Novel AC / DC converter surge current suppression method and system

Abstract

The invention provides a novel AC / DC converter surge current suppression method and system, and the method specifically comprises the steps: S1, detecting whether the dv / dt control of a switch capacitor valve is enabled or not, and whether the power protection control of a novel switch valve is enabled or not; s2, if the dv / dt control of the switched capacitor valve is enabled, executing the dv / dt control of the switched capacitor valve; if the novel switch valve power protection control is enabled, the novel switch valve power protection control is executed; s3, if a shutdown instruction of the converter is received, ending the method; otherwise, skipping to the step S1. According to the invention, the surge current generated by charging the novel switch valve by the switch capacitor valve due to the rise of the output voltage of the switch capacitor valve can be obviously suppressed, so that circuit components are protected from being damaged.

Description

Technical Field

[0001] The invention belongs to the technical field of power systems, and in particular relates to a novel AC / DC converter surge current suppression method and system. Background Art

[0002] Flexible DC transmission technology is a new type of DC transmission technology. Compared with conventional DC transmission technology, flexible DC transmission has the advantages of strong controllability, small size, and small harmonics. It is the main development direction of DC transmission technology in the future. Flexible DC transmission converter is a key device to complete AC / DC conversion. There are many existing flexible DC transmission converter topologies. The topology represented by modular multilevel converter (MMC) has been widely used due to its modular structure, which is conducive to the expansion of voltage and capacity. However, MMC has three-phase 12 bridge arms, a large number of modules, large size, and high cost, which hinders the application of flexible DC transmission technology to a certain extent.

[0003] The new AC / DC converter topology can reduce module capacitance by nearly 80% compared to MMC, significantly reducing cost and volume. For applications with scarce land resources, such as offshore wind power and urban power grids, it has a very significant advantage of small footprint and good application prospects.

[0004] However, since the topology of the new AC / DC converter is significantly different from that of the existing flexible DC transmission converter, there are some problems - the switch capacitor valve and the new switch valve are connected in parallel in the circuit. When the output voltage of the switch capacitor valve increases and is higher than the sum of the voltages of the new switch modules that shut down the bridge arm of the new switch valve, the switch capacitor valve will charge the module capacitor of the new switch valve. Since the impedance of the parallel connection between the switch capacitor valve and the new switch valve is very small, it only contains the impedance of stray components, so the charging current is very large, which can easily cause damage to circuit components.

[0005] Therefore, it is necessary to design a new AC / DC converter surge current suppression method and system to solve the above technical problems. Summary of the invention

[0006] In view of the above technical problems, the present invention provides a novel AC / DC converter surge current suppression method, wherein the method comprises:

[0007] Step S1: Detect whether the switch capacitor valve dv / dt control is enabled, and whether the new switch valve power conservation control is enabled;

[0008] Step S2: If the switch capacitor valve dv / dt control is enabled, the switch capacitor valve dv / dt control is performed; if the new switch valve power conservation control is enabled, the new switch valve power conservation control is performed;

[0009] Step S3: If a converter shutdown instruction is received, the method ends; otherwise, the method jumps to step S1.

[0010] Further, the converter comprises a switch valve unit, wherein:

[0011] The switch valve unit includes three switch valve sub-units connected in series, and the switch valve sub-unit includes the switch capacitor valve and two new switch valves connected in parallel, and the switch capacitor valve includes multiple switch capacitor modules connected in series; the new switch valve includes an upper bridge arm and a lower bridge arm connected by a connecting midpoint, and the upper bridge arm and the lower bridge arm each include multiple power modules connected in series.

[0012] Further, the switched capacitor valve dv / dt control includes:

[0013] Step SA1: receiving an instruction to control the output voltage Usc of the switch capacitor valve to increase by ΔUsc, where Usc is the output voltage of the switch capacitor valve;

[0014] Step SA2: If the additional determination is not enabled, then execute step S3.1; otherwise, execute the additional determination, i.e., step SA3.2;

[0015] Step SA3.1: Control the output voltage of the switched capacitor valve to increase by △Usc over time at a slope not higher than k, and end the dv / dt control of the switched capacitor valve;

[0016] Step SA3.2: Determine the difference between Usc' and Uhmax', and according to the result of the determination, terminate the dv / dt control of the switch capacitor valve, wherein Usc' is the value of the output voltage of the switch capacitor valve after the voltage increases by △Usc, and Uhmax' is the minimum of the sum of the power module voltage of the bridge arm turned off by one of the new switch valves and the sum of the power module voltage of the bridge arm turned off by the other new switch valve;

[0017] Further, the size between Usc' and Uhmax' is determined, and according to the result of the determination, the dv / dt control of the switched capacitor valve is terminated, including:

[0018] If Usc'≤Uhmax', the output voltage of the switched capacitor valve is allowed to increase by △Usc without limiting the slope, and the dv / dt control of the switched capacitor valve is terminated;

[0019] If Usc'>Uhmax', the switched capacitor valve output voltage is first allowed to increase by Uhmax'-Usc without limiting the slope, and then the switched capacitor valve output voltage is allowed to increase over time by the difference between Usc' and Uhmax' at a slope not higher than k, and the switched capacitor valve dv / dt control is terminated.

