Fault ride-through control method and device for network construction type converter

Abstract

The invention provides a fault ride-through control method and device for a network construction type converter, and relates to the technical field of control. The method comprises the steps that if it is determined that the voltage amplitude of an alternating-current bus is smaller than the output grid-connected point voltage of a reactive loop, a control switch is turned on; the I coefficient, the D coefficient and the P coefficient are sequentially adjusted, the power deviation, the generalized inertia coefficient and the generalized damping coefficient are corrected by improving the electromagnetic active power until the grid-forming converter reaches fault ride-through, and the I coefficient, the D coefficient and the P coefficient at the moment are determined to be target parameters of the angular frequency PID compensator; and if it is determined that the AC bus voltage amplitude is greater than or equal to the reactive loop output grid-connected point voltage, the control switch is turned off. The device executes the method. According to the method and the device provided by the embodiment of the invention, the transient stability of the network-forming converter can be improved.

Description

Technical Field

[0001] The present invention relates to the field of control technology, and in particular to a fault ride-through control method and device for a grid-connected converter. Background Art

[0002] With the continuous increase in the penetration rate of high-proportion renewable energy and its supporting converters, the access of renewable energy converters to the power system has caused certain harm to the safe and stable operation of the power grid, which is specifically manifested in the situation that the power grid presents low inertia and underdamped operating characteristics, which has caused new challenges such as broadband oscillation, small disturbance and large disturbance instability. At present, converter control is mainly divided into grid-following converter and grid-building converter. Among them, the converter with grid-building control structure simulates the external characteristics of synchronous machine, provides "strong" damping and "high" inertia for the system, and can act as a "voltage source" to actively support the power grid. It is an excellent control that adapts to the current power system structure. However, the grid-building converter has the problem of transient instability when a large disturbance fault occurs in the power grid. Therefore, it is particularly important to design the fault ride-through control of the grid-building converter. Considering that the current design method of fault ride-through control of the grid-building converter includes a series of combined methods such as power and voltage command switching, active loop parameter switching, and virtual impedance control design, there will be some problems as follows. First, the control is more complicated, which is mainly reflected in the need for precise design processes of various control parameters; second, with the long-term operation of the converter, the converter components will age, and the various electrical parameters, mechanical parameters and control parameters of the converter will change slightly, and the converter may fail to ride through faults under parameter changes; third, converters of different grid types exist in a common power system, and their respective fault ride-through controls are different. Under fault ride-through control, protecting equipment safety is the top priority, 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 totally unacceptable. Summary of the invention

[0003] In view of the problems in the prior art, an embodiment of the present invention provides a method and device for controlling fault ride-through of a grid-connected converter, which can at least partially solve the problems in the prior art.

[0004] On the one hand, the present invention proposes a fault ride-through control method for a grid-type converter, the fault ride-through control method for a grid-type converter is applied to an active loop transfer function model of a grid-type converter with an angular frequency PID compensator attached thereto, one end of the angular frequency PID compensator is connected to the angular frequency deviation of the active loop of the grid-type converter, and the other end is connected to a comparison node connected to the inverse of the rated angular frequency of the active loop of the grid-type converter, the fault ride-through control method for the grid-type converter comprises:

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

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

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

[0008] The method of sequentially adjusting the I coefficient, the D coefficient and the P coefficient to respectively 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 includes:

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

[0010] Wherein, the grid-type converter fault ride-through control method further includes:

[0011] In the process of increasing 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] Wherein, the grid-type converter fault ride-through control method further includes:

[0013] In the process of increasing the P coefficient, the power angle overshoot indicator is monitored until the power angle overshoot is less than a preset power angle overshoot interval, and the target parameter is determined.

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

[0015] Corresponding steps are executed according to the pre-constructed determination result of whether the fault drop of the grid-type converter is crossed, so as to start adding the angular frequency PID compensator to the active loop transfer function model of the original grid-type converter.

[0016] The method of executing corresponding steps according to the pre-constructed determination result of whether the fault drop of the grid-type converter is crossed to start adding the angular frequency PID compensator to the active 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 occurs through, the fault drop level is increased until instability occurs, and the angular frequency PID compensator is added to the active loop transfer function model of the original grid-type converter.

