Low common mode PWM (Pulse Width Modulation) method of electric energy conversion module

Abstract

The invention discloses a low-common-mode PWM (Pulse Width Modulation) method for an electric energy conversion module, which comprises the following steps of: selecting a center switching frequency according to factors such as control performance, device loss and output filtering characteristics of the electric energy conversion module, calculating a carrier register period value and initial phases of No.0 and No.1 carriers, and calculating by adopting vector control to obtain a given voltage and a comparison register value; the three phases are used as units for sorting, given voltages in a certain unit under a natural coordinate system are sorted, and corresponding carriers are selected according to whether the voltages are intermediate values or not; and performing offset processing on the comparison register value according to the current carrier number and the last period carrier number to avoid narrow pulse, and finally acting the updated comparison register value on pulse width PWM modulation of the N-level H-bridge converter. By adopting the method provided by the invention, the low common mode PWM modulation of the rectification or inversion electric energy conversion module under the H-bridge topology can be realized.

Description

Technical Field

[0001] The present invention belongs to the field of power electronics technology, and specifically relates to a low common-mode PWM modulation method for an electric energy conversion module, which is suitable for high-quality electric energy conversion modules based on high-frequency power semiconductor devices such as third-generation SiC and GaN, and is particularly suitable for places with strict electromagnetic compatibility requirements such as emergency UPS power supplies and electric propulsion. Background Art

[0002] With the development of the third-generation semiconductor material manufacturing process, production design and other levels, new power devices represented by high-power density SiC and GaN are widely used in fields with strict requirements on efficiency and harmonic characteristics due to their advantages such as lower conduction losses and faster switching frequencies.

[0003] The development of technology is often not comprehensive, and the changes in the characteristics of new power semiconductors also bring new problems. Compared with traditional IGBT and IGCT silicon devices, the parasitic distributed capacitance between the power module and the motor winding, frame, and core presents lower impedance at high frequencies. Under the action of the common-mode component of the power conversion module, it brings a series of problems such as increased leakage current and reduced efficiency.

[0004] In order to suppress the high frequency problem caused by unipolar frequency doubling SPWM modulation, many scholars have proposed a series of low common mode PWM modulation methods by using the switching frequency and multi-phase output freedom while maintaining the differential mode component unchanged. However, the existing two-level H-bridge switching frequency modulation method has the following disadvantages:

[0005] 1. The problem of too low impedance in the local frequency band of the winding can be solved by optimizing the switching frequency; however, the switching frequency is also restricted by the equipment control performance and efficiency indicators, which only avoids the problem but does not solve it.

[0006] 2. Taking three phases as the smallest unit, the common mode interference of components such as the motor side bearings can be suppressed by carrier phase shifting between units, but attention should also be paid to the interference of the inverter power conversion module and the motor winding. Summary of the invention

[0007] The purpose of the invention is to address the above problems and to propose a reliable and feasible low common mode PWM modulation method for an electric energy conversion module.

[0008] The technical solution adopted by the present invention to solve the technical problem is: a low common mode PWM modulation method of an electric energy conversion module, which is used for a power module with a two-level H-bridge topology structure, and a control system composed of a basic carrier initialization setting link, a vector control link, a carrier selection link, a pulse optimization link and a modulation action link, and the steps are:

[0009] Step 1, select the center switching frequency f c, and calculate the period value T of the carrier register pr , the initial phase values ​​of carriers 0 and 1 are T 0_phase 、T 1_phase ;

[0010] Step 2, using vector control to calculate and obtain voltage setting and comparison register values, and sorting them by three phases, numbered as m;

[0011] Step 3, sorting the voltage given in a unit in the natural coordinate system, and selecting the corresponding carrier according to whether the voltage is an intermediate value;

[0012] Step 4: According to the current carrier number S n and the carrier number S of the previous cycle n-1 , perform offset processing on the comparison register value;

[0013] Step 5: Apply the updated comparison register value to the pulse width PWM modulation of the N-level H-bridge converter.

