A voltage source type high frequency isolation matrix converter and modulation method thereof

Abstract

The present invention discloses a voltage source type high frequency isolation matrix converter and a modulation method thereof, belonging to the technical field of power generation, power transformation or power distribution. The converter includes: a matrix converter, a high frequency isolation transformer, a full-bridge converter, and a battery. A new four-step commutation method is adopted to realize safe and reliable commutation between switch tubes; the secondary side clamping and space vector coordinated control technology are adopted to eliminate the voltage spikes caused by the sudden change of the transformer leakage inductance current. The technical solution of the present invention utilizes a high frequency isolation transformer to replace the power frequency transformer to realize the isolation function, reduce the leakage current of the system, and reduce the volume and weight of the converter; the voltage source full-bridge converter and the matrix converter are adopted to remove the intermediate electrolytic capacitor of the two-stage converter, thereby improving the reliability of the system and extending the service life. There is no commutation capacitor on the low-frequency AC side, which further reduces the volume of the converter and increases the power density.

Description

Technical Field

[0001] The present invention belongs to the field of new energy power generation, and particularly relates to a voltage-source high-frequency isolation matrix converter and its modulation method. Background Art

[0002] Under the background of carbon peaking and carbon neutrality, new energy technologies are developing day by day, and the demand for high-efficiency and high-reliability converters is gradually increasing. In order to suppress the leakage current of grid-connected power generation systems and protect the insulation of power sources such as wind turbines and storage batteries, a power frequency transformer is usually added between the power grid and the power source to achieve the isolation function. However, the power frequency transformer is large in volume, heavy in weight, and the power density of the power converter is relatively low. The high-frequency isolation converter uses a high-frequency isolation transformer to achieve the isolation function, and has the advantages of high efficiency, high power density, and easy voltage matching. Therefore, the importance of high-frequency isolation converters in grid-connected new energy power generation is becoming increasingly prominent.

[0003] However, there are currently problems in dual-active full-bridge matrix converters, such as a relatively large peak value of leakage inductance current, limited soft-switching range, and difficult duty cycle calculation, which limit further industrial applications. Although the current-source matrix converter can reduce the peak value of the leakage inductance current and reduce the calculation time of the modulation ratio, the filter capacitors on the three-phase input side increase the volume and cost of the system, and the DC-side inductor increases the conduction loss of the converter. Summary of the Invention

[0004] In a first aspect, in view of the deficiencies of the prior art, the present invention aims to provide a voltage-source high-frequency isolation matrix converter, which solves one or more technical problems proposed in the background art.

[0005] The present invention adopts the following technical solutions to achieve the above-mentioned invention objectives:

[0006] A voltage-source high-frequency isolation matrix converter, characterized by comprising:

[0007] A matrix converter, whose input AC bus is connected to the three-phase stator winding of the generator,

[0008] A high-frequency isolation transformer, whose primary coil is connected to the output end of the matrix converter, and

[0009] A voltage-source full-bridge converter, whose input is connected to the output end of the high-frequency isolation transformer, and the DC output is connected to the storage battery;

[0010] Under the action of the voltage vector, the matrix converter sequentially experiences the first zero-vector action stage in the positive half-cycle, the transformer leakage inductance current commutation stage, the voltage-source full-bridge converter freewheeling stage, the first active vector action stage, the second active vector action stage, and the second zero-vector action stage in the positive half-cycle.

[0011] In some disclosures, the modulation method of the matrix converter:

[0012] The voltage-source full-bridge converter includes: one arm formed by series connection of a first switching tube and a second switching tube, and another arm formed by series connection of a third switching tube and a fourth switching tube. The matrix converter includes: an a-phase arm formed by series connection of a first bidirectional switching tube and a fourth bidirectional switching tube, a b-phase arm formed by series connection of a third bidirectional switching tube and a sixth bidirectional switching tube, and a c-phase arm formed by series connection of a fifth bidirectional switching tube and a second bidirectional switching tube;

[0013] During the positive half-cycle of a switch, the four voltage vectors acting on the matrix converter are the first zero vector V 7 and the second zero vector V 8 , the first active vector V 1+ , and the second active vector V 2+ ; The first zero vector V 7 and the second zero vector V 8 both correspond to the input current of the matrix converter being I 0 ; The first active vector V 1+ , the second active vector V 2+ respectively correspond to the input current of the matrix converter being I 1 , I 2 . After comparing the input current of the motor winding, the action sequence of the four voltage vectors is determined as V 7 ->V 1+ ->V 2+ ->V 8 At this time, I 2 >I 1 >I 0 .

