents the photovoltaic reference voltage; pv(t) represents the photovoltaic voltage;

[0024] The control framework is as follows:

[0025]

[0026] In Equation (4), k i , k p , k r , h are control parameters; e(τ) represents the voltage tracking error; e(t - h) represents the voltage tracking error when t approaches h; t represents the variable;

[0027]

[0028] In Equation (5), represents the voltage tracking error, represents the PV reference voltage, represents the actual PV voltage;

[0029] Thus, the quasi-binomial control equation is obtained:

[0030]

[0031] In Equation (6), Q(s,k p ,k i ,k r ,h) represents the quasi-binomial equation of the voltage tracking error, s represents a constant, and e -sh represents a specific value of the transfer function.

[0032] In the DC boost system, the boost converter module boosts the voltage output by the PV input system to generate a voltage that meets the standard of the shipboard DC bus. The boost control module collects the output voltage and current of the PV input system, and through PI feedback control, the boost converter module outputs a DC voltage of 110V and transmits it to the shipboard DC bus.

[0033] The boost converter module uses an inductor to store and transfer energy, and a capacitor to keep the voltage constant. By changing the duty cycle of the PWM modulation signal, the on-time and off-time of the switching tube are controlled, so as to raise the input voltage to a higher output voltage level. Specifically, as Figure 5 shown, the circuit shown is a boost converter for maximum power output. When the switching tube IGBT is on, the current output by the PV cell flows through the inductor to charge the inductor. When the switching tube IGBT is off, the PV cell current flows through the inductor and the diode for the system function. The inductor discharges to act as a boost voltage to achieve a certain boost effect, and at the same time, the voltage and current of the PV cell are collected to control the stable output of the power.

[0034] When analyzing the principle of the boost converter module, it is first assumed that the values of the inductor L and capacitor C in the boost converter module are very large. When the IGBT is triggered to become on, the power supply U d charges the inductor L, and the capacitor C discharges to the load R; when the IGBT is turned off due to reverse voltage, the power supply U d and the inductor L supply energy to the resistor and charge the capacitor C at the same time. The inductor L plays a voltage boost role, and the capacitor C plays a role in maintaining the output voltage. The inductor L and capacitor C jointly complete the boost and hold functions; specifically, as Figure 6 shown, when the switching tube is on, the current forms a loop through the IGBT, and the power supply U d charges the inductor, and the capacitor C is responsible for supplying power to the load. As Figure 7 shown, when the switching tube is off, the current flows through the diode, and finally forms a loop for the load. The inductor discharges to play a voltage boost role, and the output voltage increases.

[0035] According to the energy transfer relationship, it can be known that the energy absorbed and released by the inductor L during the working cycle are equal, that is:

[0036] U d ·I·t on =U o -U d ·I·t off (7)

[0037] In formula (7), U d represents the power supply input, U o represents the circuit output, I represents the constant current of the circuit, and t on is the conduction time of the IGBT, and t off is the turn-off time of the IGBT.

[0038]

[0039] In formula (8), α represents the duty cycle.

[0040] In the energy storage system, the energy storage bin exchanges energy with the shipboard DC bus through the bidirectional DC converter module. Energy can flow from the energy storage bin to the shipboard DC bus for use by the ship's load; energy can also flow from the shipboard DC bus to the energy storage bin to charge the battery.

[0041] The circuit breaker module functions as protection. When a fault occurs in the energy storage bin or the shipboard DC bus, it disconnects to protect the battery in the energy storage bin.

[0042] The shipboard DC bus is connected to DC loads, and the DC loads include one or several of on-board instruments, ship electrical lighting, and power electronic devices.

[0043] The constant-voltage output electric ship photovoltaic power supply system based on the perturbation observation method of the present invention has the following technical effects:

[0044] 1) In the present invention, the photovoltaic input system adopts the maximum power point tracking algorithm based on the perturbation observation method, which can track and adjust the working point of the photovoltaic array in real time, ensure that the maximum power is always output under the condition of changing light intensity, and avoid the efficiency loss caused by power fluctuation.

[0045] 2) The present invention boosts the voltage output by the photovoltaic input system through the boost converter module to obtain a stable voltage power and transmits it to the shipboard DC bus. The voltage level can be adaptively switched according to the ship type, and it can keep the output voltage of the electric ship power system stable under different load conditions, avoid the influence of voltage fluctuation on the ship drive system and other electronic devices, and ensure normal operation.

