CN100517937C - Power conversion system - Google Patents

Abstract

There is provided a power conversion system capable of minimizing the capacity of a smoothing capacitor in a DC intermediate circuit. This power conversion system, having the smoothing capacitor 6 between a converter 1 and an inverter 2, includes a carrier generator 301 with a phase difference and is set with a predetermined phase difference [Delta] between a carrier C<SB>C</SB>for PWM controlling the converter 1 and a carrier C<SB>I</SB>for PWM controlling the inverter 2 to reduce the magnitude of a current flowing through the smoothing capacitor 6 by adjusting the phase difference [Delta], thus minimizing the capacitance of the smoothing capacitor 6.

Description

Power conversion system

Technical field

[0001]

The present invention relates to a kind of power conversion system that between rectifier part and inverter section, has the capacitor of the level and smooth usefulness of direct voltage, especially relate to a kind of rectifier part and inverter section power conversion system with the pulse width modulation mode action.

Background technology

[0002]

In recent years, in the control of alternating current motor that with induction motor and synchronous motor is representative, bring into use the power conversion system of the variable ratio frequency changer transformation that is called as VVVF inverter etc.At this moment, connect the power conversion system that rectifier part (converter) and inverter section (inverter) form across DC circuit in the middle of general the use.

[0003]

And, as shown in Figure 8, in above-mentioned power conversion system, for example the interchange (three-phase alternating current) of supplies such as source power supply is transformed into direct current (direct current) by rectifier, and to the smmothing capacitor charging that is arranged on the direct-flow intermediate circuit, the dc voltage conversion that will carry out this smmothing capacitor of charging by inverter becomes to have as exchange (three-phase alternating current) of the needed voltage of the alternating current motor of load with frequency then.

[0004]

Below power conversion system shown in Figure 8 is elaborated.Illustrated power conversion system is configured to have rectifier 1 and inverter 2, by PWM (pulse-width modulation) rectifier 1 and inverter 2 are controlled, adopt rectifier 1 to be transformed into direct current from the three-phase alternating current that the source power supply 3 that exchanges is supplied through reactor 7, by inverter 2 this direct current is transformed into three-phase alternating current, and is supplied to the motor 4 of three phase induction motor etc.

[0005]

And, in rectifier 1 side, the voltage that at first will constitute between the terminal of smmothing capacitor 6 of direct-flow intermediate circuit feeds back as direct voltage e, generates the current-order iA* of mains sides by AVR (voltage control part) 101, so that direct voltage e instructs e* consistent with direct voltage.Then, according to this current-order iA*, generate the voltage instruction E* of corresponding to rectifier 1 mains side of mains side electric current and instruction value by ACR (Current Control part) 102.

[0006]

Then, control, to pass through PWM (pulse width control part) 103, carrier wave CA and this voltage instruction E* of the triangular waveform of carrier forming device 104 output are compared, generate the driving pulse PA of PWM control usefulness, make each switch element SRP, SSP, STP, SRN, SSN and the STN conduction and cut-off of rectifier 1, the terminal voltage of smmothing capacitor 6 is stablized control, improve the current waveform and the power factor of AC power 3 simultaneously.

[0007]

Below inverter 2 sides are described.At first, as mentioned above, be connected with motor 4 as load in inverter 2 sides.At this moment, detect speed (rotary speed) R of this motor 4 by encoder 5, and,, make the speed of this motor 4 consistent with speed command R* to pass through the current-order iB* that ASR (speed control part) 201 generates inverters 2 with its feedback.

[0008]

Then, according to this current-order iB*, make the corresponding to inverter 2 voltage instruction V* of motor current and instruction value by ACR (Current Control part) 202 generations, and with this as modulating wave, by PWM (pulse width control part) 203, with the carrier wave CB of the triangular waveform of itself and carrier forming device 204 outputs relatively, to generate the driving pulse PB of PWM control usefulness, make each switch element SUP, SVP, SWP, SUN, SVN and the SWN conduction and cut-off of inverter 2, to supply three-phase alternating currents to motor 4.

[0009]

In the power conversion system of said PWM control mode, the input of the output of rectifier 1 and inverter 2 all becomes the cycle pulse identical with carrier wave, at this moment, in the described power conversion system of Fig. 8, as mentioned above, the carrier forming device 204 of the carrier forming device 104 of rectifier 1 side and inverter 2 sides is provided with separately, rectifier 1 and inverter 2 carry out PWM control individually by the other carrier wave different with carrier wave CB with carrier wave CA, so can't avoid phase deviation occurring in the pulse between the input current of the output current of rectifier 1 side and inverter 2 sides.

