Parameter security domain determination method and system for grid connection of power electronic device, and medium

Abstract

The invention discloses a parameter security domain determination method and system for power electronic device grid connection and a medium. The method comprises the steps of obtaining target data corresponding to a power electronic device; based on the target data, establishing a corresponding negative feedback frequency domain model with a phase-locked loop transfer function as a forward path and an outer loop transfer function as a feedback path, and based on the negative feedback frequency domain model, obtaining an open loop transfer function; based on the open-loop transfer function, obtaining a phase-frequency feature and an amplitude-frequency feature corresponding to the open-loop transfer function, and determining a stability margin of the power system based on the amplitude-frequency feature; and determining a phase-locked loop parameter security domain range corresponding to the power electronic device based on the stability margin. According to the method, the security domain range of the parameters of the power electronic device can be simply and accurately determined under the consideration of the interaction effect of the phase-locked loop and the outer loop in the power electronic system.

Description

Technical Field

[0001] The present application relates to the field of power electronic devices, and in particular to a method, system and medium for determining a parameter safety domain of a power electronic device connected to a grid. Background Art

[0002] With the rapid development of electric power technology, more and more power electronic equipment are being integrated into modern power grids on a large scale. The interaction between power electronic equipment and the power grid will cause oscillations in the subsynchronous and supersynchronous frequency ranges of the power grid. This oscillation will not only affect the normal operation of the power grid and reduce the stability of the system, but also pose a serious threat to the safe and stable operation of the power system. Therefore, in-depth research on the stability mechanism and stability conditions of power electronic equipment when connected to the power grid has become an important issue that needs to be urgently solved in the current power system field.

[0003] In the existing power electronics technology, the Phase-Locked Loop (PLL) is a key component for synchronization and phase detection. The determination of the safe domain range of its parameters is crucial to ensuring the stable operation of the entire power system. However, traditional methods often only adjust certain specific links or components in the power electronics system, ignoring the complex interactions between these links. At the same time, the existing phase-locked loop parameter adjustment method is complicated and overly conservative. Therefore, considering the interactions between various links in the power electronics system, seeking a simple and accurate method to adjust the safe domain range of the phase-locked loop parameters to ensure the stable operation of the system under various working conditions has become an important issue that needs to be urgently solved in the current power electronics technology field.

[0004] Application Contents

[0005] The present application provides a method, system and medium for determining the parameter safety domain of power electronic devices connected to the grid, which simply and accurately determines the safety domain range of power electronic device parameters while taking into account the interaction between the phase-locked loop and the outer loop in the power electronic system.

[0006] In a first aspect, the present application provides a method for determining a parameter safety domain of a power electronic device connected to a grid, comprising:

[0007] Acquiring target data corresponding to the power electronic device;

[0008] Based on the target data, a corresponding negative feedback frequency domain model is established with a phase-locked loop transfer function as a forward path and an outer loop transfer function as a feedback path, and an open-loop transfer function is obtained based on the negative feedback frequency domain model;

[0009] Based on the open-loop transfer function, a phase-frequency characteristic and an amplitude-frequency characteristic corresponding to the open-loop transfer function are obtained, and a stability margin of the power system is determined based on the amplitude-frequency characteristic;

[0010] Based on the stability margin, a safe domain range of a phase-locked loop parameter corresponding to the power electronic device is determined.

[0011] The embodiment of the present application obtains the target data corresponding to the power electronic device, thereby facilitating the subsequent accurate determination of the negative feedback model with the phase-locked loop transfer function as the forward path and the outer loop transfer function as the feedback path, thereby facilitating the subsequent determination of the safety domain range of the power electronic device parameters; by establishing a negative feedback model with the phase-locked loop transfer function as the forward path and the outer loop transfer function as the feedback path, the open-loop transfer function can be accurately determined, facilitating the subsequent determination of the phase-frequency characteristics and amplitude-frequency characteristics, thereby understanding the influence of the interaction between the phase-locked loop and the outer loop on the system stability, thereby facilitating the subsequent determination of the safety domain range of the power electronic device parameters; by determining the stability margin of the power system, the safety domain range of the power electronic device parameters can be simply and accurately determined while taking into account the interaction between the phase-locked loop and the outer loop in the power electronic system.

[0012] Furthermore, the target data includes: electrical parameters, circuit diagram and control strategy, the electrical parameters include: transmission line impedance, power frequency angular velocity and input power, the circuit diagram is the circuit diagram corresponding to when the power electronic device is connected to the power grid, and the control strategy is the strategy corresponding to when the power electronic device is connected to the power grid.

[0013] In this way, by obtaining the target data corresponding to the power electronic device, it is convenient to accurately determine the negative feedback model in the subsequent process, and thus it is convenient to determine the safety domain range of the power electronic device parameters in the subsequent process.

[0014] Furthermore, based on the target data, a corresponding negative feedback frequency domain model is established with the phase-locked loop transfer function as the forward path and the outer loop transfer function as the feedback path, specifically:

[0015] Based on the target data, respectively calculating a phase-locked loop transfer function and an outer loop transfer function;

[0016] A negative feedback frequency domain model is established with the phase-locked loop transfer function as a forward path and the outer loop transfer function as a feedback path.

[0017] In this way, by establishing a negative feedback model, the open-loop transfer function can be accurately determined, which facilitates the subsequent determination of the phase-frequency characteristics and amplitude-frequency characteristics, and then understands the influence of the interaction between the unlocked loop and the outer loop on the system stability, which facilitates the subsequent determination of the safe domain range of the power electronic device parameters.

