A parameter self-tuning implementation method of grid electromotive force feedforward control

Abstract

This invention provides a parameter self-tuning method for grid electromotive force (EMF) feedforward control, comprising the following steps: charging the DC-side capacitor voltage of a voltage source converter to its rated value; generating a three-phase modulation wave signal based on the grid EMF feedforward control parameters and the current closed-loop control parameters, and generating drive control signals for corresponding power electronic devices through a selected modulation strategy to achieve grid connection of the voltage source converter; automatically correcting the grid EMF feedforward control parameter k1 based on the DC-side capacitor voltage value after grid connection and the rated value of the DC-side capacitor voltage; and gradually decreasing the current closed-loop control parameter k1. p The system adjusts the grid electromotive force (EMF) feedforward control parameter k2 to 0, and simultaneously corrects it. Based on the adjusted EMF feedforward control parameters k1 and k2, a new three-phase modulation wave signal is generated. This invention enables self-tuning of the EMF feedforward control parameters, effectively suppressing grid-connected inrush current and achieving safe grid-connected operation of the voltage source converter based on EMF feedforward control.

Description

Technical Field

[0001] This invention belongs to the field of electrical technology, specifically relating to a method for parameter self-tuning of power grid electromotive force feedforward control. Background Technology

[0002] When a voltage source converter is connected to the grid, it is essential to ensure that the voltage generated by the converter has the same phase sequence, frequency, amplitude, and phase as the distribution network voltage. Otherwise, a large inrush current will be generated, which may shorten the equipment's lifespan or even cause a serious accident. Current technologies mostly use external PTs, employing oscilloscopes for primary and secondary phase matching. This requires additional circuitry or tools, is cumbersome, and lacks both economic efficiency and reliability. Furthermore, current technologies do not offer methods for adjusting the grid electromotive force feedforward control parameters to suppress the grid-connected inrush current. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the aforementioned background technology and provide a method for parameter self-tuning of grid electromotive force feedforward control, which can effectively suppress grid-connected inrush current. The technical solution adopted by this invention is: a method for parameter self-tuning of grid electromotive force feedforward control, comprising the following steps:

[0004] Charge the DC-side capacitor voltage of the voltage source converter to its rated value;

[0005] Based on the instantaneous sampling values ​​of the three-phase voltage on the grid side of the voltage source converter, the instantaneous sampling values ​​of the three-phase current of the voltage source converter, the grid electromotive force feedforward control parameters k1 and k2, and the current closed-loop control parameter k... p Generate a three-phase modulated wave signal;

[0006] The driving control signals for the power electronic devices in the main circuit of the voltage source converter are generated by the three-phase modulated wave signal and the selected modulation strategy, thereby controlling the on and off of the power electronic devices and realizing the grid connection of the voltage source converter.

[0007] The DC-side capacitor voltage value after the voltage source converter is connected to the grid is compared with the rated DC-side capacitor voltage value, and the grid electromotive force feedforward control parameter k1 is automatically corrected based on the comparison result.

[0008] Gradually decrease the current closed-loop control parameter k p As the voltage source converter decreases to 0, the grid electromotive force feedforward control parameter k2 is synchronously adjusted according to the changing trend of the three-phase grid-connected current of the voltage source converter until the three-phase grid-connected current of the voltage source converter reaches the setting standard, thus completing the setting of the grid electromotive force feedforward control parameter k2.

[0009] Based on the grid electromotive force feedforward control parameters k1 and k2 after tuning, a new three-phase modulation wave signal is generated. The new three-phase modulation wave signal and the selected modulation strategy are used to generate a new drive control signal for the power electronic devices in the main circuit of the voltage source converter.

[0010] In the above technical solution, before the voltage source converter is connected to the grid, the estimated values ​​of the grid electromotive force feedforward control parameters k1 and k2 are first obtained; based on engineering experience, the current closed-loop control parameter k with a current command value of zero before grid connection is obtained. p The estimated values ​​are obtained by using the above-estimated grid electromotive force feedforward control parameters k1, k2 and current closed-loop control parameter k. p Generate a three-phase modulated wave signal.

[0011] In the above technical solution, the process of obtaining the estimated value of the grid electromotive force feedforward control parameter k1 includes:

[0012] The estimated value of the grid electromotive force feedforward control parameter k1 is obtained by calculating the following formula. 10 :

[0013] k 10 =u m / (U dc * *M)

[0014] Among them, u m U is the peak value of the phase voltage on the grid side. dc * The rated value of the DC-side capacitor voltage is given by M, which is the correlation coefficient determined by the circuit parameters and circuit topology of the voltage source converter.

