Test method for forced inverter protection

Abstract

The embodiment of the present invention discloses a test method for forced inversion protection. The test method for forced inversion protection includes: connecting an AC voltage to the AC input terminal of a transformer; connecting a DC voltage to the first DC input terminal and / or the second DC input terminal of the transformer; connecting a DC load to the second DC input terminal; adjusting the trigger angle of the rectifier module of the transformer; and obtaining the forced inversion performance of the transformer according to the voltage waveform changes at the AC input terminal, the first DC input terminal or the second DC input terminal. This scheme can obtain the attenuation rate of the DC current during forced inversion of the transformer and the magnitude and threshold of the voltage and current fluctuations after the inversion starts through the voltage waveform changes at the AC input terminal, the first DC input terminal or the second DC input terminal, thereby analyzing the forced inversion performance of the transformer, thereby solving the problem that the DC current cannot be quickly reduced and the short-circuit branch cannot be disconnected when a sudden fault occurs in the DC system of the transformer.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of power electronics technology, and in particular to a test method for forced inversion protection. Background Art

[0002] In power electronics technology, rectification is defined as the conversion of sinusoidal alternating current into direct current by using power electronic components (high-speed switches made with power transistors as basic elements), while inversion is defined as the conversion of direct current into sinusoidal alternating current by using power electronic components and filtering devices.

[0003] When a fault occurs on the load side of a traditional AC transformer, the fault location is usually cut off and isolated to protect the line and transformer. The main way to achieve this function is to disconnect the current through the circuit breaker when it passes through the zero point to achieve the arc extinguishing effect. However, in a system with AC-DC conversion, when a fault occurs in the DC line, a large amount of residual electromagnetic energy will remain in the line for a short time, and the current in the DC line has no zero point. Therefore, the normal working current and fault current of the DC system cannot be effectively disconnected in a short time through the circuit breaker. At present, there is no DC circuit breaker with good arc extinguishing ability, so a new method is needed to solve this problem. Summary of the invention

[0004] The embodiment of the present invention provides a test method for forced inverter protection to detect the performance of an electronic transformer and solve the problem that the DC current cannot be quickly reduced and the short-circuit branch line cannot be disconnected when a DC system of the transformer suddenly fails.

[0005] In a first aspect, an embodiment of the present invention provides a test method for forced inversion protection, which includes:

[0006] Connect the AC voltage to the AC input terminal of the transformer;

[0007] Connecting a DC voltage to a first DC input terminal and / or a second DC input terminal of a transformer;

[0008] Connecting a DC load to the second DC input terminal;

[0009] Adjust the trigger angle of the rectifier module of the transformer;

[0010] The forced inversion performance of the transformer is obtained according to the voltage waveform change of the AC input terminal, the first DC input terminal or the second DC input terminal.

[0011] Optionally, the test method for forced inversion protection further includes:

[0012] The harmonic pollution degree of forced inversion is obtained according to the voltage harmonic change of the AC input terminal, the first DC input terminal or the second DC input terminal.

[0013] Optionally, the AC input terminal of the transformer includes a first AC input terminal and a second AC input terminal;

[0014] The AC voltage includes a first-level AC voltage and a second-level AC voltage, and the first-level AC voltage is not equal to the second-level AC voltage;

[0015] The DC voltage includes a first-level DC voltage and a second-level DC voltage, and the first-level DC voltage and the second-level DC voltage are not equal;

[0016] The trigger angle of the rectifier module of the regulating transformer includes:

[0017] Adjust the trigger angle on the rectifier side of the transformer to 150 degrees.

[0018] Optionally, connecting an AC voltage to an AC input terminal of a transformer includes:

[0019] Inputting a first level AC voltage into a first AC input terminal;

[0020] Connecting a DC voltage to a first DC input terminal and / or a second DC input terminal of a transformer comprises:

[0021] Inputting a first level DC voltage into a first DC input terminal;

[0022] The performance of forced inversion is obtained according to the voltage waveform change of the first DC input terminal.

[0023] Optionally, connecting an AC voltage to an AC input terminal of a transformer includes:

[0024] Inputting a second level AC voltage into the second AC input terminal;

[0025] Connecting a DC voltage to a first DC input terminal and / or a second DC input terminal of a transformer comprises:

[0026] Inputting a first level DC voltage into a first DC input terminal;

[0027] The performance of forced inversion is obtained according to the voltage waveform change of the first DC input terminal.

