Current-limiting reactance protection control method and device and energy storage type distribution transformer

Abstract

The invention discloses a current-limiting reactance protection control method and device and an energy storage type distribution transformer, and relates to the field of energy storage protection.The energy storage type distribution transformer is internally provided with a current transformation loop, and the method comprises the steps that whether the alternating current side connected with the distribution transformer breaks down or not is judged according to the voltage and current of the current transformation loop; if the alternating current side connected with the distribution transformer has a fault, controlling a variable current loop to limit a fault current; judging whether the iron core is saturated or not according to the magnetic flux of the iron core of the converter loop; and if the iron core is saturated, controlling the iron core of the converter loop to demagnetize. Whether a fault occurs in the energy storage type distribution transformer except for an energy storage system is determined through the current and the voltage, if the fault occurs, a current transformation loop needs to be controlled to limit the fault current, and due to the fact that an iron core is gradually saturated in the working process of the current transformation loop, saturation of the iron core is determined through the magnetic flux, demagnetization is carried out, subsequent current limiting is facilitated, and the reliability of the energy storage type distribution transformer is improved. And the energy storage system is protected.

Description

Technical Field

[0001] The present invention relates to the field of energy storage protection, and in particular to a current limiting reactance protection control method and device and an energy storage type distribution transformer. Background Art

[0002] Energy storage distribution transformers that are designed and controlled through the integration of battery energy storage systems and traditional distribution transformers can achieve higher equipment investment economy and operational flexibility. They can achieve resource complementarity and coordination through software-level virtualization, which is one of the new forms of energy storage applications. Given the importance of battery energy storage systems in distribution networks, the protection of battery energy storage systems has also become a concern when distribution networks fail. Short circuits in distribution networks can cause overcurrents in all power sources. As a power source connected to distribution transformers, battery energy storage systems are greatly affected by faults. Overcurrents can easily damage the power electronic converter switches, battery management systems, and battery packs of the distribution network. Therefore, it is very important to detect faults in devices other than battery energy storage systems in distribution networks. Summary of the invention

[0003] The purpose of the present invention is to provide a current-limiting inductor protection control method, device and energy storage type distribution transformer, which can determine whether a device other than an energy storage system in the energy storage type distribution transformer fails by current and voltage. If a fault occurs, it is necessary to control the DC inductor to limit the fault current, determine the core saturation by magnetic flux, and perform demagnetization to facilitate subsequent current limiting and protect the energy storage system.

[0004] In order to solve the above technical problems, the present invention provides a current-limiting reactance protection control method, which is applied to a current-limiting reactance protection control device in an energy storage type distribution transformer, wherein the energy storage type distribution transformer also includes an energy storage system, a distribution transformer, and a current conversion circuit arranged between the energy storage system and the distribution transformer;

[0005] The current limiting reactance protection control method comprises:

[0006] Determining whether a fault occurs on the AC side to which the distribution transformer is connected according to the voltage and current of the conversion circuit;

[0007] If a fault occurs on the AC side to which the distribution transformer is connected, the current conversion circuit is controlled to limit the fault current;

[0008] judging whether the iron core is saturated according to the magnetic flux of the iron core of the current conversion circuit;

[0009] If the iron core is saturated, the iron core is controlled to be demagnetized.

[0010] On the other hand, the current conversion circuit includes a full-bridge rectifier and a DC reactor;

[0011] The common end at which the anode of the first diode and the cathode of the third diode in the full-bridge rectifier are connected is connected to the distribution transformer, the common end at which the anode of the third diode and the anode of the second diode in the full-bridge rectifier are connected is connected to the input end of the DC reactor, the common end at which the cathode of the second diode and the anode of the fourth diode in the full-bridge rectifier are connected is connected to the energy storage system, and the common end at which the cathode of the fourth diode and the cathode of the first diode are connected is connected to the output end of the DC reactor;

[0012] The full-bridge rectifier is used to convert the alternating current output by the distribution transformer into direct current, and the direct current reactor is used to limit the fault current.

