CN114244106A - Converter and suspension voltage suppression method - Google Patents
Converter and suspension voltage suppression method Download PDFInfo
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- CN114244106A CN114244106A CN202111679326.8A CN202111679326A CN114244106A CN 114244106 A CN114244106 A CN 114244106A CN 202111679326 A CN202111679326 A CN 202111679326A CN 114244106 A CN114244106 A CN 114244106A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/04—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage
- H02H9/042—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage comprising means to limit the absorbed power or indicate damaged over-voltage protection device
Abstract
The application discloses a converter and a suspension voltage suppression method, which suppress suspension voltage generated by a suspended input end. The main circuit of the converter comprises a plurality of paths of input and single-path output DC/DC units, the negative poles of all paths of input ends of the DC/DC units are directly connected with a negative direct current bus, all paths of input voltage sampling circuits of the DC/DC units are grounded, and the sampling reference ground of the input voltage sampling circuits is isolated from the negative direct current bus; the input end of the DC/DC unit is provided with a suspension voltage suppression circuit; the floating voltage suppression circuit includes: and the resistance unit is connected between the anode and the cathode of the input end of the circuit.
Description
Technical Field
The invention relates to the technical field of power electronics, in particular to a converter and a suspension voltage suppression method.
Background
Fig. 1 shows a converter whose main circuit comprises a multi-input single-output DC/DC unit. The DC/DC unit includes: the multi-path DC/DC module (fig. 1 only takes two paths of DC/DC modules as an example, PV1+ and PV 1-respectively represent the positive and negative input poles of the DC/DC module 1, PV2+ and PV 2-respectively represent the positive and negative input poles of the DC/DC module 2), the output end of each path of DC/DC module is connected in parallel with a DC BUS, the input end of each path of DC/DC module is independently connected with a power supply, and the negative input pole of each path of DC/DC module is directly connected with a negative DC BUS BUS-.
When the input voltage sampling circuits respectively arranged for each DC/DC module are grounded, and the DC/DC unit adopts a floating design (the floating design refers to that a negative direct current BUS BUS is isolated from a sampling reference ground AGND of the input voltage sampling circuit), if the input end of the individual DC/DC module is not connected with a power supply and is suspended, the suspended input end generates a suspension voltage, and when the suspension voltage is high, the risk of personal electric shock is brought, and the converter control system can make a misjudgment that the suspended input end is connected with the power supply.
Disclosure of Invention
Accordingly, the present invention provides a converter and a floating voltage suppressing method for suppressing a floating voltage generated at a floating input terminal.
A converter comprises a main circuit and a plurality of input single-output DC/DC units, wherein the negative poles of all input ends of the DC/DC units are directly connected with a negative direct-current bus, all input voltage sampling circuits of the DC/DC units share the ground, and the sampling reference ground of all input voltage sampling circuits of the DC/DC units is isolated from the negative direct-current bus;
the input end of the DC/DC unit is provided with a suspension voltage suppression circuit; the floating voltage suppression circuit includes: and the resistance unit is connected between the anode and the cathode of the input end of the circuit.
Optionally, the floating voltage suppression circuit includes: the detection unit and the two resistance units with different resistance values; the detection unit is used for selecting one of the two resistance units with different resistance values to be connected between the positive electrode and the negative electrode of the input end of the circuit according to whether the input end of the circuit is suspended or not.
Optionally, the detection unit is specifically configured to, when the input end of the current path is suspended, access the resistance unit with a smaller resistance value between the positive electrode and the negative electrode of the input end of the current path, and otherwise, access the resistance unit with a larger resistance value between the positive electrode and the negative electrode of the input end of the current path.
Optionally, the detecting unit includes: the device comprises a resistance voltage division unit and a judgment unit;
the resistance voltage division unit is connected between the anode and the cathode of the input end of the circuit;
the judging unit judges whether the input end of the circuit is suspended according to the difference of the voltage applied to the resistance voltage dividing unit when the input end of the circuit is suspended, the resistance unit with smaller resistance is connected between the positive pole and the negative pole of the input end of the circuit, otherwise, the resistance unit with larger resistance is connected between the positive pole and the negative pole of the input end of the circuit.
