High voltage ride through control method and device of grid-connected converter, controller and grid-connected converter

Abstract

The invention provides a high-voltage ride-through control method and device of a grid-connected converter, a controller and the grid-connected converter. The method comprises the following steps: monitoring a power grid voltage of a common coupling point of a power grid and a grid-connected converter in real time, and judging whether the grid-connected converter enters a high voltage ride through state or not according to the power grid voltage; if the grid-connected converter enters the high-voltage ride-through state, reducing a reactive current regulation coefficient within a first preset duration of entering the high-voltage ride-through state; determining a reactive current given value based on the power grid voltage and the reactive current adjustment coefficient; the reactive current adjusting coefficient is in positive correlation with the absolute value of the reactive current given value; and controlling the grid-connected converter by adopting the reactive current given value. According to the method, sudden change of the reactive current given value can be restrained from the source, the reactive current overshoot phenomenon is avoided, and therefore the jitter problem that when the power grid voltage enters the high-voltage ride-through state, uprush is conducted firstly, and then falling back is conducted is effectively relieved.

Description

Technical Field

[0001] This invention relates to the field of converter control technology, and in particular to a high-voltage ride-through control method, device, controller, and grid-connected converter for a grid-connected converter. Background Technology

[0002] With the rapid development of new energy power generation technologies, grid-connected converters, as core equipment for connecting new energy power to the grid, play an irreplaceable role in power conversion, power regulation, and grid connection control. High and low voltage ride-through capability is a crucial technical performance requirement for grid-connected converters, directly determining whether they can maintain continuous and stable operation under grid fault ride-through conditions, and also relating to the converter's own safety and reliability. Reliable high and low voltage ride-through control technology can prevent converters from frequently disconnecting from the grid due to abnormal grid voltage, ensuring the continuous transmission of new energy power, reducing the impact of voltage fluctuations on the power system, and is of great significance for maintaining grid frequency and voltage stability and the large-scale development of the new energy power generation industry.

[0003] In practical high-voltage ride-through (HVRT) applications, when the grid overvoltage reaches a certain level, the grid-connected converter needs to quickly activate its HVRT control strategy to adapt to the abnormal voltage condition. However, when the converter enters the HVRT phase, reactive current overshoot is prone to occur, leading to a voltage fluctuation problem where the grid voltage initially surges and then falls back. This results in significant fluctuations in both grid voltage and current, affecting not only the stability of the HVRT process but also potentially posing risks to the safe operation of grid-connected equipment and the grid. Summary of the Invention

[0004] This invention provides a high-voltage ride-through control method, device, controller, and grid-connected converter for grid-connected converters, in order to solve the problem that grid voltage fluctuations are caused by high-voltage ride-through of grid-connected converters.

[0005] In a first aspect, embodiments of the present invention provide a high-voltage ride-through control method for a grid-connected converter, comprising: The grid voltage at the common coupling point between the grid and the grid-connected converter is monitored in real time, and it is determined whether the grid-connected converter has entered a high-voltage ride-through state based on the grid voltage. If the grid-connected converter enters a high-voltage ride-through state, the reactive current regulation coefficient is reduced within a first preset time period after entering the high-voltage ride-through state. The reactive current setpoint is determined based on the grid voltage and the reactive current regulation coefficient; the reactive current regulation coefficient is positively correlated with the absolute value of the reactive current setpoint. The grid-connected converter is controlled using the given reactive current value.

[0006] Secondly, embodiments of the present invention provide a high-voltage ride-through control device for a grid-connected converter, comprising: The fault ride-through monitoring module is used to monitor the grid voltage at the common coupling point between the grid and the grid-connected converter in real time, and to determine whether the grid-connected converter has entered a high-voltage ride-through state based on the grid voltage. The reactive current coefficient adjustment module is used to reduce the reactive current adjustment coefficient within a first preset time period after the grid-connected converter enters the high voltage ride-through state. The reactive current setpoint calculation module is used to determine the reactive current setpoint based on the grid voltage and the reactive current adjustment coefficient; the reactive current adjustment coefficient is positively correlated with the absolute value of the reactive current setpoint. The control module is used to control the grid-connected converter using the given reactive current value.

[0007] Thirdly, embodiments of the present invention provide a controller, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the high-voltage ride-through control method for a grid-connected converter as described in any possible implementation of the first aspect above.

[0008] Fourthly, embodiments of the present invention provide a grid-connected converter, which includes: a controller as described in the third aspect above.

