Difference analysis method and system for dynamic characteristics of parallel networking type converter

Abstract

The invention relates to a dynamic characteristic difference analysis method and system for a parallel grid-forming converter, and belongs to the technical field of converter evaluation. The method comprises the following steps: establishing a mathematical model of a double-mechanism grid-type converter grid-connected system under a dq coordinate system taking a power grid as a reference system, solving the mathematical model to obtain a voltage steady-state value and a power angle steady-state value of the converter during steady-state operation of the system; the method comprises the following steps: for an actual model of a double-mechanism grid-type converter grid-connected system, enabling a converter and a power grid to be equivalent to a voltage source model with series impedance to obtain an equivalent circuit model, and transforming and analyzing the equivalent circuit model to obtain a relational expression of output active power of each converter about a power angle, impedance and voltage; and solving the instantaneous power synchronization coefficient difference, and evaluating the influence effect of different parameters on the dynamic characteristic difference of the converter by adopting the instantaneous power synchronization coefficient difference. According to the method, the dynamic characteristic difference detection efficiency of the system is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of converter evaluation, and in particular to a method and system for analyzing dynamic characteristics differences of parallel-network converters. Background Art

[0002] As the penetration rate of renewable energy in the power system continues to climb and the load accelerates the electrification of power, the problem of hollowing out of synchronous power sources in local power grids has become prominent, short-circuit capacity has dropped significantly, and dynamic reactive power reserve capacity is insufficient, weakening the voltage stability of the power grid. Furthermore, the power regulation of renewable energy is decoupled from the power grid and cannot participate in the inertial response of the power grid, further weakening the frequency stability of the power grid. Grid-connected energy storage technology can shape the control characteristics of grid-connected converters to build a voltage source that supports the stable operation of large power grids, achieve rapid frequency and voltage regulation, increase inertia and short-circuit capacity, and suppress broadband oscillations. It is an important means to support new power systems dominated by renewable energy. It has been discovered that dynamic characteristics differences may occur between converters due to different steady-state operating points. These mainly include: different AGC instructions for each unit within the grid-connected energy storage power station and different equivalent impedances between each unit and the common bus.

[0003] In order to detect and evaluate the differences in the dynamic characteristics of the converter, it is necessary to model the converter. The model can analyze the dynamic characteristics of the converter when responding to AGC instructions and performing active support, which can be obtained by transfer functions or state-space equations. The transfer function is simple and easy to observe the dynamic characteristics of the indicators, but this method is only suitable for analyzing the dynamic characteristics of a single input and a single output. In the case of multiple inputs and multiple outputs, multiple transfer functions need to be solved, and the solution process is relatively complex and repetitive. The state-space model uses the converter expression after small signal linearization to obtain the state-space equation of the converter as a whole. The dynamic characteristics of the converter are obtained by changing the input and disturbance terms of the state-space equation. At present, most converter dynamic characteristics modeling methods use state-space models. State-space models include complete and simplified models. The complete model is obtained by integrating all linearized expressions of the converter's small signals. While it can generally accurately describe the converter's dynamic characteristics, it is computationally complex, especially when the network model is large. Simplified converter models can be obtained by reducing the order of the complete model. Methods for simplifying the complete model typically include parameter sensitivity analysis, dominant time constant analysis, and state variable equivalent coefficient analysis. The simplified converter dynamic characteristic model is relatively close to the actual model and can still be used as a method for predicting converter state characteristics. However, the state-space model is only suitable for analyzing converter dynamic characteristic differences when the station impedance between the grid-type converter and the point of common coupling (PCC) is relatively small, that is, when the converter voltage-power angle is relatively small. When the dynamic characteristics differ significantly due to different steady-state operating points, the power angle value of the converter is large. At this time, it is impossible to simulate the dynamic response characteristics by establishing a small signal state space model of the converter grid-connected system. Therefore, at present, the only way is to obtain the dynamic characteristic curves between converter units through experiments or simulation tests, and then quantify the dynamic characteristic differences through dynamic characteristic indicators such as dynamic response time, peak time, and overshoot. The process is very complicated, and the displayed waveform data needs to be stored and analyzed in real time in large quantities, which is very time-consuming and has many repetitive processes. As a result, there is low efficiency in analyzing the dynamic characteristic differences caused by different steady-state operating points, resulting in a waste of resources. Summary of the Invention

[0004] Aiming at the problem that the detection and evaluation of the current dynamic characteristics differences of converters are complex and inefficient, the present invention provides a method and system for analyzing the dynamic characteristics differences of parallel networked converters, thereby improving the efficiency of detecting the dynamic characteristics differences of the system.

[0005] The technical solution adopted by the present invention to solve its technical problem is:

[0006] In a first aspect, the present invention provides a method for analyzing the dynamic characteristics differences of a parallel grid-connected converter, comprising:

[0007] Establishing a mathematical model of a dual-mechanism grid-type converter grid-connected system in a dq coordinate system with the grid as a reference system, and solving the mathematical model to obtain the steady-state voltage value and the steady-state power angle value of the converter when the system is in steady-state operation;

[0008] For the actual model of a dual-mechanism grid-connected converter system, the converter and the grid are both equivalent to voltage source models with series impedances, resulting in an equivalent circuit model. By transforming and analyzing the equivalent circuit model, the relationship between the output active power of each converter and the power angle, impedance, and voltage is obtained.

[0009] Based on the steady-state voltage and power angle values ​​of the converter during steady-state operation of the system and the relationship between the output active power of each converter and the power angle, impedance and voltage, the instantaneous power synchronization coefficient difference is solved. The instantaneous power synchronization coefficient difference is used to evaluate the impact of different parameters on the dynamic characteristics of the converter.

[0010] As a further improvement of the present invention, the mathematical model of the dual-mechanism grid-type converter grid-connected system in the dq coordinate system with the grid as the reference system is established, including:

[0011] For the i-th converter, in the abc coordinate system, the mathematical model is expressed as:

[0012]

[0013] Where, e abci ,u oabci are the internal potential and output voltage of the i-th converter in the abc coordinate system respectively; u pccabc is the voltage of the common coupling point PCC in the abc coordinate system; i Labci ,i oabci are the inductor current and output current of the i-th converter in the abc coordinate system respectively; L fi , R fi , C fi , L linei , R linei are the equivalent inductance of the filter inductor of the i-th converter plus the virtual inductor, the resistance in series with the filter inductor, the filter capacitor, the line inductance, and the line resistance;

[0014] Convert the abc coordinate system to the dq coordinate system. The dq transformation equation is:

[0015]

[0016] Where, P dq0 represents the voltage and current values ​​in the local rotating dq reference frame; P abcrepresents the instantaneous values ​​of voltage and current in the three-phase stationary abc reference coordinate system; θ represents the angle between the d-axis in the rotating reference system and the a-axis in the stationary reference system; the mathematical model in the dq coordinate system is:

[0017]

[0018] Where: e di , e qi are the internal potential of the i-th converter in the dq coordinate system; u odi ,u oqi are the output voltages of the i-th converter in the dq coordinate system; i Ldi ,i Lqi are the inductor currents of the i-th converter in the dq coordinate system; i odi ,i oqi are the output currents of the i-th converter in the dq coordinate system; u pccd ,u pccq are the voltages of the common coupling point PCC in the dq coordinate system; ω is the angular frequency of the system;

[0019] As a further improvement of the present invention, solving the mathematical model to obtain the steady-state voltage value and the steady-state power angle value of the converter when the system is in steady-state operation includes:

[0020] When solving for the steady-state value, the mathematical model becomes:

[0021]

