Single-stage single-phase matrix type DCAC converter and control method thereof

Abstract

The invention relates to the field of DCAC converters, and discloses a single-stage single-phase matrix type DCAC converter and a control method thereof. The single-stage single-phase matrix DCAC converter comprises a DC power supply, a first primary side branch and a second primary side branch which are connected in parallel; the alternating current power supply, the first secondary side branch and the second secondary side branch are connected in parallel; one end of the primary side of the transformer is connected between the first primary side switch tube and the second primary side switch tube, and the other end of the primary side of the transformer is connected between the third primary side switch tube and the fourth primary side switch tube; one end of the secondary side of the transformer is connected between the second secondary side switch tube and the third secondary side switch tube, and the other end of the secondary side of the transformer is connected between the first secondary side branch capacitor and the second secondary side branch capacitor; one end of the secondary side of the transformer is connected in series with a secondary inductor and a secondary capacitor. In the embodiment of the invention, the conversion efficiency of the converter is improved by optimizing the direct-current side phase shift angle and the direct-current side and alternating-current side phase shift angles.

Description

Technical Field

[0001] The present invention relates to the field of DCAC converters, and in particular to a single-stage single-phase matrix DCAC converter and a control method thereof. Background Art

[0002] A DC-AC converter, also known as an inverter, is a power electronic circuit that converts DC power into AC power. The inverter converts DC power into AC power by turning on and off semiconductor power switching devices (such as IGBT, MOSFET, etc.).

[0003] In order to obtain high-quality AC power, inverters usually use PWM (pulse width modulation) technology to control the on-time of switching devices to generate AC voltage close to a sine wave. Since the switching process will generate harmonics, inverters are usually equipped with filters to smooth the output waveform and reduce the harmonic content. However, existing DCAC converters usually use a two-stage structure to achieve isolation and inversion functions, resulting in low conversion efficiency of DCAC converters. A new technology is needed to solve the current problem. Summary of the invention

[0004] The main purpose of the present invention is to solve the technical problem that the existing DCAC converter adopts a two-stage structure to realize isolation and inversion functions, resulting in low conversion efficiency of the DCAC converter.

[0005] A first aspect of the present invention provides a single-stage single-phase matrix DCAC converter, the single-stage single-phase matrix DCAC converter comprising:

[0006] AC power supply, DC power supply, transformer, first primary switch tube, second primary switch tube, third primary switch tube, fourth primary switch tube, first secondary switch tube, second secondary switch tube, third secondary switch tube, fourth secondary switch tube, first secondary branch capacitor, second secondary branch capacitor, secondary capacitor, secondary inductor;

[0007] The first primary switch tube and the second primary switch tube are connected in series to form a first primary branch, and the third primary switch tube and the fourth primary switch tube are connected in series to form a second primary branch; the DC power supply, the first primary branch, and the second primary branch are connected in parallel;

[0008] The source of the first secondary switch tube is connected to the source of the second secondary switch tube, the drain of the second secondary switch tube is connected to the drain of the third secondary switch tube, the source of the third secondary switch tube is connected to the source of the fourth secondary switch tube, the first secondary switch tube, the second secondary switch tube, the third secondary switch tube, and the fourth secondary switch tube are connected in series to form a first secondary branch; the first secondary branch capacitor and the second secondary branch capacitor are connected in series to form a second secondary branch; the AC power supply, the first secondary branch, and the second secondary branch are connected in parallel;

[0009] One end of the primary side of the transformer is connected between the first primary side switch tube and the second primary side switch tube, and the other end of the primary side of the transformer is connected between the third primary side switch tube and the fourth primary side switch tube;

[0010] One end of the secondary side of the transformer is connected between the second secondary side switch tube and the third secondary side switch tube, and the other end of the secondary side of the transformer is connected between the first secondary side branch capacitor and the second secondary side branch capacitor;

[0011] One end of the secondary side of the transformer is connected in series with the secondary side inductor and the secondary side capacitor.

[0012] Optionally, in a first implementation method of the first aspect of the present invention, the single-stage single-phase matrix DCAC converter also includes: a first AC inductor, one end of the first AC inductor is connected to the AC power supply, and the other end of the first AC inductor is respectively connected to the drain of the first secondary side switch tube and the first secondary side branch capacitor.

[0013] Optionally, in a second implementation of the first aspect of the present invention, the single-stage single-phase matrix DCAC converter also includes: a second AC inductor, one end of the second AC inductor is connected to the AC power supply, and the other end of the second AC inductor is respectively connected to the drain of the fourth secondary side switch tube and the second secondary side branch capacitor.