[0010]

At this moment, the electric current as the difference of the pulse type input current of the pulse type output current of rectifier 1 side and inverter 2 sides flows through smmothing capacitor 6.Therefore, if deviation occurs in the phase place of these electric currents, the electric current of the smmothing capacitor 6 of coming in and going out will increase, thereby causes variation in voltage to strengthen.

[0011]

So,, realize the smoothing of direct voltage in order to suppress the fluctuation of direct current, also be necessary to increase the capacity of smmothing capacitor 6 this moment, therefore, in power conversion system shown in Figure 8, need jumbo capacitor, thereby problems such as device maximization and cost increase can occur.

[0012]

For this reason, for example the Japanese patent of invention spy of patent documentation one opens and discloses a kind of technical scheme that addresses the above problem in the flat 4-121065 communique.Followingly the related power conversion system of this scheme is described with reference to Fig. 9.Power conversion system shown in Figure 9 is the independent carrier forming device 304 that rectifier side carrier forming device 104 of the prior art shown in Figure 8 and inverter side carrier forming device 204 are combined, and its other structures are identical with prior art shown in Figure 8.

[0013]

For this reason, in power conversion system shown in Figure 9, the PWM control of rectifier 1 and inverter 2 is undertaken by the identical carrier wave C of these carrier forming device 304 outputs after reunification, therefore, in the pulse type input current of the pulse type output current of rectifier 1 side and inverter 2 sides, therefore the leeway of phase difference does not appear in pulse, and can keep phase difference is 0 state always.

[0014]

Its result according to power conversion system shown in Figure 9, can not occur because of the impulse phase deviation causes flowing into the problem that the electric current of smmothing capacitor 6 increases, capacity that therefore can corresponding reduction smmothing capacitor 6.

Patent documentation: the spy opens flat 4-121065 communique

[0015]

There is following problem in above-mentioned prior art, promptly, do not exist the waveform difference this point to make consideration between the impulse waveform to the impulse waveform of rectifier side output current and inverter side input current, thereby have the problem that big capacity smmothing capacitor need be set in direct-flow intermediate circuit.

[0016]

In above-mentioned prior art, the rectifier side is identical with the carrier wave that the PWM of inverter side uses, but owing to exist impulse waveform poor between rectifier side and the inverter side, therefore, PWM is 0 o'clock with the phase difference of carrier wave, minimum value not necessarily appears in condenser current, so there is the problem that needs further inhibition to flow into the electric current of smmothing capacitor.

Summary of the invention

[0017]

The object of the present invention is to provide a kind of power conversion system, this power conversion system can be suppressed at Min. with the capacity that is arranged on the smmothing capacitor in the direct-flow intermediate circuit.

[0018]

Above-mentioned purpose realizes by following power conversion system, in this power conversion system, has smmothing capacitor between the rectifier part of pulse width modulation mode and the inverter section of pulse width modulation mode, wherein, be provided with the phase difference applicator, it partly carries out the carrier wave of pulse-width modulation and is used for described inverter section carrying out the carrier wave of pulse-width modulation and giving phase difference to being used for described rectifier, and the output current pulse that described phase difference is configured to described rectifier part is the phase difference during for maximum with the overlapping area of the input current pulse of described inverter section.

[0019]

At this moment, even being set in 30 °, described phase difference also can realize above-mentioned purpose with interior value, the output current pulse of perhaps described phase difference being set for described rectifier part and the overlapping area of the input current pulse of the described inverter section phase difference when maximum also can be realized above-mentioned purpose, and to set described phase difference for flow into described smmothing capacitor electric current be that hour phase difference also can be realized above-mentioned purpose.

The effect of invention

[0020]

According to the present invention, need not increase the capacity of smmothing capacitor owing to can suppress the voltage fluctuation of direct-flow intermediate circuit, so can realize the miniaturization of system and reduce cost.

Description of drawings

Fig. 1 is the square construction drawing of expression power conversion system one execution mode of the present invention.

Fig. 2 is the performance plot of the condenser current in the power conversion system.

Fig. 3 is the square construction drawing of control system one example in expression an embodiment of the present invention.

Fig. 4 is the oscillogram that is used to illustrate the action of PWM timing unit.

Fig. 5 is the flow chart of the action of control system one example in expression an embodiment of the present invention.

Fig. 6 is another the routine square construction drawing of control system in expression an embodiment of the present invention.

Fig. 7 is the flow chart of the action of another example of control system in expression an embodiment of the present invention.

Fig. 8 is the square construction drawing that power conversion system one example of prior art is adopted in expression.

Fig. 9 is another routine square construction drawing of power conversion system that prior art is adopted in expression.

