A modular water electrolysis hydrogen production system and its control method

Abstract

The present invention specifically relates to a modular water electrolysis hydrogen production system and its control method. The system includes a renewable energy power generation system, an energy management and monitoring system, an electrolysis unit module group, and an energy storage system. The renewable energy power generation system includes a renewable energy power generation device and a rectifier-inverter device. The electrolysis unit module group includes a number of electrolysis unit modules. The energy storage system includes an inverter device and an energy storage battery pack. The energy management and monitoring system is communicatively connected to the renewable energy power generation system, the electrolysis unit module group, and the energy storage system respectively. The method is to obtain the number of electrolysis unit modules in the production state, standby state, and shutdown state, calculate the total remaining load P<subgt;total< / subgt; of the electrolysis unit modules in the production state and standby state, based on the weather forecasting system, predict the power generation increments ΔP1 and ΔP2 of the renewable energy power generation system in the next time period and the next next time period, and determine how to convert the electrolysis unit state and the conversion quantity according to the relationship between ΔP1, ΔP2 and P<subgt;total< / subgt>.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy, and particularly to a modular water electrolysis hydrogen production system and a control method thereof. Background Art

[0002] With the proposal of the 3060 dual-carbon goal, hydrogen has gradually been mentioned as an energy carrier due to its green and environmentally friendly characteristics. Among various hydrogen production technologies, water electrolysis hydrogen production technology is considered to be the mainstream hydrogen production technology in the future because when it is coupled with renewable energy, the entire hydrogen production process can truly achieve zero carbon. However, the current hydrogen production capacity of a single electrolyzer is relatively small, making it difficult to meet the rapid growth of hydrogen demand in future industrial and other fields. At the same time, the volatility problem of renewable energy will also pose potential hazards to the safety and hydrogen purity of water electrolysis hydrogen production.

[0003] To increase the hydrogen production scale and overcome the volatility problem of renewable energy, a method of combining multiple electrolysis unit modules can be adopted to achieve large-scale and centralized hydrogen production. At the same time, the change in the number of electrolyzer switches is controlled to cope with the power fluctuations of renewable energy.

[0004] However, this strategy usually ignores the start-up and shutdown time of the electrolyzer and the power consumption during start-up and shutdown. In actual applications, problems such as unstable hydrogen production and slow response of the electrolyzer system may be faced, affecting the safety of the entire system.

[0005] Meanwhile, when multiple electrolyzers are involved in the electrolysis process simultaneously, how to effectively allocate the power of each hydrogen production unit is also a difficult problem that urgently needs to be solved for the modular electrolyzer group. For a water electrolysis hydrogen production system, the electrolysis current determines the hydrogen production amount, and the electrolysis voltage determines the electrolysis efficiency. Therefore, even when the external input power is the same, the number of operating electrolysis units will affect the hydrogen production amount of the entire system. From the perspective of electrolysis principle, the smaller the working load of the electrolyzer, the higher the working efficiency of the electrolyzer. Therefore, under general conditions, choosing to let multiple electrolyzers operate at low load will obtain greater electrolysis efficiency and more hydrogen production amount than letting a small number of electrolyzers operate at high load. However, under low load conditions, there will be safety problems caused by low oxygen purity. At the same time, due to the existence of auxiliary system energy consumption, the system efficiency will decrease with the decrease of load at a certain critical point. Summary of the Invention

[0006] The purpose of the present invention is to provide a modular water electrolysis hydrogen production system and a control method thereof, so as to solve the problems of unstable hydrogen production, slow response of the electrolyzer, low hydrogen production efficiency, low hydrogen production amount, and potential safety hazards in the existing water electrolysis hydrogen production system.

