Converter self-adaptive to power grid voltage change and control method and device thereof

Abstract

The invention provides a self-adaptive power grid voltage change converter and a control method and device thereof. The method comprises the following steps: acquiring grid-connected point voltage and active power of the grid side of the converter; according to the voltage deviation control quantity between the amplitude of the grid-connected point voltage and the voltage rated value, the value of a voltage amplitude control flag bit is updated, and the value of the voltage amplitude control flag bit is used for controlling a PI regulator with an integral output freezing function; according to the value of the voltage amplitude control flag bit, a PI regulator with an integral output freezing function is adopted to regulate the voltage deviation control quantity, and a voltage amplitude regulation control quantity is obtained; performing active power control according to the active power of the converter grid-connected point to obtain an active adjustment control quantity; determining a wave generating voltage instruction at least according to the voltage amplitude adjustment control quantity and the active adjustment control quantity; and carrying out space vector modulation on the wave sending voltage instruction to generate a driving signal required by converter control. The method provided by the invention solves the problem of contradiction between the voltage support strength of the new energy unit and the grid-connected small disturbance stability, and improves the power grid voltage support characteristics of the new energy unit.

Description

Technical Field

[0001] This invention relates to the field of converter control technology, and in particular to a converter that adapts to changes in grid voltage, and its control method and apparatus. Background Technology

[0002] Building a new power system with renewable energy as the mainstay is a major trend. Renewable energy generation is connected to the grid via converters. However, the current weak support characteristics of renewable energy sources mean that their large-scale integration poses a significant challenge to the system's voltage stability.

[0003] To ensure system stability during large-scale integration of renewable energy sources and guarantee the stable grid-connected operation of renewable energy units, it is necessary to strengthen their ability to support system voltage. Under current inductive grid conditions, voltage support for renewable energy units typically employs droop control. This approach can accommodate the current-sharing requirements of different units when supporting voltage; however, the strength of droop control is limited by the unit's stability under small disturbances. A weak droop control, on the other hand, can lead to insufficient voltage support when grid strength weakens, and in severe cases, can also cause grid instability in renewable energy integration. Summary of the Invention

[0004] This invention provides an adaptive converter for grid voltage changes, as well as its control method and device, to resolve the contradiction between the voltage support strength of new energy generating units and the stability of grid connection under small disturbances, thereby improving the grid voltage support characteristics of new energy generating units.

[0005] According to a first aspect of the present invention, a converter control method for adaptive grid voltage changes is provided, the method comprising:

[0006] Obtain the grid connection point voltage and active power on the grid side of the converter;

[0007] The voltage amplitude control flag is updated based on the voltage deviation control amount between the voltage amplitude at the grid connection point and the voltage rating. The voltage amplitude control flag is used to control the PI regulator with integral output freeze function.

[0008] Based on the value of the voltage amplitude control flag, a PI regulator with integral output freeze function is used to adjust the voltage deviation control quantity to obtain the voltage amplitude adjustment control quantity.

[0009] Active power control is performed based on the active power at the converter's grid connection point to obtain the active power regulation control quantity;

[0010] The transmission voltage command should be determined based at least on the voltage amplitude regulation control quantity and the active power regulation control quantity;

[0011] The transmitted voltage command is space vector modulated to generate the drive signal required for converter control.

[0012] In one possible implementation, the amplitude of the grid connection point voltage is the amplitude of the positive sequence component of the grid connection point voltage, or the amplitude of the instantaneous value of the grid connection point voltage.

[0013] The voltage amplitude control flag is updated based on the voltage deviation control amount between the voltage amplitude and the rated voltage, including:

[0014] Determine the difference between the amplitude of the positive sequence component of the grid connection point voltage and the rated voltage value, or determine the difference between the amplitude of the instantaneous value of the grid connection point voltage and the rated voltage value, and use the difference as the voltage deviation control quantity;

[0015] The value of the voltage amplitude control flag is updated based on the relationship between the voltage deviation control quantity and the preset deviation range.

[0016] In one possible implementation, the value of the voltage amplitude control flag is updated based on the relationship between the voltage deviation control amount and the preset deviation range, including:

[0017] The value of the voltage amplitude control flag is determined using the following formula:

[0018]

[0019] In the formula, VCtrlEnhanceFlag represents the value of the voltage amplitude control flag; u Ctrlerr Indicates the voltage deviation control quantity; Δu lo1 >0, -Δu lo1 This indicates that a control threshold for adjusting the voltage amplitude is triggered when the voltage amplitude at the grid connection point is lower than the rated voltage; Δu up1 >0, Δu up1 This indicates that the voltage amplitude adjustment control threshold is triggered when the voltage amplitude at the grid connection point exceeds the rated voltage value; Δu lo2 ≤Δu lo1 , -Δu lo2 This indicates that the control threshold for adjusting the voltage amplitude will be exited when the voltage amplitude at the grid connection point is lower than the rated voltage; Δu up2 ≤Δu up1 ,Δu up2 This indicates that the control threshold for adjusting the voltage amplitude will be exited when the voltage amplitude at the grid connection point exceeds the rated voltage.

