A power decoupling control method for self-synchronous voltage source

Abstract

The present invention proposes a power decoupling control method for a self-synchronous voltage source, which specifically includes: constructing a self-synchronous voltage source grid-connected control model, equivalent inverter and synchronous generator electrical parts, and designing active and reactive loop control. The small signal mathematical model is obtained by simplifying the model to reveal the power cross-coupling relationship. The decoupling conditions are analyzed, a power compensation link based on power angle and voltage regulation is proposed, a power small signal model containing decoupling control is established, and power decoupling is realized. This scheme is not limited by system parameter changes, is applicable to a variety of working conditions, and has a small decoupling error. It can reduce system oscillation problems caused by power coupling problems, improve the control accuracy and stability of the system, and realize complete decoupling of active power and reactive power.

Description

Technical Field

[0001] The invention relates to the field of self-synchronous voltage source converter control, and in particular to a power decoupling control method of a self-synchronous voltage source. Background Art

[0002] As the proportion of renewable energy in energy consumption continues to rise, the proportion of distributed power sources in the power grid is increasing, and the number of power electronic equipment is also increasing. Its reliability problem has become an important factor restricting the safe operation of the power grid. After large-scale renewable energy is connected to the grid, the inertial support capacity of the power grid is insufficient, showing low inertia and low damping characteristics. The self-synchronous voltage source can provide inertia, frequency and voltage support for the power grid, which can effectively solve the stability problems of voltage and frequency in the power system. However, the lines of the power system with a high proportion of renewable energy are resistive and inductive, and the application scenarios are complex. It is impossible to ensure the independent control of the active loop and the reactive loop, resulting in serious cross-coupling of active and reactive power. Power coupling has become one of the important factors affecting the stability of the self-synchronous voltage source grid connection. Power coupling has a significant impact on the power system, making the active and reactive power control inaccurate, and even causing active and reactive power oscillation, which can seriously lead to loss of synchronization.

[0003] Teng et al. proposed a virtual power method based on coordinate rotation transformation. This method realizes virtual power decoupling by operating the virtual power supply in the inductive grid. However, it cannot achieve true power coupling.

[0004] Guerrero et al. proposed that the coupling of active power and reactive power can be easily reduced by introducing a virtual inductor. However, power coupling still exists because the virtual inductor is different from the actual inductor.

[0005] According to the relationship between active power and reactive power, Feng et al. eliminated the influence of active power on reactive power by adjusting the terminal voltage amplitude. However, this method ignores the power loss in the grid impedance. The actual relationship between active power and reactive power is relatively complicated, which makes it difficult to correctly adjust the terminal voltage amplitude.

[0006] According to the working conditions of medium and low voltage power grids, Qu Zisen and other scholars proposed a method to use the output power to estimate the power angle and then calculate the virtual impedance value to alleviate the power coupling phenomenon. However, this document focuses on the impact of active power changes on reactive power, and the reactive power does not reach the given value after stabilization.

[0007] The invention patent with application number 202311429714.X discloses a method for power decoupling control and reactive power rapid regulation of a weak grid self-synchronous power supply. This method adopts a virtual impedance method to solve the power decoupling problem by determining a suitable virtual impedance range. However, this method mainly considers the influence of the line impedance angle on power coupling, and ignores other possible influencing factors. In addition, the decoupling method is also limited by changes in system parameters. The parameters in the actual system may change with changes in time, temperature, load and other factors. Such parameter changes may render the virtual impedance method invalid or reduce its effect. Finally, although the virtual impedance method can alleviate power coupling to a certain extent, due to the non-ideal nature of the system and the use of approximate methods, there may still be certain decoupling errors. This error may become more significant under specific operating conditions or when the system changes dynamically.

