TWI721897B - Detection apparatus for unbalanced dc link capacitor voltage - Google Patents

Abstract

A detection apparatus for unbalanced DC link capacitor voltage, and the DC link provides a DC voltage and includes a plurality of capacitors coupled in series to two ends of the DC link and a plurality of balanced resistors, respectively corresponding to the capacitors, coupled in series to two ends of the DC link. The detection apparatus includes a plurality of detection resistors and a current sensor. One end of each detection resistor is coupled to a common contact of two adjacent capacitors, and the other end thereof is coupled to a common contact of two adjacent balanced resistors. The current sensor is coupled to one of the detection resistors and detects a current value flowing through the corresponding detection resistor.

Description

Device for detecting unbalanced DC link capacitor voltage

The present invention relates to a detection device for capacitor voltage, especially a detection device for unbalanced DC link capacitor voltage.

Please refer to FIG. 1A and FIG. 1B, which are the circuit block diagrams of the current DC link capacitor voltage distribution for single-phase AC voltage conversion and the current circuit block diagrams of the DC link capacitor voltage distribution for three-phase AC voltage conversion. Take the DC link capacitor voltage distribution of single-phase AC voltage conversion as an example. The AC voltage V _{AC is} converted by an AC/DC converter (for example, but not limited to a three-level converter) to make it in DC The DC link has a first DC voltage V ₁ and a second DC voltage V ₂ , or the DC link voltage is converted into an AC voltage V _AC through an AC/DC converter. There is a neutral point N between the first DC voltage V ₁ (across the first capacitor C ₁₁ ) and the second DC voltage V ₂ (across the second capacitor C _{21 ).} Due to the three-level characteristic, the first DC voltage V ₁ and the second DC voltage V ₂ are limited to half of the DC link voltage V _3. Generally speaking, in order to enable the first capacitor C ₁₁ and the second capacitor C ₂₁ to equally bear (share) the DC link voltage V ₃ , the first balancing resistor R is connected in parallel to the first capacitor C ₁₁ and the second capacitor C _{21 11} and the second balancing resistor R ₂₁ . Among them, the DC link voltage V ₃ can be the DC link end of any power product, for example, but not limited to solar panels, wind energy, or microgrids. The principle of the DC link capacitor voltage distribution in the three-phase AC voltage conversion of FIG. 1B is similar to that of FIG. 1A, so it will not be repeated here.

Please refer to Figure 2, which is a circuit block diagram of another method of current single-phase DC link capacitor voltage distribution. With the maximum power and efficiency of power products, in order to maintain the same conduction loss of the internal components of the power products, it is imperative to increase the voltage range of the power products. Therefore, a series of multiple capacitors that increase the power of the power supply by increasing the DC link voltage V ₃ is proposed to share the voltage on the DC link, that is, the capacitor C ₁₁ and the capacitor C ₁₂ share the first DC voltage V ₁ , the capacitor C ₂₁ and capacitor C ₂₂ share the second DC voltage V ₂ . In order to achieve the _{average voltage across the capacitors in the first DC voltage V 1} and the second DC voltage V ₂ , each capacitor is connected in parallel to achieve a passive voltage average. As shown in Figure 2, the capacitor C ₁₁ and the capacitor C are connected in parallel with the resistor ₁₂ and the resistor R ₁₁ R _12, and a capacitor C ₂₁ and the capacitor C ₂₂ are connected in parallel a resistor R ₂₁ and the resistor R _22. Among them, the capacitances of the capacitors C ₁₁ , C ₁₂ , C ₂₁ and C _{22 are} approximately equal, and the resistances of the resistors R ₁₁ , R ₁₂ , R ₂₁ and R _{22 are} approximately equal.

However, once any one of the capacitors corresponding to the first DC voltage V ₁ or the second DC voltage V ₂ is open or shorted, its voltage will cross over other components that are still working normally, causing problems such as damage to the normal components. . In order to solve this problem, the current technology mainly adopts the detection of the voltage feedback of each capacitor to determine whether the voltage is abnormal. However, this method is more expensive and causes an increase in uncertain factors in the feedback control. Furthermore, when the capacitor is connected in series The greater the number, the lower the effectiveness of the current technology.

For this reason, how to design a detection device for DC link capacitor voltage imbalance to detect the occurrence of DC link voltage imbalance is an important subject studied by the inventors of this case.

