High and low voltage continuous ride-through test detection circuit and detection cabinet

Abstract

The present invention relates to the technical field of power systems, and provides a high and low voltage continuous ride-through test detection circuit and detection cabinet. The detection circuit adopts the impedance voltage division / resistance-capacitance voltage boosting principle to realize the voltage drop / increase of the power grid. The large bypass function is realized by the bypass circuit breaker, so that the power grid side and the power station side do not need to be powered off during the debugging and maintenance of the equipment; it does not affect the power generation of the owner, and the safety of the test personnel is guaranteed while improving the efficiency. The continuous ride-through test function of the fault voltage is realized by connecting the reactors in parallel, adding a drop switch and a boost switch and a set of boost capacitors and resistors.

Description

Technical Field

[0001] The invention relates to the technical field of power systems, and in particular to a high and low voltage continuous ride-through test detection circuit and a detection cabinet. Background Art

[0002] In order to ensure the stability of the power grid after large-scale access to new energy sources such as wind power and photovoltaic power generation, it is necessary that when the voltage drops sharply in a short period of time due to a transient fault in the power grid, wind power, photovoltaic and other power generation units can still remain in the power grid and continue to operate stably until the power grid returns to normal, thereby "crossing" this low voltage period. This ability is called low voltage ride-through capability. Similarly, the power generation unit is required to have high voltage ride-through capability when the voltage rises sharply in a short period of time due to a transient fault in the power grid. The low voltage ride-through capability and high voltage ride-through capability can be collectively referred to as fault ride-through capability, that is, high and low voltage ride-through capability.

[0003] To verify whether a power generation unit has the ability to ride through a fault, a detection device is needed to simulate the voltage rise and / or voltage drop caused by a grid fault. Therefore, the industry is in urgent need of a detection device that can detect the fault ride-through ability of a power generation unit. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a high and low voltage continuous ride-through test detection circuit and a detection cabinet.

[0005] A first aspect of the present invention provides a high and low voltage continuous ride-through test detection circuit, comprising:

[0006] A power grid inlet terminal, used for electrical connection to the power grid;

[0007] The generator side outlet terminal is used for electrical connection with the power generation unit;

[0008] A bypass circuit breaker, wherein two ends of the bypass circuit breaker are respectively connected to the power grid inlet and the generator-side outlet;

[0009] A grid-side circuit breaker, a current-limiting reactor and a machine-side circuit breaker connected in series in sequence, one end of the grid-side circuit breaker being connected to the grid inlet terminal, and one end of the machine-side circuit breaker being connected to the machine-side outlet terminal;

[0010] Also includes: low penetration test module and high penetration test module;

[0011] The low penetration test module comprises a drop switch, a drop reactor and a drop three-phase unbalanced selection switch\grounding switch connected in series in sequence, and one end of the drop switch is connected to the connection line between the current limiting reactor and the machine-side circuit breaker;

[0012] The high-penetration test module includes two parallel high-penetration test units, and the high-penetration test unit includes a boost switch, a boost three-phase unbalanced selection switch, a boost capacitor and a boost damping resistor connected in series in sequence; one end of the boost switch is connected to the connecting line between the current limiting inductor and the machine-side circuit breaker.

[0013] Optionally, the current limiting reactor and the drop reactor are adjustable reactors, the boost capacitor is an adjustable capacitor, and the boost damping resistor is an adjustable resistor.

[0014] Optionally, a voltage transformer is provided at the grid inlet terminal and / or the generator-side outlet terminal.

[0015] Optionally, a lightning arrester is connected to the bypass circuit breaker, the grid-side circuit breaker, the current-limiting reactor, the machine-side circuit breaker, the low-penetration test module and the high-penetration test module.

[0016] Optionally, the current limiting reactor, the drop reactor and the boost damping resistor are all provided with a temperature detector.

[0017] Optionally, the connecting line between the current-limiting reactor and the machine-side circuit breaker is a busbar copper bar.

