Method and system for obtaining broadband positive and negative sequence impedance parameters of grid-connected converter

Abstract

The present invention relates to the field of impedance measurement technology and provides a method and system for obtaining broadband positive and negative sequence impedance parameters of a grid-connected converter. The method comprises: building a grid-connected converter simulation model; adding a positive and negative sequence harmonic disturbance small signal injection unit, an auxiliary phase-locked loop unit, a current signal auxiliary processing unit, and an RLC circuit equivalent unit to the grid-connected converter simulation model; the positive and negative sequence harmonic disturbance small signal injection unit superimposes a harmonic disturbance of preset frequency and phase sequence on the power frequency three-phase voltage source port of the power grid; the auxiliary phase-locked loop unit obtains the phase angle of the power frequency three-phase voltage source of the power grid; the current signal auxiliary processing unit processes the grid connection point current signal; and the RLC circuit equivalent unit obtains the impedance parameters of the grid-connected converter by measuring the effective value and phase angle of the loop current. The present invention can obtain positive and negative sequence impedance parameters with clear physical meaning and has the characteristics of a simple algorithm, easy use, accurate results, and fast impedance data acquisition speed.

Description

Technical Field

[0001] The present invention relates to the field of impedance measurement technology, and in particular to a method and system for obtaining broadband positive and negative sequence impedance parameters of a grid-connected converter. Background Art

[0002] Current renewable energy grid-connected systems primarily utilize grid-following voltage source converters (GF-VSCs). VSCs synchronize with the grid voltage through a phase-locked loop (PLL) and employ current vector control for rapid power regulation, appearing as controlled current sources. VSCs, due to their simple control structure, mature technology, and ability to operate at their maximum power point, are widely used in grid-connected control for wind power, photovoltaic power, and energy storage. With the increasing number of renewable energy sites, their installed capacity, and their share of power generation, a large number of these sites are interconnected to the public grid via long-distance transmission lines and multiple transformers. This is leading to an increasing intensity of weak grid characteristics (a weak system refers to a grid with a short-circuit ratio (SCR) below 3, where the SCR refers to the ratio of the short-circuit capacity at the grid connection point to the site's installed capacity). This low SCR leads to increasingly prominent stability issues caused by interactions between renewable energy sites and the grid. The interaction between VSCs and the weak grid leads to frequent broadband oscillation incidents. The risk and impact of broadband oscillation are expanding, posing significant challenges to system stability.

[0003] Establishing an impedance model for grid-connected converters through small-signal analysis can better understand the mechanisms and interaction conditions for broadband oscillations in renewable energy stations, enabling the design of more effective protection and control strategies to ensure rapid and stable system recovery in the face of transient disturbances, thereby providing technical support and assurance for the reliable grid connection of renewable energy. However, grid-connected converters have nonlinear, time-varying characteristics, complex internal control, and mutual coupling between different control links such as coordinate (inverse) transformation, phase-locked loops, and proportional-integral regulation. Furthermore, the impedance characteristics are closely related to the operating power point of the equipment, making it difficult to establish an accurate impedance model for grid-connected converters.

[0004] Current methods for modeling the impedance of grid-connected converters are relatively cumbersome and difficult to directly apply to engineering projects. For example, invention patent application number 202110937215.6 requires the establishment of a continuous analytical model of the main power circuit of a modular multilevel converter and is applicable only to modular multilevel converter grid-connected systems. Invention patent application number 202311820303.3 requires the construction of a converter switching function. This function is divided into linear and nonlinear parts using sinusoidal pulse width modulation to determine the nonlinear characteristics of the converter during the modulation phase. Based on the real-time operating data of the renewable energy grid-connected system and the nonlinear characteristics of the converter during the modulation phase, a pre-defined multiharmonic linearization method is used to determine the harmonic transfer function of the renewable energy grid-connected system. The harmonic transfer function describes the frequency coupling characteristics of the converter during the modulation phase. A small-signal model of the renewable energy grid-connected system is constructed based on the converter switching function, the harmonic transfer function, and the actual control architecture of the renewable energy grid-connected system. Each step involves complex mathematical processing. Summary of the Invention

[0005] The object of the present invention is to solve at least one technical problem in the background technology and to provide a method and system for obtaining broadband positive and negative sequence impedance parameters of a grid-connected converter.

[0006] To achieve the above objectives, the present invention provides a method for obtaining broadband positive and negative sequence impedance parameters of a grid-connected converter, comprising:

[0007] Obtain the main circuit parameters and control circuit parameters of the grid-connected converter, and build a grid-connected converter simulation model in the electromagnetic simulation software based on the main circuit parameters and control circuit parameters;

[0008] Four simulation units are added to the grid-connected converter simulation model, namely, the positive and negative sequence harmonic disturbance small signal injection unit, the auxiliary phase-locked loop unit, the current signal auxiliary processing unit, and the RLC circuit equivalent unit;

[0009] The positive and negative sequence harmonic disturbance small signal injection unit is used to superimpose the harmonic disturbance of preset frequency and phase sequence on the power frequency three-phase voltage source port of the power grid to obtain the harmonic disturbance voltage signal;

[0010] The phase angle of the three-phase voltage source of the power grid is obtained through the auxiliary phase-locked loop unit;

[0011] The current signal auxiliary processing unit processes the grid-connected point current signal based on the phase angle and outputs a three-phase voltage signal;

[0012] The three-phase voltage signal, the output value of the original current signal processing unit in the grid-connected converter simulation model and the harmonic disturbance voltage signal are input into the RLC circuit equivalent unit after deviation calculation. The RLC circuit equivalent unit obtains the impedance parameters of the grid-connected converter by measuring the effective value and phase angle of the loop current.

[0013] According to one aspect of the present invention, the positive and negative sequence harmonic disturbance small signal injection unit is composed of a set of three-phase symmetrical voltage sources U pa 、U pb 、U pc It is composed of a three-phase voltage source U connected in series with the grid point and the external grid. sa、 U sb、 U sc Between, among which U pa with U sa Series, U pb with U sb Series, U pc with U sc Series connection;

[0014] U pa 、U pb 、U pc The effective value of the voltage is also U prms , U prms =kU srms , k≤0.1, U srms is the effective value of the equivalent three-phase voltage source of the external power grid.

