P2022,2080 WO E / P220053WO01 August 23, 2022 1 POWER-TO-HYDROGEN PLANT, CONTROL UNIT AND CONTROL METHOD THEREOF TECHNICAL FILED [0001] The disclosure relates to a maximum efficiency point tracking (MEPT) control for a power-to-hydrogen (PtH) plant. BACKGROUND [0002] Power-to-Hydrogen (PtH) is regarded as one of the most important technologies in the process of decarbonization and carbon-neutral. Against this backdrop, PtH is becoming more and more popular because of its advantages of high mass energy density and being environmentally friendly. However, in the prior art, a PtH plant is usually operated under constant parameters, which causes a problem of deviating from a high efficiency point of the PtH plant, especially when the PtH plant takes renewable energy that might change intermittently. This is particularly problematic for a large-scale PtH system because any deviation from the high efficiency point will result in high power losses. SUMMARY [0003] According to an embodiment of the disclosure, a control unit for a Power- to-Hydrogen (PtH) plant is provided. The control unit includes at least one model and is configure to: calculate maximum efficiency point tracking of the PtH plant by solving an objective function having a predetermined hydrogen production rate of the PtH plant or a predetermined amount of energy input to the PtH plant using the at least one model, wherein the control unit receives measured parameters indicative of status of components of the PtH plant as an input to the at least one model; determine one or more set points for a coordinated operation of the components of the PtH plant P2022,2080 WO E / P220053WO01 August 23, 2022 2 based on a solution obtained by solving the objective function; and provide the one or more set points to one or more of the components of the PtH plant to operate the PtH at the maximum efficiency point. [0004] According to another embodiment of the disclosure, a PtH plant is provided. The PtH plant includes: an electrolyzer for generating hydrogen; a power supply unit for supplying power to the electrolyzer; an auxiliary equipment coupled with the electrolyzer; and a control unit in communication with the electrolyzer, the power supply unit, and the auxiliary equipment. The control unit includes at least one model and is configure to: calculate maximum efficiency point tracking of the PtH plant by solving an objective function having a predetermined hydrogen production rate of the electrolyzer or a predetermined amount of energy input to the PtH plant using the at least one model, wherein the control unit receives measured parameters indicative of status of components of the PtH plant as an input to the at least one model; determine one or more set points for a coordinated operation of the components of the PtH plant based on a solution obtained by solving the objective function; and provide the one or more set points to one or more of the components of the PtH plant to operate the PtH at the maximum efficiency point. [0005] According to yet another embodiment of the disclosure, a control method for a Power-to-Hydrogen (PtH) plant is provided. The control method includes: calculating maximum efficiency point tracking of the PtH plant by solving an objective function having a predetermined hydrogen production rate of the PtH plant or a predetermined amount of energy input to the PtH plant using at least one model, wherein the control unit receives measured parameters indicative of status of components of the PtH plant as an input to the at least one model; determining one or more set points for a coordinated operation of the components of the PtH plant based on a solution obtained by solving the objective function; and providing the one or more set points to one or more of the components of the PtH plant to operate the PtH at the maximum efficiency point. P2022,2080 WO E / P220053WO01 August 23, 2022 3 BRIEF DESCRIPTION OF THE DRAWINGS [0006] The disclosed aspects will hereinafter be described in connection with the appended drawings that are provided to illustrate but not to limit the scope of the disclosure. [0007] Figure 1 illustrates the multi-energy interconversion in a PtH plant. [0008] Figure 2 illustrates the bubble effect in an electrolyzer. [0009] Figure 3 illustrates a PtH plant according to an example of the disclosure. [0010] Figure 4 illustrates an implementation of the PtH plant shown in Figure 3. [0011] Figure 5 illustrates an example of a distributed control unit. [0012] Figure 6 illustrates an example of a central control unit. [0013] Figure 7 is a flowchart of a MEPT controlling process according to an example of the disclosure. [0014] Figure 8 is a flowchart of a MEPT controlling process according to another example of the disclosure. [0015] Figure 9 illustrates an example the two optimizations of the power distribution. [0016] Figure 10 illustrates an implementation of the PtH shown in Figure 4. [0017] Figure 11 illustrates another implementation of the PtH shown in Figure 4. [0018] Figure 