Stability interaction analysis method for parallel connection of network following / network constructing converters

Abstract

The invention provides a stability interaction analysis method for parallel connection of a grid-following converter and a grid-constructing converter. The method comprises the following steps: establishing a first grid-connected simulation model when the grid-following converter and the grid-constructing converter are connected in parallel; establishing a second grid-connected simulation model when the first grid-connected simulation model is connected to the alternating current system; based on the second grid-connected simulation model, establishing a damping torque model during grid connection of the grid-constructing converter and the grid-following converter; based on the damping torque model, constructing an interaction analytic expression between a network-constructing type converter and a network-following type converter, wherein the interaction analytic expression is related to control parameters; the control parameters are used for compensating the disturbance quantity in the power grid. The invention provides a mechanism for quantitatively analyzing interaction between network construction equipment and network following equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of hybrid station stability analysis, and in particular to a stability interaction analysis method for a parallel-connected grid / network converter. Background Art

[0002] New energy wind and solar power stations and energy storage devices often use power electronic converters to connect to the grid. As power systems evolve toward a high proportion of renewable energy and power electronics, the converters currently used in wind and solar power stations are primarily based on phase-locked loop (PLL) grid-following control, which carries the risk of broadband oscillation when connected to weak grids. With the continued growth of renewable energy, AC grids will weaken further in the future. Currently, grid-following converters, exemplified by virtual synchronous control, offer strong stability in weak grids and can improve the stability of grid-following converters when connected to the grid.

[0003] In the existing technology, there are more schemes for analyzing the stability of grid-following converters connected to the power grid alone, while there are relatively few analyses of the interaction between grid-following converters and grid-forming converters in parallel. Therefore, there is an urgent need for a method that can effectively analyze the interaction mechanism between grid-following converters and grid-forming converters. Summary of the Invention

[0004] The present invention provides a stability interaction analysis method for parallel connection of network-following / network-building converters, which is used for quantitatively analyzing the interaction mechanism between network-building and network-following devices.

[0005] According to one aspect of the present invention, a stability interaction analysis method for a parallel connected grid / interconnected grid converter is provided, comprising: Establishing a first grid-connected simulation model when a grid-following converter and a grid-forming converter are connected in parallel; Establishing a second grid-connected simulation model when the first grid-connected simulation model is connected to an AC system; Establishing a damping torque model when the grid-forming converter and the grid-following converter are grid-connected based on the second grid-connected simulation model; An analytical expression for the interaction between the grid-forming converter and the grid-following converter is constructed based on the damping torque model. The analytical expression for the interaction is related to a control parameter; the control parameter is used to compensate for a disturbance in the grid.

[0006] Optionally, the step of establishing a first grid-connected simulation model when the grid-following converter and the grid-connecting converter are connected in parallel includes: The first grid-connected simulation model includes a grid-following converter model, a control system model of the grid-following converter, a grid-forming converter model, and a control system model of the grid-forming converter.

[0007] Optionally, the grid-following converter model is: ; Where, E d1 、E q1 Indicates the output voltage dq axis voltage of the grid-following converter; L f1 Indicates the filter inductance of the grid-type converter; u dm 、u qm are the dq axis components of the voltage at the grid-following converter terminal, i dm1 、i qm1 are the dq axis components of the output current of the grid-following converter respectively; C dc1 、U dc1 、P out1 、P in1 are the capacitance value, voltage value, output active power and input active power of the DC capacitor respectively; ω0 is the rated angular velocity; The control system model of the grid-following converter includes a mathematical model of a phase-locked loop and a converter control system model; the phase-locked loop is used to obtain the phase of the output voltage and / or output current of the grid-following converter, and adjust the phase of the dq-axis components of the voltage and / or current at the grid-following converter terminal to adjust the phase difference between the voltage and / or current output by the converter control system and the output voltage and / or output current of the grid-following converter; the converter control system is used to control the dq-axis components of the voltage and / or current at the grid-following converter terminal, and output the controlled voltage and / or current to the grid-following converter; The mathematical model of the phase-locked loop is:

[0008] Where k p_pll and k i_pll are the proportional and integral coefficients of the phase-locked loop respectively; x pll is the phase-locked loop state variable; θ pll is the angle of the phase-locked loop output; The converter control system model is:

[0009] In the formula, the voltage control loop is composed of the DC capacitor voltage control, which gives the reference value of the active current by controlling the capacitor voltage; the reactive power setpoint is 0, which means that the grid-fed photovoltaic / wind turbine does not generate reactive power; U dc1 is the DC capacitor voltage, u dcref is the reference value of the DC capacitor voltage, i qref The current control loop is based on the active and reactive current reference values ​​given by the voltage control loop. i dref and iqref , the dq axis component i of the output current of the grid-following converter dm1 and i qm1 Control and finally output modulation voltage u gd 、 u gq As the input of the grid-following converter; x udc Indicates the state quantity corresponding to the DC voltage control loop; x d 、x q They represent the state quantities corresponding to the d-axis current control loop and the q-axis current control loop respectively; k p_udc 、k i_udc are the proportional parameter and integral parameter of the DC voltage control loop respectively; k p_d 、k i_d are the proportional and integral parameters of the d-axis current control loop respectively; k p_q 、k i_q are the proportional and integral parameters of the q-axis current control loop respectively.

[0010] Optionally, the meshed converter model is:

[0011] Where: E d2 、E q2 Represents the dq axis voltage at the outlet of the grid-type converter; L f2 Represents the filter inductance of the network converter; u dm2 、u qm2 are the dq axis components of the voltage at the terminal of the grid-type converter, i dm2 、i qm2 are the dq axis components of the output current of the grid-type converter respectively; ω0 is the rated angular velocity; The control system model of the grid-type converter includes the mathematical model of the active control link, the mathematical model of the reactive control link and the mathematical model of the voltage and current control loop; The mathematical model of the active power control link is:

[0012] Where ω is the angular velocity of the grid-type converter, P ref Represents the active reference value of the grid-type converter, P e2 Represents the active power of the grid-type converter; K D is the virtual damping coefficient; T j is the virtual inertia coefficient; θ v is the virtual power angle of the grid-type converter; ω0 is the rated angular velocity; The mathematical model of the reactive power control link is:

[0013] Where, E v is the virtual voltage, Q ref Represents the reactive power reference value of the grid-type converter, Q e2 Represents the reactive power of the grid-type converter; K Q is the reactive droop coefficient, U0 is the rated value of the voltage amplitude of the grid-type converter; The mathematical models of the voltage control loop and current control loop of the grid-type converter are:

[0014] Where x Evd represents the state quantity corresponding to the d-axis of the voltage control loop of the network converter; x Evq represents the state quantity corresponding to the q-axis of the voltage control loop of the network converter; k p_ud 、k i_ud are the proportional and integral parameters of the d-axis voltage control loop respectively; k p_uq 、k i_uq are the proportional and integral parameters of the q-axis voltage control loop respectively; E vd 、E vq They are the inputs of the q-axis and d-axis voltage control loops, u dm2 、u qm2 are the dq axis components of the voltage at the terminal of the grid-type converter, i vdref 、i vqref are the reference values ​​of the current controller respectively; x id 、x iq They represent the state quantities corresponding to the current control loop respectively; k p_id 、k i_id are the proportional and integral parameters of the d-axis current control loop respectively; k p_iq 、k i_iq are the proportional and integral parameters of the q-axis current control loop respectively; L f2 Represents the filter inductance of the network converter; i dm2 、i qm2 are the dq axis components of the output current of the grid-type converter respectively; the current control loop is based on the reference value i of the current controller given by the voltage control loop vdref and i vqref , the dq axis component i of the output current of the grid-type converter dm2 and i qm2 Control is performed and the final output is the dq axis voltage E of the grid-type converter output. d2 、E q2 As the input of the network converter.