[0015] According to one aspect of the present invention, a positive and negative sequence harmonic disturbance small signal injection unit is used to superimpose a harmonic disturbance of preset frequency and phase sequence on the power frequency three-phase voltage source port of the power grid to obtain a harmonic disturbance voltage signal, including:

[0016] The frequency of the positive and negative sequence harmonic disturbance small signal injected by the positive and negative sequence harmonic disturbance small signal injection unit is Select a preset frequency within the frequency range of 1~10kHz;

[0017] The phase angle of the input positive sequence disturbance signal is set to 0°, -120°, and 120°, and the phase angle of the input negative sequence disturbance signal is set to 0°, 120°, and -120°;

[0018] When a three-phase positive sequence small signal disturbance is injected, the three-phase disturbance voltage components are:

[0019] ;

[0020] When a three-phase negative sequence disturbance small signal is injected, the three-phase disturbance voltage components are:

[0021] ;

[0022] Where: t is time.

[0023] According to one aspect of the present invention, the input voltage of the auxiliary phase-locked loop unit is U2, which corresponds to the three-phase voltage Usa 、U sb 、U sc , the effective value is U srms , the phase angles are 0°, -120°, and 120°, and the voltage U2 signal is input into the auxiliary phase-locked loop unit to obtain the phase angle θ2.

[0024] According to one aspect of the present invention, the voltage U2 signal is input into the auxiliary phase-locked loop unit to obtain the phase angle θ2, including:

[0025] The voltage signal U2 is input into the auxiliary phase-locked loop unit and then processed by the coordinate forward transformation to output the dq axis component U d2 and U q2 ;

[0026] U q2 The output value after proportional integral processing is integrated, and the output value after integration processing is the voltage signal U2 synchronous phase angle θ2;

[0027] Among them, the coordinate forward transformation is a synchronous rotating coordinate transformation, and the synchronous phase angle is θ2.

[0028] According to one aspect of the present invention, the current signal auxiliary processing unit processes the grid-connected point current signal based on the phase angle and outputs a three-phase voltage signal, including:

[0029] Grid connection point current After entering the current signal auxiliary processing unit, the coordinates are transformed to obtain Axis component and , the coordinate transformation is synchronous rotation coordinate transformation, and the synchronous phase angle is ;

[0030] The current is calculated by the deviation 、 and target value 、 Compare and calculate the deviation value;

[0031] The deviation value is processed by proportional integration, and the output value after proportional integration is decoupled and a decoupling component is added, where the d-axis decoupling component is U d2 and-KI q2 , the q-axis decoupling component is U q2 and KI d2 The output value after proportional integral processing is summed with the d-axis and q-axis decoupling components respectively. K is the coupling coefficient, which is ;

[0032] The output value after decoupling is subjected to inverse coordinate transformation, and the output result is U abc2 ; Among them, the coordinate inverse transformation is the synchronous rotation coordinate inverse transformation, and the synchronous phase angle is θ2.

[0033] According to one aspect of the present invention, the RLC circuit equivalent unit includes: an RLC equivalent circuit and an impedance phase angle measurement module;

[0034] The three-phase voltage signal, the output value of the original model current signal processing unit, and the harmonic disturbance voltage signal are input into the RLC circuit equivalent unit after deviation calculation. The impedance parameters of the grid-connected converter can be obtained by measuring the effective value and phase angle of the loop current, including:

[0035] The three-phase voltage signal U output by the original model current signal processing unit abc1 Phase A voltage U a1 The three-phase voltage signal U output by the current signal auxiliary processing unit abc2 Phase A voltage U a2 Perform deviation calculation to obtain the difference signal U a1- U a2 ;

[0036] The three-phase positive sequence small signal disturbance A phase voltage signal is U pa (f p ), the three-phase positive sequence disturbance small signal disturbs the A phase voltage signal U pa (f p ) and the difference signal U a1- U a2 Deviation calculation is performed and the output signal is U pa (f p )-(U a1- U a2 );

[0037] The output signal U pa (f p )-(U a1- U a2 ) Input is from a single-phase controlled voltage source U DZ 、Inductor L DZ , resistor R DZ , capacitor C DZ The RLC equivalent circuit is composed to obtain the current signal I;

[0038] The three-phase positive sequence disturbance signal disturbs the A phase voltage signal U pa The current signal I of the RLC equivalent circuit is input to the impedance phase angle measurement module, and the output impedance and phase angle .

[0039] To achieve the above objectives, the present invention further provides a system for acquiring broadband positive and negative sequence impedance parameters of a grid-connected converter, comprising:

[0040] A grid-connected converter simulation model construction module obtains the main circuit parameters and control circuit parameters of the grid-connected converter, and builds a grid-connected converter simulation model in the electromagnetic simulation software based on the main circuit parameters and control circuit parameters;

[0041] The simulation unit setting module adds four simulation units to the grid-connected converter simulation model, namely the positive and negative sequence harmonic disturbance small signal injection unit, the auxiliary phase-locked loop unit, the current signal auxiliary processing unit and the RLC circuit equivalent unit;

[0042] The harmonic disturbance voltage signal acquisition module uses the positive and negative sequence harmonic disturbance small signal injection unit to superimpose the harmonic disturbance of preset frequency and phase sequence on the power frequency three-phase voltage source port of the power grid to obtain the harmonic disturbance voltage signal;

[0043] Phase angle acquisition module, which obtains the phase angle of the power frequency three-phase voltage source of the power grid through the auxiliary phase-locked loop unit;

[0044] A three-phase voltage signal acquisition module, a current signal auxiliary processing unit processes the grid-connected point current signal based on the phase angle and outputs a three-phase voltage signal;

[0045] The impedance parameter acquisition module calculates the deviation of the three-phase voltage signal, the output value of the original current signal processing unit in the grid-connected converter simulation model, and the harmonic disturbance voltage signal, and then inputs them into the RLC circuit equivalent unit. The RLC circuit equivalent unit obtains the impedance parameters of the grid-connected converter by measuring the effective value and phase angle of the loop current.

