Calculation Method for the Number of Power Modules in a High-Capacity High-Frequency Transformer Test System

Abstract

The present invention belongs to the field of high-frequency transformer testing, and specifically relates to a method for calculating the number of power modules of a large-capacity high-frequency transformer test system, aiming to solve the problems in the prior art that the power modules cannot be flexibly switched, the test voltage range is relatively narrow, and the power absorbed / sent from the AC network side is large. The present invention includes: a high-voltage side multi-winding power frequency transformer with 1 primary side three-phase winding and N secondary side three-phase windings, and N high-voltage side power modules; a low-voltage side multi-winding power frequency transformer with 1 primary side three-phase winding and M secondary side three-phase windings, and M low-voltage side power modules. According to the working state of the high-frequency transformer to be tested, combined with the square wave voltages to be tested on the high-voltage side and the low-voltage side and the DC voltage reference values of the power modules, the numbers of the high-voltage side power modules and the low-voltage side power modules put into operation in different states are respectively obtained. The test voltage output range of the present invention is wide, the test power can be flexibly adjusted, and the power absorbed / sent from the AC network side is small.

Description

Background Art

[0002] Compared with traditional AC power frequency transformers, high-frequency transformers are widely used in power electronic transformers and DC transformers due to their high operating frequency and small size. By conducting tests on high-frequency transformers to obtain important electrical parameters and performance, and then realizing the efficient and reliable operation of power electronic transformers and DC transformers, has become a common practice in the field.

[0003] Patent CN107966626A proposes a power module drag test scheme that combines a high-frequency transformer with a power electronic converter to test the voltage, current, and temperature rise of the high-frequency transformer. However, this scheme requires a matching power module during testing, increasing the system cost, being inconvenient to operate, and having high requirements for test personnel. Patent 201810997060.3 proposes a single power module test scheme that combines a high-frequency transformer with a power electronic converter. However, this scheme requires a unit turns ratio high-frequency transformer and cannot achieve the test of a multi-voltage turns ratio high-frequency transformer. In addition, with the increase in the port voltage level and capacity of the high-frequency transformer, the number of power semiconductor devices used in power electronic transformers and DC transformers can be effectively reduced, thereby improving the power density of the equipment.

[0004] Generally speaking, there is no perfect test system for high-voltage level and large-capacity high-frequency transformers in this field. In particular, it is impossible to accurately control and flexibly switch the number of power modules required on the high-voltage side and low-voltage side of the test system for different working conditions. As a result, the test voltage range is relatively narrow, and the power absorbed / sent from the AC network side is relatively large. Summary of the Invention

[0005] To solve the above problems in the prior art, that is, the power modules in the prior art cannot be flexibly switched, the test voltage range is relatively narrow, and the power absorbed / sent from the AC network side is relatively large, the present invention provides a method for calculating the number of power modules of a large-capacity high-frequency transformer test system. The method for calculating the number of power modules includes:

[0006] If the high-frequency transformer to be tested operates in a resonant state and energy flows from the high-voltage side to the low-voltage side, obtain the number of high-voltage side power modules Q1 and the number of low-voltage side power modules Q2 through a preset first power module input calculation method, and control Q1 high-voltage side power modules and Q2 low-voltage side power modules through a first control strategy;

[0007] If the high-frequency transformer to be tested operates in a resonant state and energy flows from the low-voltage side to the high-voltage side, obtain the number of high-voltage side power modules Q1 and the number of low-voltage side power modules Q2 through a preset first power module input calculation method, and control Q1 high-voltage side power modules and Q2 low-voltage side power modules through a second control strategy;

[0008] If the high-frequency transformer under test is operating in a phase-shifted state and energy flows from the high-voltage side to the low-voltage side, the number of high-voltage side power modules Q3 and the number of low-voltage side power modules Q4 to be put into operation are obtained through a preset calculation method for the second power module input, and Q3 high-voltage side power modules and Q4 low-voltage side power modules are controlled through a third control strategy;

[0009] If the high-frequency transformer under test is operating in a phase-shifted state and energy flows from the low-voltage side to the high-voltage side, the number of high-voltage side power modules Q3 and the number of low-voltage side power modules Q4 to be put into operation are obtained through a preset calculation method for the second power module input, and Q3 high-voltage side power modules and Q4 low-voltage side power modules are controlled through a fourth control strategy;

[0010] Among them, Q1 ∈ [1, N], Q2 ∈ [1, M], Q3 ∈ [1, N], Q4 ∈ [1, M], N ∈ [2, 15] is the number of secondary three-phase windings of the multi-winding power-frequency transformer on the high-voltage side of the large-capacity high-frequency transformer test system, and M ∈ [2, 15] is the number of secondary three-phase windings of the multi-winding power-frequency transformer on the low-voltage side of the large-capacity high-frequency transformer test system.

[0011] In some preferred embodiments, the first power module input calculation method and the second power module input calculation method are respectively:

[0012]

[0013]

[0014]

[0015]

[0016] Among them, when the high-frequency transformer under test is operating in a resonant state, U Hsr is the amplitude of the square wave voltage u Hsr to be measured, U Lsr is the amplitude of the square wave voltage u Lsr to be measured, U H_ref is the reference value of the DC voltage u H of the high-voltage side power module, U L_ref is the reference value of the DC voltage u L of the low-voltage side power module; when the high-frequency transformer under test is operating in a phase-shifted state, U Hps is the amplitude of the square wave voltage u Hps to be measured, U Lps is the amplitude of the square wave voltage u Lps to be measured, U H_ref is the reference value of the DC voltage u H of the high-voltage side power module, UL_ref is the reference value of the DC voltage u of the low-voltage side power module; ceiling is the ceiling function. L

[0017] In some preferred embodiments, the first control strategy is as follows:

[0018] For the three-phase PWM converters in the first to Q1 high-voltage side power modules, a dual closed-loop control strategy with voltage u H in the outer loop and three-phase currents i pa , i pb , i pc in the inner loop is adopted. For the three-phase PWM converters in the first to Q2 low-voltage side power modules, a closed-loop control strategy with three-phase currents i sa , i sb , i sc is adopted. The single-phase bridge converters in the first to Q1 high-voltage side power modules and the first to Q2 low-voltage side power modules output square-wave voltages u res with a test frequency of f sqH , u sqL that are in the same phase and have a duty cycle of 50%.

