A short-circuit overvoltage suppression protection device and method

Abstract

The application relates to the technical field of intelligent power distribution networks, in particular to a short-circuit overvoltage suppression protection device and method. The device comprises a main controller, a sampling unit, a bridge rectifier circuit, a current limiting circuit and a filter capacitor; the bridge rectifier circuit is connected with the current limiting circuit at the DC side; the filter capacitor is connected in parallel at both ends of the bridge rectifier circuit; the AC side of the bridge rectifier circuit is connected with a secondary side of a series transformer T; wherein the rectifier circuit is used for rectifying input AC power into DC power output; the current limiting circuit is used for releasing the energy of large current through a resistor R to realize the current limiting effect when the circuit is short-circuited; the filter capacitor is used for filtering the AC wave in the DC power to obtain stable DC power; the sampling unit is used for collecting the voltage of the secondary side of the series transformer T or the main loop current of the power grid and outputting the voltage or the current to the main controller; and the main controller controls the working of the current limiting circuit according to the collected voltage or current value. When the circuit is short-circuited, the IGBT is controlled to be immediately turned on, the release circuit is immediately involved, and there is no time delay; the IGBT can be turned off in real time, the release circuit can be controlled to quit working at any time, and the dynamic response speed is fast.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of intelligent power distribution network, in particular to a short-circuit overvoltage suppression protection device and method. BACKGROUND

[0002] With the development of power electronic technology, more and more new energy power generation equipment and power quality management equipment are connected to the power grid, such as photovoltaic power generation system, energy storage equipment, active power filter, etc. These devices improve power quality and increase the flexibility of the power grid, but also bring new challenges to the power grid protection.

[0003] In the prior art, in order to realize short-circuit current limiting protection, a circuit breaker is usually connected in parallel to the primary side of the series transformer. When the circuit is short-circuited, the circuit breaker KM is closed to make the secondary side of the transformer have an induced voltage of 0, so that the series compensation device is withdrawn. However, the above existing scheme has the problem of long response time. When the power quality management equipment such as series side device connected to the power grid is short-circuited, if it cannot be disconnected at the fastest speed, it may cause serious consequences such as power outage of the transformer area, which will cause great loss to the power grid and users. SUMMARY

[0004] The present application aims to solve the problem of long response time of the series compensation device withdrawal in the prior art.

[0005] The technical scheme of the present application is a short-circuit overvoltage suppression protection device, which comprises a main controller, a sampling unit, a bridge rectifier circuit, a current limiting circuit and a filter capacitor.

[0006] The bridge rectifier circuit is connected to the current limiting circuit at the DC side, and the filter capacitor is connected in parallel across the bridge rectifier circuit. The AC side of the bridge rectifier circuit is connected to the secondary side of the series transformer T.

[0007] The rectifier circuit is used to rectify the input AC power to DC power output.

[0008] The current limiting circuit is used to release the energy of large current through the resistor R to realize the current limiting effect when the circuit is short-circuited.

[0009] The filter capacitor is connected in parallel across the bridge rectifier circuit to eliminate high-frequency interference and obtain more stable current and voltage signals.

[0010] The sampling unit is used to collect the voltage or current of the secondary side of the series transformer T and output to the main controller. The main controller controls the operation of the current limiting circuit according to the collected voltage or current value.

[0011] Preferably, the bridge rectifier circuit is composed of six diodes connected in series in pairs and connected in parallel to the winding of the transformer on the secondary side; for reducing the time of large current through each diode.

[0012] Preferably, the current limiting circuit comprises an IGBT transistor and an RD circuit.

[0013] The collector of the IGBT transistor is connected to the RD circuit, the emitter is connected to the negative pole of the bridge rectifier circuit, and the gate is connected to the main control signal terminal.

[0014] Preferably, the RD circuit is composed of a high-power small-resistance resistor and a diode connected in parallel.

[0015] The cathode of the diode is connected to the DC side of the bridge rectifier circuit. After the diode is connected, the cathode potential of the diode is clamped at a certain voltage value, and the circuit voltage is suppressed from increasing.

[0016] Preferably, the filter capacitor is determined according to the working frequency of the bridge rectifier circuit, the average current of the series side device, and the maximum allowed value of the output voltage ripple,

[0017] C = I l / 2*f*ΔV(I l is the average current of the series side device, f is the working frequency of the bridge rectifier current, and ΔV is the maximum allowed value of the output voltage ripple).

[0018] Preferably, the sampling unit is a voltage sampling circuit or a current sampling circuit.

[0019] When the sampling unit is a voltage sampling circuit, it is connected in parallel at the winding of the transformer T on the secondary side.

