Power Management and Decomposition Method for a Renewable Energy DC Hydrogen Production Island System

Abstract

The present invention provides a power management and decomposition method for a renewable energy DC hydrogen production island system, including Step 1: establishing a static and dynamic model of the electrolyzer, determining the static and dynamic response characteristics of the electrolyzer, and obtaining the dynamic response analytical equation of the electrolyzer; Step 2: determining the power management method of the renewable energy DC hydrogen production island system; Step 3: taking into account the dynamic response characteristics of the electrolyzer, proposing a power command decomposition method for the renewable energy and hydrogen production unit; Step 4: determining the control methods for the wind power generation unit, photovoltaic power generation unit, hydrogen production unit, and battery energy storage unit under different operating modes; Step 5: determining the control architecture of the renewable energy DC hydrogen production island system. The present invention ensures the stability of the system under the condition of limited energy storage capacity configuration, flexibly adjusts the power of the hydrogen production unit through the distribution coefficient, avoids the control mode switching between the battery energy storage unit and the renewable energy power generation unit, and reduces the complexity of the coordinated control of the wind-solar-hydrogen storage system.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy utilization, and particularly relates to a power management and decomposition method for a renewable energy DC hydrogen production island system. Background Art

[0002] Energy crisis and environmental pollution are important factors restricting the rapid economic development of countries around the world. Optimizing energy allocation, promoting energy transformation, and increasing the proportion of renewable energy power generation are important measures to achieve the great goals of "carbon peak" and "carbon neutrality". In recent years, the grid-connected installed capacity of new energy in the country has been continuously increasing, and the curtailment rates of wind and light in some areas rich in new energy are relatively high, resulting in a large amount of energy waste. How to efficiently and economically absorb large-scale renewable energy is a key technical challenge for future new power systems.

[0003] Due to the uncertainty, intermittency, and wide power range fluctuation characteristics of the output power of wind and light renewable energy, it is difficult to match the source-load power. Therefore, it is necessary to configure energy storage units to absorb or compensate for the unbalanced power between renewable energy and load. As a power carrier, hydrogen has the characteristics of high power density, large capacity, long life, convenient storage and transmission, etc. Using excess renewable energy for hydrogen production is an effective solution to improve the utilization rate of renewable energy. Hydrogen energy is usually used as a long-term energy storage unit, and its time response scale is in minutes or seconds, which is difficult to apply to microgrids that require a high dynamic regulation speed and short-term frequent start and stop. Therefore, a hybrid electric-hydrogen energy storage can be formed by combining hydrogen energy storage and batteries, using batteries to compensate for transient unbalanced power, and hydrogen energy storage to compensate for long-term and steady-state unbalanced power.

[0004] Since the hydrogen production unit, lithium battery energy storage, photovoltaic power generation unit, and wind power unit can be integrated into DC to reduce the number of power conversions and improve system efficiency, the DC integration scheme is a more efficient and economical networking scheme. The typical structure of a renewable energy DC hydrogen production island system is as Figure 1 shown. According to Figure 1 , the island system includes wind and light renewable energy power generation units, battery energy storage units, hydrogen production units, and load units, and each unit is jointly connected to the DC bus. In a renewable energy DC hydrogen production island system, the battery energy storage unit usually serves as a balancing node to maintain the stability of the DC bus voltage. However, in order to reduce the investment cost, the capacity configuration of lithium batteries in the system is limited. In addition, due to the difficulty in matching the dynamic responses of the hydrogen production unit and renewable energy, the lithium battery energy storage unit with a small capacity is difficult to stabilize the DC voltage, and even leads to system collapse. Therefore, there are still some technical problems in how to use a small-capacity electric energy storage unit to balance the power difference caused by mismatched dynamic characteristics and ensure the stable operation of the renewable energy hydrogen production island system. Summary of the Invention

[0005] To solve the above technical problems, the present invention takes into account the dynamic response characteristics of the hydrogen production unit and provides a power management and decomposition method for a renewable energy DC hydrogen production island system, which specifically includes the following steps:

[0006] Step 1: Establish a static and dynamic model of the electrolyzer, determine the static and dynamic response characteristics of the electrolyzer, and obtain the dynamic response analytical equation of the electrolyzer;

[0007] Step 2: Determine the power management method of the renewable energy DC hydrogen production island system;

[0008] Step 3: Considering the dynamic response characteristics of the electrolyzer, propose a power command decomposition method for renewable energy and the hydrogen production unit;

[0009] Step 4: Determine the control methods of the wind power generation unit, photovoltaic power generation unit, hydrogen production unit, and battery energy storage unit under different operating modes;

[0010] Step 5: Determine the control architecture of the renewable energy DC hydrogen production island system.