[0018] The method of executing corresponding steps according to the pre-constructed determination result of whether the fault drop of the grid-type converter is crossed to start adding the angular frequency PID compensator to the active 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 does not occur through-going, the angular frequency PID compensator is directly started to be added to the active loop transfer function model of the original grid-type converter.

[0020] On the one hand, the present invention proposes a grid-type converter fault ride-through control device, the grid-type converter fault ride-through control device is applied to an active loop transfer function model of a grid-type converter with an angular frequency PID compensator attached, one end of the angular frequency PID compensator is connected to the angular frequency deviation of the active loop of the grid-type converter, and the other end is connected to a comparison node connected to the inverse of the rated angular frequency of the active loop of the grid-type converter, the grid-type converter fault ride-through control device comprises:

[0021] An opening unit, used for opening the control switch to make the angular frequency PID compensator effective if it is determined that the AC bus voltage amplitude is less than the reactive loop output grid connection point voltage;

[0022] an adjusting unit, for adjusting the I coefficient, the D coefficient and the P coefficient in sequence, so as to respectively 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 the fault ride-through, and determining that the I coefficient, the D coefficient and the P coefficient at this time are the target parameters of the angular frequency PID compensator respectively;

[0023] The closing unit is used to close 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 ring output grid connection point voltage.

[0024] In another aspect, an embodiment of the present invention provides 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 calls the program instructions to execute the following method:

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

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

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

[0030] An embodiment of the present invention provides a non-transitory computer-readable storage medium, including:

[0031] The non-transitory computer-readable storage medium stores computer instructions, which cause the computer to execute the following method:

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

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

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

[0035] The embodiment of the present invention provides a fault ride-through control method and device for a grid-type converter. If it is determined that the AC bus voltage amplitude is less than the reactive loop output grid-connected point voltage, the control switch is turned on to make the angular frequency PID compensator effective; by adjusting the I coefficient, D coefficient and P coefficient in sequence, the power deviation is corrected by increasing the electromagnetic active power, the generalized inertia coefficient is corrected and the generalized damping coefficient is corrected, 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 respectively; if it is determined that the AC bus voltage amplitude is greater than or equal to the reactive loop output grid-connected point voltage, the control switch is turned off to make the angular frequency PID compensator invalid, the active loop is modified, and the fault ride-through of the grid-type converter in most cases is achieved through additional control of the angular frequency deviation PID module fed back to the input. The method and device have wider engineering applicability, improve the transient stability of the grid-type converter, and achieve fault ride-through of the grid-type converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0037] Figure 1 It is a flow chart of a fault ride-through control method for a grid-connected converter provided in one embodiment of the present invention.

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

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

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

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

[0042] Figure 6 It is a flow chart of a fault ride-through control method for a grid-connected converter provided in another embodiment of the present invention.

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

[0044] FIG8( a ) is a schematic diagram illustrating the comparative effects of power angles of three schemes provided in an embodiment of the present invention.

[0045] FIG8( b ) is a schematic diagram illustrating the angular velocity comparison effects of three solutions provided in an embodiment of the present invention.

[0046] FIG8( c ) is a schematic diagram illustrating the comparison of grid connection point voltages of three schemes provided in an embodiment of the present invention.

[0047] FIG8( d ) is a schematic diagram illustrating the comparison of active power and reactive power output effects of three solutions provided in an embodiment of the present invention.

[0048] FIG8( e ) is a schematic diagram illustrating the comparison of grid-connected point currents of three schemes provided in an embodiment of the present invention.

[0049] FIG8( f ) is a schematic diagram illustrating the frequency comparison effects of three schemes provided in an embodiment of the present invention.

[0050] Fig. 9 It is a structural schematic diagram of a grid-type converter fault ride-through control device provided in one embodiment of the present invention.

[0051] Fig.10 A schematic diagram of the physical structure of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention more clear, the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention. It should be noted that, in the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other arbitrarily.

[0053] Figure 1 FIG. 1 is a flow chart of a fault ride-through control method for a grid-connected converter provided in an embodiment of the present invention. Figure 1 As shown, the grid-type converter fault ride-through control method provided by the embodiment of the present invention is applied to the active loop transfer function model of the grid-type converter with an angular frequency PID compensator attached, one end of the angular frequency PID compensator is connected to the angular frequency deviation of the active loop of the grid-type converter, and the other end is connected to the comparison node connected after the inverse of the rated angular frequency of the active loop of the grid-type converter. The grid-type converter fault ride-through control method includes:

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

[0055] Step S2: by adjusting the I coefficient, D coefficient and P coefficient in sequence, 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 AC bus voltage amplitude is greater than or equal to the reactive loop output grid connection point voltage, the control switch is closed to disable the angular frequency PID compensator.

