An IPOS-DAB communication-free switching harmonic elimination control method

Abstract

The application discloses an IPOS-DAB non-communication switch harmonic elimination control method, which comprises the following steps: firstly, collecting input side voltage, extracting the DC component and the harmonic component of double switch frequency of the voltage, and extracting the amplitude and phase of the total harmonic component of double switch frequency; calculating the harmonic component of double switch frequency of the common point voltage generated by the self module; subtracting the self module harmonic component from the total harmonic component to obtain the sum of other module components; adjusting the phase of the self module harmonic component to be opposite to the phase of the sum of other module harmonic components, so that the total amount of switch frequency harmonics is minimum. On the basis of the IPOS-DAB converter topology, by analyzing the harmonic component of the switch frequency, only certain voltage signals need to be collected, the PWM phase of the self module is closed-loop adjusted, and any communication signal is not needed, so that the sum of the twice switch harmonic vectors of each module is zero, the true modularization is achieved, namely, plug and play, the total voltage and current harmonics are reduced, and the filter capacity is reduced.

Description

Technical Field

[0001] This invention relates to the field of switch harmonic elimination technology, specifically to an IPOS-DAB non-communication switch harmonic elimination control method. Background Technology

[0002] The DAB (dual active bridge) converter, as an isolated DC-DC converter, boasts advantages such as high power density, medium-to-high frequency transformer isolation, bidirectional power flow, and easy modular series-parallel connection. DAB converters are widely used in DC microgrids, photovoltaics, and wind power. However, a single converter has limited power capacity, high harmonic content, and requires a large filter, making it unsuitable for applications with high capacity requirements. In modular parallel operation, theoretically, an unlimited number of modules can be connected in parallel, arbitrarily increasing power capacity. When each module is interleaved, it can also eliminate total voltage and current switching harmonics, increasing the ripple frequency to n times its original value, significantly reducing filter capacity requirements. Parallel operation greatly improves the stability of the power supply system; if a few modules fail or require maintenance, only those modules need to be disconnected, without affecting the operation of the entire power supply system.

[0003] Most research on distributed control focuses on the equal distribution of steady-state power, with little attention paid to whether the PWM control waveforms of each module are interleaved or synchronized. Existing literature almost entirely lacks methods for achieving interleaved parallel control without communication. For interleaved parallel converters, traditional solutions often employ centralized control or require high-speed communication between modules to transmit synchronization signals. The stable operation of each module depends on high-speed and stable communication; in centralized control mode, if the main controller fails, the entire system will be paralyzed. When synchronizing the phase of each module through high-speed communication, communication delay, line length, and communication stability all affect the synchronization effect. To reduce filter capacity and simultaneously reduce total voltage and current harmonics, there is an urgent need for a communication-free interleaved parallel control method or a high-frequency switching harmonic cancellation control method. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide an IPOS-DAB harmonic cancellation control method without communication switches. Under the premise of satisfying the phase-shift control of dual active bridges, the overall PWM phase can be freely shifted, and the phase of each module can be adjusted according to the calculated harmonic phase to achieve switch harmonic cancellation. The technical solution is as follows:

[0005] A harmonic cancellation control method for IPOS-DAB without communication switches includes the following steps:

[0006] Step 1: For the DAB converter input parallel-output series operation circuit, collect its input side voltage u. in (t), and extract the DC component u of the voltage. in_dcThe total harmonic component h of the second switching harmonic at twice the switching frequency 2nd Its amplitude and phase; the operating circuit includes n DAB converter modules using single-phase-shift control;

[0007] Step 2: For module i in the n DAB converter modules, calculate the harmonic component h of the common point voltage generated by its own module at twice the switching frequency. i 2nd ;

[0008] Step 3: Subtract the harmonic components of module i from the total harmonic components to obtain the sum h of the components of the other DAB converter modules. 2nd -h i 2nd ;

[0009] Step 4: Adjust the phase of the harmonic component of module i to be opposite to the phase of the sum of the harmonic components of other DAB converter modules, so as to minimize the total amount of harmonics at the second switching frequency.

[0010] Step 5: Output voltage feedback, the PI controller generates a single shift ratio compared to the d control to stabilize the output voltage.