[0013] On the other hand, the current conversion circuit further includes a first controllable switch, a second controllable switch, a damping resistor and an external resistor;

[0014] The first end of the first controllable switch is connected to the third end of the full-bridge rectifier and the first end of the damping resistor respectively, the second end of the first controllable switch is connected to the second end of the damping resistor and the first end of the DC reactor respectively, the second end of the DC reactor is connected to the first end of the external resistor, the second end of the external resistor is connected to the first end of the second controllable switch, and the second end of the second controllable switch is connected to the third end of the DC reactor and the third end of the full-bridge rectifier;

[0015] Controlling the current conversion circuit to limit the fault current includes:

[0016] The first controllable switch and the second controllable switch are both controlled to be turned off.

[0017] On the other hand, controlling the demagnetization of the core includes:

[0018] The first controllable switch is controlled to be opened, and the second controllable switch is controlled to be closed.

[0019] On the other hand, it also includes:

[0020] When the distribution transformer does not fail and the iron core is not saturated, the first controllable switch is controlled to be closed and the second controllable switch is controlled to be open.

[0021] On the other hand, the current conversion circuit also includes a voltage sensor, a current sensor and a magnetic flux sensor;

[0022] The voltage sensor and the current sensor are both connected to the DC reactor, and the magnetic flux sensor is arranged in the DC reactor and connected to the iron core of the DC reactor;

[0023] Judging whether a fault occurs on the AC side connected to the distribution transformer according to the voltage and current of the conversion circuit, including:

[0024] When the voltage drop detected by the voltage sensor is greater than a reference voltage drop or the current detected by the current sensor is greater than a reference current, it is determined that a fault occurs on the AC side to which the distribution transformer is connected.

[0025] Judging whether the iron core is saturated according to the magnetic flux of the iron core of the current conversion circuit includes:

[0026] When the magnetic flux detected by the magnetic flux sensor is greater than a reference magnetic flux, it is determined that the core is saturated.

[0027] In order to solve the above technical problems, the present invention also provides a current limiting reactance protection control device, comprising:

[0028] Memory for storing computer programs;

[0029] A processor is used to implement the steps of the above-mentioned current limiting reactor protection control method when executing the computer program.

[0030] In order to solve the above technical problems, the present invention also provides a

[0031] An energy storage type distribution transformer, characterized in that it comprises an energy storage system, a distribution transformer, a current conversion circuit arranged between the energy storage system and the distribution transformer, and the current limiting reactance protection control device as claimed in claim 7;

[0032] The current conversion circuit is used to limit the fault current between the energy storage system and the distribution transformer based on the control of the current limiting reactance protection control device.

[0033] On the other hand, it also includes a full-bridge rectifier, a DC reactor, a first controllable switch, a second controllable switch, a damping resistor and an external resistor;

[0034] The common end at which the anode of the first diode and the cathode of the third diode in the full-bridge rectifier are connected is connected to the distribution transformer, the common end at which the anode of the third diode and the anode of the second diode in the full-bridge rectifier are connected is connected to the input end of the DC reactor, the common end at which the cathode of the second diode and the anode of the fourth diode in the full-bridge rectifier are connected is connected to the energy storage system, and the common end at which the cathode of the fourth diode and the cathode of the first diode are connected is connected to the output end of the DC reactor;

[0035] The first end of the first controllable switch is connected to the third end of the full-bridge rectifier and the first end of the damping resistor respectively, the second end of the first controllable switch is connected to the second end of the damping resistor and the first end of the DC reactor respectively, the second end of the DC reactor is connected to the first end of the external resistor, the second end of the external resistor is connected to the first end of the second controllable switch, and the second end of the second controllable switch is connected to the third end of the DC reactor and the third end of the full-bridge rectifier;

[0036] The full-bridge rectifier is used to realize energy exchange between the distribution transformer and the energy storage system. The DC reactor is used to limit current based on the control of the processor in the current limiting reactor protection control device. When the first controllable switch and the second controllable switch are both disconnected, the DC reactor limits the fault current. When the first controllable switch is disconnected and the second controllable switch is closed, the DC reactor is demagnetized. When the first controllable switch is closed and the second controllable switch is disconnected, it indicates that the distribution transformer is not faulty and the iron core is not saturated.

