JP4779542B2 - Power converter design method - Google Patents

Description

 The present invention relates to a method for designing a power converter.

  Power converters (AC / DC converters, etc.) used in the power system are roughly classified into separately excited converters and self-excited converters. The separately-excited converter mainly uses a thyristor as a switching element for power conversion and has a small loss. However, there is a problem that it cannot be operated in an asymmetrical accident. On the other hand, self-excited converters have the advantage of being able to continue operation even during asymmetrical accidents, but use IGBTs (Insulated Gate Bipolar Transistors) or GTOs (Gate Turn-Off thyristors) as switching elements for power conversion. However, there is a problem that the loss is larger than that of the separately excited converter.

For example, Japanese Patent Laid-Open No. 10-108474 discloses a technique for reducing the loss of a multilevel switching power converter that uses an IGBT or the like as a power conversion switching element. This technology is a multi-level switching type power converter composed of power conversion switching elements that operate with different switching times and conduction periods, and has less conduction loss for power conversion switching elements with fewer switching times and longer conduction times. By selecting an element and selecting an element having a small switching loss for an element having a large number of switching times and a short conduction time, the loss as a system is reduced.
JP-A-10-108474

  By the way, although the multilevel switching type power converter is composed of a plurality of switching elements for power conversion having different switching frequencies as described above, generally used power converters operate at the same switching frequency. It is comprised from the switching element for power conversion. Therefore, the technique disclosed in Japanese Patent Laid-Open No. 10-108474 can surely reduce the loss of the multilevel switching power converter, but it can be applied to a power converter used in a general power system. It was not possible and lacked versatility.

On the other hand, power converters used in large-capacity power systems are generally configured using a small number of large-capacity power conversion switching elements in order to simplify the device configuration. It may be advantageous to use a large number of switching elements for power conversion with a small capacity from the viewpoint of cost reduction or the like. Thus, in the case where a large number of switching elements for power conversion with a small capacity are used, a method for selecting a switching element for power conversion that takes loss reduction and cost reduction into consideration has not been established.
The present inventor considered loss reduction and cost reduction in the design stage of a power converter in view of the current situation that various types and specifications of switching elements for power conversion have been developed along with the recent development of power electronics. The establishment of a method for selecting a switching element for power conversion is considered an urgent need, and the present invention is filed.

This invention is made | formed in view of the situation mentioned above, and aims at the following points.
(1) A power converter design method that achieves a predetermined loss target value is realized.
(2) To realize a power converter design method that achieves predetermined loss target values and cost target values.

 In order to achieve the above object, according to the present invention, as a first solution, a method for designing a power converter composed of a plurality of power conversion switching elements, which is a candidate for the power conversion switching element A first step of calculating the number of selection target elements for one or a plurality of selection target elements based on a parameter relating to the specifications of the power converter and a parameter relating to a use condition of the selection target element; A second step of calculating a loss of each selection target element when each of the selection target elements is used based on a parameter relating to an electrical characteristic of the element, a parameter relating to a use condition, and a parameter relating to the specification of the power converter; The power converter is based on the number of elements to be selected calculated in the first step and the loss calculated in the second step. A third step of calculating the total loss that the total loss and a fourth step of selecting a selection subject element satisfying a predetermined target loss value as a power converter switching elements, to adopt a means of.

 According to the present invention, as the second solving means, in the first solving means, in the fourth step, the selection target element having the smallest total loss is selected as a power conversion switching element. To do.

 Further, in the present invention, as the third solving means, in the first or second solving means, each selection is made from the unit price of each selection target element and the used number of each selection target element calculated in the first step. A step of calculating an initial cost when the target element is used, a step of calculating a running cost based on an operation plan and a total loss of the power converter, and a total cost in the power converter based on the initial cost and the running cost And a step of selecting, as a power conversion switching element, a selection target element whose total cost satisfies a predetermined cost target value.

In the present invention, as a fourth solving means, in the third solving means, the selection target element having the smallest total cost is selected as a switching element for power conversion.

