A method and system for testing coefficients of grid-type converters based on an improved phase-locked loop

Abstract

The present invention discloses a method and system for testing the coefficients of a meshed converter based on an improved phase-locked loop, and relates to the technical field of meshed converters. The method obtains a frequency reference signal and a phase reference output signal of the meshed converter through frequency control; uses the phase reference output signal to output a PWM control signal through voltage control, and uses the PWM control signal to control the output three-phase voltage; uses an improved phase-locked loop to perform frequency measurement and active power measurement based on the output three-phase voltage and the phase reference output signal, wherein the improved phase-locked loop refers to a control structure consisting of an integral link and a lead compensation link in which the original PI control link in the phase-locked loop is replaced; and calculates the meshed converter coefficient based on the frequency measurement results and the active power measurement results. The present invention can quickly and accurately capture the frequency and its rate of change signal, and can efficiently obtain key coefficient test results such as the damping coefficient and the inertia coefficient without building a complex model.

Description

Technical Field

[0001] The present invention relates to the technical field of grid-type converters in power electronics, and in particular to a method and system for testing coefficients of a grid-type converter based on an improved phase-locked loop. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Compared to grid-following converters, grid-building converters have the ability to actively build grids. They not only enable black start functionality but also possess flexible frequency and voltage regulation characteristics and superior adaptability to weak grids. Furthermore, by simulating the mechanical inertia of the power system, grid-building converters can effectively increase the system's inertia and enhance its rapid response to frequency disturbances. At the same time, the damping services they provide help suppress grid oscillations and maintain system stability. With these advantages, grid-building converters can significantly improve the economic efficiency and reliability of the grid, becoming a key piece of equipment supporting the integration of a high proportion of renewable energy.

[0004] The damping and inertia coefficients of grid-connected converters are key factors affecting grid stability. Accurately testing these factors not only helps comprehensively evaluate the performance of grid-connected converters from different manufacturers, but also verifies their compliance with grid connection standards and technical specifications, effectively ensuring system safety and reliability.

[0005] Existing damping and inertia coefficient testing methods can be mainly divided into disturbance-based methods and disturbance-independent methods. The former relies on system disturbance events, the source of which can be a fault in the power system itself or an artificially injected excitation signal. After the disturbance occurs, the damping and inertia coefficients are estimated by analyzing the power response and frequency response of the system. The disturbance-independent method usually uses environmental observation methods to collect power and frequency-related data, and uses data-driven or modeling methods to test the system damping and inertia coefficients. However, the above methods are mainly aimed at power systems rather than grid-connected converters. When applied to grid-connected converters, there are problems such as complex mathematical models and difficulty in decoupling damping power and inertia power. At the same time, when the test method involves frequency change rate information in the frequency response, how to accurately and quickly obtain the frequency change rate signal remains a challenge. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a grid-type converter coefficient testing method and system based on an improved phase-locked loop, which can quickly and accurately capture the frequency and its rate of change signals, and accurately compensate for the errors in the signal capture process. It does not need to build a complex model and does not rely on a large amount of historical data, and can efficiently obtain key coefficient test results such as the damping coefficient and inertia coefficient.

[0007] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0008] A first aspect of the present invention provides a method for testing a coefficient of a grid-type converter based on an improved phase-locked loop, comprising the following steps:

[0009] Obtaining frequency reference signal and phase reference output signal of the grid-type converter through frequency control;

[0010] Using the phase reference output signal to output a PWM control signal through voltage control, and using the PWM control signal to control the output three-phase voltage;

[0011] An improved phase-locked loop is used to measure frequency and active power based on the output three-phase voltage and the phase reference output signal, wherein the improved phase-locked loop refers to a control structure consisting of an integral link and a lead compensation link replacing the original PI control link in the phase-locked loop;

[0012] Active power measurement based on output three-phase voltage, output side current and phase reference output signal;

[0013] The grid-type converter coefficient is calculated according to the frequency measurement result and the active power measurement result, wherein the grid-type converter coefficient includes an inertia coefficient and a damping coefficient.

