Dab inverter transient pulsating current control method, system, device and medium

Abstract

The application discloses a DAB inverter transient pulsating current control method, system, device and medium, relates to the DAB type inverter control strategy technical field, and solves the technical problem that the existing frequency conversion DAB inverter cannot output reactive power and there is transient switching current pulsation when outputting reactive power, and the technical solution points are based on the characteristics of bidirectional power flow of the DAB type inverter, alternating operation of the forward power transmission mode and the reverse power transmission mode is utilized, the function of outputting reactive power of the frequency conversion DAB type inverter is realized, and the current pulsation during transient switching of the inverter is inhibited.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of DAB inverter control strategy, and particularly relates to a DAB inverter transient pulsating current control method, system, device and medium. BACKGROUND

[0002] DAB micro-inverter has the characteristics of less switching devices, large soft switching range and bidirectional power transmission, and has advantages compared with other micro-inverter topologies. The current modulation method of DAB micro-inverter is mainly divided into constant frequency and variable frequency, and although the output active efficiency of the variable frequency control method is very high, there is little research on the output reactive power.

[0003] Figure 1 The structure flow chart of the typical DAB inverter control method of the prior art, the inverter can only output active power, and the output current phase is consistent with the grid voltage; when the phase of the given current is inconsistent with the phase of the grid voltage, the output current will oscillate sharply in the area where the instantaneous output power is negative. DAB micro-inverter has the characteristic of bidirectional power transmission, so by imitating the forward power transmission mode of output active power, the reverse power transmission mode of input active power is proposed, and when the forward power transmission mode and the reverse power transmission mode are alternately operated, the reactive power can be output, but the grid voltage u g Switching will cause transient switching current pulsation of the inverter. Figure 2 The experimental waveform when the output current is consistent with the phase of the grid voltage by using the existing control method, Figure 3 The experimental waveform when the output current is inconsistent with the phase of the grid voltage by using the existing control method, Figure 2 And Figure 3 It can be seen that when the instantaneous output power is negative, the system is unstable.

[0004] Based on the above problems, the present application comprehensively considers the voltage switching transient impact and realizes a specific function, and proposes a variable frequency DAB inverter transient pulsating current control method with reactive power output capability. SUMMARY

[0005] The present application provides a DAB inverter transient pulsating current control method, system, device and medium, and the technical purpose is to make the variable frequency DAB inverter effectively output reactive power and suppress transient switching current pulsation at the voltage switching point.

[0006] The above technical purpose of the present application is realized by the following technical scheme:

[0007] A DAB inverter transient pulsating current control method, comprising:

[0008] the phase of the grid voltage ωg t and grid voltage phase ω g t corresponding positive period signal p and negative period signal n is acquired;

[0009] through grid voltage phase ω g t generating phase-shift angle control coefficient k ;

[0010] converting phase-shift angle control coefficient k into coefficient m ;

[0011] through expected current amplitude I o * obtaining current amplitude correction value I o ;

[0012] judging positive period signal of grid voltage p , on the basis of positive period signal p judgment, according to current amplitude correction value I o generating corresponding phase-shift angle amplitude φ n , according to phase-shift angle amplitude φ n and current phase function sin(ω g t+α) obtaining phase-shift angle signal φ(t) ;

[0013] judging AC side instantaneous output power Sgn_Pac , on the basis of instantaneous output power Sgn_Pac judgment, according to coefficient m and phase-shift angle signal φ(t) generating control frequency f s ;

[0014] according to positive period signal p , negative period signal n , phase-shift angle control coefficient k , control frequency f s and phase-shift angle signal φ(t) generating control signal of switching tube PWM , according to PWM control signal, realizing transient pulsating current control of variable frequency DAB type inverter;

[0015] wherein, in the switching phase, the phase-shift angle control coefficient t 1 is equal to 0.5 to suppress the pulsating current of transient switching; in the non-switching phase the phase-shift angle control coefficient k is kept at a certain value k k x to realize the corresponding function, t 1 is less than 0.05 T S , 0 < k < 0.5 k x <0.5.