[0018] Optionally, it also includes:

[0019] A first isolating switch, connected in series with the bypass circuit breaker;

[0020] A second isolating switch connected in series with the grid-side circuit breaker;

[0021] The third isolating switch is connected in series with the machine-side circuit breaker.

[0022] The second aspect of the present invention also provides a detection cabinet including a cabinet body and a high and low voltage continuous ride-through test detection circuit as described in the first aspect and arranged in the cabinet body; the cabinet body is provided with a power grid incoming line connection port and a machine side outgoing line connection port, the power grid incoming line connection port is electrically connected to the power grid incoming line terminal, and the machine side outgoing line connection port is electrically connected to the machine side outgoing line terminal.

[0023] Optionally, it also includes: a smoke alarm.

[0024] Optionally, it also includes:

[0025] The alarm is used to sound an alarm when it detects that the cabinet is opened by mistake.

[0026] The high and low voltage continuous ride-through test detection circuit and detection cabinet provided by the present invention adopt the impedance voltage division / resistance-capacitance voltage boosting principle to realize the voltage drop / increase of the power grid. The bypass circuit breaker realizes the large bypass function, which meets the need of power outage on the power grid side and the power station side during equipment commissioning and maintenance; it does not affect the power generation of the owner, and ensures the safety of the test personnel while improving efficiency. The continuous ride-through test function of the fault voltage is realized by connecting the reactors in parallel, adding a drop switch and a boost switch, and a set of boost capacitors and resistors. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 A schematic diagram of a high and low voltage continuous ride-through test detection circuit provided in an embodiment of the present invention.

[0029] Figure 2 A schematic diagram of a voltage continuous ride-through fault curve provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] As green energy accounts for an increasing proportion of electric energy, the impact of wind turbines and photovoltaic power generation systems on the power grid cannot be ignored. Especially with the large-scale centralized development of wind power and photovoltaic power in my country, when a fault occurs in the power grid and causes the voltage at the grid connection point to drop or increase, once the wind turbines and photovoltaic inverters are automatically disconnected from the grid, it may cause the collapse of the grid voltage and frequency, seriously affecting the safe and stable operation of the grid. Therefore, wind turbines and high-power photovoltaic grid-connected inverters must have high and low voltage ride-through capabilities. Their grid connection must meet the corresponding technical standards. Wind turbines and photovoltaic inverters are only allowed to be disconnected from the grid when the grid voltage drops below the specified curve. When the voltage is in the concave and convex parts, wind turbines and photovoltaic inverters should provide corresponding reactive power to support grid recovery.

[0032] Generally, a detection device is used to simulate a grid fault to test whether the power generation unit has high and low voltage ride-through capabilities. However, the detection device provided in the prior art can realize the high voltage ride-through detection function, the low voltage ride-through detection function, the high-low voltage interlocking ride-through detection function and the low-high voltage interlocking ride-through detection function, but cannot realize the continuous ride-through detection function, such as the high-low-high-low voltage continuous ride-through detection function and the low-high-low-high voltage continuous ride-through detection function.

[0033] In order to improve the detection capability of grid-connected operation of wind turbines and photovoltaic inverters in my country, an embodiment of the present invention provides a high and low voltage continuous ride-through test detection circuit. The device adopts impedance voltage division and resistance-capacitance boosting, centralized structure, and compact design, and has the advantages of convenient transportation, flexible testing, and small footprint. This set of high and low voltage continuous ride-through test detection circuit is suitable for high and low voltage continuous ride-through tests of wind turbines and photovoltaic grid-connected inverters of 25MVA and 18MW and below, and can flexibly select the voltage drop depth and short-circuit mode according to user needs.