[0022] Where: E di , E qi are the steady-state values ​​of the internal potential of the i-th converter in the dq coordinate system; U odi , U oqi are the steady-state output voltage values ​​of the i-th converter in the dq coordinate system; I Ldi , I Lqi are the steady-state values ​​of the inductor current of the i-th converter in the dq coordinate system; I odi , I oqi are the steady-state output current values ​​of the i-th converter in the dq coordinate system; U pccd , U pccq are the steady-state voltage values ​​of the PCC point in the dq coordinate system, ω0 is the rated angular frequency of the system;

[0023] The active power and reactive power output by the i-th converter are expressed in the dq coordinate system as follows:

[0024]

[0025] According to the reactive power-voltage droop relationship, the active power output in steady state is:

[0026]

[0027] When the active power is output in steady state, P outi =P refi

[0028] According to the current flowing into the grid is equal to the sum of the output currents of all converters, in steady state:

[0029]

[0030] Equivalently treating the power grid as an ideal voltage source and grid impedance, in the abc coordinate system, the following relationship exists on the grid side:

[0031]

[0032] Where u gabc is the grid voltage in the abc coordinate system, i abcg is the grid current in the abc coordinate system; L g , R g are the grid inductance and grid resistance respectively;

[0033] In the dq coordinate system with the power grid as the reference system, then:

[0034]

[0035] Where u gd ,u gq is the grid voltage in the dq coordinate system, i gd ,i gq is the grid current in the dq coordinate system;

[0036] In steady state, we get:

[0037]

[0038] Where U g is the steady-state value of the d-axis grid voltage in the dq coordinate system, I gd , I gq is the steady-state value of the grid current in the dq coordinate system;

[0039] Then the steady-state values ​​of each voltage and current are obtained;

[0040] According to the relationship:

[0041]

[0042] Obtain the steady-state value of the power angle of the i-th converter.

[0043] As a further improvement of the present invention, the actual model of the dual-mechanism grid-type converter grid-connected system is obtained by equating the converter and the grid to voltage source models with series impedances, including:

[0044] Taking the grid as the reference node and assuming the grid voltage phase to be 0, for the actual model of the dual-mechanism grid-connected converter system, both the converter and the grid are equivalent to voltage source models with series impedances to obtain the equivalent circuit model.

[0045] As a further improvement of the present invention, the expression for the relationship between the output active power of each converter and the power angle, impedance and voltage is obtained by transforming and analyzing the equivalent circuit model, including:

[0046] Combined with the steady-state voltage and power angle values ​​of the converter during system steady-state operation, the active power-power angle relationship of each of the two converters is derived based on the dual-mechanism grid-connected converter system, specifically:

[0047] Considering the contribution of each voltage source to the output current of the first converter, the output current of the first converter is obtained by the superposition principle:

[0048]

[0049] Where U1, U2, U g are the effective values ​​of the first converter, the second converter and the grid voltage respectively; δ1 and δ2 are the voltage phase angles of the first converter and the second converter respectively; Z1, Z2, Z g are the impedance values ​​of the first converter, the second converter, and the grid voltage respectively; θ1, θ2, θ g They are the impedance angles of the first converter, the second converter and the grid voltage, and there exists Z1∠θ1=R1+jX1, Z2∠θ2=R2+jX2, Z g ∠θ g =R g +jX g ;

[0050] The output active power of the first converter is:

[0051]

[0052] The output active power of the second converter is:

[0053]

[0054] Then, the relationship expression of the output power of each converter with respect to the power angle, impedance and voltage is obtained.

[0055] As a further improvement of the present invention, the instantaneous power synchronization coefficient difference is solved based on the relationship expression of the steady-state voltage value and the steady-state power angle value of the converter when the system is in steady-state operation and the output active power of each converter with respect to the power angle, impedance and voltage, including:

[0056] Based on the relationship expression of the output active power of each converter with respect to the power angle, impedance and voltage, the difference between the output powers of two converters derived with respect to their respective power angles is defined as the instantaneous power synchronization coefficient difference. The steady-state voltage value and the steady-state power angle value of the converter during steady-state operation of the system are substituted into the instantaneous power synchronization coefficient difference. The instantaneous power synchronization coefficient difference is used as an indicator to evaluate the size of the difference in the dynamic characteristics of the converter.

[0057] As a further improvement of the present invention, the definition of the difference between the output powers of the two converters derived with respect to their respective power angles as the instantaneous power synchronization coefficient difference includes:

[0058] In the dynamic characteristics difference evaluation phase, the instantaneous power synchronization coefficient of each converter is obtained based on the relationship between the output power of each converter and the power angle, impedance, and voltage:

[0059]

[0060]

[0061] In a dual-mechanism grid-connected converter system, the instantaneous power synchronization coefficient difference is defined as the difference between the output powers of the two converters derived with respect to their respective power angles:

[0062]

[0063] In a second aspect, the present invention provides a system for analyzing the dynamic characteristics differences of parallel grid-connected converters, comprising:

[0064] The system steady-state calculation module is used to establish a mathematical model of the grid-connected dual-mechanism grid-type converter system in a dq coordinate system with the grid as the reference system, and solve the mathematical model to obtain the steady-state voltage value and power angle steady-state value of the converter when the system is in steady-state operation;

[0065] The output power angle relationship calculation module is used to calculate the actual model of the dual-mechanism grid-connected converter system. The converter and the grid are both equivalent to voltage source models with series impedances to obtain an equivalent circuit model. By transforming and analyzing the equivalent circuit model, the relationship between the output active power of each converter and the power angle, impedance, and voltage is obtained.

[0066] The dynamic characteristics difference evaluation module is used to solve the instantaneous power synchronization coefficient difference based on the steady-state voltage value and power angle steady-state value of the converter during system steady-state operation and the relationship expression of the output active power of each converter with the power angle, impedance and voltage. The instantaneous power synchronization coefficient difference is used to evaluate the impact of different parameters on the dynamic characteristics of the converter.

[0067] As an optional embodiment, in the system steady-state calculation module, establishing a mathematical model of a dual-mechanism grid-type converter grid-connected system in a dq coordinate system with the grid as a reference system includes:

[0068] For the i-th converter, in the abc coordinate system, the mathematical model is expressed as:

[0069]

[0070] Where, e abci ,u oabci are the internal potential and output voltage of the i-th converter in the abc coordinate system respectively; u pccabc is the voltage of the common coupling point PCC in the abc coordinate system; i Labci ,i oabci are the inductor current and output current of the i-th converter in the abc coordinate system respectively; L fi , R fi , C fi , L linei , R linei are the equivalent inductance of the filter inductor of the i-th converter plus the virtual inductor, the resistance in series with the filter inductor, the filter capacitor, the line inductance, and the line resistance;

[0071] Convert the abc coordinate system to the dq coordinate system. The dq transformation equation is:

[0072]

[0073] Where, P dq0 represents the voltage and current values ​​in the local rotating dq reference frame; P abc represents the instantaneous values ​​of voltage and current in the three-phase stationary abc reference coordinate system; θ represents the angle between the d-axis in the rotating reference system and the a-axis in the stationary reference system; the mathematical model in the dq coordinate system is:

[0074]

[0075] Where: e di , e qi are the internal potential of the i-th converter in the dq coordinate system; u odi ,u oqi are the output voltages of the i-th converter in the dq coordinate system; i Ldi,i Lqi are the inductor currents of the i-th converter in the dq coordinate system; i odi ,i oqi are the output currents of the i-th converter in the dq coordinate system; u pccd ,u pccq are the voltages at the common coupling point PCC in the dq coordinate system; ω is the angular frequency of the system.

