Semi-direct-drive direct-current type wind turbine generator based on multi-winding transformer and control method

Abstract

The invention belongs to the technical field of wind power generation, and particularly provides a semi-direct-drive direct-current type wind turbine generator based on a multi-winding transformer and a control method.The wind turbine generator comprises an impeller and the multi-winding transformer, and the impeller is connected with a wind driven generator through a gearbox; the output end of the wind driven generator is connected with a primary winding of the multi-winding transformer, and each secondary three-phase winding of the multi-winding transformer is connected with an electric energy conversion unit through a three-phase alternating-current circuit breaker; the anode output end of each electric energy conversion unit is used as a first electrical interface of the electric energy conversion unit after passing through a direct current circuit breaker; the cathode output end of each electric energy conversion unit passes through a direct current circuit breaker and then is used as a second electrical interface of the electric energy conversion unit; a bypass switch is connected between the first electrical interface and the second electrical interface of the same electric energy conversion unit; the output ends of the electric energy conversion units are connected in series. No circulating current problem exists, and the output voltage grade of the wind turbine generator is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of wind power generation, and in particular to a semi-direct-drive DC wind turbine set based on a multi-winding transformer and a control method thereof. Background Art

[0002] As one of the most promising power generation methods in renewable energy generation technology, wind power generation is currently developing towards large-capacity units and large-scale wind farms.

[0003] In order to increase the capacity of the wind turbine, it is necessary to improve the wind turbine power transmission and transformation technology used for power transmission and conversion in the wind turbine. In the traditional wind turbine power transmission and transformation technology for increasing the capacity of wind turbines, the capacity of the wind turbine can be increased by increasing the capacity of a single converter or connecting multiple ordinary converters in parallel.

[0004] However, in the traditional unit capacity improvement plan, when the unit voltage level remains unchanged, increasing the capacity of a single-machine converter means increasing the current level, which will place higher requirements on power cables and converter power devices; the use of ordinary converter parallel solutions increases the complexity of the unit's power transmission and transformation system, and at the same time, the circulating current problem caused by the voltage fluctuation between parallel units will also become more serious. Summary of the invention

[0005] In view of the fact that the parallel connection of converters in the existing unit capacity improvement scheme will increase the complexity of the unit's power transmission and transformation system and aggravate the problem of circulating current between parallel units, the present invention provides a semi-direct-drive DC wind turbine unit based on a multi-winding transformer and a control method.

[0006] In a first aspect, the technical solution of the present invention provides a semi-direct-drive DC wind turbine based on a multi-winding transformer, comprising an impeller and a multi-winding transformer, wherein the multi-winding transformer comprises one primary winding and n secondary three-phase windings; wherein n≥2 and n is an integer; The impeller is connected to a wind generator via a gear box; The output end of the wind turbine generator is connected to the primary winding of the multi-winding transformer, and each secondary three-phase winding of the multi-winding transformer is connected to an electric energy conversion unit through a three-phase AC circuit breaker; the positive output end of each electric energy conversion unit passes through a DC circuit breaker and serves as the first electrical interface of the electric energy conversion unit; the negative output end of each electric energy conversion unit passes through a DC circuit breaker and serves as the second electrical interface of the electric energy conversion unit; a bypass switch is connected between the first electrical interface and the second electrical interface of the same electric energy conversion unit; Among them, the first electrical interface of the first power conversion unit is the positive output terminal of the wind turbine set, and the second electrical interface of the nth power conversion unit is the negative output terminal of the wind turbine set; and the first electrical interface of the i-th power conversion unit is electrically connected to the second electrical interface of the i-1th power conversion unit; the second electrical interface of the i-th power conversion unit is electrically connected to the first electrical interface of the i+1th power conversion unit; 1<i<n and i is an integer.

[0007] As a preferred embodiment of the technical solution of the present invention, the electric energy conversion unit includes an AC / DC converter and a DC / DC converter; The secondary three-phase winding is connected to the input end of the AC / DC converter through a three-phase AC circuit breaker, the positive pole of the output end of the AC / DC converter is connected to the positive pole of the input end of the DC / DC converter; the negative pole of the output end of the AC / DC converter is connected to the negative pole of the input end of the DC / DC converter.

[0008] As a preferred embodiment of the technical solution of the present invention, a DC support capacitor and an energy consumption circuit connected in parallel are arranged between the AC / DC converter and the DC / DC converter; the positive electrode of the output end of the AC / DC converter is connected to the DC support capacitor, the energy consumption circuit and the positive electrode of the input end of the DC / DC converter; the negative electrode of the output end of the AC / DC converter is connected to the DC support capacitor, the energy consumption circuit and the negative electrode of the input end of the DC / DC converter.

