CN116345758A - Self-synchronization voltage source grid-connected stability improving method based on voltage control loop reshaping - Google Patents

Abstract

The invention discloses a self-synchronization voltage source grid-connected stability improving method based on voltage control loop reshaping, and belongs to the technical field of grid-connected inverter control; the grid-connected stability improving method comprises the following steps: collecting port voltage and output current of a three-phase inverter; calculating the output active power and reactive power of the three-phase inverter according to the port voltage and the output current; according to the active power and the reactive power, calculating the amplitude and the phase of an internal potential reference value, and calculating the internal potential reference value; reshaping the voltage control loop and utilizing the internal potential reference value to generate a current control loop reference value; generating a modulation wave by utilizing a current control loop and grid voltage feedforward control; sending the modulated wave into a PWM module, and generating a driving signal so as to control an inverter; compared with the existing self-synchronizing voltage source control method, the method of the invention improves the stable operation capability of the self-synchronizing voltage source under the strong network working condition on the premise of not increasing the hardware cost.

Description

Method for improving grid-connected stability of self-synchronized voltage source based on voltage control loop reshaping

technical field

The invention belongs to the technical field of grid-connected inverter control, and in particular relates to a self-synchronizing voltage source grid-connected stability improvement method based on voltage control loop reshaping.

Background technique

The current source grid-connected inverter belongs to the grid-connected inverter, which has the advantages of fast power regulation and high utilization rate of renewable energy, but it generally takes maximizing active power output as its main operating goal, and cannot generate synchronously as traditional The machine supports the grid voltage and frequency stability. With the continuous improvement of the penetration rate of new energy power generation, the power grid is gradually changing from a strong grid to a weak grid. In order to enhance the adaptability of grid-connected inverters under complex working conditions, grid-connected inverters have emerged as the times require.

The self-synchronizing voltage source belongs to the grid-constructed inverter and has the potential to simulate the damping and inertia of the traditional synchronous generator. Although it can provide frequency and voltage support for the grid, the self-synchronizing voltage source using the voltage and current double inner loop control structure is In the case of a strong network, there is a risk of oscillation.

Contents of the invention

Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a self-synchronous voltage source grid-connected stability improvement method based on voltage control loop reshaping.

The purpose of the present invention can be achieved through the following technical solutions:

A self-synchronous voltage source grid-connected stability improvement method based on reshaping the voltage control loop. The applied topology includes a three-phase inverter. The three-phase inverter includes a three-phase inverter circuit, a three-phase LC filter, a three-phase A voltage sensor, a three-phase current sensor and a three-phase inverter controller; the method comprising the steps of:

Collect the port voltage and output current of the three-phase inverter;

calculating the output active power and reactive power of the three-phase inverter according to the port voltage and output current;

calculating the magnitude and phase of the internal potential reference value based on the active power and the reactive power, and calculating the internal potential reference value;

reshaping the voltage control loop, and using said internal potential reference value to generate a current control loop reference value;

Using the current control loop and grid voltage feed-forward control to generate modulation waves;

The modulated wave is sent to the PWM module to generate a driving signal to control the three-phase inverter.

Further, the steps of collecting the port voltage and output current of the three-phase inverter include:

S11, using the three-phase voltage sensor to collect the three-phase voltage of the three-phase LC filter filter capacitor as the three-phase inverter port voltage v _abc , using the three-phase current sensor to collect the three-phase current of the three-phase LC filter filter inductor as the three-phase inverter The device output current i _abc ;

S12, converting the port voltage v _abc and the output current i _abc of the three-phase inverter from analog to digital and transmitting them to the three-phase inverter controller.

Further, the calculation process of the active power and reactive power includes:

S21, converting the port voltage v _abc and the port current i _abc from a three-phase stationary coordinate system to a two-phase stationary coordinate system;

The transformation formula for converting the voltage of the three-phase stationary coordinate system to the voltage of the two-phase stationary coordinate system is:

In the formula, v _a , v _b , and v _c are the port voltages of phase A, phase B, and phase C in the three-phase stationary coordinate system, respectively, and v _α , v _β are the port voltages of the α-axis and β-axis in the two-phase stationary coordinate system, respectively. .

