CN117766278A - Combined transformer based on multi-winding transformer and converter and its control method - Google Patents
Combined transformer based on multi-winding transformer and converter and its control method Download PDFInfo
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Abstract
本发明公开了一种基于多绕组变压器与变流器的组合式变压器及其控制方法，涉及变压器领域；包括单相电路拓扑结构和三相电路拓扑结构，所述三相电路拓扑结构是在单相电路拓扑结构上进行组合而成；所述单相电路拓扑结构包括：电磁式多绕组变压器、AC/AC电力电子变流器和旁路开关K。电磁式多绕组变压器每相由绕制在同一铁芯上的一套高压绕组WHV和两套低压绕组Wlv1、Wlv2组成。本发明中变流器输出电压和容量分别仅为组合式变压器输出电压和容量的1/(n+1)(n>1)，从而降低了变流器的容量和成本。通过调节变流器输出电压u2实现对负载供电电压uan的调节，通过调节变流器输入电流ix实现谐波治理和无功补偿。
The invention discloses a combined transformer based on a multi-winding transformer and a converter and a control method thereof, and relates to the field of transformers. It includes a single-phase circuit topology and a three-phase circuit topology. The three-phase circuit topology is based on a single-phase circuit topology. The single-phase circuit topology includes: electromagnetic multi-winding transformer, AC/AC power electronic converter and bypass switch K. Each phase of the electromagnetic multi-winding transformer consists of a set of high-voltage windings W HV and two sets of low-voltage windings W lv1 and W lv2 wound on the same iron core. In the present invention, the output voltage and capacity of the converter are only 1/(n+1)(n>1) of the output voltage and capacity of the combined transformer respectively, thereby reducing the capacity and cost of the converter. The load supply voltage u an is adjusted by adjusting the converter output voltage u2 , and harmonic control and reactive power compensation are realized by adjusting the converter input current ix .
Description
Technical Field
The invention relates to the field of transformers, in particular to a combined transformer with low cost, high reliability and voltage regulation, harmonic wave control and reactive compensation capability based on a multi-winding transformer and a converter and a control method thereof.
Background
The power transformer is one of the most important electrical equipment in a power system, and has the functions of interconnection and power exchange of power grids with different voltage levels in the power system, and the safe and stable operation of the power transformer is directly related to the safety and stability of the power system. Along with large-scale access of new energy and increase of high-precision sensitive loads, higher requirements are put forward on power supply quality of a power grid, and the traditional transformer has the advantages of low cost, high reliability and the like, but cannot meet the requirements of voltage regulation, harmonic wave management, reactive compensation and the like. Therefore, research on a low-cost high-reliability power transformer with multiple functions such as voltage fast regulation is needed.
The power electronic transformer combines the power electronic converter with the high-frequency transformer, has the basic functions of voltage conversion, electric isolation and energy transfer of the traditional power transformer, and also has the functions of active voltage control, reactive compensation and harmonic suppression. However, the power electronic device at the present stage is limited by the level of the power semiconductor device, and the problems of high cost, large volume and the like still exist, so that the power electronic device is difficult to continuously operate under the fault of the power semiconductor device, and the popularization and the application of the power electronic device in the field of high voltage and large capacity are limited. The on-load voltage regulating transformer regulates voltage by adopting a tap joint regulating method, and cannot realize rapid smooth voltage regulation, so that the problems of voltage sag and the like cannot be solved, and the functions of harmonic wave control, reactive compensation and the like cannot be realized.
In order to overcome the problems in the prior art, patent cn201711335407.X proposes a three-stage power electronic transformer with ac input and ac output, which can reduce the number of power semiconductor devices and conversion links of the power electronic transformer, thereby reducing the cost, but the modulation technology is complex, resulting in lower electric energy conversion efficiency. Patent CN202010443606.8 proposes a capacitive isolation type power electronic transformer which can reduce the number of high frequency transformers, but is difficult to be applied to high voltage transformation ratio occasions. Patent CN201910634405.3 proposes an on-load voltage regulating circuit of a staggered parallel multi-gear transformer, which can reduce the on-off frequency of an on-off switch, increase the service life of the corresponding voltage regulating switch, and does not need to skip gear voltage regulation. But the on-load voltage regulating transformer can only be regulated according to fixed step length, waveform transition is not smooth enough during voltage regulation, accurate voltage regulation cannot be realized, and reactive compensation and harmonic treatment cannot be realized.
Disclosure of Invention
The invention aims to overcome the defects that the existing power electronic transformer is high in cost, on-load voltage regulation cannot be performed quickly and smoothly, and has single function, and provides a combined transformer based on a multi-winding transformer and a converter and a control method thereof.