[0037] On the other hand, it also includes a voltage sensor, a current sensor, a magnetic flux sensor, a first drive circuit and a second drive circuit;

[0038] The current collected by the current sensor is input to the current input terminal of the processor, the voltage collected by the voltage sensor is input to the voltage input terminal of the processor, the first output terminal of the processor is connected to the input terminal of the first drive circuit, the output terminal of the first drive circuit is connected to the control terminal of the first controllable switch, the magnetic flux collected by the magnetic flux sensor is input to the magnetic flux input terminal of the processor, the second output terminal of the processor is connected to the input terminal of the second drive circuit, and the output terminal of the second drive circuit is connected to the control terminal of the second controllable switch;

[0039] The processor is specifically used to send a first signal to the first drive circuit when the current collected by the current sensor is greater than a reference current or the voltage drop collected by the voltage sensor is greater than a reference voltage drop, so that the first drive circuit controls the first controllable switch to be disconnected based on the first signal, and send a second signal to the second drive circuit when the magnetic flux collected by the magnetic flux sensor is greater than the reference magnetic flux, so that the second drive circuit controls the second controllable switch to be disconnected based on the second signal.

[0040] The present invention discloses a current-limiting reactance protection control method, device and energy storage type distribution transformer, which relate to the field of energy storage protection. A current conversion circuit is provided in the energy storage type distribution transformer, and the method comprises judging whether a fault occurs on the AC side connected to the distribution transformer according to the voltage and current of the current conversion circuit; if a fault occurs in the distribution transformer, controlling the current conversion circuit to limit the fault current; judging whether the iron core is saturated according to the magnetic flux of the iron core of the current conversion circuit; if the iron core is saturated, controlling the current conversion circuit to demagnetize. Whether a fault occurs in the device other than the energy storage system in the energy storage type distribution transformer is determined by current and voltage. If a fault occurs, the current conversion circuit needs to be controlled to limit the fault current. Since the iron core will gradually saturate during the operation of the current conversion circuit, the iron core saturation is determined by magnetic flux, and demagnetization is performed to facilitate subsequent current limiting, thereby realizing protection of the energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the prior art and the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0042] Figure 1 A flow chart of a current limiting reactance protection control method provided by the present invention;

[0043] Figure 2 A schematic structural diagram of an energy storage type distribution transformer provided by the present invention;

[0044] Figure 3 A schematic diagram of a control strategy of a current limiting reactance protection control method provided by the present invention;

[0045] Figure 4 A schematic diagram of a control strategy for an energy storage distribution transformer provided by the present invention. DETAILED DESCRIPTION

[0046] The core of the present invention is to provide a current-limiting reactance protection control method, device and energy storage type distribution transformer, which determines whether the devices other than the energy storage system in the energy storage type distribution transformer are faulty through current and voltage. If a fault occurs, it is necessary to control the current conversion circuit to limit the fault current, determine the core saturation through magnetic flux, and perform demagnetization to facilitate subsequent current limiting, thereby protecting the energy storage system.

[0047] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments 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.

[0048] Figure 1 This is a flow chart of a current-limiting reactor protection control method provided by the present invention. The current-limiting reactor protection control method uses a current-limiting reactor protection control device in an energy storage distribution transformer. Figure 2 A schematic diagram of the structure of an energy storage type distribution transformer provided by the present invention, wherein the energy storage type distribution transformer further comprises an energy storage system, a distribution transformer and a current conversion circuit arranged between the energy storage system and the distribution transformer;

[0049] Current limiting reactance protection control methods include:

[0050] S11: judging whether there is a fault on the AC side connected to the distribution transformer according to the voltage and current of the conversion circuit; if so, proceeding to step S12;

[0051] S12: Control the current conversion circuit to limit the fault current;

[0052] S13: judging whether the core is saturated according to the magnetic flux of the core of the converter circuit; if so, proceeding to step S14;

[0053] S14: Control the demagnetization of the core.