[0009] As a preferred embodiment of the technical solution of the present invention, the energy consumption circuit includes an energy consumption resistor and a normally open switch tube connected in series; One end of the energy dissipation resistor is connected to the positive output terminal of the AC / DC converter, and the other end is connected to the normally closed end of the normally open switch tube. The normally open end of the normally open switch tube is connected to the negative output terminal of the AC / DC converter.

[0010] As a preferred embodiment of the technical solution of the present invention, the positive pole of the output end of the DC / DC converter serves as the first electrical interface of the DC / DC converter after passing through the DC circuit breaker, that is, the first electrical interface of the electric energy conversion unit; the negative pole of the output end of the DC / DC converter serves as the second electrical interface of the DC / DC converter after passing through the DC circuit breaker, that is, the second electrical interface of the electric energy conversion unit.

[0011] As a preferred embodiment of the technical solution of the present invention, the AC / DC converter is a three-phase bridge voltage source PWM rectifier; specifically, it includes three bridge arms, each bridge arm includes two commutation switch units, each commutation switch unit includes an IGBT and a diode, wherein the IGBT and the diode are connected in anti-parallel.

[0012] As a preferred embodiment of the technical solution of the present invention, the three bridge arms of the AC / DC converter are respectively an A-phase bridge arm, a B-phase bridge arm and a C-phase bridge arm; The upper end of each commutation switch unit is a first interface of the commutation switch unit, and the lower end of the commutation switch unit is a second interface of the commutation switch unit; The two commutation switch units of each bridge arm are respectively an upper bridge arm commutation switch unit and a lower bridge arm commutation switch unit; the first interface of the upper bridge arm commutation switch unit of the A phase bridge arm, the first interface of the upper bridge arm commutation switch unit of the B phase bridge arm, the first interface of the upper bridge arm commutation switch unit of the C phase bridge arm and the positive electrode of the DC support capacitor are connected; the second interface of the lower bridge arm commutation switch unit of the A phase bridge arm, the second interface of the lower bridge arm commutation switch unit of the B phase bridge arm, the second interface of the lower bridge arm commutation switch unit of the C phase bridge arm and the negative electrode of the DC support capacitor are connected; the second interface of the upper bridge arm commutation switch unit of the A phase bridge arm, the first interface of the lower bridge arm commutation switch unit of the A phase bridge arm and the A phase AC line are electrically connected; the second interface of the upper bridge arm commutation switch unit of the B phase bridge arm, the first interface of the lower bridge arm commutation switch unit of the B phase bridge arm and the B phase AC line are electrically connected; the second interface of the upper bridge arm commutation switch unit of the C phase bridge arm, the first interface of the lower bridge arm commutation switch unit of the C phase bridge arm and the C phase AC line are electrically connected.

[0013] As a preferred embodiment of the technical solution of the present invention, the DC / DC converter is a non-isolated DC / DC converter with an H-bridge structure; specifically, it includes two bridge arms, each bridge arm includes two commutation switch units, each commutation switch unit includes an IGBT and a diode, wherein the IGBT and the diode are connected in anti-parallel.

[0014] As a preferred embodiment of the technical solution of the present invention, the two bridge arms of the DC / DC converter are respectively a first bridge arm and a second bridge arm; The first interface of the upper bridge arm commutation switch unit of the first bridge arm, the first interface of the upper bridge arm commutation switch unit of the second bridge arm, and the positive electrode of the DC support capacitor are electrically connected; the second interface of the lower bridge arm commutation switch unit of the first bridge arm, the second interface of the lower bridge arm commutation switch unit of the second bridge arm, and the negative electrode of the DC support capacitor are electrically connected; the second interface of the upper bridge arm commutation switch unit of the first bridge arm, the first interface of the lower bridge arm commutation switch unit of the first bridge arm, and the positive electrode of the output end of the DC / DC converter are electrically connected; the second interface of the upper bridge arm commutation switch unit of the second bridge arm, the first interface of the lower bridge arm commutation switch unit of the second bridge arm, and the negative electrode of the output end of the DC / DC converter are electrically connected.