[0020] When the sampling unit is a current sampling circuit, it is connected in series on the main circuit of the power grid.

[0021] A short-circuit overvoltage suppression protection method, using the above device, comprising the following specific steps:

[0022] S1, a sampling unit is arranged on the secondary side of the transformer for collecting circuit information;

[0023] S2, when the sampling unit is a current sampling circuit, step S3 is performed, and when the sampling unit is a voltage sampling circuit, step S6 is performed;

[0024] S3, the collected I0 current value is fed back to the main controller; the main controller compares the sampled I0 value with the preset overcurrent protection threshold I of the series side device;

[0025] S4, when I0≥I, the main controller sends an instruction to close the IGBT transistor through PWM control, and the voltage of the secondary side of the series transformer T is clamped at a voltage value U, while KM1 is disconnected.

[0026] S5, after the series side device exits the grid operation, the main controller issues an instruction to disconnect the IGBT transistor;

[0027] S6, the collected voltage value U1 is fed back to the main control; the main controller compares the sampled U1 value with the preset overvoltage protection value N;

[0028] S7, when U1≥N, the main controller issues an instruction to close the IGBT transistor through PWM control, and the secondary side voltage of the series transformer T is clamped at the voltage value U, while KM1 is disconnected;

[0029] S8, after the series side device exits the grid operation, the main controller issues an instruction to disconnect the IGBT transistor.

[0030] Compared with the prior art, the present application has the following beneficial technical effects:

[0031] The present application uses a parallel mode, under normal circumstances, the IGBT is in an off state, the rectifier bridge is connected in parallel in the circuit, in an idle mode, without output current, without any impact on the operation of the device.

[0032] When a short circuit fault occurs in the circuit, the IGBT is immediately turned on, and the release circuit is immediately involved without delay.

[0033] The IGBT uses PWM control, the switching frequency can reach 10K or even higher, the IGBT is used as a switching device, and the release circuit current is sampled and fed back to the main controller, the main controller dynamically adjusts the PWM duty cycle according to the feedback value, and the size of the release current can be controlled. Using PWM control can greatly reduce the impact on power devices when the circuit is working, improve the reliability of the circuit; real-time monitoring of the release current, limiting the release current to prevent power devices from being burned out by overcurrent, which is more beneficial to device selection and cost reduction. The IGBT can be turned off in real time, the release circuit can be withdrawn from work at any time, and the dynamic response speed is fast. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 It is a schematic diagram of the short circuit overvoltage suppression protection device of the present application.

[0035] Figure 2 It is one of the logic flowcharts of the short circuit overvoltage suppression protection method of the present application.

[0036] Figure 3 It is the second logic flowchart of the short circuit overvoltage suppression protection method of the present application.

[0037] Figure 4 It is a circuit diagram of a short circuit voltage suppression protection device. DETAILED DESCRIPTION

[0038] Embodiment 1

[0039] The short-circuit overvoltage suppression protection device comprises a main controller, a sampling unit, a bridge rectifier circuit, a current limiting circuit and a filter capacitor.

[0040] The bridge rectifier circuit is connected with the current limiting circuit at the DC side, and the filter capacitor is connected in parallel with the bridge rectifier circuit at both ends.

[0041] The current limiting circuit comprises an IGBT transistor and an RD circuit.

[0042] The filter capacitor is connected in parallel with the bridge rectifier circuit at both ends to eliminate high-frequency interference and obtain more stable current and voltage signals.

[0043] The sampling unit is used to collect the voltage or current of the secondary side of the series transformer T and output to the main controller.

[0044] In this embodiment, the sampling unit is a voltage sampling circuit connected in parallel with the winding of the secondary side of the series transformer T.

[0045] Specifically, the voltage sampling circuit is connected in parallel with the winding of the secondary side of the series transformer T, and a high-precision voltage sensor is used to collect the voltage value of the winding of the secondary side of the series transformer T in real time and feed back to the main controller.

[0046] In normal operation, the IGBT is in an off state, and the short-circuit protection circuit does not work.

[0047] When a short circuit occurs in the main circuit of the power grid, the primary side current of the series transformer instantaneously increases, and the secondary side voltage of the series transformer increases. When the voltage increase exceeds the overvoltage protection value N of the series transformer, the equipment on the series side will be damaged.

