DCAC power conversion device and power conversion method thereof

Abstract

The invention discloses a DCAC power conversion device and a power conversion method thereof, and the device comprises a full-bridge inverter which is used for converting an input DC voltage into a high-frequency AC voltage; the LCL resonance network is connected to the output end of the full-bridge inverter and is used for being equivalent to a current source in a target frequency range to realize zero voltage switching ZVS and harmonic suppression; the primary side of the high-frequency isolation transformer is connected with the LCL resonance network, and the secondary side of the high-frequency isolation transformer is connected with a load to realize electrical isolation of input and output; and the load phase angle detection module is used for detecting current and voltage signals of a load in real time, calculating a load phase angle # imgabs0 # hybrid control unit and dynamically switching control modes according to the numerical relationship between the load phase angle # imgabs1 # and a preset threshold # imgabs2 # so as to control the output current, and the control modes comprise pulse frequency modulation (PFM) and phase shift pulse width modulation (PS-PWM). According to the device and the method, through the cooperative operation of the LCL resonance network and the hybrid control unit, the problems of large switching loss, low constant current precision and difficulty in EMI suppression in high-frequency application are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a DC / AC power conversion device and a power conversion method thereof. Background Art

[0002] Existing DC / AC power conversion devices have the following technical defects in high-frequency applications:

[0003] Large switching losses: Traditional hard-switching converters face a significant increase in switching losses when the switching frequency increases. In contrast, converters based on resonant topology effectively suppress the increase in switching losses by adopting zero voltage switching (ZVS) technology. Among them, the LCL type converter is a resonant converter that can achieve constant current performance and can effectively reduce switching losses.

[0004] Insufficient constant current control accuracy: LCL inverters are sensitive to resonant parameters, especially changes in resistive and inductive loads, which have a significant impact on the gain curve and may even exceed the adjustment range of the switching frequency, resulting in a loss of precise control over the output current.

[0005] High EMI suppression cost: The broadband EMI noise generated by high-frequency switching requires the use of bulky LC filters. However, traditional filters are prone to coupling with the system resonant network, increasing the risk of oscillation. Summary of the Invention

[0006] In order to solve the technical problems existing in the background technology, the present invention proposes a DCAC power conversion device and a power conversion method thereof.

[0007] The present invention provides a DC-AC power conversion device, comprising:

[0008] A full-bridge inverter for converting the input DC voltage into a high-frequency AC voltage;

[0009] The LCL resonant network is connected to the output of the full-bridge inverter and is used to be equivalent to a current source within the target frequency range to achieve zero voltage switching (ZVS) and harmonic suppression;

[0010] High-frequency isolation transformer, with the primary side connected to the LCL resonant network and the secondary side connected to the load, to achieve electrical isolation between input and output;

[0011] The load phase angle detection module detects the current and voltage signals of the load in real time and calculates the load phase angle

[0012] Hybrid control unit, according to the load phase angle With preset threshold The numerical relationship dynamically switches the control mode to achieve output current control. The control modes include pulse frequency modulation PFM and phase-shift pulse width modulation PS-PWM;

[0013] The closed-loop control unit includes an output voltage / current detection module, a PID compensation module and a drive module, and is used to adjust the control signal to achieve output current tracking.

[0014] Preferably, in the hybrid control unit, the load phase angle With preset threshold The numerical relationship between the control mode and the output current is dynamically switched to achieve the control of the output current, specifically:

[0015] when Using pulse frequency modulation PFM, the switching frequency range is dynamically adjusted to 360kHz-430kHz;

[0016] when Switch to phase-shift pulse width modulation (PS-PWM), fix the switching frequency to 400kHz, and adjust the output current by adjusting the phase difference between the two bridge arms of the full-bridge inverter.

[0017] Preferably, the adjustment range of the phase difference is 0° to 90°.

[0018] Preferably, the preset threshold is 30°.