[0011] Furthermore, obtaining the dynamic response analytical equation of the electrolyzer in Step 1 includes the following steps:

[0012] 1) Establish an output voltage-current model of the electrolyzer;

[0013] 2) Establish a thermal model of the electrolyzer;

[0014] 3) Establish a hydrogen production model of the electrolyzer;

[0015] 4) Establish a compressor model of the hydrogen production unit;

[0016] 5) Establish a hydrogen storage tank model;

[0017] 6) Build a complete simulation model of the hydrogen production unit through simulation software, including the hydrogen production unit body model and the control system model;

[0018] 7) Conduct a current or power step response test on the basis of the hydrogen production unit simulation model, and obtain the dynamic response equation of the electrolyzer output power P AE (t) through fitting of simulation data:

[0019] P AE (t) = a3t 3 + a2t 2 + a1t + a0

[0020] In the formula: t is time; a0, a1, a2, and a3 are dynamic characteristic fitting coefficients.

[0021] Furthermore, Step 2 specifically includes:

[0022] Define S SOC as the state of charge of the storage battery, S BH as the upper limit of the storage battery SOC, S BL as the lower limit of the storage battery SOC; P AE,min as the lower limit for the electrolyzer to operate; P AE,max as the upper limit for the electrolyzer to operate; P wt,T as the predicted value of wind power; P pv,T as the predicted value of photovoltaic power; then the renewable energy DC hydrogen production island system includes the following operating modes:

[0023] Mode 1: S BH > S SOC > S BL and P wt,T + P pv,T ≤ P AE,min , the wind power generation unit and the photovoltaic power generation unit both operate in the maximum power tracking mode, the hydrogen production unit operates at the minimum power operating point, and the energy storage discharges and stabilizes the DC voltage;

[0024] Mode 2: S BH > S SOC > S BL and P wt,T + P pv,T > P AE,min , the wind power generation unit and the photovoltaic power generation unit both operate in the power scheduling mode. At steady state, the power of the hydrogen production unit is approximately equal to the sum of the output powers of wind power generation and photovoltaic power generation. The battery energy storage unit charges and discharges to stabilize the voltage, and at the same time compensates for the unbalanced power caused by the wind and light prediction deviation;

[0025] Mode 3: S SOC ≤ S BL and P wt,T + P pv,T ≤ P AE,min , the wind power generation unit and the photovoltaic power generation unit both operate in the maximum power tracking mode, the hydrogen production unit stands by, and the energy storage charges and stabilizes the DC voltage;

[0026] Mode 4: S SOC ≤ S BL and P wt,T + P pv,T > P AE,min , the wind power generation unit and the photovoltaic power generation unit both operate in the power scheduling mode. The power of the hydrogen production unit is equal to β times the sum of the output powers of wind power generation and photovoltaic power generation, where the power distribution coefficient β < 1, and the energy storage charges and stabilizes the DC voltage;

[0027] Mode 5: S SOC ≥ S BH and P wt,T + Ppv,T ≤P AE,min When the wind power generation unit and the photovoltaic power generation unit are both operating in the maximum power tracking mode, the hydrogen production unit operates at the minimum power operating point, and the energy storage discharges to stabilize the DC voltage;

[0028] Mode 6: S SOC ≥S BH and P wt,T +P pv,T >P AE,min At this time, the wind power generation unit and the photovoltaic power generation unit are both operating in the power dispatch mode. The power of the hydrogen production unit is equal to β times the sum of the output powers of the wind power generation and photovoltaic power generation, where the power distribution coefficient β > 1, and the energy storage discharges to stabilize the DC voltage.