The transformation formula for converting the current in the three-phase stationary coordinate system to the current in the two-phase stationary coordinate system is:

In the formula, i _a , i _b , and i _c are the output currents of phase A, phase B, and phase C in the three-phase stationary coordinate system, respectively, and i _α , i _β are the output currents of the α-axis and β-axis in the two-phase stationary coordinate system, respectively. .

S22. Obtain the output active power p and reactive power q of the three-phase inverter through the instantaneous power calculation formula; the instantaneous power calculation formula is:

p=1.5×(v _α i _α +v _β i _β )

q=1.5×(v _β i _α −v _α i _β ).

Further, the calculation process of the internal potential reference value includes:

S31. Calculate the phase θ of the internal potential reference value according to the calculation formula of the active power loop, and the calculation formula of the active power loop is:

In the formula, P _set is the reference value of the active power output by the three-phase inverter, ω _n is the rated angular frequency of the three-phase power grid, D _p is the active damping coefficient, J is the virtual moment of inertia, and s is the Laplacian operator;

S32. Calculate the amplitude U of the internal potential reference value according to the reactive power loop calculation formula, and the reactive power loop calculation formula is:

In the formula, Q _set is the reference value of reactive power output by the three-phase inverter, V _n is the rated voltage amplitude of the three-phase grid, D _q is the reactive damping coefficient, K is the reactive inertia coefficient, and v _Amp is the three-phase inverter The amplitude of the output voltage of the transformer. ;

S33, according to the phase θ of the internal potential reference value and the amplitude U of the internal potential reference value, the internal potential reference value u _φ-ref is obtained through the internal potential calculation formula, and the internal potential calculation formula is:

In the formula, u _{φ-ref_a} , u _{φ-ref_b} and u _{φ-ref_c} are the internal potential reference values of phase A, phase B and phase C respectively.

Further, the step of calculating the reference value of the current control loop includes:

S41, using the internal potential reference value as a reference value of the voltage control loop;

S42, calculating the reshaping branch of the voltage control loop, multiplying the reference value of the current control loop in the previous control cycle by the virtual impedance to obtain the feedback value 1 of the voltage control loop, denoted as u _fb1 ;

S43, taking the port voltage as the feedback quantity 2 of the voltage control loop, denoted as u _fb2 , and calculating the feedback quantity u _fb of the voltage control loop, the calculation formula is: u _fb =u _fb1 +u _fb2 ;

S44, the reference value of the voltage control loop minus the feedback value u _fb of the voltage control loop is used as the input of the voltage control loop, and the voltage control loop outputs the reference value i _ref of the current control loop.

Further, the step of generating the modulated wave includes:

S51, subtracting the output current of the three-phase inverter from the reference value of the current control loop as the input of the current control loop, and the output modulation wave component 1 of the current control loop is recorded as v _mabc1 ;

S52, the power grid voltage feedforward component v _ff is the modulation wave component 2, denoted as v _mabc2 , and the modulation wave v _mabc is calculated, the calculation formula is v _mabc =v _mabc1 +v _mabc2 .

Further, the step of generating the driving signal includes: comparing the modulated wave with a three-phase triangular carrier wave, and generating the driving signal through a space vector modulation method.

Self-synchronized voltage source grid-connected stability improvement system based on voltage control loop remodeling, including:

Data acquisition module: collect the port voltage and output current of the three-phase inverter;

Power calculation module: calculate the active power and reactive power output by the three-phase inverter according to the port voltage and output current;

Potential reference value calculation module: calculate the amplitude and phase of the internal potential reference value according to the active power and reactive power, and calculate the internal potential reference value;

Current reference value calculation module: reshape the voltage control loop, and use the internal potential reference value to generate a current control loop reference value;

Modulation wave generation module: use the current control loop and grid voltage feed-forward control to generate modulation waves;

And, the driving signal generating module: sending the modulated wave into the PWM module to generate the driving signal.

Beneficial effects of the present invention:

1. The present invention realizes reshaping the impedance of the self-synchronizing voltage source by reshaping the voltage control loop. Compared with the current voltage and current double closed-loop control self-synchronizing voltage source, it can avoid output current oscillation and achieve stability under strong network conditions run.

2. The present invention reshapes the impedance of the self-synchronizing voltage source by optimizing the control loop. Compared with the scheme of adding actual impedance, the hardware cost can be saved.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, In other words, other drawings can also be obtained from these drawings on the premise of not paying creative work.