[0015] In a second aspect, a control method for a semi-direct-drive DC wind turbine generator set based on a multi-winding transformer is provided, wherein the wind turbine generator set comprises the semi-direct-drive DC wind turbine generator set based on a multi-winding transformer according to the first aspect, and the method comprises the following steps: Collect the three-phase voltage of the nth secondary winding of the multi-winding transformer and input it into the phase-locked loop to obtain the phase-locked angle; The three-phase current of the nth secondary winding of the multi-winding transformer is collected, and abc / dq transformation is performed simultaneously with the phase-locking angle to obtain the d-axis current component and the q-axis current component; The three-phase voltage of the nth secondary winding and the phase-locking angle are simultaneously transformed by abc / dq to obtain the d-axis voltage component and the q-axis voltage component; Collecting the active power of the wind turbine generator set and inputting the collected active power and the active power reference value of the wind turbine generator set into the active outer loop control system to obtain a d-axis current reference value; Inputting the d-axis current reference value, the d-axis current component and the q-axis current component into the current inner loop control system to obtain the d-axis voltage reference value and the q-axis voltage reference value; Perform dq / abc transformation on the d-axis voltage reference value and the q-axis voltage reference value and the phase-locking angle to obtain a three-phase voltage reference value; The three-phase voltage reference values ​​are compared with the carrier respectively, and PWM modulation is performed to obtain the on-off signals of the IGBTs in the three upper bridge arms in the AC / DC converter. The on-off signals of the IGBTs in the three upper bridge arms are inverted to obtain the on-off signals of the IGBTs in the corresponding three lower bridge arms in the AC / DC converter, thereby realizing the control of the AC / DC converter; After collecting the voltage of the DC support capacitor and comparing the collected voltage of the DC support capacitor with the DC support capacitor reference voltage, the voltage is input into the PI controller for PI calculation to obtain the first modulation ratio and the difference between 1 and the first modulation ratio, i.e., the second modulation ratio; The first modulation ratio and the second modulation ratio are compared with the carrier respectively, and PWM modulation is performed to obtain the on-off signals of the IGBTs in the two upper bridge arms in the DC / DC converter. The on-off signals of the IGBTs in the two upper bridge arms are inverted to obtain the on-off signals of the IGBTs in the corresponding two lower bridge arms in the DC / DC converter, thereby realizing the control of the AC / DC converter.

[0016] It can be seen from the above technical scheme that the present invention has the following advantages: (1) a multi-winding transformer is adopted, that is, the transformer includes a primary winding and at least two secondary windings, ① which can convert the single AC power output by the wind turbine into multiple AC power, reduce the current value, and thus reduce the requirements for power cables and power devices; ② the number of loops for power conversion and transmission is increased, and the redundancy capacity of the wind turbine output conversion power is improved. When a power conversion unit (the power conversion unit is a combination of an AC / DC converter and a DC / DC converter) fails, it is only necessary to disconnect the circuit breakers on both sides of the power conversion unit to achieve fault isolation, and the non-faulty power conversion unit can still operate normally; ③ the number of secondary windings can be flexibly configured according to the unit capacity, which is easier to increase the capacity of the wind turbine; ④ installed at the outlet of the wind turbine, it can play a role in electrical isolation and reduce the insulation requirements for the wind turbine.

[0017] (2) The advantages of using multiple power conversion units are: ① It is equivalent to splitting the large-capacity power conversion link in the traditional scheme into multiple small-capacity power conversion links, which reduces the capacity requirements and design difficulty of the power conversion link; ② The outlets of multiple power conversion units are connected in series. Compared with the traditional parallel converter scheme, there is no circulation problem; ③ The outlets of multiple power conversion units are connected in series, which can improve the output voltage level of the wind turbine. The output voltage of the wind turbine is the sum of the outlet voltages of all power conversion units. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 It is a semi-direct-drive DC wind turbine topology based on a multi-winding transformer.

[0020] Figure 2 It is an AC / DC converter topology.

[0021] Figure 3 It is a DC / DC converter topology.

[0022] Figure 4 It is a diagram showing the control strategy of a semi-direct-drive DC wind turbine based on a multi-winding transformer.

[0023] Figure 5 It is an extended topology diagram of a semi-direct-drive DC wind turbine based on a multi-winding transformer.