[0014] Furthermore, the specific steps of obtaining the frequency reference signal and phase reference output signal of the grid-type converter through frequency control are as follows:

[0015] A step signal generator is used to generate a frequency change rate input signal;

[0016] The frequency change rate input signal is superimposed on the reference frequency change rate input signal, and then superimposed on the reference frequency input signal through the integration link to obtain the frequency reference signal;

[0017] The frequency reference signal is multiplied and integrated to obtain the phase reference output signal.

[0018] Furthermore, the specific steps of outputting a PWM control signal through voltage control using the phase reference output signal are as follows:

[0019] The capacitor voltage and inverter current are combined with the phase reference output signal to abc-dq Convert and extract voltage and current d Axis and q Axis component;

[0020] Using the voltage reference value to adjust the capacitor voltage d Axis and qThe axis components are calculated and adjusted through the PI controller to obtain the reference value of the inverter side current;

[0021] The inverter side current is sampled using the inverter side current reference value. dq The components are PI regulated to generate inverter voltage signals;

[0022] The inverter voltage signal is compared with the phase reference output signal dq-abc After inverse transformation, it is input to the PWM modulation module, and the output PWM control instruction is used to control the output three-phase voltage.

[0023] Furthermore, the specific steps of using the improved phase-locked loop to perform frequency measurement based on the output three-phase voltage and the phase reference output signal are as follows:

[0024] The output three-phase voltage is linearly abc - dq Coordinate transformation obtains d Axis components and q Axis component, q After the advance compensation link and division operation, the axis component is superimposed with the reference frequency change rate input signal to obtain the frequency change rate output signal. The frequency change rate output signal is then superimposed with the reference frequency input signal through an integration link to obtain the frequency output signal.

[0025] Furthermore, the specific steps for measuring active power based on the output three-phase voltage, output side current and phase reference output signal are as follows:

[0026] The output three-phase voltage is compared with the phase reference signal abc-dq Coordinate transformation, get the voltage d Axis and q Axis component;

[0027] The same is done for the output current and phase reference signal abc-dq Convert, extract current d Axis and q Axis component;

[0028] Based on the above voltage and current d Axis and q The axis components are calculated to obtain the output signal of active power.

[0029] Furthermore, the specific steps for calculating the inertia coefficient of the grid-connected converter based on the frequency measurement results and the active power measurement results are as follows:

[0030] The difference between the active power output signal and the active power reference value, the difference between the frequency output signal and the reference frequency input signal, and the frequency change rate output signal are all normalized. Then, the active power change caused by the damping coefficient is removed by subtraction. Finally, the inertia coefficient of the measured grid-type converter is obtained by dividing it with the normalized value of the frequency change rate output signal. 。

[0031] Furthermore, the specific steps for calculating the damping coefficient of the grid-connected converter based on the frequency measurement results and the active power measurement results are as follows:

[0032] The difference between the active power output signal and the active power reference value and the difference between the frequency output signal and the reference frequency input signal are both normalized, and then the damping coefficient of the measured grid-type converter is obtained by dividing the two normalized values.

[0033] A second aspect of the present invention provides a network-type converter coefficient testing system based on an improved phase-locked loop, comprising:

[0034] A frequency control module is configured to obtain a frequency reference signal and a phase reference output signal of the grid-type converter through frequency control;

[0035] a voltage control module configured to output a PWM control signal by voltage control using the phase reference output signal, and to control the output three-phase voltage using the PWM control signal;

[0036] a frequency measurement module configured to perform frequency measurement based on the output three-phase voltage and the phase reference output signal using an improved phase-locked loop, wherein the improved phase-locked loop refers to a control structure in which the original PI control link in the phase-locked loop is replaced with an integral link and a lead compensation link;

[0037] an active power measurement module configured to perform active power measurement based on the output three-phase voltage, the output side current and the phase reference output signal;

[0038] The coefficient calculation module is configured to calculate the grid-type converter coefficient according to the frequency measurement result and the active power measurement result, wherein the grid-type converter coefficient includes the inertia coefficient and the damping coefficient.

[0039] A third aspect of the present invention provides a medium having a program stored thereon, which, when executed by a processor, implements the steps of the method for testing coefficients of a meshed converter based on an improved phase-locked loop as described in the first aspect of the present invention.

