阅读说明：本技术 分析直流电力系统的变频器内熔断器对于短路电流的响应能力的仿真建模分析方法 (Simulation modeling analysis method for analyzing response capability of fuse in frequency converter of direct-current power system to short-circuit current ) 是由 乌云翔 邵诗逸 岳凡 常国梅 武治江 高双建 于 2020-03-18 设计创作，主要内容包括：本发明公开了一种分析直流电力系统的变频器内熔断器对于短路电流的响应能力的仿真建模分析方法。本方法通过计算模型的建立,可以准确得出变频器直流短路时,各个设备内熔断器的I<Sup>2</Sup>T,可以有效验证直流组网系统故障选择性切除的可靠性,也可为熔断器的设计选型提供依据。(The invention discloses a simulation modeling analysis method for analyzing the response capability of a fuse in a frequency converter of a direct-current power system to a short-circuit current. The method can accurately obtain the I of the fuse in each device when the direct current of the frequency converter is short-circuited by establishing the calculation model 2 And T, the reliability of selective fault removal of the direct-current networking system can be effectively verified, and a basis can be provided for design and type selection of the fuse.)

1. A simulation modeling analysis method for analyzing the response capability of a fuse in a frequency converter of a direct current power system to a short-circuit current is specifically as follows;

1) building a cabinet model, for example, building a single cabinet, modeling a capacitor C formed by a frequency converter therein_M1And its equivalent direct current resistance R_ESRcThe fuse comprises a series model, two groups of fuses of direct current buses are respectively connected with the input side and the output side of a frequency converter, the fuses of each group of direct current buses comprise two fuse monomers which are arranged in parallel, the fuse monomers are modeled into a resistor, and cables or copper bars between the input side and the output side of the frequency converter and the fuses are marked as CO 1; cables or copper bars from the two groups of fuses to the direct current busbar are marked as CO 2; the copper bar on the DC bus is marked as CO3 and consists of a positive group and a negative groupComposition is carried out; the single cables or copper bars CO1 and CO2 are simplified into a model of series connection of a resistor and an inductor, the single copper bar CO3 is simplified into a model of series connection of a resistor and an inductor, and the capacitor of the copper bar CO3 is simplified into an integral capacitor C arranged between a positive direct current bus and a negative direct current bus_int(ii) a Calculating to obtain specific parameters of the cabinet body model; the specific calculation is as follows:

(a) calculating the equivalent direct current resistance through the steady-state direct current power consumption and the rated current of the fuse, and obtaining the following formula:wherein: r_VFuseIs the steady state dc power consumption of the fuse;is the steady state direct current of the fuse; r_FuseIs a steady state dc resistance;

equivalent short-circuit resistance R of fuse in simulation model in short-circuit state_SCFuseModeling by adopting a mode of carrying out short-circuit test on the fuse and carrying out curve fitting after acquiring an actual fusing waveform of the fuse;

(b) calculating the value R of the resistance and the direct current inductance formed by simplifying the cable or the copper bar_co1,R_co2,R_co3,L_co1,L_co2,L_co3Calculating the equivalent capacitance C of the copper bar CO3_int；

2) Establishing a cabinet simplified circuit model, and removing a capacitor C between the positive and negative direct current buses_M1And its equivalent direct current resistance R_ESRcThe external resistance is equivalent to a resistance Ra, and a capacitor C is arranged between the positive and negative direct current buses_M1And its equivalent direct current resistance R_ESRcThe external inductance is equivalent to an inductance L a, the resistances on the positive and negative direct current buses are equivalent to a resistance Rb, the inductances on the positive and negative direct current buses are equivalent to an inductance L b, and a simplified model is obtained, wherein:

3) establishing a system circuit model, and establishing an integral circuit model of the C-PP system including all cabinets by referring to the steps;

4) and obtaining I of fuses in each frequency converter in the cabinet body when the direct current of the frequency converter in a certain cabinet body is in short circuit by using MAT L AB analog calculation²T；

Accumulation of current and time of the fault loop fuse reaches its fuse I quickly²T, cutting off a fault loop; if the current and time accumulation of all other non-fault loop fuses does not exceed the pre-arc I of the corresponding fuse when the fault loop is cut off²T, indicating that the non-faulty loop is not affected; if the current and time of the non-fault circuit fuse exceeds the pre-arc I of the corresponding fuse when the fault circuit is cut off²T, the fuse at the position needs to be replaced by a fuse I before the arc²T larger fuse.

