Transient stability control method for network construction type converter

Abstract

The invention provides a transient stability control method for a network construction type converter, and the method comprises the steps: carrying out the modeling of the network construction type converter, and obtaining a first model corresponding to the network construction type converter; arranging a power feedback module between the power deviation value and the power reference value of the first model, wherein the power feedback module is used for providing compensation power; acquiring a power reference value and electromagnetic power; and based on the compensation power, the power reference value and the electromagnetic power, determining a current power deviation value, and based on the current power deviation value, determining a power angle of the network-forming type energy storage converter. According to the method provided by the invention, the power compensation module is added for providing compensation power and adjusting a power reference value, so that the acceleration energy during a fault period is reduced and the braking energy is increased, so that the angular frequency of the virtual rotor can be recovered to a rated angular frequency before a system working point reaches an unstable equilibrium point (UEP); therefore, the transient power angle stability of the grid-forming converter is improved.

Description

Technical Field

[0001] The present application relates to the field of distributed power generation technology, and in particular to a transient stability control method for a grid-type converter. Background Art

[0002] In recent years, building a new power system architecture based on renewable energy has become a key development goal. However, renewable energy is typically connected to the grid through power electronic converters, and their large-scale integration significantly alters the operating characteristics of the power system. Currently, power electronic converters are primarily categorized by control method: grid-following converters and grid-forming converters. Grid-forming converters, simulating the rotor motion characteristics of synchronous generators, can provide the necessary voltage and frequency support for power systems, demonstrating broad application prospects. However, when subjected to large disturbances, grid-forming converters may experience transient power angle instability, similar to that of synchronous generators. Summary of the Invention

[0003] In order to overcome the above technical defects, the present application provides a method for transient stability control of a grid-type converter. To achieve the above objectives, the present application is implemented according to the following technical solutions:

[0004] The present application provides a method for transient stability control of a grid-type converter, comprising:

[0005] Modeling the meshed converter to obtain a first model corresponding to the meshed converter;

[0006] A power feedback module is provided between the power deviation of the first model and the power reference value, wherein the power feedback module is used to provide compensation power;

[0007] Obtaining power reference value and electromagnetic power;

[0008] determining a current power deviation based on the compensation power, the power reference value, and the electromagnetic power;

[0009] Based on the current power deviation, a power angle of the grid-type energy storage converter is determined.

[0010] Optionally, the compensation power is obtained based on the previous power deviation and is expressed as:

[0011]

[0012] Where ΔP0 is the compensation power, K p is the power regulation coefficient, s is the Laplace operator, and ΔP1 is the previous power deviation value.

[0013] Optionally, determining the current power deviation based on the compensation power, the power reference value, and the electromagnetic power includes:

[0014] Subtracting the compensation power from the power reference value to obtain an effective input power;

[0015] The effective input power is subtracted from the electromagnetic power to determine a current power deviation.

[0016] Optionally, determining the power angle of the grid-type energy storage converter based on the current power deviation includes:

[0017] Acquisition system current angular frequency;

[0018] Get the rated angular frequency;

[0019] The power angle of the grid-type energy storage converter is determined based on the current power deviation, the current angular frequency of the system, and the rated angular frequency.

[0020] Optionally, the electromagnetic power is obtained in the following manner:

[0021] Obtaining the grid voltage and the grid-type converter port voltage;

[0022] The electromagnetic power is determined based on the grid voltage and the grid-type converter port voltage.

[0023] Optionally, the grid-type energy storage converter is controlled by a virtual synchronous machine.

[0024] This application has the following beneficial effects:

[0025] The method proposed in this application adds a power compensation module to provide compensation power and adjust the power reference value, thereby reducing the acceleration energy during the fault and increasing the braking energy. This allows the angular frequency of the virtual rotor to return to the rated angular frequency before the system operating point reaches the unstable equilibrium point, thereby improving the transient power angle stability of the grid-type converter.