Fig. 1 is the circuit topological diagram of three-phase grid-connected inverter of the present invention;

Fig. 2 is a schematic diagram of a self-synchronous voltage source control method for reshaping the voltage control loop of the present invention;

Fig. 3 is before adopting the inventive method and after adopting the inventive method the inverter A phase port voltage and the output current waveform figure;

Fig. 4 is a waveform diagram of active power and reactive power output by the inverter before and after adopting the method of the present invention.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

A self-synchronous voltage source grid-connected stability improvement method based on voltage control loop reshaping, as shown in Figure 1, the grid-connected inverter topology using this method includes: DC side power supply, three-phase inverter, three-phase phase grid impedance and three-phase grid; wherein, the three-phase inverter includes a three-phase inverter circuit, a three-phase LC filter, a three-phase voltage sensor, a three-phase current sensor and a three-phase inverter controller;

In the three-phase inverter: the three-phase inverter circuit is connected to the three-phase LC filter, the three-phase voltage sensor and the three-phase current sensor respectively sample the three-phase voltage of the filter capacitor and the three-phase current of the filter inductor in the three-phase LC filter, and The sampling signal is transmitted to the three-phase inverter controller; after calculation, the three-phase inverter controller outputs a driving signal to control the three-phase inverter circuit.

As shown in Figure 2, the self-synchronous voltage source grid-connected stability improvement method based on voltage control loop reshaping includes the following steps:

S1, collecting the port voltage v _abc and output current i _abc of the three-phase inverter;

The specific process includes:

S11, using the three-phase voltage sensor to collect the three-phase voltage of the three-phase LC filter filter capacitor as the three-phase inverter port voltage v _abc , using the three-phase current sensor to collect the three-phase current of the three-phase LC filter filter inductor as the three-phase inverter The device output current i _abc ;

S12, converting the port voltage v _abc and the output current i _{abc of} the three-phase inverter into digital quantities through the analog quantity acquisition circuit and transmitting them to the three-phase inverter controller.

S2. Calculate the output active power and reactive power of the three-phase inverter according to the port voltage v _abc and the output current i _abc ;

The specific process includes:

S21, converting the port voltage v _abc and port current i _abc of the three-phase inverter from the three-phase stationary coordinate system to the two-phase stationary coordinate system;

The transformation formula for converting the voltage of the three-phase stationary coordinate system to the voltage of the two-phase stationary coordinate system is:

In the formula, v _a , v _b , and v _c are the port voltages of phase A, phase B, and phase C in the three-phase stationary coordinate system, respectively, and v _α , v _β are the port voltages of the α-axis and β-axis in the two-phase stationary coordinate system, respectively. .

The transformation formula for converting the current in the three-phase stationary coordinate system to the current in the two-phase stationary coordinate system is:

In the formula, i _a , i _b , and i _c are the output currents of phase A, phase B, and phase C in the three-phase stationary coordinate system, respectively, and i _α , i _β are the output currents of the α-axis and β-axis in the two-phase stationary coordinate system, respectively. .

S22. Obtain the active power p and reactive power q output by the inverter through the instantaneous power calculation formula; the instantaneous power calculation formula is:

p=1.5×(v _α i _α +v _β i _β )

q＝1.5×(v _β i _α -v _α i _β )

S3, according to the active power p and the reactive power q, calculate the amplitude U of the internal potential reference value and the phase θ of the internal potential reference value, and calculate the internal potential reference value u _φ-ref ;

Specific steps include:

S31. Calculate the phase θ of the internal potential reference value according to the calculation formula of the active power loop, and the calculation formula of the active power loop is:

In the formula, P _set is the reference value of the active power output by the three-phase inverter, ω _n is the rated angular frequency of the three-phase power grid, D _p is the active damping coefficient, J is the virtual moment of inertia, and s is the Laplacian operator;

S32. Calculate the amplitude U of the internal potential reference value according to the reactive power loop calculation formula, and the reactive power loop calculation formula is:

In the formula, Q _set is the reference value of the reactive power output by the three-phase inverter, V _n is the rated voltage amplitude of the three-phase grid, D _q is the reactive damping coefficient, K is the reactive inertia coefficient, and s is the Laplace Operator, v _Amp is the amplitude of the output voltage of the three-phase inverter;

S33, according to the phase θ of the internal potential reference value and the amplitude U of the internal potential reference value, the internal potential reference value u _φ-ref is obtained through the internal potential calculation formula, and the internal potential calculation formula is:

In the formula, u _{φ-ref_a} , u _{φ-ref_b} and u _{φ-ref_c} are the internal potential reference values of phase A, phase B and phase C respectively.

