Single-phase differential Boost inverter voltage zero-crossing compensation method based on DSP

Abstract

The invention discloses a single-phase differential Boost inverter voltage zero-crossing compensation method based on a DSP (Digital Signal Processor). According to the method provided by the invention, the single-phase differential Boost inverter works under a discontinuous modulation strategy, and two Boost circuit modules alternately output positive and negative half cycles of alternating current sinusoidal voltage, so that the differential total output is the required alternating current sinusoidal voltage; wherein in the last switching period before the positive-negative half-cycle switching, the bridge arm switch actively turns off the interrupted current so as to eliminate zero crossing point oscillation caused by the residual energy of the inductor after the positive-negative half-cycle zero crossing point; in a first switching period after negative-positive half cycle switching, an initial pulse is widened for eliminating zero crossing point oscillation caused by inductive current mutation after negative-positive half cycle zero crossing.

Description

Technical Field

[0001] This invention belongs to the field of inverter technology, specifically relating to a method for zero-crossing voltage compensation in a single-phase differential Boost inverter based on a digital signal processor (DSP). Background Technology

[0002] Traditional inverters can only limit the peak AC voltage output to within the input DC voltage. The output range must be expanded by adding a boost circuit in the front stage or a boost transformer in the back stage, but this often leads to increased system complexity and efficiency loss.

[0003] Single-phase differential Boost inverters are based on Boost converter topologies. By changing the duty cycles of the two converters, they achieve differential output sinusoidal AC voltages. Based on the output waveforms and operating modes of the two converters, modulation strategies can be categorized into continuous modulation and discontinuous modulation strategies. With a continuous modulation strategy, both converters operate at high frequency, outputting two sets of sinusoidal waves with the same DC bias, amplitudes half the peak value of the target output voltage, and out of phase. A pure sine wave is obtained by subtracting the two phase voltages. With a discontinuous modulation strategy, the two converters alternately operate at high frequency within one power frequency cycle. Their output voltages constitute the positive and negative half-cycles of the target sinusoidal voltage, respectively, with the duty cycle calculated according to the Boost circuit gain. Since each converter operates at high frequency for only half the time within one power frequency cycle, the discontinuous modulation strategy effectively reduces the circuit's switching losses.

[0004] However, numerous studies have shown that due to the mode switching in discontinuous modulation strategies, mid-frequency oscillations (approximately 500Hz-1.5kHz) occur at the zero-crossing point, leading to a degraded output voltage waveform quality and increased losses. Traditional solutions typically improve the design at the topology level by adding clamping MOSFETs or IGBTs to provide a low-impedance voltage clamping path when the output voltage crosses zero, clamping the corresponding capacitor voltage to the input voltage. While this method can eliminate zero-crossing oscillations, it requires additional switching elements and control circuitry, increasing cost and reducing system power density. Furthermore, this method only compensates for positive-to-negative half-cycle mode switching, neglecting the oscillations caused by negative-to-positive half-cycle mode switching. Therefore, it is necessary to improve the circuit's control method in software without altering the basic hardware structure, reducing zero-crossing oscillations while offering advantages in cost and operation. Summary of the Invention

[0005] To address the problems and needs in the background technology, this invention provides a DSP-based method for zero-crossing voltage compensation in a single-phase differential Boost inverter. The proposed method eliminates zero-crossing oscillations caused by residual inductor energy after the zero-crossing point of the positive-negative half-cycle by actively shutting off the freewheeling current of the bridge arm switch during the last switching cycle before the positive-negative half-cycle switching. Furthermore, it eliminates zero-crossing oscillations caused by sudden changes in inductor current after the zero-crossing point of the negative-positive half-cycle by widening the initial pulse during the first switching cycle after the negative-positive half-cycle switching.

[0006] The technical solution of the present invention is as follows: I. A DSP-based method for zero-crossing voltage compensation in a single-phase differential Boost inverter The single-phase differential Boost inverter operates under a discontinuous modulation strategy. The two Boost circuit modules alternately output the positive and negative half-cycles of the AC sinusoidal voltage, so that the total differential output is the required AC sinusoidal voltage. In the last switching cycle before the positive-negative half-cycle switching, the bridge arm switch actively cuts off the freewheeling current to eliminate the zero-crossing oscillation caused by the residual energy of the inductor after the zero-crossing point of the positive-negative half-cycle. In the first switching cycle after the negative-positive half-cycle switching, the initial pulse is widened to eliminate the zero-crossing oscillation caused by the sudden change in inductor current after the zero-crossing point of the negative-positive half-cycle.

