Transient state control method for network construction type new energy power generation unit under resistance-inductance network

Abstract

The invention discloses a transient state control method for a network construction type new energy power generation unit under a resistance-inductance network, and the method comprises the steps: S1, analyzing the power coupling characteristics in the resistance-inductance network, obtaining the state parameters of a controller, and designing a pre-feedback control method to achieve the power decoupling; s2, on the basis of the control structure after power decoupling, establishing a network construction type new energy power generation unit mathematical model conforming to a port Hamiltonian structure; and S3, controller state parameters are acquired, a pre-feedback decoupling-energy shaping two-stage control method is implemented in combination with a port Hamiltonian model, input reference power is adjusted, and transient control of the network construction type new energy power generation unit is completed. On the basis of a Hamiltonian model of a network construction type new energy power generation unit port under a resistance-inductance network, a pre-feedback decoupling-energy shaping two-stage control method is provided, the problems of serious power coupling and frequent transient instability in the resistance-inductance network can be effectively solved under the condition of not depending on fault power grid information, and the reliability of the system is improved. The transient stability of the system during the fault period is improved, and support is provided for stable operation of a novel power system.

Description

Technical Field

[0001] This invention belongs to the field of new energy power system technology, specifically relating to a transient control method for grid-type new energy power generation units under a resistive-inductive network. Background Technology

[0002] With the rapid development of renewable energy technologies, the penetration rate of new energy power generation systems, represented by photovoltaics and wind power, in the power system is constantly increasing. Against this backdrop, grid-based technologies based on power electronic converters have become one of the key solutions for achieving stable operation of power grids with a high proportion of new energy sources.

[0003] However, the stable architecture of traditional power grids is mainly built upon the operating characteristics of synchronous generators. While grid-connected inverters replace traditional generating units, they also introduce frequent transient stability problems. To address this, the industry has proposed various methods to improve the transient stability of grid-connected inverters, primarily including control parameter optimization, adaptive reference active power regulation, and the addition of auxiliary control loops. For example, this can be achieved by designing adaptive virtual impedance, dynamically adjusting the reference active power during faults to maintain a stable equilibrium point, or introducing auxiliary control loops such as transient damping and frequency difference feedforward.

[0004] However, the aforementioned methods have significant limitations: while one type of method can effectively improve transient stability, its implementation relies on additional grid fault voltage information; another type of method cannot maintain system transient stability when the grid voltage drops severely. These shortcomings greatly limit the application of existing methods in practical engineering. Furthermore, these methods all neglect the influence of line resistance and fail to consider the significant impact of active and reactive power control coupling on transient stability, making them difficult to apply practically in grid-connected renewable energy generation units under resistive-inductive networks. Therefore, based on the needs of renewable energy grid-connected operation and development, and combining the advantages of grid-connected renewable energy generation units, designing a transient control method for grid-connected renewable energy generation units under resistive-inductive networks is particularly important. Summary of the Invention

[0005] In view of this, the purpose of this invention is to overcome the shortcomings of the prior art and provide a transient control method for grid-connected new energy power generation units in resistive-inductive networks. This method solves the problems of existing grid-connected new energy power generation units in resistive-inductive networks, which are difficult to implement effective transient control due to severe power coupling, and the excessive reliance on real-time grid voltage measurement. By establishing a port Hamiltonian model suitable for resistive-inductive networks and designing a two-stage control method of "pre-feedback decoupling - energy shaping," this invention achieves efficient transient stability control of the system under severe fault conditions without relying on grid voltage information during fault periods, significantly improving the system's operational reliability and engineering applicability.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A transient control method for a grid-type new energy power generation unit under a resistive-inductive network includes the following steps:

[0008] S1. Analyze the power coupling characteristics under the resistive-inductive network, obtain the state parameters of the controller, and design a pre-feedback control law based on the power coupling characteristics and state parameters to achieve power decoupling;

[0009] S2. Based on the control system after power decoupling in step S1, establish a mathematical model of a grid-type new energy power generation unit that conforms to the port Hamiltonian structure;

[0010] S3. Obtain the controller state parameters, combine the port Hamiltonian model to implement the "pre-feedback decoupling - energy shaping" two-stage control method, adjust the input reference power, and complete the transient control of the grid-type new energy power generation unit.