The purpose of the present invention is to provide a detection device for the voltage imbalance of the DC link capacitor, which solves the problems of the prior art.

In order to achieve the aforementioned purpose, the present invention proposes a device for detecting unbalanced DC link capacitor voltage, wherein the DC link provides a DC voltage, and includes a plurality of capacitors coupled in series to both ends of the DC link, and two capacitors coupled in series to the DC link The terminals correspond to the complex balancing resistances of the complex capacitors respectively. The detection device includes a plurality of detection resistors and current detectors. One end of each detection resistor is coupled to the common junction of the two capacitors, and the other end of each detection resistor is coupled to the common junction of the two balancing resistors. The current detector is coupled to one of the plurality of detection resistors for detecting the current value flowing through the corresponding detection resistor.

In one embodiment, the DC voltage is obtained by converting the AC voltage by an AC/DC converter, or the DC voltage is used to provide the AC/DC converter to convert the AC voltage.

In one embodiment, the AC/DC converter is a converter with a multi-stage architecture.

In one embodiment, the DC voltage is obtained by converting another DC voltage through a DC-DC converter, or the DC voltage is used to provide the DC-DC converter to convert into another DC voltage.

In one embodiment, the current detector is a Hall current sensor or a current sense amplifier.

In one embodiment, the DC voltage is a voltage greater than 1000 volts.

With the proposed detection device for DC link capacitor voltage imbalance, it can be detected whether a plurality of capacitors bear the DC voltage balance or not, so as to eliminate the situation when abnormal voltage occurs.

Another object of the present invention is to provide a device for detecting unbalanced DC link capacitor voltage, which solves the problems of the prior art.

In order to achieve the purpose of the foregoing disclosure, the DC link capacitor voltage unbalance detection device proposed by the present invention has a neutral point, provides a first DC voltage and a second DC voltage, and includes a device coupled in series to both ends of the DC link A complex capacitor, and a complex balancing resistor coupled in series to both ends of the DC link and corresponding to the complex capacitor. The detection device includes a plurality of detection resistors and current detectors. One of each detection resistor One end is coupled to the common junction of the two capacitors, and the other end of each detection resistor is coupled to the common junction of the two balancing resistors. The current detector is coupled to one of the plurality of detection resistors for detecting the current value flowing through the corresponding detection resistor.

In one embodiment, the first DC voltage and the second DC voltage are obtained by converting the AC voltage through an AC/DC converter, or the first DC voltage and the second DC voltage are used to provide the AC/DC converter to convert the AC voltage , And the AC/DC converter is a multi-stage architecture converter.

In one embodiment, the current detector is a Hall current sensor or a current sense amplifier.

With the proposed detection device for DC link capacitor voltage imbalance, it can be detected whether a plurality of capacitors bear the DC voltage balance or not, so as to eliminate the situation when abnormal voltage occurs.

Yet another object of the present invention is to provide a detection device for the voltage imbalance of the DC link capacitor to solve the problems of the prior art.

In order to achieve the purpose of the foregoing disclosure, the present invention proposes a device for detecting unbalanced DC link capacitor voltage, wherein the DC link has a neutral point and provides a first DC voltage and a second DC voltage, and includes two DC links coupled in series. The complex capacitors at the end and the complex balancing resistors coupled in series to the two ends of the DC link and corresponding to the complex capacitors respectively. The detecting device includes a plurality of detecting resistors, a first current detector and a second current detector. One end of each detection resistor is coupled to the common junction of the two capacitors, and the other end of each detection resistor is coupled to the common junction of the two balance resistors, but there is no detection resistor at the neutral point. The first current detector is coupled to one of the plurality of detection resistors corresponding to the first DC voltage for detecting the first current value flowing through the corresponding detection resistor. The second current detector is coupled to one of the plurality of detection resistors corresponding to the second DC voltage for detecting the second current value flowing through the corresponding detection resistor.

In one embodiment, the first DC voltage and the second DC voltage are obtained by converting the AC voltage through an AC/DC converter, or the first DC voltage and the second DC voltage are used to provide the AC/DC converter to convert the AC voltage , And the AC/DC converter is a multi-stage architecture converter.

In one embodiment, the first current detector and the second current detector are a Hall current sensor or a current sense amplifier.

With the proposed detection device for the voltage imbalance of the DC link capacitor, it can be detected whether the plurality of capacitors bear the balance between the first DC voltage and the second DC voltage, so as to eliminate the situation when the abnormal voltage occurs.