[0040] The fourth aspect of the present invention provides a device comprising a memory, a processor, and a program stored in the memory and executable on the processor. When the processor executes the program, the steps of the method for testing the coefficient of a meshed converter based on an improved phase-locked loop as described in the first aspect of the present invention are implemented.

[0041] One or more of the above technical solutions have the following beneficial effects:

[0042] The present invention discloses a method and system for testing the coefficients of a grid-type converter based on an improved phase-locked loop (PLL). The method includes voltage control, frequency control, frequency measurement, and active power measurement. Traditional methods often suffer from slow response speed and low accuracy when measuring frequency and its rate of change. The present invention, through an improved PLL structure, can quickly and accurately capture frequency and its rate of change signals and precisely compensate for errors in the signal capture process. This method eliminates the need to construct complex models, rely on large amounts of historical data, or obtain information about converter internal parameters. It offers the advantages of simple operation and efficient testing, thereby enabling accurate testing of the damping and inertia coefficients of grid-type converters.

[0043] The damping coefficient of the present invention is measured by normalizing the difference between the active power output signal and the reference active power input signal, and the difference between the frequency output signal and the reference frequency input signal, and then performing a division operation. The measurement of the inertia coefficient further takes into account the frequency change rate output signal, removes the damping effect by subtraction, and then performs a division operation with the normalized value of the frequency change rate output signal. Through a series of precise signal processing and calculation steps, high-precision measurement of the damping and inertia coefficient of the grid-type converter is achieved. The present invention has high test accuracy and practical feasibility. The principle of the method is simple and effective, easy to implement, and convenient for promotion and application. It can effectively support the measurement requirements of the damping and inertia coefficient of the grid-type converter. During the operation of the power grid, accurate damping and inertia coefficient measurement can help optimize the control strategy, improve the system's anti-interference ability and dynamic response performance, and ensure the safe and stable operation of the power grid.

[0044] The frequency control stage of the present invention uses a step signal generator to generate a frequency rate-of-change input signal. Through integration and superposition, it generates a frequency reference signal and a phase reference output signal. The voltage control stage outputs a PWM control signal based on the phase reference output signal, the filter capacitor voltage, and the inverter-side current to control the output three-phase voltage. This simplified measurement process not only improves test efficiency but also reduces measurement costs, facilitating widespread application.

[0045] Advantages of additional aspects of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0047] Figure 1 Schematic diagram of a method for testing damping and inertia coefficient of a grid-type converter according to a first embodiment of the present invention;

[0048] Figure 2 This is a schematic diagram of a frequency control structure according to a first embodiment of the present invention;

[0049] Figure 3 This is a schematic diagram of a voltage control structure according to a first embodiment of the present invention;

[0050] Figure 4 This is a schematic diagram of a frequency measurement structure according to a first embodiment of the present invention;

[0051] Figure 5 This is a schematic diagram of the active power measurement structure of the first embodiment of the present invention;

[0052] Figure 6 1 is a schematic diagram of a damping measurement structure according to an embodiment of the present invention;

[0053] Figure 7 This is a schematic diagram of an inertia measurement structure according to an embodiment of the present invention;

[0054] Figure 8 This is a diagram of the simulation results of the frequency change rate measurement according to the first embodiment of the present invention;

[0055] Figure 9 This is a diagram of frequency measurement simulation results of Example 1 of the present invention.

[0056] Figure 10 1 is a diagram showing the damping measurement simulation results of a grid-type converter according to a first embodiment of the present invention;

[0057] Figure 11 This is a diagram of the inertia measurement simulation results of a grid-type converter according to an embodiment of the present invention. DETAILED DESCRIPTION

[0058] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0059] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or their combinations;

[0060] Example 1:

[0061] The first embodiment of the present invention provides a method for testing the coefficient of a grid-type converter based on an improved phase-locked loop, such as Figure 1 As shown in the figure, the grid-type converter test system includes a test structure and a grid-type converter to be tested. The main circuit of the test structure includes six switching tubes. L ti and L tg and capacitors C tf Composed of LCL The filter is connected to the grid-type converter under test. v tfabc Represents the capacitor voltage at the test end, i tiabc is the inverter side current, v tgabc and i tgabc Representing the output three-phase AC voltage and three-phase AC current, respectively. The control link includes a frequency control link: generating a frequency reference signal and a phase reference output signal through frequency control; a voltage control link: outputting a PWM control signal based on the phase reference output signal, the filter capacitor voltage, and the inverter-side current to control the output three-phase voltage; a frequency measurement link: processing the output three-phase voltage and the phase reference output signal using an improved phase-locked loop to obtain a frequency change rate output signal and a frequency output signal; an active power measurement link: measuring the active power output signal based on the output three-phase voltage, the output-side current, and the phase reference output signal; a damping coefficient measurement link: processing the active power output signal, frequency output signal, reference active power input signal, reference frequency input signal, and related set parameters to obtain the damping coefficient; and an inertia coefficient measurement link: processing the active power output signal, frequency change rate output signal, frequency output signal, reference active power input signal, reference frequency input signal, and related set parameters to obtain the inertia coefficient.

[0062] The specific steps include:

[0063] Step 1: Obtain the frequency reference signal and phase reference output signal of the grid-type converter through frequency control, such as Figure 2 shown.

[0064] Step 1.1: Generate a frequency-rate-of-change input signal using a step generator r 0.

[0065] Step 1.2: Frequency rate of change input signal and given reference frequency rate of change input signal r ref After superposition, it passes through the integration link and is then combined with the given reference frequency input signal f ref Superposition is performed to obtain the frequency reference signal.

[0066] Step 1.3: The frequency reference signal undergoes multiplication and integration to obtain a phase reference output signal.

[0067] Specifically, the frequency reference signal is multiplied by 2π and then integrated to obtain the phase reference output signal θ t , phase reference output signal θ t It will serve as the input signal for the voltage control link, frequency measurement link and active power measurement link.

[0068] Step 2: Use the phase reference output signal to output a PWM control signal through voltage control, and use the PWM control signal to control the output three-phase voltage, such as Figure 3 shown.

[0069] Step 2.1: The capacitor voltage and inverter current are combined with the phase reference output signal to abc-dq Convert and extract voltage and current d Axis and q Axis component.

[0070] Specifically, the capacitor voltage at the test end v tfabc and inverter side current i tiabc Sampling is performed, and the sampling signal is used as the input signal combined with the phase reference input signal θ t Passing respectively abc-dq Transformation, get the capacitor sampling voltage d Axis component v tfd 、 q Axis component v tfq and current d Axis component i tid 、 q Axis component i tiq .

[0071] Step 2.2: Use the given voltage reference value to calculate the capacitor voltage. d Axis and q The axis components are calculated and adjusted through the PI controller to obtain the reference value of the inverter side current.

[0072] Specifically, v tfd and v tfq and capacitor voltage d Axis and q Axis input reference value v tfd_ref and v tfq_ref Perform subtraction and get d Axis and q The voltage error in the axis direction is then fed into d Axis and q In the PI controller of the axis, the output of the PI controller is the inverter side current d Axis reference value i tid_ref and q Axis reference value i tiq_ref .

[0073] Step 2.3: Use the reference value of the inverter side current to adjust the sampling current of the inverter side. dq The components are PI regulated to generate inverter voltage signals.

[0074] After calculation and PI control, the inverter voltage signal of the test device is obtained. Specifically, i tid and i tiq The input reference value i of the inverter side current d axis and q axis tfd_ref and i tfq_ref Subtraction operation is performed to obtain the current errors in the d-axis and q-axis directions, which are then sent to the PI controllers of the d-axis and q-axis respectively. The output of the PI controller is the voltage control quantity in the d-axis and q-axis directions of the inverter. This output will be used to control the PWM module to drive the power devices and realize voltage closed-loop regulation.

[0075] Step 2.4: Invert the voltage signal and the phase reference output signal dq-abc After inverse transformation, it is input to the PWM modulation module, and the output PWM control instruction is used to control the output three-phase voltage.

[0076] Specifically, the inverter voltage signal and the frequency control link output phase reference signal θ t conduct dq-abcAfter conversion, it is input to the PWM modulation link, and finally outputs the PWM signal. By adjusting the duty cycle of the PWM wave output by the voltage control link, the ratio of the switch on time to the off time is controlled, thereby setting the output three-phase AC voltage v tgabc The frequency change rate and frequency.

