Reactive power compensation circuit and capacitance compensation module

Abstract

The invention discloses a reactive power compensation circuit and a capacitance compensation module. The reactive power compensation circuit comprises: a magnetic balance coil comprising a primary winding and a secondary winding; the first loop comprises a first capacitor which is connected in series with the primary winding; the second loop comprises an impedance adjusting unit connected in series with the secondary winding, and the impedance adjusting unit is used for enabling the impedance characteristic of the second loop to be capacitive when fundamental voltage is applied and / or enabling the impedance characteristic of the second loop to be inductive in a harmonic environment; the second loop is connected with the first loop and is used for being capacitive when fundamental voltage is applied to the first loop, so that impedance of the magnetic balance coil in the first loop is reduced to guarantee that the first capacitor compensates reactive power, and / or the second loop is inductive when the first loop is in a harmonic environment, so that impedance of the magnetic balance coil in the first loop is increased to guarantee that the first capacitor compensates reactive power. Therefore, the harmonic current in the first capacitor is suppressed. Therefore, reactive compensation can be better carried out by adopting the power capacitor (namely the first capacitor).

Description

Technical Field

[0001] The present application relates to the technical field of power systems, and in particular to a reactive power compensation circuit and a capacitor compensation module. Background Art

[0002] Due to the presence of a large number of inductive loads in the power system, the power factor of the power system will be reduced. When the power factor of the power system is too low, it will bring a series of adverse effects, such as: 1) The energy conversion efficiency of the power system will decrease, which will increase energy consumption and reduce system efficiency; 2) If the power factor of the power system is too low, the current in the power grid will increase, and the greater the current, the greater the loss on the power grid transmission line, which increases the line loss of the power supply system; 3) When the power factor of the power system is too low, the internal loss of the connected power equipment will increase, resulting in an increase in the operating temperature of the equipment, which will affect the reliability and service life of the equipment. 4) If the power factor of the power system connected to the power grid is too low, the relevant enterprises will be subject to certain force adjustment fines and increase electricity costs. In addition, the reduction of the power factor of the power system will also cause a waste of power resources, so measures need to be taken to avoid the reduction of the power factor of the power system.

[0003] The use of power capacitors for reactive power compensation (or reactive power compensation) in power systems is one of the common measures to improve the power factor of power systems. Power capacitors can effectively compensate for reactive power and improve the power factor.

[0004] However, in actual use, when using power capacitors for reactive power compensation, since the impedance characteristic of the power capacitor is that the impedance decreases as the frequency increases, the harmonics in the power system will cause the harmonic current flowing into the power capacitor to be amplified, thereby causing damage to the power capacitor. Therefore, the power capacitor is easily affected by the harmonics in the power system. In the process of conceiving and realizing this application, the inventor found that how to use power capacitors to better perform reactive power compensation is a technical problem that needs to be solved urgently by those skilled in the art.

[0005] The preceding description is intended to provide general background information and does not necessarily constitute prior art. Summary of the invention

[0006] In response to the above technical problems, the present application provides a reactive power compensation circuit and a capacitor compensation module, which can achieve better reactive power compensation using power capacitors.

[0007] The present application provides a reactive power compensation circuit, comprising: a first loop, a second loop and a magnetic balance coil; the magnetic balance coil includes a primary winding and a secondary winding; the first loop includes a first capacitor, and the first capacitor is connected in series with the primary winding; the second loop includes an impedance adjustment unit connected in series with the secondary winding, and the impedance adjustment unit is configured to make the impedance characteristic of the second loop capacitive when a fundamental voltage is applied, and / or make the impedance characteristic of the second loop inductive in a harmonic environment; the second loop is connected to the first loop and is configured to be capacitive when a fundamental voltage is applied to the first loop, so that the impedance of the magnetic balance coil in the first loop is reduced to ensure that the first capacitor compensates for reactive power, and / or be inductive when the first loop is in a harmonic environment, so that the impedance of the magnetic balance coil in the first loop is increased to suppress the harmonic current in the first capacitor.