[0046] 3) In the energy storage system of the present invention, the circuit breaker module ensures the electrical safety of the hull and disconnects the battery in case of emergency to avoid battery failures.

[0047] 4) The present invention ensures that the electric ship can maintain a stable power supply under different lighting conditions. This system can improve the energy utilization efficiency of the electric ship and the endurance of the ship, providing a constant voltage and stable power solution for the ship. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The present invention will be further described below in conjunction with the drawings and embodiments;

[0049] Figure 1 It is a structural diagram of a photovoltaic power supply system for an electric ship with constant voltage output based on the perturbation observation method.

[0050] Figure 2 It is a control block diagram for maximum power output of the photovoltaic.

[0051] Figure 3 It is the first system simulation result;

[0052] Figure 4 It is the second system simulation result.

[0053] Figure 5 It is a schematic diagram of the boosting working principle of the boost converter module.

[0054] Figure 6 It is a schematic diagram of the working principle of the boost converter module (when the switch tube is turned on);

[0055] Figure 7 It is a schematic diagram of the working principle of the boost converter module (when the switch tube is closed). DETAILED DESCRIPTION OF THE INVENTION

[0056] As Figure 1 shown, a photovoltaic power supply system for an electric ship with constant voltage output based on the perturbation observation method, which system includes: a photovoltaic input system, a DC boost system, and an energy storage system;

[0057] The photovoltaic input system includes a photovoltaic cell module 1, a power converter module 2, and a power control module 3; the photovoltaic cell module 1 is respectively connected to the power converter module 2 and the power control module 3, and the power converter module 2 is connected to the power control module 3; the power control module 3 is used to collect the voltage and current information of the photovoltaic cell module 1 and process and generate a control signal to be transmitted to the power converter module 2 to control the power output.

[0058] The photovoltaic cell module 1 is a device that converts solar energy into DC electrical energy. The rated power output of a single photovoltaic cell is 300W, and the working voltage is 36.68v.

[0059] The power converter module 2 is for maximizing the power output of the DC power supply output by the photovoltaic cell module. The module includes a number of IGBTs, and the model of the IGBT is FF1400R12IP4, with a voltage rating of 1200v.

[0060] The power control module 3 is responsible for collecting the voltage and current output by the photovoltaic cell, and generating a reference voltage according to the maximum power point search algorithm to control the output of the power converter module 4. The module mainly includes the DSP digital processing chip TMS320F283335. The DC boost system includes a boost converter module 4 and a boost control module 5. The boost converter module 4 and the boost control module 5 are both connected to the power converter module 2, and the boost converter module 4 is connected to the shipboard DC bus 6; the boost control module 5 collects the output voltage and current of the power converter module 2, and generates a control signal through PI control and outputs it to the boost converter module 4 to ensure a stable DC output voltage.

[0061] The boost converter module 4 is responsible for boosting the voltage output by the power converter module 2 to 110v and delivering it to the DC bus. The module includes IGBTs, and the model of the IGBT is FF1400R12IP4, with a voltage rating of 1200v.

[0062] The boost control module 5 is mainly responsible for collecting the voltage output by the boost converter module 4, comparing it with the reference voltage to obtain a control error and delivering it to the PI control to achieve the stability of the output voltage. The module mainly includes the DSP digital processing chip TMS320F283335.

[0063] The energy storage system includes an energy storage bin 7, a bidirectional DC converter module 8, and a circuit breaker module 9; the energy storage bin 7 is connected to the bidirectional DC converter module 8, the bidirectional DC converter module 8 is connected to the circuit breaker module 9, and the circuit breaker module 9 is connected to the shipboard DC bus 6.

[0064] The energy storage bin 7 is an energy storage unit composed of lead-acid batteries with a capacity of 3.44 MWh, which is constituted by 16 parallel-connected 215kW PCSs, and the input / output voltage is 48v to 72v.

[0065] The bidirectional DC converter module 8 is a device for bidirectional step-up and step-down conversion of DC power. The direction from the energy storage bin module 7 to the DC bus is step-up, and the direction from the DC bus to the energy storage bin is step-down. The step-up output voltage V boost is 110v, and the step-down output V buckIt is 72V. The module includes several IGBTs, and the model of the IGBT is FF1400R12IP4, with a withstand voltage level of 1200V. The circuit breaker module 9 is responsible for connecting the bidirectional DC converter module 8 and the DC bus 6, and disconnecting the energy storage system in special cases. The module mainly includes an industrial molded case circuit breaker, model ABB Tmax XT2N 250, rated value: 690V AC, 250A, breaking capacity 36kA.