[0020] Furthermore, the new switch valve power-saving control includes:

[0021] Step SB1: If the synchronous switching control is not enabled, execute step SB2.1; otherwise, execute step SB2.2;

[0022] Step SB2.1: If flexible control is enabled, that is, step SB2.1.1 is enabled, then execute step SB2.1.1; otherwise, execute step SB2.1.2;

[0023] Step SB2.1.1: Check whether Uhmax' is less than the control threshold Uth. If so, execute step SB2.1.2; otherwise, directly terminate the power conservation control of the new switch valve;

[0024] Step SB2.1.2: Check whether the timing reaches the repetitive execution cycle T. If the timing ≥ T, execute the synchronous switching control, and after waiting for the delay tc, cancel the synchronous switching control, reset the timing, and restart the timing, and end the new switch valve power conservation control at the same time; otherwise, directly end the new switch valve power conservation control;

[0025] Step SB2.2: Execute synchronous switching control and end the power conservation control of the new switch valve.

[0026] Furthermore, synchronous switching includes:

[0027] The novel switch valve is selected to shut off m power modules in the bridge arm, so that the fully controlled power semiconductor switch device of the lower tube of the selected power module is turned on.

[0028] Furthermore, the control threshold satisfies Uth≤N*Usm, wherein Usm is the rated voltage of the power module on the bridge arm in the novel switch valve, and N is the number of power modules contained in each bridge arm.

[0029] Furthermore, the converter further comprises a first filtering branch, wherein:

[0030] The two ends of the switch valve unit are respectively connected to a DC positive bus and a DC negative bus, wherein the DC positive bus is connected in series with DC inductors L1 and L2, and the DC negative bus is connected in series with DC inductors L3 and L4; the two ends of the first filter branch are respectively connected to the connection point between L1 and L2, and the connection point between L3 and L4;

[0031] One end of L1 is connected to the positive terminal of the DC port of the converter, and one end of L3 is connected to the negative terminal of the DC port of the converter;

[0032] The two connection midpoints of each switch valve subunit are connected to a second filter branch, wherein each second filter branch is also connected to a transformer, and one end of the same side windings of the three transformers are connected to form an AC port of the converter.

[0033] Further, the switch capacitor module is any one or more combinations of a half-bridge module, a full-bridge module and a hybrid module, wherein:

[0034] The hybrid module includes a first number of half-bridge modules connected in series and a second number of full-bridge modules connected in series. The first number of half-bridge modules connected in series and the second number of full-bridge modules connected in series are connected in series.

[0035] Furthermore, the power module includes a first bridge arm, a voltage-sharing capacitor C1 and an energy-consuming element H1 connected in parallel, wherein:

[0036] The first bridge arm includes a power switch device T1 and a diode D1, wherein the anode of the diode D1 is connected to the anode or collector of the power switch device T1;

[0037] One end of the voltage-equalizing capacitor C1 is connected to the cathode of the diode D1 , and the other end of the voltage-equalizing capacitor C1 is connected to the cathode or emitter of the power switch device T1 . A diode D2 is connected in anti-parallel to the power switch device T1 .

[0038] Further, the first filtering branch includes a first filter, wherein:

[0039] The first filter is any one or a combination of a single tuned filter, a single tuned filter with damping, a first order high pass filter, a first order high pass filter with damping, a second order high pass filter, a double tuned filter, a double tuned filter with damping, and a triple tuned filter.

[0040] Further, the second filtering branch includes a second filter, wherein:

[0041] The second filter is any one or a combination of an L filter, an LC filter, an LC filter with damping, an LCL filter, and an LCL filter with damping.

[0042] In one aspect, the present invention provides a novel AC / DC converter surge current suppression system, wherein the system comprises:

[0043] A detection device, used to detect whether the dv / dt control of the switch capacitor valve is enabled, and whether the power conservation control of the new switch valve is enabled;

[0044] An actuator, used to execute the switch capacitor valve dv / dt control when the switch capacitor valve dv / dt control is enabled; and to execute the new switch valve power conservation control when the new switch valve power conservation control is enabled;

[0045] The control device is used to end the method when receiving a converter shutdown instruction; otherwise, jump to the execution step of the detection device.

[0046] Further, the converter comprises a switch valve unit, wherein:

[0047] The switch valve unit includes three switch valve sub-units connected in series, and the switch valve sub-unit includes the switch capacitor valve and two new switch valves connected in parallel, and the switch capacitor valve includes multiple switch capacitor modules connected in series; the new switch valve includes an upper bridge arm and a lower bridge arm connected by a connecting midpoint, and the upper bridge arm and the lower bridge arm each include multiple power modules connected in series.

[0048] The present invention provides a novel AC / DC converter surge current suppression method and system, which can significantly suppress the surge current generated by the switching capacitor valve charging the novel switching valve due to the increase in the output voltage of the switching capacitor valve, thereby protecting circuit components from damage.

[0049] Other features and advantages of the present invention will be described in the following description, and partly become obvious from the description, or be understood by implementing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0051] Figure 1 A topology diagram of a novel AC / DC converter according to an embodiment of the present invention is shown.

[0052] Figure 2 FIG. 4 shows a topological diagram of a switch valve unit according to an embodiment of the present invention.

[0053] Figure 3 A topological diagram of a power module according to an embodiment of the present invention is shown.

[0054] Figure 4 FIG. 4 shows a topological diagram of an energy consumption element H1 according to an embodiment of the present invention.

[0055] Figure 5 A topology diagram of a single tuned filter according to an embodiment of the present invention is shown.

[0056] Figure 6 FIG. 4 shows a plot of a single tuned filter with damping according to an embodiment of the present invention.

[0057] Figure 7 A topological diagram of a first-order high-pass filter according to an embodiment of the present invention is shown.

[0058] Figure 8 A topology diagram of a damped first-order high-pass filter according to an embodiment of the present invention is shown.

[0059] Fig. 9 A topological diagram of a second-order high-pass filter according to an embodiment of the present invention is shown.