[0015] Optionally, the second grid-connected simulation model is a model formed by an equivalent circuit after the output end of the grid-following converter and the output end of the grid-connecting converter are both connected to the AC system power supply; the grid mathematical model in the second grid-connected simulation model is:

[0016] Where u dm 、u qm are the dq axis components of the voltage at the terminal of the grid-type converter respectively; i dm1 、i qm1 are the dq axis components of the output current of the grid-following converter respectively; i dm2 、i qm2 are the dq axis components of the output current of the grid-type converter respectively; L g is the grid inductance; ω0 is the rated angular velocity. Optionally, the damping torque model includes:

[0017]

[0018]

[0019]

[0020]

[0021]

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028] Where, I dm01 is the stable operating value of the d-axis component of the output current of the grid-following converter, I qm02 is the stable operating value of the q-axis component of the output current of the grid-type converter, U dm0 、U qm0 is the grid connection point voltage between the grid-forming converter and the grid-following converter, L g is the grid inductance, Y GFMrepresents the closed-loop transfer function of the network converter, G Mvd is the d-axis control transfer function of the voltage control loop of the grid-type energy storage, k p_Mud and k i_Mud They represent the proportional coefficient and integral coefficient of the voltage control loop of the grid-type energy storage, G Mid is the d-axis control transfer function of the current control loop of the grid-type energy storage, k p_Mid and k i_Mid They represent the proportional coefficient and integral coefficient of the current control loop of the grid-type converter, Y GFL It represents the closed-loop transfer function of the voltage and current control link of the grid-following converter, G Ldc is the voltage control loop transfer function of the grid-following converter, G Lid is the d-axis control transfer function of the current control loop of the grid-following converter, k p_Ldc , k i_Ldc They represent the proportional coefficient and integral coefficient of the voltage control loop of the grid-following converter respectively, k p_Lid , k i_Lid They represent the proportional coefficient and integral coefficient of the d-axis current control loop of the grid-following converter, D Q is the proportional coefficient of the virtual synchronization link of the network converter, G 12 G represents the damping transfer function of the grid-following converter on the grid-forming converter; 22 G represents the damping transfer function of the network converter acting on itself; 21 G represents the damping transfer function of the grid-forming converter on the grid-following converter; 11 G represents the damping transfer function of the grid-following converter acting on itself; 121 A represents the transfer function from input to output of the grid-forming converter when the small disturbance stability between the grid-following converter and the grid-forming converter is connected in parallel; M1 Indicates an intermediate quantity; L f1 Indicates the filter inductance of the grid-type converter; L f2 Represents the filter inductor of the grid-type converter.

[0029] Optionally, the interaction analytical formula includes:

[0030] Where, D 12ML Re represents the real part of the transfer function.

[0031] Optionally, after establishing the damping torque model when the grid-connected converter and the grid-following converter are connected to the grid based on the second grid-connected simulation model, the method further includes: Obtain the control parameters of the grid-following converter and the grid-forming converter, bring the operating parameters of the target power system at the operating equilibrium point into the damping torque model, and calculate the damping transfer function G of the grid-following converter on the grid-forming converter respectively. 12 , the damping transfer function G of the grid-type converter on the grid-type converter 21 And the small disturbance stability between the grid-type converter and the grid-type converter in parallel, the transfer function G from the input to the output of the grid-type converter 121 ; The G 12 , G 21 and G 121 Substitute it into the interaction analytical formula to analyze the interaction between the grid-forming converter and the grid-following converter.

[0032] Optionally, the control parameters include the voltage control loop proportional coefficient and integral coefficient of the grid-following converter, the current control loop proportional coefficient and integral coefficient of the grid-following converter, the voltage control loop proportional coefficient and integral coefficient of the grid-forming converter, and the current control loop proportional coefficient and integral coefficient of the grid-forming converter.

[0033] According to another aspect of the present invention, there is provided an interaction analysis device connected in parallel with a network and a network-forming converter, comprising: A first model building unit is used to build a first grid-connected simulation model when the grid-following converter and the grid-building converter are connected in parallel; A second model establishing unit, configured to establish a second grid-connected simulation model when the first grid-connected simulation model is connected to an AC system; A third model building unit is used to build a damping torque model when the grid-building converter and the grid-following converter are grid-connected based on the second grid-connected simulation model; A relationship establishing unit is used to construct an analytical expression of the interaction between the grid-forming converter and the grid-following converter based on the damping torque model, wherein the analytical expression of the interaction is related to a control parameter; the control parameter is used to compensate for the disturbance in the grid.

[0034] According to a third aspect of the present invention, there is further provided an electronic device, comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein, The memory stores a computer program executable by the at least one processor, and the computer program is executed by the at least one processor so that the at least one processor can perform the stability interaction analysis method in parallel with the grid / grid converter.

[0035] According to a fourth aspect of the present invention, a computer-readable storage medium is further provided, wherein the computer-readable storage medium stores computer instructions, and the computer instructions are used to implement the stability interaction analysis method of the parallel connection with the grid / grid-forming converter when the processor executes the computer instructions.

[0036] The technical solution of the present invention establishes a damping torque model for a parallel connection between a grid-following converter and a grid-forming converter. Using the damping transfer function, it constructs an analytical expression for the interaction between the two converters. This expression then quantitatively analyzes how this interaction changes with control parameters using the mutual damping coefficient. This approach clearly and quantitatively illustrates the dynamic coupling mechanism between the parallel connection of the grid-following converter and the grid-forming converter, effectively resolving the inability of previous research methods to quantitatively analyze the interaction mechanism between the two converters.

[0037] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present invention, nor is it intended to limit the scope of the present invention. Other features of the present invention will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0039] Figure 1 This is a flow chart of a stability interaction analysis method for parallel connection with a grid / network-forming converter provided by an embodiment of the present invention; Figure 2 Schematic diagram of the structure of a parallel system of a grid-following converter and a grid-forming converter in one embodiment of the present invention; Figure 3 A control block diagram of a phase-locked loop according to an embodiment of the present invention; Figure 4 This is a control block diagram of a grid-following converter in one embodiment of the present invention; Figure 5 This is a control block diagram of a voltage and current control loop of a network-type converter in one embodiment of the present invention; Figure 6 This is a block diagram of virtual synchronous control of a meshed converter in one embodiment of the present invention; Figure 7 This is a block diagram of a damping torque model of a parallel system of a grid-following converter and a grid-forming converter in one embodiment of the present invention; Figure 8 Schematic diagram of a calculation method of the damping coefficient in the damping torque model in one embodiment of the present invention; Figure 9 Schematic diagram of the structure of an interaction analysis device connected in parallel with a network and a network-forming converter in one embodiment of the present invention; Figure 10 A schematic structural diagram of an electronic device for implementing the stability interaction analysis method in parallel with a grid / network-connected converter according to an embodiment of the present invention. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the 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.

[0041] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0042] Figure 1 A flow chart of a method for analyzing the stability interaction of a grid / network-connected converter in parallel is provided for the first embodiment of the present invention. Figure 1 As shown, the method includes: S101. Establish a first grid-connected simulation model when a grid-following converter and a grid-forming converter are connected in parallel.

[0043] To simulate the model of the grid-following converter and the grid-forming converter in parallel, a dq impedance modeling method or a sequence impedance modeling method can be used. In this embodiment, only the dq impedance modeling method is analyzed.

