Dynamic complex power angle model-based network-constructing inverter power control method

Abstract

The invention discloses a dynamic complex power angle model-based network construction type inverter power control method, and belongs to the technical field of grid-connected inverter network construction control. The method comprises the following steps: acquiring a complex power controller model designed based on a dynamic complex power angle model of a network-forming inverter; acquiring voltage amplitudes and phase angles of a grid-connected point and a power grid and reference values of active power and reactive power injected into the power grid by an inverter; calculating a complex power reference quantity according to the active power reference value and the reactive power reference value, and calculating the actual output complex power of the inverter according to the grid-connected point and the voltage amplitude and the phase angle of the power grid; based on the deviation between the complex power reference quantity and the actual output complex power, a complex power controller model is utilized to obtain a composite control signal comprising the phase angle adjustment quantity and the voltage amplitude correction quantity; and obtaining a modulated inverter control signal based on a difference value between the composite control signal and the grid-connected point voltage vector. According to the invention, accurate control of the output voltage and current of the inverter can be realized, the control performance of the grid-connected inverter is improved, and the design difficulty of a system controller is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of grid-connected inverter grid-forming control, and particularly to a power control method for a grid-forming inverter based on a dynamic complex power angle model. Background Art

[0002] Grid-forming (GFM) control is a technology that replaces grid-following control in grid-connected inverters. It has attracted extensive interest among scholars around the world. GFM inverters operate as voltage sources connected to the grid and have robust small-signal stability and grid-forming capabilities. Recently, many GFM control schemes have been proposed in the industry, such as traditional droop control, virtual synchronous generator (VSG) control, power synchronous control (PSC), synchronous power control (SPC), and multivariable feedback GFM control (MFC). The above grid-forming controls aim to be widely applied to the field of power systems highly dependent on renewable energy, including multiple key links from renewable energy grid connection control to microgrid operation management, to power market trading assistance, power system planning and design, and even rapid grid restoration in emergency situations.

[0003] Traditional droop, VSG, PSC, and SPC control methods use transfer function models to design ideal damping and adjustment time for GFM inverter power control. The above GFM control methods control active power and reactive power respectively based on a real variable (RV) model. The system is modeled as a double-input double-output (DIDO) system, where the inputs are voltage phase angle and amplitude, and the outputs are active power and reactive power. Therefore, this model is called the phase-amplitude-active-reactive power model. In this case, compared with a single-input single-output (SISO) system, multivariable design and a higher system order need to be considered. In a three-phase system, complex variable (CV) control is usually adopted to reduce the system order and handle coupling terms. Thus, CV-based control has been successfully applied to the current and voltage control of inverters for synchronization. However, due to the asymmetry of active power and reactive power, the complex variable model and control of power synchronous GFM control have not been fully developed.

[0004] Before designing the control of GFM inverter power control, a complex power model should be established first. Recently, a complex-valued droop control has been designed for a single inverter in the industry. However, the output of the complex-valued droop controller is the reference of the dq voltage control loop, rather than the frequency, because the phase angle difference is replaced by the q-axis voltage. In addition, there is also a complex-valued droop controller for the voltage control loop in the αβ frame. This controller uses frequency as the control variable, but the parameters of the active and reactive power loops are still designed separately.

[0005] The above traditional network-forming control faces challenges to the stability of power systems brought about by renewable energy, especially limitations exist when dealing with complex working conditions, including problems such as the complexity of power control and power coupling. Summary of the Invention

[0006] The object of the present invention is to provide a power control method for a network-forming inverter based on a dynamic complex power angle model. Through the dynamic complex power angle model, the application of CV technology is extended to GFM control, turning the GFM power control system into a single-input single-output (SISO) system, achieving precise control of the output voltage and current of the inverter, improving control performance, and reducing the design difficulty of the system. The technical solution adopted by the present invention is as follows.

[0007] On the one hand, the present invention provides a power control method for a network-forming inverter based on a dynamic complex power angle model, including:

[0008] Obtain a complex power controller model designed based on the dynamic complex power angle model of the network-forming inverter;

[0009] Obtain the amplitude and phase angle of the grid connection point and grid voltage, as well as the reference values of the active power and reactive power injected by the inverter into the grid;

[0010] Calculate the complex power reference quantity according to the reference values of the active power and reactive power, and calculate the actual output complex power of the inverter according to the amplitude and phase angle of the grid connection point and grid voltage;

[0011] Based on the deviation between the complex power reference quantity and the actual output complex power, use the complex power controller model to obtain a composite control signal including a phase angle adjustment quantity and a voltage amplitude correction quantity;

[0012] Based on the difference between the composite control signal and the grid connection point voltage vector, obtain the modulated inverter control signal.

