Model predictive control method and device for variable speed constant frequency hydroelectric power generation system

Abstract

The application discloses a variable-speed constant-frequency hydraulic power generation system model predictive control method and device, and the method comprises the following steps: calculating an instruction magnetic chain and an instruction electromagnetic torque of a machine side converter of the variable-speed constant-frequency hydraulic power generation system through MPC; screening eight voltage vectors of the machine side converter according to the instruction magnetic chain and the instruction electromagnetic torque; and substituting the switch vector left after the screening into a value function to form a control signal at the next moment. The application can realize variable-speed constant-frequency adjustment of the generator, and improves the power generation quality and efficiency of the system. The generator used in the variable-frequency hydraulic power generation system targeted by the application is a permanent magnet synchronous generator, the control object comprises a double-PWM converter, and the application has the advantages of good universality and wide application range. The application considers the converter, the generator and the power grid model, and is suitable for high-performance control of the hydraulic power generation system under various working conditions.

Description

Technical Field

[0001] This invention relates to control technology for variable speed constant frequency hydropower systems, specifically a model predictive control method for variable speed constant frequency hydropower systems. Background Technology

[0002] With the continuous development of the global economy, energy demand is constantly increasing, while fossil fuels are extremely limited. Furthermore, environmental pollution, climate change, and a series of other problems have seriously affected the health and sustainable development of human society. Therefore, hydropower has become an indispensable part of new energy power generation and will make a significant contribution to the future development of human society.

[0003] Currently, most power generation systems employ PID control. While convenient, PID control performs poorly when controlling complex processes with nonlinearity, time-varying characteristics, and uncertain parameters and structures. Model predictive control (MPC), a model-based control method, uses the model to predict and select an optimal input value that meets the value function requirements. Therefore, given my country's emphasis on clean energy and policy support, research into the application of MPC in hydropower has significant potential. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention provides a model predictive control method and apparatus for a variable speed constant frequency hydropower generation system, in order to solve at least one of the above-mentioned technical problems.

[0005] This invention provides a model predictive control method for a variable-speed constant-frequency hydropower system, used for model predictive torque control of the generator-side converter in the system. The method includes:

[0006] 1) Obtain the d-axis and q-axis currents i at the current moment. sd i sq Turbine speed ω, command flux linkage and command torque Te ref And calculate the flux linkage at all times using MPC. And electromagnetic torque Te;

[0007] 2) According to the instruction magnet link and command torque Te ref The eight voltage vectors of the machine-side converter are screened;

[0008] 3) Substitute the filtered switch vectors into the preset value function to generate the control signal of the machine-side converter at the next moment;

[0009] The expression for calculating the d-axis current at time k+1 using MPC is as follows:

[0010]

[0011] In the above formula, i sd (k+1), i sq (k+1) represent the d-axis and q-axis currents at the (k+1)th time, respectively; R sd R sq These are the d-axis and q-axis resistances, respectively; L sd L sq These are the d-axis and q-axis inductances, respectively; T s For control cycle; i sd (k), i sq (k) represents the d-axis and q-axis currents at the k-th time, respectively; U sd (k), U sq (k) represents the d-axis and q-axis voltage values ​​at the k-th time, respectively, and ω represents the turbine rotational speed. For permanent magnets;

[0012] Calculate flux linkage using MPC And the expression for electromagnetic torque Te is:

[0013]

[0014]

[0015] In the above formula, Let the stator flux linkage be at time k+1. denoted by , and denoted by , respectively, the flux linkages along the d and q axes at time k+1; Te(k+1) represents the electromagnetic torque at time k+1; and p represents the number of pole pairs of the permanent magnet synchronous motor.

[0016] The above technical solution provides a model predictive torque control method for a variable frequency hydropower system, which can achieve variable speed constant frequency regulation of the generator, thereby improving the power generation quality and efficiency of the system. The generator used in the variable frequency hydropower system addressed by this technical solution is a permanent magnet synchronous generator, and the controlled object includes a dual PWM converter. It has the advantages of good versatility and wide applicability; moreover, it considers the converter, generator, and grid model, making it suitable for high-performance control under various operating conditions of the hydropower system.