[0015] In the above technical solution, the process of obtaining the grid electromotive force feedforward control parameter k2 includes:

[0016] The estimated value of the grid electromotive force feedforward control parameter k2 is obtained by calculating the following formula. 20 :

[0017] k 20 =k 10 *N

[0018] Where, k 10 The value of k1 is the estimated value of the feedforward control parameter of the grid electromotive force before grid connection, and N is the correlation coefficient, which is determined by the sensor delay, sampling delay and control delay.

[0019] In the above technical solution, the three-phase modulated wave signal t is generated using the following formula. a t b t c :

[0020] t a =k1ua +k2(u b -u c )+k p (0-i a )

[0021] t b =k1u b +k2(u a -u c )+k p (0-i b )

[0022] t c =k1u c +k2(u a -u b )+k p (0-i c )

[0023] Among them, u a u b u c i represents the instantaneous value of the three-phase voltage sampled on the grid side of the voltage source converter. a i b i c This represents the instantaneous value of the three-phase current sampled by the voltage source converter.

[0024] In the above technical solution, the process of comparing the DC-side capacitor voltage value after the voltage source converter is connected to the grid with the rated DC-side capacitor voltage value, and automatically correcting the grid electromotive force feedforward control parameter k1 based on the comparison result includes:

[0025] Compare the DC-side capacitor voltage value after the voltage source converter is connected to the grid with the rated DC-side capacitor voltage value:

[0026] If it is determined that the DC-side capacitor voltage of the voltage source converter after grid connection is greater than the rated value of the DC-side capacitor voltage, then the grid electromotive force feedforward control parameter k1 is increased; otherwise, the grid electromotive force feedforward control parameter k1 is decreased until the DC-side capacitor voltage of the voltage source converter is equal to the rated value of the DC-side capacitor voltage, thus completing the tuning of the grid electromotive force feedforward control parameter k1.

[0027] In the above technical solution, if the grid electromotive force feedforward control parameter k2 is set at the moment of completion, the current closed-loop control parameter k p If the current has not yet decreased to 0, then the current closed-loop control parameter k will be adjusted. p The value is directly set to 0, thus completing the current closed-loop control parameter k. p The adjustment.

[0028] In the above technical solution, the process of synchronously correcting the grid electromotive force feedforward control parameter k2 according to the changing trend of the three-phase grid-connected current of the voltage source converter includes:

[0029] By adjusting the grid electromotive force feedforward control parameter k2, the phase difference between the leading / lagging phase current of the voltage source converter and the corresponding phase voltage on the grid side of the voltage source converter is canceled out until the three-phase grid-connected current of the voltage source converter reaches the setting standard, and the grid electromotive force feedforward control parameter k2 is set.

[0030] The beneficial effects of this invention are: This invention determines the phase sequence and frequency by sampling the three-phase voltage on the grid side of the voltage source converter and the three-phase current of the voltage source converter. In the modulation signal, the amplitude is determined by the grid electromotive force feedforward control parameter k1, and the phase is determined by the grid electromotive force feedforward control parameter k2, so as to ensure that the voltage generated by the device connected to the grid and the voltage of the distribution network have the same phase sequence, frequency, amplitude and phase.

[0031] This invention is easy to operate and can effectively suppress inrush current by simply self-tuning the feedforward control parameters. It does not require additional circuitry and has high practical value. Attached Figure Description

[0032] Figure 1 The diagram shown is a schematic diagram of the power electronic device provided in an embodiment of the present invention.

[0033] Figure 2 The diagram shown is a schematic representation of the main flow of an embodiment of the present invention. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments to facilitate a clear understanding of the present invention, but these descriptions do not constitute a limitation on the present invention.

[0035] like Figure 2 As shown, this invention provides a parameter self-tuning method for grid electromotive force feedforward control, comprising the following steps:

[0036] Charge the DC-side capacitor voltage of the voltage source converter to its rated value;

[0037] Based on the instantaneous sampling values ​​of the three-phase voltage on the grid side of the voltage source converter, the instantaneous sampling values ​​of the three-phase current of the voltage source converter, the grid electromotive force feedforward control parameters k1 and k2, and the current closed-loop control parameter k... p Generate a three-phase modulated wave signal;

[0038] The driving control signals for the power electronic devices in the main circuit of the voltage source converter are generated by the three-phase modulated wave signal and the selected modulation strategy, thereby controlling the on and off of the power electronic devices and realizing the grid connection of the voltage source converter.