[0019] In some preferred embodiments, the second control strategy is as follows:

[0020] For the three-phase PWM converters in the first to Q1 high-voltage side power modules, a closed-loop control strategy with three-phase currents i pa , i pb , i pc is adopted. For the three-phase PWM converters in the first to Q2 low-voltage side power modules, a dual closed-loop control strategy with voltage u L in the outer loop and three-phase currents i sa , i sb , i sc in the inner loop is adopted. The single-phase bridge converters in the first to Q1 high-voltage side power modules and the first to Q2 low-voltage side power modules output square-wave voltages u res with a test frequency of f sqH , u sqL that are in the same phase and have a duty cycle of 50%.

[0021] In some preferred embodiments, the third control strategy is as follows:

[0022] For the three-phase PWM converters in the first to Q1 high-voltage side power modules, a dual closed-loop control strategy with voltage u H in the outer loop and three-phase currents i pa , i pb , i pc in the inner loop is adopted. For the three-phase PWM converters in the first to Q2 low-voltage side power modules, a dual closed-loop control strategy with voltage uL The outer ring and three-phase current i sa ,i sb ,i sc The double closed-loop control strategy of the inner loop, and the single-phase bridge converters in the first to Q1 high-voltage side power modules and the first to Q2 low-voltage side power modules output square-wave voltages u s with a test frequency of f sqH and u sqL ,u sqH whose phase is sqL ahead of the phase of u degrees, which is the phase shift angle to be measured.

[0023] In some preferred embodiments, the fourth control strategy is as follows:

[0024] In the first to Q1 high-voltage side power modules, the three-phase PWM converters adopt the voltage u H The outer ring and three-phase current i pa ,i pb ,i pc The double closed-loop control strategy of the inner loop, and in the first to Q2 low-voltage side power modules, the three-phase PWM converters adopt the voltage u L The outer ring and three-phase current i sa ,i sb ,i sc The double closed-loop control strategy of the inner loop, and the single-phase bridge converters in the first to Q1 high-voltage side power modules and the first to Q2 low-voltage side power modules output square-wave voltages u s with a test frequency of f Hps and u Lps ,u Hps whose phase is Lps lagging behind the phase of u degrees, which is the phase shift angle to be measured.

[0025] In some preferred embodiments, the large-capacity high-frequency transformer test system includes a high-voltage side multi-winding power frequency transformer, a plurality of high-voltage side power modules, a low-voltage side multi-winding power frequency transformer, and a plurality of low-voltage side power modules;

[0026] For the high-voltage side multi-winding power frequency transformer, the number of primary three-phase windings is 1, and the number of secondary three-phase windings is N;

[0027] For the high-voltage side power modules, the number thereof is the same as the number N of the secondary three-phase windings of the high-voltage side multi-winding power frequency transformer, and each high-voltage side power module includes a parallel-connected high-voltage side three-phase PWM converter and a high-voltage side single-phase bridge converter;

[0028] For the low-voltage side multi-winding power frequency transformer, the number of primary side three-phase windings is 1, and the number of secondary side three-phase windings is M;

[0029] The number of the low-voltage side power modules is the same as the number M of the secondary side three-phase windings of the low-voltage side multi-winding power frequency transformer. The low-voltage side power module includes a parallel-connected low-voltage side three-phase PWM converter and a low-voltage side single-phase bridge converter.

[0030] In some preferred embodiments, for the large-capacity high-frequency transformer test system, the connection relationship of its components is as follows:

[0031] For the high-voltage side multi-winding power frequency transformer and the low-voltage side multi-winding power frequency transformer, their primary side three-phase windings are respectively connected to the three phases of the power grid;

[0032] For the high-voltage side multi-winding power frequency transformer, its N secondary side three-phase windings are respectively and correspondingly connected to the input three phases of N high-voltage side power modules;

[0033] For the low-voltage side multi-winding power frequency transformer, its M secondary side three-phase windings are respectively and correspondingly connected to the input three phases of M low-voltage side power modules;

[0034] The multiple high-voltage side power modules are connected in cascade. The first output terminal of the first high-voltage side power module is connected to the first input terminal of the high-frequency transformer to be tested, and the second output terminal of the Nth high-voltage side power module is connected to the second input terminal of the high-frequency transformer to be tested;

[0035] The multiple low-voltage side power modules are connected in cascade. The first output terminal of the first low-voltage side power module is connected to the third input terminal of the high-frequency transformer to be tested, and the second output terminal of the Mth low-voltage side power module is connected to the fourth input terminal of the high-frequency transformer to be tested.

[0036] In some preferred embodiments, for the high-voltage side power module, the connection relationship of its components is as follows:

[0037] The S HA terminal, S HB terminal, and S HC terminal of the high-voltage side three-phase PWM converter are the input three phases of the high-voltage side power module;

[0038] The DCH+ terminal and DCH- terminal of the high-voltage side three-phase PWM converter are respectively connected to the DCPH+ terminal and DCPH- terminal of the high-voltage side single-phase bridge converter;

[0039] The S HpA terminal and S HpB terminal of the high-voltage side single-phase bridge converter are respectively the first output terminal and the second output terminal of the high-voltage side power module;

[0040] The S of the high-voltage side single-phase bridge converter HpA terminal and S HpB There is a high-voltage side bypass switch S between the terminals WH .

[0041] In some preferred embodiments, for the low-voltage side power module, the connection relationship of its components is as follows:

[0042] The S of the low-voltage side three-phase PWM converter LA terminal, S LB terminal and S LC The terminals are the input three phases of the low-voltage side power module;

[0043] The DCL+ terminal and DCL- terminal of the low-voltage side three-phase PWM converter are respectively connected to the DCSL+ terminal and DCSL- terminal of the low-voltage side single-phase bridge converter;

[0044] The S of the low-voltage side single-phase bridge converter HsA terminal and S HsB The terminals are respectively the first output terminal and the second output terminal of the voltage side power module;

[0045] The S of the low-voltage side single-phase bridge converter HsA terminal and S HsB There is a low-voltage side bypass switch S between the terminals WL .