2. The simulation modeling analysis method for analyzing the response capability of the fuse in the frequency converter of the direct current power system to the short-circuit current according to claim 1, characterized in that: the numerical value R of the resistance into which the cable or the copper bar is simplified is calculated_co1,R_co2,R_co3The specific calculation formula is as follows:wherein: resistance value R, unit omega; resistivity ρ, unit: omega m²(ii)/m; length l of cable or copper bar, unit: m; the sectional area A of the cable or the copper bar, unit: m is²。

3. The simulation modeling analysis method for analyzing response capability of fuse in frequency converter of DC power system to short-circuit current according to claim 2, characterized in that the calculation cable is simplified to DC inductance value L_co1,L_co2,L_co3The calculation formula of (2) is:wherein: magnetic permeability mu in vacuum₀Is a constant 4 π × 10^-7(ii) a The unit H/m; the center distance a of 2 round cables is unit M; radius r of the cable_LThe unit M; single cable length l, unit M.

4. The simulation modeling analysis method for analyzing the response capability of the fuse in the frequency converter of the DC power system to the short-circuit current as claimed in claim 2, wherein the calculation of the value L of the DC inductance simplified by the copper bar_co1,L_co2,L_co3The calculation formula of (2) is:wherein: the average distance a between the positive copper bar and the negative copper bar; the unit M; the width b of the single-phase copper bar is calculated by overlapping the widths if the single-phase copper bar is a plurality of copper bars; the unit M; the height h of the copper bar; the unit M; the length l of the single-phase copper bar is unit M.

5. The simulation modeling analysis method for analyzing the response capability of the fuse in the frequency converter of the direct current power system to the short-circuit current according to claim 3 or 4, characterized in that: the calculation formula of the equivalent capacitance of the copper bar CO3 is as follows:

wherein_diIs a capacitance constant with a value of 8.854 × 10^-12F/m, a is the average distance between the positive copper plate and the negative copper plate, m and b are the width of the copper bar, and m and h are the length of the single-phase copper bar and m.

Technical Field

The invention relates to an electrical system applied to a ship, in particular to a simulation modeling analysis method for analyzing the response capability of a fuse in a frequency converter of a direct-current power system to short-circuit current.

Background

The networking mode of the C-PP direct-current networking technology is a direct-current network, namely a shore power supply and a lithium battery pack on a ship are connected with a power load through a C-PP frequency converter networking, and the whole electric power is distributed through a direct-current bus with high efficiency and high dynamic characteristics. In a C-PP system, when a short-circuit fault occurs in a certain device, an obvious overcurrent may occur at a dc bus, a frequency converter or an ac output terminal, and if the fault device is not selectively removed, a ship may be completely powered off, the ship may lose maneuverability, that is, lose propulsion capability, and a ship collision or a ship fire may be seriously caused.

Therefore, when a short-circuit failure occurs in a certain device, the failed device needs to be removed from the entire system as soon as possible to avoid the enlargement of the failure. According to the selective overcurrent protection guidelines for marine power systems, the CCS code provides for the selective implementation of faults, which provides for the automatic switching of the electrical system, and all short-circuit protection, including critical equipment circuits, should be selective, except in the case of double sets of critical equipment powered by different distribution panels. Meanwhile, on the premise of satisfying selective protection, a fault circuit should be cut off as soon as possible, thereby reducing the influence on the power system and the risk of fire.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the simulation modeling analysis method for analyzing the response capability of the fuse in the frequency converter of the direct-current power system to the short-circuit current is provided.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a simulation modeling analysis method for analyzing the response capability of a fuse in a frequency converter of a direct current power system to a short-circuit current is specifically as follows;

