Ship hybrid energy storage system capacity planning method based on multilayer power distribution

Abstract

The invention relates to the technical field of energy storage system-containing ship power control, in particular to a ship hybrid energy storage system capacity planning method based on multilayer power distribution, which comprises the following steps of: S1, establishing a power generation side operation constraint of an all-electric ship hybrid energy storage system; s2, constructing a ship hybrid energy storage system robust capacity planning model with the goal of minimizing the investment cost of the ship hybrid energy storage system and the operation cost of the ship microgrid; s3, solving the robust capacity planning model of the ship hybrid energy storage system to obtain the optimal capacity of the ship hybrid energy storage system; and S4, taking the optimal capacity as the design capacity of the ship hybrid energy storage system, performing power distribution under the multilayer time scale in combination with the actual propulsion power demand to obtain an optimal power distribution scheme, and realizing power distribution of each component of the ship hybrid energy storage system through the optimal power distribution scheme. According to the invention, the safety and stability of all-electric ship navigation can be ensured.

Description

Technical Field

[0001] This invention relates to the field of power control for ships with energy storage systems, and more specifically to a capacity planning method for ship hybrid energy storage systems based on multi-layer power allocation. Background Technology

[0002] With a growing global consensus on reducing carbon emissions, the shipping industry is facing unprecedented pressure to transform. The carbon reduction targets set by the International Maritime Organization (IMO) are forcing ship operators to seek cleaner and more efficient energy solutions. To reduce carbon emissions in the shipping industry and promote its green transformation, ship electrification has received significant attention in recent years, exemplified by all-electric ships (AES), whose propulsion systems use electricity, and whose power networks can be viewed as microgrids.

[0003] To ensure the safe and stable operation of ships, the electrical system needs to provide reliable and stable power to the ship's loads. Therefore, ship microgrids typically combine multiple power sources. Diesel generator sets meet the main load requirements of ship navigation, but they can cause high carbon emissions, water pollution, and noise pollution. Fuel cells, with their high energy conversion efficiency, reliable performance, environmental friendliness, and noise reduction, are a green power source that can replace traditional diesel engine sets. However, ship navigation and operations are easily affected by the uncertain marine environment, leading to power fluctuations in the ship's microgrid, causing a drop in DC bus voltage, which in turn affects the power output of the fuel cells. Therefore, a hybrid energy storage system is needed to mitigate power fluctuations.

[0004] The applicant found that hybrid energy storage systems need to flexibly match the power fluctuations of the ship's electrical system to maintain the economical operation of generator sets and fuel cells. Therefore, capacity planning for hybrid energy storage systems is a critical issue. If the system is too small, it will lead to an inability to achieve power balance between the ship's power generation and load sides; if it is too large, it will increase the ship's weight and system investment costs. Furthermore, the power allocation problem across multiple power sources at different time scales is also a major challenge for all-electric ships. All-electric ships have multiple large-scale power sources. If an appropriate power allocation strategy is not adopted, high-frequency and low-frequency power fluctuations at different time scales will affect the ship's normal navigation, as propulsion power is the primary load demand during navigation. Summary of the Invention

[0005] To address the shortcomings of the existing technologies, the technical problem to be solved by this invention is: how to provide a capacity planning method for a ship hybrid energy storage system based on multi-layer power allocation. By solving a model with the goal of minimizing the investment cost and operating cost of the ship hybrid energy storage system and the ship microgrid, the optimal capacity of the hybrid energy storage system is obtained. Through a three-layer power allocation strategy, the roles of different types of energy storage units and power supply are fully utilized to achieve the purpose of smoothing power fluctuations, reducing DC bus voltage drops, and ensuring the safety and stability of all-electric ship navigation.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A capacity planning method for shipboard hybrid energy storage systems based on multi-level power allocation includes:

[0008] S1: Analyze the power balance characteristics of the generation side and load side of the ship microgrid under the wave propulsion scenario, and establish the operation constraints of the generation side of the all-electric ship hybrid energy storage system;

[0009] S2: Based on the operational constraints of the power generation side of the all-electric ship hybrid energy storage system, a robust capacity planning model for the ship hybrid energy storage system is constructed with the goal of minimizing the investment cost of the ship hybrid energy storage system and the operating cost of the ship microgrid.