In order to have a better understanding of the technology, means and effects adopted by the present invention to achieve the intended purpose, please refer to the following detailed description and drawings of the present invention. I believe that the purpose, features and characteristics of the present invention can be obtained from this in depth and For specific understanding, however, the accompanying drawings are only provided for reference and illustration, and are not intended to limit the present invention.

V _AC : AC voltage

V _{AC_R} ,V _{AC_S} ,V _{AC_T} : AC voltage

V ₁ : the first DC voltage

V ₂ : Second DC voltage

V ₃ : DC link voltage

N: neutral point

C ₁₁ : the first capacitor

C ₂₁ : second capacitor

R ₁₁ : The first balance resistor

R ₂₁ : The second balance resistor

V _DC : DC voltage

V _DC1 : the first DC voltage

V _DC2 : second DC voltage

C ₁₁ ~C _1N : Capacitance

R _B11 ~R _B1N : Balancing resistance

R _S1 ~R _SM : Detection resistance

C ₁₁ ~C _1P ,C ₂₁ ~C _2Q : Capacitance

R _B11 ~R _B1P ,R _B21 ~R _B2Q : Balancing resistance

C ₁₁ ~C _1N ,C ₂₁ ~C _2N : Capacitance

R _B11 ~R _B1N ,R _B21 ~R _B2N : Balancing resistance

R _S11 ~R _S1M ,R _S21 ~R _S2M : detection resistance

A: Current detector

A ₁ : The first current detector

A ₂ : The second current detector

I _S : current value

I _S1 : the first current value

I _S2 : second current value

Figure 1A: It is a circuit block diagram of the existing DC link capacitor voltage distribution for single-phase AC voltage conversion.

Figure 1B: It is a circuit block diagram of the DC link capacitor voltage distribution for the existing three-phase AC voltage conversion.

Figure 2: It is a circuit block diagram of another method of DC link capacitor voltage distribution for the existing single-phase AC voltage conversion.

Fig. 3 is a circuit block diagram of the detection device of the DC link capacitor voltage imbalance of the present invention.

Fig. 4 is a circuit block diagram of the first embodiment of the detection device for the DC link capacitor voltage imbalance of the present invention.

FIG. 5 is a circuit block diagram of the second embodiment of the detection device for detecting the unbalanced DC link capacitor voltage according to the present invention.

Fig. 6 is a circuit block diagram of the third embodiment of the detection device for the DC link capacitor voltage imbalance of the present invention.

Fig. 7 is a circuit diagram of the current sense amplifier of the present invention.

The technical content and detailed description of the present invention are described below in conjunction with the drawings.

Please refer to FIG. 3, which is a circuit block diagram of the detection device for the DC link capacitor voltage imbalance of the present invention. At the DC link of the AC/DC converter, in order to detect whether the first DC voltage V ₁ and the second DC voltage V ₂ are unbalanced, the detection resistors R _S1 and R _{S2 are provided} for detection. One end of the detection resistor R _S1 is coupled to the common junction of the two capacitors C ₁₁ and C _{12 , and the other end of the detection resistor R S1} is coupled to the common junction of the two balancing resistors R ₁₁ and R _12. One end of the detection resistor R _S2 is coupled to the common junction of the two capacitors C ₂₁ and C _{22 , and the other end of the detection resistor R S2} is coupled to the common junction of the two balancing resistors R ₂₁ and R _22.

The principle of detecting whether the first DC voltage V ₁ and the second DC voltage V ₂ are unbalanced by the detection resistors R _S1 and R _{S2 is: taking the detection of the first DC voltage V 1} as an example, when the first DC voltage V _{When the voltages of the capacitors of 1} (ie, the capacitor C ₁₁ and the capacitor C ₁₂ ) are balanced, the detection resistor R _S1 does not flow current, so the _{voltage across the detection resistor R S1} is 0 volts.