[0008] Optionally, the impedance adjustment unit includes an inductor and a second capacitor; the secondary winding, the inductor and the second capacitor are connected in series in sequence.

[0009] Optionally, the same-named terminals of the primary winding and the secondary winding in the magnetic balance coil are reversed.

[0010] Optionally, the inductor is a magnetic ring coil.

[0011] Optionally, the primary winding is a magnetic ring coil; and / or, the secondary winding is a magnetic ring coil.

[0012] Optionally, the value range of the inductor is: , where represents the inductive reactance value of the inductor, represents the capacitive reactance value of the second capacitor; where, when the impedances of the first loop and the second loop are in opposite directions and the first loop is capacitive in a harmonic environment, the value of the inductor makes the second loop inductive, and makes the magnetic flux generated by the first harmonic current in the primary winding of the first loop and the magnetic flux generated by the second harmonic current in the secondary winding of the second loop in the same direction and mutually reinforcing, so as to increase the impedance of the magnetic balance coil to the first loop; where the first harmonic current is a capacitive current and the second harmonic current is an inductive current.

[0013] Optionally, the harmonic order of the harmonic environment is k, and k≥3.

[0014] Optionally, the turn ratio of the primary winding to the secondary winding is set to be equal to the ratio of the first fundamental current of the first loop to the second fundamental current of the second loop when a fundamental voltage is applied to the first loop, so that when the first fundamental current and the second fundamental current flow into the same-named terminals of the magnetic balance coil in opposite directions, the magnetic flux generated by the first fundamental current in the primary winding and the magnetic flux generated by the second fundamental current in the secondary winding cancel each other out, so that the impedance of the magnetic balance coil in the first loop and the second loop is zero or close to zero.

[0015] The present application further provides a capacitance compensation module, which includes at least one reactive power compensation circuit described in any one of the above.

[0016] Optionally, the capacitance compensation module includes three reactive power compensation circuits; and / or, the three reactive power compensation circuits are connected in a Y shape or a delta shape.

[0017] Optionally, the capacitance compensation module is connected to a three-phase power supply through a switching control switch and a fuse; wherein, the switching control switch is used to control the input and cut-off of the capacitance compensation module; wherein, fuses are respectively arranged on the three phase lines connecting the three-phase power supply to the capacitance compensation module, and the fuses are used for overcurrent protection.

[0018] The present application provides a reactive power compensation circuit and a capacitance compensation module. The reactive power compensation circuit includes: a first loop, a second loop and a magnetic balance coil; the magnetic balance coil includes a primary winding and a secondary winding; the first loop includes a first capacitor, and the first capacitor is connected in series with the primary winding; the second loop includes an impedance adjustment unit connected in series with the secondary winding, and the impedance adjustment unit is used to make the impedance characteristic of the second loop capacitive when a fundamental voltage is applied, and / or make the impedance characteristic of the second loop inductive in a harmonic environment; the second loop is connected to the first loop and is capacitive when a fundamental voltage is applied to the first loop, so that the impedance of the magnetic balance coil in the first loop is reduced to ensure that the first capacitor compensates reactive power, and / or is inductive when the first loop is in a harmonic environment, so that the impedance of the magnetic balance coil in the first loop is increased to suppress the harmonic current in the first capacitor. Through the technical solution of the present application, the reactive power compensation circuit can utilize the capacitive and inductive impedance characteristics of the second loop when a fundamental voltage is applied and in a harmonic environment respectively, so that the magnetic balance coil has a low impedance characteristic for the fundamental current on the first loop when a fundamental voltage is applied to the first loop, so as to avoid canceling the reactive power compensation of the first capacitor in the first loop, thereby ensuring that the first capacitor compensates reactive power, and / or making the magnetic balance coil have a high impedance characteristic for the harmonic current on the first loop in a harmonic environment, so as to avoid or reduce the problem that the harmonic current enters the first capacitor and causes the harmonic current in the first capacitor to be amplified, thereby achieving a better harmonic suppression effect. Therefore, the technical solution of the present application can realize better reactive power compensation using a power capacitor (i.e., the first capacitor). BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings here are incorporated into the description and form a part of this description, showing embodiments consistent with the present application, and are used together with the description to explain the principles of the present application. In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, for those of ordinary skill in the art, other drawings can be obtained according to these drawings without creative efforts.

