CN106169879A - Revise VIENNA rectifier modulator approach, controller and the system injecting zero-sequence component - Google Patents

Abstract

The invention discloses a VIENNA rectifier modulation method, controller and system for correcting and injecting zero-sequence components. Among them, the modulation method includes correcting the instantaneous polarity of the reference voltage according to the input current; calculating the zero-sequence component of the corrected reference voltage; injecting the zero-sequence component and calculating the duty cycle corresponding to the reference voltage; generating PWM to drive the VIENNA rectifier based on dual-carrier. The invention is simple, efficient, and easy to implement numerically, so that the VIENNA rectifier has high-quality input and output, and operates efficiently and stably, greatly expanding the application occasions of the VIENNA rectifier.

Description

Modulation method, controller and system for modifying VIENNA rectifier injected with zero-sequence components

technical field

The invention belongs to the field of power electronics, and in particular relates to a VIENNA rectifier modulation method, controller and system for correcting and injecting zero-sequence components.

Background technique

The three-phase three-level three-switch rectifier, that is, the VIENNA rectifier, can realize input unit power factor correction, has the advantages of low switching loss and small electromagnetic interference, and has simple circuit structure, small number of switches, and no bridge arm through-through. Research hotspots.

The voltage space vector of the VIENNA rectifier is determined by the switch state and the current polarity. However, due to the effect of inductive loads such as inductance in the circuit, the input grid current lags behind the voltage, and the polarity of the input current and the reference voltage is different. Still using the original reference voltage will generate a wrong voltage space vector, resulting in an increase in input current harmonics. The popularization and application of the VIENNA rectification method is limited. Therefore, it is of great practical significance to realize the high-efficiency work of VIENNA rectifier.

Contents of the invention

In order to solve the shortcomings of the prior art, the present invention provides a VIENNA rectifier modulation method, controller and system for correcting and injecting zero-sequence components. The invention can solve the problem of harmonic increase caused by the lagging voltage of the input current and the polarity difference between the current and the reference voltage. Moreover, the VIENNA rectifier modulation method of the present invention, which corrects and injects zero-sequence components, is simple, efficient, and easy to realize numerically, so that the VIENNA rectifier has high-quality input and output, and operates efficiently and stably, greatly expanding the application occasions of the VIENNA rectifier.

To achieve the above object, the present invention adopts the following technical solutions:

The invention provides a VIENNA rectifier modulation method for correcting and injecting zero-sequence components, including:

Step 1: Correct the instantaneous polarity of the three-phase reference voltage according to the instantaneous polarity of the three-phase input current;

Step 2: Calculate the zero-sequence component of the corrected three-phase reference voltage according to the space vector reference voltage corresponding to the three-phase reference voltage;

Step 3: Inject the zero-sequence component, and then calculate the dual-carrier SVM equivalent duty cycle corresponding to the three-phase reference voltage;

Step 4: Based on the dual-carrier SVM equivalent duty cycle, generate a PWM modulation signal to drive the VIENNA rectifier.

The SVM equivalent gain is After the three-phase reference voltage is multiplied by the SVM equivalent gain, the value range of the corresponding space vector reference voltage is [-1.15～1.15].

The process of correcting the instantaneous polarity of the three-phase reference voltage according to the instantaneous polarity of the three-phase input current is:

Calculate the corresponding space vector reference voltage after the three-phase reference voltage is multiplied by the SVM equivalent gain; in each sector of the space vector, if the instantaneous polarity of a phase input current is positive, then the corresponding phase reference voltage in the corresponding sector The space vector reference voltage remains unchanged; otherwise, a correction value is superimposed on the space vector reference voltage corresponding to the phase reference voltage, wherein the correction value is equal to the maximum value of the three-phase reference voltages.

The process of calculating the zero-sequence component of the corrected three-phase reference voltage is:

Sorting the space vector reference voltages corresponding to the modified three-phase reference voltages by size, to obtain the maximum value V' _max of the space vector reference voltage, the intermediate value V' _mid of the space vector reference voltage and the minimum value V' _min of the space vector reference voltage;

The zero-sequence component of the corrected three-phase reference voltage V′ _com =(1-V′ _max +V′ _min )·KV′ _min , where the K value is used to adjust the midpoint balance of the VIENNA rectifier and is a constant coefficient.

