ACDC module input current harmonic suppression method based on pattern recognition

Abstract

The invention discloses an ACDC module input current harmonic suppression method based on pattern recognition, which comprises a primary side equivalent resistor R1, a primary side leakage inductor L1, an excitation inductor L2, a transformer T1, a secondary side leakage inductor L3 and a secondary side equivalent resistor R2, the input end of the primary side equivalent resistor R1 is connected with a positive AC current input, the output end of the primary side equivalent resistor R1 is electrically connected with the input end of the primary side leakage inductor L1, and the output end of the primary side leakage inductor L2 is electrically connected with the output end of the secondary side equivalent resistor R2. The output end of the primary side leakage inductor L1 is connected to the first terminal of the transformer T1, and the second terminal of the transformer T1 is connected with the negative AC current input. According to the ACDC module input current harmonic suppression method based on mode recognition provided by the invention, only the inductive current needs to be sampled and controlled, and a power device is protected, so that the economic cost is saved; field adjustment is easy, parameter robustness is good, and adaptability is high; high-frequency components can be suppressed; a good inhibition effect is achieved on different resonance points, and the reliability and the stability are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of ACDC module input current harmonic suppression, and in particular to an ACDC module input current harmonic suppression method based on pattern recognition. Background Art

[0002] With the advent of the 5G era, large communication companies such as BAT and the three major operators have launched the infrastructure construction of data centers. As a power supply equipment, data center power supply is undoubtedly the guarantee for the normal operation of the data center. Information communication uses 10kV AC input DC uninterruptible power supply as a kind of data center power supply, such as Figure 7 As shown in the figure, the structure of the phase-shifting transformer + ACDC module can offset the current harmonic THDI characteristics by utilizing the phase difference of each winding of the phase-shifting transformer, eliminating the PFC part of the ACDC module, making it have the advantages of fewer intermediate links, high efficiency, and good performance. However, the secondary leakage inductance of the phase-shifting transformer will resonate with the input capacitor and high-frequency inductance of the ACDC module, thus affecting the operating stability, and in severe cases, damaging the ACDC module.

[0003] like Figure 7 As shown, the LCL filter has a filtering effect on the input voltage / current, but there is a resonance spike problem. In view of the resonance spike problem of the LCL filter, there are currently two main methods: passive damping and active damping. Passive damping has a good suppression effect but will increase losses, and the added damping device absorbs the high-frequency components in the circuit for a long time. Poor heat dissipation may cause device damage and reduce product reliability; active damping has a certain suppression effect on fixed resonance peaks, but the secondary leakage inductance of phase-shifting transformers of different capacities varies greatly. Even if the secondary leakage inductance of phase-shifting transformers of the same capacity has a certain discrete type, only the fixed resonance point is suppressed, and there will still be a large harmonic component in the input current, and there is a situation where the resonance cannot be suppressed; the secondary leakage inductance of the phase-shifting transformer cannot be ignored and has a certain discrete type. For the DC uninterruptible power supply with 10kV AC input for information communication, the present invention proposes a method for suppressing the input current harmonics of the ACDC module based on pattern recognition. Summary of the invention

[0004] The purpose of the present invention is to provide an ACDC module input current harmonic suppression method based on pattern recognition, which only needs to sample the inductor current, and protect the power device while controlling it, saving economic costs, having good parameter robustness and high adaptability, being able to suppress high-frequency components, having good suppression effects on different resonance points, and having high reliability and stability, so as to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a method for suppressing harmonics of input current of an ACDC module based on pattern recognition, comprising a primary equivalent resistor R1, a primary leakage inductance L1, an excitation inductance L2, a transformer T1, a secondary leakage inductance L3 and a secondary equivalent resistor R2, wherein the input end of the primary equivalent resistor R1 is connected to the positive AC current input, the output end of the primary equivalent resistor R1 is electrically connected to the input end of the primary leakage inductance L1, and the output end of the primary leakage inductance L1 is connected to the Terminal 1, terminal 2 of the transformer T1 is connected to the negative AC current input, the input end of the excitation inductor L2 is connected to the output end of the primary leakage inductor L1, and the output end of the excitation inductor L2 is connected to terminal 2 of the transformer T1; terminal 3 of the transformer T1 is connected to the input end of the secondary leakage inductor L3, the output end of the secondary leakage inductor L3 is connected to the input end of the secondary equivalent resistor R2, and the output end of the secondary equivalent resistor R2 is connected to the positive DC output terminal; terminal 4 of the transformer T1 is connected to the negative DC output terminal.

