Method and system for improving stability of single-phase grid-connected converter based on delay compensation

Abstract

The present invention discloses a method and system for improving the stability of a single-phase grid-type converter based on delay compensation, and belongs to the field of power electronics technology. The present invention provides a delay compensation unit for the active and reactive power controllers of a single-phase grid-type converter, which adds a zero point in the power controller to cancel the pole generated by the power measurement delay, thereby eliminating the negative impact of single-phase power measurement. The present invention improves the stability of a single-phase grid-type converter through a simple and effective implementation method, can significantly reduce the instability phenomenon of a single-phase grid-type converter, and is easy to expand and apply.

Description

Technical Field

[0001] The present invention relates to the field of power electronics technology, and in particular to a method and system for improving the stability of a single-phase grid-connected converter based on delay compensation. 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] The mainstream grid-connected converter is a grid-following converter, which is equivalent to a controllable current source. It has fundamental defects such as poor frequency / voltage regulation capability, inability to operate independently, and easy instability in weak networks. The high proportion of grid-following converters causes the vulnerability of the power grid to increase, the stability to decrease, and the risk of large-scale power outages to increase. The grid-building converter is equivalent to a controllable voltage source, which has the advantages of strong frequency / voltage regulation capability, independent operation, and good stability in weak networks. It has become an enabling technology to ensure the stable operation of new power systems.

[0004] In addition, due to the wide distribution and high flexibility of new energy sources such as wind and light, distributed power generation units are becoming more and more popular, such as rooftop photovoltaic power generation. Under the trend of distributed power generation, single-phase power generation equipment has been widely welcomed due to its small size, easy installation and maintenance, etc. Therefore, single-phase grid-connected converters have become a key technology to promote the friendly grid connection of new energy converters and accelerate energy transformation.

[0005] However, the control method of single-phase grid-connected converter is not mature yet, which may cause the stability and safety of power system to decrease. Single-phase grid-connected converter is different from three-phase equipment. This is mainly reflected in its power measurement unit. The instantaneous power fluctuations of the three phases will cancel each other out, forming a constant three-phase power sum. Through abc / dq0 transformation and power measurement, the average reactive / active power without delay can be obtained. However, single-phase grid-connected converter has inherent power fluctuations, and a nonlinear orthogonal signal generation unit is required to measure the average power.

[0006] Currently, there are few studies on single-phase grid-connected converters, and the research methods ignore the dynamics of the power measurement part. There are problems with controller and parameter design, and it is difficult to solve the problem of poor stability of single-phase grid-connected converters. Summary of the invention

[0007] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a method and system for improving the stability of a single-phase grid-type converter based on delay compensation, which compensates for the power measurement delay of the single-phase grid-type converter, adds a zero point in the active or reactive controller, and cancels the pole generated by the power measurement delay, thereby eliminating the negative impact of single-phase power measurement, suppressing the instability of the single-phase grid-type converter, and overcoming the defects of the existing methods.

[0008] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0009] A first aspect of the present invention provides a method for improving stability of a single-phase grid-connected converter based on delay compensation, comprising the following steps:

[0010] Obtaining the operating parameters of the single-phase grid-forming converter and establishing a dynamic phasor model of the single-phase grid-forming converter;

[0011] According to the dynamic phasor model of single-phase grid-connected converter, the influence of power measurement dynamics on the stability of grid-connected converter is analyzed, and the power measurement delay is obtained;

[0012] A power measurement delay compensation unit for a single-phase grid-connected converter is designed, and the power measurement delay compensation unit is used to compensate for active power and reactive power according to the power measurement delay, thereby improving the stability of the single-phase grid-connected converter.

[0013] Furthermore, the single-phase grid-connected converter dynamic phasor model includes a power measurement model, an active power controller and a reactive power controller model.

[0014] Furthermore, the single-phase grid-type converter power measurement delay compensation unit can perform power measurement delay compensation on a virtual synchronous machine control strategy or a droop control strategy of the grid-type converter.

[0015] Furthermore, the power measurement delay compensation unit of the single-phase grid-connected converter adds a zero point in the active power controller and the reactive power controller.

[0016] Furthermore, the single-phase grid-connected converter power measurement delay compensation unit does not change the inertia and damping of the single-phase grid-connected converter.

