Converter control method, device and equipment adaptive to new energy power supply network and medium

Abstract

The application discloses a kind of variable flow control method, device, equipment and medium suitable for new energy power supply network, belong to power grid field, for the power equipment of the power grid with new energy power generation system, carry out variable flow control, solve the poor operation stability of the power equipment of the power grid with new energy power generation system;The application first injects harmonic voltage to power grid at multiple frequency injection points of first preset frequency band by the way of frequency sweep, then according to the harmonic voltage and its corresponding harmonic current response, determine the risk frequency that there is resonance risk, finally can construct the virtual impedance corresponding to risk frequency, and inject it into the control loop of grid-side converter, so by injecting virtual impedance to adjust the equivalent impedance of grid-side converter, the grid-side converter and power grid can meet system stability criterion at risk frequency, reduce the probability of resonance, improve the operation stability of power equipment.

Description

Technical Field

[0001] This invention relates to the field of power grids, and in particular to a converter control method, device, equipment and medium adapted to new energy power grids. Background Technology

[0002] With the grid connection of new energy power generation systems, the power grid connected to these systems will serve as a power supply system to supply power to certain electrical equipment (such as rail vehicles). However, there is a lack of mature converter control methods in related technologies that are adapted to new energy power grids (i.e., power grids connected to new energy power generation systems), resulting in poor operational stability of electrical equipment under the power supply of power grids connected to new energy power generation systems.

[0003] Therefore, how to provide a solution to the above-mentioned technical problems is a problem that needs to be solved by those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to provide a converter control method, device, equipment, and medium adapted to new energy power grids. This invention first injects harmonic voltage into the power grid at multiple frequency injection points in a first preset frequency band by frequency sweeping. Then, based on the harmonic voltage and its corresponding harmonic current response, the risk frequency with resonance risk can be determined. Finally, a virtual impedance corresponding to the risk frequency can be constructed and injected into the control loop of the grid-side converter. Therefore, by adjusting the equivalent impedance of the grid-side converter through the injection of virtual impedance, the grid-side converter and the power grid can meet the system stability criterion at the risk frequency, reducing the probability of resonance and improving the operational stability of electrical equipment.

[0005] To address the aforementioned technical problems, this invention provides a converter control method adapted to a new energy power grid, applied to the grid-side converter of electrical equipment, wherein the power grid to which the electrical equipment is connected has a new energy power generation system connected in parallel, comprising: By sweeping the frequency, harmonic voltages are injected into the grid at multiple frequency injection points in the first preset frequency band, and the corresponding harmonic current responses are detected; the first preset frequency band is from the first preset frequency to the switching frequency of the grid-side converter. Based on the harmonic voltage and its corresponding harmonic current response, determine the frequency injection point where resonance risk exists, and use it as the risk frequency; A virtual impedance corresponding to the risk frequency is constructed and injected into the control loop of the grid-side converter in order to adjust the equivalent impedance of the grid-side converter so that the grid-side converter and the power grid meet the system stability criterion at the risk frequency.

[0006] On the other hand, the electrical equipment is rail vehicles; The step of injecting harmonic voltage into the power grid at multiple frequency injection points in a first preset frequency band and detecting the corresponding harmonic current response by frequency sweeping includes: When the operating range of the rail vehicle changes, harmonic voltage is injected into the power grid at multiple frequency injection points in the first preset frequency band by frequency sweeping and the corresponding harmonic current response is detected.

[0007] On the other hand, the virtual impedance constructed corresponding to the risk frequency includes: The amplitude of the voltage component corresponding to the virtual impedance is determined based on the harmonic voltage and harmonic current response corresponding to the risk frequency. The phase of the voltage component corresponding to the virtual impedance is determined based on the absolute value of the phase difference between the harmonic voltage and harmonic current responses corresponding to the risk frequency. The risk frequency is taken as the frequency of the corresponding voltage component of the virtual impedance; Based on the amplitude, phase, and frequency of the voltage component corresponding to the virtual impedance, construct the virtual impedance corresponding to the risk frequency.

[0008] On the other hand, the converter control method adapted to the new energy power grid also includes: By high-speed sampling and spectrum analysis of the grid voltage, the core harmonic frequency in the grid voltage located in the second preset frequency band is determined; the second preset frequency band is a frequency band higher than the switching frequency of the grid-side converter. With the goal of minimizing the resonance probability between the grid-side converter and the power grid, the target switching frequency is determined based on the core harmonic frequency. Switch the switching frequency of the switches in the grid-side converter to the target switching frequency.

[0009] On the other hand, the method of determining the target switching frequency based on the core harmonic frequency with the goal of minimizing the resonance probability between the grid-side converter and the power grid includes: Determine the set of selectable switching frequencies for the grid-side converter; For any selectable switching frequency in the set of selectable switching frequencies, determine multiple current harmonic frequencies of the electrical equipment corresponding to the selectable switching frequency; For any selectable switching frequency, the current harmonic frequency with the smallest absolute value of the difference from the core harmonic frequency is taken as the anti-coupling characteristic frequency of the selectable switching frequency. The controllable switching frequency corresponding to the anticoupling characteristic frequency with the largest value is taken as the target switching frequency.

[0010] On the other hand, the grid-side converter has a carrier phase-shifting harmonic cancellation function; The set of selectable switching frequencies for the grid-side converter includes: The selectable switching frequency is the one that has an integer multiple relationship with the fundamental frequency of the grid voltage within the selectable range of switching frequencies of the grid-side converter. Construct a set of optional switching frequencies based on each optional switching frequency.