[0014] Optionally, in a third implementation of the first aspect of the present invention, the source of the first primary switch tube is connected to the drain of the second primary switch tube, and the source of the third primary switch tube is connected to the drain of the fourth primary switch tube.

[0015] Optionally, in a fourth implementation of the first aspect of the present invention, the drain of the first primary switch tube is connected to the drain of the third primary switch tube, and the source of the second primary switch tube is connected to the source of the fourth primary switch tube.

[0016] Optionally, in a fifth implementation of the first aspect of the present invention, the single-stage single-phase matrix DCAC converter further includes: a filter capacitor, and the filter capacitor is connected in parallel with the DC power supply.

[0017] A second aspect of the present invention provides a control method for a single-stage single-phase matrix DCAC converter, the control method for the single-stage single-phase matrix DCAC converter comprising:

[0018] Collecting the primary DC voltage value, secondary AC voltage value, and secondary AC frequency corresponding to the transformer;

[0019] According to the primary DC voltage value, calculating the interval duration between the driving signal of the first primary switch tube and the driving signal of the fourth primary switch tube, and calculating the ratio of the interval duration to a preset switching period, to obtain a first phase shift angle;

[0020] According to the primary DC voltage value, the secondary AC voltage value, and the secondary AC frequency, the axis interval length between the primary voltage symmetry axis of the transformer and the secondary voltage symmetry axis of the transformer is calculated, and the ratio of the axis interval length to a preset switching period is calculated to obtain a second phase shift angle;

[0021] According to a preset modulation algorithm, the first phase shift angle and the second phase shift angle are modulated to generate a first modulation phase shift angle and a second modulation phase shift angle;

[0022] A PWM switch tube drive signal is generated according to the first modulation phase shift angle and the second modulation phase shift angle, wherein the PWM switch tube drive signal is used to drive the switch tube of the single-stage single-phase matrix DCAC converter to switch on and off.

[0023] Optionally, in a first implementation manner of the second aspect of the present invention, performing modulation processing on the first phase shift angle and the second phase shift angle according to a preset modulation algorithm to generate the first modulation phase shift angle and the second modulation phase shift angle includes:

[0024] Collecting the primary side current value of the converter, and calculating the transmission power corresponding to the transformer based on the primary side current value;

[0025] Calculating the quotient of the AC side power and the transmission power to obtain a power transfer ratio;

[0026] determining a mode type of the single-stage single-phase matrix DCAC converter based on a dynamic threshold value corresponding to the power transfer ratio and the first phase shift angle;

[0027] Based on the power transfer ratio and the mode type, performing a first adjustment process on the first phase shift angle to generate a first modulation phase shift angle;

[0028] Based on the first modulation phase shift angle, the power transfer ratio, and the mode type, a second adjustment process is performed on the second phase shift angle to generate a second modulation phase shift angle.

[0029] Optionally, in a second implementation manner of the second aspect of the present invention, performing a first adjustment process on the first phase shift angle based on the power transfer ratio and the mode type to generate a first modulation phase shift angle includes:

[0030] Calculating a value range of a first modulation phase shift angle based on a voltage gain of the transformer, the power transfer ratio, and the mode type;

[0031] According to the value range, the fundamental effective value of the inductor current value is optimized to determine the first modulation phase shift angle.

[0032] Optionally, in a third implementation of the second aspect of the present invention, the mode of the single-stage single-phase matrix DCAC converter includes: a first mode and a second mode, and the second adjustment processing is performed on the second phase shift angle based on the first modulation phase shift angle, the power transfer ratio, and the mode type, and the second modulation phase shift angle is generated. The processing includes:

[0033] When the single-stage single-phase matrix DCAC converter is in the first mode, the second modulation phase shift angle is calculated according to a preset first adjustment formula, wherein the first adjustment formula includes:

[0034]

[0035] Wherein, D'1 is the first adjustment phase shift angle, m is the power transfer ratio, Vac is the secondary AC voltage value, D'2 is the second modulation phase shift angle, and sgn() is the sgn function;

[0036] When the single-stage single-phase matrix DCAC converter is in the second mode, the second modulation phase shift angle is calculated according to a preset second adjustment formula, wherein the second adjustment formula includes:

[0037]

[0038] Wherein, D'1 is the first adjustment phase shift angle, m is the power transfer ratio, Vac is the secondary side AC voltage value, D'2 is the second modulation phase shift angle, and sgn() is the sgn function.