[0007] The bridge arm switch actively cuts off the freewheeling current, thus reducing the inductor charging time during this cycle. T 0 satisfies the following formula:

[0008] in, V in Input voltage; V m To output AC voltage amplitude; T s The switching frequency; L For Boost inductors; I end This represents the final value of the inductor current after the zero-crossing point and before entering the negative half-cycle. The remaining time of this switching cycle... T s - T 0 is used for inductive discharge.

[0009] The widened initial pulse specifically refers to the conduction time of the initial pulse. T ini Satisfy the following formula:

[0010] in, V in Input voltage; V m To output AC voltage amplitude;ω The angular frequency of the output AC voltage; L For Boost inductors; C This is the output capacitor.

[0011] II. A DSP-based single-phase differential Boost inverter voltage zero-crossing compensation device The controller is used to control the two Boost circuit modules in the single-phase differential Boost inverter to work in differential mode and alternately output the positive and negative half cycles of the AC sinusoidal voltage. In the differential mode controller, during the last switching cycle before the positive-negative half cycle switching, the bridge arm switch actively turns off the freewheeling current; during the first switching cycle after the negative-positive half cycle switching, the initial pulse is widened.

[0012] III. A computer device The device includes a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of the DSP-based single-phase differential Boost inverter voltage zero-crossing compensation method.

[0013] IV. A computer-readable storage medium The medium stores a computer program, which, when executed by a processor, implements the steps of the DSP-based single-phase differential Boost inverter voltage zero-crossing compensation method.

[0014] V. A computer program product The product includes a computer program / instruction that, when executed by a processor, implements the steps of the DSP-based single-phase differential Boost inverter voltage zero-crossing compensation method.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: The control signal of the switching transistor can be controlled cycle by cycle by the DSP discrete controller. Specifically, in the last switching cycle before the positive-negative half-cycle switching, the bridge arm switch actively turns off the freewheeling current, and in the first switching cycle after the negative-positive half-cycle switching, the initial pulse is widened. This can not only significantly reduce zero-crossing oscillation and improve voltage waveform quality, but also reduce losses and improve system efficiency. Attached Figure Description

[0016] Figure 1 This is the circuit topology diagram of a single-phase differential Boost inverter; Figure 2 This is the equivalent circuit diagram of the first Boost circuit module in the negative half-cycle; Figure 3 This is a schematic diagram of the active shutdown continuous current operating mode of the zero-crossing compensation method proposed in this invention; Figure 4 This is a schematic diagram of the active shutdown continuous current working waveform of the zero-crossing compensation method proposed in this invention; Figure 5 This is a schematic diagram of the widened initial pulse working mode of the zero-crossing compensation method proposed in this invention; Figure 6 This is a schematic diagram of the widened initial pulse working waveform of the zero-crossing compensation method proposed in this invention; Figure 7 This is a schematic diagram of the DSP register operation before and after the zero-crossing point of the positive and negative half-cycles; Figure 8 This is an experimental waveform diagram of zero-crossing oscillation during the positive and negative half cycles of a single-phase differential Boost inverter using the traditional method. Figure 9 This is an experimental waveform diagram of the zero-crossing points of the positive and negative half-cycles of a single-phase differential Boost inverter after adopting this invention; Figure 10 This is the experimental waveform of the initial wide pulse after the zero point of the positive half-cycle; Figure 11 This is the experimental waveform diagram of the additional transition mode before the zero point of the negative half-cycle. Detailed Implementation

[0017] To enable those skilled in the art to better understand and implement the present invention, the technical solution of the present invention will be described in detail below with reference to the accompanying drawings.

[0018] This invention proposes a DSP-based method for zero-crossing voltage compensation in a single-phase differential Boost inverter, specifically including: like Figure 1 As shown, the single-phase differential Boost inverter includes a first Boost circuit module and a second Boost circuit module. The capacitance, inductance, and other parameters of the two Boost circuit modules are completely symmetrical. The first Boost circuit module contains two switching transistors. S 1 and S 2. Complementary conduction, its duty cycle is expressed as: d 1. Two switching transistors in the second Boost circuit module S 3 and S 4. Complementary conduction, its duty cycle is expressed as: d2. The single-phase differential Boost inverter operates under a discontinuous modulation strategy. The two Boost circuit modules alternately output the positive and negative half-cycles of the AC sinusoidal voltage, so that the total differential output is the required AC sinusoidal voltage. Specifically, in the last switching cycle before the positive-negative half-cycle switching, the bridge arm switch actively cuts off the freewheeling current to eliminate the zero-crossing oscillation caused by the residual energy of the inductor after the zero-crossing point of the positive-negative half-cycle. In the first switching cycle after the negative-positive half-cycle switching, the initial pulse is widened to eliminate the zero-crossing oscillation caused by the sudden change in inductor current after the zero-crossing point of the negative-positive half-cycle.

