Isolated power grid simulation power supply and control method thereof

Abstract

The invention discloses an isolated power grid analog power supply and a control method thereof. The isolated power grid analog power supply comprises a soft start unit, an input converter, an output converter and a voltage sensor, the input converter comprises an A-phase power unit, a B-phase power unit and a C-phase power unit, each phase power unit comprises a plurality of cascaded first power modules, and each first power module comprises a first H-bridge converter and an isolated DC / DC converter which are connected in sequence; the output converter comprises four bridge arms, each of the four bridge arms comprises an upper bridge arm and a lower bridge arm, each of the upper bridge arm and the lower bridge arm comprises a bridge arm inductor and a plurality of cascaded second power modules, and a connection point of the bridge arm inductor in the upper bridge arm and the bridge arm inductor in the lower bridge arm forms an alternating current output end or a midpoint output end. Direct connection between the power supply and the power grid is achieved by configuring the first power modules in cascade connection, isolation and voltage reduction of a power frequency converter are not needed, and the overall size of the power supply is reduced.

Description

Technical Field

[0001] This application relates to the field of grid connection technology, and in particular to an isolated grid analog power supply and its control method. Background Technology

[0002] As the proportion of new energy power generation equipment in the power system continues to increase, the power industry has higher and higher requirements for the grid connection performance of new energy power generation equipment. Furthermore, with the increase in power generation equipment capacity, it is urgent and necessary to carry out various grid-connected performance tests of new energy power generation equipment by developing a fully functional high-voltage, high-capacity grid simulation power supply.

[0003] Patents CN215493890U and CN103969578A disclose a three-phase power grid simulation device or a wind turbine power grid adaptability testing device and testing method. Such devices can simulate various voltage disturbance characteristics such as output voltage deviation, frequency deviation, flicker, and voltage imbalance.

[0004] However, the problem with this type of device is that it requires a multi-winding transformer for voltage reduction on the grid connection side and electrical isolation between the input terminals of each power module in the device, resulting in a relatively large device size. Summary of the Invention

[0005] This application provides an isolated grid simulation power supply and its control method to reduce the overall size of the power supply.

[0006] This application provides an isolated grid simulation power supply, including a soft-start unit, an input converter, an output converter, and a voltage sensor;

[0007] The input converter includes an A-phase power unit, a B-phase power unit, a C-phase power unit, an A-phase AC input terminal, a B-phase AC input terminal, a C-phase AC input terminal, a positive DC output terminal, and a negative DC output terminal; the output converter includes a first bridge arm, a second bridge arm, a third bridge arm, a fourth bridge arm, a positive DC input terminal, a negative DC input terminal, an A-phase AC output terminal, a B-phase AC output terminal, a C-phase AC output terminal, and a midpoint output terminal;

[0008] The A-phase AC input terminal, the B-phase AC input terminal, and the C-phase AC input terminal are connected to the power grid through the soft-start unit. The positive DC output terminal is connected to the positive DC input terminal, and the negative DC output terminal is connected to the negative DC input terminal. The A-phase AC output terminal, the B-phase AC output terminal, and the C-phase AC output terminal are connected to the device under test. The midpoint output terminal is connected to the A-phase AC output terminal, the B-phase AC output terminal, and the C-phase AC output terminal through the voltage sensor.

[0009] The first AC input terminal of the A-phase power unit forms the A-phase AC input terminal of the input converter, the first AC input terminal of the B-phase power unit forms the B-phase AC input terminal of the input converter, and the first AC input terminal of the C-phase power unit forms the C-phase AC input terminal of the input converter. The second AC input terminals of the A-phase power unit, the B-phase power unit, and the C-phase power unit are connected together. The DC output terminal of the A-phase power unit is cascaded with the DC output terminals of the B-phase power unit and the C-phase power unit to form the positive DC output terminal and the negative DC output terminal of the input converter.

[0010] The A-phase power unit, the B-phase power unit, and the C-phase power unit each include multiple cascaded first power modules, and each first power module includes a first H-bridge converter and an isolated DC / DC converter connected in sequence.

[0011] The first bridge arm, the second bridge arm, the third bridge arm, and the fourth bridge arm each include an upper bridge arm and a lower bridge arm. The upper bridge arm and the lower bridge arm each include a bridge arm inductor and multiple cascaded second power modules. The connection point between the bridge arm inductor in the upper bridge arm and the bridge arm inductor in the lower bridge arm forms one of the A-phase AC output terminal, the B-phase AC output terminal, the C-phase AC output terminal, and the midpoint output terminal.

