A method and device for grid-forming converter fault ride-through control

Abstract

The application provides a network-constructed converter fault ride-through control method and device, and relates to the technical field of control. The method comprises the following steps: if it is determined that the AC bus voltage amplitude is less than the reactive ring output grid-connected point voltage, a control switch is turned on; by adjusting I coefficient, D coefficient and P coefficient in sequence, power deviation is corrected by increasing electromagnetic active power, generalized inertia coefficient is corrected and generalized damping coefficient is corrected until the network-constructed converter reaches fault ride-through, and the I coefficient, the D coefficient and the P coefficient at this time are determined as target parameters of the angular frequency PID compensator; if it is determined that the AC bus voltage amplitude is greater than or equal to the reactive ring output grid-connected point voltage, the control switch is turned off. The device executes the above method. The method and device provided in the application embodiment can improve the transient stability of the network-constructed converter.

Description

Technical Field

[0001] This invention relates to the field of control technology, and specifically to a fault ride-through control method and device for a grid-type converter. Background Technology

[0002] With the increasing penetration rate of high-proportion new energy sources and their supporting converters, the integration of new energy converters into the power system poses certain risks to the safe and stable operation of the power grid. Specifically, this manifests as the grid exhibiting low inertia and underdamped operating characteristics, leading to new challenges such as wide-frequency oscillations, instability under small and large disturbances. Currently, converter control is mainly divided into grid-connected converters and grid-connected converters. Grid-connected converters, due to simulating the external characteristics of synchronous machines, provide strong damping and high inertia to the system, acting as a "voltage source" to actively support the power grid, making them an excellent control method suitable for the current power system structure. However, grid-connected converters suffer from transient instability under large disturbance faults in the power grid; therefore, designing fault ride-through control for grid-connected converters is particularly important. Considering the current design methods for fault ride-through control of grid-connected converters, which combine power and voltage command switching, active power loop parameter switching, and virtual impedance control design, the following problems may arise. First, the control is relatively complex, mainly because the design process of each control parameter needs to be precise. Second, with the long-term operation of the converter, the converter components will age, and at this time, the various electrical, mechanical and control parameters of the converter will change slightly, which may lead to the failure of the converter to ride through faults under parameter changes. Third, converters of different grid types exist in a shared power system, and their fault ride-through control is different. Under fault ride-through control, the primary task is to protect the safety of the equipment, which may weaken the safety and stability capabilities of other converters and power system equipment to a certain extent, and worsen the transient stability characteristics of the power system under large disturbances, which is completely unacceptable. Summary of the Invention

[0003] To address the problems in the prior art, embodiments of the present invention provide a fault ride-through control method and apparatus for grid-type converters, which can at least partially solve the problems existing in the prior art.

[0004] On one hand, this invention proposes a fault ride-through control method for a grid-type converter. This method is applied to the active power loop transfer function model of a grid-type converter equipped with an angular frequency PID compensator. One end of the angular frequency PID compensator is connected to the angular frequency deviation of the active power loop of the grid-type converter, and the other end is connected to a comparator node connected to the reciprocal of the rated angular frequency of the active power loop. The fault ride-through control method includes:

[0005] If it is determined that the AC bus voltage amplitude is less than the reactive power loop output grid connection point voltage, then the control switch is turned on to enable the angular frequency PID compensator.

[0006] By sequentially adjusting the I coefficient, D coefficient, and P coefficient, the power deviation, generalized inertia coefficient, and generalized damping coefficient are corrected by increasing the electromagnetic active power, respectively, until the grid-type converter reaches fault ride-through, and the I coefficient, D coefficient, and P coefficient at this time are determined to be the target parameters of the angular frequency PID compensator.

[0007] If it is determined that the amplitude of the AC bus voltage is greater than or equal to the voltage at the grid connection point of the reactive power loop output, then the control switch is turned off to disable the angular frequency PID compensator.

[0008] The step of sequentially adjusting the I, D, and P coefficients to correct power deviation by increasing electromagnetic active power, correcting the generalized inertia coefficient, and correcting the generalized damping coefficient, until the grid-type converter achieves fault ride-through, includes:

[0009] Increase the I coefficient until the power angle reaches the pre-built power angle balance point, then start adjusting the D coefficient.

[0010] The fault ride-through control method for grid-type converters further includes:

[0011] During the adjustment of the D coefficient, the power angle stability index is monitored. If it is determined that the power angle stability index is abnormal, the adjustment of the D coefficient is terminated, and the adjustment of the P coefficient is started.

[0012] The fault ride-through control method for grid-type converters further includes:

[0013] During the process of increasing the P coefficient, the power angle overshoot index is monitored until the power angle overshoot is less than the preset power angle overshoot range, and the target parameter is determined.

[0014] Prior to adding the angular frequency PID compensator, the fault ride-through control method for the grid-type converter further includes:

[0015] Based on the pre-built determination result of whether the fault drop of the grid-type converter has been crossed, the corresponding steps are executed to start attaching the angular frequency PID compensator to the active power loop transfer function model of the original grid-type converter.

[0016] The step of executing corresponding steps based on the pre-built judgment result of whether the fault drop of the grid-type converter has been crossed, to initiate the attachment of the angular frequency PID compensator to the active power loop transfer function model of the original grid-type converter, includes:

[0017] If it is determined that the fault drop of the grid-type converter has crossed, the fault drop level is increased until instability occurs, and the angular frequency PID compensator is added to the active power loop transfer function model of the original grid-type converter.

