Background technology
Along with the raising of the semiconductor element characteristic that is used for electric power, the high frequency of switching frequency is achieved.With the power inverter of supply unit as representative, to quick response, the requirement of low low noise, the considerations such as miniaturization requirement of filter, extensively adopt the high frequency switch mode that has used PWM control take non-break power supply, communication.
Along with the development of switching frequency high frequency, the high-frequency leakage current that flow into ground via direct-current chain or cable also increases.This high-frequency leakage current flow in the AC system, becomes noise, and other devices that are connected on the AC system are caused bad influence, and this has become social concern.For example, in non-break power supply, especially connect in (floating) mode of floating in the situation of storage battery of large electric capacity in DC side, existence flows into the tendency of larger high-frequency leakage current earthward from this storage battery and long direct current cables, and this high-frequency leakage current brings bad influence for other alternating current equipments that are connected on the AC system.
Flow out to the method for the high-frequency leakage current of AC system as reduction, the known active filter that record in the patent documentation 1 is for example arranged.Fig. 5 is the existing denoising device of record in the patent documentation 1 and the structure chart of power inverter.Among Fig. 5, ground wire E0, E1, E2 are public earth terminals, for convenience of explanation, give respectively different symbols.
Three-phase alternating-current supply 1, power inverter 3, load 5 have been shown among Fig. 5 and be arranged at three-phase alternating-current supply 1 and power inverter 3 between active filter 7.
Be wound with the power line 1a~1c of 1 circle and the detection line 20a of N circle on the current transformer 20 as current detector, detect the common mode current io of generation on the power inverter 3 with the detection ratio of 1/N (N is greater than 1) by detection line, as detecting current i o/N output.Capacitor C2 has capacitor C1's (N-1) admittance doubly.
(emitter is connected with detection line 20a between emitter), flows into the current i o/N that equates with the detection electric current among the capacitor C1 for the input (base stage) of the amplifier 11 that is made of transistor 11a, 11b and output.And the electric current that flow into capacitor C2 is (N-1) electric current (N-1) io/N doubly that flow into the current i o/N of capacitor C1.That is the electric current that, flow into ground wire E1 is the N current i o doubly that detects current i o/N.
Detect electric current and be power inverter 3 common mode current io 1/N doubly, the electric current that flow into amplifier 11 equates with common mode current i o, can offset with the common mode current that flows out to AC system.Thus, can reduce the common mode current that flows out to AC system.
But in power inverter shown in Figure 53, in the situation that flows into larger offset current, the terminal voltage of capacitor C1, C2 can increase.If this terminal voltage surpasses the supply voltage of amplifier 11, then amplifier 11 is saturated, can not get the reduction effect of common mode current.In order to address this problem, come the supply voltage of Design enlargement device 11 according to maximum offset current.
Fig. 6 and Fig. 7 are the concrete structure examples of the DC power supply of existing active filter.Among Fig. 6, just utilize diode D7 and capacitor C5 that the alternating voltage of the three-phase alternating-current supply 1 of AC system is carried out rectification level and smooth, generate the DC power supply (working power) of amplifier 11.Among Fig. 7, utilize diode D7, D8, D9, capacitor C5, C6, transistor Q7 and resistance 13c, the alternating voltage of the three-phase alternating-current supply 1 of AC system is carried out 1/2 voltage commutation level and smooth, generate the DC power supply (working power) of amplifier 11.
Patent documentation 1: TOHKEMY 2008-312429 communique
But, in Fig. 6, structure shown in Figure 7, all the time transistor 11a, the 11b that consists of amplifier 11 applied the roughly voltage of half of DC power supply Vc (terminal voltage of capacitor C5), the shortcoming that exists transistor 11a, 11b heating to increase.And the loss of transistor 11a, 11b is directly proportional with the supply voltage (and offset current) of amplifier 11.When the offset current that is used for compensation (counteractings) common mode current hour, the loss of larger amplifier still occurs, the efficient of entire system is poor.
Summary of the invention
The object of the invention is to, provide a kind of can be at offset current active filter and the power inverter of hour step-down amplifier loss.
The first invention relates to a kind of active filter, it is arranged between the three-phase alternating-current supply and power inverter of 1 power line as Earth Phase among 3 power lines, for reducing the noise that is caused by the common mode current that flow into described power line, this power inverter will convert predetermined alternating electromotive force or direct current power to from the alternating electromotive force that described three-phase alternating-current supply is supplied with and supply with to load, and has earth terminal on the housing of this power inverter, described active filter is characterised in that, described active filter possesses: variable DC power supply, it obtains electric power from described power line, changes into arbitrarily VD and output; Current detecting unit, it is inserted and is connected with described power line and detection line, detects described common mode current by described detection line, the output common mode current detection signal; Amplifier, it as supply voltage, amplifies with 1 times magnification ratio the VD of described variable DC power supply to described common mode current detection signal, via the first capacitor, electric current is flowed between the power line and ground of described Earth Phase; And voltage detection unit, it detects the output amplitude of described amplifier, according to the output amplitude detection signal that described voltage detection unit detects, changes the VD of described variable DC power supply.