[0010] S3: Solve the robust capacity planning model of the ship hybrid energy storage system to obtain the optimal capacity of the ship hybrid energy storage system;

[0011] S4: The optimal capacity is taken as the design capacity of the ship hybrid energy storage system. The optimal power allocation scheme is obtained by combining the actual propulsion power demand under multiple time scales. The power allocation of each component of the ship hybrid energy storage system is realized through the optimal power allocation scheme.

[0012] Preferably, in step S1, the operational constraints on the generation side of the all-electric ship hybrid energy storage system include:

[0013] 1) Maximum capacity constraint equation for hybrid energy storage system

[0014]

[0015] In the formula: This refers to the rated power capacity of the hybrid energy storage system. This refers to the rated energy storage capacity of the hybrid energy storage system. This represents the maximum power capacity of the hybrid energy storage system. This represents the maximum energy storage capacity of the hybrid energy storage system.

[0016] 2) Power supply constraint equations

[0017]

[0018] In the formula: These are the active power and rated active power of the nth generator, respectively. These are the active power and rated active power of the nth fuel cell, respectively. These are the on / off state variables of the nth generator and the nth fuel cell, respectively; N represents the load factor of the nth generator and the nth fuel cell, respectively; G N FC These are the sets of quantities for generators and fuel cells, respectively.

[0019] 3) Power generation fuel cost constraint equation

[0020]

[0021] In the formula: These represent the fuel costs for generating electricity for the nth generator and the nth fuel cell during time period t, respectively. These are the cost parameters for the nth generator; These are the cost parameters for the nth fuel cell.

[0022] Preferably, in step S2, the objective function of the robust capacity planning model for the ship hybrid energy storage system is expressed as:

[0023]

[0024] Where: H c This represents the total daily investment cost; I nvP I nvE These are the daily net annual values ​​for power capacity and energy storage capacity, respectively.

[0025] Preferably, in step S2, the system power balance constraints of the robust capacity planning model for the ship hybrid energy storage system include:

[0026] 1) Power / energy constraint equations for hybrid energy storage systems

[0027]

[0028] In the formula: This is the battery's maximum rated active power; This refers to the battery's maximum rated storage capacity. η represents the energy stored in the battery during time period t. dis η ch These represent the battery charging efficiency and discharging efficiency, respectively; Δt is the time duration.

[0029] 2) System total power balance constraint equations

[0030]

[0031] In the formula: The active power of the hybrid energy storage system; These are respectively the ship's daily service load and the ship's propulsion load;

[0032] 3) System active power reserve constraint equations

[0033]

[0034] In the formula: η APR For rotational reserve ratio.

[0035] Preferably, in step S4, power allocation based on the optimal capacity of the hybrid energy storage system across three time scales is performed through the following steps:

[0036] S401: Calculate the output power of generator sets and fuel cells in a ship's hybrid energy storage system on a daily timescale;

[0037] S402: Calculate the compensation power of batteries and fuel cells in a ship's hybrid energy storage system on an hourly timescale;

[0038] S403: Calculate the compensation power of supercapacitors in a ship hybrid energy storage system for smoothing minute-level power fluctuations on a minute-by-minute timescale.

[0039] S404: The optimal power allocation scheme is determined by the output power of the generator set and fuel cell on a daily time scale, the compensation power of the battery and fuel cell on an hourly time scale, and the compensation power of the supercapacitor on a minute time scale.

[0040] Preferably, in step S401, the processing step of calculating the output power of the generator set and the fuel cell includes:

[0041] 1) The generator set in the ship's hybrid energy storage system uses an excitation voltage system with voltage follower control to control the output power P. DG ;

[0042] 2) In the ship's hybrid energy storage system, the fuel cell uses PI control to output a constant power P. FC .

