Full-power frequency converter grid-side converter control method and device

Abstract

This application provides a control method and apparatus for a grid-side converter of a full-power frequency converter. The method includes: acquiring the grid connection point voltage; inputting the grid connection point voltage into a grid connection point voltage feedforward regulator, which outputs a grid connection point voltage feedforward signal; superimposing the grid connection point voltage feedforward signal with a modulation wave signal output by a current regulator to generate a target modulation wave signal; and determining a control signal based on the target modulation wave signal. This application, through a grid connection point voltage feedforward control strategy, can effectively reduce the interference of background harmonics in the grid connection point voltage, ensure that the grid impedance in the system remains stable over a wide range of variations, and significantly improve the grid-connected power quality.

Description

Technical Field

[0001] This application relates to the field of pumped storage technology, and in particular to a control method and device for a full-power frequency converter grid-side converter. Background Technology

[0002] Variable-speed pumped storage units can optimize power generation efficiency and have broad application prospects. Figure 1 The diagram illustrates a pumped-storage variable-speed generator unit based on a full-power frequency converter. The generator motor is a variable-speed motor, and its stator is connected to the power grid via the full-power frequency converter, achieving a flexible connection between the generator motor and the grid. When the generator motor speed changes, the frequency of its stator voltage also changes accordingly, while the grid frequency remains a stable power frequency. The full-power frequency converter is used to convert the alternating current with varying stator frequency into power frequency alternating current acceptable to the grid, simultaneously achieving bidirectional transmission of active and reactive power.

[0003] Full-power frequency converters include machine-side converters and grid-side converters. Grid-side converters typically employ active-reactive power control, tracking the grid voltage phase via a phase-locked loop (PLL) and controlling the grid-connected power by controlling the grid-connected current. Due to the increasing number of various power electronic devices in the power grid, the background harmonic content of the grid voltage caused by nonlinear load currents has also increased significantly. These background harmonics can cause grid-connected current distortion, leading to increased equipment losses and reduced lifespan. Simultaneously, due to factors such as transformer leakage inductance and line impedance, the equivalent grid impedance at the grid-side converter port is not negligible. Furthermore, with the increasing penetration of distributed generation, the grid impedance may vary over a wide range, affecting the grid-connected current loop gain. The various power electronic devices connected to the grid connection point further complicate the grid impedance, making it non-negligible and subject to wide variations. These uncertainties all deteriorate the grid-connected environment and may even lead to system instability. Therefore, how to reduce the adverse effects of various uncertainties on the system through grid-connected control using full-power frequency converters is a problem that needs to be solved in this field. Summary of the Invention

[0004] In view of this, the purpose of this application is to propose a control method for the grid-side converter of a full-power frequency converter.

[0005] To achieve the above objectives, this application provides a full-power frequency converter grid-side converter control method, comprising:

[0006] Collect grid connection point voltage;

[0007] The grid connection point voltage is input to the grid connection point voltage feedforward regulator, and the grid connection point voltage feedforward regulator outputs the grid connection point voltage feedforward signal.

[0008] The target modulated wave signal is generated by superimposing the grid connection point voltage feedforward signal with the modulated wave signal output by the grid connection current regulator.

[0009] Optionally, the method further includes:

[0010] The target modulated wave signal is compared with a predetermined carrier signal to obtain a comparison result;

[0011] Based on the comparison results, a control signal for controlling the grid-connected current is determined.

[0012] Optionally, the grid connection point voltage feedforward regulator G ff The expression is:

[0013] G ff (s)=λ0·A0+λ1·A1s+λ2·A2s 2 +...+λ n ·A n s n (7)

[0014] The grid connection point voltage includes the fundamental frequency and various harmonics, λ i λ is the weighting coefficient of the transfer function of the grid connection point voltage in the i-th frequency band, 0≤λ i ≤1, A i Let be the initial gain of the transfer function of the grid connection point voltage in the i-th frequency band; s is the Laplace operator.

[0015] Optionally, the method further includes:

[0016] The weighting coefficient is adjusted by the grid connection point voltage feedforward regulator so that, under the control of the control signal, the phase of the output impedance of the grid-side converter is above -90° across the entire frequency band.