Optionally, the resistance voltage dividing unit divides voltage by connecting two resistance modules in series, and the divided voltage of one of the resistance modules is sent to the judging unit;
the judgment unit compares the divided voltage with a preset value, when the voltage of the resistance voltage division unit is larger than the preset value, the input end of the circuit is judged to be suspended, the resistance unit with smaller resistance value is connected between the positive electrode and the negative electrode of the input end of the circuit, otherwise, the resistance unit with larger resistance value is connected between the positive electrode and the negative electrode of the input end of the circuit.
Optionally, the resistance unit with smaller resistance value is marked as a resistance unit R3The resistance unit with larger resistance value is marked as a resistance unit R2(ii) a Two resistance modules in the resistance voltage division unit are respectively marked as resistance modules R1And a resistance module R4；
The judging unit includes: resistance module R5Resistance module R6The switch module T1, the switch module T2 and the voltage regulator tube module D1;
wherein R is1、R2And R3One end of the first and second switches is connected to the positive pole of the input end of the current path;
R1and the other end of T1 is connected with the control end of T1 and R4One end of (a);
R2another end of the D1 is connected with the power input end of T1, the cathode of D1 and R5One end of (a);
R5at the other end R6And a control terminal of T2;
R3the other end of the T-shaped connector is connected with the power input end of the T2;
R4the other end of (1), the power output end of T1, the anode of D1, R6The other end of the T2 and the power output end of the T2 are both connected to the negative pole of the input end of the circuit;
the resistance value setting satisfies: when the input end of the current path is connected with a power supply, R4The voltage at two ends is greater than the threshold voltage of T1; when the input end of the current path is suspended, R4Voltage acrossLess than the threshold voltage of T1, and R6The voltage across is greater than the threshold voltage of T2.
Optionally, the switch module T1 and the switch module T2 are both switch tubes.
Optionally, the converter is a multi-input single-output DC/DC converter, or the converter is a photovoltaic inverter with multi-MPPT input.
Optionally, the DC/DC unit is a Boost type, Buck type, or Boost-Buck type DC/DC unit.
Optionally, the input voltage sampling circuit is a non-isolated differential sampling circuit.
A suspension voltage suppression method is applied to a converter, a main circuit of the converter comprises a plurality of paths of input and single-path output DC/DC units, the negative poles of all paths of input ends of the DC/DC units are directly connected with a negative direct current bus, all paths of input voltage sampling circuits of the DC/DC units are grounded, and the sampling reference ground of all paths of input voltage sampling circuits of the DC/DC units is isolated from the negative direct current bus; the input end of the DC/DC unit is provided with a suspension voltage suppression circuit, and the suspension voltage suppression circuit comprises two resistance units with different resistance values;
the method comprises the following steps:
the suspension voltage suppression circuit detects whether the input end of the circuit is suspended or not;
the suspension voltage suppression circuit selects one of the two resistance units with different resistance values to be connected between the positive electrode and the negative electrode of the input end of the circuit according to whether the input end of the circuit is suspended or not.
Optionally, selecting one of the two resistance units with different resistance values to be connected between the positive electrode and the negative electrode of the input end of the local circuit according to whether the input end of the local circuit is suspended or not, includes:
when detecting that the input end of the current path is suspended, the resistor unit with smaller resistance is connected between the positive electrode and the negative electrode of the input end of the current path, otherwise, the resistor unit with larger resistance is connected between the positive electrode and the negative electrode of the input end of the current path.
Optionally, the floating voltage suppression circuit is connected with a resistance voltage division unit between the positive electrode and the negative electrode of the input end of the circuit;
correspondingly, the floating voltage suppression circuit detects whether the input end of the circuit is suspended, and the method comprises the following steps: and judging whether the input end of the current path is suspended or not according to the difference of the voltages applied to the resistance voltage division units when the input end of the current path is suspended or not.