[0011] On the other hand, the converter control method adapted to the new energy power grid also includes: The sampled signal of the grid voltage is low-pass filtered to filter out harmonic components higher than the second preset frequency; The grid-side converter is controlled based on the sampled signal of the grid voltage after low-pass filtering.

[0012] On the other hand, the converter control method adapted to the new energy power grid also includes: When there is oscillation in the grid voltage of the third preset frequency band, a reactive power curve is generated that is inversely correlated with the fluctuation component of the grid voltage in the third preset frequency band; the third preset frequency band is a frequency band that is higher than the second preset frequency and lower than the first preset frequency. Reactive power is generated according to the aforementioned reactive power curve in order to compensate for the fluctuation component of the third preset frequency band in the grid voltage.

[0013] On the other hand, when there is oscillation in the grid voltage of the third preset frequency band, generating a reactive power curve that is inversely correlated with the fluctuation component of the grid voltage in the third preset frequency band includes: The fundamental voltage peak value of the grid voltage is extracted at a granularity of half a voltage cycle to form a peak sequence; Extract the fluctuation component of the third preset frequency band from the peak sequence; Determine whether the amplitude of the fluctuation component in the third preset frequency band is greater than the first preset threshold. If it is greater than that, then based on the fluctuation characteristics of the fluctuation component of the third preset frequency band, a reactive power curve that is inversely correlated with the fluctuation component of the third preset frequency band is generated.

[0014] On the other hand, the converter control method adapted to the new energy power grid also includes: Based on the preset first correspondence, the target reactive power corresponding to the grid connection point voltage detection value of the electrical equipment is determined; the first correspondence is the correspondence between grid connection point voltage and reactive power. Output the target reactive power so that the grid connection point voltage returns to the target voltage range.

[0015] On the other hand, the converter control method adapted to the new energy power grid also includes: When the grid voltage frequency is lower than the rated frequency, the target active power corresponding to the grid voltage frequency is determined according to the preset second correspondence relationship; the second correspondence relationship is the positive correlation between the grid voltage frequency and the active power of the electrical equipment. Control the electrical equipment to output the target active power.

[0016] On the other hand, the electrical equipment includes rail vehicles; The converter control method adapted to new energy power grids also includes: When the grid voltage frequency is higher than the rated frequency, the target regenerative braking power corresponding to the grid voltage frequency is determined according to the preset third correspondence relationship; the third correspondence relationship is the negative correlation between the grid voltage frequency and the regenerative braking power of the electrical equipment. The regenerative braking power supplied by electrical equipment to the power grid shall be limited to the target regenerative braking power.

[0017] To address the aforementioned technical problems, this invention also provides a converter control device applied to the grid-side converter of electrical equipment, wherein the power grid to which the electrical equipment is connected has a new energy power generation system in parallel, comprising: The first action module is used to inject harmonic voltage into the power grid at multiple frequency injection points in the first preset frequency band by frequency sweeping and to detect the corresponding harmonic current response; the first preset frequency band is from the first preset frequency to the switching frequency of the grid-side converter. The first determining module is used to determine the frequency injection point where there is a risk of resonance based on the harmonic voltage and its corresponding harmonic current response, as the risk frequency; The second action module is used to construct a virtual impedance corresponding to the risk frequency and inject it into the control loop of the grid-side converter in order to adjust the equivalent impedance of the grid-side converter so that the grid-side converter and the power grid meet the system stability criteria at the risk frequency.

[0018] To address the aforementioned technical problems, the present invention also provides a converter control device, comprising: Memory, used to store computer programs; A processor is used to execute the computer program to implement the steps of the converter control method adapted to the new energy power grid as described above.

[0019] To address the aforementioned technical problems, the present invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the converter control method adapted to the new energy power grid as described above.

[0020] Beneficial Effects: This invention provides a converter control method adapted to new energy power grids. Considering that resonance can be avoided by injecting virtual impedance at risk frequencies, this invention first injects harmonic voltage into the grid at multiple frequency injection points in a first preset frequency band through frequency sweeping. Then, based on the harmonic voltage and its corresponding harmonic current response, the risk frequencies with resonance risk can be determined. Finally, a virtual impedance corresponding to the risk frequency can be constructed and injected into the control loop of the grid-side converter. Therefore, by adjusting the equivalent impedance of the grid-side converter through the injection of virtual impedance, the grid-side converter and the grid can meet the system stability criteria at the risk frequency, reducing the probability of resonance and improving the operational stability of electrical equipment.

[0021] The present invention also provides a converter control device, equipment and medium, which have the same beneficial effects as the converter control method adapted to the new energy power grid. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention, the relevant technologies and the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A flowchart illustrating a converter control method adapted to a new energy power grid provided by the present invention; Figure 2 This is a structural schematic diagram of a new energy distributed power grid and rail vehicle. Figure 3 This is a control logic diagram for a first preset frequency band provided by the present invention; Figure 4 This is a control logic diagram for the second preset frequency band provided by the present invention; Figure 5 This is a control logic diagram for a third preset frequency band provided by the present invention; Figure 6 A schematic diagram of a first correspondence relationship provided by the present invention; Figure 7 A schematic diagram illustrating a second and third correspondence relationship provided by the present invention; Figure 8 The overall framework diagram of the converter control method adapted to new energy power grid provided by the present invention; Figure 9 A schematic diagram of the structure of a converter control device provided by the present invention; Figure 10 This is a schematic diagram of the structure of a converter control device provided by the present invention. Detailed Implementation

[0024] The core of this invention is to provide a converter control method, device, equipment, and medium adapted to new energy power grids. This invention first injects harmonic voltages into the power grid at multiple frequency injection points within a first preset frequency band through frequency sweeping. Then, based on the harmonic voltages and their corresponding harmonic current responses, the risk frequencies with resonance risk are determined. Finally, a virtual impedance corresponding to the risk frequency is constructed and injected into the control loop of the grid-side converter. Therefore, by adjusting the equivalent impedance of the grid-side converter through the injection of virtual impedance, the grid-side converter and the power grid can meet the system stability criteria at the risk frequency, reducing the probability of resonance and improving the operational stability of electrical equipment.