[0017] Optionally, adjusting the weighting coefficients includes:

[0018] Determine the frequency band where the phase of the output impedance is below -90°;

[0019] The weighting coefficients corresponding to the frequency band are adjusted until the phase of the output impedance is above -90° across the entire frequency band.

[0020] Optionally, adjusting the weighting coefficients includes:

[0021] The weighting coefficients are gradually adjusted from an initial value of 1 to a smaller value.

[0022] Optionally, the carrier signal is a triangular carrier signal; comparing the target modulated wave signal with the predetermined carrier signal to obtain a comparison result includes:

[0023] The target modulated wave signal and the triangular carrier signal are normalized to obtain the processed signal;

[0024] Based on the processed target modulated wave signal and the triangular carrier signal, the amplitudes of the two are compared. When the amplitude of the target modulated wave signal is greater than the amplitude of the triangular carrier signal, a high level is output; when the amplitude of the modulated wave signal is less than the amplitude of the triangular carrier signal, a low level is output.

[0025] Optionally, adjusting the weighting coefficient using the grid connection point voltage feedforward regulator includes:

[0026] Ignoring the power outer loop or voltage outer loop, set the current command value to zero and calculate the grid-side converter output impedance and grid impedance;

[0027] Plot the frequency response curves of the grid-side converter output impedance and the grid impedance in the same coordinate system; wherein, the frequency response curves include amplitude-frequency curves;

[0028] At the intersection of the amplitude-frequency curves, calculate the phase difference between the output impedance of the grid-side converter and the grid impedance;

[0029] The weighting coefficients are fine-tuned until the phase difference is less than 180°, thus obtaining the determined weighting coefficients.

[0030] This application embodiment also provides a full-power frequency converter grid-side converter control device, including:

[0031] The data acquisition module is used to acquire the voltage at the grid connection point.

[0032] The feedforward module is used to input the grid connection point voltage into the grid connection point voltage feedforward regulator, and the grid connection point voltage feedforward regulator outputs the grid connection point voltage feedforward signal.

[0033] The modulation module is used to superimpose the grid connection point voltage feedforward signal with the modulation wave signal output by the grid connection current regulator to generate the target modulation wave signal.

[0034] Optionally, the device further includes:

[0035] The comparison module is used to compare the target modulated wave signal with a predetermined carrier signal to obtain a comparison result;

[0036] The control module is used to determine a control signal for controlling the grid-connected current based on the comparison result.

[0037] As can be seen from the above, the full-power inverter grid-side converter control method and apparatus provided in this application embodiment employs a grid-connected point voltage feedforward regulator to output a grid-connected point voltage feedforward signal based on the input grid-connected point voltage. This feedforward signal is then superimposed with a modulation wave signal output by a grid-connected current regulator to generate a target modulation wave signal. The control signal is then determined based on this target modulation wave signal. This application's grid-connected point voltage feedforward control strategy effectively reduces interference from background harmonics in the grid-connected point voltage, ensuring the grid impedance remains stable over a wide range, and significantly improving grid-connected power quality. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 These are schematic diagrams of the grid connection structure of variable speed generator units in some embodiments;

[0040] Figure 2 These are schematic diagrams of grid-connected structures for grid-side converters in some embodiments;

[0041] Figure 3 Schematic diagrams of grid-side converter topologies and control structures in some embodiments;

[0042] Figure 4 Schematic diagrams of mathematical models of grid-side converters in some embodiments;

[0043] Figure 5 for Figure 4 A schematic diagram of the equivalent transformation model of the mathematical model shown;

[0044] Figure 6 for Figure 5 A schematic diagram of a further equivalent transformation model of the mathematical model shown;

[0045] Figure 7 for Figure 4 A schematic diagram of the equivalent model for system stability analysis of the mathematical model shown;

[0046] Figure 8 In some embodiments, the output impedance Z of the grid-side converter is... o and grid impedance Z g The frequency response curve;

[0047] Figure 9 This is a schematic diagram of the method flow of an embodiment of this application;

[0048] Figure 10 This is a schematic diagram of the grid-side converter topology according to an embodiment of this application;

[0049] Figure 11 This is a schematic diagram of the mathematical model of the grid-side converter in an embodiment of this application;

[0050] Figure 12A , 12B This is a schematic diagram of the simulation waveforms when the grid connection point voltage feedforward strategy is not adopted.

