Medium voltage direct-hung DC power supply

Abstract

The medium voltage direct-hung DC power supply belongs to the field of power electronics. The power supply includes two converters and an output filter capacitor C o The two converters are converter No. 1 and converter No. 2. Converter No. 1 and converter No. 2 use the same circuit topology and control method. Each converter consists of a medium voltage rectifier circuit, a medium voltage inverter circuit, a single-phase transformer, a low voltage rectifier circuit and an output filter capacitor C. o1 Composition. The power supply uses a diode valve group and a thyristor valve group to bear current and transmit power, and adjusts the output voltage and transmission power by controlling the voltage at both ends of the bridge arm in series with the submodule; the structure of two converter outputs in parallel significantly improves the transmission power of the power supply, and at the same time, the medium voltage side is directly connected to the power grid, with a simple structure and high ease of use. The present invention has the advantages of a small number of devices, high power density, low cost, a wide output voltage range, and fault current limiting capability, and is also suitable for data centers, electric vehicle charging stations, hydrogen production and other fields.

Description

Technical Field

[0001] The present invention belongs to the field of power electronics, and in particular relates to a medium-voltage AC power grid directly connected DC power supply, which can be applied to data centers, charging stations, electrolytic hydrogen production and other fields. Background Art

[0002] With the development of carbon peak and carbon neutrality strategies, data centers, electric vehicle charging stations, hydrogen production and other fields have developed rapidly, and power consumption has gradually become a major source of electricity consumption in my country. The power supply form of these loads all needs to be drawn from the medium-voltage AC power grid, and after power conversion, a low-voltage DC of about hundreds of volts is obtained to supply power to the loads, and the power capacity usually reaches above megawatts.

[0003] Traditional power supply solutions mostly use industrial frequency transformers to step down the voltage, which is then rectified by an AC / DC converter to obtain a DC voltage. However, there are problems such as a narrow DC voltage regulation range, large size and weight of the industrial frequency transformer, large footprint, and large standby and no-load losses.

[0004] Publication number: CN108778823A, titled "Electric Vehicle Charging Station with Medium Voltage Input", proposed a solution based on a multi-winding phase-shifting transformer, but the structure and process of the multi-winding phase-shifting transformer are more complicated. Publication number: CN114465267A, titled "A Charging Station System with an Integrated Photo-Storage and Charging Energy Router", proposed a circuit topology based on a series of H-bridge circuits and a resonant DC / DC converter input parallel output series design, but there are a large number of devices and power modules. Due to the insulation distance limitation between multiple modules, the volume and weight of the whole equipment are large. In addition, the insulation cost of the medium-frequency transformer in the DC / DC converter is high and the life is short. The aforementioned technical economy, volume, and reliability issues limit the application of this solution.

[0005] In summary, the medium-voltage direct-mounted power supply in data centers, electric vehicle charging stations, hydrogen production and other fields needs to meet technical requirements such as high power, wide output voltage range, fault current limiting, low cost, high power density and high reliability. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention proposes a medium voltage direct-hung DC power supply, which has the characteristics of a small number of components, high power density, low cost, a wide output voltage range and fault current limiting capability.

[0007] The technical solution adopted by the present invention is:

[0008] Medium voltage direct-hung DC power supply, which is connected to a three-phase AC grid, with phases A, B and C. The power supply includes two converters and an output filter capacitor C o, the two converters are converter No. 1 and converter No. 2, and the output filter capacitor C o The two ends are low-voltage DC output ends of the power supply, and the low-voltage DC output ends include a low-voltage DC positive output end (UL+) and a low-voltage DC negative output end (UL-);

[0009] Converter 1 and converter 2 use the same circuit topology and control method. Each converter consists of a medium voltage rectifier circuit, a medium voltage inverter circuit, a single-phase transformer, a low voltage rectifier circuit and an output filter capacitor C. o1 composition;

[0010] The medium voltage rectifier circuit comprises a diode valve group D M1 , diode valve group D M2 , diode valve group D M3 and diode valve group D M4 ;

[0011] The medium voltage inverter circuit comprises a thyristor valve group T1, a thyristor valve group T2, a bridge arm reactor L1, a bridge arm reactor L2, a submodule series bridge arm S1 and a submodule series bridge arm S2;

[0012] The single-phase transformer TR comprises a primary side of the transformer, a secondary side of the transformer and a leakage inductance L k1 , wherein the primary side of the transformer includes two terminals, namely, a primary side first terminal (TR11) and a primary side second terminal (TR12), the secondary side of the transformer includes two terminals, namely, a secondary side first terminal (TR21) and a secondary side second terminal (TR22), and the primary side first terminal (TR11) and the secondary side first terminal (TR21) are the same-name terminals; the transformation ratio of the transformer is n:1; n is a real number;

[0013] The low voltage rectifier circuit comprises: a diode D L1 , diode D L2 , diode D L3 、Diode D L4 and output filter capacitor C o1 ;

[0014] In the medium voltage rectifier circuit, the diode valve group D M1 The anode and diode valve group D M3 The cathode of the diode valve group D is connected to form the first bridge arm of the medium voltage rectifier circuit; M2 The anode and diode valve group D M4 The cathode of the medium voltage rectifier circuit is connected to form the second bridge arm;

[0015] In the medium voltage inverter circuit, the anode of the thyristor valve group T1 is connected to the first terminal of the bridge arm reactor L1, and the cathode of the thyristor valve group T1 is connected to the positive electrode of the submodule series bridge arm S1, forming the first bridge arm of the medium voltage inverter circuit; the anode of the thyristor valve group T2 is connected to the first terminal of the bridge arm reactor L2, and the cathode of the thyristor valve group T2 is connected to the positive electrode of the submodule series bridge arm S2, forming the second bridge arm of the medium voltage inverter circuit;

[0016] The second terminal of the bridge arm inductor L1, the second terminal of the bridge arm inductor L2, the diode valve group D M1 Cathode, diode valve group D M2 The cathode of is connected;

[0017] The submodule is connected in series with the negative electrode of the bridge arm S1, the negative electrode of the bridge arm S2, and the diode valve group D M3 Anode, diode valve group D M4 The anode of is connected;

[0018] The single-phase transformer TR has a first terminal (TR11) on the primary side connected to a leakage inductor L k1 One end, leakage inductance L k1 The other end is connected to the cathode of the thyristor valve group T1 and the positive electrode of the submodule series bridge arm S1 at the same time; the second terminal (TR12) of the primary side of the single-phase transformer TR is connected to the cathode of the thyristor valve group T2 and the positive electrode of the submodule series bridge arm S2 at the same time;

[0019] In the low voltage rectifier circuit, the diode D L1 The anode and diode D L3 The cathode of the diode D L2 The anode and diode D L4 The cathode forms the second bridge arm of the low voltage rectifier circuit;

[0020] The secondary side first terminal (TR21) of the single-phase transformer TR is connected to a diode D L1 The anode and diode D L3 The cathode of the single-phase transformer TR is connected to the second terminal (TR21) of the secondary side of the diode D L2 The anode and diode D L4 The cathode;

[0021] Output filter capacitor C o1 The two ends of the diode D constitute the low voltage DC output end of the first converter; L1 The cathode of diode D L2 The cathode of the output filter capacitor C o1 The positive poles of the diodes DL3 The anode of diode D L4 Anode, output filter capacitor C o1 The negative poles are connected together to the low voltage DC negative output terminal (UL-);