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Please refer to Figure 1 , Figure 1 This is a flowchart illustrating a converter control method adapted to a new energy power grid provided by the present invention. This converter control method is applied to the grid-side converter of electrical equipment, where the power grid to which the electrical equipment is connected is connected in parallel with a new energy power generation system, and includes: S101: By sweeping the frequency, harmonic voltage is injected into the power grid at multiple frequency injection points in the first preset frequency band and the corresponding harmonic current response is detected; the first preset frequency band is from the first preset frequency to the switching frequency of the grid-side converter. Specifically, for a better explanation of the embodiments of the present invention, please refer to... Figure 2 and Figure 3 , Figure 2 This is a structural schematic diagram of a new energy distributed power grid and rail vehicle. Figure 3 This is the control logic diagram for the first preset frequency band provided by the present invention. Figure 2 The electrical equipment used in the middle is an electric locomotive, and the three-phase bus voltage of the grid it is connected to is 110kV. The new energy power generation system connected to the grid includes at least one of photovoltaic arrays, wind power generation (systems) and energy storage batteries. Finally, the power is integrated through a unidirectional AC27.5kV bus. The system is also equipped with a unidirectional traction transformer, a matching transformer, a grid-side converter, and a converter on the traction motor side.

[0027] Considering the technical problems mentioned above, and taking into account that after the new energy power generation system is connected to the grid, the grid exhibits wideband time-varying characteristics, and the grid-side converter of the power equipment is prone to interactive instability with the grid impedance, in order to solve this problem, this embodiment of the invention intends to set up an active impedance reshaping scheme based on frequency sweeping. In this scheme, harmonic voltages can be injected into the grid at multiple frequency injection points in the first preset frequency band by frequency sweeping and the corresponding harmonic current responses can be detected so as to serve as the data basis for subsequent steps.

[0028] Specifically, the frequency sweeping method can be flexibly set. For example, frequency sweeping can be performed between the first preset frequency and the preset intermediate frequency using a first preset frequency sweeping step size, while frequency sweeping can be performed between the preset intermediate frequency and the switching frequency using a second preset frequency sweeping step size, and the second preset frequency sweeping step size is greater than the first preset frequency sweeping step size; the embodiments of the present invention are not limited here.

[0029] The preset intermediate frequency, the first preset sweep step size, and the second preset sweep step size can all be flexibly set. For example, the preset intermediate frequency is 150Hz, the first preset sweep step size is 10Hz, and the second preset sweep step size is 50Hz. This embodiment of the invention does not limit these settings.

[0030] The first preset frequency band can be regarded as the mid-frequency band of the power grid voltage. The first preset frequency can be set flexibly and independently. For example, it can be set as a preset value multiple of the fundamental frequency of the power grid voltage. The preset value can be a decimal between 0 and 1, such as 0.2. This embodiment of the invention does not limit this.

[0031] S102: Based on the harmonic voltage and its corresponding harmonic current response, determine the frequency injection point where there is a risk of resonance, and use it as the risk frequency; Specifically, based on the harmonic voltage and its corresponding harmonic current response determined in the aforementioned steps, it can be determined whether there is a resonance risk at each frequency injection point. Frequency injection points with resonance risk can be used as risk frequencies in subsequent steps.

[0032] In one specific example, the frequency injection points at which resonance risk is identified, based on the harmonic voltage and its corresponding harmonic current response, include: If the absolute value of the phase difference between the harmonic voltage and the corresponding harmonic current response is greater than 90 degrees, then there is a risk of resonance at the injection point at that frequency.

[0033] S103: Construct a virtual impedance corresponding to the risk frequency and inject it into the control loop of the grid-side converter in order to adjust the equivalent impedance of the grid-side converter so that the grid-side converter and the power grid meet the system stability criterion at the risk frequency.

[0034] Specifically, considering that by injecting a virtual impedance corresponding to the risk frequency into the control loop of the grid-side converter, an additional damping component can be introduced at the risk frequency, so that the equivalent impedance of the grid-side converter and the grid impedance satisfy the system stability criterion at the risk frequency, a virtual impedance corresponding to the risk frequency can be constructed in this step and injected into the control loop of the grid-side converter.

[0035] This invention provides a converter control method adapted to new energy power grids. Considering that resonance can be avoided by injecting virtual impedance for risk frequencies with resonance risk, this invention first injects harmonic voltage into the grid at multiple frequency injection points in a first preset frequency band through frequency sweeping. Then, based on the harmonic voltage and its corresponding harmonic current response, the risk frequency with resonance risk can be determined. Finally, a virtual impedance corresponding to the risk frequency can be constructed and injected into the control loop of the grid-side converter. Therefore, by adjusting the equivalent impedance of the grid-side converter by injecting virtual impedance, the grid-side converter and the grid can meet the system stability criterion at the risk frequency, reducing the probability of resonance and improving the operational stability of electrical equipment.

[0036] Based on the above embodiments: As an optional embodiment, the electrical equipment is a rail vehicle; By sweeping frequencies, harmonic voltages are injected into the power grid at multiple frequency injection points within a first preset frequency band, and the corresponding harmonic current responses are detected, including: When the operating range of the rail vehicle changes, harmonic voltage is injected into the power grid at multiple frequency injection points in the first preset frequency band by frequency sweeping and the corresponding harmonic current response is detected.