[0060] Fig.10 A topology diagram of a double tuned filter according to an embodiment of the present invention is shown.

[0061] Fig.11 FIG. 4 shows a topology diagram of a double-tuned filter with damping according to an embodiment of the present invention.

[0062] Fig.12 A topology diagram of a triple tuned filter according to an embodiment of the present invention is shown.

[0063] Fig.13 A topology diagram showing two identical first-order high-pass filters connected in series according to an embodiment of the present invention, with the connection point of the series connection directly grounded.

[0064] Fig.14 A topological diagram showing two identical first-order high-pass filters connected in series according to an embodiment of the present invention, with the connection point of the series connected being grounded via a grounding resistor.

[0065] Fig.15 A topological diagram is shown in which two identical first-order high-pass filters are connected in series according to an embodiment of the present invention, and the connection point of the series connection is grounded via a grounding switch.

[0066] Fig.16 A topological diagram is shown in which two identical first-order high-pass filters are connected in series according to an embodiment of the present invention, and the connection point of the series connection is grounded via a grounding resistor and a grounding switch.

[0067] Fig.17 FIG. 4 shows a topological diagram of an L filter according to an embodiment of the present invention.

[0068] Fig.18 A topology diagram of an LC filter according to an embodiment of the present invention is shown.

[0069] Fig.19FIG. 4 shows a topology diagram of a damped LC filter according to an embodiment of the present invention.

[0070] Fig. 20 FIG. 4 shows a topological diagram of an LCL filter according to an embodiment of the present invention.

[0071] Fig.21 FIG. 4 shows a topology diagram of a damped LCL filter according to an embodiment of the present invention.

[0072] Fig. 22 A flow chart of a novel AC / DC converter surge current suppression method according to an embodiment of the present invention is shown.

[0073] Fig.23 A flow chart of a switched capacitor valve dv / dt control method according to an embodiment of the present invention is shown.

[0074] Fig.24 A flow chart of a novel switch valve power conservation control method according to an embodiment of the present invention is shown.

[0075] Fig.25 The structure diagram of a novel AC / DC converter surge current suppression system according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0076] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0077] The present invention provides a novel AC / DC converter surge current suppression method, wherein the method is based on Figure 1 The topology of the novel AC / DC converter (hereinafter referred to as converter) shown is realized. The converter topology of the present invention is described in detail below.

[0078] In some embodiments of the present invention, Figure 1 As shown, the converter includes a switch valve unit and a first filter branch, which are described in detail below.

[0079] In some embodiments of the present invention, Figure 1As shown, the two ends of the switch valve unit are respectively connected to a DC positive bus and a DC negative bus, wherein the DC positive bus is connected in series with DC inductors L1 and L2, and the DC negative bus is connected in series with DC inductors L3 and L4; the two ends of the first filter branch are respectively connected to the connection point between L1 and L2, and the connection point between L3 and L4; one end of L1 is connected to the positive terminal (+) of the DC port of the converter, and one end of L3 is connected to the negative terminal (-) of the DC port of the converter; specifically:

[0080] exist Figure 1 In the definition, the DC positive bus has points P1 and P3, the DC negative bus has points P2 and P4, point P1 is between L1 and L2, and point P2 is between L3 and L4. The DC inductor L1 is connected between the positive terminal (+) of the DC port and P1; the DC inductor L2 is connected between points P1 and P3; the DC inductor L3 is connected between the negative terminal (-) of the DC port and P2; the DC inductor L4 is connected between points P2 and P4, and the two ends of the switch valve unit are connected between P3 and P4. In addition, any one or more of the inductors L1 to L4 may not be configured (i.e., replaced by a section of wire), and the first filter branch is connected between P1 and P2.

[0081] In some embodiments of the present invention, Figure 1 As shown, the switch valve unit includes three switch valve sub-units connected in series, such as Figure 2 As shown, the switch valve subunit includes a parallel switch capacitor valve and two new switch valves, and the switch capacitor valve includes multiple switch capacitor modules connected in series; the new switch valve includes an upper bridge arm and a lower bridge arm connected by a connecting midpoint, and the upper bridge arm and the lower bridge arm both include power modules.

[0082] In some embodiments of the present invention, Figure 1 As shown, the two connection midpoints of each switch valve subunit are connected to the second filter branch, and each second filter branch is also connected to the transformer. The two connection midpoints of each switch valve subunit are defined as the AA end of the switch valve subunit, and the valve side of the transformer is the BB end. The second filter is connected between the AA end of each phase and the BB end of the valve side of the transformer. One end of the same side windings of the three transformers is connected to form the AC port of the converter, that is, for each transformer, the corresponding second filter branch is connected to the two ends of the winding on one side of the transformer (that is, one end of the transformer), and one end of the windings on the other side of the three transformers is connected to each other, and the other ends of the windings on the other side of the three transformers respectively form an a-phase AC port, a b-phase AC port, and a c-phase AC port.

[0083] In some embodiments of the present invention, Figure 3As shown, the power module includes a first bridge arm, a voltage-equalizing capacitor C1 and an energy-consuming element H1 connected in parallel, wherein: the first bridge arm includes a power switching device T1 and a diode D1, the anode of the diode D1 is connected to the anode or collector of the power switching device T1; one end of the voltage-equalizing capacitor C1 is connected to the cathode of the diode D1, and the other end of the voltage-equalizing capacitor C1 is connected to the cathode or emitter of the power switching device T1, and a diode D2 is anti-parallel to the power switching device T1.