[0066] Figure 2 It is the control block diagram for the maximum power output of the photovoltaic. The power control module 3 of the maximum power point search algorithm collects the output voltage v of the photovoltaic cell pv and current i pv , and calculates the power p pv =v pv *i pv , to obtain the voltage reference value v related to the maximum power of the photovoltaic module * pv . The control scheme adjusts the duty cycle of the DC-DC power converter to ensure that the photovoltaic voltage tracks the calculated reference voltage.

[0067] Figure 3 、 Figure 4 It is the system simulation result. As shown in Figure 3 、 Figure 4 , changing the illumination condition of the photovoltaic cell, the illumination intensity is 800W / m from 0 to 2s 2 , 1000W / m from 2 to 4s 2 , 900W / m from 4 to 6s 2 . The photovoltaic cell outputs the corresponding maximum power under the maximum power point search algorithm, and the output voltage of the photovoltaic cell is 29V. The power converter module 2 boosts the 29V voltage output by the photovoltaic to a stable voltage of 50V and transports it to the shipboard DC bus 6.

[0068] Compared with the traditional photovoltaic energy input system for electric ships, the constant voltage output electric ship photovoltaic power supply system based on the perturbation observation method proposed by the present invention has construction significance for solving the efficiency loss caused by the output power fluctuation due to the change of illumination intensity, effectively improves the clean energy utilization efficiency of electric ships, and realizes the maximization of the input power of the ship photovoltaic system and can automatically adjust the voltage level to output a stable voltage according to the requirements of the ship bus. The photovoltaic cell can not only ensure the cruising range of the ship, improve the efficiency and stability of the system, but also achieve the goals of energy conservation, emission reduction and environmental protection, providing an effective solution for the sustainable development of electric ships.

Claims

1. A constant-voltage output photovoltaic power supply system for electric ships based on the disturbance observation method, characterized in that The system includes: a photovoltaic input system, a DC boost system, and an energy storage system; The photovoltaic input system includes a photovoltaic cell module (1), a power converter module (2), and a power control module (3); the photovoltaic cell module (1) is respectively connected to the power converter module (2) and the power control module (3), and the power converter module (2) is connected to the power control module (3); the power control module (3) is used to collect the voltage and current information of the photovoltaic cell module (1) and process it to generate a control signal and transmit it to the power converter module (2) to control the power output; The DC boost system includes a boost converter module (4) and a boost control module (5), both the boost converter module (4) and the boost control module (5) are connected to the power converter module (2), and the boost converter module (4) is connected to the shipboard DC bus (6); the boost control module (5) collects the output voltage and current of the power converter module (2), and generates a control signal through PI control and outputs it to the boost converter module (4) to ensure a stable DC output voltage; The energy storage system includes an energy storage bin (7), a bidirectional DC converter module (8), and a circuit breaker module (9); the energy storage bin (7) is connected to the bidirectional DC converter module (8), the bidirectional DC converter module (8) is connected to the circuit breaker module (9), and the circuit breaker module (9) is connected to the shipboard DC bus (6).

2. The constant-voltage output electric ship photovoltaic power supply system based on the disturbance observation method according to claim 1, characterized in that: The photovoltaic input system adopts the maximum power point tracking algorithm to ensure that the photovoltaic array always outputs the maximum power under different illumination and temperature conditions; the power control module (3) collects the output voltage and current of the photovoltaic cell module (1), and controls the power converter module (2) through the maximum power point tracking algorithm to make the output power of the photovoltaic cell module (1) maximum and have a stable voltage output at the same time.