[0037] Specifically, considering that the impedance characteristics of the power grid change significantly as the rail vehicle moves geographically (e.g., entering different substation power supply sections or areas with abrupt changes in contact network parameters), a triggering mechanism based on changes in operating section is implemented in this embodiment of the invention to capture such impedance changes caused by spatial location changes. This avoids the waste of computational resources and potential power quality interference caused by continuous high-frequency sweeping, and only initiates frequency sweep detection at critical moments when power grid parameters may change (i.e., when the operating section changes), thus improving the timeliness and targeting of the control strategy.

[0038] In addition to the aforementioned embodiments, when the electrical equipment is a rail vehicle, the triggering condition for the frequency sweep action can be linked to the vehicle's operating status. Specifically, the rail vehicle's automatic train control system or global positioning system module monitors the vehicle's location information in real time. When the system determines that the rail vehicle is about to enter or has already entered a new operating section (e.g., passing through a phase-splitting zone, entering the power supply arm of a different traction substation), it generates a "section change trigger signal." Upon receiving this signal, the control unit of the grid-side converter initiates the frequency sweep procedure, injecting harmonic voltage into the grid at multiple frequency injection points in the first preset frequency band and detecting the corresponding harmonic current response to reassess the resonance risk of the new operating section and update the virtual impedance parameters.

[0039] As an optional embodiment, constructing the virtual impedance corresponding to the risk frequency includes: The amplitude of the voltage component corresponding to the virtual impedance is determined based on the harmonic voltage and harmonic current response corresponding to the risk frequency. The phase of the voltage component corresponding to the virtual impedance is determined based on the absolute value of the phase difference between the harmonic voltage and harmonic current responses corresponding to the risk frequency. The risk frequency is taken as the frequency of the corresponding voltage component of the virtual impedance; Based on the amplitude, phase, and frequency of the voltage component corresponding to the virtual impedance, construct the virtual impedance corresponding to the risk frequency.

[0040] Specifically, considering that the suppression effect of virtual impedance depends on the degree of matching between its parameters (amplitude, phase) and the characteristics of the power grid at the risk frequency, a parameter construction scheme based on measured response is set up in this embodiment of the invention to achieve precise damping injection. This scheme can dynamically calculate the most suitable virtual impedance parameters based on real-time harmonic voltage and current responses, ensuring that the generated virtual impedance can maximally offset the resonance trend of the power grid, rather than simply compensating with fixed parameters.

[0041] In a specific instance, the steps for constructing a virtual impedance may include: First, based on the harmonic voltage and harmonic current response amplitudes corresponding to the risk frequency, Ohm's law is used to calculate the target impedance magnitude at that frequency point. This allows for the determination of the amplitude of the voltage component corresponding to the virtual impedance, ensuring a moderate injection strength. Second, the absolute value of the phase difference between the harmonic voltage and harmonic current responses corresponding to the risk frequency is analyzed. If this phase difference is close to 180 degrees, the phase of the voltage component corresponding to the virtual impedance is adjusted to provide a resistive component; if capacitive or inductive characteristics exist, the phase is adjusted accordingly to introduce a reverse impedance component. Finally, the risk frequency is directly used as the frequency of the voltage component corresponding to the virtual impedance. The determined amplitude, phase, and frequency parameters are combined into a virtual impedance control signal, which is then superimposed on the modulation wave signal of the grid-side converter, thereby realizing the construction of the virtual impedance corresponding to the risk frequency.

[0042] As an optional embodiment, the converter control method adapted to the new energy power grid also includes: By high-speed sampling and spectrum analysis of the grid voltage, the core harmonic frequency in the grid voltage located in the second preset frequency band is determined; the second preset frequency band is a frequency band higher than the switching frequency of the grid-side converter. With the goal of minimizing the resonance probability between the grid-side converter and the power grid, the target switching frequency is determined based on the core harmonic frequency. Switch the switching frequency of the switches in the grid-side converter to the target switching frequency.

[0043] Specifically, for a better explanation of the embodiments of the present invention, please refer to... Figure 4 , Figure 4 This is the control logic diagram for the second preset frequency band provided by the present invention. Figure 4 The steps include: (1) detection of high-frequency harmonics of grid voltage, (2) low-pass filtering of grid voltage as control signal, and (3) adaptive selection of switching frequency.

[0044] Specifically, considering that the switching frequency harmonics of the grid-side converter may resonate with the high-frequency harmonics of the power grid, and that traditional fixed switching frequencies are difficult to adapt to changes in the high-frequency characteristics of the power grid, an adaptive switching frequency adjustment scheme is set up in this embodiment of the invention to avoid such high-frequency resonance. This scheme uses a second preset frequency band as the high-frequency band; by adjusting its own switching frequency in real time to keep it away from the core harmonic frequencies present in the power grid, the coupling and amplification of switching frequency harmonics and power grid harmonics are avoided from the source, thus achieving stability control in the high-frequency band.

[0045] Among them, spectrum analysis can be of various types. For example, it can be performed using fast Fourier transform to determine the energy concentration point in the grid voltage located in the second preset frequency band (i.e., the frequency band higher than the switching frequency of the grid-side converter), i.e. the core harmonic frequency. This embodiment of the invention does not limit the specific types of analysis.

[0046] Additionally, as an optional embodiment, switching the switching frequency of the switches in the grid-side converter to the target switching frequency includes: By using a preset step size, the switching frequency of the switches in the grid-side converter is gradually switched to the target switching frequency to avoid transient impacts caused by sudden changes in the switching frequency.

[0047] The preset step size can be flexibly set, for example, it can be 50Hz, etc., and the embodiments of the present invention are not limited here.