[0011] As a further improvement to the present invention, step S1 is specifically as follows:

[0012] In step S1, the control method of the grid-type new energy power generation unit and the power coupling characteristics under the resistive-inductive network are considered. In the control method, the active power-frequency control adopts a virtual synchronous machine control structure to generate a virtual rotor phase angle δ, and the reactive power-voltage control generates the internal potential amplitude E. Therefore, the third-order mathematical model of the control outer loop is described as follows:

[0013] (1)

[0014] Among them, J and D p P represents the rotor inertia and damping coefficient of the virtual synchronous machine, respectively. e P0 and Q represent the converter output active power and reference active power, respectively. e Q0 and Q0 are the converter output reactive power and reference reactive power, respectively, K is the integral coefficient, and D is the reference reactive power. q This is the reactive power loop droop factor. These represent the angular frequency of the grid-connected new energy power generation unit, the grid angular frequency, and the rated angular frequency, respectively. E0 is the rated voltage amplitude, and D... q K and K represent the droop coefficient and integral gain of the reactive power loop, respectively;

[0015] Based on grid-connected transmission characteristics, a mathematical model of the output power of grid-connected renewable energy generation units can be obtained:

[0016] (2)

[0017] Where Y = G + jB is the network admittance, and its corresponding network impedance is expressed as: The impedance angle is expressed as Vg This refers to the grid voltage.

[0018] Define state parameters Then formula (1) can be rewritten as:

[0019] (3)

[0020] Reactive power introduces asymmetric coupling terms. This hinders the construction of a reasonable Hamiltonian function using the first integration method, considering the coupling terms. The control structure (3) consists of a pre-feedback control input u based on state parameters x1 and x3. q0 Designed by:

[0021] (4)

[0022] Modified prefeedback control input Represented as

[0023] (5)

[0024] The first term in the above equation This is the pre-feedback term; the other terms are used to reset the equilibrium point. Parameters a, b, and c must satisfy the following conditions:

[0025] (6)

[0026] in, This represents the stable equilibrium point of the system under normal operating conditions.

[0027] As a further improvement to the present invention, step S2 is specifically as follows:

[0028] In step S2, the control system after power decoupling using pre-feedback control in step S1 is applied to establish the port Hamiltonian model of the grid-type new energy power generation unit as follows:

[0029] (7)

[0030] in, , , , ,

[0031] ,

[0032]

[0033] Therefore, a reasonable Hamiltonian function H can be derived as follows:

[0034] (8).

[0035] As a further improvement to the present invention, step S3 is specifically as follows:

[0036] The energy shaping equation proposed in step S3 for realizing transient control of grid-connected new energy power generation units is as follows:

[0037] (9)

[0038] in, It is the expected stable equilibrium point during a fault. It is represented as a positive definite gain matrix;

[0039] Meanwhile, a symmetric positive definite matrix is ​​used to enhance the original dissipation matrix R, thereby constructing a new closed-loop structure matrix M. d The new closed-loop structure matrix M d It is expressed as follows:

[0040] (10)

[0041] Therefore, according to formulas (7) and (9), the expected Hamiltonian function and model obtained through energy shaping during the fault period are expressed as follows:

[0042] (11)

[0043] By using matching equations and energy shaping control methods, a new control law is derived as follows:

[0044] (12)

[0045] in, This indicates the grid voltage during the fault. , , ;

[0046] Finally, the proposed transient control method for grid-connected new energy power generation units is expressed as follows:

[0047] (13)

[0048] Under normal conditions, S = 0, and the system operates under pre-feedback control. Under fault conditions, S = 1, the controller state parameters are read, and the new control input u is calculated. p and u q The system is configured in real time to modify the reference power, ultimately maintaining system stability at the desired operating point. Furthermore, the rated voltage amplitude E0 is updated to the expected voltage amplitude. This enhances the dynamic response of the system.