[0046] Advantages of the present invention:

[0047] (1) For the method for calculating the number of power modules of the large-capacity high-frequency transformer test system of the present invention, according to the working state of the high-frequency transformer to be tested, combined with the square wave voltages to be tested on the high-voltage side and low-voltage side and the DC voltage reference values of the power modules, the numbers of the high-voltage side power modules and low-voltage side power modules put into use in different states are respectively obtained, realizing precise regulation and flexible adjustment of the test power, with a wide test voltage range and small power absorption / sending from the AC grid side.

[0048] (2) For the method for calculating the number of power modules of the large-capacity high-frequency transformer test system of the present invention, the large-capacity high-frequency transformer test system can output a relatively wide test voltage range through power module switching and cascading methods, and at the same time, the modular degree of the test system is relatively high, facilitating the later maintenance of the test platform and on-site testing of the sub-units. Description of the drawings

[0049] By reading the detailed description of the non-limiting embodiments with reference to the following drawings, other features, purposes and advantages of the present application will become more obvious:

[0050] Figure 1It is a schematic flow chart of the method for calculating the number of power modules of the large-capacity high-frequency transformer test system of the present invention;

[0051] Figure 2 It is a schematic diagram of the resonant working mode of the high-frequency transformer to be tested in an embodiment of the method for calculating the number of power modules of the large-capacity high-frequency transformer test system of the present invention;

[0052] Figure 3 It is a schematic diagram of the phase-shifting working mode of the high-frequency transformer to be tested in an embodiment of the method for calculating the number of power modules of the large-capacity high-frequency transformer test system of the present invention;

[0053] Figure 4 It is a schematic diagram of the composition of the large-capacity high-frequency transformer test system in an embodiment of the method for calculating the number of power modules of the large-capacity high-frequency transformer test system of the present invention;

[0054] Figure 5 It is a schematic diagram of the composition of the high-voltage side power module in an embodiment of the method for calculating the number of power modules of the large-capacity high-frequency transformer test system of the present invention;

[0055] Figure 6 It is a schematic diagram of the composition of the low-voltage side power module in an embodiment of the method for calculating the number of power modules of the large-capacity high-frequency transformer test system of the present invention. Detailed implementation manners

[0056] The present application will be further described in detail below with reference to the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the related invention, rather than limiting the invention. Additionally, it should be noted that for the sake of description, only the parts related to the relevant invention are shown in the drawings.

[0057] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present application will be described in detail below with reference to the drawings and embodiments.

[0058] The present invention provides a method for calculating the number of power modules of a large-capacity high-frequency transformer test system. The large-capacity high-frequency transformer test system adopts a power frequency multi-winding + power module cascade method. During operation, according to the working state of the high-frequency transformer to be tested, combined with the square wave voltages to be tested on the high-voltage side and the low-voltage side, and the DC voltage reference value of the power module, the number of power modules put into operation on the high-voltage side power module and the low-voltage side power module are respectively obtained under different states. Then, by controlling the bypass switches of each power module, flexible switching can be realized. The multi-power module cascade method can achieve a relatively wide transformer test voltage range. In addition, during the test process, the power loop can be realized by the AC side counter-dragging method, and thus less power is absorbed / sent from the AC grid side.

[0059] A method for calculating the number of power modules in a large-capacity high-frequency transformer test system of the present invention, the method for calculating the number of power modules includes:

[0060] If the high-frequency transformer to be tested operates in a resonant state and energy flows from the high-voltage side to the low-voltage side, the number of high-voltage side power modules Q1 and the number of low-voltage side power modules Q2 are obtained through a preset first power module input calculation method, and Q1 high-voltage side power modules and Q2 low-voltage side power modules are controlled through a first control strategy;

[0061] If the high-frequency transformer to be tested operates in a resonant state and energy flows from the low-voltage side to the high-voltage side, the number of high-voltage side power modules Q1 and the number of low-voltage side power modules Q2 are obtained through a preset first power module input calculation method, and Q1 high-voltage side power modules and Q2 low-voltage side power modules are controlled through a second control strategy;

[0062] If the high-frequency transformer to be tested operates in a phase-shifting state and energy flows from the high-voltage side to the low-voltage side, the number of high-voltage side power modules Q3 and the number of low-voltage side power modules Q4 are obtained through a preset second power module input calculation method, and Q3 high-voltage side power modules and Q4 low-voltage side power modules are controlled through a third control strategy;

[0063] If the high-frequency transformer to be tested operates in a phase-shifting state and energy flows from the low-voltage side to the high-voltage side, the number of high-voltage side power modules Q3 and the number of low-voltage side power modules Q4 are obtained through a preset second power module input calculation method, and Q3 high-voltage side power modules and Q4 low-voltage side power modules are controlled through a fourth control strategy;

[0064] Wherein, Q1 ∈ [1, N], Q2 ∈ [1, M], Q3 ∈ [1, N], Q4 ∈ [1, M], N ∈ [2, 15] is the number of secondary side three-phase windings of the multi-winding power frequency transformer on the high-voltage side of the large-capacity high-frequency transformer test system, and M ∈ [2, 15] is the number of secondary side three-phase windings of the multi-winding power frequency transformer on the low-voltage side of the large-capacity high-frequency transformer test system.

[0065] For a clearer description of the large-capacity high-frequency transformer test system of the present invention, the following combines Figure 1 Details of each step in the embodiments of the present invention are described in detail.

[0066] A method for calculating the number of power modules in a large-capacity high-frequency transformer test system according to the first embodiment of the present invention, the method for calculating the number of power modules includes:

[0067] Parameter definition: Q1 ∈ [1, N], Q2 ∈ [1, M], Q3 ∈ [1, N], Q4 ∈ [1, M], where N ∈ [2, 15] is the number of secondary three-phase windings of the high-voltage side multi-winding power frequency transformer in the large-capacity high-frequency transformer test system, and M ∈ [2, 15] is the number of secondary three-phase windings of the low-voltage side multi-winding power frequency transformer in the large-capacity high-frequency transformer test system.