[0076] As an optional embodiment, in the system steady-state calculation module, solving the mathematical model to obtain the steady-state voltage value and the steady-state power angle value of the converter when the system is in steady-state operation includes:

[0077] When solving for the steady-state value, the mathematical model becomes:

[0078]

[0079] Where: E di , E qi are the steady-state values ​​of the internal potential of the i-th converter in the dq coordinate system; U odi , U oqi are the steady-state output voltage values ​​of the i-th converter in the dq coordinate system; I Ldi , I Lqi are the steady-state values ​​of the inductor current of the i-th converter in the dq coordinate system; I odi , I oqi are the steady-state output current values ​​of the i-th converter in the dq coordinate system; U pccd , U pccq are the steady-state voltage values ​​of the PCC point in the dq coordinate system, ω0 is the rated angular frequency of the system;

[0080] The active power and reactive power output by the i-th converter are expressed in the dq coordinate system as follows:

[0081]

[0082] According to the reactive power-voltage droop relationship, the active power output in steady state is:

[0083]

[0084]

[0085] When the active power is output in steady state, P outi =P refi

[0086] According to the current flowing into the grid is equal to the sum of the output currents of all converters, in steady state:

[0087]

[0088] Equivalently treating the power grid as an ideal voltage source and grid impedance, in the abc coordinate system, the following relationship exists on the grid side:

[0089]

[0090] Where u gabc is the grid voltage in the abc coordinate system, i abcg is the grid current in the abc coordinate system; L g , R g are the grid inductance and grid resistance respectively;

[0091] In the dq coordinate system with the power grid as the reference system, then:

[0092]

[0093] Where u gd ,u gq is the grid voltage in the dq coordinate system, i gd ,i gq is the grid current in the dq coordinate system;

[0094] In steady state, we get:

[0095]

[0096] Where U g is the steady-state value of the d-axis grid voltage in the dq coordinate system, I gd , I gq is the steady-state value of the grid current in the dq coordinate system;

[0097] Then the steady-state values ​​of each voltage and current are obtained;

[0098] According to the relationship:

[0099]

[0100] Obtain the steady-state value of the power angle of the i-th converter.

[0101] As an optional embodiment, in the output power angle relationship calculation module, the actual model of the dual-mechanism grid-type converter grid-connected system is obtained by equating the converter and the grid to voltage source models with series impedances, including:

[0102] Taking the grid as the reference node and assuming the grid voltage phase to be 0, for the actual model of the dual-mechanism grid-connected converter system, both the converter and the grid are equivalent to voltage source models with series impedances to obtain the equivalent circuit model.

[0103] As an optional embodiment, in the output power angle relationship calculation module, by transforming and analyzing the equivalent circuit model, an expression for the relationship between the output active power of each converter and the power angle, impedance, and voltage is obtained, including:

[0104] Combined with the steady-state voltage and power angle values ​​of the converter during system steady-state operation, the active power-power angle relationship of each of the two converters is derived based on the dual-mechanism grid-connected converter system, specifically:

[0105] Considering the contribution of each voltage source to the output current of the first converter, the output current of the first converter is obtained by the superposition principle:

[0106]

[0107] Where U1, U2, U g are the effective values ​​of the first converter, the second converter and the grid voltage respectively; δ1 and δ2 are the voltage phase angles of the first converter and the second converter respectively; Z1, Z2, Z g are the impedance values ​​of the first converter, the second converter, and the grid voltage respectively; θ1, θ2, θ g They are the impedance angles of the first converter, the second converter and the grid voltage, and there exists Z1∠θ1=R1+jX1, Z2∠θ2=R2+jX2, Z g ∠θ g =R g +jX g ;

[0108] The output active power of the first converter is:

[0109]

[0110] The output active power of the second converter is:

[0111]

[0112] Then, the relationship expression of the output power of each converter with respect to the power angle, impedance and voltage is obtained.

[0113] As an optional embodiment, the dynamic characteristic difference evaluation module solves the instantaneous power synchronization coefficient difference based on the steady-state voltage value and the steady-state power angle value of the converter during system steady-state operation and the relationship expression of the output active power of each converter with respect to the power angle, impedance, and voltage, including:

[0114] Based on the relationship expression of the output active power of each converter with respect to the power angle, impedance and voltage, the difference between the output powers of two converters derived with respect to their respective power angles is defined as the instantaneous power synchronization coefficient difference. The steady-state voltage value and the steady-state power angle value of the converter during steady-state operation of the system are substituted into the instantaneous power synchronization coefficient difference. The instantaneous power synchronization coefficient difference is used as an indicator to evaluate the size of the difference in the dynamic characteristics of the converter.

[0115] As an optional embodiment, defining the difference between the output powers of the two converters derived with respect to their respective power angles as the instantaneous power synchronization coefficient difference includes:

[0116] In the dynamic characteristics difference evaluation phase, the instantaneous power synchronization coefficient of each converter is obtained based on the relationship between the output power of each converter and the power angle, impedance, and voltage:

[0117]

[0118]

[0119] In a dual-mechanism grid-connected converter system, the instantaneous power synchronization coefficient difference is defined as the difference between the output powers of the two converters derived with respect to their respective power angles:

[0120]

[0121] In a third aspect, the present invention provides an electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the method for analyzing the differences in dynamic characteristics of parallel-grid-type converters when executing the computer program.

[0122] In a fourth aspect, the present invention provides a computer-readable storage medium storing a computer program, which implements the method for analyzing the differences in dynamic characteristics of parallel-grid-type converters when executed by a processor.

[0123] In a fifth aspect, the present invention provides a computer program product, which includes computer instructions, and the computer instructions instruct a computer to execute the method for analyzing the dynamic characteristics differences of parallel grid-connected converters.

[0124] The beneficial effects of the present invention are:

[0125] The present invention provides a method for analyzing the dynamic characteristics differences of parallel-grid-connected converters based on the instantaneous power synchronization coefficient difference. This method establishes a mathematical model of a dual-machine parallel system in a dq coordinate system with the power grid as the reference system. The steady-state voltage and power angle values ​​of the converters under given conditions are calculated, and a mathematical model and equivalent circuit model are established, thus avoiding the complex modeling process. An equivalent circuit model of the dual-machine grid-connected converter system is established, and the relationship between the active power output and the power angle of each converter is derived. The instantaneous power synchronization coefficient difference is defined as the difference between the derivatives of the output power of the two converters with respect to their respective power angles. Parameters related to steady-state calculations are substituted into the instantaneous power synchronization coefficient difference, and the instantaneous power synchronization coefficient difference is used as an indicator for evaluating the magnitude of the differences in the converter's dynamic characteristics. Defining the instantaneous power synchronization coefficient difference as an evaluation indicator eliminates the need for lengthy repeated experiments to obtain a dynamic characteristic curve. The evaluation indicator is directly obtained through calculation, eliminating the need for extensive storage and analysis of waveform data. The instantaneous power synchronization coefficient difference is related to the steady-state value of the converter's output active power, the station impedance, and the grid impedance. This allows for an accurate assessment of the impact of these parameters on the dynamic characteristic differences between converters. This approach greatly simplifies the detection and evaluation process for dynamic characteristic differences, improving efficiency. This improved efficiency in detecting system dynamic characteristic differences provides a comprehensive understanding for R&D personnel, engineers, and decision makers. This method eliminates the need for complex modeling and lengthy, repetitive experiments to obtain inter-unit dynamic characteristic curves. It is highly practical and can accurately assess the impact of these parameters on the dynamic characteristic differences between converters. BRIEF DESCRIPTION OF THE DRAWINGS

[0126] Figure 1 A flow chart of a method for analyzing the dynamic characteristics differences of a parallel grid-connected converter provided by the present invention;

[0127] Figure 2 It is a mathematical model of the grid-connected system of the dual-mechanism grid-type converter in the dq coordinate system with the grid as the reference system of the present invention;

[0128] Figure 3 It is an equivalent circuit model of the dual-mechanism grid-type converter grid-connected system of the present invention;

[0129] Figure 4 Figure 1 shows the results of an embodiment of the present invention when the steady-state output active power of two converters remains unchanged, the short-circuit ratio (SCR) increases, and the station impedance remains the same but increases. (a) shows the dynamic characteristics evaluation results based on the instantaneous power synchronization coefficient difference; (b) shows the dynamic characteristics difference results obtained in the actual experiment.