[0022] Diode valve group D M1 With diode valve group D M3 The connection point is used as a medium voltage AC input terminal of the power supply, and the diode valve group D M2 With diode valve group D M4 The connection point of is used as another medium voltage AC input terminal of the power supply;

[0023] The input end of the first converter includes two terminals, namely the first terminal N i1 、Second terminal N i2 The input end of the second converter includes two terminals, namely the third terminal N i3 、The fourth terminal N i4 ; The four terminals together constitute a medium voltage AC input terminal; the medium voltage AC input terminal is connected to a three-phase AC grid, the first terminal N i1 Connect the A-phase terminal of the three-phase AC power grid, the second terminal N i2 Connect to the B-phase terminal of the three-phase AC power grid; the third terminal N i3 Connect the A-phase terminal of the three-phase AC power grid, the fourth terminal N i4 Connect to the C-phase terminal of the three-phase AC power grid;

[0024] The output end of the first converter includes two terminals, namely the first terminal N o1 、Second terminal N o2 The output end of the second converter includes two terminals, namely the third terminal N o3 、The fourth terminal N o4 ; The four terminals together constitute a low voltage DC output terminal; Among them, the first terminal N o1 and the third terminal N o3 Connect together, the second terminal N o2 and the fourth terminal N o4 Connected together, that is, the output ends of converter No. 1 and converter No. 2 are connected in parallel; two output filter capacitors C o1 The output filter capacitor C o .

[0025] Preferably, the diode valve group D in the medium voltage rectifier circuit M1 , diode valve group D M2 , diode valve group D M3 And diode valve group D M4Each of them can also be composed of n diodes connected in series, and the diode valve group in the medium voltage rectifier circuit can also be composed of diodes, thyristors, insulated gate bipolar transistors IGBT, MOSFET, injection enhanced gate transistors IEGT, integrated gate commutation thyristor IGCT devices connected in series and in parallel;

[0026] The thyristor valve group T1 and the thyristor valve group T2 in the medium voltage inverter circuit can also be composed of n thyristors connected in series, and the thyristor valve group in the medium voltage inverter circuit can also be composed of thyristors, insulated gate bipolar transistors IGBT, MOSFET, injection enhanced gate transistors IEGT, and integrated gate-level commutation thyristor IGCT devices connected in series and in parallel;

[0027] The submodule series bridge arm S1 and the submodule series bridge arm S2 in the medium voltage inverter circuit are both composed of n full bridges connected in series, and the submodule series bridge arm in the medium voltage inverter circuit can also be composed of half-bridge and full-bridge hybrid submodules or other feasible submodule structures connected in series and parallel;

[0028] The diode D in the low voltage rectifier circuit L1 、Diode D L2 、Diode D L3 And diode D L4 It can also be composed of diodes, thyristors, insulated gate bipolar transistors IGBTs, MOSFETs, injection enhanced gate transistors IEGTs, and integrated gate-level commutation thyristors IGCTs connected in series and in parallel;

[0029] Wherein, n is a real number.

[0030] Preferably, the control timing of the No. 1 converter and the No. 2 converter in the medium voltage direct-hung DC power supply differs by a quarter of a control cycle;

[0031] Taking converter No. 1 as an example, the diode valve group D in the medium voltage rectifier circuit M1 , diode valve group D M2 , diode valve group D M3 And diode valve group D M4 The medium voltage AC input voltage is rectified into a DC voltage, and the thyristor valve group T1 and the thyristor valve group T2 are respectively turned on for half of the control cycle, and each thyristor valve group maintains a fixed conduction timing. The working process of the sub-module series bridge arm S1 and the sub-module series bridge arm S2 differs by half of the control cycle, and the output voltage and transmission power are adjusted by changing the voltage of the sub-module series bridge arm;

[0032] The second converter in the medium voltage direct-hung DC power supply also adopts the same control method;

[0033] Assume a working period of T h, and divide it into eight working stages, corresponding to nine working nodes, namely t0~t8. Taking the No. 1 converter mentioned as an example, I M I is the current after the medium voltage AC input current is rectified by the medium voltage rectifier circuit. L It is low voltage DC output current.

[0034] Preferably, working stage 1: t0-t1, in which the thyristor valve group T1 is turned on, the thyristor valve group T2 is turned off, the two ends of the sub-module series bridge arm S1 maintain a higher voltage, and the two ends of the sub-module series bridge arm S2 maintain a lower voltage, and the current flowing through the thyristor valve group T1 is I M , the current of the submodule series bridge arm S1 is I M -I L / n, the current of the submodule series bridge arm S2 is I L / n, the transformer current is consistent with the current of the submodule series bridge arm S2, and the diode D in the low-voltage rectifier circuit L1 and diode D L4 In the on state, the diode D L2 and diode D L3 is in a blocked state;

[0035] Preferably, working stage 2: t1-t2, in which the thyristor valve group T1 is turned on, the thyristor valve group T2 is turned off, the two ends of the sub-module series bridge arm S1 maintain a higher voltage, and the two ends of the sub-module series bridge arm S2 maintain a lower voltage, and the current of the thyristor valve group T1 is I M , the current of the submodule series bridge arm S1 changes from I M -I L / n rises to I M , the current of the submodule series bridge arm S2 changes from I L / n drops to zero, the transformer current is consistent with the current of the sub-module series bridge arm S2, and the diode D in the low-voltage rectifier circuit L1 and diode D L4 The current gradually decreases to zero, and the diode D L2 and diode D L3 Still in a blocked state;

[0036] Preferably, working stage three: t2-t3, in which the current of the thyristor valve group T1 decreases and is turned off by the reverse voltage, the thyristor valve group T2 is turned on by zero voltage, the voltage at both ends of the sub-module series bridge arm S1 decreases, the voltage at both ends of the sub-module series bridge arm S2 increases, the current of the sub-module series bridge arm S1 decreases, the current of the sub-module series bridge arm S2 increases, the current of the transformer remains zero, and the diode D in the low-voltage rectifier circuit L1 、Diode D L2 、Diode D L3 、Diode D L4All are in blocking state;

[0037] Preferably, working stage four: t3-t4, in which the thyristor valve group T1 is turned off, the thyristor valve group T2 is turned on, the two ends of the sub-module series bridge arm S1 are at a lower voltage, the two ends of the sub-module series bridge arm S2 are at a higher voltage, and the current of the thyristor valve group T2 is I M , the current of the sub-module series bridge arm S1 increases, the current of the sub-module series bridge arm S2 decreases, the transformer current is consistent with the current of the sub-module series bridge arm S1, and the diode D in the low-voltage rectifier circuit L2 And diode D L3 The current rises to I L , diode D L1 and diode D L4 is in a blocked state;

[0038] Preferably, working stage five: t4-t5, in which the thyristor valve group T1 is turned off, the thyristor valve group T2 is turned on, the two ends of the sub-module series bridge arm S1 are at a lower voltage, the two ends of the sub-module series bridge arm S2 are at a higher voltage, and the current of the thyristor valve group T2 is I M , the current of the submodule series bridge arm S1 is maintained at I L / n, the current of the submodule series bridge arm S2 is kept at I M -I L / n, the transformer current is consistent with the current of the submodule series bridge arm S1, and the diode D in the low-voltage rectifier circuit L2 and diode D L3 In the on state, the diode D L1 and diode D L4 is in a blocked state;