12 is flowchart of a control method for a PtH plant according to an example of the disclosure. [0019] Figure 13 is a simulation figure showing a coordination of the temperature and the velocity for the maximum PtH efficiency. [0020] Figure 14 is a simulation figure showing the maximum efficiency and the optimized power of the pump, the heater and the electrolyzer with different supplied P2022,2080 WO E / P220053WO01 August 23, 2022 4 current. [0021] Figure 15 is a simulation figure showing the maximum efficiency point of efficiency (Figure 15(a)), temperature (Figure 15(b)), velocity (Figure 15(c)), and voltage (Figure 15(d)) with fluctuating supplied current. DETAILED DESCRIPTION [0022] Examples of the disclosure relate to MEPT control for a PtH plant. The PtH plant comprises components such as an electrolyzer, an auxiliary equipment (such as a pump, a heater, a cooler and a heater exchanger) coupled with the electrolyzer, and a power supply unit for supplying power to the electrolyzer and the auxiliary equipment. The PtH plant is a multi-energy system where various types of energy, such as electrical energy, thermal energy, mechanical energy and chemical energy, interact and interconvert each other. The multi-energy interconversion in the PtH plant is shown in Figure 1. As shown in Figure 1, the PtH plant is powered by electricity taken from an energy source, the taken energy is distributed among the electrolyzer and the auxiliary equipment such as the pump and the thermal conditioning equipment (e.g., a heater, a cooler or a heat exchanger) and transformed into mechanical, thermal and chemical energy. Different types of energy are carried to the electrolyzer by the flowing electrolyte and transformed into chemical energy stored in hydrogen. [0023] The mechanical energy (e.g., the flowing electrolyte) provided by the pump has an important impact on the PtH plant due to so-called bubble effect, as shown in Figure 2. For the zero-gap cell (see Figure 2(a)), the adhering bubbles on the catalyst isolate the contact of the electrolyte and the catalyst, which means the covered area on the catalyst is invalid for the electrolyte (e.g., water electrolysis). Therefore, the bubble effect tends to reduce the effective area of electrochemical reactions on electrodes of the electrolyzer. For the gap cell (see Figure 2(b)), the bubbles will not only reduce the effective area of the electrode but also decrease the P2022,2080 WO E / P220053WO01 August 23, 2022 5 conductivity of the electrolyte. This is because the flow channel is contained in the electrically conductive path. Since the conductivity of the bubbles is far lower than the electrolyte, the existence of bubbles possesses negative effects on cell resistance. Therefore, adequate power should be allocated to the pump to guarantee the bubble detachment. [0024] Thermal energy is also important for high-performance of the PtH plant. There are two main benefits of high temperature for electrolyzation (e.g., water electrolysis). From the thermodynamic point of view, the electrical energy required for the electrolyzation (e.g., water splitting) is reduced since more thermal energy is supplied to the electrolyzer. On the other hand, the electrodes are better activated under a high temperature, which indicates the energy conversion efficiency increases. [0025] An important improvement of the disclosure is that it provides a coordinated control of various components of the PtH plant using a model to ensure the PtH plant can operate at a maximum efficiency point. Examples of the disclosure are described below. [0026] The MEPT control according to examples of the disclosure can be applied to a middle-scale PtH plant as well as a large-scale PtH plant. For example, the power, current and voltage of a medium-scale electrolyzer in the PtH plant can be 0.5MW, 1800A, and 250V, respectively. The power, current and voltage of a large-scale electrolyzer in the PtH plant can be 5 MW, 5000A, and 1000V, respectively. [0027] Figure 3 illustrates a PtH plant 100 according to an example of the disclosure. The PtH plant 100 takes energy from an energy source 200. The energy source 200 can be renewable energy source such as wind, solar, water, or geothermal. The energy source 200 also can be an on-grid system or an off-grid system. The energy source 200 also can be a hybrid system of grid and battery that can deliver power during either on-grid or off-grid conditions. [0028] According to examples of the disclosure, the efficiency of the PtH plant 100 is represented by a ratio of hydrogen energy generated by the PtH plant 100 to P2022,2080 WO E / P220053WO01 August 23, 2022 6 energy consumed by the PtH plant 100. Examples of the disclosure aims to achieve a maximum efficiency point of the PtH plant. The maximum efficiency point is represented by an objective function including a maximum ratio that corresponds to the maximum efficiency point of the PtH plant. [0029] The objective function is written as: maxP_H ₂ / ΣP_i 1≤i≤n (1) where P_H2 