On-load voltage regulation switch, voltage regulation transformer and dynamic on-load voltage regulation method

Abstract

The invention provides an on-load voltage regulation switch, a voltage regulation transformer and a dynamic on-load voltage regulation method, a voltage regulation winding of the voltage regulation transformer is a plurality of groups of sub-windings which are connected in series, each group of sub-windings comprises a forward winding and a reverse winding, one ends of the forward winding and the reverse winding are fixedly connected, and the other ends of the forward winding and the reverse winding are connected through the on-load voltage regulation switch. In the whole closing and opening process of the on-load tap changer, the power electronic switch can protect contacts of the main relay and the auxiliary relay, the two relays also protect each other, arc-free closing and opening are achieved, the service life of the relays is greatly prolonged, and the service life of the on-load tap changer is prolonged. The on-load tap changer composed of the relay and the electronic power switch is simple in structure, small in size, low in power consumption, light in weight, low in cost and high in reliability. When the on-load tap changer is applied to the on-load tap changer, the forward winding and the reverse winding are connected in parallel or disconnected by dynamically adjusting the on and off of the on-load tap changer, and dynamic, arc-free, rapid, stable, safe and reliable voltage regulation is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of distribution transformers, and in particular to an on-load voltage regulating switch, a voltage regulating transformer and a dynamic on-load voltage regulating method. Background Art

[0002] Voltage quality is an important indicator for assessing the power supply service level of the power grid, especially the size of the power supply voltage deviation, which directly affects the quality and output of industrial product production, affects people's normal work and life, and affects the safety and economic operation of the power grid. The most commonly used method in distribution network voltage control technology is to adjust the voltage through distribution transformers. At present, there are two types of distribution transformers: no-load voltage-regulating transformers and on-load voltage-regulating transformers. Although no-load voltage-regulating transformers have the advantages of reliable operation and low cost, they have disadvantages such as necessary power outages and too small voltage regulation range. The application of on-load voltage-regulating transformers in power systems is becoming more and more widespread, and its role in improving system voltage quality and power supply reliability is crucial.

[0003] However, most of the mechanical on-load tap-changers used to drive load-adjusting voltage in traditional on-load voltage-regulating transformers adopt the form of current-limiting resistor transition and oil arc extinguishing, and the contacts of the tap-changers are immersed in transformer oil. Generally, the size of the tap-changers is large, and a large arc is generated when the tap-changers are switched under load, which easily burns the contacts and causes the deterioration of the transformer oil, affecting the insulation properties and service life of the transformer. Therefore, the transformer oil needs to be replaced regularly, resulting in high operating costs. In addition, the voltage regulation response speed of the tap-changer is slow, it cannot be operated frequently, the efficiency is low, the mechanical transmission structure is complex, the failure rate is high, and the maintenance workload is large. Summary of the invention

[0004] In order to overcome the above-mentioned deficiencies of the prior art, an object of the present invention is to provide an on-load voltage regulating switch, a voltage regulating transformer and a dynamic on-load voltage regulating method to improve the safety and reliability of the on-load voltage regulating transformer.

[0005] The present invention provides an on-load voltage regulating switch, comprising a main relay, an auxiliary relay, a power electronic switch and a relay control module; the static contact of the main relay is connected to the static contact of the auxiliary relay, the moving contact of the main relay is connected to the first end of the power electronic switch; the moving contact of the auxiliary relay is connected to the second end of the power electronic switch; the relay control module is used to control the closing of the main relay and the auxiliary relay at the moment when the input voltage passes through zero, and control the disconnection of the main relay and the auxiliary relay at the moment when the output current passes through zero.

[0006] According to an on-load voltage regulating switch provided by the present invention, the power electronic switch is a diode, the cathode of the diode serves as the first end of the power electronic switch, and the anode of the diode serves as the second end of the power electronic switch.

[0007] According to an on-load voltage regulating switch provided by the present invention, the power electronic switch is a thyristor, an IGBT or a MOSFET.

[0008] According to an on-load tap-changing switch provided by the present invention, the relay control module comprises: a measurement and control unit, used for detecting the input voltage and the output current, and sending a control instruction to a trigger unit; the trigger unit is used for providing a trigger signal for the main relay and the auxiliary relay according to the control instruction.

[0009] According to an on-load tap-changing switch provided by the present invention, the relay control module further comprises a control power supply unit, and the control power supply unit is used to supply power to the control coils of the main relay and the auxiliary relay according to the trigger signal.