[0018] The step of executing corresponding steps based on the pre-built judgment result of whether the fault drop of the grid-type converter has been crossed, to initiate the attachment of the angular frequency PID compensator to the active power loop transfer function model of the original grid-type converter, includes:

[0019] If it is determined that the fault drop of the grid-type converter has not occurred, then the angular frequency PID compensator is directly added to the active power loop transfer function model of the original grid-type converter.

[0020] On one hand, this invention proposes a fault ride-through control device for a grid-type converter. This device is applied to the active power loop transfer function model of a grid-type converter equipped with an angular frequency PID compensator. One end of the angular frequency PID compensator is connected to the angular frequency deviation of the active power loop of the grid-type converter, and the other end is connected to a comparator node connected after the reciprocal of the rated angular frequency of the active power loop. The fault ride-through control device includes:

[0021] The activation unit is used to activate the control switch if it is determined that the AC bus voltage amplitude is less than the reactive power loop output grid connection point voltage, so that the angular frequency PID compensator takes effect.

[0022] The adjustment unit is used to adjust the I coefficient, D coefficient and P coefficient in sequence to correct the power deviation by increasing the electromagnetic active power, correct the generalized inertia coefficient and correct the generalized damping coefficient, until the grid-type converter reaches fault ride-through, and to determine the I coefficient, D coefficient and P coefficient at this time as the target parameters of the angular frequency PID compensator.

[0023] The shutdown unit is used to shut down the control switch if it is determined that the amplitude of the AC bus voltage is greater than or equal to the voltage at the grid connection point of the reactive power loop output, so as to disable the angular frequency PID compensator.

[0024] In another aspect, embodiments of the present invention provide an electronic device, including: a processor, a memory, and a bus, wherein,

[0025] The processor and the memory communicate with each other via the bus;

[0026] The memory stores program instructions that can be executed by the processor, and the processor can execute the following methods by calling the program instructions:

[0027] If it is determined that the AC bus voltage amplitude is less than the reactive power loop output grid connection point voltage, then the control switch is turned on to enable the angular frequency PID compensator.

[0028] By sequentially adjusting the I coefficient, D coefficient, and P coefficient, the power deviation, generalized inertia coefficient, and generalized damping coefficient are corrected by increasing the electromagnetic active power, respectively, until the grid-type converter reaches fault ride-through, and the I coefficient, D coefficient, and P coefficient at this time are determined to be the target parameters of the angular frequency PID compensator.

[0029] If it is determined that the amplitude of the AC bus voltage is greater than or equal to the voltage at the grid connection point of the reactive power loop output, then the control switch is turned off to disable the angular frequency PID compensator.

[0030] This invention provides a non-transitory computer-readable storage medium, comprising:

[0031] The non-transitory computer-readable storage medium stores computer instructions that cause the computer to perform the following methods:

[0032] If it is determined that the AC bus voltage amplitude is less than the reactive power loop output grid connection point voltage, then the control switch is turned on to enable the angular frequency PID compensator.

[0033] By sequentially adjusting the I coefficient, D coefficient, and P coefficient, the power deviation, generalized inertia coefficient, and generalized damping coefficient are corrected by increasing the electromagnetic active power, respectively, until the grid-type converter reaches fault ride-through, and the I coefficient, D coefficient, and P coefficient at this time are determined to be the target parameters of the angular frequency PID compensator.

[0034] If it is determined that the amplitude of the AC bus voltage is greater than or equal to the voltage at the grid connection point of the reactive power loop output, then the control switch is turned off to disable the angular frequency PID compensator.

[0035] The fault ride-through control method and apparatus for grid-type converters provided in this invention, if it is determined that the AC bus voltage amplitude is less than the reactive power loop output grid connection point voltage, then the control switch is turned on to enable the angular frequency PID compensator. By sequentially adjusting the I coefficient, D coefficient, and P coefficient, the power deviation is corrected by increasing the electromagnetic active power, the generalized inertia coefficient is corrected, and the generalized damping coefficient is corrected, until the grid-type converter achieves fault ride-through. The I coefficient, D coefficient, and P coefficient at this time are determined to be the target parameters of the angular frequency PID compensator. If it is determined that the AC bus voltage amplitude is greater than or equal to the reactive power loop output grid connection point voltage, then the control switch is turned off to disable the angular frequency PID compensator, and the active power loop is modified. The additional control fed back to the input by the angular frequency deviation PID module realizes fault ride-through of the grid-type converter in most cases, has wider engineering applicability, improves the transient stability of the grid-type converter, and realizes fault ride-through of the grid-type converter. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:

[0037] Figure 1 This is a flowchart illustrating a fault ride-through control method for a grid-type converter provided in an embodiment of the present invention.

[0038] Figure 2 This is a schematic diagram of a grid-connected converter system and control provided in an embodiment of the present invention.

[0039] Figure 3 This is a schematic diagram illustrating the control strategy of the phase-locked loop system provided in an embodiment of the present invention.

[0040] Figure 4 This is a schematic diagram illustrating the active power loop transfer function of a grid-type converter provided in an embodiment of the present invention.

[0041] Figure 5 This is a schematic diagram illustrating the derivation of the active power loop transfer function of a grid-type converter provided in an embodiment of the present invention.

[0042] Figure 6 This is a flowchart illustrating a fault ride-through control method for a grid-type converter provided in another embodiment of the present invention.

[0043] Figure 7 This is a schematic diagram of a grid-connected converter system and control provided in another embodiment of the present invention.

[0044] Figure 8(a) is a schematic diagram illustrating the power angle comparison effect of the three schemes provided in the embodiments of the present invention.

[0045] Figure 8(b) is a schematic diagram illustrating the comparison of angular velocities among the three schemes provided in the embodiments of the present invention.

