Inverter switching loss calculation method considering zero current loss

Abstract

The invention discloses an inverter switching loss calculation method considering zero current loss. The method comprises the following steps: S1, analyzing a zero current loss generation principle of an upper bridge IGBT (Insulated Gate Bipolar Translator) and a lower bridge IGBT; s2, deducing a zero current loss calculation formula, and obtaining a fitting formula of single zero current switching loss through independent fitting of a working condition point with the current being 0; and S3, deducing a switching loss calculation formula containing zero current loss. The invention discloses an inverter switching loss calculation method considering zero current loss, and aims to solve the problem of inaccurate result caused by neglecting the zero current loss when a traditional method is used for calculating the switching loss.

Description

Technical Field

[0001] This invention belongs to the field of inverter technology, specifically relating to a method for calculating inverter switching losses considering zero current loss. Background Technology

[0002] In the efficiency simulation of automotive inverters, the inverter's losses mainly originate from the power module, which in turn includes conduction losses and switching losses. When performing efficiency simulations, a formula-based method is typically used to calculate the average losses.

[0003] Traditional formula-based methods for calculating switching losses have a significant drawback: they only calculate the switching losses during the sinusoidal half-cycle, completely ignoring the switching losses at zero current (as shown in Figure 1). This calculation method directly leads to an underestimation of the calculated switching losses, resulting in an overestimation of the inverter efficiency in the final simulation. Consequently, the simulation fails to accurately reflect the actual operating efficiency of the inverter, negatively impacting inverter design, optimization, and performance evaluation. Summary of the Invention

[0004] The main objective of this invention is to provide a method for calculating inverter switching losses that considers zero current loss, so as to solve the problem that the traditional method of calculating switching losses ignores zero current loss and thus results in inaccurate results.

[0005] To achieve the above objectives, this invention provides a method for calculating inverter switching losses considering zero current loss, comprising the following steps: Step S1: Analyze the zero current loss generation principle of the upper bridge IGBT and the lower bridge IGBT; Step S2: Derive the zero current loss calculation formula. By fitting the operating point with zero current individually, obtain the fitting formula for single zero current switching loss. Step S3: Derive the formula for calculating switching losses including zero current loss.

[0006] As a further preferred technical solution to the above technical solution, step S1 is specifically implemented as follows: Step S1.1: For the upper IGBT: When the lower bridge is turned off and the upper bridge is turned on, the parasitic junction capacitance C at the ce terminals of the upper bridge IGBT... ce_UH Through the equivalent resistance R of the series circuit ce_UH Discharge occurs, junction capacitance C ce_UH Voltage V across the terminals ce_UH Decrease; parasitic junction capacitance C at the ce terminals of the lower-bridge IGBT ce_UL The DC-supported capacitor C is charged through the upper bridge IGBT, and the junction capacitance C ce_UL Voltage V across the terminals ce_ULAs the current rises, the upper bridge IGBT generates zero current turn-on loss. When the lower bridge is turned on and the upper bridge is turned off, the parasitic junction capacitance C at the ce terminals of the lower bridge IGBT... ce_UL Through the equivalent resistance R of the series circuit ce_UL Discharge occurs, junction capacitance C ce_UL Voltage V across the terminals ce_UL Decrease; parasitic junction capacitance C at the ce terminals of the upper IGBT ce_UH The DC-supported capacitor C is charged through the lower bridge IGBT, and the current flows through R. ce_UH At this time, the upper bridge IGBT generates zero current turn-off loss; Step S1.2: For the lower bridge IGBT, the principle of zero current loss generation of the lower bridge IGBT is the same as that of the upper bridge IGBT.