[0020] In one possible implementation, Δu lo1 =Δu up1 =0.1V n ,Δu lo2 =Δu up2 =0.05V n , where V n This is the rated voltage.

[0021] In one possible implementation, based on the value of the voltage amplitude control flag, a PI regulator with an integral output freeze function is used to adjust the voltage deviation control quantity to obtain the voltage amplitude adjustment control quantity, including:

[0022] When the voltage amplitude control flag is 0, the integrator in the PI regulator is frozen, the integrator output remains unchanged, and the proportional controller in the PI regulator adjusts the voltage deviation control amount to obtain the voltage amplitude adjustment control amount.

[0023] When the voltage amplitude control flag is 1, the integrator in the PI regulator is unfrozen, and the integrator and proportional controller in the PI regulator simultaneously adjust the voltage deviation control quantity to obtain the voltage amplitude adjustment control quantity.

[0024] In one possible implementation, when the converter adopts grid-based control, the voltage amplitude regulation control quantity is used as the reactive current command, and the active power regulation control quantity is used as the active power current command. The reactive current command and the active power current command together constitute the vector of current command on the dq axis.

[0025] The transmission voltage command shall be determined based at least on the voltage amplitude regulation control quantity and the active power regulation control quantity, including:

[0026] Based on the phase-locked loop output phase, the grid-side current of the converter is transformed into a coordinate system to obtain the vector of the grid-side current in the dq coordinate system.

[0027] The vector of the grid-side current in the dq coordinate system is adjusted based on the vector of the current command on the dq axis to obtain the vector of the transmission voltage command on the αβ axis.

[0028] In one possible implementation, when the converter adopts grid-type control, the voltage amplitude regulation control quantity is used as the virtual internal potential amplitude, and the active power regulation control quantity is used as the phase of the virtual internal potential.

[0029] The transmission voltage command shall be determined based at least on the voltage amplitude regulation control quantity and the active power regulation control quantity, including:

[0030] Based on the phase of the virtual internal potential, the grid-side current and grid-connected voltage of the converter are transformed into coordinates to obtain the vector of the grid-connected voltage in the dq coordinate system and the vector of the grid-side current in the dq coordinate system.

[0031] By adjusting the vectors of the grid connection point voltage and the grid-side current in the dq coordinate system according to the voltage reference value, the vector of the transmitting voltage command on the dq axis is obtained.

[0032] Based on the voltage phase, the vector of the transmitted voltage command on the dq axis is transformed to output the vector of the transmitted voltage command on the αβ axis.

[0033] In one possible implementation, the transmitted voltage command is space vector modulated to generate the drive signals required for converter control, including:

[0034] Based on the vector of the transmitted voltage command on the αβ axis and the DC voltage of the converter bus, the vector of the transmitted voltage command on the αβ axis is modulated and the drive signals of each switching transistor required for converter control are output to realize the control of the converter.

[0035] According to a second aspect of the present invention, an adaptive converter control device for grid voltage variations is provided, the device comprising:

[0036] The acquisition module is used to acquire the grid connection point voltage and active power of the converter on the grid side;

[0037] The update module is used to update the value of the voltage amplitude control flag based on the voltage deviation control amount between the voltage amplitude at the grid connection point and the voltage rating.

[0038] The adjustment module is used to adjust the voltage deviation control amount according to the value of the voltage amplitude control flag to obtain the voltage amplitude adjustment control amount;

[0039] The active power control module performs active power control based on the active power at the converter grid connection point to obtain the active power regulation control quantity;

[0040] The determination module is used to determine the waveform voltage command based at least on the voltage amplitude regulation control quantity and the active power regulation control quantity.

[0041] The generation module is used to perform space vector modulation on the transmitted voltage command to generate the drive signal required for converter control.

[0042] According to a third aspect of the present invention, an adaptive grid voltage change converter is provided. The converter includes a control unit, which is configured to execute the adaptive grid voltage change converter control method in the first aspect of the present invention or any possible implementation thereof.

[0043] This invention provides an adaptive converter for grid voltage changes, along with its control method and apparatus. Based on the magnitude of the voltage deviation control quantity between the grid connection point voltage amplitude and the rated voltage, it determines whether to freeze the integrator in a PI regulator. The PI regulator adjusts the voltage deviation control quantity, and then, based on the voltage amplitude adjustment control quantity and the active power adjustment control quantity, a waveform voltage command is determined. This waveform voltage command is then subjected to space vector modulation to generate the drive signal required for converter control. By using a PI regulator with integral output freezing function to adaptively start and stop the integral regulation function of the converter to adjust for changes in the grid connection point voltage, it not only enhances the grid connection point voltage support of the unit while ensuring grid connection stability, resolving the contradiction between voltage support strength and grid stability under small disturbances in new energy units, but also allows the converter to automatically adapt to changes in grid strength without relying on information such as the grid short-circuit ratio, improving the grid voltage support characteristics of new energy units. Furthermore, the control method is simple to implement, requires no hardware modifications, and does not require monitoring grid strength information, making it highly practical for engineering applications. Attached Figure Description

[0044] 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 embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0045] Figure 1 This is a schematic diagram of a converter control system structure provided in an embodiment of the present invention;

[0046] Figure 2 A flowchart illustrating an adaptive converter control method for grid voltage variations provided in an embodiment of the present invention;

[0047] Figure 3-a and Figure 3-b A schematic diagram illustrating the control effect of the method of the present invention when the grid intensity changes during converter operation;

[0048] Figure 4-a , Figure 4-b and Figure 4-c This diagram illustrates the control effect of traditional droop control with varying control strengths when the grid intensity changes during converter operation.