[0018] Furthermore, the calculation formula of the phase-locked loop transfer function is:

[0019]

[0020] In the formula, G pll (s) is the phase-locked loop transfer function, Δθ pll is the angle between the xy coordinate system and the dq coordinate system, ΔI d is the line current in the dq coordinate system, ω0 is the steady-state value of the power frequency angular velocity, L g is the grid side reactance, k p,pll is the proportional coefficient of the phase-locked loop, k i,pll is the integral coefficient of the phase-locked loop, s is the differential operator, U g is the grid side voltage, θ pll0 is the steady-state value of the phase-locked loop angle, I d0 is the steady-state value of the line current in the dq coordinate system;

[0021] Wherein, the calculation formula of the outer loop transfer function is:

[0022]

[0023] In the formula, G ocl (s) is the outer loop transfer function, k p,ocl is the proportional coefficient of the outer ring, k i,ocl is the integral coefficient of the outer loop, s is the differential operator, C dc is the DC capacitance, U dc0 is the steady-state value of the DC voltage outer loop, U g is the grid side voltage, I d0 is the steady-state value of the line current in the dq coordinate system, θ pll0 is the steady-state value of the phase-locked loop angle.

[0024] Furthermore, based on the open-loop transfer function, the phase-frequency characteristic corresponding to the open-loop transfer function is obtained, specifically:

[0025] Respectively dividing the phase-locked loop transfer function and the outer loop transfer function into products of three corresponding proportional links;

[0026] Respectively calculating the first phase frequency and the second phase frequency corresponding to the three links of the phase-locked loop transfer function and the outer loop transfer function;

[0027] Based on the first phase frequency and the second phase frequency, obtaining a third phase frequency and a fourth phase frequency corresponding to the phase-locked loop transfer function and the outer loop transfer function;

[0028] Based on the third phase frequency and the fourth phase frequency, a phase-frequency characteristic corresponding to the open-loop transfer function is obtained.

[0029] In this way, by dividing the phase-locked loop transfer function and the outer loop transfer function into three proportional links respectively, the phase-frequency of the corresponding proportional links can be easily calculated one by one, thereby facilitating the subsequent accurate calculation of the phase-frequency characteristics corresponding to the open-loop transfer function.

[0030] Furthermore, the calculation formula of the third phase frequency corresponding to the phase-locked loop transfer function is specifically:

[0031]

[0032] In the formula, φ pll is the third phase frequency, k p,pll is the proportional coefficient of the phase-locked loop, k i,pll is the integral coefficient of the phase-locked loop, ω is the power frequency angular velocity, U g is the grid side voltage, θ pll0 is the steady-state value of the phase-locked loop angle, L g is the grid side reactance, I d0 is the steady-state value of the line current in the dq coordinate system;

[0033] The calculation formula of the fourth phase frequency corresponding to the outer loop transfer function is specifically:

[0034]

[0035] In the formula, φ ocl is the fourth phase frequency, C dc is the DC capacitance, U dc0 is the steady-state value of the DC voltage outer loop, k p,ocl is the proportional coefficient of the outer ring, k i,ocl is the integral coefficient of the outer loop, U g is the grid side voltage, θ pll0 is the steady-state value of the phase-locked loop angle, and ω is the industrial frequency angular velocity.

[0036] Further, the determining of the stability margin of the power system based on the amplitude-frequency characteristics is specifically as follows:

[0037] Analyzing the open-loop transfer function to determine a crossover frequency corresponding to the open-loop transfer function;

[0038] Based on the amplitude-frequency characteristic corresponding to the crossover frequency, a stability margin of the power system is determined.

[0039] In this way, by determining the stability margin of the power system, the safety domain range of the power electronic device parameters can be simply and accurately determined while taking into account the interactions between various links in the power electronic system.

[0040] Furthermore, the calculation formula for determining the safe range of the phase-locked loop parameter corresponding to the power electronic device is specifically:

[0041] when When the following equation is satisfied, the power system remains stable;

[0042]

[0043] In the formula, k p,ocl is the proportional coefficient of the outer ring, k i,ocl is the integral coefficient of the outer loop, ω0 is the steady-state value of the power frequency angular velocity, L g is the grid side reactance, I d0 is the steady-state value of the line current in the dq coordinate system, θ pll0 is the steady-state value of the phase-locked loop angle, U g is the grid side voltage, C dc is the DC capacitance, U dc0 is the steady-state value of the DC voltage outer loop, k p,pll is the proportional coefficient of the phase-locked loop,

[0044] In a second aspect, the present application provides a parameter security domain determination system for grid-connected power electronic devices, including: an acquisition module, a first processing module, a second processing module, and a third processing module;

[0045] The acquisition module is used to acquire target data corresponding to the power electronic device;

[0046] The first processing module is used to establish, based on the target data, a corresponding negative feedback frequency domain model with a phase-locked loop transfer function as a forward path and an outer loop transfer function as a feedback path, and obtain an open-loop transfer function based on the negative feedback frequency domain model;

[0047] The second processing module is used to obtain a phase-frequency characteristic and an amplitude-frequency characteristic corresponding to the open-loop transfer function based on the open-loop transfer function, and determine a stability margin of the power system based on the amplitude-frequency characteristic;

[0048] The third processing module is used to determine a safe domain range of a phase-locked loop parameter corresponding to the power electronic device based on the stability margin.

[0049] The embodiment of the present application obtains the target data corresponding to the power electronic device, thereby facilitating the subsequent accurate determination of the negative feedback model with the phase-locked loop transfer function as the forward path and the outer loop transfer function as the feedback path, thereby facilitating the subsequent determination of the safety domain range of the power electronic device parameters; by establishing a negative feedback model with the phase-locked loop transfer function as the forward path and the outer loop transfer function as the feedback path, the open-loop transfer function can be accurately determined, facilitating the subsequent determination of the phase-frequency characteristics and amplitude-frequency characteristics, thereby understanding the influence of the interaction between the phase-locked loop and the outer loop on the system stability, thereby facilitating the subsequent determination of the safety domain range of the power electronic device parameters; by determining the stability margin of the power system, the safety domain range of the power electronic device parameters can be simply and accurately determined while taking into account the interaction between the phase-locked loop and the outer loop in the power electronic system.