[0012] Another aspect of this application provides a control method for the isolated grid analog power supply described above, the control method comprising:

[0013] Obtain the output voltage of each phase detected by the voltage sensor;

[0014] Based on the output voltage of each phase, the output voltage of the midpoint output terminal is controlled to be equal to half the voltage between the positive DC input terminal and the negative DC input terminal.

[0015] The isolated grid simulation power supply and its control method provided in this application achieve direct connection between the power supply and the grid by configuring a cascaded first power module, eliminating the need for a power frequency inverter for isolation and voltage reduction, thus reducing the overall size of the power supply. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of an isolated power grid simulation power supply provided in an embodiment of this application;

[0017] Figure 2 A schematic diagram of the first power module provided in an embodiment of this application;

[0018] Figure 3 This is a schematic diagram of another first power module provided in an embodiment of this application;

[0019] Figure 4 A schematic diagram of the second power module provided in an embodiment of this application;

[0020] Figure 5 This is a schematic diagram of another second power module provided in an embodiment of this application;

[0021] Figure 6 A schematic diagram of the control method for an isolated power grid analog power supply provided in an embodiment of this application.

[0022] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0023] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer and more understandable, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit the scope of this application.

[0024] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0025] like Figure 1 As shown in the figure, an isolated grid simulation power supply provided in this application embodiment includes a soft-start unit, an input converter, an output converter, and a voltage sensor;

[0026] The input converter includes an A-phase power unit, a B-phase power unit, a C-phase power unit, an A-phase AC input terminal, a B-phase AC input terminal, a C-phase AC input terminal, a positive DC output terminal (as shown in BUS+ in the reference figure), and a negative DC output terminal (as shown in BUS- in the reference figure).

[0027] The output converter includes a first bridge arm, a second bridge arm, a third bridge arm, a fourth bridge arm, a positive DC input terminal (as shown in BUS+ in the reference figure), a negative DC input terminal (as shown in BUS- in the reference figure), an A-phase AC output terminal, a B-phase AC output terminal, a C-phase AC output terminal, and a midpoint output terminal (as shown in N in the reference figure).

[0028] The AC input terminals of phase A, phase B, and phase C are connected to the power grid through a soft-start unit. The positive DC output terminal is connected to the positive DC input terminal, and the negative DC output terminal is connected to the negative DC input terminal. The AC output terminals of phase A, phase B, and phase C are connected to the device under test. The midpoint output terminal is connected to the AC output terminals of phase A, phase B, and phase C through voltage sensors (such as Va, Vb, and Vc shown in the figure).

[0029] The first AC input terminal of phase A power unit (as shown in Figure 1) forms the phase A AC input terminal of the input converter. The first AC input terminal of phase B power unit (as shown in Figure 1) forms the phase B AC input terminal of the input converter. The first AC input terminal of phase C power unit (as shown in Figure 1) forms the phase C AC input terminal of the input converter. The second AC input terminals of phase A power unit (as shown in Figure 2), phase B power unit (as shown in Figure 2), and phase C power unit (as shown in Figure 2) are connected together. The DC output terminal of phase A power unit is connected to the DC output terminal of phase B power unit and... The DC output terminals of the C-phase power units are cascaded together to form the positive and negative DC output terminals of the input converter; that is, the first DC output terminal of the A-phase power unit (as shown in Figure 3) forms the positive DC output terminal of the input converter, the second DC output terminal of the A-phase power unit (as shown in Figure 4) is connected to the first DC output terminal of the B-phase power unit (as shown in Figure 3), the second DC output terminal of the B-phase power unit (as shown in Figure 4) is connected to the first DC output terminal of the C-phase power unit (as shown in Figure 3), and the second DC output terminal of the C-phase power unit (as shown in Figure 4) forms the negative DC output terminal of the input converter.

[0030] Phase A power unit, phase B power unit and phase C power unit each include multiple cascaded first power modules, each first power module including a first H-bridge converter and an isolated DC / DC converter connected in sequence;

[0031] The first bridge arm, the second bridge arm, the third bridge arm, and the fourth bridge arm each include an upper bridge arm and a lower bridge arm. Both the upper and lower bridge arms include a bridge arm inductor and multiple cascaded second power modules (as shown in the "Modules" section of the figure). The connection point between the bridge arm inductor in the upper bridge arm and the bridge arm inductor in the lower bridge arm forms one of the following output terminals: phase A AC output terminal, phase B AC output terminal, phase C AC output terminal, and midpoint output terminal.