[0008] The invention patent with application number 201711040473.4 discloses that the output active power of the virtual synchronous machine is first used to estimate the fluctuation of the power angle, and then the virtual resistance value and virtual inductance value of the virtual impedance are calculated, and then the virtual impedance value is introduced into the inverter voltage control loop, and the obtained voltage given value is used as the given signal of the inner loop voltage control loop, and finally the output signal of the inner loop control is used as the control signal of the inverter to realize the power decoupling of the virtual synchronous machine and eliminate the influence of the active power loop on the reactive power control loop. When realizing power decoupling, the method of this patent, compared with the comparative patent, additionally considers the influence of reactive power on active power for the power coupling problem. First, the small signal model of the self-synchronous voltage source is analyzed to obtain the cross-coupling relationship between active power and reactive power, and obtain the complete decoupling condition corresponding to the small signal model, and further proposes a power decoupling method that comprehensively considers the voltage influence and the power angle influence, which not only eliminates the influence of active power on reactive power, but also eliminates the influence of reactive power on active power, and realizes the complete decoupling between active power and reactive power. At the same time, when calculating the change in power angle, the compared patent simply estimates based on active power, thereby calculating the virtual impedance value and introducing a control signal for the inverter voltage control loop, while this patent linearizes the active power and reactive power near the steady-state operating point to obtain the power change deviation matrix equation, further obtain the equations for the change in active power and reactive power, and finally obtain the power angle change calculation equation and voltage conversion calculation equation containing power coupling terms, which can accurately calculate the power angle fluctuation and voltage fluctuation, thereby compensating for power coupling and achieving complete power decoupling. Therefore, the two patents are different in terms of power decoupling method and ultimate purpose.

[0009] Therefore, there is an urgent need to find a power decoupling method that takes multiple coupling factors into consideration, is not limited by changes in system parameters, is suitable for a variety of working conditions, and has a small decoupling error, so as to reduce system oscillations caused by power coupling problems and improve the control accuracy and stability of the system. Summary of the invention

[0010] The technical problem to be solved by the present invention is to provide a power decoupling control method of a self-synchronous voltage source in view of the deficiencies in the prior art.

[0011] To achieve the above object, the technical solution adopted by the present invention is:

[0012] A power decoupling control method for a self-synchronous voltage source comprises the following steps:

[0013] Step 1: Establish a grid-connected control structure model of the self-synchronous voltage source, make the main circuit of the self-synchronous voltage source inverter equivalent to the electrical part of the synchronous generator, and construct a self-synchronous voltage source control scheme including active loop control and reactive loop control;

[0014] Step 2: Based on the power loop control, the self-synchronous voltage source grid-connected control structure model can be simplified to obtain the self-synchronous voltage source grid-connected equivalent model. Based on the simplified model, the corresponding small signal mathematical model is calculated to obtain the cross-coupling relationship between active power and reactive power.

[0015] Step 3: According to the cross-coupling relationship between active power and reactive power, a complete decoupling condition corresponding to the small signal model is obtained;

[0016] Step 4: Analyze the known and unknown quantities in the complete decoupling condition, propose a power compensation link based on power angle regulation and voltage regulation design, establish a self-synchronous voltage source power small signal model with decoupling control, and realize self-synchronous voltage source power decoupling.

[0017] Further, the step 1 specifically includes the following steps:

[0018] Step 1-1: Establish a grid-connected control structure model of the self-synchronous voltage source, and make the main circuit of the self-synchronous voltage source equivalent to the electrical part of the synchronous generator, specifically including: making the fundamental voltage equivalent to the internal potential of the synchronous generator; making the filter inductor equivalent to the synchronous reactance of the synchronous generator; making the output voltage of the common coupling point equivalent to the terminal voltage of the synchronous generator; and making the filter current on the bridge arm side equivalent to the output current of the synchronous generator;

[0019] Step 1-2: The active power loop provides virtual inertia by simulating the rotor motion equation. The mechanical motion equation of the synchronous generator rotor is:

[0020]

[0021] Where: J is the virtual inertia coefficient; D is the virtual damping coefficient; ω is the grid voltage angular frequency; ω 0 is the rated angular frequency of the power grid; P and P ref Respectively represent the actual output active power and the active power command value;

[0022] Step 1-3: The reactive loop adjusts the voltage at the common coupling point, simulates the primary voltage regulation characteristics of the synchronous generator, and uses steady-state error to control reactive power. The reactive power error (Q ref -Q) through the proportional controller k q Produces a voltage increment ΔV t , the QV droop control equation is:

[0023] V t -V g =k q (Q ref -Q)

[0024] Where: V t is the output voltage; V g is the grid voltage; Q and Q ref Respectively represent the actual output reactive power and reactive power command value; k q is the proportional control coefficient.

