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

Abstract

The invention discloses a DAB inverter transient pulsating current control method, system and device and a medium, relates to the technical field of DAB inverter control strategies, and solves the technical problems that an existing variable-frequency DAB inverter cannot output reactive power and transient switching current pulsation exists during reactive power output. According to the technical scheme, the reactive power output function of the variable-frequency DAB type inverter is achieved by means of alternate operation of a forward power transmission mode and a reverse power transmission mode on the basis of the characteristic of bidirectional power flow of the DAB type inverter, and meanwhile current pulsation during transient switching of the inverter is restrained.

Description

Technical Field

[0001] This application relates to the field of DAB inverter control strategy technology, and in particular to a transient pulsating current control method, system, device and medium for DAB inverters. Background Technology

[0002] DAB-type microinverters have advantages over other microinverter topologies, including fewer switching devices, a wider soft-switching range, and bidirectional power transmission. Currently, DAB-type microinverters mainly use two modulation methods: fixed-frequency and variable-frequency. While the variable-frequency control method has high active power efficiency, its reactive power output has received little attention.

[0003] Figure 1 This is a flowchart illustrating the typical control method for a DAB-type inverter in existing technology. This inverter can only output active power, and its output current phase is synchronized with the grid voltage. When the phase of the given current is out of phase with the grid voltage, the output current will oscillate violently in the region where the instantaneous output power is negative. DAB-type micro-inverters have the characteristic of bidirectional power transmission; therefore, by mimicking the forward power transmission mode of output active power, a reverse power transmission mode of input active power is proposed. When the forward power transmission mode and the reverse power transmission mode operate alternately, reactive power can be output, but the grid voltage... u g Switching will cause transient switching current pulsation in the inverter. Figure 2 The experimental waveforms are shown when the output current is in phase with the grid voltage using the existing control method. Figure 3 The experimental waveforms are obtained when the output current and the grid voltage are out of phase when using the existing control method. Figure 2 and Figure 3 It can be seen that the system becomes unstable when the instantaneous output power is negative.

[0004] Based on the above problems, this application comprehensively considers the transient impact of voltage switching and the realization of specific functions, and proposes a transient pulsating current control method for a variable frequency DAB inverter with reactive power output capability. Summary of the Invention

[0005] This application provides a method, system, device, and medium for controlling transient pulsating current in a DAB inverter. The technical objective is to enable the frequency conversion DAB inverter to effectively output reactive power and suppress transient switching current pulsation at the voltage switching point.

[0006] The above-mentioned technical objective of this application is achieved through the following technical solution: A method for controlling transient pulsating current in a DAB inverter includes: Phase of grid voltage oh g tand grid voltage phase oh g t Corresponding positive periodic signal p and negative periodic signals n To obtain; Through grid voltage phase oh g t Generate phase shift angle control coefficients k ; Phase shift angle control coefficient k Convert to coefficients m ; By the expected current amplitude I o * Obtain the current amplitude correction value I o ; 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 f n According to the phase shift angle magnitude f n and current phase function sin(ω g t+α) Obtain the phase shift angle signal φ(t) ; 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 and phase shift angle signal φ(t) Generate control frequency f s ; Based on positive periodic signals p Negative periodic signal n Phase shift angle control coefficient k Control frequency f s and phase shift angle signal φ(t) Generating switching transistors PWM Control signals, according to PWM The control signal enables transient pulsating current control of the DAB inverter. During the switching phase, before and after the voltage switching point t 1 Phase shift angle control coefficient within a given time period k Equal to 0.5 to suppress pulsating current during transient switching; phase shift angle control coefficient during non-switching phases.k Keep it as a specific value k x In order to achieve the corresponding function, t 1 Less than 0.05 T S ,0< k x <0.5.

[0007] Preferably, the phase shift angle control coefficient k Convert to coefficients m , represented as: ; in, k This represents the phase shift angle control coefficient. m Represents coefficients m .

[0008] Preferably, the phase shift angle amplitude f n Represented as: ; in, L lk Indicates leakage inductance. U dc Indicates the DC side voltage. N This indicates the transformer's turns ratio.

[0009] Preferably, the step of determining the phase shift angle magnitude... f n and current amplitude correction value I o Obtain the phase shift angle signal φ(t) This includes: adjusting the phase shift angle magnitude. f n Phase function of current sin(ω g t+α) Multiplying them yields the phase shift angle signal. φ(t) .

[0010] Preferably, the control frequency f s Represented as: ; in, f s max This indicates the maximum switching frequency.

[0011] Preferably, 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 t2 - t 1 To achieve a smooth rise and a smooth fall, the slope of the rising function is... a + and the slope of the descending function a - They are represented as follows: ; Where, ω g Indicates angular frequency; t 2 - t 1 Less than 0.05 T S .

[0012] Preferably, the desired current amplitude is... I o * Obtain the current amplitude correction value I o ,include: 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 .