 In the present invention, as a fifth solving means, there is provided a method for designing a power converter composed of a plurality of power conversion switching elements, wherein one or a plurality of selections as candidates for the power conversion switching elements are selected. A first step of calculating the number of use of each selection target element based on a parameter relating to the specifications of the power converter and a parameter relating to a use condition of the selection target element, and an electrical characteristic of each selection target element; A second step of calculating, as a function of the switching frequency, a loss of the individual selection target element when each of the selection target elements is used based on a parameter, a parameter relating to usage conditions, and a parameter relating to the specifications of the power converter; Calculate the total loss in the power converter based on the target loss value and parameters related to the power converter specifications A switching frequency for operating each selection target element based on the third step, the total loss calculated in the third step, and the loss that is a function of the switching frequency calculated in the second step. And a fifth step of selecting the selection target element having the highest switching frequency as a power conversion switching element.

  According to the present invention, it is possible to select a power conversion switching element that achieves a predetermined loss target value, and to select a power conversion switching element that achieves a predetermined loss target value and cost target value. It is possible. As a result, it becomes possible to design a power converter that achieves a predetermined loss target value and cost target value, and by arbitrarily changing the loss target value and cost target value, for example, loss and cost can be minimized. It is also possible to design a suppressed power converter.

Embodiments of the present invention will be described below with reference to the drawings. This embodiment, the design method of the AC / DC power converter C which converts the 3-phase AC power P _in supplied through a transformer B from 3-phase power system A as shown in Figure 18 into DC power P _out It is about. In FIG. 18, the three-phase power system A supplies, for example, three-phase AC power with a system frequency of 60 Hz to the transformer B. The transformer B transforms the three-phase AC power supplied from the three-phase power system A into a predetermined voltage value, and converts the three-phase AC power P _in , specifically, the a-phase AC power Pa and the b-phase AC power. The Pb and c-phase AC power Pc is output to the AC / DC power converter C.

  The AC / DC power converter C includes first power conversion switching elements c1 to sixth power conversion switching elements c6. The a-phase AC power Pa output from the transformer B is input to one end of the first power conversion switching element c1 and the second power conversion switching element c2, and the b-phase AC power Pb is used for the third power conversion. The switching element c3 and the fourth power conversion switching element c4 are input to one end, and the c-phase AC power Pc is input to one end of the fifth power conversion switching element c5 and the sixth power conversion switching element c6. The

The other ends of the first power conversion switching element c1, the third power conversion switching element c3, and the fifth power conversion switching element c5 are connected to one end of the first output terminal 1 and the smoothing capacitor d. . On the other hand, the other ends of the second power conversion switching element c2, the fourth power conversion switching element c4, and the sixth power conversion switching element c6 are connected to the second output terminal 2 and the other end of the smoothing capacitor d. Has been. The first power conversion switching element c1 to the sixth power conversion switching element c6 are semiconductor switching elements such as IGBTs (Insulated Gate Bipolar Transistors). AC / DC power converter C outputs these IGBT in PWM (Pulse Width Modulation) control the first output terminal 1 converts the three-phase AC power _{P in} the DC power _{P out} by. The smoothing capacitor d is provided to reduce the AC component contained in the DC power _Pout . In FIG. 18, a control unit that performs PWM control of the IGBT is omitted.

 Based on the configuration of the AC / DC power converter C as described above, a design method of the AC / DC power converter C will be described below. FIG. 1 is a flowchart showing a procedure for selecting a switching element for power conversion that minimizes the converter loss of the AC / DC power converter C.

 First, a power conversion switching element to be selected is determined (step 1). The switching element for power conversion may be selected from commercially available ones. In this embodiment, four IGBTs having a rating of 1700 V-800 A, a rating of 3300 V-800 A, a rating of 1700 V-1200 A, and a rating of 3300 V-1200 A are used. The case where it determines as a selection object element is demonstrated. Of course, IGBTs with other specifications may be selected, or more than one may be selected. Also, other power conversion switching elements such as GTO (Gate Turn-Off thyristor) may be selected.

 The following steps S2 to S5 are steps for obtaining a power conversion switching element that minimizes the converter loss of the AC / DC power converter C by numerical calculation by computer simulation. Therefore, the processing described below is performed on computer simulation.

Now, when the element to be selected is determined as described above, as shown in FIG. 2, next, as shown in FIG. 2, the converter capacitance P, the use voltage V ₁ , the first use current I _P , the second use current I _rms , the modulation factor m, Power factor cos φ, snubber capacitance Cs, switching frequency fs, output power X _pu , first maximum collector-emitter voltage V _CM1 , first constant β, second constant s1, third constant t, fourth constant u, first 5 constants w, second maximum collector-emitter voltage V _CM2 , sixth constant s2, maximum collector current I _CM , turn-on loss energy E _ONM , turn-off loss energy E _OFFM , freewheeling diode recovery loss energy E _RECM , DC voltage The line-to-line AC voltage ratio k (= V _dc / V _ac ) is input to the computer simulation (step S2).