[0049] Compared with the prior art, the advantages of the present invention are as follows:

[0050] 1) This invention fully considers the power coupling characteristics of grid-type new energy power generation units under inductive networks. Based on a more accurate and practical engineering scenario-compliant Hamiltonian model of grid-type new energy power generation unit port, a more universal "pre-feedback decoupling-energy shaping" two-stage transient control method is designed.

[0051] 2) This invention fully considers the advantages of digital controllers in real-time reading of state variables and rewriting of control inputs. It updates the control inputs up and uq to the digital controller in real time to modify the reference power, guiding the system to quickly converge to the desired stable equilibrium point after a fault. This achieves autonomous configuration of the system's operating state during a fault, making it more feasible in engineering applications.

[0052] 3) This invention eliminates the need to detect real-time grid voltage information during faults throughout the entire control process, reducing reliance on additional sensors and improving the system's control reliability and feasibility for engineering applications.

[0053] 4) Even under extreme conditions of severe grid faults, this invention can effectively maintain the transient stability of the system, ensuring the continuous and stable operation of grid-connected renewable energy power generation units during fault ride-through. Based on this, the invention is applied to actual grid-connected renewable energy power generation units and compared with other control schemes, which to some extent verifies the practicality and effectiveness of the invention. Attached Figure Description

[0054] Figure 1 This is a schematic diagram of the transient control method for grid-type new energy power generation units in this embodiment;

[0055] Figure 2 This is a schematic diagram of the structure and control of the grid-connected operation system of the grid-type new energy power generation unit in this embodiment;

[0056] Figure 3 This is a detailed schematic diagram of the transient control method for grid-type new energy power generation units in this embodiment;

[0057] Figure 4 This is the grid-connected operation experimental platform for the grid-type new energy power generation unit in this embodiment;

[0058] Figure 5 This is a schematic diagram comparing the waveforms of a power grid fault experiment (pure inductive network) in this embodiment.

[0059] Figure 6 This is a schematic diagram comparing waveforms from a power grid fault experiment (resistive-inductive network) in this embodiment. Detailed Implementation

[0060] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. It should be understood that the described embodiments are only some examples of the present invention and not all of the present invention. Other embodiments obtained by those skilled in the art without creative effort should also be considered within the scope of protection covered by the present invention.

[0061] This invention presents a transient control method for grid-connected renewable energy power generation units in resistive-inductive networks. This method addresses the challenges of effective transient control in existing grid-connected renewable energy power generation units within resistive-inductive networks due to severe power coupling, and the excessive reliance on real-time grid voltage measurements. By establishing a port Hamiltonian model suitable for resistive-inductive networks and designing a two-stage control method of "pre-feedback decoupling—energy shaping," this invention achieves efficient transient stability control of the system under severe fault conditions without relying on grid voltage information during fault periods, significantly improving the system's operational reliability and engineering applicability.

[0062] like Figure 1 As shown, this embodiment is a transient control method for a grid-type new energy power generation unit under a resistive-inductive network, and the steps include:

[0063] S1. Analyze the power coupling characteristics in the resistive-inductive network, obtain the controller state parameters, and design a pre-feedback control method to achieve power decoupling;

[0064] Figure 2 The topology and control framework of a grid-connected system in the dq rotating coordinate system are illustrated. In this embodiment, the grid-connected renewable energy generation unit typically employs a DC voltage controller or is equipped with an energy storage system to maintain a stable DC bus voltage, which can therefore be considered a constant value. The AC-side inverter is connected via L... f and C f The LC filter is connected to the point of common coupling of the power grid, and the power grid impedance is determined by Z. g The grid voltage vector and the inverter output voltage vector are respectively represented as follows: and .

[0065] from Figure 2 The control framework shown can be seen with reference phase angle. The active power control loop regulates the voltage, while the reference voltage amplitude E is regulated by the reactive power control loop; together, they form the outer power loop. P0, Q0, and P... e Q e Let these represent the reference power and the output power, respectively. Therefore, the control equations for the power outer loop can be expressed in the following form:

[0066] (1)

[0067] Among them, J and D p P represents the rotor inertia and damping coefficient of the virtual synchronous machine, respectively. e P0 and Q represent the converter output active power and reference active power, respectively. e Q0 and Q0 represent the converter output reactive power and reference reactive power, respectively. K is the integral coefficient, and D... q This is the reactive power loop droop coefficient. These are the angular frequencies of the grid-connected new energy power generation unit, the grid angular frequency, and the rated angular frequency, respectively. E0 is the rated voltage amplitude, and D... q K and K represent the droop coefficient and integral gain of the reactive power loop, respectively.

