Self-adaptive current amplitude limiting control method of voltage source type converter

Abstract

The invention discloses a self-adaptive current amplitude limiting control method for a voltage source type current converter. The method comprises the following steps: acquiring active power, grid-connected point voltage and output current of the current converter; d-axis and q-axis components of the converter grid-connected point voltage and the converter output current under the dq rotating coordinate system are calculated; calculating a phase reference value of the alternating current side of the converter; according to the maximum allowable value and the actual value of the output current of the converter, d-axis and q-axis reference values of the output current of the converter after adaptive current amplitude limiting control are calculated; d-axis and q-axis reference values of modulation voltage at an outlet of the converter are calculated; and calculating the reference value of the modulation voltage at the outlet of the converter under the abc static coordinate system. According to the method, the adaptive coefficient is introduced into the current amplitude limiting link of the converter, so that the converter adjusts the d-axis current component and the q-axis current component of the output current after amplitude limiting according to requirements, meanwhile, the dynamic characteristics of the system after a fault are improved, and the converter can automatically recover a normal voltage control mode after the fault is removed.

Description

Technical Field

[0001] The present invention belongs to the technical field of voltage source converter control, and particularly relates to an adaptive current limiting control method for a voltage source converter. Background Art

[0002] At present, most new energy voltages are connected to the power grid through converters. Different from synchronous generators, voltage source converters achieve synchronization with the power grid through control. Moreover, voltage source converters are composed of power electronic devices and have poor overcurrent capabilities. Therefore, a current limiting link needs to be added in the converter control to limit the output current of the converter. The existing limiting control methods can be mainly divided into direct current limiting method and virtual impedance current limiting method. The virtual impedance current limiting method limits the grid connection point voltage of the converter by introducing a virtual resistance and a virtual reactance, so as to achieve the purpose of limiting the output current amplitude. It retains the external characteristics of the converter voltage source under faults and has good transient stability, but its current limiting effect is not as good as that of the direct current limiting method.

[0003] The direct current limiting method limits the output current amplitude by limiting the magnitude of the current reference value. Its current limiting effect is good, but if the current limiting method is not properly designed, in some working conditions, even if the fault is removed in time, the converter will still be unable to exit the current limiting control mode by itself.

[0004] Therefore, there is an urgent need for a current limiting control method that enables the converter to exit the current limiting control mode by itself under various working conditions regardless of whether the fault is removed in time. Summary of the Invention

[0005] The main purpose of the present invention is to solve the problem that in some working conditions, even if the fault is removed in time, the converter is still unable to exit the current limiting control mode by itself in the existing direct current limiting method. Aiming at this, an adaptive current limiting control method for a voltage source converter is proposed. This control method can adaptively adjust the magnitudes of the d-axis component and q-axis component of the output current of the converter in the current limiting state according to requirements, and at the same time improve the dynamic characteristics of the power system under large disturbance faults, ensuring that the converter can restore the normal voltage control mode by itself under various working conditions.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] An adaptive current limiting control method for a voltage source converter, the adaptive current limiting control method comprising the following steps:

[0008] S1. Obtain the reference value and actual value of the active power of the voltage source converter in the power system, obtain the reference value and actual value of the grid connection point voltage, and obtain the maximum allowable value and actual value of the output current of the converter;

[0009] S2. Calculate the d-axis and q-axis components of the converter connection point voltage and the converter output current in the dq rotating coordinate system;

[0010] S3. Calculate the phase reference value of the converter AC side;

[0011] S4. Calculate the d-axis reference value and q-axis reference value of the converter output current in the dq rotating coordinate system;

[0012] S5. Calculate the d-axis current reference value and q-axis current reference value of the converter output current after amplitude limiting control in the dq rotating coordinate system according to the maximum allowable value and the actual value of the converter output current;

[0013] S6. Calculate the d-axis voltage reference value and q-axis voltage reference value of the modulation voltage at the converter AC outlet in the dq rotating coordinate system;

[0014] S7. Calculate the a-axis voltage reference value, b-axis voltage reference value and c-axis voltage reference value of the modulation voltage at the converter AC outlet in the abc stationary coordinate system;

[0015] S8. Generate corresponding control pulses to achieve the control of the converter by using the pulse width modulation theory according to the phase reference value of the converter AC side and the reference value of the modulation voltage in the dq rotating coordinate system.