As can be seen from the above technical solution, the coupling relationship between the input voltages of the DC/DC unit determines: after the resistance unit is connected between the positive electrode and the negative electrode of the input end of the DC/DC unit, the suspension voltage generated when the input end of the current path is suspended is the partial voltage of the resistance unit, the smaller the resistance value of the resistance unit is set, and the smaller the partial voltage of the resistance unit, namely the suspension voltage, is when the input end of the current path is suspended, so that the suspension voltage can be effectively inhibited.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic diagram of a converter structure disclosed in the prior art;
FIG. 2 is a schematic diagram of a converter according to an embodiment of the present invention;
FIG. 3 is a specific topology example of a converter without the introduction of a floating voltage suppression circuit;
FIG. 4 is an equivalent circuit diagram of the coupling relationship between the input voltages of the DC/DC modules in the example shown in FIG. 3;
fig. 5 is an equivalent circuit diagram of the example shown in fig. 3 when the input terminal of the DC/DC module 2 is floating and the floating voltage suppression circuit is introduced;
fig. 6 is an equivalent circuit diagram of the example shown in fig. 3 when the input terminal of the DC/DC module 2 is connected to the power supply and the floating voltage suppression circuit is introduced (the resistor R2 in fig. 6 > the resistor R3 in fig. 5);
fig. 7 is a schematic diagram of a floating voltage suppression circuit according to an embodiment of the present invention;
FIG. 8 is a schematic view of the unit of FIG. 7 as applied to FIG. 6;
FIG. 9 is a schematic view of the unit of FIG. 7 as applied to FIG. 5
Fig. 10 is a flowchart of a floating voltage suppression method according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 2, an embodiment of the present invention discloses a converter, a main circuit of which includes a multi-input single-output DC/DC unit (fig. 2 also takes only the DC/DC unit sharing two DC/DC modules as an example);
the negative electrode of each input end of the DC/DC unit is directly connected with a negative direct current BUS (direct connection means direct electrical communication), and each input voltage sampling circuit of the DC/DC unit is grounded in common (namely each input voltage sampling circuit shares one sampling reference ground AGND), and the sampling reference ground AGND is isolated from the negative direct current BUS; the input end of the DC/DC unit is provided with a floating voltage suppression circuit (in fig. 2, the floating voltage suppression circuits corresponding to the DC/DC module 1 and the DC/DC module 2 are respectively referred to as a floating voltage suppression circuit 1 and a floating voltage suppression circuit 2), and the floating voltage suppression circuit can adopt any one of the following two implementation modes 1) -2):
1) the floating voltage suppression circuit includes: and the resistance unit is connected between the anode and the cathode of the input end of the circuit.
The coupling relationship between the input voltages of the DC/DC unit given in fig. 2 determines: after the resistance unit is connected between the positive electrode and the negative electrode of the input end of the DC/DC unit, the suspension voltage generated when the input end of the current path is suspended is the partial voltage of the resistance unit, so that the smaller the resistance value of the resistance unit is set, the smaller the partial voltage of the resistance unit, namely the suspension voltage, is when the input end of the current path is suspended, and the suspension voltage can be effectively inhibited. However, there is a disadvantage that a certain loss is caused when the input terminal of the present path is connected to a power supply, and the smaller the resistance value of the resistor unit is set, the larger the loss is, so the resistance value of the resistor unit is recommended to be selected in a compromise manner according to the low power loss and the suppression effect of the floating voltage.
2) The floating voltage suppression circuit includes: the detection unit and the two resistance units with different resistance values; the detection unit is used for selecting one of the two resistance units with different resistance values to be connected between the positive electrode and the negative electrode of the input end of the circuit according to whether the input end of the circuit is suspended or not. The detection unit is particularly used for connecting a resistance unit with a smaller resistance value between the positive electrode and the negative electrode of the input end of the circuit when the detection unit detects that the input end of the corresponding DC/DC module is suspended, so that the voltage of the input end of the circuit is clamped at a lower value, the suspension voltage is restrained, and the risk of personal electric shock is avoided; on the contrary, the resistance unit with larger resistance value is connected between the positive electrode and the negative electrode of the input end of the circuit, so that the voltage of the input end of the circuit is clamped at a higher value and the converter is not subjected to larger power loss. It can be seen that, compared to the above implementation 1), this preferred solution achieves both low power consumption and the floating voltage suppression effect without compromising the effect.
The functions of the detection unit may be implemented by software, hardware, or a combination of software and hardware, without limitation.
Optionally, the converter may be a DC/DC converter with multi-input and single-output, or the converter may also be a photovoltaic inverter with multi-MPPT (Maximum Power Point Tracking) input, and is not limited. When the converter is a multi-input single-output DC/DC converter, the power supply can be a photovoltaic assembly or an energy storage battery and the like; when the converter is a photovoltaic inverter with multiple MPPT inputs, the power source is a photovoltaic cell. In addition, the DC/DC module may be a Boost topology, a Buck topology, or a Boost-Buck topology, and is not limited. In addition, the input voltage sampling circuit is a non-isolation resistance voltage division + operational amplifier type sampling circuit, such as a non-isolation type differential sampling circuit commonly used in the industry. In addition, each of the two resistance units with different resistance values may be a single resistance element or a combination of multiple resistance elements, and the combination may be a series combination, a parallel combination or a series-parallel combination.