When the VIENNA rectifier is equivalent to space vector modulation SVM, the value of K is 1/2.

The present invention also provides a controller for modifying the VIENNA rectifier injected with zero-sequence components, including:

The instantaneous polarity modification module of the three-phase reference voltage is used for modifying the instantaneous polarity of the three-phase reference voltage according to the instantaneous polarity of the three-phase input current;

A zero-sequence component calculation module, which is used to calculate the zero-sequence component of the corrected three-phase reference voltage according to the space vector reference voltage corresponding to the three-phase reference voltage;

An equivalent duty cycle calculation module, which is used to inject the zero-sequence component, and then calculate the dual-carrier SVM equivalent duty cycle corresponding to the three-phase reference voltage;

The modulation signal generation module is used for generating a PWM modulation signal to drive the VIENNA rectifier based on the equivalent duty cycle of the dual-carrier SVM.

The instantaneous polarity modification module of the three-phase reference voltage is also used to calculate the corresponding space vector reference voltage after the three-phase reference voltage is multiplied by the SVM equivalent gain; in each sector of the space vector, if the instantaneous polarity of a phase input current If the polarity is positive, the space vector reference voltage corresponding to the phase reference voltage in the corresponding sector remains unchanged; otherwise, a correction value is superimposed on the space vector reference voltage corresponding to the phase reference voltage, where the correction value is equal to the three-phase reference voltage the maximum value.

The SVM equivalent gain is After the three-phase reference voltage is multiplied by the SVM equivalent gain, the value range of the corresponding space vector reference voltage is [-1.15～1.15].

The zero-sequence component calculation module includes:

A space vector reference voltage sorting module, which is used to sort the space vector reference voltages corresponding to the modified three-phase reference voltage by size, to obtain the space vector reference voltage maximum value _V'max , the space vector reference voltage intermediate value _V'mid , and the space vector reference voltage Minimum reference voltage V'_min;

A zero-sequence component acquisition module, which is used to obtain the zero-sequence component of the corrected three-phase reference voltage according to V′ _com =(1-V′ _max +V′ _min )·KV′ _min , wherein the K value is used to adjust the VIENNA The mid-point balance of the rectifier is a constant coefficient.

When the VIENNA rectifier is equivalent to the space vector modulation SVM, the value of K is 1/2.

Based on the modified VIENNA rectifier controller injected with zero-sequence components, the present invention also provides a VIENNA rectifier control system, including the controller; the controller is used to receive three-phase input current and three-phase reference voltage, Output PWM modulation signal to drive VIENNA rectifier.

The beneficial effects of the present invention are:

(1) The reference voltage lags the grid current within the angle θ. This method solves the problem of current harmonic distortion caused by the difference between the polarity of the current and the reference voltage by correcting the zero-sequence component, and improves the power quality;

(2) This method can reduce the design capacity of the AC side filter and save the volume and cost of the three-level VIENNA rectifier;

(3) This method is equivalent to space vector modulation (SVM), which simplifies the VIENNA modulation method, reduces the amount of calculation, and is easy to implement digitally.

Description of drawings

Figure 1 is a topology diagram of a three-level VIENNA rectifier;

Fig. 2 is the schematic diagram of the modified zero-sequence component injection modulation of the proposed new VIENNA rectifier;

Figure 3 is the vector diagram of the VIENNA rectifier;

Fig. 4 (a) is before adding the zero-sequence component, a, b, c three-phase reference voltage amplitudes and corresponding switch states in sector I;

Fig. 4 (b) is the reference voltage amplitude and the corresponding switch state after the instantaneous polarity correction of the three phases a, b, and c in sector I;

Fig. 4 (c) is after adding the zero-sequence component correction, a, b, c three-phase reference voltage amplitudes and corresponding switch states in sector I;

Fig. 5 is an equivalent space vector three-phase reference voltage waveform diagram;

Figure 6 is a waveform diagram of the modified space vector three-phase reference voltage after adding the algorithm;

Figure 7 is a simulation waveform diagram of the zero-sequence component and the three-phase equivalent duty cycle generated by adding the algorithm;

Fig. 8 is the AC test simulation result without adding the algorithm;

Fig. 9 is the simulation result of the AC measurement of the present invention.

detailed description

Below in conjunction with accompanying drawing and embodiment the present invention will be further described:

The rectifier control strategy is described with the three-level VIENNA rectifier structure shown in Figure 1.

