Method and device for calculating maximum output voltage of two-level voltage type frequency converter

Abstract

The invention discloses a method and device for calculating the maximum output voltage of a two-level voltage type frequency converter, and the method comprises the steps: forming an equilateral triangle according to the straight lines where two basic voltage vectors are located and the vertexes in a sector where a space electrical angle is located, calculating the length of a vertical line perpendicular to the third side of the equilateral triangle from the central point of the space voltage vector distribution diagram; mapping the difference between the working durations of the two basic voltage vectors to the third edge; taking the vertical line as a right-angle side, taking the difference between the working durations of the two basic voltage vectors on the third side as the other right-angle side, calculating the lengths of bevel edges corresponding to the two right-angle sides by adopting a preset optimal gradient method, and taking the lengths of the bevel edges as the maximum output voltage of the frequency converter; according to the optimal gradient method, the hypotenuse of the triangle is calculated by using two right-angle sides through a dichotomy and an error feedback updating mode. The maximum output voltage of the two-level voltage type frequency converter can be quickly and accurately calculated, and the calculation efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of frequency converter technology, and in particular to a method and apparatus for calculating the maximum output voltage of a two-level voltage type frequency converter. Background Technology

[0002] The overall system of a two-level voltage-source inverter includes a rectifier, a DC bus, and a two-level three-phase inverter. The core components of this two-level three-phase inverter consist of three independent bridge arms: A, B, and C. Each bridge arm is equipped with two switching devices (upper and lower). The upper and lower switching devices on the same bridge arm follow a complementary conduction rule: when one switching device is on, the other must be off to avoid a short circuit on the DC bus. Based on this conduction rule, the industry typically standardizes the definition of bridge arm states: the state of lower switch on and upper switch off is recorded as 0, and the state of upper switch on and lower switch off is recorded as 1. Since the switching states of the three bridge arms A, B, and C are independent, there are a total of 2 × 2 × 2 = 8 possible state combinations. Each state combination corresponds to a specific set of line voltages and phase voltages at the inverter output. In the Space Vector Pulse Width Modulation (SVPWM) technology theory, these 8 voltage output combinations are defined as 8 space voltage vectors. The magnitudes of the six non-zero vectors are all 2 / 3Udc (where Udc is the DC bus voltage), reference. Figure 1 , Figure 1 The diagram shows the spatial voltage vector distribution in the prior art. Six non-zero vectors are evenly arranged at a 60° angle in the spatial vector plane, and the lines connecting their endpoints form a regular hexagon. This regular hexagon is the maximum boundary of the voltage vector that the frequency converter can output.

[0003] The frequency converter needs to calculate the maximum output voltage value Umax of the frequency converter at the angle theta (phase angle of the target vector) based on the measured DC bus voltage Udc.

[0004] In existing technologies, calculating the maximum output voltage Umax of the frequency converter based on the DC bus voltage Udc and the theta angle requires complex calculations. These calculations typically require the use of a floating-point coprocessor, consuming a large amount of MCU processor resources and time. This is especially true when calculations are frequent, resulting in very low computational efficiency. Summary of the Invention

[0005] This invention provides a method for calculating the maximum output voltage of a two-level voltage-type frequency converter, which can quickly and accurately calculate the maximum output voltage of the two-level voltage-type frequency converter and improve calculation efficiency. The method includes:

[0006] Two fundamental voltage vectors are used to determine the boundary of the sector where the spatial electrical angle is located; the sector is one of the sectors in the spatial voltage vector distribution diagram of a two-level voltage type three-phase inverter.

[0007] Within the sector where the spatial electric angle is located, based on the equilateral triangle formed by the lines and vertices of the two basic voltage vectors, calculate the length of the perpendicular line from the center point of the spatial voltage vector distribution diagram to the third side of the equilateral triangle; the third side is the third side of the equilateral triangle excluding the lines of the two basic voltage vectors.

[0008] The operating duration of each basic voltage vector is obtained based on the electrical angle and carrier period;

[0009] The difference in operating time between the two basic voltage vectors is mapped onto the third edge;

[0010] Using the vertical line as one right-angled side and the difference in working time between the two basic voltage vectors on the third side as the other right-angled side, the hypotenuse lengths corresponding to the two right-angled sides are calculated using a preset optimal gradient method, and the hypotenuse lengths are used as the maximum output voltage of the frequency converter; the optimal gradient method is to calculate the hypotenuse of the triangle by using the two right-angled sides through a bisection method and error feedback update.