[0034] Figure 1 A schematic diagram of a high and low voltage continuous ride-through test detection circuit provided by an embodiment of the present invention is shown in FIG. Figure 1 As shown, the high and low voltage continuous ride-through test detection circuit includes:

[0035] The grid inlet terminal A and the machine side outlet terminal B, wherein the grid inlet terminal A is electrically connected to the grid, and the machine side outlet terminal B is electrically connected to the power generation unit. The power generation unit can be a wind power or photovoltaic power generation unit, such as a wind turbine. The location of the grid inlet terminal A can be used as a grid capacity calculation point, and the location of the machine side outlet terminal B can be used as a test point capacity calculation point.

[0036] It also includes a bypass circuit breaker CB2, and two ends of the bypass circuit breaker CB2 are respectively connected to the power grid inlet terminal A and the machine-side outlet terminal B.

[0037] It also includes a grid-side circuit breaker CB1, a current-limiting reactor X1 and a machine-side circuit breaker CB3. One end of the grid-side circuit breaker CB1 is connected to the grid input terminal A, and the other end is connected to the current-limiting reactor X1. One end of the machine-side circuit breaker CB3 is connected to the machine-side output terminal B, and the other end is connected to the current-limiting reactor X1, thereby forming a structure connected in series in sequence.

[0038] As can be seen from the above, when the bypass circuit breaker CB2 is in the disconnected state, the wind turbine and the power grid are electrically connected through the first path where the grid-side circuit breaker CB1, the current limiting reactor X1 and the machine-side circuit breaker CB3 are located. When the bypass circuit breaker CB2 is in the closed state, the wind turbine and the power grid can be directly connected through the bypass circuit breaker CB2 to achieve the large bypass function. At this time, the grid-side circuit breaker CB1, the current limiting reactor X1 and the machine-side circuit breaker CB3 are not energized, and maintenance and debugging work can be carried out.

[0039] In the high and low voltage continuous ride-through test detection circuit provided in the embodiment of the present invention, a low-voltage ride-through test module C is also included. The low-voltage ride-through test module C includes a drop switch CB5, a drop reactor X2 and a drop three-phase unbalanced selection switch\grounding switch SW1 connected in series in sequence, and one end of the drop switch CB5 is connected to the connecting line between the current limiting reactor X1 and the machine-side circuit breaker CB3. By controlling the drop switch CB5 to close, the low-voltage ride-through test module C is electrically connected to the first path, and a low-voltage ride-through test can be performed at this time. By controlling the drop switch CB5 to open, the low-voltage ride-through test module C is electrically isolated from the first path. SW1 includes Q1, Q2, Q3 and Q4 as shown in the figure.

[0040] The high and low voltage continuous ride-through test detection circuit is connected in series between the power grid and the power generation unit under test. By putting in a current limiting reactor X1 with a certain impedance value to reduce the impact of the voltage drop test on the power grid, a drop reactor X2 with a specific impedance value is put in to generate a power grid short circuit fault, thereby generating a voltage drop at the test point. The voltage drop depth at the test point is equal to the ratio of the current limiting impedance to the total impedance, that is, Udip=X1 / (X1+X2)╳Un, where Udip is the voltage drop depth and Un is the rated voltage of the system. When testing different voltage drop depths, by changing the number of current limiting reactors X1 and drop reactors X2 put in, the impedance voltage divider point can be changed, thereby changing the depth of the voltage drop.

[0041] The high and low voltage continuous ride-through test detection circuit provided in the embodiment of the present invention also includes a high-throughput test module D. Figure 1 As shown, the high penetration test module D includes two high penetration test units in parallel. Among them, one high penetration test unit includes a first boost switch CB6, a boost three-phase unbalanced selection switch SW2, a boost capacitor XC and a boost damping resistor XR connected in series, and the other high penetration test unit includes a second boost switch CB7, a boost three-phase unbalanced selection switch SW3, a boost capacitor XC and a boost damping resistor XR connected in series. One end of the first boost switch CB6 and the second boost switch CB7 are both connected to the connecting line between the current limiting reactor X1 and the machine-side circuit breaker CB3. Among them, SW2 includes Q6 as shown in the figure, and SW3 includes Q7 as shown in the figure.