[0048] As an optional embodiment, to minimize the resonance probability between the grid-side converter and the grid, the target switching frequency is determined based on the core harmonic frequency, including: Determine the set of selectable switching frequencies for the grid-side converter; For any selectable switching frequency in the set of selectable switching frequencies, determine the multiple current harmonic frequencies of the electrical equipment corresponding to the selectable switching frequency; For any selectable switching frequency, the current harmonic frequency with the smallest absolute value of the difference from the core harmonic frequency is taken as the anti-coupling characteristic frequency of the selectable switching frequency. The controllable switching frequency corresponding to the anticoupling characteristic frequency with the largest value is taken as the target switching frequency.

[0049] Specifically, considering that for any selectable switching frequency, there are multiple current harmonic frequencies of the corresponding electrical equipment, and that the influence of these multiple current harmonic frequencies on the core harmonic frequency is different, in this embodiment of the invention, the current harmonic frequency with the smallest absolute value of the difference between the selectable switching frequency and the core harmonic frequency (i.e., the current harmonic frequency with the greatest influence) can be selected as the anti-coupling characteristic frequency of the selectable switching frequency. Then, the controllable switching frequency corresponding to the anti-coupling characteristic frequency with the largest value is selected as the target switching frequency, thereby minimizing the probability of resonance between the switching frequency harmonics of the grid-side converter and the high-frequency harmonics of the grid.

[0050] In this embodiment of the invention, the proximity of the switching frequency harmonics to the core harmonics of the power grid is quantified by calculating the absolute value of the difference, thereby enabling the precise selection of the switching frequency furthest from the power grid harmonics and maximizing the resonance avoidance effect.

[0051] Additionally, as an optional embodiment, for any optional switching frequency in the set of optional switching frequencies, determining the multiple current harmonic frequencies of the electrical equipment corresponding to the optional switching frequency includes: The first relational formula is used to determine multiple current harmonic frequencies of electrical equipment corresponding to the selectable switching frequency; the first relational formula includes: Current harmonic frequency = 2 × J × M × Fcx; Where M is the total number of grid-side converters in the electrical equipment, Fcx is the selectable switching frequency, and J is the preset value, J∈[1,2,3].

[0052] As an optional embodiment, the grid-side converter has a carrier phase-shifting harmonic cancellation function; The set of selectable switching frequencies for grid-side converters includes: The selectable switching frequency is the one that has an integer multiple relationship with the fundamental frequency of the grid voltage within the selectable range of switching frequencies of the grid-side converter. Construct a set of optional switching frequencies based on each optional switching frequency.

[0053] Specifically, considering that the carrier phase-shifting harmonic cancellation technology requires the switching frequency to maintain a specific synchronization relationship with the fundamental frequency of the power grid in order to achieve mutual cancellation of harmonics between modules, in this embodiment of the invention, the switching frequency that has an integer multiple relationship with the fundamental frequency of the power grid voltage in the selectable range of the switching frequency of the grid-side converter is selected as the selectable switching frequency, so that the selectable switching frequency supports the carrier phase-shifting harmonic cancellation function.

[0054] Of course, in addition to this specific form, the set of selectable switching frequencies for the grid-side converter can also be determined in other ways, and this embodiment of the invention does not limit it here.

[0055] As an optional embodiment, the converter control method adapted to the new energy power grid also includes: The sampled signal of the grid voltage is low-pass filtered to filter out harmonic components higher than the second preset frequency; The grid-side converter is controlled based on the sampled signal of the grid voltage after low-pass filtering.

[0056] Specifically, considering that high-frequency harmonics (higher than the second preset frequency) in the power grid may interfere with the control loop of the grid-side converter, especially when entering the voltage feedforward link, which may lead to misjudgment or oscillation of the control system, the scheme in the embodiment of the present invention is set up. By using low-pass filtering, the path of high-frequency harmonics to the control core is physically cut off, ensuring the purity of the converter control signal, thereby assisting in the stability control of the high-frequency band.

[0057] As an optional embodiment, the converter control method adapted to the new energy power grid also includes: When there is oscillation in the grid voltage of the third preset frequency band, a reactive power curve is generated that is inversely correlated with the fluctuation component of the grid voltage in the third preset frequency band; the third preset frequency band is a frequency band that is higher than the second preset frequency and lower than the first preset frequency. Reactive power is generated according to the reactive power curve in order to compensate for the fluctuation component of the third preset frequency band in the grid voltage.

[0058] Specifically, for a better explanation of the embodiments of the present invention, please refer to... Figure 5 , Figure 5 The control logic diagram for the third preset frequency band provided by the present invention includes low-frequency fluctuation detection, fluctuation feature extraction, and dynamic reactive power compensation curve setting.

[0059] Specifically, considering that the power grid is prone to power oscillations and voltage fluctuations in the third preset frequency band (low frequency band), and that simple impedance reshaping is insufficient to completely eliminate such large fluctuations, a control strategy based on reverse reactive power compensation, as described in this embodiment of the invention, is implemented to provide active support. By generating a reactive power curve that is inversely correlated with the fluctuation component, the reactive power regulation capability of the converter is utilized to raise the voltage during voltage troughs and lower the voltage during voltage peaks, thereby acting as a "damper" to smooth out low-frequency oscillations in the power grid.

[0060] The second preset frequency can be set flexibly and independently, for example, it can be 1Hz, etc., and the embodiments of the present invention are not limited here.