[0044] The model for simulating a parallel connection between a grid-following converter and a grid-forming converter can include the primary and control systems of the grid-following and grid-forming converters. The primary model includes the grid-following converter model and the grid-forming converter model; the control model includes the control system model of the grid-following converter and the control system model of the grid-forming converter.

[0045] like Figure 2 The schematic diagram of the structure of the parallel system of the grid-following converter and the grid-forming converter shown in the figure includes the grid-following converter and the control system of the grid-following converter, the grid-forming converter and the control system of the grid-forming converter, and the circuit of the grid part.

[0046] In this embodiment, the first grid-connected simulation model refers to a model including a grid-following converter and its control system, a grid-forming converter and its control system. The following is a description of each model in the first grid-connected simulation model.

[0047] First, the process of establishing a grid-following converter model can include: Assume that the machine side of the grid-following converter can be a direct-drive wind turbine or a photovoltaic unit. The source side unit, permanent magnet synchronous generator and machine side converter of the direct-drive wind turbine unit / photovoltaic unit are equivalent to a controlled current source. Without loss of generality, the grid-following direct-drive wind turbine unit is set as unit 1, and the subscript of its physical quantity is represented by 1. Figure 2 The upper middle part is the equivalent circuit of the grid-type converter. Figure 2 The DC capacitor C is included in the grid-type converter model. dc1 , equivalent current source I dc01 The specific connection relationship of the grid-following converter is that the DC capacitor is connected in parallel with the equivalent current source, which serves as the input of the grid-following converter; the control system model of the grid-following converter includes a grid-following controller, which is used to obtain the output voltage u of the grid-following converter. abc1 and / or output current i abc1 , and adjust the output voltage u of the grid-following converter abc1 and / or output current i abc1 , output PWM1 signal as the input of the grid-following converter. The main circuit expression of the grid-following device is:

[0048] In the formula: In the formula, E d1 、E q1 Indicates the output voltage dq axis voltage of the grid-following converter; L f1 Indicates the filter inductance of the grid-type converter; u dm 、u qm are the dq axis components of the voltage at the grid-following converter terminal, i dm1 、iqm1 are the dq axis components of the output current of the grid-following converter respectively; C dc1 、U dc1 、P out1 、P in1 are the capacitance value, voltage value, output active power and input active power of the DC capacitor respectively; ω0 is the rated angular velocity.

[0049] Since the control system model of the grid-following converter includes the mathematical model of the phase-locked loop and the converter control system model, the phase-locked loop is used to obtain the output voltage u of the grid-following converter. abc1 and / or output current i abc1 The phase of the grid-following converter is adjusted to adjust the dq axis component u of the voltage and / or current at the end of the grid-following converter. dm 、u qm and / or i dm1 、i qm1 The phase of the converter control system is used to adjust the phase difference between the voltage and / or current output by the converter control system and the output voltage and / or current of the grid-following converter. The converter control system is used to control the dq-axis components of the voltage and / or current at the grid-following converter terminal and output the PWM2 signal to the grid-following converter. Therefore, the control system modeling of the grid-following device includes: The mathematical model of the phase-locked loop is:

[0050] Where k p_pll and k i_pll are the proportional and integral coefficients of the phase-locked loop respectively; x pll is the phase-locked loop state variable; θ pll is the angle of the phase-locked loop output. Figure 3 The block diagram of the phase-locked loop control in the figure shows that the output of the grid-type converter is u a ,u b ,u c ,u a ,u b ,u c There will be a certain delay after the dq axis transformation, and finally the dq axis component u of the output voltage of the grid-following converter is obtained. dm 、u qm In this embodiment, the phase-locked loop can calculate the angle of the phase-locked loop output to adjust the output of the grid-following converter to u a ,u b ,u c When performing dq axis transformation u dm 、u qm phase.

[0051] When modeling the grid-following converter control system, the voltage control loop can be set to consist of a DC capacitor voltage control. The DC capacitor voltage control gives a reference value for the active current by controlling the capacitor voltage; the reactive power setpoint is 0, which means that the grid-following wind turbine / photovoltaic unit does not generate reactive power. The current control loop controls the output current of the grid-side converter according to the active and reactive power command values ​​given by the voltage control loop, and ultimately outputs a modulated voltage E d1 、E q1 The grid-side converter control model can be found in Figure 4 The grid-side converter voltage and current control loop control block diagram is shown in FIG. , and the grid-side converter control system model is:

[0052] In the formula, Figure 4 As shown, the voltage control loop is composed of the DC capacitor voltage U dc1 Control composition, DC capacitor voltage control gives active current by controlling capacitor voltage i dref The reference value of reactive power is 0, which means that the grid-following converter does not generate reactive power. i qref The current control loop is based on the active and reactive current reference values ​​given by the voltage control loop. i dref and i qref , the dq axis component i of the output current of the grid-following converter dm1 and i qm1 Control and finally output modulation voltage u gd 、 u gq As the input of the grid-following converter; x udc Indicates the state quantity corresponding to the DC voltage control loop; x d 、x q They represent the state quantities corresponding to the d-axis current control loop and the q-axis current control loop respectively; k p_udc 、k i_udc are the proportional parameter and integral parameter of the DC voltage control loop respectively; k p_d 、k i_d are the proportional and integral parameters of the d-axis current control loop respectively; k p_q 、k i_q are the proportional and integral parameters of the q-axis current control loop respectively.

[0053] When modeling the grid-type converter, we can take the grid-type energy storage as an example and assume that the DC voltage of the grid-type energy storage remains constant. Without loss of generality, the grid-type energy storage is set as unit 2, and the subscript of its physical quantity is represented by 2. Figure 2The equivalent circuit of the mesh converter in the middle part. The mesh converter model includes the DC capacitor C dc2 , equivalent current source I dc02 And the network converter, its specific connection relationship is DC capacitor C dc2 Parallel equivalent current source I dc02 , as the input of the network converter; the control system model of the network converter includes a network controller, which obtains the output voltage u of the network converter abc2 and / or output current iabc2 , and adjust the output voltage and / or output current of the grid-forming converter, and output PWM2 as the input of the grid-following converter. Then the main circuit expression of the grid-forming device is:

[0054] Where: E d2 、E q2 Represents the dq axis voltage at the outlet of the grid-type converter; L f2 Represents the filter inductance of the network converter; u dm2 、u qm2 are the dq axis components of the voltage at the terminal of the grid-type converter, i dm2 、i qm2 are the dq axis components of the output current of the grid-type converter respectively; ω0 is the rated angular velocity.

[0055] When modeling the control system of a grid-type converter, the control system model of the grid-type converter includes the mathematical model of the active control link, the mathematical model of the reactive control link, and the mathematical model of the voltage and current control loop. In addition, the grid-type energy storage can use the virtual synchronous control link to simulate the characteristics of the synchronous machine. The active control link can simulate the rotor motion equation and primary frequency modulation, and the reactive control link simulates the excitation regulation process. The GFM reactive control link generates a virtual voltage based on the reactive reference value. The active control model can refer to Figure 6 The block diagram in the upper part of the figure shows that the mathematical model of the active power control link is:

[0056] Where ω is the angular velocity of the grid-type converter, P ref Represents the active reference value of the grid-type converter, P e2 Represents the active power of the grid-type converter; K D is the virtual damping coefficient; T j is the virtual inertia coefficient; θ v is the virtual power angle of the grid-type converter; ω0 is the rated angular velocity.

[0057] The reactive power control model can be referred to Figure 6 In the block diagram in the lower part of the figure, the mathematical model of the reactive power control link is:

[0058] Where, E v is the virtual voltage, Q ref Represents the reactive power reference value of the grid-type converter, Q e2 Represents the reactive power of the grid-type converter; K Q is the reactive droop coefficient, and U0 is the rated value of the voltage amplitude of the grid-type converter.