[0057] In the above step S1, if the device determines that the AC bus voltage amplitude is less than the reactive ring output grid connection point voltage, the control switch is turned on to make the angular frequency PID compensator effective. The device can be a computer device that executes the method. It should be noted that the acquisition and analysis of data involved in the embodiments of the present invention are authorized by the user.

[0058] In the above step S2, 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 the above step S3, if the device determines that the AC bus voltage amplitude is greater than or equal to the reactive loop output grid connection point voltage, the control switch is closed to disable the angular frequency PID compensator.

[0060] like Figure 2 As shown in Figure 1, the grid-connected system and control system model of the grid-connected converter includes a power loop, a voltage and current double closed loop, and SPWM modulation. The grid-connected control unit is connected to the grid point PCC through a line impedance of The infinite power grid AC bus voltage amplitude U g ; L f and C f is the filter inductor and capacitor; U dc is a constant DC voltage source; U pcc and I pcc is the voltage and current at PCC; θ pcc and θ g are the grid-connected point phase angle and the grid-connected point voltage reference phase, respectively. VSI is the voltage source converter, I cf is the current output by the converter, Grid is a simulated power grid composed of infinite busbar and line impedance, P and Q are the active power and reactive power output by the grid connection point, and Z v is the 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 the synchronous generator, and the reactive loop simulates the mathematical model of the excitation generator, which is specifically expressed as formula (1):

[0062]

[0063] Among them, J eq and D eq 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 is the active power command value and electromagnetic active power; Q ref and Q e is the reactive power command value and electromagnetic reactive power; E and U0 are the grid-type converter output voltage command value and rated value; k ev is the reactive voltage correction coefficient; k ei is the reactive power integral coefficient.

[0064] In order to analyze the influence of the active loop on the transient frequency and power angle stability, the active loop of formula (1) is transformed into formula (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 to obtain the power angle deviation Δδ is as follows:

[0069]

[0070] Analyzing equations (3) and (4), we can see that the size and change trend of Δω and Δδ are related to ΔP and J. eq , D eq There is a direct or indirect correlation between the three parameters, and ΔP = P ref -P e , change P ref , P e , J eq , D eq Four parameters can be used to optimize Δω and Δδ, thereby improving the transient frequency and power angle stability of the grid-connected converter. The influence of a single change of the four parameters on Δω and Δδ can be solved by using a single variable derivative method, such as Figure 3 As shown, increasing D eq , reduce P ref , increase Pe and reduce J eq , can reduce Δδ and thus improve the transient power angle stability; increase D eq , reduce P ref , increase P e and increase J eq , which can reduce Δω and thus improve transient frequency stability. eq There is a contradictory trend between power angle stability and frequency stability, but under transient conditions, J eq Frequency stability should be emphasized more, and power angle stability can be determined by ΔP and D eq Therefore, increasing D eq , increase J eq and increase P e (Reduce P ref ) can improve the transient stability of the grid-type converter. Therefore, the above parameters can be improved by adding a compensator, the transient stability of the grid-type converter can be improved, and the fault ride-through of the grid-type converter can be realized.

[0071] As for the active loop parameters, as long as the D of the active loop is increased during the transient process, eq , J eq and P e That is, transient stability can be improved. Based on formula (1), the active loop transfer function model of the grid-connected converter is constructed, as follows: Figure 4 shown.

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

[0073] observe Figure 4 The rotor motion equation of formula (1) has the coefficients corresponding to the angular frequency deviation Δω, Δω integral and Δω differential in the active loop, respectively: eq , P e and J eq , and by controlling the angular frequency deviation Δω, the proportional-integral-differential compensator can be used in proportion to K p , integral K i and differential K d The form of feedback to the input, thereby correcting the corresponding parameter D eq , P e and J eq, because the effect of the proportional-integral-differential compensator is similar to "PID control, it is also called the angular frequency deviation proportional-integral-differential compensator as the angular frequency "PID" compensator, such as Figure 5 The derivation process of the active loop transfer function model of the grid-type converter with the additional angular frequency "PID" compensator shown is as follows:

[0074]

[0075] Therefore, the grid-type converter using the angular frequency "PID" compensator can increase the damping D of the active loop. eq 、Inertia J eq and electromagnetic power P e , thereby improving the stability of the grid-connected converter under transient conditions.