[0013] In the present invention, the control parameters of the complex power controller are determined based on the dynamic complex power angle model of the network-forming inverter, and the dynamic complex power angle model of the network-forming inverter turns the complex GFM power control system into a single-input single-output (SISO) system, greatly simplifying the decoupling control design process, reducing the design difficulty of the system controller, and being able to ensure the control performance of the system.

[0014] Optionally, the dynamic complex power angle model is expressed as:

[0015]

[0016] Where s is the Laplace operator, is the complex power output by the inverter, is the complex disturbance variable of the inverter voltage, is the complex disturbance variable of the grid voltage, is the angular frequency of the network-forming inverter, is the amplitude of the output voltage of the network-forming inverter, and are the line inductance and resistance, 、 are the equivalent complex coefficients, and there is , .

[0017] Optionally, the actual output complex power of the inverter is calculated according to the amplitude and phase angle of the grid connection point voltage, and the formula is:

[0018]

[0019] In the formula, is the current flowing through the line impedance, and "*" represents the conjugate of the complex variable.

[0020] Optionally, the construction of the dynamic complex power angle model of the network-forming inverter includes:

[0021] Simplify the control object of the power control of the network-forming inverter to an impedance two-node system, where one node is the equivalent voltage source of the network-forming inverter with adjustable frequency and amplitude, and the other node is the equivalent voltage source of the power grid. The complex power between the two nodes is expressed as:

[0022] (1)

[0023] Where and are the active power and reactive power injected into the power grid by the network-forming inverter respectively;

[0024] By taking the derivative of the complex power, there is:

[0025] (2)

[0026] Where is the grid voltage;

[0027] Let , , where, is the amplitude of the inverter output voltage; is the amplitude of the grid voltage, and represent the phase angle of the inverter output voltage and the phase angle of the grid voltage respectively. According to complex number operation, there is:

[0028] (3)

[0029] Where the small-signal perturbation of the phase difference , and respectively represent the small-signal perturbation of the output voltage phase angle of the network-forming inverter and the small-signal perturbation of the grid voltage phase angle ;

[0030] Define the control quantities of active and reactive power as and , respectively, and there is:

[0031] (4)

[0032] Substitute Equation (4) into Equation (2), and separate the real and imaginary parts to obtain:

[0033] (5)

[0034] Perform small-signal analysis on Equation (4) to obtain:

[0035] (6)

[0036] Among them, is the amplitude perturbation of the inverter output voltage; is the amplitude perturbation of the grid voltage.

[0037] Use the vector to represent the small-signal perturbations of the active and reactive power control quantities, and write them in the form of the complex variable , then Equation (6) becomes:

[0038] (7)

[0039] Among them, the intermediate complex variables and are expressed as:

[0040] (8)

[0041] Then there is:

[0042] (9)

[0043] Since the amplitude difference and phase difference between the two node voltage sources are small, can be ignored, and then the complex power angle transfer function of the network-forming inverter is obtained, that is, the dynamic complex power angle model of the network-forming inverter.

[0044] Optionally, the complex power controller model is expressed as:

[0045]

[0046] Among them, is the gain coefficient of the complex power controller, is the controller model based on the traditional synchronous generator swing equation, expressed as:

[0047]

[0048] In the formula, is the rated angular frequency, is the virtual moment of inertia, is the virtual damping coefficient, , , The values of can be comprehensively determined through inertia demand analysis, frequency domain / time domain optimization, and stability verification and then used for complex power control.

[0049] Optionally, the open-loop transfer function of the power control target system of the network-forming inverter is:

[0050] .

[0051] Optionally, the closed-loop transfer function of the power control target system of the network-forming inverter is:

[0052] .

[0053] In a second aspect, the present invention provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, it implements the power control method of the network-forming inverter based on the dynamic complex power angle model as described in the first aspect.

[0054] In a third aspect, the present invention provides a computer device, which includes:

[0055] A memory for storing a computer program;

[0056] A processor for executing the computer program to implement the power control method of the network-forming inverter based on the dynamic complex power angle model as described in the first aspect.