[0039] In an embodiment of the present invention, a new DCAC converter is designed, which enables direct current to achieve isolation function through a single-stage circuit and output a set alternating current in a closed loop. The present invention adopts a DCAC converter with two mode controls that can be smoothly switched. The control variables of each mode include the DC side phase shift angle and the phase shift angle between the DC side and the AC side, which can be obtained through the critical conditions of each mode, and the switching of the mode does not need to be judged according to the load power value. By taking the effective value current of the transformer high-frequency current as the optimization target, the DC side phase shift angle and the DC side and AC side phase shift angle are optimized to improve the conversion efficiency of the converter, solving the technical problem that the existing DCAC converter uses a two-stage structure to achieve isolation and inversion functions, resulting in low conversion efficiency of the DCAC converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A schematic diagram of a structural embodiment of a single-stage single-phase matrix DCAC converter in an embodiment of the present invention;

[0041] Figure 2 1 is a first mode and a second mode waveform diagram of a single-stage single-phase matrix DCAC converter in an embodiment of the present invention;

[0042] Figure 3A Schematic diagram of the switch opening and closing and current flow direction of the first mode t1-t2 of the single-stage single-phase matrix DCAC converter in an embodiment of the present invention;

[0043] Figure 3B Schematic diagram of the switch opening and closing and current flow direction of the first mode t2-t3 of the single-stage single-phase matrix DCAC converter in an embodiment of the present invention;

[0044] Figure 3C Schematic diagram of the switch opening and closing and current flow direction of the first mode t3-t4 of the single-stage single-phase matrix DCAC converter in an embodiment of the present invention;

[0045] Figure 3D Schematic diagram of the switch opening and closing and current flow direction of the single-stage single-phase matrix DCAC converter in the first mode t4-t5 in an embodiment of the present invention;

[0046] Figure 3E Schematic diagram of the switch opening and closing and current flow direction of the first mode t5-t6 of the single-stage single-phase matrix DCAC converter in an embodiment of the present invention;

[0047] Figure 4A Schematic diagram of the switch opening and closing and current flow direction of the second mode t0-t1 of the single-stage single-phase matrix DCAC converter in an embodiment of the present invention;

[0048] Figure 4BSchematic diagram of the switch opening and closing and current flow direction of the second mode t1-t2 of the single-stage single-phase matrix DCAC converter in an embodiment of the present invention;

[0049] Figure 4C Schematic diagram of the switch opening and closing and current flow direction of the second mode t2-t3 of the single-stage single-phase matrix DCAC converter in an embodiment of the present invention;

[0050] Figure 4D Schematic diagram of the switch opening and closing and current flow direction of the second mode t3-t4 of the single-stage single-phase matrix DCAC converter in an embodiment of the present invention;

[0051] Figure 4E Schematic diagram of the switch opening and closing and current flow direction of the second mode t4-t5 of the single-stage single-phase matrix DCAC converter in an embodiment of the present invention;

[0052] Figure 4F Schematic diagram of the switch opening and closing and current flow direction of the second mode t5-t6 of the single-stage single-phase matrix DCAC converter in an embodiment of the present invention;

[0053] Figure 5 A schematic diagram of an embodiment of a control method for a single-stage single-phase matrix DCAC converter in an embodiment of the present invention;

[0054] Figure 6 Schematic diagram of an embodiment of step 504 of a control method for a single-stage single-phase matrix DCAC converter in an embodiment of the present invention;

[0055] Figure 7 Schematic diagram of the technical effect of a single-stage single-phase matrix DCAC converter in an embodiment of the present invention. DETAILED DESCRIPTION

[0056] The embodiment of the present invention provides a single-stage single-phase matrix DCAC converter and a control method thereof.

[0057] The embodiments disclosed in the present invention will be described in more detail below with reference to the accompanying drawings. Although certain embodiments disclosed in the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as being limited to the embodiments described herein, which are instead provided for a more thorough and complete understanding of the present invention. It should be understood that the drawings and embodiments disclosed in the present invention are only for exemplary purposes and are not intended to limit the scope of protection disclosed in the present invention.

[0058] In the description of the embodiments disclosed in the present invention, the term "including" and similar terms should be understood as open inclusion, that is, "including but not limited to". The term "based on" should be understood as "based at least in part on". The term "one embodiment" or "the embodiment" should be understood as "at least one embodiment". The terms "first", "second", etc. may refer to different or the same objects. Other explicit and implicit definitions may also be included below.