[0010] According to an on-load voltage regulating switch provided by the present invention, the closing and opening time of the main relay is within 10 ms, and the closing and opening time of the auxiliary relay is within 10 ms.

[0011] According to an on-load voltage regulating switch provided by the present invention, the main relay is a magnetic latching relay.

[0012] According to an on-load voltage regulating switch provided by the present invention, the number of the on-load voltage regulating switches to be set is determined according to the voltage regulating level of the transformer using a 1248 encoding method.

[0013] The present invention also provides an on-load voltage-regulating transformer, comprising: a low-voltage side and a high-voltage side, the low-voltage side comprising a low-voltage winding, the high-voltage side comprising the above-mentioned on-load voltage-regulating switch, and also comprising a high-voltage side winding; the high-voltage side winding comprises a fixed winding and a voltage-regulating winding connected in series; the voltage-regulating winding is a plurality of groups of sub-windings connected in series, each group of the sub-windings comprises a forward winding and a reverse winding, the forward winding is fixedly connected to one end of the reverse winding, and the other end is connected through the on-load voltage-regulating switch.

[0014] The present invention also provides a dynamic on-load voltage regulation method applied to the above-mentioned on-load voltage regulation transformer, comprising: generating a voltage regulation instruction according to the output voltage of the on-load voltage regulation transformer on the low-voltage side; according to the voltage regulation instruction, controlling the closing of the main relay and the auxiliary relay at the moment when the input voltage passes through zero, and controlling the opening of the main relay and the auxiliary relay at the moment when the output current passes through zero.

[0015] The present invention provides an on-load voltage-regulating switch, a voltage-regulating transformer and a dynamic on-load voltage-regulating method. The voltage-regulating winding of the voltage-regulating transformer is a plurality of groups of sub-windings connected in series, each group of sub-windings includes a forward winding and a reverse winding, one end of the forward winding is fixedly connected to the reverse winding, and the other end is connected through the on-load voltage-regulating switch. During the entire closing and opening process of the on-load voltage-regulating switch, the power electronic switch can protect the contacts of the main relay and the auxiliary relay, and the two relays also protect each other, so as to achieve arc-free closing and opening, which greatly prolongs the life of the relay. In addition, the on-load voltage-regulating switch composed of the relay and the power electronic switch has a simple structure, small size, low power consumption, light weight, low cost and high reliability. When the on-load voltage-regulating switch is applied to the on-load voltage-regulating transformer, the forward winding and the reverse winding are connected in parallel or disconnected by dynamically adjusting the closing and opening of the on-load voltage-regulating switch, so as to achieve dynamic, arc-free, fast, stable, safe and reliable voltage regulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 It is a structural schematic diagram of an on-load voltage regulating switch provided by the present invention;

[0018] Figure 2 It is a schematic diagram of a simple mathematical model of a 400V distribution network including distributed photovoltaic provided by the present invention;

[0019] Figure 3 It is a schematic diagram of the structure of the on-load voltage regulation circuit provided by the present invention;

[0020] Figure 4 It is a schematic diagram of voltage analysis of two coupled coils provided by the present invention;

[0021] Figure 5 It is a structural schematic diagram of another on-load voltage regulating switch provided by the present invention;

[0022] Figure 6 It is a schematic diagram of the 9-level on-load voltage regulation structure of the 10kV distribution transformer provided by the present invention;

[0023] Figure 7 This is a connection structure diagram of a coil and an on-load voltage regulator using a 1248 encoding method provided by the present invention;

[0024] Figure 8 The present invention provides a 9-level voltage regulation circuit schematic diagram using a 1248 encoding method. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Combine the following Figure 1-Figure 8 The invention describes an on-load voltage regulating switch, a voltage regulating transformer and a dynamic on-load voltage regulating method.

[0027] Please refer to Figure 1 , Figure 1 The present invention provides a schematic structural diagram of an on-load voltage regulating switch.

[0028] The present invention provides an on-load voltage regulating switch, comprising a main relay 1, an auxiliary relay 2, a power electronic switch 3 and a relay control module 4; the static contact of the main relay 1 is connected to the static contact of the auxiliary relay 2, the moving contact of the main relay 1 is connected to the first end of the power electronic switch 3; the moving contact of the auxiliary relay 2 is connected to the second end of the power electronic switch 3; the relay control module 4 is used for controlling the closing of the main relay 1 and the auxiliary relay 2 at the moment when the input voltage passes through zero, and controlling the opening of the main relay 1 and the auxiliary relay 2 at the moment when the output current passes through zero.