[0068] If the high-frequency transformer under test operates in a resonant state and energy flows from the high-voltage side to the low-voltage side, the number of high-voltage side power modules Q1 and the number of low-voltage side power modules Q2 are obtained through a preset first power module input calculation method, and Q1 high-voltage side power modules and Q2 low-voltage side power modules are controlled through a first control strategy.

[0069] If the high-frequency transformer under test operates in a resonant state and energy flows from the low-voltage side to the high-voltage side, the number of high-voltage side power modules Q1 and the number of low-voltage side power modules Q2 are obtained through a preset first power module input calculation method, and Q1 high-voltage side power modules and Q2 low-voltage side power modules are controlled through a second control strategy.

[0070] As Figure 2 shown, it is a schematic diagram of the resonant working mode of the high-frequency transformer under test in an embodiment of the power module number calculation method for the large-capacity high-frequency transformer test system of the present invention. The high-frequency transformer under test operates in a resonant state, and energy flows from the high-voltage side to the low-voltage side. After the high- and low-voltage side power modules are cascaded, the square wave voltages u Hsr and u Lsr have the same phase and a duty cycle of 50%. The value range of the square wave voltage u Hsr is 1 kV to 10 kV, and the value range of the square wave voltage u Lsr is 750 V to 10 kV.

[0071] The number of high-voltage side power modules put into operation is Q1, and the value range of Q1 is 1 to N. The number of low-voltage side power modules put into operation is Q2, and the value range of Q2 is 1 to M, as shown in Equations (1) and (2):

[0072]

[0073]

[0074] Among them, U Hsr is the amplitude of the square wave voltage u Hsr , and its value range is 500 V to 3.3 kV. U Lsr is the amplitude of the square wave voltage u Lsr , and its value range is 500 V to 3.3 kV. U H_refis the reference value of the DC voltage u of the high-voltage side power module H , U L_ref is the reference value of the DC voltage u of the low-voltage side power module L , and ceiling is the ceiling function.

[0075] By disconnecting the bypass switches S of the single-phase bridge converters in the first to Q1 high-voltage side power modules WH , and closing the bypass switches S of the single-phase bridge converters in the (Q1 + 1)-th to N-th high-voltage side power modules WH , Q1 high-voltage side power modules can be put into operation.

[0076] By disconnecting the bypass switches S of the single-phase bridge converters in the first to Q2 low-voltage side power modules WL , and closing the bypass switches S of the single-phase bridge converters in the (Q2 + 1)-th to M-th low-voltage side power modules WL , Q2 low-voltage side power modules can be put into operation.

[0077] First control strategy: When the high-frequency transformer under test operates in the resonant state and energy flows from the high-voltage side to the low-voltage side, the three-phase PWM converters in the first to Q1 high-voltage side power modules adopt the traditional double closed-loop control strategy of DC voltage u H outer loop + three-phase currents i pa , i pb , i pc inner loop, and the three-phase PWM converters in the first to Q2 low-voltage side power modules only adopt the closed-loop control strategy of three-phase currents i sa , i sb , i sc inner loop. The single-phase bridge converters in the first to Q1 high-voltage side power modules and the first to Q2 low-voltage side power modules output square-wave voltages u res with a test frequency of f sqH , a 50% duty cycle, and the same phase, and u sqL , f res ranges from 400 Hz to 20 kHz, and u sqH and u sqL range from 500 V to 3.3 kV.

[0078] Second control strategy: When the high-frequency transformer under test operates in the resonant state and energy flows from the low-voltage side to the high-voltage side, the three-phase PWM converters in the first to Q1 high-voltage side power modules only adopt the closed-loop control strategy of three-phase currents i pa , i pb , i pc inner loop, and the three-phase PWM converters in the first to Q2 low-voltage side power modules adopt the traditional double closed-loop control strategy of DC voltage u L outer loop + three-phase currents isa , i sb , i sc The double closed-loop control strategy of the inner loop, and the single-phase bridge converters in the first to Q1 high-voltage side power modules and the first to Q2 low-voltage side power modules output a test frequency of f res , 50% duty cycle, and square wave voltages u sqH and u sqL .

[0079] If the high-frequency transformer under test operates in the phase-shifting state and energy flows from the high-voltage side to the low-voltage side, the number of high-voltage side power modules Q3 and the number of low-voltage side power modules Q4 are obtained through a preset calculation method for the input of the second power module, and Q3 high-voltage side power modules and Q4 low-voltage side power modules are controlled through the third control strategy.

[0080] If the high-frequency transformer under test operates in the phase-shifting state and energy flows from the low-voltage side to the high-voltage side, the number of high-voltage side power modules Q3 and the number of low-voltage side power modules Q4 are obtained through a preset calculation method for the input of the second power module, and Q3 high-voltage side power modules and Q4 low-voltage side power modules are controlled through the fourth control strategy.

[0081] As Figure 3 shown, it is a schematic diagram of the phase-shifting working mode of the high-frequency transformer under test in an embodiment of the calculation method for the number of power modules of the large-capacity high-frequency transformer test system of the present invention, and the high-frequency transformer under test operates in the phase-shifting state.

[0082] The number of high-voltage side power modules input is Q3, and the value range of Q3 is 1 to N. The number of low-voltage side power modules input is Q4, and the value range of Q4 is 1 to M, as shown in Equations (3) and (4):

[0083]

[0084]

[0085] Among them, U Hps is the amplitude of the square wave voltage u Hps , and the value range is 500V to 3.3kV. U Lps is the amplitude of the square wave voltage u Lps , and the value range is 500V to 3.3kV. U H_ref is the reference value of the DC voltage u H of the high-voltage side power module. U L_ref is the reference value of the DC voltage u L of the low-voltage side power module, and ceiling is the ceiling function.

[0086] By disconnecting the single-phase bridge converter bypass switches S in the first to Q3 high-voltage side power modules WH , and closing the single-phase bridge converter bypass switches S in the (Q3 + 1)-th to N-th high-voltage side power modules WH , Q3 high-voltage side power modules can be put into operation.