[0059] For ease of understanding, the specific process of the embodiment of the present invention is described below. Figure 1 , a schematic diagram of a structural embodiment of a single-stage single-phase matrix DCAC converter in an embodiment of the present invention, wherein the single-stage single-phase matrix DCAC converter comprises:

[0060] AC power supply AC, DC power supply BAT, transformer T1, first primary switch tube S1, second primary switch tube S2, third primary switch tube S3, fourth primary switch tube S4, first secondary switch tube S5, second secondary switch tube S6, third secondary switch tube S7, fourth secondary switch tube S8, first secondary branch capacitor C1, second secondary branch capacitor C2, secondary capacitor Cr, secondary inductor Lr;

[0061] The first primary switch tube S1 and the second primary switch tube S2 are connected in series to form a first primary branch, and the third primary switch tube S3 and the fourth primary switch tube S4 are connected in series to form a second primary branch; the DC power supply BAT, the first primary branch, and the second primary branch are connected in parallel;

[0062] The source of the first secondary switch tube S5 is connected to the source of the second secondary switch tube S6, the drain of the second secondary switch tube S6 is connected to the drain of the third secondary switch tube S7, the source of the third secondary switch tube S7 is connected to the source of the fourth secondary switch tube S8, the first secondary switch tube S5, the second secondary switch tube S6, the third secondary switch tube S7, and the fourth secondary switch tube S8 are connected in series to form a first secondary branch; the first secondary branch capacitor C1 and the second secondary branch capacitor C2 are connected in series to form a second secondary branch; the AC power supply AC, the first secondary branch, and the second secondary branch are connected in parallel;

[0063] One end of the primary side of the transformer T1 is connected between the first primary side switch tube S1 and the second primary side switch tube S2, and the other end of the primary side of the transformer T1 is connected between the third primary side switch tube S3 and the fourth primary side switch tube S4;

[0064] One end of the secondary side of the transformer T1 is connected between the second secondary side switch tube S6 and the third secondary side switch tube S7, and the other end of the secondary side of the transformer T1 is connected between the first secondary side branch capacitor C1 and the second secondary side branch capacitor C2;

[0065] One end of the secondary side of the transformer T1 is connected in series with a secondary side inductor Lr and a secondary side capacitor Cr.

[0066] Specifically, the single-stage single-phase matrix DCAC converter further includes: a first AC inductor L1, one end of the first AC inductor L1 is connected to the AC power source AC, and the other end of the first AC inductor L1 is respectively connected to the drain of the first secondary switch tube S5 and the first secondary branch capacitor C1. The single-stage single-phase matrix DCAC converter further includes: a second AC inductor L2, one end of the second AC inductor L2 is connected to the AC power source AC, and the other end of the second AC inductor L2 is respectively connected to the drain of the fourth secondary switch tube S8 and the second secondary branch capacitor C2.

[0067] Specifically, the first primary switch tube S1 and the second primary switch tube S2 are connected in series to form a first primary branch, and the third primary switch tube S3 and the fourth primary switch tube S4 are connected in series to form a second primary branch. The connection method is: the source of the first primary switch tube S1 is connected to the drain of the second primary switch tube S2, and the source of the third primary switch tube S3 is connected to the drain of the fourth primary switch tube S4.

[0068] Specifically, the first primary branch and the second primary branch are connected in parallel as follows: the drain of the first primary switch tube S1 is connected to the drain of the third primary switch tube S3 , and the source of the second primary switch tube S2 is connected to the source of the fourth primary switch tube S4 .

[0069] Specifically, the single-stage single-phase matrix DCAC converter further includes: a filter capacitor Cb, the filter capacitor Cb is connected in parallel with the DC power supply BAT, and the filter capacitor Cb is used to filter the noise output by the DC power supply BAT.

[0070] How it works: See Figure 2 , Figure 2 1 is a waveform diagram of the first mode and the second mode of the single-stage single-phase matrix DCAC converter in an embodiment of the present invention. Figure 2 Where S1-S8 are the driving time of the first primary switch tube S1, the second primary switch tube S2, the third primary switch tube S3, the fourth primary switch tube S4, the first secondary switch tube S5, the second secondary switch tube S6, the third secondary switch tube S7, and the fourth secondary switch tube S8; D1 is the ratio of the time that the driving signal of S1 leads the driving signal of S4 to the switching period; D2 is the ratio of the time that the symmetric axis of the primary voltage of the transformer leads the symmetric axis of the secondary voltage to the switching period; the DC side transformer voltage is Vp, the AC side transformer voltage is Vs, and is is the current of the secondary inductor Lr.

[0071] See also Figure 3A-3E , Figure 3A-3E Schematic diagram of the switching of switches and current flow corresponding to t1-t6 of the first mode of the single-stage single-phase matrix DCAC converter in an embodiment of the present invention.

[0072] See also Figure 4A-4F , Figure 4A-4F Schematic diagram of the switching of the switch tube and the current flow direction corresponding to t0-t6 of the second mode of the single-stage single-phase matrix DCAC converter in an embodiment of the present invention.