[0077] Step 3: Use the improved phase-locked loop to measure the frequency based on the output three-phase voltage and the phase reference output signal.

[0078] Among them, the improved phase-locked loop refers to replacing the original PI control link in the traditional phase-locked loop with a composite control structure consisting of an integral link and a lead compensation link, so as to achieve direct response to the frequency change rate and synergistic improvement of system stability.

[0079] In traditional phase-locked loop (PLL) architectures, the PI controller is used to adjust phase error and output a stable frequency signal. However, the PI controller cannot directly reflect the frequency rate of change signal, limiting its ability to track the system's dynamic behavior. To overcome this limitation, this embodiment removes the proportional component of the PI controller, retaining only the integral component. This output is converted to the integral of the frequency rate of change, enabling direct extraction of the frequency rate of change signal before the integral component.

[0080] However, using the integral stage alone can result in excessively high closed-loop gain in the low- and mid-frequency ranges, leading to delayed dynamic response and decreased system stability. To overcome this shortcoming, the improved phase-locked loop structure introduces a first-order lead compensation stage after the integral stage to increase the system's phase margin, improve dynamic performance, and ensure rapid convergence and robustness during the phase-locking process.

[0081] In this embodiment, the structure of the lead compensation link adopts the following form:

[0082] (1).

[0083] in, G lead (s) is the transfer function, T 1 is the zero time constant, T 2 is the pole time constant, s is a complex frequency variable in the Laplace transform domain.

[0084] The transfer function provides phase lead compensation in the intermediate frequency region to improve the system phase margin and frequency response characteristics, thereby effectively overcoming the phase lag problem introduced by the integrator. The phase is enhanced near the , and its maximum enhancement angle is:

[0085] (2).

[0086] in, Φ max is the maximum phase boost angle, ω m is the open loop crossover frequency. k = T 1 / T 2 can control the phase boost amplitude. The general value range is 3~10, corresponding to a phase boost of 25°~75°.

[0087] Under this structure, the output of the phase-locked loop not only contains the synchronous frequency information, but can also directly reflect the frequency change rate after conditioning through the compensation and integration network, eliminating the additional differential estimation module. The structure is simpler and the response is faster. It is particularly suitable for power electronic systems that are sensitive to dynamic characteristics such as inertia and damping.

[0088] Frequency measurements, such as Figure 4 As shown. The output three-phase voltage is linearly abc - dq Coordinate transformation obtains d Axis components and q Axis component, q After the advance compensation link and division operation, the axis component is superimposed with the reference frequency change rate input signal to obtain the frequency change rate output signal. The frequency change rate output signal is then superimposed with the reference frequency input signal through an integration link to obtain the frequency output signal.

[0089] Specifically, the voltage input signal v TGABC combines the phase reference input signal θ t goes through linear abc - dq Coordinate transformation obtains d Axis and q Two voltage components of the axis v tgd and v tgq, v After the lead compensation link, tgq is divided by the coefficient 2π and the reference frequency change rate input signal r ref superposition to obtain the frequency change rate output signal r t; the signal is then integrated and compared with the reference frequency input signal f ref superposition to obtain frequency output signal f t. Among them, the frequency output signal f t will be used as the input signal of the damping measurement link and the inertia measurement link, and the frequency change rate output signal r t will serve as the input signal of the inertia measurement link. Figure 8 and Figure 9 The effects of frequency change rate signal and frequency signal obtained by applying the improved phase-locked loop structure are demonstrated respectively.

[0090] Step 4: Measure active power based on the output three-phase voltage, output side current, and phase reference output signal.

[0091] Active power measurement, such as Figure 5 This link measures the three-phase voltage v tgabc and three-phase current i tgabc The amplitude of the test device is calculated to obtain the active power output signal p t , this signal will serve as the input signal for the damping measurement link and the inertia measurement link.

[0092] Step 4.1: Compare the output three-phase voltage with the phase reference signal abc-dq Coordinate transformation, get the voltage d Axis and q Axis component.

[0093] Step 4.2: Perform the same operation on the output current and phase reference signal. abc-dq Convert, extract current d Axis and q Axis component.