[0007] The modular water electrolysis hydrogen production system provided by the present invention includes a renewable energy power generation system and an energy management and monitoring system. The renewable energy power generation system includes a renewable energy power generation device and a rectification and inversion device. The energy management and monitoring system is communicatively connected to the renewable energy power generation system. It further includes an electrolysis unit module group and an energy storage system. The electrolysis unit module group includes a number of electrolysis unit modules. Each electrolysis unit module includes a power supply system, an electrolytic cell, and an alkali solution heating system. The alkali solution heating system heats the alkali solution entering the electrolytic cell. The power supply system is electrically connected to the electrolytic cell. The energy storage system includes an inversion device and an energy storage battery pack. The power supply system of each electrolysis unit module is electrically connected to the rectification and inversion device respectively. The alkali solution heating system of each electrolysis unit module is electrically connected to the inversion device of the energy storage system. The rectification and inversion device of the renewable energy power generation system is electrically connected to the inversion device of the energy storage system. The energy management and monitoring system is communicatively connected to the electrolysis unit module group and the energy storage system respectively.

[0008] Preferably, the electrolysis unit module group further includes an alkali tank, a separation and purification system, a water replenishment system, and a cooling system. The alkali tank contains alkali solution, and the alkali solution enters the alkali solution heating system for heating. The separation and purification system is connected to the electrolytic cell. The cooling system is connected to the separation and purification system. The water replenishment system is connected to the separation and purification system.

[0009] Preferably, the renewable energy power generation device can be one or a combination of a photovoltaic power generation device, a hydraulic power generation device, and a wind power generation device.

[0010] Preferably, the alkali solution heating system includes a heating device and an alkali solution pipeline. The heating device uses an explosion-proof electric heater, and the explosion-proof electric heater is electrically connected to the inversion device of the energy storage system.

[0011] The present invention also provides a control method for a modular water electrolysis hydrogen production system. The method sequentially includes the following steps:

[0012] S1. Respectively obtain the numbers of electrolysis unit modules in the production state, standby state, and shutdown state, and record them as N L 、N S 、N I ;

[0013] S2. Calculate the total remaining load P total ,

[0014]

[0015] where f max is the upper limit of the optimal load range of the electrolytic cell of a certain electrolysis unit module, and f nowis the current load of the electrolyzer in the electrolysis unit module, P e is the rated power of the electrolyzer;

[0016] S3. Based on the weather forecasting system, predict the power generation increments ΔP1 and ΔP2 of the renewable energy power generation system in the next time period and the next next time period, where ΔP1 is the difference between the power in the next time period and the current time period, and ΔP2 is the difference between the power in the next next time period and the current time period;

[0017] S4. When ΔP1 > 0, if ΔP1 < P total , then switch the electrolysis unit modules from standby to production state in the next time period, and the number of switched electrolysis unit modules is calculated according to the principle of optimal efficiency; if ΔP1 > P total , and ΔP2 > P total , then pre-start the electrolysis unit modules in the shutdown state, that is, switch from shutdown to standby state, and the number of switched electrolysis unit modules is calculated according to the principle of optimal operation; if ΔP1 > P total , but ΔP2 < P total , the energy storage system absorbs the increment ΔP1 - P of the power generation of the renewable energy system in the next time period total , if the load of the energy storage system is full, then perform a load reduction operation on the renewable energy system;

[0018] S5. When ΔP1 < 0, if ΔP2 < 0, then perform a shutdown operation on the electrolysis unit modules in the production and standby states, that is, switch from production to shutdown and from standby to shutdown states, and the number of switched electrolysis unit modules is calculated according to the principle of optimal operation, and the standby to shutdown state switch is preferred; if ΔP2 > 0, then switch the electrolysis unit modules in the production state to the standby state, and the number of switched units is calculated according to the principle of optimal efficiency;

[0019] Among them, the principle of optimal efficiency described in step S4 and step S5 means that when calculating the number of electrolysis unit modules to be switched between the production and standby states, it is required that the working loads of the electrolysis unit modules in the production state after switching are within the optimal range; the principle of optimal operation means that when calculating the number of electrolysis unit modules to be switched between the standby and shutdown states and between the production and shutdown states, it is required that the predicted working loads of the electrolysis unit modules in the production and standby states after switching are within the full range.

[0020] Preferably, the method further includes the principle of balanced distribution, and the principle of balanced distribution means that when the rated powers of the electrolysis unit modules are equal, at any moment, the working powers of the electrolysis unit modules in the production state are evenly distributed, that is, the working powers of the electrolysis unit modules in the production state are equal.