[0020] Figure 1 It is a schematic structural diagram of the reactive power compensation circuit shown in the first embodiment of the present application.

[0021] Figure 2 It is a circuit structure diagram of the reactive power compensation circuit shown in the first embodiment of the present application.

[0022] Figure 3 It is a circuit structure diagram of the capacitor compensation loop provided in the second embodiment of the present application.

[0023] The realization of the purpose of the present application, functional features and advantages will be further described in conjunction with the embodiments with reference to the accompanying drawings. Through the above-mentioned accompanying drawings, specific embodiments of the present application have been shown, and there will be more detailed descriptions hereinafter. These drawings and text descriptions are not intended to limit the scope of the concept of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. Detailed implementation manners

[0024] Here, the exemplary embodiments will be described in detail, and the examples are shown in the accompanying drawings. When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementation manners described in the following exemplary embodiments do not represent all implementation manners consistent with the present application. On the contrary, they are only examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0025] It should be noted that in this document, the term "including", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of another identical element in the process, component or device including the element. In addition, components, features, and elements with the same name in different embodiments of the present application may have the same meaning or different meanings, and their specific meanings need to be determined based on their explanations in the specific embodiment or further in combination with the context of the specific embodiment.

[0026] It should be understood that although the terms first, second, etc. may be used herein to describe various information (such as circuits, capacitors, etc.), such information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of this document, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "when" or "while" or "in response to determining". Furthermore, as used in this document, the singular forms "a", "an", and "the" are also intended to include the plural forms unless the context indicates otherwise. It should be further understood that the terms "comprising", "including" indicate the presence of the described features, steps, operations, elements, components, items, types, and / or groups, but do not exclude the presence, occurrence, or addition of one or more other features, steps, operations, elements, components, items, types, and / or groups. The terms "or", "and / or", "including at least one of the following", etc. used in this application may be interpreted inclusively, or mean any one or any combination. For example, "including at least one of the following: A, B, C" means "any one of the following: A; B; C; A and B; A and C; B and C; A and B and C", and again, "A, B or C" or "A, B and / or C" means "any one of the following: A; B; C; A and B; A and C; B and C; A and B and C". An exception to this definition only occurs when the combination of elements, functions, steps, or operations are inherently mutually exclusive in some way.

[0027] It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit this application.

[0028] In the following description, the suffixes such as "module", "component", or "unit" used to represent elements are only for the convenience of explaining this application and have no specific meaning in themselves. Therefore, "module", "component", or "unit" can be used interchangeably.

[0029] The first embodiment Refer to Figure 1 and Figure 2 , Figure 1 is a schematic structural diagram of a reactive power compensation circuit shown in the first embodiment of this application; Figure 2 is a circuit structure diagram of a reactive power compensation circuit shown in the first embodiment of this application.

[0030] The reactive power compensation circuit provided in this embodiment includes: a first circuit, a second circuit, and a magnetic balance coil.

[0031] Among them, the magnetic balance coil includes a primary winding and a secondary winding.

[0032] Optionally, the polarities of the primary winding and the secondary winding in the magnetic balance coil are reversed.

[0033] Optionally, the primary winding is a magnetic ring coil; and / or, the secondary winding is a magnetic ring coil.

[0034] Wherein, the first loop includes a first capacitor, and the first capacitor is connected in series with the primary winding.

[0035] Wherein, the second loop includes an impedance adjustment unit connected in series with the secondary winding. The impedance adjustment unit is configured to make the impedance characteristic of the second loop capacitive when a fundamental voltage is applied, and / or make the impedance characteristic of the second loop inductive in a harmonic environment.