[0029] Furthermore, the specific steps of Step 3 include the following steps:

[0030] Decompose and distribute the power command according to the dynamic response equation of the electrolyzer and the control period to avoid the transient power compensated by the battery energy storage system from exceeding the limit; the method for decomposing the power command includes:

[0031] (1) Calculate the total predicted value of the wind and light power P pw,T ;

[0032] (2) Calculate the proportion k pv of the power of the wind power generation unit and the photovoltaic power generation unit, k wt ;

[0033] (3) Calculate the adjustable power P AE,A of the hydrogen production unit in a unit control period according to the dynamic response equation:

[0034] When P AE,A <P B,rate , the adjustable power in each control period is equal to P AE,A ;

[0035] When P AE,A ≥P B,rate , multiple control periods are required for adjustment to reach the expected value; among them, the adjustable power in each control period is the rated power P B,rate of the battery energy storage system;

[0036] The adjustable power of the hydrogen production unit is:

[0037] P AE,T =P pw,T (t + 1) - P AE (t)

[0038] n = sgn(P AE,T )

[0039] Where: P AE,T is the dispatchable power of the hydrogen production unit; P AE (t) is the power at the current moment; P pw,T (t + 1) is the sum of the predicted wind and solar power values at the next moment; sgn() is the sign function;

[0040] When n > 0, it indicates that the hydrogen production power increases in the next control cycle; when n < 0, it indicates that the hydrogen production power decreases in the next control cycle; when n = 0, it indicates that the current hydrogen production power is equal to the sum of the predicted wind and solar power;

[0041] When P AE,T > P AE,A , the reference value of the hydrogen production power is:

[0042] P AE,ref = P AE + nP AE,A

[0043] When P AE,T < P AE,A , the reference value of the hydrogen production power is:

[0044] P AE,ref = P AE + nP AE,T

[0045] In the power management method, when the wind power generation unit and the photovoltaic power generation unit are in the power dispatch mode, the energy storage power under steady-state conditions is close to zero. Therefore, the wind power generation unit and the photovoltaic power generation system share the power according to the power ratio. The power reference values of the wind power generation unit and the photovoltaic unit are as follows:

[0046] P wt,ref = P wt + k wt nP AE,ref

[0047] P pv,ref = P pv + k pv nP AE,ref

[0048] Where: P wt is the power of the wind power generation unit, P pv is the power of the photovoltaic power generation unit.

[0049] At the same time, the power reference values of the wind power generation unit and the photovoltaic power generation unit should satisfy the following constraint conditions:

[0050] P wt,min ≤ P wt,ref ≤ P wt,rate

[0051] Ppv,min ≤P pv,ref ≤P pv,rate

[0052] Wherein: P wt,min and P wt,rate are respectively the minimum and rated operating powers allowed for the wind power generation unit; P pv,min and P pv,rate are respectively the minimum and rated operating powers allowed for the photovoltaic power generation unit.

[0053] The power of the hydrogen production unit is adjusted by adjusting the power distribution coefficient β, and the reference value of the power of the hydrogen production unit is:

[0054] P AE,ref = P AE + βnP AE,T

[0055]

[0056] Furthermore, the fourth step includes:

[0057] 1) There are three control methods in the wind power generation system, including standby mode, maximum power tracking mode and power scheduling mode;

[0058] 2) There are three control methods in the photovoltaic power generation system, including standby mode, maximum power tracking mode and power scheduling mode;

[0059] 3) The battery energy storage system is used as the main control unit, and its control methods include constant voltage control and standby mode;

[0060] 4) The hydrogen production unit is a flexible controllable load, and its control methods include constant power control and standby mode.

[0061] Furthermore, the fifth step includes the following steps:

[0062] 1) Adopt a two-layer control architecture, where the upper layer is the power management layer and the lower layer is the local device control layer;

[0063] 2) The upper-layer power management layer includes a power management method and a power command decomposition method considering the dynamic characteristics of hydrogen production; the upper-layer power management system needs to collect electrical parameters in the local device layer through communication;

[0064] 3) In the local device control layer, each device has multiple control modes and receives control mode conversion commands and power commands issued by the upper-layer power management system.

[0065] Furthermore, the electrical parameters include the power P wt of the wind power generation unit, and the power P pv, the power P required by the hydrogen production unit AE , the DC bus voltage U dc , the state of charge S of the battery SOC .