[0050] In a third aspect, the present application also provides a computer-readable storage medium, which includes a stored computer program, wherein when the computer program is running, the device where the computer-readable storage medium is located is controlled to execute the parameter safety domain determination method for the grid-connected power electronic device as described in the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a flow chart of an embodiment of a method for determining a parameter safety domain of a power electronic device connected to the grid provided by the present application;

[0052] Figure 2 It is a circuit diagram of the grid-connected power electronic device provided by the present application;

[0053] Figure 3 It is a schematic diagram of the control strategy for grid connection of power electronic devices provided by the present application;

[0054] Figure 4 It is a structural schematic diagram of the negative feedback frequency domain model provided by this application;

[0055] Figure 5 This is the Bode diagram that may appear in the phase-locked loop transfer function and the outer loop transfer function provided by the present application;

[0056] Figure 6 6 are amplitude-frequency characteristic diagrams of the open-loop transfer function provided by the present application;

[0057] Figure 7 It is a schematic diagram of the effect of the interaction between the phase-locked loop transfer function and the outer loop transfer function provided by the present application on stability;

[0058] Figure 8 It is a structural schematic diagram of an embodiment of a parameter safety domain determination system for grid-connected power electronic devices provided in the present application. DETAILED DESCRIPTION

[0059] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0060] It should be understood that the step numbers used in this article are only for the convenience of description and are not intended to limit the order in which the steps are executed.

[0061] It should be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, the singular forms "a", "an" and "the" are intended to include plural forms unless the context clearly indicates otherwise.

[0062] The terms “include” and “comprising” indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0063] The term "and / or" means and includes any and all possible combinations of one or more of the associated listed items.

[0064] With the rapid development of electric power technology, a large number of power electronic devices are connected to the power grid. The interaction between power electronic devices and the power grid will cause the power grid to oscillate in the sub- / super-synchronous frequency range, which will affect the stability of the power system. Therefore, it is an important topic to study the stability mechanism and conditions of power electronic devices connected to the power grid. In power electronics technology, the phase-locked loop (PLL) is a key component, and its parameter safety domain determination is crucial to system stability. However, traditional methods only adjust specific links and ignore the interaction between these links. In addition, the existing phase-locked loop parameter adjustment method is complicated and overly conservative. Therefore, considering the system interaction, seeking a simple and accurate method to adjust the PLL parameter safety domain to ensure the stable operation of the power system has become an important issue that needs to be solved urgently.

[0065] Next, the nouns involved in this application are analyzed:

[0066] Power electronic equipment refers to equipment with power electronic devices as the main functional components, also known as power semiconductor devices, which are mainly used in power equipment power conversion and control circuits. Power electronic equipment, if classified by function, can include power conversion equipment, power control equipment and power regulation equipment. If classified by application field, it can include industrial power electronic equipment and power electronic equipment for power. Industrial equipment is mainly used for power conversion and control in industrial production processes, such as motor drives, electric welding machines, electrolysis equipment, etc., while power equipment is mainly used for power conversion and control of power systems, such as inverters, static VAR compensators, active power filters, etc. Among them, power electronic equipment plays an important role in power systems. They can realize accurate conversion and control of electric energy, thereby improving the stability and efficiency of power systems.

[0067] Based on this, an embodiment of the present application provides a method, system and medium for determining the parameter safety domain of a power electronic device connected to the grid, which simply and accurately determines the safety domain range of the power electronic device parameters while taking into account the interaction between the phase-locked loop and the outer loop in the power electronic system.

[0068] The present application provides a method, system and medium for determining a parameter security domain for a power electronic device connected to the grid, which are specifically described through the following embodiments. First, the method for determining a parameter security domain for a power electronic device connected to the grid in the embodiment of the present application is described. The method for determining a parameter security domain for a power electronic device connected to the grid provided by the embodiment of the present application relates to the field of power electronic devices and is applied to power electronic devices.

[0069] Embodiment 1

[0070] Please refer to Figure 1 , Figure 1 It is a flowchart of an embodiment of a method for determining a parameter safety domain of a power electronic device connected to the grid provided by the present application, including steps S101 to S104;

[0071] Step S101, obtaining target data corresponding to the power electronic device;

[0072] It can be understood that the target data includes: electrical parameters, circuit diagram and control strategy, the electrical parameters include: transmission line impedance, power frequency angular velocity and input power, the circuit diagram is the circuit diagram corresponding to the power electronic device when it is connected to the power grid, and the control strategy is the strategy corresponding to the power electronic device when it is connected to the power grid.

[0073] It is understandable that the electrical parameters can be directly obtained through direct measurement or a data acquisition system, and the circuit diagram and the control strategy can be obtained from technical manuals, materials, professional websites or forums corresponding to the power electronic device.

[0074] like Figure 2 As shown, Figure 2 is a schematic diagram of a circuit for connecting a power electronic device to the grid provided in the present application, wherein E vsc is the internal potential of vsc, U t is the grid connection point voltage, pcc is the grid connection point, U g is the grid voltage, vsc is the voltage source converter, R l is the line resistance, X l is the line reactance and j is the imaginary unit.

[0075] like Figure 3 As shown, Figure 3 is a schematic diagram of the control strategy for the grid connection of the power electronic device provided in the present application, wherein P in is the input power, P is the VSC output power, C dc is the DC capacitance, U dc is the DC voltage output by the outer loop, U dcref Specifies the value of the DC voltage output by the outer loop, PI ocl is the d-axis voltage control link, I d is the line current in the dq coordinate system, I is the line current in the xy coordinate system, U abc is the grid connection point voltage in the abc coordinate system, xy is the xy coordinate system, dq is the dq coordinate system, I q is the q-axis current value, U q is the q-axis component of the grid-connected point voltage, PI pll is the phase-locked loop control link, ω pll is the angular velocity of the phase-locked loop, θ pll is the angle of the phase-locked loop, and s is the differential operator.

[0076] It should be noted that the abc coordinate system is a coordinate system established based on the power grid, the xy coordinate system is obtained by Parker transformation of the abc coordinate system, the dq coordinate system is a coordinate system established based on the VSC, the d-axis is the direct axis in the dq coordinate system, and the q-axis is the cross axis in the dq coordinate system.

[0077] In this way, by obtaining the target data corresponding to the power electronic device, it is convenient to accurately determine the negative feedback model in the subsequent process, and thus it is convenient to determine the safety domain range of the power electronic device parameters in the subsequent process.