[0048] The sampling unit collects the voltage value U1 of the secondary side winding of the series transformer in real time and feeds back to the main controller. When the main controller detects that the voltage value U1 is greater than or equal to the preset overvoltage protection value N of the series transformer, the main controller sends a trigger instruction, and the IGBT is triggered to conduct. The voltage across the current limiting circuit is limited to the voltage value U, so that the winding voltage of the transformer is reduced to the voltage value U. The current is rectified into direct current after passing through the bridge rectifier circuit. After the filtering capacitor filters out the high-frequency interference signal, the filtered current passes through the high-power resistor R, and the energy is released. At the same time, the main controller disconnects KM1, and the whole device exits the operation of the power grid, and the main circuit of the power grid works normally.

[0049] Embodiment 2

[0050] The short-circuit overvoltage suppression protection device provided by the application comprises a main controller, a sampling unit, a bridge rectifier circuit, a current limiting circuit and a filtering capacitor.

[0051] The bridge rectifier circuit is connected to the current limiting circuit at the direct current side, and the filtering circuit is connected in parallel at both ends of the bridge rectifier circuit. The alternating current side of the bridge rectifier circuit is connected to the secondary side of the series transformer T. The bridge rectifier circuit is connected to both ends of the secondary side winding of the series transformer T by connecting two diodes in series and then connecting the two series of diodes in parallel. The diodes are made of germanium or silicon, which can reduce the time of large current passing through each diode, prolong the service life of the diodes, and convert the input alternating current into direct current output.

[0052] The current limiting circuit comprises an IGBT transistor, an RD circuit and a filtering capacitor. The collector of the IGBT transistor is connected to the RD circuit, the emitter is connected to the negative electrode of the bridge rectifier circuit, and the gate is connected to the main control signal end. The filtering capacitor is connected in parallel at both ends of the bridge rectifier circuit to eliminate high-frequency interference and obtain more stable current and voltage signals. The RD circuit comprises a high-power small-resistance resistor and a diode connected in parallel. The cathode of the diode is connected to the direct current side of the bridge rectifier circuit. After the diode is connected, the cathode potential of the diode is clamped to a certain voltage value, and the voltage increase of the circuit is suppressed.

[0053] The filtering circuit is used for filtering out the alternating current in the direct current to obtain stable direct current.

[0054] The sampling unit is used for collecting the voltage or current of the secondary side of the series transformer T in real time and outputting to the main controller. The main controller controls the working of the current limiting circuit according to the collected voltage or current value.

[0055] In this embodiment, unlike in Embodiment 1, the sampling unit is a current sampling circuit, which is connected in series on the power grid main circuit to feed back the current value I0 of the power grid main circuit to the main controller in real time, and the main controller presets a series side device overcurrent protection threshold I.

[0056] The bridge rectifier circuit is composed of six rectifier bridge diodes, the diodes are selected from germanium or silicon diodes, the AC measurement of the rectifier circuit is connected with the secondary side of the series voltage regulator T, the filter capacitor is a common filter capacitor, which is connected in parallel with the bridge rectifier circuit, the resistance R is selected from a high-power small resistance, which is connected in parallel with the clamping diode D to form an RD circuit, one end of the RD circuit is connected with the DC side of the bridge rectifier circuit, and the other end is connected with the collector of the IGBT, the emitter of the IGBT is connected with the bridge rectifier circuit, and the gate is connected with the main control signal.

[0057] In normal operation, the IGBT is in an off state, and the short-circuit protection circuit does not work.

[0058] When a short circuit occurs in the power grid main circuit, the power grid current instantaneously increases, the sampling unit feeds back the current value I0 to the main controller in real time, when the main controller detects that the current value I0 is equal to or greater than the series side device overcurrent protection threshold I, the main controller sends a trigger instruction, the IGBT is triggered to conduct, and the voltage across the current limiting circuit is limited to a voltage value U, which acts on the secondary side of the series transformer, the current is rectified into direct current after passing through the bridge rectifier circuit, high-frequency interference signals are filtered out through the filter capacitor, and the filtered current passes through the high-power resistance R, energy is released, and at the same time, the main controller disconnects KM1, and the entire device exits the power grid operation.

[0059] Embodiment 3

[0060] A short-circuit overvoltage suppression protection method, which applies the device of Embodiment 1 and Embodiment 2, includes the following specific steps:

[0061] S1, a sampling unit is arranged on the secondary side of the transformer to collect circuit information;

[0062] S2, when the sampling unit is a current sampler, step S3 is performed, and when the sampling unit is a voltage sampler, step S6 is performed;

[0063] S3, the collected I0 current value is fed back to the main controller; the main controller compares the sampled I0 value with the preset series side device overcurrent protection threshold I;

[0064] S4, when I0≥I, the main controller sends an instruction to close the IGBT transistor through PWM control, the voltage of the secondary side of the series transformer T is clamped to a voltage value U, and KM1 is disconnected at the same time;

[0065] S5, after the series side device exits the power grid operation, the main controller sends an instruction to disconnect the IGBT transistor;

[0066] S6, the collected voltage value U1 is fed back to the main control; the main controller compares the sampled U1 value with the preset overvoltage protection value N;

[0067] S7, when U1≥N, the main controller sends an instruction to close the IGBT transistor through PWM control, and the voltage value U of the series transformer T is clamped, and KM1 is disconnected;

[0068] S8, after the series side device exits the grid operation, the main controller sends an instruction to disconnect the IGBT transistor.