The technical scheme adopted by the invention is as follows:
the combined transformer based on the multi-winding transformer and the converter is characterized by comprising a single-phase circuit topological structure and a three-phase circuit topological structure, wherein the three-phase circuit topological structure is formed by combining the single-phase circuit topological structure; the single-phase circuit topology includes: an electromagnetic multi-winding transformer, an AC/AC power electronic converter and a bypass switch K; each phase of the electromagnetic multi-winding transformer is formed by winding a set of high-voltage winding W on the same iron core HV And two sets of low-voltage windings W lv1 、W lv2 Composition, low-voltage winding W lv2 Turns of (2) are low-voltage winding W lv1 1/n of (2), where n>1, a step of; the AC/AC power electronic converter input and the low-voltage winding W lv2 The AC/AC power electronic converter output is connected in parallel with the bypass switch K, and the AC/AC power electronic converter output is connected with the low-voltage winding W lv1 The series connection supplies power to a load, the voltage u of the load an And the output voltage u of the AC/AC power electronic converter 2 The low-voltage winding W lv1 Low voltage output voltage u of (2) 1 Satisfy u an＝ u 1 +u 2 。
Further, the three-phase circuit topology structure comprises four combination modes based on a single-phase circuit topology structure, which are respectively as follows: high-voltage side star connection/low-voltage side star connection, high-voltage side star connection/low-voltage side star connection.
Further, the three-phase power frequency electromagnetic transformer adopted by the three-phase circuit topological structure is three single-phase transformers or three-phase common-core transformers.
Further, the AC/AC power electronic converter comprises an AC/DC rectifier, a DC/AC inverter and a DC capacitor C dc The AC/DC rectifier comprises a power semiconductor switching device S 1 、S 2 、S 3 、S 4 And a filter inductance L i The DC/AC inverter comprises a power semiconductor switching device S 5 、S 6 、S 7 、S 8 And a filter inductance L f Ac filter capacitor C f The method comprises the steps of carrying out a first treatment on the surface of the The specific connection mode is as follows: power semiconductor switching device S 1 、S 3 、S 5 、S 7 The drain electrode of (C) is connected with a DC capacitor C dc Positive electrode of power semiconductor switching device S 2 、S 4 、S 6 、S 8 The source electrode of (2) is connected with a DC capacitor C dc Is a negative electrode of (a); power semiconductor switching device S 1 Source and S of (2) 2 Is connected with the drain electrode of the input filter inductance L i Filter inductance L i The other end is connected with an output terminal x; power semiconductor switching device S 3 Source and S of (2) 4 The drain electrode of the capacitor is connected with an alternating current output terminal y; power semiconductor switching device S 5 Source and S of (2) 6 The drain electrode of (1) is connected with the output filter inductance L f Filter inductance L f The other end is connected with an output terminal z; power semiconductor switching device S 7 Source and S of (2) 8 The drain electrode of the capacitor is connected with an alternating current output terminal t; AC filter capacitor C f One end is connected to the ac output terminal z, and the other end is connected to the ac output terminal t.
The control method of the combined transformer based on the multi-winding transformer and the converter is characterized by comprising the following steps:
(1) The control method of the inverter in the AC/AC power electronic converter comprises the following steps:
during normal operation, the reference voltage u at the output end of the combined transformer of the multi-winding transformer and the converter an_ref Output voltage u of electromagnetic multi-winding transformer 1 The difference is used as the reference voltage u of the inverter of the AC/AC power electronic converter 2_ref The inverter output voltage control adopts a voltage-current double closed-loop control strategy, and the reference voltage u 2_ref Actual output voltage u from AC/AC power electronic converter 2 The difference passes through a first proportional resonance controller PR to generate an inductive current inner loop reference value i L_ref Filter inductance L f Current inner loop reference value i L_ref And filter inductance L f Actual value i of current L The difference passes through a first proportional integral controller PI to generate an inverter reference voltage u c_ref Inverter reference voltage u c_ref Generating power via a first PWM modulationSemiconductor device S 5 、S 6 、S 7 、S 8 Is a driving signal of (a);
(2) The rectifier control method in the AC/AC power electronic converter comprises the following steps:
during normal operation, the rectifier of the AC/AC power electronic converter adopts a voltage-current double-closed-loop control strategy, and the direct-current capacitor references the voltage u Cdc_ref And the actual voltage u Cdc The difference generates a part i of the current inner loop reference value through a second proportional integral controller PI dc At the same time through the load current i load Extracting harmonic current component i h And reactive current component i q ，i dc -(i h+ i q ) Is the reference value i of the inner loop current x_ref The method comprises the steps of carrying out a first treatment on the surface of the Current inner loop reference value i x_ref And the current actual value i x The difference generates a rectifier reference voltage u through a second proportional resonance controller PR r_ref Rectifier reference voltage u r_ref Generating a power semiconductor device S through a second PWM modulation 1 、S 2 、S 3 、S 4 Is provided.