[0013] A transient pulsating current control system for a DAB inverter, the control system being used to implement the aforementioned transient pulsating current control method for a DAB inverter, the control system comprising: Phase-locked loop (PLL) for grid voltage phase oh g t and grid voltage phase oh g t Corresponding positive periodic signal pand negative periodic signals n To obtain; k The module, via the grid voltage phase oh g t Generate phase shift angle control coefficients k ; m The module will control the phase angle coefficients. k Convert to coefficients m ; Feedforward controllers and PI controllers are used to determine the desired current amplitude. I o * Obtain the current amplitude correction value I o ; f n The module responds to the positive periodic signal 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 f n Phase shift angle magnitude f n Phase function of current sin(ω g t+ α) Multiply to get φ(t) ; f s Module, 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 ; 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.

[0014] 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.

[0015] A computer storage medium storing a computer program, which, when executed by a processor, implements the DAB inverter transient pulsating current control method.

[0016] The above technical solution can achieve at least some of the following technical effects: (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.

[0017] (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

[0018] Figure 1 Here is a flowchart illustrating the structure of the existing DAB-type inverter control method; 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; 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. Figure 4 This is a flowchart illustrating the transient pulsating current control method for DAB inverters in this application embodiment; Figure 5 Examples of embodiments in this application k Module implementation flowchart; Figure 6 Examples of embodiments in this application PWM Module implementation flowchart; Figure 7 This application uses the control method but does not specify the phase shift angle control coefficient. k The experimental waveform exhibits transient switching current pulsation during modulation; Figure 8 The time-shift phase angle control coefficients for the control method of this application k The experimental waveform; Figure 9 The experimental waveform of capacitive reactive power and grid current leading grid voltage when the control method of this application is adopted is shown. Figure 10The experimental waveforms of inductive reactive power generated when the control method of this application is adopted are shown, and the grid current lags behind the grid voltage. Detailed Implementation

[0019] The technical methods of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] like Figure 4 As shown, the DAB inverter transient pulsating current control system described in this application includes a phase-locked loop, k Module, m Module, feedforward controller, PI controller f n Module, f s Modules and PWM Generate the module.

[0021] Phase-locked loops are used to control the phase of the grid voltage. oh g t and grid voltage phase oh g t Corresponding positive periodic signal p and negative periodic signals n Obtain it.

[0022] k The module is used to transmit the phase of the grid voltage. oh g t 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.

[0023] 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). t1 Less than 0.05 T S ,0< k x <0.5.

[0024] 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: ; in, oh g Indicates the angular frequency of the grid voltage; t 2 - t 1 Less than 0.05 T S .

[0025] when hour, k During the transitional descent phase, the calculation formulas differ depending on the interval. and ;when hour, k During the transitional upward phase, the calculation formulas differ depending on the interval. and .

[0026] m The module is used to control the phase angle. k Convert to coefficients m .

[0027] Preferably, the phase shift angle control coefficient k Convert to coefficients m , represented as: ; in, k This represents the phase shift angle control coefficient. m Represents coefficients m .

[0028] Feedforward controllers and PI controllers are used to determine the desired current amplitude. I o * Obtain the current amplitude correction value I o .

[0029] Specifically, the controller used in this application includes a feedforward controller and a feedback PI controller. The feedforward controller can eliminate the deviation caused by the inductive element of the filter, while the feedback PI controller can enable the inverter output current to accurately and stably track the set value, while effectively suppressing the influence of various interferences. Figure 3 , Figure 4 , Figure 7 , Figure 8 , Figure 9 and Figure 10 The experimental results demonstrate that, compared to traditional DAB-type inverters, this application can effectively output reactive power and suppress transient switching current ripple at voltage switching points.

[0030] Preferably, the desired current amplitude is... I o * Obtain the current amplitude correction value I o ,include: 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 .

[0031] f 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 f n Phase shift angle magnitude f n Phase function of current sin (oh g t+α) Multiply to get φ(t) .

[0032] Preferably, the phase shift angle amplitude f n Represented as: ; in, L lk Indicates leakage inductance. U dc Indicates the DC side voltage. N This indicates the transformer's turns ratio.

[0033] Preferably, the step of determining the phase shift angle magnitude... f n and current amplitude correction value I o Obtain the phase shift angle signal φ(t) This includes: adjusting the phase shift angle magnitude. f n Phase function of current sin(ω g t+α) Multiplying them yields the phase shift angle signal. φ(t) .

[0034] 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 .

[0035] Preferably, the control frequency f s Represented as: ; in, f s maxThis indicates the maximum switching frequency.

[0036] 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.

[0037] 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 .

[0038] like Figure 4 As shown, the transient pulsating current control method for DAB inverters described in this application includes: 100: Phase of grid voltage oh g t and grid voltage phase oh gt Corresponding positive periodic signal p and negative periodic signals n Obtain it.

[0039] 101: Through grid voltage phase oh g t Generate phase shift angle control coefficients k .

[0040] 102: Phase shift angle control coefficient k Convert to coefficients m .