[0049] Figure 5 The implementation principle of the active power and voltage control module of the converter provided in the embodiment of the present invention when grid-connected control is adopted;

[0050] Figure 6The implementation principle of the active power and voltage control module of the converter provided in the embodiments of the present invention when using grid-type control;

[0051] Figure 7 This is a schematic diagram of the structure of a converter control device that adapts to changes in grid voltage, provided in an embodiment of the present invention. Detailed Implementation

[0052] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] Converter: An electrical device that changes the voltage, frequency, number of phases, and other electrical quantities or characteristics of a power supply system. It includes rectifiers (AC to DC), inverters (DC to AC), AC converters, and DC converters. New energy power generation is connected to the grid via converters.

[0054] Example 1

[0055] This invention provides a converter control system, the structure of which is as follows: Figure 1 As shown, it includes a power grid, a converter, a converter control loop, and a power feeder side. The power grid and the power feeder side are connected through a DC bus.

[0056] The converter's control loop includes an active power and voltage control unit, a voltage command generation unit, and a pulse width modulation (PWM) unit. The active power and voltage control unit and the voltage command generation unit are connected, and the voltage command generation unit is also connected to the PWM unit. The PWM drive signal output by the PWM unit drives the converter. The energy feed side can be one or more of the following: a wind power converter's DC / AC rectification, a power electronic load such as an energy storage DC / DC chopper, or a battery.

[0057] in:

[0058] u g : Power grid voltage;

[0059] Z g : Power grid impedance;

[0060] u oabc : Grid connection point voltage;

[0061] i oabc : Grid connection point current;

[0062] i LabcInductor current;

[0063] L pfc : The filter inductor of the converter;

[0064] C f AC filter capacitors for the converter;

[0065] C dc DC-side capacitor;

[0066] u dc DC voltage;

[0067] P ref Q ref : Active power command and reactive power command of the converter;

[0068] E ref : Virtual internal potential amplitude;

[0069] θ vsc Virtual internal potential phase;

[0070] θ pll Phase-locked loop output phase;

[0071] e αβ_ref : Vector of the transmitted voltage command on the αβ axis

[0072] This invention provides a converter control method that adapts to changes in grid voltage, applied to the converter in the aforementioned converter control system, such as... Figure 2 As shown, it includes the following steps:

[0073] S210, obtain the grid connection point voltage and active power on the grid side of the converter;

[0074] Collect the grid connection point voltage and grid connection point current on the grid side of the converter, and calculate the active power based on the grid connection point voltage and grid connection point current.

[0075] S220 updates the value of the voltage amplitude control flag based on the voltage deviation control amount between the voltage amplitude at the grid connection point and the rated voltage.

[0076] The value of the voltage amplitude control flag is used to control the PI regulator with integral output freeze function.

[0077] Calculate the difference between the voltage amplitude at the grid connection point and the rated voltage value, and use this difference as the relationship between the voltage deviation control quantity and the preset deviation range. Update the value of the voltage amplitude control flag bit, which can be either 0 or 1.

[0078] S230: Based on the value of the voltage amplitude control flag, a PI regulator with integral output freeze function is used to adjust the voltage deviation control quantity to obtain the voltage amplitude adjustment control quantity.

[0079] When the voltage amplitude control flag is 0, the integrator in the PI regulator is frozen, the integrator output remains unchanged, and the proportional controller in the PI regulator adjusts the voltage deviation control amount to obtain the voltage amplitude adjustment control amount.

[0080] When the voltage amplitude control flag is 1, the integrator in the PI regulator is unfrozen, and the integrator and proportional controller in the PI regulator simultaneously adjust the voltage deviation control quantity to obtain the voltage amplitude adjustment control quantity.

[0081] S240 performs active power control based on the active power at the converter's grid connection point to obtain the active power regulation control quantity.

[0082] S250 determines the wave transmission voltage command based at least on the voltage amplitude regulation control quantity and the active power regulation control quantity.

[0083] When the converter adopts grid-following control, the waveform voltage command is determined based on the voltage amplitude adjustment control quantity, active power adjustment control quantity, grid connection point current, and phase-locked loop output phase.

[0084] When the converter adopts grid-type control, the waveform voltage command is determined based on the voltage amplitude regulation control quantity, active power regulation control quantity, grid connection point current and grid connection point voltage.

[0085] S260 performs space vector modulation on the transmitted voltage command to generate the drive signal required for converter control.

