A method for automatically compensating for tube voltage drop in a three-phase inverter

Abstract

This invention belongs to the field of power electronics technology, specifically relating to an automatic IGBT voltage drop compensation method for a three-phase inverter. First, the upper and lower arms of one phase of the three-phase inverter are turned off, the upper arm of another phase is turned off and the lower arm is turned on, while the upper and lower arms of the third phase remain operational. This constructs the three-phase inverter as a DC-DC converter topology. A microcontroller segments the current and rate of the PI regulator, changing the carrier frequency of the PWM module's voltage. The voltage drop of the IGBTs under different given currents and carrier frequencies is calculated using voltage equations. This enables automatic identification and compensation of the IGBT voltage drop in the three-phase inverter, as well as closed-loop control of the inverter's output current. This automatic voltage drop compensation method effectively solves the problem of inaccurate compensation for IGBT voltage drops caused by load current variations, thereby improving inverter output current distortion and significantly enhancing inverter performance.

Description

Technical Field

[0001] This invention belongs to the field of power electronics technology, specifically relating to an automatic compensation method for tube voltage drop in a three-phase inverter. Background Technology

[0002] The voltage drop across the inverter's power devices causes an error between the actual and expected output voltage, leading to increased output current harmonics, especially in three-phase inverters with lower output voltages, resulting in severe waveform distortion. Voltage drop compensation significantly improves the performance of three-phase inverters, making it essential. However, due to the nonlinear characteristics of IGBTs, changes in load current cause variations in IGBT voltage drops. Existing voltage drop compensation schemes often fail to achieve satisfactory results. Therefore, adaptive compensation under different load conditions is a major challenge for three-phase inverter voltage drop compensation and a significant hurdle for improving the performance of power electronic devices. Summary of the Invention

[0003] To address the above issues, this invention provides an automatic compensation method for IGBT voltage drop based on piecewise linearization of a given current. This method can effectively improve the current distortion problem caused by the IGBT voltage drop of the inverter due to changes in load current, and significantly enhance the performance of the three-phase inverter.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] An automatic compensation method for tube voltage drop in a three-phase inverter, wherein the three-phase inverter includes a three-phase bridge circuit, the input terminal of the three-phase bridge circuit is connected to a DC power supply, and the output terminal is connected to a load. Each phase of the bridge circuit includes an upper bridge arm and a lower bridge arm, and each upper and lower bridge arm is composed of an IGBT connected in parallel with a freewheeling diode.

[0006] The automatic voltage drop compensation method for the tubes of this three-phase inverter includes the following steps:

[0007] S1. The DC-DC converter topology can be constructed by turning off the upper and lower arms of phase U of the three-phase inverter, turning off the upper arm of phase V and turning on the lower arm, while keeping the upper and lower arms of phase W working normally; it can also be constructed by turning off the upper and lower arms of phase V of the three-phase inverter, turning off the upper arm of phase W and turning on the lower arm, while keeping the upper and lower arms of phase U working normally; it can also be constructed by turning off the upper and lower arms of phase W of the three-phase inverter, turning off the upper arm of phase U and turning on the lower arm, while keeping the upper and lower arms of phase V working normally; the turning off of the upper and lower arms of each phase of the three-phase inverter is achieved by pulse blocking.

[0008] S2. Closed-loop control of the DC-DC converter topology output current is achieved through a PI regulator and a PWM module. The given current is input to the setpoint of the PI regulator and is divided into n segments, with n = 10 to 15 segments; further optimization is n = 13, that is, the given current is divided into 13 segments in ascending order of 1 / 13I. max 2 / 13I max 3 / 13I max ...I max The voltage is sequentially fed to the PI regulator; the PI regulator obtains the voltage given by the PWM module and feeds it to the PWM module; then the PWM module controls the DC-DC converter topology so that the output voltage of the DC-DC converter topology follows the voltage given by the PWM module.

[0009] S3. Change the carrier frequency of the PWM module's given voltage to m times, where m = 1 to 3; more preferably, m = 2, that is, repeat the operation in step S2 at twice the carrier frequency. The segmented setting of the PI regulator's given current and the multiplier change of the PWM module's given voltage's carrier frequency are both implemented by the microcontroller through program control.

[0010] S4. Based on the DC-DC converter topology, the output voltage equations of the PI regulator given current at m times different carrier frequencies are solved, and the voltage drop of the freewheeling diode and the IGBT are solved accordingly. Then, the output voltage equations corresponding to the n given current segments are solved one by one, and the voltage drop of the freewheeling diode and the IGBT are solved accordingly, thereby realizing automatic compensation of the voltage drop of the three-phase inverter and closed-loop control of the output current of the three-phase inverter.