Symbol description among the figure: 1 rectifier, 2 inverters, 3 source power supplies, 4 motor (alternating current motor), 5 encoders, 6 smmothing capacitors, 101,201AVR (voltage control part), 102,202ACR (Current Control part), 103,203PWM (pulse width control part), 104,204 carrier forming devices, 301 band phase difference carrier forming devices, 1000,2000,3000MPU, 1001,2001,3001CPU, 1002,1003,2002, the 3002PWM timing unit.

Embodiment

[0021]

Followingly power conversion system of the present invention is elaborated according to illustrated execution mode.

[0022]

Fig. 1 represents one embodiment of the present invention, among the figure, the generating apparatus of 301 expression band phase difference carrier waves, by this carrier forming device can generate carrier wave CC with triangular waveform and relatively this carrier wave CC have these two kinds of carrier waves of carrier wave CI of the triangular waveform of certain phase difference, and these carrier waves can be supplied with PWM103 and PWM203 respectively.In addition, other structures are identical with the described power conversion system of the prior art of Fig. 9 with Fig. 8.

[0023]

And, in the execution mode of Fig. 1, equally at first the voltage between the terminal of smmothing capacitor 6 is fed back as direct voltage e, by the current-order iA* of AVR101 generation mains side, so that direct voltage e is consistent with direct voltage instruction e* in rectifier 1 side.Then, according to this current-order iA*, generate the mains side voltage instruction E* that makes the corresponding to rectifier 1 of mains side electric current and instruction value by ACR102.

[0024]

And, by PWM103 above-mentioned voltage instruction E* and the carrier wave Cc that carries 304 outputs of phase difference carrier forming device are compared, generate the driving pulse PA of PWM control usefulness, drive each switch element SRP, SSP, STP, SRN, SSN, the STN conduction and cut-off of rectifier 1, the terminal voltage of smmothing capacitor 6 is controlled to be certain the time, obtains the AC wave shape of AC power 3 and the improvement of power factor.

[0025]

And, in inverter 2 sides, feed back by speed R equally, and, make the speed of this motor 4 consistent with speed command R* by the current-order iB* that ASR201 generates inverter 2 to encoder 5 detected motor 4.

[0026]

Then, according to this current-order iB*, make the corresponding to inverter 2 voltage instruction V* of motor current and instruction value by the ACR202 generation, and with this as modulating wave, by PWM203, another carrier wave CI that exports with band phase difference carrier forming device 304 compares, to generate the driving pulse PB of PWM control usefulness, make each switch element SUP, SVP, SWP, SUN, SVN and the SWN conduction and cut-off of inverter 2, to supply three-phase alternating currents to motor 4.

[0027]

Therefore, in execution mode shown in Figure 1, equally rectifier 1 and inverter 2 are carried out PWM control, the three-phase alternating current of source power supply 3 being supplied by rectifier 1 is transformed into direct current, and this direct current is transformed into three-phase alternating current by inverter 2, to supply with the motor 4 of three phase induction motor 4 grades, above structure is identical with above-mentioned power conversion system of the prior art, different is that employed carrier wave is another carrier wave CI that has certain phase difference with respect to the carrier wave CC that uses among the PWM103 in PWM203.

[0028]

Its result, in Fig. 1 execution mode, become the phase place identical from the impulse phase of the electric current of rectifier 1 output with carrier wave CC, and the impulse phase that is input to the electric current of inverter 2 becomes the phase place identical with carrier wave CI, its result is from the impulse phase of the electric current of rectifier 1 output be input between the impulse phase of electric current of inverter 2 and be endowed the phase difference suitable with phase difference.

[0029]

As mentioned above, the electric current as the difference of the pulse type input current of the pulse type output current of rectifier 1 side and inverter 2 sides flows through smmothing capacitor 6.Therefore, can infer at an easy rate that as long as deviation appears in the impulse phase of these electric currents, the electric current of the smmothing capacitor 6 of coming in and going out will increase.

[0030]

Therefore, in the described prior art of Fig. 9, use identical carrier wave C in rectifier 1 side with inverter 2 sides, making the phase difference of the pulse type input current of the pulse type output current of rectifier 1 side and inverter 2 sides is 0, and Fig. 2 estimates as the size of the parameter pair condenser current (coming in and going out in the electric current of smmothing capacitor 6) relative with the carrier phase difference of this moment and the performance plot that obtains with the size of load.

[0031]

At this moment, Fig. 2 is a benchmark when representing to be 90 ° with carrier phase difference, the capacitor electrode flow valuve of this moment is normalized to 1.0 situation.So-called herein carrier phase difference refers to that the carrier phase of relative rectifier 1 deducts the phase difference that obtains after the carrier phase of inverter 2.In addition, so-called load refers to the power output of inverter 2, is 100% with rated power.