[0073] See also Figure 5 , Figure 5 The control method of a single-stage single-phase matrix DCAC converter in an embodiment of the present invention is a schematic diagram of an embodiment of the control method of a single-stage single-phase matrix DCAC converter, and the control method of the single-stage single-phase matrix DCAC converter includes:

[0074] 501. Collect the primary DC voltage value, the secondary AC voltage value, and the secondary AC frequency corresponding to the transformer;

[0075] In this embodiment, the primary DC voltage value Vbat, the secondary AC voltage value Vg, and the secondary AC frequency Vacref corresponding to the transformer T1 are first collected.

[0076] In order to maintain the stability of the output secondary AC voltage value Vg, a voltage controller is set on the AC side to obtain an error signal by subtracting the sampled voltage from the AC voltage amplitude reference after PARK transformation. The secondary AC frequency 1 / Ts and the secondary AC voltage value Vg after PARK transformation are passed through the PI controller to obtain the AC voltage amplitude reference, and then the AC voltage sinusoidal reference value is obtained through PARK inverse transformation.

[0077] Finally, the DC side phase shift angle D1 and the phase shift angle D2 between the DC side and the AC side are calculated through the modulation strategy.

[0078] 502. Calculate, according to the primary DC voltage value, the interval duration between the driving signal of the first primary switch tube and the driving signal of the fourth primary switch tube, and calculate the ratio of the interval duration to a preset switching period to obtain a first phase shift angle;

[0079] In this embodiment, the collected primary DC voltage value is used to analyze and calculate the interval between the drive signal of the first primary switch tube S1 and the drive signal of the fourth primary switch tube S4, and then the ratio of the interval to the preset switching period is calculated to obtain the first phase shift angle D1. The first phase shift angle D1 is simply collected data and has not been modulated or sorted.

[0080] 503. Calculate the axis interval length between the primary voltage symmetry axis of the transformer and the secondary voltage symmetry axis of the transformer according to the primary DC voltage value, the secondary AC voltage value, and the secondary AC frequency, and calculate the ratio of the axis interval length to a preset switching period to obtain a second phase shift angle;

[0081] In this embodiment, based on the changes in the collected primary DC voltage value Vbat, the changes in the secondary AC voltage value Vg, and the secondary AC frequency Vacref, the axis interval length between the primary voltage symmetry axis of the transformer and the secondary voltage symmetry axis of the transformer is calculated, and the ratio of the axis interval length to the preset switching period is calculated to obtain the second phase shift angle D2. This second phase shift angle D2 is simply collected data and has not been modulated or sorted.

[0082] 504. Perform modulation processing on the first phase shift angle and the second phase shift angle according to a preset modulation algorithm to generate a first modulation phase shift angle and a second modulation phase shift angle;

[0083] In this embodiment, according to the symmetry of the odd harmonic function of the secondary inductor Lr current, the current expressions of the two modes corresponding to the time nodes can be obtained as follows:

[0084] The current expression in the first mode is:

[0085]

[0086] The current expression in the second mode is:

[0087]

[0088] Among them, the primary DC voltage value Vbat, the secondary AC voltage value Vg (instantaneous voltage), the switching period Ts, the switching frequency fs, the inductance Lr of the secondary inductor, the transformer ratio n, and the instantaneous current Is(t) of the secondary inductor.

[0089]

[0090] The formula for the transmission power P can be obtained by integrating the secondary side AC voltage value Vg (instantaneous voltage) and equations (1) to (6) with equation (7) as follows:

[0091] Transmission power of the first mode:

[0092]

[0093] Second mode transmission power:

[0094]

[0095] Based on the ratio between the AC side power Pac and the transmission power P, the power transfer ratio m is obtained, and the modal type of the current single-stage single-phase matrix DCAC converter is determined by comparing the power transfer ratio with the dynamic threshold value corresponding to the first phase shift angle D1. Then, based on the modal type and the power transfer ratio m, the first phase shift angle D1 is subjected to a first adjustment process to generate a first modulation phase shift angle D'1. After the first modulation phase shift angle D'1 is determined by modulation, the second modulation phase shift angle D'2 is generated based on the first modulation phase shift angle D'1.