[0059] Afterwards, the virtual voltage Ev generates a reference voltage through the voltage and current double closed-loop control link, and the mathematical model of the voltage and current control loop is:

[0060] Where x Evd represents the state quantity corresponding to the d-axis of the voltage control loop of the network converter; x Evq represents the state quantity corresponding to the q-axis of the voltage control loop of the network converter; k p_ud 、k i_ud are the proportional and integral parameters of the d-axis voltage control loop respectively; k p_uq 、k i_uq are the proportional and integral parameters of the q-axis voltage control loop respectively; E vd 、E vq They are the inputs of the q-axis and d-axis voltage control loops, u dm2 、u qm2 are the dq axis components of the voltage at the terminal of the grid-type converter, i vdref 、i vqref are the reference values ​​of the current controller respectively; x id 、x iq They represent the state quantities corresponding to the current control loop respectively; k p_id 、k i_id are the proportional and integral parameters of the d-axis current control loop respectively; k p_iq 、k i_iq are the proportional and integral parameters of the q-axis current control loop respectively; L f2 Represents the filter inductance of the network converter; i dm2 、i qm2 are the dq axis components of the output current of the grid-type converter respectively. Figure 5 The control diagram of the network-type voltage control loop and current control loop is shown in the figure. Figure 5 In the virtual voltage Ev and E vq Input voltage control loop, generate reference value i for current control loop vdref 、i vqref The current control loop is based on the reference value i of the current controller given by the voltage control loop. vdref and i vqref, the dq axis component i of the output current of the grid-type converter dm2 and i qm2 Control is performed and the final output is the dq axis voltage E of the grid-type converter output. d2 、E q2 As the input of the network converter.

[0061] S102: Establish a second grid-connected simulation model when the first grid-connected simulation model is connected to an AC system.

[0062] The first grid-connected simulation model includes a grid-following converter model, a control system model of the grid-following converter, a grid-forming converter model, and a control system model of the grid-forming converter. The second grid-connected simulation model is a model of the entire power grid after the first grid-connected simulation model is connected to the power grid, that is, the second grid-connected simulation model includes a grid-following converter model, a control system model of the grid-following converter, a grid-forming converter model, a control system model of the grid-forming converter, and a model of the entire power grid.

[0063] In one embodiment, if Figure 2 The schematic diagram of the structure of the grid-following converter and the grid-forming converter when connected to the grid in parallel is shown. The second grid-connected simulation model is a model composed of the equivalent circuit after the output terminals of the grid-following converter and the grid-forming converter are both connected to the AC system power supply. The mathematical model of the entire grid in the second grid-connected simulation model is:

[0064] Where udm and uqm are the dq-axis components of the terminal voltage of the grid-forming converter, idm1 and iqm1 are the dq-axis components of the output current of the grid-following converter, idm2 and iqm2 are the dq-axis components of the output current of the grid-forming converter, Lg is the grid inductance, and ω0 is the rated angular velocity.

[0065] S103: Establishing a damping torque model when the grid-forming converter and the grid-following converter are grid-connected based on the second grid-connected simulation model.

[0066] This embodiment can construct a damping torque model based on a second grid-connected simulation model when a grid-type converter and a grid-forming converter are connected in parallel to a grid.

[0067] In one embodiment, the influence of grid-type energy storage on the small signal stability of grid-type wind-solar equipment can be quantitatively analyzed in the form of mutual damping coefficient. The damping torque model block diagram of the parallel system of grid-type converter and grid-type converter is as follows: Figure 7 As shown, Figure 7G12 represents the damping transfer function of the grid-type converter 1 on the grid-type converter 2; G22 represents the damping transfer function of the grid-type converter 2 on itself; G11 represents the damping transfer function of the grid-type converter 1 on itself; G21 represents the damping transfer function of the grid-type converter 2 on the grid-type converter 1; G121 represents the transfer function from the input to the output of the grid-type converter 2 when analyzing the small disturbance stability between the grid-type converter and the grid-type converter in parallel. In addition, Figure 7 Medium ΔQ e Represents the small disturbance of reactive power; ΔEv represents the small disturbance of output voltage of virtual synchronous link; Δi d1 Indicates the small disturbance of the d-axis current output by device 1; Δi d2 Indicates the small disturbance of the d-axis current output by device 2; ΔU dc1 Indicates the small disturbance of DC capacitor voltage; ΔP e1 Represents the small disturbance of the input active power of device 1.

[0068] The corresponding damping transfer function can be calculated separately, and the calculation formula is:

[0069]

[0070]

[0071]

[0072]

[0073]

[0074]

[0075]

[0076]

[0077]

[0078]

[0079]

[0080] Where, I dm01 is the stable operating value of the d-axis component of the output current of the grid-following converter, I qm02 is the stable operating value of the q-axis component of the output current of the grid-type converter, U dm0 、U qm0is the grid connection point voltage between the grid-forming converter and the grid-following converter, L g is the grid inductance, Y GFM represents the closed-loop transfer function of the network converter, G Mvd is the d-axis control transfer function of the voltage control loop of the grid-type energy storage, k p_Mud and k i_Mud They represent the proportional coefficient and integral coefficient of the voltage control loop of the grid-type energy storage, G Mid is the d-axis control transfer function of the current control loop of the grid-type energy storage, k p_Mid and k i_Mid They represent the proportional coefficient and integral coefficient of the current control loop of the grid-type converter, Y GFL It represents the closed-loop transfer function of the voltage and current control link of the grid-following converter, G Ldc is the voltage control loop transfer function of the grid-following converter, G Lid is the d-axis control transfer function of the current control loop of the grid-following converter, k p_Ldc , k i_Ldc They represent the proportional coefficient and integral coefficient of the voltage control loop of the grid-following converter respectively, k p_Lid , k i_Lid They represent the proportional coefficient and integral coefficient of the d-axis current control loop of the grid-following converter, D Q is the proportional coefficient of the virtual synchronization link of the network converter, G 12 G represents the damping transfer function of the grid-following converter on the grid-forming converter; 22 G represents the damping transfer function of the network converter acting on itself; 21 G represents the damping transfer function of the grid-forming converter on the grid-following converter; 11 G represents the damping transfer function of the grid-following converter acting on itself; 121 A represents the transfer function from input to output of the grid-forming converter when the small disturbance stability between the grid-following converter and the grid-forming converter is connected in parallel; M1 Represents an intermediate quantity.

[0081] S104: constructing an analytical expression for the interaction between the grid-forming converter and the grid-following converter based on the damping torque model, wherein the analytical expression for the interaction is related to a control parameter.

[0082] In this embodiment, the mutual damping coefficient D 12MLThe influence of the network-forming converter on the grid-following converter is quantitatively analyzed in the form of . Without loss of generality, the grid-following converter is set as converter 1 and the network-forming converter is set as converter 2. The expression is as follows:

[0083] Where: Re represents the real part of the transfer function. 12 G represents the damping transfer function of the grid-following converter 1 on the grid-forming converter 2; 22 G represents the damping transfer function of the network converter 2 acting on itself; 21 G represents the damping transfer function of the grid-forming converter 2 on the grid-following converter 1; 121 It represents the transfer function from the input to the output of the grid-type converter 2 when analyzing the small disturbance stability between the grid-type converter and the grid-type converter in parallel. Figure 8 is the calculation method of the damping coefficient in the damping torque model, where G(jω) can represent the G of the target power system at the operating equilibrium point. 12 , G 21 and G 121 The sum of the transfer function G 12 , G 21 and G 121 The mutual damping coefficient can be quickly determined by taking the real part of the sum.