[0043] Preferably, in step S402, the compensation power of the storage battery and the fuel cell is calculated using the following formula:

[0044]

[0045] In the formula: P FC-refT1 represents the minimum frequency power requirement of the fuel cell on an hourly timescale, i.e., the compensation power; P represents the fuel cell filter time constant; bat-ref T1 represents the second lowest frequency power demand of the battery on an hourly timescale, i.e., the compensation power; T2 is the battery filtering time constant.

[0046] Preferably, in step S403, the compensation power of the supercapacitor for smoothing minute-level power fluctuations is calculated using the following formula:

[0047]

[0048] In the formula: P uc-ref (t) represents the highest frequency power demand of the supercapacitor on a timescale of one minute, i.e., the compensation power.

[0049] Preferably, in steps S402 and S403, the compensation power on both the hourly and minute time scales satisfies the following conditions:

[0050]

[0051] In the formula: I dc-ref This represents the DC bus current requirement; U dc-ref The rated voltage of the DC bus; U dc K is the DC bus voltage. p and K i These are the proportional and integral coefficients of the voltage controller, respectively; I load This represents the DC bus load current value.

[0052] Compared with existing technologies, the capacity planning method for ship hybrid energy storage systems based on multi-layer power allocation in this invention has the following advantages:

[0053] This invention analyzes the power balance characteristics of the generation and load sides of a ship's microgrid under fluctuating propulsion scenarios and establishes operational constraints on the generation side of an all-electric ship hybrid energy storage system. Under fluctuating propulsion scenarios, the power on both the generation and load sides of the ship is dynamically changing. By deeply analyzing the power balance characteristics and establishing operational constraints on the generation side, the hybrid energy storage system can accurately sense and respond to these power fluctuations, avoiding voltage fluctuations and frequency shifts in the ship's power system caused by power imbalances. This ensures the stable operation of the ship's microgrid and guarantees normal navigation under complex sailing conditions. Simultaneously, these operational constraints provide clear boundary conditions for the capacity planning of the hybrid energy storage system, clarifying the power balance between the generation and load sides under different power fluctuation conditions, laying the foundation for achieving power balance between the generation and load sides, and facilitating coordinated control among multiple large-scale power sources in the ship's microgrid.

[0054] This invention, based on the operational constraints of the power generation side of an all-electric marine hybrid energy storage system, constructs a robust capacity planning model for the system, aiming to minimize the investment cost and operating cost of the marine microgrid, and solves for the optimal capacity. By constructing a robust capacity planning model with the goal of minimizing the investment cost of the marine hybrid energy storage system, and comprehensively considering various factors and uncertainties, it can find the most economical and reasonable energy storage capacity configuration scheme while satisfying the operational constraints of the power generation side. Compared with traditional capacity planning methods, this significantly reduces the equipment cost of the marine hybrid energy storage system. Simultaneously, considering the minimization of the marine microgrid operating cost, the model can rationally arrange the output of the power generation equipment and the charging and discharging strategy of the energy storage system according to the power demand and energy storage capacity under different operating conditions, reducing operating costs such as fuel consumption and equipment wear.

[0055] The optimal capacity obtained by this invention is used as the design capacity. Combined with actual propulsion power requirements, a multi-timescale power allocation scheme is derived. During the navigation of an all-electric ship, propulsion power requirements exhibit high-frequency and low-frequency fluctuations at different time scales. Multi-timescale power allocation, combined with actual propulsion power requirements, allows the hybrid energy storage system to better adapt to these complex power variations. This layered allocation strategy ensures that the ship receives stable propulsion power at different navigation stages, avoiding disruptions to normal navigation due to excessive power fluctuations and guaranteeing navigation safety. Simultaneously, through power allocation at three time scales, the output power fluctuations of the ship's main generator and fuel cells caused by the shipping environment at each time scale are smoothed out, reducing the DC bus voltage deviation of the ship's microgrid, ensuring normal power supply to the ship's propulsion load, thereby improving the power supply quality of the ship's microgrid, guaranteeing the safety and stability of all-electric ship navigation, and providing greater possibilities for the widespread application of all-electric ships. Attached Figure Description

[0056] To make the objectives, technical solutions, and advantages of the invention clearer, the invention will now be described in further detail with reference to the accompanying drawings, wherein:

[0057] Figure 1 This is a logic block diagram of a capacity planning method for a ship hybrid energy storage system based on multi-layer power allocation.