[0016] Further, in the step S2, the d-axis component E d and q-axis component E q of the converter connection point voltage in the dq coordinate system are calculated as follows:

[0017]

[0018] where E a , E b , E c are the a-axis component, b-axis component and c-axis component of the converter connection point voltage in the abc coordinate system, and θ * is the phase reference value of the converter AC side; through dq decomposition, the alternating connection point voltage in the abc coordinate system can be converted into a DC quantity in the dq coordinate system, which is convenient for subsequent control.

[0019] The d-axis component I d and q-axis component I q of the converter output current in the dq coordinate system are calculated as follows:

[0020]

[0021] where I a , I b , I c$i_{a}$, $i_{b}$, and $i_{c}$ are the a-axis component, b-axis component, and c-axis component of the converter output current in the abc coordinate system. Through the above Park transformation, the d-axis component and q-axis component of the converter connection point voltage and the converter output current can be obtained.

[0022] Further, in step S3, the phase reference value θ of the AC side of the converter * The calculation formula is as follows:

[0023]

[0024] where s is the Laplace operator, ω0 is the synchronous angular frequency of the AC side power grid, J and D are the virtual inertia and damping coefficient respectively, P ref is the reference value of the active power output by the converter, and P is the actual value of the active power output by the converter. Through the above control law, the phase angle reference value of the AC side of the converter can be obtained. The control equation in step S3 actively constructs the system frequency by simulating the rotor motion equation of a traditional synchronous generator to achieve the active support function for the power grid frequency.

[0025] Further, in step S4, the d-axis reference value and q-axis reference value of the AC output current of the converter

[0026]

[0027] The calculation formula is as follows: PV and K IV are the proportional parameter and integral parameter of the voltage controller respectively, E ref is the reference value of the power grid voltage amplitude, E d is the d-axis voltage component of the converter connection point, and E q is the q-axis voltage component of the converter connection point. Through the above control law, the d-axis component and q-axis component of the converter output current reference value can be obtained. The main purpose of obtaining the dq-axis reference value of the converter output current is to facilitate subsequent current limiting control to limit it, thereby preventing the converter output current from exceeding the maximum value.

[0028] Further, in step S5, the d-axis reference value and q-axis reference value of the converter output current after being limited by the current limiting control in the dq rotating coordinate system

[0029]

[0030] The calculation formula is as follows: maxis the maximum allowable value of the converter output current. Through the above current limiting control method, the d-axis component and q-axis component of the converter output current under the limiting state can be adjusted according to requirements, and the d-axis component and q-axis component of the converter output current reference value after current limiting control can be obtained. There are mainly two functions that the adaptive limiting control can achieve: First, it limits the converter output current to prevent the output current from exceeding the limit and damaging the power electronic devices inside the converter; the second function is to flexibly change the dq-axis components of the output current under the limiting state by using the adaptive coefficient, adjust the power angle curve of the converter under the limiting state, and improve the dynamic characteristics of the system during the fault process. And by reasonably selecting the value of the adaptive coefficient, the defect of the traditional current limiting control can be avoided - that is, "locking" in the current limiting mode after the fault is removed, ensuring that the converter can resume the normal voltage control mode by itself after the fault is removed.