[0024] In the figure, 1-impeller, 2-gearbox, 3-wind turbine, 4-multi-winding transformer, 5-AC circuit breaker, 6-AC / DC converter, 7-DC support capacitor, 8-energy consumption circuit, 9-DC / DC converter, 10-DC circuit breaker, 11-bypass switch, 12-active outer loop control system, 13-current inner loop control system, 61-A phase bridge arm, 62-commutation switch unit of AC / DC converter, 91-first bridge arm, 92-circulating current switch unit of DC / DC converter. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0026] like Figure 1 As shown, an embodiment of the present invention provides a semi-direct drive DC wind turbine based on a multi-winding transformer, comprising an impeller 1 and a multi-winding transformer 4, wherein the multi-winding transformer 4 comprises a primary winding and n secondary three-phase windings; wherein n≥2 and n is an integer; The impeller 1 is connected to a wind generator 3 via a gear box 2; The output end of the wind turbine 3 is connected to the primary winding of the multi-winding transformer 4, and each secondary three-phase winding is connected to an electric energy conversion unit through an AC circuit breaker 5; the positive output end of each electric energy conversion unit passes through a DC circuit breaker and serves as the first electrical interface of the electric energy conversion unit; the negative output end of each electric energy conversion unit passes through a DC circuit breaker and serves as the second electrical interface of the electric energy conversion unit; a bypass switch is connected between the first electrical interface and the second electrical interface of the same electric energy conversion unit; Among them, the first electrical interface of the first power conversion unit is the positive output terminal of the wind turbine set, and the second electrical interface of the nth power conversion unit is the negative output terminal of the wind turbine set; and the first electrical interface of the i-th power conversion unit is electrically connected to the second electrical interface of the i-1th power conversion unit; the second electrical interface of the i-th power conversion unit is electrically connected to the first electrical interface of the i+1th power conversion unit; 1<i<n and i is an integer.

[0027] The electric energy conversion unit includes an AC / DC converter 6 and a DC / DC converter 9; The secondary three-phase winding is connected to the input end of the AC / DC converter through a three-phase AC circuit breaker, the positive pole of the output end of the AC / DC converter is connected to the positive pole of the DC support capacitor 7, the energy consumption circuit 8 and the input end of the DC / DC converter 9; the negative pole of the output end of the AC / DC converter 6 is connected to the negative pole of the DC support capacitor, the energy consumption circuit and the input end of the DC / DC converter.

[0028] The impeller absorbs wind energy and converts it into mechanical energy; the gearbox converts the low-speed mechanical energy of the impeller into medium- and high-speed mechanical energy and then transmits it to the wind turbine; the wind turbine converts the mechanical energy transmitted by the gearbox into AC power; the multi-winding transformer converts the AC power output by the wind turbine into multiple AC powers; the AC circuit breaker can control the on and off of the AC power between the secondary winding of the multi-winding transformer and the AC / DC converter; the AC / DC converter converts the AC power into DC power; the DC support capacitor maintains the voltage on the DC side of the AC / DC converter to a given value; the energy consumption circuit can discharge the electric energy, suppress DC overvoltage, and protect the converter; the DC / DC converter converts DC power of one voltage level into DC power of another voltage level; the DC circuit breaker 10 can control the on and off of the DC power output by the DC / DC converter; the bypass switch 11 can bypass the power conversion unit after the fault.

[0029] The multi-winding transformer includes one primary winding and n (n≥2 and n is an integer) secondary windings, and each secondary winding is divided into three phases of Ai, Bi, and Ci (i≥1 and i is an integer); The output end of the wind turbine generator is electrically connected to the primary winding of the multi-winding transformer; each set of secondary three-phase windings of the multi-winding transformer is electrically connected to the input end of the AC / DC converter through three-phase AC circuit breakers KAi, KBi, KCi; The AC / DC converter is a three-phase bridge voltage source PWM rectifier; The positive electrode of the output end of the AC / DC converter is electrically connected to the DC support capacitor, the energy consumption circuit and the positive electrode of the input end of the DC / DC converter; the negative electrode of the output end of the AC / DC converter is electrically connected to the DC support capacitor, the energy consumption circuit and the negative electrode of the input end of the DC / DC converter; The energy consumption circuit consists of energy consumption resistor Rc and normally open switch tube K R constitute; The DC / DC converter is a non-isolated DC / DC converter with an H-bridge structure; The positive pole of the output end of the DC / DC converter passes through the DC circuit breaker Ki1 and serves as the first electrical interface of the DC / DC converter; the negative pole of the output end of the DC / DC converter passes through the DC circuit breaker Ki2 and serves as the second electrical interface of the DC / DC converter; The output voltage between the first electrical interface and the second electrical interface of the i-th DC / DC converter is U dci ; A bypass switch is connected between the first electrical interface and the second electrical interface of the DC / DC converter; The first electrical interface of the first DC / DC converter serves as the positive output terminal of the wind turbine generator set; the second electrical interface of the nth DC / DC converter serves as the negative output terminal of the wind turbine generator set; the first electrical interface of the i-th (1<i<n and i is an integer) DC / DC converter is electrically connected to the second electrical interface of the (i-1)th DC / DC converter; the second electrical interface of the i-th DC / DC converter is electrically connected to the first electrical interface of the (i+1)th DC / DC converter; Among them, the voltage between the positive and negative output terminals of the wind turbine is ,and ; When the i-th AC / DC converter or DC / DC converter fails, the AC circuit breakers KAi, KBi, KCi and DC circuit breakers Ki1, Ki2 corresponding to the i-th secondary winding of the transformer can be disconnected, and the bypass switch Si can be closed to cut off the faulty AC / DC converter and DC / DC converter and ensure the normal operation of the unit.