[0046] Figure 8(c) is a schematic diagram illustrating the comparison of grid connection point voltage effects of the three schemes provided in the embodiments of the present invention.

[0047] Figure 8(d) is a schematic diagram illustrating the comparison of active and reactive power output of the three schemes provided in the embodiments of the present invention.

[0048] Figure 8(e) is a schematic diagram illustrating the comparison of grid connection point current effects of the three schemes provided in the embodiments of the present invention.

[0049] Figure 8(f) is a schematic diagram illustrating the frequency comparison effect of the three schemes provided in the embodiment of the present invention.

[0050] Figure 9 This is a schematic diagram of the structure of a grid-type converter fault ride-through control device provided in an embodiment of the present invention.

[0051] Figure 10 This is a schematic diagram of the physical structure of an electronic device provided in an embodiment of the present invention. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Here, the illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other.

[0053] Figure 1 This is a flowchart illustrating a fault ride-through control method for a grid-type converter according to an embodiment of the present invention, as shown below. Figure 1 As shown, the fault ride-through control method for a grid-type converter provided in this embodiment of the invention is applied to the active power loop transfer function model of a grid-type converter with an added angular frequency PID compensator. One end of the angular frequency PID compensator is connected to the angular frequency deviation of the active power loop of the grid-type converter, and the other end is connected to a comparator node connected after the reciprocal of the rated angular frequency of the active power loop of the grid-type converter. The fault ride-through control method for the grid-type converter includes:

[0054] Step S1: If it is determined that the AC bus voltage amplitude is less than the reactive power loop output grid connection point voltage, then turn on the control switch to enable the angular frequency PID compensator.

[0055] Step S2: By sequentially adjusting the I coefficient, D coefficient, and P coefficient, the power deviation is corrected by increasing the electromagnetic active power, the generalized inertia coefficient is corrected, and the generalized damping coefficient is corrected, until the grid-type converter reaches fault ride-through, and the I coefficient, D coefficient, and P coefficient at this time are determined to be the target parameters of the angular frequency PID compensator.

[0056] Step S3: If it is determined that the amplitude of the AC bus voltage is greater than or equal to the voltage at the grid connection point of the reactive power loop output, then turn off the control switch to disable the angular frequency PID compensator.

[0057] In step S1 above, if the device determines that the AC bus voltage amplitude is less than the reactive power loop output grid connection point voltage, it turns on the control switch to activate the angular frequency PID compensator. The device can be a computer device executing this method. It should be noted that the data acquisition and analysis involved in this embodiment of the invention are authorized by the user.

[0058] In step S2 above, the device adjusts the I coefficient, D coefficient and P coefficient in sequence to correct the power deviation by increasing the electromagnetic active power, correct the generalized inertia coefficient and correct the generalized damping coefficient, until the grid-type converter reaches fault ride-through, and determines that the I coefficient, D coefficient and P coefficient at this time are the target parameters of the angular frequency PID compensator.

[0059] In step S3 above, if the device determines that the amplitude of the AC bus voltage is greater than or equal to the voltage at the grid connection point of the reactive power loop output, it turns off the control switch to disable the angular frequency PID compensator.

[0060] like Figure 2 As shown, the grid-connected converter system and control system model includes a power loop, voltage and current dual closed loops, and SPWM modulation. The grid-connected control unit is connected to the line with an impedance of [insert impedance here]. The amplitude of the AC bus voltage of the infinite power grid U g L f and C f For filter inductors and capacitors; U dc A constant DC voltage source; U pcc and I pcc Here are the voltage and current at PCC; θ pcc and θ g These are the grid connection point phase angle and the grid connection point voltage reference phase, respectively. VSI is the voltage source converter, and I... cf Z represents the current output by the converter, Grid represents the simulated power grid consisting of an infinite bus and line impedance, P and Q represent the active and reactive power outputs at the grid connection point, and Z represents the reactive power output by the converter. v This is a virtual impedance.

[0061] The power loop includes an active loop and a reactive loop. The active loop simulates the second-order rotor motion equation of a synchronous generator, and the reactive loop simulates the mathematical model of an excitation generator, specifically expressed as equation (1):

[0062]

[0063] Among them, J eq and D eq These are the generalized inertia coefficient and the generalized damping coefficient; δ, ω, ω0, and Δω are the power angle, angular frequency, rated angular frequency, and angular frequency deviation, respectively; P ref and P e It is the active power command value and electromagnetic active power; Q ref and Q e These are the reactive power command value and electromagnetic reactive power; E and U0 are the output voltage command value and rated value of the grid-type converter; k ev k is the reactive voltage correction factor. ei This is the reactive power integral coefficient.

[0064] To analyze the impact of the active power loop on transient frequency and power angle stability, equation (1) of the active power loop is transformed into equation (2), where the angular frequency deviation Δω = ω0 - ω and the power deviation ΔP = P ref -P e :

[0065]

[0066] Solving this differential equation yields:

[0067]

[0068] Integrating Δω, the work angle deviation Δδ is obtained as follows:

[0069]

[0070] Analysis of equations (3) and (4) shows that the magnitudes and trends of Δω and Δδ are related to ΔP and J. eq D eq The three parameters are directly or indirectly correlated, and ΔP = P ref -P e Change P ref P e J eq D eq Four parameters are sufficient to optimize Δω and Δδ, thereby improving the transient frequency and power angle stability of the grid-type converter. The effect of a single change in any of the four parameters on Δω and Δδ can be solved using the method of differentiating the single variable, such as... Figure 3 As shown, increasing D eq Decrease P ref Increase Pe and reduce J eq This can reduce Δδ, thereby improving transient power angle stability; increasing D eq Decrease P ref Increase P e and increase J eq This can reduce Δω, thereby improving transient frequency stability. eq There is a tendency for a contradiction between power angle stability and frequency stability, but under transient conditions, J eq Frequency stability should be given more emphasis, while power angle stability can be determined by ΔP and D. eq Increase. Therefore, increase D. eq Increase J eq and increase P e (Decrease P) ref This can improve the transient stability of grid-type converters. Therefore, by adding compensators, the above parameters can be improved, thereby enhancing the transient stability of grid-type converters and enabling fault ride-through.

