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CN-116488176-B - Multiport alternating current-direct current hybrid converter device and multiport alternating current-direct current hybrid system

CN116488176BCN 116488176 BCN116488176 BCN 116488176BCN-116488176-B

Abstract

The invention discloses a multi-port AC/DC hybrid converter and a multi-port AC/DC hybrid system, wherein the device comprises n converter units with independent regulation and control capability and a plurality of multi-winding transformers, the DC sides of the n converter units are connected in series and are led out of n+1 DC terminals, the n+1 DC terminals can be combined into n DC ports capable of being independently and flexibly controlled at most, and the multi-winding transformers comprise n windings connected with the AC side of the converter units and m windings connected with an AC power grid, wherein n is more than or equal to 2, and m is more than or equal to 0. When m=0, the device can realize the direct current-direct current conversion function of two or more direct current ports, when m is more than or equal to 1, the device can realize the alternating current-direct current conversion function and the direct current-direct current conversion function simultaneously, the direct current-direct current conversion is realized by connecting a plurality of direct current ports of the device, the device multiplexing technology is adopted, fewer power electronic devices are needed, the cost performance and the efficiency are improved, and the system can obtain flexible alternating current-direct current conversion, control and transmission and distribution.

Inventors

  • GUO HUAN

Assignees

  • 暨南大学

Dates

Publication Date
20260505
Application Date
20220518
Priority Date
20220113

Claims (7)