[0030] The topology of AC / DC converter is as follows Figure 2 As shown, the AC / DC converter adopts a three-phase bridge voltage source PWM rectifier, which includes three bridge arms, each bridge arm is composed of two commutation switch units, and each commutation switch unit 62 of the AC / DC converter is composed of an IGBT and a diode, wherein the IGBT and the diode are connected in anti-parallel. The three bridge arms of the AC / DC converter are the A-phase bridge arm 61, the B-phase bridge arm and the C-phase bridge arm; T A1 With diode D A1 The upper arm commutation switch unit constituting the A phase bridge arm, T A2 With diode D A2 The lower bridge arm commutation switch unit constituting the A phase bridge arm; T B1 With diode D B1 The upper arm commutation switch unit constituting the B phase bridge arm, T B2 With diode D B2 The lower arm commutation switch unit constituting the B phase bridge arm; T C1 With diode D C1 The upper arm commutation switch unit constituting the C phase bridge arm, T C2 With diode D C2 A lower bridge arm commutation switch unit constituting a C-phase bridge arm; The upper end of the commutation switch unit is the first interface of the commutation switch unit, and the lower end of the commutation switch unit is the second interface of the commutation switch unit; the first interface of the upper bridge arm commutation switch unit of the A phase bridge arm, the first interface of the upper bridge arm commutation switch unit of the B phase bridge arm, the first interface of the upper bridge arm commutation switch unit of the C phase bridge arm, and the positive electrode of the capacitor are electrically connected; the second interface of the lower bridge arm commutation switch unit of the A phase bridge arm, the second interface of the lower bridge arm commutation switch unit of the B phase bridge arm, and the first interface of the lower bridge arm commutation switch unit of the C phase bridge arm are electrically connected. The second interface and the negative pole of the capacitor are electrically connected; the second interface of the upper bridge arm commutation switch unit of the A phase bridge arm, the first interface of the lower bridge arm commutation switch unit of the A phase bridge arm and the A phase AC line are electrically connected; the second interface of the upper bridge arm commutation switch unit of the B phase bridge arm, the first interface of the lower bridge arm commutation switch unit of the B phase bridge arm and the B phase AC line are electrically connected; the second interface of the upper bridge arm commutation switch unit of the C phase bridge arm, the first interface of the lower bridge arm commutation switch unit of the C phase bridge arm and the C phase AC line are electrically connected.

[0031] The topology of the DC / DC converter is as follows Figure 3 As shown, the DC / DC converter is a non-isolated DC / DC converter with an H-bridge structure. The converter is mainly composed of two bridge arms and a capacitor C. Each bridge arm includes two circulating current switch units. Figure 3 The example shown in FIG. 1 shows a first bridge arm 91 and a circulating current switch unit 92 of a DC / DC converter; T 11 With diode D 11 The upper bridge arm commutation switch unit constituting the first bridge arm, T 12 With diode D 12 A lower bridge arm commutation switch unit constituting the first bridge arm; T 21 With diode D 21 The upper bridge arm commutation switch unit constituting the second bridge arm, T 22 With diode D 22 The lower bridge arm commutation switch unit constitutes the second bridge arm; the first interface of the upper bridge arm commutation switch unit of the first bridge arm, the first interface of the upper bridge arm commutation switch unit of the second bridge arm, and the positive electrode of the capacitor are electrically connected; the second interface of the lower bridge arm commutation switch unit of the first bridge arm, the second interface of the lower bridge arm commutation switch unit of the second bridge arm, and the negative electrode of the capacitor are electrically connected; the second interface of the upper bridge arm commutation switch unit of the first bridge arm, the first interface of the lower bridge arm commutation switch unit of the second bridge arm, and the positive electrode of the output end of the DC / DC converter are electrically connected; the second interface of the upper bridge arm commutation switch unit of the second bridge arm, the first interface of the lower bridge arm commutation switch unit of the second bridge arm, and the negative electrode of the output end of the DC / DC converter are electrically connected; The specific control process is as follows: First, the three-phase voltage e of the nth secondary winding of the multi-winding transformer is collected. wt,a 、e wt,b 、ewt,c , and input it into the phase-locked loop PLL to obtain the phase-locked angle θ PLL ; Collect the three-phase current i of the nth secondary winding of the multi-winding transformer wt,a 、i wt,b 、i wt,c , and with θ PLL At the same time, abc / dq transformation is performed to obtain the dq axis current component i wt,d ,i wt,q ; e wt,a 、e wt,b 、e wt,c With θ PLL At the same time, abc / dq transformation is performed to obtain the dq axis current component e wt,d , e wt,q ; The collected active power p s , and the wind turbine active power reference value p s-ref Input the active outer loop control system to obtain the d-axis current reference value i wt,d-ref ;change i wt,d-ref 、i wt,d-ref =0, i wt,d ,i wt,q Input current inner loop control system to get dq axis voltage reference value v wt,q 、v wt,d ; v wt,q 、v wt,d With θ PLL Perform dq / abc transformation to obtain the three-phase current reference value u ga-ref 、u gb-ref 、u gc-ref ; will u ga-ref 、u gb-ref 、u gc-ref PWM modulation is performed to obtain the on-off signal of the IGBT in the AC / DC converter to achieve control of the AC / DC converter.