[0058] Figure 2 This is a diagram of a ship's microgrid structure.

[0059] Figure 3 A block diagram of a three-layer power allocation strategy. Detailed Implementation

[0060] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but only to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0061] The following detailed explanation illustrates the specific implementation methods:

[0062] Example:

[0063] This embodiment discloses a capacity planning method for a ship hybrid energy storage system based on multi-layer power allocation.

[0064] like Figure 1 As shown, the capacity planning method for ship hybrid energy storage systems based on multi-layer power allocation includes:

[0065] S1: Analyze the power balance characteristics of the generation side and load side of the ship microgrid under the wave propulsion scenario, and establish the operation constraints of the generation side of the all-electric ship hybrid energy storage system;

[0066] S2: Based on the operational constraints of the power generation side of the all-electric ship hybrid energy storage system, a robust capacity planning model for the ship hybrid energy storage system is constructed with the goal of minimizing the investment cost of the ship hybrid energy storage system and the operating cost of the ship microgrid.

[0067] S3: Solve the robust capacity planning model of the ship hybrid energy storage system to obtain the optimal capacity of the ship hybrid energy storage system;

[0068] S4: The optimal capacity is taken as the design capacity of the ship hybrid energy storage system. Power allocation is carried out under multiple (three-layer) time scales in combination with the actual propulsion power demand to obtain the optimal power allocation scheme. The power allocation of each component of the ship hybrid energy storage system is realized through the optimal power allocation scheme.

[0069] In this embodiment, the optimal capacity allocation of the hybrid energy storage system and the elimination of power fluctuations in the ship's microgrid at different time scales are taken as the objectives of the three-layer power allocation technology for the capacity configuration of the ship's hybrid energy storage system. By solving the robust capacity mixed integer quadratic programming model of the ship's hybrid energy storage system, the optimal capacity allocation of each component of the ship's hybrid energy storage system is determined. Based on this, a three-layer power allocation strategy is adopted to achieve reasonable power allocation of multiple large-scale power sources at different time scales, reduce DC bus voltage deviation, smooth out the output power fluctuations of the ship's main generator and fuel cells, improve the power supply quality of the ship's microgrid, and ensure the safe and stable operation of the all-electric ship.

[0070] This invention analyzes the power balance characteristics of the generation and load sides of a ship's microgrid under fluctuating propulsion scenarios and establishes operational constraints on the generation side of an all-electric ship hybrid energy storage system. Under fluctuating propulsion scenarios, the power on both the generation and load sides of the ship is dynamically changing. By deeply analyzing the power balance characteristics and establishing operational constraints on the generation side, the hybrid energy storage system can accurately sense and respond to these power fluctuations, avoiding voltage fluctuations and frequency shifts in the ship's power system caused by power imbalances. This ensures the stable operation of the ship's microgrid and guarantees normal navigation under complex sailing conditions. Simultaneously, these operational constraints provide clear boundary conditions for the capacity planning of the hybrid energy storage system, clarifying the power balance between the generation and load sides under different power fluctuation conditions, laying the foundation for achieving power balance between the generation and load sides, and facilitating coordinated control among multiple large-scale power sources in the ship's microgrid.

[0071] This invention, based on the operational constraints of the power generation side of an all-electric marine hybrid energy storage system, constructs a robust capacity planning model for the system, aiming to minimize the investment cost and operating cost of the marine microgrid, and solves for the optimal capacity. By constructing a robust capacity planning model with the goal of minimizing the investment cost of the marine hybrid energy storage system, and comprehensively considering various factors and uncertainties, it can find the most economical and reasonable energy storage capacity configuration scheme while satisfying the operational constraints of the power generation side. Compared with traditional capacity planning methods, this significantly reduces the equipment cost of the marine hybrid energy storage system. Simultaneously, considering the minimization of the marine microgrid operating cost, the model can rationally arrange the output of the power generation equipment and the charging and discharging strategy of the energy storage system according to the power demand and energy storage capacity under different operating conditions, reducing operating costs such as fuel consumption and equipment wear.