[0046] To achieve the above-mentioned objectives, the present invention also provides an electronic device, comprising a processor, a memory, and a computer program stored in the memory and executable on the processor. When the computer program is executed by the processor, the method for obtaining the wide-band positive and negative sequence impedance parameters of the grid-connected converter as described above is implemented.

[0047] To achieve the above objectives, the present invention also provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, it implements the method for obtaining the wide-band positive and negative sequence impedance parameters of the grid-connected converter as described above.

[0048] According to the solution of the present invention, the present invention can obtain the positive and negative sequence impedance parameters of the universal grid-connected converter at any frequency point, which has clear and distinct physical meanings, and the positive and negative sequence impedance parameters are independent and have no cross-coupling influence, which simplifies subsequent stability analysis.

[0049] The present invention does not require the establishment of complex mathematical equations for the grid-connected converter. Instead, it only requires the construction of a simulation model and the addition of four supplementary units to obtain the impedance characteristics of the grid-connected converter. Therefore, the present invention can be applied to modeling the impedance of a grid-connected converter with any structure and parameters.

[0050] The present invention has good versatility. When the parameters of the main circuit and the control circuit of the grid-connected converter change, the parameter setting principles of the four auxiliary units remain unchanged and new impedance parameters can be directly output. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 Schematic diagram of the method for obtaining broadband positive and negative sequence impedance parameters of a grid-connected converter according to 1;

[0052] Figure 2 This is a simulation interface diagram of the grid-connected converter simulation model for implementation 1;

[0053] Figure 3 The three-phase voltage and three-phase current simulation waveforms of the grid-connected converter for implementation 1;

[0054] Figure 4 The d-axis and q-axis current simulation waveforms of the grid-connected converter for implementation 1 are shown;

[0055] Figure 5 This is a diagram of the positive and negative sequence harmonic disturbance small signal injection unit added to the simulation model of implementation 1;

[0056] Figure 6 FIG1 is a diagram of an auxiliary phase-locked loop unit added to the simulation model of Implementation 1;

[0057] Figure 7 FIG. 1 is a diagram of a current signal auxiliary processing unit added to the simulation model of Implementation 1;

[0058] Figure 8 The figure is an equivalent unit diagram of the RLC circuit added to the simulation model of embodiment 1;

[0059] Figure 9 This is the simulation result diagram of implementation 1;

[0060] Figure 10 MATLAB code diagram for implementing impedance parameter verification in 1;

[0061] Figure 11 A comparison chart of the impedance / phase angle values obtained by simulation of implementation 1 and the theoretically calculated values;

[0062] Figure 12 The positive and negative sequence impedance curves of the grid-connected converter obtained by cyclic scanning in implementation 1 are shown in FIG. DETAILED DESCRIPTION

[0063] The present invention will now be discussed with reference to exemplary embodiments. It should be understood that the embodiments discussed are only intended to enable those skilled in the art to better understand and implement the present invention, rather than to imply any limitation on the scope of the present invention.

[0064] As used herein, the term "including" and variations thereof are to be interpreted as open-ended terms meaning "including, but not limited to." The term "based on" is to be interpreted as "based, at least in part, on." The terms "one embodiment" and "an embodiment" are to be interpreted as "at least one embodiment."

[0065] According to one embodiment of the present invention, a method for obtaining broadband positive and negative sequence impedance parameters of a grid-connected converter includes:

[0066] Obtain the main circuit parameters and control circuit parameters of the grid-connected converter, and build a grid-connected converter simulation model in the electromagnetic simulation software based on the main circuit parameters and control circuit parameters;

[0067] Four simulation units are added to the grid-connected converter simulation model, namely, the positive and negative sequence harmonic disturbance small signal injection unit, the auxiliary phase-locked loop unit, the current signal auxiliary processing unit, and the RLC circuit equivalent unit;

[0068] Using the positive and negative sequence harmonic disturbance small signal injection unit, a harmonic disturbance of preset frequency and phase sequence is superimposed on the power frequency three-phase voltage source port of the power grid to obtain a harmonic disturbance voltage signal (a three-phase voltage signal with a specific harmonic disturbance component);

[0069] The phase angle of the three-phase voltage source of the power grid is obtained through the auxiliary phase-locked loop unit;

[0070] The current signal auxiliary processing unit processes the grid-connected point current signal based on the phase angle and outputs a three-phase voltage signal;

[0071] The three-phase voltage signal, the output value of the original current signal processing unit in the grid-connected converter simulation model and the harmonic disturbance voltage signal are input into the RLC circuit equivalent unit after deviation calculation. The RLC circuit equivalent unit obtains the impedance parameters of the grid-connected converter by measuring the effective value and phase angle of the loop current.

[0072] Furthermore, it is worth noting that a typical grid-connected converter consists of a main circuit and a control circuit. The main circuit includes a DC side support capacitor C V , three-phase bridge voltage source converter VSC, connected to the reactor L, the control loop consists of a phase-locked loop (PLL), a current signal processing unit, and a PWM signal generation unit. The phase-locked loop (PLL) contains three links: coordinate forward transformation, proportional integration, and integration. The current signal processing unit includes five links: coordinate forward transformation, deviation calculation, decoupling, proportional integration, and coordinate inverse transformation. The DC side voltage of the three-phase bridge voltage source converter VSC is U dc , the voltage at the grid connection point (the point where the reactor is connected to the grid) is U1.

[0073] The typical grid-connected converter operating mode and process are as follows:

[0074] Step 1: Connect capacitor C to the DC side of the three-phase bridge voltage source converter VSC V To maintain DC voltage stability, the AC side is connected to the grid through the reactor L. The grid connection point voltage is U1 and the grid connection point current is I g ;

[0075] Step 2: The grid-connected point voltage U1 is passed through a phase-locked loop to obtain the phase angle θ1. The phase-locked loop consists of three steps: coordinate forward transformation, proportional integral, and integral. The grid-connected point voltage U1 is first subjected to a coordinate forward transformation to output the dq axis component U d1 and U q1 , U q1 Enter proportional integral (proportional and integral coefficients are K pllp and K plli ), the output value of the proportional integral link enters the integral link, and the output value of the integral link is the grid-connected point voltage U1 synchronous phase angle θ1. The coordinate forward transformation is a synchronous rotating coordinate transformation, the synchronous phase angle is θ1, and the coordinate forward transformation formula is as follows:

[0076] ;

[0077] Step 3: Grid-connected current I g Entering the current signal processing unit, the current signal processing unit includes five links: coordinate forward transformation, deviation calculation, proportional integration, decoupling and coordinate inverse transformation.