[0071] For the active power loop parameters, simply increase the D of the active power loop during the transient process. eq J eq and P e This can improve transient stability. Based on equation (1), a transfer function model of the active power loop of a grid-type converter is constructed, such as... Figure 4 As shown.

[0072] Figure 4 ΔP ref For the small-signal form of the active power command value, ΔP e For small-signal active power, E0 is the output voltage amplitude of the grid-type converter, and U... g For AC bus voltage amplitude, X g Let K1 = E0U be the transmission impedance from the converter to the AC bus. g / X g , where K1 is the torque coefficient.

[0073] observe Figure 4 The rotor motion equations of equation (1) and the coefficients corresponding to the angular frequency deviation Δω, the integral of Δω, and the derivative of Δω in the active power loop are respectively D eq P e and J eq However, by controlling the angular frequency deviation Δω proportional-integral-differential compensator, it is possible to achieve a proportional K p Integral K i and differential K d The feedback is sent to the input in the form of [the parameter], thereby correcting the corresponding parameter D. eq P e and J eqBecause the effect of the proportional-integral-derivative compensator is similar to that of PID control, it is also called an angular frequency "PID" compensator. Figure 5 The derivation process of the active loop transfer function model of the grid-type converter with the added angular frequency "PID" compensator is as follows:

[0074]

[0075] Therefore, grid-type converters employing angular frequency "PID" compensators can increase the damping D of the active power loop. eq Inertia J eq and electromagnetic power P e This improves the stability of grid-type converters under transient operating conditions.

[0076] The method of the present invention has the following advantages:

[0077] 1. The designed compensator is structurally similar to traditional PID control. By adjusting the proportional, integral, and derivative parameters of the compensator, it can achieve an effect similar to traditional PID control. The structure is simple and the design is convenient.

[0078] 2. This compensator can simultaneously adjust the active loop inertia J. eq and damping D eq Parameters and electromagnetic power P e The three types of variables can optimize the active power loop parameters of the grid converter to the greatest extent to adapt to transient operating conditions, thereby improving the transient stability of the grid converter.

[0079] 3. Compared with other controls, the biggest feature of this control is that it adjusts through feedback. It can adaptively adjust the power angle to achieve fault ride-through control of the grid-type converter without knowing the parameters of the grid-type converter, thus avoiding the failure of fault ride-through control due to unknown parameters or parameter changes.

[0080] Specific implementations of the embodiments of the present invention include:

[0081] (1) Establish a traditional grid-connected converter system in Maltab / Simulink:

[0082] Modeling the grid-connected converter using the power loop (1), the active loop output grid connection point phase angle θ pcc =θ ref The reactive power loop output grid connection point voltage U pcc =U ref Vector synthesis V * abc =U ref ∠θ ref As the input for the voltage and current dual closed loop.

[0083] A dual closed-loop control based on the dq coordinate system for voltage and current is adopted, and compensation for load current feedforward and output voltage feedforward is added.

[0084] Solve for the grid connection point V abc The dq-axis components are derived from Park transform equation (6), where: V a V b V c V is the three-phase voltage at the grid connection point of the grid-connected converter. d V q Let θ be the direct-axis and quadrature-axis voltages. g V is the reference phase of the grid connection point voltage. m θ represents the peak voltage along the dq axis and θ represents the voltage phase at the grid connection point.

[0085]

[0086] Similarly, solve for the corresponding V dref and V qref From the derivation of park, equation (7) is obtained, where V* a V* b V* c The combined three-phase voltage output by the power loop:

[0087]

[0088] Depend on Figure 2 The structure of the three-phase inverter topology and the voltage and current on the filter inductor and capacitor are derived. According to KVL, the equations are written as shown in equation (8), where C f For filter capacitors, L f For filter inductor, U g For grid voltage, V L i is the filter inductor voltage, i0 is the converter output current, and i L For filter inductor current, R f The resistor added to the filter inductor:

[0089]

[0090] Using equation (7), the listed equation (8) is transformed by Park transformation, which transforms the voltage and current of the inductor and capacitor in the abc coordinate system into the d-axis and q-axis variables in the dq coordinate system.

[0091] The inductor voltage equation under the dq axis is given by equation (9), where i d and i q These are the current components transformed to the d-axis and q-axis, respectively, and V. gd and V gq U gVoltage components transformed to the d-axis and q-axis by Park transformation:

[0092]

[0093] The equation for the capacitor current along the dq axis is:

[0094]

[0095] Observing equations (9) and (10), it can be seen that voltage and current are coupled to each other on the dq axis. This coupling between the dq axis may affect the power control of the inverter when it is connected to the grid. Therefore, it is necessary to add compensation for load current feedforward and output voltage feedforward, that is, to eliminate the q-axis component on the d axis and the d-axis component on the q axis, and complete the decoupling. Both the voltage outer loop and the current inner loop adopt proportional-integral (PI) regulation, which can realize that the grid connection point voltage and current are controlled and responded to according to voltage commands and current commands.