[0014] In some disclosures, the regulation of the high-frequency isolation matrix converter during the positive half-cycle of a switch is as follows:

[0015] a. State 1: The stage of the action of the first zero vector in the positive half-cycle

[0016] At the start of the switching period, the first zero vector V 7 acts on the matrix converter. The fourth bidirectional switch and the sixth bidirectional switch in the matrix converter are turned on, the second bidirectional switch is turned on, the second switching tube and the third switching tube in the voltage-source full-bridge converter are turned on, and no current flows. At this time, there is no energy exchange between the low-frequency AC power supply and the battery;

[0017] b. State 2: The commutation stage of the transformer leakage inductance current

[0018] After the action time of the zero vector ends, the first active vector V 1+Acting on the matrix converter, the second and third switching tubes in the voltage-source full-bridge converter remain conducting; the first bidirectional switching tube in the matrix converter is turned on, the fourth bidirectional switching tube is turned off, and the DC battery charges the leakage inductance current. The leakage inductance current of the high-frequency isolation transformer is equal to the current of the a-phase winding of the low-frequency AC power supply;

[0019] c. State 3: Freewheeling stage of the voltage-source full-bridge converter

[0020] In the voltage-source full-bridge converter, the second and fourth switching tubes are turned off, and the transformer current freewheels through the anti-parallel diodes of the first and fourth switching tubes. The first, sixth, and second bidirectional switching tubes in the matrix converter remain conducting. The primary current of the high-frequency isolation transformer is equal to the current of the a-phase winding of the low-frequency AC power supply, and the secondary voltage of the high-frequency isolation transformer is equal to the battery voltage. Energy is fed from the AC side to the DC side;

[0021] d. State 4: Acting stage of the first active vector

[0022] In the matrix converter, the first, sixth, and second bidirectional switching tubes remain conducting. The first and fourth switching tubes of the voltage-source full-bridge converter conduct with zero voltage, and energy is fed from the AC side to the DC side;

[0023] e. State 5: Acting stage of the second active vector

[0024] After the acting time of the first active vector V in the matrix converter 1+ ends, the second active vector V 2+ starts to act. The sixth bidirectional switching tube in the matrix converter is turned off, and the third bidirectional switching tube is turned on. The primary current of the high-frequency isolation transformer is equal to the sum of the currents of the a-phase and b-phase windings, and the secondary voltage is equal to the battery voltage. Energy is fed from the AC side to the DC side;

[0025] f. State 6: Acting stage of the second zero vector in the positive half cycle

[0026] After the acting time of the second active vector V in the matrix converter 2+ ends, the second zero vector V 8 acts on the matrix converter. The first, third, and fifth bidirectional switching tubes in the matrix converter remain conducting, and the first and fourth switching tubes in the voltage-source full-bridge converter remain conducting. At this time, there is no energy exchange between the low-frequency AC power supply and the battery.

[0027] In some disclosures, the acting times of the four voltage vectors are as follows: Among them, T 1 , and T 2 are respectively the acting time of the first active vector V 1+, the second active vector V 2+ ; T 0 is the action time of the first zero vector V 7 and the second zero vector V 8 , m a and θ i are the modulation ratio and angle of space vector modulation respectively, and T s is a switching period.

[0028] In some disclosures, when the leakage inductance current commutes, the battery voltage is mapped through the high-frequency isolation transformer and applied to the leakage inductance to force the leakage inductance current to change direction.

[0029] In a second aspect, aiming at the deficiencies of the prior art, the present invention aims to provide a modulation system for a voltage-source high-frequency isolation matrix converter; one or more technical problems proposed in the background art are solved.

