阅读说明：本技术 低载波比下Vienna整流器的相位补偿装置与方法 (Phase compensation device and method of Vienna rectifier under low carrier ratio ) 是由 吕建国 范林勇 戚志东 吕勋 解艳宇 于 2019-10-16 设计创作，主要内容包括：本发明公开了一种低载波比下Vienna整流器的相位补偿装置与方法。该装置包括Vienna整流器、数字处理控制模块和驱动电路。方法为：采样交流侧三相电压和电流,计算出满足相位补偿要求的调制波幅值相位条件,进而得到移相后的调制波信号；采样直流侧上下电容电压,计算出中点电压控制单元输出信号；将移相后的调制波信号与中点电压控制单元输出信号相加,得到调制信号；采样直流侧上下电容电压,得到三角载波信号；调制信号与三角载波信号经过处理得到脉宽调制信号,驱动Vienna整流器开关管工作。本发明硬件成本低、控制准确、适用范围广,同时使得Vienna整流器交流侧实现单位功率因数运行。(The invention discloses a phase compensation device and method of a Vienna rectifier under a low carrier ratio. The device comprises a Vienna rectifier, a digital processing control module and a driving circuit. The method comprises the following steps: sampling three-phase voltage and current at the alternating current side, and calculating a modulation wave amplitude phase condition meeting the phase compensation requirement so as to obtain a modulation wave signal after phase shifting; sampling the voltage of upper and lower capacitors on the direct current side, and calculating the output signal of the midpoint voltage control unit; adding the phase-shifted modulation wave signal and the output signal of the midpoint voltage control unit to obtain a modulation signal; sampling the voltage of an upper capacitor and a lower capacitor on the direct current side to obtain a triangular carrier signal; the modulation signal and the triangular carrier signal are processed to obtain a pulse width modulation signal, and the Vienna rectifier switching tube is driven to work. The invention has low hardware cost, accurate control and wide application range, and simultaneously enables the alternating current side of the Vienna rectifier to realize unit power factor operation.)

1. A phase compensation device of a Vienna rectifier under a low carrier ratio is characterized by comprising the Vienna rectifier, a digital processing control module and a driving circuit, wherein the digital processing control module comprises a sampling unit, a phase shift angle calculation unit, an orthogonal signal generator unit of a second-order generalized integrator, a phase shift unit, a direct current voltage stabilization control unit, a midpoint voltage control unit, a carrier generation unit and a sine pulse width modulation unit;

The sampling unit is used for respectively acquiring upper and lower capacitor voltage signals on the direct current side of the Vienna rectifier, three-phase voltage signals on the alternating current side of the Vienna rectifier and three-phase current signals on the alternating current side of the Vienna rectifier, and respectively sending the three-phase voltage signals to the phase shift angle calculation unit, the orthogonal signal generator unit of the second-order generalized integrator, the midpoint voltage control unit and the direct current voltage stabilization control unit; the phase shift angle calculation unit calculates and obtains a modulation wave phase shift angle meeting the phase compensation requirement according to the three-phase voltage signals and the current signals on the alternating current side obtained by sampling; the quadrature signal generator unit of the second-order generalized integrator lags the three-phase current signals obtained by sampling by 90 degrees, and sends the signals, the three-phase current signals on the alternating current side and the output signals of the phase shift angle calculation unit to the phase shift unit to obtain three-phase modulation wave signals after phase shifting; the midpoint voltage control unit obtains an output signal of the midpoint voltage control unit according to the sampled upper and lower capacitor voltage signals on the direct current side, and adds the signal and the output signal of the phase shift unit respectively to obtain a modulation signal; the direct current voltage stabilization control unit obtains the amplitude of a carrier signal according to the sampled upper and lower capacitor voltages on the direct current side, and then sends the amplitude to the carrier generation unit to obtain a triangular carrier signal; and the modulation signal and the triangular carrier signal are sent to a sinusoidal pulse width modulation unit, and the output end of the sinusoidal pulse width modulation unit is connected to each switching tube of each phase of bridge arm in the Vienna rectifier through a driving circuit.