[0130] Figure 5This is a graph showing the results of an embodiment of the present invention when the station impedance is the same and unchanged, the difference between the steady-state output active power values ​​of the two converters remains unchanged, and the steady-state output active power values ​​increase by the same value simultaneously, while the short-circuit ratio (SCR) increases. (a) shows the dynamic characteristics evaluation result based on the instantaneous power synchronization coefficient difference; (b) shows the dynamic characteristics difference result obtained in the actual experiment.

[0131] Figure 6 This figure shows the results of an embodiment of the present invention when the station impedance is constant and unchanged, the steady-state output active power value of the first converter remains unchanged, the steady-state output active power value of the second converter increases, and the short-circuit ratio (SCR) increases. (a) shows the dynamic characteristics evaluation result based on the instantaneous power synchronization coefficient difference; (b) shows the dynamic characteristics difference result obtained in the actual experiment.

[0132] Figure 7 This figure shows the results of an embodiment of the present invention when the impedance of the first converter station increases, the impedance of the second converter station remains unchanged, the steady-state value of the converter output active power remains the same, and the short-circuit ratio (SCR) increases. (a) shows the dynamic characteristics evaluation result based on the instantaneous power synchronization coefficient difference; (b) shows the dynamic characteristics difference result obtained in the actual experiment.

[0133] Figure 8 The present invention is a parallel network type converter dynamic characteristics detection and evaluation system;

[0134] Figure 9 This is a schematic diagram of an electronic device provided by the present invention. DETAILED DESCRIPTION

[0135] The technical solutions of the present invention will be described clearly and completely below with reference to the accompanying drawings and embodiments. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

[0136] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0137] Example 1

[0138] like Figure 1 As shown, the present invention provides a method for analyzing the dynamic characteristics difference of parallel grid-connected converters based on the instantaneous power synchronization coefficient difference, thereby improving the efficiency of detecting the dynamic characteristics difference of the system. The specific steps of the method for analyzing the dynamic characteristics difference of parallel grid-connected converters include:

[0139] S1, by establishing a mathematical model of the grid-connected dual-mechanism grid-type converter system in the dq coordinate system with the grid as the reference system, and on this basis, solving the steady-state voltage and power angle values ​​of the converter under given conditions when the system is in steady-state operation;

[0140] In the system steady-state calculation link, a mathematical model of the dual-mechanism grid-connected converter system is established in the dq coordinate system with the grid as the reference system, such as Figure 2 As shown, on this basis, the steady-state voltage value and the steady-state power angle value of the converter when the system is in steady-state operation under given conditions are solved.

[0141] For the i-th converter, in the abc coordinate system, its mathematical model can be expressed as:

[0142]

[0143] Where, e abci ,u oabci are the internal potential and output voltage of the i-th converter in the abc coordinate system respectively; u pccabc is the voltage of the common coupling point PCC in the abc coordinate system; i Labci ,i oabci are the inductor current and output current of the i-th converter in the abc coordinate system respectively; L fi , R fi , C fi , L linei , R linei are the equivalent inductance of the filter inductor of the i-th converter plus the virtual inductor, the resistance in series with the filter inductor, the filter capacitor, the line inductance, and the line resistance.

[0144] To simplify the calculation, transform equation (1) from the abc coordinate system to the dq coordinate system. The dq transformation equation is:

[0145]

[0146] Where, P dq0 represents the voltage and current values ​​in the local rotating dq reference frame; P abc represents the instantaneous value of voltage and current in the three-phase stationary abc reference frame; θ represents the angle between the d-axis in the rotating reference frame and the a-axis in the stationary reference frame. The mathematical model of formula (1) in the dq coordinate system is:

[0147]

[0148] Where: e di , e qi are the internal potential of the i-th converter in the dq coordinate system; u odi ,u oqiare the output voltages of the i-th converter in the dq coordinate system; i Ldi ,i Lqi are the inductor currents of the i-th converter in the dq coordinate system; i odi ,i oqi are the output currents of the i-th converter in the dq coordinate system; u pccd ,u pccq are the voltages at the common coupling point PCC in the dq coordinate system; ω is the angular frequency of the system.

[0149] Since the change of the inductor current and capacitor voltage with respect to time is zero when the system is in steady state operation, equation (3) can be transformed into:

[0150]

[0151] Where: E di , E qi are the steady-state values ​​of the internal potential of the i-th converter in the dq coordinate system; U odi , U oqi are the steady-state output voltage values ​​of the i-th converter in the dq coordinate system; I Ldi , I Lqi are the steady-state values ​​of the inductor current of the i-th converter in the dq coordinate system; I odi , I oqi are the steady-state output current values ​​of the i-th converter in the dq coordinate system; U pccd , U pccq are the steady-state voltage values ​​of the PCC point in the dq coordinate system, and ω0 is the rated angular frequency of the system.

[0152] In addition, the active power and reactive power output by the i-th converter can be expressed in the dq coordinate system as follows:

[0153]

[0154] According to the reactive power-voltage droop relationship, the active power output in steady state is:

[0155]

[0156] and exists

[0157]

[0158] When the active power is output in steady state, there is

[0159] P outi =P refi (8)

[0160] According to the fact that the current flowing into the grid is equal to the sum of the output currents of all converters, it can be seen that in steady state:

[0161]

[0162] Equivalently treating the power grid as an ideal voltage source and grid impedance, in the abc coordinate system, the following relationship exists on the grid side:

[0163]

[0164] Where u gabc is the grid voltage in the abc coordinate system, i abcg is the grid current in the abc coordinate system; L g , R g are the grid inductance and grid resistance respectively.

[0165] In the dq coordinate system with the power grid as the reference system, equation (9) is converted to:

[0166]

[0167] Where u gd ,u gq is the grid voltage in the dq coordinate system, i gd ,i gq is the grid current in the dq coordinate system.

[0168] In steady state, equation (10) is converted to:

[0169]

[0170] Where U g is the steady-state value of the d-axis grid voltage in the dq coordinate system, I gd , I gq is the steady-state value of the grid current in the dq coordinate system.

[0171] By combining equations (4)-(8) and (11), we can obtain the steady-state values ​​of each voltage and current. According to the relationship:

[0172]

[0173] The steady-state value of the power angle of the i-th converter can be obtained.

[0174] In this approach, establishing a mathematical model in the dq coordinate system simplifies complex three-phase system analysis and facilitates subsequent calculations. Determining steady-state values ​​provides basic data for subsequent analysis, avoiding the complexity and uncertainty of actual measurements. This approach accurately reflects the steady-state operating characteristics of the system under different conditions, providing a reference for analyzing differences in dynamic characteristics.

[0175] S2, for the actual model of the dual-mechanism grid-connected converter system, the converter and the grid are both equivalent to voltage source models with series impedances to obtain an equivalent circuit model. By transforming and analyzing the equivalent circuit model, the relationship between the output active power of each converter and the power angle, impedance, and voltage is obtained;

[0176] In the output power angle relationship calculation link, combined with the calculation results of the steady-state calculation link, the active power-power angle relationship of the two converters' outputs is derived based on the dual-mechanism grid-type converter grid-connected system.