[0054] By calculating the winding of the DC reactor, the equivalent topology is obtained as follows: Figure 2 As shown, in this structure, diodes D1-D4 are used as full-bridge rectifiers. The AC part of the rectifier is connected in series with the distribution transformer, and the DC part is connected to the DC reactor. The reactor includes a main coil with a ferromagnetic core, which is magnetically coupled with a control secondary coil. After the reactor is converted through the winding, it can be shown as follows Figure 1 As shown in the gray box. Insulated gate bipolar transistors (IGBTs) are used to control the on and off of the primary and secondary windings of the DC reactor to change the topology of the CRFCL. In the figure, L1 and L2 are the leakage inductances of the primary and secondary sides, respectively. Assume that the resistance of the primary and secondary windings are both 0, R2 is the external resistor connected to the secondary side, R1 in parallel with IGBT S1 is the damping resistor, and L m is the mutual inductance of the primary and secondary windings.

[0055] When a fault occurs, as the current rises and the voltage drop increases, it enters the action state, temporarily limiting the fault current and increasing the core flux. When the flux sensor detects that the DC reactor is saturated, it enters the reset state and connects R2 to the secondary winding of the DC reactor to desaturate the core.

[0056] The present invention discloses a current-limiting reactance protection control method, which relates to the field of energy storage protection. A current conversion circuit is provided in an energy storage distribution transformer. The method includes judging whether a fault occurs on the AC side connected to the distribution transformer according to the voltage and current of the current conversion circuit; if a fault occurs in the distribution transformer, controlling the current conversion circuit to limit the fault current; judging whether the iron core is saturated according to the magnetic flux of the iron core of the current conversion circuit; if the iron core is saturated, controlling the current conversion circuit to demagnetize. Whether a fault occurs in a device other than an energy storage system in the energy storage distribution transformer is determined by current and voltage. If a fault occurs, the current conversion circuit needs to be controlled to limit the fault current. Since the iron core will gradually saturate during the operation of the current conversion circuit, the iron core saturation is determined by magnetic flux, and demagnetization is performed to facilitate subsequent current limiting, thereby protecting the energy storage system.

[0057] Based on the above embodiments:

[0058] In some embodiments, the current conversion circuit includes a full-bridge rectifier and a DC reactor;

[0059] The common end at which the anode of the first diode and the cathode of the third diode in the full-bridge rectifier are connected is connected to the distribution transformer, the common end at which the anode of the third diode and the anode of the second diode in the full-bridge rectifier are connected is connected to the input end of the DC reactor, the common end at which the cathode of the second diode and the anode of the fourth diode in the full-bridge rectifier are connected is connected to the energy storage system, and the common end at which the cathode of the fourth diode and the cathode of the first diode are connected is connected to the output end of the DC reactor;

[0060] The full-bridge rectifier is used to convert the AC power output by the distribution transformer into DC power, and the DC reactor is used to limit the fault current.

[0061] In some embodiments, the current conversion circuit further includes a first controllable switch, a second controllable switch, a damping resistor and an external resistor;

[0062] The first end of the first controllable switch is respectively connected to the third end of the full-bridge rectifier and the first end of the damping resistor, the second end of the first controllable switch is respectively connected to the second end of the damping resistor and the first end of the DC reactor, the second end of the DC reactor is connected to the first end of the external resistor, the second end of the external resistor is connected to the first end of the second controllable switch, and the second end of the second controllable switch is connected to the third end of the DC reactor and the third end of the full-bridge rectifier;

[0063] Control the current conversion circuit to limit the fault current, including:

[0064] The first controllable switch and the second controllable switch are both controlled to be disconnected.

[0065] When a fault occurs outside the energy storage system, before IGBT S1 is turned off, the DC reactor current can be and Indicates that α f is the reciprocal of the time constant, which is the ratio of the sum of all inductances to the sum of all resistances (including those on the AC side). f and I max Calculated by the following formula: , In this state, the rising rate of the source current is taken into account. When the CRFCL voltage drop is no longer 0, the source current can be calculated by the above formula.