[0096] The d-axis component i of the outer voltage loop output of the grid converter dref and q-axis component i qref Equation (11), where K up and K ui These are the proportional and integral coefficients of the voltage controller, V dref and V qref The voltage commands for the d-axis and q-axis are respectively obtained from equation (7):

[0097]

[0098] The d-axis component E of the output voltage modulation of the inner current loop of the grid converter. dref and q-axis component E qref Equation (12), where K ip and K ii These are the proportional and integral coefficients of the current controller:

[0099]

[0100] The voltage and current dual closed loop decoupling method described above achieves parameter decoupling of the dq axis.

[0101] (2) Additional virtual impedance control is designed to improve the static current quality of grid-type converters:

[0102] In designing virtual impedance, since virtual impedance introduces an equivalent virtual impedance in the inverter control loop, it enables the inverter to have characteristics similar to physical impedance during grid-connected operation, which can suppress harmonics and improve the static current quality of grid-connected converters. The virtual impedance control modeling expression is (13), where R v and L vThese are virtual resistance and virtual inductance, respectively:

[0103]

[0104] Integrating virtual impedance control into the control system of the grid-type converter, the voltage reference value is modified by adding virtual impedance terms to the d-axis V values ​​based on the original dq coordinate system voltage reference values. zd V along the q-axis zd Compensate V respectively dref and V qref Compensated V* dref and V* qref For equation (14):

[0105]

[0106] After designing (1) and (2), the relevant parameters for the design simulation are shown in Table 1:

[0107] Table 1

[0108]

[0109] (3) Design an angular frequency "PID" compensator module:

[0110] like Figure 6 As shown, it can be put into operation instantly during a fault and removed after the fault is recovered. The frequency deviation Δω of the active power loop of the grid-type converter is extracted and expressed as a compensator via proportional K. p Integral K i and differential K d The coefficients are fed back to the input side P. ref To achieve damping D under transient operating conditions of the active power loop eq Power P ref and inertia J eq The correction. The design order is to design K first. i Coefficients, then design K d coefficients, and finally design K p Coefficient. That is, first construct the work angle equilibrium point, since K i Increasing the equivalent electromagnetic power P e The size of ΔP, K is used to correct ΔP, K i The larger the value of P, the better. e The faster the change, the faster the equilibrium point is established, but an excessively large K... i The value will cause the small signal to become unstable at the final power corner point, therefore K i It should not be too large; secondly, the design of K... d Increasing the equivalent is to increase the inertia J eq When J eqIncreasing K will weaken the power angle stability to some extent, but improve the frequency stability. d The value of K should not be too large, otherwise it will lead to overshoot of the power angle and large disturbance instability. d The value should be relatively small. Then, the design increases Kp, which is equivalent to increasing the damping D. eq When damping D eq Increase the power angle until it achieves zero overshoot, therefore K p The value should be relatively large. Finally, the three parameters of the angular frequency "PID" compensator are designed because of the large value of K. p Smaller K d And the maximum K i Select parameter K of the angular frequency "PID" compensator for simulation operation. p K i and K d The coefficients are 80, 3000, and 3 respectively.

[0111] like Figure 7 The figure shows a grid-connected converter system with an additional angular frequency "PID" compensator.

[0112] Model all the above modules in maltab / Simulink, run the simulation for 6 seconds, take the grid fault drop depth as 0.1 pu, and verify the effect of the angular frequency "PID" compensator after it is put into operation and the control of the traditional grid-type converter.

[0113] As shown in Figure 8(a), it can be seen that the conventional VSG control cannot achieve power angle stability during a fault without the addition of fault ride-through control, and the power angle will become unstable and oscillate. The existing solution achieves a certain degree of power angle stability through power command switching control, but since power command switching cannot always make ΔP zero, there will always be a slight change in the power angle. The "PID" compensator proposed in this invention achieves dynamic pursuit of the power angle balance point through feedback, so that ΔP is always zero during the fault, thereby clamping the power angle during the fault and improving the power angle stability of the grid-type converter during the fault.

[0114] As shown in Figure 8(b), it can be seen that the conventional VSG control without fault ride-through control cannot eliminate angular velocity during the fault, which results in it constantly acting on the power angle, causing the grid-type converter to become transiently unstable during the fault. Existing solutions eliminate angular velocity to a great extent, but there is a certain deviation, which will cause the power angle to change during the fault. The "PID" compensator proposed in this invention realizes the rapid clearing of angular velocity to zero at the moment of the fault through feedback.

[0115] As shown in Figure 8(c), it can be seen that without the addition of fault ride-through control, the grid connection point voltage oscillates with the instability of the power angle in the conventional VSG control. The existing scheme achieves grid connection point voltage stability by improving the power angle stability to a certain extent. However, due to the accumulation of a certain power angle offset during the fault, there is a voltage surge at the moment of fault recovery. The "PID" compensator achieves rapid power angle stabilization and suppresses the voltage surge at the moment of fault recovery, thus achieving voltage smoothing.

[0116] As shown in Figure 8(d), it can be seen that without fault ride-through control, the output active and reactive power of the conventional VSG control oscillate with the instability of the power angle, and a large power surge will be generated at the moment of fault recovery, which can easily damage the devices of the grid-type converter. The existing solution has achieved the transmission of active and reactive power during the fault due to the improved power angle stability to a certain extent, but there will also be a certain power surge at the moment of fault recovery. The "PID" compensator achieves rapid power angle stabilization and can achieve smooth output of active and reactive power during both the fault period and the moment of fault recovery, thus achieving power smoothing.