is the power of hydrogen produced by the PtH plant; and ΣP_i is a sum of power consumed by components of the PtH plant, and n is a number of the components. [0030] In an example, the energy input to the PtH plant 100 is distributed among a pump, a heater and an electrolyzer, and the objective function is written as: where P_H ₂ is the power of hydrogen produced by the PtH plant; P _pump is the power consumed by the pump; P _heater is the power consumed by the heater; and P _electrolyzer is the power consumed by the electrolyzer. [0031] In a scenario where the output of the PtH plant 100 is predetermined, i.e., the hydrogen production rate of the PtH plant 100 is predetermined, for example, the hydrogen production rate is prefixed to a certain level according to a user requirement, the maximum ratio is a ration of hydrogen energy corresponding to the predetermined hydrogen production rate to a minimum amount of energy required by the PtH plant 100. That is to say, in the case that the output energy is prefixed and the energy required to input to the PtH plant is minimum, the maximum efficiency point of the PtH plant 100 can be achieved. [0032] In another scenario where the input of the PtH planet 100 is predetermined, i.e., the amount of energy input to the PtH plant 100 is predetermined, for example, P2022,2080 WO E / P220053WO01 August 23, 2022 7 the amount of the input energy is prefixed to a certain level according to a specific use case, the maximum ratio is a ration of hydrogen energy generated by the PtH plant 100 to the predetermined amount of energy input to the PtH plant 100. That is to say, in the case that the input energy is prefixed and the output energy generated by consuming the prefixed input energy is maximum, the maximum efficiency point of the PtH plant 100 can be achieved. [0033] With reference to Figure 3, the PtH plant 100 comprises an electrolyzer 10, a power supply unit 20, an auxiliary equipment 30 and a control unit 40. [0034] The electrolyzer 10 is used to electrolyze the electrolyte, such as alkaline solution or water, to generate hydrogen gas, and also to generate oxygen gas. The disclosure relates only to the production of hydrogen gas. [0035] The electrolyzer 10 is a core component of the PtH plant 100. Various types of water electrolyzers can be used, for example, alkaline water electrolysis (AE), proton exchange membrane water electrolysis (PEM), and anion exchange membrane water electrolysis (AEM). These electrolyzers have their own characteristics. For example, AE is recognized as the most mature technology with low investment cost and high capacity. PEM features high current density and part load range due to the excellent performance of the polymer membrane. The MEPT control of the disclosure can be applied to those types of water electrolyzers. [0036] The power supply unit 20 receives electricity that is taken from the energy source 200 and supplies electric power to the electrolyzer 10 and the auxiliary equipment 30. The output of the power supply unit 20 is adjustable, for example, by controlling at least one of an output current, an output voltage and an output power of the power supply unit 20, and thus the electric power supplied to each of the electrolyzer 10 and the auxiliary equipment 30 is also adjustable. [0037] The auxiliary equipment 30 is coupled to the electrolyzer 10. In an example, the auxiliary equipment 30 is integrated with the electrolyzer 10 to form a single device. The auxiliary equipment 30 includes a pump for pumping electrolyte P2022,2080 WO E / P220053WO01 August 23, 2022 8 into the electrolyzer 10. The pump has an adjustable pump speed to adjust the flow velocity of the electrolyte pumped into the electrolyzer 10. The auxiliary equipment 30 may further include at least one of a heater, a cooler, and a heat exchanger for regulating the temperature of the electrolyte. [0038] The control unit 40 is in communication with the electrolyzer 10, the power supply unit 20, and the auxiliary equipment 30, respectively. The control unit 40 includes such a MEPT control strategy that components of the PtH plant are cooperatively controlled such that the PtH plant can operate at the maximum efficiency point. [0039] Continuing with reference to Figure 3, the control unit 40 includes at least one model 41. The at least one model can be implemented by means of a variety of techniques such as look up table, formula, equation, AI-based model, and NM-based model. In an example, the at least one model includes variables, coefficients and constants. [0040] In an example, the control unit 40 receives the predetermined information Info_1 (i.e., the predetermined hydrogen production rate or the predetermined amount of energy input to the PtH plant 100) and the measured information Info_2 (i.e. measured parameters indicative status of the components of the PtH plant 100). The measured parameters are input to the at least one model 41 as variables of the at least model 41. Then, the control unit 40 calculates MEPT of the