Among the above variables, the converter capacity P, the modulation factor m, the power factor cosφ, the switching frequency fs, the output power _Xpu, and the DC voltage / line AC voltage ratio k relate to the specifications of the AC / DC power converter C. The use voltage V ₁ , the first use current I _P , the second use current I _rms, and the snubber capacity Cs are parameters relating to the use conditions of the element to be selected, and the first maximum collector-emitter voltage V _CM1 , First constant β, second constant s1, third constant t, fourth constant u, fifth constant w, second maximum collector-emitter voltage V _CM2 , sixth constant s2, maximum collector current I _cm , turn-on loss The energy E _ONM , the turn-off loss energy E _OFFM, and the recovery loss energy E _RECM are parameters related to the electrical characteristics of the element to be selected.

Here, the converter capacity P is a value determined by specifications in advance when designing the AC / DC power converter C, and in this embodiment, the converter capacity P = 300 (MVA). Use voltages V ₁ is the use voltage of the power converter switching elements, and approximately half of the value of the rating. Therefore, in this embodiment, as shown in FIG. 2, a switching element for power conversion rated at 1700V-800A (hereinafter referred to as a first element) and a switching element for power conversion rated at 1700V-1200A (hereinafter referred to as a third element). use voltages _{V 1} to 850 (V)) of the power conversion switching element rated 3300V-800A (hereinafter, the power conversion switching element referred to as a second element) and rated 3300V-1200A (hereinafter, referred to as a fourth element) the use voltages _{V 1} and 1650 (V).

The first use current _IP is a peak value of the use AC current of the switching element for power conversion, and is approximately 2/3 or less of the rating. In the present embodiment, as shown in FIG. 2, the first and second elements both have a first use current I _P = 368 (A), and the third and fourth elements both have a first use current I _P = 566 ( A). The second use current I _rms is an effective value of the first use current I _P , and I _rms = I _P / √2. The second use current I _rms is may be inputted in advance calculated value, may be calculated automatically from the first use current I _P.

The modulation factor m is a modulation factor in PWM control, and the following relationship is established with respect to the line-to-line AC voltage V _ac (effective value) and the DC voltage V _dc after power conversion. In the present embodiment, the modulation factor m = 1.

  The power factor cosφ is a converter power factor, and in this embodiment, the power factor cosφ = 1. The snubber capacity Cs is a capacity of a snubber capacitor used in a snubber circuit added to the power conversion switching element. As is well known, the snubber circuit is a circuit inserted for the purpose of protecting the power conversion switching element from an overvoltage caused by the accumulated energy of the wiring inductance of the circuit when the power conversion switching element is turned off. The snubber capacity Cs is changed according to the value of the current flowing through the power conversion switching element. In this embodiment, the snubber capacitance Cs = 0.1 (μF) in the first element and the second element, and the snubber capacitance Cs = 0.15 (μF) in the third element and the fourth element.

The switching frequency fs is a switching frequency of the switching element for power conversion in PWM control, and in this embodiment, the switching frequency fs = 1000 (Hz). The output power X _pu is a ratio of output power during operation to the maximum output power of the AC / DC power converter C. That is, when 100% operation is performed with respect to the maximum output power, the output power X _pu = 1, and when 50% operation is performed with respect to the maximum output power, the output power X _pu = 0.5. It becomes. In the present embodiment, the output power X _pu = 1.

The first maximum collector-emitter voltage _VCM1 is input based on a data sheet indicating the electrical characteristics of the first to fourth elements. In the present embodiment, the first maximum collector-emitter voltage V _CM1 is set to a value when the gate-emitter voltage V _GE = 15 (V) and the junction temperature T _j = 125 ° C. 3 (V), 4.8 (V) for the second element, 3.4 (V) for the third element, and 4.8 (V) for the fourth element.

The first constant β is β = I _P / I _{CM when} the first use current phase current I _P and the maximum collector current I _CM of the power switching element are used. The maximum collector current I _CM is also a value based on the data sheet. In the present embodiment, the first constant β is set to 0.75 for both the first to fourth elements.