[0025] Further, the step 2 specifically includes the following steps:

[0026] Step 2-1: Based on the power loop control, the equivalent model of the self-synchronous voltage source grid connection is obtained. Through Kirchhoff's voltage law, the relationship between the grid current and the power angle, grid impedance, and voltage in the equivalent model of the self-synchronous voltage source grid connection is obtained, and then the complex power flow equation is derived as follows:

[0027]

[0028] Where: S is the apparent power; is the conjugate of the grid current;

[0029] Step 2-2: Linearize the equations in step 1-2 and step 1-3 at the steady-state operating point to obtain the linearized equation:

[0030]

[0031] Where: Δδ is the power angle change; ΔV t is the output voltage change; s is a complex variable;

[0032] Step 2-3: Linearize the active power and reactive power near the steady-state operating point to obtain the power change deviation matrix equation:

[0033]

[0034] Where H(s) is the coupling transfer function matrix; g 11 , g 12 , g 21 , g 22 It is the coupling term between active power, reactive power, output voltage amplitude and power angle;

[0035] Step 2-4: Combining the equations in step 2-2 and step 2-3, the small signal mathematical model is:

[0036]

[0037] From this mathematical model, it can be seen that active power and reactive power are connected through the cross-coupling term g 12 and g 21 Coupled.

[0038] Further, in step 3, the complete decoupling conditions are as follows:

[0039] From the power change deviation matrix equation described in step 2-3, the equations for the active power change and reactive power change are obtained as follows:

[0040]

[0041] It can be seen from the equation that by adjusting the power angle and voltage, the change in active power and reactive power can be made zero, thus achieving power decoupling.

[0042] Further, the step 4 specifically includes the following steps:

[0043] Step 4-1: When a disturbance occurs, the active power P changes. At this time, setting the reactive power change ΔQ to zero can eliminate the effect of active power on reactive power. Therefore, substituting ΔQ=0 into the equation in step 3-1, we can get ΔV t The equation is:

[0044]

[0045] From the equation, it can be seen that reasonable adjustment of the output voltage can eliminate the coupling effect on reactive power when active power changes;

[0046] Step 4-2: When a disturbance occurs, Q changes. At this time, setting ΔP to zero can eliminate the influence of active power on reactive power. Therefore, substituting ΔP=0 into the equation in step 3-1, the equation for Δδ is:

[0047]

[0048] It can be seen from the equation that reasonable adjustment of the power angle can eliminate the coupling effect of reactive power changes on active power;

[0049] Step 4-3: In the small signal model, introduce the power compensation link designed based on steps 3-2 and 3-3, establish a self-synchronous voltage source power small signal model with decoupling control, and realize power decoupling of the self-synchronous voltage source.

[0050] Beneficial effects:

[0051] In order to solve the problem of power coupling when the self-synchronous voltage source is connected to the grid, compared with the prior art, the present invention comprehensively considers various coupling factors and proposes a power decoupling method based on voltage compensation and power angle compensation. The method is not limited by changes in system parameters and is applicable to various working conditions. The decoupling error is small, and the system oscillation problem caused by power coupling can be reduced, the control accuracy and stability of the system can be improved, and the complete decoupling of active power and reactive power can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 is a flow chart of the present invention;

[0053] Figure 2 It is the grid-connected control structure model of the self-synchronous voltage source;

[0054] Figure 3 It is the grid-connected equivalent model of self-synchronous voltage source;