[0026] In addition to the above-described purposes, features and advantages, the present application has other purposes, features and advantages. The present application will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of this application. The exemplary embodiments and descriptions of this application are intended to explain this application and do not constitute an improper limitation on this application. In the accompanying drawings:

[0028] Figure 1 1 is a flow chart of a transient stability control method for a grid-type converter provided in an embodiment of the present application;

[0029] Figure 2This is a transient stability control block diagram provided by an embodiment of the present application;

[0030] Figure 3 Schematic diagram of the effect of the power regulation coefficient on the transient characteristics of the system provided in the embodiment of the present application;

[0031] Figure 4 This is a schematic diagram of simulation results of a meshed converter using a traditional virtual synchronous machine strategy provided by the experimental simulation of an embodiment of the present application;

[0032] Figure 5 This is a schematic diagram of the simulation results of the meshed converter using the improved virtual synchronous machine strategy proposed in this application, provided by the experimental simulation of the embodiment of this application. DETAILED DESCRIPTION

[0033] The embodiments of the present application are described in detail below with reference to the accompanying drawings, but the present application can be implemented in many different ways as defined and covered by the claims.

[0034] Therefore, in order to solve the problem of transient instability in the above-mentioned grid-type converter, Figure 1 As shown, the present application provides a transient stability control method for a grid-type converter, comprising:

[0035] Step S101: Modeling the meshed converter to obtain a first model corresponding to the meshed converter;

[0036] A grid-forming converter (GFC) is a power electronic device that simulates the characteristics of a synchronous generator. Its core function is to provide frequency, voltage, and rotational inertia for the power grid, improving the stability and reliability of renewable energy grid-connected systems. Here, we model this GFC to obtain the first model corresponding to the GFC.

[0037] Step S102: setting a power feedback module between the power deviation of the first model and the power reference value, wherein the power feedback module is used to provide compensation power;

[0038] like Figure 2 As shown in the figure, a power compensation module is set between the power deviation ΔP1 and the power reference value P0. The compensation power ΔP0 generated by the power feedback module is used to adjust the power reference value P0, thereby reducing the acceleration energy and increasing the braking energy during the fault period. This allows the angular frequency of the virtual rotor to return to the rated angular frequency before the system operating point reaches the unstable equilibrium point, thereby effectively improving the transient stability of the grid-type converter.

[0039] The compensation power ΔP0 is obtained based on the previous power deviation and is expressed as:

[0040]

[0041] Where ΔP0 is the compensation power, K p is the power regulation coefficient, s is the Laplace operator, and ΔP1 is the previous power deviation value.

[0042] Step S103: obtaining a power reference value and electromagnetic power;

[0043] At this time, obtain the power reference value P0 and electromagnetic power P e .

[0044] The electromagnetic power determination process is as follows:

[0045] Get the grid voltage U g ∠0 and the port voltage U of the network converter s ∠δ; then the grid voltage is used as the system reference voltage, and the electromagnetic power is determined based on the system reference voltage and the port voltage of the grid-type converter, as shown in formula (4):

[0046]

[0047] Where, δ is the power angle of the grid-type energy storage converter, α1=R / [R 2 +X 2 ], X is the line inductance, and R is the line resistance.

[0048] It should be noted that the grid-type energy storage converter of the present application adopts virtual synchronous machine control.

[0049] Step S104: determining a current power deviation based on the compensation power, the power reference value and the electromagnetic power.

[0050] First, the compensation power and the power reference value are calculated to obtain the effective input power, and the effective input power is calculated to obtain the difference between the electromagnetic power to determine the current power deviation.

[0051] Step S105: Determine the power angle of the grid-type energy storage converter based on the current power deviation.

[0052] The system's current angular frequency ω is collected, followed by the rated angular frequency ω0. The power angle of the grid-type energy storage converter is then determined based on the system's current angular frequency ω, the rated angular frequency ω0, and the current power deviation ΔP1, as calculated in Equation (5). The power feedback module adaptively adjusts the power deviation to minimize power angle overshoot after a fault, which is beneficial to the system's transient stability.

[0053]

[0054] Where, J is the virtual inertia coefficient, D p is the damping coefficient.

