Networking operation control method and system of fuel cell / electrolytic cell system

Abstract

The invention discloses a network construction operation control method and system for a fuel cell / electrolytic cell system, and the method comprises the steps: 1, carrying out the modeling of an FC / ELZ control system; and step 2, the DC bus voltage is controlled by using a double-loop controller, the double-loop controller comprises an outer loop controller and an inner loop controller, the outer loop controller is used for realizing the DC bus voltage control, and the inner loop controller is used for realizing the current control of the FC boost converter and the current control of the ELZ buck converter. The method provided by the invention ensures that the voltage of the direct current link is constant, so that the DC-AC inverter can realize alternating current voltage control and power synchronous control of network construction type application.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cell / electrolyzer system control, and in particular to a control method for a fuel cell / electrolyzer system networking type. Background Art

[0002] For power systems based on renewable energy, fluctuations and intermittency are harmful to the stable operation of the system. As a promising method to compensate for the fluctuations and intermittency of renewable energy (RES), power-to-gas (P2G) technology can use excess electricity to produce hydrogen through electrolyzers (ELZ), and when there is a shortage of energy, the energy can be fed back to the grid through fuel cells (FC) using the produced hydrogen. Therefore, P2G units can provide multiple services such as intermittency compensation and frequency support, integrating RES into the grid.

[0003] With the popularity of renewable energy in wind power and photovoltaic power generation, the problems of reduced inertia and stability have received more attention. To solve this problem, grid-connected control is an effective solution to increase the penetration of RES. Since the grid-connected inverter can directly provide a voltage source with virtual inertia, virtual inertia and frequency support can be easily achieved through grid-connected control. However, frequency support usually requires energy storage so that the grid-connected inverter can achieve virtual inertia by providing or storing additional energy from the grid, but after the fuel cell / electrolyzer system is connected to the grid, how to achieve AC voltage control and power synchronization control is a further problem that needs to be solved. Summary of the invention

[0004] The technical problem to be solved by the present invention is: how to achieve AC voltage control and power synchronization control after the fuel cell / electrolyzer system is connected to the grid.

[0005] In order to solve the above technical problems, the present invention provides a grid-building operation control method for a fuel cell / electrolyzer system, wherein the FC and ELZ are connected to a DC bus through an FC boost converter and an ELZ buck converter, respectively, and the DC bus is connected to an AC bus through a bidirectional DC-AC inverter;

[0006] The following steps are involved:

[0007] Model the FC / ELZ control system to obtain the electrical model of FC and the electrical model of ELZ;

[0008] The electrical model of the FC represents the relationship between the voltage of the fuel cell and the current of the fuel cell;

[0009] The electrical model of the ELZ represents the relationship between the voltage of the electrolytic cell and the current of the electrolytic cell;

[0010] A dual-loop controller is used to control the DC bus voltage, the current of the FC boost converter, and the current of the ELZ buck converter, wherein the dual-loop controller includes an outer-loop controller and an inner-loop controller.

[0011] In the aforementioned method for controlling the grid-building operation of a fuel cell / electrolyzer system, the outer loop controller is used to realize DC bus voltage control;

[0012] The inner loop controller implements current control of the FC boost converter based on the current of the fuel cell;

[0013] The inner loop controller implements current control of the ELZ buck converter based on the voltage and current of the electrolyzer.

[0014] In the aforementioned method for controlling the grid operation of a fuel cell / electrolyzer system, the electrical model of FC is expressed as:

[0015]

[0016] where u FC_cell is the voltage of the fuel cell, i FC_cell is the current of the fuel cell, E 0 is the open circuit voltage of the fuel cell, K is the cell polarization coefficient, and are the effective partial pressures of hydrogen and oxygen, respectively, e is a constant, H(s) is a first-order filter with a fast time constant;

[0017] The electrical model of ELZ is expressed as:

[0018]

[0019] Among them, u rev , T ELZ and A are the reversible voltage, temperature and area of ​​the electrode, respectively, K i is the temperature T ELZ The function of u ELZ_cell is the voltage of the electrolytic cell, i ELZ_cell is the current of the electrolytic cell, r 1 is the resistance of the electrolyte, r 2 is the contact resistance between the electrolyte and the electrode.

[0020] In the above-mentioned fuel cell / electrolyzer system grid operation control method, during the current control process of the ELZ buck converter, the voltage signal V d2 For the control input, the closed-loop transfer function (TF) of the current loop is:

[0021]

[0022] where iELZ is the current of the electrolytic cell, i ELZref is the reference current of the electrolytic cell, k pi is the proportional link coefficient, k ii is the integral link coefficient, L sc is the equivalent inductance of the inner current loop, R sc The equivalent resistance of the inner current loop, G cr (s) is the tracking gain, which is a second-order transfer function, and s is the complex frequency variable in the Laplace transform.

[0023] In the above-mentioned fuel cell / electrolyzer system grid operation control method, during the current control process of the FC boost converter, the voltage signal V d1 And the voltage signal is V d2 As the control input, the closed-loop transfer function of the current loop is

[0024] I fc is the fuel cell current, I ref is the reference current or set current, L d is the boost circuit inductor, R d is the boost circuit resistance, U fc is the voltage of the fuel cell, and s is the complex frequency variable in the Laplace transform.

[0025] The above-mentioned fuel cell / electrolyzer system grid operation control method, in the process of DC bus voltage control, has a capacitor C d The power model of the DC bus is expressed as:

[0026]

[0027] where p i Represents the instantaneous power of the inverter, p d is the instantaneous power of FC / ELZ, when p d >0, the instantaneous power comes from FC, when p d <0, instantaneous power will flow into ELZ.

[0028] In the aforementioned grid-building operation control method of the fuel cell / electrolyzer system, the closed loop TF of the DC bus voltage control is:

[0029]

[0030] Among them, u dc is the DC bus voltage, u dcref is the DC bus reference voltage, k pv is the ratio link coefficient, k iv is the integral link coefficient, C d is the equivalent capacitance of the voltage outer loop.

[0031] The aforementioned grid-connected operation control method of the fuel cell / electrolyzer system further includes performing AC side voltage control. The complex state space-based model of the three-phase inverter with an LC filter is as follows:

[0032]

[0033] in, is the state vector of the system, A p is the state matrix, B p1 , B p2 are input matrix one and input matrix two, v c is the control input voltage, i l is the input current of the three-phase AC side, y is the output vector, C p is the output matrix;

[0034] In formula (6), the complex state variable x p :[i L u C ] T =[i Ld +ji Lq u Cd +ju Cq ] T represents the inductor current and capacitor voltage, i l =i ld +ji lq Represents the disturbance from the outside; the midpoint voltage of the bridge arm v c =v Cd +jv cq is the control input, define A 1 =1 / L and A 2 =1 / C, where i Ld is the inductor d-axis current vector, i Lq is the inductor q-axis current vector, u Cd is the capacitor d-axis voltage vector, u Cq is the capacitor q-axis voltage vector, T represents transposition, i ld is the external disturbance d-axis current vector, i lq is the external disturbance q-axis current vector, v Cd Input voltage d-axis voltage vector, v cq is the input voltage q-axis voltage vector, L and C are the equivalent inductance and equivalent capacitance respectively, so the matrix in formula (7) is derived:

[0035]

[0036] Among them, a 1 、a 2is the coefficient of the system dynamic characteristics, ω is the angular frequency, and R is the resistance of the AC side transmission line;