[0072] The optimal capacity obtained by this invention is used as the design capacity. Combined with actual propulsion power requirements, a multi-timescale power allocation scheme is derived. During the navigation of an all-electric ship, propulsion power requirements exhibit high-frequency and low-frequency fluctuations at different time scales. Multi-timescale power allocation, combined with actual propulsion power requirements, allows the hybrid energy storage system to better adapt to these complex power variations. This layered allocation strategy ensures that the ship receives stable propulsion power at different navigation stages, avoiding disruptions to normal navigation due to excessive power fluctuations and guaranteeing navigation safety. Simultaneously, through power allocation at three time scales, the output power fluctuations of the ship's main generator and fuel cells caused by the shipping environment at each time scale are smoothed out, reducing the DC bus voltage deviation of the ship's microgrid, ensuring normal power supply to the ship's propulsion load, thereby improving the power supply quality of the ship's microgrid, guaranteeing the safety and stability of all-electric ship navigation, and providing greater possibilities for the widespread application of all-electric ships.

[0073] To better illustrate the technical solution of the present invention, this embodiment is described in the following parts.

[0074] This embodiment takes an all-electric ship microgrid with different types of energy storage units as an example, such as Figure 2 As shown, its power generation side includes a main generator and a fuel cell, while the load side includes propulsion load and daily service load. This invention first analyzes the power balance characteristics of the power generation side and load side of the ship's microgrid under fluctuating propulsion scenarios, establishes the operating constraints of the power generation side of the all-electric ship hybrid energy storage system, and, based on the composition of the power generation side and load side of the ship's microgrid under fluctuating propulsion scenarios, the power generation model, the power fluctuation of the propulsion load, and combined with the power generation model and the capacity requirements of the energy storage system, finally establishes the operating constraints of the power generation side system.

[0075] I. Operational Constraints on the Generation Side of All-Electric Ship Hybrid Energy Storage Systems

[0076] In this embodiment, the composition of the power generation side and load side of the ship microgrid, the power generation model, and the power fluctuation of the propulsion load are analyzed under the wave propulsion scenario. Based on the power generation model and the capacity requirements of the energy storage system, the operating constraints of the power generation side system are established.

[0077] A typical 1500V DC ring network is chosen to represent the microgrid structure of the all-electric ship under study. The main generator, fuel cells, and hybrid energy storage system provide the necessary electrical energy to the ship's loads through the microgrid to meet the ship's propulsion and daily service needs. In practical use, the capacity of the hybrid energy storage system should be lower than a certain threshold set during construction. The power generation side mainly includes the main generator and fuel cells, and a dynamic power generation model can be established based on their active power and rated active power. Furthermore, the cost of fuel for power generation also affects the operating cost of the all-electric ship.

[0078] Specifically, the operational constraints on the generation side of the all-electric ship hybrid energy storage system include:

[0079] 1) Maximum capacity constraint equation for hybrid energy storage system

[0080]

[0081] In the formula: This refers to the rated power capacity of the hybrid energy storage system. This refers to the rated energy storage capacity of the hybrid energy storage system. This represents the maximum power capacity of the hybrid energy storage system. This represents the maximum energy storage capacity of the hybrid energy storage system.

[0082] 2) Power supply constraint equations

[0083]

[0084] In the formula: These are the active power and rated active power of the nth generator, respectively. These are the active power and rated active power of the nth fuel cell, respectively. These are the on / off state variables of the nth generator and the nth fuel cell, respectively; N represents the load factor of the nth generator and the nth fuel cell, respectively; G N FC τ represents the number of generators and fuel cells, respectively; τ is the operating time in a day, containing integers from 1 to 24.