The second constant s1 is obtained as follows based on the data sheet. FIG. 3 shows an example of the collector current I _C -collector-emitter voltage V _CE characteristics at the junction temperature T _j = 125 ° C. of the power conversion switching element and the gate-emitter voltage V _GE = 15 (V). It is. As shown in this figure, the collector current _{I C} is a non-linear - performs a linear approximation of the collector-emitter voltage _{V CE} characteristic, when the intersection between the approximate straight line L1 and the horizontal axis is _{V C1, V C1 = s1 ·} V The relationship of _CM1 is established. That is, the second constant s1 = V _C1 / V _CM1 . As described above, the second constant s1 is obtained in advance for each of the first to fourth elements based on the data sheet. In the present embodiment, the second constant s1 of the first element, the second element, and the fourth element is set to 0.38, and the second constant s1 of the third element is set to 0.32.

Similarly, the third constant t is obtained as follows based on the data sheet. 4 (a) is the switching loss and the vertical axis, which is an example of the turn-on loss energy E _ON characteristics when the horizontal axis represents the collector current I _C. As shown in this figure, performs a linear approximation of turn-on loss energy _{E ON} characteristic is non-linear, when the intersection between the approximate straight line L2 and the vertical axis the _{E ON1,} E ON1 = relationship t _{· E ONM} is established ( E _ONM is the turn-on loss energy at the maximum collector current I _CM ). That is, the third constant t = E _ON1 / E _ONM . As described above, the third constant t is obtained in advance for each of the first to fourth elements based on the data sheet. In the present embodiment, the third constant t of the first element, the second element, and the third element is 0, and the third constant t of the fourth element is 0.01.

Similarly, the fourth constant u is obtained as follows based on the data sheet. FIG. 4 (b) switching loss and the vertical axis, which is an example of a turn-off loss energy E _OFF characteristics when the horizontal axis represents the collector current I _C. As shown in this figure, when a linear approximation of the non-linear turn-off loss energy E _OFF characteristic is performed and the intersection of the approximate straight line L3 and the vertical axis is E _OFF1 , the relationship of E _OFF1 = u · E _OFFM is established ( E _OFFM is the turn-off loss energy at the maximum collector current I _CM ). That is, the fourth constant u = E _OFF1 / E _OFFM . As described above, the fourth constant u is obtained in advance for each of the first to fourth elements based on the data sheet. In the present embodiment, the fourth constant u of the first element is 0.5, the fourth constant u of the second element is 0.19, the fourth constant u of the third element is 0.31, and the fourth constant u of the fourth element is fourth. The constant u is set to 0.16.

Similarly, the fifth constant w is obtained as follows based on the data sheet. FIG. 4 (c) switching loss and the vertical axis, which is an example of a recovery loss energy E _REC characteristics when the horizontal axis represents the collector current I _C. As shown in this figure, when a linear approximation of the nonlinear recovery loss energy E _REC characteristic is performed and the intersection of the approximate straight line L4 and the vertical axis is E _REC1 , the relationship of E _REC1 = w · E _RECM is established ( E _RECM is recovery loss energy at maximum collector current I _CM ). That is, the fifth constant _{w = E} REC1 _/ E _RECM. As described above, the fifth constant w is obtained in advance for each of the first to fourth elements based on the data sheet. In the present embodiment, the fifth constant w of the first element is 0.33, the fifth constant w of the second element is 0.67, the fifth constant w of the third element is 0.27, and the fifth constant w of the fourth element. The constant w is set to 0.59.

The second maximum collector-emitter voltage _VCM2 is the maximum collector-emitter voltage of the IGBT _freewheeling diode, and is input based on the data sheet in the same manner as the first maximum collector-emitter voltage _VCM1 . In the present embodiment, the second maximum collector-emitter voltage _VCM2 of the first element is 2.1 (V), and the second maximum collector-emitter voltage _VCM2 of the second element is 3.2 (V). , the second maximum collector-emitter voltage _{V CM2} of the third element 2.1 (V), the second maximum collector-emitter voltage _{V CM2} of the fourth element 3.2 and (V).