[0037] The state variables of the integrator are defined as:

[0038]

[0039] in, is the small change in the state variable of the integrator, x c is the state variable of the integrator, e c is the control error, u Cref is the desired control input voltage, u C is the actual control input voltage;

[0040] The open-loop system of the AC voltage control process is expressed as:

[0041]

[0042] where x = [x p x c ] T =[i L u C x c ] T represents the augmented state variable, is the derivative of x, then the capacitor voltage control equation is: c =-k p1 i L -k p2 u C -k c x c +k d i l +k r u Cref (10)

[0043] k p1 , k p2 is the proportional coefficient 1 and proportional coefficient 2 of the AC voltage closed-loop control, k c is the integral coefficient of AC voltage closed-loop control, k d is the integral coefficient of AC voltage closed-loop control, k r is the proportional coefficient of AC voltage closed-loop control;

[0044] The closed-loop system is expressed as:

[0045]

[0046] Among them, A c is the state matrix of the closed-loop system, B 2c , B rcare input matrix one and input matrix two, is a state vector of the voltage vector, in formula (11),

[0047]

[0048] B 2c =[a 1 k d -a 2 0] T , B rc =[a 1 k r 0 1] T ;

[0049] State feedback gain K = -[k p1 k p2 k c ] The integral coefficient k of the feedforward AC voltage closed-loop control is set by the pole configuration method. d And the proportional coefficient k of AC voltage closed loop control r By setting the pole-zero elimination, the closed-loop TF is expressed as:

[0050]

[0051] Among them, s represents the variable in Laplace transform, I represents the identity matrix, and y ref represents the reference output, p n represents the natural pole of the system, represents the pole position expected by control design, G d , G r , Z d (s), Z r (s) respectively represent the preset transfer function 1, preset transfer function 2, preset transfer function 3, and preset transfer function 4 related to the reference input to the output. In equation (12),

[0052] Z d (s) = a 2 s(a 1 k d -s-jω-a 1 Ra 1 k p1 ) (13)

[0053] Z r (s) = a 1 a 2 (k r sk c ) (14).

[0054] In the above-mentioned fuel cell / electrolyzer system grid operation control method, the inverter adopts power synchronization control to control the active power output p of the inverter. i and the inverter's reactive power output q i The mathematical model is expressed as ΔU = U c -U g ,

[0055]

[0056] Where Δδ represents the phase difference, X = ωL g , p i represents the active power output of the inverter, q i Indicates the reactive power output of the inverter, U c Indicates the inverter output voltage, U g Indicates the grid voltage, L g Equivalent inductance of the inverter output filter.

[0057] In the aforementioned grid-building operation control method of the fuel cell / electrolyzer system, the TF of the active power control is expressed as:

[0058]

[0059] Among them G rp (s) is the transfer function of the active power controller, G ωp (s) is the transfer function of angular velocity, p iref is the reference value of active power, k iω is the control gain coefficient of angular velocity, Δω g Represents the change of grid frequency, Δω g =ω n -ω g ,ω n represents the natural frequency or intrinsic frequency of the system, ω g Indicates the angular frequency of the power grid.

[0060] In the aforementioned grid-connected operation control method of the fuel cell / electrolyzer system, the reactive power first-order closed-loop controller is:

[0061]

[0062] Among them, q i is the input of the controller, G rq (s) is the transfer function of the reactive power controller, G Vq (s) is the transfer function of the input voltage, ΔV is the change in voltage, B is the damping coefficient, k iq is the controller gain factor, q iref It is the reference value of reactive power.

[0063] A computer device / equipment / system, comprising a memory, a processor and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the following method:

[0064] A method for controlling the networking and operation of a fuel cell / electrolyzer system, comprising:

[0065] The FC and ELZ are connected to the DC bus through the FC boost converter and the ELZ buck converter respectively, and the DC bus is connected to the AC bus through a bidirectional DC-AC inverter;

[0066] Model the FC / ELZ control system to obtain the electrical model of FC and the electrical model of ELZ;

[0067] The electrical model of the FC represents the relationship between the voltage of the fuel cell and the current of the fuel cell;

[0068] The electrical model of the ELZ represents the relationship between the voltage of the electrolytic cell and the current of the electrolytic cell;

[0069] A dual-loop controller is used to control the DC bus voltage, the current of the FC boost converter, and the current of the ELZ buck converter, wherein the dual-loop controller includes an outer-loop controller and an inner-loop controller;

[0070] The outer loop controller is used to realize DC bus voltage control;

[0071] The inner loop controller implements current control of the FC boost converter based on the current of the fuel cell;

[0072] The inner loop controller implements current control of the ELZ buck converter based on the voltage and current of the electrolyzer.

[0073] The electrical model of the computer device / equipment / system mentioned above is represented as follows:

[0074]

[0075] where u FC_cell is the voltage of the fuel cell, i FC_cell is the current of the fuel cell, E 0 is the open circuit voltage of the fuel cell, K is the cell polarization coefficient, and are the effective partial pressures of hydrogen and oxygen, respectively, e is a constant, H(s) is a first-order filter with a fast time constant;

[0076] The electrical model of ELZ is expressed as:

[0077]

[0078] Among them, u rev 、T ELZ and A are the reversible voltage, temperature and area of ​​the electrode, respectively, K i is the temperature T ELZ The function of u ELZ_cell is the voltage of the electrolytic cell, i ELZ_cell is the current of the electrolytic cell, r 1 is the resistance of the electrolyte, r 2 is the contact resistance between the electrolyte and the electrode.

[0079] The aforementioned computer device / equipment / system performs current control of the ELZ buck converter, and the voltage signal V d2 For the control input, the closed-loop transfer function (TF) of the current loop is:

[0080]

[0081] where i ELZ is the current of the electrolytic cell, i ELZref is the reference current of the electrolytic cell, k pi is the proportional link coefficient, k ii is the integral link coefficient, L sc is the equivalent inductance of the inner current loop, R sc The equivalent resistance of the inner current loop, G cr (s) is the tracking gain, which is a second-order transfer function, and s is the complex frequency variable in the Laplace transform.

[0082] The aforementioned computer device / equipment / system performs current control of the FC boost converter, and the voltage signal V d1 And the voltage signal is V d2 As the control input, the closed-loop transfer function of the current loop is

[0083] I fc is the fuel cell current, I ref is the reference current or set current, L d is the boost circuit inductor, R d is the boost circuit resistance, U fc is the voltage of the fuel cell, and s is the complex frequency variable in the Laplace transform.

[0084] The aforementioned computer device / equipment / system, during the DC bus voltage control process, has a capacitor C d The power model of the DC bus is expressed as:

[0085]

[0086] where p i Represents the instantaneous power of the inverter, p d is the instantaneous power of FC / ELZ, when p d > 0, the instantaneous power comes from FC, when p d <0, instantaneous power will flow into ELZ.

[0087] In the aforementioned computer device / equipment / system, the closed loop TF of the DC bus voltage control is:

[0088]

[0089] Among them, u dc is the DC bus voltage, u dcref is the DC bus reference voltage, k pv is the ratio link coefficient, k iv is the integral link coefficient, C d is the equivalent capacitance of the voltage outer loop.