Three-level VIENNA rectifier, including three-phase bridge arms connected in parallel, each phase bridge arm includes two fast recovery diodes connected in series, equivalent bidirectional switches S _a , S _b , S _c connected in series on the midpoint side of each phase bridge arm, That is, two IGBT tubes with different directions, the other side is connected to the power grid through a filter; two capacitors C ₁ and C ₂ with the same capacitance are connected to the input terminals of each bridge arm connected in parallel; the midpoint O of the discrete capacitor is connected to each phase The other side of the IGBT tube with different directions of the bridge arms; the midpoint of the two capacitors is connected to the other end of the two IGBT tubes with different directions of the bridge arms of each phase, the DC output terminals of the two capacitors are connected in parallel with the load resistor R _L , and the two capacitors in three-phase series The IGBT tube can be driven by a PWM signal circuit. The filters are filter inductors L _a , L _b , and L _c .

This topology belongs to the BOOST structure, and the function of bidirectional switching can also be realized by using two switching tubes in reverse series. Since the two switching tubes of each phase are controlled in the same way, not only the power devices are reduced, the cost of the circuit is reduced, but also the complexity of the control. The inductor works in the BOOST state, the current on the inductor is continuous, and there is no zero-sequence current; the maximum voltage drop of the switch tube is half of the bus voltage, which reduces the withstand voltage of the switch tube and can be well used in high-voltage applications; The input current ripple is low, the power density is high, and the input inductor is small; it can operate at unity power factor.

However, due to the filter in the VIENNA rectifier, the input current always lags the input voltage. It can be clearly seen from Figure 3 that the reference voltage lags the grid current by the angle θ, and the rectifier can achieve unity power factor. The polarity of the input current within the angle θ is different from the polarity of the reference voltage. When the polarity of the input current is changed, the polarity of the reference voltage remains unchanged, which will lead to problems such as increased circuit harmonics and the inability to guarantee unity power factor. Therefore, the purpose of the present invention is to solve the problem that the polarity of the input current is different from the polarity of the equivalent duty cycle of the reference voltage within the angle θ lagging behind the grid current by the reference voltage, so as to realize reliable operation per unit power.

The principle of the modified zero-sequence component injection modulation method of the VIENNA rectifier in the present invention is shown in Figure 2, including:

Step 1: Correct the instantaneous polarity of the three-phase reference voltage according to the instantaneous polarity of the three-phase input current;

Step 2: Calculate the zero-sequence component of the corrected three-phase reference voltage according to the space vector reference voltage corresponding to the three-phase reference voltage;

Step 3: Inject the zero-sequence component, and then calculate the equivalent duty cycle of the dual-carrier SVM corresponding to the three-phase reference voltage;

Step 4: Based on the dual-carrier SVM equivalent duty cycle, generate a PWM modulation signal to drive the VIENNA rectifier.

The process of correcting the instantaneous polarity of the three-phase reference voltage according to the instantaneous polarity of the three-phase input current is:

Calculate the corresponding space vector reference voltage after the three-phase reference voltage is multiplied by the SVM equivalent gain; in each sector of the space vector, if the instantaneous polarity of a phase input current is positive, then the corresponding phase reference voltage in the corresponding sector The space vector reference voltage remains unchanged; otherwise, a correction value is superimposed on the space vector reference voltage corresponding to the phase reference voltage, wherein the correction value is equal to the maximum value of the three-phase reference voltages.

In step 1, the three-phase reference voltages U _aref , U _bref , U _cref are multiplied by the SVM equivalent gain The corresponding space vector reference voltages V _as , V _bs , V _cs , V _xs (x takes a, b, c) range from [-1.15 to 1.15].

The SVM equivalent gain is consistent. The three-phase reference voltage is m*cos(θ1), m*cos(θ1+2π/3), m*cos(θ1-2π/3), where m is the modulation ratio of the three-phase reference voltage, and the modulation ratio is m ∈[0,1]; θ1 is the modulation angle of the three-phase reference voltage, θ1∈[0,2π].