[0066] By providing the first controllable switch IGBT S1 and the second controllable switch IGBT S2, the DC reactor can be controlled.

[0067] When IGBT S1 is turned off, the DC reactor topology becomes an RL circuit that can control the magnitude of the fault current and delay the rise of the fault current. The current of the DC reactor is expressed as: , and , between R1 and L m It is much larger than other resistances and inductances in the circuit, so other resistances and inductances can be ignored. In this state, the current of BESS can be calculated using KVL as follows: and .

[0068] In some embodiments, controlling the demagnetization of the core includes:

[0069] The first controllable switch is controlled to be opened, and the second controllable switch is controlled to be closed.

[0070] In the reset state, IGBT S2 is turned on to restore the DC reactor core from the saturation state. The current of the DC reactor does not pass through the high inductance magnetizing branch, but mainly through the series branch of the leakage inductance and the resistor R2. This operation temporarily increases the current of CRFCL until the control pulse of the switch is changed to the nominal state mode. The current of the DC reactor is expressed as: , and In this state, the source current can be calculated by applying KVL as follows: .

[0071] In some embodiments, it also includes:

[0072] When the distribution transformer has no faults and the iron core is not saturated, the first controllable switch is controlled to be closed and the second controllable switch is controlled to be opened.

[0073] The normal operating state is the nominal state, S1 is turned on, and S2 is closed.

[0074] In the nominal state, IGBT S1 is turned on and IGBT S2 is turned off. Figure 2 Applying Kirchhoff's voltage law (KVL), we get: , V FB is the full bridge DC voltage, i dc is the DC reactor current. The current of the DC reactor during charging can be expressed as the solution of the RL circuit ordinary differential equation (ODE): and .

[0075] The DC reactor charging current direction is BESS, including all series impedances of the system: L th is the inductance of the energy storage system, L line is the line inductance, L load is the load inductance; the resistance R th , R line , R d and R load are the resistances of the energy storage system, line, diode and load respectively; I max is the maximum current of the line, I in is the initial current of the DC reactor; the time constant τ c is the ratio of the sum of all inductances and resistances, α c is the inverse of the time constant.

[0076] When the DC reactor current is greater than the line current, the DC reactor is in a discharge state. Figure 1 The diode in is a bidirectional diode, which provides a very low resistance value in the discharge circuit of the DC reactor. Therefore, the solution of ODE is: and .

[0077] Among them, τ d is the time constant of the DC reactor current, α d is the inverse of the time constant, because the R d is small, so τ c Ratio τ d Therefore, it can be considered that the DC current of the DC reactor changes very little in steady state and remains constant when the line current is at its maximum value.

[0078] The voltage drop of the DC reactor in steady state is almost zero, and the BESS current can be calculated by KVL: and , where Vs(t) is the fault point voltage, which is the voltage between the fault point and the BESS, so it contains Figure 1 The resistance and inductance on the DC side and the resistance, inductance and load on the AC side can be used to calculate the fault current of the energy storage system.

[0079] Figure 3 A schematic diagram of a control strategy of a current limiting reactance protection control method provided by the present invention;

[0080] In some embodiments, the current conversion circuit further includes a voltage sensor, a current sensor, and a magnetic flux sensor;

[0081] The voltage sensor and the current sensor are both connected to the DC reactor, and the magnetic flux sensor is arranged in the DC reactor and connected to the iron core of the DC reactor;

[0082] Determine whether there is a fault on the AC side connected to the distribution transformer based on the voltage and current of the conversion circuit, including:

[0083] When the voltage drop detected by the voltage sensor is greater than the reference voltage drop or the current detected by the current sensor is greater than the reference current, it is determined that a fault occurs on the AC side connected to the distribution transformer;

[0084] Judging whether the core is saturated based on the magnetic flux of the core of the converter circuit includes:

[0085] When the magnetic flux detected by the magnetic flux sensor is greater than the reference magnetic flux, it is determined that the core is saturated.