2. The apparatus of claim 1, wherein the digital processing control module employs chips TMS320F28335 and EPM 1270T.

3. A phase compensation method of a Vienna rectifier under a low carrier ratio is characterized by comprising the following steps:

Step 1, a sampling unit samples three-phase voltage e at an alternating current side_a、e_b、e_cAlternating side three-phase current i_a、i_b、i_ccapacitor voltage U on the DC side_C1Lower capacitor voltage U on the DC side_C2；

step 2, sampling three-phase voltage e_a、e_b、e_cThree-phase current i_a、i_b、i_csending the phase shift angle to a phase shift angle calculation unit, and calculating to obtain a phase deviation angle theta of the modulated wave meeting the phase compensation requirement_a、θ_b、θ_c；

Step 3, detecting three-phase voltage e at alternating current side_a、e_b、e_cZero-crossing point of (d), and e_a、e_b、e_cThe amplitude of (d);

Step 4, according to the three-phase voltage e of the alternating current side_a、e_b、e_cZero crossing point of (d) and (e)_a、e_b、e_cThe amplitude value of the system is judged whether the power grid is connected or not in the running process of the systemGenerating a change;

Step 5, sampling three-phase current i_a、i_b、i_cAre respectively multiplied by sampling coefficients R_sto obtain i_aR_s、i_bR_s、i_cR_sSending the signal to an orthogonal signal generator unit of a second-order generalized integrator to obtain an orthogonal signal i_aqR_s、i_bqR_s、i_cqR_s；

Step 6, calculating the phase deviation angle theta obtained in the step 2_a、θ_b、θ_cSampling the resulting i_aR_s、i_bR_s、i_cR_sThe orthogonal signal obtained in the step 5 is sent to a phase shifting unit, and a modulated wave signal after phase shifting is obtained through calculation;

Step 7, the phase-shifted modulation wave signal m obtained in the step 6 is subjected to phase shifting_a、m_b、m_cAnd the output u of the midpoint voltage control unit_fAdding to obtain final modulated wave signal m_a+u_f、m_b+u_f、m_c+u_f；

Step 8, adding the sampled upper and lower capacitor voltages, sending the added voltages to a direct current voltage stabilization control unit to obtain a triangular carrier amplitude, and then obtaining a triangular carrier signal through a carrier generation unit;

And 9, connecting the three-phase modulation signal obtained in the step 7 with the triangular carrier signal obtained in the step 8 to generate a pulse width modulation signal, and controlling the switch tube of the Vienna rectifier to work through a driving circuit.

4. The method for phase compensation of a Vienna rectifier under low carrier-to-carrier ratio as claimed in claim 3, wherein said calculating in step 2 obtains a phase deviation angle θ of the modulated wave satisfying the phase compensation requirement_a、θ_b、θ_cThe formula is as follows:

Wherein ω isFundamental angular velocity of the grid voltage, L being the filter inductance value, I_a、I_b、I_cRespectively the input current amplitude, E_ano、E_bno、E_cnoRespectively are the non-zero sequence component amplitude values of the power grid,The phase difference between each phase voltage and the corresponding non-zero sequence component is respectively.

5. The phase compensation method for the Vienna rectifier under the low carrier to carrier ratio of claim 3, wherein the step 4 is based on the three-phase voltage e at the AC side_a、e_b、e_czero crossing point of (d) and (e)_a、e_b、e_cThe amplitude value of the power grid is judged to be changed or not in the running process of the system, and the method specifically comprises the following steps:

Step 4.1, sampling three-phase power grid voltage at the alternating current side, and calculating a modulation wave phase deviation angle meeting the phase compensation requirement;