[0094] Step 4.3: Based on the above voltage and current d Axis and q The axis components are calculated to obtain the output signal of active power.

[0095] Specifically, the three-phase voltage signal will be output v tgabc And output three-phase current signal i tgabc Combined with the phase reference input signal θ t Separately abc-dq Convert voltage and current d Axis components and q Axis component, based on this calculation, the active power signal is obtained. The specific calculation process is shown in the following formula:

[0096] (3).

[0097] Where, v tgd and v tgq Represent the output three-phase voltage signal v tgabc The d-axis and q-axis components, i tgd and i tgq Represent the output three-phase current signal i tgabc The d-axis and q-axis components of

[0098] Step 5: Calculate the grid-type converter coefficient based on the frequency measurement results and the active power measurement results, where the grid-type converter coefficient includes the inertia coefficient and the damping coefficient, such as Figure 6 and Figure 7 shown.

[0099] During inertia coefficient measurement, the system frequency changes in a ramp-like manner. Subsequent measurements require accurate tracking of this signal and its rate of change. Compared to traditional phase-locked loops, the improved phase-locked loop structure not only achieves zero-error tracking of the frequency signal, but also has the ability to track the frequency rate of change signal without static errors.

[0100] Specifically, the improved phase-locked loop structure replaces the traditional PI control link with a composite control structure consisting of an integral link and a first-order lead compensation link, which not only retains the ability to accurately lock the frequency, but also enhances the response performance to ramp-type inputs. Based on the internal model principle, it can be seen that this structure achieves zero steady-state error tracking for the rate of change of the frequency signal of the linear ramp input, so that the system can output a high-precision df / dt signal in real time. In addition, this embodiment does not need to perform numerical differentiation on the frequency signal in the process of obtaining the frequency change rate signal, which avoids the high-frequency noise amplification and numerical instability problems brought by the traditional differential structure from the source, and significantly improves the acquisition accuracy and robustness of the frequency change rate signal. Based on the above advantages, accurate and rapid measurement of the inertia coefficient can be achieved.

[0101] Step 5.1: Obtain the damping coefficient of the grid-connected converter based on the active power output signal, the frequency output signal, the reference active power input signal, the reference frequency input signal and related setting parameters.

[0102] Specifically, the difference between the active power output signal and the active power reference value and the difference between the frequency output signal and the reference frequency input signal are both normalized, and then the damping coefficient of the measured grid-type converter is obtained by dividing the two normalized values.

[0103] This link outputs the active power signal p t With the reference active power input signal p ref The difference and frequency output signal f t With the reference frequency input signal f ref The difference between them is normalized, and then the damping coefficient of the measured grid-type converter is obtained by dividing the two normalized values. D g , the specific calculation process is shown in the following formula:

[0104] (4).

[0105] In the formula K p and K f is the normalized gain coefficient. Figure 10 The damping measurement effect of the measurement link is demonstrated.

[0106] Step 5.2: Obtain the inertia coefficient of the grid-connected converter based on the active power output signal, the frequency change rate output signal, the frequency output signal, the reference active power input signal, the reference frequency input signal and related setting parameters.

[0107] Specifically, the difference between the active power output signal and the active power reference value, the difference between the frequency output signal and the reference frequency input signal, and the frequency change rate output signal are all normalized, and then the active power change caused by the damping coefficient is removed by subtraction. Finally, it is divided by the normalized value of the frequency change rate output signal to obtain the inertia coefficient of the measured grid-type converter. 。

[0108] This link first outputs the active power signal p t With the reference active power input signal p ref The difference and frequency output signal f t With the reference frequency input signal f ref The difference between the input signal and the frequency change rate r t All are normalized, and then the damping effect is removed by subtraction to obtain the inertia H g The per-unit value of the active power change part generated is then compared with the frequency change rate input signal r t The inertia coefficient of the measured grid-type converter is obtained by dividing the per-unit value of H g , the specific calculation process is as follows:

[0109] (5).

[0110] Figure 11 The inertia measurement effect of the measurement link is demonstrated.