[0019] For a single-phase differential Boost inverter operating under a discontinuous modulation strategy, the output voltage of its first Boost circuit module is... v c for: (1) in, V in Input voltage; V m To output AC voltage amplitude; ω The angular frequency of the output AC voltage.

[0020] Due to the inherent energy storage components of the circuit itself, the circuit mode switches after the zero crossing point. The energy stored in the inductor and capacitor cannot be quickly consumed by damping such as line resistance or component parasitic resistance (i.e., the inductor current and capacitor voltage cannot change abruptly), which will cause resonance of the inductor and capacitor.

[0021] First, let's analyze the negative half-cycle. After the zero-crossing point of both the positive and negative half-cycles, the first Boost circuit module will maintain the switching transistor during the negative half-cycle. S 1. Normally closed S 2. Normally open circuit, circuit equivalent diagram as follows: Figure 2 As shown. At this time, the second Boost circuit module can be regarded as a constant current source on the load side, injecting a sinusoidal alternating current into the first Boost circuit module. i o : (2) in, I o This represents the output current amplitude.

[0022] During the negative half-cycle, since the overall circuit damping is very small, the circuit evolution can be regarded as the transient response of a second-order circuit, and the equation is: (3) The general solution to the equation is: (4) in V end andI end Let be the initial values ​​of the capacitor voltage and inductor current when entering the negative half-cycle after crossing zero. The first and second terms of the solution represent the intermediate-frequency oscillations caused by the remaining stored energy in the capacitor and inductor, with parameters... ω c The third term represents the LC resonant frequency of this oscillation. The third term represents the forced oscillation caused by the excitation of a sinusoidal current source, the amplitude of which is very small and negligible. This invention mainly focuses on the first two terms.

[0023] To eliminate zero-crossing oscillations caused by residual inductor energy after the zero-crossing of the positive and negative half-cycles, this invention introduces an additional mode transition switching cycle at the end of the positive half-cycle. In the last switching cycle before the zero-crossing, the switching transistor is first... S 1. Turn off S 2 is on, duration is T At this point, the energy of the capacitor is transferred to the inductor and stored, causing the capacitor voltage to drop to near the input voltage. V in If the initial current of this switching cycle is I end Then the final value of the inductor current during the charging phase I min for: (5) Then, the switching transistor S 1 and S Both are in the off state, not in a complementary on state. At this time, the inductor current flows through... S The freewheeling diode of 1 feeds back to the input DC source, thereby achieving energy recovery. The operating mode during this cycle is as follows: Figure 3 As shown. Among them Figure 3 (a) is S 2. Schematic diagram of conduction modes; Figure 3 (b) is S 1 and S Schematic diagram of the two-mode turn-off.

[0024] If the final value of the inductor current during this transition switching cycle is exactly 0, then the following condition is met: (6) Solving equations (5) and (6) simultaneously, we get... T The maximum value of 0 is (7) in, V in Input voltage; V m To output AC voltage amplitude; T s Operating frequency; L For Boost inductors;I end This is the initial value of the inductor current when it enters the negative half-cycle after crossing zero.

[0025] Considering the difficulty in precisely controlling the inductor current to be exactly zero in actual operation, the inductor current can be appropriately shortened to enhance robustness. T The inductor current reaches 0 before the end of the switching cycle. After this, since both switches are off, the inductor current remains at 0 and no longer changes, and the circuit enters discontinuous conduction mode. The diagram showing the inductor current waveform and corresponding switching states throughout the process is as follows: Figure 4 As shown. After this mode ends, the remaining energy of the inductor and capacitor is recovered, which can significantly reduce or even eliminate the zero-crossing oscillation when entering the negative half-cycle.