[0066] Beneficial effects:

[0067] The present invention proposes a power management method for a renewable energy DC hydrogen production island system, and designs a power command decomposition method considering the dynamic response characteristics of the hydrogen production unit, which can ensure the stability of the system under the condition of limited energy storage capacity configuration, and flexibly adjust the power of the hydrogen production unit through the distribution coefficient, avoiding the control mode switching between the battery energy storage unit and the renewable energy power generation unit, and reducing the complexity of the coordinated control of the wind-solar-hydrogen system.

[0068] In addition, since fuel vehicles are the main contributors to carbon dioxide emissions, in order to achieve clean, low-carbon and green rail transit, hydrogen fuel cell vehicles have developed rapidly. To meet the hydrogen refueling needs of hydrogen fuel cell vehicles, it is necessary to quickly layout hydrogen refueling stations. Since the cost of laying pipelines to transport hydrogen is very high, the renewable energy power generation, hydrogen production stations and hydrogen refueling stations are deeply integrated to form a production-supply integrated business model, reducing the long-distance hydrogen transportation link. To ensure the stable operation of the system, the present invention proposes a power management and power command decomposition method considering the dynamic characteristics of the hydrogen production unit, filling the relevant technical gaps and having broad application prospects. Description of the drawings

[0069] Figure 1 is a schematic diagram of the typical structure of a renewable energy DC hydrogen production island system;

[0070] Figure 2 is a schematic diagram of the process for obtaining the dynamic response analysis equation of the electrolytic cell of the present invention;

[0071] Figure 3 is a flowchart of the power management of the present invention;

[0072] Figure 4 is a flowchart of the power command decomposition method for renewable energy and hydrogen production units of the present invention;

[0073] Figure 5 is the overall control block diagram of the system of the present invention. Detailed implementation manners

[0074] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used 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.

[0075] As Figure 1 shown in the typical structure of the renewable energy DC hydrogen production island system, the island system includes a wind power generation unit, a photovoltaic power generation unit, a battery energy storage unit, a hydrogen production unit, and a load unit, and each unit is jointly connected to the DC bus. In the renewable energy DC hydrogen production island system, the battery energy storage unit is usually used as a balancing node to maintain the stability of the DC bus voltage. The battery energy storage unit is a lithium battery energy storage unit.

[0076] The power management and decomposition method of the renewable energy DC hydrogen production island system of the present invention includes the following steps:

[0077] Step 1, establish a static and dynamic model of the electrolyzer, determine the static and dynamic response characteristics of the electrolyzer, and obtain the dynamic response analytical equation of the electrolyzer.

[0078] Step 2, determine the power management method of the renewable energy DC hydrogen production island system.

[0079] Step 3, taking into account the dynamic response characteristics of the electrolyzer, propose a power command decomposition method for renewable energy and the hydrogen production unit.

[0080] Step 4, determine the control methods of the wind power generation unit, the photovoltaic power generation unit, the hydrogen production unit, and the battery energy storage unit under different operating modes.

[0081] Step 5, determine the control architecture of the renewable energy DC hydrogen production island system.

[0082] Specifically, the first step includes the following steps:

[0083] (1) Obtain the dynamic response analytical equation of the electrolyzer, and its process schematic diagram is as Figure 2 shown, and the specific steps are as follows:

[0084] 1) Establish an output voltage-current model of the electrolyzer;

[0085] 2) Establish a thermal model of the electrolyzer;

[0086] 3) Establish a hydrogen production model of the electrolyzer;

[0087] 4) Establish a compressor model of the hydrogen production unit;

[0088] 5) Establish a hydrogen storage tank model;

[0089] 6) Build a complete simulation model of the hydrogen production unit through simulation software, mainly including the hydrogen production unit body model and the control system model. In order to better simulate the dynamic response characteristics of the hydrogen production unit, the control system includes a current / power control unit, a pressure control unit, a temperature control unit, a liquid level control unit, etc.;

[0090] 7) Conduct a current or power step response test based on the hydrogen production unit simulation model, and obtain the dynamic response equation of the electrolyzer output power P AE (t) through fitting the simulation data:

[0091] P AE (t) = a3t 3 + a2t 2 + a1t + a0 (1)

[0092] Where: t is time; a0, a1, a2, and a3 are dynamic characteristic fitting coefficients.