  1. 1. A multi-port AC/DC hybrid converter device is characterized in that: The multi-winding transformer is combined and led out of n first alternating current ports connected with the alternating current side of the alternating current units in the alternating current-direct current hybrid converter device and m second alternating current ports connected with an alternating current power grid, wherein m is more than or equal to 0, the number n of the alternating current units is not less than 2 under a direct current transmission and distribution monopole structure, and n is not less than 3 under a direct current transmission and distribution true dipole structure and a pseudo dipole structure; The n converter units are used for converting alternating current and direct current, converting alternating current and direct current and voltage, and have direct current-direct current conversion functions through connection; the multi-winding transformer is used for electrically isolating n first alternating current ports and m second alternating current ports, and exchanging alternating current transformation and electric energy; The direct current sides of the n current transformation units are connected in series, at least n+1 direct current terminals are led out, so that at most n direct current ports capable of being independently regulated and controlled can be formed, or at most (n+1) n/2 direct current ports capable of being independently controlled and non-independently controlled can be formed, the number of the direct current ports can be independently regulated and controlled to be not less than 2 under a direct current transmission and distribution monopole structure and a pseudo bipolar structure, and the number of the direct current ports can be independently regulated and controlled to be not less than 3 under a direct current transmission and distribution true bipolar structure; When m=0, the multi-port AC/DC hybrid converter device realizes the DC-DC conversion function of more than two DC ports, and when m is more than or equal to 1, the multi-port AC/DC hybrid converter device simultaneously realizes the AC-DC conversion function and the DC-DC conversion function.
  2. 2. The multi-port ac/dc hybrid current transformer according to claim 1, wherein: The multi-winding transformer comprises 1 multi-winding transformers or autotransformers of n first alternating current ports and m second alternating current ports, or a plurality of transformers are formed by serial and parallel combination and lead out n first alternating current ports and m second alternating current ports, and realize electric isolation, alternating current transformation and electric energy exchange between the n first alternating current ports and the m second alternating current ports; The n current transformation units adopt the same or different current transformation topological structures, and comprise a multi-level voltage source current transformer with more than two levels, a modularized multi-level voltage source current transformer and a bridge type alternating current-direct current transformation structure, the n current transformation units select circuit topologies, voltage and current rated values according to requirements, and each current transformation unit can also adopt a multi-structure formed by a plurality of current transformation circuits in series-parallel connection; The multi-winding transformer and the current transformation unit are of a single-phase structure or a three-phase structure or a mixed structure of single phase and three phase, and the alternating current port of the current transformation unit and the first alternating current port of the multi-winding transformer are of a single-phase structure or a three-phase structure or a mixed structure of single phase and three phase respectively; when the number of externally connected alternating current ports m=0 in the multi-winding transformer, the multi-port alternating current-direct current hybrid converter forms a topological structure with two or more port direct current-direct current conversion functions, and the multi-port direct current-direct current converter is formed.
  3. 3. The multi-port ac/dc hybrid current transformer according to claim 1, wherein: in the direct current ports of the direct current sides of the n direct current units, the voltage of the direct current port with a higher voltage level is formed by superposing the voltage of the direct current port with a lower voltage level and the direct current voltage of the direct current unit between the two direct current ports, so that the direct current unit and the power electronic device in each direct current port can be reused in the direct current port with the higher voltage level, the number of required power electrons is obviously reduced, meanwhile, a direct current-direct current conversion function is arranged between different direct current ports, the number of devices through which current flows during direct current-direct current conversion is reduced, and the direct current-direct current conversion efficiency is improved; When the current transformer device comprising n current transformer units is applied in a unipolar direct current system, n independently controllable direct current ports can be led out at most, the number of the independently controllable direct current ports is not less than 2, the direct current ports are led out from high to low according to the voltage, the led-out direct current ports are d1-dn+1, d2-dn+1, the number of the direct current ports is dn-dn+1, the corresponding port voltages are Vdt,1> Vdt,2> Vdt,3> Vdt, n, and the relationship between the direct current port voltages Vdt, i and the direct current terminal potentials Vd, i is Vdt, i=Vd, i-Vd, n+1, i=1, 2, the direct current of the current transformer units is Idu, i, the relationship between the direct current voltages Vdu, i and the direct current Idt, i, the direct current voltages Vdt, i of the direct current ports meets the following formulas; p dt,i represents the input active power of the ith dc port; When the converter device comprising n converter units is applied to a true bipolar direct current system, at most n independently controllable direct current ports can be led out, and the number of the independently controllable direct current ports is not less than 3; for symmetrical structures, n is even and not less than 4; at this time, a neutral line is led out from a dn/2+1 terminal at a DC neutral point potential and is grounded, the neutral line is respectively positive and negative, the positive and negative electrodes can be respectively and independently controlled to operate, the led-out DC ports are d1-dn/2+1, d2-dn/2+1, dn/2+2-dn/2+1, dn+1-dn/2+1, the corresponding port voltages are Vdt,1> Vdt,2> Vdt,3> Vdt, n, and the port voltages are respectively positive and negative, and the relationship between the DC port voltages and the DC terminal potential is as follows: vdt, i=vd, i-Vd, n/2+1, when i=1, 2,..n/2; vdt, i=vd, i+1-Vd, n/2+1, when i=n/2+1, n/2+2,..n., the relationship between the dc current Idu, i, dc voltage Vdu, i of the converter unit and the dc current Idt, i, dc voltage Vdt, i of the dc port satisfies the following formula; For an asymmetric structure, n is an odd number and not less than 3, and at the moment, the positive electrode and the negative electrode of the bipolar mode are asymmetric and are respectively configured according to the monopole mode; When the current transformer device comprising n current transformer units is applied