[0007] As a further preferred technical solution to the above technical solution, step S2 is specifically implemented as follows: Step S2.1: The magnitude of single switching loss and the bus voltage V dc Current I and module junction temperature T j Relatedly, the single-cycle switching loss under different operating conditions was tested, and these single-cycle switching losses were fitted to obtain the fitting formula for the single-cycle switching loss, which satisfies the following: (1); Where a0, a1, b1, a2, b2, a3, b3, and c3 are fitting coefficients; Step S2.2: Let I = 0 in equation (1), then we have: (2); The loss in equation (2) is the single-cycle zero-current loss. From equation (2), we know that the single-cycle zero-current loss is only related to the bus voltage V. dc and the junction temperature T of the module j It is related to, but not to, the current I; Step S2.3: Fit the data for all operating points where the current is 0, and obtain the fitting formula for single-cycle zero-current switching loss that satisfies: (3); Among them, a 0_0 a 0_1 b 0_1 a 0_2 b 0_2 The fitting coefficients are denoted as .

[0008] As a further preferred technical solution to the above technical solution, step S3 is specifically implemented as follows: Step S3.1: Assuming current harmonics are ignored, the output current i u The expression is written as: (4); Among them, I p The fundamental frequency amplitude of the output current is given by T, and the fundamental frequency period is given by T. Step S3.2: The average switching loss of the IGBT within one fundamental cycle T consists of the switching loss of the sinusoidal half-cycle plus the zero current loss of the other half-cycle. Let the switching frequency be f. sw The average switching loss over one fundamental cycle is: (5); Substituting equations (1), (3), and (4) into equation (5) and simplifying, we get: (6); Equation (6) is the formula for calculating the switching loss including zero current loss.

[0009] As a further preferred technical solution to the above technical solution, it can be seen from equation (6) that regardless of the fundamental amplitude I of the output current p The magnitude, zero current loss always exists in each fundamental frequency cycle, when I p When I is large, the proportion of zero current loss in the total switching loss is small; while when I p When the current is relatively small, the proportion of zero current loss in the total switching loss will increase.

[0010] The beneficial effects of this invention are as follows: This invention proposes a method for calculating inverter switching losses considering zero current loss. Addressing the inaccuracy caused by traditional methods that only calculate sinusoidal half-cycle switching losses and neglect zero current loss, this method incorporates zero current loss calculations into the traditional switching loss formula. By fitting the zero-current operating point separately, a more accurate zero-current loss calculation formula is obtained. Then, combining the output current expression and the traditional single-cycle switching loss formula, a switching loss calculation formula including zero current loss is derived. This method corrects the incompleteness of traditional switching loss calculations, significantly improving the accuracy of switching loss calculations. This results in more accurate inverter efficiency simulation results and provides more reliable data support for inverter design optimization, performance evaluation, and practical applications. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the traditional calculation of switching loss region (showing that the traditional method only considers the sinusoidal half-cycle region when calculating switching loss, without involving the zero-current related region).

[0012] Figure 2This is a schematic diagram illustrating the principle of zero-current switching loss (the diagram shows the parasitic junction capacitance, equivalent resistance, and voltage across the upper and lower IGBTs, clearly illustrating the basic circuit structure for generating zero current loss). Detailed Implementation

[0013] The following description is intended to disclose the present invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art. The basic principles of the invention defined in the following description can be applied to other embodiments, modifications, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the invention.

[0014] In the preferred embodiments of the present invention, those skilled in the art should note that the inverters and the like involved in the present invention can be considered as prior art.

[0015] Preferred embodiment.

[0016] like Figure 1-2 As shown, this invention discloses a method for calculating inverter switching losses considering zero current loss, comprising the following steps: Step S1: As Figure 2 As shown, the principle of zero current loss generation of the upper bridge IGBT and the lower bridge IGBT is analyzed. Step S2: Derive the zero current loss calculation formula. By fitting the operating point with zero current individually, obtain the fitting formula for single zero current switching loss. Step S3: Derive the formula for calculating switching losses including zero current loss.