Step 4.2, setting the maximum allowable error angle of each phaseMeasuring the zero crossing point of each phase voltage in the first power frequency periodThen, each power frequency period detects the zero crossing point of each phase voltage, and the zero crossing point of the kth period is set asWill be compared with the zero crossing point of the previous cycleMake a comparison ifWhere x is a, b, c, then the phase compensation requirement needs to be satisfied by recalculationIs modulated wave phase shift angle theta_a、θ_b、θ_cSkipping to step 4.1; if it isthe phase of the grid voltage does not change between the kth period and the kth-1 period, and the step 4.3 is carried out;

Step 4.3, setting the maximum allowable error amplitude E of each phase_erroMeasuring the amplitude of the grid voltage in the kth period, comparing the amplitude with the amplitude of the kth-1 period, and determining if the amplitude is E_xk-E_x(k-1)|<E_erroif x is a, b and c, the voltage of the power grid is not changed, and the next power frequency period is started; if | E_xk-E_x(k-1)|>E_erroIf the grid voltage changes, the phase deviation angle theta of the modulated wave meeting the phase compensation requirement is recalculated_a、θ_b、θ_cAnd skipping to step 4.1.

6. The method for phase compensation of a Vienna rectifier under low carrier-to-carrier ratio as claimed in claim 3, wherein said calculating in step 6 obtains a phase-shifted modulated wave signal, and the formula is as follows:

In the formula, R_sFor sampling the coefficient of the AC side current, i_a、i_b、i_cIs a three-phase current of the AC side, i_aq、i_bq、i_cqIs a signal orthogonal to the AC side current, θ_a、θ_b、θ_cFor each phase shift phase angle.

7. The phase compensation method for the Vienna rectifier under the low carrier ratio of claim 3, wherein the step 9 of connecting the three-phase modulation signal obtained in the step 7 with the triangular carrier signal obtained in the step 8 to generate the pulse width modulation signal, and controlling the switch tube of the Vienna rectifier to operate through the driving circuit, specifically comprises the following steps:

The core control equation for improving the single-cycle control is as follows:

In the formula of U_mFor the output signal of the DC regulation control unit, d_A、d_B、d_CRespectively the conduction duty ratio, R, of each phase of switching tube_sFor sampling the coefficient of the AC side current, i_a、i_b、i_cIs a three-phase current of the AC side, i_aq、i_bq、i_cqIs a signal orthogonal to the AC side current, θ_a、θ_b、θ_cFor each phase shift phase angle u_fThe output signal is the midpoint voltage control unit.

Technical Field

The invention belongs to the technical field of power electronic conversion, and particularly relates to a phase compensation device and method of a Vienna rectifier under a low carrier ratio.

Background

The Vienna rectifier is a three-level topology, and has the advantages of low voltage stress borne by power switches, small number of power switches, high power density, low input current harmonic content and good adaptability to various PFC control methods, so that the Vienna rectifier is widely applied to the research of power factor correction technology. Meanwhile, in recent years, many documents deeply research a three-phase PFC rectifier based on single-cycle control, a controller for single-cycle control generally does not need a multiplier, only needs to perform simple integration and addition and subtraction operation on input current, and can realize a switching element control waveform with constant modulation frequency by directly comparing the input current with a reference signal. The traditional single-period control can realize the same phase of input current and input voltage under the condition of input balance and high switching frequency, but under the condition of input unbalance and low switching frequency, because the carrier ratio is low, a Vienna rectifier cannot be equivalent to a DC/DC converter in each switching period, the voltage drop of a filter inductor is increased, and further the input impedance Z (R) at the alternating current side of the rectifier is caused_eThe + j ω L is not purely resistive, so that the input current and the input voltage generate phase shift, and the target of unit power factor control cannot be achieved.