[0117] As shown in Figure 8(e), it can be seen that without fault ride-through control, the output current of the conventional VSG control oscillates with the instability of the power angle, and a large fault current surge is generated at both the moment of fault and the moment of fault recovery, which can easily damage the devices of the grid-type converter. The existing solution has achieved a stable output current during the fault by improving the transient power angle stability to a certain extent, but it is obviously insufficient to suppress the current surge during the moment of fault and the moment of fault recovery. The "PID" compensator achieves rapid power angle stabilization and can achieve smooth current output during both the fault and the moment of fault recovery, thus achieving the effect of suppressing surge current and limiting short-circuit current.

[0118] As shown in Figure 8(f), it can be seen that if the VSG conventional control is not accompanied by fault ride-through control, the frequency will be transiently unstable and cannot meet the grid connection requirements. The existing solution improves the transient frequency stability to a certain extent, but there is still a certain degree of frequency deviation and small oscillation at the moment of fault and the moment of fault recovery. The "PID" compensator improves the transient frequency stability of the grid-type converter and greatly suppresses the frequency disturbance during the fault.

[0119] In summary, the angular frequency "PID" compensator proposed in this invention achieves superior fault ride-through performance in terms of power angle, angular velocity, grid connection point voltage (RMS), active power, reactive power, grid connection point current (RMS), and grid connection point frequency during both fault periods and fault recovery periods compared to conventional VSG control and existing technical solutions.

[0120] The fault ride-through control method for grid-type converters provided in this invention has the following beneficial technical effects:

[0121] The grid-type converter control using an angular frequency "PID" compensator effectively solves the problem of converter fault ride-through failure under deep faults, improves the transient stability of the grid-type converter, and has certain advantages in six indicators: power angle, angular velocity, grid connection point voltage (RMS), active power, reactive power, grid connection point current (RMS), and grid connection point frequency. Most importantly, the parameter design of the "PID" compensator is simpler and more efficient than the current fault ride-through control parameter design for grid-type converters, making it suitable for engineering applications and engineer parameter tuning.

[0122] The fault ride-through control method for grid-type converters provided in this invention involves the following steps: If the AC bus voltage amplitude is determined to be less than the reactive power loop output grid connection point voltage, a control switch is activated to enable the angular frequency PID compensator. By sequentially adjusting the I, D, and P coefficients, the power deviation is corrected by increasing the electromagnetic active power, the generalized inertia coefficient is corrected, and the generalized damping coefficient is corrected until the grid-type converter achieves fault ride-through. The I, D, and P coefficients at this point are determined to be the target parameters of the angular frequency PID compensator. If the AC bus voltage amplitude is determined to be greater than or equal to the reactive power loop output grid connection point voltage, the control switch is deactivated to disable the angular frequency PID compensator. The active power loop is modified, and the additional control fed back to the input by the angular frequency deviation PID module enables fault ride-through in most cases for the grid-type converter. This method has wider engineering applicability, improves the transient stability of the grid-type converter, and achieves fault ride-through for the grid-type converter.

[0123] Furthermore, the step of sequentially adjusting the I coefficient, D coefficient, and P coefficient to correct the power deviation by increasing the electromagnetic active power, correcting the generalized inertia coefficient, and correcting the generalized damping coefficient, until the grid-type converter achieves fault ride-through, includes:

[0124] Increase the I coefficient until the power angle reaches the pre-built power angle balance point, then start adjusting the D coefficient. Refer to the relevant instructions in "(3) Design of the Angular Frequency "PID" Compensator Module" above, which will not be repeated here.

[0125] Furthermore, the fault ride-through control method for the grid-type converter also includes:

[0126] During the adjustment of the D coefficient, the power angle stability index is monitored. If the power angle stability index is found to be abnormal, the adjustment of the D coefficient is terminated, and the adjustment of the P coefficient is started. Refer to the relevant instructions in "(3) Design of Angular Frequency "PID" Compensator Module" above, which will not be repeated here.

[0127] Furthermore, the fault ride-through control method for the grid-type converter also includes:

[0128] During the process of increasing the P coefficient, monitor the power angle overshoot index until the power angle overshoot is less than the preset power angle overshoot range, and determine the target parameter. Refer to the relevant instructions in "(3) Design of Angular Frequency "PID" Compensator Module" above, which will not be repeated here.

[0129] Furthermore, prior to adding the angular frequency PID compensator, the grid-type converter fault ride-through control method further includes:

[0130] Based on the pre-built determination result of whether the fault drop of the grid-type converter has been overcome, corresponding steps are executed to initiate the addition of the angular frequency PID compensator to the active power loop transfer function model of the original grid-type converter. Refer to the above. Figure 6 The relevant explanations will not be repeated here.

[0131] Further, the step of executing corresponding steps based on the pre-constructed determination result of whether the fault drop of the grid-type converter has been overcome, to initiate the attachment of the angular frequency PID compensator to the active power loop transfer function model of the original grid-type converter, includes:

[0132] If a fault sag is determined to have crossed over in the grid-type converter, the fault sag level is increased until instability occurs, and the angular frequency PID compensator is added to the original active power loop transfer function model of the grid-type converter. Refer to the above. Figure 6 The relevant explanations will not be repeated here.

[0133] Further, the step of executing corresponding steps based on the pre-constructed determination result of whether the fault drop of the grid-type converter has been overcome, to initiate the attachment of the angular frequency PID compensator to the active power loop transfer function model of the original grid-type converter, includes:

[0134] If it is determined that the fault drop in the grid-type converter has not occurred, then the angular frequency PID compensator is directly added to the active power loop transfer function model of the original grid-type converter. Refer to the above. Figure 6 The relevant explanations will not be repeated here.