[0009] This invention provides a high-voltage ride-through control method, apparatus, controller, and grid-connected converter for a grid-connected converter. The method rapidly identifies the high-voltage ride-through state by real-time monitoring of the grid voltage at the point of common coupling, providing a prerequisite for the timely activation of subsequent control strategies and avoiding control inaccuracies caused by state recognition delays. Furthermore, to prevent a sudden increase in the absolute value of the reactive current setpoint (negative value) when the converter enters the high-voltage ride-through state, which causes the grid voltage to surge and then fall back, this application reduces the reactive current regulation coefficient within a first preset time period after entering the high-voltage ride-through state. This suppresses sudden changes in the reactive current setpoint from the source, preventing reactive current overshoot and effectively mitigating the grid voltage surge and fall back problem when entering the high-voltage ride-through state, thus reducing grid voltage and current fluctuations. Finally, based on the grid voltage and the adjusted reactive current regulation coefficient, the reactive current setpoint is determined and used to control the converter. This ensures that the converter does not disconnect from the grid during high voltage ride-through, maintains the voltage and current stability of the grid, improves the smoothness of the high voltage ride-through process, and provides technical support for the continuous transmission of new energy power. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the embodiments of the present invention, 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 This is an application scenario diagram of the high voltage ride-through control method for grid-connected converters provided in this embodiment of the invention; Figure 2 This is a flowchart illustrating the implementation of the high-voltage ride-through control method for grid-connected converters provided in this embodiment of the invention. Figure 3 This is a schematic diagram of the control loop of the high voltage ride-through control method for grid-connected converters provided in this embodiment of the invention; Figure 4 This is a schematic diagram of the high voltage ride-through control device for a grid-connected converter provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the controller provided in an embodiment of the present invention. Detailed Implementation

[0012] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0013] To make the objectives, technical solutions, and advantages of the present invention clearer, specific embodiments will be described below in conjunction with the accompanying drawings.

[0014] Figure 1 This diagram illustrates an application scenario of the high-voltage ride-through control method for grid-connected converters provided in this embodiment of the invention. (Example:) Figure 1As shown, taking a photovoltaic grid-connected system as an example, the photovoltaic device is connected to the grid through a grid-connected converter. Under normal circumstances, the high-voltage ride-through control loop of the grid-connected converter includes a decision loop, a current loop, and a voltage loop. In the decision loop, the grid voltage value is obtained, and then the corresponding reactive current setpoint is determined based on the grid voltage value. In the current loop, the output current of the grid-connected converter is first transformed from the abc coordinate system to the dq coordinate system to obtain the reactive current feedback value. Then, based on the difference between the reactive current setpoint and the reactive current feedback value, the current loop control quantity is calculated, and then a PWM (Pulse Width Modulation) signal for controlling the grid-connected converter is generated based on the current loop control quantity. The grid-connected converter can be a grid-connected inverter or an energy storage converter connected to an energy storage system; no restriction is imposed here.

[0015] Currently, when a grid-connected system enters a high-voltage ride-through state, the grid-connected converter needs to activate a ride-through control strategy to suppress overvoltage by absorbing reactive power from the grid. However, existing technologies are prone to voltage surge problems: On the one hand, light-load conditions are a high-incidence scenario for voltage surges. At this time, the grid's equivalent impedance is high, its carrying capacity is weak, and its sensitivity to reactive power changes is much higher than that of heavy-load conditions. Even a small fluctuation in reactive power regulation can trigger a significant voltage response. On the other hand, when the converter enters the high-voltage ride-through state, in order to quickly suppress overvoltage, the absolute value of the reactive current setpoint (negative value) will rapidly increase with the sudden change in grid voltage, resulting in overshoot of the reactive current absorption. In the initial stage of the reactive power absorption command execution, there is a brief response delay. The original overvoltage state of the grid has not yet been suppressed. At the same time, the transient disturbance of the converter's own power regulation has a reaction effect on the grid, superimposed to form the phenomenon of voltage surge.

[0016] To avoid the aforementioned problems, this application provides a high-voltage ride-through control method for grid-connected converters. The execution subject of this method is the high-voltage ride-through controller of the grid-connected converter. See [link to relevant documentation]. Figure 2 The flowchart illustrating the implementation of the high-voltage ride-through control method for grid-connected converters provided in this embodiment of the invention is described in detail below: S101: Monitor the grid voltage at the common coupling point between the grid and the grid-connected converter in real time, and determine whether the grid-connected converter has entered a high-voltage ride-through state based on the grid voltage.

[0017] In this embodiment, the high-voltage ride-through state refers to a forced operating mode in which the grid-connected converter is required to remain connected to the grid and absorb excess reactive power from the grid to support grid recovery when the grid voltage suddenly rises due to a fault. The point of common coupling is the point where the grid-connected side of the grid-connected converter connects to the grid. The grid voltage U at the point of common coupling between the grid and the grid-connected converter can be obtained using a voltage sensor. g This ensures that the collected signals reflect the true interaction between the power grid and the converter.

[0018] After acquiring the grid voltage, the actual grid voltage value is subtracted from the upper limit of the grid voltage to obtain the voltage difference. If this voltage difference is greater than a preset voltage difference threshold, the grid-connected converter is determined to have entered a high-voltage ride-through state. The upper limit of the grid voltage can be 1.1 to 1.3 times the rated grid voltage.