[0090] The aforementioned computer device / equipment / system further includes a complex state space-based model of a three-phase inverter with an LC filter for performing AC side voltage control as follows:

[0091]

[0092] in, is the state vector of the system, A p is the state matrix, B p1 , B p2 are input matrix one and input matrix two, v c is the control input voltage, i l is the input current of the three-phase AC side, y is the output vector, C p is the output matrix;

[0093] In formula (6), the complex state variable x p :[i L u C ] T =[i Ld +ji Lq u Cd +ju Cq ] T represents the inductor current and capacitor voltage, i l =i ld +ji lq Represents the disturbance from the outside; the midpoint voltage of the bridge arm v c =v Cd +jv cq is the control input, define A 1 =1 / L and A2 =1 / C, where i Ld is the inductor d-axis current vector, i Lq is the inductor q-axis current vector, u Cd is the capacitor d-axis voltage vector, u Cq is the capacitor q-axis voltage vector, T represents transposition, i ld is the external disturbance d-axis current vector, i lq is the external disturbance q-axis current vector, v Cd Input voltage d-axis voltage vector, v cq is the input voltage q-axis voltage vector, L and C are the equivalent inductance and equivalent capacitance respectively, so the matrix in formula (7) is derived:

[0094]

[0095] Among them, a 1 、a 2 is the coefficient of the system dynamic characteristics, ω is the angular frequency, and R is the resistance of the AC side transmission line;

[0096] The state variables of the integrator are defined as:

[0097]

[0098] in, is the small change in the state variable of the integrator, x c is the state variable of the integrator, e c is the control error, u Cref is the desired control input voltage, u C is the actual control input voltage;

[0099] The open-loop system of the AC voltage control process is expressed as:

[0100]

[0101] where x = [x p x c ] T =[i L u C x c ] T represents the augmented state variable, is the derivative of x, then the capacitor voltage control equation is: c =-k p1 i L -k p2 u C -k c x c +k d i l +kr u Cref (10)

[0102] k p1 , k p2 is the proportional coefficient 1 and proportional coefficient 2 of the AC voltage closed-loop control, k c is the integral coefficient of AC voltage closed-loop control, k d is the integral coefficient of AC voltage closed-loop control, k r is the proportional coefficient of AC voltage closed-loop control;

[0103] The closed-loop system is expressed as:

[0104]

[0105] Among them, A c is the state matrix of the closed-loop system, B 2c , B rc are input matrix one and input matrix two, is a state vector of the voltage vector, in formula (11),

[0106]

[0107] B 2c =[a 1 k d -a 2 0] T , B rc =[a 1 k r 0 1] T ;

[0108] State feedback gain K = -[k p1 k p2 k c ] The integral coefficient k of the feedforward AC voltage closed-loop control is set by the pole configuration method. d And the proportional coefficient k of AC voltage closed loop control r By setting the pole-zero elimination, the closed-loop TF is expressed as:

[0109]

[0110] Among them, s represents the variable in Laplace transform, I represents the identity matrix, and y ref represents the reference output, p n represents the natural pole of the system, represents the pole position expected by control design, G d , G r , Z d (s), Z r(s) respectively represent the preset transfer function 1, preset transfer function 2, preset transfer function 3, and preset transfer function 4 related to the reference input to the output. In equation (12),

[0111] Z d (s) = a 2 s(a 1 k d -s-jω-a 1 Ra 1 k p1 ) (13)

[0112] Z r (s) = a 1 a 2 (k r sk c ) (14).

[0113] The aforementioned computer device / equipment / system, the inverter adopts power synchronization control to control the active power output p of the inverter i and the inverter's reactive power output q i The mathematical model is expressed as ΔU = U c -U g ,

[0114]

[0115] Where Δδ represents the phase difference, X = ωL g , p i represents the active power output of the inverter, q i Indicates the reactive power output of the inverter, U c Indicates the inverter output voltage, U g Indicates the grid voltage, L g Equivalent inductance of the inverter output filter.

[0116] In the aforementioned computer device / equipment / system, the TF of active power control is expressed as:

[0117]

[0118] Among them G rp (s) is the transfer function of the active power controller, G ωp (s) is the transfer function of angular velocity, p iref is the reference value of active power, k iω is the control gain coefficient of angular velocity, Δω g Represents the change of grid frequency, Δω g =ω n -ω g ,ω nrepresents the natural frequency or intrinsic frequency of the system, ω g Indicates the angular frequency of the power grid.

[0119] In the aforementioned computer device / equipment / system, the reactive power first-order closed-loop controller is:

[0120]

[0121] Among them, q i is the input of the controller, G rq (s) is the transfer function of the reactive power controller, G Vq (s) is the transfer function of the input voltage, ΔV is the change in voltage, B is the damping coefficient, k iq is the controller gain factor, q iref It is the reference value of reactive power.

[0122] A computer-readable storage medium stores a computer program / instruction, which implements the steps of the above method when executed by a processor.

[0123] A computer program product comprises a computer program / instruction, which implements the steps of the above method when executed by a processor.

[0124] Beneficial effects achieved by the present invention: A grid-connected operation control method for a fuel cell / electrolyzer system of the present invention controls the FC / ELZ system as a grid-connected application to provide frequency support for the power grid, the voltage of the DC loop is controlled by FC and ELZ through step-up and step-down converters, and the DC-AC inverter is controlled as a voltage source to achieve grid-connected control, ensuring that the entire system can operate independently, the DC and AC ports can be used to connect other DC and AC power sources or loads, the DC bus voltage is controlled by a dual-loop controller, wherein the outer loop is DC voltage control, and the inner loop includes FC current control and ELZ current control, thereby ensuring that the DC link voltage is constant, enabling the DC-AC inverter to achieve AC voltage control and power synchronization control for grid-connected applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0125] Figure 1 This is a schematic diagram of the structure of the fuel cell and electrolyzer system in Example 1;

[0126] Figure 2 The overall control principle diagram of the fuel cell and electrolyzer system in Example 1;

[0127] Figure 3 Schematic diagram of the small signal control principle of the ELZ current in Example 1;

[0128] Figure 4 This is a schematic diagram of the small signal control principle of the FC current in Example 1;

[0129] Figure 5 This is a schematic diagram of the DC bus voltage control principle based on the power model in Example 2;

[0130] Figure 6 This is a schematic diagram of the small signal control principle of active power control in Example 2. DETAILED DESCRIPTION

[0131] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0132] Example 1

[0133] like Figure 1 As shown, the fuel cell and electrolyzer control system includes a fuel cell and an electrolyzer, the fuel cell and the electrolyzer are connected to a DC bus through a boost converter and a buck converter respectively, and the DC bus is connected to an AC bus through a bidirectional DC-AC inverter.

[0134] The present invention controls the fuel cell and electrolyzer system as a grid-connected application to provide frequency support for the grid. The voltage of the DC loop must be controlled by FC and ELZ through step-up and step-down converters, and the DC-AC inverter will be controlled as a voltage source to achieve grid-connected application, thereby ensuring that the entire system can operate independently. The DC and AC ports can be used to connect other DC and AC power sources or loads.