[0032] For example, in the first bridge arm, the connection point of the bridge arm inductor in the upper bridge arm and the bridge arm inductor in the lower bridge arm forms the midpoint output terminal N; in the second bridge arm, the connection point of the bridge arm inductor in the upper bridge arm and the bridge arm inductor in the lower bridge arm forms the A-phase AC output terminal; in the third bridge arm, the connection point of the bridge arm inductor in the upper bridge arm and the bridge arm inductor in the lower bridge arm forms the B-phase AC output terminal; and in the fourth bridge arm, the connection point of the bridge arm inductor in the upper bridge arm and the bridge arm inductor in the lower bridge arm forms the C-phase AC output terminal.

[0033] In one example, the soft start unit includes a three-phase soft start circuit. Each phase soft start circuit includes a first soft start switch, a second soft start switch, and a current-limiting resistor. The second soft start switch and the current-limiting resistor are connected in parallel and then connected in series with the first soft start switch.

[0034] For example, the C-phase soft start circuit includes a first soft start switch K1, a second soft start switch K2, and a current limiting resistor R1. The second soft start switch K2 and the current limiting resistor R1 are connected in parallel and then connected in series with the first soft start switch K1.

[0035] In one example, a first reactor is also included, through which the AC input terminals of phase A, phase B, and phase C are connected to the soft-start unit.

[0036] For example, the AC input terminal of phase A is connected to the soft starter unit through reactor La, the AC input terminal of phase B is connected to the soft starter unit through reactor Lb, and the AC input terminal of phase C is connected to the soft starter unit through reactor Lc.

[0037] Please refer to Figure 2 To understand this, in one example, the isolated DC / DC converter includes a second H-bridge converter Q2, a first transformer T1, and a third H-bridge converter Q3 connected in sequence. Q1 in the figure is the first H-bridge converter.

[0038] The DC input terminal of the second H-bridge converter Q2 is connected to the DC output terminal of the first H-bridge converter Q1. The AC output terminal of the second H-bridge converter Q2 is connected to the primary winding of the first transformer T1. The secondary winding of the first transformer T1 is connected to the AC input terminal of the third H-bridge converter Q3. The AC input terminal of the first H-bridge converter Q1 is the AC input terminal of the first power module (refer to a and b in the figure). The DC output terminal of the third H-bridge converter Q3 is the DC output terminal of the first power module (refer to c and d in the figure).

[0039] Furthermore, the isolated DC / DC converter also includes a first capacitor C1 and / or a second capacitor C2; the first capacitor C1 is connected in parallel to the DC input terminal of the second H-bridge converter Q2, and the second capacitor C2 is connected in parallel to the DC output terminal of the third H-bridge converter Q3.

[0040] When multiple first power modules are cascaded, the AC input terminal 'a' of one first power module is connected to the AC input terminal 'b' of another first power module, and the DC output terminal 'c' of one first power module is connected to the DC output terminal 'd' of another first power module. After multiple first power modules are cascaded, the AC input terminal 'a' of the first first power module forms the first AC input terminal of a certain phase power unit, the AC input terminal 'b' of the last first power module forms the second AC input terminal of that phase power unit, the DC output terminal 'c' of the first first power module forms the first DC output terminal of that phase power unit, and the DC output terminal 'd' of the last first power module forms the second DC output terminal of that phase power unit.

[0041] Please refer to Figure 3 To understand this further, in another example, the isolated DC / DC converter includes a first half-bridge converter Q20, a third capacitor C10, a second reactor L10, a second transformer T10, and a second half-bridge converter Q30 connected in sequence. Q10 in the figure is the first H-bridge converter.

[0042] The DC input terminal of the first half-bridge converter Q20 is connected to the DC output terminal of the first H-bridge converter Q10. The AC output terminal of the first half-bridge converter Q20 is connected to the primary winding of the second transformer T10 after passing through the third capacitor C10 and the second reactor L10. The secondary winding of the second transformer T10 is connected to the AC input terminal of the second half-bridge converter Q30. The AC input terminal of the first H-bridge converter Q10 is the AC input terminal of the first power module (refer to a and b in the figure). The DC output terminal of the second half-bridge converter Q30 is the DC output terminal of the first power module (refer to c and d in the figure).

[0043] Furthermore, the isolated DC / DC converter also includes a fourth capacitor C3 and / or a fifth capacitor C4; the fourth capacitor C3 is connected in parallel to the DC input terminal of the first half-bridge converter Q20, and the fifth capacitor C4 is connected in parallel to the DC output terminal of the second half-bridge converter Q30.

[0044] In this example, the cascading of multiple first power modules can be referenced in the preceding section.