[0087] By disconnecting the single-phase bridge converter bypass switches S in the first to Q4 low-voltage side power modules WL , and closing the single-phase bridge converter bypass switches S in the (Q4 + 1)-th to M-th low-voltage side power modules WL , Q4 low-voltage side power modules can be put into operation.

[0088] The third control strategy is as follows: when energy flows from the high-voltage side to the low-voltage side, after the high- and low-voltage side power modules are cascaded, the square-wave voltages u Hps and r Lps are output to the port of the high-frequency transformer system under test. The duty cycle is 50%, and there is a phase difference which is the phase shift angle to be measured, and its value range is 0° to 90°. The value range of the square-wave voltage u Hps is 1 kV to 10 kV, and the value range of the square-wave voltage u Lps is 750 V to 10 kV. The three-phase PWM converters in the first to Q3 high-voltage side power modules adopt the double closed-loop control strategy of the traditional DC voltage u H outer loop + three-phase currents i pa , i pb , i pc inner loop. The three-phase PWM converters in the first to Q4 low-voltage side power modules adopt the double closed-loop control strategy of the traditional DC voltage u L outer loop + three-phase currents i sa , i sb , i sc inner loop. The single-phase bridge converters in the first to Q3 high-voltage side power modules and the first to Q4 low-voltage side power modules output square-wave voltages u s and u sqH with a test frequency of f sqL and a 50% duty cycle. The value range of f s is 400 Hz to 20 kHz, and the value ranges of u sqH and u sqL are 500 V to 3.3 kV. At the same time, the phase of the square-wave voltage u sqH leads the phase of the square-wave voltage u sqL by degrees.

[0089] Similarly, the number of high-voltage side power modules put into operation is Q3, and the value range of Q3 is 1 to N. The number of low-voltage side power modules put into operation is Q4, and the value range of Q4 is 1 to M. As shown in Equations (3) and (4), it will not be elaborated here.

[0090] By disconnecting the bypass switch S of the single-phase bridge converter in the first to Q3 high-voltage side power modules WH , and closing the bypass switch S of the single-phase bridge converter in the (Q3 + 1)-th to N-th high-voltage side power modules WH , Q3 high-voltage side power modules can be put into operation.

[0091] By disconnecting the bypass switch S of the single-phase bridge converter in the first to Q4 low-voltage side power modules WL , and closing the bypass switch S of the single-phase bridge converter in the (Q4 + 1)-th to M-th low-voltage side power modules WL , Q4 low-voltage side power modules can be put into operation.

[0092] The fourth control strategy is as follows: when energy flows from the low-voltage side to the high-voltage side, the square-wave voltages u Hps and u Lps output after the high- and low-voltage side power modules are cascaded to the port of the high-frequency transformer system to be measured have a duty cycle of 50%, and there is a phase difference which is the phase shift angle to be measured, and its value range is 0° to 90°. The three-phase PWM converters in the first to Q3 high-voltage side power modules adopt the double closed-loop control strategy of the traditional DC voltage u H outer loop + three-phase currents i pa , i pb , i pc inner loop. The three-phase PWM converters in the first to Q4 low-voltage side power modules adopt the double closed-loop control strategy of the traditional DC voltage u L outer loop + three-phase currents i sa , i sb , i sc inner loop. The single-phase bridge converters in the first to Q3 high-voltage side power modules and the first to Q4 low-voltage side power modules output square-wave voltages u s and u sqH with a test frequency of f sqL and a duty cycle of 50%. The value range of f s is 400 Hz to 20 kHz, and the value ranges of u sqH and u sqL are 500 V to 3.3 kV. At the same time, the phase of the square-wave voltage u sqH lags behind the phase of the square-wave voltage u sqL by degrees.

[0093] The large-capacity high-frequency transformer test system according to the second embodiment of the present invention is as follows Figure 4 shown, and includes a high-voltage side multi-winding power frequency transformer, a plurality of high-voltage side power modules, a low-voltage side multi-winding power frequency transformer, and a plurality of low-voltage side power modules. Each module is described in detail as follows:

[0094] The high-voltage side multi-winding power frequency transformer has 1 three-phase winding on the primary side and N three-phase windings on the secondary side.

[0095] The number of high-voltage side power modules is the same as the number N of the three-phase windings on the secondary side of the high-voltage side multi-winding power frequency transformer. The high-voltage side power module includes a parallel-connected high-voltage side three-phase PWM converter and a high-voltage side single-phase bridge converter.

[0096] The operating frequency of the high-voltage side multi-winding power frequency transformer is 50Hz / 60Hz. The terminals A1, B1, and C1 of each phase of its primary winding are respectively connected to the A, B, and C phases of the three-phase AC power grid through parallel nodes S1, S2, and S3, and the terminals X1, Y1, and Z1 of each phase are star-connected to point S P1 . The winding between terminal A1 and terminal X1 is the A-phase winding in the primary winding of the high-voltage side multi-winding power frequency transformer, the winding between terminal B1 and terminal Y1 is the B-phase winding in the primary winding of the high-voltage side multi-winding power frequency transformer, and the winding between terminal C1 and terminal Z1 is the C-phase winding in the primary winding of the high-voltage side multi-winding power frequency transformer.

[0097] The terminals a1, b1, and c1 of each phase of the N three-phase windings on the secondary side of the high-voltage side multi-winding power frequency transformer are respectively connected to the input three-phase x1, y1, and z1 of N high-voltage side power modules in a one-to-one correspondence, and the terminals x1, y1, and z1 of each phase are star-connected to point S s1 . The winding between terminal a1 and terminal x1 is the a-phase winding in the secondary winding of the high-voltage side multi-winding power frequency transformer, the winding between terminal b1 and terminal y1 is the b-phase winding in the secondary winding of the high-voltage side multi-winding power frequency transformer, and the winding between terminal c1 and terminal z1 is the c-phase winding in the secondary winding of the high-voltage side multi-winding power frequency transformer.