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

[0077] 1. The designed compensator is similar to the traditional PID control in structure. It can achieve the effect similar to the traditional PID control by adjusting the proportional, integral and differential parameters of the compensator. It has a simple structure and is easy to design.

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

[0079] 3. Compared with other controls, the biggest feature of this control is that it is adjusted through feedback. It can adaptively adjust the power angle to achieve fault ride-through control of the grid-type converter based on unknown parameters of the grid-type converter, thus avoiding the failure of fault ride-through control caused by unknown parameters and parameter changes.

[0080] The specific implementation of the embodiment of the present invention includes:

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

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

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

[0084] Solve the grid connection point V abc The dq axis component of the quartz crystal is derived from equation (6) by park transformation, where: V a 、V b 、V c is the three-phase voltage of the grid-connected point of the grid-connected converter, V d 、V q are the direct-axis and quadrature-axis voltages, θ g is the grid-connected point voltage reference phase, V m is the dq axis voltage peak value, and θ is the grid-connected point voltage phase.

[0085]

[0086] Similarly, solve the corresponding V dref and V qref , derived from the park change formula (7), where V* a 、V* b 、V* c The synthetic three-phase voltage output by the power loop is:

[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, and the equation is written as equation (8) according to KVL, where C f is the filter capacitor, L f is the filter inductor, U g is the grid voltage, V L is the filter inductor voltage, i0 is the converter output current, i L is the filter inductor current, R f The resistance added to the filter inductor is:

[0089]

[0090] Using equation (7), Park transformation is performed on equation (8) to transform the voltage and current of the inductor and capacitor in the abc coordinate system into d-axis and q-axis variables in the dq coordinate system.

[0091] The inductor voltage equation under the dq axis is (9), where i d and i q They are the current components transformed to the d-axis and q-axis by park, V gd and V gq U gThe voltage components of the d-axis and q-axis after park transformation are:

[0092]

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

[0094]

[0095] From equations (9) and (10), we can see that the voltage and current are coupled on the dq axis. The coupling between the dq axis may affect the control of power when the inverter 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 to complete the decoupling. The voltage outer loop and the current inner loop both use proportional integral PI regulation, which can realize the control and response of the voltage and current at the grid connection point according to the voltage command and current command.

[0096] The d-axis component i of the voltage outer loop output of the grid-type converter dref and the q-axis component i qref is formula (11), where K up and K ui are the proportional coefficient and integral coefficient of the voltage controller, V dref and V qref are the d-axis voltage command and the q-axis voltage command respectively, and are obtained by formula (7):

[0097]

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

[0099]

[0100] The above decoupling form of voltage and current double closed loop realizes the parameter decoupling of dq axes.

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

[0102] In the design of virtual impedance, by introducing an equivalent virtual impedance in the inverter control loop, the virtual impedance makes the inverter have characteristics similar to physical impedance when connected to the grid, which can suppress harmonics and improve the static current quality of the grid-connected converter. The virtual impedance control modeling expression is (13), where R v and L vThey are virtual resistance and virtual inductance respectively:

[0103]

[0104] Put virtual impedance control into the control system of the grid-type converter, modify the voltage reference value, add the virtual impedance term V of the d-axis on the basis of the original dq coordinate system voltage reference value, and zd and V of the q axis zd , respectively compensate V dref and V qref , V* after compensation dref and V* qref Formula (14):

[0105]

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

[0107] Table 1

[0108]

[0109] (3) Design of angular frequency “PID” compensator module:

[0110] like Figure 6 As shown, it can be put into operation at the moment of fault and removed after fault recovery. The frequency deviation Δω of the active loop of the grid-type converter is proposed and used as a compensator through the ratio K p , integral K i and differential K d The coefficient is fed back to the input side P ref , to achieve the active loop transient damping D eq , power P ref and inertia J eq The design order is to design K first. i coefficient, then design K d coefficient, and finally design K p That is, first construct the power angle balance point, because K i Increasing the equivalent is to increase the electromagnetic power P e The size of ΔP is used to correct K i The larger the value of P e The faster the change, the faster the equilibrium point is built, but too large K i The value will cause the small signal instability at the final power corner, so K i Not too large; secondly, design K d Increasing is equivalent to increasing the inertia J eq , when J eqWhen it increases, it will weaken the power angle stability to a certain extent and improve the frequency stability, so K d The selection of K should not be too large, otherwise the power angle will be over-adjusted and the large disturbance will cause instability. d Should be smaller, then, the design Kp increase is equivalent to increasing the damping D eq , when the damping D eq Increase until the power angle can achieve no overshoot, so K p Finally, the three parameters of the design angular frequency "PID" compensator are due to the large K p , smaller K d and maximum K i , select the parameter K of the simulation running angular frequency "PID" compensator p , K i and K d The coefficients are 80, 3000, and 3 respectively.

[0111] like Figure 7 As shown, a grid-connected system of a grid-connected converter with an additional angular frequency "PID" compensator is shown.

[0112] All the above modules are modeled in Maltab / Simulink, and the simulation runs for 6 seconds. The grid fault drop depth is 0.1pu to verify the effect of the angular frequency "PID" compensator after it is put into use and compared with the traditional grid-connected converter control.

[0113] As shown in FIG8(a), it can be found that conventional VSG control cannot achieve power angle stability during a fault without additional fault ride-through control, and the power angle will become unstable and oscillate. The existing scheme achieves a certain degree of power angle stability through power command switching control, but the power command switching cannot always make ΔP zero, which leads to a certain slight change in the power angle. The "PID" compensator proposed in the method of the present invention achieves a dynamic pursuit of the power angle balance point through feedback, so that ΔP is always zero during a fault, thereby clamping the power angle during the fault, thereby improving the power angle stability of the grid-connected converter during a fault.

[0114] As shown in Figure 8(b), it can be found that conventional VSG control without additional fault ride-through control cannot eliminate the angular velocity during the fault period, which causes the power angle to act all the time, causing the grid-type converter to be transiently unstable during the fault period. The existing scheme eliminates the angular velocity to a great extent, but there is a certain deviation, which will cause the power angle to change during the fault period. The "PID" compensator proposed in the patent of this invention realizes the rapid zeroing of the angular velocity at the moment of the fault through feedback.

[0115] As shown in Figure 8(c), it can be found that if the conventional VSG control is not supplemented with fault ride-through control, the grid connection point voltage oscillates as the power angle becomes unstable. The existing scheme achieves grid connection point voltage stability due to improved power angle stability to a certain extent. However, due to the accumulation of a certain power angle offset during the fault period, there is a voltage shock at the moment of fault recovery. The "PID" compensator achieves rapid stabilization of the power angle, suppresses the voltage shock at the moment of fault recovery, and achieves voltage smoothing.

[0116] As shown in Figure 8(d), it can be found that if the conventional control of VSG is not supplemented with fault ride-through control, the output active power and reactive power will oscillate as the power angle becomes unstable, and a large power shock will be generated at the moment of fault recovery, which is easy to break down the components of the grid-connected converter; the existing scheme has achieved the transmission of active power and reactive power during the fault period due to the improvement of the power angle stability to a certain extent, but there will also be a certain degree of power shock at the moment of fault recovery, while the "PID" compensator realizes the rapid stabilization of the power angle, and can achieve smooth output of active power and reactive power both during the fault period and at the moment of fault recovery, thus achieving power smoothing.

[0117] As shown in Figure 8(e), it can be found that if the conventional control of VSG is not supplemented with fault ride-through control, the output current oscillates as the power angle becomes unstable, and a huge fault current shock will be generated at the moment of fault and the moment of fault recovery, which is easy to break down the components of the grid-type converter; the existing scheme improves the transient power angle stability to a certain extent, thereby achieving a stable current output during the fault, but it is obviously insufficient to suppress the current shock at the moment of fault and during the fault recovery period; the "PID" compensator realizes a rapid stabilization of the power angle, and can achieve smooth current output during the fault period and the moment of fault recovery, achieving the effect of suppressing the shock current and limiting the short-circuit current.