[0135] This embodiment provides a method for controlling the networking operation of a fuel cell / electrolyzer system, comprising the following steps:

[0136] Step 1: Model the overall FC / ELZ control system, select the models of FC and ELZ, and design a dual-loop control method for voltage and current. From the perspective of control design, the electrical models of FC and ELZ are represented by the output VI characteristics. The electrical model of FC represents the relationship between the voltage of the fuel cell and the current of the fuel cell; the electrical model of ELZ represents the relationship between the voltage of the electrolyzer and the current of the electrolyzer;

[0137] The electrical model of FC is expressed as:

[0138]

[0139] where u FC_cell is the voltage of the fuel cell, E 0 is the open circuit voltage of the fuel cell, K is the cell polarization coefficient, and are the effective partial pressures of hydrogen and oxygen respectively. The third term in equation (1) represents the voltage drop, where λ e is a constant, H(s) is a first-order filter with a fast time constant;

[0140] like Figure 2 As shown, the electrical model of ELZ is expressed as:

[0141]

[0142] Among them, u rev , T ELZ and A are the reversible voltage, temperature and area of ​​the electrode, respectively, K i is the temperature T ELZ The function of u ELZ_cell is the voltage of the electrolytic cell, i ELZ_cell is the current of the electrolytic cell, r 1 is the resistance of the electrolyte, r 2 is the contact resistance between the electrolyte and the electrode, Figure 2 The current reference direction is marked in the middle;

[0143] Step 2: Use a dual-loop controller to control the DC bus voltage, the current of the FC boost converter, and the current of the ELZ buck converter. The dual-loop controller includes an outer loop controller and an inner loop controller, such as Figure 2 As shown, the outer loop controller is used to realize the DC link voltage control, and the inner loop controller is used to realize the current control of the FC boost converter and the current control of the ELZ buck converter. The ELZ and FC current references are respectively subject to [-I max ,0] and [0,I max ] to ensure the correct power direction; the dual-loop controller ensures the constant voltage of the DC link, enabling the DC-AC inverter to achieve grid-type control, thereby ensuring AC voltage control and power synchronization control. Figure 2 The overall control of the DC-DC and DC-AC converters shown by the blue arrows in the middle has a fast dynamic response and achieves power balance of the FC / ELZ system. The pressure of the hydrogen tank can be managed by the Energy Management System (EMS), which adjusts the power baseline of the system to achieve energy optimization.

[0144] Step 21: Perform current control of the ELZ buck converter;

[0145] ELZ current control small signal control diagram is as follows Figure 3 As shown, the voltage signal is V d2 For the control input, a switching frequency average model is adopted. The disturbance of the ELZ voltage can be ignored because the offset voltage is constant according to formula (2), and the dynamic part can be linearized into a resistor, which can be regarded as the equivalent series resistance (ESR) of the inductor. However, considering the worst damping condition of the system, the ESR is omitted in the model. In this case, the closed-loop transfer function (TF) of the current loop is:

[0146]

[0147] where i ELZ is the current of the electrolytic cell, i ELZref is the reference current of the electrolytic cell, k pi is the proportional link coefficient, k ii is the integral link coefficient, L sc is the equivalent inductance of the inner current loop, R sc The equivalent resistance of the inner current loop.

[0148] Reference tracking gain G cr (s) is the second-order transfer function. According to the system's requirement for fast dynamic response, the bandwidth should be as high as possible. Therefore, the PI parameters can be determined by selecting the characteristic roots with higher damped oscillation frequency and critical damping factor. s is the complex frequency variable in the Laplace transform.

[0149] Step 22: Perform current control of the FC boost converter;

[0150] Figure 4 This is the small signal control principle diagram of FC boost current control. Figure 3 and Figure 4 It can be seen that the voltage signal is selected as V d1 And the voltage signal is V d2 As the control input, the boost current control and the buck current control of ELZ have the same transfer function (3). This symmetrical design is beneficial to the DC bus voltage control because both the FC and ELZ current loops act as the inner loop of the DC voltage loop but have different current directions. Therefore, the FC current loop uses the same control parameters and the same model can be used for the external DC bus voltage control. Voltage signal - v d1 And the voltage signal is V d2 The voltage can be modulated by corresponding pulse width modulation (PWM);

[0151] The closed-loop transfer function of the current loop is I fc is the fuel cell current, I ref is the reference current or set current, L d is the boost circuit inductor, R d is the boost circuit resistance, U fc is the voltage of the fuel cell, and s is the complex frequency variable in the Laplace transform.

[0152] Step 23: Perform DC voltage control;

[0153] The DC voltage control is designed based on the power model, ignoring the instantaneous power of the inductor, with capacitor C dThe power model of the DC bus is expressed as:

[0154]

[0155] where p i Represents the instantaneous power of the inverter, p d is the instantaneous power of FC / ELZ, when p d >0, the instantaneous power comes from FC, when p d <0, the instantaneous power will flow into ELZ, which is automatically determined by the reference limit of the current loop of FC and ELZ.

[0156] The outer loop bandwidth is designed to be one fifth of the current loop bandwidth. Therefore, the inner loop can be regarded as a link. The instantaneous power of the DC-AC inverter is used as feedforward to improve the dynamic response of the system. The closed-loop TF of the DC bus voltage control is:

[0157]

[0158] Among them, u dc is the DC bus voltage, u dcref is the DC bus reference voltage, k pv is the ratio link coefficient, k iv is the integral link coefficient, C d is the equivalent capacitance of the voltage outer loop.

[0159] Example 2

[0160] A method for controlling the networking and operation of a fuel cell / electrolyzer system, based on Embodiment 1, further comprising:

[0161] Step 24: Perform AC side voltage control;

[0162] When the DC voltage is constant, the voltage control of the inverter can be designed. The complex state space-based model of the three-phase inverter with LC filter is as follows:

[0163]

[0164] in, is the state vector of the system, A p is the state matrix, B p1 , B p2 are input matrix one and input matrix two, v c is the control input voltage, i l is the input current of the three-phase AC side, y is the output vector, C p is the output matrix.

[0165] In this model, the complex state variable x p :[iL u C ] T =[i Ld +ji Lq u Cd +ju Cq ] T represents the inductor current and capacitor voltage, i l =i ld +ji lq Represents the disturbance from the outside; the midpoint voltage of the bridge arm v c =v Cd +jv cq is the control input, define A 1 =1 / L and A 2 =1 / C, where i Ld is the inductor d-axis current vector, i Lq is the inductor q-axis current vector, u Cd is the capacitor d-axis voltage vector, u Cq is the capacitor q-axis voltage vector, T represents the transpose, i ld is the external disturbance d-axis current vector, i lq is the external disturbance q-axis current vector, v Cd Input voltage d-axis voltage vector, v cq is the input voltage q-axis voltage vector, L and C are the equivalent inductance and equivalent capacitance respectively, so the matrix in formula (6) can be derived:

[0166]

[0167] where a 1 、a 2 is the coefficient of the system dynamic characteristics, ω is the angular frequency, and R is the resistance of the AC side transmission line;

[0168] The state variables of the integrator are defined as:

[0169]

[0170] Among them, x c is the state variable of the integrator, is the state variable derivative of the integrator, e c is the control error, u Cref is the desired control input voltage, u C is the actual control input voltage;

[0171] The open-loop system of the AC voltage control scheme is expressed as:

[0172]

[0173] where x = [x px c ] T =[i L u C x c ] T represents the augmented state variable, is the derivative of x, then the capacitor voltage control equation is: c =-k p1 i L -k p2 u C -k c x c +k d i l +k r u Cref (10)

[0174] k p1 , k p2 is the proportional coefficient 1 and proportional coefficient 2 of the AC voltage closed-loop control, k c is the integral coefficient of AC voltage closed-loop control, k d is the integral coefficient of AC voltage closed-loop control, k r is the proportional coefficient of AC voltage closed-loop control.