The second invention relates to a kind of active filter, it is arranged between the three-phase alternating-current supply and power inverter of 1 power line as Earth Phase among 3 power lines, described active filter is for reducing the noise that is caused by the common mode current that flow into described power line, this power inverter will convert predetermined alternating electromotive force or direct current power to from the alternating electromotive force that described three-phase alternating-current supply is supplied with and supply with to load, and has earth terminal on the housing of this power inverter, described active filter is characterised in that, described active filter possesses: variable DC power supply, it obtains electric power from described power line, changes into arbitrarily VD and output; Current detecting unit, it is inserted and is connected with described power line and detection line, by the detection ratio detection described common mode current of described detection line with 1/N (N>1), output common mode current detection signal; Amplifier, it as supply voltage, amplifies with 1 times magnification ratio the VD of described variable DC power supply to described common mode current detection signal, via the first capacitor, electric current is flowed between the power line and ground of described Earth Phase; The second capacitor, (N-1) admittance doubly that it has described the first capacitor, make electric current from and described amplifier roughly idiostatic terminal flow between the power line and ground of described Earth Phase; And voltage detection unit, it detects the output amplitude of described amplifier, according to the output amplitude detection signal that described voltage detection unit detects, changes the VD of described variable DC power supply.
The 3rd invention relates to a kind of power inverter, it will convert predetermined alternating electromotive force or direct current power to from the alternating electromotive force that three-phase alternating-current supply is supplied with and supply with to load, described power inverter is characterised in that, the first or second active filter of inventing is arranged at input side.
According to the present invention, the output amplitude of voltage detection unit detecting amplifier, the output amplitude detection signal that detects according to voltage detection unit, change the VD of variable DC power supply, so at offset current hour, the supply voltage of amplifier diminishes, loss that can step-down amplifier.
Embodiment
Below, with reference to accompanying drawing, describe the execution mode of active filter of the present invention and power inverter in detail.
[embodiment 1]
Fig. 1 is the active filter of embodiment 1 and the structure chart of power inverter.Three-phase alternating-current supply 1, power inverter 3, load 5 have been shown among Fig. 1 and be arranged at three-phase alternating-current supply 1 and power inverter 3 between active filter 7-1.
Be connected with mutually power line 1a, the S power line 1b of usefulness and the T power line 1c of usefulness mutually mutually of usefulness of R on the three-phase alternating-current supply 1, the S mutually power line 1b of usefulness is the power line of Earth Phase, ground connection.The housing of power inverter 3 (framework) 3a links to each other and ground connection with earth terminal E.Between power inverter 3 and the housing 3a direct-to-ground capacitance is arranged everywhere, these summary sheets are shown the negative pole of capacitor C0 of power inverter 3 and the direct-to-ground capacitance 4 between the earth terminal E.
R is connected on terminal R1, S1, the T1 of active filter 7-1 with power line 1a~1c with, T mutually mutually with, S mutually.Amplifier 11, low frequency de-couple capacitors C1 (the first capacitor), diode D7, capacitor C5, uninsulated variable DC power supply 30, diode D8, capacitor C3, resistance R 1, R2 that active filter 7-1 has current transformer 10 (current detecting unit), is made of NPN transistor 11a and PNP transistor 11b.
Uninsulated variable DC power supply 30 has input terminal, lead-out terminal, public terminal and output voltage and adjusts terminal, DC input voitage is input between input terminal and the public terminal, and the corresponding VD of signal that will and be input to output voltage adjustment terminal outputs between lead-out terminal and the public terminal.This variable DC power supply 30 is by consisting of such as chopper-type transducer etc.
Reel on the helical coil of current transformer 10 (running through) have 1T (circle) to use mutually power line 1a~1c, and be wound with 1T detection line 10a with, T mutually with, S mutually as the R of main power line.
The anode of diode D7 (anode) is connected to R mutually on the power line 1a of usefulness, and the negative electrode of diode D7 (cathode) is connected on the end of the input terminal of variable DC power supply 30 and capacitor C5.The other end of capacitor C5 is connected on the public terminal of the collector electrode (Collector) of power line 1b, transistor 11b of Earth Phase and variable DC power supply 30.The two ends of capacitor C5 are connected between the input terminal and public terminal of variable DC power supply 30.The direct voltage of capacitor C5 is applied on the variable DC power supply 30 as DC input voitage.