[0011] This invention also provides a device for calculating the maximum output voltage of a two-level voltage-type frequency converter, wherein the device includes:

[0012] The sector perpendicular line processing module is used to determine the two basic voltage vectors of the sector where the spatial electrical angle is located; the sector is one of the sectors in the spatial voltage vector distribution diagram of a two-level voltage type three-phase inverter; within the sector where the spatial electrical angle is located, based on the equilateral triangle formed by the lines and vertices of the two basic voltage vectors, the length of the perpendicular line from the center point of the spatial voltage vector distribution diagram to the third side of the equilateral triangle is calculated; the third side is the third side of the equilateral triangle excluding the lines of the two basic voltage vectors.

[0013] The working duration calculation module is used to obtain the working duration of each basic voltage vector based on the electrical angle and carrier period; and to map the difference between the working durations of two basic voltage vectors onto the third edge.

[0014] The optimal gradient method calculation module is used to calculate the hypotenuse lengths corresponding to the two right-angled sides using the vertical line as one right-angled side and the difference in working time between the two basic voltage vectors on the third side as the other right-angled side, and to use the hypotenuse length as the maximum output voltage of the frequency converter. The optimal gradient method is to calculate the hypotenuse of the triangle by using the two right-angled sides through a bisection method and error feedback update.

[0015] This invention also provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the above-described method for calculating the maximum output voltage of a two-level voltage inverter.

[0016] This invention also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described method for calculating the maximum output voltage of a two-level voltage-type frequency converter.

[0017] This invention also provides a computer program product, which includes a computer program that, when executed by a processor, implements the above-described method for calculating the maximum output voltage of a two-level voltage-type frequency converter.

[0018] In this embodiment of the invention, the difference in operating time between two basic voltage vectors is mapped to the third side of an equilateral triangle within the sector where the spatial electrical angle is located. A right-angled side is defined by the perpendicular line to the third side, and the other right-angled side is defined by the difference in operating time between the two basic voltage vectors on the third side. A preset optimal gradient method is used to calculate the hypotenuse lengths corresponding to the two right-angled sides. The hypotenuse length is then used as the maximum output voltage of the inverter. The optimal gradient method calculates the hypotenuse of the triangle using a bisection method and error feedback updates. This optimal gradient method, based on a bisection method and error feedback updates, calculates the hypotenuse of the triangle. By introducing bisection and error feedback data, it achieves rapid convergence of the solution results, enabling fast and accurate calculation of the maximum output voltage of a two-level voltage inverter, significantly improving computational efficiency. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:

[0020] Figure 1 This is a spatial voltage vector distribution diagram in the prior art;

[0021] Figure 2 This is a flowchart illustrating the method for calculating the maximum output voltage of a two-level voltage-type frequency converter in an embodiment of the present invention.

[0022] Figure 3 This is a specific example diagram of the method for calculating the maximum output voltage of a two-level voltage-type frequency converter in an embodiment of the present invention;

[0023] Figure 4 This is another specific example of the method for calculating the maximum output voltage of a two-level voltage-type frequency converter in the embodiments of the present invention;

[0024] Figure 5 This is a comparison chart of the errors of the bisection method and the optimal gradient method in an embodiment of the present invention;

[0025] Figure 6 This is a schematic diagram of the maximum output voltage calculation device for a two-level voltage-type frequency converter in an embodiment of the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0027] The acquisition, storage, use, and processing of data in this application comply with relevant laws and regulations.

[0028] The overall system of a two-level voltage-type frequency converter includes a rectifier, a DC bus, and a two-level three-phase inverter. The core components of this two-level three-phase inverter consist of three independent bridge arms: A, B, and C. Each of these three bridge arms has two states: 0 (lower transistor on, upper transistor off) and 1 (upper transistor on, lower transistor off). There are a total of eight combinations of these two states for the three bridge arms, corresponding to eight vectors. The corresponding voltage relationships are shown in Table 1 below, where Sa, Sb, and Sc represent the switching states; Vab, Vbc, and Vca represent the line voltages; Van, Vbn, and Vcn are the phase voltages output by the inverter; and Udc is the DC bus voltage.

[0029] Table 1

[0030]

[0031] There are two zero vectors and six non-zero vectors. The entire space is also divided as follows: Figure 1 The six sectors are shown.

[0032] To minimize losses, the switching of each sector (including those within a sector) must only modify the operation of one bridge arm. This minimizes heat generation and allows for higher power density. (Reference) Figure 1 100 can be changed to 110 or 101, which is the difference between forward and reverse rotation of the motor. Assuming counterclockwise is the forward rotation of the motor, 100 switches to 110–010—011—001—101—100, forming a cycle. 100—101—001—011—010—110—100, this cycle is the motor running in the other direction.