[0055] Experimental simulation

[0056] To verify the effectiveness of the above method, a simulation experiment of a grid-connected converter system was conducted in MATLAB / Simulink, including simulation of the traditional virtual synchronous machine strategy and the improved virtual synchronous machine strategy proposed in this application. The simulation parameters are shown in Table 1:

[0057] Table 1 Simulation parameters

[0058] variable name illustrate Numerical <![CDATA[f n ]]> Rated frequency 50Hz <![CDATA[L f ]]> filter inductors 2.2mH <![CDATA[C f ]]> filter capacitors 10uF <![CDATA[R c / L c ]]> Line impedance 0.2Ω / 6mH <![CDATA[V p ]]> AC voltage peak 311V <![CDATA[D p ]]> Damping coefficient 40 J Virtual inertia constant 0.5 <![CDATA[P0]]> Input power 30,000kW

[0059] Figure 3 Shows the power regulation factor K p The impact of changes on the transient performance of the system. The system steady-state operating point is at SEP, and the fault condition is: the grid voltage drops from 1p.u. to 0.6pu. Figure 3 It can be seen that the power angle of the grid-type converter using the traditional virtual synchronous machine strategy continues to increase, and transient instability occurs. After adopting the power feedback module, the system can operate stably and increase the power regulation coefficient K p The smaller the power angle overshoot after a fault, the more beneficial it is to the transient stability of the system.

[0060] Initially, the input power of the grid-type converter is P0 = 30 kW. At t = 3 s, the grid voltage drops to 0.7 pu and remains at this level until the end of the simulation. Figure 4 and Figure 5 These are the simulation waveforms of the traditional virtual synchronous machine strategy and the virtual synchronous machine strategy based on power feedback.

[0061] Simulation results show that a grid-type converter using a traditional virtual synchronous machine strategy experiences transient power angle instability during a fault. However, a grid-type converter using the improved virtual synchronous machine strategy proposed in this application maintains normal operation during the fault. Simulation experiments validate the effectiveness of the transient power angle stabilization control method for grid-type converters.

[0062] In summary, the method proposed in this application adds a power compensation module to provide compensation power and adjust the power reference value, thereby reducing the acceleration energy during the fault and increasing the braking energy. This allows the angular frequency of the virtual rotor to return to the rated angular frequency before the system operating point reaches the unstable equilibrium point, thereby improving the transient power angle stability of the grid-type converter.

[0063] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A transient stability control method for a grid-type converter, characterized in that: include: Modeling the meshed converter to obtain a first model corresponding to the meshed converter; A power feedback module is provided between the power deviation of the first model and the power reference value, wherein the power feedback module is used to provide compensation power; Obtaining power reference value and electromagnetic power; determining a current power deviation based on the compensation power, the power reference value, and the electromagnetic power; Based on the current power deviation, a power angle of the grid-type energy storage converter is determined.

2. The method according to claim 1, characterized in that The compensation power is obtained based on the previous power deviation and is expressed as: Where ΔP0 is the compensation power, K p is the power regulation coefficient, s is the Laplace operator, and ΔP1 is the previous power deviation value.

3. The method according to claim 1, characterized in that The determining of the current power deviation based on the compensation power, the power reference value, and the electromagnetic power includes: Subtracting the compensation power from the power reference value to obtain an effective input power; The effective input power is subtracted from the electromagnetic power to determine a current power deviation.

4. The method according to claim 1, wherein The determining the power angle of the grid-type energy storage converter based on the current power deviation includes: Acquisition system current angular frequency; Get the rated angular frequency; The power angle of the grid-type energy storage converter is determined based on the current power deviation, the current angular frequency of the system, and the rated angular frequency.

5. The method according to claim 1 or 3, characterized in that The electromagnetic power is obtained in the following manner: Obtaining the grid voltage and the grid-type converter port voltage; The electromagnetic power is determined based on the grid voltage and the grid-type converter port voltage.

6. The method according to claim 4, characterized in that The grid-type energy storage converter is controlled by a virtual synchronous machine.

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