[0016] Preferably, the phase-shift angle control coefficient k is converted into a coefficient m , expressed as:

[0017] ;

[0018] wherein, k denotes the phase-shift angle control coefficient, m denotes the coefficient m .

[0019] Preferably, the phase-shift angle amplitude φ n is expressed as:

[0020] ;

[0021] wherein, L lk denotes the leakage inductance, U dc denotes the DC side voltage, N denotes the transformation ratio of the transformer.

[0022] Preferably, the phase-shift angle amplitude φ n and the current amplitude correction value I o obtain the phase-shift angle signal φ(t) , comprising: multiplying the phase-shift angle amplitude φ n and the current phase function sin(ω g t+α) to obtain the phase-shift angle signal φ(t) .

[0023] Preferably, the control frequency f s is expressed as:

[0024] ​ ;

[0025] wherein, f s max represents the maximum switching frequency.

[0026] Preferably, the phase-shifting angle control coefficient k is equal to 0.5 and equal to a specific value k x there is a time interval t 2 - t 1 to achieve a smooth rise and a smooth fall, the rise function slope a + and the fall function slope a - are respectively:

[0027] ;

[0028] wherein, ω g represents the angular frequency; t 2 - t 1 is less than 0.05 T S .

[0029] Preferably, the current amplitude correction value I o * is obtained by subtracting I o from the expected current amplitude

[0030] . I o * The sine signal of the expected current amplitude i o * , i o * is subtracted by a subtractor i o and then passed through a PI controller to obtain I 1 . I o * The expected current amplitude I 2 is passed through a feedforward controller to obtain I 1 and I 2 . I The current amplitude correction value is finally obtained by adding the two values through an addero .

[0031] A DAB inverter transient pulsating current control system for implementing the DAB inverter transient pulsating current control method, the control system comprising:

[0032] a phase-locked loop for obtaining the grid voltage phase ω g t and the grid voltage phase ω g t corresponding positive period signal p and negative period signal n ;

[0033] k a module for generating a phase-shift angle control coefficient ω g t by the grid voltage phase k ;

[0034] m a module for converting the phase-shift angle control coefficient k into a coefficient m ;

[0035] a feedforward controller and a PI controller for obtaining a current amplitude correction value I o * according to the desired current amplitude I o ;

[0036] φ n a module for judging the positive period signal p of the grid voltage, and generating a corresponding phase-shift angle amplitude p according to the current amplitude correction value I o based on the judgment of the positive period signal φ n , and multiplying the phase-shift angle amplitude φ n and a current phase function sin(ω g t+ α) to obtain φ(t) ;

[0037] f s a module for judging the instantaneous output power Sgn_Pac of the AC side, and generating a control frequency Sgn_Pac according to the coefficient m based on the judgment of the instantaneous output power ;f s ;

[0038] PWM The generation module, based on the positive periodic signal p Negative periodic signal n Control frequency f s as well as φ(t) Generating switching transistors PWM Control signals, according to PWM The control signal enables transient pulsating current control of the DAB inverter.

[0039] A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the DAB inverter transient pulsating current control method.

[0040] A computer storage medium storing a computer program, which, when executed by a processor, implements the DAB inverter transient pulsating current control method.

[0041] The above technical solution can achieve at least some of the following technical effects:

[0042] (1) Based on the bidirectional power flow characteristics of DAB inverter, the function of outputting reactive power of DAB inverter is realized, and the transient switching current pulsation at the zero point of grid voltage switching is suppressed.

[0043] (2) During the non-switching phase of the grid voltage, the control method proposed in this application can realize other functions of the frequency conversion DAB inverter. Attached Figure Description

[0044] Figure 1 Here is a flowchart illustrating the structure of the existing DAB-type inverter control method;

[0045] Figure 2 This is a schematic diagram of the experimental waveform when the output current is in phase with the grid voltage using the existing control method;

[0046] Figure 3 The experimental waveforms are shown when the output current and the grid voltage are out of phase when using the existing control method.