Assuming that any capacitor voltage is abnormal, the detection resistor R _S1 will instantaneously flow current, that is, a cross voltage will be generated on the detection resistor R _S1 . For example, suppose that the first DC voltage V ₁ is 2 _{kV, where the voltage borne by the capacitor C 11} is 0.9 k volts, and _{the voltage borne by the capacitor C 12} is 1.1 k volts. Obviously, any capacitor voltage imbalance occurs (When balanced, the capacitor C ₁₁ and the capacitor C ₁₂ should each bear 1k volts). At this time, a current flows through the _{capacitor C 12} through the detection resistor R _S1 to the balancing resistor R _{12 , and another current flows through the balancing resistor R 11} through the capacitor C ₁₁ to the detection resistor R _S1 . Therefore, the detection resistor R _{For S1} , the net current flowing through is the sum of the two currents, and the direction is from left to right (viewed from the front view direction of FIG. 3) flowing through the detection resistor R _S1 . Therefore, when the current flowing through the detection resistor R _S1 is non-zero, it indicates that the voltages of the capacitors (ie, the capacitor C ₁₁ and the capacitor C ₁₂ ) of the _{first DC voltage V 1 are unbalanced.} Similarly, assuming that the first DC voltage V ₁ is 2k volts, _{the voltage borne by the capacitor C 11} is 1.1 k volts, and _{the voltage borne by the capacitor C 12} is 0.9 k volts. Obviously, any capacitor voltage imbalance occurs situation. At this time, a current flows through the _{capacitor C 11} through the balancing resistor R ₁₁ to the detection resistor R _{S1 , and another current flows through the balancing resistor R 12} through the detection resistor R _S1 to the capacitor C ₁₂ , therefore, the detection resistor R _{For S1} , the net current flowing through is the sum of the two currents, and its direction is from right to left (viewed from the front view direction of FIG. 3) flowing through the detection resistor R _S1 . Therefore, when the current flowing through the detection resistor R _S1 is non-zero, it indicates that the voltages of the capacitors (ie, the capacitor C ₁₁ and the capacitor C ₁₂ ) of the _{first DC voltage V 1 are unbalanced.}

Therefore, as long as the detection resistor R _{S1 is} provided with a current detector, such as, but not limited to, a Hall current sensor, or a current sense amplifier implemented by an operational amplifier (OPA) as shown in Figure 7, It can measure whether the current flowing through the detection resistor R _S1 is zero to determine whether the voltages of the capacitors are balanced. For the current sense amplifier of Figure 7, as long as _{the current flowing through the detection resistor R S} (ie, the current I _S ) is zero, _{the cross voltage V S} formed at both ends of the _{detection resistor R S} is also zero. Therefore, after amplification through the gain resistor R _a and the resistor R _B to provide the output voltage V _S 'is zero volts. Conversely, as long as the current flowing through the detection resistor R _S I _S is not zero, voltage V _S across the sensing resistor R _S is formed at both ends of zero nor, therefore, provided through a resistor R _A and the resistor R _B of After the gain is amplified, the output voltage V _S ′ is a certain non-zero voltage value. Therefore, it can be determined that the voltages of the capacitors (ie, the capacitor C ₁₁ and the capacitor C _{12 ) of the first DC voltage V 1} are unbalanced. Among them, the detection method of the detection resistor R _S2 in FIG. 3 is the same as that of the detection resistor R _S1 , so it is not repeated here.

Please refer to FIG. 4, which is a circuit block diagram of the first embodiment of the detection device for the DC link capacitor voltage imbalance of the present invention. The DC link provides a DC voltage V _DC , where the DC voltage V _DC can be an AC/DC converter (for example, but not limited to a converter with a multi-level architecture) to convert the DC output from the _{AC voltage V AC} Voltage, or another DC voltage output by converting a DC voltage (not shown) through a DC-to-DC converter. The direct current voltage V _DC is a voltage greater than 1k volts. Furthermore, in FIG. 4, the DC link capacitor voltage converted from single-phase AC voltage is taken as an example. In different applications, it can also be the DC link capacitor voltage converted from three-phase AC voltage (see FIG. 1B).

Referring again to Figure 4, the circuit includes capacitors C ₁₁ ~C _1N , balancing resistors R _B11 ~R _B1N , detecting resistors R _S1 ~R _SM and current detector A. The capacitors C _{11 ˜C 1N are} coupled in series to form a DC link, so as to averagely bear the DC voltage V _DC . The balancing resistors R _B11 ~R _{B1N are} coupled in series and correspond to the parallel capacitors C ₁₁ ~C _1N . For example, the balancing resistor R _B11 corresponds to the capacitor C ₁₁ , and so on, the balancing resistor R _B1N corresponds to the capacitor C _1N . One end of each detection resistor R _S1 ~R _SM is coupled to the common connection of two capacitors C ₁₁ ~ C _1N , and the other end of each detection resistor R _S1 ~ R _SM is coupled to the common connection of two balancing resistors R _B11 ~ R _B1N point. For example, one end of the _{detection resistor R S1} is coupled to the common junction _{of the capacitor C 11} and the capacitor C ₁₂ , and the other end of the _{detection resistor R S1 is coupled to the common junction of the balance resistor R B11} and the balance resistor R _B12 . The current detector A is coupled to one of the detection resistors R _S1 ~ R _SM to detect the current value flowing through the corresponding detection resistor R _S1 ~ R _SM . Taking Figure 4 as an example, the current detection The device A detects the current value I _S flowing through the detection resistor R _SM .