[0017] Specifically, step S1 is implemented as follows: Step S1.1: For the upper IGBT: When the lower bridge is turned off and the upper bridge is turned on, the parasitic junction capacitance C at the ce terminals of the upper bridge IGBT... ce_UH Through the equivalent resistance R of the series circuit ce_UH Discharge occurs, junction capacitance C ce_UH Voltage V across the terminals ce_UH Decrease; parasitic junction capacitance C at the ce terminals of the lower-bridge IGBT ce_UL The DC-supported capacitor C is charged through the upper bridge IGBT, and the junction capacitance C ce_UL Voltage V across the terminals ce_UL As the current rises, the upper bridge IGBT generates zero current turn-on loss. When the lower bridge is turned on and the upper bridge is turned off, the parasitic junction capacitance C at the ce terminals of the lower bridge IGBT... ce_UL Through the equivalent resistance R of the series circuit ce_UL Discharge occurs, junction capacitance C ce_ULVoltage V across the terminals ce_UL Decrease; parasitic junction capacitance C at the ce terminals of the upper IGBT ce_UH The DC-supported capacitor C is charged through the lower bridge IGBT, and the current flows through R. ce_UH At this time, the upper bridge IGBT generates zero current turn-off loss; Step S1.2: For the lower bridge IGBT, the principle of zero current loss generation of the lower bridge IGBT is the same as that of the upper bridge IGBT.

[0018] More specifically, step S2 is implemented as follows: Step S2.1: The magnitude of single switching loss and the bus voltage V dc Current I and module junction temperature T j Relatedly, the single-cycle switching loss under different operating conditions was tested, and these single-cycle switching losses were fitted to obtain the fitting formula for the single-cycle switching loss, which satisfies the following: (1); Where a0, a1, b1, a2, b2, a3, b3, and c3 are fitting coefficients; Step S2.2: Let I = 0 in equation (1), then we have: (2); The loss in equation (2) is the single-cycle zero-current loss. From equation (2), we know that the single-cycle zero-current loss is only related to the bus voltage V. dc and the junction temperature T of the module j It is related to, but not to, the current I; Step S2.3: (Since the fitting coefficients in equation (2) are obtained from equation (1), and equation (1) considers all different operating conditions when calculating the fitting coefficients, including operating points with zero current and operating points with non-zero current, the fitting error of operating points with zero current may be large.) Fit all operating points with zero current to obtain the fitting formula for single zero current switching loss that satisfies: (3); Among them, a 0_0 a 0_1 b 0_1 a 0_2 b 0_2 The fitting coefficients are denoted as .

[0019] Furthermore, step S3 is specifically implemented as follows: Step S3.1: Assuming current harmonics are ignored, then ( Figure 1 (middle) Output current i u The expression is written as: (4); Among them, I p The fundamental frequency amplitude of the output current is given by T, and the fundamental frequency period is given by T. Step S3.2: (by) Figure 1 As can be seen from the above analysis, the average switching loss of an IGBT within one fundamental cycle T consists of the switching loss of the sinusoidal half-cycle plus the zero current loss of the other half-cycle. Let the switching frequency be f. sw The average switching loss over one fundamental cycle is: (5); Substituting equations (1), (3), and (4) into equation (5) and simplifying, we get: (6); Equation (6) is the formula for calculating the switching loss including zero current loss.

[0020] Furthermore, as can be seen from equation (6), regardless of the fundamental amplitude I of the output current... p The magnitude, zero current loss always exists in each fundamental frequency cycle, when I p When I is large, the proportion of zero current loss in the total switching loss is small; while when I p When the current is small, the proportion of zero current loss in the total switching loss will increase (in the efficiency simulation of the inverter, the actual low current condition often occurs more frequently, so zero current loss cannot be ignored).

[0021] It is worth mentioning that the technical features such as inverters involved in this patent application should be regarded as prior art. The specific structure, working principle, and possible control methods and spatial arrangement of these technical features can be adopted using conventional choices in the field, and should not be regarded as the inventive point of this patent. This patent will not be further elaborated in detail.

[0022] For those skilled in the art, modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the protection scope of this invention.