[0041] 103: Through the desired current amplitude I o * Obtain the current amplitude correction value I o .

[0042] 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 f n According to the phase shift angle magnitude f n and current phase function sin(ω g t+α) Obtain the phase shift angle signal φ(t) .

[0043] 105: 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 and phase shift angle signal φ(t) Generate control frequency f s .

[0044] 106: Based on positive periodic signals p Negative periodic signal n Phase shift angle control coefficient k Control frequency f s and phase shift angle signal φ(t) Generate a PWM control signal for the switching transistor, and use the PWM control signal to control the transient pulsating current of the DAB inverter.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method of controlling transient inrush current in a DAB inverter, the method comprising: include: to the grid voltage phase ω g t and the grid voltage phase ω g t the corresponding positive cycle signal p and the negative cycle signal n are obtained; by the grid voltage phase ω g t generating a phase-shift angle control coefficient k ; The phase-shifting angle control coefficient k is converted into a coefficient m ; By the expected current amplitude I o * Obtaining a current amplitude correction value I o ; A positive cycle signal of a grid voltage p A determination is made as to whether the positive cycle signal p A current amplitude correction value is corrected on the basis of the determination I o A corresponding phase-shifted angle amplitude is generated φ n A phase-shifted angle signal is generated on the basis of the phase-shifted angle amplitude φ n and a current phase function sin(ω g t+α) φ(t) ​​ determining an instantaneous output power on an ac side Sgn_Pac determining an instantaneous output power on an ac side Sgn_Pac determining an instantaneous output power on an ac side m determining an instantaneous output power on an ac side φ(t) determining an instantaneous output power on an ac side f s ; Based on positive periodic signals p Negative periodic signal n Phase shift angle control coefficient k Control frequency f s and phase shift angle signal φ(t) Generating switching transistors PWM Control signals, according to PWM The control signal enables transient pulsating current control of the DAB inverter. wherein, during the switching phase, the phase-shift angle control coefficient t 1 is equal to 0.5 to damp the pulsating current of the transient switching; during the non-switching phase the phase-shift angle control coefficient k is maintained at a certain value k k x to implement the corresponding function, t 1 is less than 0.05 T S , 0 < a < 0.5 k x < 0.5.​ 2. The control method as described in claim 1, characterized in that, The phase shift angle control coefficient k is converted into a coefficient m is expressed as: ； wherein k denotes a phase shift angle control coefficient, m denotes a coefficient m .

3. The control method as described in claim 2, characterized in that, The phase shift angle amplitude φ n is represented as: ； wherein, L lk represents leakage inductance, U dc represents DC side voltage, N represents the transformation ratio of the transformer.

4. The control method as described in claim 3, characterized in that, The phase-shift angle amplitude φ n and the current phase function sin(ω g t+α) The phase-shift angle signal φ(t) is obtained by multiplying the phase-shift angle amplitude φ n and the current phase function sin(ω g t+α) The phase-shift angle signal φ(t) .

5. The control method as described in claim 4, characterized in that, The control frequency f s is represented as: ； wherein f s max denotes the maximum switching frequency.

6. The control method as described in claim 5, characterized in that, the phase-shifting angle control coefficient k there is a time interval between the value equal to 0.5 and the value equal to a certain value k x t 2 - t 1 to achieve a gentle rise and a gentle fall, the rise function slope a + and the fall function slope a - are respectively represented as:​ ； wherein represents the angular frequency; t 2 - t 1 less than 0.05 T S .

7. The control method as described in claim 6, characterized in that, The passing through expected current amplitude I o * Obtaining current amplitude correction value I o comprising: desired current amplitude I o * sinusoidal signal is i o * , i o * subtracted by a subtractor i o after which a PI controller is obtained I 1 , desired current amplitude I o * after which a feedforward controller is obtained I 2 , I 1 and I 2 which are added by an adder to finally obtain the current amplitude correction value I o .

8. A DAB inverter transient ripple current control system for implementing the control method of any one of claims 1 to 7, characterized by, The control system includes: phase-locked loop, to the grid voltage phase ω g t and to the grid voltage phase ω g t a corresponding positive periodic signal p and a negative periodic signal n is obtained; k module, by grid voltage phase ω g t generating phase-shift angle control coefficient k ; m modules, the phase shift angle control coefficient k converted into a coefficient m ; a feed forward controller and a PI controller for adjusting the current amplitude according to a desired current amplitude I o * obtaining a current amplitude correction value I o ; φ n module, positive cycle signal of the grid voltage p determines, on the basis of the positive cycle signal p determined, on the basis of the current amplitude correction value I o corresponding phase-shifted angle amplitude φ n , the phase-shifted angle amplitude φ n and the current phase function sin(ω g t+α) are multiplied to obtain φ(t) ; f s Module, 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 ; 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 PW M control signal, according to PWM The control signal enables transient pulsating current control of the DAB inverter.

9. 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 7.

10. 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 7.

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