[0078] First, the grid current Enter the coordinate transformation to get Axis component and , the coordinate transformation is the synchronous rotation coordinate transformation (same as formula 1), and the synchronous phase angle is ;

[0079] Then, the deviation calculation link converts the current 、 and target value 、 Compare and calculate the deviation value;

[0080] Then, the deviation value is sent to the proportional integral, and its proportional and integral coefficients are and ;

[0081] Then, the output value of proportional integral is added with decoupling component in the decoupling link, where the d-axis decoupling component is U d1 and-KI q1 , the q-axis decoupling component is U q1 and KI d1 The output value of the proportional integral link is summed with the d-axis and q-axis decoupling components respectively. K is the coupling coefficient, which is generally taken as .

[0082] Finally, the output value of the decoupling link is subjected to inverse coordinate transformation, and the output result is U abc1 The coordinate inverse transformation is synchronous rotation coordinate inverse transformation, the synchronous phase angle is θ1, and the coordinate inverse transformation formula is as follows:

[0083] ;

[0084] Step 4: The current signal processing unit outputs the result U abc1 PWM modulation is performed through the PWM signal generation unit, and the output signal S abc Connect to the three-phase bridge voltage source converter VSC.

[0085] Using the above control strategy, the grid-connected converter outputs a steady-state current to the grid-connected point. of Axis component 、 and target value 、 Will remain consistent.

[0086] As can be seen from the above, the main loop parameters and control loop parameters of the grid-connected converter can be obtained through the above typical grid-connected converter and its working process.

[0087] After obtaining the main circuit and control circuit parameters of the grid-connected converter, a complete model of the grid-connected converter can be built in electromagnetic simulation software (such as MATLAB or PSCAD).

[0088] Furthermore, according to one embodiment of the present invention, the positive and negative sequence harmonic disturbance small signal injection unit is composed of a set of three-phase symmetrical voltage sources U pa 、U pb 、U pc It is composed of a three-phase voltage source U connected in series with the grid point and the external grid. sa、 U sb、 U sc Between, among which U pa with U sa Series, U pb with U sb Series, U pc with U sc Series connection;

[0089] U pa 、U pb 、U pc The effective value of the voltage is also U prms , U prms =kU srms , k≤0.1, U srms is the effective value of the equivalent three-phase voltage source of the external power grid.

[0090] Furthermore, according to an embodiment of the present invention, a positive and negative sequence harmonic disturbance small signal injection unit is used to superimpose a harmonic disturbance of preset frequency and phase sequence on a power frequency three-phase voltage source port of a power grid to obtain a harmonic disturbance voltage signal, including:

[0091] The frequency f of the positive and negative sequence harmonic disturbance small signal injected by the positive and negative sequence harmonic disturbance small signal injection unit is p Take a specific frequency within the frequency range of 1~10kHz;

[0092] The phase angle of the input positive sequence disturbance signal is set to 0°, -120°, and 120°, and the phase angle of the input negative sequence disturbance signal is set to 0°, 120°, and -120°;

[0093] When a three-phase positive sequence small signal disturbance is injected, the three-phase disturbance voltage components are:

[0094] ;

[0095] When a three-phase negative sequence disturbance small signal is injected, the three-phase disturbance voltage components are:

[0096] ;

[0097] Where: t is time, unit is s.

[0098] Furthermore, according to an embodiment of the present invention, the auxiliary phase-locked loop unit has the same structure and parameters as the phase-locked loop in the typical grid-connected converter, with only the input signal being different. The input voltage of the phase-locked loop is the grid-connected point voltage U1, and the input voltage of the auxiliary phase-locked loop unit is U2, which corresponds to the three-phase voltage U sa 、U sb 、U sc , the effective value is U srms , the phase angles are 0°, -120°, and 120°, and the voltage U2 signal is input into the auxiliary phase-locked loop unit to obtain the phase angle θ2.

[0099] Furthermore, according to one embodiment of the present invention, the auxiliary phase-locked loop is composed of three steps: coordinate forward transformation, proportional integration, and integration. The voltage U2 signal is input into the auxiliary phase-locked loop unit to obtain the phase angle θ2, including:

[0100] The voltage signal U2 is input into the auxiliary phase-locked loop unit and then processed by the coordinate forward transformation to output the dq axis component U d2 and U q2 ;

[0101] After proportional integration (the proportional and integral parameters are and , which is strictly consistent with the phase-locked loop parameters) is processed and the output value is integrated. The output value after integration is the voltage signal Synchronous phase angle ;

[0102] Among them, the coordinate transformation is a synchronous rotation coordinate transformation, and the synchronous phase angle is θ2. The coordinate transformation 2 formula is as follows:

[0103] .

[0104] Furthermore, according to an embodiment of the present invention, the current signal auxiliary processing unit includes five steps, namely, coordinate forward transformation, deviation calculation, decoupling, proportional integration and coordinate inverse transformation.

[0105] The current signal auxiliary processing unit processes the grid-connected point current signal based on the phase angle and outputs a three-phase voltage signal, including:

[0106] Grid connection point current After entering the current signal auxiliary processing unit, the coordinates are transformed to obtain Axis component and , the coordinate transformation is the synchronous rotation coordinate transformation (same as formula 5), and the synchronous phase angle is ;

[0107] The current is calculated by the deviation 、 and target value 、 Compare and calculate the deviation value;

[0108] The deviation value is proportionally integrated (the proportional and integral coefficients are and , and the parameters of the proportional integral link in the above phase-locked loop are strictly consistent) processing, the output value after proportional integral processing is decoupled, and the decoupling component is added, where The axis decoupling component is and , The axis decoupling component is and , the output values after proportional integral processing are respectively axis, Summation of axis decoupling components, is the coupling coefficient, which is ;

[0109] The output value after decoupling is subjected to inverse coordinate transformation, and the output result is U abc2; Among them, the coordinate inverse transformation is the synchronous rotation coordinate inverse transformation, and the synchronous phase angle is θ2. The coordinate inverse transformation 2 formula is as follows:

[0110] .