[0019] S102: If the grid-connected converter enters a high-voltage ride-through state, the reactive current regulation coefficient is reduced within a first preset time period after entering the high-voltage ride-through state.

[0020] In this embodiment, the reactive current setpoint is the target reactive current value that the converter needs to track during high-voltage ride-through. A negative value represents the reactive power absorbed by the grid-connected converter from the grid, and its absolute value determines the reactive power absorption intensity. A positive value represents the reactive power support provided by the grid-connected converter to the grid, and its absolute value determines the reactive power support intensity.

[0021] The reactive current regulation coefficient is a proportional parameter used to adjust the magnitude of the reactive current setpoint. It is a core indicator for balancing reactive current absorption / support and grid stability.

[0022] Specifically, this embodiment determines the initial reactive current setpoint based on the overvoltage depth of the grid voltage and the rated current of the grid-connected converter. Then, the initial reactive current setpoint is adjusted using a reactive current regulation coefficient to obtain the reactive current setpoint output by the decision-making layer. During normal operation, the reactive current regulation coefficient serves as a baseline value. Upon detecting that the grid-connected converter has entered a high-voltage ride-through state, the reactive current regulation coefficient is immediately switched to a high-voltage ride-through value, which is lower than the conventional value.

[0023] In this embodiment, since the high-voltage ride-through initiation phase is a transient process in which both the grid voltage and the converter state are undergoing drastic changes, the high-voltage ride-through fault is usually sudden, causing the common coupling point voltage to surge rapidly from its rated value to above 1.1Un, resulting in a sudden increase in voltage deviation. Furthermore, the grid-connected converter's control loop has an inherent response delay, making it unable to execute reactive power absorption commands instantaneously. If the reactive current regulation coefficient k is not reduced, the sudden increase in grid voltage deviation and the fixed reactive current regulation coefficient k will cause the absolute value of the reactive current setpoint to rise instantaneously. However, due to the response delay, the grid-connected converter cannot keep up in time. At this point, the grid overvoltage is not suppressed, and the sudden change in the reactive current setpoint will trigger current and voltage oscillations within the grid-connected converter. These oscillations react back to the grid, further exacerbating the grid voltage surge. After the grid-connected converter responds, the reactive current setpoint I will again rise. q_ref An excessively large absolute value leads to over-absorption, causing the voltage to drop.

[0024] Therefore, within the first preset time period after detecting that the grid-connected converter has entered a high-voltage ride-through fault state, the controller actively reduces the reactive current regulation coefficient. This reduces the sudden change in the reactive current setpoint, allowing the reactive power absorption of the grid-connected converter to increase slowly, matching the converter's response speed. This buffering process effectively suppresses transient oscillations, avoids the superposition effect of voltage surges, and allows the grid voltage and grid-connected converter current to smoothly transition to a stable high-voltage ride-through state, laying the foundation for subsequent precise regulation.

[0025] In one embodiment, when entering a high-voltage ride-through fault state, the reactive current regulation coefficient can be gradually reduced from its normal value to the high-voltage ride-through value to avoid grid voltage fluctuations caused by sudden changes in the reactive current setpoint. Simultaneously, to prevent the reactive current setpoint adjustment from being too slow, the reactive current regulation coefficient can be set to gradually decrease from its normal value to the high-voltage ride-through value over a second preset time period, where the second preset time period is shorter than the first preset time period. For example, the first preset time period can be 20ms, and the second preset time period can be 2ms.

[0026] S103: Determine the reactive current setpoint based on the grid voltage and the reactive current regulation coefficient; the reactive current regulation coefficient is positively correlated with the absolute value of the reactive current setpoint.

[0027] In this embodiment, the overvoltage depth is an indicator that quantifies the severity of grid overvoltage. This embodiment subtracts the upper voltage limit from the actual grid voltage value to obtain the voltage difference. Then, the voltage difference is divided by the upper voltage limit to obtain the grid overvoltage depth. The upper voltage limit can be 1.1U. n ~1.3U n Un represents the rated voltage.

[0028] After determining the overvoltage depth of the power grid, multiply the overvoltage depth by the rated current, and then multiply by the reactive current adjustment coefficient to obtain the absolute value of the reactive current setpoint. During high voltage ride-through, the reactive current setpoint is negative.

[0029] S104: The grid-connected converter is controlled using the given reactive current value.

[0030] In this embodiment, reference Figure 3 After obtaining the reactive current setpoint Then, the current amplitude constraint formula can be used. Determine the active current setpoint .in, This indicates the device's maximum short-time withstand current.

[0031] Next, the current control loop is entered. In the reactive current loop, the actual value of the output current Io of the grid-connected converter is obtained, and the actual value of the output current is transformed from the abc coordinate system to the dq coordinate system to obtain the actual value of the active current I. d_fdb and the actual value of reactive current I q_fdb Then, the reactive current setpoint I q_ref Subtract the actual value of reactive current I q_fdb The reactive current difference is obtained and input into the PI controller to obtain the reactive current loop output. In the active current loop, the active current setpoint is... Subtract the actual value of active current I d_fdb The active current difference is obtained; the active current difference is input into the PI controller to obtain the active current loop output.