[0039] Preferably, working stage six: t5-t6, in this stage, the thyristor valve group T1 is turned off, the thyristor valve group T2 is turned on, the two ends of the sub-module series bridge arm S1 are at a lower voltage, the two ends of the sub-module series bridge arm S2 are at a higher voltage, and the current of the thyristor valve group T2 is I M , the current of the submodule series bridge arm S1 is kept from I L / n drops to zero, and the current of the submodule series bridge arm S2 changes from I M -I L / n rises to I M The transformer current is consistent with the current of the submodule series bridge arm S1, and the diode D in the low-voltage rectifier circuit L2 and diode D L3 The current from I L drops to zero, diode D L1 and diode D L4 is in a blocked state;

[0040] Working stage seven: t6~t7, in this stage, the thyristor valve group T1 realizes zero voltage opening, the current of the thyristor valve group T2 decreases and is turned off under reverse pressure, the voltage at both ends of the sub-module series bridge arm S1 increases, the voltage at both ends of the sub-module series bridge arm S2 decreases, the current of the sub-module series bridge arm S1 increases, the current of the sub-module series bridge arm S2 decreases, the current of the transformer remains zero, and the diode D in the low-voltage rectifier circuit L1 、Diode D L2 、Diode D L3 、Diode D L4 All are in blocking state;

[0041] Working stage eight: t7-t8, in this stage, the thyristor valve group T1 is turned on, the thyristor valve group T2 is turned off, the two ends of the sub-module series bridge arm S1 are at a higher voltage, the two ends of the sub-module series bridge arm S2 are at a lower voltage, and the current of the thyristor valve group T2 is I M , the current of the submodule series bridge arm S1 gradually decreases to I M -I L / n, the current of the submodule series bridge arm S2 gradually rises to I L / n, the transformer current is consistent with the current of the submodule series bridge arm S2, and the diode D in the low-voltage rectifier circuit L1 and diode D L4 The current rises from zero to I L , diode D L2 and diode D L3 In blocked state.

[0042] Preferably, the working process of the No. 2 converter is consistent with the working process of the No. 1 converter on the basis of a control timing difference of one quarter with the No. 1 converter.

[0043] Beneficial effects:

[0044] The present invention has the following advantages:

[0045] 1. Compared with the traditional power supply scheme using industrial frequency transformer to step down the voltage, the present invention uses sub-modules in series to adjust the output voltage, which has the advantages of wide voltage regulation range and flexible output voltage regulation.

[0046] 2. Compared with the circuit topology of the H-bridge circuit and the resonant DC / DC converter input parallel output series design, the present invention has fewer transformers and modules, and has high overall reliability and ease of use.

[0047] 3. The present invention adopts a diode and thyristor structure topology with low cost and large capacity, and the overall equipment cost is low and the transmission power capacity is high.

[0048] 4. The present invention has smooth input and output currents, no harmonic problems, and high power quality.

[0049] 5. The medium-voltage direct-hung DC power supply proposed in the present invention has the characteristics of small size, high efficiency, low cost and high power density, and is very suitable for data centers, electric vehicle charging stations, hydrogen production and other fields.

[0050] In the present invention, a diode valve group and a thyristor valve group are used in a medium voltage rectifier circuit, a medium voltage inverter circuit and a low voltage rectifier circuit to bear current and transmit power, and have the characteristics of high efficiency, low cost and high reliability; the output voltage and transmission power are adjusted by controlling the voltage at both ends of the bridge arm of the sub-module in series, and have the characteristics of a wide voltage regulation range and fault current limiting; the structure of two converter outputs connected in parallel can significantly improve the transmission power of the power supply, and at the same time, the medium voltage side is directly connected to the power grid, and the structure is simple and easy to use. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is a schematic diagram of the topology circuit of the medium voltage direct-hung DC power supply proposed in the present invention;

[0052] Figure 2 The thyristor drive timing and main voltage and current waveforms of the medium voltage direct-hung DC power supply proposed by the present invention;

[0053] Figure 3 A schematic diagram of the current path of the medium voltage direct-hung DC power supply in the first working stage of the present invention;

[0054] Figure 4 A schematic diagram of the current path of the medium voltage direct-hung DC power supply in the second working stage of the present invention;

[0055] Figure 5 A schematic diagram of the current path of the medium voltage direct-hung DC power supply in the third working stage of the present invention;

[0056] Figure 6 A schematic diagram of the current path of the medium voltage direct-hung DC power supply in the fourth working stage of the present invention;

[0057] Figure 7 A schematic diagram of the current path of the medium voltage direct-hung DC power supply in the fifth working stage of the present invention;

[0058] Figure 8 A schematic diagram of the current path of the medium voltage direct-hung DC power supply provided by the present invention in the sixth working stage;

[0059] Fig. 9 A schematic diagram of the current path of the medium voltage direct-hung DC power supply provided by the present invention in working stage seven;

[0060] Fig.10 A schematic diagram of the current path of the medium voltage direct-hung DC power supply provided by the present invention in working stage eight;

[0061] Fig.11 This is a circuit diagram of the evolutionary topology of the medium voltage direct-hung DC power supply proposed in the present invention;

[0062] Fig.12 This is a circuit diagram of the second evolutionary topology of the medium voltage direct-hung DC power supply proposed in the present invention;

[0063] Fig.13 This is the third circuit diagram of the evolutionary topology of the medium voltage direct-hung DC power supply proposed in the present invention. DETAILED DESCRIPTION

[0064] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings, but it is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be included in the protection scope of the present invention.

[0065] Note: Converter No. 1 is Converter 1, Converter No. 2 is Converter 2, and so on.

[0066] like Figure 1-10 As shown, Example 1

[0067] The present invention proposes a medium voltage direct current power supply, such as Figure 1 As shown, the medium voltage direct-hung DC power supply includes converter one and converter two. Converter one and converter two adopt the same circuit topology and control method. Each converter includes a medium voltage rectifier circuit, a medium voltage inverter circuit, a single-phase transformer, and a low voltage rectifier circuit.

[0068] Taking converter 1 as an example, the circuits of each part are as follows:

[0069] The medium voltage rectifier circuit mentioned includes: diode valve group D M1 , diode valve group D M2 , diode valve group D M3 And diode valve group D M4 ;

[0070] The medium voltage inverter circuit mentioned comprises: a thyristor valve group T1, a thyristor valve group T2, a bridge arm reactor L1, a bridge arm reactor L2, a submodule series bridge arm S1 and a submodule series bridge arm S2;

[0071] The single-phase transformer mentioned includes a primary side of the transformer and a secondary side of the transformer, wherein the primary side includes a first terminal and a second terminal, the secondary side includes a first terminal and a second terminal, and the first terminal of the primary side of the transformer and the first terminal of the secondary side of the transformer are the same terminal. The transformer has a transformation ratio of n:1 and includes a leakage inductance L k1 ;

[0072] The low voltage rectifier circuit mentioned includes: diode D L1, diode D L2 , diode D L3 、Diode D L4 ;

[0073] The circuits and components of the converter 2 mentioned above are consistent with those of the converter 1, and the output filter capacitors of the converter 1 and the converter 2 are combined into one output filter capacitor C o Connected in parallel to the low voltage DC output port;