[0036] Wherein, the second loop is connected to the first loop and is capacitive when a fundamental voltage is applied to the first loop, so that the impedance of the magnetic balance coil in the first loop is reduced to ensure that the first capacitor compensates for reactive power, and / or is inductive when the first loop is in a harmonic environment, so that the impedance of the magnetic balance coil in the first loop is increased to suppress the harmonic current in the first capacitor.

[0037] Optionally, the impedance adjustment unit represents any element or combination of elements that can make the impedance characteristic of the second loop capacitive when a fundamental voltage is applied and make the impedance characteristic of the second loop inductive in a harmonic environment. For example, see Figure 2 , the impedance adjustment unit may include an inductor and a second capacitor. Therefore, the second loop can be an LC loop composed of the inductor and the second capacitor, so that the impedance characteristic of the second loop is capacitive when a fundamental voltage is applied and the impedance characteristic of the second loop is inductive in a harmonic environment. Again, the impedance adjustment unit can be an active circuit (such as an operational amplifier circuit), which can dynamically adjust the impedance characteristic of the circuit to achieve the switching between capacitive and inductive. Also, the impedance adjustment unit can be a digital controller, which can dynamically adjust the impedance characteristic of the circuit according to a control signal to achieve the switching between capacitive and inductive.

[0038] Optionally, the secondary winding, the inductor, and the second capacitor are connected in series in sequence.

[0039] Optionally, the inductor can be a magnetic ring coil or other conventional inductors.

[0040] In some current implementations, in the method of using power capacitors for reactive power compensation, a reactor can be connected in series with the power capacitor to suppress harmonics. A reactor is a special type of inductor mainly used in power systems. It can be used to limit short-circuit current, regulate voltage, suppress harmonics, etc. And the reactor usually has an iron core to increase the inductance and magnetic flux density. When using an iron-core reactor as the series reactor, there are the following deficiencies: (1) Since the magnetic permeability of the iron core is not high, to achieve the inductive reactance required for series harmonic suppression, the number of turns required for the series reactor coil is large, resulting in a large volume of the reactor; (2) The iron-core reactor has high losses, and due to the heating of the iron-core reactor, the power consumption for special temperature control and heat dissipation also increases accordingly; (3) Since the traditional reactor has to bear all the current, in order to avoid the saturation of the iron core, a large cross-section of the iron core and a large cross-section of the wire (such as copper wire) are required, resulting in a large amount of iron core and wire usage, and thus the cost is much higher than the power capacitor itself, and the cost composition shows an obvious cost inversion. Thus, in the technical solution of this embodiment, the primary winding in the magnetic balance coil is connected in series with the first capacitor (i.e., the power capacitor), which is equivalent to using the magnetic ring coil of the primary winding (which can also be regarded as a magnetic ring inductor) as the reactor to replace the traditional iron-core reactor, which can greatly reduce the volume, losses and cost of the reactor. In addition, it can also greatly improve the circuit integration, increase the power module capacity of the power system, and at the same time reduce losses.

[0041] Optionally, the value range of the inductance can be: , where represents the inductive reactance value of the inductance, represents the capacitive reactance value of the second capacitor.

[0042] Optionally, when the impedance of the first loop and the impedance of the second loop are in opposite directions and the first loop is capacitive in a harmonic environment, the value of the inductance makes the second loop inductive, and makes the magnetic flux generated by the first harmonic current (capacitive current) of the first loop in the primary winding in the same direction as and mutually reinforcing with the magnetic flux generated by the second harmonic current (inductive current) of the second loop in the secondary winding, so as to increase the impedance of the magnetic balance coil to the first loop.

[0043] Optionally, the harmonic order of the harmonic environment is k, and k≥3. The harmonic order of the harmonic environment, for example, 3, 5, 7, 11, 13.