[0111] Example 2:

[0112] A second embodiment of the present invention provides a network-type converter coefficient testing system based on an improved phase-locked loop, comprising:

[0113] A frequency control module is configured to obtain a frequency reference signal and a phase reference output signal of the grid-type converter through frequency control;

[0114] a voltage control module configured to output a PWM control signal by voltage control using the phase reference output signal, and to control the output three-phase voltage using the PWM control signal;

[0115] a frequency measurement module configured to perform frequency measurement based on the output three-phase voltage and the phase reference output signal using an improved phase-locked loop, wherein the improved phase-locked loop refers to a control structure in which the original PI control link in the phase-locked loop is replaced with an integral link and a lead compensation link;

[0116] an active power measurement module configured to perform active power measurement based on the output three-phase voltage, the output side current and the phase reference output signal;

[0117] The coefficient calculation module is configured to calculate the grid-type converter coefficient according to the frequency measurement result and the active power measurement result, wherein the grid-type converter coefficient includes the inertia coefficient and the damping coefficient.

[0118] Example 3:

[0119] A third embodiment of the present invention provides a medium having a program stored thereon. When the program is executed by a processor, the steps of the method for testing the coefficients of a meshed converter based on an improved phase-locked loop as described in the first embodiment of the present invention are implemented.

[0120] Example 4:

[0121] Embodiment 4 of the present invention provides a device, including a memory, a processor, and a program stored in the memory and runnable on the processor. When the processor executes the program, the steps in the method for testing the coefficient of a meshed converter based on an improved phase-locked loop as described in Embodiment 1 of the present invention are implemented.

[0122] The steps involved in the above embodiments 2, 3 and 4 correspond to those in the method embodiment 1. For the specific implementation methods, please refer to the relevant description part of the embodiment 1.

[0123] Those skilled in the art will appreciate that the modules or steps of the present invention described above can be implemented using a general-purpose computer device. Alternatively, they can be implemented using program code executable by a computing device, which can then be stored in a storage device and executed by the computing device. Alternatively, they can be fabricated into separate integrated circuit modules, or multiple modules or steps can be fabricated into a single integrated circuit module for implementation. The present invention is not limited to any specific combination of hardware and software.

[0124] Although the above describes the specific embodiments of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without any creative work are still within the scope of protection of the present invention.

Claims

1. A method for testing the coefficient of a grid-type converter based on an improved phase-locked loop, characterized in that: The following steps are involved: The frequency reference signal and phase reference output signal of the grid-type converter are obtained by frequency control, and the specific steps are as follows: using a step signal generator to generate a frequency change rate input signal; The frequency change rate input signal is superimposed on the reference frequency change rate input signal, and then superimposed on the reference frequency input signal through the integration link to obtain the frequency reference signal; The frequency reference signal is multiplied and integrated to obtain the phase reference output signal; The phase reference output signal is used to output a PWM control signal through voltage control, and the PWM control signal is used to control the output three-phase voltage. The specific steps of using the phase reference output signal to output a PWM control signal through voltage control are as follows: the capacitor voltage and the inverter side current are respectively combined with the phase reference output signal to perform abc-dq Convert and extract voltage and current d Axis and q axis component; using the voltage reference value to the capacitor voltage d Axis and q The axis components are calculated and adjusted through the PI controller to obtain the reference value of the inverter side current; The inverter side current is sampled using the inverter side current reference value. dq The components are PI regulated to generate an inverter voltage signal; the inverter voltage signal is compared with the phase reference output signal. dq-abc After inverse transformation, it is input to the PWM modulation module, and the output PWM control instruction is used to control the output three-phase voltage; Frequency measurement is performed based on the output three-phase voltage and the phase reference output signal using an improved phase-locked loop, wherein the improved phase-locked loop refers to a control structure consisting of an integral link and a lead compensation link replacing the original PI control link in the phase-locked loop; The specific steps of using the improved phase-locked loop to measure the frequency based on the output three-phase voltage and the phase reference output signal are as follows: The output three-phase voltage is linearly abc - dq Coordinate transformation obtains d Axis components and q Axis component, q After the advance compensation link and division operation, the axis component is superimposed on the reference frequency change rate input signal to obtain the frequency change rate output signal. The frequency change rate output signal is then superimposed on the reference frequency input signal through an integration link to obtain the frequency output signal. Active power measurement based on output three-phase voltage, output side current and phase reference output signal; The grid-type converter coefficient is calculated according to the frequency measurement result and the active power measurement result, wherein the grid-type converter coefficient includes an inertia coefficient and a damping coefficient.