[0029] In recent years, with the development of distributed photovoltaic construction, for example, a village in the north has 137 distributed photovoltaic power stations with a capacity of 1,128 kW, involving 7 substations. Faced with a large number of photovoltaic power sources connected, the substation access rate is as high as 64%, exceeding the access capacity. The weak absorption capacity of the regional power grid has led to low power generation efficiency for some users, affecting the benefits of residents.

[0030] After the large-scale access of distributed photovoltaics, problems such as power backflow in the power grid and overvoltage in users have gradually emerged. For example, a certain power grid currently has 143,000 photovoltaic distribution transformers connected, accounting for 33% of public distribution transformers, of which 117,000 distribution transformers have power backflow. Taking a certain area as an example, 89% of photovoltaic users have overvoltage problems, of which 36% of users have overvoltage multiples exceeding 1.14 times the rated voltage, posing a great challenge to the safe use of electricity by users' electrical equipment.

[0031] Please refer to Figure 2 , Figure 2 A schematic diagram of a simple mathematical model of a 400V distribution network containing distributed photovoltaics provided by the present invention.

[0032] The power factor of a 400V distribution network is generally very high, close to 1.0. To simplify the derivation and calculation, it is assumed that all impedances are resistive. Based on a simple mathematical model of a 400V distribution network with distributed photovoltaics, it can be deduced that:

[0033] U L =(I s +I p )*Z

[0034] Among them, U L is the load voltage, U S is the power distribution voltage, I s is the power distribution current, I p is the photovoltaic current source current, Z L is the load, z p is the internal impedance of the photovoltaic current source, z s is the internal impedance of the power supply, Z0 is the line impedance, and Z is Z L and z p The equivalent impedance after parallel connection is Z = Z L *z p / (Z L +z p )

[0035] It can be seen that when I p Keep U when increasing L Stable, only reduce I s and (or) Z, where a reduction in Z means an increase in the load, which has a higher implementation cost.

[0036] Because I s =(U S -U L ) / (z s +Z0), for the established distribution network, (z s +Z0) is basically unchanged, so it mainly affects I s What changes is U S , which is the output voltage of the distribution transformer. Therefore, to dynamically change the output voltage of the distribution transformer, on-load voltage regulation is one of the main measures.

[0037] In order to solve the technical problems in the prior art that a large electric arc is generated when a mechanical on-load tap changer switches load, which easily burns the contacts and causes the deterioration of the transformer oil, resulting in high operating costs, and the tap changer has a slow voltage regulation response speed, cannot be operated frequently, has low efficiency, a complex mechanical transmission structure, a high failure rate, and a large maintenance workload, the present invention uses coupled inductor theory and AC soft switching technology to propose an on-load voltage regulating switch, a voltage regulating transformer and a dynamic on-load voltage regulating method, which are applied to low-voltage distribution transformers, so that the distributed photovoltaic absorption capacity of the substation can be increased to more than 90%, and the cost is controllable.

[0038] Please refer to Figure 3 , Figure 3 This is a schematic diagram of the structure of the on-load voltage regulation circuit provided by the present invention.

[0039] The on-load voltage regulating circuit proposed in the present invention is to set a voltage regulating winding, which is a plurality of groups of sub-windings connected in series, each group of sub-windings includes a forward winding and a reverse winding, one end of the forward winding is fixedly connected to the reverse winding, and the other end is connected through an on-load voltage regulating switch. The reverse winding is added to offset the magnetic flux of part of the forward winding, thereby equivalently changing the voltage ratio between the primary and secondary sides of the transformer. The number of turns, material and cross-sectional area of ​​the forward winding and the reverse winding can be the same. Assuming that the winding direction of the fixed winding is forward, the forward winding in the voltage regulating winding is connected in series with the fixed winding. In each group of sub-voltage regulating windings, under the action of voltage, if the on-load voltage regulating switch is closed, the forward winding and the reverse winding with the same number of turns are connected in parallel. When the current with the same direction and the same value flows through the two windings, the magnetic flux generated by them cancels each other, which is equivalent to two wires connected in parallel, becoming a non-inductive resistor with a very small resistance value; if the on-load voltage regulating switch is turned on, the magnetic flux generated by the current of the forward winding is not affected because there is no current in the reverse winding.