[0032] In the reactive voltage loop, the output of the reactive current loop is used as the reactive voltage setpoint U. q_ref The reactive voltage setpoint U is adopted. q_ref Subtract the actual value of reactive voltage U q_fdb The reactive voltage difference is obtained, and this difference is input into a PI controller to obtain the reactive power control quantity. The actual reactive voltage value U... q_fdb It is obtained by converting the grid voltage from the abc coordinate system to the dq axis.

[0033] In the active voltage loop, the output of the active current loop is used as the active voltage setpoint. Then the active voltage setpoint Subtract the actual value of active voltage U d_fdb The active voltage difference is obtained, and this difference is input to another PI controller to obtain the active control quantity. The actual active voltage value U... d_fdb It is obtained by converting the grid voltage from the abc coordinate system to the dq axis.

[0034] Finally, the active and reactive control quantities are transformed into the abc coordinate system to obtain the final control quantity, which is then used to generate the PWM (Pulse Width Modulation) signal to control the rectifier.

[0035] As can be seen from the above embodiments, this embodiment quickly identifies the high-voltage ride-through state by monitoring the grid voltage at the common coupling point in real time, providing a prerequisite guarantee for the timely activation of subsequent control strategies and avoiding control inaccuracies caused by state recognition delays. Next, to avoid a sudden increase in the absolute value of the reactive current setpoint (negative value) when the converter enters the high-voltage ride-through state, causing the grid voltage to surge and then fall back, this application reduces the reactive current regulation coefficient within the first preset time period after entering the high-voltage ride-through state. This can suppress sudden changes in the reactive current setpoint from the source, avoiding reactive current overshoot, thereby effectively alleviating the grid voltage surge and then fall back problem when entering the high-voltage ride-through state and reducing the fluctuation amplitude of grid voltage and current. Finally, based on the grid voltage and the adjusted reactive current regulation coefficient, the reactive current setpoint is determined and used to control the converter. This ensures that the converter does not disconnect from the grid during high-voltage ride-through, maintains the voltage and current stability of the grid, improves the smoothness of the high-voltage ride-through process, and provides technical support for the continuous transmission of new energy power.

[0036] In one possible implementation, the specific implementation process of S102 includes: A first value is determined based on the load rate of the power grid; the load rate is positively correlated with the first value. Within a first preset time period after entering the high voltage ride-through state, the reactive current regulation coefficient is reduced to the first value.

[0037] In this embodiment, when the power grid is lightly loaded, the equivalent impedance of the power grid is relatively high, and it is highly sensitive to changes in reactive power. Even a small fluctuation in reactive power regulation can trigger a significant voltage response. Rapid reactive power absorption commands can easily cause transient oscillations in the current and voltage inside the grid-connected converter, further aggravating voltage fluctuations at the common coupling point of the power grid, and ultimately forming a jitter phenomenon of first surging and then falling back. This not only affects the stability of the high voltage ride-through process, but may also pose potential risks to the insulation of grid-connected equipment and the safe operation of the power grid.

[0038] To address the aforementioned issues, this embodiment uses the load factor as a reference for the reactive current regulation coefficient. The grid load factor reflects the current load carrying capacity of the grid and directly determines the grid's tolerance to reactive power fluctuations. A higher load factor results in a lower equivalent impedance and stronger tolerance to fluctuations. Therefore, when the load factor is low, a smaller reactive current regulation coefficient can be set, effectively suppressing sudden increases in the absolute value of the reactive current setpoint (negative value). When the load factor is high, the grid's carrying capacity is stronger, and its tolerance to reactive current absorption fluctuations is higher. In this case, setting a relatively high initial value ensures that the reactive current supports the grid voltage regulation without causing severe fluctuations due to excessive absorption.

[0039] In one possible implementation, the load rate can be divided into multiple load rate zones, such as a high load rate zone (100%~70%), a medium load rate zone (70%~40%), and a low load rate zone (40%~0%). A corresponding reactive current regulation coefficient is set for each load rate zone. In practical applications, the current load rate of the power grid is obtained, the corresponding load rate range is determined, and then the reactive current regulation coefficient corresponding to that load rate range is used as the first value. This method is simple to implement, requires little computation, and can quickly adapt to different load ranges of the power grid.

[0040] In one possible implementation, it can also be done through a formula. ;in, k 1 represents the first value. This represents the maximum reactive current regulation coefficient corresponding to 100% load rate. This represents the unit adjustment coefficient. This represents the difference between the current load rate and the maximum load rate. Using the above formula, the reactive current regulation coefficient corresponding to each load rate can be obtained, thereby improving the accuracy of high-voltage ride-through control.

