Overcurrent suppression method for grid-connected converter fault recovery based on active power angle control

Abstract

The present invention discloses a method for suppressing overcurrent during fault recovery of a grid-connected converter based on active power angle control, and belongs to the field of power electronic control technology. The method includes: obtaining the actual power value and the power reference value of the grid-connected converter in real time, and obtaining the power error value; limiting the power error value with an upper limit value of 0 to obtain a limiting result; multiplying the obtained limiting result by a proportional gain coefficient to obtain an adjustment value of the phase angle after the fault is cleared; obtaining the original phase angle value generated in the active power control loop of the grid-connected converter, adding the adjustment value to the original phase angle value to obtain the actual phase angle value of the grid-connected converter, and using the actual phase angle value to perform closed-loop control and space vector modulation of the grid-connected converter to complete overcurrent suppression during fault recovery of the grid-connected converter. The present invention retains the original control architecture of the grid-connected converter, and effectively suppresses the overcurrent problem in the fault recovery stage while maintaining the output capacity of the transient voltage source of the grid-connected converter.

Description

Technical Field

[0001] The invention belongs to the technical field of power electronic control, and in particular relates to a method for suppressing overcurrent during fault recovery of a grid-connected converter based on active power angle control. Background Art

[0002] With the large-scale grid-connected power generation of renewable energy sources such as wind power and photovoltaic power through power electronic converters, the proportion of traditional synchronous generators with system support capabilities in power generation units has dropped significantly, resulting in a series of power accidents such as instability oscillation, voltage limit exceeding, shutdown and disconnection from the grid in the new power system dominated by new energy, which seriously threatens the safe and stable operation of the power system. The grid-building converter with the ability to build voltage and frequency can autonomously participate in the voltage and frequency regulation of the power system during steady-state operation to achieve steady-state grid support, and has become one of the most critical basic equipment in the new power system dominated by new energy. By reasonably configuring a certain degree of overload capacity, the grid-building converter can also present transient voltage source characteristics during the duration of the grid fault and realize active support of the faulty grid, which significantly improves the safety and stability margin of the power system in steady and transient states.

[0003] However, after the grid fault is cleared, the grid-connected converter usually experiences a large power angle swing in the process of resynchronizing with the post-fault grid, resulting in the grid-connected converter outputting a fault recovery transient current with an amplitude much higher than the fault current. Since the grid fault has been cleared at this stage and the grid voltage has been restored to the normal range, the extremely high fault recovery transient current will not only not serve the grid support, but will also directly cause the grid-connected converter to be damaged due to overcurrent during the fault recovery stage. Therefore, the fault recovery transient current of the grid-connected converter needs to be reasonably suppressed within the allowable range during the grid fault recovery stage.

[0004] Existing overcurrent suppression strategies for grid-connected converters focus on suppressing overcurrent problems during the duration of grid faults. Usually, current limiting strategies are used in the inner loop control of grid-connected converters to directly limit the output current or virtual impedance algorithms are used to increase the port output impedance to suppress fault short-circuit current. However, in the fault clearing and recovery phase, these methods will significantly deteriorate the resynchronization capability of the grid-connected converter and the grid after the fault is cleared, and even cause transient power angle instability problems. Therefore, it is necessary to construct an overcurrent suppression method in the fault recovery phase to meet the special needs of overcurrent suppression in the fault recovery phase, so as to ensure the safe and stable operation of the grid-connected converter in the resynchronization phase with the grid after fault recovery. Summary of the invention

[0005] In order to solve the problems in the prior art, the present invention provides a method for suppressing overcurrent during fault recovery of a grid-connected converter based on active power angle control.

[0006] The technical solution of the present invention is as follows:

[0007] The present invention discloses a method for suppressing overcurrent during fault recovery of a grid-connected converter based on active power angle control, comprising the following steps:

[0008] 1) In the active power control loop of the grid-connected converter, the actual power value and the power reference value of the grid-connected converter are obtained in real time, and the power error value is obtained;

[0009] 2) limiting the power error value with an upper limit value of 0 to obtain a limiting result; wherein, if the power error value is greater than or equal to 0, the limiting result is 0; otherwise, the limiting result is the current power error value;

[0010] 3) Obtain the proportional gain coefficient, multiply the limiting result obtained in step 2) by the proportional gain coefficient to obtain the adjustment value of the phase angle after the fault is cleared;

[0011] 4) Obtaining the original phase angle value generated in the active power control loop of the grid-connecting converter, adding the adjusted value of the phase angle after the fault is cleared to the original phase angle value, obtaining the actual phase angle value of the grid-connecting converter, and using the actual phase angle value to perform closed-loop control and space vector modulation of the grid-connecting converter to complete overcurrent suppression after fault recovery of the grid-connecting converter.