[0084] In some embodiments of the present invention, the energy-consuming element H1 is any one or a combination of an energy-taking power supply, a first energy-consuming resistor, and a switchable energy-consuming resistor, wherein the energy-taking power supply is used to obtain energy from the corresponding voltage-equalizing capacitor C1 to power the control circuit of the corresponding power module, and the switchable energy-consuming resistor includes a second energy-consuming resistor and a switch connected in series with the second energy-consuming resistor.

[0085] like Figure 4 As shown, when the energy-consuming element H1 is a switchable energy-consuming resistor, the switchable energy-consuming resistor includes a second energy-consuming resistor and a switch (exemplarily, the switch can be a relay, a contactor, a circuit breaker, a semiconductor switch, etc., which has a current that can be disconnected), one end of the switch is connected to one end of the second energy-consuming resistor, the other end of the switch is connected to the positive electrode of the corresponding voltage-equalizing capacitor, the other end of the second energy-consuming resistor is connected to the negative electrode of the corresponding voltage-equalizing capacitor, and the energy source is connected to both ends of the corresponding voltage-equalizing capacitor. The switching control of the second energy-consuming resistor can be realized by setting the switch.

[0086] In one embodiment of the present invention, in some embodiments of the present invention, the switch capacitor module is any one or more combinations of a half-bridge module, a full-bridge module and a hybrid module, wherein:

[0087] The hybrid module includes a first number of half-bridge modules connected in series and a second number of full-bridge modules connected in series. The first number of half-bridge modules connected in series and the second number of full-bridge modules connected in series are connected in series.

[0088] In one embodiment of the present invention, in this embodiment, the power switching devices T1 and T2 can be fully controlled power semiconductor switching devices such as insulated gate bipolar transistors (IGBT), integrated gate-commutated thyristors (IGCT), and field-effect transistors (FET).

[0089] In some embodiments of the present invention, Figure 3As shown, a bypass switch K may be configured in the power module, that is, one end of the bypass switch S1 in the power module is connected to the anode or collector of the power switch device T1 , and the other end is connected to the cathode or emitter of the power switch device T1 .

[0090] In some embodiments of the present invention, the first filtering branch includes a first filter, wherein: the first filter is any one or a combination of a single tuned filter, a single tuned filter with damping, a first order high pass filter, a first order high pass filter with damping, a second order high pass filter, a double tuned filter, a double tuned filter with damping, and a triple tuned filter, wherein:

[0091] like Figure 5 As shown, the single tuned filter includes a capacitor C3 and an inductor L5 connected in series.

[0092] like Figure 6 As shown, the single tuned filter with damping includes a resistor R1, a capacitor C3 and an inductor L5 which are sequentially connected in series.

[0093] like Figure 7 As shown, the first order high pass filter includes capacitor C3.

[0094] like Figure 8 As shown, the first-order high-pass filter with damping includes a capacitor C3 and a resistor R1, wherein the resistor R1 is connected in parallel or in series with the capacitor C3.

[0095] like Fig. 9 As shown, the second-order high-pass filter includes an inductor L5, a capacitor C3 and a resistor R1, wherein the capacitor C3 is connected in series with the inductor L5, and the resistor R1 is connected in parallel with the inductor L5.

[0096] like Fig.10 As shown, the double tuned filter includes an inductor L5, a capacitor C3, a capacitor C4 and an inductor L6, wherein the capacitor C3, the inductor L5 and the capacitor C4 are sequentially connected in series, and the inductor L6 is connected in parallel with the capacitor C4.

[0097] like Fig.11 As shown, the double-tuned filter with damping includes an inductor L5, a capacitor C3, a capacitor C4, an inductor L6 and a resistor R1, wherein the capacitor C3, the inductor L5 and the capacitor C4 are sequentially connected in series, the inductor L6 is connected in parallel with the capacitor C4, and the resistor R1 is connected in parallel with the inductor L6 and the capacitor C3 or the inductor L5 and the capacitor C4 are sequentially connected in series and connected in parallel as a whole.

[0098] like Fig.12As shown in the left figure, the three-tuned filter includes an inductor L5, a capacitor C3, a capacitor C4, an inductor L6, a resistor R1, a capacitor C5 and an inductor L7, wherein the capacitor C3, the inductor L5, the capacitor C4 and the capacitor C5 are connected in series in sequence, the inductor L6 is connected in parallel with the capacitor C4, and the inductor L7 is connected in parallel with the capacitor C5. In addition, as Fig.12 As shown in the right figure, based on the left figure, the triple-tuned filter has another topology, that is, the triple-tuned filter can also include a resistor R1 and a resistor R2, wherein the resistor R1 is connected in parallel with the inductor L6, and the resistor R2 is connected in parallel with the inductor L5.

[0099] In the present invention, the DC port and the port formed by P3 and P4 are used as the input and output ports of the passive filter network composed of the first filter and L1 to L4. Assuming the AC grid frequency is f g , then the resonance point of the passive filter network should avoid 2f g , and 6f g and its integer multiple frequency points to avoid harmonic amplification caused by resonance.

[0100] Furthermore, the passband cutoff frequency of the passive filter network should be lower than 6f g , thereby weakening the 6f at both ends of P3 and P4 g The harmonic voltage of the frequency and its multiples can improve the power quality of the DC port.

[0101] Furthermore, for a converter with active damping control, the first filter may not be configured with damping (ie, corresponding resistance).

[0102] In addition, in some embodiments of the present invention, any two first filters of the same type or different types connected in series can form a new first filter, and the series connection point can be directly grounded, grounded via a resistor, grounded via a grounding switch, or grounded via a resistor and a grounding switch, thereby achieving the grounding of the converter. The following takes any two first filters of the same type connected in series to form a new first filter as an example for detailed description, specifically:

[0103] like Fig.13 As shown above, Figure 7 Two identical first-order high-pass filters are shown connected in series, with the connection point of the series connected directly to ground.