[0028] Optionally, connecting an AC voltage to an AC input terminal of a transformer includes:

[0029] Inputting a first level AC voltage into a first AC input terminal;

[0030] Connecting a DC voltage to a first DC input terminal and / or a second DC input terminal of a transformer comprises:

[0031] Inputting a second level DC voltage into the second DC input terminal;

[0032] The performance of forced inversion is obtained according to the voltage waveform change of the second DC input terminal.

[0033] Optionally, connecting an AC voltage to an AC input terminal of a transformer includes:

[0034] Inputting a second level AC voltage into the second AC input terminal;

[0035] Connecting a DC voltage to a first DC input terminal and / or a second DC input terminal of a transformer comprises:

[0036] Inputting a second level DC voltage into the second DC input terminal;

[0037] The performance of forced inversion is obtained according to the voltage waveform change of the second DC input terminal.

[0038] Optionally, connecting an AC voltage to an AC input terminal of a transformer includes:

[0039] Inputting a first level AC voltage into a first AC input terminal;

[0040] Inputting a second level AC voltage into the second AC input terminal;

[0041] The performance of forced inversion is obtained according to the voltage waveform change of the first AC input terminal or the second AC input terminal.

[0042] Optionally, connecting an AC voltage to an AC input terminal of a transformer includes:

[0043] Inputting a first level AC voltage into a first AC input terminal;

[0044] Connecting a DC voltage to a first DC input terminal and / or a second DC input terminal of a transformer comprises:

[0045] Inputting a first level DC voltage into a first DC input terminal;

[0046] Inputting a second level DC voltage into the second DC input terminal;

[0047] The performance of forced inversion is obtained according to the voltage waveform changes of the first AC input terminal, the first DC input terminal and the second DC input terminal.

[0048] Optionally, connecting an AC voltage to an AC input terminal of a transformer includes:

[0049] Inputting a second level AC voltage into the second AC input terminal;

[0050] Connecting a DC voltage to a first DC input terminal and / or a second DC input terminal of a transformer comprises:

[0051] Inputting a first level DC voltage into a first DC input terminal;

[0052] Inputting a second level DC voltage into the second DC input terminal;

[0053] The performance of forced inversion is obtained according to the voltage waveform changes of the second AC input terminal, the first DC input terminal and the second DC input terminal.

[0054] The embodiment of the present invention connects an AC voltage to the AC input terminal of the transformer; connects a DC voltage to the first DC input terminal and / or the second DC input terminal of the transformer; connects a DC load to the second DC input terminal; adjusts the trigger angle of the rectifier module of the transformer; and obtains the attenuation rate of the DC current during forced inversion and the magnitude and threshold of the voltage and current fluctuations after the start of inversion according to the voltage waveform changes at the AC input terminal, the first DC input terminal or the second DC input terminal, thereby analyzing the availability of the transformer and the impact on the equipment, that is, the forced inversion performance of the transformer. In addition, the optimal forced inversion trigger angle of the transformer under load can be obtained according to the specifically measured DC voltage and current, thereby solving the problem that the DC current cannot be quickly reduced and the short-circuited branch cannot be disconnected when a sudden fault occurs in the DC system of the transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, although the drawings described below are some specific embodiments of the present invention, for those skilled in the art, the basic concepts of the device structure, driving method and manufacturing method disclosed and suggested by the various embodiments of the present invention can be expanded and extended to other structures and drawings, and there is no doubt that these should be within the scope of the claims of the present invention.

[0056] Figure 1 A schematic flow chart of a test method for forced inversion protection provided by an embodiment of the present invention;

[0057] Figure 2 A voltage value variation diagram of a three-phase AC voltage provided by an embodiment of the present invention;

[0058] Figure 3 A diagram showing the instantaneous voltage value variation of a DC voltage when the trigger angle on the rectifier side is 60 degrees during a transformer rectification process provided by an embodiment of the present invention;

[0059] Figure 4 A diagram showing the instantaneous voltage value change of a DC voltage when the trigger angle on the rectifier side is 90 degrees during a transformer rectification process provided by an embodiment of the present invention;

[0060] Figure 5 A schematic diagram of the structure of a test device for simulating forced inversion protection provided by an embodiment of the present invention;

[0061] Figure 6 An attenuation diagram of a direct current during forced inversion provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0062] 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.