[0078] Step S102: based on the target data, establishing a corresponding negative feedback frequency domain model with a phase-locked loop transfer function as a forward path and an outer loop transfer function as a feedback path, and obtaining an open-loop transfer function based on the negative feedback frequency domain model;

[0079] It can be understood that after obtaining the target data of the power electronic device, the phase-locked loop transfer function and the outer loop transfer function including the power grid information can be calculated based on the target data; then a negative feedback frequency domain model is established with the phase-locked loop transfer function as the forward path and the outer loop transfer function as the feedback path.

[0080] The phase-locked loop transfer function G pll The calculation process of (s) is as follows. Specifically, first, based on the control strategy, the angle θ of the phase-locked loop can be obtained. pll The expression is: In the formula, θ pll is the angle of the phase-locked loop, U q is the q-axis component of the grid-connected point voltage, k p,pll is the proportional coefficient of the phase-locked loop, k i,pll is the integral coefficient of the phase-locked loop, s is the differential operator, and the angle θ of the phase-locked loop pll Linearize and get the phase-locked loop angle θ pll Linearized Expression Secondly, according to the circuit structure diagram, the grid-connected point q-axis voltage U can be obtained: q The expression of U is: q =U gq +(ω0+ω pll )L g I d +R g I q =-U g sinθ pll +(ω0+ω pll )L g I d +R g I q , where U q is the q-axis component of the grid-connected point voltage, U gq is the q-axis component of the grid voltage, ω0 is the steady-state value of the power frequency angular velocity, ω pll is the angular velocity of the phase-locked loop, L g is the grid side reactance, R g is the grid side resistance, I d is the line current in the dq coordinate system, I q is the q-axis current value, θ pll is the phase-locked loop angle, and the q-axis voltage U q Linearization is performed to obtain the grid-connected point q-axis voltage U q Linearized expression ΔU q =-U g cosθ pll0 Δθ pll +ω0L g ΔId +L g I d0 Δω pll Then, based on the phase-locked loop angle θ pll Linearized expression Δθ pll and the q-axis voltage U at the grid connection point q Linearized expression ΔU q ,get Finally, we can get d As input, Δθ pll The phase-locked loop transfer function G is obtained as the output pll (s), wherein the phase-locked loop transfer function G pll The calculation formula of (s) is: In the formula, G pll (s) is the phase-locked loop transfer function, Δθ pll is the angle between the xy coordinate system and the dq coordinate system, ΔI d is the line current in the dq coordinate system, ω0 is the steady-state value of the power frequency angular velocity, L g is the grid side reactance, k p,pll is the proportional coefficient of the phase-locked loop, k i,pll is the integral coefficient of the phase-locked loop, s is the differential operator, U g is the grid side voltage, θ pll0 is the steady-state value of the phase-locked loop angle, I d0 is the steady-state value of the line current in the dq coordinate system.

[0081] The outer loop transfer function G ocl The calculation process of (s) is as follows: First, according to the control strategy, the output d-axis current I can be obtained. d The expression is: In the formula, I d is the line current in the dq coordinate system, P in is the input power, P is the VSC output power, C dc is the DC capacitance, U dc0 is the steady-state value of the DC voltage outer loop, s is the differential operator, k p,ocl is the proportional coefficient of the outer ring, k i,ocl is the integral coefficient of the outer loop, for the d-axis current I d Linearization is performed to obtain the d-axis current I d The linearized expression is: Secondly, according to the circuit structure diagram, the expression of power P is obtained as follows: Linearize the power P and get the linear expression of power P: ΔP=U g cosθ pll0 ΔI d-U g I d0 sinθ pll0 Δθ pll , where U g is the grid voltage, θ pll0 is the steady-state value of the phase-locked loop angle, ΔI d is the d-axis current I d Linearized expression, I d0 is the steady-state value of the line current in the dq coordinate system, Δθ pll is the q-axis voltage U at the grid connection point q Linearize the expression. Then, based on the d-axis current I d Linearized expression ΔI d And power P linear expression ΔP, get: Finally, we can get pll As input, ΔI d As the output outer loop transfer function, where the outer loop transfer function G ocl The calculation formula of (s) is: In the formula, G ocl (s) is the outer loop transfer function, k p,ocl is the proportional coefficient of the outer ring, k i,ocl is the integral coefficient of the outer loop, s is the differential operator, C dc is the DC capacitance, U dc0 is the steady-state value of the DC voltage outer loop, U g is the grid side voltage, I d0 is the steady-state value of the line current in the dq coordinate system, θ pll0 is the steady-state value of the phase-locked loop angle.

[0082] When the phase-locked loop transfer function G is calculated pll (s) and the outer loop transfer function G ocl (s) After that, the phase-locked loop transfer function G can be established pll (s) is the forward path, with the outer loop transfer function G ocl (s) is a negative feedback frequency domain model of the feedback path, wherein the structural schematic diagram of the negative feedback frequency domain model provided by the present application is as follows Figure 4 shown.

[0083] After the negative feedback frequency domain model is determined, the open-loop transfer function G can be obtained based on the negative feedback frequency domain model: op (s), wherein the open-loop transfer function G op The calculation formula of G (s) is: op (s) = G pll (s)(-G ocl(s)).

[0084] According to the limitations of engineering constraints, the damping ratio of the phase-locked loop can be determined as the optimal damping ratio, that is: In the formula, ξ pll is the optimal damping ratio, k p,pll is the proportional coefficient of the phase-locked loop, k i,pll is the integral coefficient of the phase-locked loop; simplifying the above formula, the relationship between the proportional coefficient and the integral coefficient of the phase-locked loop is: According to the phase-locked loop transfer function G pll (s) It can be seen that if the phase-locked loop is to be stable, the denominator must be greater than zero, then: Where, L g is the grid side reactance, I d0 is the steady-state value of the line current in the dq coordinate system, k p,pll is the proportional coefficient of the phase-locked loop, U g is the grid side voltage, θ pll0 is the steady-state value of the phase-locked loop angle, k i,pll is the integral coefficient of the phase-locked loop; therefore, we can get k p,pll and k i,pll Constraints:

[0085] In this way, by establishing a negative feedback model, the open-loop transfer function can be accurately determined, which facilitates the subsequent determination of the phase-frequency characteristics and amplitude-frequency characteristics, and then understands the influence of the interaction between the unlocked loop and the outer loop on the system stability, which facilitates the subsequent determination of the safe domain range of the power electronic device parameters.