[0096] For details, please refer to Figure 6 , Figure 6 This is a schematic diagram of an embodiment of step 504 of a control method for a single-stage single-phase matrix DCAC converter in an embodiment of the present invention. Step 504 includes the following specific implementation methods:

[0097] 5041. Collect the primary side current value of the converter, calculate the transmission power corresponding to the transformer based on the primary side current value, collect the inductor current value of the secondary side inductor, and calculate the AC side power corresponding to the transformer based on the inductor current value;

[0098] 5042. Calculate the quotient of the AC side power and the transmission power to obtain a power transmission ratio;

[0099] 5043. Determine a mode type of the single-stage single-phase matrix DCAC converter based on a dynamic threshold value corresponding to the power transfer ratio and the first phase shift angle;

[0100] 5044. Based on the power transfer ratio and the mode type, perform a first adjustment process on the first phase shift angle to generate a first modulation phase shift angle;

[0101] 5045. Based on the first modulation phase shift angle, the power transfer ratio, and the mode type, perform a second adjustment process on the second phase shift angle to generate a second modulation phase shift angle.

[0102] In steps 5041-5045, the primary current value Ip of the converter T1 is collected, and based on the primary current value Ip, the transmission power P corresponding to the transformer T1 is calculated by integrating the primary DC voltage value Vbat. This is the transmission power P collected and calculated initially. Then, similarly, the inductor current value Is of the secondary inductor Lr in the converter T1 is collected, and based on the inductor current value Is, the AC side power Pac corresponding to the transformer T1 is calculated by integrating the secondary AC voltage value Vg. This is the AC side power Pac collected and calculated initially.

[0103] The power transfer ratio m is calculated as follows:

[0104]

[0105] The calculation method of the voltage gain k is as follows:

[0106]

[0107] Taking the equality of the instantaneous power of two modes as the condition for smooth switching, and combining equations (8) - (11), we obtain: m = D1 * (1 - 2 * D1), that is, the dynamic threshold corresponding to the first phase - shift angle D1 is D1 * (1 - 2 * D1).

[0108] When m < D1 * (1 - 2 * D1), the mode type of the single - stage single - phase matrix - type DC - AC converter is the second mode.

[0109] When m ≥ D1 * (1 - 2 * D1), the mode type of the single - stage single - phase matrix - type DC - AC converter is the first mode.

[0110] The above calculation is to determine the mode state of the current single - stage single - phase matrix - type DC - AC converter by using principle analysis and collecting the power transfer ratio m and the first phase - shift angle D1 of the single - stage single - phase matrix - type DC - AC converter when the mode state is not clear at the beginning.

[0111] After determining the mode state, by optimizing the calculation of the fundamental effective value of the current Is of the secondary - side inductor, the first adjustment process is performed on the first phase - shift angle to generate the first modulation phase - shift angle D’1.

[0112] After the first modulation phase - shift angle D’1 is determined, the second modulation phase - shift angle D’2 is calculated based on the pre - set adjustment formula.

[0113] Specifically, the following specific implementation manners are included in step 5044:

[0114] 50441. Calculate the value range of the first modulation phase - shift angle based on the voltage gain of the transformer, the power transfer ratio, and the mode type;

[0115] 50442. According to the value range, optimize the fundamental effective value of the inductor current value to determine the first modulation phase - shift angle.

[0116] In steps 50441 - 50442, according to equations (1) - (3), when the switch tubes on the DC side and the AC side are ZVS in the first mode, that is, when the node current is zero, the value range of D’1 is:

[0117]

[0118] According to (4) - (6), when the switch tubes on the DC side and the AC side are ZVS in the second mode, that is, when the node current is zero, the value range of D’1 is:

[0119]

[0120] Based on the above value range of the first modulation phase shift angle D'1 in different modes, the fundamental effective value of the inductor current value Is is optimized to determine the specific value of the first modulation phase shift angle D'1.

[0121] The modes of the single-stage single-phase matrix DCAC converter include: a first mode and a second mode, and step 5045 includes the following specific implementations:

[0122] 50451. When the single-stage single-phase matrix DCAC converter is in the first mode, the second modulation phase shift angle is calculated according to a preset first adjustment formula, wherein the first adjustment formula includes:

[0123]

[0124] Wherein, D'1 is the first adjustment phase shift angle, m is the power transfer ratio, Vac is the secondary side AC voltage value (instantaneous value), D'2 is the second modulation phase shift angle, and sgn() is the sgn function;

[0125] 50452. When the single-stage single-phase matrix DCAC converter is in the second mode, a second modulation phase shift angle is calculated according to a preset second adjustment formula, wherein the second adjustment formula includes:

[0126]

[0127] Wherein, D'1 is the first adjustment phase shift angle, m is the power transfer ratio, Vac is the secondary side AC voltage value (instantaneous value), D'2 is the second modulation phase shift angle, and sgn() is the sgn function.

[0128] 505. Generate a PWM switch tube drive signal according to the first modulation phase shift angle and the second modulation phase shift angle, wherein the PWM switch tube drive signal is used to drive the switch tube of the single-stage single-phase matrix DCAC converter to switch on and off.