[0042] The high and low voltage continuous ride-through test detection circuit is connected in series between the power grid and the power generation unit under test, and the high-throughput test units corresponding to each other in the high-throughput test module D are electrically connected to the first path by controlling the first boost switch CB6 and the second boost switch CB7 to be closed, and a continuous high-voltage ride-through test can be performed at this time. The high-throughput test units corresponding to each other in the high-throughput test module D are electrically isolated from the first path by controlling the first boost switch CB6 and the second boost switch CB7 to be opened.

[0043] Since the bypass circuit breaker in the fault voltage detection device provided by the prior art is generally set at both ends of the current limiting reactor, when debugging and maintenance are required on site, the power grid of the equipment must be cut off and the wind turbine must stop generating electricity before personnel can enter the operation. Because the power supply and power outage on the on-site grid side requires the coordination of multiple departments, not only is the process complicated, but it also has a great impact on the owner's power generation, and there are safety and hidden dangers for testers. The high and low voltage continuous crossing test detection circuit provided by the embodiment of the present invention, since the two ends of the bypass circuit breaker CB2 are respectively connected to the grid incoming line end and the machine side outgoing line end, that is, CB1\CB2\CB3 are used in parallel cabinets to realize the CB2 large bypass function, which meets the need for the equipment to be debugged and maintained without the need to cut off the power on the grid side and the power station side; it also does not affect the owner's power generation, and improves efficiency while ensuring the safety of testers.

[0044] The high and low voltage continuous ride-through test detection circuit provided in the embodiment of the present invention also includes a ground switch G1 / G2 and a drop circuit breaker CB4.

[0045] The high and low voltage continuous ride-through test detection circuit provided by the embodiment of the present invention includes a passive reactor, a capacitor, a resistor, a circuit breaker, various switches and a data acquisition device. The impedance voltage division / resistance-capacitance voltage boosting principle is adopted to realize the voltage drop / increase of the power grid. By connecting the reactors in parallel, adding a drop switch and a boost switch and a set of boost capacitors and resistors, the high voltage ride-through detection function, the low voltage ride-through detection function, the high-low voltage interlocking ride-through detection function, the low-high voltage interlocking ride-through detection function, the high-high voltage continuous ride-through function, the low-low voltage continuous ride-through detection function, the high-low-high-low voltage continuous ride-through detection function and the low-high-low-high voltage continuous ride-through detection function are realized to meet the detection requirements for the continuous ride-through of wind turbines.

[0046] The high and low voltage continuous ride-through test detection circuit provided by the embodiment of the present invention adopts an impedance voltage division and resistance-capacitance boosting structure, and can realize various types of voltage faults such as three-phase symmetrical fault, two-phase asymmetrical fault and low-through single-phase grounding fault through control. The detection circuit can be connected in series between the high-voltage side of the wind turbine or photovoltaic inverter box transformer and the power grid, and the voltage fault on the high-voltage side of the box transformer is realized by changing the impedance voltage division and resistance-capacitance boosting ratio, so as to complete the test of the high and low voltage ride-through capability of the wind turbine photovoltaic inverter. All the detection circuits are controllable circuit breakers. Among them, the three-phase symmetrical drop means that when the grid voltage drops, the amplitude of the three-phase voltage decreases at the same time, and the phase remains symmetrical. The two-phase asymmetrical drop means that in the power system, the voltage of two phases of the three-phase voltage suddenly decreases or drops, while the voltage of the other phase remains normal.

[0047] Furthermore, the current limiting reactor and the drop reactor included in the detection circuit are adjustable reactors, the boost capacitor is an adjustable capacitor, and the boost damping resistor is an adjustable resistor. That is, the reactor, resistor, and capacitor are all designed with adjustable taps, and various high and low voltage fault tests can be implemented through adjustment, effectively compensating for the deviation of the drop accuracy caused by the change of the system operation mode.

[0048] Furthermore, a voltage transformer PT is also provided at the grid inlet terminal A and / or the machine-side outlet terminal B, for respectively measuring the system access voltage value and the test point drop voltage value.

