A DC power grid fault current controller

Abstract

The present invention discloses a DC grid fault current controller, comprising a primary circuit and a controller; the primary circuit comprises an inductor, a filter capacitor, a resistor, an IGBT switch, a diode, a contactor and a current Hall sensor; the inductor, a first resistor and a second contactor are connected in series to form a series circuit; the series circuit is connected in parallel with the first contactor; the second resistor and the first diode are connected in series to form a first branch; the third resistor and the second diode are connected in series to form a second branch; the first branch and the second branch are both connected in parallel with the inductor; the filter capacitor and the IGBT switch are both connected in parallel with the first resistor; the current Hall sensor is arranged on the series circuit; the controller controls the different opening and closing combinations of the IGBT switch and the two contactors in the primary circuit, so that the primary circuit forms different working modes. The present invention can realize DC grid fault protection, and avoids the temporary feeder fault from causing the DC grid main power supply to be locked and causing the entire DC distribution network to be powered off.

Description

Technical Field

[0001] The invention relates to a DC power grid fault current controller, in particular to a controller for protecting a DC power supply from being immediately locked out in the event of a feeder fault in a low-voltage distribution network, and belongs to the field of new topology and control technology for low-voltage DC distribution networks. Background Art

[0002] When a DC load in the DC distribution network fails, the load feeder switch will detect the fault current and immediately (us level) lock before the DC power supply is disconnected, causing the entire DC distribution network to lose power and other loads to be forced to lose power as well. Summary of the invention

[0003] The main purpose of the present invention is to overcome the deficiencies in the prior art and provide a DC grid fault current controller that can implement DC grid fault protection and avoid temporary feeder failures that will cause the DC grid main power supply to be locked and cause a power outage in the entire DC distribution network.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] A DC power grid fault current controller, comprising a primary circuit and a controller;

[0006] The primary circuit includes an inductor, a filter capacitor, a resistor, an IGBT switch, a diode, a contactor and a current Hall sensor;

[0007] The inductor, the first resistor and the second contactor are connected in series to form a series circuit; the series circuit is connected in parallel with the first contactor;

[0008] The second resistor and the first diode are connected in series to form a first branch;

[0009] A third resistor and a second diode are connected in series to form a second branch;

[0010] The first branch and the second branch are both connected in parallel with the inductor; the filter capacitor and the IGBT switch are both connected in parallel with the first resistor;

[0011] The current Hall sensor is arranged in a series circuit;

[0012] The controller controls different on-off combinations of the IGBT switch and two contactors in the primary circuit, so that the primary circuit forms different working modes.

[0013] Furthermore, the working modes include:

[0014] Mode 1: Normal operating conditions;

[0015] Mode 2: transient fault condition;

[0016] Mode 3: Permanent fault condition;

[0017] Mode 4: Bypass shutdown condition.

[0018] Furthermore, the primary circuit has two ports, and is connected in series in a line to be protected in the DC power grid through the two ports.

[0019] Furthermore, when the controller controls the IGBT switch to close, the second contactor to close, and the first contactor K1 to open, the primary circuit is in a normal operating condition.

[0020] Furthermore, when the controller controls the IGBT switch to be disconnected, the second contactor to be closed, and the first contactor to be disconnected, the primary circuit is in a transient fault condition.

[0021] Furthermore, when the controller controls the IGBT switch to be disconnected, the second contactor to be disconnected, and the first contactor to be disconnected, the primary circuit is in a permanent fault condition.

[0022] Furthermore, when the controller controls the IGBT switch to be disconnected, the second contactor to be disconnected, and the first contactor to be closed, the primary circuit is in a bypass shutdown state.

[0023] Furthermore, the current Hall sensor is arranged beside the second contactor in the series circuit, and is used to measure the current flowing through the second contactor.