The sixth constant s2 is obtained in the same manner as the second constant s1 based on the collector current I _C -collector-emitter voltage V _CE characteristics in the freewheeling diode. Specifically, the collector current I _C in the wheeling diode as shown in FIG. 5 - performs a linear approximation of the collector-emitter voltage V _CE characteristic, when the intersection of the approximate line L5 and the horizontal axis is V _C2, V _C2 = S2 · _VCM2 is established. That is, the sixth constant s2 = V _C2 / V _CM2 . As described above, the sixth constant s2 is obtained in advance for each of the first to fourth elements. In the present embodiment, the sixth constant s2 of the first element is 0.38, the sixth constant s2 of the second element and the fourth element is 0.34, and the sixth constant s2 of the third element is 0.36. .

Maximum collector current I _CM is the maximum rating of the collector current I _C, in the present embodiment, the maximum collector current I _CM of the first element and second element 800 (A), the maximum collector of the third element and the fourth element The current I _{CM is set} to 1200 (A). As described above, the turn-on loss energy E _ONM , the turn-off loss energy E _OFFM, and the recovery loss energy E _RECM are obtained from FIG. In this embodiment, the turn-on loss energy E _ONM is 0.3 (J) for the first element, 1.6 (J) for the second element, 0.45 (J) for the third element, and _1.5 for the fourth element. 75 (J) is used. Further, the turn-off loss energy E _OFFM is 0.3 (J) for the first element, 0.8 (J) for the second element, 0.45 (J) for the third element, and 1.02 (J for the fourth element). ). Further, the recovery loss energy E _RECM is 0.15 (J) for the first element, 0.3 (J) for the second element, 0.22 (J) for the third element, and 0.44 (J for the fourth element). ).

 The DC voltage / line AC voltage ratio k depends on the modulation factor m as shown in the above equation (1). Therefore, since the modulation factor m = 1 in the present embodiment, the DC voltage / line AC voltage ratio k is 1.6 for both the first to fourth elements from the above equation (1). The DC voltage / line AC voltage ratio k may be a value calculated in advance, or may be automatically calculated from the modulation factor m.

As described above, when each variable is input based on the specifications of the AC / DC power converter C and the data sheet of each element, the number N of elements is calculated (step S3). For example, one power conversion switching element as shown in FIG. 18 (a power conversion switching element c6 sixth in FIG. 18) is composed of a parallel number N _P × number of series the N _S power conversion switching element assuming that, the line-to-line AC voltage _{V ac} is expressed by the following equation (2) consisting of converter capacity P, second working current _{I rms} and the number of parallel _{N P.}

 Further, when the formula (2) is substituted into the formula (1), the following formula (3) is obtained.

On the other hand, the series number _{N S,} since a DC voltage _{V dc} / operating voltage _{V 1,} the following (4) from equation (3) is obtained. Namely, the parallel number _{N P} × series number _{N S} is expressed by the following equation (5). Therefore, the number N of elements in the entire AC / DC power converter C is expressed by the following equation (6).

FIG. 6 shows the result of calculating the number N of elements when each of the first to fourth elements is used from the above equation (6). Subsequently, the conduction loss P _COND1 , the turn-on loss P _ON , the turn-off loss P _OFF , the snubber loss P _SNB , the conduction loss P _COND2 , and the recovery loss P _{REC in the freewheeling} diode in each of the first to fourth elements are represented by the following (7) to ( 12) Calculate based on the equation (step S4). These calculation results are shown in FIG.

Then, the total loss _{Ptotal in the} entire AC / DC power converter C is calculated based on the following equation (13), and the converter loss δ is calculated based on the following equation (14) (step S5).

FIG. 6 shows the calculation results of the total loss _Ptotal and the converter loss δ. As can be seen from the calculation result of the converter loss δ, when the third element is used, the converter loss δ is the smallest, and in the following order, the first element, the fourth element, and the second element. That is, the third element is selected as the power conversion switching element of the AC / DC power converter C (step S6). As described above, the third element is selected according to the processing procedure shown in FIG. 1, and the AC / DC power converter C is configured by using N (4892) third elements, thereby converting the converter loss δ. Can be minimized.

 FIG. 7 shows the calculation result of the converter loss δ when only the switching frequency fs is changed to 800 Hz. FIG. 8 shows the calculation result of the converter loss δ when only the switching frequency fs is changed to 500 Hz. From these calculation results, it can be seen that when the switching frequency fs changes, the magnitude of the converter loss δ changes, and the selection order of the power conversion switching elements also changes. Moreover, the selection order of the switching elements for power conversion changes similarly by changing other variables. Therefore, if the converter loss δ of each power conversion switching element is obtained in advance for various conditions, an optimum power conversion switching element that meets the design conditions can be obtained at the design stage of the AC / DC power converter C. It is possible to select efficiently.