[0017] As a further technical solution, the method also includes real-time calculation and generation of command electromagnetic torque Te. ref Steps: Detect the current turbine speed ω and water flow velocity V, and calculate the optimal tip speed ratio λ at water flow velocity V. opt According to the optimal tip speed ratio λ opt And the optimal turbine speed ω is obtained by calculating the turbine radius. ref Calculate the turbine speed ω and the optimal turbine speed ω. refThe difference between them is calculated, and the calculated difference is used to obtain the command current i of the q-axis through the PI controller. sqref Calculate the commanded electromagnetic torque Te ref Command magnet link It is approximately equivalent to the magnetic flux linkage of a permanent magnet.

[0018] As a further technical solution, based on the instruction magnet link and command torque Te ref The eight voltage vectors of the generator-side converter are screened, further including:

[0019] 2.1) Calculate the stator flux linkage at time k+1 using the d-axis and q-axis currents and the turbine speed. The electromagnetic torque Te(k+1) at time k+1;

[0020] 2.2) Based on stator flux linkage The switching vector is filtered by the electromagnetic torque Te(k+1) to find the switching vector corresponding to the minimum value of the value function, which is the control signal.

[0021] This invention provides a model predictive torque control device for a variable-speed constant-frequency hydropower system, used for model predictive torque control of the generator-side converter in the variable-speed constant-frequency hydropower system. The device includes:

[0022] The calculation module is used to obtain the d-axis and q-axis currents i at the current moment. sd i sq Turbine speed ω, command flux linkage and command torque Te ref And calculate the flux linkage at all times using MPC. And electromagnetic torque Te;

[0023] The filtering module is used to filter according to the instruction magnet link. and command torque Te ref The eight voltage vectors of the machine-side converter are screened;

[0024] The signal generation module is used to substitute the filtered switch vector into a preset value function to generate the control signal of the machine-side converter at the next moment.

[0025] This invention also provides a model predictive control method for a variable-speed constant-frequency hydropower system, used for model predictive current control of the grid-side converter of the variable-speed constant-frequency hydropower system, the method comprising:

[0026] 1) Obtain the current DC bus voltage Udc, d-axis and q-axis current i. gd i gq Turbine speed ω, d, q-axis command current i gdref igqref And calculate i at all times using MPC gd i gq ;

[0027] 2) According to the command current i gdref i gqref The eight voltage vectors of the grid-side converter are screened;

[0028] 3) Substitute the filtered switch vector into the preset value function to generate the control signal of the grid-side converter at the next moment.

[0029] As a further technical solution, i is calculated via MPC. gd i gq The expression is:

[0030] in,

[0031] i gd (k+1), i gq (k+1) represent the d-axis and q-axis currents at the (k+1)th time, respectively; R gd R gq These are the d-axis and q-axis resistances, respectively; L gd L gq These are the d-axis and q-axis inductances, respectively; T s For control cycle; i gd (k), i gq (k) represents the d-axis and q-axis currents at the k-th time, respectively; U gd (k), U gq (k) represents the d-axis and q-axis voltage values ​​at the k-th time, respectively, and ω represents the turbine rotational speed. It is the magnetic flux of a permanent magnet.

[0032] As a further technical solution, the method also includes real-time calculation and generation of command current i gdref i gqref Steps: Detect the DC bus voltage Udc and the DC bus voltage Udc given by the grid-side controller. ref Calculate the DC bus voltage Udc and the given DC bus voltage Udc. ref The difference between them is calculated, and the calculated difference is used to obtain the d-axis command current i through a PI controller. gdref q-axis command current in i gqref Controlled by 0.

[0033] As a further technical solution, based on the command current i gdref i gqref The eight voltage vectors of the grid-side converter are screened, further including:

[0034] 2.1) Calculate the d-axis and q-axis current i at time k+1 using the d-axis and q-axis currents at time k. gd (k+1) and i gq (k+1);

[0035] 2.2) Based on the d-axis current i, the q-axis current i gd (k+1) and i gq (k+1) Filter the switch vectors to find the switch vector corresponding to the minimum value of the value function, which is the control signal.