[0111] Further, according to an embodiment of the present invention, the RLC circuit equivalent unit includes: an RLC equivalent circuit and an impedance phase angle measurement module;

[0112] The three-phase voltage signal, the output value of the original model current signal processing unit, and the harmonic disturbance voltage signal are input into the RLC circuit equivalent unit after deviation calculation. The impedance parameters of the grid-connected converter can be obtained by measuring the effective value and phase angle of the loop current, including:

[0113] The three-phase voltage signal U output by the original model current signal processing unit abc1 Phase A voltage U a1 The three-phase voltage signal U output by the current signal auxiliary processing unit abc2 Phase A voltage U a2 Perform deviation calculation to obtain the difference signal U a1- U a2 ;

[0114] The three-phase positive sequence small signal disturbance A phase voltage signal is U pa (f p ), the three-phase positive sequence disturbance small signal disturbs the A phase voltage signal U pa (f p ) and the difference signal U a1- U a2 Deviation calculation is performed and the output signal is U pa (f p )-(U a1- U a2 );

[0115] The output signal U pa (f p )-(U a1- U a2 ) Input is from a single-phase controlled voltage source U DZ 、Inductor L DZ , resistor R DZ , capacitor C DZ The RLC equivalent circuit is composed to obtain the current signal I;

[0116] The single-phase controlled voltage source U DZ The control signal is the output signal U pa (f p )-(U a1- U a2 ),Right now:

[0117] ;

[0118] Resistor R DZ The value is similar to the proportional parameter K in the proportional integral link of the current signal processing unit in the typical grid-connected converter mentioned above. p Stay consistent, that is:

[0119] ;

[0120] For positive sequence harmonic small signal disturbance, inductor L DZ The value of is taken as follows:

[0121] ;

[0122] Where, L is the value of the reactor connected to the main circuit, f1 is the reference frequency of the equivalent power supply of the external power grid, and f p is the disturbance frequency;

[0123] For negative sequence harmonic small signal disturbance, inductor L DZ The value of is taken as follows:

[0124] ;

[0125] Where, L is the value of the reactor connected to the main circuit, f1 is the reference frequency of the equivalent power supply of the external power grid, and f p is the disturbance frequency;

[0126] For positive sequence harmonic small signal disturbance, the value of capacitor C is determined as follows:

[0127] ;

[0128] Where K i is the integral parameter of the proportional integral link in the current signal processing unit of the typical grid-connected converter, f1 is the external grid equivalent power supply reference frequency, f p is the disturbance frequency;

[0129] For negative sequence harmonic small signal disturbance, the value of capacitor C is taken as follows:

[0130] ;

[0131] Where K i is the integral parameter of the proportional integral link in the current signal processing unit of a typical grid-connected converter, f1 is the equivalent power reference frequency of the external grid, and f p is the disturbance frequency.

[0132] The three-phase positive sequence disturbance signal disturbs the A phase voltage signal U pa The current signal I of the RLC equivalent circuit is input to the impedance phase angle measurement module, and the output impedance and phase angle .

[0133] Furthermore, according to an embodiment of the present invention, when the frequency of the three-phase positive sequence small signal disturbance A phase, B phase, and C phase voltage signal is changed, the impedance at other frequency points can be obtained. and phase angle Value; by changing the phase sequence of the three-phase positive sequence small signal disturbance A phase, B phase, C phase voltage signal, you can get the corresponding sequence impedance value. If the disturbance signal is a positive sequence component, the impedance value is the positive sequence impedance. If the disturbance signal is set to a negative sequence component, the impedance value is the negative sequence impedance.

[0134] According to the above-mentioned scheme of the present invention, the present invention provides a method for obtaining the wide-band positive and negative sequence impedance parameters of a grid-connected converter based on dual synchronous coordinate transformation and RLC equivalent circuit. The present invention can obtain the positive and negative sequence impedance parameters of a universal grid-connected converter at any frequency point, has a clear and distinct physical meaning, and the positive and negative sequence impedance parameters are independent and free of cross-coupling influence, which simplifies subsequent stability analysis.

[0135] The present invention does not require the establishment of complex mathematical equations for the grid-connected converter. Instead, it only requires the construction of a simulation model and the addition of four supplementary units to obtain the impedance characteristics of the grid-connected converter. Therefore, the present invention can be applied to modeling the impedance of a grid-connected converter with any structure and parameters.

[0136] The present invention has good versatility. When the parameters of the main circuit and the control circuit of the grid-connected converter change, the parameter setting principles of the four auxiliary units remain unchanged and new impedance parameters can be directly output.

[0137] Furthermore, to achieve the above-mentioned object, the present invention also provides a system for acquiring broadband positive and negative sequence impedance parameters of a grid-connected converter, comprising:

[0138] A grid-connected converter simulation model construction module obtains the main circuit parameters and control circuit parameters of the grid-connected converter, and builds a grid-connected converter simulation model in the electromagnetic simulation software based on the main circuit parameters and control circuit parameters;

[0139] The simulation unit setting module adds four simulation units to the grid-connected converter simulation model, namely the positive and negative sequence harmonic disturbance small signal injection unit, the auxiliary phase-locked loop unit, the current signal auxiliary processing unit and the RLC circuit equivalent unit;

[0140] The harmonic disturbance voltage signal acquisition module uses the positive and negative sequence harmonic disturbance small signal injection unit to superimpose the harmonic disturbance of preset frequency and phase sequence on the power frequency three-phase voltage source port of the power grid to obtain the harmonic disturbance voltage signal;

[0141] Phase angle acquisition module, which obtains the phase angle of the power frequency three-phase voltage source of the power grid through the auxiliary phase-locked loop unit;

[0142] A three-phase voltage signal acquisition module, a current signal auxiliary processing unit processes the grid-connected point current signal based on the phase angle and outputs a three-phase voltage signal;

[0143] The impedance parameter acquisition module calculates the deviation of the three-phase voltage signal, the output value of the original current signal processing unit in the grid-connected converter simulation model, and the harmonic disturbance voltage signal, and then inputs them into the RLC circuit equivalent unit. The RLC circuit equivalent unit obtains the impedance parameters of the grid-connected converter by measuring the effective value and phase angle of the loop current.

