Constant common-mode voltage type three-level Boost converter and hybrid modulation method thereof

Abstract

The invention discloses a constant common-mode voltage type three-level Boost converter and a hybrid modulation method thereof, a third switch tube, a fourth switch tube, a third diode and a fourth diode are added on the basis of a traditional converter, the drain electrode of the third switch tube is connected with the negative end of the first diode, the source electrode of the third switch tube is connected with the positive end of the third diode, and the drain electrode of the fourth switch tube is connected with the negative end of the fourth diode. The negative end of the third diode is connected with the positive end of a third capacitor, the negative end of the third capacitor is connected with the positive end of a fourth diode, the negative end of the fourth diode is connected with the drain electrode of a fourth switch tube, and the source electrode of the fourth switch tube is connected with the positive end of the second switch tube; according to the duty ratio of the constant common-mode voltage type three-level Boost converter, on the premise that interleaving modulation is adopted, the switching frequency in a low-frequency working area is switched into low frequency, and the high-frequency switching frequency is still kept to work in other working areas. By cutting off a common-mode loop and adding a clamping structure, the constant common-mode voltage of the circuit can be maintained, and the leakage current is effectively reduced.

Description

Technical Field

[0001] The present invention belongs to the field of power electronics, and in particular relates to a constant common-mode voltage three-level Boost converter and a hybrid modulation method thereof. Background Art

[0002] With the increase in photovoltaic installed capacity, photovoltaic-connected low-voltage direct current (PV-LVDC) systems often require multiple DC converter outputs to be connected in series to provide a higher DC bus voltage. In this case, the three-level boost converter has attracted much attention due to its simple topology, high efficiency, voltage balancing, low voltage stress on power switches and diodes, and low switching losses.

[0003] Traditional three-level boost converters (Three-Level DC Converters and Their Soft-Switching Technology, 2006) are non-isolated structures. Due to the lack of a transformer, there is no electrical isolation between the photovoltaic panel and the DC bus. The photovoltaic panel has parasitic capacitance to ground. The switching action of the power devices in the non-isolated TTL-Boost converter may generate a high-frequency, time-varying voltage acting on this parasitic capacitance, thereby generating a leakage current i in the common mode (CM) loop composed of the panel parasitic capacitance, the boost converter, the DC bus, and the ground. cm The generation of high-frequency leakage current (also called common-mode current or ground current) will cause conducted and radiated interference, increased current distortion and loss, and even endanger the safety of personnel and equipment. Therefore, measures must be taken to limit the leakage current. Summary of the Invention

[0004] The purpose of the present invention is to provide a constant common-mode voltage three-level Boost converter and its hybrid modulation method. By cutting off the common-mode loop and adding a clamping structure, the circuit common-mode voltage can be maintained constant and leakage current can be effectively reduced.

[0005] In order to achieve the above object, the solution of the present invention is:

[0006] A constant common-mode voltage three-level Boost converter includes a first switching tube, a second switching tube, a first capacitor, a second capacitor, a third capacitor, a first diode, a second diode, a first inductor, and a second inductor. One end of the first inductor is connected to the positive electrode of a power supply, the other end of the first inductor is connected to the drain of the first switching tube, the source of the first switching tube is connected to the drain of the second switching tube, the source of the second switching tube is connected to one end of the second inductor, and the other end of the second inductor is connected to the negative electrode of the power supply. The drain of the first switching tube is also connected to the positive end of the first diode, the negative end of the first diode is connected to the positive end of the first capacitor, the negative end of the first capacitor is connected to the positive end of the second capacitor, the negative end of the second capacitor is connected to the positive end of the second diode, and the negative end of the second diode is connected to the source of the second switching tube. The connecting point between the first and second switching tubes is short-circuited with the connecting point between the first and second capacitors.