[0055] Figure 4 It is a small signal mathematical model;

[0056] Figure 5 It is a small signal power model of self-synchronous voltage source with decoupling control;

[0057] Figure 6 is the reactive power waveform under active power step disturbance;

[0058] Figure 7 is the reactive power waveform under active power oscillation disturbance;

[0059] Figure 8 is the active power waveform under reactive power step disturbance;

[0060] Fig. 9 It is the active power waveform under the reactive power oscillation disturbance. DETAILED DESCRIPTION

[0061] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments:

[0062] The present invention discloses a self-synchronous voltage source power decoupling control method, the flow chart is as follows Figure 1 As shown, including:

[0063] Step 1: Establish the grid-connected control structure model of the self-synchronous voltage source, make the main circuit of the self-synchronous voltage source inverter equivalent to the electrical part of the synchronous generator, and construct a self-synchronous voltage source control scheme including active loop control and reactive loop control.

[0064] Step 2: Based on the power loop control, the self-synchronous voltage source grid-connected control structure model can be simplified to obtain the self-synchronous voltage source grid-connected equivalent model. Based on the simplified model, the corresponding small signal mathematical model is calculated to obtain the cross-coupling relationship between active power and reactive power.

[0065] Step 3: According to the cross-coupling relationship between active power and reactive power, a complete decoupling condition corresponding to the small signal model is obtained.

[0066] Step 4: Analyze the known and unknown quantities in the complete decoupling condition, propose a power compensation link based on power angle regulation and voltage regulation design, establish a self-synchronous voltage source power small signal model with decoupling control, and realize self-synchronous voltage source power decoupling.

[0067] In step 1, the following steps are specifically included:

[0068] Step 1-1: Establish the grid-connected control structure model of the self-synchronous voltage source, such as Figure 2 As shown in the figure, the grid-connected control structure model of the self-synchronous voltage source consists of the main circuit topology and the self-synchronous voltage source control algorithm. In order to simplify the analysis, the distributed power source is equivalent to a DC power source. The main circuit topology consists of a DC power source, a three-phase voltage source inverter and a power grid. The control algorithm consists of active frequency control and reactive voltage control. dc is the DC voltage source equivalent to the distributed new energy; C dc is the DC bus capacitance; S 1 ~S 6 To form a three-phase inverter bridge; a 、e b 、e c is the fundamental voltage; L c and C are the inductance and capacitance of the inverter side that constitute the LC filter respectively; L g and R g Respectively represent the inductance and capacitance of the equivalent circuit between the inverter and the grid; i La 、i Lb 、i Lc is the filter current on the bridge arm side, i Ldq is the dq axis component of the current on the bridge arm side; u ta 、u tb 、u tc is the output voltage amplitude at the common coupling point (PCC), u tdqis the dq axis component of the output voltage; u ga 、u gb 、u gc is the voltage amplitude of the power grid; i ga 、i gb 、i gc is the grid-connected current, i gdq is the dq axis component of the grid-connected current; P and P ref Respectively represent the actual output active power and active power command value; Q and Q ref Respectively represent the actual output reactive power and reactive power command value; E and They represent the virtual internal potential and virtual rotor angle of the virtual synchronous machine respectively; U sd and U sq They represent the dq axis components of the modulation wave sent to the PWM link respectively. The main circuit of the self-synchronous voltage source is equivalent to the electrical part of the synchronous generator, specifically including: the fundamental voltage is equivalent to the internal potential of the synchronous generator; the filter inductance is equivalent to the synchronous reactance of the synchronous generator; the output voltage of the common coupling point is equivalent to the terminal voltage of the synchronous generator; the filter current on the bridge arm side is equivalent to the output current of the synchronous generator;

[0069] Step 1-2: The active power loop provides virtual inertia by simulating the rotor motion equation. The mechanical motion equation of the synchronous generator rotor is:

[0070]

[0071] Where: J is the virtual inertia coefficient; D is the virtual damping coefficient; ω is the grid voltage angular frequency; ω 0 is the rated angular frequency of the power grid; P and P ref Respectively represent the actual output active power and the active power command value;