[0063] The inherent circuit structure and rectification-inversion characteristics of the transformer can convert a certain value of AC voltage (current) into another or several different values ​​of voltage (current) with the same frequency. When a DC line fault occurs, the rectification characteristics of the transformer can be used to quickly reduce the fault current in the DC line, that is, by adjusting the control parameters in the DC controller of the transformer, the trigger characteristics of the rectifier side are changed, so as to achieve a rapid reduction of the fault current, that is, forced inversion. Forced inversion is used to solve the problem that the DC current cannot be quickly reduced and the short-circuited branch line cannot be disconnected when a DC system connected to the transformer suddenly fails. Through forced inversion, the transformer can quickly reduce the current in the DC line to 0 without using a circuit breaker, which is equivalent to the circuit breaker disconnection. The forced inversion of the transformer is to extend the life of the DC system cabinet circuit breaker, reduce the damage of the complete set of switchgear, and improve the hot standby speed of the system through soft adjustment, thereby achieving the purpose of improving economy and safety.

[0064] Figure 1 The present invention provides a flow chart of a test method for forced inversion protection, which can be applied to the test of forced inversion performance of transformers. The method specifically includes the following steps:

[0065] S110, connecting an AC voltage to an AC input terminal of a transformer.

[0066] The transformer has multiple AC input terminals that can be used as both power input and power output, and each AC input terminal has a different voltage level. The AC voltage is connected to the AC input terminal of the transformer, and the AC input terminal of the transformer is used as the power output terminal during normal operation; when the DC system of the transformer suddenly fails, the transformer is forced to be inverted, and the AC input terminal of the transformer is used as the power input terminal. At this time, the electric energy of the DC system can flow back through the transformer into the AC system connected to the AC input terminal of the transformer.

[0067] S120: Connect a DC voltage to the first DC input terminal and / or the second DC input terminal of the transformer.

[0068] The first DC input terminal and the second DC input terminal of the transformer can be used as both power input and power output DC input terminals, and the first DC input terminal and the second DC input terminal input different voltage levels. In normal operation, the first DC input terminal and the second DC input terminal of the transformer are both used as power input terminals; when the DC system of the transformer suddenly fails, the transformer is forced to be inverted, and the first DC input terminal and the second DC input terminal of the transformer will be used as power output terminals. At this time, the electric energy of the DC system can flow back through the transformer into the AC system connected to the AC input terminal of the transformer.

[0069] S130, connecting a DC load to the second DC input terminal.

[0070] The DC load is an adjustable DC load, which is used to simulate the working load of the transformer when it works normally after the AC input terminal of the transformer is connected to an AC voltage and the first DC input terminal and / or the second DC input terminal of the transformer is connected to a DC voltage.

[0071] S140: Adjust the trigger angle of the rectifier module of the transformer.

[0072] Among them, in order to address the problem that the line cannot respond quickly and cut off the current when a transformer fails in the DC system, the trigger angle α on the rectifier side of the transformer can be increased (or the trigger angle β on the inverter side can be reduced) so that the DC system can briefly operate in an active inverter condition, and the energy of the DC system can be quickly fed into the AC system, thereby achieving the purpose of quickly reducing the DC system current, thereby protecting the line and the internal devices of the power electronic transformer.

[0073] Figure 2 A voltage value variation diagram of a three-phase AC voltage provided by an embodiment of the present invention; Figure 3 A diagram showing the instantaneous voltage value variation of a DC voltage when the trigger angle on the rectifier side is 60 degrees during a transformer rectification process provided by an embodiment of the present invention; Figure 4 A diagram showing the instantaneous voltage value change of a DC voltage when the trigger angle is 90 degrees on the rectifier side during a transformer rectification process provided by an embodiment of the present invention; Figure 2 It is a graph showing the voltage value changes of the three-phase AC phase voltage in two cycles. Figure 3 It is a function diagram of the instantaneous value of the DC voltage after rectification when the trigger angle of the transformer on the rectifier side is 60 degrees. Through effective value calculation, it can be obtained that the effective value of the DC output voltage is at the critical point where it begins to decrease. Figure 4It is a function diagram of the instantaneous value of the DC voltage after rectification when the trigger angle of the rectifier side of the transformer is 90 degrees. At this time, by calculating the effective value of the DC voltage, it can be found that the instantaneous value of the DC voltage output is negative, that is, part of the power in the circuit is reverse power. Therefore, in the DC system operating under the 90-degree working condition, the effective value of the DC voltage is 0.