The unbalance of three-phase input alternating-current voltage is a special phenomenon in a rectifier power supply system, and can affect the normal operation of the rectifier power supply system, for example, the problems of output direct-current voltage low-frequency pulsation, input power low-frequency pulsation, input current distortion and the like can be caused. For the problems of unbalanced three-phase input ac voltage and phase compensation, document 1(Jin Aijuan, LiHangtian, Li sharp, and advanced control strategy of the one-cycle controlled-phase PFC receiver under balanced control [ J ]. Transactions of Chinese electronic technical Society,2006,21(7):115-121.) improves the conventional single-cycle control by introducing an asymmetric coefficient concept, and adjusts the sampling value of each phase of input current by using the asymmetric coefficient, thereby realizing that each phase of current is in phase with each voltage, and improving the quality of the input current. The low switching frequency can effectively reduce the switching loss and improve the system efficiency. When the traditional single-period control Vienna rectifier has a low carrier ratio, the input impedance of the alternating current side of the traditional single-period control Vienna rectifier is not pure resistance, so that the power factor of the rectifier is influenced. For the phase compensation problem caused by the low carrier ratio, document 2 (mao peng, xiu jun, francisco, etc.. single-cycle control PFC converter current phase lag and compensation thereof [ J ]. the report of electrotechnical science, 2010, 25 (12): 111- & 118.) performs phase compensation by solving the amplitude phase condition that the modulation wave should satisfy when the low carrier ratio is solved under the rated power condition, but the method does not consider the analysis imbalance condition under the balanced condition.

Disclosure of Invention

The invention aims to provide a phase compensation device and a phase compensation method of a Vienna rectifier under low carrier ratio, which can realize zero phase difference of input voltage and current of each phase under the conditions of unbalanced input and low switching frequency, realize unit power factor operation, reduce the total harmonic distortion rate of alternating current side current, have simple and reliable operation and accurate control.

The technical solution for realizing the purpose of the invention is as follows: a phase compensation device of a Vienna rectifier under a low carrier ratio comprises the Vienna rectifier, a digital processing control module and a driving circuit, wherein the digital processing control module comprises a sampling unit, a phase shift angle calculation unit, an orthogonal signal generator unit of a second-order generalized integrator, a phase shift unit, a direct current voltage stabilization control unit, a midpoint voltage control unit, a carrier generation unit and a sine pulse width modulation unit;

The sampling unit is used for respectively acquiring upper and lower capacitor voltage signals on the direct current side of the Vienna rectifier, three-phase voltage signals on the alternating current side of the Vienna rectifier and three-phase current signals on the alternating current side of the Vienna rectifier, and respectively sending the three-phase voltage signals to the phase shift angle calculation unit, the orthogonal signal generator unit of the second-order generalized integrator, the midpoint voltage control unit and the direct current voltage stabilization control unit; the phase shift angle calculation unit calculates and obtains a modulation wave phase shift angle meeting the phase compensation requirement according to the three-phase voltage signals and the current signals on the alternating current side obtained by sampling; the quadrature signal generator unit of the second-order generalized integrator lags the three-phase current signals obtained by sampling by 90 degrees, and sends the signals, the three-phase current signals on the alternating current side and the output signals of the phase shift angle calculation unit to the phase shift unit to obtain three-phase modulation wave signals after phase shifting; the midpoint voltage control unit obtains an output signal of the midpoint voltage control unit according to the sampled upper and lower capacitor voltage signals on the direct current side, and adds the signal and the output signal of the phase shift unit respectively to obtain a modulation signal; the direct current voltage stabilization control unit obtains the amplitude of a carrier signal according to the sampled upper and lower capacitor voltages on the direct current side, and then sends the amplitude to the carrier generation unit to obtain a triangular carrier signal; and the modulation signal and the triangular carrier signal are sent to a sinusoidal pulse width modulation unit, and the output end of the sinusoidal pulse width modulation unit is connected to each switching tube of each phase of bridge arm in the Vienna rectifier through a driving circuit.

Further, the digital processing control module adopts TMS320F28335 and EPM1270T chips.