[0019] Preferably, the load phase angle detection module includes:

[0020] The current sensor and voltage sensor collect the load current signal and voltage signal respectively;

[0021] Signal conditioning circuit, filtering and amplifying the collected load current signal and voltage signal;

[0022] The digital signal processor DSP and four-quadrant multiplier process and transform the load current and voltage signals and calculate the load phase angle

[0023] Preferably, the signal transmission process of the closed-loop control unit includes:

[0024] The output voltage / current detection module collects the output current and voltage in real time and converts them into feedback signals;

[0025] The feedback signal is compared with the preset target value and then input into the PID compensation module to generate an error compensation signal;

[0026] The error compensation signal is transmitted to the hybrid control unit to adjust the control parameters of the control mode PFM or PS-PWM;

[0027] The drive module generates a pulse signal according to the adjusted control parameters to drive the switch tube of the full-bridge inverter.

[0028] Preferably, the driving module includes:

[0029] Isolated gate drivers that convert logic signals generated by the hybrid control unit into high-voltage drive pulses;

[0030] Dead time control circuit to prevent direct conduction of upper and lower bridge arms of full-bridge inverter;

[0031] The overcurrent and overvoltage protection circuit cuts off the driving signal when the output voltage, current or input voltage exceeds the threshold.

[0032] The present invention proposes a DCAC power conversion device, which is applied to any of the above-mentioned DCAC power conversion devices, and the method includes:

[0033] S1. Obtain the load current and voltage signals in real time through the load phase angle detection module and calculate the load phase angle

[0034] S2, hybrid control unit compares load phase angle With preset threshold when Using pulse frequency modulation PFM, the switching frequency range is dynamically adjusted to 360kHz-430kHz;

[0035] when Switch to phase-shift pulse width modulation (PS-PWM) with a fixed switching frequency of 400kHz, and adjust the output current by adjusting the phase difference between the two bridge arms of the full-bridge inverter;

[0036] S3, the closed-loop control unit collects the output current, generates an error signal through compensation by the PID compensation module, and feeds the error signal back to the hybrid control unit to adjust the control parameters;

[0037] S4. The driving module generates a driving pulse according to the adjusted control parameters and controls the operation of the full-bridge inverter switch tube to achieve high-frequency soft switching and constant current output.

[0038] The proposed DC-AC power conversion device and method, through the coordinated operation of a full-bridge inverter, an LCL resonant network, and a hybrid control unit, address the issues of high switching losses, low constant current accuracy, and difficulty in EMI suppression in high-frequency applications. Zero-voltage switching is achieved across the full load range, making it suitable for applications such as remote plasma sources in semiconductor manufacturing, new energy sources, and high-frequency power supplies. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A schematic diagram of the device architecture of a DCAC power conversion device proposed in the present invention;

[0040] Figure 2 This is a schematic diagram of the implementation structure of a DCAC power conversion device proposed by the present invention;

[0041] Figure 3 This is a schematic diagram of the circuit structure of a DCAC power conversion device proposed in the present invention;

[0042] Figure 4 This is a schematic diagram of the output voltage and current waveform structure of the first embodiment of a DCAC power conversion device proposed by the present invention;

[0043] Figure 5 This is a schematic diagram of the output voltage and current waveform structure of a second implementation of a DCAC power conversion device proposed by the present invention;

[0044] Figure 6 This is a comparison diagram of the resonant cavity input waveform and output voltage and current waveforms before and after implementing the hybrid control strategy of a DCAC power conversion device proposed by the present invention. DETAILED DESCRIPTION

[0045] Reference Figure 1-6 The present invention proposes a DC-AC power conversion device, comprising:

[0046] A full-bridge inverter is used to convert the input DC voltage into a high-frequency AC voltage.

[0047] The LCL resonant network is connected to the output end of the full-bridge inverter and is used to be equivalent to a current source within the target frequency range to achieve zero voltage switching (ZVS) and harmonic suppression.

[0048] A high-frequency isolation transformer has its primary side connected to an LCL resonant network and its secondary side connected to a load, achieving electrical isolation between input and output.

[0049] In this embodiment, if Figure 3 As shown in FIG, the full-bridge inverter, LCL resonant network, and high-frequency isolation transformer constitute the LCL main topology.

[0050] The load phase angle detection module detects the current and voltage signals of the load in real time and calculates the load phase angle

[0051] In this embodiment, the load phase angle detection module includes:

[0052] The current sensor and voltage sensor collect the load current signal and voltage signal respectively;

[0053] Signal conditioning circuit, filtering and amplifying the collected load current signal and voltage signal;

[0054] The digital signal processor DSP and four-quadrant multiplier process and transform the load current and voltage signals and calculate the load phase angle

[0055] Hybrid control unit, according to the load phase angle With preset threshold The control mode is dynamically switched based on the numerical relationship to achieve control of the output current. The control modes include pulse frequency modulation (PFM) and phase-shift pulse width modulation (PS-PWM).