[0036] The present invention also provides a model predictive current control device for a variable-speed constant-frequency hydropower system, used for model predictive current control of the grid-side converter of the variable-speed constant-frequency hydropower system, the device comprising:

[0037] The calculation module is used to obtain the current DC bus voltage Udc and the d-axis and q-axis current i. gd i gq Turbine speed ω, d, q-axis command current i gdref i gqref And calculate i at all times using MPC gd i gq ;

[0038] The filtering module is used to filter according to the command current i gdref i gqref The eight voltage vectors of the grid-side converter are screened;

[0039] The signal generation module is used to substitute the filtered switch vector into a preset value function to generate the control signal of the grid-side converter at the next moment.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] 1. This invention enables variable speed and constant frequency regulation of the generator, thereby improving the power generation quality and efficiency of the system.

[0042] 2. The generator used in the variable frequency hydropower generation system targeted by this invention is a permanent magnet synchronous generator, and the controlled object includes a dual PWM converter, which has the advantages of good versatility and wide applicability.

[0043] 3. This invention takes into account converter, generator and power grid models, and is suitable for high-performance control under various operating conditions of hydropower generation systems. Attached Figure Description

[0044] Figure 1 This is a control block diagram illustrating the basic principle of model predictive control in this embodiment of the invention.

[0045] Figure 2This is a flowchart of the model predictive torque control for the machine-side converter in an embodiment of the present invention.

[0046] Figure 3 This is a schematic diagram of the switch vector voltage sector distribution in an embodiment of the present invention. Detailed Implementation

[0047] The technical solutions of various embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] like Figure 1 The model predictive torque control method for a variable-speed constant-frequency hydropower system in this embodiment includes the control of the generator-side converter of the variable-speed constant-frequency hydropower system. The method includes the following steps:

[0049] Step 1), obtain the current d-axis and q-axis currents i sd i sq Turbine speed ω, command flux linkage and command torque Te ref And calculate the flux linkage at all times using MPC. And electromagnetic torque Te;

[0050] Step 2), according to the instruction magnet link and command torque Te ref The eight voltage vectors of the machine-side converter are screened;

[0051] Step 3) Substitute the filtered switch vector into the preset value function to generate the control signal of the machine-side converter at the next moment;

[0052] In this embodiment, the purpose of controlling the turbine-side converter of the variable frequency hydropower system in steps 1) to 3) is to control the hydropower generator to obtain water energy.

[0053] In this embodiment, the expression for calculating the d-axis current at time k+1 using MPC in step 1) is:

[0054]

[0055] In the above formula, i sd (k+1), i sq (k+1) represent the d-axis and q-axis currents at the (k+1)th time, respectively; R sd R sq These are the d-axis and q-axis resistances, respectively; L sd L sqThese are the d-axis and q-axis inductances, respectively; T s For control cycle; i sd (k), i sq (k) represents the d-axis and q-axis currents at the k-th time, respectively; U sd (k), U sq (k) represents the d-axis and q-axis voltage values ​​at the k-th time, respectively, and ω represents the turbine rotational speed. It is the magnetic flux of a permanent magnet.

[0056] Step 1) calculates the flux linkage using MPC. And the expression for electromagnetic torque Te is:

[0057]

[0058]

[0059] In the above formula, Let the stator flux linkage be at time k+1. Let be the flux linkages of the d and q axes at time k+1, respectively; Te(k+1) be the electromagnetic torque at time k+1; and p be the number of pole pairs of the permanent magnet synchronous motor. In this embodiment, the model predictive controller executes the machine-side current increment equation shown in equation (1), thereby optimizing the control under complex operating conditions and enhancing the control effect.

[0060] See Figure 1 In step 1) of this embodiment, the command electromagnetic torque Te is also calculated and generated in real time. ref Steps: Detect the current turbine speed ω and water flow velocity V, and calculate the optimal tip speed ratio λ at water flow velocity V. opt According to the optimal tip speed ratio λ opt And the optimal turbine speed ω is obtained by calculating the turbine radius. ref Calculate the turbine speed ω and the optimal turbine speed ω. ref The difference between them is calculated, and the calculated difference is used to obtain the command current i of the q-axis through the PI controller. sqref The commanded electromagnetic torque Te is calculated using the above formula. ref Command magnet link It is approximately equivalent to the magnetic flux linkage of a permanent magnet.