A phase compensation method of a Vienna rectifier under a low carrier ratio comprises the following steps:

Step 1, a sampling unit samples three-phase voltage e at an alternating current side_a、e_b、e_cAlternating side three-phase current i_a、i_b、i_cCapacitor voltage U on the DC side_C1Lower capacitor voltage U on the DC side_C2；

step 2, sampling three-phase voltage e_a、e_b、e_cThree-phase current i_a、i_b、i_cSending the phase shift angle to a phase shift angle calculation unit, and calculating to obtain a phase deviation angle theta of the modulated wave meeting the phase compensation requirement_a、θ_b、θ_c；

step 3, detecting three-phase voltage e at alternating current side_a、e_b、e_czero-crossing point of (d), and e_a、e_b、e_cThe amplitude of (d);

Step 4, according to the three-phase voltage e of the alternating current side_a、e_b、e_cZero crossing point of (d) and (e)_a、e_b、e_cJudging whether the power grid changes in the operation process of the system;

Step 5, sampling three-phase current i_a、i_b、i_cAre respectively multiplied by sampling coefficients R_sTo obtain i_aR_s、i_bR_s、i_cR_sSending the signal to an orthogonal signal generator unit of a second-order generalized integrator to obtain an orthogonal signal i_aqR_s、i_bqR_s、i_cqR_s；

Step 6, calculating the phase deviation angle theta obtained in the step 2_a、θ_b、θ_cSampling the resulting i_aR_s、i_bR_s、i_cR_sthe orthogonal signal obtained in the step 5 is sent to a phase shifting unit, and a modulated wave signal after phase shifting is obtained through calculation;

Step 7, the phase-shifted modulation wave signal m obtained in the step 6 is subjected to phase shifting_a、m_b、m_cAnd the output u of the midpoint voltage control unit_fAdding to obtain final modulated wave signal m_a+u_f、m_b+u_f、m_c+u_f；

Step 8, adding the sampled upper and lower capacitor voltages, sending the added voltages to a direct current voltage stabilization control unit to obtain a triangular carrier amplitude, and then obtaining a triangular carrier signal through a carrier generation unit;

and 9, connecting the three-phase modulation signal obtained in the step 7 with the triangular carrier signal obtained in the step 8 to generate a pulse width modulation signal, and controlling the switch tube of the Vienna rectifier to work through a driving circuit.

Further, the calculation in step 2 obtains a phase deviation angle θ of the modulated wave meeting the phase compensation requirement_a、θ_b、θ_cThe formula is as follows:

Where ω is the grid voltage fundamental angular velocity, L is the filter inductance value, I_a、I_b、I_crespectively the input current amplitude, E_ano、E_bno、E_cnorespectively are the non-zero sequence component amplitude values of the power grid,The phase difference between each phase voltage and the corresponding non-zero sequence component is respectively.

further, the step 4 is based on the three-phase voltage e of the AC side_a、e_b、e_cZero crossing point of (d) and (e)_a、e_b、e_cThe amplitude value of the power grid is judged to be changed or not in the running process of the system, and the method specifically comprises the following steps:

Step 4.1, sampling three-phase power grid voltage at the alternating current side, and calculating a modulation wave phase deviation angle meeting the phase compensation requirement;

step 4.2, setting the maximum allowable error angle of each phaseMeasuring the zero crossing point of each phase voltage in the first power frequency periodThen, each power frequency period detects the zero crossing point of each phase voltage, and the zero crossing point of the kth period is set asWill be compared with the zero crossing point of the previous cycleMake a comparison ifWhere x is a, b, c, the modulated wave satisfying the phase compensation requirement needs to be recalculatedphase offset angle theta_a、θ_b、θ_cSkipping to step 4.1; if it isThe phase of the grid voltage does not change between the kth period and the kth-1 period, and the step 4.3 is carried out;

Step 4.3, setting the maximum allowable error amplitude E of each phase_erromeasuring the amplitude of the grid voltage in the kth period, comparing the amplitude with the amplitude of the kth-1 period, and determining if the amplitude is E_xk-E_x(k-1)|<E_erroif x is a, b and c, the voltage of the power grid is not changed, and the next power frequency period is started; if | E_xk-E_x(k-1)|>E_erroIf the grid voltage changes, the phase deviation angle theta of the modulated wave meeting the phase compensation requirement is recalculated_a、θ_b、θ_cAnd skipping to step 4.1.

further, in step 6, the calculation obtains a modulated wave signal after phase shifting, and the formula is as follows:

In the formula, R_sFor sampling the coefficient of the AC side current, i_a、i_b、i_cIs a three-phase current of the AC side, i_aq、i_bq、i_cqIs a signal orthogonal to the AC side current, θ_a、θ_b、θ_cFor each phase shift phase angle.