Compared with the prior art, the most obvious difference of the embodiment of the invention is that a suspension voltage suppression circuit is arranged for the DC/DC module. The working principle of the preferable scheme is detailed only by taking the converter as an example, wherein the converter has two DC/DC modules which are both in Boost topology, the input voltage sampling circuit is a non-isolated differential sampling circuit, the parameters of the two non-isolated differential sampling circuits are consistent, the input end of the DC/DC module 1 is connected with a power supply, and the input end of the DC/DC module 2 is suspended (before a suspended voltage suppression circuit is introduced, a circuit diagram corresponding to the example is shown in FIG. 3; reference numerals Ri and Rf in FIG. 3 represent both sampling resistors in the non-isolated differential sampling circuit and resistance values of the sampling resistors, reference numerals Vi1 and Vi2 represent input voltages of the DC/DC module 1 and the DC/DC module 2 respectively, and reference numerals Vo1 and Vo2 represent corresponding sampling voltages of Vi1 and Vi2 respectively):
since the sampling voltages Vo1 and Vo2 are very small and have values very close to the sampling reference ground AGND, the voltages of Vo1, Vo2 and AGND can be viewed as the same potential, and on the basis, since PV 1-and PV 2-in the example shown in fig. 3 are directly connected to BUS, the non-isolated differential sampling circuits are connected to the same ground, and the sampling reference ground AGND is isolated from BUS, the coupling relationship between the input voltage of the DC/DC module 1 and the input of the DC/DC module 2 can be represented as an equivalent circuit shown in fig. 4, and the current loop thereof is: the current flows out from the positive electrode of a power supply accessed by the DC/DC module 1, and is divided into two paths after sequentially passing through a resistor Ri and a resistor Rf, one path of current flows back to the negative electrode of the power supply after sequentially passing through a second resistor Rf and a second resistor Ri, and the other path of current flows back to the negative electrode of the power supply after sequentially passing through a third resistor Rf and a third resistor Ri; since no current flows between PV2+ and the sampling reference ground AGND, PV2+ and the sampling reference ground AGND are equipotential, and current flows between the sampling reference ground AGND and PV2-, the input voltage Vi2 of the DC/DC module 2 (i.e. the voltage of PV2+ against PV 2-) is equal to the voltage of the sampling reference ground AGND against PV2-, Vi2 is calculated to be Vi1/3, Vi1/3 is the floating voltage generated at the input terminal of the DC/DC module 2, and the floating voltage not only brings human body electric shock risk, but also causes the converter control system to make a false judgment that "the DC/DC module 2 is also connected to the power supply, and the voltage of the power supply connected to the DC/DC module 2 is equal to the voltage/3 of the power supply connected to the DC/DC module 1".
In this regard, a preferable solution of the embodiment of the present invention is to provide the DC/DC module in the example shown in fig. 3 with a floating voltage suppression circuit, and then:
when the input terminal of the DC/DC module 2 is suspended, the suspended voltage suppression circuit corresponding to the DC/DC module 2 will connect a resistor unit with a smaller resistance (such as the resistor R3 shown in fig. 5) between PV2+ and PV2-, the voltage of the sampling reference AGND relative to PV 2-is equivalent to an ideal voltage source with Vi2, the sampling resistor Ri + Rf with a large resistance connected between PV2+ and the sampling reference AGND is connected in series with the small-resistance resistor unit connected between PV2+ and PV2-, and then connected to both ends of the ideal voltage source, when the resistance of the small-resistance resistor unit is set to be much smaller than Ri + Rf, the partial voltage of the resistor unit with the small resistance value is small, the input voltage Vi2 (namely the voltage of PV2+ relative to PV 2-) of the DC/DC module 2 can be pulled down to be basically zero, and the suspension voltage suppression is realized.
When the DC/DC module 2 is connected to the power supply, the power supply connected to the DC/DC module 2 is equivalent to a voltage source with a small internal resistance Rin, the floating voltage suppression circuit corresponding to the DC/DC module 2 is connected to a resistor unit with a large resistance (such as the resistor R2 shown in fig. 6) between PV2+ and PV2-, the internal resistance and the resistor unit with the large resistance are connected in series at two ends of the voltage source, and when the resistance of the resistor unit with the large resistance is set to be much larger than the internal resistance, the voltage division of the resistor unit with the large resistance is large, so the input voltage Vi2 (i.e., the voltage of PV2+ relative to PV 2-) of the DC/DC module 2 is still maintained at a high voltage level, which is convenient for the converter control system to distinguish whether the DC/DC module 2 is connected to the power supply. And, according to the formula P ═ U2The larger the resistance value is, the smaller the power is, so that the resistance unit with the larger resistance value has little workThe rate is lost.