[0061] In this embodiment, the detailed steps of step 2) include:

[0062] 2.1) Calculate the stator flux linkage at time k+1 using the d-axis and q-axis currents and the turbine speed. The electromagnetic torque Te(k+1) at time k+1;

[0063] 2.2) Based on stator flux linkage The switching vector is filtered by the electromagnetic torque Te(k+1) to find the switching vector corresponding to the minimum value of the value function, which is the control signal.

[0064] In this embodiment, the value function expression in step 3) is:

[0065]

[0066] In the above formula, C g For value function, Let Te(k+1) be the stator flux linkage at time k+1, and Te(k+1) be the electromagnetic torque at time k+1. Let Te(k+1) be the stator flux linkage at time k+1, Te(k+1) be the electromagnetic torque at time k+1, and K be the weighting coefficient. The value function with the minimum value in (4) is the optimal voltage vector at the next time step.

[0067] As an optional implementation method, such as Figure 1 As shown, the control method for the variable-speed constant-frequency hydropower generation system in this embodiment also includes a model prediction current control step for the grid-side converter:

[0068] 1) Obtain the current DC bus voltage Udc, d-axis and q-axis current i gd i gq Turbine speed ω, d, q-axis command current i gdref i gqref And calculate i at all times using MPC gd i gq ;

[0069] 2) According to the command current i gdref i gqref The eight voltage vectors of the grid-side converter are screened;

[0070] 3) Substitute the filtered switch vector into the preset value function to generate the control signal of the machine-side converter at the next moment.

[0071] In this embodiment, the purpose of controlling the grid-side converter of the variable frequency hydropower system in steps 1) to 3) above is to achieve current control and stabilize the DC bus voltage.

[0072] In this embodiment, step 1) calculates i using MPC. gd i gq The expression is:

[0073]

[0074] In the above formula, i gd (k+1), i gq(k+1) represent the d-axis and q-axis currents at the (k+1)th time, respectively; R gd R gq These are the d-axis and q-axis resistances, respectively; L gd L gq These are the d-axis and q-axis inductances, respectively; T s For control cycle; i gd (k), i gq (k) represents the d-axis and q-axis currents at the k-th time, respectively; U gd (k), U gq (k) represents the d-axis and q-axis voltage values ​​at the k-th time, respectively, and ω represents the turbine rotational speed. It is the magnetic flux of a permanent magnet.

[0075] See Figure 1 In step 1) of this embodiment, the command current i is also generated in real time. gdref i gqref Steps: Detect the DC bus voltage Udc and the DC bus voltage Udc given by the grid-side controller. ref Calculate the DC bus voltage Udc and the given DC bus voltage Udc. ref The difference between them is calculated, and the calculated difference is used to obtain the d-axis command current i through a PI controller. gdref q-axis command current in i gqref Controlled by 0.

[0076] In this embodiment, the detailed steps of step 2) include:

[0077] 2.1) Calculate the d-axis and q-axis current i at time k+1 using the d-axis and q-axis currents at time k. gd (k+1) and i gq (k+1);

[0078] 2.2) Based on the d-axis current i, the q-axis current i gd (k+1) and i gq (k+1) Filter the switch vectors to find the switch vector corresponding to the minimum value of the value function, which is the control signal.

[0079] In this embodiment, the value function expression in step 3) is:

[0080] C g =(i gdref -i gd (k+1)) 2 +(i gqref -i gq (k+1)) 2 (6)

[0081] In the above formula, C g Let i be the value function.sd (k+1), i sq (k+1) represent the d-axis and q-axis currents at the (k+1)th time, respectively, and i gdref i gqref The command voltages for the d and q axes are respectively, and the one that minimizes the value function value of (6) is the optimal voltage vector for the next moment.

[0082] The variable frequency hydropower system model predictive current control method in this embodiment can realize variable speed constant frequency regulation of the generator, which improves the power generation quality and efficiency of the system. Moreover, it has a compact structure, small size, high reliability and system efficiency.