[0061] As an optional embodiment, when there is oscillation in the grid voltage of the third preset frequency band, generating a reactive power curve that is inversely correlated with the fluctuation component of the grid voltage in the third preset frequency band includes: The fundamental voltage peak value of the grid voltage is extracted at a granularity of half a voltage cycle to form a peak sequence; Extract the fluctuation component of the third preset frequency band from the peak sequence; Determine whether the amplitude of the fluctuation component in the third preset frequency band is greater than the first preset threshold. If it is greater than that, then based on the fluctuation characteristics of the fluctuation component of the third preset frequency band, a reactive power curve that is inversely correlated with the fluctuation component of the third preset frequency band is generated.

[0062] Specifically, considering that low-frequency fluctuations are often accompanied by periodic changes in voltage peak values, and that it is necessary to distinguish between normal voltage fluctuations and fault oscillations requiring intervention, a half-cycle peak sequence-based extraction and judgment mechanism is established in this embodiment of the invention to accurately identify fluctuation characteristics and trigger compensation. This embodiment utilizes the half-cycle peak detection method to quickly capture changes in the voltage envelope, and avoids false triggering by minor fluctuations by setting a threshold, ensuring that reactive power compensation is only activated when the oscillation amplitude exceeds a first preset threshold, thus improving the economy and reliability of control.

[0063] Additionally, as an optional embodiment, generating a reactive power curve that is inversely correlated with the fluctuation component of the third preset frequency band based on the fluctuation characteristics of the fluctuation component of the third preset frequency band includes: Based on the period and amplitude characteristics of the fluctuation component, a reactive power curve that is inversely related to it is generated through the second relational formula; The second relation includes: Qcom(t)=K×Aosc×sin(2πt / Tosc+Φ); Where Qcom(t) is the reactive power curve, K is the preset compensation coefficient, Aosc is the amplitude of the fluctuation component, Tosc is the period of the fluctuation component, and Φ is the phase of the reactive power curve.

[0064] As an optional embodiment, the converter control method adapted to the new energy power grid also includes: Based on the preset first correspondence, the target reactive power corresponding to the grid connection point voltage detection value of the electrical equipment is determined; the first correspondence is the correspondence between grid connection point voltage and reactive power. Output target reactive power so that the grid connection point voltage returns to the target voltage range.

[0065] Specifically, considering that the integration of new energy sources may lead to prolonged steady-state deviations in grid voltage (such as persistently high or low voltage), and that extremely low frequencies (<1Hz) or DC currents are difficult to eliminate through dynamic oscillation suppression, a reactive power regulation scheme based on a static mapping relationship is implemented in this embodiment of the invention to maintain the voltage within a safe range. Through a preset first correspondence, the converter acquires voltage support capabilities similar to those of a "grid-connected" device. When the voltage deviates, the target reactive power is automatically output to help the grid connection point voltage return to the target voltage range, thereby improving the static stability of the system.

[0066] Specifically, for a better explanation of the embodiments of the present invention, please refer to... Figure 6 , Figure 6 This invention provides a schematic diagram of a first correspondence relationship; the first correspondence relationship can be set flexibly and independently, for example, it can be set to... Figure 6 In the form shown in the figure, when the voltage is higher than the preset high limit Uhight (e.g., 27.5kV), the reactive power command increases linearly with the voltage increase (inductive); when the voltage is lower than the preset low limit Ulow (e.g., 25kV), the reactive power command increases linearly with the voltage decrease (capacitive). This embodiment of the invention is not limited here.

[0067] As an optional embodiment, the converter control method adapted to the new energy power grid also includes: When the grid voltage frequency is lower than the rated frequency, the target active power corresponding to the grid voltage frequency is determined according to the preset second correspondence relationship; the second correspondence relationship is the positive correlation between the grid voltage frequency and the active power of the electrical equipment. Control the output target active power of electrical equipment.

[0068] Specifically, considering that the active power of electrical equipment directly affects the grid frequency when the grid voltage frequency is lower than the rated frequency, an active power limiting strategy based on frequency deviation is set up in this embodiment of the invention to prevent the system from collapsing further when the grid voltage frequency is lower than the rated frequency. When the grid frequency is lower than the rated frequency (indicating a power deficit), by limiting the consumption of active power, the load impact on the grid is reduced, further frequency collapse is prevented, and the system's ability to cope with the power deficit is enhanced.

[0069] Specifically, for a better explanation of the embodiments of the present invention, please refer to... Figure 7 , Figure 7 This is a schematic diagram of a second correspondence and a third correspondence provided by the present invention. The second correspondence can be set flexibly and independently, for example, it can be set as follows: Figure 7 In the form of [the above], for example, when the grid voltage frequency is detected to be lower than the rated frequency and the deviation exceeds the preset lower limit threshold, the target active power corresponding to the grid voltage frequency is determined according to the positive correlation linear relationship, thereby limiting the active power and reducing its current draw from the grid in the low frequency state, thus assisting the grid frequency recovery.

[0070] As an optional embodiment, the electrical equipment includes rail vehicles; Converter control methods adapted to new energy power grids also include: When the grid voltage frequency is higher than the rated frequency, the target regenerative braking power corresponding to the grid voltage frequency is determined according to the preset third correspondence relationship; the third correspondence relationship is the negative correlation between the grid voltage frequency and the regenerative braking power of the electrical equipment. The regenerative braking power supplied by electrical equipment to the power grid shall be limited to the target regenerative braking power.

[0071] Specifically, considering that rail vehicles feed energy back to the grid during regenerative braking, if the grid frequency is too high at this time (indicating excess energy), the fed-back energy will further deteriorate frequency stability. To balance system energy, a frequency-based regenerative braking power limiting strategy is set up in this embodiment of the invention. When the grid frequency is higher than the rated frequency, the regenerative braking power is limited through a negative correlation to prevent excessive energy feedback from causing grid voltage and frequency runaway, thereby improving the system's safety under excess energy conditions.