[0086] Based on the vector of the transmitted voltage command on the αβ axis and the DC voltage of the converter bus, the vector of the transmitted voltage command on the αβ axis is modulated and the drive signals of each switching transistor required for converter control are output to realize the control of the converter.

[0087] The grid strength is positively correlated with the short-circuit ratio; the higher the short-circuit ratio, the stronger the grid strength. When using the adaptive grid voltage variation converter control method provided in this embodiment of the invention, the simulation results of the converter as the grid short-circuit ratio decreases and increases are as follows: Figure 3-a and Figure 3-b As shown, when the short-circuit ratio of the power grid is changed at 2.0s, the three-phase voltage and current of the power grid return to steady-state operation before 2.3s after a brief adjustment process, without any excessive overshoot or continuous oscillation.

[0088] Figure 4 shows the simulation results of the converter when the grid short-circuit ratio changes, using traditional droop control with different control strengths. Figure 4-a Simulation results are shown when the converter droop coefficient is moderate. The grid short-circuit ratio decreases at 2.0s, and the three-phase voltage and current of the grid converge to a steady state after a small fluctuation. The simulation waveform when the converter droop coefficient is small is as follows: Figure 4-b As shown, after the grid short-circuit ratio decreases at 2.0s, the system becomes unstable due to insufficient voltage support from the converter under weak grid conditions. A larger droop coefficient increases the risk of system instability under strong grid conditions, such as... Figure 4-c As shown, after the short-circuit ratio of the power grid increases at 2.0s, the three-phase voltage and current of the power grid oscillate, and the system becomes unstable.

[0089] Will Figure 3-a , 3-b and Figure 4-a , 4-b As can be seen from the comparison of 4-c, the converter control method for adaptive grid voltage changes provided by the embodiments of the present invention can ensure grid connection stability while improving the voltage support strength at the grid connection point of the unit, and can enable the converter to automatically adapt to changes in grid strength without relying on information such as grid short-circuit ratio.

[0090] This invention provides a converter control method that adapts to changes in grid voltage. Based on the magnitude of the voltage deviation control quantity between the amplitude of the grid connection point voltage and the rated voltage, it determines whether to freeze the integrator in a PI regulator. The PI regulator is then used to adjust the voltage deviation control quantity. Then, based on the voltage amplitude adjustment control quantity and the active power adjustment control quantity, a waveform voltage command is determined. This waveform voltage command is then subjected to space vector modulation to generate the drive signal required for converter control. By using a PI regulator with integral output freezing function to adaptively start and stop the integral regulation function of the converter to adjust for changes in the grid connection point voltage, it not only improves the grid connection point voltage support strength of the unit while ensuring grid connection stability, resolving the contradiction between voltage support strength and grid stability under small disturbances in new energy units, and improving the grid voltage support characteristics of new energy units, but also allows the converter to automatically adapt to changes in grid strength without relying on information such as the grid short-circuit ratio. Furthermore, the control method is simple to implement, requires no hardware modification, and does not require monitoring grid strength information, making it highly practical for engineering applications.

[0091] Example 2

[0092] In one embodiment, the amplitude of the grid connection point voltage is the amplitude of the positive sequence component of the grid connection point voltage, or the amplitude of the instantaneous value of the grid connection point voltage; S220: Update the value of the voltage amplitude control flag bit according to the voltage deviation control amount between the voltage amplitude and the voltage rating, including:

[0093] When the amplitude of the grid connection point voltage is the amplitude of the positive sequence component of the grid connection point voltage, the difference between the amplitude of the positive sequence component of the grid connection point voltage and the rated voltage value is determined, and the difference is used as the voltage deviation control quantity.

[0094] When the amplitude of the grid connection point voltage is equal to the amplitude of the instantaneous value of the grid connection point voltage, the difference between the amplitude of the instantaneous value of the grid connection point voltage and the rated voltage value is determined, and the difference is used as the voltage deviation control quantity.

[0095] The value of the voltage amplitude control flag is updated based on the relationship between the voltage deviation control quantity and the preset deviation range.

[0096] In one example, the value of the voltage amplitude control flag is updated based on the relationship between the voltage deviation control amount and the preset deviation range, including:

[0097] The value of the voltage amplitude control flag is determined using the following formula:

[0098]

[0099] In the formula, VCtrlEnhanceFlag represents the value of the voltage amplitude control flag; u Ctrlerr Indicates the voltage deviation control quantity; Δu lo1 >0, -Δu lo1 This indicates that a control threshold for adjusting the voltage amplitude is triggered when the voltage amplitude at the grid connection point is lower than the rated voltage; Δu up1 >0, Δu up1 This indicates that the voltage amplitude adjustment control threshold is triggered when the voltage amplitude at the grid connection point exceeds the rated voltage value; Δu lo2 ≤Δu lo1 , -Δu lo2 This indicates that the control threshold for adjusting the voltage amplitude will be exited when the voltage amplitude at the grid connection point is lower than the rated voltage; Δu up2 ≤Δu up1 ,Δu up2 This indicates that the control threshold for adjusting the voltage amplitude will be exited when the voltage amplitude at the grid connection point exceeds the rated voltage.