[0074] contrast Figure 2-Figure 4 It can be seen that the trigger angle of the rectifier module of the regulating transformer can be broken by breaking the theoretical trigger angle limit (90 degrees) and using the inherent system of the transformer to increase the trigger angle of the rectifier side to more than 150 degrees, so that the DC voltage is completely at the maximum effective value of reverse power operation. In this way, the residual energy in the DC system is quickly fed back to the AC system in the form of reverse power, thereby quickly reducing the DC current, so that the equipment can quickly respond to the fault current without using a circuit breaker, thereby effectively extending the life of the cabinet circuit breaker.

[0075] S150, obtaining the forced inversion performance of the transformer according to the voltage waveform change of the AC input terminal, the first DC input terminal or the second DC input terminal.

[0076] By obtaining the voltage waveform changes at the AC input terminal, the first DC input terminal or the second DC input terminal, an oscilloscope can be used to record the voltage and current waveforms on the DC system bus at the start of forced inversion, and the attenuation rate of the DC current during forced inversion and the magnitude and threshold of the voltage and current fluctuations after the start of inversion can be obtained based on the voltage and current waveforms on the DC system bus, thereby analyzing the availability of the transformer, that is, the forced inversion performance of the transformer. In addition, the optimal forced inversion trigger angle of the transformer under different loads can be obtained based on the specific measured DC voltage and current.

[0077] The embodiment of the present invention connects the AC voltage to the AC input terminal of the transformer; connects the DC voltage to the first DC input terminal and / or the second DC input terminal of the transformer; connects the DC load to the second DC input terminal; adjusts the trigger angle of the rectifier module of the transformer; and obtains the attenuation rate of the DC current during forced inversion and the magnitude and threshold of the voltage and current fluctuations after the inversion starts according to the voltage waveform changes at the AC input terminal, the first DC input terminal or the second DC input terminal, thereby analyzing the availability of the transformer, that is, the forced inversion performance of the transformer. In addition, the optimal forced inversion trigger angle of the transformer under different loads can be obtained according to the specifically measured DC voltage and current, thereby solving the problem that the DC current cannot be quickly reduced and the short-circuited branch cannot be disconnected when a sudden fault occurs in the DC system of the transformer.

[0078] Optionally, the test method for forced inversion protection further includes: obtaining a harmonic pollution degree of forced inversion according to a voltage harmonic change at the AC input terminal, the first DC input terminal or the second DC input terminal.

[0079] Among them, the power quality detector can be used to record the voltage harmonic changes at the AC input terminal, the first DC input terminal or the second DC input terminal to determine the degree of harmonic pollution caused by the forced inversion of the transformer to the surrounding power equipment, so as to timely and effectively protect the equipment around the transformer and clean the power of the power grid.

[0080] Optionally, the AC input end of the transformer includes a first AC input end and a second AC input end; the AC voltage includes a first level AC voltage and a second level AC voltage, and the first level AC voltage is not equal to the second level AC voltage; the DC voltage includes a first level DC voltage and a second level DC voltage, and the first level DC voltage and the second level DC voltage are not equal; adjusting the trigger angle of the rectifier module of the transformer includes: adjusting the trigger angle of the rectifier side of the transformer to 150 degrees.

[0081] Among them, the first level AC voltage can be input into the first AC input terminal of the transformer, the second level AC voltage can be input into the second AC input terminal of the transformer, the first level DC voltage can be input into the first DC input terminal of the transformer, and the second level DC voltage can be input into the second DC input terminal of the transformer. The first level AC voltage is not equal to the second level AC voltage, and the first level DC voltage is not equal to the second level DC voltage. It can be seen that different levels of AC voltage can only be connected to the AC input terminal of the transformer that matches it, and different levels of DC voltage can only be connected to the DC input terminal of the transformer that matches it.

[0082] Adjusting the trigger angle on the rectifier side of the transformer to 150 degrees can keep the DC voltage completely at the maximum effective value of reverse power operation, so that the residual energy in the DC system can be quickly fed back to the AC system in the form of reverse power, thereby quickly reducing the DC current, allowing the equipment to quickly respond to the fault current without the need for a circuit breaker, effectively extending the life of the cabinet circuit breaker.

[0083] For example, Figure 5 A structural diagram of a test device for simulating forced inversion protection provided by an embodiment of the present invention is shown in FIG. Figure 5 As shown, the transformer has four ports, namely, 10kV AC input terminal A (first AC input terminal), 380V AC input terminal B (second AC input terminal), 10kV DC input terminal C (first DC input terminal), ±375V DC input terminal D (second DC input terminal). Among the four ports, by controlling the rectification-inversion control of the power electronic transformer, power can flow between any two ports. In terms of power supply type, it can perform AC-AC conversion, AC-DC conversion, and DC-DC conversion; in terms of voltage level, it can freely convert high and low voltages.