PtH plant 100 by solving the objective function using the at least one model 41. Then, the control unit 40 determines one or more set points for a coordinated operation of the components of the PtH plant 100 based on a solution obtained by solving the objective function. The obtained solution can be seen as an optimal solution to achieve the maximum efficiency defined by the objective function. Then, the control unit 40 provides the one or more set points to one or more of the components of the PtH plant 100 to operate the PtH 100 at the maximum efficiency point. [0041] In some cases, there may a problem with aging of the electrolyzer 10 and P2022,2080 WO E / P220053WO01 August 23, 2022 9 thus the at least one model 41 is not suitable for the current situation of the PtH plant 100 anymore. In view of this problem, according to an example of the disclosure, the control unit 40 performs an update of the at least one model 41 to solve this problem. The update can be performed on-line and/or off-line. The update can be performed periodically (e.g., once a month or once a year) or in response to a trigger signal indicating that the aging of the electrolyzer has reached a certain level. [0042] In an example, the control unit 40 calculates the update of the at least one model 41 based on the measured parameters. The update of the at least one model 41 includes an update of the coefficients and/or constants of the at least one model 41. [0043] The coefficients and constants of the at least one model 41 include those parameters related to an electrochemical reaction, diphasic flow and temperature dependence of the electrolyzer 10. An example of the coefficients and constants of the at least one model 41 is described in Table 1 below. Table 1 P2022,2080 WO E / P220053WO01 August 23, 2022 10 [0044] In an example, the measured parameters include parameters that are measured at the components of the PtH plant 100 and indicative of status of the components. For example, the measured parameters include: a current in the electrolyzer 10 (e.g., a current flowing from an anodic electrode of the electrolyzer to a cathodic electrode of the electrolyzer); a voltage across the electrolyzer 10; a velocity of electrolyte flowing into the electrolyzer 10; and a temperature of the electrolyte in the electrolyzer 10. [0045] In addition, an aging indicator indicating an aging degree of the electrolyzer 10 can be derived from the measured parameters. For example, the aging indicator is calculated based on the measured electrolyzer voltage and current, and the hydrogen production rate. In an example, the control unit 40 calculates the aging indicator based on the measured parameters. In another example, the aging indicator is calculated at a computing device associated with the electrolyzer 10 and the control unit 40 receives the aging indicator from the computing device. [0046] In an example, the measured parameters include variables related to an electrochemical reaction, diphasic flow and temperate dependence of the electrolyzer P2022,2080 WO E / P220053WO01 August 23, 2022 11 10. An example of those variables is described in Table 2 below. Table 2 P2022,2080 WO E / P220053WO01 August 23, 2022 12 [0047] In an example, the measure parameters may also include operating parameters of the pump. The measured parameters may also include operating parameters of one or more of the heater, cooler and heat exchanger. [0048] The set points comprise one or more of the following references that should be co-operated: a reference current for the power supply unit 20, a reference voltage for the power supply unit 20, a reference power for the power supply unit 20, a reference temperature for the at least of the heater 32, the cooler 33 and the heat exchanger 34, and a reference velocity for the pump 31. In an example, the control unit 40 determines one set point including all the determined references, for example, the determined set point includes the reference voltage, the reference temperature and the reference velocity. In another example, the control unit 40 determines a set of set points each of which includes a reference, for example, the determined set of set points includes a set point for setting the reference voltage, a set point for setting the reference temperature and set point for setting the reference velocity. [0049] The set points including references are provided to corresponding components as orders. Each component may be associated with a controller (e.g., the controller can be seen as a low-level controller/subordinate controller of the control unit 40) for receiving and performing the order. For example, a set point for setting the reference velocity is provided to a pump controller associated with the pump and the pump controller controls the pump such that the pump pumps electrolyte into the electrolyzer 10 with the reference velocity. In this way, components of the PtH plant 100 can be coordinately controlled based on a co-operation according to the set point orders. [0050] Figure 