in a pseudo bipolar direct current system, n is an odd number and not less than 3, at most (n+1)/2 direct current ports which can be independently controlled can be led out, and the number of the direct current ports can be independently controlled is not less than 2, the led direct current ports are d1-dn+1, d2-dn, according to the arrangement of direct current port voltages from high to low, d (n+1)/2-d (n+3)/2, the corresponding port voltages are Vdt,1> Vdt,2> Vdt,3>, vdt, (n+1)/2, the relation between the direct current port voltages and the direct current terminal potentials is Vdt, i=Vd, i-Vd, n+2-i, i=1, 2, i, (n+1)/2, and the direct current voltages Vdu, i and the direct current ports of the current cells meet the following formulas under the conditions of Vdt, i, and Idt; The current transformer device comprising n current transforming units further comprises a mixed application of unipolar, true bipolar and pseudo bipolar direct currents, wherein n is not less than 3, the number of direct current ports can be independently controlled to be not less than 3, meanwhile, part of direct current ports are connected in a unipolar structure mode, part of direct current ports are led out by using positive and negative direct current terminals and neutral wire terminals with corresponding voltage levels to form the true bipolar direct current connection, and part of direct current ports are led out by using positive and negative direct current terminals with corresponding voltage levels to form the pseudo bipolar direct current connection, and the neutral wire of the device is not connected at the moment; the three structures of the monopole, the true dipole and the pseudo dipole are applied to two or all of the structures to form a mixed structure.
  4. 4. The multi-port ac/dc hybrid current transformer according to claim 3, wherein: Each converter unit is respectively connected with a control unit, and the control units are used for controlling and adjusting the voltage, current and power of the direct current side and/or alternating current side of the converter unit so as to directly or indirectly control and adjust the voltage, current and power of the direct current port and/or alternating current port of the multi-port alternating current-direct current hybrid converter device, and because the influence of the direct current flowing through the converter unit with a higher voltage level is considered in the control of the converter unit with a lower voltage level, the control units are set according to all the formulas, and the required voltage, current or power control is completed on the basis of the control of the voltage, the current and the power: Or n converter units are connected with a device-level total control unit, and the device-level total control unit is used for coordinately controlling the input and output and the total power of all the converter units, so that the flexible power conversion, control and stable operation of the AC/DC ports of the multi-port AC/DC hybrid converter device are realized; the control unit or the device-level overall control unit should satisfy the following formula when controlling the converter unit: In the formula, nt indicates that nt direct current ports are arranged in the converter device, na indicates that voltage control of na direct current ports in the nt direct current ports is completed by other equipment of a connected direct current loop, nb indicates that nb direct current ports are completed by the multi-port alternating current-direct current hybrid converter device, nc indicates that nc current units without direct leading-out of the direct current ports adopt direct current voltage control, nd indicates that nd current units adopt non-direct current voltage control.
  5. 5. The multi-port AC/DC hybrid current transformer of claim 4, wherein said multi-port AC/DC hybrid current transformer can realize the access and power interaction of DC loads and distributed DC power sources with different voltage levels, and can also realize the power conversion and interaction between different DC ports and between DC ports and AC ports by selecting and matching control methods, and comprises: When the input power of more than one DC ports which are arbitrarily combined into a first part of DC port A is more than zero or less than zero and the sum of the input powers is PA, the input power of the rest of more than one DC ports which are combined into a second part of DC port B is less than zero or more than zero and the sum of the input powers is PB, the input active power of the AC ports is PAC, and the loss of the multi-port AC-DC hybrid converter device is ignored, the following is that when m=0, PA+PB=0, when m is more than or equal to 1, PA+PB+PAC=0, and: when m is more than or equal to 0, if pa+pb=0, PA >0 is the power conversion and power transmission from the first part of direct current port a to the second part of direct current port B, whereas if pa+pb=0, PA <0 is the power conversion and power transmission from the second part of direct current port B to the first part of direct current port a; when m is more than or equal to 1, if PA+PB >0, PA >0, PB <0, the power conversion and power transmission from the first part of direct current port A to the second part of direct current port B and the alternating current port are performed, otherwise, if PA+PB <0, PA <0, PB >0, the power conversion and power transmission from the second part of direct current port B and the alternating current port to the first part of direct current port A are performed; when m is greater than or equal to 1, if PA+PB >0, PA >0, PB >0, the power conversion and power transmission from the first part DC port A and the second part DC port B to the AC port are performed, whereas if PA+PB <0, PA <0, PB <0, the power conversion and power transmission from the AC port to the first part DC port A and the second part DC port B are performed.
  6. 6. A multi-port AC/DC hybrid transmission and distribution system is characterized by comprising more than two multi-port AC/DC hybrid conversion devices according to any one of claims 1-5, wherein one or more DC ports of the more than two multi-port AC/DC hybrid conversion devices are respectively connected with DC loops with corresponding voltage levels, and one or more second AC ports of the more than two multi-port AC/DC hybrid conversion devices are respectively connected with AC loops with corresponding voltage levels, so that the multi-port AC/DC hybrid transmission and distribution system is formed, and the access, interconnection and interaction of multiple places, different voltage levels of DC loads and multiple voltage levels of DC power supplies are realized.
  7. 7. The multi-port AC/DC hybrid transmission and distribution system according to claim 6, further comprising a system level control unit for controlling the coordinated operation of each multi-port AC/DC hybrid converter device to realize AC/DC flexible power conversion and mutual aid across different areas and stable operation of the AC/DC transmission and distribution network, wherein the AC/DC flexible power conversion and mutual aid across different areas comprises flexible power exchange and mutual aid between different-place AC circuits of the same or different voltage levels realized by DC loops of different voltage levels; Flexible power exchange and mutual compensation between different direct current loops with the same or different voltage levels; flexible power conversion and mutual aid between alternating current and direct current in different places.