  According to the method for selecting a switching element for power conversion as described above, the converter loss δ when the switching frequency fs is arbitrarily changed can be obtained, but the target converter loss δ is preliminarily determined. Then, it is possible to calculate the switching frequency fs by calculating backward from the target converter loss δ. The higher the switching frequency fs, the higher the response of the AC / DC power converter C and the less the generated harmonics. Therefore, the switching frequency for achieving the target converter loss δ in a plurality of selection target elements. It is reasonable to reversely calculate fs and compare to select an element having the highest switching frequency fs. In the following, the procedure for determining the switching frequency fs from the target converter loss δ using the flowchart of FIG. 9 and selecting the element with the highest switching frequency fs will be described.

First, the switching element for power conversion used as a selection object element is determined (step 10). Next, the converter capacity P, the use voltage V ₁ , the first use current I _P , the second use current I _rms , the modulation factor m, the power factor cos φ, the snubber capacity Cs, the output power X _pu , the first maximum collector · Emitter voltage V _CM1 , first constant β, second constant s1, third constant t, fourth constant u, fifth constant w, second maximum collector-emitter voltage V _CM2 , sixth constant s2, maximum collector Input current I _CM , turn-on loss energy E _ONM , turn-off loss energy E _OFFM , recovery loss energy E _RECM , DC voltage / line AC voltage ratio k (= V _dc / V _ac ), target converter loss δ into computer simulation (Step S11). Here, the difference from the flowchart of FIG. 1 is that a target converter loss δ is input instead of the switching frequency fs.

Subsequently, the number N of elements for each power conversion switching element determined in step S1 based on the above equation (6) is calculated (step S12), and the conduction loss P _COND1 and the turn-on loss P in each power conversion switching element are calculated. _ON , turn-off loss P _OFF , snubber loss P _SNB , conduction loss P _{COND2 in the freewheeling} diode, and recovery loss P _REC are calculated based on the above equations (7) to (12) (step S13). Here, the turn-on loss P _ON , the turn-off loss P _OFF , the snubber loss P _SNB and the recovery loss P _REC are functions of the switching frequency fs.

Next, the total loss _Ptotal is calculated by substituting the target converter loss δ and the converter capacity P into the above equation (14) (step S14). Then, the total loss P _total obtained in step S14, the conduction loss P _COND1 , the turn-on loss P _ON , the turn-off loss P _OFF , the snubber loss P _SNB , the conduction loss P _{COND2 in the freewheeling} diode, the recovery loss P _REC , The switching frequency fs is calculated by substituting the number N of elements obtained in step S12 into the above equation (13) (step S15). The higher the switching frequency fs, the higher the response of the AC / DC power converter C and the lower the harmonics. Therefore, the switching frequency fs of each power conversion switching element obtained in step S15 is compared, and the highest switching frequency is obtained. A power conversion switching element operable at fs is selected (step S16).

 According to such a method for selecting a switching element for power conversion, switching for power conversion that can realize an AC / DC power converter C that satisfies a target converter loss δ, has high response, and has low harmonics. It is possible to select an element.

Next, a method for selecting a switching element for power conversion for minimizing the cost of the AC / DC power converter C will be described with reference to the flowchart of FIG.
First, the switching element for power conversion used as a selection object element is determined similarly to FIG. 1 (step 20). Here, in addition to the first to fourth elements, a GTO (Gate Turn-Off thyristor) with a rating of 6000 V-6000 A is selected (hereinafter, this GTO is referred to as a fifth element).

Subsequently, the converter capacitance P, the use voltage V ₁ , the first use current I _P , the second use current I _rms , the modulation factor m, the power factor cos φ, the snubber capacitance Cs, the switching frequency fs, the output power X _pu , the first Maximum collector-emitter voltage V _CM1 , first constant β, second constant s1, third constant t, fourth constant u, fifth constant w, second maximum collector-emitter voltage V _CM2 , sixth constant s2, maximum collector current I _CM , turn-on loss energy E _ONM , turn-off loss energy E _OFFM , recovery loss energy E _RECM , DC voltage / line AC voltage ratio k (= V _dc / V _ac ) are input to the computer simulation ( Step S21). The input method in step S21 is performed in the same manner as step S2 in FIG. FIG. 11 shows an example of input values of the above parameters.