Further, when the AC/AC power electronic converter fails, the bypass switch K is closed to bypass the converter, so that continuous power supply to the load is realized; when the power grid is short-circuited, the fault is isolated by the fast turn-off capability of the AC/AC power electronic converter.
The invention has the advantages that:
the AC/AC power electronic converter consists of a non-isolated rectifier and an inverter, and the output voltage and the capacity of the AC/AC power electronic converter are respectively only 1/(n+1) (n > 1) of the output voltage and the capacity of the combined transformer, so that the capacity and the cost of the converter are greatly reduced.
In the invention, taking a single phase as an example, an AC/AC power electronic converter inverter part adopts a double closed-loop control strategy of an alternating voltage outer ring and an alternating current inner ring to control the alternating output voltage u of the inverter 2 Realizing output voltage u of transformer an Is provided. The rectifier part of the AC/AC power electronic converter adopts a double closed-loop control strategy of a direct-current voltage outer ring and an alternating-current inner ring to extract load current harmonic waves and reactive powerThe current is added in the current inner loop reference value, and the harmonic wave control and reactive compensation functions are realized by controlling the current of the rectifier. The control method is also suitable for the three-phase combined transformer.
In the invention, when the AC/AC power electronic converter fails, the bypass of the converter can still continuously supply power to a load through the electromagnetic transformer by closing the switch K, and the reliability is higher than that of the existing full-capacity power electronic transformer. When the power grid is in short circuit fault, the power semiconductor device of the AC/AC power electronic converter is locked to realize quick fault isolation.
Drawings
FIG. 1 is a schematic diagram of a single-phase circuit of a combined transformer based on a multi-winding transformer and a converter according to the present invention;
FIG. 2 is a schematic diagram of a three-phase circuit of a combined transformer based on a multi-winding transformer and a converter according to the present invention;
fig. 3 is a schematic diagram of an AC/AC power electronic converter circuit in accordance with the present invention;
FIG. 4 is a flow chart of a method of controlling an inverter of an AC/AC power electronic converter according to the present invention;
fig. 5 is a flow chart of a method of controlling a rectifier of an AC/AC power electronic converter according to the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments.
Example 1
As shown in fig. 1, a multi-winding transformer and converter-based combined single-phase transformer comprises an electromagnetic multi-winding transformer, an AC/AC power electronic converter and a bypass switch K; each phase of the electromagnetic multi-winding transformer is formed by winding a set of high-voltage winding W on the same iron core hv And two sets of low-voltage windings W lv1 、W lv2 Composition is prepared. Low voltage winding W lv2 Turns of (2) are only the low voltage winding W lv1 1/n (n)>1). AC/AC power electronic converter input and low voltage winding W lv2 Parallel connection, AC/AThe output of the C power electronic converter is connected with the bypass switch K in parallel, and the output of the AC/AC power electronic converter is connected with the low-voltage winding W lv1 Series-connected power supply for load, voltage u of load an And an output voltage u of the AC/AC power electronic converter 2 Low voltage winding W lv1 Low voltage output voltage u of (2) 1 Satisfy u an＝ u 1 +u 2 。
The combined three-phase transformer winding connection mode based on the multi-winding transformer and the converter comprises four connection modes of high-voltage side star connection low-voltage side star connection, high-voltage side star connection low-voltage side corner connection, high-voltage side corner connection low-voltage side star connection and high-voltage side corner connection low-voltage side corner connection, and a three-phase common iron core or independent iron core mode is adopted as a transformer iron core. Fig. 2 is a schematic circuit diagram of a connection mode of a high-voltage side corner joint and a low-voltage side star joint, wherein the iron core adopts a three-phase independent iron core.