[0175] The closed-loop system is expressed as:

[0176]

[0177] Among them, A c is the state matrix of the closed-loop system, B 2c , B rc are input matrix one and input matrix two, is a state vector of the voltage vector, including the α phase component and the β phase component,

[0178] In formula (11),

[0179]

[0180] B 2c =[a 1 k d -a 2 0] T , B rc =[a 1 k r 0 1] T ;

[0181] State feedback gain K = -[k p1 k p2 k c ] is set by the pole placement method, the feedforward kd and k r By setting the pole-zero elimination, the closed-loop TF is expressed as:

[0182]

[0183] Among them, s represents the variable in Laplace transform, I represents the identity matrix, and y ref represents the reference output, p n represents the natural pole of the system, represents the desired pole position through control design (such as pole placement), G d , G r , Z d (s), Z r (s) represent preset transfer function 1, preset transfer function 2, preset transfer function 3, and preset transfer function 4 respectively related to the reference input to the output;

[0184] In formula (12), Z d (s) = a 2 s(a 1 k d -s-jω-a 1 Ra 1 k p1 ) (13)

[0185] Z r (s) = a 1 a 2 (k r sk c ) (14)

[0186] In formula (14), k d and k r It can be determined by pole-zero cancellation.

[0187] Because the active power between the inverter and the grid is adjusted according to the frequency, in order to achieve grid-type control, the inverter can adopt power synchronization control (PSC). PSC is as follows Figure 5 As shown, ignoring the line resistance, the active power output p of the inverter is controlled i and the inverter's reactive power output q i The mathematical model is expressed as ΔU = U c -U g ,

[0188]

[0189] Where Δδ represents the phase difference, X = ωL g , p i represents the active power output of the inverter, q iIndicates the reactive power output of the inverter, U c Indicates the inverter output voltage, U g Represents the grid voltage, ω n represents the natural frequency or intrinsic frequency of the system, ω g represents the angular frequency of the power grid, Δω g Indicates the change of grid frequency, L g The equivalent inductance of the inverter output filter and the small signal schematic diagram of active power control are given by Figure 6 As shown, where Δω g =ω n -ω g .

[0190] The TF for active power control can be derived as:

[0191]

[0192] Among them G rp (s) is the transfer function of the active power controller, G ωp (s) is the transfer function of angular velocity, p iref is the reference value of active power, k iω is the control gain coefficient of angular velocity.

[0193] It can be seen from formula (16) that G rp (0) = 1 and G ωp (0) = D p , proves that the proposed controller can achieve power reference tracking and droop functions, D p represents the droop coefficient. In addition, unlike traditional power control, the gain k is introduced pω To adjust the damping ratio of the loop, so that D p can be released and used only as a droop coefficient. Finally, based on equation (16), the parameters of active power control can be designed based on the desired droop coefficient, damped oscillation frequency and damping factor.

[0194] The reactive power controller is a simple integrator, and the resulting first-order closed-loop controller is:

[0195]

[0196] Among them, q i is the input of the controller, G rq (s) is the transfer function of the reactive power controller, G Vq (s) is the transfer function of the input voltage, ΔV is the change in voltage, B is the damping coefficient, k iq is the controller gain factor, q iref It is the reference value of reactive power.

[0197] It can also be observed from (17) that when the grid voltage changes, due to G Vq (s) = 0, so QV droop cannot be achieved. The QV droop in equation (17) can be simply achieved by replacing the integrator with a first-order low-pass filter.

[0198] A computer device / equipment / system, comprising a memory, a processor and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the following method, specifically comprising the following steps:

[0199] A grid-building operation control method for a fuel cell / electrolyzer system, wherein FC and ELZ are connected to a DC bus through an FC boost converter and an ELZ buck converter, respectively, and the DC bus is connected to an AC bus through a bidirectional DC-AC inverter;

[0200] Model the FC / ELZ control system to obtain the electrical model of FC and the electrical model of ELZ;

[0201] The electrical model of the FC represents the relationship between the voltage of the fuel cell and the current of the fuel cell;

[0202] The electrical model of the ELZ represents the relationship between the voltage of the electrolytic cell and the current of the electrolytic cell;

[0203] A dual-loop controller is used to control the DC bus voltage, the current of the FC boost converter, and the current of the ELZ buck converter, wherein the dual-loop controller includes an outer-loop controller and an inner-loop controller;

[0204] The outer loop controller is used to realize DC bus voltage control;

[0205] The inner loop controller implements current control of the FC boost converter based on the current of the fuel cell;

[0206] The inner loop controller implements current control of the ELZ buck converter based on the voltage and current of the electrolyzer.

[0207] In the above-mentioned method for controlling the grid operation of a fuel cell / electrolyzer system, the electrical model of FC is expressed as:

[0208]

[0209] where u FC_cell is the voltage of the fuel cell, i FC_cell is the current of the fuel cell, E 0 is the open circuit voltage of the fuel cell, K is the cell polarization coefficient, and are the effective partial pressures of hydrogen and oxygen, respectively, eis a constant, H(s) is a first-order filter with a fast time constant;

[0210] The electrical model of ELZ is expressed as:

[0211]

[0212] Among them, u rev 、T ELZ and A are the reversible voltage, temperature and area of ​​the electrode, respectively, K i is the temperature T ELZ The function of u ELZ_cell is the voltage of the electrolytic cell, i ELZ_cell is the current of the electrolytic cell, r 1 is the resistance of the electrolyte, r 2 is the contact resistance between the electrolyte and the electrode.

[0213] The above-mentioned fuel cell / electrolyzer system grid operation control method performs the current control process of the ELZ buck converter, and the voltage signal is V d2 For the control input, the closed-loop transfer function (TF) of the current loop is:

[0214]

[0215] where i ELZ is the current of the electrolytic cell, i ELZref is the reference current of the electrolytic cell, k pi is the proportional link coefficient, k ii is the integral link coefficient, L sc is the equivalent inductance of the inner current loop, R sc The equivalent resistance of the inner current loop, G cr (s) is the tracking gain, which is a second-order transfer function, and s is the complex frequency variable in the Laplace transform.

[0216] In the above-mentioned fuel cell / electrolyzer system grid operation control method, during the current control process of the FC boost converter, the voltage signal V d1 And the voltage signal is V d2 As the control input, the closed-loop transfer function of the current loop is

[0217] I fc is the fuel cell current, I ref is the reference current or set current, L d is the boost circuit inductor, R d is the boost circuit resistance, U fc is the voltage of the fuel cell, and s is the complex frequency variable in the Laplace transform.

[0218] The above-mentioned fuel cell / electrolyzer system grid operation control method, in the process of DC bus voltage control, has a capacitor C d The power model of the DC bus is expressed as:

[0219]

[0220] where p i Represents the instantaneous power of the inverter, p d is the instantaneous power of FC / ELZ, when p d >0, the instantaneous power comes from FC, when p d <0, instantaneous power will flow into ELZ.

[0221] In the aforementioned grid-building operation control method of the fuel cell / electrolyzer system, the closed loop TF of the DC bus voltage control is:

[0222]

[0223] Among them, u dc is the DC bus voltage, u dcref is the DC bus reference voltage, k pv is the ratio link coefficient, k iv is the integral link coefficient, C d is the equivalent capacitance of the voltage outer loop.