As can be seen from the above analysis based on fig. 3 to 6, in the preferred embodiment of the present invention, the circuit units with different resistances are connected between the positive electrode and the negative electrode of the input terminal according to whether the input terminal is suspended, so that the suspended voltage generated at the suspended input terminal is suppressed without causing large power loss to the converter, and the problems in the prior art are solved.
As can be seen from the foregoing description of the operation principle of the preferred embodiment, if a circuit unit with a fixed resistance value is connected between the positive electrode and the negative electrode of the input terminal as in implementation mode 1), regardless of whether the input terminal is suspended, the problem of suspension voltage suppression can also be solved, but the power loss of the circuit unit is increased compared with that of the preferred embodiment because the resistance value of the circuit unit is set to be smaller.
Optionally, in a preferred aspect of the embodiment of the present invention, the detecting unit includes a resistance voltage dividing unit and a determining unit; the resistance voltage division unit is connected between the anode and the cathode of the input end of the circuit; the judging unit judges whether the input end of the local circuit is suspended according to the difference of voltages applied to the resistance voltage dividing unit when the input end of the local circuit is suspended (because the internal resistance of the power supply is far smaller than that of the sampling resistor, the voltage of the resistance voltage dividing unit is much smaller than that when the input end of the local circuit is connected with the power supply when the input end of the local circuit is suspended), then selects one of two resistance units with different resistance values to be connected between the positive electrode and the negative electrode of the input end of the local circuit according to the judgment result, particularly selects the resistance unit with smaller resistance value to be connected when the input end of the local circuit is suspended, and selects the resistance unit with larger resistance value to be connected when the input end of the local circuit is connected with the power supply.
Optionally, in order to reduce the requirement on withstand voltage and current of the elements in the determination unit, in the embodiment of the invention, the resistance voltage division unit is designed to divide voltage by connecting two resistance modules in series, and then the divided voltage of one resistance module, not the total voltage of the whole resistance voltage division unit, is sent to the determination unit. The judgment unit compares the divided voltage with a preset value, when the voltage of the resistance voltage division unit is larger than the preset value, the input end of the circuit is judged to be suspended, the resistance unit with smaller resistance value is connected between the positive electrode and the negative electrode of the input end of the circuit, otherwise, the resistance unit with larger resistance value is connected between the positive electrode and the negative electrode of the input end of the circuit.
Alternatively, referring to fig. 7, two resistance modules in the resistance voltage division unit respectively use R1、R4And (4) showing. The resistor unit with smaller resistance in the suspension voltage suppression circuit is marked as a resistor unit R3The resistance unit with larger resistance is marked as the resistance unit R2. Still referring to fig. 7, the determining unit may adopt a topology including: resistance module R5Resistance module R6The switch module T1, the switch module T2 and the voltage regulator tube module D1;
resistance module R1Resistance module R2And a resistance module R3One end of each of the first and second switches is connected to the input anode of the DC/DC module corresponding to the floating voltage suppression circuit;
resistance module R1And the other end of the resistor module R is connected with the control end of the switch module T1 and the resistor module R4One end of (a);
resistance module R2The other end of the resistor module R is connected with the power input end of the switch module T1, the cathode of the voltage regulator tube module D1 and the resistor module R5One end of (a);
resistance module R5Another terminating resistance module R6And the control terminal of switch module T2;
resistance module R3The other end of the switch module T2 is connected with the power input end of the switch module T2;
resistance module R4The other end of the resistor, the power output end of the switch module T1, the anode of the voltage regulator tube module D1 and the resistor module R6And the other end of the switch module T2 and the power output end of the switch module T2 are both connected to the input cathode of the DC/DC module corresponding to the floating voltage suppression circuit.