Therefore the maximum modulation ratio m _max =1. For example m _max multiplied by the SVM equivalent gain The sine amplitude can reach up to 1.15. After injecting zero-sequence components, the maximum amplitude of the modulation waveform can be re-limited to 1, that is, the DC voltage utilization rate of SVM modulation is that of SPWM modulation times (inherent advantages of SVM modulation). Therefore, the modulation method of zero-sequence component injection can be equivalent to the SVM debugging method, and the modulation ratio is m∈[0,1].

The actual simulation waveform is shown in Figure 5. As shown in Figure 5, the modulation ratio of the three-phase reference voltage is m=1. For example, if the reference voltage is in sector I, the amplitudes of the three-phase reference voltages a, b, and c and the corresponding switch states are shown in FIG. 4( a ). According to the instantaneous polarity of the input current _ia , _ib , _ic , rather than the polarity of V _xs , V _xs is corrected respectively, and the correction rules are shown in Table 1.

Table 1 Reference voltage correction value of each sector

If i _x ≥ 0, then V' _xs =V _xs , otherwise V' _xs =V _xs +1.

The actual waveform of the corrected space vector reference voltage is shown in Figure 6. The corresponding space vector reference voltage after the three-phase reference voltage shown in Figure 6 is multiplied by the SVM equivalent gain is obtained according to the correction rules in Table 1.

For example, if the reference voltage is in sector I, the reference voltage amplitudes and corresponding switching states of the three-phase reference voltages a, b, and c after instantaneous polarity correction are shown in Fig. 4(b).

In step 2, sort the V' _as , V' _bs , and V' _cs obtained in step 1 into V' _max , V' _mid , and V' _min as shown in the following formula:

Then calculate the zero-sequence component V' _com , the expression is

V′ _com ＝(1-V′ _max +V′ _min )·KV′ _min

The K value can be used to adjust the midpoint balance of the three-level VIENNA rectifier, and the value is 1/2 when the equivalent space is moderately modulated.

In step 3, the three-phase space vector reference voltage V _as , V _bs , V _cs plus the zero-sequence component V' _com obtains the equivalent duty cycle d' _a , d' _b , d' _c of the dual-carrier SVM, the expression for

The actual waveforms of the corrected zero-sequence component _V'com and the equivalent duty cycle d' _a , d' _b , and d' _c are shown in Figure 7. For example, if the reference voltage is in sector I, the three-phase reference The voltage a, b, c three-phase reference voltage amplitude and the corresponding switch state are shown in Fig. 4(c).

In step 4, the equivalent duty cycles d' _a , d' _b , and d' _c of the dual-carrier SVM are modulated by dual-carrier PWM to obtain switching signals S _a , S _b , and S _c of the VIENNA rectifier.

The input current harmonic distortion rate THD is verified by MATLAB simulation, which proves that the proposed new method is effective. The simulation software uses MATLAB/simulink 2014A, and the simulation parameters are shown in Table 2. The simulation results prove that the proposed new method solves the problem of inconsistency between the input current and the equivalent duty ratio of the reference voltage within the angle θ of the reference voltage lagging the grid current. .

Table 2 Reference voltage correction value of each sector

Grid phase voltage effective value V _g (RMS) 220V DC side voltage V _dc 600V DC side capacitors C ₁ , C ₂ 1000μF output frequency f 50Hz Filter inductance L 3mH Line resistance R _s 0.05Ω Simulation step 2.5μs

_Fig . 8 shows the actual simulation waveforms of _VIENNA rectifier input currents _ia , ib, and ic when the polarity of the reference voltage is corrected. From the FFT analysis of the three-phase current waveform from 0.1s to 0.2s, it can be seen that there are a large number of harmonics caused by the lag angle θ at this time, and the current total harmonic distortion (THD) is THD = 3.64%.

Fig. 9 is the simulation result of the AC measurement after adding the algorithm of the present invention, and the total harmonic distortion rate of the input current is THD=2.06%.

Comparing the analysis results of Fig. 7 and Fig. 8, it can be seen that the new modulation method of the VIENNA rectifier by correcting and injecting zero-sequence components proposed by the present invention can reduce the harmonic distortion rate of the input current of the VIENNA rectifier and ensure stable operation under high power factor.

The present invention also provides a controller for modifying VIENNA rectifiers injected with zero-sequence components, including: an instantaneous polarity modification module for three-phase reference voltages, a zero-sequence component calculation module, an equivalent duty cycle calculation module, and a modulation signal generation module .