[0040] To simplify the explanation, we will take a reverse winding as an example to highlight the key points. Figure 3 The transformer core is not drawn in the figure. Assume that the number of turns of the forward fixed windings at both ends is m, and the sum is 2m, and the number of turns of the middle forward winding is n. The coil of the forward winding and the coil of the fixed winding are connected in series. The number of turns of the reverse winding is n. One end of the middle forward winding is fixedly connected to one end of the reverse winding, and the other end of the reverse winding is connected to the other end of the middle forward winding through the on-load voltage regulator K. When the on-load voltage regulator K is disconnected, the reverse winding does not work; when the on-load voltage regulator K is closed, it is equivalent to the reverse winding and the forward winding being connected in parallel. Since they have opposite spiral directions and the same number of turns, the magnetic flux is offset under the action of the current in the same direction, and the whole is a resistance. Therefore, when the on-load voltage regulator K is disconnected, the equivalent number of turns of the on-load voltage regulator circuit is 2m+n, and when the on-load voltage regulator K is closed, the equivalent number of turns of the on-load voltage regulator circuit is 2m. In this way, the on-off of the on-load voltage regulator K plays a role in adjusting the equivalent number of turns of the on-load voltage regulator circuit.

[0041] Please refer to Figure 4 , Figure 4 A schematic diagram of voltage analysis of two coupled coils provided by the present invention.

[0042] Decompose the coil of the forward winding and the coil of the reverse winding. Assume that the two ends of the middle coil of the forward winding are A and B, and the two ends of the coil of the reverse winding are C and D, and the applied voltage is U 施 , current i enters from A and exits from B, then the magnetic flux The direction of Figure 4 As shown. According to the definition of the same-name terminals of the transformer, A and D can be judged as the same-name terminals, so the induced electromotive force U of the reverse winding 感 C is positive and D is negative. Since the two coils have the same number of turns, U 施 =U 感 If A and C are connected together, due to U 施 =U 感 , so the potential of B and D is the same, that is, there is no potential difference between B and D. If a switch is connected between B and D, there is almost no requirement for the withstand voltage of the switch.

[0043] In addition, according to the single-ended different-side connection method of the two coupled inductors, it can also be deduced that the potentials of the B and D terminals are the same after the A and C terminals are connected together.

[0044] The on-load voltage regulating switch of the present invention comprises a main relay 1, an auxiliary relay 2, a power electronic switch 3 and a relay control module 4.

[0045] The relay control module 4 controls the closing of the main relay 1 and the auxiliary relay 2 according to the zero-crossing moment of the input voltage. Specifically, before the on-load voltage-adjusting switch is closed, the main relay 1 and the auxiliary relay 2 are both in the disconnected state. When the input voltage passes through zero from positive to negative, the relay control module 4 controls the auxiliary relay 2 to close. During the closing process of the auxiliary relay 2, due to the blocking effect of the power electronic switch 3, there is no current in the circuit, so the contacts of the auxiliary relay 2 will not arc. After the auxiliary relay 2 is closed, when the input voltage passes through zero from negative to positive, due to the closing effect of the power electronic switch 3, current flows through the circuit. At this time, the relay control module 4 controls the main relay 1 to close. Since the voltage across the contacts of the main relay 1 is close to zero, no arcing occurs. Afterwards, in order to extend the life of the auxiliary relay 2, the auxiliary relay 2 is disconnected again, thereby completing the closing process of the on-load voltage-adjusting switch.

[0046] The relay control module 4 controls the disconnection of the main relay 1 and the auxiliary relay 2 according to the zero-crossing moment of the output current. Specifically, before the on-load voltage regulator is disconnected, the main relay 1 is in a closed state, the auxiliary relay 2 is in an open state, and the relay control module 4 controls the auxiliary relay 2 to close. During the closing process of the auxiliary relay 2, since the main relay 1 is in a closed state, the contacts of the auxiliary relay 2 do not arc. After the auxiliary relay 2 is closed, the relay control module 4 controls the main relay 1 to disconnect when the output current passes from negative zero to positive. Due to the bypass closing effect of the series circuit of the power electronic switch 3 and the auxiliary relay 2 on the forward current, the voltage across the contacts of the main relay 1 is close to zero and no arcing occurs. After the output current changes from positive to zero, the auxiliary relay 2 is disconnected, thereby completing the disconnection process of the on-load voltage regulator.