[0057] Beneficial effects

[0058] The power control method of the present invention is based on the dynamic complex power angle model of the network-forming inverter. Based on the power-phase angle (PPA) model, a dynamic complex power angle (CPPA) model of the network-forming inverter is constructed. Based on the dynamic CPPA model, the GFM power control is transformed into a single-input single-output (SISO) system, and then a complex power controller based on the traditional synchronous generator swing equation is realized. Through the coordinated operation of the voltage controller and the network-forming complex power controller, precise control of the output voltage and current of the inverter is achieved, thereby providing frequency and voltage support for the power grid in distributed generation or microgrids. The present invention greatly improves the control efficiency and performance of the grid-connected inverter, enabling it to respond more precisely and quickly to grid fluctuations, enhancing the overall stability and response speed of the power system, providing strong technical support for building a more intelligent, efficient, and stable green power grid, and being of great significance for improving the stability and reliability of the power grid. At the same time, the present invention also simplifies the decoupling control design process and reduces the design difficulty of the system controller. Description of the Drawings

[0059] Figure 1 The control schematic diagram of the power control method of the network-forming inverter in the embodiment of the present invention is shown;

[0060] Figure 2 The closed-loop control block diagram of the complex power of the network-forming inverter based on the CPPA model in the small-signal mode in the embodiment of the present invention is shown. Detailed Embodiments

[0061] The following is further described in conjunction with the drawings and specific embodiments.

[0062] Embodiment 1

[0063] This embodiment introduces a power control method of a network-forming inverter based on a dynamic complex power angle model. As Figure 1 shown, the method of this embodiment includes:

[0064] Obtain the dynamic complex power angle model and the complex power controller model of the network-forming inverter;

[0065] Obtain the amplitude and phase angle of the grid connection point and the grid voltage, as well as the reference values of the active power and reactive power injected by the inverter into the grid;

[0066] Calculate the complex power reference quantity according to the reference values of the active power and reactive power, and calculate the actual output complex power of the inverter according to the amplitude and phase angle of the grid connection point and the grid voltage;

[0067] Based on the deviation between the complex power reference quantity and the actual output complex power, use the complex power controller model to obtain a composite control signal including the phase angle adjustment quantity and the voltage amplitude correction quantity;

[0068] Based on the difference between the composite control signal and the grid connection point voltage vector, the modulated inverter control signal is obtained.

[0069] The specific implementation of the method in this embodiment includes the following content.

[0070] I. Establish a dynamic complex model of the GFM-controlled grid-connected inverter

[0071] The general control objective of GFM power control can be simplified to a two-node system with impedance Z = R + jX = Zejφ. Generally, one of the nodes is a controllable GFM voltage source with adjustable frequency and amplitude. The other node is the grid equivalent voltage source, usually regarded as a voltage source with fixed frequency and amplitude (such as an infinite grid), and its phase angle and amplitude are constant values or affected by the grid operating state. In order to unify the design of the active power controller (APC) and the reactive power controller (RPC), the present invention establishes a dynamic CPPA model of the GFM inverter. The complex power between the two nodes can be expressed as:

[0072]

[0073] where p and q are the active power and reactive power injected into the grid by the GFM inverter respectively, is the output voltage of the inverter, is the current flowing through the line impedance.

[0074] By taking the derivative of the complex power, we have:

[0075]

[0076] where L and R are the line inductance and resistance, is the angular frequency of the GFM inverter, is the grid voltage, and "*" represents the conjugate of the complex variable.

[0077] Let , , according to complex number operations, we have:

[0078]

[0079] is the amplitude of the inverter output voltage; is the amplitude of the grid voltage.

[0080] Define the control quantities of active and reactive power as and :

[0081]

[0082] Substitute Equation (4) into Equation (2), and separate the real and imaginary parts to obtain:

[0083]

[0084] Then, perform a small-signal analysis on Equation (4):

[0085]

[0086] where and represent the amplitude perturbations of the inverter output voltage and the grid voltage, Δθ = θ1 − θ2 = Δθ1 − Δθ2 represents the phase difference, θ1 and θ2 represent the phase angles of the inverter output voltage and the grid voltage respectively; Δθ 1、 Δθ2 represents the phase angle perturbations of the inverter output voltage and the grid voltage. Therefore, the "Δ" in Δθ also represents a small-signal perturbation.

[0087] In this case, use the vector [Δu p Δu q T to represent the dynamic input perturbations of active and reactive power, which can be written in the form of the complex variable Δu s = Δu p + jΔu q Equation (6) becomes:

[0088]

[0089] where is the complex perturbation variable of the inverter voltage, is the complex perturbation variable of the grid voltage.