[0041] As can be seen from the above embodiments, this embodiment determines the first value based on the grid load rate, and the load rate is positively correlated with this first value. When the grid load rate is high, the grid has a stronger carrying capacity and a higher tolerance for fluctuations in reactive current absorption. In this case, setting a relatively high first value can ensure the regulatory support of reactive current on grid voltage without causing severe fluctuations due to excessive absorption. However, when the grid is under light load conditions, the grid's carrying capacity is weaker, making it a high-incidence scenario for excessive reactive current absorption. By further reducing the first value, the sudden increase in the absolute value of the reactive current setpoint can be effectively suppressed, fundamentally avoiding voltage fluctuations and current fluctuations caused by excessive reactive current absorption. This method of adaptively adjusting the regulation coefficient based on the load rate achieves precise control under different load conditions, breaking the one-size-fits-all control limitations of existing technologies. It enables grid-connected converters to obtain appropriate reactive current absorption control effects when entering high-voltage ride-through under various load conditions such as heavy load and light load, significantly improving the adaptability and stability of high-voltage ride-through technology under different load scenarios, and further ensuring the safe operation of the grid and converter.

[0042] In one possible implementation, the specific implementation process of S102 includes: The second value is determined based on the grid short-circuit ratio; the grid short-circuit ratio is positively correlated with the second value. Within a first preset time period after entering the high voltage ride-through state, the reactive current regulation coefficient is reduced to the second value.

[0043] In this embodiment, the short circuit ratio (SCR) is a core electrical indicator reflecting the strength of the power grid. It is the ratio of the short circuit capacity of the power grid to the rated capacity of the grid-connected converter. The larger the SCR, the greater the inertia of the power grid and the stronger its ability to withstand voltage and current fluctuations. Conversely, the smaller the short circuit ratio, the weaker the power grid and the lower its tolerance to fluctuations.

[0044] Specifically, in strong power grids, a fixed reactive current regulation coefficient may lead to insufficient reactive power absorption, making it impossible to quickly stabilize the grid voltage; while in weak power grids, a fixed coefficient may result in an excessively large absolute value of reactive current, exacerbating grid fluctuations due to excessive reactive power absorption. This embodiment links the second value to the grid short-circuit ratio (SCR). In strong power grid scenarios (SCR value greater than a preset threshold), a higher reactive current regulation coefficient is set to ensure sufficient reactive current absorption for rapid response to voltage anomalies. In weak power grid scenarios (SCR value not greater than a preset threshold), a lower reactive current regulation coefficient is set to strictly suppress excessive reactive current absorption, avoiding additional impact on the weak grid. This control method, adapting to both strong and weak power grid conditions, allows the high-voltage ride-through control strategy of the grid-connected converter to flexibly adapt to different grid environments, significantly improving the versatility and adaptability of this embodiment. It enables stable control of reactive current absorption under both strong and weak power grid conditions, reducing grid voltage and current fluctuations and ensuring the safety and stability of the high-voltage ride-through process.

[0045] In one embodiment, after obtaining the grid short-circuit ratio (SCR), the controller can classify the grid into weak, medium-intensity, and strong grids based on the SCR value. Specifically, a grid is classified as weak if the SCR value is less than a first preset threshold, as medium-intensity if the SCR value is greater than or equal to the first preset threshold but less than a second preset threshold, and as strong if the SCR value is greater than or equal to the second preset threshold. The first preset threshold is less than the second preset threshold. For example, the first preset threshold can be 2, and the second preset threshold can be 3. The controller can determine the type of the current grid based on its SCR value, and then determine the corresponding reactive current regulation coefficient based on the grid type. A larger SCR value corresponds to a larger reactive current regulation coefficient, thus ensuring sufficient reactive current absorption for rapid response to voltage anomalies in strong grid scenarios and strictly suppressing excessive reactive current absorption in weak grid scenarios to avoid additional impact on the weak grid.

[0046] In one possible implementation, another step of S102 includes: determining a third value based on the grid short-circuit ratio and the current load rate of the grid; Within a first preset time period after entering the high voltage ride-through state, the reactive current regulation coefficient is reduced to the third value.

[0047] Specifically, this embodiment can be achieved through the formula Calculate the comprehensive index; among which, This represents a comprehensive indicator. , Let represent the weighting coefficients, and . This indicates the load rate.

[0048] After obtaining the comprehensive index, the corresponding third value is determined based on the comprehensive index, and the comprehensive index and the third value are positively correlated.

[0049] As can be seen from the above embodiments, this embodiment determines the third value through dual parameter coupling, which can provide the optimal control scheme for various complex combined operating conditions, thereby improving the accuracy and adaptability of the third value. It can fully cover high-voltage ride-through scenarios with different combinations of grid strength and load rate, effectively stabilize grid voltage and current, and further optimize the stability and reliability of the high-voltage ride-through process.

[0050] In one possible implementation, the specific implementation process of S103 includes: Input the grid voltage and the reactive current regulation coefficient into the reactive current setpoint calculation formula. The given value of reactive current is obtained; in, This represents the reactive current setpoint. Indicates the grid voltage. Indicates the upper limit of voltage. This represents the reactive current regulation coefficient. Indicates the rated current.