[0039] The DC-side capacitor voltage value after the voltage source converter is connected to the grid is compared with the rated DC-side capacitor voltage value, and the grid electromotive force feedforward control parameter k1 is automatically corrected based on the comparison result.

[0040] Gradually decrease the current closed-loop control parameter k p As the voltage source converter decreases to 0, the grid electromotive force feedforward control parameter k2 is synchronously adjusted according to the changing trend of the three-phase grid-connected current of the voltage source converter until the three-phase grid-connected current of the voltage source converter reaches the setting standard, thus completing the setting of the grid electromotive force feedforward control parameter k2.

[0041] Based on the grid electromotive force feedforward control parameters k1 and k2 after tuning, a new three-phase modulation wave signal is generated. The new three-phase modulation wave signal and the selected modulation strategy are used to generate a new drive control signal for the power electronic devices in the main circuit of the voltage source converter.

[0042] In the above technical solution, before the voltage source converter is connected to the grid, the estimated values ​​of the grid electromotive force feedforward control parameters k1 and k2 are first obtained; based on engineering experience, the current closed-loop control parameter k with a current command value of zero before grid connection is obtained. p The estimated values ​​are obtained by using the above-estimated grid electromotive force feedforward control parameters k1, k2 and current closed-loop control parameter k. p Generate a three-phase modulated wave signal.

[0043] A specific embodiment of the present invention provides a method for parameter self-tuning of grid electromotive force feedforward control, wherein the power electronic device structure is as follows: Figure 1 As shown, it includes the following steps:

[0044] Step 1: Using a certain charging method, increase the DC-side capacitor voltage of the voltage source converter to the rated value.

[0045] Step 2: Calculate the estimated value k1 of the grid electromotive force feedforward control parameter using the following formula. 10 :

[0046] k 10 =u m / (U dc * *M)

[0047] Among them, u m U is the peak value of the phase voltage on the grid side. dc * The rated value of the DC-side capacitor voltage is given, and M is the correlation coefficient determined by the circuit parameters and circuit topology of the voltage source converter.

[0048] Step 3: Calculate the estimated value of the grid electromotive force feedforward control parameter k2 using the following formula.20 :

[0049] k 20 =k 10 *N

[0050] Where, k 10 The value of k1 is the estimated value of the feedforward control parameter of the grid electromotive force before grid connection. N is the correlation coefficient, which is determined by the sensor delay, sampling delay, control delay, etc., and is taken with reference to similar devices.

[0051] Step 4: Based on engineering experience, adjust the current closed-loop control parameter k. p The estimated value is used to determine the value.

[0052] Step 5: Use the grid electromotive force feedforward control parameters k1 and k2, and the current closed-loop control parameter k, which are taken as their corresponding estimated values. p The instantaneous values ​​of the three-phase voltage sampling on the grid side of the voltage source converter and the instantaneous values ​​of the three-phase current sampling on the voltage source converter generate a three-phase modulated wave signal t. a t b t c :

[0053] t a =k 10 u a +k 20 (u b -u c )+k p0 (0-i a )

[0054] t b =k 10 u b +k 20 (u a -u c )+k p0 (0-i b )

[0055] t c =k 10 u c +k 20 (u a -u b )+k p0 (0-i c ).

[0056] Step 6: Using the three-phase modulated wave signal t a t b t cFor different voltage source converter main circuit topologies, a specific modulation strategy is adopted to generate drive control signals for the main circuit power electronic devices, controlling the on / off switching of the power electronic devices and realizing grid connection of the voltage source converter. For different converter topologies, more advantageous modulation methods can be adopted, such as SPWM, SVPWM, and CPS-PWM.

[0057] Step 7: Compare the DC-side capacitor voltage value after the voltage source converter is connected to the grid with the rated DC-side capacitor voltage value. Based on the comparison result, further adjust the grid electromotive force feedforward control parameter k1 from the estimated value k. 10 To the set value k 1last .

[0058] Specifically, if it is determined that the DC-side capacitor voltage of the voltage source converter after grid connection is greater than the rated value of the DC-side capacitor voltage, then the grid electromotive force feedforward control parameter k1 is increased; conversely, the grid electromotive force feedforward control parameter k1 is decreased until the DC-side capacitor voltage of the voltage source converter is equal to the rated value of the DC-side capacitor voltage. At this point, the value of the grid electromotive force feedforward control parameter k1 is determined to be the setpoint k. 1last The control parameter k1 for the feedforward control of the grid electromotive force is tuned.