[0177] Taking the grid as the reference node and assuming the grid voltage phase to be 0, for the actual model of the dual-mechanism grid-connected converter system, both the converter and the grid are equivalent to voltage source models with series impedances, and the equivalent circuit model is obtained, as shown in the following example: Figure 3 shown.

[0178] Considering the contribution of each voltage source to the output current of the first converter, the output current of the first converter can be obtained by the superposition principle:

[0179]

[0180] Where U1, U2, U g are the effective values ​​of the first converter, the second converter and the grid voltage respectively; δ1 and δ2 are the voltage phase angles of the first converter and the second converter respectively; Z1, Z2, Z g are the impedance values ​​of the first converter, the second converter, and the grid voltage respectively; θ1, θ2, θ g They are the impedance angles of the first converter, the second converter and the grid voltage, and there exists Z1∠θ1=R1+jX1, Z2∠θ2=R2+jX2, Z g ∠θ g =R g +jX g .

[0181] Since X>>R exists, formula (14) can be further simplified as:

[0182]

[0183] Therefore, the output active power of the first converter is:

[0184]

[0185] Similarly, the output active power of the second converter is:

[0186]

[0187] From equations (16) and (17), we can know the relationship between the output power of each converter and the power angle, impedance and voltage.

[0188] In the above scheme, the system model is simplified, so that the complex converter and power grid system can be represented by a simple equivalent circuit. It is easy to apply circuit analysis methods, such as the superposition principle, to derive the relationship between output power and power angle. This improves calculation efficiency and reduces the complexity of modeling and analysis. Figure 3 As shown in the figure, the converter and the grid are both equivalent to voltage source models with series impedance. This equivalent model makes it easy to apply circuit analysis methods to derive the relationship between output power and power angle.

[0189] S3, define the difference between the output powers of the two converters derived with respect to their respective power angles as the instantaneous power synchronization coefficient difference, and substitute the converter's steady-state voltage and power angle values ​​during system steady-state operation into the instantaneous power synchronization coefficient difference, and use the instantaneous power synchronization coefficient difference as an indicator to evaluate the size of the difference in the converter's dynamic characteristics.

[0190] In the dynamic characteristic difference evaluation link, the instantaneous power synchronization coefficient of each converter is obtained based on the power angle relationship of formula (16) and formula (17):

[0191]

[0192]

[0193] Since the instantaneous power synchronization coefficient K in a single-machine system is related to the dynamic characteristics of the system, in a dual-mechanism grid-connected converter system, the instantaneous power synchronization coefficient difference is defined as the difference between the output powers of the two converters derived with respect to their respective power angles:

[0194]

[0195] By calculating the operating state of the system before the steady-state change and substituting the relevant parameters into the instantaneous power synchronization coefficient difference, the instantaneous power synchronization coefficient difference is used as an indicator to evaluate the difference in the dynamic characteristics of the converter. As can be seen from Equation (20), the instantaneous power synchronization coefficient difference is related to the steady-state value of the converter output active power, the station impedance, and the grid impedance.

[0196] In the above scheme, the superposition principle allows each voltage source's contribution to the output current to be considered separately, simplifying the analysis process. The resulting expression directly reflects the relationship between output power and various parameters (such as voltage, impedance, and power angle), facilitating subsequent analysis. This provides the necessary mathematical foundation for calculating the instantaneous power synchronization coefficient difference.

[0197] The instantaneous power synchronization coefficient difference is defined as the difference between the output powers of two converters, derived with respect to their respective power angles. This provides a quantitative metric for evaluating differences in converter dynamic characteristics, avoiding complex time-domain simulation and waveform analysis. This metric directly reflects the difference in power sensitivity to power angle variations and effectively characterizes differences in dynamic characteristics. The calculation is simple, requiring only the derivative of the obtained power expression, significantly improving analysis efficiency.

[0198] Since the instantaneous power synchronization coefficient difference is related to the steady-state value of the converter output active power, the station impedance and the grid impedance, the considered situations are divided into four types.

[0199] like Figure 4 The evaluation results in (a) show that when the steady-state values ​​of the active power outputs of the two converters remain unchanged, P1 = 0.1 pu, P2 = 0.9 pu, the grid impedance decreases (i.e., the short-circuit ratio SCR increases), and the station impedances X1 and X2 are the same and increase, the instantaneous power synchronization coefficient difference between the two converters becomes larger, which is consistent with the actual dynamic characteristics difference results obtained in the experiment. Figure 4 The conclusion is the same as in (b).

[0200] Among them, when the steady-state value of the active power output of the two converters remains unchanged (P1=P2), the short-circuit ratio SCR increases (that is, the grid impedance decreases), and the station impedance Z1=Z2 is the same and increases: the steady-state value of the converter voltage and the steady-state value of the power angle are solved through the system steady-state calculation module. The relationship expression between the output active power and the power angle of the two converters is obtained through the output power angle relationship calculation module. The instantaneous power synchronization coefficient difference ΔK of the two converters is calculated. The results show (as shown in Figure 4 As shown in Figure a), as the impedance in the station increases, ΔK gradually increases, indicating that the dynamic characteristics difference between the two converters becomes larger. This is consistent with the actual dynamic characteristics difference results obtained in the experiment ( Figure 4 b), verifying the effectiveness of this method. This example demonstrates that this method can accurately evaluate the impact of station impedance changes on converter dynamic characteristics without the need for complex experiments and data analysis.

[0201] like Figure 5 The evaluation results in (a) show that when the station impedances X1 and X2 are the same and unchanged, the difference in the steady-state output active power values ​​of the two converters remains unchanged, ΔP = P1-P2 = 0.5pu. At this time, when the output active power steady-state values ​​P1 and P2 increase by the same value at the same time and the grid impedance decreases (i.e., the short-circuit ratio SCR increases), the instantaneous power synchronization coefficient difference between the two converters becomes larger, which is consistent with the dynamic characteristic difference results obtained in the experiment. Figure 5 Same as (b).

[0202] like Figure 6The evaluation results in (a) show that when the station impedances X1 and X2 are the same and unchanged, the steady-state value of the active power output of the first converter P1 remains unchanged, the steady-state value of the active power output of the second converter P2 increases, and the grid impedance decreases (i.e., the short-circuit ratio SCR increases), the instantaneous power synchronization coefficient difference between the two converters becomes larger, which is consistent with the dynamic characteristics difference results obtained in the experiment. Figure 6 Same as (b).

[0203] like Figure 7 The evaluation results in (a) show that when the internal impedance X1 of the first converter increases and the internal impedance X2 of the second converter remains unchanged, the steady-state values ​​of the converter output active power P1 and P2 are the same and unchanged, and the grid impedance decreases (i.e., the short-circuit ratio SCR increases), the instantaneous power synchronization coefficient difference between the two converters becomes larger, which is consistent with the dynamic characteristic difference results obtained in the experiment. Figure 7 Same as (b).

[0204] Therefore, the method for analyzing the dynamic characteristics differences of parallel-grid converters based on the instantaneous power synchronization coefficient difference proposed in the present invention does not require a complex modeling process, nor does it require long-term repeated experiments to obtain the dynamic characteristics curves between units. It has good practicality and can accurately evaluate the influence of relevant parameters on the dynamic characteristics differences between converters.

[0205] In large-scale photovoltaic power plants, parallel operation of multiple converters is a common scenario. These converters must work in coordination to ensure grid stability and power generation efficiency. However, differences in the physical location of the converters, the length of the connecting lines, and other factors can lead to subtle differences in their dynamic characteristics. These differences may not be noticeable during normal operation, but can cause problems during grid disturbances or sudden load changes.