[0033] The maximum voltage that the frequency converter can output is formed by a regular hexagon. Therefore, the frequency converter needs to calculate the maximum voltage value Umax that the frequency converter can output at the theta angle based on the measured DC bus voltage Udc.

[0034] In existing technologies, calculating the maximum output voltage Umax of the frequency converter based on the DC bus voltage Udc and the theta angle requires complex calculations. These calculations typically require the use of a floating-point coprocessor, consuming a large amount of MCU processor resources and time. This is especially true when calculations are frequent, resulting in very low computational efficiency.

[0035] To address the shortcomings of existing technologies, this invention proposes a method for calculating the maximum output voltage of a two-level voltage-type frequency converter. Figure 2 This is a flowchart illustrating the method for calculating the maximum output voltage of a two-level voltage-type frequency converter in an embodiment of the present invention, as shown below. Figure 2 As shown, the method includes:

[0036] Step 201: Determine the two basic voltage vectors of the sector boundary where the spatial electrical angle is located; the sector is one of the sectors in the spatial voltage vector distribution diagram of a two-level voltage type three-phase inverter;

[0037] Step 202: Within the sector where the spatial electric angle is located, based on the equilateral triangle formed by the lines and vertices of the two basic voltage vectors, calculate the length of the perpendicular line from the center point of the spatial voltage vector distribution diagram to the third side of the equilateral triangle; the third side is the third side of the equilateral triangle excluding the lines of the two basic voltage vectors.

[0038] Step 203: Obtain the operating duration of each basic voltage vector based on the electrical angle and carrier period;

[0039] Step 204: Map the difference in operating time between the two basic voltage vectors onto the third edge;

[0040] Step 205: Using the vertical line as one right-angled side and the difference in working time between the two basic voltage vectors on the third side as the other right-angled side, calculate the length of the hypotenuse corresponding to the two right-angled sides using the preset optimal gradient method, and use the length of the hypotenuse as the maximum output voltage of the frequency converter; the optimal gradient method: calculates the hypotenuse of the triangle by using the two right-angled sides through the bisection method and error feedback update.

[0041] The following describes in detail the method for calculating the maximum output voltage of the two-level voltage type frequency converter in the embodiments of the present invention.

[0042] During implementation, the two basic voltage vectors of the sector boundary where the spatial electrical angle is located are first determined; the sector is one of the sectors in the spatial voltage vector distribution diagram of a two-level voltage type three-phase inverter.

[0043] Since all six sectors are equivalent, calculating the maximum voltage of one sector allows us to extrapolate the maximum voltage of the other five sectors, and the calculation methods are similar.

[0044] Each sector is bounded by two adjacent basic voltage vectors. By determining the position of the current spatial electrical angle, the two basic voltage vectors corresponding to the sector can be accurately determined.

[0045] For example Figure 1 In this context, theta represents the spatial electric angle, and the sector it belongs to is sector I. The two fundamental voltage vectors at the boundary of sector I are U4 and U6.

[0046] Next, an equilateral triangle is formed by the lines and vertices of the two fundamental voltage vectors. Since the spatial voltage vector distribution has a regular hexagonal structure, the triangle formed by any two adjacent fundamental voltage vectors and the origin is an equilateral triangle. This geometric property provides a mathematical basis for subsequent calculations.

[0047] Next, calculate the length of the perpendicular line from the center point of the spatial voltage vector distribution diagram to the third side of the equilateral triangle. The third side is the straight line connecting the endpoints of the two basic voltage vectors. The length of the perpendicular line drawn from the center point to this line represents the vertical component of the voltage vector in the current sector.

[0048] In step 203, the operating duration of each basic voltage vector is obtained based on the electrical angle and carrier period. In the SVPWM control strategy, the two basic voltage vectors U1 and U2 operate for different durations within each switching cycle, and these operating durations directly affect the magnitude and direction of the output voltage. Accurate operating duration data can be obtained through real-time monitoring and calculation.

[0049] Taking the first sector as an example, for the theta angle, the output voltage is constructed by vector summation of U4 and U6. The different time proportions of each vector constitute the final output voltage vector. With a carrier period of T0, the traditional method is theta / 60°×T0 for the operating duration of vector U4, and (60-theta) / 60°×T0 for the operating duration of vector U6. However, for the output voltage, the maximum output voltage differs at different angles within the sector and is constrained by the hypotenuse.