[0084] Optionally, an AC voltage is connected to the AC input terminal of the transformer, including:

[0085] Inputting a first level AC voltage into a first AC input terminal;

[0086] Connecting a DC voltage to a first DC input terminal and / or a second DC input terminal of a transformer comprises:

[0087] Inputting a first level DC voltage into a first DC input terminal;

[0088] The performance of forced inversion is obtained according to the voltage waveform change of the first DC input terminal.

[0089] For example, continue to refer to Figure 5 , connect the 10kV AC input terminal A (first AC input terminal) to the 10kV power grid, and then the 10KV AC voltage (first-level AC voltage) can be input into the 10KV AC input terminal A. The 10kV DC input terminal C is connected to the photovoltaic panel, and the photovoltaic panel can generate a 10KV DC voltage, and then the 10KV DC voltage (first-level DC voltage) can be input into the 10KV DC input terminal C. At this time, the transformer is in a dual-port operation mode. By adjusting the trigger angle of the rectifier module of the transformer and installing an oscilloscope at the first DC input terminal, the voltage waveform change of the electric energy fed from the 10KV DC input terminal C to the 10KV AC input terminal A can be measured, thereby obtaining the forced inversion capability of the electric energy fed from the 10KV DC input terminal C to the 10KV AC input terminal A.

[0090] Figure 6 The attenuation diagram of the DC current during forced inversion provided by the embodiment of the present invention is as follows: Figure 6 As shown in the figure, the vertical axis is the attenuation rate of the DC current during forced inversion, and the horizontal axis is the time of forced inversion. It can be seen from the figure that the current on the DC input side will show a very obvious and rapid attenuation downward trend during forced inversion. Figure 6 To evaluate the performance of forced inversion, the time difference between the current decaying to 10% and 90% is selected to evaluate the performance of forced inversion. When a DC system fault occurs, the size of the time difference between the current decaying to 10% and 90% directly reflects the speed of fault current decay. If the time difference between the current decaying to 10% and 90% is smaller, it indicates that the effect of transformer forced inversion is better, and the protection effect of the line is also better.

[0091] Optionally, connecting an AC voltage to an AC input terminal of a transformer includes:

[0092] Inputting a second level AC voltage into the second AC input terminal;

[0093] Connecting a DC voltage to a first DC input terminal and / or a second DC input terminal of a transformer comprises:

[0094] Inputting a first level DC voltage into a first DC input terminal;

[0095] The performance of forced inversion is obtained according to the voltage waveform change of the first DC input terminal.

[0096] For example, continue to refer to Figure 5 , connect the 380V AC input terminal B (the second AC input terminal) to the 380V power grid, and then the 380V AC voltage (the second level AC voltage) can be input into the 380V AC input terminal B. Connect the 10kV DC input terminal C to the photovoltaic panel, and then the 10KV DC voltage (the first level DC voltage) can be input into the 10KV DC input terminal C. At this time, the transformer is in dual-port operation mode. By adjusting the trigger angle of the rectifier module of the transformer and installing an oscilloscope at the first DC input terminal, the voltage waveform change of the electric energy fed from the 10KV DC input terminal C to the 380V AC input terminal B can be measured, thereby obtaining the forced inversion capability of the electric energy fed from the 10KV DC input terminal C to the 380V AC input terminal B.

[0097] The forced inversion performance of the transformer 10KV DC input terminal C to the 380V AC input terminal B is evaluated, which is similar to the above embodiment and will not be described again.

[0098] Optionally, connecting an AC voltage to an AC input terminal of a transformer includes:

[0099] Inputting a first level AC voltage into a first AC input terminal;

[0100] Connecting a DC voltage to a first DC input terminal and / or a second DC input terminal of a transformer comprises:

[0101] Inputting a second level DC voltage into the second DC input terminal;

[0102] The performance of forced inversion is obtained according to the voltage waveform change of the second DC input terminal.