[0044] Exemplarily, since the impedances of the first loop and the second loop show opposite-direction changes in a harmonic environment, the capacitive reactance value of the first capacitor of the first loop in the harmonic environment is , and it is still capacitive; the impedance value of the inductor of the second loop in the harmonic environment is / k - k* , and as long as the selected inductive reactance value of the inductance When the harmonic order k is greater than 3, the impedance of the second loop is inductive; under the same voltage condition, the first loop and the second loop respectively obtain the first harmonic current and the second harmonic current . The magnetic fluxes generated by the first harmonic current and the second harmonic current in the magnetic balance coil are in the same direction and reinforce each other. Moreover, the first harmonic current in the primary winding of the magnetic balance coil is relatively large. The magnetic balance coil presents the characteristic of a relatively large series inductance to the first harmonic current flowing into the first capacitor in the first loop, thereby realizing the suppression of the harmonic current flowing into the first capacitor.

[0045] Optionally, the impedance characteristics of the reactive power compensation circuit in a harmonic environment are as follows (in the power system, odd harmonics such as 3, 5, 7, 11, 13, 21, 23, etc. usually exist. The following analyzes with the 3rd harmonic as an example): In the second loop, due to the impedance of the original inductance and the second capacitor in the second loop under the 3rd harmonic state, as long as the fundamental inductance value of the inductance is greater than 12% of the fundamental capacitance value of the second capacitor, the following can be satisfied: ; ; Among them, represents the imaginary unit (satisfying ), represents the angular frequency (equal to , 50 Hz), C1 represents the capacitance of the first capacitor, C2 represents the capacitance of the second capacitor, and L represents the inductance of the inductance; That is, under the 3rd harmonic state, the second is inductive and can be equivalent to an inductor. The harmonic current is a capacitive current and leads the voltage phase by 90°, the harmonic current is an inductive current and lags the voltage phase by 90°, and the current directions of the harmonic current and the harmonic current differ by 180° and are in opposite directions. When the primary winding and the secondary winding are still reversely and heterosidally connected in parallel at the same name ends, it is equivalent to a homosidally connected parallel circuit, and the current and voltage satisfy the following formulas: ① ; ② ; ③ ; Among them, Represents the system voltage in the circuit Represents the inductance of the coupled primary winding, and L represents the inductance of the inductor in the impedance adjustment unit Represents the imaginary unit (satisfying ) Represents the angular frequency (equal to , 50 Hz), C1 represents the capacitance of the first capacitor, and C2 represents the capacitance of the second capacitor Represents the mutual inductance between the primary winding and the secondary winding (mutual inductance is the phenomenon that a voltage is induced in another winding due to a change in current in one winding) Represents the current phase of the circuit The series inductance value of the second loop at the 3rd harmonic: ④ ; When , the first is inductive. Similarly, the second loop is inductive in a harmonic environment above the 3rd harmonic

[0046] Optionally, the turns ratio of the primary winding to the secondary winding is set to be equal to the ratio of the first fundamental current of the first loop to the second fundamental current of the second loop when the fundamental voltage is applied to the first loop, so that when the first fundamental current and the second fundamental current flow into the same-named ends of the magnetic balance coil in opposite directions, the magnetic flux generated by the first fundamental current in the primary winding cancels out the magnetic flux generated by the second fundamental current in the secondary winding, making the impedance of the magnetic balance coil in the first loop and the second loop zero or close to zero

[0047] In some current implementations, in the method of using power capacitors for reactive power compensation, a reactor can be used in series with the power capacitor to suppress harmonics. However, when a fundamental voltage is applied and a fundamental current flows through the series connection of the reactor and the power capacitor, the reactor will cancel out the actual reactive power compensation of the power capacitor (i.e., the reactor will cancel out the capacity of the power capacitor), resulting in a significant reduction in the effective output capacity of the compensation device or compensation circuit corresponding to the power capacitor, thus falling below the rated capacity, and further reducing the utilization efficiency of the power capacitor. Therefore, the technical solution of this embodiment uses a magnetic balance coil with an asymmetric primary winding and secondary winding, such that when a fundamental voltage is applied to the first loop, the ratio of the first fundamental current in the first loop to the second fundamental current in the second loop is equal. When the directions of the first fundamental current and the second fundamental current flowing into the same-named ends of the magnetic balance coil are opposite, the magnetic flux generated by the first fundamental current in the primary winding cancels out the magnetic flux generated by the second fundamental current in the secondary winding, making the impedance of the magnetic balance coil in the first loop and the second loop zero or close to zero (i.e., due to the cancellation effect of the magnetic circuit, the impedance of the fundamental current flowing into the first capacitor in the first loop is zero or close to zero), so as to improve the compensation efficiency of the first capacitor (i.e., the power capacitor).