[0051] In this embodiment, when the grid-connected converter is in normal operating condition, the value of k is usually greater than 1, specifically ranging from 1.1 to 1.6. When the grid-connected converter enters the high-voltage ride-through state, the reactive current regulation coefficient is reduced, and its value can range from 0.3 to 0.9, with the specific value determined based on the grid short-circuit ratio and / or load factor.

[0052] In one possible implementation, prior to S102, the method provided in this embodiment further includes: The first preset duration is determined based on the overvoltage depth of the power grid voltage, and the overvoltage depth is positively correlated with the first preset duration.

[0053] In this embodiment, since the greater the overvoltage depth of the grid voltage, the greater the reactive power that needs to be absorbed from the grid voltage, and the more volatile the grid voltage and current, this embodiment determines the corresponding first preset duration based on the overvoltage depth of the grid voltage. The greater the overvoltage depth, the longer the first preset duration, so as to avoid restoring the reactive current regulation coefficient when the grid voltage is still in a period of large fluctuations, which would affect the high voltage ride-through stability.

[0054] The overvoltage depth of the grid voltage is calculated when the grid-connected converter enters the high-voltage ride-through state.

[0055] Specifically, the overvoltage depth of the power grid can be proportional to the first preset duration, that is, it can be determined by the formula... Calculate the first preset duration corresponding to the current overpressure depth, where t Indicates the preset duration. t 0 represents the base duration. Indicates the depth of overpressure. a This indicates the unit of time. The base time is included. t 0 can represent 10ms.

[0056] In one embodiment, the overvoltage depth of the grid voltage can be divided into multiple segments, each segment corresponding to a preset duration. After obtaining the overvoltage depth of the grid voltage, the corresponding preset duration is determined according to the segment where the current overvoltage depth is located, thereby simplifying the overall calculation and improving control efficiency.

[0057] After determining the first preset duration based on the overvoltage depth, it is necessary to limit the first preset duration within a certain range. This is achieved by using a reactive current response time limit to constrain the first preset duration. The reactive current response time limit refers to the maximum allowable time threshold for the grid-connected converter to adjust its output reactive current from the initial state (e.g., the normal reactive current level before high-voltage ride-through) to the target reactive current level (e.g., the reactive current setpoint that meets grid support requirements) after the grid voltage rises and enters the high-voltage ride-through state. It is a constraint indicator balancing the timeliness of grid reactive power support and the stability of converter control. It determines that reactive current regulation cannot be too slow, otherwise it will be unable to support the grid voltage in time; nor can it sacrifice stability for speed, otherwise it will cause current spikes or oscillations. Therefore, the first preset duration determined based on the grid voltage overvoltage depth cannot exceed the aforementioned reactive current response time limit; otherwise, the entire reactive current response time will time out.

[0058] As can be seen from the above embodiments, this embodiment solves the problem of insufficient adaptability caused by a fixed first preset duration by determining the first preset duration based on the voltage overvoltage depth and then constraining the first preset duration with a reactive current response time limit. This significantly improves the adaptability and timeliness of the control strategy to different power grid disturbance scenarios. Furthermore, this dual mechanism of dynamic calculation and limit constraint not only ensures the sufficiency of transient suppression under different high-voltage ride-through scenarios but also meets the power grid's timeliness requirements for reactive power support. It avoids the dual problems of unstable control due to excessively short duration and delayed response due to excessively long duration, significantly improving the engineering practicality and compliance of high-voltage ride-through control.

[0059] In one possible implementation, after S102, the method provided in this embodiment further includes: After a first preset time period of entering the high voltage ride-through state, the reactive current regulation coefficient is restored to the value before entering the high voltage ride-through state.

[0060] In this embodiment, the reactive current regulation coefficient before high voltage ride-through is the reactive current regulation coefficient used by the grid-connected converter under normal grid-connected operating conditions. This coefficient is optimized for steady-state operation and has good reactive current regulation capability and stability.

[0061] Specifically, the controller reduces the reactive current regulation coefficient within the first preset time period to suppress excessive increase in the absolute value of reactive current in the initial stage, ensuring the stability of the high-voltage ride-through phase. However, this state is not optimal in the long term: after the first preset time period ends, the grid voltage and current have stabilized through previous control. If the reduced regulation coefficient is maintained, it will lead to insufficient reactive current absorption, making it unable to respond promptly to potential small voltage fluctuations in the grid, and may even cause the grid voltage to deviate from the reasonable range. Therefore, in this embodiment, when the controller detects that the first preset time period for the grid-connected converter to enter the high-voltage ride-through state has elapsed, it restores the reactive current regulation coefficient to the value before the high-voltage ride-through, that is, based on the overvoltage depth, obtains a normal reactive current setpoint value that can optimally support the grid voltage, thereby avoiding the reactive current setpoint value being continuously too low and unable to quickly absorb the reactive power from the grid, resulting in reactive response timeout or delay.