[0051] Figure 13A , 13B This is a schematic diagram of the simulation waveform when the grid connection point voltage feedforward strategy of the embodiment of this application is adopted;

[0052] Figure 14 This is a schematic diagram of the device structure according to an embodiment of this application;

[0053] Figure 15 This is a schematic diagram of the electronic device structure according to an embodiment of this application. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0055] It should be noted that, unless otherwise defined, the technical or scientific terms used in the embodiments of this application should have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms "first," "second," and similar terms used in the embodiments of this application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are only used to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0056] Figure 2 This is a grid-connected topology diagram for a full-power frequency converter grid-side converter. Considering the large number of grid-connected devices, various reactive power compensation devices, power electronic equipment, etc., and the influence of factors such as line distribution parameters, this example uses a typical grid-side network with impedance and a purely inductive grid impedance as an illustration. Furthermore, for ease of analysis, a single-phase converter is used as an example below; the analysis method is also applicable to three-phase systems. Figure 3 As shown, Vdc The DC side voltage of the grid-side converter is typically controlled to a constant value by the outer loop, V. g For grid voltage, i g For grid-connected current, v PCC Z is the grid connection point voltage. g Given the mains impedance, which is considered purely inductive, the corresponding equivalent inductance is L. g Then Z g (s)=sL g .

[0057] The control target of the grid-side converter current inner loop is the grid-connected current i. g The command value i for controlling the grid-connected current ref The current amplitude I output from the power outer loop or voltage outer loop * The frequency and phase sinθ of the phase-locked loop output are combined. According to the sampling period T... s For grid-connected current i g Sampling is performed, and the sampled grid-connected current value is calculated to match the command value i. ref The difference between them is input into the grid-connected current regulator G. i (z)(Digital Controlled Grid-Connected Current Regulator G) i In the discrete domain expression, the grid-connected current regulator obtains the modulated wave signal v based on this difference. m1 (s) Then, based on the comparison result between the modulation wave signal and the triangular carrier signal (generated by the full-power inverter controller, usually using a per-unit value of 1), a PWM control signal is generated. The PWM control signal controls the switching transistor to turn on or off. The frequency of the triangular carrier signal is the switching frequency, and the frequency of the modulation wave signal is the AC side fundamental frequency.

[0058] Figure 4 The figure shows the mathematical model of the system in the s-domain, G. d The 1.5-step pure delay stage introduced for digital control includes a one-step calculation delay and a half-step PWM delay, expressed as follows: The Converter Model represents the controlled object, namely the mathematical model of the grid-side converter established based on the main circuit topology and impedance network; the specific topology is not limited. Figure 4 The mathematical model shown is simplified to obtain Figure 5 The model shown, where G x1 (s) and G x2 (s) is obtained from the mathematical model of the grid-side converter of the Converter Model through equivalent transformation, G i (s), i g (s), i ref (s), v PCC(s) represent the grid-connected current regulator, the grid-connected current, the command value of the grid-connected current, and the grid-connected point voltage in the s-domain, respectively. Based on this simplified model, the loop gain of the closed-loop system can be obtained as:

[0059] T(s) = G i (s)G d (s)G x1 (s)G x2 (s) (1)

[0060] The command value i of the grid-connected current ref Setting it to 0 yields the grid connection point voltage v. PCC For grid-connected current i g The transfer function, such as Figure 6 As shown, the dashed line portion can be considered as the output admittance 1 / Z of the grid-side converter. o Z o This refers to the output impedance of the grid-side converter, expressed as:

[0061]

[0062] According to the superposition theorem, the grid-connected current can be expressed as the sum of the command value of the grid-connected current of the grid-side converter and the response of the grid voltage, which is expressed as:

[0063]

[0064] Among them, i o It serves as the equivalent current source for the grid-side converter.

[0065] Due to the grid connection point voltage v PCC =v g +Z g ·i g Substituting it into equation (3), we get:

[0066]

[0067] The system function H(s) can be expressed as:

[0068]

[0069] Based on the above analysis, the system stability depends on the stability of the grid-connected current as shown in equation (4). If grid impedance is neglected, Z g =0, then as long as the grid-side converter itself is designed to be stable, the system will definitely be stable. If grid impedance is considered, then the stability of the system depends on the stability of the system function H(s). According to equation (4), H(s) can be regarded as the equivalent current source i of the grid-side converter. o to grid-connected current i gThe transfer function of Z is stable and its stability is related to the grid impedance and the output impedance of the grid-side converter. g (s) and Z o When the magnitudes of H(s) are equal but their phases are opposite, the magnitude of the system function H(s) will be infinite, which may cause system oscillations and, in severe cases, system instability.