[0074] The diode valve group D M1 The anode and diode valve group D M3 The cathode of the diode valve group D is connected to form the first bridge arm of the medium voltage rectifier circuit; M2 The anode and diode valve group D M4 The cathode of the medium voltage rectifier circuit is connected to form the second bridge arm;

[0075] One end of the medium voltage AC input port of converter 1 is connected to the diode valve group D M1 With diode valve group D M3 The other end is connected to the diode valve group D M2 With diode valve group D M4 The intermediate node of

[0076] The anode of the thyristor valve group T1 is connected to the first terminal of the bridge arm reactor L1, and the cathode of the thyristor valve group T1 is connected to the positive electrode of the submodule series bridge arm S1, forming the first bridge arm of the medium voltage inverter circuit; the anode of the thyristor valve group T2 is connected to the first terminal of the bridge arm reactor L2, and the cathode of the thyristor valve group T2 is connected to the positive electrode of the submodule series bridge arm S2, forming the second bridge arm of the medium voltage inverter circuit;

[0077] The second terminal of the bridge arm inductor L1, the second terminal of the bridge arm inductor L2 and the diode valve group D M1 Cathode, diode valve group D M2 The cathodes are connected together;

[0078] The mentioned submodule series bridge arm S1 negative electrode, submodule series bridge arm S2 negative electrode and diode valve group D M3 Anode, diode valve group D M4 The anodes are connected together;

[0079] The first terminal of the primary side of the single-phase transformer mentioned above is connected to the middle node of the thyristor valve group T1 and the submodule series bridge arm S1; the second terminal of the primary side of the single-phase transformer is connected to the middle node of the thyristor valve group T2 and the submodule series bridge arm S2;

[0080] The diode D mentioned L1 The anode and diode DL3 The cathode of the diode D L2 The anode and diode D L4 The cathode forms the second bridge arm of the low voltage rectifier circuit;

[0081] The first terminal of the secondary side of the single-phase transformer is connected to a diode D L1 and diode D L3 The second terminal of the secondary side of the single-phase transformer is connected to the diode D L2 and diode D L4 The intermediate node of

[0082] The diode D mentioned L1 The cathode of diode D L2 The cathodes are connected together and are connected through the output filter capacitor C o The positive electrode of the diode D is connected to the positive electrode of the low voltage DC output terminal of converter 1. L3 The anode and diode D L4 The anodes are connected together and then pass through the output filter capacitor C o The negative electrode is connected to the negative electrode of the low voltage DC output terminal of converter 1, and the output filter capacitor C o The two ends constitute a low-voltage DC output end of the converter.

[0083] The medium voltage direct-hung DC power supply has the same internal circuit connection mode as the converter one, that is, the medium voltage rectifier circuit, medium voltage inverter circuit, single-phase transformer, and low voltage rectifier circuit in the converter two are connected in the same way as in the converter one. The medium voltage direct-hung DC power supply has four terminals at the medium voltage AC input end, namely, the first terminal N i1 、Second terminal N i2 、The third terminal N i3 、The fourth terminal N i4 , where the first terminal N i1 and the second terminal N i2 The third terminal N i3 and the fourth terminal N i4 The medium voltage direct-hung DC power supply is connected to the three-phase AC grid at the medium voltage AC input terminal. Specifically, the first terminal N i1 Connect the A-phase terminal of the three-phase AC power grid, the second terminal N i2 Connect to the B-phase terminal of the three-phase AC power grid; the third terminal N i3 Connect the A-phase terminal of the three-phase AC power grid, the fourth terminal N i4 Connect to the C-phase terminal of the three-phase AC power grid;

[0084] The medium voltage direct-hung DC power supply has four terminals at the low voltage DC output end, namely, the first terminal N o1 、Second terminal N o2 、The third terminal N o3 、The fourth terminal N o4 , where the first terminal N o1 and the second terminal N o2 The output terminal of the converter is formed; the third terminal N o3 and the fourth terminal N o4 The output terminal of the second converter is formed; wherein the first terminal N o1 and the second terminal N o2 Connect together, the third terminal N o3 and the fourth terminal N o4 The output filter capacitors of converter 1 and converter 2 are connected together, that is, the output terminals of converter 1 and converter 2 are connected in parallel. The output filter capacitors of converter 1 and converter 2 are combined into one output filter capacitor C o Connected in parallel to the low voltage DC output port.

[0085] The thyristor valve group driving timing and main voltage and current waveforms of the medium voltage direct-hung DC power supply proposed by the present invention are as follows: Figure 2 As shown, taking the converter 1 mentioned above as an example, the diode valve group D in the medium voltage rectifier circuit M1 and diode valve group D M4 Conductive, diode valve group D M2 and diode valve group D M3 Block, rectify the medium voltage AC input voltage into DC voltage, thyristor valve group T1 and thyristor valve group T2 are turned on for half of the control cycle respectively, each thyristor valve group maintains a fixed conduction timing, the working process of the sub-module series bridge arm S1 and the sub-module series bridge arm S2 differs by half of the control cycle, and the output voltage and transmission power are adjusted by changing the voltage of the sub-module series bridge arm; the converter 2 mentioned above also adopts the same control method. Among them, I M is the current after the medium voltage AC is rectified by the converter-medium voltage rectifier circuit, i T1 and i T2 are the currents of thyristor valve group T1 and thyristor valve group T2 in converter 1, i t1 is the transformer current of converter 1, u S1 and u S2 are the currents of the submodule series bridge arm S1 and the submodule series bridge arm S2 in converter 1, I L1 and I L2 are the output currents of converter 1 and converter 2 respectively. Assume a working cycle is T h , the time is t0~t8, taking the converter 1 mentioned as an example, the specific working stages are:

[0086] Working stage 1: t0~t1, such as Figure 3 As shown, in this stage, the thyristor valve group T1 is turned on, the thyristor valve group T2 is turned off, the two ends of the sub-module series bridge arm S1 maintain a higher voltage, and the two ends of the sub-module series bridge arm S2 maintain a lower voltage. The current flowing through the thyristor valve group T1 is I M1 , the current of the submodule series bridge arm S1 is I M1 -I L1 / n, the current of the submodule series bridge arm S2 is I L1 / n, the transformer current is consistent with the current of the submodule series bridge arm S2, and the diode D in the low-voltage rectifier circuit L1 and diode D L4 In the on state, the diode D L2 and diode D L3 is in a blocked state;

[0087] Working stage 2: t1~t2, such as Figure 4 As shown, in this stage, the thyristor valve group T1 is turned on, the thyristor valve group T2 is turned off, the two ends of the sub-module series bridge arm S1 maintain a higher voltage, and the two ends of the sub-module series bridge arm S2 maintain a lower voltage. The current of the thyristor valve group T1 is I M1 , the current of the submodule series bridge arm S1 changes from I M1 -I L1 / n rises to I M1 , the current of the submodule series bridge arm S2 changes from I L1 / n drops to zero, the transformer current is consistent with the current of the sub-module series bridge arm S2, and the diode D in the low-voltage rectifier circuit L1 and diode D L4 The current gradually decreases to zero, and the diode D L2 and diode D L3 Still in a blocked state;