[0017] A second aspect of the present invention provides a single-phase grid-connected converter stability improvement system based on delay compensation, comprising:

[0018] A dynamic model building module is configured to obtain operating parameters of a single-phase grid-forming converter and establish a dynamic phasor model of the single-phase grid-forming converter;

[0019] The power measurement module is configured to analyze the influence of the power measurement dynamics on the stability of the grid-type converter according to the dynamic phasor model of the single-phase grid-type converter, and obtain the power measurement delay;

[0020] The power compensation module is configured to design a single-phase grid-type converter power measurement delay compensation unit, and use the single-phase grid-type converter power measurement delay compensation unit to compensate for active power and reactive power according to the power measurement delay, thereby improving the stability of the single-phase grid-type converter.

[0021] Furthermore, in the dynamic model construction module, the single-phase grid-connected converter dynamic phasor model includes a power measurement model, an active power controller and a reactive power controller model.

[0022] Furthermore, in the power compensation module, the single-phase grid-type converter power measurement delay compensation unit can perform power measurement delay compensation on the virtual synchronous machine control strategy or droop control strategy of the grid-type converter.

[0023] Furthermore, in the power compensation module, a zero point is added to the active power controller and the reactive power controller of the single-phase grid-connected converter power measurement delay compensation unit.

[0024] Furthermore, in the power compensation module, the single-phase grid-type converter power measurement delay compensation unit does not change the inertia and damping of the single-phase grid-type converter.

[0025] One or more of the above technical solutions have the following beneficial effects:

[0026] The present invention discloses a method and system for improving the stability of a single-phase grid-type converter based on delay compensation, which compensates for the power measurement delay of the single-phase grid-type converter, adds a zero point in the active or reactive controller, and cancels the pole generated by the power measurement delay, thereby eliminating the negative impact of the power measurement delay on the stability of the single-phase grid-type converter and improving the stability margin of the single-phase grid-type converter. The present invention improves the stability of the single-phase grid-type converter through a simple and effective implementation method, can significantly reduce the instability phenomenon of the single-phase grid-type converter, does not require additional hardware equipment, does not increase costs, and is easy to expand and apply.

[0027] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings in the specification, 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.

[0029] Figure 1 This is a flow chart of a method for improving stability of a single-phase grid-connected converter based on delay compensation in Embodiment 1 of the present invention;

[0030] Figure 2 This is a schematic diagram of the structure of a single-phase grid-connected converter in Embodiment 1 of the present invention;

[0031] Figure 3Schematic diagram of active power controller of grid-type converter in Embodiment 1 of the present invention;

[0032] Figure 4 Schematic diagram of reactive power controller of grid-type converter in Embodiment 1 of the present invention;

[0033] Figure 5 Schematic diagram of a small signal model of a single-phase grid-connected converter in Embodiment 1 of the present invention;

[0034] Figure 6 The Bodet diagram of the active loop open-loop gain considering the dynamic influence of each unit in the first embodiment of the present invention;

[0035] Figure 7 A Bodet diagram of the reactive loop open-loop gain considering the dynamic influence of each unit in the first embodiment of the present invention;

[0036] Figure 8 It is a schematic diagram of the design of an active power controller of a single-phase grid-connected converter according to a method for improving the stability of a single-phase grid-connected converter based on delay compensation in Embodiment 1 of the present invention;

[0037] Fig. 9 It is a schematic diagram of the design of a reactive power controller of a single-phase grid-type converter according to a method for improving the stability of a single-phase grid-type converter based on delay compensation in Embodiment 1 of the present invention;

[0038] Fig.10 It is a simulation waveform diagram of active power and reactive power of a single-phase grid-type converter when the single-phase grid-type converter stability improvement method based on delay compensation is not used in the first embodiment of the present invention;

[0039] Fig.11 This is a simulation waveform diagram of active power and reactive power of a single-phase grid-type converter after using the single-phase grid-type converter stability improvement method based on delay compensation in Example 1 of the present invention. DETAILED DESCRIPTION

[0040] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0041] 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 also intended to include the plural form. In addition, it should be understood that when the terms "include" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or their combinations;

[0042] Embodiment 1:

[0043] Embodiment 1 of the present invention provides a method for improving the stability of a single-phase grid-connected converter based on delay compensation, such as Figure 1 As shown, the following steps are included:

[0044] Step 1: Obtain the operating parameters of the single-phase grid-connected converter and establish a dynamic phasor model of the single-phase grid-connected converter.