1) modeling cabinets to build individual cabinetsBy way of example, the capacitance C into which the frequency converter is modeled_M1And its equivalent direct current resistance R_ESRcThe fuse comprises a series model, two groups of fuses of direct current buses are respectively connected with the input side and the output side of a frequency converter, the fuses of each group of direct current buses comprise two fuse monomers which are arranged in parallel, the fuse monomers are modeled into a resistor, and cables or copper bars between the input side and the output side of the frequency converter and the fuses are marked as CO 1; cables or copper bars from the two groups of fuses to the direct current busbar are marked as CO 2; the copper bar on the direct current bus is marked as CO3 and consists of a positive group and a negative group; the single cables or copper bars CO1 and CO2 are simplified into a model of series connection of a resistor and an inductor, the single copper bar CO3 is simplified into a model of series connection of a resistor and an inductor, and the capacitor of the copper bar CO3 is simplified into an integral capacitor C arranged between a positive direct current bus and a negative direct current bus_int(ii) a (ii) a Calculating to obtain specific parameters of the cabinet body model; the specific calculation is as follows:

(a) calculating the equivalent direct current resistance through the steady-state direct current power consumption and the rated current of the fuse, and obtaining the following formula:

wherein: p_{V Fuse}Is the steady state dc power consumption of the fuse;is the steady state direct current of the fuse; r_FuseIs a steady state dc resistance;

equivalent short-circuit resistance R of fuse in simulation model in short-circuit state_SCFuseModeling by adopting a mode of carrying out short-circuit test on the fuse and carrying out curve fitting after acquiring an actual fusing waveform of the fuse;

(b) calculating the value R of the resistance and the direct current inductance formed by simplifying the cable or the copper bar_co1,R_co2,R_co3,L_co1,L_co2,L_co3Calculating the equivalent capacitance C of the copper bar CO3_int；

2) Establishing a cabinet simplified circuit model, and removing a capacitor C between the positive and negative direct current buses_M1And its equivalent direct current resistanceR_ESRcThe external resistance is equivalent to a resistance Ra, and a capacitor C is arranged between the positive and negative direct current buses_M1And its equivalent direct current resistance R_ESRcThe external inductance is equivalent to an inductance L a, the resistances on the positive and negative direct current buses are equivalent to a resistance Rb, the inductances on the positive and negative direct current buses are equivalent to an inductance L b, and a simplified model is obtained, wherein R is_a＝2R_CO1+R_SCFuse+2R_CO2；L₈＝2L_CO1+2L_CO2；R_b＝2R_CO3；L_b＝2L_CO3；

3) Establishing a system circuit model, and establishing an integral circuit model of the C-PP system including all cabinets by referring to the steps;

4) and obtaining I of fuses in each frequency converter in the cabinet body when the direct current of the frequency converter in a certain cabinet body is in short circuit by using MAT L AB analog calculation²T；

Accumulation of current and time of the fault loop fuse reaches its fuse I quickly²T, cutting off a fault loop; if the current and time accumulation of all other non-fault loop fuses does not exceed the pre-arc I of the corresponding fuse when the fault loop is cut off²T, indicating that the non-faulty loop is not affected; if the current and time of the non-fault circuit fuse exceeds the pre-arc I of the corresponding fuse when the fault circuit is cut off²T, the fuse at the position needs to be replaced by a fuse I before the arc²T larger fuse.

Preferably, the calculation of the value R of the resistance into which the cable or the copper bar is simplified is performed_co1,R_co2,R_co3The specific calculation formula is as follows:wherein: resistance value R, unit omega; resistivity ρ, unit: omega m²(ii)/m; length l of cable or copper bar, unit: m; the sectional area A of the cable or the copper bar, unit: m is²。

Preferably, the calculation cable is simplified to obtain a direct current inductance value L_co1,L_co2,L_co3The calculation formula of (2) is:wherein: magnetic permeability mu in vacuum₀Is a constant 4 π × 10^-7(ii) a The unit H/m; the center distance a of 2 round cables is unit M; radius r of the cable_LThe unit M; single cable length l, unit M.