[0021] Preferably, when the power of the renewable energy power generation system is less than the minimum working load of the electrolysis unit module group, the hydrogen production process is stopped, and the energy storage system absorbs the electric energy of the renewable energy power generation system; when the power of the renewable energy system is greater than the maximum load of the electrolysis unit module group, the energy storage system absorbs the surplus electric energy; when both of the above two situations occur and the energy storage system reaches full load, the renewable energy system reduces its load.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] Through the form of combining multiple electrolysis unit modules, the present invention breaks through the limitation of the small hydrogen production capacity of a single electrolysis unit at present and realizes large-scale and centralized hydrogen production; at the same time, fully considering the problem of the long start-stop time of the electrolyzer, by adding a pre-start step for the electrolysis unit module and adding an alkali solution heating system in the electrolysis unit module, the rapid response ability of the water electrolysis hydrogen production system to the power fluctuation of renewable energy is improved; by adding an energy storage system, on the one hand, it provides power supply for the pre-startup process and shutdown process of the electrolyzer, and on the other hand, it ensures the stability of the system under extreme weather conditions; based on the control method provided by the present invention, the efficiency of the hydrogen production system can be effectively improved, the maximum supply of green hydrogen can be realized, and at the same time, according to the prediction of future power generation and dual judgment, the frequent start-stop of the electrolysis unit module is avoided, the service life of the electrolyzer and the safety of electrolysis are improved, and the operation and maintenance cost during the electrolysis process is reduced. Description of the Drawings

[0024] Figure 1 It is the principle block diagram of the modular water electrolysis hydrogen production system of the present invention;

[0025] Figure 2 It is the principle block diagram of the electrolysis unit module in the modular water electrolysis hydrogen production system of the present invention;

[0026] Figure 3 It is the flow chart of the control method of the modular water electrolysis hydrogen production system of the present invention;

[0027] Figure 4 It is the schematic diagram of the working state switching of the electrolysis unit module in the modular water electrolysis hydrogen production system of the present invention. Detailed Embodiments

[0028] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0029] Embodiment

[0030] Please refer to Figure 1 and 2 . The modular water electrolysis hydrogen production system provided in this embodiment includes a renewable energy power generation system, an electrolysis unit module group, an energy storage system, and an energy management and monitoring system. The renewable energy power generation system includes a renewable energy power generation device and a rectifier-inverter device. The electrolysis unit module group includes a number of electrolysis unit modules. The electrolysis unit modules are connected in series / parallel or work independently. The electrolysis unit module includes a power supply system, an electrolytic cell, and an alkali solution heating system. The alkali solution heating system heats the alkali solution entering the electrolytic cell. The power supply system is electrically connected to the electrolytic cell. The energy storage system includes an inverter device and an energy storage battery pack. The power supply system of each electrolysis unit module is electrically connected to the rectifier-inverter device of the renewable energy power generation system respectively. The alkali solution heating system of each electrolysis unit module is electrically connected to the inverter device of the energy storage system. The rectifier-inverter device of the renewable energy power generation system is electrically connected to the inverter device of the energy storage system. The energy management and monitoring system is communicatively connected to the renewable energy power generation system, the electrolysis unit module group, and the energy storage system respectively.

[0031] As a preferred implementation manner of this embodiment, the renewable energy power generation device can adopt one or a combination of a photovoltaic power generation device, a hydraulic power generation device, and a wind power generation device. The renewable energy power generation device is responsible for providing electric energy for the entire modular water electrolysis hydrogen production system, and the rectifier-inverter device is responsible for power conversion. If the renewable energy power generation device is a photovoltaic power generation device, the rectifier-inverter device can be a busbar box (the system outputs direct current) or a combination of a busbar box and a grid-connected inverter (the system outputs alternating current); if the renewable energy power generation device is a wind turbine or a hydraulic generator, the rectifier-inverter device is a wind power or hydropower converter, which converts unstable wind power and hydropower into electric energy with voltage, frequency, and phase meeting the requirements through the principles of rectification and inversion.