[0007] It also includes a third switching tube, a fourth switching tube, a third diode and a fourth diode, wherein the drain of the third switching tube is connected to the negative end of the first diode, the source of the third switching tube is connected to the positive end of the third diode, the negative end of the third diode is connected to the positive end of the third capacitor, the negative end of the third capacitor is connected to the positive end of the fourth diode, the negative end of the fourth diode is connected to the drain of the fourth switching tube, and the source of the fourth switching tube is connected to the positive end of the second switching tube.

[0008] The first to fourth switching tubes are all connected in parallel with reverse-connected diodes.

[0009] A negative terminal of the third capacitor is grounded.

[0010] As described above, the hybrid modulation method of the constant common mode voltage type three-level Boost converter obtains the duty cycle D of the constant common mode voltage type three-level Boost converter; if the duty cycle D is (0, D th1 ) range, high frequency interleaved modulation strategy is adopted; if the duty cycle D is within [D th1 ,D th2 ] range, a low-frequency interleaved modulation strategy is adopted; if the duty cycle D is within (D th2 ,1) High-frequency interleaved modulation strategy is adopted within the range.

[0011] When a high-frequency interleaved modulation strategy is adopted, the first and second switching tubes are controlled to operate at high frequency, and the operating states of the third and fourth switching tubes are obtained by performing an exclusive OR logic operation on the first and second switching tubes.

[0012] When the low-frequency interleaved modulation strategy is adopted, the first switch tube and the second switch tube are controlled to operate at a low frequency, and the third switch tube and the fourth switch tube are controlled to be normally on.

[0013] After adopting the above scheme, compared with the prior art, the present invention has the following advantages:

[0014] The present invention can maintain the circuit common-mode voltage constant by cutting off the common-mode loop and adding a switch tube structure without affecting the differential-mode characteristics, thereby improving the common-mode characteristics and effectively reducing leakage current, which is beneficial to reducing the conducted and radiated interference, current harmonics, and losses caused by high-frequency leakage current, thereby protecting personnel and equipment safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 1 is a structural diagram of a constant common-mode voltage three-level Boost converter according to the present invention;

[0016] Figure 2 It is the operating mode diagram of the constant common mode voltage three-level Boost converter;

[0017] Among them, (a) is dual-inductor energy storage, (b) is lower capacitor charging, (c) is upper capacitor charging, and (d) is dual capacitor discharge;

[0018] Figure 3 This is the operating timing diagram of the constant common-mode voltage three-level Boost converter;

[0019] Among them, (a) is interleaved modulation D < 0.5, (b) is interleaved modulation D > 0.5;

[0020] Figure 4 This is the operating waveform of the constant common-mode voltage three-level Boost converter when D=0.5;

[0021] Figure 5 It is a schematic diagram of hybrid modulation strategy;

[0022] Figure 6 This is the low-frequency operating modal diagram of the constant common-mode voltage three-level Boost converter;

[0023] Among them, (a) is dual-inductor energy storage, (b) is lower capacitor charging, (c) is upper capacitor charging, and (d) is dual capacitor discharge;

[0024] Figure 7 is the effective value of the current of switches S3 and S4 when the constant common mode voltage three-level boost converter adopts high frequency interleaved modulation strategy;

[0025] Figure 8 It is the time difference mode characteristic of different topologies using different modulation strategies when D=0.3;

[0026] Among them, (a) is the differential mode voltage of the TTL-Boost converter using synchronous modulation strategy, (b) is the inductor current of the TTL-Boost converter using synchronous modulation strategy, (c) is the differential mode voltage of the TTL-Boost converter using interleaved modulation strategy, (d) is the inductor current of the TTL-Boost converter using interleaved modulation strategy, (e) is the differential mode voltage of the ITL-Boost converter using hybrid modulation strategy, and (f) is the inductor current of the ITL-Boost converter using hybrid modulation strategy;

[0027] Figure 9 It is the common mode characteristic when different topologies adopt different modulation strategies when D=0.3;

[0028] Among them, (a) is the common-mode voltage of the TTL-Boost converter using the synchronous modulation strategy, (b) is the leakage current of the TTL-Boost converter using the synchronous modulation strategy, (c) is the common-mode voltage of the TTL-Boost converter using the interleaved modulation strategy, (d) is the leakage current of the TTL-Boost converter using the interleaved modulation strategy, (e) is the common-mode voltage of the ITL-Boost converter using the hybrid modulation strategy, and (f) is the leakage current of the ITL-Boost converter using the hybrid modulation strategy.