[0011] Furthermore, the parameters in step 1 are represented as follows:

[0012]

[0013] Among them, u in (t) represents the input voltage, obtained through sampling. Due to the parallel connection on the input sides, the input voltage of each module is equal; u in_dc h is the DC component of the input voltage. 2nd The total harmonic components of the second switching harmonic of the input voltage, including amplitude and phase information, are the result of the combined action of n DAB converter modules; h i 2nd f represents the component of module i in the total harmonics; sw The switching frequency; ω1 = 4πf sw ; B is the sum of harmonics of the input voltage at 4k and above. k The amplitude of the 2kth switching harmonic; The 2kth switching harmonic phase; c i,1 and d i,1 The cosine and sine functions, respectively, are the contents of the Fourier decomposition, T. s The switching cycle.

[0014] Furthermore, in step 2, the harmonic component h of module i i 2nd The specific calculations are as follows:

[0015] Step 2.1: Under the control of single-phase shifting, the phase-shifting inductor current i of the DAB converter... L The phase-shifting inductor current i is obtained from the current operating parameters. L Within half a cycle, it is represented as:

[0016]

[0017] Where d represents the difference between single displacement and u ini The input voltage of module i; u outi L is the output voltage of module i; i I1 is the phase-shifting inductance value of module i, and N is the transformer turns ratio; Li (dT s ), I2=i Li (0.5dT s );

[0018] Step 2.2: Based on the calculated phase-shifting inductor current i L The input current i of the DAB converter module i is doubled by the switching frequency and the base frequency. ini Its harmonic information is obtained by performing Fourier series decomposition:

[0019]

[0020] Among them, a i,0 For i ini DC component; A i,k The 2kth switching harmonic amplitude of the input current to DAB module i; The k-th switching harmonic phase of the input current to DAB module i; u ini The input voltage of module i; u outi f is the output voltage of module i; sw f is the switching frequency. sw =1 / T s ;a i,k and b i,k The amplitudes of the cosine and sine functions were obtained by Fourier decomposition of the 2kth switching harmonics, respectively.

[0021] Step 2.3: Based on the calculated input current i ini The harmonic components h of module i are calculated. i 2nd :

[0022]

[0023] Among them, L f For the input-side filter inductor; C in The sum of the parallel capacitors on the input side; ω1 = 4πf swA i,1 The second switching harmonic amplitude of the input current to module i; The second switching harmonic phase of the input current to module i; L i a is the phase-shifting inductance value of module i; i,1 and b i,1 The amplitudes of the cosine and sine functions were obtained by Fourier decomposition of the second-order switching harmonics.

[0024] The beneficial effects of this invention are:

[0025] 1) This invention employs a non-communication switching harmonic cancellation control method, which can effectively cancel the secondary switching harmonics of the DAB without any communication, thereby reducing the high-frequency harmonics and filter capacity of the entire system.

[0026] 2) This invention can minimize secondary switching harmonics even under conditions of parameter asymmetry or operating power asymmetry;

[0027] 3) The method proposed in this invention has no requirement on the number of modules and can be expanded with any number of modules without affecting the original DAB control. Attached Figure Description

[0028] Figure 1 This is a circuit diagram showing the input parallel and output series operation of a modular DAB converter.

[0029] Figure 2 The key waveforms under DAB single-phase shift control provided in the embodiments of this application are shown.

[0030] Figure 3 The diagram below shows the harmonic cancellation control block diagram of the IPOS-DAB secondary switch provided in the embodiments of this application. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0032] The IPOS-DAB harmonic elimination control method of the present invention includes the following steps:

[0033] Step 1: In a DAB converter input-parallel-output-series (IPOS) operating circuit containing n DAB converter modules, the input voltage is acquired, and the DC component of the voltage and the total harmonic component h of the second switching harmonic at twice the switching frequency are extracted. 2nd .

[0034] Modular DAB converter input parallel operation circuit with series output, such as Figure 1As shown, the entire system consists of n DAB converter modules connected in parallel. The modules adopt distributed control, and each module only needs to collect its own voltage and current without communicating with other modules.