[0072] Step 1-3: The reactive loop adjusts the voltage at the common coupling point, simulates the primary voltage regulation characteristics of the synchronous generator, and uses steady-state error to control reactive power to improve voltage support capability. ref -Q) through the proportional controller k q Produces a voltage increment ΔV t , the QV droop control equation is:

[0073] V t -V g =k q (Q ref -Q)

[0074] Where: V t is the output voltage; V g is the grid voltage; Q and Q ref Respectively represent the actual output reactive power and reactive power command value; kq is the proportional control coefficient.

[0075] In step 2, the following steps are specifically included:

[0076] Step 2-1: Based on the power loop control, the grid-connected equivalent model of the self-synchronous voltage source is obtained, as follows: Figure 3 As shown in the self-synchronous voltage source grid-connected equivalent model, θ zg is the grid impedance angle, whose magnitude is tan -1 (X g / R g );Z g is the grid impedance amplitude, which is δ is θ g The phase difference between and θ is obtained through Kirchhoff's voltage law, and the relationship between the grid current and the power angle, grid impedance, and voltage in the equivalent model of the self-synchronous voltage source grid connection is obtained, and then the complex power flow equation is derived as follows:

[0077]

[0078] Where: S is the apparent power; is the conjugate of the grid current;

[0079] Step 2-2: Linearize the equations in step 1-2 and step 1-3 at the steady-state operating point to obtain the linearized equation:

[0080]

[0081] Where: Δδ is the power angle change; ΔV t is the output voltage change; s is a complex variable;

[0082] Step 2-3: Linearize the active power and reactive power near the steady-state operating point, and the power change deviation matrix equation can be obtained as follows:

[0083]

[0084] Where H(s) is the coupling transfer function matrix; g 11 , g 12 , g 21 , g 22 It is the coupling term between active power, reactive power, output voltage amplitude and power angle;

[0085] Step 2-4: Combining the equations in step 2-2 and step 2-3, the small signal mathematical model is:

[0086]

[0087] Based on this mathematical model, a small signal equivalent model can be obtained, such as Figure 4 As shown in the small signal mathematical model, active power and reactive power are obtained through the cross-coupling term g 12 and g 21 Coupled.

[0088] In step 3, the complete decoupling conditions are as follows:

[0089] From the power change deviation matrix equation described in step 2-3, the equations for active power change and reactive power change can be obtained as follows:

[0090]

[0091] It can be seen from the equation that by adjusting the power angle and voltage, the change in active power and reactive power can be made zero, thus achieving power decoupling.

[0092] In step 4, the following steps are specifically included:

[0093] Step 4-1: When a disturbance occurs, the active power P changes. At this time, setting the reactive power change ΔQ to zero can eliminate the effect of active power on reactive power. Therefore, substituting ΔQ=0 into the equation in step 3-1, we can get ΔV t The equation is:

[0094]

[0095] From the equation, it can be seen that reasonable adjustment of the output voltage can eliminate the coupling effect on reactive power when active power changes;

[0096] Step 4-2: When a disturbance occurs, Q changes. At this time, setting ΔP to zero can eliminate the influence of active power on reactive power. Therefore, substituting ΔP=0 into the equation in step 3-1, the equation for Δδ is:

[0097]

[0098] It can be seen from the equation that reasonable adjustment of the power angle can eliminate the coupling effect of reactive power changes on active power;

[0099] Step 4-3: In the small signal model, introduce the power compensation link designed based on steps 3-2 and 3-3, and establish a self-synchronous voltage source power small signal model with decoupling control, such as Figure 5 As shown, it is brought into the MATLAB / Simulink simulation model for verification. The system simulation parameters are shown in Table 1. The simulation results are shown in Figure 6 , Figure 7 , Figure 8 , Fig. 9 shown.