[0098] As Figure 5 shown, it is a schematic diagram of the composition of the high-voltage side power module in an embodiment of the method for calculating the number of power modules in the large-capacity high-frequency transformer test system of the present invention. The S HA terminal, S HB terminal, and S HC terminal of the high-voltage side three-phase PWM converter are the input three-phase of the high-voltage side power module. The DCH+ terminal and DCH- terminal of the high-voltage side three-phase PWM converter are respectively connected to the DCPH+ terminal and DCPH- terminal of the high-voltage side single-phase bridge converter. The S HpA terminal and S HpBThe two ends are respectively the first output end and the second output end of the boost-side power module.

[0099] Multiple boost-side power modules are connected in cascade. The AC terminal S of the single-phase bridge converter in the first boost-side power module HpB is connected to the AC terminal S of the single-phase bridge converter in the second boost-side power module HpA , the AC terminal S of the single-phase bridge converter in the second boost-side power module HpB is connected to the AC terminal S of the single-phase bridge converter in the third boost-side power module HpA , and so on. The AC terminal S of the single-phase bridge converter in the (N - 1)th boost-side power module HpB is connected to the AC terminal S of the single-phase bridge converter in the Nth boost-side power module HpA . The first output end S of the first boost-side power module HpA is connected to the first input end (HFTA end) of the high-frequency transformer to be measured, and the second output end S of the Nth boost-side power module HpB is connected to the second input end (HFTX end) of the high-frequency transformer to be measured.

[0100] A high-voltage side bypass switch S is provided between the S HpA end and the S HpB end of the high-voltage side single-phase bridge converter of each boost-side power module among multiple boost-side power modules. WH .

[0101] A low-voltage side multi-winding power frequency transformer, the number of primary side three-phase windings is 1, and the number of secondary side three-phase windings is M.

[0102] A low-voltage side power module, the number of which is the same as the number M of the secondary side three-phase windings of the low-voltage side multi-winding power frequency transformer. The low-voltage side power module includes a parallel-connected low-voltage side three-phase PWM converter and a low-voltage side single-phase bridge converter.

[0103] The operating frequency of the low-voltage side multi-winding power frequency transformer is 50Hz / 60Hz. The terminals A2, B2, and C2 of each phase of its primary side winding are respectively connected to the A, B, and C phases of the three-phase AC power grid through the parallel nodes S1, S2, and S3, and the terminals X2, Y2, and Z2 of each phase are star-connected to the point S P2 . The winding between terminal A2 and terminal X2 is the A-phase winding in the primary side winding of the low-voltage side multi-winding power frequency transformer, the winding between terminal B2 and terminal Y2 is the B-phase winding in the primary side winding of the low-voltage side multi-winding power frequency transformer, and the winding between terminal C2 and terminal Z2 is the C-phase winding in the primary side winding of the low-voltage side multi-winding power frequency transformer.

[0104] The phase terminals a2, b2, and c2 of the M secondary three-phase windings of the low-voltage side multi-winding power frequency transformer are respectively and correspondingly connected to the input three-phase x2, y2, and z2 of the M low-voltage side power modules, and the phase terminals x2, y2, and z2 are star-connected to the point S. s2 Between the terminal a2 and the terminal x2 is the a-phase winding in the secondary winding of the low-voltage side multi-winding power frequency transformer. Between the terminal b2 and the terminal y2 is the b-phase winding in the secondary winding of the low-voltage side multi-winding power frequency transformer. Between the terminal c2 and the terminal z2 is the c-phase winding in the secondary winding of the low-voltage side multi-winding power frequency transformer.

[0105] As Figure 6 shown, it is a schematic diagram of the composition of the low-voltage side power module of an embodiment of the power module quantity calculation method of the large-capacity high-frequency transformer test system of the present invention. The S LA terminal, S LB terminal, and S LC terminal of the low-voltage side three-phase PWM converter are the input three-phase of the low-voltage side power module. The DCL+ terminal and the DCL- terminal of the low-voltage side three-phase PWM converter are respectively connected to the DCSL+ terminal and the DCSL- terminal of the low-voltage side single-phase bridge converter. The S HsA terminal and the S HsB terminal of the low-voltage side single-phase bridge converter are respectively the first output terminal and the second output terminal of the low-voltage side power module.

[0106] Multiple low-voltage side power modules are cascaded. The AC terminal S HsB of the single-phase bridge converter in the first low-voltage side power module is connected to the AC terminal S HsA of the single-phase bridge converter in the second low-voltage side power module. The AC terminal S HsB of the single-phase bridge converter in the second low-voltage side power module is connected to the AC terminal S HsA of the single-phase bridge converter in the third low-voltage side power module, and so on. The AC terminal S HsB of the single-phase bridge converter in the M-1th low-voltage side power module is connected to the AC terminal S HsA of the single-phase bridge converter in the Mth low-voltage side power module. The first output terminal S HsA of the first low-voltage side power module is connected to the third input terminal (HFTa terminal) of the high-frequency transformer to be tested. The second output terminal S HsB of the Nth low-voltage side power module is connected to the fourth input terminal (HFTx terminal) of the high-frequency transformer to be tested.

[0107] For the three-phase PWM converters in the high-voltage side power module and the low-voltage side power module, a two-level three-phase full-bridge or a three-level diode clamped three-phase full-bridge converter can be adopted.

[0108] The single-phase bridge converters in the high-voltage side power module and the low-voltage side power module can adopt a two-level H-bridge, a two-level half-bridge, a three-level diode-clamped single-phase full-bridge or a three-level diode-clamped single-phase half-bridge converter.

[0109] The high-frequency transformer to be measured can operate in the resonant or phase-shifted working state:

[0110] When operating in the resonant state, resonant capacitors C r1 、C r2 need to be connected in series in the high-voltage and low-voltage side windings of the high-frequency transformer to be measured. The high-voltage side AC terminal HFTA of the high-frequency transformer to be measured is connected to the HA end of the high-voltage side winding of the high-frequency transformer through C r1 . The high-voltage side AC terminal HFTX of the high-frequency transformer to be measured is connected to the HX end of the high-voltage side winding of the high-frequency transformer. The low-voltage side AC terminal HFTa of the high-frequency transformer to be measured is connected to the Ha end of the high-voltage side winding of the high-frequency transformer through C r2 . The low-voltage side AC terminal HFTx of the high-frequency transformer to be measured is connected to the Hx end of the low-voltage side winding of the high-frequency transformer.