[0049] Furthermore, if Figure 1 As shown, the bypass circuit breaker, the grid-side circuit breaker, the current-limiting reactor, the machine-side circuit breaker, the low-break test module, and the high-break test module are all connected with a lightning arrester. Specifically, a lightning arrester is connected between the reactor taps and between each phase and the ground, which plays a good protective role for the reactor and the equipment as a whole.

[0050] Furthermore, the connection line between the current limiting reactor and the machine-side circuit breaker is a busbar copper bar, such as Figure 1 The busbar copper bar at the short-circuit point is shown.

[0051] Furthermore, if Figure 1 As shown, the detection circuit may further include a first isolating switch S2 connected in series with the bypass circuit breaker CB2; a second isolating switch S1 connected in series with the grid-side circuit breaker CB1; and a third isolating switch S3 connected in series with the machine-side circuit breaker CB3.

[0052] Furthermore, the detection circuit may also include a plurality of reactors CT as shown in the figure, such as a grid-side CT, a power station test CT, a low-penetration test CT, and a high-penetration test CT.

[0053] The high and low voltage continuous ride-through test detection circuit provided in the embodiment of the present invention can be applicable to, for example, 25MVA fault voltage ride-through detection by increasing the capacity of the boost capacitor. It is mainly used for fault ride-through capability detection of wind farms, and realizes combined testing under the conditions of three-phase symmetrical voltage drop and increase, and three-phase asymmetrical voltage drop and increase, to meet the continuous ride-through requirements. Within the voltage assessment range, the wind turbines and reactive compensation devices in the wind farm should not be disconnected from the grid and operate continuously.

[0054] Figure 2 A schematic diagram of a voltage continuous ride-through fault curve provided by an embodiment of the present invention is shown in FIG. Figure 2 As shown, PU is the ratio of the actual voltage to the nominal voltage. For example, in a circuit rated at 380V, the voltage temporarily drops to 300V, and the PU is about 0.8. First, a low voltage ride-through test is performed, and the voltage drops to 0.2PU for 100ms; then a high voltage ride-through test is performed, and the voltage rises to 1.3PU for 100ms, thus completing the low-high voltage chain ride-through test; then the low voltage ride-through test is continued, and the voltage drops to 0.2PU for 100ms; then a high voltage ride-through test is performed again, and the voltage rises to 1.3PU for 100ms, thus completing the low-high-low-high voltage continuous ride-through test.

[0055] The high and low voltage continuous ride-through test detection circuit provided by the embodiment of the present invention has a low voltage ride-through test accuracy of ±5% and a high voltage ride-through test accuracy of ±2%.

[0056] An embodiment of the present invention further provides a detection cabinet, comprising a cabinet body and a high and low voltage continuous ride-through test detection circuit arranged in the cabinet body. Among them, the high and low voltage continuous ride-through test detection circuit can adopt the high and low voltage continuous ride-through test detection circuit provided by the above-mentioned embodiments, and the specific structure is not repeated here. Two interfaces are arranged on the cabinet body, namely, a power grid incoming line connection port and a machine side outgoing line connection port. Specifically, the power grid incoming line connection port is electrically connected to the power grid incoming line terminal, and the machine side outgoing line connection port is electrically connected to the machine side outgoing line terminal.

[0057] Furthermore, the cabinet can be designed as an integrally enclosed container body with high integration. The container is specially designed and insulated. The container body has a professional earthquake-resistant design and is suitable for offshore wind power platforms / northern desertification / semi-desertification areas to carry out wind power and photovoltaic grid-connected testing; and is suitable for long-distance highway or field transportation under special environmental conditions such as severe climate and bumpy road conditions. It can also be equipped with power supply systems, lighting equipment, heating, dehumidification, refrigeration devices, etc.