[0206] As a further preferred solution, to address the power oscillation problem caused by small differences in dynamic characteristics between converters, this application proposes a real-time oscillation monitoring and adaptive adjustment method based on the instantaneous power synchronization coefficient difference. This method adds the following key steps to the existing instantaneous power synchronization coefficient difference calculation:

[0207] Real-time oscillation detection: Continuously monitors changes in the instantaneous power synchronization coefficient difference ΔK. If ΔK shows periodic changes within a certain period of time and the amplitude exceeds a preset threshold, the system is determined to have power oscillation.

[0208] Oscillation characteristic analysis: Analyze the time series of ΔK using Fast Fourier Transform (FFT) to extract the main frequency and amplitude information of the oscillation. Adaptive parameter adjustment: Automatically adjust the converter control parameters, such as PLL bandwidth and current loop gain, based on the oscillation characteristics to reduce dynamic characteristic differences and suppress power oscillations. The specific adjustment strategy is as follows:

[0209] If the oscillation frequency is low (e.g. <1Hz), adjust the PLL parameters to reduce the response speed difference.

[0210] If the oscillation frequency is high (e.g. >10Hz), adjust the current loop parameters to balance the fast response capability. The adjustment amplitude is proportional to the detected oscillation amplitude to ensure the effectiveness and stability of the adjustment.

[0211] Effect evaluation and iterative optimization: After parameter adjustments, continue to monitor changes in ΔK. If oscillations are effectively suppressed, maintain the current parameter settings. If oscillations persist, perform a new round of feature analysis and parameter adjustments until oscillations are effectively suppressed or the preset upper limit of iterations is reached.

[0212] This optimization solution, through real-time monitoring and adaptive adjustment, can promptly detect and suppress power oscillations caused by subtle differences in dynamic characteristics, thereby improving system stability and power generation efficiency. Furthermore, this method requires only the addition of software algorithms to the existing system, without requiring additional hardware investment, making it highly practical and cost-effective. Through continuous monitoring and adaptive adjustment, this solution can also adapt to long-term changes in system parameters and maintain excellent long-term performance.

[0213] Example 2

[0214] The dynamic characteristics detection and evaluation system studied in this invention is as follows Figure 8 As shown in the figure, it can be mainly divided into the system steady-state calculation link, the output power angle relationship calculation link and the dynamic characteristic difference evaluation link. Figure 8 As shown, the present invention addresses the current problem of complex and inefficient detection and evaluation of converter dynamic characteristic differences. It provides a method and system for analyzing the dynamic characteristic differences of parallel-network converters based on instantaneous power synchronization coefficient differences, thereby improving the efficiency of detecting system dynamic characteristic differences. The method mainly includes:

[0215] The system steady-state calculation module solves the steady-state voltage and power angle values ​​of the converter when the system is in steady-state operation under given conditions by establishing a mathematical model of the dual-mechanism grid-type converter grid-connected system in the dq coordinate system with the power grid as the reference system.

[0216] The output power angle relationship calculation module establishes an equivalent circuit model of the dual-mechanism grid-connected converter system and combines the calculation results of the steady-state calculation module to solve the relationship between the output active power of each converter and the power angle, impedance and voltage.

[0217] The dynamic characteristic difference evaluation module solves the instantaneous power synchronization coefficient difference based on the system steady-state calculation module and the output power angle relationship calculation module, and is used to evaluate the impact of different parameters on the dynamic characteristics of the converter.

[0218] Example 3

[0219] like Figure 9 As shown, an electronic device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the following method for analyzing the dynamic characteristics difference of parallel grid-connected converters is implemented:

[0220] Establishing a mathematical model of a dual-mechanism grid-type converter grid-connected system in a dq coordinate system with the grid as a reference system, and solving the mathematical model to obtain the steady-state voltage value and the steady-state power angle value of the converter when the system is in steady-state operation;

[0221] For the actual model of a dual-mechanism grid-connected converter system, the converter and the grid are both equivalent to voltage source models with series impedances, resulting in an equivalent circuit model. By transforming and analyzing the equivalent circuit model, the relationship between the output active power of each converter and the power angle, impedance, and voltage is obtained.

[0222] Based on the steady-state voltage and power angle values ​​of the converter during steady-state operation of the system and the relationship between the output active power of each converter and the power angle, impedance and voltage, the instantaneous power synchronization coefficient difference is solved. The instantaneous power synchronization coefficient difference is used to evaluate the impact of different parameters on the dynamic characteristics of the converter.

[0223] Example 4

[0224] A fourth object of an embodiment of the present invention is to provide a computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the method for analyzing the dynamic characteristics difference of a parallel grid-connected converter is implemented. The method for analyzing the dynamic characteristics difference of a parallel grid-connected converter comprises:

[0225] Establishing a mathematical model of a dual-mechanism grid-type converter grid-connected system in a dq coordinate system with the grid as a reference system, and solving the mathematical model to obtain the steady-state voltage value and the steady-state power angle value of the converter when the system is in steady-state operation;

[0226] For the actual model of a dual-mechanism grid-connected converter system, the converter and the grid are both equivalent to voltage source models with series impedances, resulting in an equivalent circuit model. By transforming and analyzing the equivalent circuit model, the relationship between the output active power of each converter and the power angle, impedance, and voltage is obtained.

[0227] Based on the steady-state voltage and power angle values ​​of the converter during steady-state operation of the system and the relationship between the output active power of each converter and the power angle, impedance and voltage, the instantaneous power synchronization coefficient difference is solved. The instantaneous power synchronization coefficient difference is used to evaluate the impact of different parameters on the dynamic characteristics of the converter.

[0228] Example 5

[0229] A fifth object of an embodiment of the present invention is to provide a computer program product, the computer program product comprising computer instructions, the computer instructions instructing a computer to execute the above-mentioned method for analyzing the dynamic characteristics differences of parallel grid-connected converters. The above-mentioned method for analyzing the dynamic characteristics differences of parallel grid-connected converters comprises:

[0230] Establishing a mathematical model of a dual-mechanism grid-type converter grid-connected system in a dq coordinate system with the grid as a reference system, and solving the mathematical model to obtain the steady-state voltage value and the steady-state power angle value of the converter when the system is in steady-state operation;

[0231] For the actual model of a dual-mechanism grid-connected converter system, the converter and the grid are both equivalent to voltage source models with series impedances, resulting in an equivalent circuit model. By transforming and analyzing the equivalent circuit model, the relationship between the output active power of each converter and the power angle, impedance, and voltage is obtained.

[0232] Based on the steady-state voltage and power angle values ​​of the converter during steady-state operation of the system and the relationship between the output active power of each converter and the power angle, impedance and voltage, the instantaneous power synchronization coefficient difference is solved. The instantaneous power synchronization coefficient difference is used to evaluate the impact of different parameters on the dynamic characteristics of the converter.

[0233] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0234] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0235] The present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, readable storage media, optical storage, etc.) containing computer-usable program code.

[0236] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0237] Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0238] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A method for analyzing the dynamic characteristics difference of parallel grid-connected converters, characterized in that: include: Establishing a mathematical model of a dual-mechanism grid-type converter grid-connected system in a dq coordinate system with the grid as a reference system, and solving the mathematical model to obtain the steady-state voltage value and the steady-state power angle value of the converter when the system is in steady-state operation; For the actual model of a dual-mechanism grid-connected converter system, the converter and the grid are both equivalent to voltage source models with series impedances, resulting in an equivalent circuit model. By transforming and analyzing the equivalent circuit model, the relationship between the output active power of each converter and the power angle, impedance, and voltage is obtained. Based on the steady-state voltage and power angle values ​​of the converter during steady-state operation of the system and the relationship between the output active power of each converter and the power angle, impedance and voltage, the instantaneous power synchronization coefficient difference is solved. The instantaneous power synchronization coefficient difference is used to evaluate the impact of different parameters on the dynamic characteristics of the converter.