[0047] Figure 4 This is a flowchart illustrating the transient pulsating current control method for DAB inverters in this application embodiment;

[0048] Figure 5 Examples of embodiments in this application k Module implementation flowchart;

[0049] Figure 6 For the embodiment of the present application PWM The implementation flowchart of the module;

[0050] Figure 7 For the experimental waveform of the phase shift angle control coefficient k When the control method of the present application is adopted but the phase shift angle control coefficient is not modulated, there is a transient switching current pulse;

[0051] Figure 8 For the experimental waveform of the phase shift angle control coefficient k When the control method of the present application is adopted;

[0052] Figure 9 For the experimental waveform of the phase shift angle control coefficient When the control method of the present application is adopted, the capacitive reactive power is sent, and the grid current leads the grid voltage;

[0053] Figure 10 For the experimental waveform of the phase shift angle control coefficient When the control method of the present application is adopted, the inductive reactive power is sent, and the grid current lags behind the grid voltage. DETAILED DESCRIPTION

[0054] The technical method in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0055] As Figure 4 shown, the DAB inverter transient pulse current control system described in the present application includes a phase-locked loop, k a module, m a module, a feedforward controller, a PI controller, φ n a module, f s a module and PWM a generation module.

[0056] The phase-locked loop is used to obtain the phase ω g t and the phase of the grid voltage ω g t The corresponding positive period signal p and negative period signal n are obtained.

[0057] k The module is used to obtain the phase ω gt Generate phase shift angle control coefficients k . k Module flowchart as follows Figure 5 As shown, control coefficients k Waveform diagram as follows Figure 8 As shown.

[0058] Preferably, during the switching phase, before and after the voltage switching point... t 1 Within a time period, that is At that time, the phase shift angle control coefficient k Equal to 0.5 to suppress pulsating current during transient switching; in the non-switching phase, i.e. At that time, the phase shift angle control coefficient k Keep it as a specific value k x To achieve the corresponding function (such as reducing the inverter's return power). t 1 Less than 0.05 T S ,0< k x <0.5.

[0059] Preferably, when transitioning from a switching phase to a non-switching phase, or from a non-switching phase to a switching phase, the phase shift angle control coefficient... k Cannot mutate, such as Figure 8 As shown, the phase shift angle control coefficient k In the case of equal to 0.5 and equal to a specific value k x There is a time interval t 2 - t 1 , t 2 - t 1 Generally less than 0.05 T S To achieve a gradual rise and fall between the two, the slope of the rising function is... a + and the slope of the descending function a - They are represented as follows:

[0060] ;

[0061] in, ω g Indicates the angular frequency of the grid voltage; t 2 - t 1 Less than 0.05 TS .

[0062] When , k is in the transition descending phase, due to the different intervals, the calculation formulas are and ; when , k is in the transition ascending phase, due to the different intervals, the calculation formulas are and .

[0063] m The module is used for converting the phase shift angle control coefficient k into the coefficient m .

[0064] Preferably, the phase shift angle control coefficient k is converted into the coefficient m , which is expressed as:

[0065] ;

[0066] Wherein, k represents the phase shift angle control coefficient, m represents the coefficient m .

[0067] The feedforward controller and the PI controller are used to obtain the current amplitude correction value I o * from the expected current amplitude I o .

[0068] Specifically, the controller used in the present application comprises a feedforward controller and a feedback PI controller, wherein the feedforward controller can eliminate the deviation caused by the inductive element of the filter, and the feedback PI controller can make the inverter output current accurately and stably track the set value, while effectively suppressing the influence of various disturbances. Figure 3 、 Figure 4 、 Figure 7 、 Figure 8 、 Figure 9 and Figure 10 The experimental results prove that the present application can effectively output reactive power and suppress transient switching current ripple at the voltage switching point compared with the traditional DAB type variable frequency inverter.

[0069] Preferably, the current amplitude correction value I o * is obtained from the expected current amplitude I o , comprising:

[0070] Desired current amplitude I o * The sinusoidal signal is i o * , i o * Subtract by the subtractor i o Then obtained through a PI controller I 1 Expected current amplitude I o * After passing through the feedforward controller, the result is... I 2 , I 1 and I 2 The current amplitude correction value is finally obtained by adding the values ​​using an adder. I o .