[0085] 3) Power generation fuel cost constraint equation

[0086]

[0087] In the formula: These represent the fuel costs for generating electricity for the nth generator and the nth fuel cell during time period t, respectively. These are the cost parameters for the nth generator; These are the cost parameters for the nth fuel cell.

[0088] II. Robust Capacity Planning Model for Marine Hybrid Energy Storage Systems

[0089] In this embodiment, a robust capacity planning model is proposed to address the issue of optimal capacity configuration of all-electric ship hybrid energy storage systems under different time scales and power demands, which has received little attention recently. Based on this model, the optimal capacity of the hybrid energy storage system is determined, and the optimization of the capacity configuration of the hybrid energy storage system lays the foundation for further implementation of power allocation strategies.

[0090] To ensure the safe and stable operation of all-electric ships, the power balance between the hybrid energy storage system and the load side is analyzed, and system power balance constraints are established. The hybrid energy storage system acts as a power / energy buffer within the all-electric ship's microgrid, with the batteries bearing the power... Certain constraints must be met. Batteries primarily handle hourly loads; after determining the battery capacity based on its power output, the supercapacitor capacity can be determined to handle other power fluctuations. For all-electric ships, power balance is required between the generator and load sides. Furthermore, to ensure reliable power supply, the generator side also needs a certain reserve of active power.

[0091] The system power balance constraints of the robust capacity planning model for a ship hybrid energy storage system include:

[0092] 1) Power / energy constraint equations for hybrid energy storage systems

[0093]

[0094] In the formula: This is the battery's maximum rated active power; This refers to the battery's maximum rated storage capacity. η represents the energy stored in the battery during time period t. dis η ch These represent the battery charging efficiency and discharging efficiency, respectively; Δt is the time duration.

[0095] 2) System total power balance constraint equations

[0096]

[0097] In the formula: The active power of the hybrid energy storage system; These are respectively the ship's daily service load and the ship's propulsion load;

[0098] 3) System active power reserve constraint equations

[0099]

[0100] In the formula: η APR For rotational reserve ratio.

[0101] Based on system power balance constraints, a robust capacity planning model for a shipboard hybrid energy storage system is established. This model is a mixed-integer quadratic programming model, which can achieve optimal planning of the capacity of an all-electric shipboard hybrid energy storage system. The objective function of the robust capacity planning model for the shipboard hybrid energy storage system includes the investment cost of the hybrid energy storage system and the operating cost of the shipboard microgrid.

[0102] The formula for the robust capacity planning model of a ship hybrid energy storage system is expressed as follows:

[0103]

[0104] Where: H c This represents the total daily investment cost; I nvP I nvE These are the daily net annual values ​​for power capacity and energy storage capacity, respectively.

[0105] In this embodiment, the robust capacity planning model of the ship hybrid energy storage system is a mixed integer quadratic programming model, which can be solved using existing solvers such as gurobi.

[0106] III. Three-layer power allocation strategy

[0107] In this embodiment, after determining the optimal capacity allocation of the hybrid energy storage system, the present invention proposes a three-layer power allocation strategy for multiple large-scale power sources at different time scales, based on a hierarchical approach. The first layer coordinates and controls the main generator and fuel cells to meet the ship's main propulsion load requirements on a daily time scale, thereby reducing fuel consumption. The second layer coordinates and controls the batteries and fuel cells to meet low-frequency power requirements on an hourly time scale, thereby smoothing out power fluctuations on an hourly time scale. The third layer controls the supercapacitor to meet high-frequency power requirements on a minute-by-minute time scale, thereby smoothing out power fluctuations on a minute-by-minute time scale.

[0108] Combination Figure 3 As shown, power allocation across three time scales based on the optimal capacity of the hybrid energy storage system is performed through the following steps:

[0109] S401: Calculate the output power of generator sets and fuel cells in a ship's hybrid energy storage system on a daily timescale;

[0110] S402: Calculate the compensation power of batteries and fuel cells in a ship's hybrid energy storage system on an hourly timescale;

[0111] S403: Calculate the compensation power of supercapacitors in a ship hybrid energy storage system for smoothing minute-level power fluctuations on a minute-by-minute timescale.