[0011] Solve for the given current I and carrier frequency f of the PI controller. s The formula for the DC output voltage at that time is:

[0012] V W1 =V D [f s ,I]+V T [f s ,I]+R s I

[0013] The formula for solving the DC output voltage of the PI regulator when the given current is I and the carrier frequency is m is as follows:

[0014] V W2 =V D [f s ,I]+mV T [f s ,I]+R s I

[0015] The formula for calculating the voltage drop compensation value of the freewheeling diode is as follows:

[0016] V W2 -V W1 =V D [f s ,I rate ]

[0017] The formula for calculating the IGBT voltage drop compensation value is as follows:

[0018] mV W2 -V W1 -R s I rate =V T [f s ,I rate ]

[0019] In the above formulas, V D [f s [I] indicates that the carrier frequency is f s The voltage drop of the freewheeling diode when the current is I, V T [f s [I] indicates that the carrier frequency is f s The voltage drop across the IGBT when the current is I, R s I is the load resistance of the three-phase inverter. rate This is the rated current of the three-phase inverter.

[0020] The present invention also includes other components that enable its normal use, all of which are conventional means in the art. In addition, any devices or components not limited in the present invention adopt the prior art in the art.

[0021] The beneficial effects of this invention are as follows:

[0022] The automatic voltage drop compensation method for three-phase inverters provided by this invention can effectively improve the current distortion problem caused by the IGBT voltage drop of the inverter due to load current changes, without changing the circuit hardware and mechanical structure of the three-phase inverter, and significantly improve the working performance of the three-phase inverter. It is implemented through microcontroller programming control, without increasing hardware costs, and overcomes the technical challenge of automatic voltage drop compensation for three-phase inverters under different load conditions. It can also be applied to offline parameter identification of frequency converters, and has a certain promoting effect on the performance improvement of related power electronic devices. When the driving load is a motor, it can ensure that the motor is in a stationary state, which is more convenient for operation and control than existing voltage drop compensation methods. Attached Figure Description

[0023] Figure 1 This is a topology diagram of the three-phase inverter in this invention.

[0024] Figure 2 This is a structural diagram of the DC-DC converter topology in Example 1.

[0025] Figure 3 This is a structural diagram of the DC-DC converter topology in Example 2.

[0026] Figure 4 This is a structural diagram of the DC-DC converter topology in Example 3.

[0027] Figure 5 The control principle diagram of the automatic pipe pressure drop compensation method provided by the present invention is shown.

[0028] Figure 6 The flowchart illustrates the workflow of the automatic pipe pressure drop compensation method provided by this invention. Detailed Implementation

[0029] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0030] Example 1

[0031] like Figure 1 , 2 As shown in Figures 5 and 6, an automatic compensation method for tube voltage drop in a three-phase inverter is provided. The three-phase inverter includes a three-phase bridge circuit. The input terminal of the three-phase bridge circuit is connected to a DC power supply, and the output terminal is connected to a load. Each phase of the bridge circuit includes an upper bridge arm and a lower bridge arm, and both the upper and lower bridge arms are composed of an IGBT connected in parallel with a freewheeling diode.

[0032] The automatic compensation method for tube voltage drop in a three-phase inverter is as follows:

[0033] S1. The upper and lower bridge arms of the U phase of the three-phase inverter are turned off by pulse blocking, the upper bridge arm of the W phase is also turned off by pulse blocking, the lower bridge arm is turned on, and the upper and lower bridge arms of the V phase are kept working normally to construct the DC converter topology.

[0034] S2. Closed-loop control of the DC-DC converter topology output current is achieved through a PI regulator and a PWM module. The given current is input to the setpoint of the PI regulator and is divided into 13 segments. The microcontroller controls the current to be controlled in ascending order of 1 / 13I. max 2 / 13I max 3 / 13I max ...I max The voltage is sequentially fed to the PI regulator; then the PI regulator obtains the voltage from the PWM module and feeds it to the PWM module; finally, the PWM module controls the DC-DC converter topology so that the output voltage of the DC-DC converter topology follows the voltage fed to the PWM module.

[0035] S3. The microcontroller then controls the change of the given voltage of the PWM module. Under the condition of twice the carrier frequency, the operation in step S2 is repeated again. The segmented given current of the PI regulator and the change of the carrier frequency of the given voltage of the PWM module are both achieved by the microcontroller through program control. The microcontroller adopts the DSP28335 controller.

[0036] S4. Based on the DC-DC converter topology, the output voltage equations of the PI regulator given current at m times different carrier frequencies are solved, and the voltage drop of the freewheeling diode and the IGBT are solved accordingly. Then, the output voltage equations corresponding to the n given current segments are solved one by one, and the voltage drop of the freewheeling diode and the IGBT are solved accordingly, thereby realizing automatic compensation of the voltage drop of the three-phase inverter and closed-loop control of the output current of the three-phase inverter.