[0071] φ n The module is used for positive periodic signals of the mains voltage. p Make a judgment on the positive periodic signal. p Based on the judgment, the correction value is determined according to the current amplitude. I o Generate the corresponding phase shift angle magnitude φ n Phase shift angle magnitude φ n Phase function of current sin (ω g t+α) Multiply to get φ(t) .

[0072] Preferably, the phase shift angle amplitude φ n Represented as:

[0073] ;

[0074] in, L lk Indicates leakage inductance. U dc Indicates the DC side voltage. N This indicates the transformer's turns ratio.

[0075] Preferably, the step of determining the phase shift angle magnitude... φ n and current amplitude correction value Io Obtain the phase shift angle signal φ(t) This includes: adjusting the phase shift angle magnitude. φ n Phase function of current sin(ω g t+α) Multiplying them yields the phase shift angle signal. φ(t) .

[0076] f s The module is used to measure the instantaneous output power on the AC side. Sgn_Pac Make a judgment on the instantaneous output power. Sgn_Pac Based on the judgment and the coefficient m Generate control frequency f s .

[0077] Preferably, the control frequency f s Represented as:

[0078] ;

[0079] in, f s max This indicates the maximum switching frequency.

[0080] PWM The generation module is used to generate based on positive periodic signals. p Negative periodic signal n Control frequency f s as well as φ(t) Generate switching transistors S1 to S8 of PWM Control signals, according to PWM The control signal enables transient pulsating current control of the DAB inverter, such as... Figure 6 As shown. In the existing PWM Based on the generation module, the switching transistor S1-S5 as well as S7 A total of 6 PWM signals XOR positive periodic signals p It is used to solve the problem of switching between forward and reverse power transfer modes.

[0081] This application's control method is based on the bidirectional power flow characteristic of DAB inverters. It utilizes the alternating operation of forward and reverse power transfer modes to achieve reactive power output from the frequency conversion DAB inverter. Specifically, within one cycle, when the instantaneous power on the AC side is positive, the DAB inverter is in forward power transfer mode, transferring energy from the DC side to the AC side. W +When the instantaneous power on the AC side is negative, the DAB inverter is in reverse power transfer mode, transferring energy from the AC side to the DC side. W- The alternating operation of these two power transmission modes results in some of the transmitted energy being offset, thus generating reactive power. Q The active power output of the DAB inverter P reduce, Due to apparent power S The active power output remains unchanged. P The reactive power output decreases. Q Then increase, Q Represented as This manifests as a phase difference in the output voltage and current. α ,available .

[0082] like Figure 4 As shown, the transient pulsating current control method for DAB inverters described in this application includes:

[0083] 100: Phase of grid voltage ω g t and grid voltage phase ω g t Corresponding positive periodic signal p and negative periodic signals n Obtain it.

[0084] 101: Through grid voltage phase ω g t Generate phase shift angle control coefficients k .

[0085] 102: Phase shift angle control coefficient k Convert to coefficients m .

[0086] 103: Through the desired current amplitude I o * Obtain the current amplitude correction value I o .

[0087] 104: Positive periodic signal of grid voltage p Make a judgment on the positive periodic signal. p Based on the judgment, the correction value is determined according to the current amplitude. I o Generate the corresponding phase shift angle magnitude φ n According to the phase shift angle amplitude φn and current phase function sin(ω g t+α) obtaining phase shift angle signal φ(t) .

[0088] 105: judging the instantaneous output power of AC side Sgn_Pac , and judging the instantaneous output power of AC side Sgn_Pac , and generating control frequency based on coefficient m and phase shift angle signal φ(t) f s .

[0089] 106: generating PWM control signal of switching tube based on positive period signal p , negative period signal n , phase shift angle control coefficient k , control frequency f s and phase shift angle signal φ(t) , and realizing transient pulsating current control of variable frequency DAB type inverter based on PWM control signal.