[0083] This embodiment of the variable frequency hydropower system model predictive current control method addresses a variable frequency hydropower system using a permanent magnet synchronous generator or a synchronous generator with a fixed excitation current. The control method includes a generator-side converter and a grid-side converter. The generator-side control method aims to control the turbine generator to obtain hydropower, while the grid-side control method aims to achieve power control and stabilize the DC bus voltage. This embodiment of the variable frequency hydropower system model predictive current control method derives the current and voltage increment state equations for the generator side and the power and voltage increment state equations for the grid side. Through corresponding instruction generation methods, the sensitivity to parameters is reduced. Finally, three vectors are used for control, thus eliminating redundant SVPWM modules and reducing computational load. In summary, this embodiment of the variable frequency hydropower system model predictive current control method considers the converter, generator, and grid model, making it suitable for high-performance control under various operating conditions of hydropower systems.

[0084] As an optional implementation, the present invention also provides a model predictive torque control device for a variable-speed constant-frequency hydropower system, used for model predictive torque control of the generator-side converter of the variable-speed constant-frequency hydropower system, the device comprising:

[0085] The calculation module is used to obtain the d-axis and q-axis currents i at the current moment. sd i sq Turbine speed ω, command flux linkage and command torque Te ref And calculate the flux linkage at all times using MPC. And electromagnetic torque Te;

[0086] The filtering module is used to filter according to the instruction magnet link. and command torque Te ref The eight voltage vectors of the machine-side converter are screened;

[0087] The signal generation module is used to substitute the filtered switch vector into a preset value function to generate the control signal of the machine-side converter at the next moment.

[0088] The calculation module is also used to calculate the expression for the d-axis current at time k+1 using MPC, which is:

[0089]

[0090] In the above formula, i sd (k+1), i sq (k+1) represent the d-axis and q-axis currents at the (k+1)th time, respectively; R sd R sq These are the d-axis and q-axis resistances, respectively; L sd L sq These are the d-axis and q-axis inductances, respectively; T s For control cycle; i sd (k), i sq (k) represents the d-axis and q-axis currents at the k-th time, respectively; U sd (k), U sq (k) represents the d-axis and q-axis voltage values ​​at the k-th time, respectively, and ω represents the turbine rotational speed. It is the magnetic flux of a permanent magnet.

[0091] The calculation module is also used to calculate the magnet link via MPC. And the expression for electromagnetic torque Te is:

[0092]

[0093]

[0094] In the above formula, Let the stator flux linkage be at time k+1. denoted by , and denoted by , respectively, the flux linkages along the d and q axes at time k+1; Te(k+1) represents the electromagnetic torque at time k+1; and p represents the number of pole pairs of the permanent magnet synchronous motor.

[0095] The calculation module is also used to calculate and generate the command electromagnetic torque Te in real time. ref Steps: Detect the current turbine speed ω and water flow velocity V, and calculate the optimal tip speed ratio λ at water flow velocity V. opt According to the optimal tip speed ratio λ opt And the optimal turbine speed ω is obtained by calculating the turbine radius. ref Calculate the turbine speed ω and the optimal turbine speed ω. ref The difference between them is calculated, and the calculated difference is used to obtain the command current i of the q-axis through the PI controller. sqref The commanded electromagnetic torque Te is calculated using the above formula. ref Command magnet link It is approximately equivalent to the magnetic flux linkage of a permanent magnet.

[0096] The filtering module is also used to calculate the stator flux linkage at time k+1 using the d-axis and q-axis currents and the turbine speed. The electromagnetic torque Te(k+1) at time k+1; based on the stator flux linkage The switching vector is filtered by the electromagnetic torque Te(k+1) to find the switching vector corresponding to the minimum value of the value function, which is the control signal.

[0097] As an optional implementation, the present invention also provides a model predictive current control device for a variable-speed constant-frequency hydropower system, used for model predictive current control of the grid-side converter of the variable-speed constant-frequency hydropower system, the device comprising:

[0098] The calculation module is used to obtain the current DC bus voltage Udc and the d-axis and q-axis current i. gd i gq Turbine speed ω, d, q-axis command current i gdref i gqref And calculate i at all times using MPC gd i gq ;

[0099] The filtering module is used to filter according to the command current i gdref i gqref The eight voltage vectors of the grid-side converter are screened;

[0100] The signal generation module is used to substitute the filtered switch vector into a preset value function to generate the control signal of the grid-side converter at the next moment.