[0112] S404: The optimal power allocation scheme is determined by the output power of the generator set and fuel cell on a daily time scale, the compensation power of the battery and fuel cell on an hourly time scale, and the compensation power of the supercapacitor on a minute time scale.

[0113] Specifically, the processing steps for calculating the output power of generator sets and fuel cells include:

[0114] 1) The generator set in the ship's hybrid energy storage system uses an excitation voltage system with voltage follower control to control the output power P. DG ;

[0115] 2) In the ship's hybrid energy storage system, the fuel cell uses PI control to output a constant power P. FC .

[0116] Specifically, the compensation power of the battery and fuel cell is calculated using the following formula:

[0117]

[0118] In the formula: P FC-ref T1 represents the minimum frequency power requirement of the fuel cell on an hourly timescale, i.e., the compensation power; P represents the fuel cell filter time constant; bat-ref T1 represents the second lowest frequency power demand of the battery on an hourly timescale, i.e., the compensation power; T2 is the battery filtering time constant. Here, s represents a complex number, a Laplace transform.

[0119] Specifically, the compensation power of the supercapacitor used to smooth out minute-level power fluctuations is calculated using the following formula:

[0120]

[0121] In the formula: P uc-ref (t) represents the highest frequency power demand of the supercapacitor on a timescale of one minute, i.e., the compensation power.

[0122] Specifically, the compensation power on both the hourly and minute-scales satisfies the following conditions:

[0123]

[0124] In the formula: I dc-ref This represents the DC bus current requirement; U dc-ref The rated voltage of the DC bus is 1500V; U dc K is the DC bus voltage. p and K i These are the proportional and integral coefficients of the voltage controller, respectively; I load This represents the DC bus load current value.

[0125] This invention addresses the trend of ship electrification by constructing a robust capacity planning model for a ship hybrid energy storage system based on the power balance characteristics of the generation and load sides of the ship microgrid. Based on the optimal capacity allocation of the hybrid energy storage system, a three-layer power distribution strategy is adopted to effectively solve the power fluctuation problem caused by the shipping environment at various time scales, reduce the DC bus voltage deviation of the ship microgrid, ensure the normal power supply of the ship's propulsion load, and improve the power supply quality of the ship microgrid.

[0126] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A capacity planning method for ship hybrid energy storage systems based on multi-layer power allocation, characterized in that, include: S1: Analyze the power balance characteristics of the generation side and load side of the ship microgrid under the wave propulsion scenario, and establish the operation constraints of the generation side of the all-electric ship hybrid energy storage system; S2: Based on the operational constraints of the power generation side of the all-electric ship hybrid energy storage system, a robust capacity planning model for the ship hybrid energy storage system is constructed with the goal of minimizing the investment cost of the ship hybrid energy storage system and the operating cost of the ship microgrid. S3: Solve the robust capacity planning model of the ship hybrid energy storage system to obtain the optimal capacity of the ship hybrid energy storage system; S4: The optimal capacity obtained from the solution is used as the design capacity of the ship hybrid energy storage system. The optimal power allocation scheme is obtained by combining the actual propulsion power demand under multiple time scales. The power allocation of each component of the ship hybrid energy storage system is realized through the optimal power allocation scheme.

2. The capacity planning method for a ship hybrid energy storage system based on multi-layer power allocation as described in claim 1, characterized in that: In step S1, the operational constraints on the generation side of the all-electric ship hybrid energy storage system include: 1) Maximum capacity constraint equation for hybrid energy storage system In the formula: This refers to the rated power capacity of the hybrid energy storage system. This refers to the rated energy storage capacity of the hybrid energy storage system. This represents the maximum power capacity of the hybrid energy storage system. This represents the maximum energy storage capacity of the hybrid energy storage system. 2) Power supply constraint equations In the formula: These are the active power and rated active power of the nth generator, respectively. These are the active power and rated active power of the nth fuel cell, respectively. These are the on / off state variables of the nth generator and the nth fuel cell, respectively; N represents the load factor of the nth generator and the nth fuel cell, respectively; G N FC τ represents the number of generators and fuel cells, respectively; τ is the operating time per day. 3) Power generation fuel cost constraint equation In the formula: These represent the fuel costs for generating electricity for the nth generator and the nth fuel cell during time period t, respectively. These are the cost parameters for the nth generator; These are the cost parameters for the nth fuel cell.