[0144] The above-mentioned system for obtaining wide-band positive and negative sequence impedance parameters of a grid-connected converter according to the present invention can implement the above-mentioned method for obtaining wide-band positive and negative sequence impedance parameters of a grid-connected converter. The specific process steps are as described above and will not be repeated here.

[0145] Furthermore, to achieve the above-mentioned purpose, the present invention also provides an electronic device, comprising a processor, a memory, and a computer program stored in the memory and executable on the processor. When the computer program is executed by the processor, the method for obtaining the wide-band positive and negative sequence impedance parameters of the grid-connected converter as described above is implemented.

[0146] Furthermore, to achieve the above-mentioned purpose, the present invention also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the method for obtaining the wide-band positive and negative sequence impedance parameters of the grid-connected converter as described above is implemented.

[0147] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiment described herein is only an optimal embodiment of the present invention and is only used to explain the present invention and does not limit the scope of protection of the present invention. All other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0148] Example 1

[0149] Figure 1 This is a principle block diagram of the method for obtaining wide-band positive and negative sequence impedance parameters of a grid-connected converter according to Example 1.

[0150] The specific parameters of the grid-connected converter in this embodiment are:

[0151] Rated AC voltage: 800V;

[0152] Rated frequency: 50Hz;

[0153] d-axis (active) current target value: 500A;

[0154] q-axis (reactive) current target value: 0A;

[0155] Connect reactor L: 20mH;

[0156] The proportional coefficient of the PI inside the phase-locked loop PLL :100;

[0157] The integral coefficient of the PI inside the phase-locked loop PLL :1000;

[0158] Proportional coefficient of the PI link of the current signal processing unit :100;

[0159] Integral coefficient of the PI link of the current signal processing unit :1000;

[0160] Coupling coefficient K: 6.28;

[0161] Figure 1 in represents the impedance calculation, where , which outputs the corresponding amplitude and phase according to the input voltage and current.

[0162] According to the above parameters, a grid-connected converter simulation model is built on the MATLAB / simulink software platform, which can run normally. The simulation interface of the grid-connected converter simulation model is as follows: Figure 2 As shown, the three-phase voltage and three-phase current simulation waveforms are as follows Figure 3 As shown, the d-axis current and q-axis current simulation waveforms are as follows Figure 4 As shown. Figure 3 and Figure 4 It can be seen that the d-axis current is stable at 500A, which is consistent with the target value; the q-axis current is stable at 0A, which is consistent with the target value.

[0163] Adopt the method of the present invention, such as Figure 1 As shown in the figure, four additional unit modules are added based on the original current signal processing unit, phase-locked loop and PWM signal generation unit in the grid-connected converter simulation model, namely:

[0164] ①Positive and negative sequence harmonic disturbance small signal injection unit;

[0165] ②Auxiliary phase-locked loop unit;

[0166] ③Current signal auxiliary processing unit;

[0167] ④RLC circuit equivalent unit.

[0168] In this embodiment, the injection voltage amplitude of the positive and negative sequence harmonic disturbance small signal injection unit is set to (5% of the grid), small signal frequency for , the phases are 0°, -120°, and 120° (positive sequence disturbance), such as Figure 5 shown. Figure 5 middle For grid connection Three-phase voltage signal, For grid connection Three-phase current signal, is the inductance value of the connected reactor, Three-phase voltage source converter of Three-phase sinusoidal wave modulation signal, Three-phase voltage source converter of Three-phase sinusoidal wave modulation signal Phase signal, for Phase disturbance small signal, is the equivalent three-phase voltage source of the power grid Three-phase voltage signal.

[0169] The input signal of the auxiliary phase-locked loop unit is the equivalent voltage of the three-phase grid , the internal proportional parameter is 100, the integral parameter is 1000, which is exactly the same as the phase-locked loop parameters, and the output synchronization phase angle is ,like Figure 6 shown. Figure 6 middle is the equivalent three-phase voltage source of the power grid Three-phase voltage signal, phase-locked loop module Represents the input of this module for coordinate transformation Three-phase AC electrical quantity signal, Represents the rotation coordinate phase synchronization signal input to this phase-locked loop module, Represents the output from this phase-locked loop axis, Axis and Axis components, where The axis component is , The axis component is , The axis component output is blocked, indicating that the signal does not need to be output. represents the proportional integral link, Represents the integral link, is the equivalent three-phase voltage source of the power grid The three-phase voltage signal corresponds to the synchronous phase signal.

[0170] Current signal auxiliary processing unit such as Figure 7 As shown, the synchronous phase angles of coordinate transformation and inverse transformation are (Auxiliary phase-locked loop unit output signal), the proportional parameter of the proportional integral link is 100, and the integral parameter is 1000, which is exactly the same as the proportional integral parameters inside the current signal processing unit. Figure 7 middle For grid connection Three-phase current signal, phase-locked loop module Represents the input of this module for coordinate transformation Three-phase AC electrical quantity signal, Represents the rotation coordinate phase synchronization signal input to this phase-locked loop module, Represents the output from this phase-locked loop axis, Axis and Axis component. express Shaft current target value, express Shaft current target value, is the equivalent three-phase voltage source of the power grid The three-phase voltage signal is generated by rotating coordinate transformation Axis quantity, is the equivalent three-phase voltage source of the power grid The three-phase voltage signal is generated by rotating coordinate transformation Axis quantity, is the coefficient for Shaft decoupling, represents the proportional integral link, is the equivalent three-phase voltage source of the power grid The three-phase voltage signal corresponds to the synchronous phase signal, Output of the coordinate inverse transformation link Phase signal.