[0031] Further, in the step S6, the d-axis voltage reference value of the modulation voltage at the converter outlet in the dq rotating coordinate system and the q-axis voltage reference value The calculation formulas are as follows:

[0032]

[0033] where, E ref is the reference value of the grid voltage amplitude, and are the d-axis reference value and q-axis reference value of the converter AC output current respectively, I d and I q are the d-axis component and q-axis component of the converter output current in the dq rotating coordinate system respectively, ω is the actual angular velocity of the grid, L F is the inductance value of the LC filter on the AC side of the converter, K PC and K IC are the proportional parameter and integral parameter of the current controller respectively. Through the above control law, the d-axis component and q-axis component of the modulation voltage at the converter outlet can be obtained, and this step is the traditional current inner loop PI control. After performing the Park transformation on the dq-axis components of the modulation voltage, the three-phase voltage components in the abc coordinate system can be obtained, which is the modulation wave of the modulator.

[0034] Further, in the step S7, the a-axis voltage reference value of the modulation voltage at the converter outlet in the abc stationary coordinate system , the b-axis voltage reference value and the c-axis voltage reference value The calculation formulas are as follows:

[0035]

[0036] where, θ *is the phase reference value on the AC side of the converter. and are respectively the d-axis voltage reference value and the q-axis voltage reference value of the modulation voltage at the converter outlet.

[0037] Since the control signals ultimately required for the modulation of the converter are the voltage modulation waves in the abc stationary coordinate system, it is necessary to convert the d-axis voltage reference value and the q-axis voltage reference value of the modulation voltage to the abc stationary coordinate system. With the output voltage modulation wave, it can be input into the modulator for pulse width modulation, thereby generating the trigger signals for the IGBTs of the converter to control the conduction and turn-off of the IGBTs.

[0038] Furthermore, in the step S8, the process of generating the corresponding control pulses using the pulse width modulation theory is as follows:

[0039] S81. Compare the a-axis voltage reference value , b-axis voltage reference value and c-axis voltage reference value of the modulation voltage at the converter outlet in the abc stationary coordinate system with the triangular carrier wave respectively to obtain the trigger signals Tg1r and Tg2r for the upper and lower bridge arms IGBTs of phase a, obtain the trigger signals Tg3r and Tg4r for the upper and lower bridge arms IGBTs of phase b, and obtain the trigger signals Tg5r and Tg6r for the upper and lower bridge arms IGBTs of phase c;

[0040] S82. Use the trigger signals Tg1r, Tg2r, Tg3r, Tg4r, Tg5r, Tg6r to control the conduction and turn-off of the corresponding IGBTs to make the converter output narrow rectangular pulses. Then, using the equal area principle, when the frequency of the triangular carrier wave is relatively large, the narrow rectangular pulses approximate the sine wave.

[0041] Trigger the converter switching devices through the pulses generated above, thereby controlling the voltage source converter. After the above control, when the output current of the converter is less than the allowable maximum value and the converter is in the normal operation mode, the current limit control does not work, and the converter is equivalent to a controlled voltage source externally; when the output current of the converter is greater than the allowable maximum value and the converter is in the current limit mode, the current limit control limits the amplitude of the converter output current at the maximum value, and at this time the converter is equivalent to a controlled current source externally.

[0042] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0043] (1) The present invention can freely adjust the magnitudes of the d-axis and q-axis components of the output current of the converter after current limiting according to requirements. When the adaptive coefficient is taken as 1, this current limiting method is equivalent to the d-axis priority current limiting control method; when the adaptive coefficient is taken as 0, this current limiting method is equivalent to the q-axis priority current limiting control method. When the adaptive coefficient takes a value within the range of (0, 1), the larger the value of the adaptive coefficient, the larger the d-axis current and the smaller the q-axis current. During the actual operation process, the adaptive coefficient can be selected according to the magnitudes of the active current and reactive current actually required by the system, and the dq-axis currents are actively distributed to obtain the best performance. Usually, the value of the adaptive coefficient is close to 1 or equal to 1. At this time, the system can output the maximum active current under the current limiting state, thus giving priority to ensuring the active power transmission of the converter. When the reactive power support of the system is insufficient, the value of the adaptive coefficient is reduced, so that the system can obtain a larger reactive current under the current limiting state, providing better reactive power and voltage support for the system.

