A three-phase to single-phase power supply and transformation device based on adjustable reactor

Abstract

The invention discloses a three-phase to single-phase power supply and transformation wiring device based on an adjustable reactor, comprising a balancing transformer and a compensation circuit; the first primary winding of the balancing transformer and the first and second secondary windings form an A-phase coil, the second primary winding and the third secondary winding form a B-phase coil, and the third primary winding and the fourth and fifth secondary windings form a C-phase coil; the tail ends of the first and fourth secondary windings are connected, and the head end is connected in parallel with the first adjustable reactor; the terminals of the second, third and fifth secondary windings are connected head to tail, and the head end and tail end of the third secondary winding serve as output ends for connecting traction loads; the head end of the first secondary winding is connected to the tail end of the third secondary winding, and the head ends of the fourth and third secondary windings are connected in parallel with the second adjustable reactor; the invention adopts an adjustable reactor to realize comprehensive control of negative sequence and reactive power, and meets the national standard requirements for power quality; the operation is simple, the control is easy to realize, and the invention can be widely used in the field of AC electrified railways.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronics, and more specifically, relates to a three-phase to single-phase power supply and transformation wiring device based on an adjustable reactor. Background Art

[0002] The advantages of the single-phase system, such as simple structure, low construction cost, and convenient operation and maintenance, determine that single-phase industrial frequency AC is generally used to power locomotives in electrified railways. However, in EMU depots, especially in short-distance urban rail depots, the power supply scheme has the following problems:

[0003] At present, the power supply scheme for EMU depots adopts a separate power supply from the traction substation or a new 110kV traction substation. Due to the large short-circuit capacity of the external power supply system, the negative sequence generated by the single-phase traction power supply to the power system generally does not exceed the relevant regulations. However, when the EMU depot is far away from the traction substation, the above scheme requires a large investment and is not easy to manage and maintain. Therefore, it is necessary to study the power supply scheme of using 10kV or 35kV as the incoming power supply to the EMU depot to achieve the goal of economy and applicability. The ensuing problem is that the short-circuit capacity of the 10kV or 35kV system is relatively small, and the single-phase traction load is easy to cause three-phase imbalance, affecting the power quality of the power grid.

[0004] Therefore, it is necessary to study the three-phase to single-phase power supply and transformation wiring structure in order to achieve the goal of realizing three-phase / single-phase conversion of electric energy while reducing the three-phase imbalance and improving the quality of electric energy to meet relevant requirements. Summary of the invention

[0005] In response to at least one defect or improvement need in the prior art, the present invention provides a three-phase to single-phase power supply and transformation wiring device based on an adjustable reactor, which aims to solve the problem that the single-phase traction load in the power supply scheme using 10kV or 35kV as the incoming power supply to the EMU section is likely to cause three-phase imbalance and affect the power quality of the power grid.

[0006] To achieve the above-mentioned object, according to one aspect of the present invention, a three-phase to single-phase power supply and transformation wiring device based on an adjustable reactor is provided, the device comprising a balancing transformer and a compensation circuit; the first primary winding of the balancing transformer and the first secondary winding and the second secondary winding constitute an A-phase coil, the second primary winding and the third secondary winding constitute a B-phase coil, and the third primary winding and the fourth secondary winding and the fifth secondary winding constitute a C-phase coil; the compensation circuit comprises a first adjustable reactor and a second adjustable reactor;

[0007] The tail ends of the first secondary winding and the fourth secondary winding are connected, and the head ends of the first secondary winding and the fourth secondary winding are connected in parallel with the first adjustable reactor; the terminals of the second secondary winding, the third secondary winding and the fifth secondary winding are connected head to tail, and the head end and the tail end of the third secondary winding serve as output ends for connecting the traction load; the head end of the first secondary winding is connected to the tail end of the third secondary winding, and the head ends of the fourth secondary winding and the third secondary winding are connected in parallel with the second adjustable reactor;

[0008] By adjusting the reactance values ​​of the first adjustable reactor and the second adjustable reactor and / or the number of turns of each secondary winding of the balancing transformer, the currents between the beginning ends of the first secondary winding and the fourth secondary winding and between the beginning and tail ends of the third secondary winding are equal in magnitude and perpendicular in direction, so as to compensate for the imbalance between the three-phase currents received by the primary winding of the balancing transformer.