Preferably, the calculation of the value L of the direct current inductance simplified by the copper bar_co1,L_co2,L_co3The calculation formula of (2) is:wherein: the average distance a between the positive copper bar and the negative copper bar; the unit M; the width b of the single-phase copper bar is calculated by overlapping the widths if the single-phase copper bar is a plurality of copper bars; the unit M; the height h of the copper bar; the unit M; the length l of the single-phase copper bar is unit M.

As a preferable scheme, the calculation formula of the equivalent capacitance of the copper bar CO3 is as follows:

wherein_diIs a capacitance constant with a value of 8.854 × 10^-12F/m, a is the average distance between the positive copper plate and the negative copper plate, m and b are the width of the copper bar, and m and h are the length of the single-phase copper bar and m.

The invention has the beneficial effects that: the method can accurately obtain the I of the fuse in each device when the direct current of the frequency converter is short-circuited by establishing the calculation model²And T, the reliability of selective fault removal of the direct-current networking system can be effectively verified, and a basis can be provided for design and type selection of the fuse.

And when a frequency converter on a certain section of direct current bus has a direct current short circuit, the power electronic switch can cut out the fault half board from the direct current bus of the non-fault half board, so that for analyzing the direct current short circuit of the frequency converter, only all equipment on the single section of direct current bus where the fault frequency converter is located needs to be considered, and all the equipment on the whole board does not need to be analyzed.

Drawings

FIG. 1 is a single line diagram of a DC power system of the present invention;

FIG. 2 is a schematic diagram of the DC short circuit at the outer side of the capacitor of the frequency converter according to the present invention;

FIG. 3 is a schematic diagram of the DC short circuit inside the capacitor of the frequency converter according to the present invention;

FIG. 4 is a simulation model of the M1 cabinet of the present invention;

FIG. 5 is an equivalent circuit model of copper bar CO3 in the present invention;

FIG. 6 is a cable model of the present invention;

FIG. 7 is a copper bar model of the present invention;

FIG. 8 is a circuit model of the M1 cabinet of the present invention;

FIG. 9 is a simplified circuit model of the M1 cabinet of the present invention;

FIG. 10 is an overall model of the system of the present invention.

In the figure: 1-a shore power supply; 2-a lithium battery; networking a 3-C-PP frequency converter; 4-a generator set; 5-a propulsion motor; 6-daily load; 7-power electronic switches; 31-a frequency converter; 311-a power module; 312-capacitance; a 32-fuse; 33-direct current bus bar.

Detailed Description

Specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

As shown in fig. 1, the direct current power system comprises a shore power supply 1 on a ship, a lithium battery 2 and a generator set 4, wherein the shore power supply 1, the lithium battery 2 and the generator set 4 are connected with a daily load 4 and a propulsion motor 5 through a C-PP frequency converter network 3; the direct current power system at least comprises two groups of C-PP frequency converter networking 3, and the C-PP frequency converter networking 3 are connected through a power electronic switch 7; the C-PP frequency converter network 3 comprises a frequency converter 31, a fuse 32 and a direct current bus 33; one side of the frequency converter 31 is connected with a shore power supply 1 or a lithium battery pack 2, and the other side is connected with a direct-current bus bar 33 through a fuse 32; as shown in fig. 2 and 3, the frequency converter 31 includes a power module 311 and a capacitor 312.