[0086] Step S103: based on the open-loop transfer function, obtaining a phase-frequency characteristic and an amplitude-frequency characteristic corresponding to the open-loop transfer function, and determining a stability margin of the power system based on the amplitude-frequency characteristic;

[0087] It can be understood that after obtaining the open-loop transfer function, the amplitude-frequency characteristics and phase-frequency characteristics of the open-loop transfer function can be analyzed. Specifically, the phase-locked loop transfer function and the outer-loop transfer function are respectively divided into the products of the corresponding three proportional links; the first phase frequency and the second phase frequency corresponding to the three links of the phase-locked loop transfer function and the outer-loop transfer function are respectively calculated; based on the first phase frequency and the second phase frequency, the third phase frequency and the fourth phase frequency corresponding to the phase-locked loop transfer function and the outer-loop transfer function are obtained; based on the third phase frequency and the fourth phase frequency, the phase-frequency characteristics corresponding to the open-loop transfer function are obtained.

[0088] Analyze the phase-locked loop transfer function G pll The specific process of the phase-frequency characteristic of (s) is as follows: first, the phase-locked loop transfer function G pll (s) is expressed as the product of three parts, the proportional link Gpll1 , proportional differential link G pll2 and the second-order oscillation link G pll3 , where the expressions of the three links are,

[0089]

[0090] Where U g is the grid side voltage, ω0 is the steady-state value of the power frequency angular velocity, θ pll0 is the steady-state value of the phase-locked loop angle, k p,pll is the proportional coefficient of the phase-locked loop, k i,pll is the integral coefficient of the phase-locked loop, s is the differential operator, L g is the grid side reactance, I d0 is the steady-state value of the line current in the dq coordinate system; secondly, according to the proportional differential link G pll2 and the second-order oscillation link G pll3 The proportional differential link G can be determined by the expression pll2 and the second-order oscillation link G pll3 The turning frequencies are: pll2 = Where U g is the grid side voltage, θ pll0 is the steady-state value of the phase-locked loop angle, k p,pll is the proportional coefficient of the phase-locked loop, k i,pll is the integral coefficient of the phase-locked loop, L g is the grid side reactance, I d0 is the steady-state value of the line current in the dq coordinate system, and G pll The peak frequency is ω m,pll , due to the proportional differential link G pll2 The asymptote slope is +20dB / dec, and the second-order oscillation link G pll3 The asymptote slope is -40dB / dec, so G pll The peak frequency ω m,pll Approximately equal to ω pll3 ; Then, based on the expressions of the three links, the phase-frequency characteristics of each link are obtained as follows: φ pll1 =0°, Where U g is the grid side voltage, ω is the power frequency angular velocity, θ pll0 is the steady-state value of the phase-locked loop angle, k p,pll is the proportional coefficient of the phase-locked loop, k i,pll is the integral coefficient of the phase-locked loop, s is the differential operator, L g is the grid side reactance, I d0is the steady-state value of the line current in the dq coordinate system; finally, the phase-frequency characteristics of the three links are added together, and then according to the inverse trigonometric function addition and subtraction formula, G can be obtained. pll The total phase-frequency characteristic, that is, the third phase frequency, is: In the formula, φ pll is the third phase frequency, k p,pll is the proportional coefficient of the phase-locked loop, k i,pll is the integral coefficient of the phase-locked loop, ω is the power frequency angular velocity, U g is the grid side voltage, θ pll0 is the steady-state value of the phase-locked loop angle, L g is the grid side reactance, I d0 is the steady-state value of the line current in the dq coordinate system. It can be seen that when The value of the power frequency angular velocity ω at zero point is Therefore, based on the phase-locked loop transfer function G pll Function characteristics, we can get the phase-locked loop transfer function G pll (s) There are two possible Bode plots: Figure 5 shown.

[0091] Analyze the outer loop transfer function G op The specific process of the phase-frequency characteristic of (s) is as follows: first, the outer loop transfer function can be expressed as the product of three parts, namely, the proportional link G ocl1 , proportional differential link G ocl2 and the second-order oscillation link G ocl3 , whose expressions are: G ocl1 =I d0 tanθ pll0 , Where U g is the grid side voltage, θ pll0 is the steady-state value of the phase-locked loop angle, k p,ocl is the proportional coefficient of the outer ring, k i,ocl is the integral coefficient of the outer loop, C dc is the DC capacitance, U dc0 is the steady-state value of the DC voltage outer loop, s is the differential operator; secondly, according to the proportional differential link G ocl2 and the second-order oscillation link G ocl3 The proportional differential link G can be determined by the expression ocl2 and the second-order oscillation link G ocl3 The turning frequency: Where U g is the grid side voltage, θ pll0 is the steady-state value of the phase-locked loop angle, k p,ocl is the proportional coefficient of the outer ring, k i,ocl is the integral coefficient of the outer loop, Cdc is the DC capacitance, U dc0 is the steady-state value of the DC voltage outer loop, denoted by G ocl The peak frequency is ω m,ocl , due to the proportional differential link G ocl2 The asymptote slope is +20dB / dec, and the second-order oscillation link G ocl3 The asymptote slope is -40dB / dec, so G ocl The peak frequency ω m,ocl Approximately equal to ω ocl3 ,ω m,ocl The expression is: Then, based on the expressions of the three links, the phase-frequency characteristics of each link are obtained: ocl1 =0°, Where ω is the power frequency angular velocity, U g is the grid side voltage, θ pll0 is the steady-state value of the phase-locked loop angle, k p,ocl is the proportional coefficient of the outer ring, k i,ocl is the integral coefficient of the outer loop, C dc is the DC capacitance, U dc0 is the steady-state value of the DC voltage outer loop; finally, the phase-frequency characteristics of the three links are added together, and then according to the inverse trigonometric function addition and subtraction formula, G can be obtained. ocl The total phase-frequency characteristic, that is, the fourth phase frequency, is: In the formula, φ ocl is the fourth phase frequency, C dc is the DC capacitance, U dc0 is the steady-state value of the DC voltage outer loop, k p,ocl is the proportional coefficient of the outer ring, k i,ocl is the integral coefficient of the outer loop, U g is the grid side voltage, θ pll0 is the steady-state value of the phase-locked loop angle, ω is the power frequency angular velocity, and it can be seen that when The ω value at the zero point is 0. Therefore, based on the outer loop transfer function G ocl Function characteristics, we can get the outer loop transfer function G ocl (s) The two possible Bode diagrams are as follows Figure 5 As shown. Through this formula, it can be analyzed that G ocl The phase-frequency characteristic is that when ω=0, the phase angle is 0°, and when ω increases, the phase angle gradually decreases. Based on this phase-frequency characteristic, it can be known that G ocl The phase-frequency characteristic is always less than or equal to 0°.