[0111] When operating in the phase-shifted state, the high-voltage side AC terminal HFTA of the high-frequency transformer to be measured is directly connected to the HA end of the high-voltage side winding of the high-frequency transformer. The high-voltage side AC terminal HFTX of the high-frequency transformer to be measured is directly connected to the HX end of the high-voltage side winding of the high-frequency transformer. The low-voltage side AC terminal HFTa of the high-frequency transformer to be measured is directly connected to the Ha end of the high-voltage side winding of the high-frequency transformer. The low-voltage side AC terminal HFTx of the high-frequency transformer to be measured is directly connected to the Hx end of the low-voltage side winding of the high-frequency transformer.

[0112] Those skilled in the art can clearly understand that for the convenience and simplicity of description, the specific working process and related descriptions of the above-described method can refer to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0113] It should be noted that the method for calculating the number of power modules of the large-capacity high-frequency transformer test system and the large-capacity high-frequency transformer test system provided in the above embodiments are only illustrated by the division of the above functional modules. In actual applications, the above functions can be allocated to different functional modules according to needs, that is, the modules or steps in the embodiments of the present invention can be further decomposed or combined. For example, the modules in the above embodiments can be combined into one module, or further split into multiple sub-modules to complete all or part of the functions described above. For the names of the modules and steps involved in the embodiments of the present invention, they are only used to distinguish each module or step and are not regarded as an improper limitation of the present invention.

[0114] An apparatus according to the third embodiment of the present invention includes:

[0115] At least one processor; and

[0116] a memory communicatively connected to at least one of the processors; wherein,

[0117] the memory stores instructions executable by the processor, and the instructions are used to be executed by the processor to implement the method for calculating the number of power modules of the above-mentioned large-capacity high-frequency transformer test system.

[0118] A computer-readable storage medium according to the fourth embodiment of the present invention, the computer-readable storage medium stores computer instructions, and the computer instructions are used to be executed by the computer to implement the method for calculating the number of power modules of the above-mentioned large-capacity high-frequency transformer test system.

[0119] Those skilled in the art can clearly understand that for the convenience and brevity of description, the specific working processes and related descriptions of the above-described storage device and processing device can refer to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0120] Those skilled in the art should be able to realize that the modules and method steps of each example described in combination with the embodiments disclosed herein can be implemented by electronic hardware, computer software, or a combination of the two. The programs corresponding to the software modules and method steps can be placed in a random access memory (RAM), memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, register, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art. For the sake of clearly illustrating the interchangeability of electronic hardware and software, the components and steps of each example have been generally described according to their functions in the above description. Whether these functions are executed in the form of electronic hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0121] The terms "first", "second", etc. are used to distinguish similar objects, rather than to describe or represent a specific order or sequence.

[0122] The term "comprising" or any other similar term is intended to cover non-exclusive inclusion, so that a process, method, article, or device / device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent to these processes, methods, articles, or devices.

[0123] So far, the technical solution of the present invention has been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the protection scope of the present invention.

Claims

1. A method for calculating the number of power modules in a large-capacity high-frequency transformer test system, characterized in that, The method for calculating the number of power modules includes: If the high-frequency transformer under test operates in a resonant state and energy flows from the high-voltage side to the low-voltage side, the number of high-voltage side power modules Q1 and the number of low-voltage side power modules Q2 are obtained through a preset first power module input calculation method, and Q1 high-voltage side power modules and Q2 low-voltage side power modules are controlled through a first control strategy; The first control strategy is: The three-phase PWM converter in the first to Q1th high-voltage side power modules adopts voltage u H Outer loop and three-phase current i pa ,i pb ,i pc The inner loop double closed-loop control strategy uses a three-phase current i sa ,i sb ,i sc The closed-loop control strategy of the first to Q1 high-voltage side power modules and the first to Q2 low-voltage side power modules have a single-phase bridge converter output test frequency of f res , square wave voltage u with the same phase and 50% duty cycle sqH and u sqL ; If the high-frequency transformer to be tested operates in a resonant state and energy flows from the low-voltage side to the high-voltage side, the number of high-voltage side power modules Q1 and the number of low-voltage side power modules Q2 are obtained by a preset first power module input calculation method, and Q1 high-voltage side power modules and Q2 low-voltage side power modules are controlled by a second control strategy; The second control strategy is: The three-phase PWM converters in the first to Q1 high-voltage side power modules adopt a closed-loop control strategy for the three-phase currents i pa , i pb , i pc The three-phase PWM converters in the first to Q2 low-voltage side power modules adopt a double closed-loop control strategy with the voltage u L as the outer loop and the three-phase currents i sa , i sb , i sc as the inner loop. The single-phase bridge converters in the first to Q1 high-voltage side power modules and the first to Q2 low-voltage side power modules output square wave voltages u res with a test frequency of f sqH , the same phase, and a duty cycle of 50% for both u sqL ; If the high-frequency transformer under test operates in a phase-shifting state and energy flows from the high-voltage side to the low-voltage side, the number of high-voltage side power modules Q3 and the number of low-voltage side power modules Q4 are obtained through a preset second power module input calculation method, and Q3 high-voltage side power modules and Q4 low-voltage side power modules are controlled through a third control strategy; The third control strategy is: The three-phase PWM converters in the first to Q1 high-voltage side power modules adopt the voltage u H the outer loop and the three-phase current i pa , i pb , i pc the double closed-loop control strategy of the inner loop. The three-phase PWM converters in the first to Q2 low-voltage side power modules adopt the voltage u L the outer loop and the three-phase current i sa , i sb , i sc the double closed-loop control strategy of the inner loop. The single-phase bridge converters in the first to Q1 high-voltage side power modules and the first to Q2 low-voltage side power modules output square-wave voltages u s with a test frequency of f sqH and a duty cycle of 50%, sqL , u sqH the phase of u sqL is ahead of the phase of u degrees, and is the phase shift angle to be measured; If the high-frequency transformer under test operates in a phase-shifting state and energy flows from the low-voltage side to the high-voltage side, the number of high-voltage side power modules Q3 and the number of low-voltage side power modules Q4 are obtained through a preset second power module input calculation method, and Q3 high-voltage side power modules and Q4 low-voltage side power modules are controlled through a fourth control strategy; Wherein, Q1 ∈ [1, N], Q2 ∈ [1, M], Q3 ∈ [1, N], Q4 ∈ [1, M], N ∈ [2, 15] is the number of secondary three-phase windings of the high-voltage side multi-winding power frequency transformer of the large-capacity high-frequency transformer test system, M ∈ [2, 15] is the number of secondary three-phase windings of the low-voltage side multi-winding power frequency transformer of the large-capacity high-frequency transformer test system, and the fourth control strategy is: The three-phase PWM converters in the first to Q1 high-voltage side power modules adopt the voltage u H for the outer loop and the three-phase current i pa , i pb , i pc for the double closed-loop control strategy of the inner loop. The three-phase PWM converters in the first to Q2 low-voltage side power modules adopt the voltage u L for the outer loop and the three-phase current i sa , i sb , i sc for the double closed-loop control strategy of the inner loop. The single-phase bridge converters in the first to Q1 high-voltage side power modules and the first to Q2 low-voltage side power modules output square-wave voltages u s with a test frequency of f Hps and a duty cycle of 50%, u Lps , u Hps whose phase lags behind the phase of u Lps by degrees, being the phase shift angle to be measured.