[0090] and are the weight coefficients of perturbation transfer, which determine the influence ratio of the inverter and grid perturbations on the power dynamics, and are expressed as:

[0091]

[0092] Finally, we get:

[0093]

[0094] Generally, the phase difference between the equivalent voltage source of the GFM inverter and the equivalent voltage source of the grid is very small, and the amplitude difference is usually less than 10%. Therefore, compared with , can be ignored. Finally, the complex power angle transfer function of the grid-forming inverter can be obtained as follows:

[0095] ​

[0096] where \(k_2\) and \(k_3\) are equivalent complex coefficients, and their values are fixed, which are respectively: , .

[0097] II. Design the complex power controller of the GFM inverter.

[0098] Referring to Figure 1 and Figure 2 , the complex power control block diagram based on the dynamic complex power phase angle (CPPA) model includes a complex power controller to be designed, namely the GFM Power Controller, i.e., \(G\) CPC (s). Through the CPPA model, the two-node system can be converted into a single-input single-output (SISO) transfer function, thus simplifying the controller design.

[0099] As Figure 2 , , is the gain coefficient of the complex power controller, and the design of is flexible. In this embodiment, a controller designed based on the traditional swing equation of the synchronous generator is considered to simulate the dynamic characteristics of the synchronous generator and provide inertia and damping for the system, i.e.:

[0100]

[0101] where is the virtual moment of inertia, is the virtual damping coefficient, and is the rated angular frequency.

[0102] The open-loop transfer function of the system is:

[0103]

[0104] Then, the closed-loop transfer function of the control system including the complex power controller and the complex power angle model can be derived as:

[0105]

[0106] where is the gain coefficient of the complex power controller, the virtual moment of inertia , the virtual damping coefficient and the gain coefficient can be comprehensively determined through pole placement, inertia demand analysis, frequency domain analysis (such as Bode plots, Nyquist curves), time domain optimization, and stability verification, so that the complex power controller can, according to the complex power deviation of the system, perform virtual inertia and damping coefficient The coordinated regulation of the phase angle adjustment is outputted and voltage amplitude correction Composite control signal , so that the output complex power of the inverter tracks the complex power reference value. For pole configuration, inertia requirement analysis, frequency domain analysis (such as Bode plot, Nyquist curve), time domain optimization and stability verification, please refer to existing relevant literature.

[0107] 3. GFM inverter power control

[0108] Based on the above derivation based on the GFM inverter dynamic complex power phase angle model, , , The complex power control with all parameters determined is combined again Figure 1 and Figure 2 The implementation process of the control method of the present invention can be summarized as the following closed-loop control process: First, the voltage amplitude of the grid connection point is collected in real time. With phase angle And the voltage amplitude With phase angle , after the complex power calculation module, the actual value of the complex power is obtained, and the external setting is obtained , , used to obtain the reference complex power S r Then the actual inverter output complex power S = p + jq and the reference complex power S r The deviation signal is passed through the complex power controller Virtual Inertia and the damping coefficient The coordinated regulation of and voltage amplitude correction Composite control signal .

[0109] The working process of the voltage inner loop is as follows: receiving the complex power controller Generated complex reference voltage The three-phase voltage output by the inverter is measured in real time through sensors , calculate the complex error , and adopts complex variable control algorithm (such as PI control) to finally generate modulation signal, realize precise control of inverter, and form a complete closed loop from power detection to dynamic regulation.

[0110] Example 2

[0111] This embodiment introduces a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, it implements the power control method of the network-forming inverter based on the dynamic complex power angle model as introduced in Embodiment 1.

[0112] Embodiment 3

[0113] This embodiment introduces a computer device, which includes:

[0114] A memory for storing a computer program;

[0115] A processor for executing the computer program to implement the power control method of the network-forming inverter based on the dynamic complex power angle model as introduced in Embodiment 1.

[0116] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memories, CD-ROMs, optical memories, etc.) containing computer-usable program codes.

[0117] The present application is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram can be implemented by computer program instructions, and the combination of the flows and / or blocks in the flowchart and / or block diagram can also be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate means for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0118] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured article including instruction means, and the instruction means implements the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0119] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus, so that a series of operation steps are executed on the computer or other programmable apparatus to produce a computer-implemented process, thereby the instructions executed on the computer or other programmable apparatus provide steps for implementing the functions specified in one process or a plurality of processes and / or blocks Figure 1 one process or a plurality of processes and / or blocks Figure 1 steps of the functions specified in one block or a plurality of blocks.