4 illustrates an implementation of the PtH plant 100 in Figure 3. As shown in Figure 4, the PtH plant 100 further includes sensing unit 50. The sensing unit 50 includes one or more sensors for sensing status of the electrolyzer 10, the power supply unit 20 and the auxiliary equipment 30 and generating the aforesaid measured parameters (i.e., Info_2). In addition, the PtH plant 100 can also include a P2022,2080 WO E / P220053WO01 August 23, 2022 13 communication network 60 (shown in Figures 5 and 6). Information can be exchanged between the control unit 40 and the electrolyzer10, the power supply unit 20, the auxiliary equipment 30 or the sensing unit 50 via the communication network 60. [0051] With reference to Figure 4, the power supply unit 20 includes a power supply 21, and optionally, includes a converter 22 coupled with the power supply 21. The converter 22 may include converters such as AC-DC, DC-DC, DC-AC-DC, and the like. The power supply 21 may include one or more power supplies. The converter 22 may include one or more converters. The selection of the converter 22 and its arrangement with the power supply 21 can be designed according to specific application scenarios. The auxiliary equipment 30 includes a pump 31, and optionally, includes at least one of a heater 32, a cooler 33, and a heat exchanger 34. [0052] Continuing with reference to Figure 4, the at least one model 41 includes an electrolyzer model 411 and a pump model 412. The electrolyzer model 411 is a model of the electrolyzer 10 obtained by modelling the electrolyzer 10. The pump model 412 is a model of the pump obtained by modeling the pump 31. The at least one model 41 may further include a heater model 413, a cooler model 414 and a heat exchanger model 415. Similarly, the heater model 413 is a model of the heater 32 obtained by modelling the heater 32. The cooler model 414 is a model of the cooler 33 obtained by modelling the cooler 33. The heat exchanger model 415 is a model of the heat exchanger 34 obtained by modelling the heat exchanger 34. In an example, each of those models 411-415 is implemented as a sub-model of the model 41, and has a data interface for exchanging data with each other. Those models 411-415 perform co-processing for determining the one or more set points. [0053] According to examples of the disclosure, the control unit 40 can be implemented as a distributed control unit or a central control unit. [0054] Figure 5 illustrates an example of the distributed control unit 40. As shown in Figure 5, the control unit 40 includes a plurality of controllers 40A-40C P2022,2080 WO E / P220053WO01 August 23, 2022 14 each of which can communicate with the communication network 50. The at least one model 41 is stored in one of the controllers, for example, the controller 40A. [0055] Figure 6 illustrates an example of the central control unit 40. As shown in Figure 6, the control unit 40 includes a central controller 40D. The at least one model 41 is stored in the central controller 40D. [0056] Figure 7 is a flowchart of a MEPT controlling process 700 according to an example of the disclosure. The MEPT controlling process 700 can be implemented by means of the control unit 40 and the PtH plant 100 and thus various features described above with reference to the control unit 40 and the PtH plant 100 are also applicable in the MEPT controlling process 700. In the MEPT control process 700, the energy input to the PtH plant 100 is distributed between the electrolyzer 10 and the pump 31 using the electrolyzer model 411 and the pump model 412 for achieving the maximum efficiency point of the PtH plant 100. [0057] With reference to Figure 7, at block 702, the sensing unit 50 directly or indirectly measures status the electrolyzer 10 and the pump 31 and generates measured parameters. Examples of the measured parameters can refer to the above related descriptions. [0058] At block 704, the control unit 40 receives the measured parameters. [0059] At block 706, the control unit 40 inputs the measured parameters to the electrolyzer model 411 and the pump model 412. For example, the parameters related to the electrochemical reactions are input to the electrolyzer model 411 and the parameters related to the diphasic flow are input to the pump model 412. [0060] At block 708, the control unit 40 calculates MEPT by solving the objective function using the electrolyzer model 411 and the pump model 412. [0061] At block 710, the control unit 40 determines one or more set points for a coordinated operation of the electrolyzer 10 and the pump 31 based on a solution obtained by solving the objective function. P2022,2080 WO E / P220053WO01 August 23, 2022 15 [0062] In an example, the electrolyzer model 411 and the pump model 412 perform co-processing and output the one or more set points including a reference velocity for the pump 31 and at least one of a reference power, a reference voltage and a reference current for the power supply unit 20. [0063] In this example, the co-processing includes