[0086] like Figure 2 , use the digital sampler to measure the current and voltage, use the comparator to quickly track the given value, when the fault current rises or the voltage drop increases, the OR gate is started, thereby controlling the IGBT S1 to turn on and switch to the action state to limit the fault current; use the digital sampler to measure the DC reactor core flux, use the comparator to quickly track the given value, when the DC reactor is saturated, control the IGBT S2 to turn on and switch to the reset state to reset the core. The control flow chart is as follows Figure 3 As shown, Figure 3This is a schematic diagram of the structure of a current limiting reactor protection control device provided by the present invention. When a fault occurs, the voltage drops and the first peak current increases. Even without a control system, the DC reactor can limit the fault current, so there is no need for a control pulse. As the current rises and the voltage drop increases, the controller turns off IGBT S1, thereby entering an action state, temporarily limiting the fault current and increasing the core flux. When the flux sensor detects that the DC reactor is saturated, the controller turns on IGBT S2 and enters a reset state, connecting R2 to the secondary winding of the DC reactor to desaturate the core. Afterwards, the timer is used to reset the gate signal to the nominal state after the adjustment time. If the fault has been eliminated, the system will work in its nominal state. If the fault has not been eliminated, the fault limiting control process is repeated until the fault is eliminated. The decision of the timer instruction can be provided by a decision center or a power system operator.

[0087] Figure 4 A schematic diagram of the structure of a current limiting reactance protection control device provided by the present invention, the current limiting reactance protection control device comprises:

[0088] A memory 41, used for storing computer programs;

[0089] The processor 42 is used to implement the steps of the above-mentioned current limiting reactor protection control method when executing the computer program.

[0090] For an introduction to the current limiting reactance protection control device provided in the present application, please refer to the above embodiments, which will not be repeated here.

[0091] Figure 2 A schematic diagram of the structure of an energy storage type distribution transformer provided by the present invention, the energy storage type distribution transformer comprises an energy storage system, a distribution transformer, a current conversion circuit arranged between the energy storage system and the distribution transformer, and the above-mentioned current limiting reactance protection control device;

[0092] The current conversion circuit is used to limit the fault current between the energy storage system and the distribution transformer based on the control of the current limiting reactor protection control device.

[0093] In some embodiments, it also includes a full-bridge rectifier, a DC reactor, a first controllable switch S1, a second controllable switch S2, a damping resistor R1 and an external resistor 2;

[0094] The common end at which the anode of the first diode D1 and the cathode of the third diode D3 in the full-bridge rectifier are connected is connected to the distribution transformer, the common end at which the anode of the third diode D3 and the anode of the second diode D2 in the full-bridge rectifier are connected is connected to the input end of the DC reactor, the common end at which the cathode of the second diode D2 and the anode of the fourth diode D4 in the full-bridge rectifier are connected is connected to the energy storage system, and the common end at which the cathode of the fourth diode D4 and the cathode of the first diode D1 are connected is connected to the output end of the DC reactor;

[0095] The first end of the first controllable switch S1 is respectively connected to the third end of the full-bridge rectifier and the first end of the damping resistor R1, the second end of the first controllable switch S1 is respectively connected to the second end of the damping resistor R1 and the first end of the DC reactor, the second end of the DC reactor is connected to the first end of the external resistor 2, the second end of the external resistor 2 is connected to the first end of the second controllable switch S2, and the second end of the second controllable switch S2 is connected to the third end of the DC reactor and the third end of the full-bridge rectifier;

[0096] The full-bridge rectifier is used to realize energy exchange between the distribution transformer and the energy storage system. The DC reactor is used to limit the current based on the control of the processor in the current limiting reactor protection control device. When the first controllable switch S1 and the second controllable switch S2 are both disconnected, the DC reactor limits the fault current. When the first controllable switch S1 is disconnected and the second controllable switch S2 is closed, the DC reactor is demagnetized. When the first controllable switch S1 is closed and the second controllable switch S2 is disconnected, it indicates that the distribution transformer is not faulty and the core is not saturated.