[0012] Based on the above technical solution, the present invention has the following beneficial technical effects:

[0013] (1) The present invention actively adjusts the operating parameter of the output voltage phase of the grid-connected converter by constructing a control algorithm, and realizes active suppression of transient overcurrent in the grid fault recovery stage by transient power angle adjustment without losing the transient synchronization capability and voltage support capability of the grid-connected converter. Specifically, the present invention obtains the adjustment value of the phase angle after the fault is cleared based on the actual power value, power reference value and proportional gain coefficient of the grid-connected converter, and adds the adjustment value of the phase angle after the fault is cleared to the original phase angle value generated in the active power control loop of the grid-connected converter to obtain the actual phase angle value of the grid-connected converter, that is, the output voltage phase of the grid-connected converter. Finally, the actual phase angle value is used to perform closed-loop control and space vector modulation of the grid-connected converter to complete the overcurrent suppression of the grid-connected converter after fault recovery, thereby overcoming the problem that the prior art significantly deteriorates the resynchronization capability of the grid-connected converter and the grid after the fault is cleared. Since the proposed control algorithm only needs to modify the digital controller code to realize active suppression of transient overcurrent, it has good economic efficiency. At the same time, the traditional grid-connected converter equipment that has been put into operation can restore transient overcurrent suppression by updating the digital controller code, so the solution has good compatibility;

[0014] (2) In the active power control loop of the grid-connected converter, the present invention obtains the actual power value and the power reference value of the grid-connected converter in real time, and obtains the power error value; then the power error value is limited to an upper limit of 0 to obtain a limiting result; wherein, if the power error value is greater than or equal to 0, the limiting result is 0; otherwise, the limiting result is the current power error value. Since the grid-connected converter will only have a power error value in the recovery phase after the fault is cleared due to resynchronization with the post-fault power grid, In other cases, the power error value Therefore, the control method proposed in the present invention will only take effect when the grid-connected converter is in the grid fault recovery stage, and will not take effect when the grid-connected converter is in the normal operation state and the grid fault continues state. Therefore, this scheme will not affect the equipment characteristics of the grid-connected converter in other operating conditions;

[0015] (3) The control algorithm proposed in the present invention only relies on the active power deviation to transiently adjust the output power angle of the grid-connected converter based on the original grid-connected converter control algorithm. The control structure is simple and reliable, and the implementation process does not rely on any additional sensors or detection algorithms.

[0016] (4) The method proposed in the present invention is applicable to grid-connected converters using any hardware circuit topology and any software control architecture, and has good universality. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a flow chart of the overcurrent suppression method for grid converter fault recovery based on active power angle control of the present invention;

[0018] Figure 2 It is a schematic diagram of the equivalent circuit and control structure of the traditional grid-connected converter;

[0019] Figure 3 The equivalent circuit of the grid-connected converter based on active power angle control and its control structure schematic diagram of the present invention;

[0020] Figure 4 This is the overcurrent behavior diagram of the traditional grid-connected converter in the recovery phase after the grid fault is cleared;

[0021] Figure 5 The diagram is an overcurrent behavior diagram of the grid-connected converter based on active power angle control of the present invention during the recovery phase after the grid fault is cleared. DETAILED DESCRIPTION

[0022] The present invention is further described and illustrated below in conjunction with specific embodiments. The embodiments are merely exemplary of the present disclosure and do not define the scope of limitation. The technical features of each embodiment of the present invention may be combined accordingly without conflicting with each other.

[0023] In order to overcome the shortcomings of the prior art, the present invention proposes a method for suppressing overcurrent during fault recovery of a grid-connected converter based on active power angle control. The present invention significantly reduces the power angle value of the grid-connected converter at the initial moment of the fault recovery phase by actively adjusting the output voltage phase angle of the grid-connected converter as an operating control parameter during the fault recovery phase, and effectively suppresses the transient overcurrent problem through power angle regulation based on the grid synchronization capability of the grid-connected converter during the fault recovery phase. At the same time, the method proposed by the present invention retains the original control architecture of the grid-connected converter, effectively suppressing the overcurrent problem during the fault recovery phase while maintaining the transient voltage source output capability of the grid-connected converter.