[0009] Preferably, in the above-mentioned three-phase to single-phase power supply and transformation wiring device, the first adjustable reactor is a first inductor; and the second adjustable reactor includes a capacitor and a second inductor arranged in parallel.

[0010] Preferably, in the above three-phase to single-phase power supply and transformation wiring device, the parameters of the balancing transformer and the compensation circuit satisfy the following constraints:

[0011] (1) The voltage ratio K between the first and fourth secondary windings and the first and tail ends of the third secondary winding is equal to the current ratio between the first and tail ends of the third secondary winding and the first and fourth secondary windings. in, is the traction load power factor;

[0012] (2) The current flowing through the second adjustable reactor is the vector difference between the current of the first adjustable reactor and the current between the first end of the first secondary winding and the first end of the fourth secondary winding.

[0013] Preferably, in the above-mentioned three-phase to single-phase power supply and transformation wiring device, the first primary winding, the second primary winding and the third primary winding have their respective head ends respectively used to receive three-phase currents, and their tail ends are interconnected to form a star connection.

[0014] Preferably, in the above-mentioned three-phase to single-phase power supply and transformation wiring device, the head end of the third secondary winding is connected to the contact network, and the tail end is grounded.

[0015] Preferably, in the above-mentioned three-phase to single-phase power supply and transformation wiring device, the balancing transformer is a YNvd transformer.

[0016] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0017] (1) The three-phase to single-phase power supply and transformation wiring device based on the adjustable reactor provided by the present invention is based on the unique connection structure between the balancing transformer and the compensation circuit (the first adjustable reactor and the second adjustable reactor). By adjusting the reactance values ​​of the first adjustable reactor and the second adjustable reactor, the imbalance between the three-phase currents received by the primary winding of the balancing transformer can be compensated; while realizing the three-phase / single-phase conversion of electric energy, the three-phase imbalance is reduced, thereby improving the quality of electric energy.

[0018] (2) The three-phase to single-phase power supply and transformation wiring device based on an adjustable reactor provided by the present invention adopts a three-phase to single-phase power supply and transformation wiring structure based on an adjustable reactor to achieve comprehensive management of negative sequence and reactive power in response to the single-phase voltage required by the traction power supply system, thereby meeting the national standard requirements for power quality. The device is simple to operate, easy to control, and low in cost, and can be applied in the field of AC electrified railways, especially in the power supply of EMU sections and stations. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of a three-phase to single-phase power supply and transformation wiring device based on an adjustable reactor provided in an embodiment of the present invention;

[0020] Figure 2 It is a voltage and current vector diagram of a three-phase to single-phase power supply and transformation wiring device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0022] The terms "first", "second", "third", "fourth", "fifth", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions.

[0023] The present invention proposes a three-phase to single-phase power supply and transformation wiring device based on an adjustable reactor, which realizes comprehensive management of negative sequence and reactive power for the single-phase voltage required by the traction power supply system, and is mainly used for AC electrified railway traction power supply systems, especially for power supply of EMU depots and stations. Figure 1is a schematic diagram of a three-phase to single-phase power supply and transformation wiring device provided in this embodiment, see Figure 1 As shown, the three-phase to single-phase power supply and transformation wiring device includes a balancing transformer and a compensation circuit; the balancing transformer includes a first primary winding (A1A2), a second primary winding (B1B2), a third primary winding (C1C2), a first secondary winding (a1x1), a second secondary winding (a2x2), a third secondary winding (b1y1), a fourth secondary winding (c1z1) and a fifth secondary winding (c2z2); wherein the first primary winding (A1A2) and the first secondary winding (a1x1), the second secondary winding (a2x2) are connected to each other. 2) constitutes the A phase coil, the second primary winding (B1B2) and the third secondary winding (b1y1) constitute the B phase coil, the third primary winding (C1C2) and the fourth secondary winding (c1z1) and the fifth secondary winding (c2z2) constitute the C phase coil; in this embodiment, the first primary winding (A1A2), the second primary winding (B1B2), and the third primary winding (C1C2) respectively have their head ends (A1, B1, C1) used to receive three-phase current, and the tail ends (A2, B2, C2) are interconnected to form a star connection. The balancing transformer preferably uses a YNvd transformer.