[0097] In some embodiments, it further includes a voltage sensor, a current sensor, a magnetic flux sensor, an OR gate, a first driving circuit, and a second driving circuit;

[0098] The current collected by the current sensor is input to the current input terminal of the processor, the voltage collected by the voltage sensor is input to the voltage input terminal of the processor, the first output terminal of the processor is connected to the input terminal of the first drive circuit, the output terminal of the first drive circuit is connected to the control terminal of the first controllable switch S1, the magnetic flux collected by the magnetic flux sensor is input to the magnetic flux input terminal of the processor, the second output terminal of the processor is connected to the input terminal of the second drive circuit, and the output terminal of the second drive circuit is connected to the control terminal of the second controllable switch S2;

[0099] The processor is specifically used to send a first signal to the first drive circuit when the current collected by the current sensor is greater than a reference current or the voltage drop collected by the voltage sensor is greater than a reference voltage drop, so that the first drive circuit controls the first controllable switch S1 to be disconnected based on the first signal, and send a second signal to the second drive circuit when the magnetic flux collected by the magnetic flux sensor is greater than the reference magnetic flux, so that the second drive circuit controls the second controllable switch S2 to be disconnected based on the second signal.

[0100] For an introduction to the energy storage distribution transformer provided in this application, please refer to the above embodiments, which will not be repeated here.

[0101] It should also be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0102] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0103] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A current limiting reactance protection control method, characterized in that: A current-limiting reactance protection control device applied to an energy storage type distribution transformer, wherein the energy storage type distribution transformer further comprises an energy storage system, a distribution transformer and a current conversion circuit arranged between the energy storage system and the distribution transformer; The current limiting reactance protection control method comprises: Determining whether a fault occurs on the AC side to which the distribution transformer is connected according to the voltage and current of the conversion circuit; If a fault occurs on the AC side to which the distribution transformer is connected, the current conversion circuit is controlled to limit the fault current; judging whether the iron core is saturated according to the magnetic flux of the iron core of the current conversion circuit; If the iron core is saturated, the iron core is controlled to be demagnetized.

2. The current limiting reactance protection control method according to claim 1, characterized in that: The current conversion circuit includes a full-bridge rectifier and a DC reactor; The common end at which the anode of the first diode and the cathode of the third diode in the full-bridge rectifier are connected is connected to the distribution transformer, the common end at which the anode of the third diode and the anode of the second diode in the full-bridge rectifier are connected is connected to the input end of the DC reactor, the common end at which the cathode of the second diode and the anode of the fourth diode in the full-bridge rectifier are connected is connected to the energy storage system, and the common end at which the cathode of the fourth diode and the cathode of the first diode are connected is connected to the output end of the DC reactor; The full-bridge rectifier is used to convert the alternating current output by the distribution transformer into direct current, and the direct current reactor is used to limit the fault current.

3. The current limiting reactance protection control method according to claim 2, characterized in that: The current conversion circuit also includes a first controllable switch, a second controllable switch, a damping resistor and an external resistor; The first end of the first controllable switch is connected to the third end of the full-bridge rectifier and the first end of the damping resistor respectively, the second end of the first controllable switch is connected to the second end of the damping resistor and the first end of the DC reactor respectively, the second end of the DC reactor is connected to the first end of the external resistor, the second end of the external resistor is connected to the first end of the second controllable switch, and the second end of the second controllable switch is connected to the third end of the DC reactor and the third end of the full-bridge rectifier; Controlling the current conversion circuit to limit the fault current includes: The first controllable switch and the second controllable switch are both controlled to be turned off.

4. The current limiting reactance protection control method according to claim 3, characterized in that: Controlling the demagnetization of the iron core includes: The first controllable switch is controlled to be opened, and the second controllable switch is controlled to be closed.

5. The current limiting reactance protection control method according to claim 3, characterized in that: Also includes: When the distribution transformer does not fail and the iron core is not saturated, the first controllable switch is controlled to be closed and the second controllable switch is controlled to be open.