[0047] During the entire process of closing and opening of the on-load tap-changing switch, the power electronic switch 3 plays a dual role in protecting the contacts of the main relay 1 and the auxiliary relay 2. The two relays also protect each other, achieving arc-free closing and opening, achieving the effect of "AC soft switching", and greatly extending the life of the relay.

[0048] The relay control module 4 may include but is not limited to a single chip microcomputer. The main relay 1, the auxiliary relay 2 and the power electronic switch 3 operate in a certain time sequence to realize the automatic closing and opening of the relay and complete the switching of the transformer winding. The entire voltage regulation process does not require human intervention.

[0049] Through the on-off coordination of the main relay 1, the auxiliary relay 2 and the power electronic switch 3 in the on-load voltage regulator, on the one hand, the reverse winding can be connected in parallel with the forward winding to achieve the purpose of reducing or maintaining the original number of equivalent winding turns. On the other hand, the arc generated during the voltage regulation process can be eliminated by the action of the on-load voltage regulator. Through the joint use of multiple voltage regulating sub-windings and on-load voltage regulators, the regulation level of the voltage regulating sub-windings can be several times the order of magnitude, which increases the voltage regulation range and accuracy of the distribution transformer, so that the fluctuation of the load-end voltage is maintained within a reasonable range, greatly improving the safety and reliability of the transformer.

[0050] Please refer to Figure 5 , Figure 5 A schematic structural diagram of another on-load voltage regulating switch provided by the present invention.

[0051] As a preferred embodiment, the power electronic switch 3 is a diode, the cathode of the diode serves as the first end of the power electronic switch 3 , and the anode of the diode serves as the second end of the power electronic switch 3 .

[0052] In this embodiment, the on-load voltage regulating switch includes a main relay 1, an auxiliary relay 2, a diode D and a relay control module 4. Specifically, the static contact of the main relay 1 and the static contact of the auxiliary relay 2 are connected in parallel to form a power input terminal in, the power input terminal in is connected to the tap of the high-voltage winding, the moving contact of the main relay 1 and the cathode of the diode D are connected in parallel to form a power output terminal out, the power output terminal out is connected to the tap of the voltage regulating winding, and then the moving contact of the auxiliary relay 2 is connected to the anode of the diode D.

[0053] The relay control module 4 controls the closing of the main relay 1 and the auxiliary relay 2 at the moment when the input voltage passes through zero. Specifically, before the on-load voltage regulating switch is closed, the main relay 1 and the auxiliary relay 2 are both in the disconnected state. When the input voltage passes through zero from positive to negative, the relay control module 4 controls the auxiliary relay 2 to close. During the closing process of the auxiliary relay 2, due to the reverse blocking of the diode D, there is no current in the circuit, so the contacts of the auxiliary relay 2 will not arc. After the auxiliary relay 2 is closed, when the input voltage passes through zero from negative to positive, due to the forward conduction of the diode D, current flows through the circuit. At this time, the relay control module 4 controls the main relay 1 to close. Since the voltage across the contacts of the main relay 1 is close to zero, no arcing occurs. Afterwards, in order to extend the life of the auxiliary relay 2, the auxiliary relay 2 is disconnected again, thereby completing the closing process of the on-load voltage regulating switch.

[0054] The relay control module 4 controls the disconnection of the main relay 1 and the auxiliary relay 2 at the moment when the output current passes through zero. Specifically, before the on-load voltage regulator is disconnected, the main relay 1 is in a closed state, the auxiliary relay 2 is in an open state, and the relay control module 4 controls the auxiliary relay 2 to close. During the closing process of the auxiliary relay 2, since the main relay 1 is in a closed state, the contacts of the auxiliary relay 2 do not arc. After the auxiliary relay 2 is closed, the relay control module 4 controls the main relay 1 to disconnect when the output current passes through zero from negative to positive. Due to the bypass closing effect of the series circuit of the diode D and the auxiliary relay 2 on the forward current, the voltage across the contacts of the main relay 1 is close to zero and no arcing occurs. After the series circuit of the diode D and the auxiliary relay 2 changes from positive to zero, the auxiliary relay 2 is disconnected, thereby completing the disconnection process of the on-load voltage regulator.

[0055] The diode has the function of unidirectional conduction. Under the action of forward voltage, the resistance of the diode is very small and it is in a closed state, which is equivalent to a switched on switch. Under the action of reverse voltage, the resistance is very large and it is in a cut-off state, like a switched off switch. Various logic circuits can be formed by using the switching characteristics of the diode.