[0029] Figure 10 It is the time difference mode characteristic of different topologies using different modulation strategies when D = 0.7;

[0030] Among them, (a) is the differential mode voltage of the TTL-Boost converter using synchronous modulation strategy, (b) is the inductor current of the TTL-Boost converter using synchronous modulation strategy, (c) is the differential mode voltage of the TTL-Boost converter using interleaved modulation strategy, (d) is the inductor current of the TTL-Boost converter using interleaved modulation strategy, (e) is the differential mode voltage of the ITL-Boost converter using hybrid modulation strategy, and (f) is the inductor current of the ITL-Boost converter using hybrid modulation strategy;

[0031] Figure 11 It is the common mode characteristic when different topologies adopt different modulation strategies when D=0.7;

[0032] Among them, (a) is the common-mode voltage of the TTL-Boost converter using the synchronous modulation strategy, (b) is the leakage current of the TTL-Boost converter using the synchronous modulation strategy, (c) is the common-mode voltage of the TTL-Boost converter using the interleaved modulation strategy, (d) is the leakage current of the TTL-Boost converter using the interleaved modulation strategy, (e) is the common-mode voltage of the ITL-Boost converter using the hybrid modulation strategy, and (f) is the leakage current of the ITL-Boost converter using the hybrid modulation strategy.

[0033] Figure 12 It is the time difference mode characteristic of different topologies using different modulation strategies when D = 0.5;

[0034] Among them, (a) is the common-mode voltage of the TTL-Boost converter using the synchronous modulation strategy, (b) is the leakage current of the TTL-Boost converter using the synchronous modulation strategy, (c) is the common-mode voltage of the TTL-Boost converter using the interleaved modulation strategy, (d) is the leakage current of the TTL-Boost converter using the interleaved modulation strategy, (e) is the common-mode voltage of the ITL-Boost converter using the hybrid modulation strategy, and (f) is the leakage current of the ITL-Boost converter using the hybrid modulation strategy.

[0035] Figure 13 It is the common mode characteristic when different topologies adopt different modulation strategies when D=0.5;

[0036] Among them, (a) is the common-mode voltage of the TTL-Boost converter using the synchronous modulation strategy, (b) is the leakage current of the TTL-Boost converter using the synchronous modulation strategy, (c) is the common-mode voltage of the TTL-Boost converter using the interleaved modulation strategy, (d) is the leakage current of the TTL-Boost converter using the interleaved modulation strategy, (e) is the common-mode voltage of the ITL-Boost converter using the hybrid modulation strategy, and (f) is the leakage current of the ITL-Boost converter using the hybrid modulation strategy. DETAILED DESCRIPTION

[0037] The technical solutions and beneficial effects of the present invention will be described in detail below with reference to the accompanying drawings.

[0038] like Figure 1 As shown, the present invention proposes a three-level Boost converter that can achieve a constant common-mode voltage and effectively reduce leakage current. On the basis of the traditional three-level Boost converter, switches S3, S4 and diodes D3, D4 are added. The circuit structure is as follows: one end of the inductor L1 is directly connected to the power supply U pvThe positive pole of L1, the other end of L1 is connected to the drain of S1, the source of S1 is connected to the drain of S2, the source of S2 is connected to one end of L2, and the other end of L2 is connected to the power supply U pv The negative terminal of S1 is connected to the positive terminal of diode D1, and the negative terminal of D1 is connected to C f1 The positive end, C f1 The negative terminal is connected to C f2 The positive end, C f2 The negative end of D2 is connected to the positive end of D2, the negative end of D2 is connected to the source of S2, and the connection point of S1 and S2 is connected to C f1 、C f2 The drain of the switch tube S3 is connected to the negative terminal of D1, the source of S3 is connected to the positive terminal of the diode D3, and the negative terminal of the diode D3 is connected to C dc Positive end, C dc The negative end is connected to the positive end of diode D4, the negative end of diode D4 is connected to the drain of S4, and the source of S4 is connected to the positive end of D2.