[0059] Step 8: Gradually decrease the current closed-loop control parameter k p To reduce to 0, during the reduction process, the grid electromotive force feedforward control parameter k2 is synchronously corrected based on the changing trend of the three-phase grid-connected current of the voltage source converter from the estimated value k. 20 To the set value k 2last .

[0060] Specifically, the different load characteristics of the voltage source converter can lead to current lead / lag. The phase difference between the three-phase voltage on the grid side and the three-phase current of the voltage source converter is a significant cause of inrush current. Taking a capacitive load as an example, the phase of the voltage source converter current will lead the grid voltage. Gradually decreasing the current closed-loop control parameter k... p During the process of approaching 0, the grid electromotive force feedforward control parameters are synchronously adjusted according to the changing trend of the three-phase grid-connected current of the voltage source converter, so that the phase difference between the leading / lagging phase current of the voltage source converter and the corresponding phase voltage on the grid side of the voltage source converter cancels each other out, until the three-phase grid-connected current of the voltage source converter approaches 0. At this time, the grid electromotive force feedforward control parameter k2 is determined to be the setpoint k. 2last The tuning of the grid electromotive force feedforward control parameter k2 is completed.

[0061] The above setting standard is close to 0. At the moment of grid connection, the phase current of the voltage source converter may reach 200A. Now, by controlling k2 to reduce the grid connection impact current to 8A or 5A, it is considered to be close to 0, which means that k2 has reached a relatively good setting.

[0062] If the current closed-loop control parameter k at this moment p If the current has not yet decreased to 0, then the current closed-loop control parameter k will be adjusted. p The value is directly set to 0, thus completing the current closed-loop control parameter k. p The adjustment;

[0063] Step 9: Based on the grid electromotive force feedforward control parameter k after tuning... 1last k 2last Generate a new three-phase modulated wave signal t a1 t b1 t c1 :

[0064] t a1 =k 1last u a +k 2last (u b -u c )

[0065] t b1 =k 1last u b +k 2last (u a -u c )

[0066] t c1 =k 1last u c +k 2last (u a -u b )

[0067] A new drive control signal for the power electronic devices in the main circuit of the voltage source converter is generated by a new three-phase modulated wave signal and a selected modulation strategy. By controlling the switching on and off of the power electronic devices, the three-phase grid-connected current of the voltage source converter is brought close to 0. The grid connection and parameter self-tuning process of the voltage source converter based on grid electromotive force feedforward control is then completed.

[0068] This invention discloses a parameter self-tuning method for grid electromotive force (EMF) feedforward control. It determines the phase sequence and frequency by sampling the three-phase voltage and three-phase current of the voltage source converter on the grid side. In the modulation signal, the amplitude is determined by the grid EMF feedforward control parameter k1, and the phase is determined by the grid EMF feedforward control parameter k2. This ensures that the voltage generated by the device connected to the grid has the same phase sequence, frequency, amplitude, and phase as the distribution network voltage. Furthermore, this invention is simple to implement, easy to operate, and has a rapid response. It effectively suppresses inrush current simply by self-tuning the feedforward control parameters, without relying on additional circuitry, thus possessing high practical value.

[0069] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

Claims

1. A method for parameter self-tuning of grid electromotive force feedforward control, characterized in that, Includes the following steps: Charge the DC-side capacitor voltage of the voltage source converter to its rated value; Based on the instantaneous sampling values ​​of the three-phase voltage on the grid side of the voltage source converter, the instantaneous sampling values ​​of the three-phase current of the voltage source converter, the grid electromotive force feedforward control parameters k1 and k2, and the current closed-loop control parameter k... p Generate a three-phase modulated wave signal; The driving control signals for the power electronic devices in the main circuit of the voltage source converter are generated by the three-phase modulated wave signal and the selected modulation strategy, thereby controlling the on and off of the power electronic devices and realizing the grid connection of the voltage source converter. The DC-side capacitor voltage value after the voltage source converter is connected to the grid is compared with the rated DC-side capacitor voltage value, and the grid electromotive force feedforward control parameter k1 is automatically corrected based on the comparison result. Gradually decrease the current closed-loop control parameter k p As the voltage source converter decreases to 0, the grid electromotive force feedforward control parameter k2 is synchronously adjusted according to the changing trend of the three-phase grid-connected current of the voltage source converter until the three-phase grid-connected current of the voltage source converter reaches the setting standard, thus completing the setting of the grid electromotive force feedforward control parameter k2. Based on the grid electromotive force feedforward control parameters k1 and k2 after tuning, a new three-phase modulation wave signal is generated. The new three-phase modulation wave signal and the selected modulation strategy are used to generate a new drive control signal for the power electronic devices in the main circuit of the voltage source converter.