[0090] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.​

Claims

1. A method for controlling transient pulsating current in a DAB inverter, characterized in that, include: For grid voltage phase ω g t and grid voltage phase ω g The positive periodic signal p and the negative periodic signal n corresponding to t are obtained; Through the grid voltage phase ω g t generates the phase shift angle control coefficient k; Convert the phase shift angle control coefficient k into coefficient m; By the desired current amplitude I o * Obtain the current amplitude correction value I o ; The positive periodic signal p of the grid voltage is determined, and based on the determination of the positive periodic signal p, the current amplitude correction value I is used. o Generate the corresponding phase shift angle magnitude φ n According to the phase shift angle magnitude φ n and current phase function sin(ω) g The phase shift angle signal φ(t) is obtained by t+α). The instantaneous output power Sgn_Pac on the AC side is determined, and based on the determination of the instantaneous output power Sgn_Pac, the control frequency f is generated according to the coefficient m and the phase shift angle signal φ(t). s ; Based on the positive period signal p, the negative period signal n, the phase shift angle control coefficient k, and the control frequency f s The phase shift angle signal φ(t) generates the PWM control signal for the switching transistor, and the transient pulsating current control of the DAB inverter is realized based on the PWM control signal. During the switching phase, within a time interval t1 before and after the voltage switching point, the phase shift angle control coefficient k is equal to 0.5 to suppress the pulsating current during transient switching; during the non-switching phase, the phase shift angle control coefficient k remains at a specific value k. x To achieve the corresponding function, t1 is less than 0.05T S , 0 < k x <0.5; The conversion of the phase shift angle control coefficient k into coefficient m is expressed as follows: m=2(2k 2 -2k+1); Where k represents the phase shift angle control coefficient, and m represents the coefficient m; The control frequency f s Represented as: Among them, f smax Indicates the maximum switching frequency; The desired current amplitude I o * Obtain the current amplitude correction value I o Including: the desired current amplitude I o * The sinusoidal signal is i o * i o * Subtract i using the subtractor o Then, I1 is obtained through a PI controller, and the desired current amplitude I is obtained. o * After passing through the feedforward controller, I2 is obtained. I1 and I2 are added together by an adder to finally obtain the current amplitude correction value I. o .

2. The control method as described in claim 1, characterized in that, The phase shift angle magnitude φ n Represented as: Among them, L lk U represents leakage inductance. dc This represents the DC side voltage, and N represents the transformer turns ratio.

3. The control method as described in claim 2, characterized in that, The basis is the phase shift angle magnitude φ n and current phase function sin(ω) g The phase shift angle signal φ(t) is obtained by converting t+α) to t+α, including: converting the phase shift angle amplitude φ to t+α. n With current phase function sin(ω) g Multiplying t+α) yields the phase shift angle signal φ(t).

4. The control method as described in claim 3, characterized in that, The phase shift angle control coefficient k is equal to 0.5 and equal to a specific value k. x If there is a time interval t2-t1 between them to achieve a gradual rise and a gradual fall, then the slope of the rising function is a. + and the slope of the descending function a - They are represented as follows: Where ω represents the angular frequency; t2-t1 is less than 0.05T S .

5. A transient pulsating current control system for a DAB inverter, the control system being used to implement the control method according to any one of claims 1-4, characterized in that, The control system includes: Phase-locked loop, for the grid voltage phase ω g t and grid voltage phase ω g The positive periodic signal p and the negative periodic signal n corresponding to t are obtained; module k, via grid voltage phase ω g t generates the phase shift angle control coefficient k; The m module converts the phase shift angle control coefficient k into coefficient m; Feedforward controller and PI controller, used to determine the desired current amplitude I o * Obtain the current amplitude correction value I o ; φ n The module determines the positive periodic signal p of the grid voltage and, based on the determination of the positive periodic signal p, adjusts the current amplitude correction value I. o Generate the corresponding phase shift angle magnitude φ n The phase shift angle magnitude φ n With current phase function sin(ω) g Multiplying t+α) gives φ(t); f s The module determines the instantaneous output power Sgn_Pac on the AC side, and generates a control frequency f based on the coefficient m according to the determination of the instantaneous output power Sgn_Pac. s ; The PWM generation module generates signals based on the positive period signal p, the negative period signal n, and the control frequency f. s And φ(t) generates the PWM control signal for the switching transistor, and the transient pulsating current control of the DAB inverter is realized according to the PWM control signal.

6. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the control method as described in any one of claims 1 to 4.

7. A computer storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the control method as described in any one of claims 1 to 4.

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