[0006] Preferably, the output end of the secondary leakage inductor L3 is connected in parallel with an EMI capacitor C1, the output end of the EMI capacitor C1 is connected to terminal 4 of the transformer T1, and a PFC high-frequency inductor L4 is connected in series between the secondary leakage inductor L3 and the secondary equivalent resistor R2.

[0007] Preferably, a resistor R3 is connected in parallel at both ends of the EMI capacitor C1.

[0008] A method for suppressing harmonics of input current of an ACDC module based on pattern recognition. The ACDC module recognition process is as follows:

[0009] S1: For the resistor R3 required to suppress different resonance peaks, the required resistance value of the resistor R3 is obtained through a large number of experiments and theoretical calculations, and a GRx(s) table is prepared and stored in the control device in advance;

[0010] S2: iLabc and Uabc are obtained through experimental sampling, and then the sampled iLabc and Uabc are processed by the Fourier transform method;

[0011] S3: Processing to obtain the content of each harmonic, and judging whether resonance occurs according to the content of each harmonic detected;

[0012] S4: When it is determined that no resonance occurs, the process ends. When it is determined that resonance occurs, the frequency point with the largest harmonic content is taken as the resonance peak. The GRx(s) corresponding to the resonance peak is obtained through the GRx(s) table in the control device. The resistor R3 is adjusted to the optimal resistance value for suppressing the resonance peak, and then the process ends.

[0013] Compared with the prior art, the ACDC module input current harmonic suppression method based on pattern recognition proposed in the present invention has the following gains compared with the existing ACDC module input current harmonic suppression method and resonance suppression method:

[0014] 1. Only the inductor current needs to be sampled to protect the power devices while controlling them, thus saving economic costs.

[0015] 2. Easy to adjust on site, good parameter robustness and high adaptability;

[0016] 3. Compared with the existing harmonic suppression methods, it can suppress high-frequency components;

[0017] 4. The inductor current harmonic component of the ACDC module is controlled within 1.3%, and it can operate stably in different phase-shifting transformer systems, with good suppression effect on different resonance points, thus improving the reliability and adaptability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is the circuit principle diagram of the present invention;

[0019] Figure 2 A flow chart for module identification of the present invention;

[0020] Figure 3 is an equivalent mathematical model diagram of the control loop of the present invention;

[0021] Figure 4 The waveform diagram of the resonance peak change corresponding to the change of the transformer leakage inductance of the present invention;

[0022] Figure 5 The waveform diagram of the input current harmonic content of the present invention;

[0023] Figure 6 The input voltage and current waveform diagram of the present invention;

[0024] Figure 7 It is the principle diagram of the existing harmonic suppression circuit of the present invention;

[0025] Figure 8 is an equivalent mathematical model diagram of the existing control loop of the present invention;

[0026] Fig. 9 It is a waveform diagram of the resonance peak change corresponding to the change of leakage inductance of the existing transformer of the present invention;

[0027] Fig.10 The waveform diagram of the harmonic content of the existing input current of the present invention;

[0028] Fig.11 1 is a diagram of the existing input voltage and current waveform of the present invention. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] See also Figure 1 , a method for suppressing harmonics of input current of an ACDC module based on pattern recognition, comprising a primary equivalent resistor R1, a primary leakage inductance L1, an excitation inductance L2, a transformer T1, a secondary leakage inductance L3 and a secondary equivalent resistor R2, wherein the input end of the primary equivalent resistor R1 is connected to a positive AC current input, the output end of the primary equivalent resistor R1 is electrically connected to the input end of the primary leakage inductance L1, the output end of the primary leakage inductance L1 is connected to a No. 1 terminal of the transformer T1, the No. 2 terminal of the transformer T1 is connected to a negative AC current input, the input end of the excitation inductance L2 is connected to the output end of the primary leakage inductance L1, and the output end of the excitation inductance L2 is connected to the No. 2 terminal of the transformer T1; the No. 3 terminal of the transformer T1 is connected to the input end of the secondary leakage inductance L3, the output end of the secondary leakage inductance L3 is connected to the input end of the secondary equivalent resistor R2, and the output end of the secondary equivalent resistor R2 is connected to the positive DC output terminal; the No. 4 terminal of the transformer T1 is connected to the negative DC output terminal.