[0024] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] like Figure 1 and Figure 3 As shown, in view of the transient overcurrent problem caused by the natural swing of the power angle in the recovery stage after the power grid fault is cleared in the existing grid-connected converter, the present invention discloses a method for suppressing overcurrent during fault recovery of the grid-connected converter based on active power angle control, the method comprising:

[0026] 1) In the active power control loop of the grid-connected converter, the actual power value and the power reference value of the grid-connected converter are obtained in real time, and the power reference value is converted into Subtract the actual power value , get the power error value ;Right now:

[0027] .

[0028] 2) The power error value obtained by calculation The limiting link with the upper limit value of 0 is sent to obtain the limiting result; the mathematical expression of the limiting link is:

[0029] ;

[0030] in, is the clipping result, that is, the result of the power error value after the clipping link operation. If the power error value is greater than or equal to 0, the result of the power error value after the clipping link operation is the clipping value upper limit 0.

[0031] If the power error value is less than 0, the result of the power error value after the limit operation is the current power error value. Since the grid-connected converter will only have a power error value during the recovery phase after the fault is cleared due to resynchronization with the post-fault grid, In other cases, the power error value Therefore, the control method proposed in the present invention will only take effect when the grid-connected converter is in the grid fault recovery stage, and will not take effect when the grid-connected converter is in the normal operation state and the grid fault continues state. At this time, the grid-connected converter still maintains the original control structure and equipment characteristics;

[0032] 3) Obtain the proportional gain coefficient and obtain the limiting result Multiply by the proportional gain factor , get the adjusted value of the phase angle after the fault is cleared :

[0033] ;

[0034] Among them, the proportional gain coefficient Need to meet According to the operating condition requirements of the grid converter during the fault recovery phase, the proportional gain coefficient can be designed as

[0035] ;

[0036] in, is the maximum output power of the grid converter, It is the maximum allowable jump angle of the phase of the grid converter port voltage.

[0037] 4) Obtain the original phase angle value generated in the active power control loop of the grid converter , the phase angle adjustment value after the fault is cleared obtained in step 3) The original phase angle value generated in the active power control loop of the grid converter Add together to obtain the actual phase angle value of the grid-connected converter :

[0038] ;

[0039] Finally, the actual phase angle value is used to perform closed-loop control of the grid-connected converter and space vector modulation to complete the overcurrent suppression of the grid-connected converter fault recovery.

[0040] In order to demonstrate the implementation effect of the fault recovery overcurrent suppression method for grid-connected converter based on active power angle control proposed in the present invention, it was verified on a grid-connected converter experimental platform based on active neutral point clamped (ANPC) three-level topology, wherein the power semiconductor device selected was a silicon-based insulated gate bipolar transistor (IGBT) device of model FGHL50T65MQDTL4, and the digital controller unit of the grid-connected converter selected was TMS320F28377D which can realize pulse width modulation.

[0041] The present invention is further described in detail below by taking the overcurrent behavior of the grid-connected converter during the recovery phase after the grid voltage symmetrical drop fault is cleared as an example with reference to the accompanying drawings.

[0042] It should be noted that the method proposed in the present invention is applicable to a grid-forming converter using any hardware circuit topology, including two-level half-bridge topology / neutral point clamped (NPC) three-level topology / T-clamped (T-NPC) three-level topology and other topology types, so the applicable grid-forming converter is not limited to the grid-forming converter based on active neutral point clamped (ANPC) three-level topology in the embodiment. In addition, the method proposed in the present invention is applicable to a grid-forming converter using any software control structure, including grid-forming control architectures such as droop control, virtual oscillator control, and matching control, so the applicable grid-forming converter is not limited to the grid-forming converter based on the virtual synchronous machine control algorithm in the embodiment, and the grid fault that causes the grid-forming converter to enter the overcurrent state in the fault recovery stage can also be other types of grid faults, including single-phase to ground short circuit fault / two-phase interphase short circuit fault / single-phase line break fault and other types, and the present invention does not limit this.