[0104] like Fig.14 As shown above, Figure 7 Two identical first-order high-pass filters are shown connected in series, and the connection point of the series connection is grounded via a resistor R3.

[0105] like Fig.15 As shown above, Figure 7 The two identical first-order high-pass filters shown are connected in series, and the connection point of the series connection is grounded via the grounding switch K1.

[0106] like Fig.16 The above is Figure 7 The two identical first-order high-pass filters shown are connected in series, and the connection point of the series connection is grounded via a resistor R3 and a series grounding switch K1.

[0107] The above-mentioned new filter grounding method does not require additional grounding components, or only adds a grounding resistor R3 and a grounding switch K1, and the steady-state grounding resistor and grounding switch do not bear voltage and current, so the cost is low. And because two identical first filters are connected in series, the electrical parameters of the filters are consistent, so the DC voltage divided by the series connection is consistent. Therefore, by adopting the above-mentioned grounding method, the voltage to ground of the DC port is the same and the voltage to ground is the minimum, the insulation difficulty is the lowest, and the cost and volume are the smallest.

[0108] In some embodiments of the present invention, the second filtering branch includes a second filter, wherein: the second filter is any one or a combination of an L filter, an LC filter, an LC filter with damping, an LCL filter, and an LCL filter with damping, wherein:

[0109] like Fig.17 As shown, Fig.17 In (a), the L filter includes a wire and an inductor L8 (the wire and the inductor L8 are parallel and do not intersect each other), or Fig.17 In FIG. (b), the L filter includes two inductors L8 (the two inductors L8 are parallel and non-intersecting), wherein when the L filter includes a wire and an inductor L8, the positions of the wire and the inductor L8 are interchangeable. In the L filter, Fig.17 In Figure (c), inductor L8 can be partially or completely replaced by transformer leakage inductance.

[0110] like Fig.18 As shown, Fig.18 In Figure (a), the LC filter includes capacitor C6 and two inductors L8, or Fig.17 In (b), the LC filter includes an inductor L8, a capacitor C6, and a conductor. When the LC filter includes a capacitor C6 and two inductors L8, the two ends of the capacitor C6 are respectively connected between the same ends of the two inductors L8. When the LC filter includes an inductor L8, a capacitor C6, and a conductor, the two ends of the capacitor C6 are respectively connected between the same ends of the inductor L8 and the conductor. In the LC filter, the inductor L8 near point B can be partially or completely replaced by the transformer leakage inductance.

[0111] like Fig.19 As shown in the figure, the damped LC filter is Fig.18 A resistor R4 connected in series below the capacitor C6 is added to the L filter of Figures (a) and (b).

[0112] like Fig. 20 As shown, Fig. 20 As shown in Figure (a), the LCL filter includes capacitor C6, wires and two inductors L8, or Fig. 20 As shown in Figure (b), the LCL filter includes capacitor C6 and two inductors L8, or Fig. 20 In (c) figure, the LCL filter includes a capacitor C6 and four inductors L8. When the LCL filter includes a capacitor C6, a wire and two inductors L8, one end of the capacitor C6 is connected to the connection point of the two inductors L8 in series, and the other end is connected to the wire. When the LCL filter includes a capacitor C6 and two inductors L8, one end of one of the inductors L8 is connected to one of the A ends, the other end of the inductor L8 is connected to one of the B ends, one end of another inductor L8 is connected to another A end, the other end of the inductor L8 is connected to another B end, one end of the capacitor C6 is connected to the other end of one of the inductors L8, and the other end of the capacitor C6 is connected to one end of another inductor L8. When the LCL filter includes a capacitor C6 and four inductors L8, one end of the capacitor C6 is connected to the connection point of two of the inductors L8 in series, and the other end of the capacitor C6 is connected to the connection point of the other two inductors L8 in series.

[0113] like Fig.21 As shown in the figure, the damped LCL filter is Fig. 20 A resistor R4 is added in series below the capacitor C6 to the LCL filter in FIG.

[0114] In the present invention, if the second filter has a resonance point, the resonance point should avoid f g 、3f g , to avoid overcurrent. The converter will output the third harmonic, so the resonance point must not only avoid the power frequency, but also the third harmonic frequency.

[0115] Furthermore, if the second filter has a cutoff frequency, the cutoff frequency should be higher than f g , to avoid affecting the power frequency output.

[0116] Furthermore, for a converter with active damping control, the second filter may not be configured with passive damping (ie resistance).

[0117] Preferably, the second filter may not be configured, that is, A and B are short-circuited. When the converter is not used for transient working condition processing, such as low voltage ride-through, the AC port will not generate a large amount of harmonic voltage, so there is no need to configure the second filter.

[0118] In summary, when the second filter of the present invention is not configured, the port power quality of the converter cannot meet the national standard requirements. After adopting the filter solution of the present invention, the harmonic voltage and current of the DC port and the AC port can be significantly suppressed, so that the port power quality of the converter meets the national standard requirements. In addition, the filter is also used to achieve low-cost grounding.