[0045] Step 1.1: Obtain the operating parameters of the single-phase grid-connected converter.

[0046] like Figure 2 The figure shows the basic structure of a single-phase grid-type converter. The DC side of a single-phase grid-type converter can be a capacitor or a battery, and the DC side voltage is v gdc The AC side of the single-phase grid-connected converter is connected to the grid through LCL The filter is connected, where LCL The filter includes the converter and the filter inductor L gi , grid-side filter inductor L gg And filter capacitor C gf , the grid side includes the resistance at the common connection point R s , and the inductor connected to the resistor L s， The output voltage is v s . Figure 2 The output voltage of the converter is v gf and output current i gi , the voltage at the point of common coupling (PCC) v gg and current i gg That is, the operating parameters of the single-phase grid-connected converter are obtained, and the above operating parameters provide information for the controller. This embodiment includes an inner loop current controller G i ( s ), Central voltage controller G v ( s ), outer loop active and reactive power controller G p ( s )and G q ( s), and power measurement and modulation units. The functions of each controller are as follows: the inner loop current controller realizes the output current i gi Track its reference value i gi_ref ; The central voltage controller realizes the output capacitor voltage v gf Track its reference value v gf_ref ; Outer loop active power controller G p ( s ) Output voltage phase of grid-connected converter θ g , outer loop reactive power controller G q ( s ) Output voltage amplitude of grid-connected converter v gf_am and through v gf_ref = v gf_am cos θ g Generates the reference value of the voltage loop. The same power controller realizes the power output of the converter p g / q g Tracks the reference value of its input p g_ref / q g_ref The power measurement unit is measured by voltage v gf and current i gg Calculates the power transmitted by the converter to the grid. The modulation unit is responsible for controlling the output of the switching devices.

[0047] Figure 3 The basic structure of active power controller for grid-connected converter based on virtual synchronous machine control strategy is presented. Active power reference value p g_ref With output value p g Divide by rated power S 0 realizes per unit conversion and obtains the per unit value of active power reference p g_ref_pu The per unit value of active power output p g_pu , and then the difference between the two is calculated and passed through the virtual synchronous machine controller (1 / (2 H p s + D p ),inH p is the inertia constant of the active loop, D p is the damping coefficient of the active loop) to obtain the per-unit value of the frequency change Δ ω g_pu . Δ ω g_pu Rated value of multiplication frequency ω 0, and then integrate to get the phase difference between the converter voltage and the grid voltage φ g . Where s represents the Laplace complex frequency domain variable.

[0048] Figure 4 The basic structure of the reactive power controller for grid-connected converters based on the virtual synchronous machine control strategy is presented. q g_ref With output value q g Divide by rated power S 0 to achieve per unit conversion and obtain the per unit value of reactive power reference q g_ref_pu The per unit value of reactive power output q g_pu , and then the difference between the two is calculated and passed through the virtual synchronous machine controller (1 / (2 H q s + D q ),in H q is the inertia constant of the reactive loop, D q is the damping coefficient of the reactive loop) to obtain the per unit value dΔ of the voltage change rate v gf_am_pu / d t . For dΔ v gf_am_pu / d t Integrate to get the per unit value of voltage change Δ v gf_am_pu , Δ v gf_am_pu Multiply the voltage rating V 0 plus V 0 to get the converter voltage amplitude v gf_am .

[0049] Step 2.1: The single-phase grid-connected converter dynamic phasor model includes a power measurement model, an active power controller, and a reactive power controller model, wherein the power measurement model involves converter voltage, grid voltage, transmission line resistance and voltage, and converter current models.

[0050] Figure 5 It is a dynamic phasor model of a single-phase grid-connected converter. It includes the dynamic phasor models of power measurement, active power controller, and reactive power controller. The input of the power measurement unit model is the disturbance of the power angle Δ φ g , the disturbance of voltage amplitude Δ v gf_am , the output is the disturbance of active power Δ p g , the disturbance of reactive power Δ q g .