[0093] The specific steps of the second step are as follows:

[0094] The state of charge (SOC) of the battery is:

[0095]

[0096] Where: Q is the lithium battery capacity; i b is the lithium battery current; t is time.

[0097] Define S BH as the upper limit of the battery SOC, S BL as the lower limit of the battery SOC; P AE,min as the lower limit of the allowable operation of the electrolyzer; P AE,max as the upper limit of the allowable operation of the electrolyzer; P wt,T as the predicted value of wind power; P pv,T as the predicted value of photovoltaic power. The working mode and power management flow chart of the renewable energy DC hydrogen production island system are as Figure 3 shown, and it includes the following modes.

[0098] Mode 1: S BH > S SOC > S BL and P wt,T + P pv,T ≤ P AE,min , both the wind power generation unit and the photovoltaic power generation unit work in the maximum power tracking mode, the hydrogen production unit works at the minimum power operating point, and the energy storage discharges and stabilizes the DC voltage.

[0099] Mode 2: S BH > S SOC > S BL and P wt,T + P pv,T > P AE,min, both the wind power generation unit and the photovoltaic power generation unit operate in the power scheduling mode. At steady state, the power of the hydrogen production unit is approximately equal to the sum of the output powers of the wind power generation and the photovoltaic power generation. The battery energy storage unit charges and discharges to stabilize the voltage, and at the same time compensates for the unbalanced power caused by the prediction deviation of the wind and light.

[0100] Mode 3: S SOC ≤S BL And P wt,T +P pv,T ≤P AE,min , both the wind power generation unit and the photovoltaic power generation unit operate in the maximum power tracking mode. The hydrogen production unit is on standby, and the energy storage is charged to stabilize the DC voltage.

[0101] Mode 4: S SOC ≤S BL And P wt,T +P pv,T >P AE,min , both the wind power generation unit and the photovoltaic power generation unit operate in the power scheduling mode. The power of the hydrogen production unit is equal to the sum of the output powers of the wind power generation and the photovoltaic power generation multiplied by the power distribution coefficient β, where the power distribution coefficient β < 1. The energy storage is charged to stabilize the DC voltage.

[0102] Mode 5: S SOC ≥S BH And P wt,T +P pv,T ≤P AE,min , both the wind power generation unit and the photovoltaic power generation unit operate in the maximum power tracking mode. The hydrogen production unit operates at the minimum power operating point, and the energy storage discharges to stabilize the DC voltage.

[0103] Mode 6: S SOC ≥S BH And P wt,T +P pv,T >P AE,min , at this time, both the wind power generation unit and the photovoltaic power generation unit operate in the power scheduling mode. The power of the hydrogen production unit is equal to the sum of the output powers of the wind power generation and the photovoltaic power generation multiplied by the power distribution coefficient β, where the power distribution coefficient β > 1. The energy storage discharges to stabilize the DC voltage.

[0104] The specific steps of Step 3 include the following steps:

[0105] In the renewable energy DC hydrogen production island system, due to the limited capacity of the battery configuration and the dynamic response mismatch between the renewable energy and the hydrogen production unit, the power command should be decomposed and issued according to the dynamic response equation of the electrolyzer and the control period to avoid the transient power compensated by the battery energy storage system from exceeding the limit. The proposed power command decomposition method process is as Figure 4 shown.

[0106] According toFigure 4 , first, calculate the total predicted value of wind and light power according to the output of the wind and light prediction module as:

[0107] P pw,T =P pv,T +P wt,T (3)

[0108] Calculate the proportion of the power of the wind power generation unit and the photovoltaic power generation unit according to (3) as:

[0109]

[0110]

[0111] In the formula: k pv is the proportion coefficient of the power of the photovoltaic power generation unit; k wt is the proportion coefficient of the power of the wind power generation unit.

[0112] Calculate the adjustable power of the hydrogen production unit in a unit control period according to the dynamic response equation as:

[0113] P AE,A =a3T c 3 +a2T c 2 +a1T c +a0 (6)

[0114] In the formula: T c is the control period.

[0115] To ensure the stability of the system, the allowable adjustable power in each control period should be less than the rated power of the battery energy storage system.

[0116] When P AE,A <P B,rate , the schedulable power in each control period is equal to P AE,A .