[0032]

Can know from Fig. 2, if there is phase difference in rectifier 1 with the phase place of the carrier wave of inverter 2, then condenser current is bound to increase, yet rectifier 1 might not be the condition that minimum value appears in condenser current with the phase place identical (phase difference is 0) of the carrier wave of inverter 2.

[0033]

The chances are for its reason owing to there is the cause of different wave shape between the input current pulse of the output current pulse of rectifier 1 and inverter 2.This be because, if impulse waveform is identical, be 0 as long as make phase difference, all will be input to the inverter 2 from whole electric currents of rectifier 1 output, so condenser current should be 0 in theory.

[0034]

Can know that so in impulse waveform not simultaneously, the condition that condenser current becomes minimum value should be that both equitant areas of pulse become maximum the time, at this moment, the area of pulse overlap changes by changing phase place.For this reason, as long as the phase place of paired pulses, just the phase place of carrier wave is adjusted, and just can make condenser current become minimum.

[0035]

At this, according to the execution mode of Fig. 1, from the impulse phase of the electric current of rectifier 1 output be input between the impulse phase of electric current of inverter 2 and be endowed the phase difference suitable with phase difference.For this reason, by regulating this phase difference, just condenser current can be adjusted to minimum value.

[0036]

At this moment, Fig. 2 for example in, the minimum value of condenser current occurs when phase difference is about 30 °, and at this moment, condenser current is 0.5～0.6, with phase difference is that 0 o'clock condenser current 0.6～0.7 is compared, can reduce condenser current, therefore, according to present embodiment, can reduce the capacity of smmothing capacitor 6, thus miniaturization that can implement device.

[0037]

, in recent years, in above-mentioned power conversion system, generally adopt microcomputer, promptly so-called microcomputer is controlled rectifier and inverter.Therefore, describe with regard to an embodiment of the present invention that adopts microcomputerized control below.

[0038]

Execution mode shown in Figure 3 is the execution mode of the part beyond the main circuit that is made of rectifier 1 and inverter 2 and smmothing capacitor 6 in Fig. 1 execution mode when being made of MPU (microprocessor) 1000.For this reason, as shown in the figure, have CPU1001 and PWM timing unit 1002,1003, output port 1004,1005 and input port 1006 among the MPU1000.And, only represented among the figure to carry out the required part of following explanation, and in fact this MPU1000 also has servicing units such as RS.

[0039]

In addition, the program of CPU1001 is configured to read data necessary from input port 1006, realize the function of control system shown in Figure 1 by calculation process, result in as it, the modulation signal of rectifier 1 is supplied with PWM timing unit 1002, simultaneously the modulation signal of inverter 2 is supplied with PWM timing unit 1003, by PWM timing unit 1002 separately, 1003 carry out PWM control, the driving pulse PA of rectifier 1 and the driving pulse PB of inverter 2 are exported from output port 1004,1005 respectively.

[0040]

At this moment, be provided with not shown timer in these PWM timing units 1002,1003, carry out up timing and descending timing, can obtain the carrier signal that is used for PWM by this timer.For this reason, describe with regard to the detailed action of this moment with reference to Fig. 4 below.

[0041]

At first, have register in the PWM timing unit 1002, be set with voltage instruction E* in this register.At this, shown in Fig. 4 (a), in voltage instruction E*, last side line H is equivalent to the command voltage value with the interval of following side line L.And this voltage instruction E* and carrier wave C compare, and when both were consistent, as shown in the figure, pwm pulse PA generated and exports from output port 1004.Its result, voltage and the corresponding direct current of voltage instruction E* are from rectifier 1 output.

[0042]

In addition, in PWM timing unit 1003, have register too, be set with voltage instruction V* in this register.At this, shown in Fig. 4 (b), in this voltage instruction V*, last side line H also is equivalent to magnitude of voltage with the interval of following side line L, but this moment, it also is the sinusoidal wave shape variation according to the output frequency of inverter 2.

[0043]

And this voltage instruction V* and carrier wave C Δ compare, and when both were consistent, as shown in the figure, pwm pulse PB generated and exports from output port 1005.Its result is from inverter 2 output voltages and the corresponding three-phase alternating current of voltage instruction V*.

[0044]

In addition, the program of this CPU1001 is configured to the processing shown in further execution graph 5 flow charts.At this, the processing shown in Fig. 5 flow chart is only carried out once when 1002,1003 startings of above-mentioned PWM timing unit, afterwards, carries out the transition to and carries out described PWM timing unit 1002,1003 generation pwm pulse PA and the necessary processing of pwm pulse PB.