[0050] In the inverter control program, the working time of U1 and the working time of U2 are tracked, and the vector voltage of U1 = working time of U1 × DC bus voltage Udc and the vector voltage of U2 = working time of U2 × DC bus voltage Udc are calculated to determine the maximum value of the output voltage Umax, that is, to calculate the length of the hypotenuse of the right angle.

[0051] In step 204, the difference in the operating duration of the two basic voltage vectors is mapped onto the third side. The difference in operating duration reflects the degree of imbalance in the contribution of the two vectors to the output voltage. Geometrically mapping this difference onto the third side lays the foundation for constructing a right-angled triangle calculation model.

[0052] Next, using the vertical line as one right-angled side and the difference in operating time between the two basic voltage vectors on the third side as the other right-angled side, the hypotenuse lengths corresponding to the two right-angled sides are calculated using a pre-defined optimal gradient method. The optimal gradient method calculates the hypotenuse of the triangle using a bisection method and error feedback updates on the two right-angled sides. This method avoids complex floating-point operations and significantly improves calculation speed. Specifically, the bisection method rapidly approximates the optimal solution by continuously narrowing the search interval, while the error feedback mechanism adjusts the calculation parameters in real time to ensure calculation accuracy.

[0053] Finally, the length of the hypotenuse is taken as the maximum output voltage of the frequency converter. The length of the hypotenuse takes into account the influence of both the vertical and horizontal components, accurately reflecting the maximum voltage value Umax that the frequency converter can output under the current operating conditions.

[0054] This method, through a combination of geometric transformation and optimization algorithms, significantly improves the performance of frequency converters without increasing hardware costs. Compared to traditional calculation methods, this algorithm avoids complex floating-point operations, significantly improving computational efficiency while reducing the resource consumption of the MCU processor, thus providing strong support for the real-time control of frequency converters.

[0055] In one embodiment, the two fundamental voltage vectors that determine the boundary of the sector where the spatial electrical angle is located may include:

[0056] The mechanical position information of the rotor is obtained by an encoder, and the spatial electrical angle is determined based on the mechanical position information of the rotor.

[0057] Mapping the spatial electrical angle to the spatial voltage vector distribution map determines two fundamental voltage vectors: the sector where the spatial electrical angle is located, and the boundary of the sector where the spatial electrical angle is located.

[0058] In this example, an encoder is mounted on the motor rotor shaft to monitor changes in the rotor's mechanical position in real time and transmits this information to the control system as a digital signal. The encoder is a photoelectric encoder, characterized by high precision and fast response, capable of accurately capturing the rotor's instantaneous position. Upon receiving the rotor's mechanical position information, the control system calculates it using the conversion relationship between electrical angles and mechanical angles. For example, for a motor with P pole pairs, the electrical angle equals the mechanical angle multiplied by the number of pole pairs P. This conversion relationship transforms the mechanical position information into the corresponding spatial electrical angle.

[0059] Then, the spatial voltage vector distribution map consists of six non-zero voltage vectors, which are uniformly distributed at 60° angles within the spatial vector plane, dividing the entire space into six sectors. Each sector corresponds to a 60° electrical angle range: sector 1 (0°-60°), sector 2 (60°-120°), sector 3 (120°-180°), sector 4 (180°-240°), sector 5 (240°-300°), and sector 6 (300°-360°). By comparing the calculated spatial electrical angles with these sector ranges, the sector position corresponding to the current electrical angle is determined.

[0060] After determining the sector based on the spatial electrical angle, two fundamental voltage vectors at the sector boundary are identified. For example, when the spatial electrical angle is in the first sector, the two fundamental voltage vectors at its boundary are U1 and U2; when it is in the second sector, the two fundamental voltage vectors at its boundary are U2 and U3, and so on. These two fundamental voltage vectors will serve as the basis for subsequent spatial vector pulse width modulation calculations to determine the desired output voltage vector.

[0061] This method enables the rapid and accurate determination of the sector position of the spatial electrical angle and its corresponding basic voltage vector, providing a precise vector selection basis for the space vector pulse width modulation control of the frequency converter, thereby improving control accuracy and response speed.

[0062] In one embodiment, the operating duration of each basic voltage vector is obtained based on the electrical angle and carrier period, including:

[0063] Based on the output voltage setpoint and the spatial electrical angle, vector decomposition is performed to obtain the magnitude of each basic voltage vector;

[0064] The operating duration of each basic voltage vector is determined by the carrier period and the magnitude of each basic voltage vector.