Further, the three-phase modulation signal obtained in step 7 is connected with the triangular carrier signal obtained in step 8 in step 9 to generate a pulse width modulation signal, and the Vienna rectifier switching tube is controlled to work through the driving circuit, which specifically includes the following steps:

The core control equation for improving the single-cycle control is as follows:

In the formula of U_mFor the output signal of the DC regulation control unit, d_A、d_B、d_CRespectively the conduction duty ratio, R, of each phase of switching tube_sfor sampling the coefficient of the AC side current, i_a、i_b、i_cIs a three-phase current of the AC side, i_aq、i_bq、i_cqIs a signal orthogonal to the AC side current, θ_a、θ_b、θ_cFor each phase shift phase angle u_fThe output signal is the midpoint voltage control unit.

Compared with the prior art, the invention has the remarkable advantages that: (1) the phase shift problem between the alternating-current side voltage and the current of the Vienna rectifier under the conditions of unbalanced input and low carrier ratio is effectively solved, and the alternating-current side of the Vienna rectifier realizes unit power factor operation; (2) the total harmonic distortion rate of the alternating current side current is reduced by introducing the midpoint voltage control unit, and the waveform quality is improved; (3) the method is suitable for the conditions of unbalanced input and low switching frequency, and has the advantages of simple and reliable operation, low hardware cost, accurate control and wide application range.

Drawings

Fig. 1 is a schematic structural diagram of a phase compensation device of a Vienna rectifier under a low carrier ratio in the invention.

Fig. 2 is a schematic diagram of a quadrature signal generator unit of the second-order generalized integrator of the present invention.

fig. 3 is a topology of the Vienna rectifier of the present invention.

fig. 4 is a single-phase equivalent circuit diagram of the Vienna rectifier of the present invention.

Fig. 5 is a relation diagram of each vector in the single-phase equivalent circuit of the Vienna rectifier in the invention.

Fig. 6 is a flow chart of the calculation of the phase shift angle in the present invention.

Fig. 7 is a waveform diagram of an input unbalanced voltage in an embodiment of the present invention.

FIG. 8 is a comparison graph of the magnitude of the phase difference between the phase of the A-phase voltage and the phase of the A-phase current on the front and rear AC sides using the method of the present invention in an embodiment of the present invention, wherein (a) is a simulation waveform using the conventional single-cycle control, and (b) is a simulation waveform using the control method of the present invention.

Fig. 9 is a comparison graph of the harmonic distribution of the ac side current before and after the method of the present invention is used in the example of the present invention, where (a) is the harmonic distribution of the ac side current before the control method of the present invention is used, and (b) is the harmonic distribution of the ac side current after the control method of the present invention is used.

Detailed Description

The invention is described in further detail below with reference to the figures and specific examples.

With reference to fig. 1, 2, and 3, the phase compensation apparatus for a Vienna rectifier with a low carrier ratio of the present invention includes a Vienna rectifier, a digital processing control module and a driving circuit, wherein the digital processing control module includes a sampling unit, a phase shift angle calculation unit, a Quadrature Signal Generator unit (SOGI-QSG) of a Second-Order Generalized Integrator, a phase shift unit, a dc voltage stabilization control unit, a midpoint voltage control unit, a carrier generation unit, and a sine pulse width modulation unit;