[0045]

Processing shown in Figure 5 is from P101, in the processing of P102, P103, carries out the initial settings such as pattern setting of PWM timing unit 1002,1003 in the processing of P101.Afterwards, the timer in the PWM timing unit 1002 is picked up counting, in P105, wait for then the timer in the PWM timing unit 1003 being picked up counting the stipulated time process.

[0046]

Its result, pick up counting till the timer that plays PWM timing unit 1003 picks up counting from the timer of PWM timing unit 1002, only give delaying of stipulated time of setting among the P105, and delay corresponding with this, carrier wave to rectifier 1 and inverter 2 is given phase difference, therefore, and by will the stipulated time at this moment being set at suitable value, promptly be arranged to then can reduce the capacity of smmothing capacitor 6 for the required value of the electric current that reduces smmothing capacitor 6.

[0047]

; in execution mode shown in Figure 3; by the control of a MPU1000 execution to rectifier 1 and inverter 2; but also can use different MPU respectively rectifier 1 and inverter 2 to be controlled; at this moment; as shown in Figure 6, generate the driving pulse PA of rectifier 1, and generate the driving pulse PB of inverter 2 by another MPU3000 by a MPU2000.

[0048]

For this reason, in MPU2000, by the required processing of computing realization rectifier 1 control of CPU2001, and as its operation result, the modulation signal of rectifier 1 is sent to PWM timing unit 2002 carrying out PWM control, and from the driving pulse PA of output port 2003 output rectifiers 1.

[0049]

Equally, in MPU3000, by the required processing of computing realization inverter 2 controls of CPU3001, and as its operation result, the modulation signal of inverter 2 is sent to PWM timing unit 3002 carrying out PWM control, and from the driving pulse PB of output port 3003 output inverters 2.

[0050]

The flowcharting of Fig. 7 is carried out the action of the band phase difference carrier forming device 301 shown in Figure 1 in Fig. 6 execution mode and the processing that need carry out, Fig. 7 (a) is the process chart of the PWM timing unit 2002 of MPU2000 when starting, Fig. 7 (b), (c) be the PWM timing unit 3002 of the MPU3000 process chart when starting, these are handled all and only carry out once before entering normal control, at this moment, enter the processing of P201 and P301.

[0051]

In by the processing that MPU2000 carried out shown in Fig. 7 (a), begin to enter processing from P201, by treatment step P202, carry out the initial settings such as pattern setting of PWM timing unit 2002.Afterwards, the interrupt signal that in treatment step P203, is used for MPU3000 to output port 2004 outputs.Afterwards, in treatment step P204, the not shown timer in the PWM timing unit 2002 is picked up counting.

[0052]

In the processing of being undertaken by the MPU3000 shown in Fig. 7 (b), begin to enter processing from P301, by treatment step P302, carry out the initial settings such as pattern setting of PWM timing unit 3002.Afterwards, in treatment step P303 to wait for the state standby of interrupt signal.And, in interrupt signal port 3004, if detect interrupt signal from MPU2000, then enter treatment step P401, in treatment step P402, wait for the official hour process, in treatment step P403, the not shown timer in the PWM timing unit 3002 is picked up counting.

[0053]

Thus, the stipulated time that sets in the treatment step of phase difference by P105 of the carrier wave of rectifier 1 and inverter 2 is guaranteed, can be reduced the electric current of smmothing capacitor 6.And, in the present embodiment,,, can suppress cost so compare with the MPU1000 of Fig. 3 owing to the computational load identical with CPU1001 in Fig. 3 execution mode can be distributed to CPU2001 and two of CPU3001 carry out, therefore have the effect that reduces cost.

[0054]

And, in above-described execution mode, as shown in the figure, switch element SRP, SSP, STP, SRN, SSN and the STN of rectifier 1 and switch element SUP, SVP, SWP, SUN, SVN and the SWN of inverter 2, all be that example is illustrated, but can certainly use FET (field-effect transistor) to wait other semiconductor element with IGBT.

Claims (1)

1, a kind of power conversion system has smmothing capacitor between the inverter section of the rectifier of pulse width modulation mode part and pulse width modulation mode, it is characterized in that,

Be provided with the phase difference applicator, it partly carries out the carrier wave of pulse-width modulation and is used for described inverter section carrying out the carrier wave of pulse-width modulation and giving phase difference to being used for described rectifier,

The output current pulse that described phase difference is configured to described rectifier part is the phase difference during for maximum with the overlapping area of the input current pulse of described inverter section.

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