[0065] In the specific implementation process, vector decomposition is first performed based on the output voltage setpoint and the spatial electrical angle to obtain the magnitude of each basic voltage vector. Within the spatial vector plane, six non-zero vectors are evenly arranged at 60° angles, forming a regular hexagonal boundary. This boundary represents the maximum range of voltage vectors that the inverter can output. The vector decomposition process employs an improved algorithm, avoiding complex floating-point operations and significantly improving calculation speed. By analyzing the position of the output voltage setpoint under the spatial electrical angle, the magnitudes of two adjacent basic voltage vectors can be determined. For example, by performing vector decomposition on the output voltage, i.e., parallelogram decomposition, the magnitudes of the basic voltage vectors can be obtained. This decomposition method can accurately obtain the amplitude information required for each basic voltage vector within the control cycle.

[0066] The operating duration of each basic voltage vector is calculated based on the carrier period and the magnitude of each basic voltage vector. Using the carrier period as a time reference, and considering the magnitude ratio of each basic voltage vector, a time allocation algorithm determines the specific duration of each vector's action. The calculation of the operating duration takes into account the relationship between the vector amplitude and the carrier period, ensuring that within one carrier period, each basic voltage vector acts sequentially according to its calculated duration, thereby outputting the voltage vector.

[0067] In other words, the parallelogram decomposition method is used to decompose the output voltage vector into the direction of each basic voltage vector, obtaining the magnitude of each basic voltage vector. Based on the carrier period and vector magnitude, the operating duration of each basic voltage vector is obtained. This calculation method optimizes the operating time of vector voltages U1 and U2, enabling rapid determination of the maximum output voltage Umax. Through this duration allocation strategy, the frequency converter can precisely control the output of each phase within each carrier cycle, achieving high-precision voltage vector calculation. The entire process avoids the complex calculations of traditional methods, significantly improving the real-time performance of the control system while maintaining high accuracy and stability of the output voltage.

[0068] In one embodiment, taking the vertical line as one right-angled side and the difference in operating time between the two basic voltage vectors on the third side as the other right-angled side, the lengths of the hypotenuses corresponding to the two right-angled sides are calculated using a preset optimal gradient method, which may include:

[0069] Step 1: Let the maximum length of the hypotenuse be c_max = a + b, and the minimum length of the hypotenuse be c_min = max(a, b), where a is one leg and b is the other leg.

[0070] Step 2: Take the midpoint C1 = (c_max + c_min) / 2 between c_max and c_min, and calculate the midpoint error Err1 = C1×C1 – a×a – b×b;

[0071] Step 3: Compare the intermediate point error Err1 with the preset error threshold Err_set;

[0072] Step 4: If the absolute value of Err1 is less than or equal to Err_set, output the hypotenuse length equal to C1;

[0073] Step 5: If the absolute value of Err1 is greater than Err_set, determine whether Err1 is greater than 0;

[0074] Step 6: If Err1 is greater than 0, let c_max = C1 - Err1, and return to step 2;

[0075] Step 7: If Err1 is less than or equal to 0, let c_min = C1 - Err1, and return to step 2.

[0076] Figure 3 This is a specific example diagram illustrating the method for calculating the maximum output voltage of a two-level voltage-type frequency converter in an embodiment of the present invention. (Refer to...) Figure 3 Taking sector I as an example, O-U4-U6 form an equilateral triangle. The length of line segment U6P is the operating time of U6, and the length of line segment U4P is the operating time of U4. M is the midpoint of line segment U4U6. OMP form a right triangle. Line segment OM is a fixed-length line segment and is a known quantity; line segment OP is the maximum output voltage Umax, and line segment PM is the difference in operating time between the vectors U4 and U6, which is also a known quantity.

[0077] Given OM and MP as the legs of a right triangle, the hypotenuse OP is calculated using the optimal gradient method. In triangle OMP, the two legs are denoted as a and b, and the hypotenuse to be determined is denoted as c.

[0078] Since the sum of any two sides of a triangle is greater than the third side, therefore: a + b > c, which gives us the maximum value of c, c_max = a + b;

[0079] For a right triangle, the length of the hypotenuse is greater than any of the legs, therefore: c > max(a,b), which gives the minimum value of c, c_min = max(a,b).

[0080] Since numerical calculations in computers always involve some errors, the requirement to solve for the length of the hypotenuse c is satisfied as long as the error between the solution and the actual value is less than a certain range. The error Err is defined as |c_val×c_val – a×a – b×b|. The solution process can be terminated as long as this error is less than the error threshold Err_set.