[0068] Based on grid-connected transmission characteristics, a mathematical model of the output power of grid-connected renewable energy generation units can be obtained:

[0069] (2)

[0070] Where Y = G + jB is the network admittance, and its corresponding network impedance can be expressed as: The impedance angle is expressed as... V g This is the grid voltage.

[0071] For convenience, define state parameters. Then formula (1) can be rewritten as:

[0072] (3)

[0073] It is not difficult to see that, due to the presence of line resistance, reactive power introduces asymmetric coupling terms. This prevents the construction of a reasonable Hamiltonian function using the first-order integration method. This problem can be solved by designing a reasonable pre-feedback control method. Considering the coupling terms... The control structure (3) consists of a pre-feedback control input u based on state parameters x1 and x3. q0 It can be designed:

[0074] (4)

[0075] The pre-feedback control is designed to ensure the closed-loop system has a complete port Hamiltonian structure. Furthermore, the equilibrium point under steady-state conditions must be considered, as the pre-feedback control should not alter the steady-state operating point. Therefore, it is necessary to further refine the pre-feedback control input. Modified pre-feedback control input. It can be represented as

[0076] (5)

[0077] The first term in the above equation This is the pre-feedback term; the other terms are used to reset the equilibrium point. Parameters a, b, and c must satisfy the following conditions:

[0078] (6)

[0079] in, This represents the stable equilibrium point of the system under normal operating conditions.

[0080] S2. Based on the control system after power decoupling in step S1, establish a mathematical model of a grid-type new energy power generation unit that conforms to the port Hamiltonian structure;

[0081] In step S2, the control system after power decoupling using pre-feedback control in step S1 is applied to establish the port Hamiltonian model of the grid-type new energy power generation unit as follows:

[0082] (7)

[0083] in, , , , ,

[0084] ,

[0085]

[0086] Therefore, a reasonable Hamiltonian function H can be derived as follows:

[0087] (8)

[0088] S3. Obtain the controller state parameters, combine the port Hamiltonian model to implement the two-stage control method of "pre-feedback decoupling - energy shaping", adjust the input reference power, and complete the transient control of the grid-type new energy power generation unit;

[0089] The energy shaping equation proposed in step S3 for realizing transient control of grid-connected new energy power generation units is as follows:

[0090] (9)

[0091] in, It is the stable equilibrium point expected during a fault. It is represented as a positive definite gain matrix.

[0092] Meanwhile, a symmetric positive definite matrix is ​​used to enhance the original dissipation matrix R, thereby constructing a new closed-loop structure matrix M. dThis design enhances system damping and improves convergence speed. The new closed-loop structure matrix M... d It is expressed as follows:

[0093] (10)

[0094] Therefore, according to formulas (7) and (9), the expected Hamiltonian function and model during the fault period obtained through energy shaping can be expressed as follows:

[0095] (11)

[0096] The port Hamiltonian model of an open-loop system can be represented as:

[0097] (12)

[0098] Combining formulas (11) and (12), the matching equation can be derived as follows:

[0099] (13)

[0100] (14)

[0101] In this case, as long as the matching equation is satisfied, x2 will be restricted to zero, thus satisfying the objective of angular stability. Therefore, u p and u q The control law can be determined by the second and third terms. Through matching equations and energy shaping control methods, the new control law can be derived as follows:

[0102] (15)

[0103] in, This indicates the grid voltage during the fault. , , .