[0039] Figure 2 、 Figure 3 The figure shows the working mode diagram and working timing diagram of the constant common mode voltage three-level Boost converter. Figure 2 In the dual-inductor energy storage mode shown in (a), S1 and S2 are turned on, S3 and S4 are turned on, and the common-mode voltage is U dc / 2; when the circuit works Figure 2 (b) In the capacitor charging mode, S1 is turned on, S2 is turned off, S3 and S4 are turned off, and the common mode loop is cut off. The sum of the voltages on D4 and S4 is U pv / 4, then the common mode voltage is U pv / 2; when the circuit works Figure 2 (c) In the upper capacitor charging mode, S1 is turned off, S2 is turned on, S3 and S4 are turned off, cutting off the common mode loop. The sum of the voltages on D4 and S4 is -U pv / 4, then the common mode voltage is U pv / 2; when the circuit works Figure 2 (d) In the dual-capacitor charging mode, S1 and S2 are turned off, S3 and S4 are turned on, and the common-mode voltage is U pv By cutting off the common-mode loop and adding a switch tube structure, this circuit can maintain a constant common-mode voltage throughout the switching cycle, effectively reducing leakage current.

[0040] Depend on Figure 2 It can be found that when D = 0.5, the constant common mode voltage three-level boost converter switches between the lower capacitor charging mode and the upper capacitor charging mode as shown in Figures (b) and (c), and the switches S3 and S4 are completely turned off during the entire working cycle. At this time, the input side photovoltaic power supply U pv Unable to be capacitor Cdc Charging, capacitor C dc During continuous discharging, the voltage of the capacitor continuously drops, resulting in the inability to maintain the output voltage. At this time, the working condition is as shown in Figure 4 .

[0041] To solve this problem, the present invention proposes a hybrid modulation method. As shown in Figure 5 , the working range of the circuit is divided into three intervals. When 0 < D < D th1 , it is interval I. When D th1 ≤ D ≤ D th2 , it is interval II. When D th2 < D < 1, it is interval III. In interval I and interval III, a high-frequency interleaved modulation strategy is adopted. The switching tubes S1 and S2 work at high frequency. At the same time, the working states of the switching tubes S3 and S4 are obtained by performing an exclusive-NOR logic operation on the switching tubes S1 and S2. That is, when the switching tubes S1 and S2 are both conducting or the switching tubes S1 and S2 are both turned off, the switching tubes S3 and S4 conduct; when the switching tube S1 conducts and the switching tube S2 is turned off or the switching tube S1 is turned off and the switching tube S2 conducts, the switching tubes S3 and S4 are turned off. In interval II, a low-frequency interleaved modulation strategy is adopted. The switching tubes S1 and S2 work at low frequency. At the same time, the switching tubes S3 and S4 are always on to ensure the normal operation of the circuit, which can be coordinated with Figure 6 . Among them, the high frequency and low frequency at which the switching tubes work differ by at least 20 times. In this embodiment, the high frequency is set to 20 kHz and the low frequency is set to 1 kHz.