[0045] It should be noted that the first transformer T1 or the second transformer T10 adopts an insulating material potting structure, and the primary winding of the transformer meets the high-voltage insulation requirements to the secondary winding.

[0046] Please refer to Figure 4To understand this, in one example, the second power module includes a third half-bridge converter and a seventh capacitor C5 connected to the DC terminal of the third half-bridge converter. The third half-bridge converter consists of two switching transistors S1 and S2. In the figure, a1 is one DC output terminal of the second power module, and b1 is the other DC output terminal of the second power module.

[0047] In the upper bridge arm, when multiple second power modules are cascaded, the DC output terminal a1 of one second power module is connected to the DC output terminal b1 of another second power module. After multiple second power modules are cascaded, the DC output terminal a1 of the first second power module is connected to the positive DC input terminal, and the DC output terminal b1 of the last second power module is connected to the lower bridge arm through the bridge arm inductor L1.

[0048] In the lower bridge arm, when multiple second power modules are cascaded, the DC output terminal a1 of one adjacent second power module is connected to the DC output terminal b1 of another second power module. After multiple second power modules are cascaded, the DC output terminal a1 of the first second power module is connected to the upper bridge arm through the bridge arm inductor L2, and the DC output terminal b1 of the last second power module is connected to the negative DC input terminal.

[0049] Please refer to Figure 5 For comprehension, in one example, the second power module includes a fourth H-bridge converter and a sixth capacitor C6 connected to the DC terminal of the fourth H-bridge converter. The fourth H-bridge converter consists of four switching transistors S1, S2, S3, and S4. In the diagram, a1 is one AC output terminal of the second power module, and b1 is the other AC output terminal. Cascading multiple second power modules can be referred to the preceding sections.

[0050] In one example, an output switch is also included, through which the A-phase AC output terminal, the B-phase AC output terminal, and the C-phase AC output terminal are connected to the device under test.

[0051] In one example, a controller is also included, which is configured to perform a control method for an isolated grid analog power supply.

[0052] like Figure 6 As shown, another embodiment of this application provides a control method for an isolated grid simulation power supply, which can be referred to in the foregoing section. The control method includes the following steps:

[0053] S21. Obtain the output voltage of each phase detected by the voltage sensor;

[0054] S22. Based on the output voltage of each phase, the output voltage of the control midpoint output terminal is equal to half of the voltage between the positive DC input terminal and the negative DC input terminal.

[0055] That is, the voltage between the control midpoint output terminal N and the negative DC input terminal BUS- is equal to half the voltage between the positive DC input terminal BUS+ and the negative DC input terminal BUS-.

[0056] In one example, the output voltages of each phase (the voltages of phase A, phase B, and phase C AC output terminals in the diagram) detected by voltage sensors are acquired. Based on the detected phase output voltages, voltage-current dual closed-loop control is performed on the voltages of phase A, phase B, and phase C AC output terminals to obtain the drive signal for the second power module in the output multilevel converter. According to the drive signal of the second power module in the output multilevel converter, the output voltage at the control midpoint output terminal is equal to half the voltage between the positive and negative DC input terminals.

[0057] The preferred embodiments of this application have been described above with reference to the accompanying drawings, but this does not limit the scope of the claims. Any modifications, equivalent substitutions, and improvements made by those skilled in the art without departing from the scope and spirit of this application shall be within the scope of the claims.