[0056] In this embodiment, if Figure 2 As shown, in the hybrid control unit, according to the load phase angle With preset threshold The numerical relationship between the control mode and the output current is dynamically switched to achieve the control of the output current, specifically:

[0057] when Using pulse frequency modulation PFM, the switching frequency range is dynamically adjusted to 360kHz-430kHz;

[0058] when Switch to phase-shift pulse width modulation (PS-PWM), fix the switching frequency to 400kHz, and adjust the output current by adjusting the phase difference between the two bridge arms of the full-bridge inverter.

[0059] Specifically, the adjustment range of the phase difference is 0° to 90°, and the preset threshold is 30°.

[0060] In this embodiment, the output current is controlled by adjusting the phase difference between the two bridge arms, thereby solving the problem that it is difficult to accurately track the output current by PFM frequency modulation when the load phase angle is large.

[0061] The closed-loop control unit includes an output voltage / current detection module, a PID compensation module and a drive module, and is used to adjust the control signal to achieve output current tracking.

[0062] In this embodiment, the signal transmission process of the closed-loop control unit includes: the output voltage / current detection module collects the output current and voltage in real time and converts them into a feedback signal; the feedback signal is compared with the preset target value and then input into the PID compensation module to generate an error compensation signal; the error compensation signal is transmitted to the hybrid control unit to adjust the control parameters of the control mode PFM or PS-PWM; the drive module generates a pulse signal according to the adjusted control parameters to drive the switch tube of the full-bridge inverter.

[0063] In this embodiment, the drive module includes: an isolated gate driver for converting the logic signal generated by the hybrid control unit into a high-voltage drive pulse; a dead time control circuit for preventing the upper and lower bridge arms of the full-bridge inverter from being directly connected; and an overcurrent and overvoltage protection circuit for cutting off the drive signal when the output voltage, current or input voltage exceeds a threshold.

[0064] In this embodiment, in order to verify the effectiveness of the LCL resonant network and the PFM+PS-PWM hybrid control strategy of the present invention, two sets of parameters are simulated as shown in the following table:

[0065]

[0066] Two load conditions were simulated and analyzed respectively. Figure 4 and Figure 5 As shown in the figure, the simulation results show that regardless of whether the load phase angle is large or small, the output current can be accurately controlled to an effective value of 30A within the switching frequency range of 360kHz-430kHz, and the output waveform is close to a sine wave with extremely low harmonic content.

[0067] like Figure 6 As shown in the figure, the resonant cavity input waveform VT of the traditional PFM control and the PFM+PS-PWM hybrid control strategy mentioned in the present invention is compared when the load phase angle is large. It can be seen that when the load phase angle is large, the converter operates in the PS-PWM mode. By adjusting the phase difference between the two bridge arms of the inverter, a wide range of output current adjustment is achieved, and the output current is accurately controlled, which solves the problem that it is difficult to achieve accurate output current tracking by single PFM frequency modulation when the load phase angle is large.

[0068] Specifically, this device addresses the issues of soft switching, constant current output, low harmonics, and high reliability at high frequencies (e.g., 400kHz). The LCL resonant network exhibits inductive or capacitive impedance at specific frequencies. Taking into account the influence of MOS tube parasitic capacitance, a reasonable dead time is set to achieve zero voltage switching (ZVS), significantly reducing switching losses. The LCL resonant network acts as a current source near the resonance point. Combined with a PFM+PS-PWM hybrid control strategy, it achieves high-precision constant current output. A high-frequency isolation transformer provides electrical isolation between the input and output.

[0069] Reference Figure 1-6 The present invention proposes a DCAC power conversion method, which is applied to any of the above-mentioned DCAC power conversion devices, and the method comprises:

[0070] S1. Obtain the load current and voltage signals in real time through the load phase angle detection module and calculate the load phase angle

[0071] S2, hybrid control unit compares load phase angle With preset threshold when Using pulse frequency modulation PFM, the switching frequency range is dynamically adjusted to 360kHz-430kHz;

[0072] when Switch to phase-shift pulse width modulation (PS-PWM) with a fixed switching frequency of 400kHz, and adjust the output current by adjusting the phase difference between the two bridge arms of the full-bridge inverter;

[0073] S3, the closed-loop control unit collects the output current, generates an error signal through compensation by the PID compensation module, and feeds the error signal back to the hybrid control unit to adjust the control parameters;

[0074] S4. The driving module generates a driving pulse according to the adjusted control parameters and controls the operation of the full-bridge inverter switch tube to achieve high-frequency soft switching and constant current output.