[0032] The collected DC support capacitor voltage u c,dc With the DC support capacitor reference signal u c,dc-ref After comparison, PI calculation is performed to obtain the modulation ratio D i ; Compare 1 with Di to get the second modulation ratio (1-D i ); D i , (1-D i ) performs PWM modulation to obtain the on-off signal of the IGBT in the DC / DC converter and realize the control of the DC / DC converter.

[0033] like Figure 4As shown, an embodiment of the present invention provides a control method for a semi-direct-drive DC wind turbine generator set based on a multi-winding transformer, wherein the wind turbine generator set includes the semi-direct-drive DC wind turbine generator set based on a multi-winding transformer described in the above embodiment, and the method includes the following steps: Collect the three-phase voltage of the nth secondary winding of the multi-winding transformer and input it into the phase-locked loop to obtain the phase-locked angle; The three-phase current of the nth secondary winding of the multi-winding transformer is collected, and abc / dq transformation is performed simultaneously with the phase-locking angle to obtain the d-axis current component and the q-axis current component; The three-phase voltage of the nth secondary winding and the phase-locking angle are simultaneously transformed by abc / dq to obtain the d-axis voltage component and the q-axis voltage component; Collecting the active power of the wind turbine generator set and inputting the collected active power and the active power reference value of the wind turbine generator set into the active outer loop control system 12 to obtain the d-axis current reference value; Inputting the d-axis current reference value, the d-axis current component and the q-axis current component into the current inner loop control system 13, obtaining the d-axis voltage reference value and the q-axis voltage reference value; Perform dq / abc transformation on the d-axis voltage reference value and the q-axis voltage reference value and the phase-locking angle to obtain a three-phase voltage reference value; The three-phase voltage reference values ​​are compared with the carrier respectively, and PWM modulation is performed to obtain the on-off signals of the IGBTs in the three upper bridge arms in the AC / DC converter. The on-off signals of the IGBTs in the three upper bridge arms are inverted to obtain the on-off signals of the IGBTs in the corresponding three lower bridge arms in the AC / DC converter, thereby realizing the control of the AC / DC converter; After collecting the voltage of the DC support capacitor and comparing the collected voltage of the DC support capacitor with the DC support capacitor reference voltage, the voltage is input into the PI controller for PI calculation to obtain the first modulation ratio and the difference between 1 and the first modulation ratio, i.e., the second modulation ratio; The first modulation ratio and the second modulation ratio are compared with the carrier respectively, and PWM modulation is performed to obtain the on-off signals of the IGBTs in the two upper bridge arms in the DC / DC converter. The on-off signals of the IGBTs in the two upper bridge arms are inverted to obtain the on-off signals of the IGBTs in the corresponding two lower bridge arms in the DC / DC converter, thereby realizing the control of the AC / DC converter.

[0034] The embodiment of the present invention also provides a semi-direct drive DC type wind turbine group extension topology based on a multi-winding transformer. Figure 5 As shown, the AC / DC converter in this topology can be used in addition to Figure 3 Other converter structures that can realize AC / DC power conversion besides the three-phase bridge voltage source PWM rectifier shown in the figure; the DC / DC converter in this topology can adopt other than Figure 4For other non-isolated converter structures that can realize DC / DC power conversion besides the non-isolated DC / DC converter of the H-bridge structure shown, when using AC / DC converters and DC / DC converters of different structures, corresponding control strategies need to be used.