[0118] As shown in Figure 8(f), it can be found that if the conventional control of VSG is not supplemented with fault ride-through control, the frequency will be transiently unstable and cannot meet the grid connection requirements; the existing scheme has improved the transient frequency stability to a certain extent, but there is still a certain degree of frequency deviation and its tiny oscillation at the moment of fault and fault recovery, while the "PID" compensator improves the transient frequency stability of the grid-connected converter and greatly suppresses the frequency disturbance during the fault period.

[0119] In summary, the angular frequency "PID" compensator proposed by the method of the present invention can achieve superior fault ride-through in terms of power angle, angular velocity, grid-connected point voltage (effective value), active power, reactive power, grid-connected point current (effective value) and grid-connected point frequency during fault and fault recovery periods compared to conventional VSG control and prior art solutions.

[0120] The grid-connected converter fault ride-through control method provided by the embodiment of the present invention has the following beneficial technical effects:

[0121] The grid-type converter control using the angular frequency "PID" compensator effectively solves the problem of the converter fault being unable to ride through under deep faults, improves the transient stability of the grid-type converter, and has certain advantages in six indicators, including power angle, angular velocity, grid-connected point voltage (effective value), active power, reactive power, grid-connected point current (effective value) and grid-connected point frequency. The most important thing is that the parameter design of the "PID" compensator is more concise and efficient than the current grid-type converter fault ride-through control parameter design, and is suitable for engineering applications and engineer parameter adjustment.

[0122] The embodiment of the present invention provides a fault ride-through control method for a grid-type converter. If it is determined that the AC bus voltage amplitude is less than the reactive loop output grid-connected point voltage, the control switch is turned on to make the angular frequency PID compensator effective; by adjusting the I coefficient, D coefficient and P coefficient in sequence, the power deviation is corrected by increasing the electromagnetic active power, the generalized inertia coefficient is corrected and the generalized damping coefficient is corrected, 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 respectively; if it is determined that the AC bus voltage amplitude is greater than or equal to the reactive loop output grid-connected point voltage, the control switch is turned off to make the angular frequency PID compensator invalid, the active loop is modified, and the fault ride-through of the grid-type converter in most cases is achieved through additional control of the angular frequency deviation PID module fed back to the input. The method has wider engineering applicability, improves the transient stability of the grid-type converter, and achieves fault ride-through of the grid-type converter.

[0123] Furthermore, the I coefficient, the D coefficient and the P coefficient are adjusted in sequence to correct the power deviation by increasing the electromagnetic active power, correct the generalized inertia coefficient and correct the generalized damping coefficient, respectively, until the grid-type converter reaches fault ride-through, including:

[0124] The I coefficient is increased until the power angle reaches the pre-established power angle balance point, at which time the D coefficient is adjusted. Please refer to the relevant description of "(3) Designing the angular frequency "PID" compensator module" above, which will not be repeated here.

[0125] Furthermore, the grid-connected converter fault ride-through control method further includes:

[0126] In the process of increasing 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. Please refer to the relevant description of "(3) Design of angular frequency "PID" compensator module" above, which will not be repeated here.

[0127] Furthermore, the grid-connected converter fault ride-through control method further includes:

[0128] In 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 interval, and the target parameter is determined. Please refer to the relevant description of "(3) Designing the angular frequency "PID" compensator module" above, which will not be repeated here.

[0129] Furthermore, before the angular frequency PID compensator is added, the grid-type converter fault ride-through control method further includes:

[0130] According to the pre-built grid-type converter fault drop determination result, corresponding steps are executed to start adding the angular frequency PID compensator to the active loop transfer function model of the original grid-type converter. Figure 6 The relevant instructions will not be repeated here.

[0131] Further, the corresponding steps are executed according to the pre-constructed determination result of whether the fault drop of the grid-type converter is crossed, so as to start adding the angular frequency PID compensator to the active loop transfer function model of the original grid-type converter, including:

[0132] If it is determined that the fault drop of the grid-type converter has occurred, the fault drop level is increased until it becomes unstable, and the angular frequency PID compensator is added to the active loop transfer function model of the original grid-type converter. Figure 6 The relevant instructions will not be repeated here.