[0030] A modulation system for a voltage-source high-frequency isolation matrix converter includes:

[0031] A matrix converter module, including a matrix converter, the input AC bus of which is connected to the three-phase stator winding of the generator,

[0032] A high-frequency isolation transformer module, including a high-frequency isolation transformer, the primary coil of which is connected to the output end of the matrix converter, and,

[0033] A voltage-source full-bridge converter module, including a voltage-source full-bridge converter, the input of which is connected to the output end of the high-frequency isolation transformer, and the DC output is connected to the battery;

[0034] The matrix converter sequentially experiences a first zero vector action stage in the positive half-cycle, a transformer leakage inductance current commutation stage, a voltage-source full-bridge converter freewheeling stage, a first active vector action stage, a second active vector action stage, and a second zero vector action stage in the positive half-cycle under the action of voltage vectors;

[0035] The voltage-source full-bridge converter includes: an arm composed of a first switch tube and a second switch tube in series, and another arm composed of a third switch tube and a fourth switch tube in series. The matrix converter includes: an a-phase arm composed of a first bidirectional switch tube and a fourth bidirectional switch tube in series, a b-phase arm composed of a third bidirectional switch tube and a sixth bidirectional switch tube in series, and a c-phase arm composed of a fifth bidirectional switch tube and a second bidirectional switch tube in series;

[0036] The four voltage vectors acting on the matrix converter within a positive half-cycle of a switch are the first zero vector V 7 and the second zero vector V 8 , the first active vector V 1+ , the second active vector V2+ ; The first zero vector V 7 and the second zero vector V 8 both correspond to the input current of the matrix converter being I 0 ; The first active vector V 1+ , the second active vector V 2+ respectively correspond to the input currents of the matrix converter being I 1 , I 2 , after comparing the input currents of the motor windings, the action sequence of the four voltage vectors is determined as V 7 -> V 1+ -> V 2+ -> V 8 At this time, I 2 > I 1 > I 0 .

[0037] The present invention adopts the above technical solutions and has the following beneficial effects:

[0038] (1) The voltage-source high-frequency isolation matrix converter disclosed in this application adopts a single-stage topology composed of a voltage-source full-bridge converter, a high-frequency isolation transformer, a matrix converter, and a three-phase filter. It uses a space vector modulation strategy that determines the vector action sequence according to the low-frequency AC power supply phase current to realize the on-off of all switches of the matrix converter. It realizes safe and reliable commutation of the leakage inductance of the high-frequency isolation transformer through a commutation strategy of clamping at the secondary side, without the need to add a clamping circuit to suppress voltage spikes, which is beneficial to reducing system losses, improving efficiency and power density, and overcoming the defect that the soft-switching range of the existing dual-active full-bridge matrix converter is limited.

[0039] (2) The voltage-source high-frequency isolation matrix converter disclosed in this application does not require electrolytic capacitors to connect the voltage-source full-bridge converter and the matrix converter, overcoming the defects of poor reliability and short service life of the two-stage converter due to the need for electrolytic capacitors to connect the front and rear stages.

[0040] (3) The voltage-source high-frequency isolation matrix converter disclosed in this application has the advantage of a constant amplitude of the leakage inductance current of the transformer. The current of the high-frequency isolation transformer is in the form of a stepped wave. Compared with the dual-active full-bridge matrix converter, it reduces the current peak and lowers the system loss.

[0041] (4) The voltage-source high-frequency isolation matrix converter disclosed in this application has a continuous leakage inductance current without an intermittent state, and the duty cycle calculation is simpler, reducing the computational burden on the controller.

[0042] (5) The voltage-source high-frequency isolation matrix converter disclosed in this application does not require three-phase commutation capacitors on the low-frequency AC side, reducing the volume and cost of the system. Description of the Drawings

[0043] Figure 1 It is the main circuit topology diagram;

[0044] Figure 2 (a) and Figure 2 (b) are respectively the voltage space vector diagrams of the positive and negative half cycles of the matrix converter.

[0045] Figure 3 (a) to Figure 3 (f) are the current flow path diagrams of the converter in states 1, 2, 3, 4, 5, and 6 during the first half of the switching period.

[0046] Figure 4 It is the four-step commutation process from the upper half bridge arm of phase a to the lower half bridge arm of phase a;

[0047] Figure 5 It is the key waveform diagram within one switching period;

[0048] Figure 6 It is the diagram of the commutation process of the battery voltage forced leakage inductance current;

[0049] Figure 7 (a) to Figure 7 (c) are the current and voltage waveform diagrams of the high-frequency isolation transformer under the conditions that the rotational speeds of the wind turbine are 1000 r / min, 750 r / min, and 500 r / min;

[0050] Figure 8 The steady-state voltage and current waveform diagram of the matrix converter.

[0051] Explanation of the labels in the figure: 1.1, wind turbine; 1.2, matrix converter; 1.3, high-frequency isolation transformer; 1.4, voltage-source full-bridge converter; 1.5, battery. Specific implementation manners

[0052] Hereinafter, the technical solution of the present invention will be described in detail with reference to the accompanying drawings.