3. The capacity planning method for a ship hybrid energy storage system based on multi-layer power allocation as described in claim 2, characterized in that: In step S2, the objective function of the robust capacity planning model for the ship hybrid energy storage system is expressed as: In the formula: H c This represents the total daily investment cost; I nvP I nvE These are the daily net annual values ​​for power capacity and energy storage capacity, respectively.

4. The capacity planning method for a ship hybrid energy storage system based on multi-layer power allocation as described in claim 3, characterized in that: In step S2, the system power balance constraints of the robust capacity planning model for the ship hybrid energy storage system include: 1) Power / energy constraint equations for hybrid energy storage systems In the formula: This is the battery's maximum rated active power; This refers to the battery's maximum rated storage capacity. η represents the energy stored in the battery during time period t. dis η ch These represent the battery charging efficiency and discharging efficiency, respectively; Δt is the time duration. 2) System total power balance constraint equations In the formula: The active power of the hybrid energy storage system; These are respectively the ship's daily service load and the ship's propulsion load; 3) System active power reserve constraint equations In the formula: η APR This is the rotational reserve ratio.

5. The capacity planning method for a ship hybrid energy storage system based on multi-layer power allocation as described in claim 4, characterized in that: In step S4, power allocation is performed at three time scales based on the optimal capacity of the hybrid energy storage system through the following steps: S401: Calculate the output power of generator sets and fuel cells in a ship's hybrid energy storage system on a daily timescale; S402: Calculate the compensation power of batteries and fuel cells in a ship's hybrid energy storage system on an hourly timescale; S403: Calculate the compensation power of supercapacitors in a ship hybrid energy storage system for smoothing minute-level power fluctuations on a minute-by-minute timescale. S404: The optimal power allocation scheme is determined by the output power of the generator set and fuel cell on a daily time scale, the compensation power of the battery and fuel cell on an hourly time scale, and the compensation power of the supercapacitor on a minute time scale.

6. The capacity planning method for a ship hybrid energy storage system based on multi-layer power allocation as described in claim 5, characterized in that: In step S401, the processing steps for calculating the output power of the generator set and fuel cell include: 1) The generator set in the ship's hybrid energy storage system uses an excitation voltage system with voltage follower control to control the output power P. DG ; 2) In the ship's hybrid energy storage system, the fuel cell uses PI control to output a constant power P. FC .

7. The capacity planning method for a ship hybrid energy storage system based on multi-layer power allocation as described in claim 5, characterized in that: In step S402, the compensation power of the battery and fuel cell is calculated using the following formula: In the formula: P FC-ref T1 represents the minimum frequency power requirement of the fuel cell on an hourly timescale, i.e., the compensation power; P represents the fuel cell filter time constant; bat-ref T1 represents the second lowest frequency power demand of the battery on an hourly timescale, i.e., the compensation power; T2 is the battery filtering time constant; s represents a complex number.

8. The capacity planning method for a ship hybrid energy storage system based on multi-layer power allocation as described in claim 5, characterized in that: In step S403, the compensation power of the supercapacitor used to smooth out minute-level power fluctuations is calculated using the following formula: In the formula: P uc-ref (t) represents the highest frequency power demand of the supercapacitor on a timescale of one minute, i.e., the compensation power.

9. The capacity planning method for a ship hybrid energy storage system based on multi-layer power allocation as described in claim 8, characterized in that: In steps S402 and S403, the compensation power on both the hourly and minute time scales satisfies the following conditions: In the formula: I dc-ref This represents the DC bus current requirement; U dc-ref The rated voltage of the DC bus; U dc This is the DC bus voltage; K p and K i These are the proportional and integral coefficients of the voltage controller, respectively; I load This represents the DC bus load current value.

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