[0088] Working stage three: t2~t3, such as Figure 5 As shown, in this stage, the current of the thyristor valve group T1 decreases and is turned off due to reverse pressure, the thyristor valve group T2 is turned on with zero voltage, the voltage at both ends of the sub-module series bridge arm S1 decreases, the voltage at both ends of the sub-module series bridge arm S2 increases, the current of the sub-module series bridge arm S1 decreases, the current of the sub-module series bridge arm S2 increases, the current of the transformer remains zero, and the diode D in the low-voltage rectifier circuit L1 、Diode D L2 、Diode D L3 、Diode D L4 All are in blocking state;

[0089] Working stage 4: t3~t4, such as Figure 6As shown, in this stage, the thyristor valve group T1 is turned off, the thyristor valve group T2 is turned on, the two ends of the sub-module series bridge arm S1 are at a lower voltage, the two ends of the sub-module series bridge arm S2 are at a higher voltage, and the current of the thyristor valve group T2 is I M1 , the current of the sub-module series bridge arm S1 increases, the current of the sub-module series bridge arm S2 decreases, the transformer current is consistent with the current of the sub-module series bridge arm S1, and the diode D in the low-voltage rectifier circuit L2 And diode D L3 The current rises to I L1 , diode D L1 and diode D L4 is in a blocked state;

[0090] As the diode valve group D in the medium voltage rectifier circuit M2 and diode valve group D M3 When conducting, I M1 The waveform remains unchanged, and the working process is the same, so I will not repeat it here. In addition, the working process of the converter 2 mentioned above is consistent with that of the converter 1 on the basis of a control timing difference of one quarter, and the output current I L2 The output current I L1 The two converters are interlaced to synthesize a smooth output current. The working process of converter 2 will not be described in detail.

[0091] The working process of t4 to t8 in the mentioned converter is similar to the working process of t0 to t4. The corresponding current path is as follows: Figure 7 to Figure 10 As shown, no further description is given here.

[0092] like Fig.11 As shown, Example 2

[0093] The evolutionary topology of the medium voltage direct-hung DC power supply proposed in the present invention is as follows Fig.11 As shown, the medium voltage inverter circuit, transformer, and low voltage rectifier circuit in converter one and converter two are all adjusted to a three-phase circuit structure, and the control timings between the three phases differ by one-third of the working cycle. At this time, the topology can transmit greater power.

[0094] The medium voltage direct-hung DC power supply described in the present invention also has an evolutionary topology one. Specifically, the medium voltage inverter circuit in the mentioned converter one and converter two is adjusted to a three-phase inverter circuit structure, the single-phase transformer is adjusted to a three-phase transformer, and the low voltage rectifier circuit is adjusted to a three-phase rectifier circuit. The three bridge arms of the medium voltage inverter circuit are respectively connected to the primary side of the three-phase transformer, and the secondary side of the three-phase transformer is respectively connected to the three bridge arms of the low voltage rectifier circuit. The connection method of the remaining parts remains unchanged.

[0095] like Fig.13 As shown, Example 3

[0096] The evolutionary topology of the medium voltage direct-hung DC power supply proposed in the present invention is as follows: Fig.12 As shown, three converters are used, namely, converter one, converter two, and converter three. The medium voltage inverter circuit, transformer, and low voltage rectifier circuit in each converter are all single-phase circuit structures. The medium voltage AC input terminal, the input terminals of converter one, converter two, and converter three are respectively connected to the A, B, and C three-phase terminals of the three-phase AC power grid, and the connection sequence is also interchanged. At this time, the medium voltage direct-hook DC power supply can further increase the power.

[0097] The medium voltage direct-hung DC power supply described in the present invention also has an evolutionary topology 2. Specifically, on the basis of the converter 1 and the converter 2, a converter 3 having the same connection mode and the same control method as the converter 1 and the converter 2 is added. The components and connection modes of the converter 1, the converter 2 and the converter 3 are the same as those of the medium voltage direct-hung DC power supply. The evolutionary topology 2 mentioned has six terminals at the medium voltage AC input end, wherein the first terminal N i1 and the second terminal N i2 The third terminal N i3 and the fourth terminal N i4 The fifth terminal N constitutes the input terminal of the converter 2; i5 and the sixth terminal N i6 The first terminal N i1 Connect the A-phase terminal of the three-phase AC power grid, the second terminal N i2 Connect to the B-phase terminal of the three-phase AC power grid; the third terminal N i3 Connect the B-phase terminal of the three-phase AC power grid, the fourth terminal N i4 Connect the C-phase terminal of the three-phase AC power grid; the fifth terminal N i3 Connect the C-phase terminal of the three-phase AC power grid, the sixth terminal N i4 The A-phase terminal of the three-phase AC power grid is connected. At the low-voltage DC output end, the output ends of converter 1, converter 2, and converter 3 are connected in parallel.

[0098] like Fig.13 As shown, Example 4

[0099] The evolutionary topology of the medium voltage direct-hung DC power supply proposed in the present invention is as follows: Fig.13As shown, three converters are used, namely converter one, converter two, and converter three, and the medium voltage inverter circuit, transformer, and low voltage rectifier circuit in each converter are all three-phase circuit structures. The medium voltage AC input end, the input terminals of converter one, converter two, and converter three are respectively connected to the A, B, and C three-phase terminals of the three-phase AC power grid, and the connection sequence is also interchanged. At this time, the medium voltage direct-hung DC power supply can further increase the power, and at the same time can offset the double frequency power generated by the rectifier circuit, reducing the capacitance value in the series bridge arm of the sub-module and the current stress of the device.

[0100] The medium voltage direct-hung DC power supply described in the present invention also has an evolutionary topology three. Specifically, on the basis of converter one and converter two, a converter three is added which has the same connection mode and control method as converter one and converter two. At the same time, the medium voltage inverter circuit in converter one, converter two and converter three is adjusted to a three-phase inverter circuit structure, the single-phase transformer is adjusted to a three-phase transformer, the low voltage rectifier circuit is adjusted to a three-phase rectifier circuit, and the three bridge arms of the medium voltage inverter circuit are respectively connected to the primary side of the three-phase transformer, and the secondary side of the three-phase transformer is respectively connected to the three bridge arms of the low voltage rectifier circuit. The mentioned evolutionary topology three also contains six terminals at the medium voltage AC input end, of which the first terminal N i1 and the second terminal N i2 The third terminal N i3 and the fourth terminal N i4 The fifth terminal N constitutes the input terminal of the converter 2; i5 and the sixth terminal N i6 The first terminal N i1 Connect the A-phase terminal of the three-phase AC power grid, the second terminal N i2 Connect to the B-phase terminal of the three-phase AC power grid; the third terminal N i3 Connect the B-phase terminal of the three-phase AC power grid, the fourth terminal N i4 Connect the C-phase terminal of the three-phase AC power grid; the fifth terminal N i3 Connect the C-phase terminal of the three-phase AC power grid, the sixth terminal N i4 The A-phase terminal of the three-phase AC power grid is connected. At the low-voltage DC output end, the output ends of converter 1, converter 2, and converter 3 are connected in parallel.

[0101] The connection order of the medium-voltage direct-hung DC power supply described in the present invention and the input terminals of all the mentioned evolutionary topologies and the A-phase terminals, B-phase terminals, and C-phase terminals of the three-phase AC power grid can also be exchanged; the outputs of the converters at the low-voltage DC output end can also be connected in independent or series connections.