The quadrature signal generator unit (SOGI-QSG) of the second order generalized integrator is shown in fig. 2, where V is the input signal, V 'is the signal in phase with V, qV' is the signal lagging by V90 °, and ω is the fundamental angular velocity of the input signal;

the sampling unit is used for respectively acquiring upper and lower capacitor voltage signals on the direct current side of the Vienna rectifier, three-phase voltage signals on the alternating current side of the Vienna rectifier and three-phase current signals on the alternating current side of the Vienna rectifier, and respectively sending the three-phase voltage signals to the phase shift angle calculation unit, the orthogonal signal generator unit of the second-order generalized integrator, the midpoint voltage control unit and the direct current voltage stabilization control unit; the phase shift angle calculation unit calculates and obtains a modulation wave phase shift angle meeting the phase compensation requirement according to the three-phase voltage signals and the current signals on the alternating current side obtained by sampling; the quadrature signal generator unit of the second-order generalized integrator lags the three-phase current signals obtained by sampling by 90 degrees, and sends the signals, the three-phase current signals on the alternating current side and the output signals of the phase shift angle calculation unit to the phase shift unit to obtain three-phase modulation wave signals after phase shifting; the midpoint voltage control unit obtains an output signal of the midpoint voltage control unit according to the sampled upper and lower capacitor voltage signals on the direct current side, and adds the signal and the output signal of the phase shift unit respectively to obtain a modulation signal; the direct current voltage stabilization control unit obtains the amplitude of a carrier signal according to the sampled upper and lower capacitor voltages on the direct current side, and then sends the amplitude to the carrier generation unit to obtain a triangular carrier signal; and the modulation signal and the triangular carrier signal are sent to a sinusoidal pulse width modulation unit, and the output end of the sinusoidal pulse width modulation unit is connected to each switching tube of each phase of bridge arm in the Vienna rectifier through a driving circuit.

as a specific example, the digital processing control module adopts TMS320F28335 and EPM1270T chips.

A phase compensation method of a Vienna rectifier under a low carrier ratio comprises the following steps:

Step 1, a sampling unit samples three-phase voltage e at an alternating current side_a、e_b、e_cAlternating side three-phase current i_a、i_b、i_cCapacitor voltage U on the DC side_C1Lower capacitor voltage U on the DC side_C2；

Step 2, sampling the three-phase voltage e in each switching period_a、e_b、e_cThree-phase current i_a、i_b、i_cCalculating to obtain the phase deviation angle theta of the modulated wave meeting the phase compensation requirement_a、θ_b、θ_cthe method comprises the following steps:

According to the Vienna rectifier single-phase equivalent circuit shown in fig. 4 and the vector relationship diagram in the single-phase equivalent circuit shown in fig. 5, the following relationship can be obtained:

In the formulag＝A、B、C，I_gfor each phase current amplitude, L is the filter inductance value, E_gnoFor each phase non-zero sequence component magnitude,The difference between the voltage phase and the non-zero sequence component phase of each phase of the network, E_gOthe amplitude of the fundamental wave of the bridge arm voltage of each phase is obtained.

Further obtaining the phase deviation angle theta of the modulated wave meeting the phase compensation requirement_a、θ_b、θ_cComprises the following steps:

Where ω is the grid voltage fundamental angular velocity, L is the filter inductance value, I_a、I_b、I_cRespectively the input current amplitude, E_ano、E_bno、E_cnorespectively are the non-zero sequence component amplitude values of the power grid,The phase difference between each phase voltage and the corresponding non-zero sequence component is respectively.

Step 3, detecting three-phase voltage e at alternating current side_a、e_b、e_cZero-crossing point of (d), and e_a、e_b、e_cthe amplitude of (d);

Step 4, according to the three-phase voltage e of the alternating current side_a、e_b、e_cZero crossing point of (d) and (e)_a、e_b、e_cThe amplitude of the voltage, whether the power grid changes during the operation of the system, in combination with fig. 6, is as follows:

Step 4.1, sampling voltage and current of a three-phase power grid at the alternating current side, and calculating a phase deviation angle of a modulation wave meeting the phase compensation requirement;