[0135] Figure 9 This is a schematic diagram of the fault ride-through control device for a grid-type converter provided in an embodiment of the present invention, as shown below. Figure 9 As shown in the embodiment of the present invention, the fault ride-through control device for a grid-type converter is applied to the active power loop transfer function model of a grid-type converter with an added angular frequency PID compensator. One end of the angular frequency PID compensator is connected to the angular frequency deviation of the active power loop of the grid-type converter, and the other end is connected to a comparator node connected after the reciprocal of the rated angular frequency of the active power loop of the grid-type converter. The fault ride-through control device for the grid-type converter includes:

[0136] The activation unit 901 is used to activate the control switch to enable the angular frequency PID compensator if it is determined that the AC bus voltage amplitude is less than the reactive power loop output grid connection point voltage. The adjustment unit 902 is used to adjust the I coefficient, D coefficient, and P coefficient sequentially to correct the power deviation by increasing the electromagnetic active power, correct the generalized inertia coefficient, and correct the generalized damping coefficient, until the grid-type converter reaches fault ride-through, and to determine that the I coefficient, D coefficient, and P coefficient at this time are the target parameters of the angular frequency PID compensator. The deactivation unit 903 is used to deactivate the control switch to disable the angular frequency PID compensator if it is determined that the AC bus voltage amplitude is greater than or equal to the reactive power loop output grid connection point voltage.

[0137] Specifically, the activation unit 901 in the device is used to activate the control switch to enable the angular frequency PID compensator if it is determined that the AC bus voltage amplitude is less than the reactive power loop output grid connection point voltage; the adjustment unit 902 is used to adjust the I coefficient, D coefficient, and P coefficient sequentially to correct the power deviation by increasing the electromagnetic active power, correct the generalized inertia coefficient, and correct the generalized damping coefficient, until the grid-type converter reaches fault ride-through, and to determine that the I coefficient, D coefficient, and P coefficient at this time are the target parameters of the angular frequency PID compensator; the deactivation unit 903 is used to deactivate the control switch to disable the angular frequency PID compensator if it is determined that the AC bus voltage amplitude is greater than or equal to the reactive power loop output grid connection point voltage.

[0138] The fault ride-through control device for a grid-type converter provided in this embodiment of the invention, if it is determined that the AC bus voltage amplitude is less than the reactive power loop output grid connection point voltage, then the control switch is turned on to enable the angular frequency PID compensator. By sequentially adjusting the I coefficient, D coefficient, and P coefficient, the power deviation is corrected by increasing the electromagnetic active power, the generalized inertia coefficient is corrected, and the generalized damping coefficient is corrected, until the grid-type converter achieves fault ride-through. The I coefficient, D coefficient, and P coefficient at this time are determined to be the target parameters of the angular frequency PID compensator. If it is determined that the AC bus voltage amplitude is greater than or equal to the reactive power loop output grid connection point voltage, then the control switch is turned off to disable the angular frequency PID compensator, and the active power loop is modified. The additional control fed back to the input by the angular frequency deviation PID module realizes fault ride-through of the grid-type converter in most cases, has wider engineering applicability, improves the transient stability of the grid-type converter, and realizes fault ride-through of the grid-type converter.

[0139] The embodiments of the present invention provide a fault ride-through control device for grid-type converters, which can be used to execute the processing flow of the above-described method embodiments. Its functions will not be repeated here, but can be referred to the detailed description of the above-described method embodiments.

[0140] Figure 10 This is a schematic diagram of the physical structure of an electronic device provided in an embodiment of the present invention, such as... Figure 10 As shown, the electronic device includes: a processor 1001, a memory 1002, and a bus 1003;

[0141] The processor 1001 and the memory 1002 communicate with each other via the bus 1003.

[0142] The processor 1001 is used to call program instructions in the memory 1002 to execute the methods provided in the above-described method embodiments, including, for example:

[0143] If it is determined that the AC bus voltage amplitude is less than the reactive power loop output grid connection point voltage, then the control switch is turned on to enable the angular frequency PID compensator.

[0144] By sequentially adjusting the I coefficient, D coefficient, and P coefficient, the power deviation, generalized inertia coefficient, and generalized damping coefficient are corrected by increasing the electromagnetic active power, respectively, until the grid-type converter reaches fault ride-through, and the I coefficient, D coefficient, and P coefficient at this time are determined to be the target parameters of the angular frequency PID compensator.

[0145] If it is determined that the amplitude of the AC bus voltage is greater than or equal to the voltage at the grid connection point of the reactive power loop output, then the control switch is turned off to disable the angular frequency PID compensator.

[0146] This embodiment discloses a computer program product, which includes a computer program stored on a non-transitory computer-readable storage medium. The computer program includes program instructions, and when the program instructions are executed by a computer, the computer can perform the methods provided in the above-described method embodiments, such as:

[0147] If it is determined that the AC bus voltage amplitude is less than the reactive power loop output grid connection point voltage, then the control switch is turned on to enable the angular frequency PID compensator.

[0148] By sequentially adjusting the I coefficient, D coefficient, and P coefficient, the power deviation, generalized inertia coefficient, and generalized damping coefficient are corrected by increasing the electromagnetic active power, respectively, until the grid-type converter reaches fault ride-through, and the I coefficient, D coefficient, and P coefficient at this time are determined to be the target parameters of the angular frequency PID compensator.

[0149] If it is determined that the amplitude of the AC bus voltage is greater than or equal to the voltage at the grid connection point of the reactive power loop output, then the control switch is turned off to disable the angular frequency PID compensator.

[0150] This embodiment provides a computer-readable storage medium storing a computer program that causes the computer to execute the methods provided in the above-described method embodiments, including, for example:

[0151] If it is determined that the AC bus voltage amplitude is less than the reactive power loop output grid connection point voltage, then the control switch is turned on to enable the angular frequency PID compensator.