[0042] The range of interval II is determined depending on the effective current part of the switching tubes S3 and S4. Figure 7 As shown, when the low-leakage current type three-level Boost converter adopts a high-frequency interleaved modulation strategy and the working states of the switching tubes S3 and S4 are obtained by performing an exclusive-NOR logic operation on the switching tubes S1 and S2, the effective currents of the switching tubes S3 and S4 are shown. If the converter D → 0.5, the effective current will increase sharply, posing higher requirements on the performance of the switching tubes. When D = 0.5, since S3 and S4 are completely turned off throughout the switching cycle, their effective current drops to 0. When the strategy of always turning on the switching tubes S3 and S4 is adopted, the effective currents of S3 and S4 are relatively small near D = 0.5. Considering the requirements for the effective currents of the switching tubes S3 and S4, the working range near D = 0.5 when the effective currents borne by the switching tubes S3 and S4 increase sharply can be selected as the low-frequency working interval. Coordinated with Figure 7 , the selected low-frequency working area is [0.47, 0.53].[[]END]

[0043] Embodiment 1: Input voltage U pv = 67.2 V, output voltage U o = ±48 V, duty cycle D = 0.3 < 0.5, switching frequency f s = 20 kHz, interval I

[0044] The traditional three-level boost (TTL-Boost) converter adopts interleaved modulation strategy and synchronous modulation strategy, and the constant common mode voltage three-level boost converter (ITL-Boost) adopts hybrid modulation strategy. The simulation is carried out based on Matlab / Simulink. DM , inductor current i Lf The differential mode characteristics of the two three-level Boost converter structures in three cases are analyzed from two aspects. CM , leakage current i cm The common-mode characteristics of two three-level Boost converter structures under three conditions are analyzed from two aspects.

[0045] Figure 8 、 Figure 9 The TTL-Boost converter uses interleaved modulation strategy, synchronous modulation strategy, and the ITL-Boost converter uses a hybrid modulation strategy to measure the time difference mode and common mode characteristics. The waveforms are analyzed by FFT, and the results are summarized in Table 1.

[0046] Table 1 FFT analysis results of time difference mode characteristics and common mode characteristics of different topologies using different modulation strategies when D=0.3

[0047]

[0048]

[0049] From the above simulation results, it can be found that when the TTL-Boost converter adopts the synchronous modulation strategy, the differential mode voltage frequency and the switching frequency f s The same, the differential mode voltage amplitude is the largest at the switching frequency, the inductor current ripple is also the largest, and the common mode voltage amplitude is 0 at the switching frequency, which can maintain a constant common mode voltage and the leakage current is 0 at the switching frequency; when the TTL-Boost converter adopts the interleaved modulation strategy, the differential mode voltage frequency is 2f s The amplitude at the switching frequency is smaller than when synchronous modulation is used, and the inductor current ripple is also smaller. However, the common-mode voltage amplitude at the switching frequency is larger, and a constant common-mode voltage cannot be maintained, reaching 0.395A at the switching frequency. When using synchronous modulation, the TTL-Boost converter has poor differential-mode characteristics but good common-mode characteristics. When using interleaved modulation, the differential-mode characteristics are good, but the common-mode characteristics are poor.

[0050] When the ITL-Boost converter proposed in the present invention adopts a hybrid modulation strategy, the differential mode voltage frequency is 2f sThe common-mode voltage amplitude and inductor current ripple at the switching frequency are not much different from those when the TTL-Boost converter adopts the interleaved modulation strategy, which does not affect its good differential mode characteristics; while the common-mode voltage amplitude and leakage current amplitude at the switching frequency are very small, which are reduced by 99.75% and 99.75% respectively compared with the case when the TTL-Boost converter adopts the interleaved modulation strategy, greatly improving its common-mode characteristics.

[0051] Example 2: Input voltage U pv =28.8V, output voltage U o = ±48V, duty cycle D = 0.7> 0.5, switching frequency f s =20kHz, interval III

[0052] The three cases of TTL-Boost converter adopting interleaved modulation strategy, synchronous modulation strategy and ITL-Boost converter adopting hybrid modulation strategy are simulated based on Matlab / Simulink. DM , inductor current i Lf The differential mode characteristics of the two three-level Boost converter structures in three cases are analyzed from two aspects. CM , leakage current i cm The common-mode characteristics of two three-level Boost converter structures under three conditions are analyzed from two aspects.