Further, the division number n of the output power _Xpu, the converted electricity rate, the element life L, the maintenance cost, the interest rate, and the element unit price are input (step S22). Here, the division number n of the output power _Xpu will be described. FIG. 12 shows an example of an annual operation plan of the AC / DC power converter C. FIG. As shown in this figure, the period of operation with output power X _pu = 1, 0.75, 0.5, 0.25, 0 in one year is planned as 60 days, and the operation stop period is 65 days. Assuming that That is, the division number n of the output power _Xpu is 5 from the above operation plan.
FIG. 13 shows an example of the input value of the division number n of the output power _Xpu , the electricity charge conversion value, the element life L, the maintenance cost, the interest rate, and the element unit price. Moreover, as shown in FIG. 14, the operation plan in each output electric power _Xpu is input (step S23).

  Subsequently, the element number N is calculated for each of the first to fifth elements (step S24). The calculation method of the number N of elements is the same as that in step S3 in FIG. Next, the element cost is calculated by the following equation (15), and the converter cost is calculated by the following equation (16) (step S25). These element costs and converter costs are initial costs. FIG. 16 shows the calculation results of the number N of elements and the initial cost.

Next, for each output power X _pu based on the operation plan, conduction loss P _COND1 , turn-on loss P _ON , turn-off loss P _OFF , snubber loss P _SNB , conduction loss P _COND2 in the _freewheeling diode, The recovery loss _PREC is calculated based on the above equations (7) to (12) (step S26), and the total loss _{Ptotal in the} entire AC / DC power converter C is calculated based on the above equation (13). At the same time, the converter loss δ is calculated based on the above equation (14) (step S27). The calculation results in steps S26 and S27 are shown in FIG.

Subsequently, a total loss cost conversion value for each output power _Xpu is calculated based on the following expression (17), and a total value of the total loss cost conversion values is calculated for each selection target element. The calculation results of these total loss cost conversion values are shown in FIG. Further, the running cost is calculated based on the following equation (18) (step S28). Then, the present value of all expenses is calculated based on the following equation (19), and the total value of present values including the initial cost is calculated based on the following equation (20) (step S29). FIG. 17 shows the calculation results of the present values of all the expenses and the total value of the present values.

  As can be seen from FIG. 17, since the total value of the present values of the fourth elements is the lowest, the fourth element is selected as a power conversion switching element (step S30). Thus, the cost (including initial cost and running cost) of the AC / DC power converter C can be minimized by using the selection target element having the lowest total value of the present values.

  As described above, according to the present embodiment, it is possible to select a switching element for power conversion that can minimize the converter loss δ and cost of the AC / DC power converter C. It is also possible to select a switching element for power conversion with high responsiveness by determining the target value of the converter loss δ from the cost target value and back-calculating the switching frequency fs from the determined target value of the converter loss δ. Is possible.

  In addition, this invention is not limited to the said embodiment, For example, the following modifications can be considered.

(1) Although the AC / DC power converter C has been described in the above embodiment, the DC / DC power converter C is not limited to this, and for example, the DC / DC provided at the subsequent stage of the first output terminal 1 and the second output terminal 2 in FIG. This design method can also be applied to AC power converters and the like.

(2) In the above embodiment, the switching element for power conversion that suppresses the converter loss δ and the cost most is selected. However, the switching element is not limited to this and satisfies the predetermined loss target value and cost target value. If so, a plurality may be selected.

(3) In the above embodiment, parameters related to the electrical characteristics of the element to be selected are input (step S2, step S11, step S21). However, parameters related to the electrical characteristics of each element are input to the database in advance. Alternatively, parameters relating to the electrical characteristics of the selection target element may be read from the database in accordance with the determination of the selection target element (step S1, step S10, step S20). In addition, parameters related to the usage conditions of the element to be selected (input at step S2, step S11, step S21), element life, maintenance cost, element unit price (input at step 22) may also be made into a database. .