[0117] When P AE,A ≥P B,rate , multiple control periods are required for adjustment to reach the expected value. The schedulable power in each control period is equal to P B,rate , and the number of required control periods is as follows:

[0118]

[0119] In the formula: m is the number of required control periods; P B,rate is the rated power of the battery energy storage system.

[0120] The schedulable power of the hydrogen production unit is:

[0121] PAE,T = P pw,T (t + 1) - P AE (t)(8)

[0122] n = sgn(P AE,T )(9)

[0123] Where: P AE,T is the dispatchable power of the hydrogen production unit; P AE (t) is the power at the current moment; P pw,T (t + 1) is the sum of the predicted wind and solar power values at the next moment; sgn() is the sign function;

[0124] When n > 0, it indicates that the hydrogen production power increases in the next control cycle; when n < 0, it indicates that the hydrogen production power decreases in the next control cycle; when n = 0, it indicates that the current hydrogen production power is equal to the sum of the wind and solar predicted powers.

[0125] When P AE,T > P AE,A , the hydrogen production power reference value is:

[0126] P AE,ref = P AE + nP AE,A (10)

[0127] When P AE,T < P AE,A , the hydrogen production power reference value is:

[0128] P AE,ref = P AE + nP AE,T (11)

[0129] In the power management method, when the wind power generation unit and the photovoltaic power generation unit are in the power dispatch mode, the energy storage power under steady state conditions is close to zero. Therefore, the wind power generation unit and the photovoltaic power generation system share the power according to the power ratio. The power reference values of the wind power generation unit and the photovoltaic unit are as follows:

[0130] P wt,ref = P wt + k wt nP AE,ref (12)

[0131] P pv,ref = P pv + k pv nP AE,ref (13)

[0132] Where: P wt is the power of the wind power generation unit, P pv is the power of the photovoltaic power generation unit.

[0133] The power reference values of the wind power generation unit and the photovoltaic power generation unit should satisfy the following constraint conditions:

[0134] P wt,min ≤P wt,ref ≤P wt,rate (14)

[0135] P pv,min ≤P pv,ref ≤P pv,rate (15)

[0136] Where: P wt,min and P wt,rate are respectively the minimum and rated operating powers allowed for the wind power generation unit; P pv,min and P pv,rate are respectively the minimum and rated operating powers allowed for the photovoltaic power generation unit.

[0137] When the battery S SOC reaches the lower limit, in order to prevent the battery from being in the deep discharge area for a long time, the power of the hydrogen production unit is reduced by adjusting the power distribution coefficient β, so that the wind-solar output power is greater than the hydrogen production power, and the remaining power will automatically charge the battery. Similarly, when the battery S SOC reaches the upper limit, in order to prevent the battery from being in the deep discharge area for a long time, the power of the hydrogen production unit is increased by adjusting the power distribution coefficient β, so that the wind-solar output power is less than the hydrogen production power, and the battery discharges automatically to compensate for the unbalanced power. At this time, the power reference value of the hydrogen production unit is:

[0138] P AE,ref =P AE +βnP AE,T (16)

[0139]

[0140] Step 4: Determine the control methods for the wind power generation unit, photovoltaic power generation unit, hydrogen production unit, and battery energy storage unit under different operating modes.

[0141] 1) Wind turbine control method: According to the above analysis, there are three working modes in the wind power generation system, including: standby mode, maximum power tracking mode, and power scheduling mode;

[0142] 2) Photovoltaic power generation system control method: There are three working modes, including standby mode, maximum power tracking mode, and power scheduling mode;

[0143] 3) Battery energy storage system control method: The battery energy storage system serves as the main control unit, and its control methods include: constant voltage control and standby mode;

[0144] 4) Hydrogen production unit control method: The hydrogen production unit is a flexible and controllable load, and its control methods include: constant power control and standby mode.

[0145] In the fifth step described above, as Figure 5 shown, determining the control architecture of the renewable energy DC hydrogen production island system includes the following steps:

[0146] 1) Here, a two-layer control architecture is adopted. Among them, the upper layer is the power management layer, and the lower layer is the local device control layer;

[0147] 2) The power management layer of the upper layer includes a power management method and a power command decomposition method considering the dynamic characteristics of hydrogen production. In order to execute the power management method, the power management system of the upper layer needs to collect electrical parameters in the local device layer through communication, including the power P of the wind power generation unit wt , the power P of the photovoltaic power generation unit pv , the power P required by the hydrogen production unit AE , the DC bus voltage U dc , the state of charge S of the battery SOC ;

[0148] 3) In the local device control layer, each device has multiple control modes and receives control mode conversion instructions and power commands issued by the power management system of the upper layer.