[0171] Established by a single-phase controlled voltage source U DZ 、Inductor L DZ , resistor R DZ , capacitor C DZ The RLC circuit consists of a single-phase controlled voltage source U DZ The control signal is U pa (f p )-(U a1- U a2 ), inductor L DZ , resistor R DZ , capacitor C DZ The values are as follows:

[0172] ;

[0173] The equivalent circuit is shown in the attached Figure 8 The impedance simulation results are shown in Figure 9 shown. Figure 8 middle Three-phase voltage source converter of Three-phase sinusoidal wave modulation signal Phase signal, Output of the coordinate inverse transformation link Phase signal, for Phase disturbance small signal, Inner ring of the converter The proportionality coefficient, Inner ring of the converter The integral coefficient of is the perturbation small signal frequency, is the power frequency.

[0174] Furthermore, in order to verify whether the impedance and phase angle values obtained in Example 1 are correct, the theoretical formula of the positive sequence impedance of the grid-connected converter in Example 1 was compiled in MATLAB, as shown in FIG. Figure 10 shown.

[0175] The comparison between the impedance / phase angle values obtained by simulation in Example 1 and the theoretical calculated values is as follows: Figure 11 As shown, the impedance value obtained by simulation in Example 1 is 3.4Ω, and the theoretical calculated value is 3.3998Ω. The phase angle obtained by simulation in Example 1 is -2.882°, and the theoretical calculated value is -2.8822°, which proves that the impedance and phase angle values obtained in Example 1 at this frequency point are correct.

[0176] By adjusting the frequency point parameters, the impedance values of other frequency points can be obtained by the same method; by adjusting the phase sequence of the harmonic small signal disturbance, the negative sequence impedance value can be obtained. In order to improve efficiency, it can be set to a cyclic mode. Each time the frequency point is adjusted, the corresponding simulation model of Example 1 is automatically executed. The results are recorded and plotted to obtain the positive and negative sequence impedance curves of the grid-connected converter, such as Figure 12 shown.

[0177] Those skilled in the art will appreciate that the modules and algorithm steps described in conjunction with the embodiments disclosed herein can be implemented using electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present invention.

[0178] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described devices and equipment can refer to the corresponding processes in the aforementioned method implementation methods and will not be repeated here.

[0179] In the embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the modules is merely a logical function division. In actual implementation, there may be other division methods, such as multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or modules, which can be electrical, mechanical or other forms.

[0180] The modules described as separate components may or may not be physically separate, and the components shown as modules may or may not be physical modules, that is, they may be located in one place or distributed across multiple network modules. Some or all of the modules may be selected according to actual needs to achieve the objectives of the embodiments of the present invention.

[0181] In addition, each functional module in the embodiment of the present invention may be integrated into one processing module, or each module may exist physically separately, or two or more modules may be integrated into one module.

[0182] If the functions are implemented as software modules and sold or used as standalone products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the portion that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the energy-saving signal transmission / reception method according to various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, a mobile hard drive, ROM, RAM, a magnetic disk, or an optical disk.

[0183] The above description is merely a preferred embodiment of the present application and an illustration of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to the technical solutions formed by the specific combination of the above-mentioned technical features, but also encompasses other technical solutions formed by any combination of the above-mentioned technical features or their equivalents without departing from the inventive concept. For example, a technical solution formed by replacing the above-mentioned features with (but not limited to) technical features with similar functions disclosed in this application.

[0184] It should be understood that the size of the serial numbers of each step in the content of the invention and the implementation methods of the present invention does not absolutely mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the implementation methods of the present invention.

Claims

1. A method for obtaining broadband positive and negative sequence impedance parameters of a grid-connected converter, characterized in that: include: Obtain the main circuit parameters and control circuit parameters of the grid-connected converter, and build a grid-connected converter simulation model in the electromagnetic simulation software based on the main circuit parameters and control circuit parameters; Four simulation units are added to the grid-connected converter simulation model, namely, the positive and negative sequence harmonic disturbance small signal injection unit, the auxiliary phase-locked loop unit, the current signal auxiliary processing unit, and the RLC circuit equivalent unit; The positive and negative sequence harmonic disturbance small signal injection unit is used to superimpose the harmonic disturbance of preset frequency and phase sequence on the power frequency three-phase voltage source port of the power grid to obtain the harmonic disturbance voltage signal; The phase angle of the three-phase voltage source of the power grid is obtained through the auxiliary phase-locked loop unit; The current signal auxiliary processing unit processes the grid-connected point current signal based on the phase angle and outputs a three-phase voltage signal; The three-phase voltage signal, the output value of the original current signal processing unit in the grid-connected converter simulation model, and the harmonic disturbance voltage signal are input into the RLC circuit equivalent unit after deviation calculation. The RLC circuit equivalent unit obtains the impedance parameters of the grid-connected converter by measuring the effective value and phase angle of the loop current. The positive and negative sequence harmonic disturbance small signal injection unit is composed of a set of three-phase symmetrical voltage sources U pa 、U pb 、U pc It is composed of a three-phase voltage source U connected in series with the grid point and the external grid. sa、 U sb、 U sc Between, among which U pa with U sa Series, U pb with U sb Series, U pc with U sc Series connection; U pa 、U pb 、U pc The effective value of the voltage is also U prms , U prms =kU srms , k≤0.1, U srms is the effective value of the equivalent three-phase voltage source of the external power grid.

2. The method for obtaining broadband positive and negative sequence impedance parameters of a grid-connected converter according to claim 1, characterized in that: The positive and negative sequence harmonic disturbance small signal injection unit is used to superimpose the harmonic disturbance of preset frequency and phase sequence on the power frequency three-phase voltage source port of the power grid to obtain the harmonic disturbance voltage signal, including: The frequency f of the positive and negative sequence harmonic disturbance small signal injected by the positive and negative sequence harmonic disturbance small signal injection unit is p Select a preset frequency within the frequency range of 1~10kHz; The phase angle of the input positive sequence disturbance signal is set to 0°, -120°, and 120°, and the phase angle of the input negative sequence disturbance signal is set to 0°, 120°, and -120°; When a three-phase positive sequence small signal disturbance is injected, the three-phase disturbance voltage components are: ; When a three-phase negative sequence disturbance small signal is injected, the three-phase disturbance voltage components are: ; Where: t is time.