[0035] It should be understood that the order of execution of the steps in the above embodiment does not necessarily mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0036] Although the present invention has been described in detail with reference to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Any person of ordinary skill in the art may easily think of changes or substitutions within the technical scope disclosed by the present invention, and these shall be within the scope of protection of the present invention.

Claims

1. A semi-direct drive DC wind turbine based on a multi-winding transformer, characterized in that: It includes an impeller and a multi-winding transformer, wherein the multi-winding transformer includes one primary winding and n secondary three-phase windings; wherein n≥2 and n is an integer; The impeller is connected to a wind generator via a gear box; The output end of the wind turbine generator is connected to the primary winding of the multi-winding transformer, and each secondary three-phase winding of the multi-winding transformer is connected to an electric energy conversion unit through a three-phase AC circuit breaker; the positive output end of each electric energy conversion unit passes through a DC circuit breaker and serves as the first electrical interface of the electric energy conversion unit; the negative output end of each electric energy conversion unit passes through a DC circuit breaker and serves as the second electrical interface of the electric energy conversion unit; a bypass switch is connected between the first electrical interface and the second electrical interface of the same electric energy conversion unit; Among them, the first electrical interface of the first power conversion unit is the positive output terminal of the wind turbine set, and the second electrical interface of the nth power conversion unit is the negative output terminal of the wind turbine set; and the first electrical interface of the i-th power conversion unit is electrically connected to the second electrical interface of the i-1th power conversion unit; the second electrical interface of the i-th power conversion unit is electrically connected to the first electrical interface of the i+1th power conversion unit; 1<i<n and i is an integer.

2. The semi-direct drive DC wind turbine generator system based on a multi-winding transformer according to claim 1, characterized in that: The electric energy conversion unit includes an AC / DC converter and a DC / DC converter; The secondary three-phase winding of the multi-winding transformer is connected to the input end of the AC / DC converter through a three-phase AC circuit breaker, the positive pole of the output end of the AC / DC converter is connected to the positive pole of the input end of the DC / DC converter; the negative pole of the output end of the AC / DC converter is connected to the negative pole of the input end of the DC / DC converter.

3. The semi-direct drive DC wind turbine generator system based on a multi-winding transformer according to claim 2 is characterized in that: A DC support capacitor and an energy consumption circuit connected in parallel are arranged between the AC / DC converter and the DC / DC converter; the positive pole of the output end of the AC / DC converter is connected to the DC support capacitor, the energy consumption circuit and the positive pole of the input end of the DC / DC converter; the negative pole of the output end of the AC / DC converter is connected to the DC support capacitor, the energy consumption circuit and the negative pole of the input end of the DC / DC converter.

4. The semi-direct drive DC wind turbine generator system based on a multi-winding transformer according to claim 3 is characterized in that: The energy consumption circuit includes an energy consumption resistor and a normally open switch tube connected in series; One end of the energy dissipation resistor is connected to the positive output terminal of the AC / DC converter, the other end of the energy dissipation resistor is connected to the normally closed end of the normally open switch tube, and the normally open end of the normally open switch tube is connected to the negative output terminal of the AC / DC converter.

5. The semi-direct drive DC wind turbine generator system based on a multi-winding transformer according to claim 4 is characterized in that: The positive pole of the output end of the DC / DC converter passes through the DC circuit breaker and serves as the first electrical interface of the DC / DC converter, that is, the first electrical interface of the electric energy conversion unit; the negative pole of the output end of the DC / DC converter passes through the DC circuit breaker and serves as the second electrical interface of the DC / DC converter, that is, the second electrical interface of the electric energy conversion unit.

6. The semi-direct drive DC wind turbine generator system based on a multi-winding transformer according to claim 5, characterized in that: The AC / DC converter is a three-phase bridge voltage source PWM rectifier; specifically, it includes three bridge arms, each bridge arm includes two commutation switch units, each commutation switch unit includes an IGBT and a diode, wherein the IGBT and the diode are connected in anti-parallel.