[0075] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A DCAC power conversion device, characterized in that: include: A full-bridge inverter for converting the input DC voltage into a high-frequency AC voltage; The LCL resonant network is connected to the output of the full-bridge inverter and is used to be equivalent to a current source within the target frequency range to achieve zero voltage switching (ZVS) and harmonic suppression; High-frequency isolation transformer, with the primary side connected to the LCL resonant network and the secondary side connected to the load, to achieve electrical isolation between input and output; The load phase angle detection module detects the current and voltage signals of the load in real time and calculates the load phase angle Hybrid control unit, according to the load phase angle With preset threshold The numerical relationship dynamically switches the control mode to achieve output current control. The control modes include pulse frequency modulation PFM and phase-shift pulse width modulation PS-PWM; The closed-loop control unit includes an output voltage / current detection module, a PID compensation module and a drive module, and is used to adjust the control signal to achieve output current tracking.

2. The DCAC power conversion device according to claim 1, characterized in that: In the hybrid control unit, the load phase angle With preset threshold The numerical relationship between the control mode and the output current is dynamically switched to achieve the control of the output current, specifically: when When using PFM, the switching frequency range is dynamically adjusted to 360kHz-430kHz. when When , it switches to phase-shift pulse width modulation PS-PWM, fixes the switching frequency to 400kHz, and adjusts the output current by adjusting the phase difference between the two bridge arms of the full-bridge inverter.

3. The DCAC power conversion device according to claim 2, characterized in that: The adjustment range of the phase difference is 0° to 90°.

4. The DCAC power conversion device according to claim 2, characterized in that: The preset threshold is 30°.

5. The DCAC power conversion device according to claim 1, characterized in that: The load phase angle detection module includes: The current sensor and voltage sensor collect the load current signal and voltage signal respectively; Signal conditioning circuit, filtering and amplifying the collected load current signal and voltage signal; The digital signal processor DSP and four-quadrant multiplier process and transform the load current and voltage signals and calculate the load phase angle 6. The DCAC power conversion device according to claim 1, characterized in that: The signal transmission process of the closed-loop control unit includes: The output voltage / current detection module collects the output current and voltage in real time and converts them into feedback signals; The feedback signal is compared with the preset target value and then input into the PID compensation module to generate an error compensation signal; The error compensation signal is transmitted to the hybrid control unit to adjust the control parameters of the control mode PFM or PS-PWM; The drive module generates a pulse signal according to the adjusted control parameters to drive the switch tube of the full-bridge inverter.

7. The DCAC power conversion device according to claim 1, characterized in that: The driving module includes: Isolated gate drivers that convert logic signals generated by the hybrid control unit into high-voltage drive pulses; Dead time control circuit to prevent direct conduction of upper and lower bridge arms of full-bridge inverter; The overcurrent and overvoltage protection circuit cuts off the driving signal when the output voltage, current or input voltage exceeds the threshold.

8. A DCAC power conversion method, characterized in that: Applicable to any one of claims 1-7 The DCAC power conversion device, the method comprising: S1. Obtain the load current and voltage signals in real time through the load phase angle detection module and calculate the load phase angle S2, hybrid control unit compares load phase angle With preset threshold when When using PFM, the switching frequency range is dynamically adjusted to 360kHz-430kHz. when When , it switches to phase-shift pulse width modulation PS-PWM, with a fixed switching frequency of 400kHz, and adjusts the output current by adjusting the phase difference between the two bridge arms of the full-bridge inverter; S3, the closed-loop control unit collects the output current, generates an error signal through compensation by the PID compensation module, and feeds the error signal back to the hybrid control unit to adjust the control parameters; S4. The driving module generates a driving pulse according to the adjusted control parameters and controls the operation of the full-bridge inverter switch tube to achieve high-frequency soft switching and constant current output.

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