[0026] Let's analyze the positive half-cycle. After the zero-crossing point in the negative-positive half-cycle, the change in operating mode causes a sudden change in the reference value of the inductor current, which will also trigger zero-crossing oscillation. The theoretical value that the inductor current needs to reach in the first switching cycle can be expressed as: (8) To eliminate zero-crossing oscillations caused by sudden changes in the reference current, this invention introduces an additional mode transition period at the beginning of the positive half-cycle. In the first cycle after the zero-crossing, the lower transistor is given... S 1. An initial wide pulse ensures that the inductor current reaches the theoretical value within the first cycle. I ini : (9) Solving equations (8) and (9) simultaneously, we obtain the conduction time of the initial pulse as: (10) in, V in Input voltage; V m To output AC voltage amplitude; ω The angular frequency of the output AC voltage; L For Boost inductors; C This is the output capacitor.

[0027] Operating mode during the initial pulse period as follows Figure 5 As shown, where Figure 5 (a) is S 1. Schematic diagram of conduction mode. Figure 5 (b) is S 1. Schematic diagram of the turn-off mode; the corresponding diagram of the inductor current waveform and switching state throughout the process is shown below. Figure 6 As shown. Since the inductor current rises rapidly to the theoretical value during the first switching cycle, the zero-crossing oscillation at the beginning of the positive half-cycle can also be eliminated.

[0028] This invention also proposes a DSP-based single-phase differential Boost inverter voltage zero-crossing compensation device, specifically comprising: The controller is used to control the two Boost circuit modules in the single-phase differential Boost inverter to work in differential mode and alternately output the positive and negative half cycles of the AC sinusoidal voltage. In the differential mode controller, during the last switching cycle before the positive-negative half cycle switching, the bridge arm switch actively turns off the freewheeling current; during the first switching cycle after the negative-positive half cycle switching, the initial pulse is widened.

[0029] This embodiment uses the TI TMS320F28335 DSP as the controller and employs an EPWM module to generate the required control waveform. Those skilled in the art should understand that this invention is also applicable to other types of DSP controllers, such as the TMS320F28377, and all fall within the scope of this invention.

[0030] Unless otherwise specified below, the EPWM module configuration uses the default settings. The configuration methods for the relevant modules are given below.

[0031] DB (Dead Time) Module: EPWMxA sets the rising edge delay, and EPWMxB sets the falling edge delay before inverting the output to avoid the upper and lower switches being turned on at the same time.

[0032] The AQ (Action Limitation) module configures both EPWMxA and EPWMxB to set the EPWM output to 0 when the counter value equals that of comparator A during upward counting, and to set the output to 1 when the counter value is 0 (CAU=0, ZRO=1). EPWMxB is additionally configured to set the EPWM output to 1 when the counter value equals that of comparator B during upward counting (CBU=1). In this configuration, EPWMxA outputs a normal pulse, while the pulse generated by EPWMxB through the AQ module is inverted compared to the desired output. This pulse is then further inverted by the DB module to achieve the intended output.

[0033] CC (Count Comparison) module: Take the positive half-cycle as an example, and configure the corresponding module accordingly for the negative half-cycle.

[0034] During cycles 1 to 199, the value of the counter comparator register A (CMPA) is updated cycle by cycle to the product of the maximum count value EPWM_TIMER_TBPRD and the duty cycle, i.e., EPWM_TIMER_TBPRD*d. Meanwhile, the value of the counter comparator register B (CMPB) is set to EPWM_TIMER_TBPRD+1. At this time, the EPWM module outputs complementary PWM pulse waves with duty cycles of d and 1-d, unaffected by CMPB.

[0035] In the last switching cycle of the positive half-cycle, set CMPA to 0 and CMPB to (1 – t d / T s )×EPWM_TIMER_TBPRD. At this time, the EPWMxB module outputs a single pulse with a duty cycle of td / Ts, while the EPWMxA module outputs a constant low level. Figure 5 The key waveforms of the EPWM module's internal and output modes are shown in both normal and transition modes.

[0036] During the first switching cycle of the positive half-cycle, the duty cycle is set to the starting pulse width. d 0. The initial pulse width can be calculated using formula (10): (11) During the remaining switching cycles, the duty cycle is calculated in the same way as the conventional modulation method, that is: (12) To further illustrate the technical effects of the present invention, experimental waveforms of the single-phase differential Boost inverter of the present invention are used for explanation: Figure 8 The image shows experimental waveforms of a single-phase differential Boost inverter oscillating at the zero-crossing points of both the positive and negative half-cycles. It can be seen that after the zero-crossing point of the positive half-cycle, the current waveform is distorted, causing a corresponding distortion in the voltage waveform. After the zero-crossing point of the negative half-cycle, the current waveform oscillates, causing distortion in the voltage waveform.