It is a 1st flowchart which shows the design method of the power converter in one Embodiment of this invention. It is a 1st input example of each variable in one embodiment of the present invention. It is the 1st explanatory view of the parameter about the electrical property in one embodiment of the present invention. It is a 2nd explanatory view of the parameter about the electrical property in one embodiment of the present invention. It is a 3rd explanatory view of the parameter about the electrical property in one embodiment of the present invention. It is a calculation result of converter loss delta etc. in one embodiment of the present invention. It is 1st calculation results, such as converter loss (delta) at the time of changing the switching frequency fs in one Embodiment of this invention. It is a 2nd calculation result, such as converter loss delta at the time of changing switching frequency fs in one embodiment of the present invention. It is a 2nd flowchart which shows the design method of the power converter in one Embodiment of this invention. It is a 3rd flowchart which shows the design method of the power converter in one Embodiment of this invention. It is a 2nd input example of each variable in one embodiment of the present invention. It is explanatory drawing of the driving | operation plan of AC / DC power converter C in one Embodiment of this invention. It is a 3rd input example of each variable in one embodiment of the present invention. It is a 4th input example of each variable in one embodiment of the present invention. It is a calculation result of converter loss delta etc. based on an operation plan in one embodiment of the present invention. It is a calculation result of an initial cost in one embodiment of the present invention, and a total loss cost conversion value. It is a calculation result of the present value of all the expenses in one Embodiment of this invention, and the total value of present value. 1 is a schematic configuration diagram of an AC / DC power converter C according to an embodiment of the present invention.

Explanation of symbols

P: Converter capacity, V ₁ ... Working voltage, I _P ... First working current, I _rms ... Second working current, m ... Modulation rate, cosφ ... Power factor, Cs ... Snubber capacity, fs ... Switching frequency, X _pu ... output power, V _CM1 ... first maximum collector-emitter voltage, β ... first constant, s1 ... second constant, t ... third constant, u ... fourth constant, w ... fifth constant, V _CM2 ... Second maximum collector-emitter voltage, s2 ... sixth constant, I _CM ... maximum collector current, E _ONM ... turn-on loss energy, E _OFFM ... turn-off loss energy, E _RECM ... recovery loss energy, k ... DC voltage / line AC voltage ratio, N ... number of elements, P _COND1 ... conduction loss, P _ON ... turn-on loss, P _OFF ... turn-off loss, P _SNB ... snubber loss, P _COND2 ... in a _freewheeling diode Conduction loss, P _REC ... recovery loss, P _total ... total loss, δ ... converter loss

Claims (5)

A method of designing a power converter composed of a plurality of switching elements for power conversion,
For one or a plurality of selection target elements that are candidates for the power conversion switching element, the number of use of each selection target element is calculated based on the parameter related to the specification of the power converter and the parameter related to the use condition of the selection target element. A first step of:
A second step of calculating a loss of each individual selection target element when each of the selection target elements is used based on a parameter relating to the electrical characteristics of each selection target element, a parameter relating to use conditions, and a parameter relating to the specifications of the power converter When,
A third step of calculating a total loss in the power converter based on the used number of each selection target element calculated in the first step and the loss calculated in the second step;
And a fourth step of selecting, as a power conversion switching element, a selection target element in which the total loss satisfies a predetermined loss target value.   The method for designing a power converter according to claim 1, wherein, in the fourth step, the selection target element having the smallest total loss is selected as a switching element for power conversion. A step of calculating an initial cost when each selection target element is used from a unit price of each selection target element and a use number of each selection target element calculated in the first step;
Calculating a running cost based on the operation plan and total loss of the power converter;
Calculating a total cost in the power converter based on the initial cost and the running cost;
The method for designing a power converter according to claim 1, further comprising: selecting a selection target element whose total cost satisfies a predetermined cost target value as a switching element for power conversion. 4. The method of designing a power converter according to claim 3, wherein a selection target element having the smallest total cost is selected as a switching element for power conversion. A method of designing a power converter composed of a plurality of switching elements for power conversion,
For one or a plurality of selection target elements that are candidates for the power conversion switching element, the number of use of each selection target element is calculated based on the parameter related to the specification of the power converter and the parameter related to the use condition of the selection target element. A first step of:
Based on parameters related to the electrical characteristics of each selection target element, parameters related to usage conditions, and parameters related to the specifications of the power converter, the loss of each selection target element when the selection target element is used is calculated as a function of the switching frequency. A second step of:
A third step of calculating a total loss in the power converter based on a predetermined loss target value and a parameter relating to the specification of the power converter;
A fourth step of calculating a switching frequency for operating each element to be selected based on the total loss calculated in the third step and a loss that is a function of the switching frequency calculated in the second step;
And a fifth step of selecting a selection target element having the highest switching frequency as a switching element for power conversion.

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