[0152] By sequentially adjusting the I coefficient, D coefficient, and P coefficient, the power deviation, generalized inertia coefficient, and generalized damping coefficient are corrected by increasing the electromagnetic active power, respectively, until the grid-type converter reaches fault ride-through, and the I coefficient, D coefficient, and P coefficient at this time are determined to be the target parameters of the angular frequency PID compensator.

[0153] If it is determined that the amplitude of the AC bus voltage is greater than or equal to the voltage at the grid connection point of the reactive power loop output, then the control switch is turned off to disable the angular frequency PID compensator.

[0154] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0155] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0156] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1The function specified in one or more boxes.

[0157] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0158] In the description of this specification, the references to terms such as "an embodiment," "a specific embodiment," "some embodiments," "for example," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0159] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A fault ride-through control method for a grid-type converter, characterized in that, The fault ride-through control method for the grid-type converter is applied to the active power loop transfer function model of a grid-type converter equipped with an angular frequency PID compensator. One end of the angular frequency PID compensator is connected to the angular frequency deviation of the active power loop of the grid-type converter, and the other end is connected to a comparator node connected to the reciprocal of the rated angular frequency of the active power loop of the grid-type converter. The fault ride-through control method for the grid-type converter includes: If it is determined that the AC bus voltage amplitude is less than the reactive power loop output grid connection point voltage, then the control switch is turned on to enable the angular frequency PID compensator. By sequentially adjusting the I coefficient, D coefficient, and P coefficient, the power deviation, generalized inertia coefficient, and generalized damping coefficient are corrected by increasing the electromagnetic active power, respectively, until the grid-type converter reaches fault ride-through, and the I coefficient, D coefficient, and P coefficient at this time are determined to be the target parameters of the angular frequency PID compensator. If it is determined that the amplitude of the AC bus voltage is greater than or equal to the voltage at the grid connection point of the reactive power loop output, then the control switch is turned off to disable the angular frequency PID compensator. The process involves sequentially adjusting the I, D, and P coefficients to correct power deviations by increasing electromagnetic active power, as well as correcting the generalized inertia coefficient and the generalized damping coefficient, until the grid-type converter achieves fault ride-through. This includes: Increase the I coefficient until the power angle reaches the pre-built power angle balance point, then start adjusting the D coefficient.

2. The fault ride-through control method for grid-type converters according to claim 1, characterized in that, The fault ride-through control method for grid-type converters also includes: During the adjustment of the D coefficient, the power angle stability index is monitored. If it is determined that the power angle stability index is abnormal, the adjustment of the D coefficient is terminated, and the adjustment of the P coefficient is started.

3. The fault ride-through control method for grid-type converters according to claim 2, characterized in that, The fault ride-through control method for grid-type converters also includes: During the process of increasing the P coefficient, the power angle overshoot index is monitored until the power angle overshoot is less than the preset power angle overshoot range, and the target parameter is determined.

4. The fault ride-through control method for a grid-type converter according to any one of claims 1 to 3, characterized in that, Before adding the angular frequency PID compensator, the grid-type converter fault ride-through control method further includes: Based on the pre-built determination result of whether the fault drop of the grid-type converter has been crossed, the corresponding steps are executed to start attaching the angular frequency PID compensator to the active power loop transfer function model of the original grid-type converter.

5. The fault ride-through control method for a grid-type converter according to claim 4, characterized in that, The step of executing corresponding steps based on the pre-built judgment result of whether the fault drop of the grid-type converter has been overcome, to initiate the attachment of the angular frequency PID compensator to the active power loop transfer function model of the original grid-type converter, includes: If it is determined that the fault drop of the grid-type converter has crossed, the fault drop level is increased until instability occurs, and the angular frequency PID compensator is added to the active power loop transfer function model of the original grid-type converter.

6. The fault ride-through control method for a grid-type converter according to claim 4, characterized in that, The step of executing corresponding steps based on the pre-built judgment result of whether the fault drop of the grid-type converter has been overcome, to initiate the attachment of the angular frequency PID compensator to the active power loop transfer function model of the original grid-type converter, includes: If it is determined that the fault drop of the grid-type converter has not occurred, then the angular frequency PID compensator is directly added to the active power loop transfer function model of the original grid-type converter.

7. A fault ride-through control device for a grid-type converter, characterized in that, The fault ride-through control device for the grid-type converter is applied to the active power loop transfer function model of a grid-type converter equipped with an angular frequency PID compensator. One end of the angular frequency PID compensator is connected to the angular frequency deviation of the active power loop of the grid-type converter, and the other end is connected to a comparator node connected to the reciprocal of the rated angular frequency of the active power loop of the grid-type converter. The fault ride-through control device for the grid-type converter includes: The activation unit is used to activate the control switch if it is determined that the AC bus voltage amplitude is less than the reactive power loop output grid connection point voltage, so that the angular frequency PID compensator takes effect. The adjustment unit is used to adjust the I coefficient, D coefficient and P coefficient in sequence to correct the power deviation by increasing the electromagnetic active power, correct the generalized inertia coefficient and correct the generalized damping coefficient, until the grid-type converter reaches fault ride-through, and to determine the I coefficient, D coefficient and P coefficient at this time as the target parameters of the angular frequency PID compensator. The shutdown unit is used to shut down the control switch if it is determined that the amplitude of the AC bus voltage is greater than or equal to the voltage of the reactive power loop output grid connection point, so as to disable the angular frequency PID compensator. The adjustment unit is specifically used for: Increase the I coefficient until the power angle reaches the pre-built power angle balance point, then start adjusting the D coefficient.

8. An electronic device 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 method according to any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 6.

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