Description

Multiport alternating current-direct current hybrid converter device and multiport alternating current-direct current hybrid system Technical Field The invention relates to the technical field of power transmission and distribution of power systems, in particular to a multiport alternating current-direct current hybrid converter device and a multiport alternating current-direct current hybrid system. Background With the development of direct current power grids and direct current power transmission and distribution technologies, diversified current transformation technologies based on power electronic devices are attracting attention, and related researchers are continuously seeking low-cost, high-efficiency and high-power-density direct current transformers and alternating current/direct current converters. On the other hand, with the wider and wider application of the distributed renewable energy sources and the popularization of various direct current loads, the power electronic trend of the power distribution network also appears, and the alternating current-direct current hybrid flexible power distribution also becomes a recent hot spot, such as construction of Guangdong pearl sea and Zhejiang Hangzhou flexible direct current power distribution demonstration projects and the like. At present, a voltage source converter or a current source converter is generally adopted for AC-DC conversion in AC-DC hybrid power transmission and distribution systems and projects, and a DC transformer is adopted for DC conversion, so that the technical economic performance of equipment, the flexible and diverse functions of the system and the like still need to be further improved. And in particular, the cost of main equipment and a system is high for alternating current-direct current hybrid flexible power distribution, and the application development of the system is hindered. Disclosure of Invention Based on the defects of the prior art, the invention provides a multi-port AC/DC hybrid converter device, a converter method of the device and a multi-port AC/DC hybrid system, the device and the method can simultaneously realize AC/DC conversion and DC/DC conversion with lower cost and better technical performance, and can realize flexible AC/DC conversion, control and transmission and distribution between local and different places through the system. In order to solve the problems, the technical scheme adopted by the invention is as follows: The invention relates to a multi-port AC/DC hybrid converter device, The multi-winding transformer is combined and led out of n first alternating current ports connected with the alternating current side of the variable current units and m second alternating current ports connected with an alternating current power grid, wherein m is more than or equal to 0, the number n of the variable current units is not less than 2 under a direct current transmission and distribution monopole structure, and n is not less than 3 under a direct current transmission and distribution true dipole structure and a pseudo dipole structure; The multi-winding transformer is used for carrying out electric isolation, alternating current transformation and electric energy exchange on n first alternating current ports and m second alternating current ports; the direct current sides of the n current transformation units are connected in series, at least n+1 direct current terminals are led out, so that at most n direct current ports capable of being independently regulated and controlled can be formed, or at most (n+1) n/2 direct current ports capable of being independently controlled or not can be formed, the number of the direct current ports can be independently regulated and controlled under a direct current transmission and distribution monopole structure and a pseudo bipolar structure and is not less than 2, and the number of the direct current ports can be independently regulated and controlled under a direct current transmission and distribution true bipolar structure and is not less than 3; when m=0, the multi-port AC/DC hybrid current transformer realizes the DC-DC current transformation function of more than two DC ports, and when m is more than or equal to 1, the multi-port AC/DC hybrid current transformer simultaneously realizes the AC-DC transformation function and the DC-DC current transformation function. Further, the multi-winding transformer comprises 1 multi-winding transformers or autotransformers of n first alternating current ports and m second alternating current ports, or a plurality of transformers are formed by combining in series and parallel and lead out n first alternating current ports and m second alternating current ports, and electric isolation, alternating current transformation and electric energy exchange between the n first alternating current ports and the m second alternating current ports are realized; The n current transformation units adopt the same or different curren