[0103] For example, continue to refer to Figure 5 , connect the 10kV AC input terminal A (first AC input terminal) to the 10kV power grid, and then the 10KV AC voltage (first level AC voltage) can be input to the 10KV AC input terminal A. Connect the ±375V DC input terminal D to the photovoltaic panel, and then the ±375V DC voltage (second level DC voltage) can be input to the ±375V DC input terminal D. At this time, the transformer is in dual-port operation mode. Adjust the trigger angle of the transformer's rectifier module and install an oscilloscope at the second DC input terminal, then the voltage waveform change of the electric energy fed from the ±375V DC input terminal D to the 10KV AC input terminal A can be measured, thereby obtaining the forced inversion capability of the electric energy fed from the ±375V DC input terminal D to the 10KV AC input terminal A.

[0104] The forced inversion performance of the transformer from the ±375V DC input terminal D to the 10KV AC input terminal A is evaluated in the same manner as in the above embodiment and will not be described in detail here.

[0105] Optionally, connecting an AC voltage to an AC input terminal of a transformer includes:

[0106] Inputting a second level AC voltage into the second AC input terminal;

[0107] Connecting a DC voltage to a first DC input terminal and / or a second DC input terminal of a transformer comprises:

[0108] Inputting a second level DC voltage into the second DC input terminal;

[0109] The performance of forced inversion is obtained according to the voltage waveform change of the second DC input terminal.

[0110] For example, continue to refer to Figure 5 , connect the 380V AC input terminal B (the second AC input terminal) to the 380V power grid, and then the 380V AC voltage (the second level AC voltage) can be input to the 380V AC input terminal B. Connect the ±375V DC input terminal D to the photovoltaic panel, and then the ±375V DC voltage (the second level DC voltage) can be input to the ±375V DC input terminal D. At this time, the transformer is in dual-port operation mode. By adjusting the trigger angle of the transformer's rectifier module and installing an oscilloscope at the second DC input terminal, the voltage waveform change of the electric energy fed from the ±375V DC input terminal D to the 380V AC input terminal B can be measured, thereby obtaining the forced inversion capability of the electric energy fed from the ±375V DC input terminal D to the 380V AC input terminal B.

[0111] The forced inversion performance of the transformer from the ±375V DC input terminal D to the 380V AC input terminal B is evaluated, which is similar to the above embodiment and will not be described again.

[0112] Optionally, connecting the DC voltage to the first DC input terminal and / or the second DC input terminal of the transformer includes:

[0113] Inputting a first level DC voltage into a first DC input terminal;

[0114] Inputting a second level DC voltage into the second DC input terminal;

[0115] The performance of forced inversion is obtained according to the voltage waveform change of the first DC input terminal or the second DC input terminal.

[0116] For example, continue to refer to Figure 5, 10kV DC input terminal C is connected to the photovoltaic panel, and 10KV DC voltage (first level DC voltage) can be input to 10KV DC input terminal C. ±375V DC input terminal D is connected to the photovoltaic panel, and ±375V DC voltage (second level DC voltage) can be input to ±375V DC input terminal D. At this time, the ability of mutual forced inversion in DC systems of different voltage levels can be detected. If the trigger angle of the rectifier module of the transformer is adjusted and an oscilloscope is installed at the first DC input terminal, the voltage waveform change of the electric energy fed from 10KV DC input terminal C to ±375V DC input terminal D can be measured, thereby obtaining the forced inversion ability of the electric energy fed from 10KV DC input terminal D to ±375V DC input terminal D. If the trigger angle of the rectifier module of the transformer is adjusted and an oscilloscope is installed at the second DC input terminal, the voltage waveform change of the electric energy fed from the ±375V DC input terminal D to the 10KV DC input terminal C can be measured, thereby obtaining the forced inversion capability of the electric energy fed from the ±375V DC input terminal D to the 10KV DC input terminal C.

[0117] Evaluation of the forced inversion performance of the transformer 10KV DC input terminal C to the ±375V DC input terminal D, and evaluation of the forced inversion performance of the transformer ±375V DC input terminal D to the 10KV DC input terminal C are similar to the above embodiments and will not be repeated here.

[0118] Optionally, connecting an AC voltage to an AC input terminal of a transformer includes:

[0119] Inputting a first level AC voltage into a first AC input terminal;

[0120] Inputting a second level AC voltage into the second AC input terminal;

[0121] The performance of forced inversion is obtained according to the voltage waveform change of the first AC input terminal or the second AC input terminal.