[0048] Exemplarily, when the value range of the inductance is: and when the first loop and the second loop are applied with a fundamental voltage, the total impedance of the second loop is - which is capacitive. Therefore, the second fundamental current on the second loop is a capacitive current. At this time, the second fundamental current on the second loop and the first fundamental current on the first loop are both 90° out of phase with the phase of the fundamental voltage; when the ratio of the first fundamental current in the first loop to the second fundamental current in the second loop is equal to the turns ratio of the primary winding to the secondary winding, since the first fundamental current and the second fundamental current flow into the magnetic balance coil in opposite directions at the same-named ends, the magnetic flux generated by the first fundamental current in the primary winding and the magnetic flux generated by the first fundamental current in the secondary winding are exactly equal in magnitude and opposite in direction, and the magnetic fluxes cancel each other out, reaching a state of magnetic circuit balance. The impedance of the magnetic balance coil in the first loop and the second loop is zero, equivalent to zero impedance to the fundamental current, thereby achieving the purpose of improving the compensation efficiency of the first capacitor.

[0049] Optionally, the first fundamental current in the primary winding of the magnetic balance coil represents the fundamental voltage, represents the capacitive reactance value of the first capacitor. Among them, the capacitive reactance value of the first capacitor , where C1 represents the capacitance value of the first capacitor. Optionally, the second fundamental current in the primary winding of the magnetic balance coil , where, represents the fundamental voltage, represents the capacitive reactance value of the second capacitor, represents the inductive reactance value of the inductor. Among them, , , where C2 represents the capacitance value of the second capacitor, and L represents the inductance of the inductor. The ratio of the number of turns of the primary winding to the number of turns of the secondary winding in the magnetic balance coil is 1:n. Thus, the parameters of the first capacitor, the second capacitor, the inductor, and the transformer can be selected to determine the inductance of the inductor and the capacitance value of the second capacitor that match under the condition of the fundamental voltage ( ), so that .

[0050] Optionally, the impedance characteristic analysis of the reactive power compensation circuit under the power frequency fundamental wave is as follows: Under the fundamental voltage ( 50 Hz), the first fundamental current in the first loop is capacitive, and the second fundamental current in the second loop is also capacitive when the selected inductive reactance value is less than the capacitive reactance value of the second capacitor. Therefore, the first fundamental current and the second fundamental current are capacitive currents and lead the voltage by 90°. When the primary winding and the secondary winding of the magnetic balance coil are connected in parallel with opposite polarities and opposite sides, it is equivalent to a parallel circuit on the opposite sides, and the current and voltage satisfy the following formulas: ① ; ② ; ③ ; Among them, represents the system voltage in the circuit, represents the inductance of the coupling primary winding, represents the imaginary unit (satisfying ), represents the angular frequency (equal to , 50 Hz), C1 represents the capacitance of the first capacitor, C2 represents the capacitance of the second capacitor, represents the mutual inductance between the primary winding and the secondary winding (mutual inductance is the phenomenon that a change in current in one winding induces a voltage in the other winding), represents the current phase; Let the number of turns of the primary winding and the secondary winding be n1 and n2 respectively, and select appropriate parameter values for the capacitance of the first capacitor, the capacitance of the second capacitor, and the inductance of the inductor, so that the fundamental current of the loop under the fundamental voltage satisfies: ; Substitute into Equation ① It can be obtained that: ④ ; In the magnetic balance coil, let the magnetic core inductance coefficient be AL: ⑤ ; ⑥ ; Optionally, the primary winding and the secondary winding can be in a closed magnetic core loop. Ignoring leakage flux, the coupling factor between the primary winding and the secondary winding ≈ 1, so there is: ⑦ ; The series inductance value in the second loop: ⑧ ; Take n1:n2 = 1:k, then the series inductive reactance of the primary winding in the first loop (the sum of self-inductance and mutual inductance) can be made zero. Similarly, the series inductive reactance of the secondary winding in the second loop (the sum of self-inductance and mutual inductance) is also zero.