[0072] Specifically, for a better explanation of the embodiments of the present invention, please refer to... Figure 7 The third correspondence can be set flexibly and independently, for example, it can be set as follows: Figure 7 In some systems, when the grid voltage frequency is detected to be higher than the rated frequency and exceeds a preset upper limit threshold, a target regenerative braking power corresponding to the grid voltage frequency is determined according to a negatively correlated linear relationship. The regenerative braking power delivered by the electrical equipment to the grid is then limited to this target regenerative braking power. For example, if the frequency is too high, the system will forcibly reduce the regenerative braking power, forcing the vehicle to switch to resistor braking or air braking to avoid injecting more energy into an already "overloaded" grid.

[0073] Specifically, for a better explanation of the embodiments of the present invention, please refer to... Figure 8 , Figure 8This is an overall framework diagram of the converter control method adapted to the new energy power grid provided by the present invention. The converter control method adapted to the new energy power grid in the embodiment of the present invention can divide the grid voltage with parallel new energy power generation system into frequency bands, handle the stability problem of vehicle-grid coupling system according to frequency segment, and adopt differentiated control strategies for the oscillation mechanism of different frequency bands, so as to achieve comprehensive suppression from low frequency power oscillation to high frequency harmonic resonance. The steady-state deviation segment refers to the extremely low frequency or DC quantity of less than 1Hz.

[0074] Please refer to Figure 9 , Figure 9 This is a schematic diagram of a converter control device provided by the present invention. The converter control device is applied to the grid-side converter of an electrical appliance, and the power grid to which the electrical appliance is connected has a new energy power generation system connected in parallel. The device includes: The first action module 91 is used to inject harmonic voltage into the power grid at multiple frequency injection points in the first preset frequency band by frequency sweeping and to detect the corresponding harmonic current response; the first preset frequency band is from the first preset frequency to the switching frequency of the grid-side converter. The first determining module 92 is used to determine the frequency injection point with resonance risk based on the harmonic voltage and its corresponding harmonic current response, as the risk frequency; The second action module 93 is used to construct a virtual impedance corresponding to the risk frequency and inject it into the control loop of the grid-side converter in order to adjust the equivalent impedance of the grid-side converter so that the grid-side converter and the power grid meet the system stability criterion at the risk frequency.

[0075] For a description of the converter control device provided in the embodiments of the present invention, please refer to the aforementioned embodiments of the converter control method adapted to new energy power grids. The embodiments of the present invention will not be repeated here.

[0076] Please refer to Figure 10 , Figure 10 This is a schematic diagram of a converter control device provided by the present invention. The converter control device includes: Memory 101 is used to store computer programs; The processor 102 is used to execute computer programs to implement the steps of the converter control method adapted to the new energy power grid as described in the foregoing embodiments.

[0077] For a description of the converter control device provided in the embodiments of the present invention, please refer to the aforementioned embodiments of the converter control method adapted to new energy power grids. The embodiments of the present invention will not be repeated here.

[0078] The present invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the converter control method adapted to the new energy power grid as described in the foregoing embodiments.

[0079] For a description of the computer-readable storage medium provided in the embodiments of the present invention, please refer to the foregoing embodiments of the converter control method adapted to new energy power grids. The embodiments of the present invention will not be repeated here.

[0080] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section. It should also be noted that in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising a..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0081] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A converter control method adapted to new energy power grids, characterized in that, A grid-side converter used in electrical equipment, where the power grid to which the equipment is connected has a parallel renewable energy power generation system, including: By sweeping the frequency, harmonic voltages are injected into the grid at multiple frequency injection points in the first preset frequency band, and the corresponding harmonic current responses are detected; the first preset frequency band is from the first preset frequency to the switching frequency of the grid-side converter. Based on the harmonic voltage and its corresponding harmonic current response, determine the frequency injection point where resonance risk exists, and use it as the risk frequency; Construct a virtual impedance corresponding to the risk frequency and inject it into the control loop of the grid-side converter in order to adjust the equivalent impedance of the grid-side converter so that the grid-side converter and the grid meet the system stability criterion at the risk frequency. The constructed virtual impedance corresponding to the risk frequency includes: The amplitude of the voltage component corresponding to the virtual impedance is determined based on the harmonic voltage and harmonic current response corresponding to the risk frequency. The phase of the voltage component corresponding to the virtual impedance is determined based on the absolute value of the phase difference between the harmonic voltage and harmonic current responses corresponding to the risk frequency. The risk frequency is taken as the frequency of the corresponding voltage component of the virtual impedance; Based on the amplitude, phase, and frequency of the voltage component corresponding to the virtual impedance, construct the virtual impedance corresponding to the risk frequency.

2. The converter control method adapted to new energy power grids according to claim 1, characterized in that, The electrical equipment is a rail vehicle; The step of injecting harmonic voltage into the power grid at multiple frequency injection points in a first preset frequency band and detecting the corresponding harmonic current response by frequency sweeping includes: When the operating range of the rail vehicle changes, harmonic voltage is injected into the power grid at multiple frequency injection points in the first preset frequency band by frequency sweeping and the corresponding harmonic current response is detected.

3. The converter control method adapted to new energy power grids according to claim 1, characterized in that, The converter control method adapted to new energy power grids also includes: By high-speed sampling and spectrum analysis of the grid voltage, the core harmonic frequency in the grid voltage located in the second preset frequency band is determined; the second preset frequency band is a frequency band higher than the switching frequency of the grid-side converter. With the goal of minimizing the resonance probability between the grid-side converter and the power grid, the target switching frequency is determined based on the core harmonic frequency. Switch the switching frequency of the switches in the grid-side converter to the target switching frequency.