[0120] The embodiments of the present invention have been described above in conjunction with the accompanying drawings. However, the present invention is not limited to the above specific embodiments. The above specific embodiments are merely illustrative rather than restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can also make many forms without departing from the spirit of the present invention and the scope protected by the claims. These all fall within the protection scope of the present invention.

Claims

1. A power control method for a network-forming inverter based on a dynamic complex power angle model, characterized in that Including: Obtain a complex power controller model designed based on the dynamic complex power angle model of a network-forming inverter; Obtain the grid connection point, the grid voltage amplitude and phase angle, as well as the reference values of the active power and reactive power injected by the inverter into the grid; Calculate the complex power reference quantity according to the reference values of the active power and reactive power, and calculate the actual output complex power of the inverter according to the grid connection point, the grid voltage amplitude and phase angle; Based on the deviation between the complex power reference quantity and the actual output complex power, use the complex power controller model to obtain a composite control signal including a phase angle adjustment quantity and a voltage amplitude correction quantity; Based on the difference between the composite control signal and the grid connection point voltage vector, obtain the modulated inverter control signal.

2. The method according to claim 1, wherein The dynamic complex power angle model is expressed as: ， where s is the Laplace operator, is the complex power output by the inverter, is the complex perturbation variable of the inverter voltage, is the complex perturbation variable of the grid voltage, is the angular frequency of the grid-forming inverter, is the output voltage amplitude of the grid-forming inverter, and are the line inductance and resistance, 、 are equivalent complex coefficients, and there are , .

3. The method according to claim 1, characterized in that, The formula for calculating the actual output complex power of the inverter according to the grid connection point, the grid voltage amplitude and phase angle is: ， Wherein, is the current flowing through the line impedance, and "*" represents the conjugate of the complex variable.

4. The method according to claim 2, characterized in that, The construction of the dynamic complex power angle model of the network-forming inverter includes: Simplify the control object of the power control of the network-forming inverter to impedance The two-node system, where one node is the equivalent voltage source of the network-forming inverter with adjustable frequency and amplitude, and the other node is the equivalent voltage source of the power grid. The complex power between the two nodes is expressed as: （1）， wherein and are the active power and reactive power injected into the grid by the grid-forming inverter, respectively; By taking the derivative of the complex power, we have: （2）， wherein is the grid voltage; Let , , where is the amplitude of the inverter output voltage; is the amplitude of the grid voltage, and respectively represent the phase angle of the grid-forming inverter output voltage and the grid voltage phase angle. According to complex number operations, there is: （3）， Among them, the small-signal perturbation of the phase difference , and respectively represent the small-signal perturbation of the output voltage phase angle of the grid-forming inverter, and the small-signal perturbation of the grid voltage phase angle ; Define the control variables of active and reactive power as and , respectively. Then, we have: （4）， Substitute Equation (4) into Equation (2) and separate the real and imaginary parts to obtain: （5）， Perform small-signal analysis on Equation (4) to obtain: （6）， Among them, is the amplitude disturbance of the inverter output voltage; is the amplitude disturbance of the grid voltage; Using vectors to represent the small-signal perturbations of the active and reactive power control variables, written in the form of a complex variable the equation (6) becomes: （7）， where the intermediate complex variable and are expressed as: （8）， Then we have: （9）， Since the amplitude difference and phase difference between the two node voltage sources are small, they are ignored , and then the complex power angle transfer function of the network-forming inverter is obtained, that is, the dynamic complex power angle model of the network-forming inverter.

5. The method according to claim 2, wherein The complex power controller model is expressed as: ， Among them, is the gain coefficient of the complex power controller, is the controller model based on the traditional swing equation of the synchronous generator, expressed as: ， wherein, is the rated angular frequency, is the virtual moment of inertia, is the virtual damping coefficient.

6. The method according to claim 5, wherein The open-loop transfer function of the power control target system of the network-forming inverter is: 。 7. The method according to claim 6, wherein The closed-loop transfer function of the power control target system of the network-forming inverter is: 。 8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the power control method for a network-forming inverter based on the dynamic complex power angle model as described in any one of Claims 1-7.

9. A computer device, characterized in that it includes: A memory for storing computer programs / instructions; A processor for executing the computer programs / instructions to implement the power control method for a network-forming inverter based on the dynamic complex power angle model as described in any one of Claims 1-7.

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