[0044] (2) In the traditional d-axis priority current limiting control method and q-axis priority current limiting control method, when a grid voltage dip fault occurs, there is a defect that the converter cannot withdraw from the current limiting control mode by itself when the fault is removed. To address this defect, the present invention can flexibly adjust the power angle curve of the system under the current limiting state by changing the value of the adaptive coefficient, thereby improving the dynamic characteristics of the system under faults and ensuring that the converter resumes the normal voltage control mode after the fault is removed. Moreover, the smaller the value of the adaptive coefficient, the greater the right shift degree of the power angle curve under the current limiting state, which will reduce the accelerating area of the system and increase the decelerating area, improving the transient stability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0046] Figure 1 is a flowchart of the adaptive current limiting control method for a voltage source converter disclosed in the present invention;

[0047] Figure 2 is a schematic diagram of a comparative simulation waveform in Embodiment 2 of the present invention, showing the comparison between the adaptive current limiting control method of the voltage source converter of the present invention and the traditional d-axis priority current limiting control method under the condition that the grid voltage drops to 0.6 pu and the fault is removed in time;

[0048] Figure 3It is a schematic diagram of comparative simulation waveforms between the adaptive current limiting control method of the voltage source converter of the present invention and the traditional d-axis priority limiting control method in Embodiment 2 of the present invention under the condition that the grid voltage drops to 0.6 pu and the fault is not removed in time;

[0049] Figure 4 It is a schematic diagram of the fault removal situation of the traditional d-axis priority limiting control method and the adaptive current limiting control method in Embodiment 3 of the present invention. Specific implementation manners

[0050] In order to enable those skilled in the art to better understand the solutions of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present application.

[0051] The mention of "embodiment" in the present application means that the specific features, structures or characteristics described in connection with the embodiment may be included in at least one embodiment of the present application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described in the present application may be combined with other embodiments.

[0052] Embodiment 1

[0053] See Figure 1 , this embodiment discloses an adaptive current limiting control method for a voltage source converter, including the following steps:

[0054] S1. Obtain the reference value and actual value of the active power of the converter, obtain the reference value and actual value of the grid-connected voltage, and obtain the maximum allowable value and actual value of the output current of the converter;

[0055] S2. Calculate the d-axis and q-axis components of the grid-connected voltage of the converter and the output current of the converter in the dq rotating coordinate system;

[0056] Among them, the d-axis component E d and the q-axis component E q of the grid-connected voltage of the converter are calculated as follows:

[0057]

[0058] Among them, E a , E b , E care the a-axis component, b-axis component, and c-axis component of the converter connection point voltage in the abc coordinate system, and θ * is the phase reference value of the converter AC side.

[0059] Among them, the d-axis component I d and the q-axis component I q of the converter output current in the dq coordinate system are calculated as follows:

[0060]

[0061] Among them, I a , I b , I c are the a-axis component, b-axis component, and c-axis component of the converter output current in the abc coordinate system.

[0062] S3. Calculate the phase reference value of the converter AC side;

[0063] Among them, the phase reference value θ * of the converter AC side is calculated as follows:

[0064]

[0065] Among them, s is the Laplace operator, ω0 is the synchronous angular frequency of the AC side power grid, J and D are the virtual inertia and damping coefficient respectively, P ref is the reference value of the converter output active power, and P is the actual value of the converter output active power.

[0066] S4. Calculate the d-axis current reference value and q-axis current reference value of the converter connection point;

[0067] Among them, the d-axis current reference value and the q-axis current reference value of the converter connection point are calculated as follows:

[0068]

[0069] Among them, K PV and K IV are the proportional parameter and integral parameter of the voltage controller respectively, E ref is the reference value of the power grid voltage amplitude, E d is the d-axis voltage component of the converter connection point, and E q is the q-axis voltage component of the converter connection point.