[0129] In this embodiment, a PWM switch tube drive signal is generated based on the first modulation phase shift angle D'1 and the second modulation phase shift angle D'2. The PWM switch tube drive signal is used to drive the switch tube of the single-stage single-phase matrix DCAC converter to open and close so as to optimize the DC-to-AC function of the single-stage single-phase matrix DCAC converter.

[0130] For details, please refer to Figure 7 , Figure 7This is a schematic diagram of the technical effect of a single-stage single-phase matrix DCAC converter in an embodiment of the present invention. The achieved effects are as follows: 1kW output, resistive load, power factor PF = 0.9977, current total harmonic distortion iTHD = 0.057, which effectively reduces the current total harmonic distortion and improves the stability of the switching current of the DCAC converter.

[0131] In an embodiment of the present invention, a new DCAC converter is designed, which enables direct current to achieve isolation function through a single-stage circuit and output a set alternating current in a closed loop. The present invention adopts a DCAC converter with two mode controls that can be smoothly switched. The control variables of each mode include the DC side phase shift angle and the phase shift angle between the DC side and the AC side, which can be obtained through the critical conditions of each mode, and the switching of the mode does not need to be judged according to the load power value. By taking the effective value current of the transformer high-frequency current as the optimization target, the DC side phase shift angle and the DC side and AC side phase shift angle are optimized to improve the conversion efficiency of the converter, solving the technical problem that the existing DCAC converter uses a two-stage structure to achieve isolation and inversion functions, resulting in low conversion efficiency of the DCAC converter.

[0132] In addition, although each operation is described in a specific order, this should be understood as requiring such operation to be performed in the specific order shown or in a sequential order, or requiring that all illustrated operations should be performed to obtain desired results. Under certain circumstances, multitasking and parallel processing may be advantageous. Similarly, although some specific implementation details are included in the above discussion, these should not be interpreted as limiting the scope of the present disclosure. Some features described in the context of a separate embodiment can also be implemented in a single implementation in combination. On the contrary, the various features described in the context of a single implementation can also be implemented in multiple implementations individually or in any suitable sub-combination mode.

[0133] Although the subject matter has been described in language specific to structural features and / or methodological logical actions, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or actions described above. On the contrary, the specific features and actions described above are merely example forms of implementing the claims.

Claims

1. A single-stage single-phase matrix DCAC converter, characterized in that: The single-stage single-phase matrix DCAC converter comprises: AC power supply, DC power supply, transformer, first primary switch tube, second primary switch tube, third primary switch tube, fourth primary switch tube, first secondary switch tube, second secondary switch tube, third secondary switch tube, fourth secondary switch tube, first secondary branch capacitor, second secondary branch capacitor, secondary capacitor, secondary inductor; The first primary switch tube and the second primary switch tube are connected in series to form a first primary branch, and the third primary switch tube and the fourth primary switch tube are connected in series to form a second primary branch; the DC power supply, the first primary branch, and the second primary branch are connected in parallel; The source of the first secondary switch tube is connected to the source of the second secondary switch tube, the drain of the second secondary switch tube is connected to the drain of the third secondary switch tube, the source of the third secondary switch tube is connected to the source of the fourth secondary switch tube, the first secondary switch tube, the second secondary switch tube, the third secondary switch tube, and the fourth secondary switch tube are connected in series to form a first secondary branch; the first secondary branch capacitor and the second secondary branch capacitor are connected in series to form a second secondary branch; the AC power supply, the first secondary branch, and the second secondary branch are connected in parallel; One end of the primary side of the transformer is connected between the first primary side switch tube and the second primary side switch tube, and the other end of the primary side of the transformer is connected between the third primary side switch tube and the fourth primary side switch tube; One end of the secondary side of the transformer is connected between the second secondary side switch tube and the third secondary side switch tube, and the other end of the secondary side of the transformer is connected between the first secondary side branch capacitor and the second secondary side branch capacitor; One end of the secondary side of the transformer is connected in series with the secondary side inductor and the secondary side capacitor.

2. The single-stage single-phase matrix DCAC converter according to claim 1, characterized in that: The single-stage single-phase matrix DCAC converter also includes: a first AC inductor, one end of which is connected to the AC power supply, and the other end of which is respectively connected to the drain of the first secondary switch tube and the first secondary branch capacitor.

3. The single-stage single-phase matrix DCAC converter according to claim 1, characterized in that: The single-stage single-phase matrix DCAC converter also includes: a second AC inductor, one end of the second AC inductor is connected to the AC power supply, and the other end of the second AC inductor is respectively connected to the drain of the fourth secondary switch tube and the second secondary branch capacitor.