[0043] Figure 2 The equivalent circuit and control structure diagram of the traditional grid-connected converter are shown in Figure 2. f The current I c And filter capacitor C f The voltage U f And transform it into the dq synchronous rotating coordinate system through coordinate transformation to achieve Figure 2 The grid-type converter control is shown in Figure 1. Among them, PCC is the common connection point, V dc is the input voltage of the grid converter, I f is the machine-side current of the grid converter, X T is the impedance of the transformer in the power grid, X l is the impedance of the power grid line, X g is the impedance of the grid.

[0044] The grid control structure adopts cascade voltage control and current control as the inner loop control scheme in the dq synchronous rotating coordinate system to realize closed-loop regulation and active support of the voltage at the grid connection point. Both voltage control and current control are based on proportional-integral (PI) controller to realize closed-loop zero-static error control, and the gain coefficient is ωC. f The cross-decoupling control term avoids the voltage control coupling effect between the d-axis and the q-axis in the dq rotating coordinate system, and the gain coefficient is ωL f The cross-decoupling control term avoids the current control coupling effect between the d-axis and the q-axis in the dq rotating coordinate system. Among them, the d-axis control command value of the current control is and q-axis control command value The voltage-controlled d-axis and q-axis PI controllers generate the control command value. Set as reference value U, q-axis control command value Set to 0 to achieve active support of terminal voltage and control coordinate system orientation.

[0045] In the grid control structure, the control reference value of the node voltage U amplitude is given by reactive power-voltage droop control, and the calculation formula is U=U0+k q (Q0- Q e ), where U0 is the output voltage operating point reference value of the grid-connected converter; k q is the reactive voltage droop coefficient; Q0 is the reactive power reference value of the grid converter; Q e is the actual value of the reactive power of the grid-connected converter. At the same time, the node voltage U phase θ c It is determined by the networking control method. In this example, the networking control method adopts the virtual synchronous machine control method.

[0046] like Figure 3 As shown, in the method of the present invention, is the control command value of the active power of the grid-forming converter, that is, the reference value of the active power of the grid-forming converter; is the actual measured value of the active power of the grid converter. Based on the instantaneous power theory, it can be expressed by It is obtained by real-time calculation of voltage and current sampling values, where: is the d-axis voltage of the grid converter after the input voltage is transformed by dq; is the d-axis current of the grid converter after the input current is transformed by dq; is the q-axis voltage of the grid converter after the input voltage is transformed by dq; It is the q-axis current of the grid converter after the input current is transformed by dq.

[0047] In this example, is the grid angular frequency base value, which is set to 2π×50rad. is the output angular frequency value of the grid converter itself, which is related to the grid angular frequency base value The damping coefficient of the grid converter after subtraction Obtain the damping power, calculated as The deviation between the active power control command value (i.e., power reference value) and the actual measured value Further subtract the damping power After that, it is sent to the inertia simulation link 1 / Hs and the output angular frequency value of the grid-connected converter itself is calculated. , realize the synchronization between the grid-type controlled grid-forming converter and the power grid, wherein the output angular frequency value of the grid-forming converter itself obtained at this time is used as the output angular frequency value of the next acquisition of the original phase angle value; the output angular frequency value of the grid-forming converter itself is used as the output angular frequency value of the next acquisition of the original phase angle value; The original phase angle value is obtained by integration , the original phase angle value Used for coordinate transformation and other links. Therefore, the calculation formula of the original phase angle value is:

[0048] ;

[0049] in, is the Laplace operator; is the inertia time constant of the grid converter; is the power error value, .

[0050] Figure 3 This is a schematic diagram of the equivalent circuit and control structure of the grid-connected converter with the additional post-fault power angle active control proposed in the present invention. Except for the branch of the post-fault power angle active control proposed in the present invention (shown by the red solid line), the remaining equivalent circuit structures and control architectures are the same as Figure 2 The equivalent circuit and control structure of the traditional grid-connected converter shown are exactly the same.

[0051] The input of the additional post-fault power angle active control proposed by the present invention is the current power error value , Then the power error value is limited with an upper limit of 0 and a lower limit of negative infinity to obtain the limiting result Since the grid-connected converter will only have power error value in the recovery phase after the fault is cleared due to resynchronization with the post-fault grid, Therefore, the proposed control method will only take effect when the grid-connected converter is in the grid fault recovery stage. It will not take effect when the grid-connected converter is in the normal operation state and the grid fault continues state, and the grid-connected converter still maintains the original control structure and equipment characteristics. is the proportional gain coefficient of the proposed post-fault power angle active control, and the adjustment value of the phase angle after the fault is cleared The result of the clipping and the proportional gain factor The product of Then obtain the original phase angle value generated in the active power control loop of the grid converter , and finally the actual phase angle value of the grid-connected converter with active power angle control after the additional fault for Finally, the actual phase angle value is used to perform closed-loop control of the grid-connected converter to obtain the d-axis modulation voltage instruction and q-axis modulation voltage command , then based on the actual phase angle value, d-axis modulation voltage command and q-axis modulation voltage command A switching signal of a power semiconductor device of a grid-connected converter is generated by space vector modulation, and finally a power circuit of the grid-connected converter is driven to operate based on the switching signal, thereby realizing overcurrent suppression of the grid-connected converter after fault recovery.