[0053] Example 1:

[0054] A voltage-source high-frequency isolation matrix converter disclosed in this application, as Figure 1 shown, includes a low-frequency AC power supply, a matrix converter, a high-frequency isolation transformer, and a voltage-source full-bridge converter. The input AC bus of the matrix converter 1.2 is connected to the three-phase windings of the low-frequency AC power supply 1.1, and the output is connected to the primary side of the high-frequency isolation transformer 1.3; the secondary side of the high-frequency isolation transformer is connected to the midpoint of the bridge arm of the voltage-source full-bridge converter 1.4, and the DC output of the voltage-source full-bridge converter 1.4 is connected in parallel with the battery 1.5.

[0055] In this application, the low-frequency AC power supply 1.1 can be a wind turbine for generating low-frequency alternating current. Of course, in some other scenarios, the low-frequency AC power supply 1.1 can be a three-phase AC power grid;

[0056] In the illustration of this application, the voltage-source full-bridge converter 1.4 is a full-bridge converter composed of the first switching tube S 1 , the second switching tube S 2 , the third switching tube S 3 , and the fourth switching tube S 4 ;

[0057] The matrix converter 1.2 includes: the first bidirectional switching tube formed by the common-source connection of the switching tube S 21 and the switching tube S 11 , the second bidirectional switching tube formed by the common-source connection of the switching tube S 22 and the switching tube S 12 , the third bidirectional switching tube formed by the common-source connection of the switching tube S 23 and the switching tube S 13 , the fourth bidirectional switching tube formed by the common-source connection of the switching tube S 24 and the switching tube S 14 , the fifth bidirectional switching tube formed by the common-source connection of the switching tube S 25 and the switching tube S 15 , the sixth bidirectional switching tube formed by the common-source connection of the switching tube S 26 and the switching tube S 16 . The midpoint of the bridge arm formed by the series connection of the first bidirectional switching tube and the fourth bidirectional switching tube is denoted as a, the midpoint of the bridge arm formed by the series connection of the third bidirectional switching tube and the sixth bidirectional switching tube is denoted as b, and the midpoint of the bridge arm formed by the series connection of the fifth bidirectional switching tube and the second bidirectional switching tube is denoted as c.

[0058] The input ends of the bridge arm formed by the series connection of the first bidirectional switching tube and the fourth bidirectional switching tube, the bridge arm formed by the series connection of the third bidirectional switching tube and the sixth bidirectional switching tube, and the bridge arm formed by the series connection of the fifth bidirectional switching tube and the second bidirectional switching tube are respectively electrically connected to the three-phase windings of the low-frequency AC power supply 1.1, and the output ends are all connected to the primary side of the high-frequency isolation transformer 1.3.

[0059] Taking Figure 2 (a) Sector I as an example, within one positive half-cycle of a switch, the four voltage vectors acting on the matrix converter are the first zero vector V 7 and the second zero vector V 8 , the first active vector V 1+ , and the second active vector V 2+ ; The first zero vector V 7 and the second zero vector V 8 both correspond to the input current of the matrix converter being I 0 ; The first active vector V1+ and the second active vector V 2+ respectively correspond to the input currents of the matrix converter being I 1 and I 2 . After comparing the input currents of the motor windings, the action sequence of the four voltage vectors is determined as V 7 -> V 1+ -> V 2+ -> V 8 At this time, I 2 > I 1 > I 0 . During half of the switching period, the modulation process of the matrix converter is as follows. It experiences 6 states, and the current flow paths in the 6 states are as Figure 3 shown, and the key waveforms within one switching period are as Figure 5 shown.

[0060] Adopt a single-stage topology composed of a voltage-source full-bridge converter, a high-frequency isolation transformer, a matrix converter, and a three-phase filter. Use a space vector modulation strategy that determines the vector action sequence according to the phase current of the low-frequency AC power supply to realize the on and off of all switches of the matrix converter. Achieve safe and reliable commutation of the leakage inductance of the high-frequency isolation transformer through a commutation strategy with secondary clamping, without the need to add a clamping circuit to suppress voltage spikes, which is beneficial to reducing system losses, improving efficiency and power density, and overcoming the defect of limited soft-switching range of the existing dual-active full-bridge matrix converter.