[0224] The above-mentioned fuel cell / electrolyzer system grid operation control method also includes AC side voltage control. The complex state space-based model of the three-phase inverter with LC filter is as follows:

[0225]

[0226] in, is the state vector of the system, A p is the state matrix, B p1 , B p2 are input matrix one and input matrix two, v c is the control input voltage, i l is the input current of the three-phase AC side, y is the output vector, C p is the output matrix;

[0227] In formula (6), the complex state variable x p :[i L u C ] T =[i Ld +ji Lq u Cd +ju Cq ] T represents the inductor current and capacitor voltage, il =i ld +ji lq Represents the disturbance from the outside; the midpoint voltage of the bridge arm v c =v Cd +jv cq is the control input, define A 1 =1 / L and A 2 =1 / C, where i Ld is the inductor d-axis current vector, i Lq is the inductor q-axis current vector, u Cd is the capacitor d-axis voltage vector, u Cq is the capacitor q-axis voltage vector, T represents the transpose, i ld is the external disturbance d-axis current vector, i lq is the external disturbance q-axis current vector, v Cd Input voltage d-axis voltage vector, v cq is the input voltage q-axis voltage vector, L and C are the equivalent inductance and equivalent capacitance respectively, so the matrix in formula (7) is derived:

[0228]

[0229] Among them, a 1 、a 2 is the coefficient of the system dynamic characteristics, ω is the angular frequency, and R is the resistance of the AC side transmission line;

[0230] The state variables of the integrator are defined as:

[0231]

[0232] in, is the small change in the state variable of the integrator, x c is the state variable of the integrator, e c is the control error, u Cref is the desired control input voltage, u C is the actual control input voltage;

[0233] The open-loop system of the AC voltage control process is expressed as:

[0234]

[0235] where x = [x p x c ] T =[i L u C x c ] T represents the augmented state variable, is the derivative of x, then the capacitor voltage control equation is:c =-k p1 i L -k p2 u C -k c x c +k d i l +k r u Cref (10)

[0236] k p1 , k p2 is the proportional coefficient 1 and proportional coefficient 2 of the AC voltage closed-loop control, k c is the integral coefficient of AC voltage closed-loop control, k d is the integral coefficient of AC voltage closed-loop control, k r is the proportional coefficient of AC voltage closed-loop control;

[0237] The closed-loop system is expressed as:

[0238]

[0239] Among them, A c is the state matrix of the closed-loop system, B 2c , B rc are input matrix one and input matrix two, is a state vector of the voltage vector, in formula (11),

[0240]

[0241] B 2c =[a 1 k d -a 2 0] T , B rc =[a 1 k r 0 1] T ;

[0242] State feedback gain K = -[k p1 k p2 k c ] The integral coefficient k of the feedforward AC voltage closed-loop control is set by the pole configuration method. d And the proportional coefficient k of AC voltage closed loop control r By setting the pole-zero elimination, the closed-loop TF is expressed as:

[0243]

[0244] Among them, s represents the variable in Laplace transform, I represents the identity matrix, and yref represents the reference output, p n represents the natural pole of the system, represents the pole position expected by control design, G d , G r , Z d (s), Z r (s) respectively represent the preset transfer function 1, preset transfer function 2, preset transfer function 3, and preset transfer function 4 related to the reference input to the output. In equation (12),

[0245] Z d (s) = a 2 s(a 1 k d -s-jω-a 1 Ra 1 k p1 ) (13)

[0246] Z r (s) = a 1 a 2 (k r sk c ) (14).

[0247] In the above-mentioned fuel cell / electrolyzer system grid operation control method, the inverter adopts power synchronization control to control the active power output p of the inverter. i and the inverter's reactive power output q i The mathematical model is expressed as ΔU = U c -U g ,

[0248]

[0249] Where Δδ represents the phase difference, X = ωL g , p i represents the active power output of the inverter, q i Indicates the reactive power output of the inverter, U c Indicates the inverter output voltage, U g Indicates the grid voltage, L g Equivalent inductance of the inverter output filter.

[0250] In the above-mentioned fuel cell / electrolyzer system grid operation control method, the TF of active power control is expressed as:

[0251]

[0252] Among them G rp (s) is the transfer function of the active power controller, G ωp(s) is the transfer function of angular velocity, p iref is the reference value of active power, k iω is the control gain coefficient of angular velocity, Δω g Represents the change of grid frequency, Δω g =ω n ω g ,ω n represents the natural frequency or intrinsic frequency of the system, ω g Indicates the angular frequency of the power grid.

[0253] In the above-mentioned fuel cell / electrolyzer system grid operation control method, the reactive power first-order closed-loop controller is:

[0254]

[0255] Among them, q i is the input of the controller, G rq (s) is the transfer function of the reactive power controller, G Vq (s) is the transfer function of the input voltage, ΔV is the change in voltage, B is the damping coefficient, k iq is the controller gain factor, q iref It is the reference value of reactive power.

[0256] A computer-readable storage medium stores a computer program / instruction, which implements the steps of the above method when executed by a processor.

[0257] A computer program product, comprising a computer program / instruction, wherein when the computer program / instruction is executed by a processor, the steps of the above method are implemented, specifically comprising the following steps:

[0258] A grid-building operation control method for a fuel cell / electrolyzer system, wherein FC and ELZ are connected to a DC bus through an FC boost converter and an ELZ buck converter, respectively, and the DC bus is connected to an AC bus through a bidirectional DC-AC inverter;

[0259] Model the FC / ELZ control system to obtain the electrical model of FC and the electrical model of ELZ;

[0260] The electrical model of the FC represents the relationship between the voltage of the fuel cell and the current of the fuel cell;

[0261] The electrical model of the ELZ represents the relationship between the voltage of the electrolytic cell and the current of the electrolytic cell;

[0262] A dual-loop controller is used to control the DC bus voltage, the current of the FC boost converter, and the current of the ELZ buck converter, wherein the dual-loop controller includes an outer-loop controller and an inner-loop controller;

[0263] The outer loop controller is used to realize DC bus voltage control;

[0264] The inner loop controller implements current control of the FC boost converter based on the current of the fuel cell;

[0265] The inner loop controller implements current control of the ELZ buck converter based on the voltage and current of the electrolyzer.

[0266] In the above-mentioned method for controlling the grid operation of a fuel cell / electrolyzer system, the electrical model of FC is expressed as:

[0267]

[0268] where u FC_cell is the voltage of the fuel cell, i FC_cell is the current of the fuel cell, E 0 is the open circuit voltage of the fuel cell, K is the cell polarization coefficient, and are the effective partial pressures of hydrogen and oxygen, respectively, e is a constant, H(s) is a first-order filter with a fast time constant;

[0269] The electrical model of ELZ is expressed as:

[0270]

[0271] Among them, u rev , T ELZ and A are the reversible voltage, temperature and area of ​​the electrode, respectively, K i is the temperature T ELZ The function of u ELZ_cell is the voltage of the electrolytic cell, i ELZ_cell is the current of the electrolytic cell, r 1 is the resistance of the electrolyte, r 2 is the contact resistance between the electrolyte and the electrode.

[0272] The above-mentioned fuel cell / electrolyzer system grid operation control method performs the current control process of the ELZ buck converter, and the voltage signal is V d2 For the control input, the closed-loop transfer function (TF) of the current loop is:

[0273]

[0274] where i ELZ is the current of the electrolytic cell, i ELZref is the reference current of the electrolytic cell, k pi is the proportional link coefficient, k ii is the integral link coefficient, Lsc is the equivalent inductance of the inner current loop, R sc The equivalent resistance of the inner current loop, G cr (s) is the tracking gain, which is a second-order transfer function, and s is the complex frequency variable in the Laplace transform.