[0070] like Figure 7 As shown, the system function H(s) can be considered as a simple closed-loop system with a loop gain of Z. g (s) / Z o (s). The stability criteria for grid-connected systems considering grid impedance can be summarized as follows: 1) The grid-side converter operates stably when connected to the grid; 2) The ratio Z of the grid impedance to the output impedance of the grid-side converter is... g (s) / Z o (s) satisfies the Nyquist stability criterion.

[0071] Based on the above stability criteria, to ensure system stability, it is only necessary to ensure Z. g (s) and Z o (s) Intersection point f of the amplitude-frequency response curve t At (i.e., loop gain Z) g (s) / Z o The phase margin (PM) of the cutoff frequency (s) must be greater than zero.

[0072] PM = 180° - (∠[Z]) g (j2πf t )]-∠[Z o (j2πf t )])=90°+∠[Z o (j2πf t (6)

[0073] Considering the most extreme case, neglecting the resistive components that contribute to system stability, Z g If the system is purely inductive and its phase is always 90°, then the stability condition of the system is that at the intersection point f... t Z o The phase is greater than -90°.

[0074] Figure 8 The figure shows the output impedance Z of a grid-side converter containing a third-order impedance network. o and grid impedance Z g The frequency response curve shows the output impedance Z. oThe phase is above -90° across the entire frequency band, allowing the system to remain stable. However, it approaches -90° at some frequency points, resulting in a low stability margin. Furthermore, the magnitude is small at low frequencies, leading to a certain steady-state error in the grid-connected current, and the waveform quality is easily affected by background harmonics of the grid-connected voltage.

[0075] In view of the above reasons, this application provides a control method for the grid-side converter of a full-power frequency converter. The method utilizes a grid-connected point voltage regulator to process the grid-connected point voltage to generate a grid-connected point voltage feedforward signal. This feedforward signal is then superimposed with a modulation wave signal output from a grid-connected current regulator to obtain the final modulation wave signal. A control signal is generated based on the comparison result between the final modulation wave signal and the carrier signal. This control signal controls the operation of a switching transistor, thereby controlling the magnitude of the grid-connected current. Adjusting the grid-connected point voltage feedforward signal through the grid-connected point voltage regulator reduces harmonic interference and ensures good stability of the grid-connected current even with wide variations in grid impedance.

[0076] The technical solution of this application will be further described in detail below through specific embodiments.

[0077] like Figure 9 As shown in the figure, this application provides a full-power inverter grid-side converter control method, including:

[0078] S901: Collects grid connection point voltage;

[0079] S902: Input the grid connection point voltage into the grid connection point voltage feedforward regulator, and output the grid connection point voltage feedforward signal from the grid connection point voltage feedforward regulator;

[0080] Combination Figure 10 , 11 As shown, in this embodiment, the voltage v at the grid connection point is collected. PCC Then, the grid connection point voltage is input to the grid connection point voltage feedforward regulator G. ff The grid connection point voltage feedforward regulator generates the grid connection point voltage feedforward signal v based on the grid connection point voltage. m2 (s).

[0081] In some approaches, the pure lead-in stage 1 / G introduced by digital control is ignored. d (s) can be obtained from the grid connection point voltage feedforward regulator G. ff The function expression in the s-domain is:

[0082] G ff (s)=λ0·A0+λ1·A1s+λ2·A2s 2 +...+λ n ·A n s n (7)

[0083] The grid connection point voltage includes the fundamental frequency and all harmonics, where 0 ≤ λ. i ≤1, λ i Let A be the weighting coefficient of the transfer function of the grid connection point voltage in the i-th frequency band, and n be the theoretical order of the impedance network (i.e., the number of equivalent inductors and equivalent capacitors). In engineering applications, the entire frequency band is approximately divided into n frequency bands. i Let be the initial gain of the transfer function of the grid connection point voltage in the i-th frequency band; s is the Laplace operator, i = 0, 1, ..., n.