[0061] This application uses the inductance of the motor winding as a filtering element, eliminating the additional three-phase filter capacitor on the motor side, improving the efficiency and power density of the system; at the same time, replacing the DC filtering inductor with a thin-film capacitor further reduces the conduction loss and volume of the system.

[0062] The commutation method proposed in this application will not have the working condition of commutation failure and short circuit of the filter capacitor in the traditional commutation scheme.

[0063] This application proposes a 180° conduction type modulation scheme, that is, only one of the upper and lower two bidirectional switches of each bridge arm conducts. Similar to a three-phase voltage source converter, compared with the 120° conduction type modulation methods of current-input matrix type and dual-active full-bridge matrix type, no additional FPGA circuit is required, and it can be realized only by using a DSP, with lower cost and higher practicality.

[0064] 1) State 1: Positive half-cycle first zero vector action stage

[0065] At the beginning of the switching period, the first zero vector V 7 acts on the matrix converter 1.2, and in the matrix converter, S 14 , S 24 , S 16 , S 26 , S12 , S 22 switch conducts, and S in the full-bridge converter 2 and S 3 conduct, and no current flows. At this time, there is no energy exchange between the low-frequency AC power supply and the battery. The equivalent circuit diagram is as shown in Figure 3 (a). The output voltage u of the matrix converter p , the primary current i of the transformer p , and the drive signals g 1 &g 4 , g 2 &g 3 See Figure 5 for the waveform diagram during the time period [t 0 , t 1 .

[0066] 2) State 2: Commutation stage of the leakage inductance current of the transformer

[0067] After the zero vector action time ends, the first active vector V 1+ acts on the matrix converter 1.2, and S 2 and S 3 in the voltage-source full-bridge converter 1.4 maintain the conduction state; S 11 and S 21 in the matrix converter are turned on, S 14 and S 24 are turned off, and the DC-side battery charges the leakage inductance current. The leakage inductance current of the high-frequency isolation transformer is equal to the current of the a-phase winding of the low-frequency AC power supply. The equivalent circuit diagram is as shown in Figure 3 (b). The output voltage u of the matrix converter p , the primary current i of the transformer p , and the drive signals g 1 &g 4 , g 2 &g 3 See Figure 5 for the waveform diagram during the time period [t 1 , t 2 .

[0068] 3) State 3: Freewheeling stage of the voltage-source full-bridge converter

[0069] In the voltage-source full-bridge converter, S 2 and S 3 are turned off, and the current of the high-frequency isolation transformer freewheels through the anti-parallel diodes of S 1 and S 4 . In the matrix converter, S 11 , S 21 , S 26 , S 16 , S12 , S 22 remains conducting. The primary current of the high-frequency isolation transformer is equal to the current of the a-phase winding of the low-frequency AC power supply, and the secondary voltage of the high-frequency isolation transformer is equal to the battery voltage. Energy is fed from the AC side to the DC side. The equivalent circuit diagram is as shown in Figure 3 (c), the output voltage u of the matrix converter p , the primary current i of the transformer p , and the drive signals g of the full-bridge converter 1 & g 4 , g 2 & g 3 See Figure 5 as shown in the waveform diagram during the time period [t 2 , t 3 .

[0070] 4) State 4: First active vector action stage

[0071] In the matrix converter, S 11 , S 21 , S 26 , S 16 , S 12 , S 22 maintain the conducting state, S 1 and S 4 of the voltage-source full-bridge converter conduct with zero current, and energy is fed from the AC side to the DC side. The equivalent circuit diagram is as shown in Figure 3 (d), the output voltage u of the matrix converter p , the primary current i of the transformer p , and the drive signals g of the full-bridge converter 1 & g 4 , g 2 & g 3 See Figure 5 as shown in the waveform diagram during the time period [t 3 , t 4 .

[0072] 5) State 5: Second active vector action stage

[0073] After the action time of the first active vector V 1+ of the matrix converter ends, the second active vector V 2+ starts to act. In the matrix converter, S 26 , S 16 are turned off, and S 23 , S 13 are turned on. The primary current of the high-frequency isolation transformer is equal to the sum of the currents of the a-phase and b-phase windings, and the secondary voltage is equal to the battery voltage. Energy is fed from the AC side to the DC side. The equivalent circuit diagram is as shown in Figure 3 (e), the output voltage u of the matrix converterp , the primary current i of the transformer p , and the drive signals g of the full-bridge converter 1 &g 4 、g 2 &g 3 See Figure 5 the waveform diagram during the time period shown as [t 4 ,t 5 .