Claims

1. A method for calculating the switching losses of an inverter considering zero current loss, characterized in that, Includes the following steps: Step S1: Analyze the zero current loss generation principle of the upper bridge IGBT and the lower bridge IGBT; Step S2: Derive the zero current loss calculation formula. By fitting the operating point with zero current individually, obtain the fitting formula for single zero current switching loss. Step S3: Derive the formula for calculating switching losses including zero current loss.

2. The method for calculating inverter switching losses considering zero current loss according to claim 1, characterized in that, Step S1 is specifically implemented as follows: Step S1.1: For the upper IGBT: When the lower bridge is turned off and the upper bridge is turned on, the parasitic junction capacitance C at the ce terminals of the upper bridge IGBT... ce_UH Through the equivalent resistance R of the series circuit ce_UH Discharge occurs, junction capacitance C ce_UH Voltage V across the terminals ce_UH Decrease; parasitic junction capacitance C at the ce terminals of the lower-bridge IGBT ce_UL The DC-supported capacitor C is charged through the upper bridge IGBT, and the junction capacitance C ce_UL Voltage V across the terminals ce_UL As the current rises, the upper bridge IGBT generates zero current turn-on loss. When the lower bridge is turned on and the upper bridge is turned off, the parasitic junction capacitance C at the ce terminals of the lower bridge IGBT... ce_UL Through the equivalent resistance R of the series circuit ce_UL Discharge occurs, junction capacitance C ce_UL Voltage V across the terminals ce_UL Decrease; parasitic junction capacitance C at the ce terminals of the upper IGBT ce_UH The DC-supported capacitor C is charged through the lower bridge IGBT, and the current flows through R. ce_UH At this time, the upper bridge IGBT generates zero current turn-off loss; Step S1.2: For the lower bridge IGBT, the principle of zero current loss generation of the lower bridge IGBT is the same as that of the upper bridge IGBT.

3. The method for calculating inverter switching losses considering zero current loss according to claim 2, characterized in that, Step S2 is specifically implemented as follows: Step S2.1: The magnitude of single switching loss and the bus voltage V dc Current I and module junction temperature T j Relatedly, the single-cycle switching loss under different operating conditions was tested, and these single-cycle switching losses were fitted to obtain the fitting formula for the single-cycle switching loss, which satisfies the following: （1）； Where a0, a1, b1, a2, b2, a3, b3, and c3 are fitting coefficients; Step S2.2: Let I = 0 in equation (1), then we have: （2）； The loss in equation (2) is the single-cycle zero-current loss. From equation (2), we know that the single-cycle zero-current loss is only related to the bus voltage V. dc and the junction temperature T of the module j It is related to, but not to, the current I; Step S2.3: Fit the data for all operating points where the current is 0, and obtain the fitting formula for single-cycle zero-current switching loss that satisfies: （3）； Among them, a 0_0 a 0_1 b 0_1 a 0_2 b 0_2 The fitting coefficients are denoted as .

4. The method for calculating inverter switching losses considering zero current loss according to claim 3, characterized in that, Step S3 is specifically implemented as follows: Step S3.1: Assuming current harmonics are ignored, the output current i u The expression is written as: （4）； Among them, I p The fundamental frequency amplitude of the output current is given by T, and the fundamental frequency period is given by T. Step S3.2: The average switching loss of the IGBT within one fundamental cycle T consists of the switching loss of the sinusoidal half-cycle plus the zero current loss of the other half-cycle. Let the switching frequency be f. sw The average switching loss over one fundamental cycle is: （5）； Substituting equations (1), (3), and (4) into equation (5) and simplifying, we get: （6）； Equation (6) is the formula for calculating the switching loss including zero current loss.

5. The method for calculating inverter switching losses considering zero current loss according to claim 4, characterized in that, As can be seen from equation (6), regardless of the fundamental amplitude I of the output current p The magnitude, zero current loss always exists in each fundamental frequency cycle, when I p When I is large, the proportion of zero current loss in the total switching loss is small; while when I p When the current is relatively small, the proportion of zero current loss in the total switching loss will increase.

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