[0122] For example, continue to refer to Figure 5, connect the 10kV AC input terminal A (first AC input terminal) to the 10kV power grid, and then the 10KV AC voltage (first level AC voltage) can be input to the 10KV AC input terminal A. Connect the 380V AC input terminal B (second AC input terminal) to the 380V power grid, and then the 380V AC voltage (second level AC voltage) can be input to the 380V AC input terminal B. At this time, the ability of mutual forced inversion in AC systems of different voltage levels can be detected. If the trigger angle of the rectifier module of the transformer is adjusted, and an oscilloscope is installed at the first AC input terminal, the voltage waveform change of the electric energy fed from the 10KV AC input terminal A to the 380V AC input terminal B can be measured, thereby obtaining the forced inversion ability of the electric energy fed from the 10KV AC input terminal A to the 380V AC input terminal B. If the trigger angle of the rectifier module of the transformer is adjusted and an oscilloscope is installed at the second DC input terminal, the voltage waveform change of the electric energy fed from the 380V AC input terminal B to the 10KV AC input terminal A can be measured, thereby obtaining the forced inversion capability of the electric energy fed from the 380V AC input terminal B to the 10KV AC input terminal A.

[0123] Evaluation of the forced inversion performance of the transformer 10KV AC input terminal A to the 380V AC input terminal B, and evaluation of the forced inversion performance of the transformer 380V AC input terminal B to the 10KV AC input terminal A are similar to the above embodiments and will not be repeated here.

[0124] Optionally, connecting an AC voltage to an AC input terminal of a transformer includes:

[0125] Inputting a first level AC voltage into a first AC input terminal;

[0126] Connecting a DC voltage to a first DC input terminal and / or a second DC input terminal of a transformer comprises:

[0127] Inputting a first level DC voltage into a first DC input terminal;

[0128] Inputting a second level DC voltage into the second DC input terminal;

[0129] The performance of forced inversion is obtained according to the voltage waveform changes of the first AC input terminal, the first DC input terminal and the second DC input terminal.

[0130] For example, continue to refer to Figure 5, connect the 10kV AC input terminal A (first AC input terminal) to the 10kV power grid, and then the 10KV AC voltage (first level AC voltage) can be input to the 10KV AC input terminal A. Connect the 10kV DC input terminal C to the photovoltaic panel, and then the 10KV DC voltage (first level DC voltage) can be input to the 10KV DC input terminal C. Connect the ±375V DC input terminal D to the photovoltaic panel, and then the ±375V DC voltage (second level DC voltage) can be input to the ±375V DC input terminal D. At this time, the transformer is in multi-port operation mode. Adjust the trigger angle of the rectifier module of the transformer, and install an oscilloscope at the first AC input terminal, the first DC input terminal and the second DC AC input terminal, so that the voltage waveform changes of the first AC input terminal, the first DC input terminal and the second DC AC input terminal can be measured to obtain the performance of the transformer forced inversion.

[0131] Optionally, an AC voltage is connected to the AC input terminal of the transformer, including:

[0132] Inputting a second level AC voltage into the second AC input terminal;

[0133] Connecting a DC voltage to a first DC input terminal and / or a second DC input terminal of a transformer comprises:

[0134] Inputting a first level DC voltage into a first DC input terminal;

[0135] Inputting a second level DC voltage into the second DC input terminal;

[0136] The performance of forced inversion is obtained according to the voltage waveform changes of the second AC input terminal, the first DC input terminal and the second DC input terminal.

[0137] For example, continue to refer to Figure 5 , connect the 380V AC input terminal B (second AC input terminal) to the 380V power grid, and then input the 380V AC voltage (second-level AC voltage) to the 380V AC input terminal B. Connect the 10kV DC input terminal C to the photovoltaic panel, and then input the 10KV DC voltage (first-level DC voltage) to the 10KV DC input terminal C. Connect the ±375V DC input terminal D to the photovoltaic panel, and then input the ±375V DC voltage (second-level DC voltage) to the ±375V DC input terminal D. At this time, the transformer is in multi-port operation mode. Adjust the trigger angle of the transformer's rectifier module, and install an oscilloscope at the second AC input terminal, the first DC input terminal, and the second DC-AC input terminal, so that the voltage waveform changes of the second AC input terminal, the first DC input terminal, and the second DC-AC input terminal can be measured to obtain the performance of the transformer's forced inversion.