3. The constant-voltage output photovoltaic power supply system for electric ships based on the disturbance observer method according to claim 2, wherein: Taking the voltage of the photovoltaic cell as the output variable y(t) = v pv (t), where v pv (t) represents the input voltage at the terminals of the capacitor C pv , we can obtain: In Equation (1), represents the output voltage of the photovoltaic cell, and C pv represents the filter capacitor, i L (t) represents the current of inductor L, and u(t) represents the control signal; i pv (t) represents the output current of the photovoltaic cell; Since the control signal u(t) appears in the first derivative of y(t), the relative degree ρ of the photovoltaic input system in three-dimensional Euclidean space is 1, indicating that two internal states of the photovoltaic input system are unobservable to the control action. However, the internal stability can be guaranteed under various load conditions; Assumed state i L (t) can be used for feedback, and the linearized control law is defined as follows: Among them, γ(t) represents the auxiliary control law; substituting the control signal u(t) into Equation (1), it can be obtained that: C pv y(t) = γ(t) + i pv (t) (3) Ensure that i L (t) > 0, Define the tracking error as e(t) = y * (t) - y(t), y * (t) = v * pv(t), e(t) represents the voltage tracking error; y * (t) represents the photovoltaic reference voltage; pv(t) represents the photovoltaic voltage; The control framework is as follows: In formula (4), k i , k p , k r , where h is a control parameter; e(τ) represents the voltage tracking error; e(t - h) represents the voltage tracking error when t approaches h; t represents a variable; In Equation (5), represents the voltage tracking error, represents the photovoltaic reference voltage, represents the actual photovoltaic voltage; Thus, the quasi-binomial control equation is obtained: In Equation (6), Q(s,k p ,k i ,k r ,h) represents a quasi-binomial equation of the voltage tracking error, s represents a constant, and e -sh represents a specific value of the transfer function.

4. The constant-voltage output electric ship photovoltaic power supply system based on the disturbance observation method according to claim 1, wherein: In the DC boost system, the boost converter module (4) boosts the voltage output by the photovoltaic input system to generate a voltage that meets the standard of the shipboard DC bus (6); the boost control module (5) collects the output voltage and current of the photovoltaic input system, and controls the boost converter module (4) through PI feedback to output a DC voltage of 110V and transmit it to the shipboard DC bus (6).

5. The constant-voltage output photovoltaic power supply system for electric ships based on the disturbance observation method according to claim 4, wherein: The boost converter module (4) uses an inductor to store and transfer energy, and a capacitor to keep the voltage constant. By changing the duty cycle of the PWM modulation signal, the on-time and off-time of the switching tube are controlled, so as to raise the input voltage to a higher output voltage level.

6. The constant-voltage output photovoltaic power supply system for electric ships based on the disturbance observer method according to claim 5, wherein: When analyzing the principle of the boost converter module (4), first, assume that the values of the inductor L and the capacitor C in the boost converter module (4) are very large. After the IGBT is triggered and turned on, the power supply U d charges the inductor L, and the capacitor C discharges to the load R; after the IGBT is turned off due to reverse voltage, the power supply U d and the inductor L supply energy to the resistor and charge the capacitor C at the same time. The inductor L plays a role in boosting the voltage, and the capacitor C plays a role in maintaining the output voltage. The inductor L and the capacitor C jointly complete the function of boosting and maintaining the voltage.

7. The constant-voltage output photovoltaic power supply system for electric ships based on the disturbance observer method according to claim 6, wherein: According to the energy transfer relationship, it can be known that the energy absorbed and released by the inductor L during the working cycle is equal, that is: U d ·I·t on =U o -U d ·I·t off (7) In Equation (7), U d represents the power input, U o represents the circuit output, I represents the constant current of the circuit, and t on is the conduction time of the IGBT, and t off is the turn-off time of the IGBT; In Equation (8), α represents the duty cycle.

8. The constant-voltage output electric ship photovoltaic power supply system based on the disturbance observation method according to claim 1, characterized in that: In the energy storage system, the energy storage bin (7) exchanges energy with the on-board DC bus (6) through the bidirectional DC converter module (8); energy can flow from the energy storage bin (7) to the on-board DC bus (6) for use by the ship's load; energy can also flow from the on-board DC bus (6) to the energy storage bin (7) to charge the battery.

9. The constant-voltage-output electric ship photovoltaic power supply system based on the disturbance observation method according to claim 1, wherein: The circuit breaker module (9) functions as protection. When a fault occurs in the energy storage bin (7) or the on-board DC bus (6), it disconnects to protect the battery in the energy storage bin (7).

10. The constant-voltage output photovoltaic power supply system for electric ships based on the disturbance observation method according to claim 1, wherein: The on-board DC bus (6) is connected to the DC load (10), and the DC load (10) includes one or several of shipboard instruments, ship electrical lighting, and power electronic devices.

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