[0056] Of course, the anode of the diode also serves as the first end of the power electronic switch, and the cathode of the diode serves as the second end of the power electronic switch. The principle is the same, except that the voltage (current) zero-crossing moment for controlling the relay to close or open is different, which will not be elaborated in the present invention.

[0057] Therefore, the present invention will not cause transformer loss, and because the on-load voltage regulator does not spark or arc when it is in operation, the service life of the on-load voltage regulator will be greatly extended. At the same time, the on-load voltage regulator of the transformer can be adjusted frequently and dynamically, which is of great benefit to improving the power supply quality of the power grid.

[0058] As a preferred embodiment, the power electronic switch 3 is a thyristor or an IGBT (Insulated Gate Bipolar Transistor) or a MOSFET (Metal Oxide Semiconductor Field-Effect Transistor).

[0059] Due to the use of electronic switches such as IGBT and thyristor, especially IGBT has the advantages of fast switching speed, good thermal stability, low driving power and simple driving circuit, IGBT not only has good switching characteristics, but also eliminates the generation of conventional switching arc during the transition process.

[0060] The MOS tube has high control accuracy and a very short closing time, generally not exceeding one quarter of the AC cycle, so its overcurrent characteristics can be fully utilized.

[0061] As a preferred embodiment, the relay control module 4 includes: a measurement and control unit for detecting input voltage and output current, and sending control instructions to a trigger unit; the trigger unit is used to provide trigger signals for the main relay 1 and the auxiliary relay 2 according to the control instructions.

[0062] In this embodiment, the relay control module 4 includes a measurement and control unit and a trigger unit. The measurement and control unit first measures the input voltage of the power input terminal in and the output current of the power output terminal out to provide a reference for the voltage regulating switch action. The trigger unit generates a trigger signal according to the control instruction, closes or opens the main relay 1 or the auxiliary relay 2, and realizes the reverse winding connected to the forward winding in parallel, thereby achieving the purpose of dynamic on-load voltage regulation.

[0063] As a preferred embodiment, the relay control module 4 further includes a control power supply unit, which is used to supply power to the control coils of the main relay 1 and the auxiliary relay 2 according to the trigger signal.

[0064] In this embodiment, the relay control module 4 further includes a control power supply unit. Apply the "+" power supply, When the “-” power is applied, the contacts are closed, and when the DC power is disconnected, the contacts are opened. The main relay 1 has two control coils. and The DC pulse will close the contact of main relay 1. and Applying a DC pulse between the two coils will open the contacts of the main relay 1. It is forbidden to apply a DC pulse to the two coils at the same time.

[0065] In order to achieve rapid voltage regulation of the transformer, as a preferred embodiment, the closing and opening time of the main relay 1 is within 10ms, and the closing and opening time of the auxiliary relay 2 is within 10ms, so that the transformer can quickly regulate the voltage when using the on-load tap-changing switch.

[0066] As a preferred embodiment, the main relay 1 is a magnetic latching relay, and the auxiliary relay 2 is a magnetic latching relay or a conventional relay.

[0067] In order to reduce the power consumption of the on-load voltage regulator, in this embodiment, the main relay 1 uses a magnetic latching relay, and the auxiliary relay 2 uses a magnetic latching relay or a conventional relay, which has the advantages of safety and reliability, long life, only pulse excitation, low power consumption, strong load capacity, small size, etc., which can reduce the size of the transformer on-load voltage regulator and reduce the cost of the entire on-load voltage regulator.

[0068] Of course, when selecting the diode D and the auxiliary relay 2, attention should be paid to their half-wave peak withstand current.

[0069] As a preferred embodiment, the 1248 encoding method is used to determine the number of on-load tap-changing switches to be set according to the voltage regulation level of the transformer.

[0070] Specifically, considering the 10kV / 400V on-load voltage-changing distribution transformer used in distributed photovoltaic and load mixed occasions, multiple adjustments may be required due to the large and frequent changes in photovoltaic output.

[0071] Please refer to Figure 6 , Figure 6 This is a schematic diagram of the 9-level on-load voltage regulation structure of the 10kV distribution transformer provided by the present invention.