[0100] Taking the requirement that the converter can operate stably for a long time within ±15% of the rated voltage as an example, Δu is configured... lo1 =Δu up1 =0.1V n ,Δu lo2 =Δu up2 =0.05V n , where V n This is the rated voltage.

[0101] The control method provided in this embodiment of the invention determines whether to freeze the integrator of the PI regulator based on the magnitude of the voltage deviation control quantity. When the value of the voltage amplitude control flag is 0, the integrator in the PI regulator is frozen, the integrator output remains unchanged, and the proportional controller in the PI regulator adjusts the voltage deviation control quantity. When the value of the voltage amplitude control flag is 1, the integrator in the PI regulator is unfrozen, and the integrator and proportional controller in the PI regulator simultaneously adjust the voltage deviation control quantity to adapt to voltage changes.

[0102] Example 3

[0103] In one embodiment, when the converter employs grid-connected control, such as Figure 5 As shown, using the grid connection point current i oabc and grid connection point voltage u oabc Calculate the active power P output by the converter. g According to the grid connection point voltage u oabc Calculate the magnitude U of the voltage amplitude at the grid connection point. om and the voltage amplitude command value U at the grid connection point of the converter ref The difference is used to obtain the deviation voltage and the deviation control quantity u. Ctrlerr .

[0104] S230: Based on the value of the voltage amplitude control flag, a PI regulator with integral output freeze function is used to adjust the voltage deviation control quantity to obtain the voltage amplitude adjustment control quantity, including:

[0105] Based on the voltage deviation control quantity and the value of the voltage amplitude control flag V CtrlEnhanceFlag The voltage at the converter's grid connection point is adjusted to obtain the q-axis current command I. refq The voltage amplitude regulation control quantity can be expressed by the following formula:

[0106] I refq =G UR (U ref -U om )

[0107] In the formula, G UR For a PI controller with integral output freeze function, its frequency domain characteristics can be expressed as:

[0108]

[0109] In the formula, K pv K is the proportional coefficient of the proportional controller in a PI regulator. iv G is the integral coefficient of the integrator in the PI controller. UR The integrator output at V CtrlEnhanceFlag When = 1, by adjusting the input u CtrlerrIntegrating, we get V CtrlEnhanceFlag Freeze when =0.

[0110] Figure 5 I in refqDrop I is the output of the proportional controller in the PI regulator. refqIntg I is the output of the integrator in the PI controller. refqDrop with I refqIntg The sum of these values ​​is the voltage amplitude adjustment control quantity.

[0111] The converter control loop also includes a phase-locked loop (PLL), whose input is the grid connection point voltage u. oabc The output is the phase angle θ of the phase-locked loop. pll The voltage amplitude regulation control quantity serves as the reactive current command. The structure of the active power and voltage control unit is as follows: Figure 5 As shown, S240: Active power control is performed based on the active power at the converter grid connection point to obtain active power regulation control quantities, including:

[0112] Using the grid connection point current i oabc and grid connection point voltage u oabc Calculate the active power P output by the converter. g For the active power command value P ref and active power P g The deviation is obtained by taking the difference, and then the regulator G is used. PR The deviation is adjusted to obtain the d-axis current command I. refd I refd This refers to the active power regulation and control quantity.

[0113] Voltage amplitude regulation control quantity I refq As a reactive current command, the active power regulation control quantity I refd The active current command, reactive current command, and active current command together constitute the current command vector I on the dq axis. ref S250: Determine the transmission voltage command based at least on the voltage amplitude regulation control quantity and the active power regulation control quantity, including:

[0114] Based on the phase θ output of the phase-locked loop pll For the grid connection point current i of the converter oabc Perform coordinate transformation to obtain the grid connection point current i oabc Vector I in the dq coordinate system dq ;

[0115] According to the current command, the vector I on the dq axis ref For the vector I of the grid connection point current in the dq coordinate system dq Adjustments are made to obtain the vector e of the transmitted voltage command on the αβ axis.αβ_ref .

[0116] The control method provided in this invention, when the converter adopts grid-following control, adaptively activates and deactivates its integral regulation function by utilizing a PI regulator with integral output freezing function to adjust the converter's integral regulation function in response to changes in the grid connection point voltage. This not only enhances the support strength of the unit's grid connection point voltage while ensuring grid connection stability, resolving the contradiction between the voltage support strength of new energy units and the stability under small grid disturbances, but also allows the converter to automatically adapt to changes in grid strength without relying on information such as the grid short-circuit ratio. Moreover, the control method is simple to implement, requires no hardware modification, and does not require monitoring grid strength information, making it highly practical for engineering applications.

[0117] Example 4

[0118] In one embodiment, when the converter employs grid-based control, such as Figure 6 As shown, using the grid connection point current i oabc and grid connection point voltage u oabc Calculate the active power P output by the converter. g According to the grid connection point voltage u oabc Calculate the magnitude U of the voltage amplitude at the grid connection point. om and the voltage amplitude command value U at the grid connection point of the converter ref The difference is used to obtain the deviation voltage and the deviation control quantity u. Ctrlerr .