[0058] Furthermore, a smoke alarm can be set, and the system will automatically disconnect from the power grid when a fire occurs inside. It can also have an over-temperature alarm function, and when the temperature is too high and exceeds the set temperature value (the temperature value can be set), the device will automatically disconnect from the power grid. And an over-current protection function, when the current exceeds the set value, the test equipment will automatically disconnect from the power grid.

[0059] Furthermore, an alarm may be provided to give an alarm when the cabinet is detected to be opened by mistake. Specifically, when the container door is opened by mistake, an emergency alarm system is activated, a corresponding control program is entered, and a circuit breaker in the circuit is cut off.

[0060] Furthermore, a temperature detector may be provided in the cabinet for the current limiting reactor, the drop reactor and the boost damping resistor. The detection circuit provided in the embodiment of the present invention may have an over-temperature alarm function. When the temperature is too high and exceeds a set temperature value (the temperature value may be set), the device automatically disconnects from the power grid.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high and low voltage continuous ride-through test detection circuit, characterized in that: include: A power grid inlet terminal, used for electrical connection to the power grid; The generator side outlet terminal is used for electrical connection with the power generation unit; A bypass circuit breaker, wherein two ends of the bypass circuit breaker are respectively connected to the power grid inlet and the generator-side outlet; A grid-side circuit breaker, a current-limiting reactor and a machine-side circuit breaker connected in series in sequence, one end of the grid-side circuit breaker being connected to the grid inlet terminal, and one end of the machine-side circuit breaker being connected to the machine-side outlet terminal; Also includes: low penetration test module and high penetration test module; The low penetration test module comprises a drop switch, a drop reactor and a drop three-phase unbalanced selection switch\grounding switch connected in series in sequence, and one end of the drop switch is connected to the connection line between the current limiting reactor and the machine-side circuit breaker; The high-penetration test module includes two parallel high-penetration test units, and the high-penetration test unit includes a boost switch, a boost three-phase unbalanced selection switch, a boost capacitor and a boost damping resistor connected in series in sequence; one end of the boost switch is connected to the connecting line between the current limiting inductor and the machine-side circuit breaker.

2. The high and low voltage continuous ride-through test detection circuit according to claim 1 is characterized in that: The current limiting reactor and the drop reactor are adjustable reactors, the boost capacitor is an adjustable capacitor, and the boost damping resistor is an adjustable resistor.

3. The high and low voltage continuous ride-through test detection circuit according to claim 1 is characterized in that: A voltage transformer is provided at the power grid inlet terminal and / or the generator side outlet terminal.

4. The high and low voltage continuous ride-through test detection circuit according to claim 1, characterized in that: The bypass circuit breaker, the grid-side circuit breaker, the current-limiting reactor, the machine-side circuit breaker, the low-break test module and the high-break test module are all connected with a lightning arrester.

5. The high and low voltage continuous ride-through test detection circuit according to claim 1, characterized in that: The current limiting reactor, the drop reactor and the boost damping resistor are all provided with temperature detectors.

6. The high and low voltage continuous ride-through test detection circuit according to claim 1, characterized in that: The connecting line between the current limiting reactor and the machine-side circuit breaker is a busbar copper bar.

7. The high and low voltage continuous ride-through test detection circuit according to claim 1, characterized in that: Also includes: A first isolating switch, connected in series with the bypass circuit breaker; A second isolating switch connected in series with the grid-side circuit breaker; The third isolating switch is connected in series with the machine-side circuit breaker.

8. A detection cabinet, characterized in that: It comprises a cabinet and a high and low voltage continuous ride-through test detection circuit as described in any one of claims 1 to 7 arranged in the cabinet; the cabinet is provided with a grid incoming line connection port and a machine side outgoing line connection port, the grid incoming line connection port is electrically connected to the grid incoming line terminal, and the machine side outgoing line connection port is electrically connected to the machine side outgoing line terminal.

9. The detection cabinet according to claim 8, characterized in that: Also includes: Smoke alarm.

10. The detection cabinet according to claim 8, characterized in that: Also includes: The alarm is used to sound an alarm when it detects that the cabinet is opened by mistake.

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