an optimization (Optimization_1) of the power distribution between the power supplied to the electrolyzer 10 and the power consumed by the pump 31. This optimization is made on the basis of considering the above described bubble detachment. For example, the co-processing is performed using a trade-off algorithm to distribute power between the electrolyzer 10 and the pump 31. The trade-off algorithm includes such a rule: improved flow rate of the electrolyte will relieve the bubble effect by accelerating the bubble detachment on the electrodes, but the energy consumption of the pump will be simultaneously increased. [0064] At block 712, the control unit 40 provides the determined one or more set points to the power supply unit 20 and the pump 31. [0065] At block 714, the power supply unit 20 receives the set point including at least one of the reference power, the reference voltage and the reference current and supplies power to the electrolyzer according to the received set point. For example, the power supply controller controls the power supply unit to supply power to the electrolyzer with the reference power. [0066] At block 716, the pump 31 receives the set point including the reference velocity and pumps the electrolyte into the electrolyzer according to the received set point. For example, the pump controller controls the pump to pumps electrolyte into the electrolyzer with the reference velocity. [0067] At block 718, the control unit 40 calculates an update of the electrolyzer model 411 and the pump model 412. In an example, the update includes an update of coefficients and/or constants of the electrolyzer model 411 and an update of coefficients and/or constants of the pump model 412. P2022,2080 WO E / P220053WO01 August 23, 2022 16 [0068] Figure 8 is a flowchart of a MEPT controlling process 800 according to another example of the disclosure. The MEPT controlling process 800 can be implemented by means of the control unit 40 and the PtH plant 100 and thus various features described above with reference to the control unit 40 and the PtH plant 100 are also applicable in the MEPT controlling process 800. In the MEPT control process 800, the energy input to the PtH plant 100 is distributed between the electrolyzer 10, the pump 31 and the heater 32 using the electrolyzer model 411, the pump model 412 and the heater model 413 for achieving the maximum efficiency point of the PtH plant 100. [0069] With reference to Figure 8, at block 802, the sensing unit 50 directly or indirectly measures status the electrolyzer 10, the pump 31 and the heater 32, and generates measured parameters. Examples of the measured parameters can refer to the above related descriptions. [0070] At block 804, the control unit 40 receives the measured parameters. [0071] At block 806, the control unit 40 inputs the measured parameters to the electrolyzer model 411, the pump model 412 and the heater model 413. For example, parameters related to the electrochemical reactions are input to the electrolyzer model 411, parameters related to the diphasic flow are input to the pump model 412, and parameters related to the temperature dependence are input to the heater model 413. [0072] At block 808, the control unit 40 calculates MEPT by solving the objective function using the electrolyzer model 411, the pump model 412 and the heater model 413. [0073] At block 810, the control unit 40 determines one or more set points for a coordinated operation of the electrolyzer 10, the pump 31 and the heater 32 based on a solution obtained by solving the objective function. [0074] In an example, the electrolyzer model 411, the pump model 412 and the heater model 413 perform co-processing and output the one or more set points including a reference velocity for the pump 31, at least one of a reference power, a P2022,2080 WO E / P220053WO01 August 23, 2022 17 reference voltage and a reference current for the power supply unit 20, and reference temperature for the heater 32. [0075] In this example, in addition to the above-mentioned optimization (Optimization_1), the co-processing further includes another optimization (Optimization_2) of the power distribution between the power supplied to the electrolyzer 10 and the power consumed by the heater 32. This optimization is made on the basis of considering the above described thermodynamic point. For example, the co-processing is performed using a trade-off algorithm to distribute power between the electrolyzer 10 and the heater 32. The trade-off algorithm includes such a rule: the higher temperature tends to better activate the electrode and benefit the reaction thermodynamically, at the expense of higher energy consumption in the heater 32. [0076] Figure 9 illustrates an example the two optimizations of the power distribution. As shown in Figure 9, the maximum efficiency point _ηm is achieved based on the two optimizations, i.e., Optimaization_1 and Optimization_2. [0077] At block 812, the control unit 40 provides the determined one or more set points to the power