[0032] As a preferred implementation manner of this embodiment, the inverter device of the energy storage system is a bidirectional inverter or composed of two unidirectional inverters, which is responsible for power conversion. When the energy storage battery pack is charged, the inverter device outputs controllable direct current to charge the energy storage battery pack; the inverter device in the energy storage system is also electrically connected to the alkali solution heating systems in each electrolysis unit module in the electrolysis unit module group. When a certain electrolysis unit module is pre-started, the inverter device converts the electric energy released by the energy storage battery pack and supplies it to the alkali solution heating system of the electrolysis unit module. The energy storage battery pack of the energy storage system includes more than two battery modules to ensure that the entire energy storage system can be charged and discharged simultaneously.

[0033] As a preferred embodiment of this embodiment, the electrolysis unit module group further includes an alkali tank, a separation and purification system, a water replenishment system, and a cooling system. The alkali tank contains alkali liquor, and the alkali liquor enters the alkali liquor heating system for heating. The separation and purification system is connected to the electrolytic cell, the cooling system is connected to the separation and purification system, and the water replenishment system is connected to the separation and purification system. The alkali liquor heating system is turned on to heat the alkali liquor during the pre-startup of the electrolysis unit module. The alkali liquor heating system includes a heating device and an alkali liquor pipeline. The heating device uses an explosion-proof electric heater, and the explosion-proof electric heater is electrically connected to the inverter device of the energy storage system. The alkali liquor pipeline connects the alkali tank and the electrolytic cell, and the heating device is fixed inside the alkali liquor pipeline. The power supply system usually consists of a transformer and a rectifier cabinet, which is responsible for converting high-voltage alternating current into controllable direct current (if the input is direct current, the transformer is not required). The electrolytic cell receives the electrical energy from the power supply system and conducts a water electrolysis reaction to generate hydrogen and oxygen. A large amount of alkali liquor is carried in the generated hydrogen and oxygen, so gas-liquid separation is required. After separation, the oxygen is exhausted, and the hydrogen enters the purification system for further water removal and drying. The separated alkali liquor is cooled and heat-exchanged by the cooling system and then transported to the electrolytic cell by an alkali liquor delivery pump for alkali liquor circulation. During the electrolysis process, water is continuously consumed, so deionized water is added to the electrolysis system through the water replenishment system. The electrolytic cell in this embodiment selects an alkaline water electrolytic cell, and the electrolysis unit module is additionally provided with an alkali liquor heating system. By heating the alkali liquor, the pre-startup of the electrolysis unit module is realized. The electrical energy of the alkali liquor heating system and the auxiliary equipment required to realize the pre-startup of the electrolysis unit module is supplied by the energy storage system. During electrolysis, it is necessary to cool the alkali liquor, so the alkali liquor heating device is only used for heating when the electrolytic cell is started.

[0034] As a preferred embodiment of this embodiment, the electrolysis unit module group, the energy storage system, and the renewable energy power generation system are respectively provided with control subsystems. The energy management system communicates with each control subsystem, is responsible for the power distribution among the electrolysis unit modules in the electrolysis unit module group, the power distribution between the electrolysis unit module group and the energy storage system, and at the same time controls the energy storage system to provide electrical energy for the pre-startup process of each electrolysis unit module.

[0035] Referring to Figure 3 、 4 , this embodiment also provides a control method for a modular water electrolysis hydrogen production system. First of all, it should be noted that the control method of this embodiment follows the following three control logics:

[0036] (1) Two load range intervals are set for each electrolysis unit module. 1) Full range: The lower limit of the load in this range is the minimum working load of the electrolytic cell, and the upper limit is the maximum working load of the electrolytic cell. This range is determined by the inherent properties of the electrolytic cell; 2) Optimal range: The upper and lower limits of the load in this range are defined by the user himself, and the range is within the full range, usually including the load point when the electrolysis efficiency of the system is the highest.

[0037] (2) The working states of the electrolyzer are divided into three types: production state (L), standby state (S), and shutdown state (I). The definitions of the switching processes between these states are as Figure 4 shown.