[0084]

[0085] Among them, I dm01 is the stable operating value of the d-axis component of the output current of the grid-following wind and solar equipment, I qm02 is the stable operating value of the q-axis component of the output current of the grid-forming energy storage, that is, the mutual damping coefficient is related to the operating parameters of the grid-forming / grid-forming hybrid system in the stable state.

[0086] A damping torque model for a parallel connection between a grid-following converter and a grid-forming converter is established. The damping transfer function is used to construct an analytical expression for the interaction between the two converters. The mutual damping coefficient is then used to quantitatively analyze how this interaction varies with the control parameters. This method clearly and quantitatively illustrates the dynamic coupling mechanism between the parallel connection of the grid-following converter and the grid-forming converter, effectively resolving the inability of previous research methods to quantitatively analyze the interaction mechanism between the two converters.

[0087] In one embodiment, it further includes: Obtain the control parameters of the grid-following converter and the grid-forming converter, bring the operating parameters of the target power system at the operating equilibrium point into the damping torque model, and calculate the damping transfer function G of the grid-following converter on the grid-forming converter respectively. 12, the damping transfer function G of the grid-type converter on the grid-type converter 21 And the small disturbance stability between the grid-type converter and the grid-type converter in parallel, the transfer function G from the input to the output of the grid-type converter 121 ; The G 12 , G 21 and G 121 Substitute it into the interaction analytical formula to analyze the interaction between the grid-forming converter and the grid-following converter.

[0088] It should be noted that the control parameters of the grid-following converter and the grid-forming converter may at least include the voltage control loop proportional coefficient and integral coefficient of the grid-following wind-solar equipment, the current control loop proportional coefficient and integral coefficient of the grid-following wind-solar equipment, the voltage control loop proportional coefficient and integral coefficient of the grid-forming energy storage, and the current control loop proportional coefficient and integral coefficient of the grid-forming energy storage.

[0089] In one embodiment, the control parameters of the grid-following converter and the grid-forming converter may include: the proportional parameter and the integral parameter k of the DC voltage control loop of the grid-following converter p_udc 、k i_udc ; The proportional parameter and integral parameter k of the d-axis current control loop of the grid-following converter p_d 、k i_d ; The proportional parameter and integral parameter k of the q-axis current control loop of the grid-following converter p_q 、k i_q ; The proportional parameter and integral parameter k of the q-axis voltage control loop of the grid-type converter p_uq 、k i_uq ; The proportional parameter and integral parameter k of the d-axis voltage control loop of the grid-type converter p_ud 、k i_ud ; The proportional parameter and integral parameter k of the d-axis current control loop of the grid-type converter p_id 、k i_id ; The proportional parameter and integral parameter k of the q-axis current control loop of the grid-type converter p_iq 、k i_iq ; Proportional coefficient and integral coefficient of the voltage control loop of grid-type energy storage k p_mud and k i_mud ; The voltage control loop proportional coefficient and integral coefficient of the grid-following wind and solar equipment k p_Ldc 、 k i_Ldc ; respectively follow the proportional coefficient and integral coefficient of the d-axis current control loop of the grid-type wind and solar equipment k p_Lid 、 k i_Lid .

[0090] When the power system is at a balance point, that is, the grid-following converter and the grid-forming converter are connected to the same grid, a balance is achieved. Its operating parameters include the stable operating value of the d-axis component of the output current of the grid-following wind and solar equipment, I dm01 , the q-axis component of the output current of the grid-type energy storage is the stable operating value I qm02 ; Grid connection point voltage U of grid-connected energy storage and grid-following wind and solar equipment dm0 、U qm0 .

[0091] G 12 , G 21 and G 121 By substituting this into the interaction equation, we can track the relationship between the mutual damping coefficient and the change of the control parameters by adjusting the control parameters, thereby analyzing the interaction between the grid-type converter and the follow-grid type converter.

[0092] Figure 9 This is a schematic diagram of the structure of an interaction analysis device connected in parallel with a network and a network-forming converter provided in the third embodiment of the present invention. Figure 9 As shown, the device includes: A first model building unit 701 is used to build a first grid-connected simulation model when a grid-following converter and a grid-forming converter are connected in parallel; A second model establishing unit 702 is configured to establish a second grid-connected simulation model when the first grid-connected simulation model is connected to an AC system; A third model building unit 703 is configured to build a damping torque model when the grid-connected converter and the grid-following converter are connected to the grid based on the second grid-connected simulation model; The relationship establishing unit 704 is configured to construct an analytical expression for the interaction between the grid-forming converter and the grid-following converter based on the damping torque model, wherein the analytical expression for the interaction is related to the control parameters.

[0093] In one embodiment, the first grid-connected simulation model in the first model building unit 701 includes a grid-following converter model, a control system model of the grid-following converter, a grid-forming converter model, and a control system model of the grid-forming converter.

[0094] In one embodiment, the grid-following converter model is: ; Where, E d1 、E q1 Indicates the output voltage dq axis voltage of the grid-following converter; L f1 Indicates the filter inductance of the grid-type converter; u dm 、u qm are the dq axis components of the voltage at the grid-following converter terminal, idm1 、i qm1 are the dq axis components of the output current of the grid-following converter respectively; C dc1 、U dc1 、P out1 、P in1 are the capacitance value, voltage value, output active power and input active power of the DC capacitor respectively; ω0 is the rated angular velocity; The control system model of the grid-following converter includes a mathematical model of a phase-locked loop and a converter control system model; the phase-locked loop is used to obtain the phase of the output voltage and / or output current of the grid-following converter, and adjust the phase of the dq-axis components of the voltage and / or current at the grid-following converter terminal to adjust the phase difference between the voltage and / or current output by the converter control system and the output voltage and / or output current of the grid-following converter; the converter control system is used to control the dq-axis components of the voltage and / or current at the grid-following converter terminal, and output the controlled voltage and / or current to the grid-following converter; The mathematical model of the phase-locked loop is:

[0095] Where k p_pll and k i_pll are the proportional and integral coefficients of the phase-locked loop respectively; x pll is the phase-locked loop state variable; θ pll is the angle of the phase-locked loop output; The converter control system model is:

[0096] In the formula, the voltage control loop is composed of the DC capacitor voltage control, which gives the reference value of the active current by controlling the capacitor voltage; the reactive power set value is 0, which means that the grid-following converter does not generate reactive power; U dc1 is the DC capacitor voltage, u dcref is the reference value of the DC capacitor voltage, i qref The current control loop is based on the active and reactive current reference values ​​given by the voltage control loop. i dref and i qref , the dq axis component i of the output current of the grid-following converter dm1 and i qm1 Control and finally output modulation voltage u gd 、 u gq As the input of the grid-following converter; x udcIndicates the state quantity corresponding to the DC voltage control loop; x d 、x q They represent the state quantities corresponding to the d-axis current control loop and the q-axis current control loop respectively; k p_udc 、k i_udc are the proportional parameter and integral parameter of the DC voltage control loop respectively; k p_d 、k i_d are the proportional and integral parameters of the d-axis current control loop respectively; k p_q 、k i_q are the proportional and integral parameters of the q-axis current control loop respectively.