[0051] k pφ ( s ) represents Δ p g With Δ φ g The coupling coefficient between k pv ( s ) represents Δ p g With Δ v g The coupling coefficient between k qφ ( s ) represents Δ q g With Δ φ g The coupling coefficient between k qv ( s ) represents Δ q g With Δ v g The coupling coefficient between t 0s + 2) represents the delayed dynamics of power measurement. The input to the active power controller model is the active power reference value p g_ref With output value p g Divide by rated power S The difference after 0, after the control link ω 0 / (2 H q s 2 + D q s ) to obtain the power angle disturbance Δ φ g The reactive power controller model input is the reactive power reference value qg_ref With output value q g Divide by rated power S The difference after 0, after the control link V 0 / (2 H q s 2 + D q s ) to obtain the voltage amplitude disturbance Δ v gf_am .

[0052] Among them, the power measurement unit model is detailed as follows:

[0053] The dynamic vector method transforms the time domain signal x ( τ ) is converted to the frequency domain via a short-time Fourier transform, allowing both frequency and phase to change over time. t Dynamic phasor converted from time to frequency domain <x> k ( t ) is defined as:

[0054] (1).

[0055] in, T 0 is the fundamental period ( T 0= 1 / f 0, f 0 is the fundamental frequency), ω 0 is the fundamental angular frequency ( ω 0= 2 π f 0). k represents the frequency of the signal, that is k = 0 represents the DC component, k = ±1 represents the component with the same frequency as the fundamental wave, k = ±2 represents a component that is twice the fundamental frequency.

[0056] The inverse transformation of the dynamic phasor is:

[0057] (2).

[0058] based on Figure 2 , establish the dynamic phasor model of each unit of the grid-type converter:

[0059] (1) Voltage model of grid-connected converter

[0060] The voltage of the grid-connected converter is:

[0061] (3).

[0062] in, t Indicates the time, v gf represents the converter output voltage, v gf_am is the voltage amplitude, φ g Represents the phase difference between the converter voltage and the grid voltage, ω 0 is the rated angular frequency of the AC voltage. Substituting equation (3) into equation (1) yields the dynamic phasor model of the converter voltage:

[0063] (4).

[0064] in, k = ±1 represents taking the fundamental frequency (50 Hz) component of the converter output voltage.

[0065] (2) Grid voltage model

[0066] Grid voltage It can be expressed as:

[0067] (5).

[0068] in, V s is the amplitude of the grid voltage.

[0069] Substituting equation (5) into equation (1) yields the dynamic phasor model of the grid voltage: for:

[0070] (6).

[0071] (3) Inductance / resistance model

[0072] Transmission line inductance L gs ( L gs = L gg + L s ) The voltage across v L Dynamic phasor model of for:

[0073] (7).

[0074] Transmission line resistance R gs The voltage across v R Dynamic phasor model of for:

[0075] (8).

[0076] (4) Converter current model

[0077] Based on Kirchhoff's law, the dynamic phasor model of the converter current can be derived: for:

[0078] (9).

[0079] (5) Power measurement model

[0080] Active Power Reactive Power The time domain calculation formula is:

[0081] (10)

[0082] (11).

[0083] It contains a delay unit, that is, a nonlinear orthogonal signal generating unit. t 0= T 0 / 4 is the delay time. Substituting equation (10) and equation (11) into equation (1) yields the active power Reactive Power The dynamic phasor models are:

[0084] (12)

[0085] (13).

[0086] The superscript d represents the delayed signal. n = 0, the average power is:

[0087] (14)

[0088] (15).

[0089] in, is the average power of active power, is the average power of reactive power.

[0090] The power measurement includes the original signal product , delayed signal product , the product of the original signal and the delayed signal The dynamic phasor of . The calculation formula can be derived from equations (1) and (2) as follows:

[0091] (16)

[0092] (17)

[0093] (18).

[0094] in, and They represent two different dynamic phasors respectively, m and n both represent the frequency of the dynamic vector, and d represents the delayed signal.

[0095] The dynamic phasor model of the active and reactive power measurement unit can be obtained from equations (14)–(18):

[0096] (19).

[0097] To carry out stability analysis, the derived dynamic phasor model is linearized by replacing the derived dynamic phasor with its steady-state value <x> k (indicated by capital letters) and the disturbance value ∆ <x> k ( t ) (prefixed with ∆) to linearize the model. Through linearization and Laplace transform, the small signal expressions of active and reactive power in the complex frequency domain are obtained as follows:

[0098] (20).