The switch modules T1 to T2 are, for example, switch tubes. The switch module T1 may be a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET), an Insulated Gate Bipolar Transistor (IGBT), or a triode, but is not limited thereto. The switch module T2 may be a MOSFET or an IGBT, and is not limited as such. In addition, each of the above-mentioned resistance modules may be a single resistance element or a combination of a plurality of resistance elements, and the combination may be a series combination, a parallel combination or a series-parallel combination. The voltage stabilizing tube module can be a single voltage stabilizing tube element or a combination of a plurality of voltage stabilizing tube elements, and the combination mode can be series combination, parallel combination or series-parallel combination.
Still following the example shown in fig. 3, the operation of the unit shown in fig. 7 is detailed as follows:
referring to fig. 8, when the DC/DC module 2 is connected to the power supply, the power supply connected to the DC/DC module 2 is equivalent to a voltage source with small internal resistance, and the resistor R connected between PV2+ and PV 2-is reasonably set1And R4So that R is at this time4The voltage at both ends is greater than the threshold voltage V of T1gsth1To turn on T1, the resistor R with large resistance value2Also between PV2+ and PV 2-; meanwhile, as T1 is conducted, the CE voltage of T1 is 0, namely the grid-source voltage of T2 is 0, T2 is not conducted, and the resistor R with small resistance value is3Does not connect between PV2+ and PV 2-. At this time, the resistance connected between PV2+ and PV 2-is only R2、R1And R4Due to the large resistance value of the resistor R2So that the floating voltage suppression circuit has a large resistance value of R2、R1And R4The resistance value of the formed equivalent resistor is large and approximately equal to R2According to P ═ U2the/R shows that the equivalent resistor only generates smaller loss; in addition, the equivalent resistance is far larger than the internal resistance of the power supply, so that the equivalent resistance has large voltage division and can be basically equal to the power supply voltage.
Referring to fig. 9, when the input terminal of the DC/DC module 2 is suspended, a suspended voltage is generated between PV2+ and PV2-, which is equivalent to an ideal voltage source connected with a sampling resistor with a large resistance in series, and a resistor R is reasonably set1And R4So that R is at this time4The voltage at the two ends is smaller than the threshold voltage of T1, so that T1 is not conducted, and the large-resistance resistor R2 cannot be connected between PV2+ and PV 2-; meanwhile, since T1 is not conducted, the resistance R2And R5、R6Voltage division, reasonable setting of resistance R2、R5And R6The resistance value of (2) can make the grid-source voltage of T2 larger than the threshold voltage of T2Voltage to turn on T2 and make small resistance resistor R3Will be connected between PV2+ and PV2-, and the voltage regulator tube D1 is used to protect the gate-source voltage of T2 from overvoltage. At this time, the resistance between the accessed PV2+ and PV 2-is R1～R6Due to the small resistance value of the resistor R3Has a small resistance value, so that the floating voltage suppression circuit is controlled by R1～R6The resistance value of the formed equivalent resistor is very small and is approximately equal to R3The equivalent resistor is much smaller than Ri + Rf, so the divided voltage of the equivalent resistor is small, and the input voltage Vi2 of the DC/DC module 2 (i.e. the voltage of PV2+ relative to PV 2-) can be pulled down to substantially zero.
Wherein the minimum voltage between PV2+ and PV 2-is assumed to be Vpv_minThe internal resistance (small resistance) of the power supply connected into the DC/DC module 2 is RinWhen the DC/DC module 2 is connected to the power supply, R4The voltage at both ends is greater than the threshold voltage V of T1gsth1Then, the resistance values of the resistors in the suspension voltage suppression circuit should satisfy the relationship of the following formula (1):
AGND to PV 2-direct voltage Vpv_max(vi)/3, assuming that the maximum voltage between PV1+ and PV 1-is Vpv _ max, making the sum of the sampling resistances Rf and Ri resistances Rs, in order to make "the input of DC/DC module 2 is suspended, R4Threshold voltage V with both ends voltage smaller than T1gsth1And R is6The voltage at both ends is greater than the threshold voltage V of T2gsth2", the resistance values of the resistors in the suspension voltage suppression circuit need to satisfy the relationship of the formula (2) and the formula (3):
in summary, the parameter settings of the resistance units in fig. 7 need to satisfy: when the input end of the DC/DC unit is connected with a power supply, the voltage at the two ends of the R4 is greater than the threshold voltage of the T1; when the input end of the DC/DC unit is suspended, the voltage across the R4 is smaller than the threshold voltage of T1, and the voltage across the R6 is larger than the threshold voltage of T2.