[0024] Furthermore, the working modes include:

[0025] In mode 1, the IGBT switch is closed, the second contactor is closed, the first contactor K1 is disconnected, and the primary circuit is in normal operating condition;

[0026] In mode 2, the IGBT switch is disconnected, the second contactor is closed, the first contactor is disconnected, and the primary circuit is in a transient fault condition;

[0027] In mode 3, when the IGBT switch is disconnected, the second contactor is disconnected, and the first contactor is disconnected, the primary circuit is in a permanent fault condition;

[0028] In mode 4, when the IGBT switch is disconnected, the second contactor is disconnected, and the first contactor is closed, the primary circuit is in bypass shutdown condition;

[0029] The protection threshold is set to the first threshold I1, the second threshold I2 and I1 <I2;

[0030] Self-check whether the DC grid fault current controller device itself has a fault, and work in mode 4 when a fault occurs;

[0031] When the DC distribution network operates normally, the primary circuit operates in mode 1;

[0032] When three consecutive sampled points are greater than the first threshold value I1, or one sampled point is greater than the second threshold value I2, the IGBT switch of the primary circuit is disconnected, and it is considered that the line is faulty, and mode 2 is entered;

[0033] When the mode 2 state time exceeds the first set time period or the mode 2 is entered twice within the second set time period, the second contactor K is disconnected, which is considered as a permanent fault and the mode 3 is entered.

[0034] Mode 4 is the bypass condition and the equipment will not be used under normal circumstances.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The DC fault current controller of the current grid provided by the present invention can cooperate with the DC power supply in a protection strategy to limit the line current value when detecting a fault current, protect the DC power supply, and wait for the fault feeder to be disconnected before resuming the normal operation mode, thereby avoiding a temporary feeder fault from causing the DC grid main power supply to be locked and causing a power outage in the entire DC distribution network.

[0037] The above content is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, the present invention is further described below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A schematic diagram of a topological structure of a DC power grid fault current controller according to the present invention;

[0039] Figure 2 A typical way of connecting a DC power grid fault current controller to a DC distribution network according to the present invention;

[0040] Figure 3 The primary circuit is in normal operation in mode 1;

[0041] Figure 4 The primary circuit is in mode 2 instantaneous fault condition;

[0042] Figure 5 The primary circuit is in mode 3 permanent fault condition;

[0043] Figure 6 The primary circuit is in mode 4 bypass shutdown condition.

[0044] Figure 7 This is a control logic block diagram of the controller of the present invention. DETAILED DESCRIPTION

[0045] The present invention will be further described below in conjunction with the accompanying drawings.

[0046] The present invention adds a DC fault current controller to the DC power grid. When the DC fault current controller detects a fault current, it can cooperate with the DC power supply to limit the line current value, protect the DC power supply, and wait for the fault feeder to be disconnected before resuming the normal operation mode.

[0047] The DC grid fault current controller of the present invention has a working environment of a DC distribution network and includes a primary circuit and a controller;

[0048] The primary circuit is as follows Figure 1 As shown, it includes an inductor L, a filter capacitor C, three resistors R, R1, R2, an IGBT switch VT, two diodes V1, V2, two contactors K1, K2 and a current Hall sensor S; wherein the resistor R1 and the diode V1 are connected in series to form a first series branch, the resistor R2 and the diode V2 are connected in series to form a second series branch, the first series branch, the second series branch and the inductor L are connected in parallel to each other, the filter capacitor C and the resistor R and the IGBT switch VT are connected in parallel, and then the inductor L, the resistor R and the contactor K2 are connected in series, and then the whole is connected in parallel to the contactor K1, wherein the current Hall sensor measures the current flowing through the contactor K2.

[0049] The primary circuit has two ports D1 and D2, which are connected in series in the circuit that needs to be protected in the DC grid, such as Figure 2 shown.

[0050] The controller can control different on / off combinations of the IGBT switch and two contactors in the primary circuit, so that the primary circuit works in four different working modes. The four working modes of the DC fault current controller are:

[0051] Mode 1: Normal operating conditions, such as Figure 3 As shown;

[0052] Mode 2: Transient fault condition, such as Figure 4 As shown;

[0053] Mode 3: Permanent fault condition, such as Figure 5 As shown;

[0054] Mode 4: Bypass shutdown condition, such as Figure 6 shown.

[0055] The normal operating conditions described are as follows: Figure 3 As shown, the IGBT switch VT is closed, the contactor K2 is closed, and the contactor K1 is opened.