[0070] S5. Calculate the d-axis reference value and q-axis reference value of the converter output current after amplitude limiting control;

[0071] Among them, the current amplitude limiting control method is as follows:

[0072]

[0073] Among them, and are respectively the d-axis reference value and the q-axis reference value of the converter output current after amplitude limiting control, λ is the adaptive coefficient, and I max is the maximum allowable value of the converter output current.

[0074] S6. Calculate the d-axis voltage reference value and the q-axis voltage reference value of the modulation voltage at the AC outlet of the converter in the dq rotating coordinate system;

[0075] Among them, the d-axis voltage reference value of the modulation voltage at the converter outlet and the q-axis voltage reference value are calculated as follows:

[0076]

[0077] Among them, I d and I q are respectively the d-axis component and the q-axis component of the converter output current in the dq rotating coordinate system, ω is the actual angular velocity of the power grid, and L F is the inductance value of the LC filter on the AC side of the converter, and K PC and K IC are respectively the proportional parameter and the integral parameter of the current controller.

[0078] S7. Calculate the a-axis voltage reference value, the b-axis voltage reference value, and the c-axis voltage reference value of the modulation voltage at the AC outlet of the converter in the abc stationary coordinate system;

[0079] Among them, the a-axis voltage reference value of the modulation voltage at the converter outlet in the abc stationary coordinate system , the b-axis voltage reference value and the c-axis voltage reference value are calculated as follows:

[0080]

[0081] Among them, θ * is the phase reference value of the AC side of the converter, and are respectively the d-axis voltage reference value and the q-axis voltage reference value of the modulation voltage at the converter outlet.

[0082] S8. According to the reference value of the modulation voltage, use the pulse width modulation theory to generate corresponding control pulses to achieve the control of the converter.

[0083] Among them, the specific process of using the pulse width modulation theory to generate corresponding control pulses is as follows:

[0084] S81. The a-axis reference value, b-axis reference value, and c-axis reference value of the modulation voltage at the converter outlet generated in step S7 are respectively compared with the triangular carrier wave to obtain the trigger signals Tg1r and Tg2r of the upper and lower bridge arms IGBTs of phase a, obtain the trigger signals Tg3r and Tg4r of the upper and lower bridge arms IGBTs of phase b, and obtain the trigger signals Tg5r and Tg6r of the upper and lower bridge arms IGBTs of phase c.

[0085] S82. Use the trigger signals Tg1r, Tg2r, Tg3r, Tg4r, Tg5r, and Tg6r to control the turning on and off of the corresponding IGBTs, so that the converter outputs narrow rectangular pulses. Then, using the equal area principle, when the frequency of the triangular carrier wave is relatively large, the narrow rectangular pulses can approximate a sine wave.

[0086] Embodiment 2

[0087] Based on an adaptive current limiting control method for a voltage source converter disclosed in Embodiment 1, this embodiment uses a test system in which a DC power supply is connected to a weak grid with a short circuit ratio of 2 through a converter for simulation verification. The converter limiting method uses the adaptive current limiting control method involved in the present invention, and the adaptive coefficient is taken as 0.5. The reference value of the active power output by the converter is initially set to 3.5 MW (the rated capacity is 5 MW), and the grid voltage drops from 1 pu to 0.6 pu at time t = 10.0 s. Figure 2 For the simulation waveform of the system when the fault is removed at t = 13.5 s, Figure 3 For the simulation waveform of the system when the fault is removed at t = 13.6 s. From the simulation Figure 2 and Figure 3 it can be seen that whether the fault is removed in time or not, the converter can exit the limiting control and return to the normal operation state after the fault is removed.