[0099] According to formulas (4) and (9) and the above linearization method, the voltage dynamic phasor can be obtained: <v gf > k ( t ) <V gf > k and the disturbance value ∆ <v gf > k ( t ), current dynamic phasor gg > k ( t ) gf > k and the disturbance value ∆ gg > k ( t ):

[0100] (twenty one).

[0101] Substituting formula (21) into formula (20) yields:

[0102] (twenty two).

[0103] in, k pφ ( s ), k pv ( s ), k qφ ( s )and k qv ( s ) are different coupling coefficients, which are:

[0104] (twenty three)

[0105] The delay link in formula (22) e –st0 Through Padé approximation, it can be linearized as:

[0106] e –st0 ≈ (– t 0 s +2) / (​​​ t 0 s +2)(24).

[0107] Substituting formula (24) into (22), we can get the small signal model of the power measurement part:

[0108] (25).

[0109] Among them, 2 / ( t 0 s + 2) represents the delay dynamics introduced by the power measurement unit.

[0110] based on Figure 3 and Figure 4 The small signal model of active and reactive power controller is obtained as follows:

[0111] (26).

[0112] Combining the small signal model of the power measurement part with the small signal model of the active and reactive power controllers, we can get Figure 5 The small signal model of a single-phase grid-connected converter is shown in Figure 1. This model includes the dynamics of the transmission line and the power measurement part.

[0113] Step 2: According to the dynamic phasor model of the single-phase grid-connected converter established in step 1, the influence of the power measurement dynamics on the stability of the grid-connected converter is analyzed to obtain the power measurement delay.

[0114] Figure 6 and Figure 7 Demonstrated based on Figure 5 The open-loop gain Bodet plot of the active loop and reactive loop drawn by the model shown shows the impact of the dynamics of the transmission line and power measurement part on the system stability. Figure 6 It is the Bodet diagram of the active loop open-loop gain taking into account the dynamic influence of each unit. Figure 7 is the Bodet diagram of the reactive loop open-loop gain considering the dynamic influence of each unit. In the figure, case 1 means that the system dynamics are not considered, case 2 means that only the dynamics of the transmission line are considered, and case 3 means that only the dynamics of the power measurement part are considered. Since the power loop bandwidth is generally within 0.1 to 10 Hz, Figure 6 It can be seen that the impact of transmission line dynamics is mainly concentrated in the high frequency band, and the impact on the main frequency band (less than 10 Hz) is small. However, the nonlinear orthogonal signal generation unit in power measurement will cause phase delay, resulting in a decrease in the phase margin when the amplitude crosses 0 dB, thereby reducing the stability of the grid-connected converter.

[0115] Step 3: Design a single-phase grid-connected converter power measurement delay compensation unit, and use the single-phase grid-connected converter power measurement delay compensation unit to compensate for active power and reactive power according to the power measurement delay, thereby improving the stability of the single-phase grid-connected converter.

[0116] Figure 8 and Fig. 9 This is a schematic diagram of the improved structure of the single-phase grid-connected converter power controller proposed in the present invention. Figure 8 This is a schematic diagram of the active power controller design, including the active power reference value p g_ref With output value p g Divide by rated power S 0 realizes per unit conversion and obtains the per unit value of the active power reference value p g_ref_pu The per unit value of the active power output p g_pu , and then the difference between the two is calculated and the virtual synchronous machine controller is used to calculate 0.5( t 0s + 2) / (2 H p s + D p ) to obtain the per-unit value of the frequency change Δ ω g_pu , Δ ω g_pu Rated value of multiplication frequency ω 0, and then integrate to get the phase difference between the converter voltage and the grid voltage φ g . Fig. 9 It is a schematic diagram of reactive power controller design, including reactive power reference value q g_ref With output value q g Divide by rated power S 0 to achieve per unit conversion and obtain the per unit value of the reactive power reference value q g_ref_pu The per unit value of reactive power output q g_pu , and then the difference between the two is calculated and the virtual synchronous machine controller is used to calculate 0.5( t 0s + 2) / (2 H q s + D q ) to obtain the per unit value dΔ of the voltage change rate v gf_am_pu / d t . For dΔ v gf_am_pu / d t Integrate to get the per unit value of voltage change Δ v gf_am_pu , Δ v gf_am_pu Multiply the voltage rating V 0 plus V 0 to get the converter voltage amplitude v gf_am .