[0081] Figure 4 This is another specific example diagram of the method for calculating the maximum output voltage of a two-level voltage-type frequency converter in this invention. (Refer to...) Figure 4 :

[0082] Based on the values ​​of a and b, we can obtain c_max = a + b and c_min = max(a, b).

[0083] If a > b, then c_min = a.

[0084] Step 1: Probe the error value of the center point.

[0085] C1 = (c_max + c_min) / 2;

[0086] Err1 = C1×C1 – a×a – b×b;

[0087] Step 2: Determine the error.

[0088] If the absolute value of Err1 is less than Err_set, it means c = C1, the final solution is obtained, and the solution process ends.

[0089] If Err1 is greater than 0, it means that C1 is larger than the expected c, then the final solution c is between C1 and c_min. Since the error is Err1, we take C1-Err1 as the new maximum value, c_max=C1-Err1, and repeat the first step.

[0090] If Err1 is less than or equal to 0, it means that C1 is smaller than the expected c. Then the final solution c is between c_max and C1. Take C1-Err1 as the new minimum value, c_min=C1-Err1, and repeat the first step.

[0091] The process continues until the absolute value of the error Err1 is less than the error setpoint Err_set.

[0092] When attempting new upper and lower limits, this scheme introduces error Err1 feedback to achieve gradient descent search, resulting in a faster solution speed than the conventional method for calculating the maximum voltage of frequency converters. This meets the needs of frequent calculations and also reduces the oscillation amplitude of the solution error.

[0093] In practice, the bisection method can be used to solve the problem without introducing error Err1 feedback, but the convergence speed is faster by introducing error Err1 feedback.

[0094] Assuming the input values ​​a are 0.9 and b are 0.1, c_max = 0.9 + 0.1 = 1, and c_min = max(0.9, 0.1) = 0.9. The bisection method solution process is shown in Table 2 below.

[0095] Table 2

[0096]

[0097] The optimal gradient descent method is solved as shown in Table 3 below.

[0098] Table 3

[0099]

[0100] The errors of the conventional bisection method and the optimal gradient method are compared as follows: Figure 5 As shown, Figure 5 This is a comparison chart of the errors of the bisection method and the optimal gradient method in an embodiment of the present invention. Figure 5 The blue Err optimal method is the optimal gradient method in this embodiment of the invention, and the red Err bisection method is the conventional bisection method corresponding to Table 2. Figure 5 As can be seen from the above, the optimal gradient descent method in this embodiment of the invention has a faster convergence speed, smaller oscillation amplitude, and a faster solution speed.

[0101] This invention also provides a device for calculating the maximum output voltage of a two-level voltage inverter, as described in the following embodiments. Since the principle by which this device solves the problem is similar to the method for calculating the maximum output voltage of a two-level voltage inverter, the implementation of this device can refer to the implementation of the method for calculating the maximum output voltage of a two-level voltage inverter; repeated details will not be elaborated further.

[0102] Figure 6 This is a schematic diagram of the maximum output voltage calculation device for a two-level voltage-type frequency converter in an embodiment of the present invention, as shown below. Figure 6 As shown, the device 600 includes:

[0103] The sector perpendicular line processing module 601 is used to determine the two basic voltage vectors of the sector where the spatial electrical angle is located; the sector is one of the sectors in the spatial voltage vector distribution diagram of a two-level voltage type three-phase inverter; within the sector where the spatial electrical angle is located, based on the equilateral triangle formed by the lines and vertices of the two basic voltage vectors, the length of the perpendicular line from the center point of the spatial voltage vector distribution diagram to the third side of the equilateral triangle is calculated; the third side is the third side of the equilateral triangle excluding the lines of the two basic voltage vectors.

[0104] The working duration calculation module 602 is used to obtain the working duration of each basic voltage vector based on the electrical angle and carrier period; and to map the difference in working duration of two basic voltage vectors onto the third edge.

[0105] The optimal gradient method calculation module 603 is used to calculate the hypotenuse lengths corresponding to the two right-angled sides using the vertical line as one right-angled side and the difference in working time of the two basic voltage vectors on the third side as the other right-angled side, and to use the hypotenuse length as the maximum output voltage of the frequency converter. The optimal gradient method is to calculate the hypotenuse of the triangle by using the two right-angled sides through bisection and error feedback update.

[0106] In one embodiment, the sector vertical line processing module 601 is specifically used for:

[0107] The mechanical position information of the rotor is obtained by an encoder, and the spatial electrical angle is determined based on the mechanical position information of the rotor.