[0074] 6) State 6: The second zero vector action stage in the positive half cycle

[0075] After the action time of the second active vector V of the matrix converter 2+ ends, the second zero vector V 8 acts on the matrix converter. In the matrix converter, S 11 、S 21 、S 23 、S 13 、S 15 、S 25 maintain the on state. In the voltage-source full-bridge converter, S 1 、S 4 maintain the on state. At this time, there is no energy exchange between the low-frequency AC power supply and the battery. The equivalent circuit diagram is as shown in Figure 3 (f). The output voltage u of the matrix converter p , the primary current i of the transformer p , and the drive signals g of the full-bridge converter 1 &g 4 、g 2 &g 3 See Figure 5 the waveform diagram during the time period shown as [t 5 ,t 6 .

[0076] Among them, Figure 5 the action times of the four voltage vectors in are as follows: Among them, T 1 , and T 2 are the action times of the first active vector V 1+ and the second active vector V 2+ respectively; T 0 is the action time of the first zero vector V 7 and the second zero vector V 8 . m a and θ i are the modulation ratio and angle of space vector modulation respectively. T s is a switching period.

[0077] As shown in Figure 6As shown, when the leakage inductance current commutes, the battery voltage is mapped through the high-frequency isolation transformer and applied to the leakage inductance to force the leakage inductance current to change direction, where g 21 and g 11 and g 24 and g 14 within the range are respectively the drive signals of S 21 、S 11 、S 24 、S 14 .

[0078] As Figure 4 shown, a voltage source type high-frequency isolation matrix converter and its modulation method, the commutation method between the switching tubes of the matrix converter includes the following steps:

[0079] Taking the switching of the upper half-bridge arm of phase a to the lower half-bridge arm as an example, the switching tubes S 21 and S 11 are conducting. Among them, the switching tube S 11 is conducting forward, the switching tube S 21 is in the synchronous rectification state, and the arm input current i a is greater than 0.

[0080] The first commutation: The switching tube S 21 is turned off, and the current commutes from the channel of S 21 to the body diode of S 21 ;

[0081] The second commutation: The switching tube S 24 is turned on, and the current flows through the channel of S 24 and the body diode of S 14 ;

[0082] The third commutation: The switching tube S 11 is turned off, and all the phase a input current flows through the lower half-bridge arm;

[0083] The fourth commutation: The switching tube S 14 is turned on, and the current commutes from the body diode of S 14 to the channel of S 14 , and S 14 is in the synchronous rectification state.

[0084] As Figure 7 shown, at the rated speed, half speed and quarter speed, the amplitude of the matrix converter output current remains unchanged, reducing the conduction loss of the system and improving the wide-range speed regulation performance of the wind turbine. From Figure 8 it can be seen that the system proposed in this paper can operate stably at the rated power of 1 kW, verifying the feasibility of the single-stage matrix converter for wind power generation.

[0085] Embodiment 2:

[0086] A modulation system for a voltage-source high-frequency isolation matrix converter, comprising:

[0087] A matrix converter module, including a matrix converter, the input AC bus of which is connected to the three-phase stator winding of a generator,

[0088] A high-frequency isolation transformer module, including a high-frequency isolation transformer, the primary coil of which is connected to the output terminal of the matrix converter, and,

[0089] A voltage-source full-bridge converter module, including a voltage-source full-bridge converter, the input of which is connected to the output terminal of the high-frequency isolation transformer, and the DC output is connected to a storage battery;

[0090] Under the action of voltage vectors, the matrix converter sequentially experiences a first zero-vector action stage in the positive half-cycle, a transformer leakage inductance current commutation stage, a freewheeling stage of the voltage-source full-bridge converter, a first active-vector action stage, a second active-vector action stage, and a second zero-vector action stage in the positive half-cycle;

[0091] The voltage-source full-bridge converter includes: one bridge arm composed of a series connection of a first switch tube and a second switch tube, and another bridge arm composed of a series connection of a third switch tube and a fourth switch tube; the matrix converter includes: an a-phase bridge arm composed of a series connection of a first bidirectional switch tube and a fourth bidirectional switch tube, a b-phase bridge arm composed of a series connection of a third bidirectional switch tube and a sixth bidirectional switch tube, and a c-phase bridge arm composed of a series connection of a fifth bidirectional switch tube and a second bidirectional switch tube;

[0092] Four voltage vectors acting on the matrix converter within one positive half-cycle of a switch are the first zero vector V 7 and the second zero vector V 8 , the first active vector V 1+ , and the second active vector V 2+ ; the first zero vector V 7 and the second zero vector V 8 both correspond to the input current of the matrix converter being I 0 ; the first active vector V 1+ , the second active vector V 2+ respectively correspond to the input currents of the matrix converter being I 1 , I 2 , after comparing the input currents of the motor windings, the acting order of the four voltage vectors is determined as V 7 ->V 1+ ->V 2+ ->V 8 At this time, I 2 >I 1 >I 0 .