S4, reshape the voltage control loop, and use the internal potential reference value u _φ-ref obtained in S33 to generate the current control loop reference value i _ref ;

Specific steps include:

S41, using the internal potential reference value u _φ-ref obtained in step S33 as the reference value u _ref of the voltage control loop;

S42, calculating the reshaping branch of the voltage control loop, multiplying the reference value of the current control loop in the previous control cycle by the virtual impedance to obtain the feedback value 1 of the voltage control loop, denoted as u _fb1 ;

S43, taking the port voltage v _abc as the feedback quantity 2 of the voltage control loop, denoted as u _fb2 , and calculating the feedback quantity u _fb of the voltage control loop, the calculation formula is: u _fb =u _fb1 +u _fb2 ;

S44, the reference value u _ref of the voltage control loop minus the feedback value u _fb of the voltage control loop is used as the input of the voltage control loop, and the voltage control loop outputs the reference value i _ref of the current control loop.

S5, using the current control loop and grid voltage feed-forward control to generate modulated waves;

Specific steps include:

S51, subtract the three-phase inverter output current i _abc from the current control loop reference value i _ref obtained in step S44 as the input of the current control loop, and the current control loop outputs the modulation wave component 1, which is recorded as v _mabc1 ;

S52, the power grid voltage feedforward component v _ff is the modulation wave component 2, which is recorded as v _mabc2 , and the modulation wave v _mabc is calculated, and the calculation formula is v _mabc = v _mabc1 + v _mabc2 ;

S6, sending the modulated wave v _mabc generated by S52 into the PWM module to generate a drive signal and control the three-phase inverter;

The specific process is: the modulation wave v _mabc is compared with the three-phase triangular carrier, and the driving signal is generated by the space vector modulation (SVPWM) method.

Application example:

Figure 1 shows the main circuit of a typical grid-connected system. Among them, the DC side of the main circuit part can be regarded as a DC source with constant voltage. The DC-AC conversion part is realized by a three-phase full-bridge inverter circuit composed of 6 IGBTs. The current output by the bridge arm is connected to the power grid after being filtered by LC. The sampling part obtains the port voltage and output current of the inverter through the sampling device. Figure 2 shows the control part of the self-synchronizing voltage source. The inverter port voltage and output current are input to the power calculation module to obtain the instantaneous output active power and reactive power of the inverter, and the instantaneous output active power of the inverter is input to the active power The /frequency (P/f) adjustment module obtains the reference internal potential phase, and the instantaneous output reactive power of the inverter is input to the reactive power/voltage (Q/u) adjustment module to obtain the reference internal potential amplitude. The reference value of the voltage control loop is calculated according to the internal potential phase and amplitude, and the feedback value of the voltage control loop is calculated according to the port voltage, virtual impedance and reference current. The difference between the reference value and the feedback value of the voltage control loop is input to the voltage regulation module, and the voltage regulation module outputs the current reference value. Further, the difference between the current reference value and the output current value is input to the current control module. Then, the output value of the current control module is added to the inverter port voltage to obtain a modulated wave. Finally, the modulated wave is modulated by space vector modulation SVPWM to generate a drive signal to drive the IGBT.

The main parameter values of this embodiment are as follows: main circuit parameters, DC side voltage V _dc = 700V, inverter side filter inductance L = 150uH, filter inductance branch circuit 0.01Ω, filter capacitor C = 600uF, damping resistance R _d = 0.2 Ω, the effective value of the AC bus voltage is 315V, the AC bus voltage frequency f ₀ =50Hz, the line resistance is 0Ω, the line inductance is 0Ω, the rated capacity of the inverter is 500kW, and the switching frequency of the inverter is 3.2kHz. Controller parameters, active power given P _set ＝500kW, reactive power given Q _set ＝0kVar, virtual moment of inertia J＝0.3, reactive inertia coefficient K＝318, active damping coefficient D _p ＝252.87, reactive damping coefficient D _q =2000, virtual resistance is 0.01Ω, virtual inductance is 150uH, voltage controller proportional coefficient K _pv =50, voltage controller integral coefficient K _iv =0, current controller proportional coefficient K _pi =0.64, current controller integral Coefficient K _ii =100.