3. The method for obtaining broadband positive and negative sequence impedance parameters of a grid-connected converter according to claim 2, characterized in that: The input voltage of the auxiliary phase-locked loop unit is U2, which corresponds to the three-phase voltage U sa 、U sb 、U sc , the effective value is U srms , the phase angles are 0°, -120°, and 120°, and the voltage signal U2 is input into the auxiliary phase-locked loop unit to obtain the phase angle θ2.

4. The method for obtaining broadband positive and negative sequence impedance parameters of a grid-connected converter according to claim 3, characterized in that: The voltage signal U2 is input into the auxiliary phase-locked loop unit to obtain the phase angle θ2, including: The voltage signal U2 is input into the auxiliary phase-locked loop unit and then processed by the coordinate forward transformation to output the dq axis component U d2 and U q2 ; U q2 The output value after proportional integral processing is integrated, and the output value after integration processing is the voltage signal U2 synchronous phase angle θ2; Among them, the coordinate forward transformation is a synchronous rotating coordinate transformation, and the synchronous phase angle is θ2.

5. The method for obtaining broadband positive and negative sequence impedance parameters of a grid-connected converter according to claim 4, characterized in that: The current signal auxiliary processing unit processes the grid-connected point current signal based on the phase angle and outputs a three-phase voltage signal, including: Grid connection point current I g After entering the current signal auxiliary processing unit, the coordinate forward transformation is performed to obtain the dq axis component i d2 and i q2 , the coordinate transformation is a synchronous rotation coordinate transformation, and the synchronous phase angle is θ2; By calculating the deviation, the current i d2 、i q2 and target value i d-set 、i q-set Compare and calculate the deviation value; The deviation value is processed by proportional integration, and the output value after proportional integration is decoupled and a decoupling component is added, where the d-axis decoupling component is U d2 and-KI q2 , the q-axis decoupling component is U q2 and KI d2 The output value after proportional integral processing is summed with the d-axis and q-axis decoupling components respectively. K is the coupling coefficient, which is ; The output value after decoupling is subjected to inverse coordinate transformation, and the output result is U abc2 ; Among them, the coordinate inverse transformation is the synchronous rotation coordinate inverse transformation, and the synchronous phase angle is θ2.

6. The method for obtaining broadband positive and negative sequence impedance parameters of a grid-connected converter according to claim 5, characterized in that: The RLC circuit equivalent unit includes: an RLC equivalent circuit and an impedance phase angle measurement module; The three-phase voltage signal, the output value of the original model current signal processing unit, and the harmonic disturbance voltage signal are input into the RLC circuit equivalent unit after deviation calculation. The impedance parameters of the grid-connected converter can be obtained by measuring the effective value and phase angle of the loop current, including: The three-phase voltage signal U output by the original current signal processing unit in the grid-connected converter simulation model is converted to abc1 Phase A voltage U a1 The three-phase voltage signal U output by the current signal auxiliary processing unit abc2 Phase A voltage U a2 Perform deviation calculation to obtain the difference signal U a1- U a2 ; The three-phase positive sequence disturbance small signal disturbance A phase voltage signal is U pa (f p ), the three-phase positive sequence disturbance small signal disturbs the A phase voltage signal U pa (f p ) and the difference signal U a1- U a2 Deviation calculation is performed and the output signal is U pa (f p )-(U a1- U a2 ); The output signal U pa (f p )-(U a1- U a2 ) Input is from a single-phase controlled voltage source U DZ 、Inductor L DZ , resistor R DZ , capacitor C DZ The RLC equivalent circuit is composed to obtain the current signal I; The three-phase positive sequence disturbance signal disturbs the A phase voltage signal U pa The current signal I of the RLC equivalent circuit is input to the impedance phase angle measurement module, and the output impedance and phase angle .

7. A broadband positive and negative sequence impedance parameter acquisition system for a grid-connected converter, characterized in that: include: A grid-connected converter simulation model construction module obtains the main circuit parameters and control circuit parameters of the grid-connected converter, and builds a grid-connected converter simulation model in the electromagnetic simulation software based on the main circuit parameters and control circuit parameters; The simulation unit setting module adds four simulation units to the grid-connected converter simulation model, namely the positive and negative sequence harmonic disturbance small signal injection unit, the auxiliary phase-locked loop unit, the current signal auxiliary processing unit and the RLC circuit equivalent unit; The harmonic disturbance voltage signal acquisition module uses the positive and negative sequence harmonic disturbance small signal injection unit to superimpose the harmonic disturbance of preset frequency and phase sequence on the power frequency three-phase voltage source port of the power grid to obtain the harmonic disturbance voltage signal; Phase angle acquisition module, which obtains the phase angle of the power frequency three-phase voltage source of the power grid through the auxiliary phase-locked loop unit; A three-phase voltage signal acquisition module, a current signal auxiliary processing unit processes the grid-connected point current signal based on the phase angle and outputs a three-phase voltage signal; The impedance parameter acquisition module calculates the deviation of the three-phase voltage signal, the output value of the original current signal processing unit in the grid-connected converter simulation model, and the harmonic disturbance voltage signal, and then inputs them into the RLC circuit equivalent unit. The RLC circuit equivalent unit obtains the impedance parameters of the grid-connected converter by measuring the effective value and phase angle of the loop current; The positive and negative sequence harmonic disturbance small signal injection unit is composed of a set of three-phase symmetrical voltage sources U pa 、U pb 、U pc It is composed of a three-phase voltage source U connected in series with the grid point and the external grid. sa、 U sb、 U sc Between, among which U pa with U sa Series, U pb with U sb Series, U pc with U sc Series connection; U pa 、U pb 、U pc The effective value of the voltage is also U prms , U prms =kU srms , k≤0.1, U srms is the effective value of the equivalent three-phase voltage source of the external power grid.

8. An electronic device, characterized in that The invention comprises a processor, a memory and a computer program stored in the memory and executable on the processor, wherein when the computer program is executed by the processor, the method for obtaining the wide-band positive and negative sequence impedance parameters of the grid-connected converter according to any one of claims 1 to 6 is implemented.

9. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method for obtaining wide-band positive and negative sequence impedance parameters of a grid-connected converter according to any one of claims 1 to 6 is implemented.

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