[0138] 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 test method for forced inversion protection, characterized in that: include: Connect the AC voltage to the AC input terminal of the transformer; Connecting a DC voltage to a first DC input terminal and / or a second DC input terminal of the transformer; Connecting a DC load to the second DC input terminal; Adjusting the trigger angle of the rectifier module of the transformer; acquiring the forced inversion performance of the transformer according to a voltage waveform change at the AC input terminal, the first DC input terminal or the second DC input terminal; Wherein, the AC input end of the transformer includes a first AC input end and a second AC input end; The AC voltage includes a first-level AC voltage and a second-level AC voltage, and the first-level AC voltage is not equal to the second-level AC voltage; The DC voltage includes a first-level DC voltage and a second-level DC voltage, and the first-level DC voltage and the second-level DC voltage are not equal; Adjusting the trigger angle of the rectifier module of the transformer includes: Adjust the trigger angle of the rectifier side of the transformer to 150 degrees; According to the voltage waveform change of the AC input terminal, the first DC input terminal or the second DC input terminal, obtaining the forced inversion performance of the transformer includes: An oscilloscope is used to record the voltage and current waveforms on the DC system bus at the beginning of forced inversion. Based on the voltage and current waveforms on the DC system bus, the attenuation rate of the DC current during forced inversion and the magnitude and threshold of the voltage and current fluctuations after the inversion start are obtained, thereby analyzing the availability of the transformer, that is, the forced inversion performance of the transformer.

2. The test method for forced inversion protection according to claim 1, characterized in that: Also includes: The harmonic pollution degree of forced inversion is acquired according to the voltage harmonic change of the AC input terminal, the first DC input terminal or the second DC input terminal.

3. The test method for forced inversion protection according to claim 1, characterized in that: Connect the AC voltage to the AC input terminal of the transformer, including: Inputting the first-level AC voltage into the first AC input terminal; Connecting a DC voltage to a first DC input terminal and / or a second DC input terminal of the transformer comprises: Inputting the first level DC voltage into the first DC input terminal; The performance of forced inversion is obtained according to the voltage waveform change of the first DC input terminal.

4. The test method for forced inversion protection according to claim 1, characterized in that: Connect the AC voltage to the AC input terminal of the transformer, including: inputting the second-level AC voltage into the second AC input terminal; Connecting a DC voltage to a first DC input terminal and / or a second DC input terminal of the transformer comprises: Inputting the first level DC voltage into the first DC input terminal; The performance of forced inversion is obtained according to the voltage waveform change of the first DC input terminal.

5. The test method for forced inversion protection according to claim 1, characterized in that: Connect the AC voltage to the AC input terminal of the transformer, including: Inputting the first-level AC voltage into the first AC input terminal; Connecting a DC voltage to a first DC input terminal and / or a second DC input terminal of the transformer comprises: inputting the second-level DC voltage into the second DC input terminal; The performance of forced inversion is obtained according to the voltage waveform change of the second DC input terminal.

6. The test method for forced inversion protection according to claim 1, characterized in that: Connect the AC voltage to the AC input terminal of the transformer, including: inputting the second-level AC voltage into the second AC input terminal; Connecting a DC voltage to a first DC input terminal and / or a second DC input terminal of the transformer comprises: inputting the second-level DC voltage into the second DC input terminal; The performance of forced inversion is obtained according to the voltage waveform change of the second DC input terminal.

7. The test method for forced inversion protection according to claim 1, characterized in that: Connect the AC voltage to the AC input terminal of the transformer, including: Inputting the first-level AC voltage into the first AC input terminal; inputting the second-level AC voltage into the second AC input terminal; The performance of forced inversion is obtained according to the voltage waveform change of the first AC input terminal or the second AC input terminal.

8. The test method for forced inversion protection according to claim 1, characterized in that: Connect the AC voltage to the AC input terminal of the transformer, including: Inputting the first-level AC voltage into the first AC input terminal; Connecting a DC voltage to a first DC input terminal and / or a second DC input terminal of the transformer comprises: Inputting the first level DC voltage into the first DC input terminal; inputting the second-level DC voltage into the second DC input terminal; The performance of forced inversion is obtained according to the voltage waveform changes of the first AC input terminal, the first DC input terminal and the second DC input terminal.

9. The test method for forced inversion protection according to claim 1, characterized in that: Connect the AC voltage to the AC input terminal of the transformer, including: inputting the second-level AC voltage into the second AC input terminal; Connecting a DC voltage to a first DC input terminal and / or a second DC input terminal of the transformer comprises: Inputting the first level DC voltage into the first DC input terminal; inputting the second-level DC voltage into the second DC input terminal; The performance of forced inversion is obtained according to the voltage waveform changes of the second AC input terminal, the first DC input terminal and the second DC input terminal.

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