(1) The instantaneous polarity modification module of the three-phase reference voltage, which is used for modifying the instantaneous polarity of the three-phase reference voltage according to the instantaneous polarity of the three-phase input current.

The instantaneous polarity modification module of the three-phase reference voltage is also used to calculate the corresponding space vector reference voltage after the three-phase reference voltage is multiplied by the SVM equivalent gain; in each sector of the space vector, if the instantaneous polarity of a phase input current is positive, the space vector reference voltage corresponding to the phase reference voltage in the corresponding sector remains unchanged; otherwise, a correction value is superimposed on the space vector reference voltage corresponding to the phase reference voltage, where the correction value is equal to the maximum value of the three-phase reference voltage value.

(2) A zero-sequence component calculation module, which is used to calculate the zero-sequence component of the corrected three-phase reference voltage according to the space vector reference voltage corresponding to the three-phase reference voltage.

The zero sequence component calculation module also includes:

A space vector reference voltage sorting module, which is used to sort the space vector reference voltages corresponding to the modified three-phase reference voltage by size, to obtain the space vector reference voltage maximum value _V'max , the space vector reference voltage intermediate value _V'mid , and the space vector reference voltage Minimum reference voltage V'_min;

A zero-sequence component acquisition module, which is used to obtain the zero-sequence component of the corrected three-phase reference voltage according to V′ _com =(1-V′ _max +V′ _min )·KV′ _min , wherein the K value is used to adjust the VIENNA The mid-point balance of the rectifier is a constant coefficient.

(3) An equivalent duty cycle calculation module, which is used to inject the zero-sequence component, and then calculate and obtain the dual-carrier SVM equivalent duty cycle corresponding to the three-phase reference voltage.

(4) A modulation signal generation module, which is used to generate a PWM modulation signal to drive the VIENNA rectifier based on the dual-carrier SVM equivalent duty cycle.

The SVM equivalent gain is After the three-phase reference voltage is multiplied by the SVM equivalent gain, the value range of the corresponding space vector reference voltage is [-1.15～1.15].

When the VIENNA rectifier is equivalent to the space vector modulation SVM, the value of K is 1/2.

The invention solves the current harmonic distortion problem caused by the difference between the polarity of the current and the reference voltage polarity by correcting the zero-sequence component, and improves the power quality; the invention can reduce the design capacity of the AC side filter and save three-level VIENNA The size and cost of the rectifier; the present invention simplifies the VIENNA modulation method, reduces the calculation amount, and is easy to implement digitally.

Based on the modified VIENNA rectifier controller injected with zero-sequence components, the present invention also provides a VIENNA rectifier control system, including the controller; the controller is used to receive three-phase input current and three-phase reference voltage, Output PWM modulation signal to drive VIENNA rectifier.

The invention solves the current harmonic distortion problem caused by the difference between the polarity of the current and the reference voltage polarity by correcting the zero-sequence component, and improves the power quality; the invention can reduce the design capacity of the AC side filter and save three-level VIENNA The size and cost of the rectifier; the present invention simplifies the VIENNA modulation method, reduces the calculation amount, and is easy to implement digitally.

Although the specific implementation of the present invention has been described above in conjunction with the accompanying drawings, it does not limit the protection scope of the present invention. Those skilled in the art should understand that on the basis of the technical solution of the present invention, those skilled in the art do not need to pay creative work Various modifications or variations that can be made are still within the protection scope of the present invention.

Claims (10)

1. revise the VIENNA rectifier modulator approach injecting zero-sequence component for one kind, it is characterised in that including:

Step 1: revise the instantaneous polarity of three-phase reference voltage according to the instantaneous polarity of three-phase input current；

Step 2: according to the space vector reference voltage that three-phase reference voltage is corresponding, calculates the zero sequence of three-phase reference voltage after revising Component；

Step 3: inject described zero-sequence component, and then calculate the dual carrier SVM equivalence dutycycle that three-phase reference voltage is corresponding；

Step 4: based on dual carrier SVM equivalence dutycycle, generates PWM modulation signal and drives VIENNA rectifier.