The collector electrode of transistor 11a is connected on the lead-out terminal of variable DC power supply 30, the base stage of transistor 11a is connected on the end of the end of base stage, detection line 10a of transistor 11b and low frequency de-couple capacitors C1, and the other end of low frequency de-couple capacitors C1 is connected on the earth terminal E.
The emitter of transistor 11a is connected on the anode of the other end of emitter, detection line 10a of transistor 11b and diode D8, and the negative electrode of diode D8 is connected on the end of the end of capacitor C3 and resistance R 1.The other end of resistance R 1 is connected on the collector electrode of the other end of capacitor C3 and transistor 11b via resistance R 2.
Resistance R 1 is connected on the output adjustment terminal of variable DC power supply 30 with the tie point of resistance R 2.The voltage detection unit that is made of diode D8, capacitor C3, resistance R 1, R2 detects the voltage of the tie point between resistance R 1 and the resistance R 2, output amplitude as amplifier 11, according to the output amplitude that detects, change the VD Vr of variable DC power supply 30.
And, be connected in series with accordingly respectively choke coil L1, L2, L3 inserting on power line 1a, the 1b led to current transformer 10, the 1c.Power inverter 3 has choke coil L1, L2, L3,6 diode D1~D6, consists of switch element Q1~Q6 and capacitor C0 by 6 IGBT.The two ends of the series circuit of the two ends of the series circuit of the two ends of the series circuit of switch element Q1 and switch element Q2, switch element Q3 and switch element Q4 and switch element Q5 and switch element Q6 are connected on the two ends and load 5 of capacitor C0.
Be connected with accordingly respectively diode D1~D6 between collector electrode-emitter of switch element Q1~Q6.Be connected with choke coil L1 on the tie point between diode D1 and the diode D2, be connected with choke coil L2 on the tie point of diode D3 and diode D4, be connected with choke coil L3 on the tie point of diode D5 and diode D6.Each gate terminal of switch element Q1~Q6 is connected on the not shown control circuit, by this control circuit the on/off of switch element Q1~Q6 is controlled, power inverter 3 carries out work as transducer (converter) (AC/DC conversion equipment), will convert predetermined direct current power to from the alternating electromotive force that three-phase alternating-current supply 1 is supplied with and supplies with to load 5.
In addition, as power inverter, can also use to convert predetermined alternating electromotive force to from the alternating electromotive force that three-phase alternating-current supply 1 is supplied with and supply with inverter (inverter) to load 5.
Then, with reference to Fig. 1, the work of the active filter of embodiment 1 is described.At first, in current transformer 10, if flow into common mode current i among power line 1a~1c of 1T
0, then also flow into the current i identical with common mode current among the detection line 10a of 1T
0
Amplifier 11 with 1 times magnification ratio to flowing into the current i of detection line 10a
0Amplify, via low frequency de-couple capacitors C1, flow into ground wire E1.At this moment, utilize diode D8 and capacitor C3 that rectification is carried out in the output of the emitter of transistor 11a, 11b level and smooth, detect the voltage of the tie point between resistance R 1 and the resistance R 2, output amplitude as amplifier 11, according to the output amplitude detection signal that detects, change the VD Vr of variable DC power supply 30.Therefore, when the offset current of be used for offsetting common mode current hour, the supply voltage of amplifier 11 diminishes, loss that also can step-down amplifier 11.
Fig. 2 represents that the VD Vr of variable DC power supply 30 is according to the situation of the both end voltage change of the capacitor C3 (corresponding with the voltage of the tie point of resistance R 2 with resistance R 1) of the active filter of embodiment 1.As shown in Figure 2, proportionally linear change of the voltage of the VD Vr of variable DC power supply 30 and capacitor C3.
[embodiment 2]
Fig. 3 is the active filter of embodiment 2 and the structure chart of power inverter.The difference of the active filter 7-1 of the active filter 7-2 of embodiment 2 shown in Figure 3 and embodiment 1 shown in Figure 1 is, is wound with the detection line 20a of N circle (N>1, for example 10 circles) on the current transformer 20.
Be connected with low frequency de-couple capacitors C2 between the emitter of transistor 11a, 11b and the earth terminal E.The admittance of low frequency de-couple capacitors C2 is 9 times of admittance of low frequency de-couple capacitors C1.That is, low frequency de-couple capacitors C2 has 9 times capacitance of the electric capacity of low frequency de-couple capacitors C1.