supply unit 20, the pump 31 and the heater 32. [0078] At block 814, the power supply unit 20 receives the set point including at least one of the reference power, the reference voltage and the reference current and supplies power to the electrolyzer according to the received set point. For example, the power supply controller controls the power supply unit to supply power to the electrolyzer with the reference power. [0079] At block 816, the pump 31 receives the set point including the reference velocity and pumps the electrolyte into the electrolyzer according to the received set point. For example, the pump controller controls the pump to pumps electrolyte into the electrolyzer with the reference velocity. [0080] At block 818, the heater 32 receives the set point including the reference temperature and adjusts the temperature of the electrolyte according to the received P2022,2080 WO E / P220053WO01 August 23, 2022 18 set point. For example, the heater controller controls the heater to adjust the temperature to the reference temperature. [0081] At block 820, the control unit 40 calculates an update of the electrolyzer model 411, the pump model 412 and the heater model 413. In an example, the update includes an update of coefficients and/or constants of the electrolyzer model 411, an update of coefficients and/or constants of the pump model 412, and an update of coefficients and/or constants of the heater model 413. [0082] It is noted that various modifications of power distribution such as power distribution among the electrolyzer, the pump, and the cooler, power distribution between the elecetrolyzer and the heater/cooler, and power distribution among the electrolyzer, the pump, the cooler, and the heat exchanger, can be implemented in a manner similar to that described above. [0083] Figure 10 illustrates an implementation of the PtH 100 of Figure 4. As shown in Figure 10, the electrolyzer 10 includes set of electrolysis units 10a-10c each of which is coupled with and supplied by the power supply 21. The pump 31 includes a plurality of pumps 31a-31b arranged in a flow path of the electrolyte. The cooler 33 includes a plurality of coolers 33a-33b arranged in the flow path. Water is electrolyzed to produce hydrogen and oxygen. [0084] Figure 11 illustrates another implementation of the PtH 100 of Figure 4. As shown in Figure 11, the power supply 21 includes a set of power supplies 21a-21c, and the electrolyzer 10 includes set of electrolysis units 10a-10c. Each electrolysis unit is couple with a corresponding power supply and supplied by the corresponding power supply. For example, the electrolysis unit 10a is coupled with the power supply 21a and is supplied by the power supply 21a; the electrolysis unit 10b is coupled with the power supply 21b and is supplied by the power supply 21b; and the electrolysis unit 10c is coupled with the power supply 21c and is supplied by the power supply 21c. The pump 31 includes a plurality of pumps 31a-31e arranged in the flow path of the electrolyte. One cooler 33a is arranged in the plow path. The P2022,2080 WO E / P220053WO01 August 23, 2022 19 heat exchanger 34 includes a plurality of heat exchangers 34a-34c arranged in the flow path. Lye is electrolyzed to generate hydrogen and oxygen. [0085] It is noted that the above-mentioned configurations of the PtH plant 100 according to Figures 10 and 11 are only exemplary, and the PtH plant 100 can also be implemented in other various configurations with adaptive modifications. Those variations and modifications are within the scope of the disclosure. [0086] Figure 12 is flowchart of a control method 1200 for a PtH plant according to an example of the disclosure. The method 1200 can be implemented by means of the control unit 40 and thus various features described above with reference to the control unit 40 are also applicable to the method 1200. [0087] With reference to Figure 12, in step S1202, the control unit calculates maximum efficiency point tracking of the PtH plant by solving an objective function having a predetermined hydrogen production rate of the PtH plant or a predetermined amount of energy input to the PtH plant using at least one model. The control unit 40 receives measured parameters indicative of status of components of the PtH plant as an input to the at least one model. [0088] In step S1204, the control unit determines one or more set points for a coordinated operation of the components of the PtH plant based on a solution obtained by solving the objective function. [0089] In step S1206, the control unit 40 provides the one or more set points to one or more of the components of the PtH plant to operate the PtH at the maximum efficiency point. [0090] The disclosure also provides a non-transitory computer readable medium comprising MEPT instructions stored in a memory and executed by a processor to carry out any operation of the method 1200 for MEPT controlling of the PtH plant according to examples as described above. [0091] In an example, the at least one