[0051] That is, under the fundamental voltage, the magnetic fluxes generated by the first fundamental current and the second fundamental current cancel each other out in the magnetic core. The primary winding and the secondary winding present zero impedance in the first loop and the second loop, and have no hindrance to the flowing current.

[0052] The reactive power compensation circuit provided in this embodiment includes: a first loop, a second loop, and a magnetic balance coil; the magnetic balance coil includes a primary winding and a secondary winding; the first loop includes a first capacitor, and the first capacitor is connected in series with the primary winding; the second loop includes an impedance adjustment unit connected in series with the secondary winding, and the impedance adjustment unit is used to make the impedance characteristic of the second loop capacitive when a fundamental voltage is applied, and / or make the impedance characteristic of the second loop inductive in a harmonic environment; the second loop is connected to the first loop and is capacitive when a fundamental voltage is applied to the first loop, so that the impedance of the magnetic balance coil in the first loop is reduced to ensure that the first capacitor compensates for reactive power, and / or is inductive when the first loop is in a harmonic environment, so that the impedance of the magnetic balance coil in the first loop is increased to suppress the harmonic current in the first capacitor. Through the technical solution of this application, the reactive power compensation circuit can utilize the capacitive and inductive impedance characteristics of the second loop when a fundamental voltage is applied and in a harmonic environment respectively, so that the magnetic balance coil has a low impedance characteristic for the fundamental current on the first loop when a fundamental voltage is applied to the first loop, so as to avoid canceling the reactive power compensation of the first capacitor in the first loop, thereby ensuring that the first capacitor compensates for reactive power, and / or making the magnetic balance coil have a high impedance characteristic for the harmonic current on the first loop in a harmonic environment, so as to avoid or reduce the problem that the harmonic current enters the first capacitor and causes the harmonic current in the first capacitor to be amplified, thereby achieving a better harmonic suppression effect. Therefore, the technical solution of this application can realize better reactive power compensation using a power capacitor (i.e., the first capacitor).

[0053] The technical solution of this embodiment has a good harmonic suppression effect, has a more excellent performance of "blocking harmonics and passing fundamental waves", has a very small impedance for the power frequency fundamental current, has a high system efficiency, has a high impedance for high-order harmonic currents, and has a better harmonic suppression effect. In addition, the technical solution of this embodiment can utilize the capacitive and inductive characteristics of the auxiliary second loop under the fundamental wave and harmonics above the third order respectively, and through the magnetic balance coil, different impedance characteristics under the fundamental wave and high-frequency harmonics, have a low impedance characteristic for the fundamental current during normal fundamental wave compensation, and present a high impedance characteristic when the harmonic current flows through, achieving a better loop suppression effect.

[0054] Second Embodiment See Figure 3 , Figure 3 is the circuit structure diagram of the capacitor compensation loop provided in the second embodiment of this application.

[0055] Based on the technical concept of the technical solution of the above embodiment, the second embodiment of this application provides a capacitor compensation module, including at least one reactive power compensation circuit described in the first embodiment.

[0056] Optionally, the capacitance compensation module provided in this embodiment includes three reactive power compensation circuits; and / or, the three reactive power compensation circuits are connected in a Y shape or a delta shape (as Figure 3 shown).

[0057] Optionally, the capacitance compensation module provided in this embodiment can be installed in a capacitance compensation loop.

[0058] Optionally, the capacitance compensation module is connected to a three-phase power supply through a switching control switch and a fuse.

[0059] Among them, the switching control switch is used to control the input and cut-off of the capacitance compensation module.

[0060] Among them, fuses are respectively arranged on the three phase lines ( Figure 3 phase line A, phase line B, and phase line C in

[0061] which) of the three-phase power supply connected to the capacitance compensation module, and the fuses are used for overcurrent protection.