[0024] The compensation circuit includes a first adjustable reactor and a second adjustable reactor; wherein the first adjustable reactor is a first inductor L1; and the second adjustable reactor includes a capacitor C1 and a second inductor L2 which are arranged in parallel.

[0025] See also Figure 1 As shown, the tail ends (x1, z1) of the first secondary winding (a1x1) and the fourth secondary winding (c1z1) are connected, and the head ends (a1, c1) of the first secondary winding (a1x1) and the fourth secondary winding (c1z1) are connected in parallel with the first adjustable inductor L1; the terminals of the second secondary winding (a2x2), the third secondary winding (b1y1) and the fifth secondary winding (c2z2) are connected head to tail, and the head end and the tail end of the third secondary winding (b1y1) are used as output ends for connecting the traction load L, so that the traction load and the compensation circuit have a π-type structure and can cooperate with each other; in a specific application scenario, the head end b1 of the third secondary winding (b1y1) is connected to the contact network, and the tail end y1 is grounded to the rail (grounded).

[0026] The head end a1 of the first secondary winding (a1x1) is connected to the tail end y1 of the third secondary winding (b1y1), and the head ends (c1, b1) of the fourth secondary winding (c1z1) and the third secondary winding (b1y1) are connected in parallel to the second adjustable reactor.

[0027] The voltage of the first inductor L1 is perpendicular to the voltage of the traction load L, and the voltage of the capacitor C1 and the second inductor L2 is the difference between the voltage of the traction load L and the voltage of the first inductor L1.

[0028] By adjusting the reactance values ​​of the first adjustable reactor and the second adjustable reactor and / or the number of turns of each secondary winding of the balancing transformer, the current between the beginning ends (a1, c1) of the first secondary winding (a1x1) and the fourth secondary winding (c1z1) and the current between the beginning and tail ends (b1, y1) of the third secondary winding (b1y1) are equal in magnitude and perpendicular in direction, so as to compensate for the imbalance between the three-phase currents received by the primary winding of the balancing transformer.

[0029] Traction loads are mostly resistive and inductive loads. The traction side of the YNvd transformer contains both active and reactive loads. It is necessary to compensate for reactive power and negative sequence by adjusting the turns of each secondary winding of the transformer and / or the reactance value of the first adjustable reactor and the second adjustable reactor to achieve the goal of meeting national standards for power quality. When the device fully compensates for reactive power and negative sequence, the following constraints must be met:

[0030] (1) The voltage ratio K between the first secondary winding (a1x1), the c1a1 port of the fourth secondary winding (c1z1) and the b1y1 port of the third secondary winding (b1y1) is equal to the ratio of the current magnitude of the b1y1 port to the current magnitude of the c1a1 port. in, is the traction load power factor; I L1 =I b1y1 .

[0031] (2) The current I flowing through the capacitor C1 and the second inductor L2 LC is the current I of the first inductor L1 L1 The current I of the first secondary winding and the fourth secondary winding at the c1a1 port c1a1 At this time, the capacitive reactive power provided by the capacitor C1 and the second inductor L2 in the compensation circuit is greater than the inductive reactive power provided by the first inductor L1, but the currents at the c1a1 and b1y1 ports can still be equal and perpendicular, as shown in Figure 2 shown.