[0037] Solve for the given current I and carrier frequency f of the PI controller. s The formula for the DC output voltage at that time is:

[0038] V W1 =V D [f s ,I]+V T [f s ,I]+R s I

[0039] The formula for solving the DC output voltage of a PI regulator with a given current of I and twice the carrier frequency is:

[0040] V W2 =V D [f s ,I]+2V T [f s ,I]+R s I

[0041] The formula for calculating the voltage drop compensation value of the freewheeling diode is as follows:

[0042] V W2 -V W1 =V D [f s ,I rate ]

[0043] The formula for calculating the IGBT voltage drop compensation value is as follows:

[0044] 2V W2 -V W1 -R s I rate =V T [f s ,I rate ]

[0045] In the above formulas, V D [f s [I] indicates that the carrier frequency is f s The voltage drop of the freewheeling diode when the current is I, V T [f s [I] indicates that the carrier frequency is f s The voltage drop across the IGBT when the current is I, R s I is the load resistance of the three-phase inverter. rate This is the rated current of the three-phase inverter.

[0046] The working principle of this invention is as follows:

[0047] This invention constructs a three-phase inverter as a DC-DC converter topology, and obtains a test circuit topology for IGBT voltage drop based on the DC-DC converter topology. By segmenting the given current through a PI regulator and changing the carrier frequency of the given voltage of the PWM module by a multiplier, the voltage drop of the IGBT under different given currents and carrier frequencies is solved by the voltage equation formula. This enables automatic identification and compensation of the IGBT voltage drop of the three-phase inverter and closed-loop control of the output current of the three-phase inverter.

[0048] The workflow for implementing dynamic compensation for tube voltage drop in a three-phase inverter is as follows:

[0049] (1) After the three-phase inverter is constructed as a DC-DC converter topology, its control method is similar to that of the DC-DC converter. The output voltage is adjusted by controlling the duty cycle of the W-phase bridge arm. The error between the given current and the feedback current of the DC-DC converter topology is input to the PI controller for closed-loop control. When the given current is greater than the feedback current, the microcontroller will reduce the duty cycle of the upper bridge arm of the W-phase, thereby reducing the output voltage of the W-phase bridge arm. The opposite is true when the given current is less than the feedback current.

[0050] (2) Wait for 0.25 to 1 second (preferably 0.5 seconds) to provide sufficient adaptation time for the system to enter a steady state;

[0051] (3) Record the output voltage of the PI regulator. At this time, the output voltage and output current of the DC converter topology are both DC, which makes it easier to establish Kirchhoff's voltage equation.

[0052] (4) The given current is divided into 13 segments and given to the PI controller in ascending order.

[0053] (5) Record the output voltage of the PI regulator corresponding to the 13 segmented given currents;

[0054] (6) Increase the given voltage carrier frequency of the PWM module by 2 times and repeat the above operation;

[0055] (7) Solve the voltage equations of the two carrier frequencies given by the PWM module to obtain the voltage drop of the IGBT tube, and solve the voltage drop of the IGBT tube corresponding to the given current of the 13-segment PI regulator one by one. When the three-phase inverter is working normally, the accurate compensation voltage can be automatically selected according to the change of the load current.

[0056] Example 2

[0057] like Figure 3 As shown, the difference from Embodiment 1 is that the DC converter topology in S1 is constructed by turning off the upper and lower bridge arms of the V phase of the three-phase inverter, turning off the upper bridge arm of the W phase and turning on the lower bridge arm, while keeping the upper and lower bridge arms of the U phase working normally.

[0058] Example 3

[0059] like Figure 4 As shown, the difference from Embodiment 1 is that the DC converter topology in S1 is constructed by turning off the upper and lower bridge arms of the W phase of the three-phase inverter, turning off the upper bridge arm of the V phase and turning on the lower bridge arm, while keeping the upper and lower bridge arms of the U phase working normally.

[0060] Example 4

[0061] The difference from Example 1 is that in S2, the PI regulator's given current is divided into 10 segments.

[0062] Example 5

[0063] The difference from Example 1 is that in S2, the PI regulator's given current is divided into 15 segments.

[0064] Example 6

[0065] The difference from Example 1 is that the given voltage of the PWM module in S3 is increased to 3 times the carrier frequency.

[0066] The technical solutions of the present invention are not limited to the specific embodiments described above. Without departing from the scope and spirit of the described embodiments, many modifications and changes will be obvious to those skilled in the art. Any technical modifications made within the spirit and principles of the present invention will fall within the protection scope of the present invention.