[0053] Figure 10 、 Figure 11 The TTL-Boost converter uses interleaved modulation strategy, synchronous modulation strategy, and the ITL-Boost converter uses a hybrid modulation strategy to measure the time difference mode and common mode characteristics. The waveforms are analyzed by FFT, and the results are summarized in Table 2.

[0054] Table 2 FFT analysis results of time-difference mode characteristics and common mode characteristics of different topologies using different modulation strategies when D=0.7

[0055]

[0056]

[0057] From the above simulation results, it can be found that when the TTL-Boost converter adopts the synchronous modulation strategy, the differential mode voltage frequency and the switching frequency f s The maximum differential mode voltage amplitude at the switching frequency is 49.37V, and the inductor current pulsation is also the largest. The common mode voltage amplitude at the switching frequency is 0, which can maintain a constant common mode voltage and the leakage current is 0 at the switching frequency. When the TTL-Boost converter adopts the interleaved modulation strategy, the differential mode voltage frequency is 2f sThe amplitude at the switching frequency is smaller than when synchronous modulation is used, and the inductor current ripple is also smaller. However, the common-mode voltage amplitude at the switching frequency is larger, and a constant common-mode voltage cannot be maintained, reaching 0.395A at the switching frequency. This is consistent with the analysis previously mentioned that TTL-Boost converters have poor differential-mode characteristics and good common-mode characteristics when using synchronous modulation, while having good differential-mode characteristics and poor common-mode characteristics when using interleaved modulation.

[0058] When the ITL-Boost converter proposed in the present invention adopts the interleaved modulation strategy, the differential mode voltage frequency is 2f s The common-mode voltage amplitude and inductor current ripple at the switching frequency are not much different from those when the TTL-Boost converter adopts the interleaved modulation strategy, inheriting its good differential mode characteristics; while the common-mode voltage amplitude and leakage current amplitude at the switching frequency are very small, respectively reduced by 99.54% and 99.52% compared with the TTL-Boost converter adopting the interleaved modulation strategy, greatly improving its common-mode characteristics.

[0059] Example 3: Input voltage U pv =48V, output voltage U o = ±48V, duty cycle D = 0.5, high-frequency switching frequency f s1 =20kHz, low switching frequency f s2 =1kHz, interval II

[0060] The TTL-Boost converter adopts high-frequency interleaved modulation strategy, high-frequency synchronous modulation strategy and ITL-Boost converter adopts hybrid modulation strategy. The simulation is based on Matlab / Simulink. DM , inductor current i Lf The differential mode characteristics of the two three-level Boost converter structures in three cases are analyzed from two aspects. CM , leakage current i cm The common-mode characteristics of two three-level Boost converter structures under three conditions are analyzed from two aspects.

[0061] Figure 12 and Figure 13 The TTL-Boost converter uses interleaved modulation strategy, synchronous modulation strategy, and the ITL-Boost converter uses a hybrid modulation strategy to measure the time difference mode and common mode characteristics. The waveforms are analyzed by FFT, and the results are summarized in Table 3.

[0062] Table 3 FFT analysis results of time difference mode characteristics and common mode characteristics of different topologies using different modulation strategies when D=0.5

[0063]

[0064] When D=0.5, when the TTL-Boost converter adopts synchronous modulation strategy, the differential mode voltage is s The differential mode voltage amplitude is the largest at the switching frequency, which is 61.08V. The inductor current pulsation is large, while the common mode voltage is constant and the leakage current is basically 0. When the interleaved modulation strategy is adopted, the differential mode voltage is constant, the inductor current pulsation is 0, and the common mode voltage is s The two-level voltage has a large common-mode voltage amplitude of 30.54V at the switching frequency, and a large leakage current, which reaches 0.4885 at the switching frequency.