4. The converter control method adapted to new energy power grids according to claim 3, characterized in that, The determination of the target switching frequency based on the core harmonic frequency, with the goal of minimizing the resonance probability between the grid-side converter and the power grid, includes: Determine the set of selectable switching frequencies for the grid-side converter; For any selectable switching frequency in the set of selectable switching frequencies, determine multiple current harmonic frequencies of the electrical equipment corresponding to the selectable switching frequency; For any selectable switching frequency, the current harmonic frequency with the smallest absolute value of the difference from the core harmonic frequency is taken as the anti-coupling characteristic frequency of the selectable switching frequency. The controllable switching frequency corresponding to the anticoupling characteristic frequency with the largest value is taken as the target switching frequency.

5. The converter control method adapted to new energy power grids according to claim 4, characterized in that, The grid-side converter has a carrier phase-shifting harmonic cancellation function; The set of selectable switching frequencies for the grid-side converter includes: The selectable switching frequency is the one that has an integer multiple relationship with the fundamental frequency of the grid voltage within the selectable range of switching frequencies of the grid-side converter. Construct a set of optional switching frequencies based on each optional switching frequency.

6. The converter control method adapted to new energy power grids according to claim 3, characterized in that, The converter control method adapted to new energy power grids also includes: The sampled signal of the grid voltage is low-pass filtered to filter out harmonic components higher than the second preset frequency; The grid-side converter is controlled based on the sampled signal of the grid voltage after low-pass filtering.

7. The converter control method adapted to new energy power grids according to claim 1, characterized in that, The converter control method adapted to new energy power grids also includes: When there is oscillation in the grid voltage of the third preset frequency band, a reactive power curve is generated that is inversely correlated with the fluctuation component of the grid voltage in the third preset frequency band; the third preset frequency band is a frequency band that is higher than the second preset frequency and lower than the first preset frequency. Reactive power is generated according to the aforementioned reactive power curve in order to compensate for the fluctuation component of the third preset frequency band in the grid voltage.

8. The converter control method adapted to new energy power grids according to claim 7, characterized in that, When the grid voltage in the third preset frequency band oscillates, generating a reactive power curve that is inversely correlated with the fluctuation component of the grid voltage in the third preset frequency band includes: The fundamental voltage peak value of the grid voltage is extracted at a granularity of half a voltage cycle to form a peak sequence; Extract the fluctuation component of the third preset frequency band from the peak sequence; Determine whether the amplitude of the fluctuation component in the third preset frequency band is greater than the first preset threshold. If it is greater than that, then based on the fluctuation characteristics of the fluctuation component of the third preset frequency band, a reactive power curve that is inversely correlated with the fluctuation component of the third preset frequency band is generated.

9. The converter control method adapted to new energy power grids according to claim 1, characterized in that, The converter control method adapted to new energy power grids also includes: Based on the preset first correspondence, the target reactive power corresponding to the grid connection point voltage detection value of the electrical equipment is determined; the first correspondence is the correspondence between grid connection point voltage and reactive power. Output the target reactive power so that the grid connection point voltage returns to the target voltage range.

10. The converter control method adapted to new energy power grids according to claim 1, characterized in that, The converter control method adapted to new energy power grids also includes: When the grid voltage frequency is lower than the rated frequency, the target active power corresponding to the grid voltage frequency is determined according to the preset second correspondence relationship; the second correspondence relationship is the positive correlation between the grid voltage frequency and the active power of the electrical equipment. Control the electrical equipment to output the target active power.

11. The converter control method adapted to new energy power grids according to any one of claims 1 to 10, characterized in that, The electrical equipment includes rail vehicles; The converter control method adapted to new energy power grids also includes: When the grid voltage frequency is higher than the rated frequency, the target regenerative braking power corresponding to the grid voltage frequency is determined according to the preset third correspondence relationship; the third correspondence relationship is the negative correlation between the grid voltage frequency and the regenerative braking power of the electrical equipment. The regenerative braking power supplied by electrical equipment to the power grid shall be limited to the target regenerative braking power.

12. A converter control device, characterized in that, A grid-side converter used in electrical equipment, where the power grid to which the equipment is connected has a parallel renewable energy power generation system, including: The first action module is used to inject harmonic voltage into the power grid at multiple frequency injection points in the first preset frequency band by frequency sweeping and to detect the corresponding harmonic current response; the first preset frequency band is from the first preset frequency to the switching frequency of the grid-side converter. The first determining module is used to determine the frequency injection point where there is a risk of resonance based on the harmonic voltage and its corresponding harmonic current response, as the risk frequency; The second action module is used to construct a virtual impedance corresponding to the risk frequency and inject it into the control loop of the grid-side converter in order to adjust the equivalent impedance of the grid-side converter so that the grid-side converter and the grid meet the system stability criterion at the risk frequency. The constructed virtual impedance corresponding to the risk frequency includes: The amplitude of the voltage component corresponding to the virtual impedance is determined based on the harmonic voltage and harmonic current response corresponding to the risk frequency. The phase of the voltage component corresponding to the virtual impedance is determined based on the absolute value of the phase difference between the harmonic voltage and harmonic current responses corresponding to the risk frequency. The risk frequency is taken as the frequency of the corresponding voltage component of the virtual impedance; Based on the amplitude, phase, and frequency of the voltage component corresponding to the virtual impedance, construct the virtual impedance corresponding to the risk frequency.

13. A converter control device, characterized in that, include: Memory, used to store computer programs; A processor, configured to execute the computer program to implement the steps of the converter control method for adapting to a new energy power grid as described in any one of claims 1 to 11.

14. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the steps of the converter control method for adapting to new energy power grids as described in any one of claims 1 to 11.

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