2. The parameter self-tuning method for grid electromotive force feedforward control according to claim 1, characterized in that: Before the voltage source converter is connected to the grid, the estimated values ​​of the grid electromotive force feedforward control parameters k1 and k2 are first obtained; based on engineering experience, the current closed-loop control parameter k with a current command value of zero before grid connection is obtained. p The estimated values ​​are obtained by using the above-estimated grid electromotive force feedforward control parameters k1, k2 and current closed-loop control parameter k. p Generate a three-phase modulated wave signal.

3. The parameter self-tuning method for grid electromotive force feedforward control according to claim 2, characterized in that, The process of obtaining the estimated value of the grid electromotive force feedforward control parameter k1 includes: The estimated value of the grid electromotive force feedforward control parameter k1 is obtained by calculating the following formula. 10 : k 10 =u m / (U dc * *M) Among them, u m U is the peak value of the phase voltage on the grid side. dc * The rated value of the DC-side capacitor voltage is given by M, which is the correlation coefficient determined by the circuit parameters and circuit topology of the voltage source converter.

4. The parameter self-tuning implementation method for grid electromotive force feedforward control according to claim 2, characterized in that, The process of obtaining the feedforward control parameter k2 of the power grid electromotive force includes: The estimated value of the grid electromotive force feedforward control parameter k2 is obtained by calculating the following formula. 20 : k 20 =k 10 *N Where, k 10 The value of k1 is the estimated value of the feedforward control parameter of the grid electromotive force before grid connection, and N is the correlation coefficient, which is determined by the sensor delay, sampling delay and control delay.

5. The parameter self-tuning method for grid electromotive force feedforward control according to claim 1, characterized in that: The three-phase modulated wave signal t is generated using the following formula. a t b t c : t a =k1u a +k2(u b -u c )+k p (0-i a ) t b =k1u b +k2(u a -u c )+k p (0-i b ) t c =k1u c +k2(u a -u b )+k p (0-i c ) Among them, u a u b u c i represents the instantaneous value of the three-phase voltage sampled on the grid side of the voltage source converter. a i b i c This represents the instantaneous value of the three-phase current sampled by the voltage source converter.

6. The parameter self-tuning method for grid electromotive force feedforward control according to claim 1, characterized in that: The process of comparing the DC-side capacitor voltage value after the voltage source converter is connected to the grid with the rated DC-side capacitor voltage value, and automatically correcting the grid electromotive force feedforward control parameter k1 based on the comparison result includes: Compare the DC-side capacitor voltage value after the voltage source converter is connected to the grid with the rated DC-side capacitor voltage value: If it is determined that the DC-side capacitor voltage of the voltage source converter after grid connection is greater than the rated value of the DC-side capacitor voltage, then the grid electromotive force feedforward control parameter k1 is increased; otherwise, the grid electromotive force feedforward control parameter k1 is decreased until the DC-side capacitor voltage of the voltage source converter is equal to the rated value of the DC-side capacitor voltage, thus completing the tuning of the grid electromotive force feedforward control parameter k1.

7. The parameter self-tuning method for grid electromotive force feedforward control according to claim 1, characterized in that: If the grid electromotive force feedforward control parameter k2 is set at the moment when the current closed-loop control parameter k p If the current has not yet decreased to 0, then the current closed-loop control parameter k will be adjusted. p The value is directly set to 0, thus completing the current closed-loop control parameter k. p The adjustment.

8. The parameter self-tuning implementation method for grid electromotive force feedforward control according to claim 7, characterized in that, The process of synchronously correcting the grid electromotive force feedforward control parameters based on the changing trend of the three-phase grid-connected current of the voltage source converter includes: By adjusting the grid electromotive force feedforward control parameter k2, the phase difference between the leading / lagging phase current of the voltage source converter and the corresponding phase voltage on the grid side of the voltage source converter is canceled out until the three-phase grid-connected current of the voltage source converter reaches the setting standard, and the grid electromotive force feedforward control parameter k2 is set.

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