[0119] S230: Based on the value of the voltage amplitude control flag, a PI regulator with integral output freeze function is used to adjust the voltage deviation control quantity to obtain the voltage amplitude adjustment control quantity, including:

[0120] Based on voltage deviation control quantity u Ctrlerr The value of the voltage amplitude enhancement control flag V CtrlEnhanceFlag The voltage at the converter's grid connection point is adjusted to obtain the virtual internal potential amplitude E. ref The voltage amplitude regulation control quantity can be expressed by the following formula:

[0121] E refq =G UR (U ref -U om )

[0122] In the formula, G UR For a PI controller with integral output freeze function, its frequency domain characteristics can be expressed as:

[0123]

[0124] In the formula, K pv K is the proportional coefficient of the proportional controller in a PI regulator.iv G is the integral coefficient of the integrator in the PI controller. UR The integrator output at V CtrlEnhanceFlag When = 1, by adjusting the input u Ctrlerr Integrating, we get V CtrlEnhanceFlag Freeze when =0.

[0125] Figure 6 E in refqDrop E is the output of the proportional controller in the PI regulator. refqIntg E is the output of the integrator in the PI controller. refqDrop With E refqIntg The sum of these values ​​is the voltage amplitude adjustment control quantity.

[0126] The structure of the active power and voltage control unit is shown in Figure 4. S240: performs active power control based on the active power at the converter grid connection point to obtain active power regulation control quantities, including:

[0127] For the active power command value P ref and the active power P g The deviation is adjusted to obtain the output voltage phase θ. vsc This refers to the active power regulation control quantity. The output voltage phase can be expressed by the following formula:

[0128]

[0129] In the formula, G PR ω0 and ω0 represent the active power regulator and the grid rated frequency, respectively, G PR The frequency domain characteristics can be expressed by the following formula:

[0130]

[0131] In the formula, J is the virtual moment of inertia and D is the damping coefficient.

[0132] The voltage amplitude adjustment control quantity E ref As the amplitude of the virtual internal potential, the active power regulation control quantity is the phase θ of the virtual internal potential. vsc S250: Determine the transmission voltage command based at least on the voltage amplitude regulation control quantity and the active power regulation control quantity, including:

[0133] Based on the phase of the virtual internal potential, the grid-side current and grid-connected voltage of the converter are transformed into coordinates to obtain the vector U of the grid-connected voltage in the dq coordinate system. odq The vector I of the grid-side current in the dq coordinate system dq ;

[0134] According to the voltage reference value E ref Adjusting the vector U of the grid connection point voltage in the dq coordinate systemodq and the vector I of the grid-side current in the dq coordinate system dq The vector e of the transmitted voltage command on the dq axis is obtained. dq_ref ,;

[0135] According to voltage phase θ vsc Perform a coordinate transformation on the vector of the transmitted voltage command along the dq axis to output the vector e of the transmitted voltage command along the αβ axis. αβ_ref .

[0136] The control method provided in this invention, when the converter adopts grid-type control, adaptively activates and deactivates its integral regulation function by utilizing a PI regulator with integral output freezing function to adjust the converter's grid connection point voltage according to changes in voltage. This not only enhances the grid connection point voltage support of the unit while ensuring grid connection stability, resolving the contradiction between voltage support and grid connection stability under small disturbances in new energy units, but also allows the converter to automatically adapt to changes in grid strength without relying on information such as the grid short-circuit ratio. Moreover, the control method is simple to implement, requires no hardware modification, and does not require monitoring grid strength information, making it highly practical for engineering applications.

[0137] Example 5

[0138] Accordingly, embodiments of the present invention also provide a converter control device that adapts to changes in grid voltage, such as... Figure 7 As shown, the adaptive converter control device 700 for grid voltage changes includes an acquisition module 710, an update module 720, an adjustment module 730, an active power control module 740, a determination module 750, and a generation module 760, wherein:

[0139] The acquisition module 710 is used to acquire the grid connection point voltage and active power on the grid side of the converter;

[0140] The update module 720 is used to update the value of the voltage amplitude control flag based on the voltage deviation control amount between the voltage amplitude at the grid connection point and the voltage rating.

[0141] The adjustment module 730 is used to adjust the voltage deviation control amount according to the value of the voltage amplitude control flag bit to obtain the voltage amplitude adjustment control amount;

[0142] The active power control module 740 performs active power control based on the active power at the converter grid connection point to obtain the active power regulation control quantity.

[0143] The determination module 750 is used to determine the wave transmission voltage command based at least on the voltage amplitude regulation control quantity and the active power regulation control quantity.

[0144] The generation module 760 is used to perform space vector modulation on the transmitted voltage command to generate the drive signal required for converter control.