[0062] In this application, the descriptions of the various embodiments have their own emphases. For parts not detailed or recorded in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0063] The technical features of the technical solution of the present application can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope recorded in the present application.

[0064] The above are only the preferred embodiments of the present application, and do not limit the patent scope of the present application accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present application, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present application.

Claims

1. A reactive power compensation circuit, characterized in that: include: A first circuit, a second circuit and a magnetic balance coil; The magnetic balance coil includes a primary winding and a secondary winding; The first loop includes a first capacitor, and the first capacitor is connected in series with the primary winding; The second circuit includes an impedance adjustment unit connected in series with the secondary winding, the impedance adjustment unit being used to make the impedance characteristic of the second circuit capacitive when a fundamental voltage is applied thereto, and / or to make the impedance characteristic of the second circuit in a harmonic environment inductive; The second circuit is connected to the first circuit and is used for being capacitive when the fundamental voltage is applied to the first circuit, so that the impedance of the magnetic balance coil in the first circuit is reduced to ensure that the first capacitor compensates for reactive power, and / or being inductive when the first circuit is in the harmonic environment, so that the impedance of the magnetic balance coil in the first circuit is increased to suppress the harmonic current in the first capacitor.

2. The reactive power compensation circuit according to claim 1, characterized in that: The impedance adjustment unit includes an inductor and a second capacitor; The secondary winding, the inductor and the second capacitor are connected in series in sequence; The primary winding and the secondary winding in the magnetic balance coil have opposite ends of the same name.

3. The reactive power compensation circuit according to claim 2, characterized in that: The inductor is a magnetic ring coil.

4. The reactive power compensation circuit according to claim 1 or 2, characterized in that: The primary winding is a magnetic ring coil; and / or, The secondary winding is a magnetic ring coil.

5. The reactive power compensation circuit according to claim 2, characterized in that: The value range of the inductance is: ,in, represents the inductive reactance value of the inductor, represents the capacitive reactance value of the second capacitor; Among them, in the harmonic environment, when the impedance of the first loop and the impedance of the second loop are in opposite directions and the first loop is capacitive, the value of the inductance is The second loop is made inductive, and the magnetic flux generated by the first harmonic current of the first loop in the primary winding and the magnetic flux generated by the second harmonic current of the second loop in the secondary winding are in the same direction and reinforce each other, so as to increase the impedance of the magnetic balance coil to the first loop; The first harmonic current is a capacitive current, and the second harmonic current is an inductive current.

6. The reactive power compensation circuit according to claim 5, characterized in that: The harmonic order of the harmonic environment is k, and k≥3.

7. The reactive power compensation circuit according to claim 1 or 2, characterized in that: The turns ratio of the primary winding to the secondary winding is set to be equal to the ratio of a first fundamental current of the first circuit to a second fundamental current of the second circuit when a fundamental voltage is applied to the first circuit, so that when the first fundamental current and the second fundamental current flow into the same-name ends of the magnetic balance coil in opposite directions, the magnetic flux generated by the first fundamental current in the primary winding and the magnetic flux generated by the second fundamental current in the secondary winding cancel each other out, so that the impedance of the magnetic balance coil in the first circuit and the second circuit is zero or close to zero.

8. A capacitance compensation module, characterized in that: Comprising at least one reactive power compensation circuit as claimed in any one of claims 1 to 7.

9. The capacitance compensation module according to claim 8, characterized in that: comprising three reactive power compensation circuits; and / or, The three reactive power compensation circuits are connected in a Y-shape or a triangle.

10. The capacitance compensation module according to claim 9, characterized in that: The capacitor compensation module is connected to a three-phase power supply via a switching control switch and a fuse; Wherein, the switching control switch is used to control the switching on and off of the capacitor compensation module; Wherein, the fuses are respectively arranged on the three phase lines of the three-phase power supply connected to the capacitor compensation module, and the fuses are used for overcurrent protection.

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