2. The method for calculating the number of power modules of the large-capacity high-frequency transformer test system according to claim 1, characterized in that, The first power module input calculation method and the second power module input calculation method are respectively: Among them, when the high-frequency transformer under test works in the resonance state, U Hsr is the amplitude of the square-wave voltage u Hsr under test, U Lsr is the amplitude of the square-wave voltage u Lsr under test, U H_ref is the reference value of the DC voltage u H of the high-voltage side power module, U L_ref is the reference value of the DC voltage u L of the low-voltage side power module; when the high-frequency transformer under test works in the phase-shifting state, U Hps is the amplitude of the square-wave voltage u Hps under test, U Lps is the amplitude of the square-wave voltage u Lps under test, U H_ref is the reference value of the DC voltage u H of the high-voltage side power module, U L_ref is the reference value of the DC voltage u L of the low-voltage side power module; ceiling is the ceiling function.

3. The method for calculating the number of power modules of the large-capacity high-frequency transformer test system according to any one of claims 1-2, characterized in that, The large-capacity high-frequency transformer test system includes a high-voltage side multi-winding power frequency transformer, multiple high-voltage side power modules, a low-voltage side multi-winding power frequency transformer, and multiple low-voltage side power modules; For the high-voltage side multi-winding power frequency transformer, the number of primary three-phase windings is 1, and the number of secondary three-phase windings is N; The number of the high-voltage side power modules is the same as the number N of the secondary three-phase windings of the high-voltage side multi-winding power frequency transformer. The high-voltage side power modules include a parallel-connected high-voltage side three-phase PWM converter and a high-voltage side single-phase bridge converter; For the low-voltage side multi-winding power frequency transformer, the number of primary three-phase windings is 1, and the number of secondary three-phase windings is M; The number of the low-voltage side power modules is the same as the number M of the secondary three-phase windings of the low-voltage side multi-winding power frequency transformer. The low-voltage side power modules include a parallel-connected low-voltage side three-phase PWM converter and a low-voltage side single-phase bridge converter.

4. The method for calculating the number of power modules of the large-capacity high-frequency transformer test system according to claim 3, wherein The connection relationship of the components of the large-capacity high-frequency transformer test system is: For the high-voltage side multi-winding power frequency transformer and the low-voltage side multi-winding power frequency transformer, their primary three-phase windings are respectively connected to the three phases of the power grid; For the high-voltage side multi-winding power frequency transformer, its N secondary three-phase windings are respectively connected to the input three phases of N high-voltage side power modules one by one; For the low-voltage side multi-winding power frequency transformer, its M secondary three-phase windings are respectively connected to the input three phases of M low-voltage side power modules one by one; The multiple high-voltage side power modules are connected in cascade. The first output terminal of the first high-voltage side power module is connected to the first input terminal of the high-frequency transformer under test, and the second output terminal of the Nth high-voltage side power module is connected to the second input terminal of the high-frequency transformer under test; The multiple low-voltage side power modules are connected in cascade. The first output terminal of the first low-voltage side power module is connected to the third input terminal of the high-frequency transformer under test, and the second output terminal of the Mth low-voltage side power module is connected to the fourth input terminal of the high-frequency transformer under test.

5. The method for calculating the number of power modules of the large-capacity high-frequency transformer test system according to claim 4, wherein For the high-voltage side power module, the connection relationship of its components is: The S HA terminal, S HB terminal, and S HC terminal are the input three phases of the high-voltage side power module; The DCH+ terminal and DCH- terminal of the high-voltage side three-phase PWM converter are respectively connected to the DCPH+ terminal and DCPH- terminal of the high-voltage side single-phase bridge converter; The S terminal of the high-voltage side single-phase bridge converter HpA and the S HpB terminal are respectively the first output terminal and the second output terminal of the high-voltage side power module; The S of the high-voltage side single-phase bridge converter HpA terminal and S HpB There is a high-voltage side bypass switch S between the terminals WH .

6. The method for calculating the number of power modules of the large-capacity high-frequency transformer test system according to claim 4, characterized in that, For the low-voltage side power module, the connection relationship of its components is: The S of the low-voltage side three-phase PWM converter LA terminal, S LB terminal and S LC terminal are the input three phases of the low-voltage side power module; The DCL+ terminal and DCL- terminal of the low-voltage side three-phase PWM converter are respectively connected to the DCSL+ terminal and DCSL- terminal of the low-voltage side single-phase bridge converter; The S of the low-voltage side single-phase bridge converter HsA terminal and the S HsB terminal are respectively the first output terminal and the second output terminal of the power module on the voltage side; The S of the low-voltage side single-phase bridge converter HsA terminal and S HsB There is a low-voltage side bypass switch S between the terminals WL .

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