[0088] Embodiment 3

[0089] Based on an adaptive current limiting control method for a voltage source converter disclosed in Embodiment 1, this embodiment compares the acceleration area and the maximum deceleration area of the present invention and the traditional d-axis priority limiting control method under the same voltage drop depth and the same fault clearing angle. Set the adaptive coefficient to 0.85, the maximum allowable value of the converter output current is 1 p.u., the reference value of the converter active power is 0.7 p.u., and the grid voltage drops from the original 1 p.u. to 0.6 p.u. temporarily. Both controls remove the fault when the power angle reaches 0.66 rad, and the system power angle curve is as Figure 4As shown in the figure. After calculation, the accelerating area of the traditional d-axis priority limiter control method is 0.0549, and the maximum decelerating area is 0.0084; the accelerating area of the adaptive current limiter control is 0.0328, and the maximum decelerating area is 0.1383. It can be seen that the adaptive current limiter control method shifts the power angle curve under the limiter state to the right through the adaptive coefficient, making its accelerating area smaller and decelerating area larger. The transient stability performance of the adaptive limiter control method is better than that of the traditional current limiter control method.

[0090] Embodiment 4

[0091] In this embodiment, a comparison is made with the existing method. Based on the adaptive current limiter control method for a voltage source converter disclosed in Embodiment 1, the critical clearing time of the present invention and the traditional d-axis priority limiter method is compared in this embodiment. The reference value of the active power of the converter is set to 0.7 p.u., and the grid voltage drops transiently from the original 1 p.u. to 0.6 p.u. Under this operating condition, the critical clearing time of the traditional d-axis priority limiter control method is 12.4 s, the critical clearing time of the adaptive current limiter control method when the adaptive coefficient is 0.85 is 13.3 s, and the critical clearing time of the adaptive current limiter control method when the adaptive coefficient is 0.25 is 13.4 s, as shown in Table 1.

[0092] Table 1. Critical Clearing Time under Different Control Strategies

[0093] Control strategy Critical clearing time / s Adaptive current limiting control method (k = 0.25) 13.4 Adaptive current limiting control method (k = 0.85) 13.3 Traditional d-axis priority current limiting method 12.4

[0094] It can be seen from Table 1 that the critical clearing time of the traditional d-axis priority current limiter control method is less than that of the adaptive current limiter control method, and when the value of the adaptive coefficient decreases, the critical clearing time increases.

[0095] It should be noted that for the foregoing method embodiments, for the sake of simplicity of description, they are all expressed as a series of action combinations. However, those skilled in the art should know that the present invention is not limited by the described action sequence, because according to the present invention, certain steps can be performed in other sequences or simultaneously.

[0096] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0097] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. An adaptive current limiting control method for a voltage source converter, characterized in that: The adaptive current limiting control method comprises the following steps: S1. Obtain the reference value and actual value of the active power of the voltage source converter in the power system, obtain the reference value and actual value of the grid connection point voltage, and obtain the maximum allowable value and actual value of the converter output current; S2, calculating the d-axis and q-axis components of the converter grid connection point voltage and the converter output current in the dq rotating coordinate system; S3, calculating the phase reference value of the AC side of the converter; S4, calculating the d-axis reference value and the q-axis reference value of the converter output current in the dq rotating coordinate system; S5. Calculate the d-axis current reference value and the q-axis current reference value of the converter output current in the dq rotating coordinate system after the converter output current is limited according to the maximum allowable value and the actual value of the converter output current; S6, calculating the d-axis voltage reference value and the q-axis voltage reference value of the modulation voltage at the AC outlet of the converter in the dq rotating coordinate system; S7, calculating the a-axis voltage reference value, the b-axis voltage reference value and the c-axis voltage reference value of the modulation voltage at the AC outlet of the converter in the abc stationary coordinate system; S8. According to the phase reference value on the AC side of the converter and the reference value of the modulation voltage in the dq rotating coordinate system, the pulse width modulation theory is used to generate corresponding control pulses to realize the control of the converter.