7. The semi-direct drive DC wind turbine generator system based on a multi-winding transformer according to claim 6, characterized in that: The three bridge arms of the AC / DC converter are the A-phase bridge arm, the B-phase bridge arm, and the C-phase bridge arm; The upper end of each commutation switch unit is a first interface of the commutation switch unit, and the lower end of the commutation switch unit is a second interface of the commutation switch unit; The two commutation switch units of each bridge arm are respectively an upper bridge arm commutation switch unit and a lower bridge arm commutation switch unit; the first interface of the upper bridge arm commutation switch unit of the A phase bridge arm, the first interface of the upper bridge arm commutation switch unit of the B phase bridge arm, the first interface of the upper bridge arm commutation switch unit of the C phase bridge arm and the positive electrode of the DC support capacitor are connected; the second interface of the lower bridge arm commutation switch unit of the A phase bridge arm, the second interface of the lower bridge arm commutation switch unit of the B phase bridge arm, the second interface of the lower bridge arm commutation switch unit of the C phase bridge arm and the negative electrode of the DC support capacitor are connected; the second interface of the upper bridge arm commutation switch unit of the A phase bridge arm, the first interface of the lower bridge arm commutation switch unit of the A phase bridge arm and the A phase AC line are electrically connected; the second interface of the upper bridge arm commutation switch unit of the B phase bridge arm, the first interface of the lower bridge arm commutation switch unit of the B phase bridge arm and the B phase AC line are electrically connected; the second interface of the upper bridge arm commutation switch unit of the C phase bridge arm, the first interface of the lower bridge arm commutation switch unit of the C phase bridge arm and the C phase AC line are electrically connected.

8. The semi-direct drive DC wind turbine generator system based on a multi-winding transformer according to claim 7, characterized in that: The DC / DC converter is a non-isolated DC / DC converter with an H-bridge structure; specifically, it includes two bridge arms, each bridge arm includes two commutation switch units, each commutation switch unit includes an IGBT and a diode, wherein the IGBT and the diode are connected in anti-parallel.

9. The semi-direct drive DC wind turbine generator system based on a multi-winding transformer according to claim 8, characterized in that: The two bridge arms of the DC / DC converter are respectively a first bridge arm and a second bridge arm; The first interface of the upper bridge arm commutation switch unit of the first bridge arm, the first interface of the upper bridge arm commutation switch unit of the second bridge arm, and the positive electrode of the DC support capacitor are electrically connected; the second interface of the lower bridge arm commutation switch unit of the first bridge arm, the second interface of the lower bridge arm commutation switch unit of the second bridge arm, and the negative electrode of the DC support capacitor are electrically connected; the second interface of the upper bridge arm commutation switch unit of the first bridge arm, the first interface of the lower bridge arm commutation switch unit of the first bridge arm, and the positive electrode of the output end of the DC / DC converter are electrically connected; the second interface of the upper bridge arm commutation switch unit of the second bridge arm, the first interface of the lower bridge arm commutation switch unit of the second bridge arm, and the negative electrode of the output end of the DC / DC converter are electrically connected.

10. A control method for a semi-direct drive DC wind turbine generator system based on a multi-winding transformer according to any one of claims 2 to 9, characterized in that: The steps include: Collect the three-phase voltage of the nth secondary winding of the multi-winding transformer and input it into the phase-locked loop to obtain the phase-locked angle; The three-phase current of the nth secondary winding of the multi-winding transformer is collected, and abc / dq transformation is performed simultaneously with the phase-locking angle to obtain the d-axis current component and the q-axis current component; The three-phase voltage of the nth secondary winding and the phase-locking angle are simultaneously transformed by abc / dq to obtain the d-axis voltage component and the q-axis voltage component; Collecting the active power of the wind turbine generator set and inputting the collected active power and the active power reference value of the wind turbine generator set into the active outer loop control system to obtain a d-axis current reference value; Inputting the d-axis current reference value, the d-axis current component and the q-axis current component into the current inner loop control system to obtain the d-axis voltage reference value and the q-axis voltage reference value; Perform dq / abc transformation on the d-axis voltage reference value and the q-axis voltage reference value and the phase-locking angle to obtain a three-phase voltage reference value; The three-phase voltage reference values ​​are compared with the carrier respectively, and PWM modulation is performed to obtain the on-off signals of the IGBTs in the three upper bridge arms in the AC / DC converter. The on-off signals of the IGBTs in the three upper bridge arms are inverted to obtain the on-off signals of the IGBTs in the corresponding three lower bridge arms in the AC / DC converter, thereby realizing the control of the AC / DC converter; After collecting the voltage of the DC support capacitor and comparing the collected voltage of the DC support capacitor with the DC support capacitor reference voltage, the voltage is input into the PI controller for PI calculation to obtain the first modulation ratio and the difference between 1 and the first modulation ratio, i.e., the second modulation ratio; The first modulation ratio and the second modulation ratio are compared with the carrier respectively, and PWM modulation is performed to obtain the on-off signals of the IGBTs in the two upper bridge arms in the DC / DC converter. The on-off signals of the IGBTs in the two upper bridge arms are inverted to obtain the on-off signals of the IGBTs in the corresponding two lower bridge arms in the DC / DC converter, thereby realizing the control of the AC / DC converter.

Images