[0275] In the above-mentioned fuel cell / electrolyzer system grid operation control method, during the current control process of the FC boost converter, the voltage signal V d1 And the voltage signal is V d2 As the control input, the closed-loop transfer function of the current loop is

[0276] I fc is the fuel cell current, I ref is the reference current or set current, L d is the boost circuit inductor, R d is the boost circuit resistance, U fc is the voltage of the fuel cell, and s is the complex frequency variable in the Laplace transform.

[0277] The above-mentioned fuel cell / electrolyzer system grid operation control method, in the process of DC bus voltage control, has a capacitor C d The power model of the DC bus is expressed as:

[0278]

[0279] where p i Represents the instantaneous power of the inverter, p d is the instantaneous power of FC / ELZ, when p d >0, the instantaneous power comes from FC, when p d <0, instantaneous power will flow into ELZ.

[0280] In the aforementioned grid-building operation control method of the fuel cell / electrolyzer system, the closed loop TF of the DC bus voltage control is:

[0281]

[0282] Among them, u dc is the DC bus voltage, u dcref is the DC bus reference voltage, k pv is the ratio link coefficient, k iv is the integral link coefficient, C d is the equivalent capacitance of the voltage outer loop.

[0283] The above-mentioned fuel cell / electrolyzer system grid operation control method also includes AC side voltage control. The complex state space-based model of the three-phase inverter with LC filter is as follows:

[0284]

[0285] in, is the state vector of the system, A p is the state matrix, B p1 , B p2 are input matrix one and input matrix two, v c is the control input voltage, i l is the input current of the three-phase AC side, y is the output vector, C p is the output matrix;

[0286] In formula (6), the complex state variable x p :[i L u C ] T =[i Ld +ji Lq u Cd +ju Cq ] T represents the inductor current and capacitor voltage, i l =i ld +ji lq Represents the disturbance from the outside; the midpoint voltage of the bridge arm v c =v Cd +jv cq is the control input, define A 1 =1 / L and A 2 =1 / C, where i Ld is the inductor d-axis current vector, i Lq is the inductor q-axis current vector, u Cd is the capacitor d-axis voltage vector, u Cq is the capacitor q-axis voltage vector, T represents transposition, i ld is the external disturbance d-axis current vector, i lq is the external disturbance q-axis current vector, v Cd Input voltage d-axis voltage vector, v cq is the input voltage q-axis voltage vector, L and C are the equivalent inductance and equivalent capacitance respectively, so the matrix in formula (7) is derived:

[0287]

[0288] Among them, a 1 、a 2 is the coefficient of the system dynamic characteristics, ω is the angular frequency, and R is the resistance of the AC side transmission line;

[0289] The state variables of the integrator are defined as:

[0290]

[0291] in, is the small change in the state variable of the integrator, x c is the state variable of the integrator, e c is the control error, u Cref is the desired control input voltage, u C is the actual control input voltage;

[0292] The open-loop system of the AC voltage control process is expressed as:

[0293]

[0294] where x = [x p x c ] T =[i L u C x c ] T represents the augmented state variable, is the derivative of x, then the capacitor voltage control equation is: c =-k p1 i L -k p2 u C -k c x c +k d i l +k r u Cref (10)

[0295] k p1 , k p2 is the proportional coefficient 1 and proportional coefficient 2 of the AC voltage closed-loop control, k c is the integral coefficient of AC voltage closed-loop control, k d is the integral coefficient of AC voltage closed-loop control, k r is the proportional coefficient of AC voltage closed-loop control;

[0296] The closed-loop system is expressed as:

[0297]

[0298] Among them, A c is the state matrix of the closed-loop system, B 2c , B rc are input matrix one and input matrix two, is a state vector of the voltage vector, in formula (11),

[0299]

[0300] B 2c =[a 1 k d -a 2 0] T , B rc =[a 1 k r 0 1] T ;

[0301] State feedback gain K = -[k p1 k p2 k c ] The integral coefficient k of the feedforward AC voltage closed-loop control is set by the pole configuration method. d And the proportional coefficient k of AC voltage closed loop control r By setting the pole-zero elimination, the closed-loop TF is expressed as:

[0302]

[0303] Among them, s represents the variable in Laplace transform, I represents the identity matrix, and y ref represents the reference output, p n represents the natural pole of the system, represents the pole position expected by control design, G d , G r , Z d (s), Z r (s) respectively represent the preset transfer function 1, preset transfer function 2, preset transfer function 3, and preset transfer function 4 related to the reference input to the output. In equation (12),

[0304] Z d (s) = a 2 s(a 1 k d -s-jω-a 1 Ra 1 k p1 ) (13)

[0305] Z r (s) = a 1 a 2 (k r sk c ) (14).

[0306] In the above-mentioned fuel cell / electrolyzer system grid operation control method, the inverter adopts power synchronization control to control the active power output p of the inverter. i and the inverter's reactive power output q i The mathematical model is expressed as ΔU = U c -Ug ,

[0307]

[0308] Where Δδ represents the phase difference, X = ωL g , p i represents the active power output of the inverter, q i Indicates the reactive power output of the inverter, U c Indicates the inverter output voltage, U g Indicates the grid voltage, L g Equivalent inductance of the inverter output filter.

[0309] In the above-mentioned fuel cell / electrolyzer system grid operation control method, the TF of active power control is expressed as:

[0310]

[0311] Among them G rp (s) is the transfer function of the active power controller, G ωp (s) is the transfer function of angular velocity, p iref is the reference value of active power, k iω is the control gain coefficient of angular velocity, Δω g Represents the change of grid frequency, Δω g =ω n -ω g ,ω n represents the natural frequency or intrinsic frequency of the system, ω g Indicates the angular frequency of the power grid.

[0312] In the above-mentioned fuel cell / electrolyzer system grid operation control method, the reactive power first-order closed-loop controller is:

[0313]

[0314] Among them, q i is the input of the controller, G rq (s) is the transfer function of the reactive power controller, G Vq (s) is the transfer function of the input voltage, ΔV is the change in voltage, B is the damping coefficient, k iq is the controller gain factor, q iref It is the reference value of reactive power.

[0315] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0316] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0317] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0318] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for controlling the grid operation of a fuel cell / electrolyzer system, wherein the FC and ELZ are connected to a DC bus through an FC boost converter and an ELZ buck converter, respectively, and the DC bus is connected to an AC bus through a bidirectional DC-AC inverter, characterized in that: Model the FC / ELZ control system to obtain the electrical model of FC and the electrical model of ELZ; The electrical model of the FC represents the relationship between the voltage of the fuel cell and the current of the fuel cell; the electrical model of the ELZ represents the relationship between the voltage of the electrolyzer and the current of the electrolyzer; A dual-loop controller is used to control the DC bus voltage, the current of the FC boost converter, and the current of the ELZ buck converter, wherein the dual-loop controller includes an outer-loop controller and an inner-loop controller.

2. A method for controlling the network operation of a fuel cell / electrolyzer system according to claim 1, characterized in that: The outer loop controller is used to realize DC bus voltage control; the inner loop controller realizes current control of FC boost converter based on fuel cell current; the inner loop controller realizes current control of ELZ buck converter based on electrolyzer voltage and electrolyzer current.