When the current value I _{S is} non-zero, the detection device detects that the capacitance C ₁₁ ~ C _1N bears the DC voltage V _DC as unbalanced; on the contrary, when the current value I _S is zero, the detection device detects the capacitance C ₁₁ ~ C _1N bear the DC voltage V _DC for balance. In this embodiment, the number of capacitors C ₁₁ to C _1N and balancing resistors R _B11 to R _B1N is N each, and the number of detecting resistors R _S1 to R _SM is M, where M=N-1. As shown in Figure 4, although the current detector A is coupled to the detection resistor R _SM to measure the current value flowing through the detection resistor R _SM , it is used as a judgment capacitor C ₁₁ ~ C _{1N to} bear the DC voltage V _DC balance Whether or not, however, the current detector A can also be coupled to other detection resistors. Similarly, the principle of net current flowing through the corresponding detection resistor can be used according to the aforementioned principle, as long as there is any capacitor C ₁₁ ~C _1N When the DC voltage V _DC is unbalanced, it can be judged by the non-zero current value measured by the current detector A.

Please refer to FIG. 5, which is a circuit block diagram of the second embodiment of the detection device for the DC link capacitor voltage imbalance of the present invention. The DC link has a neutral point N and provides a first DC voltage V _DC1 and a second DC voltage V _DC2 , wherein the voltage summation of the first DC voltage V _DC1 and the second DC voltage V _{DC2 can be AC/DC} A converter (for example, but not limited to a converter with a multi-level architecture) converts the DC link voltage V _{3 output by the AC voltage V AC} , or converts the DC voltage through a DC-to-DC converter (not shown) The output of another DC link voltage V ₃ . The first DC voltage V _DC1 and the second DC voltage V _DC2 are voltages greater than 1 kV. Furthermore, in FIG. 5, the DC link capacitor voltage converted from single-phase AC voltage is taken as an example. In different applications, it can also be the DC link capacitor voltage converted from three-phase AC voltage (see FIG. 1B).

Referring again to Figure 5, the circuit includes capacitors C ₁₁ ~C _1P , C ₂₁ ~ C _2Q , balancing resistors R _B11 ~ R _B1P , R _B21 ~ R _B2Q , detection resistors R _S1 ~ R _SM and current detector A. The capacitors C ₁₁ ~C _1P , C ₂₁ ~ C _{2Q are} coupled in series to form a DC link, which is used to averagely bear the first DC voltage V _DC1 and the second DC voltage V _DC2 , that is, the capacitors C ₁₁ ~C _1P equally bear the first The DC voltage V _DC1 , and the capacitors C ₂₁ ~C _2Q assume the second DC voltage V _{DC2 on} average. The balancing resistors R _B11 ~R _B1P and R _B21 ~R _{B2Q are} coupled in series and correspond to the parallel capacitors C ₁₁ ~C _1P , C ₂₁ ~C _2Q . For example, the balancing resistor R _B11 corresponds to the capacitor C ₁₁ , and so on, the balancing resistor R _B2Q corresponds to the capacitor C _2Q . One end of each detection resistor R _S1 ~R _SM is coupled to the common junction of two capacitors C ₁₁ ~C _1P , C ₂₁ ~C _2Q , and the other end of each detection resistor R _S1 ~R _SM is coupled to two balancing resistors R _B11 ~R _B1P ,R _B21 ~R _B2Q common contact point. For example, one end of the _{detection resistor R S1} is coupled to the common junction _{of the capacitor C 11} and the capacitor C ₁₂ , and the other end of the _{detection resistor R S1 is coupled to the common junction of the balance resistor R B11} and the balance resistor R _B12 . The current detector A is coupled to one of the detection resistors R _S1 ~ R _SM to detect the current value flowing through the corresponding detection resistor R _S1 ~ R _SM . Taking Figure 5 as an example, the current detection The device A detects the current value I _S flowing through the detection resistor R _SM .