A kind of VIENNA rectifier modulator approach revising injection zero-sequence component the most as claimed in claim 1, it is characterised in that In described step 1, the process of the instantaneous polarity that instantaneous polarity according to three-phase input current revises three-phase reference voltage is:

Calculate space vector reference voltage corresponding after three-phase reference voltage is multiplied by SVM equivalent gain；At each fan of space vector In district, if the instantaneous polarity of a phase input current is just, then the space vector reference that in respective sectors, this phase reference voltage is corresponding Voltage keeps constant；Otherwise, space vector reference voltage superposition one correction value that this phase reference voltage is corresponding, wherein, correction value Maximum equal to three-phase reference voltage.

A kind of VIENNA rectifier modulator approach revising injection zero-sequence component the most as claimed in claim 1, it is characterised in that SVM equivalent gain isThree-phase reference voltage is multiplied by SVM equivalent gainThe space vector reference voltage of rear correspondence Span is [-1.15～1.15].

A kind of VIENNA rectifier modulator approach revising injection zero-sequence component the most as claimed in claim 1, it is characterised in that The process of the zero-sequence component of three-phase reference voltage after revising that calculates is:

Space vector reference voltage corresponding for three-phase reference voltage after amendment is sorted by size, obtains space vector reference voltage Maximum V '_max, space vector reference voltage intermediate value V '_midWith space vector reference voltage minimum V '_min；

The zero-sequence component V ' of three-phase reference voltage after correction_com=(1-V '_max+V′_min)·K-V′_min, wherein, K value is used for adjusting The neutral balance of VIENNA rectifier, for constant coefficient.

A kind of VIENNA rectifier modulator approach revising injection zero-sequence component the most as claimed in claim 4, it is characterised in that VIENNA rectifier is when equivalent space Vector Modulation SVM, and K value is 1/2.

6. the controller revising the VIENNA rectifier injecting zero-sequence component, it is characterised in that including:

The instantaneous polarity modified module of three-phase reference voltage, it is for revising three-phase according to the instantaneous polarity of three-phase input current The instantaneous polarity of reference voltage；

Zero-sequence component computing module, it calculates after revising for the space vector reference voltage corresponding according to three-phase reference voltage The zero-sequence component of three-phase reference voltage；

Equivalence dutycycle computing module, it is used for injecting described zero-sequence component, and then it is corresponding to be calculated three-phase reference voltage Dual carrier SVM equivalence dutycycle；

Modulated signal generation module, it, for based on dual carrier SVM equivalence dutycycle, generates PWM modulation signal and drives VIENNA rectifier.

A kind of controller revising the VIENNA rectifier injecting zero-sequence component the most as claimed in claim 6, it is characterised in that The instantaneous polarity modified module of described three-phase reference voltage, it is right to be additionally operable to after calculating three-phase reference voltage is multiplied by SVM equivalent gain The space vector reference voltage answered；In each sector of space vector, if the instantaneous polarity of a phase input current is just, the most accordingly The space vector reference voltage that in sector, this phase reference voltage is corresponding keeps constant；Otherwise, the space that this phase reference voltage is corresponding Vector reference voltage superposition one correction value, wherein, correction value is equal to the maximum of three-phase reference voltage.

A kind of controller revising the VIENNA rectifier injecting zero-sequence component the most as claimed in claim 6, it is characterised in that Zero-sequence component computing module includes:

Space vector reference voltage order module, it is for by space vector reference voltage corresponding for three-phase reference voltage after amendment Sort by size, obtain space vector reference voltage maximum V '_max, space vector reference voltage intermediate value V '_midVow with space Amount reference voltage minimum V '_min；

Zero-sequence component acquisition module, it is for according to V '_com=(1-V '_max+V′_min)·K-V′_min, three-phase reference after being revised The zero-sequence component of voltage, wherein, K value is for adjusting the neutral balance of VIENNA rectifier, for constant coefficient.

A kind of controller revising the VIENNA rectifier injecting zero-sequence component the most as claimed in claim 8, it is characterised in that VIENNA rectifier is when equivalent space Vector Modulation SVM, and K value is 1/2.

10. a VIENNA rectifier control system, it is characterised in that include the controller as described in claim 6-9 is arbitrary； Described controller is used for receiving three-phase input current and three-phase reference voltage, and output PWM modulation signal drives VIENNA rectification Device.