[0069] The embodiments of the application are described in detail above in combination with the drawings, but the application is not limited thereto, and various changes can be made within the knowledge of those skilled in the art without departing from the purpose of the application.

Claims

1. A short-circuit overvoltage suppression protection device, characterized in that: It includes a main controller, a sampling unit, a bridge rectifier circuit, a current limiting circuit and a filter capacitor; The DC side of the bridge rectifier circuit is connected to the current limiting circuit, and the filter capacitor is connected in parallel at both ends of the bridge rectifier circuit; the AC side of the bridge rectifier circuit is connected to the secondary side of the series transformer T; The rectifier circuit is used to rectify the input AC power into DC power output; The current limiting circuit is used to release the energy of the large current through the resistor R to achieve current limiting when the circuit is short-circuited; the current limiting circuit includes an IGBT transistor and an RD circuit; The RD circuit consists of a high-power, low-value resistor connected in parallel with a diode; The cathode of the diode is connected to the DC side of the bridge rectifier circuit. After the diode is connected, the cathode potential of the diode is clamped at a certain voltage value, suppressing the increase of the circuit voltage; The filter capacitor is connected in parallel at both ends of the bridge rectifier circuit to eliminate high-frequency interference and obtain more stable current and voltage signals. The filter capacitor is determined according to the operating frequency of the bridge rectifier circuit, the average current of the series-side device, and the maximum allowable value of the output voltage ripple. Specifically: C=I l / 2*f*ΔV I l is the average current of the series side devices, f is the operating frequency of the bridge rectifier current, and ΔV is the maximum allowable value of the output voltage ripple; The sampling unit is used to collect the voltage on the secondary side of the series transformer T or the current on the main circuit of the power grid and send it to the main controller; the main controller controls the operation of the current limiting circuit according to the collected circuit information; The short-circuit overvoltage suppression protection method is as follows: S1. Setting a sampling unit on the secondary side of the transformer to collect circuit information; S2. When the sampling unit is a current sampler, execute step S3; when the sampling unit is a voltage sampler, execute step S6; S3. The collected I0 current value is fed back to the main controller; the main controller compares the sampled I0 value with the preset series side device overcurrent protection threshold I; S4. When I0≥I, the main controller issues a command to control the IGBT transistor to close through PWM, and the secondary side voltage of the series transformer T is clamped at the voltage value U. At the same time, KM1 between the series side device and the secondary side of the transformer is disconnected; S5. After the series-side device exits the grid, the main controller issues a command to disconnect the IGBT transistor; S6. The collected voltage value U1 is fed back to the main controller; the main controller compares the sampled U1 value with the preset overvoltage protection value N; S7. When U1≥N, the main controller issues a command to control the IGBT transistor to close through PWM, and the secondary side voltage of the series transformer T is clamped at the voltage value U. At the same time, KM1 between the series side device and the secondary side of the transformer is disconnected; S8, after the series side equipment exits the grid operation, the main controller issues a command to disconnect the IGBT transistor; When using the parallel mode, the IGBT is normally in the off state, and the rectifier bridge is connected in parallel in the circuit, in no-load mode, with no output current. When a short circuit occurs in the circuit, the IGBT is controlled to turn on immediately and the release circuit intervenes immediately without delay.

2. The short-circuit overvoltage suppression protection device according to claim 1, characterized in that: The bridge rectifier circuit consists of six diodes connected in series in pairs and then connected in parallel to both ends of the secondary winding of the series transformer; it is used to reduce the time that a large current passes through each diode.

3. The short-circuit overvoltage suppression protection device according to claim 1, characterized in that: The collector of the IGBT transistor is connected to the RD circuit, the emitter is connected to the negative electrode of the bridge rectifier circuit, and the gate is connected to the main control signal terminal.

4. The short-circuit overvoltage suppression protection device according to claim 1, characterized in that: The sampling unit is a voltage sampling circuit or a current sampling circuit; When the sampling unit is a voltage sampling circuit, it is connected in parallel to the winding on the secondary side of the series transformer T; When the sampling unit is a current sampling circuit, it is connected in series to the main circuit of the power grid.

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