[0101] The calculation module is also used to calculate i via MPC. gd i gq The expression is:

[0102]

[0103] The calculation module is also used to calculate and generate the command current i in real time. gdref i gqref Steps: Detect the DC bus voltage Udc and the DC bus voltage Udc given by the grid-side controller. ref Calculate the DC bus voltage Udc and the given DC bus voltage Udc. ref The difference between them is calculated, and the calculated difference is used to obtain the d-axis command current i through a PI controller. gdref q-axis command current in i gqref Controlled by 0.

[0104] The filtering module is also used to calculate the d-axis current i at time k+1 using the d-axis and q-axis currents at time k. gd (k+1) and igq (k+1); According to d, the q-axis current i gd (k+1) and i gq (k+1) Filter the switch vectors to find the switch vector corresponding to the minimum value of the value function, which is the control signal.

[0105] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0106] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0107] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0108] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the embodiments of the present invention.

Claims

1. A predictive control method for a variable-speed constant-frequency hydropower system, characterized in that, The method for model predictive torque control of the generator-side converter in a variable-speed constant-frequency hydropower system includes: 1) Obtain the d-axis and q-axis currents at the current moment. , turbine speed Command magnet link and command torque And calculate the flux linkage at all times using MPC. and electromagnetic torque The expression is: ， ， in, Let the stator flux linkage be at time k+1. , Let be the flux linkages along the d and q axes at the (k+1)th time, respectively. is the electromagnetic torque at time k+1; p is the number of pole pairs of the permanent magnet synchronous motor; 2) According to the instruction magnet link and command torque The eight voltage vectors of the generator-side converter are screened, including: 1) Calculate the stator flux linkage at time k+1 using the d-axis and q-axis currents and the turbine speed. Electromagnetic torque at time k+1 ; 2) Based on stator flux linkage and electromagnetic torque The switch vectors are filtered to find the switch vector corresponding to the minimum value of the value function, which is the control signal; 3) Substitute the filtered switch vector into the preset value function to generate the control signal of the machine-side converter at the next moment; the expression of the value function is: ， in, For value function, Let the stator flux linkage be at time k+1. Let K be the electromagnetic torque at time k+1, where K is the weighting coefficient. The expression for calculating the d-axis current at time k+1 using MPC is as follows: ， In the above formula, , Let be the d-axis current and q-axis current at the (k+1)th time, respectively; , These are the resistances along the d and q axes, respectively. , These are the d-axis and q-axis inductances, respectively. To control the cycle; , Let be the d-axis current and q-axis current at the k-th time, respectively. , These are the d-axis and q-axis voltage values ​​at the k-th time. The rotational speed of the water turbine. For permanent magnets; Calculate flux linkage using MPC and electromagnetic torque The expression is: ， ， In the above formula, Let the stator flux linkage be at time k+1. , Let be the flux linkages along the d and q axes at the (k+1)th time, respectively. is the electromagnetic torque at time k+1; p is the number of pole pairs of the permanent magnet synchronous motor.

2. The model predictive control method for a variable-speed constant-frequency hydropower system according to claim 1, characterized in that, The method also includes real-time calculation and generation of command electromagnetic torque. Steps: Detect the current turbine speed And the water flow velocity V, calculate the optimal tip velocity ratio at the water flow velocity V. According to the optimal tip speed ratio And the optimal turbine speed is obtained by calculating the turbine radius. Calculate the turbine speed and optimal turbine speed The difference between them is calculated, and the calculated difference is used to obtain the command current of the q-axis through the PI controller. Calculate the commanded electromagnetic torque Command magnet link It is approximately equivalent to the magnetic flux linkage of a permanent magnet.