[0092] In this way, by dividing the phase-locked loop transfer function and the outer loop transfer function into three proportional links respectively, the phase-frequency of the corresponding proportional links can be easily calculated one by one, thereby facilitating the subsequent accurate calculation of the phase-frequency characteristics corresponding to the open-loop transfer function.

[0093] The process of determining the stability margin of the power system based on the amplitude-frequency characteristics is specifically as follows: analyzing the open-loop transfer function to determine the crossover frequency corresponding to the open-loop transfer function; and determining the stability margin of the power system based on the amplitude-frequency characteristics corresponding to the crossover frequency. pll and G ocl The phase-frequency characteristic of Figure 6 The open loop transfer function G shown op The amplitude-frequency characteristics of six cases, among which ω pll2 and ω ocl2 The smaller of ω pll2 and ω ocl2 The larger of ω pll3 and ω ocl3 The smaller of ω pll3 and ω ocl3 The larger of Figure 6 It can be seen that the open-loop transfer function G op The crossover frequency is approximately Therefore the frequency The corresponding amplitude at is the stability margin of the system. op The following conclusions can be drawn from the amplitude-frequency characteristic curves of the six cases: (1) When G pll and G ocl When the damping ratio of G is approximately constant, pll and G ocl The closer the peak frequency is, the op The larger the amplitude corresponding to the crossover frequency, the smaller the stability margin, and it may even exceed the 0dB line, and the worse the stability; (2) When G pll and G ocl When the peak frequency of G is approximately constant, pll and G ocl The smaller the damping ratio of the second-order oscillation link, the higher and sharper the peak of its amplitude-frequency curve is, resulting in G op The larger the amplitude corresponding to the crossover frequency, the smaller the stability margin and the worse the stability. Therefore, we can understand the phase-locked loop transfer function G pll and the outer loop transfer function G ocl The influence of the interaction between Figure 7 shown.

[0094] In this way, by determining the stability margin of the power system, the safety domain range of the power electronic device parameters can be simply and accurately determined while taking into account the interactions between various links in the power electronic system.

[0095] Step S104: determining a safe domain range of a phase-locked loop parameter corresponding to the power electronic device based on the stability margin.

[0096] It can be understood that after the stability margin is determined, the safety domain range of the phase-locked loop parameters corresponding to the power electronic device can be determined based on the stability margin. Specifically, let the open-loop transfer function G op The amplitude-frequency characteristic function is L op , the amplitude-frequency characteristic function of the phase-locked loop transfer function is L pll , the amplitude-frequency characteristic function of the outer loop transfer function is L ocl ,remember The crossover frequency is ω c According to the automatic control theory, when L op (ω c )<0, the system is stable. As mentioned above, the total phase-frequency characteristic of the outer loop transfer function is always less than zero, so, So the open-loop transfer function G op The crossover frequency is ω c Must be smaller than the G of the phase-locked loop transfer function pll The crossover frequency ω c,pll If the frequency ω is less than the phase-locked loop transfer function frequency ω c,pll In the range of , the amplitude-frequency characteristic of the open-loop transfer function L op If the amplitude-frequency characteristic of the open-loop transfer function L is always less than zero, the system must be stable. op At 0<ω<ω c,pll If the maximum value in the range is less than zero, the system must be stable. Further expanding the conservatism, if 0<ω<ω c,pll The amplitude-frequency characteristic of the phase-locked loop transfer function in the range L pll The maximum value and the amplitude-frequency characteristic of the open-loop transfer function L ocl If the sum of the maximum values ​​of is less than zero, then the system must be stable.

[0097] First, calculate the amplitude-frequency characteristic L of the phase-locked loop transfer function pll At 0<ω<ω c,pll The maximum value in the range is obtained by the phase-locked loop transfer function G in step S103. pll The total phase-frequency characteristic expression can be obtained from: Then, the relationship between the proportional coefficient and the integral coefficient of the phase-locked loop is Substituting into the above formula, we can get the phase-locked loop transfer function G pll The crossover frequency is: According to the above phase-locked loop transfer function, the second-order oscillation link G pll3 The peak frequency of the phase-locked loop transfer function can be obtained as Since the proportionality coefficient k of the phase-locked loop p,pll satisfy Constraint, we can get ω c,pll <ω m,pll Then L pll At 0<ω<ω c,pll The maximum value in the range is at ω = ω c,pll The maximum value is: Then we get k p,pll The following formula must be satisfied: Further calculation of L ocl At 0<ω<ω c,pll The maximum value in the range is divided into two cases for discussion below: (1) When ω m,ocl ≥ω c,pll When ω=ω, the maximum value is c,pll When ω m,ocl <ω c,pll When ω=ω, the maximum value is m,ocl Get it when.