When the current value I _{S is} non-zero, the detection device detects that the capacitors C ₁₁ ~C _1P , C ₂₁ ~ C _2Q bear the first DC voltage V _DC1 or the second DC voltage V _DC2 are unbalanced; on the contrary, when When the current value I _S is zero, the detecting device detects that the capacitors C ₁₁ ~C _1P , and C ₂₁ ~ C _2Q bear the balance between the first DC voltage V _DC1 and the second DC voltage V _DC2. In this embodiment, the number of capacitors C ₁₁ to C _1P , C ₂₁ to C _2Q and balancing resistors R _B11 to R _B1P , R _B21 to R _B2Q are P+Q, and the number of detection resistors R _S1 to R _SM The number is M, where M=P+Q-1. As shown in FIG. 5, although the current detector A is coupled to the detection resistor R _SM to measure the current value flowing through the detection resistor R _SM , it is used as the judgment capacitor C ₁₁ ~ C _{1P to} bear the first DC voltage V _DC1 and capacitors C ₂₁ ~ C _{2Q are} responsible for whether the second DC voltage V _{DC2 is} balanced or not. However, the current detector A can also be coupled to other detection resistors. Similarly, the corresponding detection can be performed through the aforementioned records The principle of the net current of the resistance, as long as any capacitor C ₁₁ ~C _1P bears the first DC voltage V _DC1 or any capacitor C ₂₁ ~C _2Q bears the second DC voltage V _DC2 imbalance, it can be detected by the current Determined by the non-zero current value measured by the device A.

Please refer to FIG. 6, which is a circuit block diagram of the third embodiment of the detection device for the DC link capacitor voltage imbalance of the present invention. The DC link has a neutral point N and provides a first DC voltage V _DC1 and a second DC voltage V _DC2 , where the first DC voltage V _DC1 and the second DC voltage V _DC2 can be AC/DC converters (for example , But not limited to multi-level (multi-level) architecture converters) convert _{the DC voltage output by the AC voltage V AC} , or convert another DC voltage output by the DC voltage (not shown) through a DC-to-DC converter . The first DC voltage V _DC1 and the second DC voltage V _DC2 are voltages greater than 1 kV. Furthermore, in FIG. 6, the DC link capacitor voltage converted from single-phase AC voltage is taken as an example. In different applications, it can also be the DC link capacitor voltage converted from three-phase AC voltage (see FIG. 1B).

Refer to Figure 6 again, the circuit includes capacitors C ₁₁ ~C _1N , C ₂₁ ~C _2N , balancing resistors R _B11 ~R _B1N , R _B21 ~R _B2N , detection resistors R _S11 ~R _S1M , R _S21 ~R _S2M , The first current detector A ₁ and the second current detector A ₂ . The capacitors C ₁₁ ~C _1N and C ₂₁ ~C _{2N are} coupled in series to form a DC link, which is used to equally bear the first DC voltage V _DC1 and the second DC voltage V _DC2 , that is, the capacitors C ₁₁ ~C _1N equally bear the first The DC voltage V _DC1 , and the capacitors C _{21 ˜C 2N} averagely bear the second DC voltage V _DC2 . Balancing resistors R _B11 to R _B1N and R _B21 to R _{B2N are} coupled in series and correspond to parallel capacitors C ₁₁ to C _1N , C ₂₁ to C _2N . For example, the balancing resistor R _B11 corresponds to the capacitor C ₁₁ , and so on, the balancing resistor R _B2N corresponds to the capacitor C _2N . One end of each detection resistor R _S11 ~R _S1M , R _S21 ~ R _S2M is coupled to the common junction of two capacitors C ₁₁ ~ C _1N , C ₂₁ ~ C _2N , and each detection resistor R _S11 ~ R _S1M , R _S21 ~ The other end of R _S2M is coupled to the common contact of two balancing resistors R _B11 ~R _B1N , R _B21 ~ R _B2N , but there is no detection resistor R _S11 ~ R _S1M , R _S21 ~ R _{S2M on the neutral point N.} For example, one end of the _{detection resistor R S11} is coupled to the common junction _{of the capacitor C 11} and the capacitor C ₁₂ , and the other end of the _{detection resistor R S11 is coupled to the common junction of the balancing resistor R B11} and the balancing resistor R _B12 . The first current detector A _{1 is} coupled to one of the detection resistors R _S11 ~ R _S1M corresponding to the first DC voltage V _DC1 for detecting the current flowing through the corresponding detection resistors R _S11 ~ R _S1M Taking FIG. 6 as an example, the first current detector A ₁ detects the first current value I _S1 flowing through the detection resistor R _S1M .