[0084] S903: The target modulation wave signal is generated by superimposing the grid connection point voltage feedforward signal with the modulation wave signal output by the grid connection current regulator.

[0085] In this embodiment, the grid connection point voltage is adjusted by the grid connection point voltage regulator G. ff After processing, the output grid connection point voltage feedforward signal v m2 (s), the collected grid-connected current value and the command value i ref The difference between them is processed by a current regulator to obtain the modulated wave signal v. m1 (s) will feed forward the grid connection point voltage signal v m2 (s) and modulated wave signal v m1 (s) After superposition, the final target modulated wave signal v is generated. m (s).

[0086] In some embodiments, the control method further includes: determining a control signal for controlling the grid-connected current based on the comparison result of the target modulation wave signal and the carrier signal. That is, after determining the target modulation wave signal, a PWM control signal is generated based on the comparison result of the target modulation wave signal and the carrier signal, and the PWM control signal controls the switching transistor to turn on or off, thereby controlling the grid-connected current through the switching of the switching transistor.

[0087] In some methods, a PWM control signal is generated based on the comparison result between the target modulation wave signal and the carrier signal. This includes: normalizing the target modulation wave signal and the triangular carrier signal, comparing their amplitudes, and outputting a high level when the amplitude of the target modulation wave signal is greater than the amplitude of the triangular carrier signal to control the switch to turn on; and outputting a low level when the amplitude of the modulation wave signal is less than the amplitude of the triangular carrier signal to control the switch to turn off.

[0088] In some embodiments, a grid connection point voltage feedforward regulator is used to adjust the weighting coefficients of the transfer function of the grid connection point voltage at the fundamental and / or harmonic frequencies, so that under the control of the generated control signal, the phase of the output impedance of the grid-side converter is above -90° across the entire frequency band, thereby ensuring system stability and a certain positive phase margin when the grid impedance varies over a wide range.

[0089] Specifically, this can be combined with the output impedance Z of the grid-side converter. of The frequency response curve is used to determine the weighting coefficients that need to be adjusted. According to formula (7), at a specific weighting coefficient λ... i (The larger i is, the higher the frequency band) If the output impedance Z of If the phase is above -90° across the entire frequency band, then no adjustment is needed to the weighting coefficients, and the system can remain stable; if the output impedance Z of If the phase of an output impedance is below -90° in a certain frequency band, then the corresponding weighting coefficient for that frequency band is determined to be the weighting coefficient that needs to be adjusted. This weighting coefficient is then adjusted until the phase of the output impedance is above -90° across the entire frequency band. In some cases, adjusting a certain weighting coefficient may cause other frequency bands to fluctuate below -90°. In this situation, the weighting coefficients below -90° can be fine-tuned simultaneously until the frequency response curve is above -90° across the entire frequency band.

[0090] In some methods, when adjusting the weighting coefficient, the weighting coefficient is gradually adjusted from the initial value of 1 to the smallest value. That is, λi can be finely adjusted from 1 to 0. During the adjustment process, the frequency response curve is used to determine whether the entire frequency band is above -90°. If it is above -90°, the adjustment of the weighting coefficient is stopped, and the current weighting coefficient is used as the determined weighting coefficient.

[0091] In some implementations, to determine the weighting coefficients, the weighting coefficients are first initialized to 1, and then determined as follows: ignoring the power outer loop or voltage outer loop, the current command value i is... gref Set the voltage to zero and calculate the grid connection point voltage v. PCC For grid-connected current i g transfer function v PCC / i g That is, the output impedance Z of the grid-side converter of Based on the actual situation at the grid connection point, calculate the grid impedance Z presented to the grid from the grid-side converter port. g Alternatively, the frequency characteristics of the grid impedance can be directly measured using methods such as frequency sweeping; the output impedance Z of the grid-side converter can be plotted in the same coordinate system. of and grid impedance Z g Frequency response curve; output impedance Z of the grid-side converter of and grid impedance Z g At the intersection of the amplitude-frequency curves (the frequency response curve includes both the amplitude-frequency curve and the phase-frequency curve, both sharing the horizontal axis), calculate the phase difference between the two curves, and apply this to the weighting coefficients λ. i Fine-tuning is performed, and when the phase difference between the two is within 180°, the final weighting coefficient is obtained (equivalent to the phase of the grid-side converter output impedance being higher than -90°).