[0072] The 10kV high-voltage side winding is equipped with 9 taps and 8 on-load tap-changing switches. The high-voltage winding is wound in the forward direction, the tap-changing winding is wound in the reverse direction, and the opposite ends (non-same-name ends) are connected. In the figure, ① indicates the number of coil turns corresponding to a basic voltage regulation level difference. This structure can achieve 9-level linear voltage regulation. Assuming that the transformation ratio when all switches are turned on is k (high voltage: low voltage), the transformation ratio corresponding to the sequential closing of K1, K2,...K8 is 0.975k, 0.95k...0.8k.

[0073] Obviously, this structure requires 8 on-load tap-changers, which is a large number.

[0074] Please refer to Figure 7 , Figure 7 This is a connection structure diagram of a coil and an on-load voltage regulator using the 1248 encoding method provided by the present invention.

[0075] The use of 1248 coding can reduce the number of taps and on-load voltage regulators, and can achieve an 8-level voltage regulation structure. In the figure, ①, ②, and ④ respectively represent the number of coil turns corresponding to one, two, and four basic voltage regulation levels. Using the coding method, only 3 on-load voltage regulators can achieve 8 levels of voltage regulation, which is better than Figure 7 The structure is more superior and the voltage regulation accuracy is higher.

[0076] Assuming that the transformation ratio when all switches are turned on is k (high voltage: low voltage), and a basic voltage regulation step is 2.5%, the transformation ratio corresponding to the opening and closing combination of K1, K2, and K3 is shown in Table 1 below.

[0077] Table 1 Voltage regulation level table

[0078]

[0079]

[0080] Note: ○ means open, ┃ means closed.

[0081] Please refer to Figure 8 , Figure 8 A schematic diagram of a 9-level voltage regulation circuit using 1248 encoding provided by the present invention.

[0082] If you want to achieve 9-level voltage regulation, you need to add an on-load voltage regulator and a coil corresponding to the basic voltage regulation level difference. When K1, K2, K3 and K4 are all closed, the transformation ratio is 0.8k.

[0083] The arrangement is arranged in 1248 coding mode, and the number of coils of the on-load voltage regulator and the voltage regulating winding is the same. Assuming that the number of coils of the on-load voltage regulator and the voltage regulating winding is n, and the number of voltage regulating stages is N, then n and N are constrained by the following relationship.

[0084] 2 (n-1) <N≤2 n

[0085] Where n=1, 2, ... For example, when n=3, the value range of N is 5-8; when n=4, the value range of N is 9-16.

[0086] Similarly, the above examples can also be applied to on-load tap-changing transformers with higher voltage levels (33kV, 110kV, etc.), adjustable reactors, and adjustable inductors in other high voltage applications, and the present invention will not be elaborated herein.

[0087] In addition, in the present invention, even if an individual on-load tap-changing switch fails, it will not affect the use of the entire transformer; of course, there is no need to set a current limiting resistor; the connection at the tap does not require a high-voltage switch, which greatly reduces the manufacturing and operation and maintenance costs of the transformer.

[0088] The present invention also provides an on-load voltage-regulating transformer, comprising: a low-voltage side and a high-voltage side, the low-voltage side comprising a low-voltage winding, the high-voltage side comprising the above-mentioned on-load voltage-regulating switch, and also comprising a high-voltage side winding; the high-voltage side winding comprises a fixed winding and a voltage-regulating winding connected in series; the voltage-regulating winding is a plurality of groups of sub-windings connected in series, each group of sub-windings comprises a forward winding and a reverse winding, one end of the forward winding is fixedly connected to the reverse winding, and the other end is connected through the on-load voltage-regulating switch.

[0089] For an introduction to an on-load voltage-regulating transformer provided by the present invention, please refer to the above-mentioned on-load voltage-regulating switch embodiment, and the present invention will not be described in detail here.

[0090] The present invention also provides a dynamic on-load voltage regulation method applied to the above-mentioned on-load voltage regulation transformer, comprising: generating a voltage regulation instruction according to the output voltage of the on-load voltage regulation transformer on the low-voltage side; according to the voltage regulation instruction, controlling the closing of the main relay and the auxiliary relay when the input voltage passes through zero, and controlling the opening of the main relay and the auxiliary relay when the output current passes through zero.