[0100] Table 1 System main circuit parameters

[0101]

[0102]

[0103] Figure 6 The waveform diagram of reactive power when active power undergoes a step disturbance is shown. Before the system active power disturbance occurs, the active power is set to 10kW and the reactive power is set to -1.8kVar. At 3s, the active power disturbance occurs, and the active power jumps to 13kW. The reactive power that adopts decoupling control considering voltage compensation and power angle compensation remains at around -1.8kVar after a brief fluctuation. The steady-state coupling error value of reactive power is approximately 0, and the reactive power coupling error caused by active power disappears. It can be found that the power decoupling control method proposed in the present invention effectively eliminates the steady-state coupling error of reactive power caused by step disturbance of active power.

[0104] Figure 7 The waveform of reactive power when active power is disturbed by oscillation is shown. Before the active power disturbance occurs, the active power is set to 10kW and the reactive power is set to -1.8kVar. At 3s, an oscillation disturbance with an amplitude of 1kW and a frequency of 10Hz is added to the active power. The reactive power is stabilized at -1.8kVar by decoupling control considering voltage compensation and power angle compensation. The steady-state coupling error value of reactive power is approximately 0, and the reactive power coupling error caused by active power disappears. It can be found that the power decoupling control method proposed in the present invention effectively eliminates the steady-state coupling error of reactive power caused by oscillation disturbance of active power.

[0105] Figure 8 The waveform diagram of active power when reactive power undergoes a step disturbance is shown. Before the system reactive power disturbance occurs, the active power is set to 10kW and the reactive power is set to -1.8kVar. Reactive power disturbance occurs at 3s, and the reactive power steps to -1.1kVar. The active power using decoupling control considering voltage compensation and power angle compensation remains at around 10kW after a brief fluctuation. The steady-state coupling error value of active power is approximately 0, and the active power coupling error caused by reactive power disappears. It can be found that the power decoupling control method proposed in the present invention effectively eliminates the steady-state coupling error of active power caused by step disturbance of reactive power.

[0106] Fig. 9The waveform diagram of active power when reactive power undergoes oscillation disturbance is shown. Before the reactive power disturbance occurs, the active power is set to 10kW and the reactive power is set to -1.8kVar. At 3s, an oscillation disturbance with an amplitude of 1.1kVar and a frequency of 10Hz is added to the reactive power. The active power is stabilized at 10kW by decoupling control considering voltage compensation and power angle compensation. The steady-state coupling error value of the active power is approximately 0, and the active power coupling error caused by the reactive power disappears. It can be found that the power decoupling control method proposed in the present invention effectively eliminates the steady-state coupling error of the active power caused by the oscillation disturbance of the reactive power.

[0107] pass Figure 6 , Figure 7 , Figure 8 , Fig. 9 The simulation results show that the self-synchronous voltage source power coupling control method proposed in the present invention can significantly reduce the power coupling error caused by active power and reactive power under different types of disturbances, thereby effectively eliminating the power coupling phenomenon. This improvement not only improves the steady-state performance of the self-synchronous voltage source when it is connected to the grid, but also greatly improves the accuracy of control, and has broad application prospects.

[0108] The above description is only a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any modification or equivalent change made based on the technical essence of the present invention still falls within the scope of protection required by the present invention.