model 41 is implemented as a multiphysics P2022,2080 WO E / P220053WO01 August 23, 2022 20 model having the above-mentioned variables and constants. Examples and constraints of the multiphysics model are described below, where the electrolyzer has been divided into N segments in y-direction, within which the variables are assumed constant. Definitions of parameters (e.g., variables and constants) can refer to Table 3 below. Electrochemical reaction constraints Diphasic flow constrains P2022,2080 WO E / P220053WO01 August 23, 2022 21 Temperature dependence constrains 298.15(K ) ^ T ^ 368.15( K ) (16) Table 3 P2022,2080 WO E / P220053WO01 August 23, 2022 22 P2022,2080 WO E / P220053WO01 August 23, 2022 23 [0092] The proposed MEPT controlling can be verified by means of simulation results. Figure 13 is a simulation figure showing a coordination of the temperature and the velocity for the maximum PtH efficiency. Figure 13 shows that there exists the coordination among the pump, the heater and the electrolyzer. With the coordination of the pump and the heater, the optimal operating parameters can be acquired at the maximum efficiency point MP. [0093] Figures 14 and 15 show such simulations that can be applied to a large industrial unit (e.g., a large-scale industrial electrolyzer) as well as a small industrial unit (e.g., a small-scale industrial electrolyzer). In Figures 14 and 15, the coordinate axes are shown without specific values. The value of each axis increases along the axis within a range corresponding to the applied scenario. For example, in the scenario where the simulation of Figure 14 is applied to a small industrial unit, the value of the horizontal axis increases along the horizontal axis and is from 1A to 10A. In the scenario where the simulation of Figure 14 is applied to a large industrial unit, the value of the horizontal axis increases along the horizontal axis and is from 1000A to 5000A. [0094] Figure 14 is a simulation figure showing the maximum efficiency and the optimized power of the pump, the heater and the electrolyzer with different supplied current. As shown in Figure 14, the maximum efficiency point of the power-to- hydrogen plant can be tracked with different supplied current. This is especially applicable to the PtH plant that takes energy from fluctuating renewable energy source. [0095] Figure 15 is a simulation figure showing the maximum efficiency point of efficiency (Figure 15(a)), temperature (Figure 15(b)), velocity (Figure 15(c)), voltage (Figure 15(d)) with fluctuating supplied current, where the solid line represents the MEPT control, and the dashed line represents a predetermined value used as a comparison example. It is seen that the MEPT controlling can also be applied to the scenario where the dynamic supplied current is required. Figure 15(a) shows the P2022,2080 WO E / P220053WO01 August 23, 2022 24 optimal efficiency, as well as the operating parameters of the PtH plant, can be acquired timely with the model when the supplied current is fluctuating. Figure 15(b) and (c) are the optimal temperature and velocity of the electrolyte. Compared with the comparison example represented by the dashed line, the optimal temperature and velocity deviate the most from the comparison example of the dashed line when the supplied current is low, this can help explain the highest incensement in efficiency shown in Figure 15(a). [0096] It is noted that all the operations described above are merely exemplary, and the disclosure is not limited to any operations or sequence orders of these operations, and should cover all other equivalents under the same or similar concepts. [0097] Processors are described in connection with various systems and methods. These processors can be implemented using electronic hardware, computer software, or any combination thereof. Whether these processors are implemented as hardware or software will depend on the specific application and the overall design constraints imposed on the system. By way of example, a processor, any portion of a processor, or any combination of processors presented in this disclosure may be implemented as a microprocessor, a micro-controller, a digital signal processor (DSP), a field programmable gate array (FPGA), a programmable logic device (PLD), state machine, gate logic, discrete hardware circuitry, and other suitable processing components configured to perform the various functions described in this disclosure. The functions of a processor, any portion of a processor, or any combination of processors presented in this disclosure may be implemented as software executed by a microprocessor, a micro-controller, a DSP, or other suitable platforms. [0098] The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein. All structural and functional equivalent P2022,2080 WO E / P220053WO01 August 23, 2022 25 transformations to the elements of the various aspects of the disclosure, which are known or to be apparent to those skilled in the art, are intended to be covered by the claims.