[0091] The on-load voltage regulation method of the present invention controls the number of reverse winding coils connected in parallel to the forward winding coils in the multi-section sub-windings of the high-voltage side voltage regulating winding according to the voltage change on the low-voltage side of the voltage regulating transformer. Specifically, the low-voltage side monitoring system detects the output voltage of the on-load voltage regulating transformer, generates a voltage regulation instruction after data processing, and sends the voltage regulation instruction to the high-voltage side monitoring system. The instruction transmission method can be wireless or optical fiber communication. Finally, the high-voltage side monitoring system will control the closing of the main relay and the auxiliary relay at the moment when the input voltage passes through zero according to the voltage regulation instruction, so as to realize the reverse winding being connected in parallel to the forward winding; and control the disconnection of the main relay and the auxiliary relay at the moment when the output current passes through zero, so as to disconnect the connection between the reverse winding and the forward winding, so as to achieve the purpose of changing the equivalent transformation ratio and thus changing the voltage on the low-voltage side.

[0092] For example, when the input voltage passes through zero from positive to negative, power is supplied to the control coil of auxiliary relay 2 to control the closing of auxiliary relay 2; when the input voltage passes through zero from negative to positive, a DC pulse is supplied to the first control coil of main relay 1 to control the closing of main relay 1; when the output current passes through zero from negative to positive, a DC pulse is supplied to the second control coil of main relay 1 to control the disconnection of main relay 1; when the output current passes through zero from positive to negative, power supply to the control coil of auxiliary relay 2 is disconnected to control the disconnection of auxiliary relay 2.

[0093] It should be noted that the actuating coil of the main relay 1 only needs pulse excitation.

[0094] For an introduction to an on-load voltage regulation method provided by the present invention and applied to the above-mentioned dynamic on-load voltage regulation transformer, please refer to the above-mentioned on-load voltage regulation switch embodiment, and the present invention will not be described in detail here.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An on-load voltage regulating switch, characterized in that: Includes main relay, auxiliary relay, power electronic switch and relay control module; The static contact of the main relay is connected to the static contact of the auxiliary relay, and the moving contact of the main relay is connected to the first end of the power electronic switch; The moving contact of the auxiliary relay is connected to the second end of the power electronic switch; The relay control module is used to control the closing of the main relay and the auxiliary relay when the input voltage passes through zero, and to control the opening of the main relay and the auxiliary relay when the output current passes through zero.

2. The on-load voltage regulating switch according to claim 1, characterized in that: The power electronic switch is a diode, the cathode of the diode serves as the first end of the power electronic switch, and the anode of the diode serves as the second end of the power electronic switch.

3. The on-load voltage regulating switch according to claim 1, characterized in that: The power electronic switch is a thyristor, an IGBT or a MOSFET.

4. The on-load voltage regulating switch according to claim 1, characterized in that: The relay control module comprises: A measurement and control unit, used for detecting the input voltage and the output current, and sending a control instruction to a trigger unit; The trigger unit is used to provide a trigger signal for the main relay and the auxiliary relay according to the control instruction.

5. The on-load voltage regulating switch according to claim 4, characterized in that: The relay control module further includes a control power supply unit, which is used to supply power to the control coils of the main relay and the auxiliary relay according to the trigger signal.

6. The on-load voltage regulating switch according to claim 1, characterized in that: The closing and opening time of the main relay is within 10ms, and the closing and opening time of the auxiliary relay is within 10ms.

7. The on-load voltage regulating switch according to claim 1, characterized in that: The main relay is a magnetic latching relay.

8. The on-load voltage regulating switch according to any one of claims 1 to 7, characterized in that: The number of on-load voltage regulators to be set is determined according to the voltage regulation level of the transformer using the 1248 coding method.

9. An on-load voltage-changing transformer, characterized in that: It includes a low-voltage side and a high-voltage side, the low-voltage side includes a low-voltage winding, the high-voltage side includes the on-load voltage-regulating switch according to any one of claims 1 to 8, and also includes a high-voltage side winding; the high-voltage side winding includes a fixed winding and a voltage-regulating winding connected in series; the voltage-regulating winding is a plurality of groups of sub-windings connected in series, each group of the sub-windings includes a forward winding and a reverse winding, the forward winding is fixedly connected to one end of the reverse winding, and the other end is connected through the on-load voltage-regulating switch.

10. A dynamic on-load voltage regulation method applied to the on-load voltage regulation transformer according to claim 9, characterized in that: include: generating a voltage regulation instruction according to the output voltage of the on-load voltage regulating transformer at the low voltage side; According to the voltage regulation instruction, the main relay and the auxiliary relay are controlled to be closed when the input voltage passes through zero, and the main relay and the auxiliary relay are controlled to be opened when the output current passes through zero.

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