[0102] The medium voltage direct-hung DC power supply described in the present invention and each converter in all the mentioned evolutionary topologies can be independently operated;

[0103] The medium voltage direct-hung DC power supply described in the present invention and all the evolutionary topologies mentioned can be expanded to use multiple low voltage rectifier circuits in parallel, series or a mixture of series and parallel, and respectively connected to multiple medium voltage inverter circuits. Multiple medium voltage inverter circuits can also be connected in parallel, series or a mixture of series and parallel, and respectively connected to the primary sides of multiple transformers. The secondary sides of multiple transformers can be connected in parallel, series or a mixture of series and parallel. At the same time, multiple low voltage rectifier circuits can also be connected in parallel, series or a mixture of series and parallel.

[0104] Elements in the present invention:

[0105] Specifically, taking converter 1 as an example, the circuits of each part are as follows:

[0106] The medium voltage rectifier circuit mentioned includes: diode valve group D M1 , diode valve group D M2 , diode valve group D M3 And diode valve group D M4 ;

[0107] The medium voltage inverter circuit mentioned comprises: a thyristor valve group T1, a thyristor valve group T2, a bridge arm reactor L1, a bridge arm reactor L2, a submodule series bridge arm S1 and a submodule series bridge arm S2;

[0108] The single-phase transformer mentioned includes a primary side of the transformer and a secondary side of the transformer, wherein the primary side includes a first terminal and a second terminal, the secondary side includes a first terminal and a second terminal, and the first terminal of the primary side of the transformer and the first terminal of the secondary side of the transformer are the same terminal. The transformer has a transformation ratio of n:1 and includes a leakage inductance L k1 ;

[0109] The low voltage rectifier circuit mentioned includes: diode D L1 , diode D L2 , diode D L3 、Diode D L4 And the output filter capacitor C o1 ;

[0110] The circuits and components of the converter 2 mentioned are consistent with those of the converter 1;

[0111] Introduce the connection method:

[0112] The diode valve group D M1 The anode and diode valve group D M3 The cathode of the diode valve group D is connected to form the first bridge arm of the medium voltage rectifier circuit;M2 The anode and diode valve group D M4 The cathode of the medium voltage rectifier circuit is connected to form the second bridge arm;

[0113] One end of the medium voltage AC input port of converter 1 is connected to the diode valve group D M1 With diode valve group D M3 The other end is connected to the diode valve group D M2 With diode valve group D M4 The intermediate node of

[0114] The anode of the thyristor valve group T1 is connected to the first terminal of the bridge arm reactor L1, and the cathode of the thyristor valve group T1 is connected to the positive electrode of the submodule series bridge arm S1, forming the first bridge arm of the medium voltage inverter circuit; the anode of the thyristor valve group T2 is connected to the first terminal of the bridge arm reactor L2, and the cathode of the thyristor valve group T2 is connected to the positive electrode of the submodule series bridge arm S2, forming the second bridge arm of the medium voltage inverter circuit;

[0115] The second terminal of the bridge arm inductor L1, the second terminal of the bridge arm inductor L2 and the diode valve group D M1 Cathode, diode valve group D M2 The cathodes are connected together;

[0116] The mentioned submodule series bridge arm S1 negative electrode, submodule series bridge arm S2 negative electrode and diode valve group D M3 Anode, diode valve group D M4 The anodes are connected together;

[0117] The first terminal of the primary side of the single-phase transformer mentioned above is connected to the middle node of the thyristor valve group T1 and the submodule series bridge arm S1; the second terminal of the primary side of the single-phase transformer is connected to the middle node of the thyristor valve group T2 and the submodule series bridge arm S2;

[0118] The diode D mentioned L1 The anode and diode D L3 The cathode of the diode D L2 The anode and diode D L4 The cathode forms the second bridge arm of the low voltage rectifier circuit;

[0119] The first terminal of the secondary side of the single-phase transformer is connected to a diode D L1 and diode D L3 The second terminal of the secondary side of the single-phase transformer is connected to the diode D L2 and diode D L4 The intermediate node of

[0120] The diode D mentioned L1 The cathode of diode D L2 The cathodes are connected together and are connected through the output filter capacitor C o1 The positive electrode of the diode D is connected to the positive electrode of the low voltage DC output terminal of converter 1. L3 The anode and diode D L4 The anodes are connected together and then pass through the output filter capacitor C o1 The negative electrode is connected to the negative electrode of the low voltage DC output terminal of converter 1, and the output filter capacitor C o1 The two ends constitute a low-voltage DC output end of the converter.

[0121] Diodes, thyristors, sub-modules in series bridge arms are alternatives to sub-modules:

[0122] The diode valve group D in the medium voltage rectifier circuit mentioned M1 , diode valve group D M2 , diode valve group D M3 And diode valve group D M4 They are all composed of a number of diodes connected in series, and the diode valve group in the medium voltage rectifier circuit mentioned above can also be composed of diodes, thyristors, insulated gate bipolar transistors IGBT, MOSFET, injection enhanced gate transistors IEGT, integrated gate commutation thyristors IGCT and other devices connected in series and parallel;

[0123] The thyristor valve group T1 and the thyristor valve group T2 in the medium voltage inverter circuit mentioned above are both composed of a plurality of thyristors connected in series, and the thyristor valve group in the medium voltage inverter circuit mentioned above can also be composed of thyristors, insulated gate bipolar transistors IGBT, MOSFET, injection enhanced gate transistors IEGT, integrated gate commutation thyristors IGCT and other devices connected in series and in parallel;

[0124] The submodule series bridge arm S1 and the submodule series bridge arm S2 in the medium voltage inverter circuit mentioned above are both composed of a number of full bridges connected in series, and the submodule series bridge arm in the medium voltage inverter circuit mentioned above can also be composed of half-bridge and full-bridge hybrid submodules or other feasible submodule structures connected in series and parallel;

[0125] The diode D in the low voltage rectifier circuit mentioned above L1 、Diode D L2 、Diode D L3 And diode D L4 It can also be composed of diodes, thyristors, insulated gate bipolar transistors IGBTs, MOSFETs, injection enhanced gate transistors IEGTs, integrated gate commutation thyristors IGCTs and other devices connected in series and parallel;

[0126] Connection method of converter 1 and converter 2

[0127] The medium voltage direct-hung DC power supply of the present invention has the same internal circuit connection mode as the converter one, that is, the medium voltage rectifier circuit, medium voltage inverter circuit, single-phase transformer, and low voltage rectifier circuit in the converter two are connected in the same way as in the converter one. The medium voltage direct-hung DC power supply has four terminals at the medium voltage AC input end, namely, the first terminal N i1 、Second terminal N i2 、The third terminal N i3 、The fourth terminal N i4 , where the first terminal N i1 and the second terminal N i2 The third terminal N i3 and the fourth terminal N i4 The medium voltage direct-hung DC power supply is connected to the three-phase AC grid at the medium voltage AC input terminal. Specifically, the first terminal N i1 Connect the A-phase terminal of the three-phase AC power grid, the second terminal N i2 Connect to the B-phase terminal of the three-phase AC power grid; the third terminal N i3 Connect the A-phase terminal of the three-phase AC power grid, the fourth terminal N i4 Connect to the C-phase terminal of the three-phase AC power grid;

[0128] The medium voltage direct-hung DC power supply has four terminals at the low voltage DC output end, namely, the first terminal N o1 、Second terminal N o2 、The third terminal N o3 、The fourth terminal N o4 , where the first terminal N o1 and the second terminal N o2 The output terminal of the converter is formed; the third terminal N o3 and the fourth terminal N o4 The output terminal of the second converter is formed; wherein the first terminal N o1 and the second terminal N o2 Connect together, the third terminal N o3 and the fourth terminal N o4 Connected together, that is, the output ends of converter one and converter two are connected in parallel, the output filter capacitor of converter one and the output filter capacitor of converter two mentioned above can also be combined into one output filter capacitor connected in parallel at the low voltage DC output port;

[0129] The present invention is described by several specific embodiments, and it should be understood by those skilled in the art that various changes and equivalent substitutions may be made to the present invention without departing from the scope of the present invention. In addition, various modifications may be made to the present invention for specific situations or specific circumstances without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed, but should include all implementation methods falling within the scope of the claims of the present invention.