When two sections of direct-current busbars 33 connected with a port and a starboard in a direct-current power system are in contact to generate short circuit or a frequency converter 31 generates direct-current short circuit, a power electronic switch 7 connected with the two sections of direct-current busbars 33 can be tripped within 15-25 microseconds, so that a fault half board is cut out of direct-current busbars of non-fault half boards, the short-circuit busbars and normally-working busbars are physically isolated, the operation capacity of equipment on the residual direct-current busbars is guaranteed, and selective protection of faults is realized;

when the frequency converter 31 has a dc short circuit, there are two short circuit situations, fig. 2 shows that the dc short circuit is on the outer side of the capacitor 312, and fig. 3 shows that the dc short circuit is on the inner side of the capacitor 312;

the short circuit loops in both cases are similar, when a short circuit occurs, P₁Capacitor C of₁Will discharge to the short-circuit point and deliver current I₁，P₂Capacitor C of₂Discharging the short-circuit point and supplying a current I through a relatively long circuit₂；I₁Does not pass through the fuse, I₂Will flow through the fuse and may cause the fuse to blow;

due to C₁Smaller, the resistance of the loop is also smaller, so the discharge time constant of the whole loop is shorter, I₁The attenuation is fast; due to C₂Is generally larger (C)₂The capacitance of all non-fault modules) and the circuit is longer and includes the impedance of the fuse, so the discharge time constant of the whole circuit is longer;

fuse F₁Due to I₂I of electric current²T is accumulated and fused, so that a loop is cut off; and F₂I of (A)²T does not reach its pre-arc I²T, cannot be damaged; therefore, fault selective removal during direct-current short circuit of the frequency converter is realized;

i due to a second short-circuit condition₂The discharge circuit of (2) is longer, the short-circuit current is smaller, and the situation is more moderate than the first situation, so that the first situation can be considered to cover the second situation, and therefore, the response capability of the fuse to the short-circuit current is analyzed in the case of the direct-current short circuit outside the capacitor of the frequency converter.

In order to verify the reliability of the selective fault removal, a simulation modeling analysis method for analyzing the response capability of a fuse in a frequency converter of a direct current power system to a short-circuit current is provided below, and is used for calculatingI of fuse 32 of each device in DC power system when DC short circuit occurs in output converter 31²T。

When short-circuit occurs, the power electronic switch connecting the two sections of direct current buses can be tripped within 15-25 mu s, the two connected direct current buses are separated, the interaction of the two sections of direct current buses within a very short time is ignored, and therefore, for direct current short-circuit analysis of the frequency converter, all equipment on a single section of direct current bus where the fault frequency converter is located only needs to be considered, and all equipment on the whole board does not need to be analyzed.

The simulation modeling analysis method for analyzing the response capability of the fuse in the frequency converter of the direct-current power system to the short-circuit current comprises the following specific steps;

1. establishing a cabinet model, taking the establishment of a main push cabinet M1 as an example, as shown in FIG. 4, modeling a capacitor C formed by a frequency converter therein_M1And its equivalent direct current resistance R_ESRcThe fuse comprises a series model, two groups of fuses of direct current buses are respectively connected with the input side and the output side of a frequency converter, the fuses of each group of direct current buses comprise two fuse monomers which are arranged in parallel, the fuse monomers are modeled into a resistor, and cables or copper bars between the input side and the output side of the frequency converter and the fuses are marked as CO 1; cables or copper bars from the two groups of fuses to the direct current busbar are marked as CO 2; the copper bar on the direct current bus is marked as CO3 and consists of a positive group and a negative group; the single cables or copper bars CO1 and CO2 are simplified into a model of series connection of resistors and inductors (because the specifications of the cables or copper bars CO1 and the cables or copper bars CO2 are small, parallel capacitors can be ignored under the condition of short circuit), the single copper bar CO3 is simplified into a model of series connection of resistors and inductors, and the capacitors of the copper bar CO3 are simplified into an integral capacitor C arranged between a positive direct current bus and a negative direct current bus_int(because in the case of a short circuit, the shunt capacitance is negligible); calculating to obtain specific parameters of the cabinet body model; the specific calculation is as follows:

(a) calculating the equivalent direct current resistance through the steady-state direct current power consumption and the rated current of the fuse, and obtaining the following formula:

wherein: p_{V Fuse}Is the steady state dc power consumption of the fuse;is the steady state direct current of the fuse; r_FuseIs the steady state dc resistance of the fuse;

equivalent short-circuit resistance R of fuse in simulation model in short-circuit state_SCFuseModeling by adopting a mode of carrying out short-circuit test on the fuse and carrying out curve fitting after acquiring an actual fusing waveform of the fuse;

usually, a large amount of short-circuit current flows into the fuse, which causes the temperature of the fuse to rise rapidly, and the equivalent short-circuit resistance R_SCFuseThe nonlinear increase along with the temperature rise is realized, in order to simulate the nonlinear fusing characteristic of the fuse more truly, short circuit test is carried out on the fuse, and the actual fusing waveform of the fuse is collected;

(b) see fig. 5, 6; calculating the values R of the resistance, the inductance and the capacitance formed by simplifying the copper bar_co1，R_co2，R_co3,，L_co1，L_co2，L_co3，c_intThe calculation formula is as follows:

the calculation formula of the series resistance of the copper bar is as follows:

wherein: resistance value R, unit omega; resistivity ρ, unit: omega m²(ii)/m; length l of cable or copper bar, unit: m; sectional area a of the copper bar, unit: m is²；

As shown in fig. 6, if a cable is used, the dc inductance value is calculated by the following formula:

wherein: magnetic permeability mu in vacuum₀Is a constant 4 π × 10^-7(ii) a The unit H/m; center distance a of 2 round cablesM; radius r of the cable_LThe unit M; length of single cable l, unit M;

as shown in fig. 7, the direct current inductance value of the copper bar is calculated by the following formula:

wherein: magnetic permeability mu in vacuum₀Is a constant 4 π × 10^-7(ii) a The unit H/m; the average distance a between the positive copper bar and the negative copper bar; the unit M; the width b of the single-phase copper bar is calculated by overlapping the widths if the single-phase copper bar is a plurality of copper bars; the unit M; the height h of the copper bar; the unit M; the length of the single-phase copper bar is 1, and the unit is M;

the capacitance calculation formula of the copper bar CO3 is as follows:

wherein_diIs a capacitance constant with a value of 8.854 × 10^-12F/m, wherein a is the average distance between the positive copper plate and the negative copper plate, m and b are the width of the copper bar, m and h are the length of the single-phase copper bar and m;

2. establishing a simplified circuit model of the cabinet body, as shown in fig. 8 and 9, removing a capacitor C between the positive and negative direct current buses_M1And its equivalent direct current resistance R_ESRcThe external resistance is equivalent to a resistor R_aThe capacitance C is removed between the positive and negative DC buses_M1And its equivalent direct current resistance R_ESRcThe external inductor is equivalent to an inductor L_a(ii) a The resistances on the positive and negative direct current buses are equivalent to a resistance R_bThe inductance on the positive and negative DC buses is equivalent to an inductance L_bSo as to obtain the simplified model,

wherein:

R_a＝2R_CO1+R_SCFuse+2R_CO2；

L_a＝2L_CO1+2L_CO2；

R_b＝2R_CO3；

L_b＝2L_CO3

3. establishing a system circuit model, and establishing an integral circuit model of the C-PP system including all cabinets by referring to the steps, as shown in FIG. 10;

4. MAT L AB analog calculation is used to obtain the I of the fuse in each frequency converter in the cabinet when the DC of the frequency converter in a certain cabinet is short-circuited²T；

Accumulation of current and time of the fault loop fuse reaches its fuse I quickly²T, cutting off a fault loop; if the current and time accumulation of all other non-fault loop fuses does not exceed the pre-arc I of the corresponding fuse when the fault loop is cut off²T, indicating that the non-faulty loop is not affected; if the current and time of the non-fault circuit fuse exceeds the pre-arc I of the corresponding fuse when the fault circuit is cut off²T, the fuse at the position needs to be replaced by a fuse I before the arc²T larger fuse.

The above-mentioned embodiments are merely illustrative of the principles and effects of the present invention, and some embodiments may be used, not restrictive; it should be noted that, for those skilled in the art, various changes and modifications can be made without departing from the inventive concept of the present invention, and these changes and modifications belong to the protection scope of the present invention.