According to the active filter of the embodiment 2 of such formation, at first, in current transformer 20, if flow into common mode current i among power line 1a~1c of 1T
0, then flow into 1/10th current i of common mode current among the detection line 20a of 10T
1=i
0/ 10.
Amplifier 11 is equal to and possesses following amplifier V1 and amplifier V2, and this amplifier V1 controls voltage, so that flow into the current i of low frequency de-couple capacitors C1
1Equal current i
0/ 10, this amplifier V2 has the voltage identical with the voltage of enlarging section V1, to the low frequency de-couple capacitors C2 inflow current i of 9 times of electric capacity with low frequency de-couple capacitors C1
2=9i
1=9i
0/ 10.
That is, 1/10th of the common mode current that detection line 20a detected with 1 times magnification ratio of enlarging section V1 current i
0/ 10 amplify, and C1 flow into ground wire E1 via the low frequency de-couple capacitors.And enlarging section V2 will flow into the current i of low frequency de-couple capacitors C1
1=i
0/ 10 9 times current i
2=9i
1=9i
0/ 10 flow into ground wire E1 via frequency separation capacitor C2.
Therefore, flow into and the common mode current i among the ground wire E1
0The current i of identical value
0So, can reduce the common mode current that flows out to AC system.So can reduce the noise that produces, can realize low cost and miniaturization.
And, utilize diode D8 and capacitor C3 that rectification is carried out in the output of the emitter of transistor 11a, 11b level and smooth, detect the voltage of the tie point of resistance R 1 and resistance R 2, output amplitude as amplifier 11, according to the output amplitude detection signal that detects, change the VD Vr of variable DC power supply 30.Therefore, when the offset current of be used for offsetting common mode current hour, the supply voltage of amplifier 11 diminishes, and can reduce the loss of amplifier 11 at ordinary times.
[embodiment 3]
Fig. 4 is the active filter of embodiment 3 and the structure chart of power inverter.The difference of the active filter 7-2 of the active filter 7-3 of embodiment 3 shown in Figure 4 and embodiment 2 shown in Figure 3 is, instead of capacitor C1, C2, be provided with resistance R 3, R4, capacitor C4, resistance R 3, R4 are connected in series, and be connected between the base stage and emitter of transistor 11a, 11b, between the tie point of resistance R 3, R4 and earth terminal E, be connected capacitor C4.
Resistance R 4 has 9 times admittance of the admittance (inverse of resistance value) of resistance R 3.That is, resistance R 4 has 1/9 times resistance value of resistance R 3.
According to the active filter of the embodiment 3 of such formation, at first, in current transformer 20, if flow into common mode current i among power line 1a~1c of 1T
0, then flow into 1/10th current i of common mode current in the detection line of 10T
1=i
0/ 10.
Amplifier 11 is equal to and possesses following amplifier V1 and amplifier V2, and this amplifier V1 controls voltage, so that flow into the current i of resistance R 3
1Equal current i
0/ 10, this amplifier V2 has the voltage identical with the voltage of enlarging section V1, to the resistance R 4 inflow current i of 9 times of resistance values with resistance R 3
2=9i
1=9i
0/ 10.
That is, 1/10th of the common mode current that detection line 20a detected with 1 times magnification ratio of enlarging section V1 current i
0/ 10 amplify, and flow into ground wire E1 via resistance R 3 and capacitor C4.And enlarging section V2 will flow into the current i of resistance R 3
1=i
0/ 10 9 times current i
2=9i
1=9i
0/ 10 flow into ground wire E1 via resistance R 4 and capacitor C4.
Therefore, flow into and the common mode current i among the ground wire E1
0The current i of identical value
0So, can reduce the common mode current that flows out to AC system.So can reduce the noise that occurs, realize low cost and miniaturization.
And, utilize diode D8 and capacitor C3 that rectification is carried out in the output of the emitter of transistor 11a, 11b level and smooth, detect the voltage of the tie point of resistance R 1 and resistance R 2, output amplitude as amplifier 11, according to the output amplitude detection signal that detects, change the VD Vr of variable DC power supply 30.Therefore, when the offset current of be used for offsetting common mode current hour, the supply voltage of amplifier 11 diminishes, loss that can step-down amplifier 11.
In addition, the invention is not restricted to the active filter of embodiment 1 to embodiment 3.In embodiment 2, can also adopt following structure, that is, be connected in series resistance R 3 at capacitor C1, be connected in series resistance R 4 at capacitor C2.
Utilizability on the industry
The present invention can be used for take non-break power supply or communicates by letter with the power inverter of supply unit as representative.