Claims

1. A medium voltage direct current power supply, which is connected to a three-phase AC power grid, with phases A, B and C; characterized in that: The power supply consists of two converters and an output filter capacitor C o , the two converters are converter No. 1 and converter No. 2, and the output filter capacitor C o The two ends are low-voltage DC output ends of the power supply, and the low-voltage DC output ends include a low-voltage DC positive output end (UL+) and a low-voltage DC negative output end (UL-); Converter 1 and converter 2 use the same circuit topology and control method. Each converter consists of a medium voltage rectifier circuit, a medium voltage inverter circuit, a single-phase transformer, a low voltage rectifier circuit and an output filter capacitor C. o1 composition; The medium voltage rectifier circuit comprises a diode valve group D M1 , diode valve group D M2 , diode valve group D M3 and diode valve group D M4 ; The medium voltage inverter circuit comprises a thyristor valve group T1, a thyristor valve group T2, a bridge arm reactor L1, a bridge arm reactor L2, a submodule series bridge arm S1 and a submodule series bridge arm S2; The single-phase transformer TR comprises a primary side of the transformer, a secondary side of the transformer and a leakage inductance L k1 , where the primary side of the transformer includes two terminals, namely the primary side first terminal (TR11) and the primary side second terminal (TR12), and the secondary side of the transformer includes two terminals, namely the secondary side first terminal (TR21) and the secondary side second terminal (TR22), and the primary side first terminal (TR11) and the secondary side first terminal (TR21) are the same-name terminals; the transformer ratio is n :1; n is a real number; The low voltage rectifier circuit comprises: a diode D L1 , diode D L2 , diode D L3 、Diode D L4 and output filter capacitor C o1 ; In the medium voltage rectifier circuit, the diode valve group D M1 The anode and diode valve group D M3 The cathode of the diode valve group D is connected to form the first bridge arm of the medium voltage rectifier circuit; M2 The anode and diode valve group D M4 The cathode of the medium voltage rectifier circuit is connected to form the second bridge arm; In the medium voltage inverter circuit, the anode of the thyristor valve group T1 is connected to the first terminal of the bridge arm reactor L1, and the cathode of the thyristor valve group T1 is connected to the positive electrode of the submodule series bridge arm S1, forming the first bridge arm of the medium voltage inverter circuit; the anode of the thyristor valve group T2 is connected to the first terminal of the bridge arm reactor L2, and the cathode of the thyristor valve group T2 is connected to the positive electrode of the submodule series bridge arm S2, forming the second bridge arm of the medium voltage inverter circuit; The second terminal of the bridge arm inductor L1, the second terminal of the bridge arm inductor L2, the diode valve group D M1 Cathode, diode valve group D M2 The cathode of is connected; The submodule is connected in series with the negative electrode of the bridge arm S1, the negative electrode of the bridge arm S2, and the diode valve group D M3 Anode, diode valve group D M4 The anode of is connected; The single-phase transformer TR has a first terminal (TR11) on the primary side of the single-phase transformer TR connected to a leakage inductor L k1 One end of the leakage inductance L k1 The other end is connected to the cathode of the thyristor valve group T1 and the positive electrode of the sub-module series bridge arm S1 at the same time; the second terminal (TR12) of the primary side of the single-phase transformer TR is connected to the cathode of the thyristor valve group T2 and the positive electrode of the sub-module series bridge arm S2 at the same time; In the low voltage rectifier circuit, the diode D L1 The anode and diode D L3 The cathode of the diode D L2 The anode and diode D L4 The cathode forms the second bridge arm of the low voltage rectifier circuit; The secondary side first terminal (TR21) of the single-phase transformer TR is connected to a diode D L1 The anode and diode D L3 The cathode of the single-phase transformer TR is connected to the diode D at the same time. L2 The anode and diode D L4 The cathode; Output filter capacitor C o1 The two ends of the diode D constitute the low voltage DC output end of the first converter; L1 The cathode of diode D L2 The cathode of the output filter capacitor C o1 The positive poles of the diodes D L3 The anode of diode D L4 Anode, output filter capacitor C o1 The negative poles are connected together to the low voltage DC negative output terminal (UL-); Diode valve group D M1 With diode valve group D M3 The connection point is used as a medium voltage AC input terminal of the power supply, and the diode valve group D M2 With diode valve group D M4 The connection point of is used as another medium voltage AC input terminal of the power supply; The input end of the first converter includes two terminals, namely the first terminal N i1 、Second terminal N i2 The input end of the second converter includes two terminals, namely the third terminal N i3 、The fourth terminal N i4 ; The four terminals together constitute a medium voltage AC input terminal; the medium voltage AC input terminal is connected to a three-phase AC grid, the first terminal N i1 Connect the A-phase terminal of the three-phase AC power grid, the second terminal N i2 Connect to the B-phase terminal of the three-phase AC power grid; the third terminal N i3 Connect the A-phase terminal of the three-phase AC power grid, the fourth terminal N i4 Connect to the C-phase terminal of the three-phase AC power grid; The output end of the first converter includes two terminals, namely the first terminal N o1 、Second terminal N o2 The output end of the second converter includes two terminals, namely the third terminal N o3 、The fourth terminal N o4 ; The four terminals together constitute a low voltage DC output terminal; Among them, the first terminal N o1 and the third terminal N o3 Connect together, the second terminal N o2 and the fourth terminal N o4 Connected together, that is, the output ends of converter No. 1 and converter No. 2 are connected in parallel; two output filter capacitors C o1 The output filter capacitor C o ; The diode valve group D in the medium voltage rectifier circuit M1 , diode valve group D M2 , diode valve group D M3 And diode valve group D M4 Each of them can also be composed of n diodes connected in series, and the diode valve group in the medium voltage rectifier circuit can also be composed of diodes, thyristors, insulated gate bipolar transistors IGBT, MOSFET, injection enhanced gate transistors IEGT, integrated gate commutation thyristor IGCT devices connected in series and in parallel; The thyristor valve group T1 and the thyristor valve group T2 in the medium voltage inverter circuit can also be composed of n thyristors connected in series, and the thyristor valve group in the medium voltage inverter circuit can also be composed of thyristors, insulated gate bipolar transistors IGBT, MOSFET, injection enhanced gate transistors IEGT, and integrated gate-level commutation thyristor IGCT devices connected in series and in parallel; The submodule series bridge arm S1 and the submodule series bridge arm S2 in the medium voltage inverter circuit are both composed of n full bridges connected in series, and the submodule series bridge arm in the medium voltage inverter circuit can also be composed of half-bridge and full-bridge hybrid submodules connected in series and parallel; The diode D in the low voltage rectifier circuit L1 