[0149] Those skilled in the art can easily understand that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A power management and decomposition method for a renewable energy DC hydrogen production island system, characterized in that, It includes the following steps: Step 1: Establish the static and dynamic models of the electrolyzer to determine the static and dynamic response characteristics of the electrolyzer; obtain the dynamic response analytical equation of the electrolyzer; Step 2: Determine the power management method of the renewable energy DC hydrogen production island system; Step 3: Considering the dynamic response characteristics of the electrolyzer, propose a method for decomposing the power commands of renewable energy and the hydrogen production unit, including: Decompose and issue the power command according to the electrolyzer dynamic response equation and the control period to avoid the transient power compensated by the battery energy storage system from exceeding the limit; the method for decomposing the power command includes: 1) Calculate the total predicted wind and solar power value P based on the output of the wind and solar prediction module pw,T ; 2) Calculate the proportion k of the power of the wind power generation unit and the photovoltaic power generation unit pv , k wt ; 3) Calculate the adjustable power P of the hydrogen production unit under a unit control period according to the dynamic response equation AE,A : When P AE,A <P B,rate is the case, the schedulable power per control period is equal to P AE,A ; When P AE,A ≥ P B,rate it requires multiple control cycles for adjustment to reach the expected value; where the schedulable power for each control cycle is the rated power P B,rate of the battery energy storage system; The dispatchable power of the hydrogen production unit is: Where: P AE,T is the dispatchable power of the hydrogen production unit; P AE (t) is the power at the current moment; P pw,T (t + 1) is the sum of the predicted values of wind and solar power at the next moment; sgn() is the sign function; When n>0, it indicates that the hydrogen production power increases in the next control period; when n<0, it indicates that the hydrogen production power decreases in the next control period; when n = 0, it indicates that the current hydrogen production power is equal to the sum of the wind power and photovoltaic power predictions; When P AE,T > P AE,A the hydrogen production power reference value is: When P AE,T <P AE,A the hydrogen production power reference value is: In the power management method, when the wind power generation unit and the photovoltaic power generation unit are in the power dispatch mode, the energy storage power under steady-state conditions is close to zero. Therefore, the wind power generation unit and the photovoltaic power generation system share the power according to the power ratio. The power reference values of the wind power generation unit and the photovoltaic unit are as follows: Where: P wt is the power of the wind power generation unit, P pv is the power of the photovoltaic power generation unit; At the same time, the power reference values of the wind power generation unit and the photovoltaic power generation unit should meet the following constraint conditions: Where: P wt,min and P wt,rate are respectively the minimum and rated operating powers allowed for the wind power generation unit; P pv,min and P pv,rate are respectively the minimum and rated operating powers allowed for the photovoltaic power generation unit; Adjust the power of the hydrogen production unit by adjusting the power distribution coefficient β. The power reference value of the hydrogen production unit is: ； Among them, S SOC is the state of charge of the storage battery, S BH is the upper limit of the state of charge of the storage battery, S BL is the lower limit of the state of charge of the storage battery; Step 4: Determine the control methods of the wind power generation unit, the photovoltaic power generation unit, the hydrogen production unit, and the battery energy storage unit under different operating modes; Step 5: Determine the control architecture of the renewable energy DC hydrogen production island system.

2. The power management and decomposition method for a renewable energy DC hydrogen production island system according to claim 1, characterized in that: The obtaining of the electrolyzer dynamic response analytical equation in Step 1 includes the following steps: 1) Establish the output voltage-current model of the electrolyzer; 2) Establish the thermal model of the electrolyzer; 3) Establish the hydrogen production model of the electrolyzer; 4) Establish the compressor model of the hydrogen production unit; 5) Establish the hydrogen storage tank model; 6) Build a complete simulation model of the hydrogen production unit through simulation software, including the hydrogen production unit body model and the control system model; 7) Conduct a current or power step response test based on the hydrogen production unit simulation model, and obtain the dynamic response equation of the electrolyzer output power P AE (t) through fitting the simulation data: In the formula: t is time; a0, a1, a2, and a3 are dynamic characteristic fitting coefficients.