2. The method for testing the coefficient of a meshed converter based on an improved phase-locked loop according to claim 1, wherein: The specific steps for calculating the inertia coefficient of the grid-type converter based on the frequency measurement results and the active power measurement results are as follows: The difference between the active power output signal and the active power reference value, the difference between the frequency output signal and the reference frequency input signal, and the frequency change rate output signal are all normalized. Then, the active power change caused by the damping coefficient is removed by subtraction. Finally, the inertia coefficient of the measured grid-type converter is obtained by dividing it with the normalized value of the frequency change rate output signal. 。 3. The method for testing the coefficient of a meshed converter based on an improved phase-locked loop according to claim 1, wherein: The specific steps for calculating the damping coefficient of the grid-type converter based on the frequency measurement results and the active power measurement results are as follows: The difference between the active power output signal and the active power reference value and the difference between the frequency output signal and the reference frequency input signal are both normalized, and then the damping coefficient of the measured grid-type converter is obtained by dividing the two normalized values.

4. A grid-type converter coefficient test system based on an improved phase-locked loop, characterized in that: include: The frequency control module is configured to obtain a frequency reference signal and a phase reference output signal of the grid-type converter through frequency control, specifically by: generating a frequency change rate input signal using a step signal generator; The frequency change rate input signal is superimposed on the reference frequency change rate input signal, and then superimposed on the reference frequency input signal through the integration link to obtain the frequency reference signal; The frequency reference signal is multiplied and integrated to obtain the phase reference output signal; The voltage control module is configured to use the phase reference output signal to output a PWM control signal through voltage control, and use the PWM control signal to control the output three-phase voltage; the specific steps of using the phase reference output signal to output the PWM control signal through voltage control are: the capacitor voltage and the inverter side current are respectively combined with the phase reference output signal to perform abc-dq Convert and extract voltage and current d Axis and q axis component; using the voltage reference value to the capacitor voltage d Axis and q The axis components are calculated and adjusted through the PI controller to obtain the reference value of the inverter side current; The inverter side current is sampled using the inverter side current reference value. dq The components are PI regulated to generate an inverter voltage signal; the inverter voltage signal is compared with the phase reference output signal. dq-abc After inverse transformation, it is input to the PWM modulation module, and the output PWM control instruction is used to control the output three-phase voltage; The frequency measurement module is configured to use an improved phase-locked loop to perform frequency measurement based on the output three-phase voltage and the phase reference output signal, wherein the improved phase-locked loop refers to a control structure in which the original PI control link in the phase-locked loop is replaced with an integral link and a lead compensation link. The specific steps of using the improved phase-locked loop to perform frequency measurement based on the output three-phase voltage and the phase reference output signal are as follows: The output three-phase voltage is linearly abc - dq Coordinate transformation obtains d Axis components and q Axis component, q After the advance compensation link and division operation, the axis component is superimposed on the reference frequency change rate input signal to obtain the frequency change rate output signal. The frequency change rate output signal is then superimposed on the reference frequency input signal through an integration link to obtain the frequency output signal. an active power measurement module configured to perform active power measurement based on the output three-phase voltage, the output side current and the phase reference output signal; The coefficient calculation module is configured to calculate the grid-type converter coefficient according to the frequency measurement result and the active power measurement result, wherein the grid-type converter coefficient includes the inertia coefficient and the damping coefficient.

5. A computer-readable storage medium, characterized in that A plurality of instructions are stored therein, and the instructions are suitable for being loaded by a processor of a terminal device and executing the method for testing a coefficient of a meshed converter based on an improved phase-locked loop according to any one of claims 1 to 3.

6. A terminal device, characterized in that: The invention comprises a processor and a computer-readable storage medium, wherein the processor is used to implement various instructions; the computer-readable storage medium is used to store multiple instructions, wherein the instructions are suitable for being loaded by the processor and executing the grid-type converter coefficient testing method based on the improved phase-locked loop according to any one of claims 1 to 3.

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