Claims

1. An isolated grid simulation power supply, characterized in that, It includes a soft-start unit, an input converter, an output converter, and a voltage sensor; The input converter includes an A-phase power unit, a B-phase power unit, a C-phase power unit, an A-phase AC input terminal, a B-phase AC input terminal, a C-phase AC input terminal, a positive DC output terminal, and a negative DC output terminal; the output converter includes a first bridge arm, a second bridge arm, a third bridge arm, a fourth bridge arm, a positive DC input terminal, a negative DC input terminal, an A-phase AC output terminal, a B-phase AC output terminal, a C-phase AC output terminal, and a midpoint output terminal; The A-phase AC input terminal, the B-phase AC input terminal, and the C-phase AC input terminal are connected to the power grid through the soft-start unit. The positive DC output terminal is connected to the positive DC input terminal, and the negative DC output terminal is connected to the negative DC input terminal. The A-phase AC output terminal, the B-phase AC output terminal, and the C-phase AC output terminal are connected to the device under test. The midpoint output terminal is connected to the A-phase AC output terminal, the B-phase AC output terminal, and the C-phase AC output terminal through the voltage sensor. The first AC input terminal of the A-phase power unit forms the A-phase AC input terminal of the input converter, the first AC input terminal of the B-phase power unit forms the B-phase AC input terminal of the input converter, and the first AC input terminal of the C-phase power unit forms the C-phase AC input terminal of the input converter. The second AC input terminals of the A-phase power unit, the B-phase power unit, and the C-phase power unit are connected together. The DC output terminal of the A-phase power unit is cascaded with the DC output terminals of the B-phase power unit and the C-phase power unit to form the positive DC output terminal and the negative DC output terminal of the input converter. The A-phase power unit, the B-phase power unit, and the C-phase power unit each include multiple cascaded first power modules, and each first power module includes a first H-bridge converter and an isolated DC / DC converter connected in sequence. The first bridge arm, the second bridge arm, the third bridge arm, and the fourth bridge arm each include an upper bridge arm and a lower bridge arm. The upper bridge arm and the lower bridge arm each include a bridge arm inductor and multiple cascaded second power modules. The connection point between the bridge arm inductor in the upper bridge arm and the bridge arm inductor in the lower bridge arm forms one of the A-phase AC output terminal, the B-phase AC output terminal, the C-phase AC output terminal, and the midpoint output terminal.

2. The isolated grid simulation power supply according to claim 1, characterized in that, The soft start unit includes a three-phase soft start circuit. Each phase soft start circuit includes a first soft start switch, a second soft start switch, and a current limiting resistor. The second soft start switch and the current limiting resistor are connected in parallel and then connected in series with the first soft start switch.

3. The isolated grid simulation power supply according to claim 1, characterized in that, It also includes a first reactor, through which the A-phase AC input terminal, the B-phase AC input terminal, and the C-phase AC input terminal are connected to the soft-start unit.

4. The isolated grid simulation power supply according to claim 1, characterized in that, The isolated DC / DC converter includes a second H-bridge converter, a first transformer, and a third H-bridge converter connected in sequence. The DC input terminal of the second H-bridge converter is connected to the DC output terminal of the first H-bridge converter, the AC output terminal of the second H-bridge converter is connected to the primary winding of the first transformer, the secondary winding of the first transformer is connected to the AC input terminal of the third H-bridge converter, the AC input terminal of the first H-bridge converter is the AC input terminal of the first power module, and the DC output terminal of the third H-bridge converter is the DC output terminal of the first power module.

5. The isolated grid simulation power supply according to claim 4, characterized in that, The isolated DC / DC converter further includes a first capacitor and / or a second capacitor; the first capacitor is connected in parallel to the DC input terminal of the second H-bridge converter, and the second capacitor is connected in parallel to the DC output terminal of the third H-bridge converter.

6. The isolated grid simulation power supply according to claim 1, characterized in that, The isolated DC / DC converter includes a first half-bridge converter, a third capacitor, a second reactor, a second transformer, and a second half-bridge converter connected in sequence. The DC input terminal of the first half-bridge converter is connected to the DC output terminal of the first H-bridge converter. The AC output terminal of the first half-bridge converter is connected to the primary winding of the second transformer after passing through the third capacitor and the second reactor. The secondary winding of the second transformer is connected to the AC input terminal of the second half-bridge converter. The AC input terminal of the first H-bridge converter is the AC input terminal of the first power module, and the DC output terminal of the second half-bridge converter is the DC output terminal of the first power module.

7. The isolated grid simulation power supply according to claim 6, characterized in that, The isolated DC / DC converter further includes a fourth capacitor and / or a fifth capacitor; the fourth capacitor is connected in parallel to the DC input terminal of the first half-bridge converter, and the fifth capacitor is connected in parallel to the DC output terminal of the second half-bridge converter.

8. The isolated grid simulation power supply according to claim 1, characterized in that, The second power module includes a fourth H-bridge converter and a sixth capacitor connected to the DC terminal of the fourth H-bridge converter; or, the second power module includes a third half-bridge converter and a seventh capacitor connected to the DC terminal of the third half-bridge converter.

9. The isolated grid simulation power supply according to claim 1, characterized in that, It also includes an output switch, through which the A-phase AC output terminal, the B-phase AC output terminal, and the C-phase AC output terminal are connected to the device under test.

10. A control method for an isolated grid analog power supply according to any one of claims 1-9, characterized in that, The control method includes: Obtain the output voltage of each phase detected by the voltage sensor; Based on the output voltage of each phase, the output voltage of the midpoint output terminal is controlled to be equal to half the voltage between the positive DC input terminal and the negative DC input terminal.

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