[0145] This invention provides a converter control device that adapts to changes in grid voltage. Based on the magnitude of the voltage deviation control quantity between the amplitude of the grid connection point voltage and the rated voltage, it determines whether to freeze the integrator in a PI regulator. The PI regulator adjusts the voltage deviation control quantity, and then, based on the voltage amplitude adjustment control quantity and the active power adjustment control quantity, a waveform voltage command is determined. This waveform voltage command is then subjected to space vector modulation to generate the drive signal required for converter control. By using a PI regulator with an integral output freezing function to adaptively start and stop the integral regulation function of the converter to adjust for changes in the grid connection point voltage, it not only improves the grid connection point voltage support strength of the unit while ensuring grid connection stability, resolving the contradiction between voltage support strength and grid connection stability under small disturbances in new energy units, but also allows the converter to automatically adapt to changes in grid strength without relying on information such as the grid short-circuit ratio. Furthermore, the control method is simple to implement, requires no hardware modification, and does not require monitoring grid strength information, making it highly practical for engineering applications.

[0146] The adaptive grid voltage change converter control device provided in this embodiment belongs to the same inventive concept as the adaptive grid voltage change converter control method provided in the above embodiments of the present invention. It can execute the adaptive grid voltage change converter control method provided in any of the above embodiments of the present invention, and possesses the corresponding functional modules and beneficial effects of the adaptive grid voltage change converter control method. Technical details not described in detail in this embodiment can be found in the specific processing content of the adaptive grid voltage change converter control method provided in the above embodiments of the present invention, and will not be repeated here.

[0147] Example 6

[0148] This invention also provides a converter, which includes a control unit. The control unit is used to execute the adaptive grid voltage change converter control method provided in any of the above embodiments of this invention, and has the corresponding functional modules and beneficial effects for executing the adaptive grid voltage change converter control method. Technical details not described in detail in this embodiment can be found in the specific processing content of the adaptive grid voltage change converter control method provided in the above embodiments of this invention, and will not be repeated here.

[0149] For the foregoing method embodiments, in order to simplify the description, they are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, because according to the present invention, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0150] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For apparatus embodiments, since they are basically similar to method embodiments, the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

[0151] The steps in the methods of the various embodiments of the present invention can be adjusted, merged, or deleted in order according to actual needs, and the technical features described in the various embodiments can be replaced or combined.

[0152] The modules and sub-modules in the various embodiments of the present invention can be merged, divided, and deleted according to actual needs.

[0153] In the embodiments provided by this invention, it should be understood that the disclosed terminals, devices, and methods can be implemented in other ways. For example, the terminal embodiments described above are merely illustrative. For instance, the division of modules or sub-modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple sub-modules or modules may be combined or integrated into another module, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection through some interfaces, devices, or modules, and may be electrical, mechanical, or other forms.

[0154] The modules or submodules described as separate components may or may not be physically separate. The components that constitute a module or submodule may or may not be physical modules or submodules; that is, they may be located in one place or distributed across multiple network modules or submodules. Some or all of the modules or submodules can be selected to achieve the purpose of this embodiment's solution, depending on actual needs.

[0155] Furthermore, the functional modules or sub-modules in the various embodiments of the present invention can be integrated into one processing module, or each module or sub-module can exist physically separately, or two or more modules or sub-modules can be integrated into one module. The integrated modules or sub-modules described above can be implemented in hardware or in the form of software functional modules or sub-modules.

[0156] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0157] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware, a software unit executed by a processor, or a combination of both. The software unit can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0158] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0159] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A converter control method for adaptive grid voltage changes, characterized in that, The method includes: Obtain the grid connection point voltage and active power on the grid side of the converter; The value of the voltage amplitude control flag is updated based on the voltage deviation control amount between the voltage amplitude at the grid connection point and the voltage rating. The value of the voltage amplitude control flag is used to control the PI regulator with integral output freeze function. Based on the value of the voltage amplitude control flag, the voltage deviation control quantity is adjusted using the PI regulator with integral output freeze function to obtain the voltage amplitude adjustment control quantity. Active power control is performed based on the active power at the grid connection point of the converter to obtain the active power regulation control quantity; The transmission voltage command is determined based at least on the voltage amplitude adjustment control quantity and the active power adjustment control quantity; The transmitted voltage command is space vector modulated to generate the drive signal required for converter control.

2. The converter control method for adaptive grid voltage changes according to claim 1, characterized in that, The amplitude of the grid connection point voltage is the amplitude of the positive sequence component of the grid connection point voltage, or the amplitude of the instantaneous value of the grid connection point voltage. The step of updating the voltage amplitude control flag based on the voltage deviation control amount between the voltage amplitude at the grid connection point and the rated voltage includes: Determine the difference between the amplitude of the positive sequence component of the grid connection point voltage and the rated voltage value, or determine the difference between the amplitude of the instantaneous value of the grid connection point voltage and the rated voltage value, and use the difference as a voltage deviation control quantity; The value of the voltage amplitude control flag is updated based on the relationship between the voltage deviation control amount and the preset deviation range.