[0038] (3) Four principles for the system operation:

[0039] 1) Safety principle. When the power of the renewable energy power generation system is less than the minimum working load of the electrolysis unit module group, the hydrogen production process is stopped, and the energy storage system absorbs the electric energy of the renewable energy power generation system; when the power of the renewable energy power generation system is greater than the maximum load of the electrolysis unit module group, the energy storage system absorbs the surplus electric energy. When both of the above two situations occur and the energy storage system reaches its full load, the renewable energy power generation system reduces its load. The safety principle is the first principle.

[0040] 2) Optimal efficiency principle. When calculating the number of electrolysis unit modules to be switched between the production and standby states, it is required that the working loads of the electrolysis unit modules in the production state after switching are within the optimal range. When calculating the number of switches from S-L, the calculated value takes the maximum value; when calculating the number of switches from L-S, the calculated value takes the minimum value. The purpose of setting this principle is to ensure the maximization of the number of electrolysis unit modules in the production state under certain conditions, improve the hydrogen production efficiency, and increase the green hydrogen output.

[0041] 3) Optimal operation principle. When calculating the number of electrolysis unit modules to be switched between the standby and shutdown states and between the production and shutdown states, it is required that the expected working loads of the electrolysis units in the production and standby states after switching are within the full range. The purpose of setting this principle is to avoid frequent startup or shutdown of the electrolyzer, ensure the service life of the electrolyzer and the safety of electrolysis, and at the same time reduce the operation and maintenance costs. The calculated results all take the minimum value.

[0042] 4) Balanced distribution principle. When the rated powers of the electrolysis unit modules are equal, at any moment, the working powers of the electrolysis unit modules in the production state are evenly distributed, that is, the working powers of the electrolysis unit modules in the production state are equal.

[0043] The control method of the modularized water electrolysis hydrogen production system in this embodiment successively includes the following steps:

[0044] S1. Respectively obtain the numbers of electrolysis unit modules in the production state, standby state, and shutdown state, and record them as N L 、N S 、N I ;

[0045] S2. Calculate the total remaining load P of the electrolysis unit modules in the production state and standby state according to formula (1) total,

[0046]

[0047] where f max is the upper limit of the optimal range of the electrolytic cell load of a certain electrolysis unit module, and f now is the current load of the electrolytic cell of this electrolysis unit module, and P e is the rated power of this electrolytic cell;

[0048] S3. Based on the weather forecasting system, predict the power generation increments ΔP1 and ΔP2 of the renewable energy power generation system in the next time period and the next next time period, where ΔP1 is the difference between the power in the next time period and the current time period, and ΔP2 is the difference between the power in the next next time period and the current time period;

[0049] S4. When ΔP1 > 0, it indicates that according to the prediction result, the power generation power of the renewable energy power generation system in the next time period is higher than the current one. If ΔP1 < Ptotal, it indicates that the total remaining load of the electrolysis unit modules in the production and standby states can meet the increment of the renewable energy power generation power in the next time period. Then, in the next time period, switch the electrolysis unit modules from standby to production states, and the number of switched electrolysis unit modules is calculated according to the principle of optimal efficiency. If ΔP1 > Ptotal and ΔP2 > Ptotal, it indicates that the total remaining load of the electrolysis units in the production and standby states at the current stage cannot meet the increment of the renewable energy power generation power in the next two time periods. Then, pre-start the electrolysis unit modules in the shutdown state, that is, switch from shutdown to standby state, and the number of switched electrolysis unit modules is calculated according to the principle of optimal operation. If ΔP1 > Ptotal but ΔP2 < Ptotal, it indicates that the renewable energy power generation power only increases significantly in the next time period. To avoid frequent startup of the electrolytic cell, no I→S switch is performed, and the energy storage system absorbs the increment of the renewable energy system power generation in the next time period. If the load of the energy storage system is full, then perform a load reduction operation on the renewable energy system;