Claims

1. A method for automatic compensation of diode voltage drop in a three-phase inverter, wherein the three-phase inverter includes a three-phase bridge circuit, the input terminal of the three-phase bridge circuit is connected to a DC power supply, and the output terminal is connected to a load. Each phase of the bridge circuit includes an upper bridge arm and a lower bridge arm, and both the upper and lower bridge arms are composed of an IGBT connected in parallel with a freewheeling diode. The method is characterized in that... Includes the following steps: S1. Turn off the upper and lower bridge arms of one phase of the three-phase inverter, turn off the upper bridge arm and turn on the lower bridge arm of another phase, and keep the upper and lower bridge arms of the third phase working normally, so that the three-phase inverter is constructed into a DC-DC converter topology. S2. Closed-loop control of the DC-DC converter topology output current is achieved through a PI regulator and a PWM module. The given current is input to the given terminal of the PI regulator. The given current is divided into n segments and given in ascending order. The given voltage of the PWM module is obtained through the PI regulator and sent to the PWM module. The PWM module then controls the DC-DC converter topology so that the output voltage of the DC-DC converter topology follows the given voltage of the PWM module. S3. Change the carrier frequency of the given voltage of the PWM module to m times, and repeat step S2. S4. Based on the DC-DC converter topology, the output voltage equations of the PI regulator given current at m times different carrier frequencies are solved, and the voltage drop of the freewheeling diode and the IGBT are solved accordingly. Then, the output voltage equations corresponding to the n given current segments are solved one by one, and the voltage drop of the freewheeling diode and the IGBT are solved accordingly, thereby realizing automatic compensation of the voltage drop of the three-phase inverter and closed-loop control of the output current of the three-phase inverter. Solve for the given current I and carrier frequency f of the PI controller. s The formula for the DC output voltage at that time is: V W1 =V D [f s ,I]+V T [f s ,I]+R s I The formula for solving the DC output voltage of the PI regulator when the given current is I and the carrier frequency is m is as follows: V W2 =V D [f s ,I]+mV T [f s ,I]+R s I The formula for calculating the voltage drop compensation value of the freewheeling diode is as follows: V W2 -V W1 =V D [f s ,I rate ] The formula for calculating the IGBT voltage drop compensation value is as follows: mV W2 -V W1 -R s I rate =V T [f s ,I rate ] In the above formulas, V D [f s [I] indicates that the carrier frequency is f s The voltage drop of the freewheeling diode when the current is I, V T [f s [I] indicates that the carrier frequency is f s The voltage drop across the IGBT when the current is I, R s I is the load resistance of the three-phase inverter. rate This is the rated current of the three-phase inverter.

2. The automatic compensation method for tube voltage drop in a three-phase inverter as described in claim 1, characterized in that: The DC-DC converter topology is constructed by turning off the upper and lower arms of the U phase of the three-phase inverter, turning off the upper arm of the V phase and turning on the lower arm, while keeping the upper and lower arms of the W phase working normally.

3. The automatic compensation method for tube voltage drop in a three-phase inverter as described in claim 1, characterized in that: The DC-DC converter topology is constructed by turning off the upper and lower arms of the V phase of the three-phase inverter, turning off the upper arm of the W phase and turning on the lower arm, while keeping the upper and lower arms of the U phase working normally.

4. The automatic compensation method for tube voltage drop in a three-phase inverter as described in claim 1, characterized in that: The DC-DC converter topology is constructed by turning off the upper and lower arms of the W phase of the three-phase inverter, turning off the upper arm of the U phase and turning on the lower arm, while keeping the upper and lower arms of the V phase working normally.

5. The automatic compensation method for tube voltage drop in a three-phase inverter as described in claim 1, characterized in that: The shutdown of each phase upper arm and / or lower arm of the three-phase inverter is achieved through pulse blocking.

6. The automatic compensation method for tube voltage drop in a three-phase inverter as described in claim 1, characterized in that: The PI regulator's set current is given in segments, with the number of segments n = 10 to 15.

7. The automatic compensation method for tube voltage drop in a three-phase inverter as described in claim 6, characterized in that: n＝13。 8. The automatic compensation method for tube voltage drop in a three-phase inverter as described in claim 1, characterized in that: The carrier frequency of the given voltage in the PWM module is changed by a factor of m = 1 to 3.

9. The automatic compensation method for tube voltage drop in a three-phase inverter as described in claim 8, characterized in that: m＝2。 10. The automatic compensation method for tube voltage drop in a three-phase inverter as described in claim 1, characterized in that: The segmented current setting of the PI regulator and the multiplier change of the carrier frequency of the voltage setting of the PWM module are both achieved by the microcontroller through program control.

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