[0062] In one possible implementation, when the controller detects that the grid-connected converter has entered a high-voltage ride-through state for a first preset period of time, it can immediately switch the current reactive current regulation coefficient to the value before the high-voltage ride-through state; or it can gradually restore the current reactive current regulation coefficient to the value before the high-voltage ride-through state over a second preset period of time.

[0063] The second preset duration can be 1 to 4 ms. Within the second preset duration, the reactive current regulation coefficient is gradually restored according to a certain unit value.

[0064] As can be seen from the above embodiments, after entering the high-voltage ride-through state for a first preset time, this embodiment restores the reactive current regulation coefficient to the value before the high-voltage ride-through state, realizing a complete closed loop of the high-voltage ride-through control strategy. This solves the problem of insufficient reactive power regulation capability caused by long-term abnormal coefficients in the prior art, avoids the decline in grid voltage stability caused by long-term low reactive current regulation coefficients, and ensures that the grid-connected converter can balance safety and regulation efficiency throughout the high-voltage ride-through process and subsequent operation, further improving the overall stability and reliability of the new energy grid-connected system.

[0065] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0066] The following are device embodiments of the present invention. For details not described in detail, please refer to the corresponding method embodiments described above.

[0067] Figure 4 A schematic diagram of the high-voltage ride-through control device provided in an embodiment of the present invention is shown. For ease of explanation, only the parts related to the embodiment of the present invention are shown, and are described in detail below: like Figure 4 As shown, the high-voltage ride-through control device 100 for the grid-connected converter includes: The fault ride-through monitoring module 110 is used to monitor the grid voltage at the common coupling point between the grid and the grid-connected converter in real time, and to determine whether the grid-connected converter has entered the high voltage ride-through state based on the grid voltage. The reactive current coefficient adjustment module 120 is used to reduce the reactive current adjustment coefficient within a first preset time period after the grid-connected converter enters the high voltage ride-through state. The reactive current setpoint calculation module 130 is used to determine the reactive current setpoint based on the grid voltage and the reactive current adjustment coefficient; the reactive current adjustment coefficient is positively correlated with the absolute value of the reactive current setpoint. The control module 140 is used to control the grid-connected converter using the given reactive current value.

[0068] In one possible implementation, the reactive current coefficient adjustment module 120 is specifically used for: A first value is determined based on the load rate of the power grid; the load rate is positively correlated with the first value. Within a first preset time period after entering the high voltage ride-through state, the reactive current regulation coefficient is reduced to the first value.

[0069] In one possible implementation, the reactive current coefficient adjustment module 120 is specifically used for: The second value is determined based on the grid short-circuit ratio; the grid short-circuit ratio is positively correlated with the second value. Within a first preset time period after entering the high voltage ride-through state, the reactive current regulation coefficient is reduced to the second value.

[0070] In one possible implementation, the reactive current coefficient adjustment module 120 is specifically used to: determine a third value based on the grid short-circuit ratio and the current load rate of the grid; Within a first preset time period after entering the high voltage ride-through state, the reactive current regulation coefficient is reduced to the third value.

[0071] In one possible implementation, the reactive current setpoint calculation module 130 is specifically used for: Input the grid voltage and the reactive current regulation coefficient into the reactive current setpoint calculation formula. The given value of reactive current is obtained; in, This represents the reactive current setpoint. Indicates the grid voltage. Indicates the upper limit of voltage. This represents the reactive current regulation coefficient. Indicates the rated current.

[0072] In one possible implementation, the high-voltage ride-through control device 100 for the grid-connected converter further includes: The preset duration adjustment module is used to determine a corresponding first preset duration based on the overvoltage depth of the power grid voltage, and the overvoltage depth is positively correlated with the first preset duration.

[0073] In one possible implementation, the high-voltage ride-through control device 100 for the grid-connected converter further includes: The coefficient recovery module is used to restore the reactive current regulation coefficient to its value before entering the high voltage ride-through state after a first preset time period.

[0074] Figure 5 This is a schematic diagram of the controller provided in an embodiment of the present invention. Figure 5 As shown, the controller 5 in this embodiment includes a processor 50, a memory 51, and a computer program 52 stored in the memory 51 and executable on the processor 50. When the processor 50 executes the computer program 52, it implements the steps in the high-voltage ride-through control method embodiments of the various grid-connected converters described above, for example... Figure 2Steps S101 to S104 are shown. Alternatively, when the processor 50 executes the computer program 52, it implements the functions of each module / unit in the above-described device embodiments.

[0075] For example, the computer program 52 may be divided into one or more modules / units, which are stored in the memory 51 and executed by the processor 50 to complete the present invention. The one or more modules / units may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program 52 in the controller 5.

[0076] The controller 5 can be a computing device such as a desktop computer, laptop, handheld computer, or cloud server. The controller 5 may include, but is not limited to, a processor 50 and a memory 51. Those skilled in the art will understand that... Figure 5 This is merely an example of controller 5 and does not constitute a limitation on controller 5. It may include more or fewer components than shown, or combine certain components, or different components. For example, the controller may also include input / output devices, network access devices, buses, etc.