Claims

1. A power decoupling control method for a self-synchronous voltage source, comprising the following steps, characterized in that: Step 1: Establish a grid-connected control structure model of the self-synchronous voltage source, make the main circuit of the self-synchronous voltage source inverter equivalent to the electrical part of the synchronous generator, and construct a self-synchronous voltage source control scheme including active loop control and reactive loop control; The step 1 specifically includes the following steps: Step 1-1: Establish a grid-connected control structure model of the self-synchronous voltage source, and make the main circuit of the self-synchronous voltage source equivalent to the electrical part of the synchronous generator, specifically including: making the fundamental voltage equivalent to the internal potential of the synchronous generator; making the filter inductor equivalent to the synchronous reactance of the synchronous generator; making the output voltage of the common coupling point equivalent to the terminal voltage of the synchronous generator; and making the filter current on the bridge arm side equivalent to the output current of the synchronous generator; Step 1-2: The active power loop provides virtual inertia by simulating the rotor motion equation. The mechanical motion equation of the synchronous generator rotor is: Where: J is the virtual inertia coefficient; D is the virtual damping coefficient; ω is the grid voltage angular frequency; ω0 is the grid rated angular frequency; P and P ref Respectively represent the actual output active power and the active power command value; Step 1-3: The reactive loop adjusts the voltage at the common coupling point, simulates the primary voltage regulation characteristics of the synchronous generator, and uses steady-state error to control reactive power. The reactive power error (Q ref -Q) through the proportional controller k q Produces a voltage increment ΔV t , the QV droop control equation is: V t -V g =k q (Q ref -Q) Where: V t is the output voltage; V g is the grid voltage; Q and Q ref Respectively represent the actual output reactive power and reactive power command value; k q is the proportional control coefficient; Step 2: Based on the power loop control, the grid-connected control structure model of the self-synchronous voltage source can be simplified to obtain the grid-connected equivalent model of the self-synchronous voltage source. The corresponding small signal mathematical model is calculated based on the simplified model to obtain the cross-coupling relationship between active power and reactive power. The step 2 specifically includes the following steps: Step 2-1: Based on the power loop control, the equivalent model of the self-synchronous voltage source grid connection is obtained. Through Kirchhoff's voltage law, the relationship between the grid current and the power angle, grid impedance, and voltage in the equivalent model of the self-synchronous voltage source grid connection is obtained, and then the complex power flow equation is derived as follows: Where: S is the apparent power; is the conjugate of the grid current; Step 2-2: Linearize the equations in step 1-2 and step 1-3 at the steady-state operating point to obtain the linearized equation: Where: Δδ is the power angle change; ΔV t is the output voltage change; s is a complex variable; Step 2-3: Linearize the active power and reactive power near the steady-state operating point to obtain the power change deviation matrix equation: Where H(s) is the coupling transfer function matrix; g 11 , g 12 , g 21 , g 22 It is the coupling term between active power, reactive power, output voltage amplitude and power angle; Step 2-4: Combining the equations in step 2-2 and step 2-3, the small signal mathematical model is: From this mathematical model, it can be seen that active power and reactive power are connected through the cross-coupling term g 12 and g 21 coupled; Step 3: According to the cross-coupling relationship between active power and reactive power, a complete decoupling condition corresponding to the small signal mathematical model is obtained; In step 3, the complete decoupling conditions are as follows: From the power change deviation matrix equation described in step 2-3, the equations for the active power change and reactive power change are obtained as follows: It can be seen from the equation that by adjusting the power angle and voltage, the change in active power and reactive power can be made zero, thus achieving power decoupling; Step 4: Analyze the known and unknown quantities in the complete decoupling condition, propose a power compensation link based on power angle regulation and voltage regulation design, establish a self-synchronous voltage source power small signal model with decoupling control, and realize power decoupling of the self-synchronous voltage source; The step 4 specifically includes the following steps: Step 4-1: When a disturbance occurs, the active power P changes. At this time, setting the reactive power change ΔQ to zero can eliminate the effect of active power on reactive power. Therefore, substituting ΔQ=0 into the equation in step 3, we can get ΔV t The equation is: From the equation, it can be seen that reasonable adjustment of the output voltage can eliminate the coupling effect on reactive power when active power changes; Step 4-2: When a disturbance occurs, Q changes. At this time, setting ΔP to zero can eliminate the influence of active power on reactive power. Therefore, substituting ΔP=0 into the equation in step 3, the equation for Δδ is: It can be seen from the equation that reasonable adjustment of the power angle can eliminate the coupling effect of reactive power changes on active power; Step 4-3: In the small signal model, introduce the power compensation link designed based on step 4-1 and step 4-2, establish a self-synchronous voltage source power small signal model with decoupling control, and realize power decoupling of the self-synchronous voltage source.

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