6. The current limiting reactance protection control method according to any one of claims 1 to 5, characterized in that: The current conversion circuit also includes a voltage sensor, a current sensor and a magnetic flux sensor; The voltage sensor and the current sensor are both connected to the DC reactor, and the magnetic flux sensor is arranged in the DC reactor and connected to the iron core of the DC reactor; Judging whether a fault occurs on the AC side connected to the distribution transformer according to the voltage and current of the conversion circuit, including: When the voltage drop detected by the voltage sensor is greater than the reference voltage drop or the current detected by the current sensor is greater than the reference current, it is determined that a fault occurs on the AC side to which the distribution transformer is connected; Judging whether the iron core of the current conversion circuit is saturated according to the magnetic flux of the iron core includes: When the magnetic flux detected by the magnetic flux sensor is greater than a reference magnetic flux, it is determined that the core is saturated.

7. A current limiting reactance protection control device, characterized in that: include: Memory for storing computer programs; A processor, configured to implement the steps of the current limiting reactor protection control method as claimed in any one of claims 1 to 6 when executing the computer program.

8. An energy storage distribution transformer, characterized in that: It comprises an energy storage system, a distribution transformer, a current conversion circuit arranged between the energy storage system and the distribution transformer, and the current limiting reactance protection control device as claimed in claim 7; The current conversion circuit is used to limit the fault current between the energy storage system and the distribution transformer based on the control of the current limiting reactance protection control device.

9. The energy storage type distribution transformer according to claim 8, characterized in that: It also includes a full-bridge rectifier, a DC reactor, a first controllable switch, a second controllable switch, a damping resistor and an external resistor; The common end at which the anode of the first diode and the cathode of the third diode in the full-bridge rectifier are connected is connected to the distribution transformer, the common end at which the anode of the third diode and the anode of the second diode in the full-bridge rectifier are connected is connected to the input end of the DC reactor, the common end at which the cathode of the second diode and the anode of the fourth diode in the full-bridge rectifier are connected is connected to the energy storage system, and the common end at which the cathode of the fourth diode and the cathode of the first diode are connected is connected to the output end of the DC reactor; The first end of the first controllable switch is connected to the third end of the full-bridge rectifier and the first end of the damping resistor respectively, the second end of the first controllable switch is connected to the second end of the damping resistor and the first end of the DC reactor respectively, the second end of the DC reactor is connected to the first end of the external resistor, the second end of the external resistor is connected to the first end of the second controllable switch, and the second end of the second controllable switch is connected to the third end of the DC reactor and the third end of the full-bridge rectifier; The full-bridge rectifier is used to realize energy exchange between the distribution transformer and the energy storage system. The DC reactor is used to limit current based on the control of the processor in the current limiting reactor protection control device. When the first controllable switch and the second controllable switch are both disconnected, the DC reactor limits the fault current. When the first controllable switch is disconnected and the second controllable switch is closed, the DC reactor is demagnetized. When the first controllable switch is closed and the second controllable switch is disconnected, it indicates that the distribution transformer is not faulty and the iron core is not saturated.

10. The energy storage type distribution transformer according to claim 9, characterized in that: It also includes a voltage sensor, a current sensor, a magnetic flux sensor, a first drive circuit and a second drive circuit; The current collected by the current sensor is input to the current input terminal of the processor, the voltage collected by the voltage sensor is input to the voltage input terminal of the processor, the first output terminal of the processor is connected to the input terminal of the first drive circuit, the output terminal of the first drive circuit is connected to the control terminal of the first controllable switch, the magnetic flux collected by the magnetic flux sensor is input to the magnetic flux input terminal of the processor, the second output terminal of the processor is connected to the input terminal of the second drive circuit, and the output terminal of the second drive circuit is connected to the control terminal of the second controllable switch; The processor is specifically used to send a first signal to the first drive circuit when the current collected by the current sensor is greater than a reference current or the voltage drop collected by the voltage sensor is greater than a reference voltage drop, so that the first drive circuit controls the first controllable switch to be disconnected based on the first signal, and send a second signal to the second drive circuit when the magnetic flux collected by the magnetic flux sensor is greater than the reference magnetic flux, so that the second drive circuit controls the second controllable switch to be disconnected based on the second signal.

Images