3. The power management and decomposition method of the renewable energy DC hydrogen production island system according to claim 1, characterized in that: Step 2 specifically includes: Define S SOC as the state of charge of the battery, S BH as the upper limit of the state of charge of the battery, S BL as the lower limit of the state of charge of the battery; P AE,min as the lower limit allowed for the electrolyzer to operate; P AE,max as the upper limit allowed for the electrolyzer to operate; P wt,T as the predicted value of wind power; P pv,T as the predicted value of photovoltaic power; then the renewable energy DC hydrogen production island system includes the following operating modes: Mode 1: S BH >S SOC >S BL and P wt,T +P pv,T ≤P AE,min , both the wind power generation unit and the photovoltaic power generation unit operate in the maximum power tracking mode, the hydrogen production unit operates at the minimum power operating point, and the energy storage discharges and stabilizes the DC voltage; Mode 2: S BH >S SOC >S BL and P wt,T +P pv,T >P AE,min , the wind power generation unit and the photovoltaic power generation unit both operate in the power dispatching mode. At steady state, the power of the hydrogen production unit is approximately equal to the sum of the output powers of the wind power generation and the photovoltaic power generation. The battery energy storage unit charges and discharges to stabilize the voltage and simultaneously compensates for the unbalanced power caused by the prediction deviation of the wind and light. Mode 3: S SOC ≤ S BL and P wt,T + P pv,T ≤ P AE,min , both the wind power generation unit and the photovoltaic power generation unit operate in the maximum power tracking mode, the hydrogen production unit is on standby, and the energy storage is charged and the DC voltage is stabilized; Mode 4: S SOC ≤S BL and P wt,T +P pv,T >P AE,min , both the wind power generation unit and the photovoltaic power generation unit operate in the power dispatch mode. The power of the hydrogen production unit is equal to β times the sum of the output powers of the wind power generation and the photovoltaic power generation, where the power distribution coefficient β < 1, and the energy storage charges and stabilizes the DC voltage; Mode 5: S SOC ≥ S BH and P wt,T + P pv,T ≤ P AE,min , both the wind power generation unit and the photovoltaic power generation unit operate in the maximum power tracking mode, the hydrogen production unit operates at the minimum power operating point, and the energy storage discharges and stabilizes the DC voltage; Mode 6: S SOC ≥ S BH and P wt,T + P pv,T > P AE,min At this time, both the wind power generation unit and the photovoltaic power generation unit are operating in the power dispatching mode. The power of the hydrogen production unit is equal to the sum of the wind power generation and photovoltaic power generation output powers multiplied by the power distribution coefficient β, where the power distribution coefficient β > 1, and the energy storage discharges to stabilize the DC voltage.

4. The power management and decomposition method of the renewable energy DC hydrogen production island system according to claim 1, characterized in that: Step 4 includes: 1) There are three control methods for the wind power generation system, including the standby mode, the maximum power tracking mode, and the power dispatch mode; 2) There are three control methods for the photovoltaic power generation system, including the standby mode, the maximum power tracking mode, and the power dispatch mode; 3) The battery energy storage system serves as the main control unit, and its control methods include constant voltage control and standby mode; 4) The hydrogen production unit is a flexible and controllable load, and its control methods include constant power control and standby mode.

5. The power management and decomposition method of the renewable energy DC hydrogen production island system according to claim 1, characterized in that: Step 5 includes the following steps: 1) Adopt a two-layer control architecture, where the upper layer is the power management layer and the lower layer is the local device control layer; 2) The upper-layer power management layer includes the power management method and the power command decomposition method considering the hydrogen production dynamic characteristics; the upper-layer power management system needs to collect the electrical parameters in the local device layer through communication; 3) In the local device control layer, each device has multiple control modes and receives the control mode conversion command and power command issued by the upper-layer power management system.

6. The power management and decomposition method of the renewable energy DC hydrogen production island system according to claim 5, characterized in that: The electrical parameters include the power P of the wind power generation unit wt , the power P of the photovoltaic power generation unit pv , the power P required by the hydrogen production unit AE , the DC bus voltage U dc , the state of charge S of the battery SOC .

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