[0098] (1) When ω m,ocl ≥ω c,pll When , the expression is: Then we can get the integral coefficient of the outer loop remember At this time, the amplitude-frequency characteristic function L of the outer loop transfer function ocl The maximum value of is: L pll (ω c,pll ) and L ocl (ω c,pll ) and make it less than zero, we get remember make Then when k p,pll =k p,cr When M3=0, M3=0. According to the expression of M3, M3 increases with the proportional coefficient k of the phase-locked loop. p,pll increases with the increase of k. p,pll <k p,cr When M3<0; when k p,pll >k p,cr When M3>0, so

[0099] The solution is When k p,pll <k p,cr When It reaches its minimum value at , and the expression is: When k p,pll ≥k p,cr When k i,ocl =M1M2 reaches its maximum value, and the expression is: Because k p,pll ≥k p,cr When M1, M2, and M3 are all greater than zero, then This is impossible, so the proportional coefficient k of the phase-locked loop is p,pll Must be less than k p,cr So in summary, first of all, k p,pll <k p,cr , secondly, when When To make the system stable, When, meet To make the system stable.

[0100] (2) When ω m,ocl <ω c,pll When At this time, the amplitude-frequency characteristic function L of the outer loop transfer function ocl The maximum value is at ω=ω m,ocl When the peak frequency of the outer loop transfer function is obtained, m,ocl Substituting in, we get: When L pll (ω c,pll ) and L ocl (ω m,ocl ) is less than zero, the system is stable, then we can get that when k p,pll <k p,cr When the following equation is satisfied, the system is stable: When k p,pll ≥k p,cr When the following equation is satisfied, the system is stable: Since the right-hand side is always less than zero, It is impossible, so the proportional coefficient k of the phase-locked loop p,pll Must be less than k p,cr In summary, when ω m,ocl <ω c,pll When k p,pll <k p,cr and Satisfy the inequality The system is stable.

[0101] Combining the above process, we can get the following safe range of phase-locked loop parameters that make the system stable, specifically:

[0102] when When the following equation is satisfied, the power system remains stable;

[0103]

[0104] In the formula, k p,ocl is the proportional coefficient of the outer ring, k i,ocl is the integral coefficient of the outer loop, ω0 is the steady-state value of the power frequency angular velocity, L g is the grid side reactance, I d0 is the steady-state value of the line current in the dq coordinate system, θ pll0 is the steady-state value of the phase-locked loop angle, U g is the grid side voltage, C dc is the DC capacitance, U dc0 is the steady-state value of the DC voltage outer loop, k p,pll is the proportional coefficient of the phase-locked loop,

[0105] When the proportionality factor of the phase-locked loop When the system is unstable.

[0106] The embodiment of the present application obtains the target data corresponding to the power electronic device, thereby facilitating the subsequent accurate determination of the negative feedback model with the phase-locked loop transfer function as the forward path and the outer loop transfer function as the feedback path, thereby facilitating the subsequent determination of the safety domain range of the power electronic device parameters; by establishing a negative feedback model with the phase-locked loop transfer function as the forward path and the outer loop transfer function as the feedback path, the open-loop transfer function can be accurately determined, facilitating the subsequent determination of the phase-frequency characteristics and amplitude-frequency characteristics, thereby understanding the influence of the interaction between the phase-locked loop and the outer loop on the system stability, thereby facilitating the subsequent determination of the safety domain range of the power electronic device parameters; by determining the stability margin of the power system, the safety domain range of the power electronic device parameters can be simply and accurately determined while taking into account the interaction between the phase-locked loop and the outer loop in the power electronic system.

[0107] Embodiment 2

[0108] Please refer to Figure 8 , Figure 8 It is a structural schematic diagram of an embodiment of a parameter security domain determination system for grid-connected power electronic devices provided by the present application, comprising: an acquisition module 100, a first processing module 200, a second processing module 300 and a third processing module 400;

[0109] The acquisition module 100 is used to acquire target data corresponding to the power electronic device;

[0110] The first processing module 200 is used to establish, based on the target data, a corresponding negative feedback frequency domain model with a phase-locked loop transfer function as a forward path and an outer loop transfer function as a feedback path, and obtain an open-loop transfer function based on the negative feedback frequency domain model;

[0111] The second processing module 300 is used to obtain a phase-frequency characteristic and an amplitude-frequency characteristic corresponding to the open-loop transfer function based on the open-loop transfer function, and determine a stability margin of the power system based on the amplitude-frequency characteristic;

[0112] The third processing module 400 is used to determine a safe domain range of a phase-locked loop parameter corresponding to the power electronic device based on the stability margin.

[0113] The information interaction, execution process, etc. between the modules within the above-mentioned parameter safety domain determination system for connecting a power electronic device to the grid are based on the same concept as the embodiment of the parameter safety domain determination method for connecting a power electronic device to the grid in the first aspect of the present invention, and the technical effects achieved are basically the same. For specific contents, please refer to the description in Embodiment 1 of the method of the present invention, and will not be repeated here.

[0114] The device embodiments described above are merely illustrative, wherein the modules described as separate components may or may not be physically separated, i.e., may be located in one place, or may be distributed to multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the method of this embodiment.

[0115] The present invention also provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the method for determining a parameter safety domain for grid-connected power electronic devices as described in the first embodiment above is implemented.

[0116] A person skilled in the art can understand that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program, and the program can be stored in a computer-monitorable storage medium, and when the program is executed, it can include the processes of the embodiments of the above-mentioned methods. The storage medium can be a disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM), etc.

[0117] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present application in detail. It should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the scope of protection of the present application.

[0118] It is particularly pointed out that for those skilled in the art, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of this application should be included in the protection scope of this application.

Claims

1. A method for determining a parameter safety region for grid-connected power electronic devices, characterized in that: include: Acquiring target data corresponding to the power electronic device; Based on the target data, a corresponding negative feedback frequency domain model is established with a phase-locked loop transfer function as a forward path and an outer loop transfer function as a feedback path, and an open-loop transfer function is obtained based on the negative feedback frequency domain model; Based on the open-loop transfer function, a phase-frequency characteristic and an amplitude-frequency characteristic corresponding to the open-loop transfer function are obtained, and a stability margin of the power system is determined based on the amplitude-frequency characteristic; Based on the stability margin, a safe domain range of a phase-locked loop parameter corresponding to the power electronic device is determined.