3. The converter control method for adaptive grid voltage changes according to claim 2, characterized in that, Based on the relationship between the voltage deviation control amount and the preset deviation range, the value of the voltage amplitude control flag is updated, including: The value of the voltage amplitude control flag is determined using the following formula: In the formula, VCtrlEnhanceFlag represents the value of the voltage amplitude control flag; u Ctrlerr This represents the voltage deviation control quantity; Δu lo1 >0, -Δu lo1 This indicates that a control threshold for adjusting the voltage amplitude is triggered when the voltage amplitude at the grid connection point is lower than the rated voltage; Δu up1 >0, Δu up1 This indicates that the voltage amplitude adjustment control threshold is triggered when the voltage amplitude at the grid connection point exceeds the rated voltage; Δu lo2 ≤Δu lo1 , -Δu lo2 This indicates that the control threshold for adjusting the voltage amplitude will be exited when the voltage amplitude at the grid connection point is lower than the rated voltage; Δu up2 ≤Δu up1 ,Δu up2 This indicates that the control threshold for adjusting the voltage amplitude will be exited when the voltage amplitude at the grid connection point exceeds the rated voltage.

4. The converter control method for adaptive grid voltage changes according to claim 3, characterized in that, Δu lo1 =Δu up1 =0.1V n ,Δu lo2 =Δu up2 =0.05V n , where V n This refers to the rated voltage.

5. The converter control method for adaptive grid voltage changes according to claim 1, characterized in that, The step of adjusting the voltage deviation control quantity using a PI regulator with integral output freeze function based on the value of the voltage amplitude control flag to obtain the voltage amplitude adjustment control quantity includes: When the value of the voltage amplitude control flag is 0, the integrator in the PI regulator is frozen, the integrator output remains unchanged, and the proportional controller in the PI regulator adjusts the voltage deviation control amount to obtain the voltage amplitude adjustment control amount. When the voltage amplitude control flag is 1, the integrator in the PI regulator is unfrozen, and the integrator and proportional controller in the PI regulator simultaneously adjust the voltage deviation control quantity to obtain the voltage amplitude adjustment control quantity.

6. The converter control method for adaptive grid voltage changes according to claim 1, characterized in that, When the converter adopts grid-based control, the voltage amplitude regulation control quantity is used as the reactive current command, the active power regulation control quantity is used as the active power current command, and the reactive current command and the active power current command together constitute the vector of current command on the dq axis. The step of determining the transmission voltage command based at least on the voltage amplitude adjustment control quantity and the active power adjustment control quantity includes: Based on the phase-locked loop output phase, the grid-side current of the converter is transformed into a coordinate system to obtain the vector of the grid-side current in the dq coordinate system. The vector of the grid-side current in the dq coordinate system is adjusted according to the vector of the current command on the dq axis to obtain the vector of the transmission voltage command on the αβ axis.

7. The converter control method for adaptive grid voltage changes according to claim 1, characterized in that, When the converter adopts grid-type control, the voltage amplitude regulation control quantity is used as the virtual internal potential amplitude, and the active power regulation control quantity is used as the phase of the virtual internal potential; The step of determining the transmission voltage command based at least on the voltage amplitude adjustment control quantity and the active power adjustment control quantity includes: Based on the phase of the virtual internal potential, the grid-side current and grid-connected voltage of the converter are transformed into coordinates to obtain the vector of the grid-connected voltage in the dq coordinate system and the vector of the grid-side current in the dq coordinate system. Adjust the vector of the grid connection point voltage in the dq coordinate system and the vector of the grid-side current in the dq coordinate system according to the voltage reference value to obtain the vector of the transmission voltage command on the dq axis. Based on the voltage phase, the vector of the transmitted voltage command on the dq axis is transformed to output the vector of the transmitted voltage command on the αβ axis.

8. The converter control method for adaptive grid voltage changes according to claim 6 or 7, characterized in that, The step of performing space vector modulation on the transmitted voltage command to generate the drive signal required for converter control includes: Based on the vector of the transmitted voltage command on the αβ axis and the DC voltage of the converter bus, the vector of the transmitted voltage command on the αβ axis is modulated and the drive signals of each switching transistor required for converter control are output to realize the control of the converter.

9. A converter control device that adapts to changes in grid voltage, characterized in that, The device includes: The acquisition module is used to acquire the grid connection point voltage and active power of the converter on the grid side; The update module is used to update the value of the voltage amplitude control flag bit according to the voltage deviation control amount between the amplitude of the grid connection point voltage and the voltage rating value; The adjustment module is used to adjust the voltage deviation control amount according to the value of the voltage amplitude control flag bit to obtain the voltage amplitude adjustment control amount; The active power control module performs active power control based on the active power at the grid connection point of the converter to obtain the active power regulation control quantity; The determining module is used to determine the transmission voltage command based at least on the voltage amplitude adjustment control quantity and the active power adjustment control quantity; The generation module is used to perform space vector modulation on the transmitted voltage command to generate the drive signal required for the converter control.

10. A converter that adapts to changes in grid voltage, characterized in that, The converter includes a control unit, which is used to execute the converter control method for adaptive grid voltage changes as described in any one of claims 1-7.

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