2. The adaptive current limiting control method of a voltage source converter according to claim 1, characterized in that: In step S2, the d-axis component E of the voltage at the converter grid connection point in the dq coordinate system a and the q-axis component E q The calculation formula is as follows: Among them, E a , E b , E c are the a-axis component, b-axis component and c-axis component of the converter grid-connected point voltage in the abc coordinate system, θ * is the phase reference value of the converter AC side; The d-axis component I of the converter output current in the dq coordinate system d and the q-axis component I q The calculation formula is as follows: Among them, I a , I b , I c are the a-axis component, b-axis component and c-axis component of the converter output current in the abc coordinate system.

3. The adaptive current limiting control method of a voltage source converter according to claim 1, characterized in that: In step S3, the phase reference value θ on the AC side of the converter * The calculation formula is as follows: Where s is the Laplace operator, ω0 is the synchronous angular frequency of the AC power grid, J and D are the virtual inertia and damping coefficient, respectively, and P ref is the reference value of the active power output by the converter, and P is the actual value of the active power output by the converter.

4. The adaptive current limiting control method of a voltage source converter according to claim 1, characterized in that: In step S4, the d-axis reference value of the converter AC output current and q-axis reference value The calculation formula is as follows: Among them, K PV and K IV are the proportional and integral parameters of the voltage controller, E ref is the reference value of the grid voltage amplitude, E d is the d-axis voltage component of the inverter grid connection point, E q is the q-axis voltage component of the converter grid-connected point.

5. The adaptive current limiting control method of a voltage source converter according to claim 1, characterized in that: In step S5, the d-axis reference value of the converter output current after the limit control in the dq rotating coordinate system is and q-axis reference value The calculation formula is as follows: Among them, λ is the adaptive coefficient, I max It is the maximum allowable output current of the converter.

6. The adaptive current limiting control method for a voltage source converter according to claim 1, characterized in that: In step S6, the d-axis voltage reference value of the modulation voltage at the converter outlet in the dq rotating coordinate system is and q-axis voltage reference value The calculation formula is as follows: Among them, E ref is the reference value of the grid voltage amplitude, and are the d-axis reference value and q-axis reference value of the converter AC output current, I d and I q are the d-axis component and q-axis component of the converter output current in the dq rotating coordinate system, ω is the actual angular velocity of the power grid, L F is the inductance of the LC filter on the AC side of the converter, K PC and K IC They are the proportional parameter and integral parameter of the current controller respectively.

7. The adaptive current limiting control method for a voltage source converter according to claim 1, characterized in that: In step S7, the a-axis voltage reference value of the modulation voltage at the converter outlet in the abc stationary coordinate system is b-axis voltage reference value and c-axis voltage reference value The calculation formula is as follows: Among them, θ * is the phase reference value of the AC side of the converter, and They are respectively the d-axis voltage reference value and the q-axis voltage reference value of the modulation voltage at the converter outlet.

8. The adaptive current limiting control method of a voltage source converter according to claim 1, characterized in that: In step S8, the process of generating the corresponding control pulse using pulse width modulation theory is as follows: S81, the modulated voltage at the converter outlet is the reference value of the a-axis voltage in the abc stationary coordinate system b-axis voltage reference value and c-axis voltage reference value Compare with the triangular carrier respectively to obtain the trigger signals Tg1r and Tg2r of the upper and lower bridge arm IGBTs of phase a, obtain the trigger signals Tg3r and Tg4r of the upper and lower bridge arm IGBTs of phase b, and obtain the trigger signals Tg5r and Tg6r of the upper and lower bridge arm IGBTs of phase c; S82. Use trigger signals Tg1r, Tg2r, Tg3r, Tg4r, Tg5r and Tg6r to control the opening and closing of the corresponding IGBTs, so that the converter outputs narrow rectangular pulses. Then, by using the equal area principle, when the frequency of the triangular carrier is large, the narrow rectangular pulses approach a sine wave.

Images