[0104] Considering that the grid voltage is difficult to obtain during a fault, the following formula can be used to replace it and obtain a new control input:

[0105] (16)

[0106] Therefore, the new control law can be derived as follows:

[0107] (17)

[0108] Overall, the proposed transient control framework is as follows: Figure 3 As shown in the figure. P ref With Q refThese represent the updated equivalent reference active power and reactive power, respectively. Under normal operating conditions, S=0, and the system operates in pre-feedback control mode, which does not affect the original normal operating state of the system. Under fault conditions, S=1, the controller status parameters are read, and the new control input u is calculated. p and u q The system is configured in real time to the digital controller to modify the reference power, ultimately maintaining system stability at the desired operating point. Furthermore, the rated voltage amplitude E0 is updated to the expected voltage amplitude. This is to enhance the dynamic response of the system.

[0109] Therefore, the two-stage transient control method of "pre-feedback decoupling-energy shaping" proposed in this invention can be expressed in the following form:

[0110] (18)

[0111] Where S represents the switch state, and its value is either 0 or 1. The updated rated voltage amplitude is determined by... definition.

[0112] This embodiment establishes a 2 kW hardware platform based on an RTU-BOX 205 controller (equipped with the control method of this invention) and an RTI-INV8020IR inverter, the structure of which is as follows: Figure 4 As shown in the figure, the system consists of a grid simulator connected to the inverter via line impedance and an LC filter, with a DC power supply providing power to the inverter. The control method of this invention is compiled and executed using a DSP-based RTU-BOX 205 controller, and the inverter switching frequency is set to 10 kHz. The main system parameters are summarized in Table 1.

[0113] Table 1 System Parameters

[0114]

[0115] The system operates under the following conditions: initially, the system is in a stable state; then, a three-phase ground fault occurs on the grid side within 2 seconds, causing the bus voltage to drop from 100V to 10V. The aforementioned control method is then verified.

[0116] The control methods compared in this embodiment are: 1) traditional virtual synchronous machine control method; 2) existing transient power angle stabilization (TAS) control method; 3) the two-stage transient control method of "pre-feedback decoupling-energy shaping" proposed in this invention.

[0117] Case 1: In this example, the line impedance is purely inductive, and its inductance value L g = 7.5 mH. Figure 5(a) shows the experimental waveforms of traditional virtual synchronous machine control. During the fault, the system exhibits power angle oscillations and transient instability. In contrast, both the TAS control method and the method proposed in this invention successfully maintained the transient stability of the system throughout the fault. Furthermore, as... Figure 5 As shown in (b) and (e), the TAS control method effectively achieves transient stability of the system by modifying the active power reference value. Figure 5 As can be clearly seen in (c) and (f), the method proposed in this invention simultaneously adjusts the reference values ​​of active and reactive power through state variable feedback. Experimental results confirm that the method proposed in this invention can guide the system to operate at the desired operating point. Through feedback control, this desired operating point becomes a globally stable equilibrium point.

[0118] Case 2: In this case, the line impedance is configured as L. g = 7.5 mH, R g = 2 Ω. Figure 6 (a) shows the experimental results when using the traditional virtual synchronous machine control method, clearly demonstrating that the system still exhibits transient instability during the fault process. Figure 6 (b) and (e) show that the system using the TAS control method exhibits a continuously increasing power angle, demonstrating transient instability characteristics. This is because in the resistive-inductive network, there is significant coupling between active and reactive power components, and adjusting only the active power reference value is insufficient to ensure transient stability. In contrast, Figure 6 (c) and (f) demonstrate that the method proposed in this invention can accurately and synergistically adjust the reference values ​​of active and reactive power, thereby maintaining system transient stability. During fault periods, grid-connected renewable energy generation units can stabilize at a pre-set desired operating point. This case study confirms the feasibility of the method proposed in this invention.

[0119] In summary, the implemented cases demonstrate the feasibility and superiority of the method proposed in this invention. This method not only effectively improves the transient stability of inductive-resistive networks but also guides the system to the desired stable equilibrium point during faults, thereby ensuring the safety and stability of system operation and providing support for the stable operation of new power systems.

[0120] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any modifications or equivalent changes made based on the technical essence of the present invention shall still fall within the scope of protection claimed by the present invention.