[0093] A single-stage topology composed of a voltage-source full-bridge converter, a high-frequency isolation transformer, a matrix converter, and a three-phase filter is adopted. The space vector modulation strategy that determines the vector action sequence according to the phase current of the low-frequency AC power supply is used to realize the on-off of all switches of the matrix converter. The commutation strategy with secondary clamping is used to realize the safe and reliable commutation of the leakage inductance of the high-frequency isolation transformer, without the need to add a clamping circuit to suppress voltage spikes, which is beneficial to reducing system losses, improving efficiency and power density, and overcoming the defect that the soft-switching range of the existing dual-active full-bridge matrix converter is limited.

[0094] Regarding other aspects, they are the same as those described in Embodiment 1; that is, other effects brought by Embodiment 1 may be reflected.

[0095] Although the present invention has been disclosed above with preferred examples, it is not intended to limit the present invention. Those with ordinary knowledge in the technical field to which the present invention pertains can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the scope defined in the claims.

Claims

1. A voltage source type high frequency isolation matrix converter, characterized in that: include: The matrix converter has an input AC bus connected to the three-phase stator winding of the generator. A high frequency isolation transformer, whose primary coil is connected to the output end of the matrix converter, and A voltage source full-bridge converter, whose input is connected to the output end of a high-frequency isolation transformer and whose DC output is connected to a battery; Under the action of the voltage vector, the matrix converter sequentially undergoes the first zero vector action stage of the positive half cycle, the transformer leakage inductance current commutation stage, the voltage source full-bridge converter freewheeling stage, the first active vector action stage, the second active vector action stage, and the second zero vector action stage of the positive half cycle; The regulation of the high-frequency isolated matrix converter in a positive half-cycle of the switch is: a. State 1: The first zero vector action stage of the positive half cycle At the beginning of the switching cycle, the first zero vector V7 acts on the matrix converter, the fourth bidirectional switch, the sixth bidirectional switch, and the second bidirectional switch in the matrix converter are turned on, the second switch tube and the third switch in the voltage source full-bridge converter are turned on, and no current flows. At this time, there is no energy exchange between the low-frequency AC power supply and the battery; b. State 2: Transformer leakage inductance current commutation stage After the zero vector action time ends, the first active vector V 1+ Acting on the matrix converter, the second switch tube and the third switch tube in the voltage source full-bridge converter remain in the on state; the first bidirectional switch tube in the matrix converter is turned on, the fourth bidirectional switch tube is turned off, the DC battery charges the leakage inductance current, and the leakage inductance current of the high-frequency isolation transformer is equal to the current of the a-phase winding of the low-frequency AC power supply; c. State 3: Freewheeling phase of voltage source full-bridge converter The second switch tube and the fourth switch tube in the voltage source full-bridge converter are turned off, the transformer current is freewheeling through the anti-parallel diodes of the first switch tube and the fourth switch tube, the first bidirectional switch tube, the sixth bidirectional switch tube and the second bidirectional switch tube in the matrix converter remain turned on, the primary current of the high-frequency isolation transformer is equal to the current of the a-phase winding of the low-frequency AC power supply, the secondary voltage of the high-frequency isolation transformer is equal to the battery voltage, and energy is fed from the AC side to the DC side; d. State 4: The first active vector action stage The first bidirectional switch tube, the sixth bidirectional switch tube and the second bidirectional switch tube in the matrix converter are maintained in the on state, the first switch tube and the fourth switch tube of the voltage source full-bridge converter are turned on at zero voltage, and energy is fed from the AC side to the DC side; e. State 5: Second active vector action stage The first active vector V of the matrix converter 1+ After the action time ends, the second active vector V 2+ It starts to work, the sixth bidirectional switch tube in the matrix converter is turned off, the third bidirectional switch tube is turned on, the primary current of the high-frequency isolation transformer is equal to the sum of the currents of the a-phase and b-phase windings, the secondary voltage is equal to the battery voltage, and energy is fed from the AC side to the DC side; f. State 6: The second zero vector action stage of the positive half cycle The second active vector V of the matrix converter 2+ After the action time ends, the second zero vector V8 acts on the matrix converter, the first bidirectional switch, the third bidirectional switch tube and the fifth bidirectional switch in the matrix converter remain in the on state, and the first switch tube and the fourth switch tube in the voltage source full-bridge converter remain in the on state. At this time, there is no energy exchange between the low-frequency AC power supply and the battery.