[0050] S5. When ΔP1 < 0, it indicates that according to the prediction result, the power generation power of the renewable energy system in the next time period is lower than the current one. If ΔP2 < 0, it indicates that the power generation power of the renewable energy system will decrease in the next two time periods. Then, perform a shutdown operation on the electrolysis unit modules in the production and standby states, that is, switch from production to shutdown and from standby to shutdown states, and the number of switched electrolysis unit modules is calculated according to the principle of optimal operation, and the standby→shutdown state switch is given priority. If ΔP2 > 0, it means that the renewable energy power generation power only temporarily decreases in the next time period. To avoid frequent shutdown of the electrolytic cell, perform a standby switch on the electrolysis unit modules only in the production state, and the number of switched units is calculated according to the principle of optimal efficiency.

[0051] Although embodiments of the present invention have been shown and described, those of ordinary skill in the art will appreciate that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A control method for a modular water electrolysis hydrogen production system, characterized in that: The method successively includes the following steps: S1. Obtain the numbers of electrolysis unit modules in the production state, standby state, and shutdown state respectively, and denote them as N l , N s , N i ; S2. Calculate the total remaining load P of the electrolysis unit modules in the production state and standby state according to formula (1). total , Among them, f max is the upper limit of the optimal range of the electrolytic cell load of a certain electrolysis unit module, and f now is the current load of the electrolytic cell of this electrolysis unit module, and P e is the rated power of this electrolytic cell; S3. Based on the weather forecasting system, predict the power generation increments ΔP1 and ΔP2 of the renewable energy power generation system in the next time period and the next next time period, where ΔP1 is the difference between the power in the next time period and the power in the current time period, and ΔP2 is the difference between the power in the next next time period and the power in the current time period; S4. When ΔP1 > 0, if ΔP1 < P total , then in the next time period, the electrolysis unit module will switch from standby to production state, and the number of electrolysis unit modules to be switched is calculated according to the principle of optimal efficiency; if ΔP1 > P total , and ΔP2 > P total , then the electrolysis unit modules in the shutdown state will be pre-started, that is, switched from shutdown to standby state, and the number of electrolysis unit modules to be switched is calculated according to the principle of optimal operation; if ΔP1 > P total , but ΔP2 < P total , the energy storage system absorbs the increment of the power generation of the renewable energy system in the next time period, ΔP1 - P total . If the load of the energy storage system is full, the renewable energy system will be load-shedding operated; S5. When ΔP1 < 0, if ΔP2 < 0, perform a shutdown operation on the electrolysis unit modules in the production and standby states, that is, perform a state switch from production to shutdown and from standby to shutdown. The number of electrolysis unit modules to be switched is calculated according to the optimal operation principle, and the standby-to-shutdown state switch is preferentially performed; if ΔP2 > 0, perform a standby switch on the electrolysis unit modules in the production state, and the number of units to be switched is calculated according to the optimal efficiency principle; Among them, the optimal efficiency principle described in step S4 and step S5 means that when calculating the number of electrolysis unit modules to be switched between the production and standby states, it is required that the working loads of the electrolysis unit modules in the production state after switching are within the optimal range; the optimal operation principle means that when calculating the number of electrolysis unit modules to be switched between the standby and shutdown states and between the production and shutdown states, it is required that the predicted working loads of the electrolysis unit modules in the production and standby states after switching are within the full range.

2. The control method of the modularized water electrolysis hydrogen production system according to claim 1, characterized in that: The method further includes an equal distribution principle, which means that when the rated powers of the electrolysis unit modules are equal, at any moment, the working powers of the electrolysis unit modules in the production state are evenly distributed, that is, the working powers of the electrolysis unit modules in the production state are equal.

3. The control method of the modular water electrolysis hydrogen production system according to claim 1, characterized in that: When the power of the renewable energy power generation system is less than the minimum working load of the electrolysis unit module group, stop the hydrogen production process, and the energy storage system absorbs the electric energy of the renewable energy power generation system; when the power of the renewable energy system is greater than the maximum load of the electrolysis unit module group, the energy storage system absorbs the surplus electric energy; when both of the above two situations occur and the energy storage system reaches full load, the renewable energy system reduces its load.

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