Claims

1. A transient control method for a grid-type new energy power generation unit under a resistive-inductive network, characterized in that, Includes the following steps: S1. Analyze the power coupling characteristics under the resistive-inductive network, obtain the state parameters of the controller, and design a pre-feedback control law based on the power coupling characteristics and state parameters to achieve power decoupling; S2. Based on the control system after power decoupling in step S1, establish a mathematical model of a grid-type new energy power generation unit that conforms to the port Hamiltonian structure; S3. Obtain the controller state parameters, combine the port Hamiltonian model to implement the "pre-feedback decoupling - energy shaping" two-stage control method, adjust the input reference power, and complete the transient control of the grid-type new energy power generation unit.

2. The transient control method for a grid-type new energy power generation unit under an inductive network according to claim 1, characterized in that: The specific steps of S1 are as follows: In step S1, the control method of the grid-type new energy power generation unit and the power coupling characteristics under the resistive-inductive network are considered. In the control method, the active power-frequency control adopts a virtual synchronous machine control structure to generate a virtual rotor phase angle δ, and the reactive power-voltage control generates the internal potential amplitude E. Therefore, the third-order mathematical model of the control outer loop is described as follows: （1） Among them, J and D p P represents the rotor inertia and damping coefficient of the virtual synchronous machine, respectively. e P0 and Q represent the converter output active power and reference active power, respectively. e Q0 and Q0 are the converter output reactive power and reference reactive power, respectively, K is the integral coefficient, and D is the reference reactive power. q This is the reactive power loop droop factor. These represent the angular frequency of the grid-connected new energy power generation unit, the grid angular frequency, and the rated angular frequency, respectively. E0 is the rated voltage amplitude, and D... q K and K represent the droop coefficient and integral gain of the reactive power loop, respectively; Based on grid-connected transmission characteristics, a mathematical model of the output power of grid-connected renewable energy generation units can be obtained: （2） Where Y = G + jB is the network admittance, and its corresponding network impedance is expressed as: The impedance angle is expressed as V g This refers to the grid voltage. Define state parameters Then formula (1) is rewritten as: （3） Reactive power introduces asymmetric coupling terms. This hinders the construction of a reasonable Hamiltonian function using the first integration method, considering the coupling terms. The control structure (3) consists of a pre-feedback control input u based on state parameters x1 and x3. q0 Designed by: （4） Modified prefeedback control input Represented as (5) The first term in the above equation This is the pre-feedback term; the other terms are used to reset the equilibrium point. Parameters a, b, and c must satisfy the following conditions: (6) in, This represents the stable equilibrium point of the system under normal operating conditions.

3. The transient control method for a grid-type new energy power generation unit under an inductive network according to claim 1, characterized in that: Step S2 is as follows: In step S2, the control system after power decoupling using pre-feedback control in step S1 is applied to establish the port Hamiltonian model of the grid-type new energy power generation unit as follows: (7) in, , , , , ， 4. Therefore, a reasonable Hamiltonian function H is derived as follows: (8)。 5. The transient control method for a grid-type new energy power generation unit under an inductive network according to claim 1, characterized in that: Step S3 is as follows: The energy shaping equation proposed in step S3 for realizing transient control of grid-connected new energy power generation units is as follows: (9) in, It is the expected stable equilibrium point during a fault. It is represented as a positive definite gain matrix; Meanwhile, a symmetric positive definite matrix is ​​used to enhance the original dissipation matrix R, thereby constructing a new closed-loop structure matrix M. d The new closed-loop structure matrix M d It is expressed as follows: (10) Therefore, according to formulas (7) and (9), the expected Hamiltonian function and model obtained through energy shaping during the fault period are expressed as follows: (11) By using matching equations and energy shaping control methods, a new control law is derived as follows: (12) in, This indicates the grid voltage during the fault. , , ; Finally, the proposed transient control method for grid-connected new energy power generation units is expressed as follows: (13) Under normal conditions, S = 0, and the system operates under pre-feedback control. Under fault conditions, S = 1, the controller state parameters are read, and the new control input u is calculated. p and u q The system is configured in real time to modify the reference power, ultimately maintaining system stability at the desired operating point. Furthermore, the rated voltage amplitude E0 is updated to the expected voltage amplitude. This enhances the dynamic response of the system.

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