2. The voltage source type high frequency isolation matrix converter according to claim 1, characterized in that: Modulation method of the matrix converter: The voltage source full-bridge converter comprises: a bridge arm formed by a first switch tube and a second switch tube connected in series, another bridge arm formed by a third switch tube and a fourth switch tube connected in series, and the matrix converter comprises: an a-phase bridge arm formed by a first bidirectional switch tube and a fourth bidirectional switch tube connected in series, a b-phase bridge arm formed by a third bidirectional switch tube and a sixth bidirectional switch tube connected in series, and a c-phase bridge arm formed by a fifth bidirectional switch tube and a second bidirectional switch tube connected in series; The four voltage vectors acting on the matrix converter in a positive half-cycle of a switch are the first zero vector V7 and the second zero vector V8, the first active vector V 1+ , the second active vector V 2+ ; The first zero vector V7 and the second zero vector V8 both correspond to the input current I0 of the matrix converter; the first active vector V 1+ , the second active vector V 2+ The input currents of the matrix converter are I1 and I2 respectively. After comparing the input currents of the motor windings, the action order of the four voltage vectors is determined to be V7->V 1+ ->V 2+ ->V8, at this time I2>I1>I0.

3. The voltage source type high frequency isolation matrix converter according to claim 1, characterized in that: The action time of the four voltage vectors is: Among them, T1 and T2 are the first active vector V 1+ , the second active vector V 2+ ; T0 is the action time of the first zero vector V7 and the second zero vector V8, m a and θ i are the modulation ratio and angle of space vector modulation, T s for one switching cycle.

4. The voltage source type high frequency isolation matrix converter according to claim 2, characterized in that: When the leakage inductance current is commutated, the battery voltage is mapped through a high-frequency isolation transformer and added to the leakage inductance, forcing the leakage inductance current to change direction.

5. A modulation system based on the voltage source high frequency isolation matrix converter according to any one of claims 1 to 4, characterized in that: include: The matrix converter module includes a matrix converter, wherein the input AC bus of the matrix converter is connected to the three-phase stator winding of the generator. A high-frequency isolation transformer module comprises a high-frequency isolation transformer, wherein the primary coil of the high-frequency isolation transformer is connected to the output end of the matrix converter, and A voltage source full-bridge converter module, comprising a voltage source full-bridge converter, wherein the input of the voltage source full-bridge converter is connected to the output end of the high-frequency isolation transformer, and the DC output is connected to the battery; The matrix converter, under the action of the voltage vector, sequentially undergoes the first zero vector action stage of the positive half cycle, the transformer leakage inductance current commutation stage, the voltage source full-bridge converter freewheeling stage, the first active vector action stage, the second active vector action stage, and the second zero vector action stage of the positive half cycle; The voltage source full-bridge converter comprises: a bridge arm formed by a first switch tube and a second switch tube connected in series, another bridge arm formed by a third switch tube and a fourth switch tube connected in series, and the matrix converter comprises: an a-phase bridge arm formed by a first bidirectional switch tube and a fourth bidirectional switch tube connected in series, a b-phase bridge arm formed by a third bidirectional switch tube and a sixth bidirectional switch tube connected in series, and a c-phase bridge arm formed by a fifth bidirectional switch tube and a second bidirectional switch tube connected in series; The four voltage vectors acting on the matrix converter in a positive half-cycle of a switch are the first zero vector V7 and the second zero vector V8, the first active vector V 1+ , the second active vector V 2+ ; The first zero vector V7 and the second zero vector V8 both correspond to the input current I0 of the matrix converter; the first active vector V 1+ , the second active vector V 2+ The input currents of the matrix converter are I1 and I2 respectively. After comparing the input currents of the motor windings, the action order of the four voltage vectors is determined to be V7->V 1+ ->V 2+ ->V8 At this time I2>I1>I0.

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