[0097] In one embodiment, the meshed converter model is:

[0098] Where: E d2 、E q2 Represents the dq axis voltage at the outlet of the grid-type converter; L f2 Represents the filter inductance of the network converter; u dm2 、u qm2 are the dq axis components of the voltage at the terminal of the grid-type converter, i dm2 、i qm2 are the dq axis components of the output current of the grid-type converter respectively; ω0 is the rated angular velocity; The control system model of the grid-type converter includes the mathematical model of the active control link, the mathematical model of the reactive control link and the mathematical model of the voltage and current control loop; The mathematical model of the active power control link is:

[0099] Where ω is the angular velocity of the grid-type converter, P ref Represents the active reference value of the grid-type converter, P e2 Represents the active power of the grid-type converter; K D is the virtual damping coefficient; T j is the virtual inertia coefficient; θ v is the virtual power angle of the grid-type converter; ω0 is the rated angular velocity; The mathematical model of the reactive power control link is:

[0100] Where, E v is the virtual voltage, Q ref Represents the reactive power reference value of the grid-type converter, Q e2 Represents the reactive power of the grid-type converter; K Q is the reactive droop coefficient, U0 is the rated value of the voltage amplitude of the grid-type converter; The mathematical models of the voltage control loop and current control loop of the grid-type converter are:

[0101] Where x Evd represents the state quantity corresponding to the d-axis of the voltage control loop of the network converter; x Evq represents the state quantity corresponding to the q-axis of the voltage control loop of the network converter; k p_ud 、k i_ud are the proportional and integral parameters of the d-axis voltage control loop respectively; k p_uq 、k i_uq are the proportional and integral parameters of the q-axis voltage control loop respectively; E vd 、E vq They are the inputs of the q-axis and d-axis voltage control loops, u dm2 、u qm2 are the dq axis components of the voltage at the terminal of the grid-type converter, i vdref 、i vqref are the reference values ​​of the current controller respectively; x id 、x iq They represent the state quantities corresponding to the current control loop respectively; k p_id 、k i_id are the proportional and integral parameters of the d-axis current control loop respectively; k p_iq 、k i_iq are the proportional and integral parameters of the q-axis current control loop respectively; L f2 Represents the filter inductance of the network converter; i dm2 、i qm2 are the dq axis components of the output current of the grid-type converter respectively; the current control loop is based on the reference value i of the current controller given by the voltage control loop vdref and i vqref , the dq axis component i of the output current of the grid-type converter dm2 and i qm2 Control is performed and the final output is the dq axis voltage E of the grid-type converter output. d2 、E q2 As the input of the network converter.

[0102] In one embodiment, the second grid-connected simulation model is a model formed by an equivalent circuit after the output terminals of the grid-following converter and the grid-connecting converter are both connected to the AC system power supply; the grid mathematical model in the second grid-connected simulation model is:

[0103] Where u dm 、u qm are the dq axis components of the voltage at the terminal of the grid-type converter respectively; idm1 、i qm1 are the dq axis components of the output current of the grid-following converter respectively; i dm2 、i qm2 are the dq axis components of the output current of the grid-type converter respectively; L g is the grid inductance; ω0 is the rated angular velocity.

[0104] In one embodiment, the damping torque model includes:

[0105]

[0106]

[0107]

[0108]

[0109]

[0110]

[0111]

[0112]

[0113]

[0114]

[0115]

[0116] Where, I dm01 is the stable operating value of the d-axis component of the output current of the grid-following converter, I qm02 is the stable operating value of the q-axis component of the output current of the grid-type converter, U dm0 、U qm0 is the grid connection point voltage between the grid-forming converter and the grid-following converter, L g is the grid inductance, Y GFM represents the closed-loop transfer function of the network converter, G Mvd is the d-axis control transfer function of the voltage control loop of the grid-type energy storage, k p_Mud and k i_Mud They represent the proportional coefficient and integral coefficient of the voltage control loop of the grid-type energy storage, G Mid is the d-axis control transfer function of the current control loop of the grid-type energy storage, kp_Mid and k i_Mid They represent the proportional coefficient and integral coefficient of the current control loop of the grid-type converter, Y GFL It represents the closed-loop transfer function of the voltage and current control link of the grid-following converter, G Ldc is the voltage control loop transfer function of the grid-following converter, G Lid is the d-axis control transfer function of the current control loop of the grid-following converter, k p_Ldc , k i_Ldc They represent the proportional coefficient and integral coefficient of the voltage control loop of the grid-following converter respectively, k p_Lid , k i_Lid They represent the proportional coefficient and integral coefficient of the d-axis current control loop of the grid-following converter, D Q is the proportional coefficient of the virtual synchronization link of the network converter, G 12 G represents the damping transfer function of the grid-following converter on the grid-forming converter; 22 G represents the damping transfer function of the network converter acting on itself; 21 G represents the damping transfer function of the grid-forming converter on the grid-following converter; 11 G represents the damping transfer function of the grid-following converter acting on itself; 121 A represents the transfer function from input to output of the grid-forming converter when the small disturbance stability between the grid-following converter and the grid-forming converter is connected in parallel; M1 Indicates an intermediate quantity; L f1 Indicates the filter inductance of the grid-type converter; L f2 Represents the filter inductor of the grid-type converter.

[0117] In one embodiment, the interaction equation includes:

[0118] Where, D 12ML Re represents the real part of the transfer function.

[0119] In one embodiment, after establishing the damping torque model when the grid-connected converter and the grid-following converter are connected to the grid based on the second grid-connected simulation model, the method further includes: Obtain the control parameters of the grid-following converter and the grid-forming converter, bring the operating parameters of the target power system at the operating equilibrium point into the damping torque model, and calculate the damping transfer function G of the grid-following converter on the grid-forming converter respectively.12 , the damping transfer function G of the grid-type converter on the grid-type converter 21 And the small disturbance stability between the grid-type converter and the grid-type converter in parallel, the transfer function G from the input to the output of the grid-type converter 121 ; The G 12 , G 21 and G 121 Substitute it into the interaction analytical formula to analyze the interaction between the grid-forming converter and the grid-following converter.

[0120] In one embodiment, the control parameters include the voltage control loop proportional coefficient and integral coefficient of the grid-following converter, the current control loop proportional coefficient and integral coefficient of the grid-following converter, the voltage control loop proportional coefficient and integral coefficient of the grid-forming converter, and the current control loop proportional coefficient and integral coefficient of the grid-forming converter.

[0121] The stability interaction analysis method and device for parallel connection of a grid / grid-forming converter provided in an embodiment of the present invention can execute the stability interaction analysis method for parallel connection of a grid / grid-forming converter provided in any embodiment of the present invention, and has functional modules and beneficial effects corresponding to the execution method.

[0122] An embodiment of the present invention further provides an electronic device, comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein, The memory stores a computer program executable by the at least one processor, and the computer program is executed by the at least one processor so that the at least one processor can perform the stability interaction analysis method in parallel with the grid / grid converter.

[0123] In one embodiment of the present invention, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores computer instructions, and the computer instructions are used to implement the stability interaction analysis method in parallel with the grid / grid converter when executed by a processor.

[0124] Figure 10A schematic diagram of an electronic device 10 that can be used to implement an embodiment of the present invention is shown. The electronic device is intended to represent various forms of digital computers, such as laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The electronic device can also represent various forms of mobile devices, such as personal digital assistants, cellular phones, smartphones, wearable devices (such as helmets, glasses, watches, etc.), and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely examples and are not intended to limit the implementation of the present invention described and / or claimed herein.

[0125] like Figure 10 As shown, electronic device 10 includes at least one processor 11 and memory, such as read-only memory (ROM) 12 and random access memory (RAM) 13, communicatively connected to at least one processor 11. The memory stores computer programs executable by the at least one processor. Processor 11 can perform various appropriate actions and processes based on the computer programs stored in ROM 12 or loaded from storage unit 18 into RAM 13. RAM 13 can also store various programs and data required for the operation of electronic device 10. Processor 11, ROM 12, and RAM 13 are interconnected via bus 14. An input / output (I / O) interface 15 is also connected to bus 14.