[0117] The improvement of the present invention is to design a single-phase grid-type converter power measurement delay compensation unit, wherein the single-phase grid-type converter power measurement delay compensation unit adds a zero point in the active power controller and the reactive power controller, that is, the original active power controller 1 / (2 H p s + D p ) becomes 0.5( t 0s + 2) / (2 H p s + D p ), the original reactive power controller 1 / (2 H q s + D q ) becomes 0.5( t 0s + 2) / (2 H q s + D q ). The newly added zero point 0.5 ( t 0s + 2) and the pole generated by the power measurement delay 2 / ( t 0s + 2) cancellation, eliminating the negative impact of the dynamics of the nonlinear orthogonal signal generation link in power measurement on the stability of the single-phase grid-connected converter.

[0118] The single-phase grid-type converter power measurement delay compensation unit does not change the inertia and damping of the single-phase grid-type converter, thereby avoiding deterioration of frequency stability.

[0119] Fig.10 Demonstrating that when the method of the present invention is not used, the single-phase grid-type converter outputs active power p g Reactive Power q g Simulation waveform. The simulation parameters are shown in Table 1.

[0120] Table 1. Simulation parameters

[0121]

[0122] It can be seen from the simulation results that when the method disclosed in the present invention is not used, active and reactive power divergence causes the converter to become unstable.

[0123] Fig.11 After using the method of the present invention, the single-phase grid-type converter outputs active power p g Reactive Power q g Simulation waveform diagram. Simulation parameters are shown in Table 1. The method proposed in the present invention solves the problem of converter stability degradation caused by single-phase power measurement delay, and ensures stable operation of the converter.

[0124] In addition, the single-phase grid-type converter power measurement delay compensation unit can perform power measurement delay compensation for the virtual synchronous machine (Virtual Synchronous Machine, VSM) control strategy or droop control (Droop Control) strategy of the grid-type converter. It should be noted that in addition to these two strategies, the single-phase grid-type converter power measurement delay compensation unit constructed by the method of this embodiment can also perform power measurement delay compensation for other strategies.

[0125] Embodiment 2:

[0126] Embodiment 2 of the present invention provides a single-phase grid-connected converter stability improvement system based on delay compensation, comprising:

[0127] A dynamic model building module is configured to obtain operating parameters of a single-phase grid-forming converter and establish a dynamic phasor model of the single-phase grid-forming converter;

[0128] In the dynamic model building module, the single-phase grid-connected converter dynamic phasor model includes a power measurement model, an active power controller and a reactive power controller model.

[0129] The power measurement module is configured to analyze the influence of the power measurement dynamics on the stability of the grid-type converter according to the dynamic phasor model of the single-phase grid-type converter, and obtain the power measurement delay;

[0130] The power compensation module is configured to design a single-phase grid-type converter power measurement delay compensation unit, and use the single-phase grid-type converter power measurement delay compensation unit to compensate for active power and reactive power according to the power measurement delay, thereby improving the stability of the single-phase grid-type converter.

[0131] In the power compensation module, the single-phase grid-type converter power measurement delay compensation unit can perform power measurement delay compensation on the virtual synchronous machine control strategy or droop control strategy of the grid-type converter.

[0132] In the power compensation module, a zero point is added to the active power controller and the reactive power controller of the single-phase grid-connected converter power measurement delay compensation unit.

[0133] In the power compensation module, the single-phase grid-type converter power measurement delay compensation unit does not change the inertia and damping of the single-phase grid-type converter.

[0134] The steps involved in the above embodiment 2 correspond to those in the method embodiment 1. For the specific implementation method, please refer to the relevant description part of the embodiment 1.

[0135] Those skilled in the art should understand that the modules or steps of the present invention described above can be implemented by a general-purpose computer device, or alternatively, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. The present invention is not limited to any specific combination of hardware and software.