2. The method for analyzing the dynamic characteristics difference of parallel grid-connected converters according to claim 1, characterized in that: The mathematical model of the dual-mechanism grid-type converter grid-connected system in the dq coordinate system with the grid as the reference system is established, including: For the i-th converter, in the abc coordinate system, the mathematical model is expressed as: Where, e abci ,u oabci are the internal potential and output voltage of the i-th converter in the abc coordinate system respectively; u pccabc is the voltage of the common coupling point PCC in the abc coordinate system; i Labci ,i oabci are the inductor current and output current of the i-th converter in the abc coordinate system respectively; L fi , R fi , C fi , L linei , R linei are the equivalent inductance of the filter inductor of the i-th converter plus the virtual inductor, the resistance in series with the filter inductor, the filter capacitor, the line inductance, and the line resistance; Convert the abc coordinate system to the dq coordinate system. The dq transformation equation is: Where, P dq0 represents the voltage and current values ​​in the local rotating dq reference frame; P abc represents the instantaneous values ​​of voltage and current in the three-phase stationary abc reference coordinate system; θ represents the angle between the d-axis in the rotating reference system and the a-axis in the stationary reference system; the mathematical model in the dq coordinate system is: Where: e di , e qi are the internal potential of the i-th converter in the dq coordinate system; u odi ,u oqi are the output voltages of the i-th converter in the dq coordinate system; i Ldi ,i Lqi are the inductor currents of the i-th converter in the dq coordinate system; i odi ,i oqi are the output currents of the i-th converter in the dq coordinate system; u pccd ,u pccq are the voltages at the common coupling point PCC in the dq coordinate system; ω is the angular frequency of the system.

3. The method for analyzing the dynamic characteristics difference of parallel grid-connected converters according to claim 2, characterized in that: Solving the mathematical model to obtain the steady-state voltage value and the steady-state power angle value of the converter when the system is in steady-state operation includes: When solving for the steady-state value, the mathematical model becomes: Where: E di , E qi are the steady-state values ​​of the internal potential of the i-th converter in the dq coordinate system; U odi , U oqi are the steady-state output voltage values ​​of the i-th converter in the dq coordinate system; I Ldi , I Lqi are the steady-state values ​​of the inductor current of the i-th converter in the dq coordinate system; I odi , I oqi are the steady-state output current values ​​of the i-th converter in the dq coordinate system; U pccd , U pccq are the steady-state voltage values ​​of the PCC point in the dq coordinate system, ω0 is the rated angular frequency of the system; The active power and reactive power output by the i-th converter are expressed in the dq coordinate system as follows: According to the reactive power-voltage droop relationship, the active power output in steady state is: When the active power is output in steady state, P outi =P refi According to the current flowing into the grid is equal to the sum of the output currents of all converters, in steady state: Equivalently treating the power grid as an ideal voltage source and grid impedance, in the abc coordinate system, the following relationship exists on the grid side: Where u gabc is the grid voltage in the abc coordinate system, i abcg is the grid current in the abc coordinate system; L g , R g are the grid inductance and grid resistance respectively; In the dq coordinate system with the power grid as the reference system, then: Where u gd ,u gq is the grid voltage in the dq coordinate system, i gd ,i gq is the grid current in the dq coordinate system; In steady state, we get: Where U g is the steady-state value of the d-axis grid voltage in the dq coordinate system, I gd , I gq is the steady-state value of the grid current in the dq coordinate system; Then the steady-state values ​​of each voltage and current are obtained; According to the relationship: Obtain the steady-state value of the power angle of the i-th converter.

4. The method for analyzing the dynamic characteristics difference of parallel grid-connected converters according to claim 1, characterized in that: The actual model of the dual-mechanism grid-type converter grid-connected system is described above. The converter and the grid are both equivalent to voltage source models with series impedances, and the equivalent circuit model is obtained, including: Taking the grid as the reference node and assuming the grid voltage phase to be 0, for the actual model of the dual-mechanism grid-connected converter system, both the converter and the grid are equivalent to voltage source models with series impedances to obtain the equivalent circuit model.

5. The method for analyzing the dynamic characteristics difference of parallel grid-connected converters according to claim 1, characterized in that: By transforming and analyzing the equivalent circuit model, the relationship expression of the output active power of each converter with respect to the power angle, impedance and voltage is obtained, including: Combined with the steady-state voltage and power angle values ​​of the converter during system steady-state operation, the active power-power angle relationship of each of the two converters is derived based on the dual-mechanism grid-connected converter system, specifically: Considering the contribution of each voltage source to the output current of the first converter, the output current of the first converter is obtained by the superposition principle: Where U1, U2, U g are the effective values ​​of the first converter, the second converter and the grid voltage respectively; δ1 and δ2 are the voltage phase angles of the first converter and the second converter respectively; Z1, Z2, Z g are the impedance values ​​of the first converter, the second converter, and the grid voltage respectively; θ1, θ2, θ g They are the impedance angles of the first converter, the second converter and the grid voltage, and there exists Z1∠θ1=R1+jX1, Z2∠θ2=R2+jX2, Z g ∠θ g =R g +jX g ; The output active power of the first converter is: The output active power of the second converter is: Then, the relationship expression of the output power of each converter with respect to the power angle, impedance and voltage is obtained.

6. The method for analyzing the dynamic characteristics difference of parallel grid-connected converters according to claim 1, characterized in that: The method of solving the instantaneous power synchronization coefficient difference based on the steady-state voltage value and the steady-state power angle value of the converter during the steady-state operation of the system and the relationship expression of the output active power of each converter with respect to the power angle, impedance and voltage includes: Based on the relationship expression of the output active power of each converter with respect to the power angle, impedance and voltage, the difference between the output powers of two converters derived with respect to their respective power angles is defined as the instantaneous power synchronization coefficient difference. The steady-state voltage value and the steady-state power angle value of the converter during steady-state operation of the system are substituted into the instantaneous power synchronization coefficient difference. The instantaneous power synchronization coefficient difference is used as an indicator to evaluate the size of the difference in the dynamic characteristics of the converter.

7. The method for analyzing the dynamic characteristics difference of parallel grid-connected converters according to claim 6, characterized in that: The definition of the difference between the output powers of the two converters derived with respect to their respective power angles as the instantaneous power synchronization coefficient difference includes: In the dynamic characteristics difference evaluation phase, the instantaneous power synchronization coefficient of each converter is obtained based on the relationship between the output power of each converter and the power angle, impedance, and voltage: In a dual-mechanism grid-connected converter system, the instantaneous power synchronization coefficient difference is defined as the difference between the output powers of the two converters derived with respect to their respective power angles:

8. A system for analyzing the dynamic characteristics difference of parallel grid-connected converters, characterized in that: include: The system steady-state calculation module is used to establish a mathematical model of the grid-connected dual-mechanism grid-type converter system in a dq coordinate system with the grid as the reference system, and solve the mathematical model to obtain the steady-state voltage value and power angle steady-state value of the converter when the system is in steady-state operation; The output power angle relationship calculation module is used to calculate the actual model of the dual-mechanism grid-connected converter system. The converter and the grid are both equivalent to voltage source models with series impedances to obtain an equivalent circuit model. By transforming and analyzing the equivalent circuit model, the relationship between the output active power of each converter and the power angle, impedance, and voltage is obtained. The dynamic characteristics difference evaluation module is used to solve the instantaneous power synchronization coefficient difference based on the steady-state voltage value and power angle steady-state value of the converter during system steady-state operation and the relationship expression of the output active power of each converter with the power angle, impedance and voltage. The instantaneous power synchronization coefficient difference is used to evaluate the impact of different parameters on the dynamic characteristics of the converter.