Finally, it should be noted that, in the above example, each input end of the DC/DC unit is provided with one floating voltage suppression circuit separately, actually, only a part of the input ends may be provided with the floating voltage suppression circuit separately, and one floating voltage suppression circuit may be switched and applied to different input ends, which is not limited.
Corresponding to the converter embodiment disclosed above, the embodiment of the present invention further discloses a floating voltage suppression method, which is applied to a converter, wherein the converter main circuit comprises a DC/DC unit with multiple inputs and single output, the negative electrodes of the input ends of the DC/DC unit are all directly connected with a negative direct current bus, and the input voltage sampling circuits of the DC/DC unit are grounded, and the sampling reference ground is isolated from the negative direct current bus; the input end of the DC/DC unit is provided with a suspension voltage suppression circuit, and the suspension voltage suppression circuit comprises two resistance units with different resistance values;
the method comprises the following steps:
the suspension voltage suppression circuit detects whether the input end of the circuit is suspended or not;
the suspension voltage suppression circuit selects one of the two resistance units with different resistance values to be connected between the positive electrode and the negative electrode of the input end of the circuit according to whether the input end of the circuit is suspended or not.
Optionally, as shown in fig. 8, the method specifically includes:
step S01: the suspension voltage suppression circuit detects whether the corresponding input end is suspended; when detecting that the corresponding input end is suspended, the suspended voltage suppression circuit proceeds to step S02; otherwise, go to step S03;
step S02: and connecting the resistance unit with smaller resistance value between the anode and the cathode of the input end of the current path, and finishing the current control.
Step S03: and connecting the resistance unit with larger resistance value between the anode and the cathode of the input end of the current path, and finishing the current control.
Optionally, the floating voltage suppression circuit is connected with a resistance unit between the positive electrode and the negative electrode of the input end of the circuit; at this time, the detecting of whether the corresponding input terminal is suspended by the floating voltage suppressing circuit includes: and judging whether the input end of the current path is suspended or not according to the difference of the voltages applied to the resistance voltage division units when the input end of the current path is suspended or not.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the method disclosed by the embodiment, the method corresponds to the converter disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the converter part for description.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the embodiments. Thus, the present embodiments are not intended to be limited to the embodiments shown herein but are to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (13)
1. A converter is characterized in that the negative poles of all input ends of the DC/DC unit are directly connected with a negative direct current bus, all input voltage sampling circuits of the DC/DC unit are connected with the same ground, and the sampling reference ground of the input voltage sampling circuits is isolated from the negative direct current bus;
the input end of the DC/DC unit is provided with a suspension voltage suppression circuit; the floating voltage suppression circuit includes: and the resistance unit is connected between the anode and the cathode of the input end of the circuit.
2. The converter of claim 1, wherein the floating voltage suppression circuit comprises: the detection unit and the two resistance units with different resistance values; the detection unit is used for selecting one of the two resistance units with different resistance values to be connected between the positive electrode and the negative electrode of the input end of the circuit according to whether the input end of the circuit is suspended or not.
3. The converter according to claim 2, wherein the detection unit is specifically configured to switch the resistance unit with a smaller resistance value between the positive and negative electrodes of the input end of the local path when the input end of the local path is suspended, and switch the resistance unit with a larger resistance value between the positive and negative electrodes of the input end of the local path otherwise.
4. The transducer of claim 3, wherein the detection unit comprises: the device comprises a resistance voltage division unit and a judgment unit;
the resistance voltage division unit is connected between the anode and the cathode of the input end of the circuit;
the judging unit judges whether the input end of the circuit is suspended according to the difference of the voltage applied to the resistance voltage dividing unit when the input end of the circuit is suspended, the resistance unit with smaller resistance is connected between the positive pole and the negative pole of the input end of the circuit, otherwise, the resistance unit with larger resistance is connected between the positive pole and the negative pole of the input end of the circuit.
5. The converter according to claim 4, wherein the resistance voltage dividing unit divides voltage by connecting two resistance modules in series, and the divided voltage of one resistance module is sent to the judging unit;
the judgment unit compares the divided voltage with a preset value, when the voltage of the resistance voltage division unit is larger than the preset value, the input end of the circuit is judged to be suspended, the resistance unit with smaller resistance value is connected between the positive electrode and the negative electrode of the input end of the circuit, otherwise, the resistance unit with larger resistance value is connected between the positive electrode and the negative electrode of the input end of the circuit.