[0092] Combination Figure 8 As shown, taking a third-order impedance network as an example, using the grid connection point voltage feedforward control strategy of this application, when the weighting coefficients λ1=0.85, λ2=1, and λ3=0.25 are set, the corresponding grid-side converter output impedance Z is obtained. of The phase-frequency characteristic curve (s, 0.85, 1, 0.25) indicates that the voltage is above -90° across the entire frequency band. Based on this set of weighting coefficients, implementing a grid-connected point voltage feedforward strategy ensures system stability. When the weighting coefficients λ1 = 1, λ2 = 1, and λ3 = 1 are set, the corresponding grid-side converter output impedance Z is obtained. of The phase frequency response curve of (s,1,1,1) indicates that the frequency range in the [f1,f2] band is below -90°. Accordingly, the weighting coefficients for this frequency band can be adjusted until the entire frequency band reaches above -90°. Additionally, the output impedance Z is compared to the output impedance Z when the grid connection point voltage feedforward control strategy is not employed. o In comparison, the output impedance Z of The frequency response curve has a higher gain in the low-frequency range, thus ensuring that the grid-connected current has good steady-state accuracy and the ability to resist background harmonic interference of the grid connection point voltage.

[0093] This application provides a full-power frequency converter grid-side converter control method. The basic idea is to invert the collected grid-connected voltage and inject it into the collection point. In practice, a grid-connected voltage feedforward regulator is constructed. The collected grid-connected voltage is input into the feedforward regulator, which outputs a grid-connected voltage feedforward signal. Based on the feedforward signal and the modulation wave signal output by the current regulator, a final target modulation wave signal is generated. A control signal is then generated based on the target modulation wave signal, and the control signal is used to control the magnitude of the grid-connected current. By adopting the grid-connected voltage feedforward control strategy, interference from background harmonics of the grid-connected voltage can be effectively suppressed, ensuring that the grid impedance remains stable over a wide range of variations, and significantly improving the grid-connected power quality.

[0094] The following simulation experiments illustrate the methods and effects of this application.

[0095] During simulation, grid voltage distortion is simulated by injecting specific subharmonic components into the grid voltage, while the grid-side converter is controlled at unity power factor. For example... Figure 12A As shown, without adopting the grid connection point voltage feedforward control strategy, under strong grid conditions and without considering grid impedance, the grid connection point voltage v PCC and grid-connected current i gThe waveform quality is poor, with a total harmonic distortion (THD) of approximately 11.86%, and the phase lags behind the grid connection point voltage V. PCC Approximately 18°, this is due to the grid-connected current regulator G. i Using PI control, the gain at the fundamental frequency is not infinite, thus introducing a certain error from the fundamental grid voltage. For example... Figure 12B As shown, without adopting the grid connection point voltage feedforward control strategy, under weak grid conditions and considering grid impedance, the grid connection voltage and grid connection current may still exhibit oscillation and divergence, meaning that the grid-connected system may be unstable under weak grid conditions.

[0096] like Figure 13A , 13B As shown, when adopting the grid connection point voltage feedforward control strategy, under the conditions of a strong power grid and a grid impedance of 0 ( Figure 13A And in the case of a weak power grid with a grid impedance of 8.5mH (corresponding to a grid short-circuit ratio of 3) Figure 13B As can be seen, the steady-state error of the grid-connected current has been eliminated, the waveform quality has been significantly improved, the total harmonic distortion rate is within 3%, and it can still maintain good stability when the grid impedance changes within a certain range.

[0097] It should be noted that the method in this embodiment can be executed by a single device, such as a computer or server. The method can also be applied in a distributed scenario, where multiple devices cooperate to complete the task. In such a distributed scenario, one of these devices may execute only one or more steps of the method in this embodiment, and the multiple devices will interact with each other to complete the method described.

[0098] It should be noted that the above description describes specific embodiments of this specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recorded in the claims may be performed in a different order than that shown in the embodiments and still achieve the desired results. Furthermore, the processes depicted in the drawings do not necessarily require the specific or sequential order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0099] like Figure 14 As shown in the illustration, this application also provides a full-power inverter grid-side converter control device, comprising:

[0100] The data acquisition module is used to acquire the voltage at the grid connection point.