[0035]

[0036] Among them, u in (t) represents the input voltage, obtained through sampling. Due to the parallel connection on the input sides, the input voltage of each module is equal; u in_dc h is the DC component of the input voltage. 2nd The second switching harmonic of the input voltage, including amplitude and phase information, is the result of the combined action of n DAB converter modules; h i 2nd f represents the component of module i in the total harmonics; sw The switching frequency; ω1 = 4πf sw ; The present invention does not consider the sum of harmonics of the input voltage at or above 4kΩ, but only considers the second switching harmonic h, which has the highest content. 2nd c i,1 d i,1 The content of cosine and sine functions in the Fourier decomposition.

[0037] Step 2: For module i, calculate the harmonic component h of the common point voltage generated by its own module at twice the switching frequency. i 2nd .

[0038] Step 2.1: Under the control of single-phase shifting, the phase-shifting inductor current i of the DAB converter... L The phase-shifting inductor current i is obtained from the current operating parameters. L Within half a cycle, it is represented as:

[0039]

[0040] Where d represents the difference between single displacement and u ini u outi These are the input and output voltages of module i, where i = 1, 2, ..., n; T s For the switching period, L i I1 is the phase-shifting inductance value of module i, and N is the transformer turns ratio; Li (dT s ), I2=i Li (0.5dT s );

[0041] Step 2.2: Based on the calculated phase-shifting inductor current i LThe input current i of the DAB converter module i is doubled by the switching frequency and the base frequency. ini The harmonic information is obtained by performing Fourier series decomposition.

[0042] Module i Input Current i ini and phase-shifting inductor current i L There is a corresponding relationship: in the range of 0-0.5T s in,i in =i L ; at 0.5T s -T s in,i in =-i L Module i input current i ini It is based on i L The calculation is obtained, and then i is applied. ini Fourier decomposition yields its second harmonic information, represented as follows:

[0043]

[0044] Among them, a i,0 For i ini DC component; A i,k The 2kth switching harmonic amplitude of the input current to DAB module i; The k-th switching harmonic phase of the input current to DAB module i; d is the single-shift ratio; N is the transformer turns ratio; L i The phase-shifting inductance value for module i; u ini The input voltage of module i; u outi f is the output voltage of module i; sw f is the switching frequency. sw =1 / T s ;a i,k and b i,k The amplitudes of the cosine and sine functions were obtained by Fourier decomposition of the 2kth switching harmonics, respectively.

[0045] Step 2.3: Based on the calculated input current i ini The harmonic components h of module i are calculated. i 2nd .

[0046] The DAB converter module uses single-phase shift control. Taking module 1 as an example, the typical control waveform of a DAB in single-phase shift is as follows: Figure 2 As shown. The switching harmonics in the DAB converter are formed by the high-frequency switching of the power switch. Taking module i as an example, under the control of single-phase shifting, the phase-shifting inductor current i L The current operating parameters (shift ratio d, input voltage u) can be used to determine the operating parameters. ini Output voltage u outiThe transformer turns ratio N is obtained. The harmonic component h of module i is calculated. i 2nd and input current i ini The relationship between them is linear, h i 2nd In fact, it is based on i ini The harmonics are obtained from the two values, which have multiple scaling factors in front of them and a phase difference of π / 2. Therefore, from equations (2) and (3), we get:

[0047]

[0048] Among them, L f For the input-side filter inductor; C in The sum of the parallel capacitors on the input side; ω1 = 4πf sw A i,1 The second switching harmonic amplitude of the input current to DAB module i; The second switching harmonic phase of the input current to DAB module i; d is the single-shift ratio; N is the transformer turns ratio; L i The phase-shifting inductance value for module i; u ini The input voltage of module i; u outi The output voltage of module i; a i,1 and b i,1 The amplitudes of the cosine and sine functions were obtained by Fourier decomposition of the second-order switching harmonics.

[0049] Step 3: Use the total harmonics h 2nd Subtract the harmonic components h of the DAB converter module itself i 2nd The sum of the components of other DAB converter modules is obtained.

[0050] Step 4: Adjust the phase of the harmonic components of the DAB converter module itself to be opposite to the phase of the sum of the harmonic components of other DAB converter modules, so as to minimize the total amount of second-order switching harmonics.

[0051] Step 5: Output voltage feedback, the PI controller generates a single shift ratio compared to the d control to stabilize the output voltage.