As shown in fig. 3, the AC/AC power electronic converter includes an AC/DC rectifier, a DC/AC inverter, and a DC capacitor C dc The AC/DC rectifier comprises a power semiconductor switching device S 1 、S 2 、S 3 、S 4 And a filter inductance L i The DC/AC inverter comprises a power semiconductor switching device S 5 、S 6 、S 7 、S 8 And a filter inductance L f Ac filter capacitor C f The method comprises the steps of carrying out a first treatment on the surface of the The specific connection mode is as follows: power semiconductor switching device S 1 、S 3 、S 5 、S 7 The drain electrode of (C) is connected with a DC capacitor C dc Positive electrode of power semiconductor switching device S 2 、S 4 、S 6 、S 8 The source electrode of (2) is connected with a DC capacitor C dc Is a negative electrode of (a); power semiconductor switching device S 1 Source and S of (2) 2 Is connected with the drain electrode of the input filter inductance L i Filter inductance L i The other end is connected with an output terminal x; power semiconductor switching device S 3 Source and S of (2) 4 The drain electrode of the capacitor is connected with an alternating current output terminal y; power semiconductor switching device S 5 Source and S of (2) 6 The drain electrode of (1) is connected with the output filter inductance L f Filter inductance L f The other end is connected with an output terminal z; power semiconductor switching device S 7 Is a source of (2)And S is 8 The drain electrode of the capacitor is connected with an alternating current output terminal t; AC filter capacitor C f One end is connected to the ac output terminal z, and the other end is connected to the ac output terminal t.
The control method of the combined transformer based on the multi-winding transformer and the converter comprises the following steps:
(1) The control method of the inverter in the AC/AC power electronic converter comprises the following steps:
as shown in fig. 4, in normal operation, the reference voltage u is applied to the output end of the combined transformer of the multi-winding transformer and the converter an_ref Output voltage u of electromagnetic multi-winding transformer 1 The difference is used as the reference voltage u of the inverter of the AC/AC power electronic converter 2_ref The inverter output voltage control adopts a voltage-current double closed-loop control strategy, and the reference voltage u 2_ref Actual output voltage u from AC/AC power electronic converter 2 The difference passes through a first proportional resonance controller PR to generate an inductive current inner loop reference value i L_ref Filter inductance L f Current inner loop reference value i L_ref And filter inductance L f Actual value i of current L The difference passes through a first proportional integral controller PI to generate an inverter reference voltage u c_ref Inverter reference voltage u c_ref Generating a power semiconductor device S through a first PWM modulation 5 、S 6 、S 7 、S 8 Is a driving signal of (a);
(2) The rectifier control method in the AC/AC power electronic converter comprises the following steps:
as shown in FIG. 5, during normal operation, the AC/AC power electronic converter rectifier adopts a voltage-current double closed-loop control strategy, and the DC capacitor references the voltage u Cdc_ref And the actual voltage u Cdc The difference generates a part i of the current inner loop reference value through a second proportional integral controller PI dc At the same time through the load current i load Extracting harmonic current component i h And reactive current component i q ，i dc -(i h+ i q ) Is the reference value i of the inner loop current x_ref The method comprises the steps of carrying out a first treatment on the surface of the Current inner loop reference value i x_ref And the current actual value i x The difference passes through a second proportional resonance controller PR to generate rectifier reference electricityPressing u r_ref Rectifier reference voltage u r_ref Generating a power semiconductor device S through a second PWM modulation 1 、S 2 、S 3 、S 4 Is provided.
When the AC/AC power electronic converter fails, the bypass switch K is closed to bypass the converter, so that continuous power supply to the load is realized; when the power grid is short-circuited, the fault is isolated by the fast turn-off capability of the AC/AC power electronic converter.
The foregoing is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art, who is within the scope of the present invention, should make equivalent substitutions or modifications according to the technical scheme of the present invention and the inventive concept thereof, and should be covered by the scope of the present invention.
Claims (6)
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN118554774A (en) * | 2024-07-26 | 2024-08-27 | 东北电力大学 | Direct AC/AC conversion single-phase source side compensation type HDT topological structure |
| CN119419717A (en) * | 2024-11-05 | 2025-02-11 | 中国船舶集团有限公司第七一九研究所 | Ultra-wide range high precision DC shore power control device |
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2023
- 2023-12-07 CN CN202311672756.6A patent/CN117766278A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN118554774A (en) * | 2024-07-26 | 2024-08-27 | 东北电力大学 | Direct AC/AC conversion single-phase source side compensation type HDT topological structure |
| CN118554774B (en) * | 2024-07-26 | 2024-11-05 | 东北电力大学 | Direct AC/AC conversion single-phase source side compensation type HDT topological structure |
| CN119419717A (en) * | 2024-11-05 | 2025-02-11 | 中国船舶集团有限公司第七一九研究所 | Ultra-wide range high precision DC shore power control device |
| CN119419717B (en) * | 2024-11-05 | 2025-09-23 | 中国船舶集团有限公司第七一九研究所 | Ultra-wide-range high-precision direct-current shore power control device |
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