[0077] The processor 50 may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor.

[0078] The memory 51 can be an internal storage unit of the controller 5, such as a hard disk or memory of the controller 5. The memory 51 can also be an external storage device of the controller 5, such as a plug-in hard disk, Smart Media Card (SMC), Secure Digital (SD) card, or Flash Card equipped on the controller 5. Furthermore, the memory 51 can include both internal storage units and external storage devices of the controller 5. The memory 51 is used to store the computer program and other programs and data required by the controller. The memory 51 can also be used to temporarily store data that has been output or will be output.

[0079] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0080] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0081] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0082] In the embodiments provided by this invention, it should be understood that the disclosed devices / controllers and methods can be implemented in other ways. For example, the device / controller embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0083] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0084] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0085] If the integrated module / unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the above embodiments of the present invention can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the high-voltage ride-through control method embodiments of the various grid-connected converters described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc.

[0086] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A high-voltage ride-through control method for a grid-connected converter, characterized in that, include: The grid voltage at the common coupling point between the grid and the grid-connected converter is monitored in real time, and it is determined whether the grid-connected converter has entered a high-voltage ride-through state based on the grid voltage. If the grid-connected converter enters the high voltage ride-through state, the reactive current regulation coefficient is reduced within a first preset time period after entering the high voltage ride-through state. The reactive current setpoint is determined based on the grid voltage and the reactive current regulation coefficient. The reactive current regulation coefficient is positively correlated with the absolute value of the reactive current setpoint; The grid-connected converter is controlled using the given reactive current value.

2. The high-voltage ride-through control method for grid-connected converters according to claim 1, characterized in that, The reduction of the reactive current regulation coefficient within a first preset time period after entering the high voltage ride-through state includes: A first value is determined based on the load rate of the power grid; the load rate is positively correlated with the first value. Within a first preset time period after entering the high voltage ride-through state, the reactive current regulation coefficient is reduced to the first value.

3. The high-voltage ride-through control method for grid-connected converters according to claim 1, characterized in that, The reduction of the reactive current regulation coefficient within a first preset time period after entering the high voltage ride-through state includes: The second value is determined based on the grid short-circuit ratio; the grid short-circuit ratio is positively correlated with the second value. Within a first preset time period after entering the high voltage ride-through state, the reactive current regulation coefficient is reduced to the second value.

4. The high-voltage ride-through control method for grid-connected converters according to claim 1, characterized in that, The reduction of the reactive current regulation coefficient within a first preset time period after entering the high voltage ride-through state includes: determining a third value based on the grid short-circuit ratio and the current load rate of the grid; Within a first preset time period after entering the high voltage ride-through state, the reactive current regulation coefficient is reduced to the third value.

5. The high-voltage ride-through control method for a grid-connected converter according to any one of claims 1 to 4, characterized in that, The determination of the reactive current setpoint based on the grid voltage and the reactive current regulation coefficient includes: Input the grid voltage and the reactive current regulation coefficient into the reactive current setpoint calculation formula. The given value of reactive current is obtained; in, This represents the reactive current setpoint. Indicates the grid voltage. Indicates the upper limit of voltage. This represents the reactive current regulation coefficient. Indicates the rated current.

6. The high-voltage ride-through control method for a grid-connected converter according to claim 1, characterized in that, Before reducing the reactive current regulation coefficient within a first preset time period after entering the high-voltage ride-through state, the method further includes: The first preset duration is determined based on the overvoltage depth of the power grid voltage, and the overvoltage depth is positively correlated with the first preset duration.

7. The high-voltage ride-through control method for grid-connected converters according to claim 1, characterized in that, After reducing the reactive current regulation coefficient within a first preset time period after entering the high-voltage ride-through state, the method further includes: After a first preset time period of entering the high voltage ride-through state, the reactive current regulation coefficient is restored to the value before entering the high voltage ride-through state.

8. A high-voltage ride-through control device for a grid-connected converter, characterized in that, include: The fault ride-through monitoring module is used to monitor the grid voltage at the common coupling point between the grid and the grid-connected converter in real time, and to determine whether the grid-connected converter has entered a high-voltage ride-through state based on the grid voltage. The reactive current coefficient adjustment module is used to reduce the reactive current adjustment coefficient within a first preset time period after the grid-connected converter enters the high voltage ride-through state. The reactive current setpoint calculation module is used to determine the reactive current setpoint based on the grid voltage and the reactive current regulation coefficient. The reactive current regulation coefficient is positively correlated with the absolute value of the reactive current setpoint; The control module is used to control the grid-connected converter using the given reactive current value.

9. A controller comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the high-voltage ride-through control method for the grid-connected converter as described in any one of claims 1 to 7.

10. A grid-connected converter, characterized in that, include: The controller as described in claim 9.

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