4. The single-stage single-phase matrix DCAC converter according to claim 1, characterized in that: The source of the first primary switch tube is connected to the drain of the second primary switch tube, and the source of the third primary switch tube is connected to the drain of the fourth primary switch tube.

5. The single-stage single-phase matrix DCAC converter according to claim 4, characterized in that: The drain of the first primary switch tube is connected to the drain of the third primary switch tube, and the source of the second primary switch tube is connected to the source of the fourth primary switch tube.

6. The single-stage single-phase matrix DCAC converter according to claim 1, characterized in that: The single-stage single-phase matrix DCAC converter further includes a filter capacitor connected in parallel with the DC power supply.

7. A control method for a single-stage single-phase matrix DCAC converter, the control method for the single-stage single-phase matrix DCAC converter being applied to the single-stage single-phase matrix DCAC converter as claimed in any one of claims 1 to 6, the control method for the single-stage single-phase matrix DCAC converter comprising: Collecting the primary DC voltage value, secondary AC voltage value, and secondary AC frequency corresponding to the transformer; According to the primary DC voltage value, calculating the interval duration between the driving signal of the first primary switch tube and the driving signal of the fourth primary switch tube, and calculating the ratio of the interval duration to a preset switching period, to obtain a first phase shift angle; According to the primary DC voltage value, the secondary AC voltage value, and the secondary AC frequency, the axis interval length between the primary voltage symmetry axis of the transformer and the secondary voltage symmetry axis of the transformer is calculated, and the ratio of the axis interval length to a preset switching period is calculated to obtain a second phase shift angle; According to a preset modulation algorithm, the first phase shift angle and the second phase shift angle are modulated to generate a first modulation phase shift angle and a second modulation phase shift angle; A PWM switch tube drive signal is generated according to the first modulation phase shift angle and the second modulation phase shift angle, wherein the PWM switch tube drive signal is used to drive the switch tube of the single-stage single-phase matrix DCAC converter to switch on and off.

8. The control method of the single-stage single-phase matrix DCAC converter according to claim 7, characterized in that: The step of performing modulation processing on the first phase shift angle and the second phase shift angle according to a preset modulation algorithm to generate the first modulation phase shift angle and the second modulation phase shift angle comprises: Collecting the primary side current value of the converter, and calculating the transmission power corresponding to the transformer based on the primary side current value, and collecting the inductor current value of the secondary side inductor, and calculating the AC side power corresponding to the transformer based on the inductor current value; Calculating the quotient of the AC side power and the transmission power to obtain a power transmission ratio; determining a mode type of the single-stage single-phase matrix DCAC converter based on a dynamic threshold value corresponding to the power transfer ratio and the first phase shift angle; Based on the power transfer ratio and the mode type, performing a first adjustment process on the first phase shift angle to generate a first modulation phase shift angle; Based on the first modulation phase shift angle, the power transfer ratio, and the mode type, a second adjustment process is performed on the second phase shift angle to generate a second modulation phase shift angle.

9. The control method of the single-stage single-phase matrix DCAC converter according to claim 8, characterized in that: The performing a first adjustment process on the first phase shift angle based on the power transfer ratio and the mode type to generate a first modulation phase shift angle comprises: Calculating a value range of a first modulation phase shift angle based on a voltage gain of the transformer, the power transfer ratio, and the mode type; According to the value range, the fundamental effective value of the inductor current value is optimized to determine the first modulation phase shift angle.

10. The control method of the single-stage single-phase matrix DCAC converter according to claim 8, characterized in that: The modes of the single-stage single-phase matrix DCAC converter include: a first mode and a second mode, and the second adjustment process is performed on the second phase shift angle based on the first modulation phase shift angle, the power transfer ratio, and the mode type to generate the second modulation phase shift angle, including: When the single-stage single-phase matrix DCAC converter is in the first mode, the second modulation phase shift angle is calculated according to a preset first adjustment formula, wherein the first adjustment formula includes: Wherein, D'1 is the first adjustment phase shift angle, m is the power transfer ratio, Vac is the secondary AC voltage value, D'2 is the second modulation phase shift angle, and sgn() is the sgn function; When the single-stage single-phase matrix DCAC converter is in the second mode, the second modulation phase shift angle is calculated according to a preset second adjustment formula, wherein the second adjustment formula includes: Wherein, D'1 is the first adjustment phase shift angle, m is the power transfer ratio, Vac is the secondary side AC voltage value, D'2 is the second modulation phase shift angle, and sgn() is the sgn function.

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