2. The method for determining the parameter safety domain of power electronic device grid connection according to claim 1, characterized in that: The target data includes: electrical parameters, circuit diagram and control strategy. The electrical parameters include: transmission line impedance, power frequency angular velocity and input power. The circuit diagram is the circuit diagram corresponding to when the power electronic device is connected to the power grid. The control strategy is the strategy corresponding to when the power electronic device is connected to the power grid.

3. The method for determining the parameter safety domain of power electronic device grid connection according to claim 1, characterized in that: Based on the target data, a corresponding negative feedback frequency domain model is established with the phase-locked loop transfer function as the forward path and the outer loop transfer function as the feedback path, specifically: Based on the target data, respectively calculating a phase-locked loop transfer function and an outer loop transfer function; A negative feedback frequency domain model is established with the phase-locked loop transfer function as a forward path and the outer loop transfer function as a feedback path.

4. The method for determining the parameter safety domain of power electronic device grid connection according to claim 3, characterized in that: The calculation formula of the phase-locked loop transfer function is: In the formula, G pll (s) is the phase-locked loop transfer function, Δθ pll is the angle between the xy coordinate system and the dq coordinate system, ΔI d is the line current in the dq coordinate system, ω0 is the steady-state value of the power frequency angular velocity, L g is the grid side reactance, k p,pll is the proportional coefficient of the phase-locked loop, k i,pll is the integral coefficient of the phase-locked loop, s is the differential operator, U g is the grid side voltage, θ pll0 is the steady-state value of the phase-locked loop angle, I d0 is the steady-state value of the line current in the dq coordinate system; Wherein, the calculation formula of the outer loop transfer function is: In the formula, G ocl (s) is the outer loop transfer function, k p,ocl is the proportional coefficient of the outer ring, k i,ocl is the integral coefficient of the outer loop, s is the differential operator, C dc is the DC capacitance, U dc0 is the steady-state value of the DC voltage outer loop, U g is the grid side voltage, I d0 is the steady-state value of the line current in the dq coordinate system, θ pll0 is the steady-state value of the phase-locked loop angle.

5. The method for determining the parameter safety domain of power electronic device grid connection according to claim 3, characterized in that: Based on the open-loop transfer function, the phase-frequency characteristic corresponding to the open-loop transfer function is obtained, specifically: Respectively dividing the phase-locked loop transfer function and the outer loop transfer function into products of three corresponding proportional links; Respectively calculating the first phase frequency and the second phase frequency corresponding to the three links of the phase-locked loop transfer function and the outer loop transfer function; Based on the first phase frequency and the second phase frequency, obtaining a third phase frequency and a fourth phase frequency corresponding to the phase-locked loop transfer function and the outer loop transfer function; Based on the third phase frequency and the fourth phase frequency, a phase-frequency characteristic corresponding to the open-loop transfer function is obtained.

6. The method for determining the parameter safety domain of power electronic device grid connection according to claim 5, characterized in that: The calculation formula of the third phase frequency corresponding to the phase-locked loop transfer function is specifically: In the formula, φ pll is the third phase frequency, k p,pll is the proportional coefficient of the phase-locked loop, k i,pll is the integral coefficient of the phase-locked loop, ω is the power frequency angular velocity, U g is the grid side voltage, θ pll0 is the steady-state value of the phase-locked loop angle, L g is the grid side reactance, I d0 is the steady-state value of the line current in the dq coordinate system; The calculation formula of the fourth phase frequency corresponding to the outer loop transfer function is specifically: In the formula, φ ocl is the fourth phase frequency, C dc is the DC capacitance, U dc0 is the steady-state value of the DC voltage outer loop, k p,ocl is the proportional coefficient of the outer ring, k i,ocl is the integral coefficient of the outer loop, U g is the grid side voltage, θ pll0 is the steady-state value of the phase-locked loop angle, and ω is the industrial frequency angular velocity.

7. The method for determining the parameter safety domain of power electronic device grid connection according to claim 1, characterized in that: The determining of the stability margin of the power system based on the amplitude-frequency characteristics is specifically: Analyzing the open-loop transfer function to determine a crossover frequency corresponding to the open-loop transfer function; Based on the amplitude-frequency characteristic corresponding to the crossover frequency, a stability margin of the power system is determined.

8. The method for determining the parameter safety domain of power electronic device grid connection according to claim 1, characterized in that: The calculation formula for determining the safe range of the phase-locked loop parameter corresponding to the power electronic device is specifically: when When the following equation is satisfied, the power system remains stable; In the formula, k p,ocl is the proportional coefficient of the outer ring, k i,ocl is the integral coefficient of the outer loop, ω0 is the steady-state value of the power frequency angular velocity, L g is the grid side reactance, I d0 is the steady-state value of the line current in the dq coordinate system, θ pll0 is the steady-state value of the phase-locked loop angle, U g is the grid side voltage, C dc is the DC capacitance, U dc0 is the steady-state value of the DC voltage outer loop, k p,pll is the proportional coefficient of the phase-locked loop, 9. A parameter safety domain determination system for power electronic device grid connection, characterized in that: include: An acquisition module, a first processing module, a second processing module and a third processing module; The acquisition module is used to acquire target data corresponding to the power electronic device; The first processing module is used to establish, based on the target data, a corresponding negative feedback frequency domain model with a phase-locked loop transfer function as a forward path and an outer loop transfer function as a feedback path, and obtain an open-loop transfer function based on the negative feedback frequency domain model; The second processing module is used to obtain a phase-frequency characteristic and an amplitude-frequency characteristic corresponding to the open-loop transfer function based on the open-loop transfer function, and determine a stability margin of the power system based on the amplitude-frequency characteristic; The third processing module is used to determine a safe domain range of a phase-locked loop parameter corresponding to the power electronic device based on the stability margin.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a stored computer program, wherein when the computer program is executed, the device where the computer-readable storage medium is located is controlled to execute the parameter security domain determination method for grid-connected power electronic devices according to any one of claims 1 to 8.

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