[0101] The feedforward module is used to input the grid connection point voltage into the grid connection point voltage feedforward regulator, and the grid connection point voltage feedforward regulator outputs the grid connection point voltage feedforward signal.

[0102] The modulation module is used to superimpose the grid connection point voltage feedforward signal to generate the target modulation wave signal.

[0103] For ease of description, the above devices are described in terms of function, divided into various modules. Of course, in implementing the embodiments of this application, the functions of each module can be implemented in one or more software and / or hardware.

[0104] The apparatus described above is used to implement the corresponding methods in the foregoing embodiments and has the beneficial effects of the corresponding method embodiments, which will not be repeated here.

[0105] Figure 15 This embodiment illustrates a more specific hardware structure of an electronic device, which may include a processor 1010, a memory 1020, an input / output interface 1030, a communication interface 1040, and a bus 1050. The processor 1010, memory 1020, input / output interface 1030, and communication interface 1040 are interconnected internally via the bus 1050.

[0106] The processor 1010 can be implemented using a general-purpose CPU (Central Processing Unit), microprocessor, application-specific integrated circuit (ASIC), or one or more integrated circuits, and is used to execute relevant programs to implement the technical solutions provided in the embodiments of this specification.

[0107] The memory 1020 can be implemented in the form of ROM (Read Only Memory), RAM (Random Access Memory), static storage device, dynamic storage device, etc. The memory 1020 can store the operating system and other applications. When the technical solutions provided in the embodiments of this specification are implemented by software or firmware, the relevant program code is stored in the memory 1020 and is called and executed by the processor 1010.

[0108] The input / output interface 1030 is used to connect input / output modules to realize information input and output. Input / output modules can be configured as components within the device (not shown in the figure) or externally connected to the device to provide corresponding functions. Input devices may include keyboards, mice, touchscreens, microphones, various sensors, etc., while output devices may include displays, speakers, vibrators, indicator lights, etc.

[0109] The communication interface 1040 is used to connect a communication module (not shown in the figure) to enable communication between this device and other devices. The communication module can communicate via wired means (such as USB, Ethernet cable, etc.) or wireless means (such as mobile network, WIFI, Bluetooth, etc.).

[0110] Bus 1050 includes a pathway for transmitting information between various components of the device, such as processor 1010, memory 1020, input / output interface 1030, and communication interface 1040.

[0111] It should be noted that although the above-described device only shows the processor 1010, memory 1020, input / output interface 1030, communication interface 1040, and bus 1050, in specific implementations, the device may also include other components necessary for normal operation. Furthermore, those skilled in the art will understand that the above-described device may only include the components necessary for implementing the embodiments of this specification, and not necessarily all the components shown in the figures.

[0112] The electronic devices described above are used to implement the corresponding methods in the foregoing embodiments and have the beneficial effects of the corresponding method embodiments, which will not be repeated here.

[0113] The computer-readable medium of this embodiment includes permanent and non-permanent, removable and non-removable media, and information storage can be implemented by any method or technology. Information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic magnetic disk storage or other magnetic storage devices, or any other non-transfer medium that can be used to store information accessible by a computing device.

[0114] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of this disclosure (including the claims) is limited to these examples; within the framework of this disclosure, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of the embodiments of this application as described above, which are not provided in the details for the sake of brevity.

[0115] Additionally, to simplify the description and discussion, and to avoid obscuring the embodiments of this application, the well-known power / ground connections to integrated circuit (IC) chips and other components may or may not be shown in the provided drawings. Furthermore, the apparatus may be shown in block diagram form to avoid obscuring the embodiments of this application, and this also takes into account the fact that the details of the implementation of these block diagram apparatuses are highly dependent on the platform on which the embodiments of this application will be implemented (i.e., these details should be fully understood by those skilled in the art). While specific details (e.g., circuits) have been set forth to describe exemplary embodiments of this disclosure, it will be apparent to those skilled in the art that the embodiments of this application can be implemented without these specific details or with variations thereof. Therefore, these descriptions should be considered illustrative rather than restrictive.

[0116] Although this disclosure has been described in conjunction with specific embodiments thereof, many substitutions, modifications, and variations of these embodiments will be apparent to those skilled in the art from the foregoing description. For example, other memory architectures (e.g., dynamic RAM (DRAM)) may be used with the embodiments discussed.