3. A method for controlling the network operation of a fuel cell / electrolyzer system according to claim 1 or 2, characterized in that: The electrical model of FC is expressed as: where u FC_cell is the voltage of the fuel cell, i FC_cell is the current of the fuel cell, E0 is the open circuit voltage of the fuel cell, K is the battery polarization coefficient, and are the effective partial pressures of hydrogen and oxygen, respectively, e is a constant, H(s) is a first-order filter with a fast time constant; The electrical model of ELZ is expressed as: Among them, u rev , T ELZ and A are the reversible voltage, temperature and area of ​​the electrode, respectively, K i is the temperature T ELZ The function of u ELz_cell is the voltage of the electrolytic cell, i ELZ_cell is the current of the electrolytic cell, r1 is the resistance of the electrolyte, and r2 is the contact resistance between the electrolyte and the electrode.

4. A method for controlling the network operation of a fuel cell / electrolyzer system according to claim 1 or 2, characterized in that: During the current control process of the ELZ buck converter, the voltage signal is d2 For the control input, the closed-loop transfer function of the current loop is: where i ELZ is the current of the electrolytic cell, i ELZerf is the reference current of the electrolytic cell, k pi is the proportional link coefficient, k ii is the integral link coefficient, L sc is the equivalent inductance of the inner current loop, R sc The equivalent resistance of the inner current loop, G cr (s) is the tracking gain, and s is the complex frequency variable in the Laplace transform.

5. A method for controlling the network operation of a fuel cell / electrolyzer system according to claim 1 or 2, characterized in that: During the current control process of the FC boost converter, the voltage signal is d1 And the voltage signal is V d2 As the control input, the closed-loop transfer function of the current loop is: I fc is the fuel cell current, I ref is the reference current or set current, L d is the boost circuit inductor, R d is the boost circuit resistance, U fc is the voltage of the fuel cell, and s is the complex frequency variable in the Laplace transform.

6. A method for controlling the network operation of a fuel cell / electrolyzer system according to claim 1 or 2, characterized in that: During the DC bus voltage control process, the capacitor C d The power model of the DC bus is expressed as: Among them, p i Represents the instantaneous power of the inverter, p d is the instantaneous power of FC / ELZ, when p d >0, the instantaneous power comes from FC, when p d <0, instantaneous power will flow into ELZ.

7. A method for controlling the network operation of a fuel cell / electrolyzer system according to claim 6, characterized in that: The closed-loop transfer function of the DC bus voltage control is: Among them, u dc is the DC bus voltage, u dcref is the DC bus reference voltage, k pv is the ratio link coefficient, k iv is the integral link coefficient, C d is the equivalent capacitance of the voltage outer loop.

8. A method for controlling the network operation of a fuel cell / electrolyzer system according to claim 1 or 2, characterized in that: The complex state space-based model of the three-phase inverter with LC filter for AC side voltage control is as follows: in, is the state vector of the inverter system, A p is the state matrix, B p1 , B p2 are input matrix one and input matrix two, v c is the control input voltage, i l is the input current of the three-phase AC side, y is the output vector, C p is the output matrix; In formula (6), the complex state variable x p :[i L u C ] T =[i Ld +ji Lq u Cd +ju Cq ] T represents the inductor current and capacitor voltage, i l =i ld +ji lq Represents the disturbance from the outside; the midpoint voltage of the bridge arm v c =v Cd +jv cq is the control input, define A1 = 1 / L and A2 = 1 / C, where i Ld is the inductor d-axis current vector, i Lq is the inductor q-axis current vector, u Cd is the capacitor d-axis voltage vector, u Cq is the capacitor q-axis voltage vector, T represents the transpose, i ld is the external disturbance d-axis current vector, i lq is the external disturbance q-axis current vector, v Cd Input voltage d-axis voltage vector, v cq is the input voltage q-axis voltage vector, L and C are the equivalent inductance and equivalent capacitance respectively, so the matrix in formula (7) is derived: Among them, a1 and a2 are the coefficients of the dynamic characteristics of the inverter system, ω is the angular frequency, and R is the resistance of the AC side transmission line; The state variables of the integrator are defined as: Among them, x c is the state variable of the integrator, is the derivative of the integrator state variable, e c is the control error, u Cref is the desired control input voltage, u C is the actual control input voltage; The open-loop system of the AC voltage control process is expressed as: Where x = [x p x c ] T =[i L u C x c ] T represents the augmented state variable, is the derivative of x, then the capacitor voltage control equation is: c =-k p1 i L -k p2 u C -k c x c +k d i l +k r u Cref (10) k p1 , k p2 is the proportional coefficient 1 and proportional coefficient 2 of the AC voltage closed-loop control, k c is the integral coefficient of AC voltage closed-loop control, k d is the integral coefficient of AC voltage closed-loop control, k r is the proportional coefficient of AC voltage closed-loop control; The closed-loop system is expressed as: Among them, A c is the state matrix of the closed-loop system, B 2c , B rc are input matrix one and input matrix two, is a state vector of the voltage vector, in formula (11), B 2c =[a1k d -a2 0] T ,B rc =[a1k r 0 1] T ; State feedback gain K = -[k p1 k p2 k c ] The integral coefficient k of the feedforward AC voltage closed-loop control is set by the pole configuration method. d And the proportional coefficient k of AC voltage closed loop control r By setting the pole-zero elimination, the closed-loop transfer function is expressed as: Where s represents the complex frequency variable in Laplace transform, I represents the identity matrix, and y ref represents the reference output, p n represents the natural pole of the system, represents the pole position expected by control design, G d , G r , Z d (s), Z r (s) respectively represent the preset transfer function 1, preset transfer function 2, preset transfer function 3, and preset transfer function 4 related to the reference input to the output. In equation (12), Z d (s)=a2s(a1k d -s-jω-a1R-a1k p1 ) (13) FROM r (s)=a1a2(k r sk c ) (14).

9. A method for controlling the network operation of a fuel cell / electrolyzer system according to claim 8, characterized in that: The inverter adopts power synchronization control to control the active power output p of the inverter i and the inverter's reactive power output q i The mathematical model is expressed as ΔU = U C -U g , Where Δδ represents the phase difference, X = ωL g , p i represents the active power output of the inverter, q i Indicates the reactive power output of the inverter, U C Indicates the inverter output voltage, U g Indicates the grid voltage, L g Represents the equivalent inductance of the inverter output filter.

10. A method for controlling the network operation of a fuel cell / electrolyzer system according to claim 9, characterized in that: The transfer function of active power control is expressed as: Among them G rp (s) is the transfer function of the active power controller, G ωp (s) is the transfer function of angular velocity, p iref is the reference value of active power, k iω is the control gain coefficient of angular velocity, Δω g Represents the change of grid frequency, Δω g =ω n -ω g ,ω n represents the natural frequency or intrinsic frequency of the system, ω g Indicates the angular frequency of the power grid.

11. A method for controlling the network operation of a fuel cell / electrolyzer system according to claim 9, characterized in that: The reactive power first-order closed-loop controller is: Among them, q i is the input of the controller, G rq (s) is the transfer function of the reactive power controller, G Vq (s) is the transfer function of the input voltage, ΔV is the change in voltage, B is the damping coefficient, k iq is the controller gain factor, q iref It is the reference value of reactive power.

12. A computer device / equipment / system comprising a memory, a processor and a computer program stored in the memory, characterized in that: The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 9.

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