[0108] Mapping the spatial electrical angle to the spatial voltage vector distribution map determines two fundamental voltage vectors: the sector where the spatial electrical angle is located, and the boundary of the sector where the spatial electrical angle is located.

[0109] In one embodiment, the working time calculation module 602 is specifically used for:

[0110] Based on the output voltage setpoint and the spatial electrical angle, vector decomposition is performed to obtain the magnitude of each basic voltage vector;

[0111] The operating duration of each basic voltage vector is determined by the carrier period and the magnitude of each basic voltage vector.

[0112] In one embodiment, the optimal gradient calculation module 603 is specifically used for:

[0113] Step 1: Let the maximum length of the hypotenuse be c_max = a + b, and the minimum length of the hypotenuse be c_min = max(a, b), where a is one leg and b is the other leg.

[0114] Step 2: Take the midpoint C1 = (c_max + c_min) / 2 between c_max and c_min, and calculate the midpoint error Err1 = C1×C1 – a×a – b×b;

[0115] Step 3: Compare the intermediate point error Err1 with the preset error threshold Err_set;

[0116] Step 4: If the absolute value of Err1 is less than or equal to Err_set, output the hypotenuse length equal to C1;

[0117] Step 5: If the absolute value of Err1 is greater than Err_set, determine whether Err1 is greater than 0;

[0118] Step 6: If Err1 is greater than 0, let c_max = C1 - Err1, and return to step 2;

[0119] Step 7: If Err1 is less than or equal to 0, let c_min = C1 - Err1, and return to step 2.

[0120] This invention also provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the above-described method for calculating the maximum output voltage of a two-level voltage inverter.

[0121] This invention also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described method for calculating the maximum output voltage of a two-level voltage-type frequency converter.

[0122] This invention also provides a computer program product, which includes a computer program that, when executed by a processor, implements the above-described method for calculating the maximum output voltage of a two-level voltage-type frequency converter.

[0123] In this embodiment of the invention, the difference in operating time between two basic voltage vectors is mapped to the third side of an equilateral triangle within the sector where the spatial electrical angle is located. A right-angled side is defined by the perpendicular line to the third side, and the other right-angled side is defined by the difference in operating time between the two basic voltage vectors on the third side. A preset optimal gradient method is used to calculate the hypotenuse lengths corresponding to the two right-angled sides. The hypotenuse length is then used as the maximum output voltage of the inverter. The optimal gradient method calculates the hypotenuse of the triangle using a bisection method and error feedback updates. This optimal gradient method, based on a bisection method and error feedback updates, calculates the hypotenuse of the triangle. By introducing bisection and error feedback data, it achieves rapid convergence of the solution results, enabling fast and accurate calculation of the maximum output voltage of a two-level voltage inverter, significantly improving computational efficiency.

[0124] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0125] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0126] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0127] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0128] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for calculating the maximum output voltage of a two-level voltage-type frequency converter, characterized in that, include: Two fundamental voltage vectors are used to determine the boundary of the sector where the spatial electrical angle is located; the sector is one of the sectors in the spatial voltage vector distribution diagram of a two-level voltage type three-phase inverter. Within the sector where the spatial electric angle is located, based on the equilateral triangle formed by the lines and vertices of the two basic voltage vectors, calculate the length of the perpendicular line from the center point of the spatial voltage vector distribution diagram to the third side of the equilateral triangle; the third side is the third side of the equilateral triangle excluding the lines of the two basic voltage vectors. The operating duration of each basic voltage vector is obtained based on the electrical angle and carrier period; The difference in operating time between the two basic voltage vectors is mapped onto the third edge; Using the vertical line as one right-angled side and the difference in working time between the two basic voltage vectors on the third side as the other right-angled side, the hypotenuse lengths corresponding to the two right-angled sides are calculated using a preset optimal gradient method, and the hypotenuse lengths are used as the maximum output voltage of the frequency converter; the optimal gradient method is to calculate the hypotenuse of the triangle by using the two right-angled sides through a bisection method and error feedback update.

2. The method as described in claim 1, characterized in that, The two fundamental voltage vectors that determine the boundary of the sector where the spatial electric angle is located include: The mechanical position information of the rotor is obtained by an encoder, and the spatial electrical angle is determined based on the mechanical position information of the rotor. Mapping the spatial electrical angle to the spatial voltage vector distribution map determines two fundamental voltage vectors: the sector where the spatial electrical angle is located, and the boundary of the sector where the spatial electrical angle is located.