[0031] As a further embodiment of the present invention, Figure 1 As shown, the output end of the secondary leakage inductor L3 is connected in parallel with the EMI capacitor C1, the output end of the EMI capacitor C1 is connected to the No. 4 terminal of the transformer T1, and the PFC high-frequency inductor L4 is connected in series between the secondary leakage inductor L3 and the secondary equivalent resistor R2, wherein the secondary leakage inductor L3 and the EMI capacitor C1 and the PFC high-frequency inductor L4 of the ACDC module form an LCL filter structure.

[0032] As a further embodiment of the present invention, Figure 1 As shown, the two ends of the EMI capacitor C1 are connected in parallel with a resistor R3.

[0033] like Figure 2 As shown, a method for suppressing harmonics of input current of an ACDC module based on pattern recognition is characterized in that the module recognition process is as follows:

[0034] Step 1: For the resistor R3 required to suppress different resonance peaks, the required resistance value of the resistor R3 is obtained through a large number of experiments and theoretical calculations, and a GRx(s) table is prepared and stored in the control device in advance;

[0035] Step 2: Get iLabc and Uabc through experimental sampling, and then process the sampled iLabc and Uabc using the Fourier transform method;

[0036] Step 3: Process and obtain the content of each harmonic, and determine whether resonance occurs according to the content of each harmonic detected;

[0037] Step 4: When it is determined that no resonance occurs, the process ends. When it is determined that resonance occurs, the frequency point with the largest harmonic content is taken as the resonance peak. The GRx(s) corresponding to the resonance peak is obtained through the GRx(s) table in the control device. The resistor R3 is adjusted to the optimal resistance value to suppress the resonance peak, and then the process ends.

[0038] In the ACDC module input current harmonic suppression method based on pattern recognition, since the current flowing through the power device is actually the inductor current, in practice, a certain protection must be performed on the inductor current to ensure that the ACDC module will not have device damage, system shutdown and other faults due to changes in the external environment during actual operation. The current flowing through the filter capacitor in the entire cycle is zero. Therefore, the input current can be controlled by closed-loop control of the inductor current. First, the inductor current and input voltage are collected, and then DFT / FFT, i.e., discrete / fast Fourier transform, is performed on the collected inductor current and input voltage to obtain each harmonic component in the inductor current and input voltage, and then it is determined whether the ACDC module is working in a normal state or a resonant state. According to different working states, the connected resistor R3 is adjusted to adjust the inductor current flowing through the power device.

[0039] The equivalent mathematical model of the control loop of the ACDC module input current harmonic suppression method based on pattern recognition is as follows: Figure 3 As shown, where u bus * (S) is the given value of the DC bus voltage of the ADDC module; u bus (s) is the sampling value of the DC bus voltage of the ADDC module; Gv(s) is the voltage outer loop transfer function; Sin() is the sine value of the parameter; PLL is the phase-locked loop; RV module is the virtual resistance value; i L * (s) is the given value of the inductor current of the ADDC module: i L (S) is the sampling value of the inductor current of the ADDC module; G I (S) is the current inner loop transfer function; |u in (S)| is the input voltage feedforward, Kspwm is the modulation ratio, which is about 0.8; L is A D DC module power inductor inductance; R is the parasitic resistance of the ADDC module power inductor; i o (S) is the output current of the ADDC module; i c(S) is the capacitor current of the ADDC module, and C is the capacitance of the power energy storage capacitor of the ADDC module.

[0040] In order to verify the feasibility of the ACDC module input current harmonic suppression method based on pattern recognition, the inverter module is built on the Matlab / Simulink simulation platform for simulation verification. The topology structure and control method refer to the content described above. Fig. 9 As shown in the figure, when the transformer leakage inductance changes, it will resonate with the module, the resonance peak is large, and the phase jumps by 180°, making it difficult for the system to operate stably. After adding the resistor R3 with the optimal harmonic suppression resistance value, as shown in the figure, Figure 4 As shown, the resonance peak is significantly suppressed and the characteristics of other frequency bands of the input filter are basically not changed, which confirms the feasibility of this method.