[0126] Multiple components in the electronic device 10 are connected to the I / O interface 15, including an input unit 16, such as a keyboard, a mouse, etc.; an output unit 17, such as various types of displays, speakers, etc.; a storage unit 18, such as a magnetic disk, an optical disk, etc.; and a communication unit 19, such as a network card, a modem, a wireless communication transceiver, etc. The communication unit 19 allows the electronic device 10 to exchange information / data with other devices via a computer network such as the Internet and / or various telecommunication networks.

[0127] Processor 11 can be any general-purpose and / or specialized processing component with processing and computing capabilities. Examples of processor 11 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various specialized artificial intelligence (AI) computing chips, various processors running machine learning model algorithms, digital signal processors (DSPs), and any other suitable processor, controller, microcontroller, etc. Processor 11 executes the various methods and processes described above, such as the stability interaction analysis method in parallel with a grid / intergrid converter.

[0128] In some embodiments, the stability interaction analysis method for parallel connection of a grid / network-forming converter can be implemented as a computer program tangibly embodied in a computer-readable storage medium, such as storage unit 18. In some embodiments, part or all of the computer program can be loaded and / or installed on electronic device 10 via ROM 12 and / or communication unit 19. When the computer program is loaded into RAM 13 and executed by processor 11, one or more steps of the stability interaction analysis method for parallel connection of a grid / network-forming converter described above can be performed. Alternatively, in other embodiments, processor 11 can be configured to execute a stability interaction analysis method for parallel connection of a grid / network-forming converter in any other suitable manner (e.g., via firmware).

[0129] Various embodiments of the systems and techniques described above can be implemented in digital electronic circuit systems, integrated circuit systems, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), system-on-chip systems (SOCs), programmable logic devices (CPLDs), computer hardware, firmware, software, and / or combinations thereof. These various embodiments can include being implemented in one or more computer programs that are executable and / or interpreted on a programmable system that includes at least one programmable processor, which can be a special purpose or general purpose programmable processor that can receive data and instructions from a storage system, at least one input device, and at least one output device, and transmit data and instructions to the storage system, the at least one input device, and the at least one output device.

[0130] Computer programs for implementing the methods of the present invention may be written in any combination of one or more programming languages. These computer programs may be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device, such that when the computer program is executed by the processor, the functions / operations specified in the flowcharts and / or block diagrams are implemented. The computer program may be executed entirely on the machine, partially on the machine, as a stand-alone software package, partially on the machine and partially on a remote machine, or entirely on a remote machine or server.

[0131] In the context of the present invention, a computer-readable storage medium may be a tangible medium that may contain or store a computer program for use by or in conjunction with an instruction execution system, device, or apparatus. A computer-readable storage medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, device, or apparatus, or any suitable combination of the foregoing. Alternatively, a computer-readable storage medium may be a machine-readable signal medium. More specific examples of machine-readable storage media may include an electrical connection based on one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0132] To provide interaction with a user, the systems and techniques described herein can be implemented on an electronic device that has: a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user; and a keyboard and pointing device (e.g., a mouse or trackball) through which the user can provide input to the electronic device. Other types of devices can also be used to provide interaction with the user; for example, the feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form (including acoustic input, voice input, or tactile input).

[0133] The systems and techniques described herein can be implemented in a computing system that includes back-end components (e.g., as a data server), or a computing system that includes middleware components (e.g., an application server), or a computing system that includes front-end components (e.g., a user computer with a graphical user interface or web browser through which a user can interact with implementations of the systems and techniques described herein), or a computing system that includes any combination of such back-end components, middleware components, or front-end components. The components of the system can be interconnected by any form or medium of digital data communication (e.g., a communication network). Examples of communication networks include: a local area network (LAN), a wide area network (WAN), a blockchain network, and the Internet.

[0134] A computing system may include clients and servers. The clients and servers are typically remote from each other and typically interact via a communication network. This client-server relationship arises through computer programs running on the respective computers, creating a client-server relationship. The server may be a cloud server, also known as a cloud computing server or cloud host. This server is a hosting product within the cloud computing service ecosystem that addresses the management difficulties and limited scalability of traditional physical hosting and VPS services.

[0135] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in the present invention can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution of the present invention can be achieved. This is not limited herein.

[0136] The above specific embodiments do not limit the scope of protection of the present invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A stability interaction analysis method for parallel connection of grid / network-connected converters, characterized in that: include: Establishing a first grid-connected simulation model when a grid-following converter and a grid-forming converter are connected in parallel; Establishing a second grid-connected simulation model when the first grid-connected simulation model is connected to an AC system; Establishing a damping torque model when the grid-forming converter and the grid-following converter are grid-connected based on the second grid-connected simulation model; Based on the damping torque model, an analytical expression of the interaction between the grid-forming converter and the grid-following converter is constructed, and the analytical expression of the interaction is related to the control parameters of the grid-forming converter; the control parameters are used to compensate for the disturbance in the power grid.

2. The stability interaction analysis method for parallel connection of grid / network converters according to claim 1 is characterized in that: The establishing of a first grid-connected simulation model when the grid-following converter and the grid-building converter are connected in parallel includes: The first grid-connected simulation model includes a grid-following converter model, a control system model of the grid-following converter, a grid-forming converter model, and a control system model of the grid-forming converter.

3. The stability interaction analysis method for parallel connection of grid / network-connected converters according to claim 2, characterized in that: The grid-following converter model is: ； Where, E d1 、E q1 Indicates the output voltage dq axis voltage of the grid-following converter; L f1 Indicates the filter inductance of the grid-type converter; u dm 、u qm are the dq axis components of the voltage at the grid-following converter terminal, i dm1 、i qm1 are the dq axis components of the output current of the grid-following converter respectively; C dc1 、U dc1 、P out1 、P in1 are the capacitance value, voltage value, output active power and input active power of the DC capacitor respectively; ω0 is the rated angular velocity; The control system model of the grid-following converter includes a mathematical model of a phase-locked loop and a converter control system model; the phase-locked loop is used to obtain the phase of the output voltage and / or output current of the grid-following converter, and adjust the phase of the dq-axis components of the voltage and / or current at the grid-following converter terminal to adjust the phase difference between the voltage and / or current output by the converter control system and the output voltage and / or output current of the grid-following converter; the converter control system is used to control the dq-axis components of the voltage and / or current at the grid-following converter terminal, and output the controlled voltage and / or current to the grid-following converter; The mathematical model of the phase-locked loop is: Where k p_pll and k i_pll are the proportional and integral coefficients of the phase-locked loop respectively; x pll is the phase-locked loop state variable; θ pll is the angle of the phase-locked loop output; The converter control system model is: In the formula, the voltage control loop is composed of the DC capacitor voltage control, which gives the reference value of the active current by controlling the capacitor voltage; the reactive power set value is 0, which means that the grid-following converter does not generate reactive power; U dc1 is the DC capacitor voltage, u dcref is the reference value of the DC capacitor voltage, i qref is the reactive current reference value; The current control loop is based on the active and reactive current reference values ​​given by the voltage control loop. i dref and i qref , the dq axis component i of the output current of the grid-following converter dm1 and i qm1 Control and finally output modulation voltage u gd 、 u gq As the input of the grid-following converter; x udc Indicates the state quantity corresponding to the DC voltage control loop; x d 、x q They represent the state quantities corresponding to the d-axis current control loop and the q-axis current control loop respectively; k p_udc 、k i_udc are the proportional parameter and integral parameter of the DC voltage control loop respectively; k p_d 、k i_d are the proportional and integral parameters of the d-axis current control loop respectively; k p_q 、k i_q are the proportional and integral parameters of the q-axis current control loop respectively.