Step 4.2, setting the maximum allowable error angle of each phaseMeasuring the zero crossing point of each phase voltage in the first power frequency periodThen, each power frequency period detects the zero crossing point of each phase voltage, and the zero crossing point of the kth period is set aswill be compared with the zero crossing point of the previous cycleMake a comparison ifwherein x is a, b and c, and the phase deviation angle theta of the modulated wave meeting the phase compensation requirement needs to be recalculated_a、θ_b、θ_cSkipping to step 4.1; if it isThe phase of the grid voltage does not change between the kth period and the kth-1 period, and the step 4.3 is carried out;

Step 4.3, setting the maximum allowable error amplitude E of each phase_erroMeasuring the amplitude of the grid voltage in the kth period, comparing the amplitude with the amplitude of the kth-1 period, and determining if the amplitude is E_xk-E_x(k-1)|<E_erro(wherein x is a, b and c), the voltage of the power grid is not changed, and the next power frequency period is started; if | E_xk-E_x(k-1)|>E_erroIf the grid voltage changes, the phase deviation angle theta of the modulated wave meeting the phase compensation requirement needs to be recalculated_a、θ_b、θ_cAnd skipping to step 4.1.

step 5, sampling three-phase current i_a、i_b、i_care respectively multiplied by sampling coefficients R_sTo obtain i_aR_s、i_bR_s、i_cR_ssending the signal to an orthogonal signal generator unit of a second-order generalized integrator to obtain an orthogonal signal i_aqR_s、i_bqR_s、i_cqR_s；

Step 6, calculating the phase deviation angle theta obtained in the step 4_a、θ_b、θ_cSampling the resulting i_aR_s、i_bR_s、i_cR_sAnd the orthogonal signal obtained in the step 5 is sent to a phase shifting unit, and a modulated wave signal after phase shifting is obtained through calculation, wherein the formula is as follows:

In the formula, R_sfor sampling the coefficient of the AC side current, i_a、i_b、i_cIs a three-phase current of the AC side, i_aq、i_bq、i_cqis a signal orthogonal to the AC side current, θ_a、θ_b、θ_cfor each phase shift phase angle.

Step 7, the phase-shifted modulation wave signal m obtained in the step 6 is subjected to phase shifting_a、m_b、m_cAnd the output u of the midpoint voltage control unit_fAdding to obtain final modulated wave signal m_a+u_f、m_b+u_f、m_c+u_f；

Step 8, adding the sampled upper and lower capacitor voltages, sending the added voltages to a direct current voltage stabilization control unit to obtain a triangular carrier amplitude, and then obtaining a triangular carrier signal through a carrier generation unit;

And 9, connecting the three-phase modulation signal obtained in the step 7 with the triangular carrier signal obtained in the step 8 to generate a pulse width modulation signal, and controlling a switch tube of the Vienna rectifier to work through a driving circuit, wherein the method specifically comprises the following steps:

the core control equation for improving the one-cycle control at this time is as follows:

In the formula of U_mFor the output signal of the DC regulation control unit, d_A、d_B、d_CRespectively the conduction duty ratio u of each phase of switching tube_fIs a midpoint electricitythe voltage control unit outputs a signal.

The modulation rule of the Vienna rectifier is: taking phase A as an example, in the positive half cycle of the modulated wave, when the carrier wave is larger than the modulated wave, let S_a1、S_a2conducting, the voltage of the A-phase bridge arm is 0, and when the carrier wave is less than the modulation wave, making S_a1、S_a2turn off, the A phase bridge arm voltage is V_DC2; in the negative half cycle of the modulated wave, when the carrier wave is smaller than the modulated wave, let S_a1、S_a2Conducting, the voltage of the A-phase bridge arm is 0, and when the carrier wave is greater than the modulation wave, making S_a1、S_a2Turn off, the A phase bridge arm voltage is-V_DC/2. B. The modulation strategy of the C two phases is the same as that of the A phase.

Wherein V_DCThe voltage is the voltage of a direct current bus at the output side of the Vienna rectifier.