[0117] The embodiments of this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the embodiments of this application should be included within the protection scope of this disclosure.

Claims

1. A method of controlling a grid-side converter of a full power frequency converter, characterized in that, The method comprises the following steps: Collecting grid point voltage; The grid-connected point voltage is input into a grid-connected point voltage feedforward regulator, and a grid-connected point voltage feedforward signal is output by the grid-connected point voltage feedforward regulator; wherein the grid-connected point voltage feedforward regulator G ff The expression is: (7) wherein the grid-connected point voltage comprises a fundamental wave and each harmonic wave, is a weight coefficient of a transfer function of the grid-connected point voltage in the first i frequency band, and , A i is an initial gain of a transfer function of the grid-connected point voltage in the first i frequency band; s is a Laplace operator, i =0,1,…, n ; Adjusting the weight coefficients by using the grid point voltage feedforward regulator, comprising: Ignoring the power outer loop or the voltage outer loop, setting the current instruction value to zero, and calculating the grid-side converter output impedance and the grid impedance; Drawing the frequency characteristic curves of the grid-side converter output impedance and the grid impedance in the same coordinate system; wherein the frequency characteristic curves comprise amplitude-frequency curves; At the intersection point of the amplitude-frequency curves, calculating the phase difference between the grid-side converter output impedance and the grid impedance; Fine-tuning each weight coefficient until the phase difference is less than 180°, and obtaining the determined weight coefficients; Superimposing the grid point voltage feedforward signal and the modulation wave signal output by the grid current regulator to generate a target modulation wave signal; Comparing the target modulation wave signal with a predetermined carrier signal to obtain a comparison result; According to the comparison result, determining a control signal for controlling the grid current.

2. The method of claim 1, wherein, The adjusting of the weight coefficients comprises: Starting from the initial value 1, gradually adjusting the weight coefficients from large to small.

3. The method of claim 1, wherein, The carrier signal is a triangular carrier signal; comparing the target modulation wave signal with the predetermined carrier signal to obtain a comparison result comprises: Normalizing the target modulation wave signal and the triangular carrier signal to obtain processed signals; Based on the processed target modulation wave signal and the triangular carrier signal, comparing the amplitudes of the two signals, outputting a high level when the amplitude of the target modulation wave signal is greater than the amplitude of the triangular carrier signal, and outputting a low level when the amplitude of the modulation wave signal is less than the amplitude of the triangular carrier signal.

4. A full power frequency converter network side converter control device, characterized by The method comprises the following steps: Collecting grid point voltage by the collecting module; The feedforward module is configured to input a grid-connected point voltage into a grid-connected point voltage feedforward regulator, and output a grid-connected point voltage feedforward signal from the grid-connected point voltage feedforward regulator; wherein the grid-connected point voltage feedforward regulator is configured to perform grid-connected point voltage feedforward regulation on the grid-connected point voltage. G ff The expression is: (7) wherein the grid-connected point voltage comprises a fundamental wave and each harmonic wave, is a weight coefficient of a transfer function of the grid-connected point voltage in the first i frequency band, and , A i is an initial gain of a transfer function of the grid-connected point voltage in the first i frequency band; s is a Laplace operator, i = 0, 1, …, n ; Adjusting the weight coefficients by using the grid point voltage feedforward regulator, comprising: Ignoring the power outer loop or the voltage outer loop, setting the current instruction value to zero, and calculating the grid-side converter output impedance and the grid impedance; Drawing the frequency characteristic curves of the grid-side converter output impedance and the grid impedance in the same coordinate system; wherein the frequency characteristic curves comprise amplitude-frequency curves; At the intersection point of the amplitude-frequency curves, calculating the phase difference between the grid-side converter output impedance and the grid impedance; Fine-tuning each weight coefficient until the phase difference is less than 180°, and obtaining the determined weight coefficients; The modulation module is configured to superimpose the grid point voltage feedforward signal and the modulation wave signal output by the grid current regulator to generate a target modulation wave signal; The comparison module is configured to compare the target modulation wave signal with a predetermined carrier signal to obtain a comparison result; The control module is configured to determine a control signal for controlling the grid current according to the comparison result.

Images