[0052] This embodiment uses the following parameter settings for verification: the base value of the AC voltage is 190V, the AC grid fundamental frequency is 50Hz, the rated capacity of the grid-connected converter is 6kVA, and the switching frequency is 10kHz. Rated value is 1.0pu, equivalent impedance from access point to grid is 0.6pu, and the grid converter filter inductance is is 0.05 pu, and the filter capacitor is is 0.06 pu, the voltage control loop proportional gain K pv is 0.07, the integral gain K iv is 32, the current control loop proportional gain K pc is 14.44, the integral gain K ic is 25.13, the damping coefficient of the grid converter is 35 pu, the inertia time constant is 4.0 s, the reactive voltage droop coefficient is 0.05 pu, the grid converter terminal voltage reference value U0 is 1.0 pu, and the active power output reference value is is 0.9 pu, and the reactive power output reference value Q0 is 0. The proportional gain coefficient of the proposed post-fault power angle active control is The design value is 0.15×10 -3 .

[0053] The overcurrent suppression capability of the proposed method is verified by using the recovery phase after the three-phase power grid symmetrical drop fault is cleared. The grid voltage drops to 0.2 pu at 0.4s and recovers to 1 pu at 0.72s. Figure 1 Under the equivalent circuit and control structure of the traditional grid-connected converter shown in FIG. 1 , the grid-connected point voltage, grid-connected point current and power angle value change waveforms of the grid-connected converter are as follows: Figure 4As shown in the figure, the time is 0.2s per grid, the voltage is 1 pu per grid (base value 190V), and the current is 1.5 pu per grid (base value 18.32A). The grid-forming converter outputs 1 pu current in steady state. After the symmetrical drop fault of the three-phase power grid occurs, the grid-forming converter outputs 1.5 pu fault short-circuit current. After the fault is cleared, due to the power angle swing process introduced by the resynchronization of the grid-forming converter, the maximum recovery transient current of 2.5 pu is output in the recovery stage. The 2.5 pu recovery transient current is much higher than the 1.5 pu fault short-circuit current required by the grid-forming converter to support the faulty power grid during the fault period, resulting in the grid-forming converter facing the risk of equipment damage due to the transient overcurrent heating seriously exceeding its own design margin.

[0054] If the method proposed by the present invention is adopted, Figure 3 Under the equivalent circuit and control structure of the grid-connected converter with active power angle control after fault, the grid-connected point voltage, grid-connected point current and power angle transient waveforms of the grid-connected converter are shown in FIG. Figure 5 As shown. In steady state, the grid-connected converter also outputs 1 pu current. After a symmetrical drop fault occurs in the three-phase power grid, the grid-connected converter also outputs a fault short-circuit current of 1.5 pu, which proves that the proposed control method will not change the operating characteristics and grid support behavior of the grid-connected converter in steady state and during the fault period. After the fault is cleared, the proposed post-fault power angle active control automatically takes effect because the power deviation is greater than 0. By actively reducing the voltage phase value of the grid-connected converter and reducing the power angle value, a maximum recovery transient current of 1.5 pu is output in the recovery phase. It can be seen that the method proposed in the present invention effectively suppresses the overcurrent problem of the grid-connected converter in the recovery phase after the fault is cleared, while ensuring that the transient voltage source support characteristics and resynchronization capabilities of the grid-connected converter are not affected.