[0119] In addition, based on the above Figure 1 The provided topology also has the following features:

[0120] For ease of explanation, Figure 2 The impedance of the parallel connection between the switch capacitor valve and the novel switch valve is very small, and only contains the impedance of stray components, and mainly the equivalent series stray inductance. Figure 2 In the figure, Lk is the equivalent series stray inductance between the switch capacitor valve and the new switch valve. It can be seen that the new switch valve and the switch capacitor valve are connected in parallel through Lk. The power module upper tube only contains a diode, so the module capacitance of the power module (i.e. Figure 3 C1 in the figure will not discharge to the outside, so when the output voltage of the switch capacitor valve Usc≤the sum of the power module voltages Uhmax( Figure 2 In the explanation using the left bridge arm as an example), the voltage across the new switch valve is Uh=Usc, at which time ULk=0; otherwise, Uh=Uhmax, at which time ULk=Usc-Uhmax.

[0121] When the converter controls the output voltage Usc of the switched capacitor valve to increase and is higher than Uhmax, ULk=Usc-Uhmax, and the Lk current change rate is (Usc-Uhmax) / Lk. Since Lk is usually in the μH level, for example, Lk=5μH, assuming Usc-Uhmax=5kV, the Lk current change rate is 1kA / μs. It can be seen that the loop current Ic (that is, the loop current of the single-phase switched capacitor valve) will also increase at a rate of 1kA / μs until the voltage of the new switch valve module increases so that Uhmax=Usc. Usually in the above process, the peak value of Ic can reach several kA to several 10kA. After the current is superimposed on the load current of the AC and DC ports, the surge current is much higher than the current tolerance level of the loop components, which can easily cause damage to the circuit components. To this end, the above surge current can be suppressed from two aspects:

[0122] (1) Limit the rate of change of Usc to reduce Usc-Uhmax, thereby reducing the surge current;

[0123] (2) Ensure that under any circumstances, the sum of the power module voltages of the left bridge arm of the new switch valve and the sum of the power module voltages of the right bridge arm are as high as possible, that is, as close to or greater than or equal to the maximum output voltage Uscmax of the switch capacitor valve as possible, so that even if the switch capacitor valve outputs the maximum voltage Uscmax, ULk = Uscmax-Uhmax is very small, so the surge current is very small.

[0124] Therefore, based on the above (1) and (2), in some embodiments of the present invention, such as Fig. 22 As shown, based on the surge suppression implemented by the above converter, the specific method includes:

[0125] Step S1: Detect whether the switch capacitor valve dv / dt control is enabled, and whether the new switch valve power conservation control is enabled;

[0126] Step S2: If the switch capacitor valve dv / dt control is enabled, the switch capacitor valve dv / dt control is performed; if the new switch valve power conservation control is enabled, the new switch valve power conservation control is performed;

[0127] Step S3: If a converter shutdown instruction is received from an external control system, the method ends; otherwise, the method jumps to step S1.

[0128] The above method is introduced in detail below.

[0129] 1) In some embodiments of the present invention, Fig.23 As shown, the switched capacitor valve dv / dt control includes:

[0130] Step SA1: receiving an instruction to control the output voltage Usc of the switch capacitor valve to increase by △Usc;

[0131] Step SA2: If the additional determination is not enabled, then execute step S3.1; otherwise, execute the additional determination, i.e., step SA3.2;

[0132] Step SA3.1: Control the output voltage of the switched capacitor valve to increase by △Usc over time at a slope not higher than k, and end the switched capacitor valve dv / dt control, wherein k is a positive real number, and the larger the k, the larger the surge current, the shorter the time required for Usc to rise, and the faster the output voltage response; conversely, the smaller the surge current, the longer the time required for Usc to rise, and the slower the output voltage response;

[0133] Step SA3.2: Determine the size between Usc' and Uhmax', and according to the result of the determination, terminate the dv / dt control of the switch capacitor valve, wherein Usc' is the value of the output voltage of the switch capacitor valve after the voltage increases by △Usc, and Uhmax' is one of the new switch valves (i.e. Figure 2The sum of the power module voltages of the left bridge arm of the switch-off bridge arm and the other new switch valve (i.e. Figure 2 The minimum of the sum of the power module voltages of the right bridge arm in the shut-off bridge arm;

[0134] In step SA3.2, the difference between Usc' and Uhmax' is determined, and according to the result of the determination, the dv / dt control of the switched capacitor valve is terminated, including:

[0135] If Usc'≤Uhmax', the output voltage of the switched capacitor valve is allowed to increase by △Usc without limiting the slope, and the dv / dt control of the switched capacitor valve is terminated;

[0136] If Usc'>Uhmax', the output voltage of the switched capacitor valve is first allowed to increase over time by Uhmax'-Usc without limiting the slope, and then the output voltage of the switched capacitor valve is allowed to increase over time by the difference between Usc' and Uhmax' (i.e., Usc'-Uhmax') at a slope not higher than k, and the dv / dt control of the switched capacitor valve is terminated.

[0137] In the switch capacitor valve dv / dt control, the following effects can be achieved: when the switch capacitor valve output voltage exceeds Uhmax', its voltage rise rate is limited, thereby reducing ULk and lowering Ic, such as Figure 2 shown.

[0138] 2) In some embodiments of the present invention, Fig.24 As shown in the figure, the new switch valve power-saving control includes:

[0139] Step SB1: If the synchronous switching control is not enabled, execute step SB2.1; otherwise, execute step SB2.2;

[0140] Step SB2.1: If flexible control is enabled, that is, step SB2.1.1 is enabled, then execute step SB2.1.1; otherwise, execute step SB2.1.2;

[0141] Step SB2.1.1: Check whether Uhmax' is less than the control threshold Uth. If so, execute step SB2.1.2; otherwise, directly terminate the power conservation control of the new switch valve;

[0142] Step SB2.1.2: Check whether the timing reaches the repetitive execution cycle T. If the timing ≥ T, execute the synchronous switching control, and after waiting for the delay tc, cancel the synchronous switching control, reset the timing, and restart the timing, and end the new switch valve power conservation control at the same time; otherwise, directly end the new switch valve power conservation control;

[0143] Step SB2.2: Execute synchronous switching control and end the power conservation control of the new switch valve.