[0032] When the negative sequence is fully compensated, the negative sequence capacity of the two secondary ports c1a1 and b1y1 of the YNvd transformer is the same. According to the power distribution principle, the active power of the traction load is evenly distributed by the two ports c1a1 and b1y1, and the reactive power is compensated by the inductor and capacitor. Therefore, there is a current of the b1y1 port. Because the current of b1y1 port is:

[0033]

[0034] For the current of a1c1 port:

[0035]

[0036] Because when the negative sequence is fully compensated, I b1y1 with I c1a1 The direction is vertical, and I L1 Direction hysteresis U c1a1 90 degrees, by vector Figure 2 It can be seen that if and only if When , equation (2) can be satisfied; and because So there is I L1 =I b1y1 ; and because I b1y1 = k·I c1a1 , can be obtained In summary:

[0037]

[0038] Since the traction load L is known, by adjusting I L1 and I LC The size of the power can be accurately distributed to achieve the purpose of negative sequence compensation.

[0039] The three-phase to single-phase power supply and transformation wiring device based on the adjustable reactor proposed in the present invention is based on the YNvd transformer and is equipped with a suitable capacitor and inductor compensation circuit to construct a three-phase to single-phase wiring structure. It can well inherit the advantages of the YNvd transformer and at the same time give play to the advantages of the adjustable reactor of low cost and easy implementation. The combination of the two can effectively compensate for the three-phase imbalance and fully give play to the superiority of the three-phase to single-phase wiring.

[0040] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A three-phase to single-phase power supply and transformation wiring device based on an adjustable reactor, characterized in that: It includes a balancing transformer and a compensation circuit; the first primary winding of the balancing transformer, the first secondary winding and the second secondary winding constitute an A-phase coil, the second primary winding and the third secondary winding constitute a B-phase coil, and the third primary winding, the fourth secondary winding and the fifth secondary winding constitute a C-phase coil; the compensation circuit includes a first adjustable reactor and a second adjustable reactor; The tail ends of the first secondary winding and the fourth secondary winding are connected, and the head ends of the first secondary winding and the fourth secondary winding are connected in parallel with the first adjustable reactor; the terminals of the second secondary winding, the third secondary winding and the fifth secondary winding are connected head to tail, and the head end and the tail end of the third secondary winding serve as output ends for connecting the traction load; the head end of the first secondary winding is connected to the tail end of the third secondary winding, and the head ends of the fourth secondary winding and the third secondary winding are connected in parallel with the second adjustable reactor; By adjusting the reactance values ​​of the first adjustable reactor and the second adjustable reactor and / or the number of turns of each secondary winding of the balancing transformer, the currents between the beginning ends of the first secondary winding and the fourth secondary winding and between the beginning and tail ends of the third secondary winding are equal in magnitude and perpendicular in direction, so as to compensate for the imbalance between the three-phase currents received by the primary winding of the balancing transformer.

2. The three-phase to single-phase power supply and transformation wiring device based on an adjustable reactor as claimed in claim 1, characterized in that: The first adjustable reactor is a first inductor; the second adjustable reactor includes a capacitor and a second inductor connected in parallel.

3. The three-phase to single-phase power supply and transformation wiring device based on an adjustable reactor as claimed in claim 2, characterized in that: The parameters of the balancing transformer and the compensation circuit satisfy the following constraints: (1) The voltage ratio K between the first and fourth secondary windings and the first and tail ends of the third secondary winding is equal to the current ratio between the first and tail ends of the third secondary winding and the first and fourth secondary windings, and K=1 / (2tanφ), where φ is the traction load power factor; (2) The current flowing through the second adjustable reactor is the vector difference between the current of the first adjustable reactor and the current between the first end of the first secondary winding and the first end of the fourth secondary winding.

4. The three-phase to single-phase power supply and transformation wiring device based on an adjustable reactor as claimed in claim 1, characterized in that: The first primary winding, the second primary winding and the third primary winding have their respective head ends used for receiving three-phase currents, and their tail ends are interconnected to form a star connection.

5. The three-phase to single-phase power supply and transformation wiring device based on an adjustable reactor as claimed in claim 1, characterized in that: The head end of the third secondary winding is connected to the contact network, and the tail end is grounded.

6. The three-phase to single-phase power supply and transformation wiring device based on adjustable reactor according to claim 1, characterized in that: The balancing transformer is a YNvd transformer.

Images