[0055] The above-mentioned embodiments only express several implementation modes of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. For those of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for suppressing overcurrent during fault recovery of a grid-connected converter based on active power angle control, characterized in that: The following steps are involved: 1) In the active power control loop of the grid-connected converter, the actual power value and the power reference value of the grid-connected converter are obtained in real time, and the power error value is obtained; 2) limiting the power error value with an upper limit value of 0 to obtain a limiting result; wherein, if the power error value is greater than or equal to 0, the limiting result is 0; otherwise, the limiting result is the current power error value; 3) Obtain the proportional gain coefficient, multiply the limiting result obtained in step 2) by the proportional gain coefficient to obtain the adjustment value of the phase angle after the fault is cleared; 4) Obtaining the original phase angle value generated in the active power control loop of the grid-connecting converter, adding the adjusted value of the phase angle after the fault is cleared to the original phase angle value, obtaining the actual phase angle value of the grid-connecting converter, and using the actual phase angle value to perform closed-loop control and space vector modulation of the grid-connecting converter to complete overcurrent suppression after fault recovery of the grid-connecting converter.

2. According to claim 1, the method for suppressing overcurrent during fault recovery of a grid-connected converter based on active power angle control is characterized in that: In step 1), the calculation formula of the actual power value is: ； in, is the actual power value of the grid converter; is the d-axis voltage of the grid converter after the input voltage is transformed by dq; is the d-axis current of the grid converter after the input current is transformed by dq; is the q-axis voltage of the grid converter after the input voltage is transformed by dq; It is the q-axis current of the grid converter after the input current is transformed by dq.

3. According to claim 2, the method for suppressing overcurrent during fault recovery of a grid-connected converter based on active power angle control is characterized in that: In step 1), the calculation formula of the power error value is: ； in, is the power error value; is the power reference value of the grid converter.

4. The method for suppressing overcurrent during fault recovery of a grid-connected converter based on active power angle control according to claim 3 is characterized in that: In step 2), the expression for limiting the power error value with an upper limit value of 0 is: ； in, is the limiting result.

5. The method for suppressing overcurrent during fault recovery of a grid-connected converter based on active power angle control according to claim 1, characterized in that: In step 3), the calculation formula of the proportional gain coefficient is: ； in, is the proportional gain coefficient, and Greater than 0; is the maximum output power of the grid converter; It is the maximum allowable jump angle of the phase of the grid converter port voltage.

6. The method for suppressing overcurrent during fault recovery of a grid-connected converter based on active power angle control according to claim 1, characterized in that: In step 3), the calculation formula of the phase angle adjustment value after the fault is cleared is: ； in, It is the adjustment value of the phase angle after the fault is cleared; is the proportional gain coefficient; is the limiting result.

7. The method for suppressing overcurrent during fault recovery of a grid-connected converter based on active power angle control according to claim 1, characterized in that: In step 4), the original phase angle value generated in the active power control loop of the grid-connected converter is obtained, including: Obtain a grid angular frequency base value, a damping coefficient of a grid-connecting converter, and a first output angular frequency value of the grid-connecting converter at the current moment; subtract the first output angular frequency value from the grid angular frequency base value and multiply the result by the damping coefficient to obtain damping power; then make a difference between the power error value and the damping power, and send the difference to an inertia simulation link to calculate a second output angular frequency value of the grid-connecting converter. The second output angular frequency value of the grid-connecting converter obtained at this time is used as the first output angular frequency value for obtaining an original phase angle value next time; and then integrate the obtained second output angular frequency value of the grid-connecting converter to obtain the original phase angle value.

8. The method for suppressing overcurrent during fault recovery of a grid-connected converter based on active power angle control according to claim 7, characterized in that: In step 4), the calculation formula of the original phase angle value is: ； in, is the original phase angle value; is the Laplace operator; is the inertia time constant of the grid converter; is the power error value; is the damping coefficient of the grid converter; is the first output angular frequency value of the grid-connected converter at the current moment; is the base value of grid angular frequency.

9. The method for suppressing overcurrent during fault recovery of a grid-connected converter based on active power angle control according to claim 7, characterized in that: In step 4), the actual phase angle value is used to perform closed-loop control and space vector modulation of the grid-connected converter to complete overcurrent suppression of fault recovery of the grid-connected converter; including: Based on the actual phase angle value, a closed-loop control of the grid-connected converter is performed to obtain a d-axis modulation voltage instruction. and q-axis modulation voltage command , then based on the actual phase angle value, d-axis modulation voltage command and q-axis modulation voltage command A switching signal of a power semiconductor device of a grid-connected converter is generated by space vector modulation, and finally a power circuit of the grid-connected converter is driven to operate based on the switching signal, thereby realizing overcurrent suppression of the grid-connected converter after fault recovery.

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