[0014] Further, the step 1 specifically includes:

[0015] Step 1.1, select the center switching frequency f according to the control performance of the power conversion module, device loss, output filter characteristics and other factors c ;

[0016] Step 1.2, the chip crystal frequency f N Calculate the carrier register period value T pr =f N / (2f c );

[0017] Step 1.3, set the initial phase T of the carriers 0 and 1 0_phase =0 and T 1_phase =T pr .

[0018] Furthermore, the step 2 specifically includes:

[0019] Step 2.1, collect position, current and other information, and calculate the voltage given u under three-phase coordinates through closed-loop control a1b1c1 ......u anbncn and the compare register C to be updated mpra1b1c1 ......C mpranbncn ; where C mpra1b1c1 Given the voltage u a1b1c1 The calculated compare register value, C mpranbncn Given the voltage u anbncn The calculated compare register value;

[0020] Step 2.2, number the three phases as units m, m = 1, 2, 3...

[0021] Furthermore, the step 3 specifically includes:

[0022] Step 3.1, sorting the voltage given in the three-phase natural coordinate system;

[0023] Step 3.2, determine whether the voltage is an intermediate value. If the voltage is an intermediate value, the carrier number S selected by the voltage n =1-[(-1) m +1] / 2, otherwise S n =[(-1) m +1] / 2.

[0024] Furthermore, the step 4 specifically includes:

[0025] Step 4.1, record the current carrier number S n and the carrier number S of the previous cycle n-1 ;

[0026] Step 4.2, determine the change of carrier number, and compare the offset of register value. If S n-1 =0, S n =1, the maximum compare register value is moved up to T pr If S n-1 =1, S n =0, the minimum compare register value is shifted down to 0.

[0027] The beneficial effects of the present invention are as follows: the present invention fully utilizes the degrees of freedom of switching pulses and multi-phase outputs, optimizes PWM output, can balance the contradictions between common-mode suppression and control performance and efficiency indicators, further develops control ideas, and has strong practicality and is easy to program, design and implement in engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the modulation method of the present invention;

[0029] The respective figures are marked as: 1—basic carrier initialization setting link, 2—vector control link, 3—carrier selection link, 4—pulse optimization link, 5—modulation action link. DETAILED DESCRIPTION

[0030] The specific implementation of the present invention is described below with reference to the accompanying drawings and examples.

[0031] Example 1

[0032] like Figure 1As shown, the present invention is used for a power module of a two-level H-bridge topology structure, and the control system is composed of a basic carrier initialization setting link 1, a vector control link 2, a carrier selection link 3, a pulse optimization link 4 and a modulation action link 5, and the modulation method includes the following steps.

[0033] Step 1, select the center switching frequency f c , and calculate the period value T of the carrier register pr , the initial phase values ​​of carriers 0 and 1 are T 0_phase 、T 1_phase The specific steps are as follows.

[0034] Step 1.1, select the center switching frequency f according to the control performance of the power conversion module, device loss, output filter characteristics and other factors c .

[0035] Step 1.2, the chip crystal frequency f N Calculate the carrier register period value T pr =f N / (2f c ).

[0036] Step 1.3, set the initial phase T of the carriers 0 and 1 0_phase =0 and T 1_phase =T pr .

[0037] Step 2: Use vector control to calculate and obtain voltage reference and comparison register values, and sort them by three phases, numbered as m. The specific steps are as follows.

[0038] Step 2.1, collect position, current and other information, and calculate the voltage given u under three-phase coordinates through closed-loop control a1b1c1 ......u anbncn and the compare register C to be updated mpra1b1c1 ......C mpranbncn . Among them, C mpra1b1c1 Given the voltage u a1b1c1 The calculated compare register value; C mpranbncn Given the voltage u anbncn The calculated compare register value.

[0039] Step 2.2, number the three phases as units m, m = 1, 2, 3...

[0040] Step 3: sort the voltage given in a unit in the natural coordinate system, and select the corresponding carrier according to whether the voltage is an intermediate value. The specific steps are as follows.