[0133] Further, the corresponding steps are executed according to the pre-constructed determination result of whether the fault drop of the grid-type converter is crossed, so as to start adding the angular frequency PID compensator to the active loop transfer function model of the original grid-type converter, including:

[0134] If it is determined that the grid-type converter fault drop does not occur through, the angular frequency PID compensator is directly started to be added to the active loop transfer function model of the original grid-type converter. Figure 6 The relevant instructions will not be repeated here.

[0135] Fig. 9 FIG. 1 is a schematic diagram of a structure of a grid-type converter fault ride-through control device provided by an embodiment of the present invention. Fig. 9 As shown, the grid-type converter fault ride-through control device provided by the embodiment of the present invention is applied to the active loop transfer function model of the grid-type converter with an angular frequency PID compensator attached, one end of the angular frequency PID compensator is connected to the angular frequency deviation of the active loop of the grid-type converter, and the other end is connected to the comparison node connected to the inverse of the rated angular frequency of the active loop of the grid-type converter. The grid-type converter fault ride-through control device includes:

[0136] The opening unit 901 is used to open the control switch if it is determined that the AC bus voltage amplitude is less than the reactive loop output grid-connected point voltage, so that the angular frequency PID compensator takes effect; the adjustment unit 902 is used to adjust the I coefficient, D coefficient and P coefficient in sequence to respectively realize the correction of power deviation by increasing electromagnetic active power, the correction of generalized inertia coefficient and the correction of generalized damping coefficient, until the grid-type converter reaches fault ride-through, and determine that the I coefficient, D coefficient and P coefficient at this time are the target parameters of the angular frequency PID compensator respectively; the closing unit 903 is used to close the control switch if it is determined that the AC bus voltage amplitude is greater than or equal to the reactive loop output grid-connected point voltage, so that the angular frequency PID compensator is invalid.

[0137] Specifically, the opening unit 901 in the device is used to open the control switch if it is determined that the AC bus voltage amplitude is less than the reactive loop output grid-connected point voltage, so that the angular frequency PID compensator takes effect; the adjustment unit 902 is used to adjust the I coefficient, D coefficient and P coefficient in sequence to respectively realize the correction of power deviation by increasing electromagnetic active power, the correction of generalized inertia coefficient and the correction of generalized damping coefficient, until the grid-type converter reaches fault ride-through, and determine that the I coefficient, D coefficient and P coefficient at this time are the target parameters of the angular frequency PID compensator respectively; the closing unit 903 is used to close the control switch if it is determined that the AC bus voltage amplitude is greater than or equal to the reactive loop output grid-connected point voltage, so as to disable the angular frequency PID compensator.

[0138] The grid-type converter fault ride-through control device provided by the embodiment of the present invention, if it is determined that the AC bus voltage amplitude is less than the reactive loop output grid-connected point voltage, then the control switch is turned on to make the angular frequency PID compensator effective; by adjusting the I coefficient, D coefficient and P coefficient in sequence, the power deviation is corrected by increasing the electromagnetic active power, the generalized inertia coefficient is corrected and the generalized damping coefficient is corrected, 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 respectively; if it is determined that the AC bus voltage amplitude is greater than or equal to the reactive loop output grid-connected point voltage, then the control switch is turned off to make the angular frequency PID compensator invalid, the active loop is modified, and the fault ride-through of the grid-type converter in most cases is realized through the additional control of the angular frequency deviation PID module fed back to the input, which has a wider range of engineering applicability, improves the transient stability of the grid-type converter, and realizes the fault ride-through of the grid-type converter.

[0139] The embodiments of the present invention provide an embodiment of a grid-type converter fault ride-through control device which can be specifically used to execute the processing flow of the above-mentioned method embodiments. Its functions are not repeated here and reference can be made to the detailed description of the above-mentioned method embodiments.

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

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

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

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

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

[0145] If it is determined that the AC bus voltage amplitude is greater than or equal to the reactive loop output grid connection point voltage, the control switch is closed 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. When the program instructions are executed by a computer, the computer can perform the methods provided by the above method embodiments, for example, including:

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

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

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

[0150] This embodiment provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, wherein the computer program enables the computer to execute the methods provided by the above method embodiments, for example, including:

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

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

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

[0154] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented 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] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0156] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1A function specified in one or more boxes.

[0157] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0158] In the description of this specification, the description with reference to the terms "one embodiment", "a specific embodiment", "some embodiments", "for example", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0159] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is 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 in the scope of protection of the present invention.