6. Converter according to claim 5, characterized in that the resistance unit of smaller resistance is denoted as resistance unit R3The resistance unit with larger resistance value is marked as a resistance unit R2(ii) a Two resistance modules in the resistance voltage division unit are respectively marked as resistance modules R1And a resistance module R4；
The judging unit includes: resistance module R5Resistance module R6The switch module T1, the switch module T2 and the voltage regulator tube module D1;
wherein R is1、R2And R3One end of the first and second switches is connected to the positive pole of the input end of the current path;
R1and the other end of T1 is connected with the control end of T1 and R4One end of (a);
R2another end of the D1 is connected with the power input end of T1, the cathode of D1 and R5One end of (a);
R5at the other end R6And a control terminal of T2;
R3the other end of the T-shaped connector is connected with the power input end of the T2;
R4the other end of (1), the power output end of T1, the anode of D1, R6The other end of the T2 and the power output end of the T2 are both connected to the negative pole of the input end of the circuit;
the resistance value setting satisfies: when the input end of the current path is connected with a power supply, R4The voltage at two ends is greater than the threshold voltage of T1; when the input end of the current path is suspended, R4The voltage at both ends is less than the threshold voltage of T1, and R6The voltage across is greater than the threshold voltage of T2.
7. The converter according to claim 6, characterized in that said switch modules T1 and T2 are both switching tubes.
8. The converter according to any one of claims 1 to 7, wherein the converter is a multi-input single-output DC/DC converter or the converter is a photovoltaic inverter with multi-MPPT input.
9. The converter according to any one of claims 1 to 7, wherein the DC/DC unit is a Boost type, Buck type or Boost-Buck type DC/DC unit.
10. The converter according to any one of claims 1 to 7, wherein the input voltage sampling circuit is a non-isolated differential sampling circuit.
11. A suspension voltage suppression method is applied to a converter, a main circuit of the converter comprises a DC/DC unit with multiple input and single output, and the suspension voltage suppression method is characterized in that the negative electrodes of all input ends of the DC/DC unit are directly connected with a negative direct current bus, all input voltage sampling circuits of the DC/DC unit are grounded, and the sampling reference ground of the input voltage sampling circuits is isolated from the negative direct current bus; the input end of the DC/DC unit is provided with a suspension voltage suppression circuit, and the suspension voltage suppression circuit comprises two resistance units with different resistance values;
the method comprises the following steps:
the suspension voltage suppression circuit detects whether the input end of the circuit is suspended or not;
the suspension voltage suppression circuit selects one of the two resistance units with different resistance values to be connected between the positive electrode and the negative electrode of the input end of the circuit according to whether the input end of the circuit is suspended or not.
12. The method for suppressing floating voltage according to claim 11, wherein selecting one of two resistor units with different resistances to be connected between the positive and negative electrodes of the input terminal according to whether the input terminal of the local circuit is suspended includes:
when detecting that the input end of the current path is suspended, the resistor unit with smaller resistance is connected between the positive electrode and the negative electrode of the input end of the current path, otherwise, the resistor unit with larger resistance is connected between the positive electrode and the negative electrode of the input end of the current path.
13. The levitation voltage suppression method according to claim 12, wherein the levitation voltage suppression circuit is connected with a resistance voltage division unit between the positive electrode and the negative electrode of the input end of the circuit;
correspondingly, the floating voltage suppression circuit detects whether the input end of the circuit is suspended, and the method comprises the following steps: and judging whether the input end of the current path is suspended or not according to the difference of the voltages applied to the resistance voltage division units when the input end of the current path is suspended or not.
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| CN104038036A (en) * | 2014-06-30 | 2014-09-10 | 阳光电源股份有限公司 | Suspension voltage restraining method and device, inverter control system and inverter of inverter control system |
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| US20180034365A1 (en) * | 2016-07-26 | 2018-02-01 | Nxp Usa, Inc. | Accurate non-isolated high voltage dc-dc feedback |
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| CN104038036A (en) * | 2014-06-30 | 2014-09-10 | 阳光电源股份有限公司 | Suspension voltage restraining method and device, inverter control system and inverter of inverter control system |
| US20180034365A1 (en) * | 2016-07-26 | 2018-02-01 | Nxp Usa, Inc. | Accurate non-isolated high voltage dc-dc feedback |
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| CN107437793A (en) * | 2017-09-07 | 2017-12-05 | 艾思玛新能源技术（扬中）有限公司 | A kind of floating pressure process circuit of multichannel MPPT photovoltaic DC-to-AC converters |
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