3. A model predictive torque control device for a variable-speed constant-frequency hydropower generation system, characterized in that, The device for model predictive torque control of the generator-side converter in a variable-speed constant-frequency hydropower system includes: The calculation module is used to obtain the d-axis and q-axis currents at the current moment. , turbine speed Command magnet link and command torque And calculate the flux linkage at all times using MPC. and electromagnetic torque The expression is: ， ， in, Let the stator flux linkage be at time k+1. , Let be the flux linkages along the d and q axes at the (k+1)th time, respectively. is the electromagnetic torque at time k+1; p is the number of pole pairs of the permanent magnet synchronous motor; The filtering module is used to filter according to the instruction magnet link. and command torque The eight voltage vectors of the generator-side converter are screened, including: calculating the d-axis and q-axis currents at time k+1 using the d-axis and q-axis currents at time k. and According to the d-axis current, the q-axis current and The switch vectors are filtered to find the switch vector corresponding to the minimum value of the value function, which is the control signal; The signal generation module is used to substitute the filtered switch vector into a preset value function to generate the control signal of the machine-side converter at the next moment; the expression of the value function is: ， in, For value function, Let the stator flux linkage be at time k+1. Let K be the electromagnetic torque at time k+1, where K is the weighting coefficient.

4. A predictive control method for a variable-speed constant-frequency hydropower system, characterized in that, The method for model-predictive current control of grid-side converters in variable-speed constant-frequency hydropower systems includes: 1) Obtain the current DC bus voltage d-axis and q-axis currents , turbine speed d, q axis command current , And calculate the full time-through rate using MPC. , The expression is: ， in, , Let be the d-axis current and q-axis current at the (k+1)th time, respectively; , These are the resistances along the d and q axes, respectively. , These are the d-axis and q-axis inductances, respectively. To control the cycle; , Let be the d-axis current and q-axis current at the k-th time, respectively. , These are the d-axis and q-axis voltage values ​​at the k-th time. The rotational speed of the water turbine. For permanent magnets; 2) According to the command current , The eight voltage vectors of the grid-side converter are filtered, including: calculating the d-axis and q-axis currents at time k+1 using the d-axis and q-axis currents at time k. and According to the d-axis current, the q-axis current and The switch vectors are filtered to find the switch vector corresponding to the minimum value of the value function, which is the control signal; 3) Substitute the filtered switch vector into the preset value function to generate the control signal of the grid-side converter at the next moment; the expression of the value function is: ， in, For value function, Let the stator flux linkage be at time k+1. Let K be the electromagnetic torque at time k+1, where K is the weighting coefficient.

5. The model predictive control method for a variable-speed constant-frequency hydropower system according to claim 4, characterized in that, The method also includes real-time calculation to generate command current. , Steps: Detect DC bus voltage and the DC bus voltage given by the grid-side controller Calculate the DC bus voltage and given DC bus voltage The difference between them is calculated, and the calculated difference is used to obtain the d-axis command current through a PI controller. q-axis command current Controlled by 0.

6. A model predictive current control device for a variable-speed constant-frequency hydropower generation system, characterized in that, The device for model-predictive current control of grid-side converters in variable-speed constant-frequency hydropower systems includes: The calculation module is used to obtain the DC bus voltage at the current moment. d-axis and q-axis currents , turbine speed d, q axis command current , And calculate the full time-through rate using MPC. , The expression is: ， in, , Let be the d-axis current and q-axis current at the (k+1)th time, respectively; , These are the resistances along the d and q axes, respectively. , These are the d-axis and q-axis inductances, respectively. To control the cycle; , Let be the d-axis current and q-axis current at the k-th time, respectively. , These are the d-axis and q-axis voltage values ​​at the k-th time. The rotational speed of the water turbine. For permanent magnets; The filtering module is used to filter according to the command current. , The eight voltage vectors of the grid-side converter are filtered, including: calculating the d-axis and q-axis currents at time k+1 using the d-axis and q-axis currents at time k. and According to the d-axis current, the q-axis current and The switch vectors are filtered to find the switch vector corresponding to the minimum value of the value function, which is the control signal; The signal generation module is used to substitute the filtered switch vector into a preset value function to generate the control signal of the grid-side converter at the next moment; the expression of the value function is: ， in, For value function, Let the stator flux linkage be at time k+1. Let K be the electromagnetic torque at time k+1, where K is the weighting coefficient.

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