3. The method as described in claim 1, characterized in that, Based on the electrical angle and carrier period, the operating duration of each basic voltage vector is obtained, including: Based on the output voltage setpoint and the spatial electrical angle, vector decomposition is performed to obtain the magnitude of each basic voltage vector; The operating duration of each basic voltage vector is determined by the carrier period and the magnitude of each basic voltage vector.

4. The method as described in claim 1, characterized in that, Using the vertical line as one right-angled side and the difference in operating time between the two basic voltage vectors on the third side as the other right-angled side, the hypotenuse lengths corresponding to the two right-angled sides are calculated using a preset optimal gradient method, including: Step 1: Let the maximum length of the hypotenuse be c_max = a + b, and the minimum length of the hypotenuse be c_min = max(a, b), where a is one leg and b is the other leg. Step 2: Take the midpoint C1 = (c_max + c_min) / 2 between c_max and c_min, and calculate the midpoint error Err1 = C1×C1 – a×a – b×b; Step 3: Compare the intermediate point error Err1 with the preset error threshold Err_set; Step 4: If the absolute value of Err1 is less than or equal to Err_set, output the hypotenuse length equal to C1; Step 5: If the absolute value of Err1 is greater than Err_set, determine whether Err1 is greater than 0; Step 6: If Err1 is greater than 0, let c_max = C1 - Err1, and return to step 2; Step 7: If Err1 is less than or equal to 0, let c_min = C1 - Err1, and return to step 2.

5. A device for calculating the maximum output voltage of a two-level voltage-type frequency converter, characterized in that, include: The sector perpendicular line processing module is used to determine the two basic voltage vectors of the sector where the spatial electrical angle is located; the sector is one of the sectors in the spatial voltage vector distribution diagram of a two-level voltage type three-phase inverter; within the sector where the spatial electrical angle is located, based on the equilateral triangle formed by the lines and vertices of the two basic voltage vectors, the length of the perpendicular line from the center point of the spatial voltage vector distribution diagram to the third side of the equilateral triangle is calculated; the third side is the third side of the equilateral triangle excluding the lines of the two basic voltage vectors. The working duration calculation module is used to obtain the working duration of each basic voltage vector based on the electrical angle and carrier period; and to map the difference between the working durations of two basic voltage vectors onto the third edge. The optimal gradient method calculation module is used to calculate the hypotenuse lengths corresponding to the two right-angled sides using the vertical line as one right-angled side and the difference in working time between the two basic voltage vectors on the third side as the other right-angled side, and to use the hypotenuse length as the maximum output voltage of the frequency converter. The optimal gradient method is to calculate the hypotenuse of the triangle by using the two right-angled sides through a bisection method and error feedback update.

6. The apparatus as claimed in claim 5, characterized in that, The sector vertical line processing module is specifically used for: The mechanical position information of the rotor is obtained by an encoder, and the spatial electrical angle is determined based on the mechanical position information of the rotor. Mapping the spatial electrical angle to the spatial voltage vector distribution map determines two fundamental voltage vectors: the sector where the spatial electrical angle is located, and the boundary of the sector where the spatial electrical angle is located.

7. The apparatus as claimed in claim 5, characterized in that, The working hours calculation module is specifically used for: Based on the output voltage setpoint and the spatial electrical angle, vector decomposition is performed to obtain the magnitude of each basic voltage vector; The operating duration of each basic voltage vector is determined by the carrier period and the magnitude of each basic voltage vector.

8. The apparatus as claimed in claim 5, characterized in that, The optimal gradient method calculation module is specifically used for: Step 1: Let the maximum length of the hypotenuse be c_max = a + b, and the minimum length of the hypotenuse be c_min = max(a, b), where a is one leg and b is the other leg. Step 2: Take the midpoint C1 = (c_max + c_min) / 2 between c_max and c_min, and calculate the midpoint error Err1 = C1×C1 – a×a – b×b; Step 3: Compare the intermediate point error Err1 with the preset error threshold Err_set; Step 4: If the absolute value of Err1 is less than or equal to Err_set, output the hypotenuse length equal to C1; Step 5: If the absolute value of Err1 is greater than Err_set, determine whether Err1 is greater than 0; Step 6: If Err1 is greater than 0, let c_max = C1 - Err1, and return to step 2; Step 7: If Err1 is less than or equal to 0, let c_min = C1 - Err1, and return to step 2.

9. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the method of any one of claims 1 to 4.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the method of any one of claims 1 to 4.

11. A computer program product, characterized in that, The computer program product includes a computer program that, when executed by a processor, implements the method of any one of claims 1 to 4.

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