Claims

1. A grid-connected converter fault ride-through control method, characterized in that: The grid-type converter fault ride-through control method is applied to an active loop transfer function model of a grid-type converter with an angular frequency PID compensator attached thereto, wherein one end of the angular frequency PID compensator is connected to the angular frequency deviation of the active loop of the grid-type converter, and the other end is connected to a comparison node connected to the inverse of the rated angular frequency of the active loop of the grid-type converter. The grid-type converter fault ride-through control method comprises: If it is determined that the AC bus voltage amplitude is less than the reactive loop output grid connection point voltage, the control switch is turned on to enable the angular frequency PID compensator to take effect; By adjusting the I coefficient, the D coefficient and the P coefficient in sequence, the power deviation is corrected by increasing the electromagnetic active power, the generalized inertia coefficient is corrected and the generalized damping coefficient is corrected, respectively, until the grid-type converter reaches fault ride-through, and the I coefficient, the D coefficient and the P coefficient at this time are determined to be the target parameters of the angular frequency PID compensator respectively; If it is determined that the AC bus voltage amplitude is greater than or equal to the reactive loop output grid connection point voltage, the control switch is closed to disable the angular frequency PID compensator.

2. The grid-connected converter fault ride-through control method according to claim 1, characterized in that: The method of sequentially adjusting the I coefficient, the D coefficient and the P coefficient to respectively 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 includes: Increase the I coefficient until the power angle reaches the pre-established power angle balance point, then start adjusting the D coefficient.

3. The grid-connected converter fault ride-through control method according to claim 2, characterized in that: The grid-type converter fault ride-through control method further includes: In the process of increasing 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.

4. The grid-connected converter fault ride-through control method according to claim 3, characterized in that: The grid-type converter fault ride-through control method further includes: In the process of increasing the P coefficient, the power angle overshoot indicator is monitored until the power angle overshoot is less than a preset power angle overshoot interval, and the target parameter is determined.

5. The grid-connected converter fault ride-through control method according to any one of claims 1 to 4, characterized in that: Before adding the angular frequency PID compensator, the grid-type converter fault ride-through control method further includes: Corresponding steps are executed according to the pre-constructed determination result of whether the fault drop of the grid-type converter is crossed, so as to start adding the angular frequency PID compensator to the active loop transfer function model of the original grid-type converter.

6. The grid-connected converter fault ride-through control method according to claim 5, characterized in that: The corresponding steps are executed according to the pre-constructed determination result of whether the fault drop of the grid-type converter is crossed, so as to start adding the angular frequency PID compensator to the active loop transfer function model of the original grid-type converter, including: If it is determined that the fault drop of the grid-type converter occurs through, the fault drop level is increased until instability occurs, and the angular frequency PID compensator is added to the active loop transfer function model of the original grid-type converter.

7. The grid-connected converter fault ride-through control method according to claim 5, characterized in that: The corresponding steps are executed according to the pre-constructed determination result of whether the fault drop of the grid-type converter is crossed, so as to start adding the angular frequency PID compensator to the active loop transfer function model of the original grid-type converter, including: If it is determined that the fault drop of the grid-type converter does not occur through-going, the angular frequency PID compensator is directly started to be added to the active loop transfer function model of the original grid-type converter.

8. A grid-type converter fault ride-through control device, characterized in that: The grid-type converter fault ride-through control device is applied to the active loop transfer function model of the grid-type converter with an angular frequency PID compensator attached, one end of the angular frequency PID compensator is connected to the angular frequency deviation of the active loop of the grid-type converter, and the other end is connected to the comparison node connected to the inverse of the rated angular frequency of the active loop of the grid-type converter. The grid-type converter fault ride-through control device includes: An opening unit, for opening the control switch to make the angular frequency PID compensator effective if it is determined that the AC bus voltage amplitude is less than the reactive loop output grid connection point voltage; an adjusting unit, for adjusting the I coefficient, the D coefficient and the P coefficient in sequence, so as to respectively 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 the fault ride-through, and determining that the I coefficient, the D coefficient and the P coefficient at this time are the target parameters of the angular frequency PID compensator respectively; The closing unit is used to close 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 loop output grid connection point voltage.

9. 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, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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