[0136] Although the above describes the specific implementation mode 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 creative work are still within the scope of protection of the present invention.< / x> < / x> < / x>

Claims

1. A method for improving the stability of a single-phase grid-connected converter based on delay compensation, characterized in that: The following steps are involved: Obtaining the operating parameters of the single-phase grid-forming converter and establishing a dynamic phasor model of the single-phase grid-forming converter; According to the dynamic phasor model of single-phase grid-connected converter, the influence of power measurement dynamics on the stability of grid-connected converter is analyzed, and the power measurement delay is obtained; A single-phase grid-type converter power measurement delay compensation unit is designed, and the single-phase grid-type converter power measurement delay compensation unit is used to compensate active power and reactive power according to the power measurement delay, thereby improving the stability of the single-phase grid-type converter; The single-phase grid-type converter power measurement delay compensation unit adds a zero point in the active power controller and the reactive power controller; Specifically: Set the active power controller 1 / (2 H p s + D p ) becomes 0.5( t 0s + 2) / (2 H p s + D p ), reactive power controller 1 / (2 H q s + D q ) becomes 0.5( t 0s + 2) / (2 H q s + D q ); the newly added zero point 0.5( t 0s + 2) and the pole generated by the power measurement delay 2 / ( t 0s + 2) cancellation, eliminating the negative impact of the dynamics of the nonlinear orthogonal signal generation link in power measurement on the stability of the single-phase grid-connected converter; Where s represents the Laplace complex frequency domain variable; H p is the inertia constant of the active loop, D p is the damping coefficient of the active loop; H q is the inertia constant of the reactive loop, D q is the damping coefficient of the reactive loop; t 0 is the delay time.

2. The method for improving stability of a single-phase grid-connected converter based on delay compensation according to claim 1, characterized in that: The single-phase grid-type converter dynamic phasor model includes a power measurement model, an active power controller and a reactive power controller model.

3. The method for improving stability of a single-phase grid-connected converter based on delay compensation according to claim 1, characterized in that: The single-phase grid-type converter power measurement delay compensation unit can perform power measurement delay compensation on a virtual synchronous machine control strategy or a droop control strategy of the grid-type converter.

4. The method for improving stability of a single-phase grid-connected converter based on delay compensation according to claim 1, characterized in that: The single-phase grid-type converter power measurement delay compensation unit does not change the inertia and damping of the single-phase grid-type converter.

5. A single-phase grid-connected converter stability improvement system based on delay compensation, characterized in that: include: A dynamic model building module is configured to obtain operating parameters of a single-phase grid-forming converter and establish a dynamic phasor model of the single-phase grid-forming converter; The power measurement module is configured to analyze the influence of the power measurement dynamics on the stability of the grid-type converter according to the dynamic phasor model of the single-phase grid-type converter, and obtain the power measurement delay; The power compensation module is configured to design a single-phase grid-forming converter power measurement delay compensation unit, and use the single-phase grid-forming converter power measurement delay compensation unit to compensate for active power and reactive power according to the power measurement delay, thereby improving the stability of the single-phase grid-forming converter; The single-phase grid-type converter power measurement delay compensation unit adds a zero point in the active power controller and the reactive power controller; Specifically: Set the active power controller 1 / (2 H p s + D p ) becomes 0.5( t 0s + 2) / (2 H p s + D p ), reactive power controller 1 / (2 H q s + D q ) becomes 0.5( t 0s + 2) / (2 H q s + D q ); Newly added zero point 0.5( t 0s + 2) and the pole generated by the power measurement delay 2 / ( t 0s + 2) cancellation, eliminating the negative impact of the dynamics of the nonlinear orthogonal signal generation link in power measurement on the stability of the single-phase grid-connected converter; Where s represents the Laplace complex frequency domain variable; H p is the inertia constant of the active loop, D p is the damping coefficient of the active loop; H q is the inertia constant of the reactive loop, D q is the damping coefficient of the reactive loop; t 0 is the delay time.

6. The single-phase grid-connected converter stability improvement system based on delay compensation according to claim 5, characterized in that: In the dynamic model building module, the single-phase grid-connected converter dynamic phasor model includes a power measurement model, an active power controller and a reactive power controller model.

7. The single-phase grid-connected converter stability improvement system based on delay compensation according to claim 5, characterized in that: In the power compensation module, the single-phase grid-type converter power measurement delay compensation unit can perform power measurement delay compensation on the virtual synchronous machine control strategy or droop control strategy of the grid-type converter.

8. The single-phase grid-connected converter stability improvement system based on delay compensation according to claim 5, characterized in that: In the power compensation module, the single-phase grid-type converter power measurement delay compensation unit does not change the inertia and damping of the single-phase grid-type converter.

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