In order to verify the effectiveness of the self-synchronous voltage source grid-connected stability improvement method based on the reshaping of the voltage control loop of the present invention, a simulation model is built in MATLAB/Simulink to verify the effectiveness of the control method. The inverter runs off-grid during 0-0.1s, connects to the grid at 0.1s, sets active power Pset=500kW, sets reactive power as 0kVar, and adopts the method of the present invention at 0.4s.

Figure 3 shows the port voltage and output current waveforms of the self-synchronizing voltage source before and after adopting the method. The time period of 0-0.1s is off-grid operation, the time period of 0.1s is connected to the grid, and the time period of 0.1s-0.4s does not use the method of the present invention, because the line impedance is 0, so the port voltage does not fluctuate, but the output current oscillates. At 0.4s, by adopting the method of the present invention, the output current oscillation decays rapidly, and at 0.8s, the output current oscillation is completely suppressed.

Figure 4 shows the waveforms of active power and reactive power output from the synchronous voltage source before and after adopting this method. The time period of 0-0.1s is off-grid operation, the time period of 0.1s is connected to the grid, and the time period of 0.1s-0.4s, if the method of the present invention is not used, the output active power and reactive power both oscillate. At 0.4s, using the method of the present invention, the output active power and reactive power are rapidly attenuated, and at 0.8s the output active power and reactive power oscillations are completely suppressed, the active power reaches a given value of 500kW, and the reactive power reaches a given value of 0kVar .

In the description of this specification, descriptions referring to the terms "one embodiment", "example", "specific example" and the like mean that specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment of the present invention. In an embodiment or example. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The basic principles, main features and advantages of the present invention have been shown and described above. Those skilled in the industry should understand that the present invention is not limited by the above-mentioned embodiments. What are described in the above-mentioned embodiments and the description only illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will also have Variations and improvements are possible, which fall within the scope of the claimed invention.

Claims (8)

1. The self-synchronous voltage source grid-connected stability improvement method based on the reshaping of the voltage control loop, the applied topology includes a three-phase inverter, and the three-phase inverter includes a three-phase inverter circuit, a three-phase LC filter, Three-phase voltage sensor, three-phase current sensor and three-phase inverter controller; It is characterized in that, described method comprises the following steps: Collect the port voltage and output current of the three-phase inverter; calculating the output active power and reactive power of the three-phase inverter according to the port voltage and output current; calculating the magnitude and phase of the internal potential reference value based on the active power and the reactive power, and calculating the internal potential reference value; reshaping the voltage control loop, and using said internal potential reference value to generate a current control loop reference value; Using the current control loop and grid voltage feed-forward control to generate modulation waves; The modulated wave is sent to the PWM module to generate a driving signal to control the three-phase inverter. 2. The self-synchronizing voltage source grid-connected stability improvement method based on voltage control loop reshaping according to claim 1, wherein the step of collecting three-phase inverter port voltage and output current comprises: S11, using the three-phase voltage sensor to collect the three-phase voltage of the three-phase LC filter filter capacitor as the three-phase inverter port voltage v _abc , using the three-phase current sensor to collect the three-phase current of the three-phase LC filter filter inductor as the three-phase inverter The device output current i _abc ; S12, converting the port voltage v _abc and the output current i _abc of the three-phase inverter from analog to digital and transmitting them to the three-phase inverter controller. 3. The self-synchronizing voltage source grid-connected stability improvement method based on voltage control loop reshaping according to claim 1, wherein the calculation process of the active power and reactive power comprises: S21, converting the port voltage v _abc and the output current i _abc from a three-phase stationary coordinate system to a two-phase stationary coordinate system; The transformation formula for converting the voltage of the three-phase stationary coordinate system to the voltage of the two-phase stationary coordinate system is:

In the formula, v _a , v _b , and v _c are the port voltages of phase A, phase B, and phase C in the three-phase stationary coordinate system, respectively, and v _α , v _β are the port voltages of the α-axis and β-axis in the two-phase stationary coordinate system, respectively. . The transformation formula for converting the current in the three-phase stationary coordinate system to the current in the two-phase stationary coordinate system is:

In the formula, i _a , i _b , and i _c are the output currents of phase A, phase B, and phase C in the three-phase stationary coordinate system, respectively, and i _α , i _β are the output currents of the α-axis and β-axis in the two-phase stationary coordinate system, respectively. . S22. Obtain the output active power p and reactive power q of the three-phase inverter through the instantaneous power calculation formula; the instantaneous power calculation formula is: p=1.5×(v _α i _α +v _β i _β ) q=1.5×(v _β i _α −v _α i _β ). 4. The self-synchronizing voltage source grid-connected stability improvement method based on voltage control loop reshaping according to claim 1, wherein the calculation process of the internal potential reference value comprises: S31. Calculate the phase θ of the internal potential reference value according to the calculation formula of the active power loop, and the calculation formula of the active power loop is:

In the formula, P _set is the reference value of the active power output by the three-phase inverter, ω _n is the rated angular frequency of the three-phase power grid, D _p is the active damping coefficient, J is the virtual moment of inertia, and s is the Laplacian operator; S32. Calculate the amplitude U of the internal potential reference value according to the reactive power loop calculation formula, and the reactive power loop calculation formula is:

In the formula, Q _set is the reference value of reactive power output by the three-phase inverter, V _n is the rated voltage amplitude of the three-phase grid, D _q is the reactive damping coefficient, K is the reactive inertia coefficient, and v _Amp is the three-phase inverter The amplitude of the output voltage of the transformer. S33, according to the phase θ of the internal potential reference value and the amplitude U of the internal potential reference value, the internal potential reference value u _φ-ref is obtained through the internal potential calculation formula, and the internal potential calculation formula is:

In the formula, u _{φ-ref_a} , u _{φ-ref_b} and u _{φ-ref_c} are the internal potential reference values of phase A, phase B and phase C respectively. 5. The self-synchronizing voltage source grid-connected stability improvement method based on voltage control loop reshaping according to claim 1, wherein the calculation step of the reference value of the current control loop comprises: S41, using the internal potential reference value as a reference value of the voltage control loop; S42, calculating the reshaping branch of the voltage control loop, multiplying the reference value of the current control loop in the previous control cycle by the virtual impedance to obtain the feedback value 1 of the voltage control loop, denoted as u _fb1 ; S43, taking the port voltage as the feedback quantity 2 of the voltage control loop, denoted as u _fb2 , and calculating the feedback quantity u _fb of the voltage control loop, the calculation formula is: u _fb =u _fb1 +u _fb2 ; S44, the reference value of the voltage control loop minus the feedback value u _fb of the voltage control loop is used as the input of the voltage control loop, and the voltage control loop outputs the reference value i _ref of the current control loop. 6. The self-synchronizing voltage source grid-connected stability improvement method based on voltage control loop reshaping according to claim 5, wherein the step of generating the modulated wave comprises: S51, subtracting the output current of the three-phase inverter from the reference value of the current control loop as the input of the current control loop, and the output modulation wave component 1 of the current control loop is recorded as v _mabc1 ; S52, the power grid voltage feedforward component v _ff is the modulation wave component 2, denoted as v _mabc2 , and the modulation wave v _mabc is calculated, the calculation formula is v _mabc =v _mabc1 +v _mabc2 . 7. The self-synchronous voltage source grid-connected stability improvement method based on voltage control loop reshaping according to claim 1 or 6, wherein the step of generating the drive signal comprises: combining the modulated wave with the three-phase Triangular carrier wave is compared to generate drive signal by space vector modulation method. 8. A self-synchronous voltage source grid-connected stability improvement system based on voltage control loop reshaping, characterized in that it includes: Data acquisition module: collect the port voltage and output current of the three-phase inverter; Power calculation module: calculate the active power and reactive power output by the three-phase inverter according to the port voltage and output current; Potential reference value calculation module: calculate the amplitude and phase of the internal potential reference value according to the active power and reactive power, and calculate the internal potential reference value; Current reference value calculation module: reshape the voltage control loop, and use the internal potential reference value to generate a current control loop reference value; A modulating wave generation module: using the current control loop and grid voltage feed-forward control to generate a modulating wave; and, a driving signal generating module: sending the modulating wave into a PWM module to generate a driving signal.

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