Wherein, when the first current value I _{S1 is} non-zero, the detection device detects that the capacitors C ₁₁ ~ C _1N bear the first DC voltage V _DC1 as unbalanced; on the contrary, when the first current value I _S1 is zero, the detection device The measuring device detects that the capacitors C ₁₁ to C _1N assume the first DC voltage V _{DC1 to} be balanced. The second current detector A _{2 is} coupled to one of the detection resistors R _S21 ~ R _S2M corresponding to the second DC voltage V _DC2 for detecting the current flowing through the corresponding detection resistors R _S21 ~ R _S2M Taking FIG. 6 as an example, the second current detector A ₂ detects the second current value I _S2 flowing through the detection resistor R _S2M . When the second current value I _{S2 is} non-zero, the detecting device detects that the capacitors C ₂₁ ~ C _2N bear the second DC voltage V _DC2 as unbalanced; on the contrary, when the second current value I _S2 is zero, the detection device The measuring device detects that the capacitors C ₂₁ ~ C _2N assume the second DC voltage V _{DC2 to} be balanced. In this embodiment, the number of capacitors C ₁₁ to C _1N , C ₂₁ to C _2N and balancing resistors R _B11 to R _B1N , R _B21 to R _B2N is 2N, and the number of detection resistors R _S11 to R _S1M , R _S21 to The number of R _S2M is 2M, where M=N-1. As shown in FIG. 6, although the first current detector A _{1 is} coupled to the detection resistor R _S1M to measure the current value flowing through the detection resistor R _S1M , the first current detector A 1 is used to determine the capacitance C ₁₁ ~C _1N . _{Whether the} DC voltage V DC1 is balanced or not. However, the first current detector A ₁ can also be coupled to other detection resistors. Similarly, the aforementioned principle of recording the net current flowing through the corresponding detection resistor can be used as long as there is any capacitor C ₁₁ ~ C _1N when the first DC voltage V _DC1 bear unbalanced, all can be judged by the current value of the a ₁ is a non-zero measured first current detector. Similarly, although the second current detector A _{2 is} coupled to the detection resistor R _S2M for measuring the current value flowing through the detection resistor R _S2M , it is used as the judgment capacitor C ₂₁ ~ C _{2N to} bear the second DC voltage V _DC2 balance or not. However, the second current detector A ₂ can also be coupled to other detection resistors. Similarly, the above-mentioned principle of net current flowing through the corresponding detection resistor can be used, as long as there is any capacitor C ₂₁ ~C _2N When the second DC voltage V _{DC2 is} unbalanced, it can be judged by the non-zero current value measured by the second current detector A _2.

The above embodiments are all described in an ideal situation. In actual situations, there will be some errors in the component values between the capacitors and the balancing resistors, so that the net current flowing through the detection resistors is balanced even when the DC voltage borne by the capacitors is balanced. In the case of, it is still not zero, so in actual conditions, a current threshold Ith (not necessarily zero) can be set as a basis for judging whether the DC voltage borne by each capacitor is balanced or unbalanced. That is, when the net current measured by the current detector is greater than the current threshold Ith, it is judged that the DC voltage borne by each capacitor is unbalanced.

In summary, the present invention has the following features and advantages:

1. The device for detecting the unbalanced DC link capacitor voltage of the present invention can be applied to a circuit structure of the DC link capacitor voltage and impedance matching for single-phase and three-phase AC voltage conversion.

2. The detection circuit of the present invention does not overlap the main circuit loop, so the detection circuit will not affect the operation of the main circuit, and this detection method does not affect the circuit control behavior.

3. For multiple sets of capacitors connected in series, it is only necessary to measure the current value of one set of detection resistors or two sets of detection resistors to determine whether the multiple sets of capacitors in series bear the balance of the corresponding DC voltage. .