4. The stability interaction analysis method for parallel connection of grid / network converters according to claim 2, characterized in that: The network-type converter model is: Where: E d2 、E q2 Represents the dq axis voltage at the outlet of the grid-type converter; L f2 Represents the filter inductance of the network converter; u dm2 、u qm2 are the dq axis components of the voltage at the terminal of the grid-type converter, i dm2 、i qm2 are the dq axis components of the output current of the grid-type converter respectively; ω0 is the rated angular velocity; The control system model of the grid-type converter includes the mathematical model of the active control link, the mathematical model of the reactive control link and the mathematical model of the voltage and current control loop; The mathematical model of the active power control link is: Where ω is the angular velocity of the grid-type converter, P ref Represents the active reference value of the grid-type converter, P e2 Represents the active power of the grid-type converter; K D is the virtual damping coefficient; T j is the virtual inertia coefficient; θ v is the virtual power angle of the grid-type converter; ω0 is the rated angular velocity; The mathematical model of the reactive power control link is: Where, E v is the virtual voltage, Q ref Represents the reactive power reference value of the grid-type converter, Q e2 Represents the reactive power of the grid-type converter; K Q is the reactive droop coefficient, U0 is the rated value of the voltage amplitude of the grid-type converter; The mathematical models of the voltage control loop and current control loop of the grid-type converter are: Where x Evd represents the state quantity corresponding to the d-axis of the voltage control loop of the network converter; x Evq represents the state quantity corresponding to the q-axis of the voltage control loop of the network converter; k p_ud 、k i_ud are the proportional and integral parameters of the d-axis voltage control loop respectively; k p_uq 、k i_uq are the proportional and integral parameters of the q-axis voltage control loop respectively; E vd 、E vq They are the inputs of the q-axis and d-axis voltage control loops, u dm2 、u qm2 are the dq axis components of the voltage at the terminal of the grid-type converter, i vdref 、i vqref are the reference values ​​of the current controller; x id 、x iq They represent the state quantities corresponding to the current control loop respectively; k p_id 、k i_id are the proportional and integral parameters of the d-axis current control loop respectively; k p_iq 、k i_iq are the proportional and integral parameters of the q-axis current control loop respectively; L f2 Represents the filter inductance of the network converter; i dm2 、i qm2 are the dq axis components of the output current of the grid-type converter respectively; the current control loop is based on the reference value i of the current controller given by the voltage control loop vdref and i vqref , the dq axis component i of the output current of the grid-type converter dm2 and i qm2 Control is performed and the final output is the dq axis voltage E of the grid-type converter output. d2 、E q2 As the input of the network converter.

5. The stability interaction analysis method for parallel connection of grid / network-connected converters according to claim 1, characterized in that: The second grid-connected simulation model is a model composed of an equivalent circuit after the output terminals of the grid-following converter and the grid-connecting converter are both connected to the AC system power supply; the grid mathematical model in the second grid-connected simulation model is: Where u dm 、u qm are the dq axis components of the voltage at the terminal of the grid-type converter respectively; i dm1 、i qm1 are the dq axis components of the output current of the grid-following converter respectively; i dm2 、i qm2 are the dq axis components of the output current of the grid-type converter respectively; L g is the grid inductance; ω0 is the rated angular velocity.

6. The stability interaction analysis method for parallel connection of grid / network-connected converters according to claim 5, characterized in that: The damping torque model includes: Where, I dm01 is the stable operating value of the d-axis component of the output current of the grid-following converter, I qm02 is the stable operating value of the q-axis component of the output current of the grid-type converter, U dm0 、U qm0 is the grid connection point voltage of the grid-forming converter and the grid-following converter, L g is the grid inductance, Y GFM represents the closed-loop transfer function of the network converter, G Mvd is the d-axis control transfer function of the voltage control loop of the grid-type energy storage, k p_Mud and k i_Mud They represent the proportional coefficient and integral coefficient of the voltage control loop of the grid-type energy storage, G Mid is the d-axis control transfer function of the current control loop of the grid-type energy storage, k p_Mid and k i_Mid They represent the proportional coefficient and integral coefficient of the current control loop of the grid-type converter, Y GFL It represents the closed-loop transfer function of the voltage and current control link of the grid-following converter, G Ldc is the voltage control loop transfer function of the grid-following converter, G Lid is the d-axis control transfer function of the current control loop of the grid-following converter, k p_Ldc , k i_Ldc They represent the proportional coefficient and integral coefficient of the voltage control loop of the grid-following converter respectively, k p_Lid , k i_Lid They represent the proportional coefficient and integral coefficient of the d-axis current control loop of the grid-following converter, D Q is the proportional coefficient of the virtual synchronization link of the network converter, G 12 G represents the damping transfer function of the grid-following converter on the grid-forming converter; 22 G represents the damping transfer function of the network converter acting on itself; 21 G represents the damping transfer function of the grid-forming converter on the grid-following converter; 11 G represents the damping transfer function of the grid-following converter acting on itself; 121 A represents the transfer function from input to output of the grid-forming converter when the small disturbance stability between the grid-following converter and the grid-forming converter is connected in parallel; M1 Indicates an intermediate quantity; L f1 Indicates the filter inductance of the grid-type converter; L f2 Represents the filter inductor of the grid-type converter.

7. The stability interaction analysis method for parallel connection of grid / network-connected converters according to claim 6, characterized in that: The interaction analytical formula includes: Where, D 12ML Re represents the real part of the transfer function.

8. The stability interaction analysis method for parallel connection of grid / network-connected converters according to claim 1, characterized in that: After establishing the damping torque model when the grid-connected converter and the grid-following converter are connected to the grid based on the second grid-connected simulation model, the method further includes: Obtain the control parameters of the grid-following converter and the grid-forming converter, bring the operating parameters of the target power system at the operating equilibrium point into the damping torque model, and calculate the damping transfer function G of the grid-following converter on the grid-forming converter respectively. 12 , the damping transfer function G of the grid-type converter on the grid-type converter 21 And the small disturbance stability between the grid-type converter and the grid-type converter in parallel, the transfer function G from the input to the output of the grid-type converter 121 ; The G 12 , G 21 and G 121 Substitute it into the interaction analytical formula to analyze the interaction between the grid-forming converter and the grid-following converter.

9. The stability interaction analysis method for parallel connection of grid / network-connected converters according to claim 8, characterized in that: The control parameters include the voltage control loop proportional coefficient and integral coefficient of the grid-following converter, the current control loop proportional coefficient and integral coefficient of the grid-following converter, the voltage control loop proportional coefficient and integral coefficient of the grid-forming converter, and the current control loop proportional coefficient and integral coefficient of the grid-forming converter.

10. A stability interaction analysis device connected in parallel with a grid / network converter, characterized in that: include: A first model building unit is used to build a first grid-connected simulation model when the grid-following converter and the grid-building converter are connected in parallel; A second model establishing unit, configured to establish a second grid-connected simulation model when the first grid-connected simulation model is connected to an AC system; A third model building unit is used to build a damping torque model when the grid-building converter and the grid-following converter are grid-connected based on the second grid-connected simulation model; A relationship establishing unit is used to construct an analytical expression of the interaction between the grid-forming converter and the grid-following converter based on the damping torque model, wherein the analytical expression of the interaction is related to a control parameter; the control parameter is used to compensate for the disturbance in the grid.

Images