[0041] according to Fig. 9 Among the three different resonance peaks shown, the resonance peak close to 8kHz is selected for further simulation analysis, and the ACDC module power is the rated power. Fig.10 As shown in Figure 1, the overall harmonic content of the input current is as high as 6.59%, of which the 8kHz content is relatively high; Fig.11 As shown in the figure, both the input current (a) and the input voltage (b) are oscillating, which causes serious heating of the power devices, increases inverter losses, and even damages the power devices, making it impossible for the system to operate stably for a long time.

[0042] By using the harmonic suppression method proposed in the present invention, the harmonic content of the input current is as follows: Figure 5 As shown in Figure 2, the overall harmonic content of the input current is reduced to 1.29%. Figure 6 As shown, the input current (a) and input voltage (b) have good sinusoidality, the voltage and current waveforms are smooth, the ACDC module loss is small, and the system can operate stably for a long time.

[0043] Compared with the existing ACDC module input current harmonic suppression method and resonance suppression method, the ACDC module input current harmonic suppression method based on pattern recognition proposed in the present invention can automatically identify the resonance point of the phase-shifting transformer and the ACDC module, perform active damping suppression, greatly improve the adaptability of the ACDC module, reduce the input current harmonics, and have the following gains:

[0044] 1. Only the inductor current needs to be sampled to protect the power devices while controlling them, thus saving economic costs.

[0045] 2. Easy to adjust on site, good parameter robustness and high adaptability;

[0046] 3. Compared with the existing harmonic suppression methods, it can suppress high-frequency components;

[0047] 4. The inductor current harmonic component of the ACDC module is controlled within 1.3%, and it can operate stably in different phase-shifting transformer systems, with good suppression effect on different resonance points, thus improving the reliability and adaptability of the system.

[0048] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for suppressing harmonics of input current of an ACDC module based on pattern recognition, comprising a primary side equivalent resistor R1, a primary side leakage inductance L1, an excitation inductance L2, a transformer T1, a secondary side leakage inductance L3 and a secondary side equivalent resistor R2, characterized in that: The input end of the primary equivalent resistor R1 is connected to the positive AC current input, the output end of the primary equivalent resistor R1 is electrically connected to the input end of the primary leakage inductance L1, the output end of the primary leakage inductance L1 is connected to terminal 1 of the transformer T1, terminal 2 of the transformer T1 is connected to the negative AC current input, the input end of the excitation inductance L2 is connected to the output end of the primary leakage inductance L1, and the output end of the excitation inductance L2 is connected to terminal 2 of the transformer T1; terminal 3 of the transformer T1 is connected to the input end of the secondary leakage inductance L3, the output end of the secondary leakage inductance L3 is connected to the input end of the secondary equivalent resistor R2, and the output end of the secondary equivalent resistor R2 is connected to the positive DC output terminal; terminal 4 of the transformer T1 is connected to the negative DC output terminal.

2. The method for suppressing harmonics of input current of an ACDC module based on pattern recognition as claimed in claim 1, characterized in that: The output end of the secondary leakage inductor L3 is connected in parallel with the EMI capacitor C1, the output end of the EMI capacitor C1 is connected to the No. 4 terminal of the transformer T1, and the PFC high-frequency inductor L4 is connected in series between the secondary leakage inductor L3 and the secondary equivalent resistor R2.

3. The method for suppressing harmonics of input current of an ACDC module based on pattern recognition as claimed in claim 2, characterized in that: The two ends of the EMI capacitor C1 are connected in parallel with a resistor R3 .

4. The method for suppressing harmonics of input current of an ACDC module based on pattern recognition as claimed in claim 1, characterized in that: The ACDC module identification process is as follows: S1: For the resistor R3 required to suppress different resonance peaks, the required resistance value of the resistor R3 is obtained through a large number of experiments and theoretical calculations, and a GRx(s) table is prepared and stored in the control device in advance; S2: iLabc and Uabc are obtained through experimental sampling, and then the sampled iLabc and Uabc are processed by the Fourier transform method; S3: Processing to obtain the content of each harmonic, and judging whether resonance occurs according to the content of each harmonic detected; S4: When it is determined that no resonance occurs, the process ends. When it is determined that resonance occurs, the frequency point with the largest harmonic content is taken as the resonance peak. The GRx(s) corresponding to the resonance peak is obtained through the GRx(s) table in the control device. The resistor R3 is adjusted to the optimal resistance value for suppressing the resonance peak, and then the process ends.

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