The above are only detailed descriptions and drawings of the preferred embodiments of the present invention. However, the features of the present invention are not limited to these, and are not intended to limit the present invention. The full scope of the present invention shall be within the scope of the following patent applications. As the standard, all embodiments that conform to the spirit of the patent application of the present invention and similar changes should be included in the scope of the present invention. Anyone familiar with the art in the field of the present invention can easily think of changes or Modifications can be covered in the following patent scope of this case.

V _AC : AC voltage

V _DC : DC voltage

C ₁₁ ~C _1N : Capacitance

R _B11 ~R _B1N : Balancing resistance

R _S1 ~R _SM : Detection resistance

A: Current detector

I _S : current value

V ₃ : DC link voltage

Claims (12)

A device for detecting unbalanced DC link capacitor voltage, wherein the DC link provides a DC voltage, and includes a plurality of capacitors coupled in series to both ends of the DC link, and a plurality of capacitors coupled in series to both ends of the DC link and corresponding to the A complex balancing resistor of a capacitor; the detection device includes: a plurality of detection resistors, one end of each detection resistor is coupled to a common contact of two capacitors, and the other end of each detection resistor is coupled to a common contact of two balancing resistors ; And a current detector, coupled to one of the detection resistors, used to detect a current value flowing through the corresponding detection resistor. The device for detecting unbalanced DC link capacitor voltage according to claim 1, wherein the DC voltage is obtained by converting an AC voltage through an AC/DC converter, or the DC voltage is used to provide the AC/DC converter Convert to this AC voltage. The device for detecting unbalanced DC link capacitor voltage according to claim 2, wherein the AC/DC converter is a converter with a multi-stage structure. The device for detecting unbalanced DC link capacitor voltage according to claim 1, wherein the DC voltage is obtained by converting another DC voltage through a DC-to-DC converter, or the DC voltage is used to provide the DC-to-DC conversion Converter to the other DC voltage. The device for detecting unbalanced DC link capacitor voltage according to claim 1, wherein the current detector is a Hall current sensor or a current sense amplifier. The device for detecting unbalanced DC link capacitor voltage according to claim 1, wherein the DC voltage is a voltage greater than 1000 volts. A device for detecting unbalanced DC link capacitor voltage, wherein the DC link has a neutral point, provides a first DC voltage and a second DC voltage, and includes two DC links coupled in series A plurality of capacitors at the two ends of the DC link, and a plurality of balancing resistors coupled in series to the two ends of the DC link and corresponding to the capacitors; the detection device includes: a plurality of detection resistors, one end of each detection resistor is coupled to a common connection Point, the other end of each detection resistor is coupled to a common contact of two balancing resistors; and a current detector is coupled to one of the detection resistors for detecting the corresponding detection resistor that flows through A current value for measuring resistance. The device for detecting unbalanced DC link capacitor voltage according to claim 7, wherein the first DC voltage and the second DC voltage are obtained by converting an AC voltage through an AC/DC converter, or the first DC The voltage and the second DC voltage are used to provide the AC/DC converter to convert to the AC voltage, and the AC/DC converter is a converter with a multi-stage structure. The device for detecting unbalanced DC link capacitor voltage according to claim 7, wherein the current detector is a Hall current sensor or a current sense amplifier. A device for detecting unbalanced DC link capacitor voltage, wherein the DC link has a neutral point, provides a first DC voltage and a second DC voltage, and includes a plurality of capacitors coupled in series to both ends of the DC link, and The detecting device includes a plurality of detecting resistors, one end of each detecting resistor is coupled to a common contact of the two capacitors, each of the detecting resistors is coupled to the two ends of the DC link and corresponding to the complex balancing resistors of the capacitors. The other end of the measuring resistor is coupled to a common contact of the two balancing resistors, but the neutral point does not have the detection resistor; a first current detector is coupled to the detection resistors corresponding to the first DC voltage One of them is used to detect a first current value flowing through the corresponding detection resistor; and a second current detector is coupled to one of the detection resistors corresponding to the second DC voltage It is used to detect a second current value flowing through the corresponding detection resistor. The device for detecting unbalanced DC link capacitor voltage according to claim 10, wherein the first DC voltage and the second DC voltage are obtained by converting an AC voltage through an AC/DC converter, or the first DC The voltage and the second DC voltage are used to provide the AC/DC converter to convert to the AC voltage, and the AC/DC converter is a converter with a multi-stage structure. The device for detecting unbalanced DC link capacitor voltage according to claim 10, wherein the first current detector and the second current detector are a Hall current sensor or a current sense amplifier.

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