[0037] Figure 9 The experimental waveforms at the zero-crossing points of the positive and negative half-cycles are shown for a single-phase differential Boost inverter after applying this invention. It can be seen that at the zero-crossing points of the positive and negative half-cycles, the zero-crossing distortion is essentially eliminated through the zero-crossing compensation method of this invention, and the voltage waveform quality is greatly improved.

[0038] Figure 10 The waveform of the initial wide pulse after the zero-crossing point of the positive half-cycle is shown. It can be seen that by widening the initial pulse, the inductor current can rise rapidly to the set value within one switching cycle, satisfying the principle of current continuity, thereby eliminating the distortion at the zero-crossing point of the positive half-cycle.

[0039] Figure 11 The waveform diagram shows the additional transition mode experiment before the zero-crossing point of the negative half-cycle. It can be seen that in the first half of the transition mode, the inductor current continues to discharge the capacitor, further reducing the capacitor voltage; in the second half, both switches are in the off state, and the inductor current is fed back to the power supply through the freewheeling diode, reducing the current to 0, thereby eliminating the zero-crossing distortion of the negative half-cycle.

[0040] In summary, the DSP-based zero-crossing compensation method for single-phase differential Boost inverters proposed in this invention requires no additional hardware costs. By changing the PWM pulse output of two switching cycles in software control, the zero-crossing distortion phenomenon can be eliminated. Compared with existing methods, it is lower in cost and easier to implement.

[0041] The present invention also proposes a computer device, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of a DSP-based single-phase differential Boost inverter voltage zero-crossing compensation method.

[0042] The present invention also proposes a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of a DSP-based single-phase differential Boost inverter voltage zero-crossing compensation method.

[0043] The present invention also proposes a computer program product, including a computer program / instruction, which, when executed by a processor, implements the steps of a DSP-based single-phase differential Boost inverter voltage zero-crossing compensation method.

Claims

1. A method for zero-crossing voltage compensation in a single-phase differential Boost inverter based on DSP, characterized in that, include: The single-phase differential Boost inverter operates under a discontinuous modulation strategy. The two Boost circuit modules alternately output the positive and negative half-cycles of the AC sinusoidal voltage, so that the total differential output is the required AC sinusoidal voltage. In the last switching cycle before the positive-negative half-cycle switching, the bridge arm switch actively cuts off the freewheeling current to eliminate the zero-crossing oscillation caused by the residual energy of the inductor after the zero-crossing point of the positive-negative half-cycle. In the first switching cycle after the negative-positive half-cycle switching, the initial pulse is widened to eliminate the zero-crossing oscillation caused by the sudden change in inductor current after the zero-crossing point of the negative-positive half-cycle.

2. The method for zero-crossing voltage compensation of a single-phase differential Boost inverter based on DSP according to claim 1, characterized in that, The bridge arm switch actively cuts off the freewheeling current, thus reducing the inductor charging time during this cycle. T 0 satisfies the following formula: ； in, V in Input voltage; V m To output AC voltage amplitude; T s The switching frequency; L For Boost inductors; I end This is the final value of the inductor current after crossing zero and before entering the negative half-cycle.

3. The method for zero-crossing voltage compensation of a single-phase differential Boost inverter based on DSP according to claim 1, characterized in that, The widened initial pulse specifically refers to the conduction time of the initial pulse. T ini Satisfy the following formula: ； in, V in Input voltage; V m To output AC voltage amplitude; ω The angular frequency of the output AC voltage; L For Boost inductors; C This is the output capacitor.

4. A DSP-based single-phase differential Boost inverter voltage zero-crossing compensation device, characterized in that, include: The controller is used to control the two Boost circuit modules in the single-phase differential Boost inverter to work in differential mode and alternately output the positive and negative half cycles of the AC sinusoidal voltage. In the differential mode controller, during the last switching cycle before the positive-negative half-cycle switching, the bridge arm switch actively shuts off the continuous current. The initial pulse is widened during the first switching cycle after the negative-positive half-cycle switching.

5. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the DSP-based single-phase differential Boost inverter voltage zero-crossing compensation method as described in any one of claims 1 to 3.

6. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the DSP-based single-phase differential Boost inverter voltage zero-crossing compensation method as described in any one of claims 1 to 3.

7. A computer program product comprising a computer program / instructions, characterized in that, When the computer program / instruction is executed by the processor, it implements the steps of the DSP-based single-phase differential Boost inverter voltage zero-crossing compensation method as described in any one of claims 1 to 3.

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