9. The parallel grid-connected converter dynamic characteristic difference analysis system according to claim 8, characterized in that: In the system steady-state calculation module, a mathematical model of a dual-mechanism grid-type converter grid-connected system in a dq coordinate system with the grid as a reference system is established, including: For the i-th converter, in the abc coordinate system, the mathematical model is expressed as: Where, e abci ,u oabci are the internal potential and output voltage of the i-th converter in the abc coordinate system respectively; u pccabc is the voltage of the common coupling point PCC in the abc coordinate system; i Labci ,i oabci are the inductor current and output current of the i-th converter in the abc coordinate system respectively; L fi , R fi , C fi , L linei , R linei are the equivalent inductance of the filter inductor of the i-th converter plus the virtual inductor, the resistance in series with the filter inductor, the filter capacitor, the line inductance, and the line resistance; Convert the abc coordinate system to the dq coordinate system. The dq transformation equation is: Where, P dq0 represents the voltage and current values ​​in the local rotating dq reference frame; P abc represents the instantaneous values ​​of voltage and current in the three-phase stationary abc reference coordinate system; θ represents the angle between the d-axis in the rotating reference system and the a-axis in the stationary reference system; the mathematical model in the dq coordinate system is: Where: e di , e qi are the internal potential of the i-th converter in the dq coordinate system; u odi ,u oqi are the output voltages of the i-th converter in the dq coordinate system; i Ldi ,i Lqi are the inductor currents of the i-th converter in the dq coordinate system; i odi ,i oqi are the output currents of the i-th converter in the dq coordinate system; u pccd ,u pccq are the voltages at the common coupling point PCC in the dq coordinate system; ω is the angular frequency of the system.

10. The parallel grid-connected converter dynamic characteristic difference analysis system according to claim 9, characterized in that: In the system steady-state calculation module, solving the mathematical model to obtain the steady-state voltage value and the steady-state power angle value of the converter when the system is in steady-state operation includes: When solving for the steady-state value, the mathematical model becomes: Where: E di , E qi are the steady-state values ​​of the internal potential of the i-th converter in the dq coordinate system; U odi , U oqi are the steady-state output voltage values ​​of the i-th converter in the dq coordinate system; I Ldi , I Lqi are the steady-state values ​​of the inductor current of the i-th converter in the dq coordinate system; I odi , I oqi are the steady-state output current values ​​of the i-th converter in the dq coordinate system; U pccd , U pccq are the steady-state voltage values ​​of the PCC point in the dq coordinate system, ω0 is the rated angular frequency of the system; The active power and reactive power output by the i-th converter are expressed in the dq coordinate system as follows: According to the reactive power-voltage droop relationship, the active power output in steady state is: When the active power is output in steady state, P outi =P refi According to the current flowing into the grid is equal to the sum of the output currents of all converters, in steady state: Equivalently treating the power grid as an ideal voltage source and grid impedance, in the abc coordinate system, the following relationship exists on the grid side: Where u gabc is the grid voltage in the abc coordinate system, i abcg is the grid current in the abc coordinate system; L g , R g are the grid inductance and grid resistance respectively; In the dq coordinate system with the power grid as the reference system, then: Where u gd ,u gq is the grid voltage in the dq coordinate system, i gd ,i gq is the grid current in the dq coordinate system; In steady state, we get: Where U g is the steady-state value of the d-axis grid voltage in the dq coordinate system, I gd , I gq is the steady-state value of the grid current in the dq coordinate system; Then the steady-state values ​​of each voltage and current are obtained; According to the relationship: Obtain the steady-state value of the power angle of the i-th converter.

11. The parallel grid-connected converter dynamic characteristic difference analysis system according to claim 8, characterized in that: In the output power angle relationship calculation module, the actual model of the dual-mechanism grid-type converter grid-connected system is obtained by equating the converter and the grid to voltage source models with series impedances, including: Taking the grid as the reference node and assuming the grid voltage phase to be 0, for the actual model of the dual-mechanism grid-connected converter system, both the converter and the grid are equivalent to voltage source models with series impedances to obtain the equivalent circuit model.

12. The parallel grid-connected converter dynamic characteristic difference analysis system according to claim 8, characterized in that: In the output power angle relationship calculation module, the equivalent circuit model is transformed and analyzed to obtain the relationship expression of the output active power of each converter with respect to the power angle, impedance, and voltage, including: Combined with the steady-state voltage and power angle values ​​of the converter during system steady-state operation, the active power-power angle relationship of each of the two converters is derived based on the dual-mechanism grid-connected converter system, specifically: Considering the contribution of each voltage source to the output current of the first converter, the output current of the first converter is obtained by the superposition principle: Where U1, U2, U g are the effective values ​​of the first converter, the second converter and the grid voltage respectively; δ1 and δ2 are the voltage phase angles of the first converter and the second converter respectively; Z1, Z2, Z g are the impedance values ​​of the first converter, the second converter, and the grid voltage respectively; θ1, θ2, θ g They are the impedance angles of the first converter, the second converter and the grid voltage, and there exists Z1∠θ1=R1+jX1, Z2∠θ2=R2+jX2, Z g ∠θ g =R g +jX g ; The output active power of the first converter is: The output active power of the second converter is: Then, the relationship expression of the output power of each converter with respect to the power angle, impedance and voltage is obtained.

13. The parallel grid-connected converter dynamic characteristic difference analysis system according to claim 8, characterized in that: In the dynamic characteristic difference evaluation module, based on the steady-state voltage and power angle values ​​of the converter during system steady-state operation and the relationship between the output active power of each converter and the power angle, impedance, and voltage, the instantaneous power synchronization coefficient difference is solved, including: Based on the relationship expression of the output active power of each converter with respect to the power angle, impedance and voltage, the difference between the output powers of two converters derived with respect to their respective power angles is defined as the instantaneous power synchronization coefficient difference. The steady-state voltage value and the steady-state power angle value of the converter during steady-state operation of the system are substituted into the instantaneous power synchronization coefficient difference. The instantaneous power synchronization coefficient difference is used as an indicator to evaluate the size of the difference in the dynamic characteristics of the converter.

14. The parallel grid-connected converter dynamic characteristic difference analysis system according to claim 13, characterized in that: The definition of the difference between the output powers of the two converters derived with respect to their respective power angles as the instantaneous power synchronization coefficient difference includes: In the dynamic characteristics difference evaluation phase, the instantaneous power synchronization coefficient of each converter is obtained based on the relationship between the output power of each converter and the power angle, impedance, and voltage: In a dual-mechanism grid-connected converter system, the instantaneous power synchronization coefficient difference is defined as the difference between the output powers of the two converters derived with respect to their respective power angles:

15. An electronic device, characterized in that: The method comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the method for analyzing the dynamic characteristics difference of the parallel grid-connected converter according to any one of claims 1 to 7 when executing the computer program.

16. 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 analyzing the dynamic characteristics difference of the parallel grid-connected converter according to any one of claims 1 to 7 is implemented.

17. A computer program product comprising computer instructions, characterized in that: The computer instructions instruct the computer to execute the method for analyzing the dynamic characteristics differences of the parallel grid-connected converter according to any one of claims 1 to 7.

Images