[0144] The synchronous switching includes: selecting the new switch valve to shut down the m power modules in the bridge arm, so that the lower tube (i.e. Figure 3 The fully controlled power semiconductor switching device T1 in is turned on.

[0145] Among them, the control threshold satisfies Uth≤N*Usm, wherein Usm is the rated voltage of the power module on the bridge arm in the new switch valve, and N is the number of power modules contained in each bridge arm. Among them, the larger Uth is, the higher the switching frequency is, the better the power protection effect of the new switch valve is, but the greater the loss is; conversely, the lower the switching frequency is, the worse the power protection effect of the new switch valve is, but the loss is lower.

[0146] Among them, the difference between the sum of the rated voltages of the selected m power modules and the output voltage Usc of the switched capacitor valve is the smallest. At this time, the smaller the difference between the voltage of the power module and its rated voltage, the larger Uhmax' is, and therefore the smaller Ic is.

[0147] The repetition period T is a positive real number. The larger T is, the more likely the switch (fully controlled power semiconductor switch device, such as Figure 3 The higher the frequency of T1 in the figure, the better the power conservation effect of the new switch valve; conversely, the lower the switching frequency, the lower the loss.

[0148] Among them, the delay tc is a positive real number. The larger tc is, the higher the switching frequency is, and the better the power conservation effect of the new switch valve is; conversely, the lower the switching frequency is, but the loss is lower.

[0149] In the above-mentioned new switch valve power protection control, the following effects can be achieved: Since there are energy-taking power sources, energy-consuming elements and other components and parts inside the power module that will consume the corresponding capacitor voltage of the power module, when the output voltage of the switch capacitor valve is low, the capacitor energy of the power module cannot be replenished, and the module voltage will be lower than the rated value, thereby reducing Uhmax' and increasing ULk (ULk is the voltage of the equivalent series stray inductance Lk between the switch capacitor valve and the new switch valve), so Ic increases. The new switch valve power protection control can ensure that the power module voltage can be stabilized near the rated value when the output voltage of the switch capacitor valve Usc≠0, thereby keeping Uhmax' close to or greater than or equal to Uscmax, thereby reducing ULk and reducing Ic.

[0150] In summary, the surge suppression method of the present invention has the following beneficial effects: it can significantly suppress the surge current generated by the switching capacitor valve charging the new switching valve due to the increase in the output voltage of the switching capacitor valve, thereby protecting circuit components from damage.

[0151] On the other hand, Fig.25 As shown, the present invention also provides a novel AC / DC converter surge current suppression system, wherein the system comprises:

[0152] The detection device is used to detect whether the dv / dt control of the switch capacitor valve is enabled and whether the power conservation control of the new switch valve is enabled.

[0153] The execution device is used to execute the switch capacitor valve dv / dt control when the switch capacitor valve dv / dt control is enabled; and to execute the new switch valve power preservation control when the new switch valve power preservation control is enabled.

[0154] The control device is used to end the method when receiving a converter shutdown instruction; otherwise, jump to the execution step of the detection device.

[0155] Among them, the functions and methods implemented by other modules of a novel AC / DC converter surge current suppression system of the present invention correspond to the functions and methods implemented in a novel AC / DC converter surge current suppression method of the present invention and other steps, and therefore, they are not repeated here.

[0156] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A novel AC / DC converter surge current suppression method, wherein: The method comprises: Step S1: Detect whether the switch capacitor valve dv / dt control is enabled, and whether the new switch valve power conservation control is enabled; Step S2: If the switch capacitor valve dv / dt control is enabled, the switch capacitor valve dv / dt control is performed; if the new switch valve power conservation control is enabled, the new switch valve power conservation control is performed; Step S3: If a converter shutdown instruction is received, the method ends; otherwise, the method jumps to step S1.

2. A novel AC / DC converter surge current suppression method according to claim 1, wherein: The converter comprises a switch valve unit, wherein: The switch valve unit includes three switch valve sub-units connected in series, and the switch valve sub-unit includes the switch capacitor valve and two new switch valves connected in parallel, and the switch capacitor valve includes multiple switch capacitor modules connected in series; the new switch valve includes an upper bridge arm and a lower bridge arm connected by a connecting midpoint, and the upper bridge arm and the lower bridge arm each include multiple power modules connected in series.

3. A novel AC / DC converter surge current suppression method according to claim 2, wherein: Switched capacitor valve dv / dt control, including: Step SA1: receiving an instruction to control the output voltage Usc of the switch capacitor valve to increase by ΔUsc, where Usc is the output voltage of the switch capacitor valve; Step SA2: If the additional determination is not enabled, then execute step S3.1; otherwise, execute the additional determination, i.e., step SA3.2; Step SA3.1: Control the output voltage of the switched capacitor valve to increase by △Usc over time at a slope not higher than k, and end the dv / dt control of the switched capacitor valve; Step SA3.2: Determine the size between Usc' and Uhmax', and based on the result of the determination, execute the end of the switch capacitor valve dv / dt control, where Usc' is the value of the switch capacitor valve output voltage after the voltage increases by △Usc, and Uhmax' is the minimum of the sum of the power module voltages of one of the new switch valves that turns off the bridge arm and the sum of the power module voltages of the other new switch valve that turns off the bridge arm.