[0052] Since the frequency of the harmonic with the largest amplitude generated during DAB operation is twice the switching frequency, the switching harmonic elimination in this invention also targets harmonics at this frequency. After extracting the total secondary switching harmonic content on the input-side capacitor and the component occupied by the module itself, the difference between the two yields the sum of the components occupied by other modules excluding the module itself. Then, the phase of the harmonic component of the module itself is adjusted to be opposite to the phase of the sum of the harmonic components of other modules, thereby minimizing the secondary switching harmonics. The complete control block diagram is as follows: Figure 3 As shown.

[0053] Compared to DAB control, which uses a fixed output voltage and output voltage feedback, and PI adjustment for single phase shift, DAB's single phase shift control and harmonic phase control do not affect each other.

Claims

1. A harmonic cancellation control method for IPOS-DAB without communication switches, characterized in that, Includes the following steps: Step 1: For the DAB converter input parallel-output series operation circuit, collect its input side voltage u. in (t), and extract the DC component u of the voltage. in_dc The total harmonic component h of the second switching harmonic at twice the switching frequency 2nd Its amplitude and phase; the operating circuit includes n DAB converter modules using single-phase-shift control; Step 2: For module i in the n DAB converter modules, calculate the harmonic component of the common point voltage generated by its own module at twice the switching frequency. Step 3: Subtract the harmonic components of module i from the total harmonic components to obtain the sum h of the components of the other DAB converter modules. 2nd -h i 2nd ; Step 4: Adjust the phase of the harmonic component of module i to be opposite to the phase of the sum of the harmonic components of other DAB converter modules, so as to minimize the total amount of harmonics at the second switching frequency. Step 5: Output voltage feedback, the PI controller generates a single shift ratio compared to the d control to stabilize the output voltage.

2. The IPOS-DAB harmonic elimination control method without communication switch according to claim 1, characterized in that, The parameters in step 1 are represented as follows: Among them, u in (t) represents the input voltage, obtained through sampling. Since the input sides are connected in parallel, the input voltage of each module is equal. u in_dc h is the DC component of the input voltage. 2nd The total harmonic components of the second switching harmonic of the input voltage, including amplitude and phase information, are the result of the combined action of n DAB converter modules; h i 2nd f represents the component of module i in the total harmonics; sw The switching frequency; ω1 = 4πf sw ; B is the sum of harmonics of the input voltage at 4k and above. k The amplitude of the 2kth switching harmonic; The 2kth switching harmonic phase; c i,1 and d i,1 The cosine and sine functions, respectively, are the contents of the Fourier decomposition, T. s The switching cycle.

3. The IPOS-DAB harmonic elimination control method without communication switch according to claim 2, characterized in that, In step 2, the harmonic component h of module i i 2nd The specific calculations are as follows: Step 2.1: Under the control of single-phase shifting, the phase-shifting inductor current i of the DAB converter... L The phase-shifting inductor current i is obtained from the current operating parameters. L Within half a cycle, it is represented as: Where d represents the difference between single displacement and u ini The input voltage of module i; u outi L is the output voltage of module i; i I1 is the phase-shifting inductance value of module i, and N is the transformer turns ratio; Li (dT s ), I2=i Li (0.5dT s ); Step 2.2: Based on the calculated phase-shifting inductor current i L The input current i of the DAB converter module i is doubled by the switching frequency and the base frequency. ini Its harmonic information is obtained by performing Fourier series decomposition: Among them, a i,0 For i ini DC component; A i,k The 2kth switching harmonic amplitude of the input current to DAB module i; The k-th switching harmonic phase of the input current to DAB module i; u ini The input voltage of module i; u outi f is the output voltage of module i; sw f is the switching frequency. sw =1 / T s ;a i,k and b i,k The amplitudes of the cosine and sine functions were obtained by Fourier decomposition of the 2kth switching harmonics, respectively. Step 2.3: Based on the calculated input current i ini The harmonic components h of module i are calculated. i 2nd : Among them, L f For the input-side filter inductor; C in The sum of the parallel capacitors on the input side; ω1 = 4πf sw A i,1 The second switching harmonic amplitude of the input current to module i; The second switching harmonic phase of the input current to module i; L i a is the phase-shifting inductance value of module i; i,1 and b i,1 The amplitudes of the cosine and sine functions were obtained by Fourier decomposition of the second-order switching harmonics.

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