、Diode D L2 、Diode D L3 And diode D L4 It can also be composed of diodes, thyristors, insulated gate bipolar transistors IGBTs, MOSFETs, injection enhanced gate transistors IEGTs, and integrated gate-level commutation thyristors IGCTs connected in series and in parallel; Where n is a real number; The control timing of the first converter and the second converter in the medium voltage direct-hung DC power supply differs by a quarter of a control cycle; In converter No. 1, the diode valve group D in the medium voltage rectifier circuit M1 , diode valve group D M2 , diode valve group D M3 And diode valve group D M4 The medium voltage AC input voltage is rectified into a DC voltage, and the thyristor valve group T1 and the thyristor valve group T2 are respectively turned on for half of the control cycle, and each thyristor valve group maintains a fixed conduction timing. The working process of the sub-module series bridge arm S1 and the sub-module series bridge arm S2 differs by half of the control cycle, and the output voltage and transmission power are adjusted by changing the voltage of the sub-module series bridge arm; The second converter in the medium voltage direct-hung DC power supply also adopts the same control method; Assume a working cycle of T h , and divide it into eight working stages, namely, Working Stage 1: t 0~ t 1. Work Phase 2: t 1~ t 2. Work phase three: t 2~ t 3. Work Phase 4: t 3~ t 4. Work Phase Five: t 4~ t 5. Work Phase 6: t 5~ t 6. Work Phase 7: t 6~ t 7. Work Phase 8: t 7~ t 8. The eight working stages correspond to nine working nodes, namely t 0~ t 8. In the first converter, I M It is the current after the medium voltage AC input current is rectified by the medium voltage rectifier circuit. I L It is low voltage DC output current; exist t 0~ t In the working stage 1, the thyristor valve group T1 is turned on, the thyristor valve group T2 is turned off, the two ends of the sub-module series bridge arm S1 maintain a higher voltage, and the two ends of the sub-module series bridge arm S2 maintain a lower voltage. The current flowing through the thyristor valve group T1 is I M , the current of the submodule series bridge arm S1 is I M - I L / n , the current of the submodule series bridge arm S2 is I L / n The transformer current is consistent with the current of the submodule series bridge arm S2, and the diode D in the low-voltage rectifier circuit L1 and diode D L4 In the on state, the diode D L2 and diode D L3 is in a blocked state; exist t 1~ t In the working stage 2, the thyristor valve group T1 is turned on, the thyristor valve group T2 is turned off, the two ends of the sub-module series bridge arm S1 maintain a higher voltage, and the two ends of the sub-module series bridge arm S2 maintain a lower voltage. The current of the thyristor valve group T1 is I M , the current of the submodule series bridge arm S1 is from I M - I L / n Rise to I M , the current of the submodule series bridge arm S2 is from I L / n The transformer current is consistent with the current of the submodule series bridge arm S2, and the diode D in the low-voltage rectifier circuit L1 and diode D L4 The current gradually decreases to zero, and the diode D L2 and diode D L3 Still in a blocked state; exist t 2~ t In the working stage 3, the current of the thyristor valve group T1 decreases and is turned off by the reverse voltage, the thyristor valve group T2 is turned on with zero voltage, the voltage at both ends of the sub-module series bridge arm S1 decreases, the voltage at both ends of the sub-module series bridge arm S2 increases, the current of the sub-module series bridge arm S1 decreases, the current of the sub-module series bridge arm S2 increases, the current of the transformer remains zero, and the diode D in the low-voltage rectifier circuit L1 、Diode D L2 、Diode D L3 、Diode D L4 All are in blocking state; exist t 3~ t In the working stage 4, the thyristor valve group T1 is turned off, the thyristor valve group T2 is turned on, the two ends of the sub-module series bridge arm S1 are at a lower voltage, the two ends of the sub-module series bridge arm S2 are at a higher voltage, and the current of the thyristor valve group T2 is I M , the current of the sub-module series bridge arm S1 increases, the current of the sub-module series bridge arm S2 decreases, the transformer current is consistent with the current of the sub-module series bridge arm S1, and the diode D in the low-voltage rectifier circuit L2 And diode D L3 The current rises to I L , diode D L1 and diode D L4 is in a blocked state; exist t 4~ t In the working stage 5, the thyristor valve group T1 is turned off, the thyristor valve group T2 is turned on, the two ends of the sub-module series bridge arm S1 are at a lower voltage, the two ends of the sub-module series bridge arm S2 are at a higher voltage, and the current of the thyristor valve group T2 is I M , the current of the submodule series bridge arm S1 is maintained at I L / n , the current of the submodule series bridge arm S2 is maintained at I M - I L / n The transformer current is consistent with the current of the submodule series bridge arm S1, and the diode D in the low-voltage rectifier circuit L2 and diode D L3 In the on state, the diode D L1 and diode D L4 is in a blocked state; exist t 5~ t In the working stage 6, the thyristor valve group T1 is turned off, the thyristor valve group T2 is turned on, the two ends of the sub-module series bridge arm S1 are at a lower voltage, the two ends of the sub-module series bridge arm S2 are at a higher voltage, and the current of the thyristor valve group T2 is I M , the current of the submodule series bridge arm S1 is kept from I L / n Drops to zero, and the current of the submodule series bridge arm S2 changes from I M - I L / n Rise to I M The transformer current is consistent with the current of the submodule series bridge arm S1, and the diode D in the low-voltage rectifier circuit L2 and diode D L3 Current from I L drops to zero, diode D L1 and diode D L4 is in a blocked state; exist t 6~ t In the working stage 7, the thyristor valve group T1 is turned on at zero voltage, the current of the thyristor valve group T2 decreases and it is turned off due to reverse pressure, the voltage at both ends of the sub-module series bridge arm S1 increases, the voltage at both ends of the sub-module series bridge arm S2 decreases, the current of the sub-module series bridge arm S1 increases, the current of the sub-module series bridge arm S2 decreases, the current of the transformer remains zero, and the diode D in the low-voltage rectifier circuit L1 、Diode D L2 、Diode D L3 、Diode D L4 All are in blocking state; exist t 7~ t In the working stage 8, the thyristor valve group T1 is turned on, the thyristor valve group T2 is turned off, the two ends of the sub-module series bridge arm S1 are at a higher voltage, the two ends of the sub-module series bridge arm S2 are at a lower voltage, and the current of the thyristor valve group T2 is I M , the current of the submodule series bridge arm S1 gradually decreases to I M - I L / n , the current of the submodule series bridge arm S2 gradually rises to I L / n The transformer current is consistent with the current of the submodule series bridge arm S2, and the diode D in the low-voltage rectifier circuit L1 and diode D L4 The current rises from zero to I L , diode D L2 and diode D L3 In blocked state.

2. The medium voltage direct-hung DC power supply according to claim 1, characterized in that: The working process of the No. 2 converter is consistent with the working process of the No. 1 converter on the basis that the control timing of the No. 2 converter differs from that of the No. 1 converter by one quarter.

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