[0041] Step 3.1, sort the voltage given in the three-phase natural coordinate system.

[0042] Step 3.2, determine whether the voltage is an intermediate value. If the voltage is an intermediate value, the carrier number S selected by the voltage n =1-[(-1) m +1] / 2, otherwise S n =[(-1) m +1] / 2.

[0043] Step 4: According to the current carrier number S n and the carrier number S of the previous cycle n-1 , to perform the offset processing of the comparison register value. The specific steps are as follows.

[0044] Step 4.1, record the current carrier number S n and the carrier number S of the previous cycle n-1 ;

[0045] Step 4.2, determine the change of carrier number, and compare the offset of register value. If S n-1 =0, S n =1, the maximum compare register value is moved up to T pr If S n-1 =1, S n =0, the minimum compare register value is shifted down to 0.

[0046] Step 5: Apply the updated comparison register value to the pulse width PWM modulation of the N-level H-bridge converter.

[0047] Example 2

[0048] As a second embodiment of the present invention, the difference from the first embodiment is that the carrier selection based on the voltage intermediate value can be changed to be based on the voltage maximum value, minimum value or fixed phase.

[0049] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A low common mode PWM modulation method for an electric energy conversion module, based on a control system consisting of a basic carrier initialization setting link (1), a vector control link (2), a carrier selection link (3), a pulse optimization link (4) and a modulation action link (5), characterized in that: Steps Step 1, select the center switching frequency f c , and calculate the period value T of the carrier register pr , the initial phase values ​​of carriers 0 and 1 are T 0_phase , T 1_phase ; Step 2, using vector control to calculate and obtain voltage setting and comparison register values, and sorting them by three phases as units, numbered as m; Step 3, sorting the voltage given in a unit in the natural coordinate system, and selecting the corresponding carrier according to whether the voltage is an intermediate value; Step 4: According to the current carrier number S n and the carrier number S of the previous cycle n-1 , perform offset processing on the comparison register value; Step 5: Apply the updated comparison register value to the pulse width PWM modulation of the N-level H-bridge converter.

2. The low common mode PWM modulation method of the electric energy conversion module according to claim 1, characterized in that: The step 1 specifically includes: Step 1.1, select the center switching frequency f according to the control performance, device loss and output filter characteristics of the power conversion module c ; Step 1.2, the chip crystal frequency f N Calculate the carrier register period value T pr =f N / (2f c ); Step 1.3, set the initial phase T of the carriers 0 and 1 0_phase =0 and T 1_phase =T pr .

3. The low common mode PWM modulation method of the electric energy conversion module according to claim 2, characterized in that: The step 2 specifically includes: Step 2.1, collect position, current and other information, and calculate the voltage given u under three-phase coordinates through closed-loop control a1b1c1 ......u anbncn and the compare register C to be updated mpra1b1c1 ......C mpranbncn ; where C mpra1b1c1 Given the voltage u a1b1c1 The calculated compare register value, C mpranbncn Given the voltage u anbncn The calculated compare register value; Step 2.2, number the three phases as units m, m = 1, 2, 3...

4. The low common mode PWM modulation method of the electric energy conversion module according to claim 3, characterized in that: The step 3 specifically includes: Step 3.1, sorting the voltage given in the three-phase natural coordinate system; Step 3.2, determine whether the voltage is an intermediate value. If the voltage is an intermediate value, the carrier number S selected by the voltage n =1-[(-1) m +1] / 2, otherwise S n =[(-1) m +1] / 2.

5. The low common mode PWM modulation method of the electric energy conversion module according to claim 4, characterized in that: The step 4 specifically includes: Step 4.1, record the current carrier number S n and the carrier number S of the previous cycle n-1 ; Step 4.2, determine the change of carrier number, and compare the offset of register value. If S n-1 =0, S n =1, the maximum compare register value is moved up to T pr If S n-1 =1, S n =0, the minimum compare register value is shifted down to 0.

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