4. A novel AC / DC converter surge current suppression method according to claim 3, wherein: The size between Usc' and Uhmax' is judged, and according to the judgment result, the dv / dt control of the switched capacitor valve is terminated, including: If Usc'≤Uhmax', the output voltage of the switched capacitor valve is allowed to increase by △Usc without limiting the slope, and the dv / dt control of the switched capacitor valve is terminated; If Usc'>Uhmax', the switched capacitor valve output voltage is first allowed to increase by Uhmax'-Usc without limiting the slope, and then the switched capacitor valve output voltage is allowed to increase over time by the difference between Usc' and Uhmax' at a slope not higher than k, and the switched capacitor valve dv / dt control is terminated.

5. A novel AC / DC converter surge current suppression method according to claim 4, wherein: New switch valve power-saving control, including: Step SB1: If the synchronous switching control is not enabled, execute step SB2.1; otherwise, execute step SB2.2; Step SB2.1: If flexible control is enabled, that is, step SB2.1.1 is enabled, then execute step SB2.1.1; otherwise, execute step SB2.1.2; Step SB2.1.1: Check whether Uhmax' is less than the control threshold Uth. If so, execute step SB2.1.2; otherwise, directly terminate the power conservation control of the new switch valve; Step SB2.1.2: Check whether the timing reaches the repetitive execution cycle T. If the timing ≥ T, execute the synchronous switching control, and after waiting for the delay tc, cancel the synchronous switching control, reset the timing, and restart the timing, and end the new switch valve power conservation control at the same time; otherwise, directly end the new switch valve power conservation control; Step SB2.2: Execute synchronous switching control and end the power conservation control of the new switch valve.

6. A novel AC / DC converter surge current suppression method according to claim 5, wherein: Synchronous switching, including: The novel switch valve is selected to shut off m power modules in the bridge arm, so that the fully controlled power semiconductor switch device of the lower tube of the selected power module is turned on.

7. A novel AC / DC converter surge current suppression method according to claim 5, wherein: The control threshold satisfies Uth≤N*Usm, wherein Usm is the rated voltage of the power module on the bridge arm in the novel switch valve, and N is the number of power modules contained in each bridge arm.

8. A novel AC / DC converter surge current suppression method according to any one of claims 2 to 7, wherein: The converter further comprises a first filtering branch, wherein: The two ends of the switch valve unit are respectively connected to a DC positive bus and a DC negative bus, wherein the DC positive bus is connected in series with DC inductors L1 and L2, and the DC negative bus is connected in series with DC inductors L3 and L4; the two ends of the first filter branch are respectively connected to the connection point between L1 and L2, and the connection point between L3 and L4; One end of L1 is connected to the positive terminal of the DC port of the converter, and one end of L3 is connected to the negative terminal of the DC port of the converter; The two connection midpoints of each switch valve subunit are connected to a second filter branch, wherein each second filter branch is also connected to a transformer, and one end of the same side windings of the three transformers are connected to form an AC port of the converter.

9. A novel AC / DC converter surge current suppression method according to claim 8, wherein: The switch capacitor module is any one or more combinations of a half-bridge module, a full-bridge module and a hybrid module, wherein: The hybrid module includes a first number of half-bridge modules connected in series and a second number of full-bridge modules connected in series. The first number of half-bridge modules connected in series and the second number of full-bridge modules connected in series are connected in series.

10. A novel AC / DC converter surge current suppression method according to claim 8, wherein: The power module includes a first bridge arm, a voltage-equalizing capacitor C1 and an energy-consuming element H1 connected in parallel, wherein: The first bridge arm includes a power switch device T1 and a diode D1, wherein the anode of the diode D1 is connected to the anode or collector of the power switch device T1; One end of the voltage-equalizing capacitor C1 is connected to the cathode of the diode D1 , and the other end of the voltage-equalizing capacitor C1 is connected to the cathode or emitter of the power switch device T1 . A diode D2 is connected in anti-parallel to the power switch device T1 .

11. A novel AC / DC converter surge current suppression method according to claim 8, wherein: The first filtering branch comprises a first filter, wherein: The first filter is any one or a combination of a single tuned filter, a single tuned filter with damping, a first order high pass filter, a first order high pass filter with damping, a second order high pass filter, a double tuned filter, a double tuned filter with damping, and a triple tuned filter.

12. A novel AC / DC converter surge current suppression method according to claim 8, wherein: The second filtering branch comprises a second filter, wherein: The second filter is any one or a combination of an L filter, an LC filter, an LC filter with damping, an LCL filter, and an LCL filter with damping.

13. A novel AC / DC converter surge current suppression system, wherein: The system comprises: A detection device, used to detect whether the dv / dt control of the switch capacitor valve is enabled, and whether the power conservation control of the new switch valve is enabled; An actuator, used to execute the switch capacitor valve dv / dt control when the switch capacitor valve dv / dt control is enabled; and to execute the new switch valve power conservation control when the new switch valve power conservation control is enabled; The control device is used to end the method when receiving a converter shutdown instruction; otherwise, jump to the execution step of the detection device.

14. A novel AC / DC converter surge current suppression system according to claim 13, wherein: The converter comprises a switch valve unit, wherein: The switch valve unit includes three switch valve sub-units connected in series, and the switch valve sub-unit includes the switch capacitor valve and two new switch valves connected in parallel, and the switch capacitor valve includes multiple switch capacitor modules connected in series; the new switch valve includes an upper bridge arm and a lower bridge arm connected by a connecting midpoint, and the upper bridge arm and the lower bridge arm each include multiple power modules connected in series.

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