[0056] The transient fault condition described is as follows: Figure 4 As shown, the IGBT switch VT is disconnected, the contactor K2 is closed, and the contactor K1 is disconnected.

[0057] The described permanent fault condition is as follows Figure 5 As shown, the IGBT switch VT is turned off, the contactor K2 is turned off, and the contactor K1 is turned off.

[0058] The described bypass shutdown condition is as follows Figure 6 As shown, the IGBT switch VT is turned off, the contactor K2 is turned off, and the contactor K1 is closed.

[0059] The control logic of the described controller is as follows Figure 7 As shown, the protection thresholds are set to I1 and I2 (I1 < I2), the sampling rate is set to f, the DC grid fault current controller checks whether the device has a fault. When a fault occurs, it operates in mode 4. When the DC distribution network is operating normally, the primary circuit operates in mode 1. If 3 consecutive sampled points are greater than I1, or 1 sampled point greater than I2 is detected, it is considered that a line fault has occurred. The VT of the primary circuit trips and operates in mode 2. When the state time of mode 2 exceeds 3 s or it enters mode 2 twice within 3 consecutive seconds, it is considered a permanent fault, and K2 trips and enters mode 3. Mode 4 is the bypass condition, and the device will not be used under normal circumstances.

[0060] The innovation of the present invention lies in that the DC fault current controller provided by the present invention can cooperate with the protection strategy of the DC power supply when detecting the fault current, thereby limiting the line current value, protecting the DC power supply, waiting for the faulty feeder to disconnect and then restoring the normal operation mode, avoiding the temporary feeder fault from causing the main power supply of the DC grid to be locked and resulting in a power outage fault of the entire DC distribution network.

[0061] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A DC grid fault current controller, characterized in that: Including a primary circuit and a controller; The primary circuit includes an inductor, a filter capacitor, a resistor, an IGBT switch, a diode, a contactor and a current Hall sensor; The inductor, the first resistor and the second contactor are connected in series to form a series circuit; the series circuit is connected in parallel with the first contactor; The second resistor and the first diode are connected in series to form a first branch; A third resistor and a second diode are connected in series to form a second branch; The first branch and the second branch are both connected in parallel with the inductor; the filter capacitor and the IGBT switch are both connected in parallel with the first resistor; The current Hall sensor is arranged in a series circuit; The controller controls the different on / off combinations of the IGBT switch and the two contactors in the primary circuit, so that the primary circuit forms different working modes; The working modes include: Mode 1: Normal operating conditions; Mode 2: transient fault condition; Mode 3: Permanent fault condition; Mode 4: Bypass shutdown condition; In mode 1, when the controller controls the IGBT switch to close, the second contactor to close, and the first contactor K1 to open, the primary circuit is in normal operating condition; In mode 2, when the controller controls the IGBT switch to be disconnected, the second contactor to be closed, and the first contactor to be disconnected, the primary circuit is in a transient fault condition; In mode 3, when the controller controls the IGBT switch to be disconnected, the second contactor to be disconnected, and the first contactor to be disconnected, the primary circuit is in a permanent fault condition; In mode 4, when the controller controls the IGBT switch to be disconnected, the second contactor to be disconnected, and the first contactor to be closed, the primary circuit is in a bypass shutdown condition.

2. The DC grid fault current controller according to claim 1, characterized in that: The primary circuit has two ports and is connected in series in a line to be protected in the DC power grid through the two ports.

3. The DC grid fault current controller according to claim 1, characterized in that: The current Hall sensor is arranged beside the second contactor in the series circuit, and is used to measure the current flowing through the second contactor.

4. The DC grid fault current controller according to claim 1, characterized in that: The protection threshold is set to the first threshold I1, the second threshold I2 and I1 <I2; Self-check whether the device itself is faulty, and work in mode 4 if it fails; When the DC distribution network operates normally, the primary circuit operates in mode 1; When three consecutive sampled points are greater than the first threshold value I1, or one sampled point is greater than the second threshold value I2, the IGBT switch of the primary circuit is disconnected and enters mode 2; When the mode 2 state time exceeds the first set time period or the mode 2 is entered twice within the second set time period, the second contactor K is disconnected and the mode 3 is entered.

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