[0065] When the ITL-Boost converter proposed in the present invention adopts a low-frequency interleaved modulation strategy at a duty cycle of D=0.5, the differential mode voltage frequency is 2f s The differential-mode voltage amplitude and inductor current ripple at the switching frequency are not much different from those when the traditional three-level Boost converter adopts the interleaved modulation strategy, inheriting its good differential-mode characteristics; while the common-mode voltage amplitude at the switching frequency is not much different from that when the traditional three-level Boost converter adopts the interleaved modulation strategy, and the leakage current amplitude at the switching frequency is reduced. At this time, the switching frequency is low, and the high-frequency common-mode voltage amplitude is reduced to 0.038V, and the high-frequency leakage current amplitude is also reduced to 0.01357. Compared with the traditional three-level Boost converter adopting the interleaved modulation strategy, the high-frequency common-mode voltage amplitude is reduced by 99.88%, and the high-frequency leakage current is reduced by 97.22%, and the common-mode characteristics are greatly improved.

[0066] The ITL-Boost converter adopts a hybrid modulation strategy. In interval II, switches S1 and S2 are interleaved at low frequency, and switches S3 and S4 are normally on. At this time, the amplitude of the high-frequency common-mode voltage and the amplitude of the high-frequency leakage current are reduced, the common-mode characteristics are greatly improved, and the normal operation of the circuit is guaranteed when D=0.5.

[0067] It will be understood by those skilled in the art that the embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented 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. The solutions in the embodiments of the present invention may be implemented in various computer languages, for example, the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0068] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts 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, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0069] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0070] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0071] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0072] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A constant common-mode voltage three-level boost converter, characterized in that: The device comprises a first switching tube, a second switching tube, a first capacitor, a second capacitor, a third capacitor, a first diode, a second diode, a first inductor, and a second inductor. One end of the first inductor is connected to the positive electrode of the power supply, the other end of the first inductor is connected to the drain of the first switching tube, the source of the first switching tube is connected to the drain of the second switching tube, the source of the second switching tube is connected to one end of the second inductor, and the other end of the second inductor is connected to the negative electrode of the power supply. The drain of the first switching tube is also connected to the positive end of the first diode, the negative end of the first diode is connected to the positive end of the first capacitor, the negative end of the first capacitor is connected to the positive end of the second capacitor, the negative end of the second capacitor is connected to the positive end of the second diode, and the negative end of the second diode is connected to the source of the second switching tube. The connection point between the first and second switching tubes is short-circuited with the connection point between the first and second capacitors. It also includes a third switching tube, a fourth switching tube, a third diode and a fourth diode, wherein the drain of the third switching tube is connected to the negative end of the first diode, the source of the third switching tube is connected to the positive end of the third diode, the negative end of the third diode is connected to the positive end of the third capacitor, the negative end of the third capacitor is connected to the positive end of the fourth diode, the negative end of the fourth diode is connected to the drain of the fourth switching tube, and the source of the fourth switching tube is connected to the positive end of the second switching tube.

2. The constant common mode voltage three-level Boost converter according to claim 1, wherein: The first to fourth switching tubes are all connected in parallel with reverse-connected diodes.

3. The constant common mode voltage three-level Boost converter according to claim 1, wherein: A negative terminal of the third capacitor is grounded.

4. The hybrid modulation method for a constant common mode voltage three-level Boost converter according to claim 1, wherein: Obtain the duty cycle D of the constant common mode voltage three-level Boost converter; if the duty cycle D is (0, D th1 ) range using high-frequency interleaved modulation strategy; If the duty cycle D is [D th1 ,D th2 ] range, a low-frequency interleaved modulation strategy is adopted; If the duty cycle D is (D th2 ,1) High-frequency interleaved modulation strategy is adopted within the range.

5. The method according to claim 4, wherein: When adopting the high-frequency interleaved modulation strategy, the first and second switching tubes are controlled to operate at high frequency, and the operating states of the third and fourth switching tubes are obtained by performing an exclusive OR logic operation on the first and second switching tubes.

6. The method according to claim 4, wherein: When the low-frequency interleaved modulation strategy is adopted, the first switch tube and the second switch tube are controlled to operate at a low frequency, and the third switch tube and the fourth switch tube are controlled to be normally on.

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