Three-port high-voltage DC-DC converter with active filtering bridge arm and control method thereof

Abstract

A three-port high-voltage DC-DC converter with an active filtering bridge arm and a control method thereof relate to the field of power electronics. The present invention is intended to solve the problem that a multi-port topology requires large-capacity magnetic components and has low transmission efficiency. The present invention has two energy buffer bridge arms connected in series; the energy transfer bridge arm is connected in parallel with the high-voltage side and medium-voltage side bridge arms, and the low-voltage side bridge arm is connected in parallel to the two ends of the lower bridge arm; one end of the high-voltage side and medium-voltage side valve groups are connected to the energy transfer bridge arm, and the other end is connected to the high-voltage side and medium-voltage side bridge arms respectively, and the two ends of the low-pressure side valve group are connected to the low-voltage side bridge arm and the lower bridge arm respectively. Adjust the opening or closing of the valve group and adjust the sum of the output voltages of all half-bridge sub-modules so that the current flowing through the energy transfer bridge arm is a trapezoidal wave to achieve charging or discharging.

Description

Technical Field

[0001] The present invention belongs to the fields of power electronics technology and flexible direct current transmission. Background Art

[0002] With continuous breakthroughs in power electronics devices and equipment, flexible direct current (DC) transmission technology based on voltage source converters has rapidly developed. Featuring rapid and independent control of active and reactive power and flexible operation, DC transmission is a key technology for large-scale renewable energy integration and optimizing regional energy utilization. Currently, DC / DC converters are primarily used in low- and medium-voltage applications, which are difficult to scale to power levels of hundreds of kilovolts and megawatts. Consequently, much recent research has focused on developing novel DC / DC converter topologies for high-voltage applications.

[0003] However, due to factors such as the scale of renewable energy, current HVDC transmission lines have different voltage levels, including ±320kV, ±420kV, ±500kV, ±800kV, and ±1100kV. Therefore, expanding their scale requires the use of DC transformers for voltage conversion. Unlike AC transformers in AC grids, DC grids cannot utilize the principle of electromagnetic induction and require high-power DC-DC converters as connecting devices to convert between different voltage levels.

[0004] When there are multiple interconnections of different voltage levels in a DC grid, a single DC / DC converter capable of multi-port operation is more desirable because it has a more compact structure, higher power density, and smaller size. However, there are currently few feasible technical solutions. Patent No. CN114362542A, "Ultra-high transformation ratio multi-port DC converter topology based on single-phase MMC," proposes a multi-port independent input and series output solution, using MMC sub-module multi-port input to achieve power aggregation. However, this multi-port topology requires large-capacity magnetic components, resulting in high construction costs and large volume and weight. Patent No. CN104022499A, "A multi-port back-to-back DC-DC converter," adopts the method of connecting multiple voltage source converters back-to-back to the same AC end to achieve interconnection of multiple different DC voltage levels. However, the topology uses two-stage power transmission of an intermediate AC transformer, which has low transmission efficiency and is large in size and cost. Summary of the Invention

[0005] The present invention aims to solve the problem that the existing multi-port topology requires large-capacity magnetic components and has low transmission efficiency. It now provides a three-port high-voltage DC-DC converter with an active filtering bridge arm and a control method thereof.

[0006] A three-port high-voltage DC-DC converter with an active filter bridge arm, comprising: an energy transfer bridge arm, three active filter bridge arms, and three converter valve groups;

[0007] The energy transfer bridge arm includes two energy buffer bridge arms connected in series, the two energy buffer bridge arms are respectively an upper bridge arm and a lower bridge arm, the three active filter bridge arms are respectively a high-pressure side, a medium-pressure side and a low-pressure side bridge arm, and the three converter valve groups are respectively a high-pressure side, a medium-pressure side and a low-pressure side valve group;

[0008] The energy transfer bridge arm is connected in parallel with the high-voltage side and medium-voltage side bridge arms, and the energy transfer bridge arm is located between the high-voltage side and medium-voltage side bridge arms, and the low-voltage side bridge arm is connected in parallel at both ends of the lower bridge arm;

[0009] One end of the high-pressure side and medium-pressure side valve groups are connected to the input end of the energy transfer bridge arm, the other ends of the high-pressure side and medium-pressure side valve groups are connected to the input ends of the high-pressure side and medium-pressure side bridge arms respectively, and the two ends of the low-pressure side valve group are connected to the input end of the low-pressure side bridge arm and the input end of the lower bridge arm respectively.

[0010] Furthermore, the structures of the above-mentioned energy buffer bridge arm and active filter bridge arm are the same, and each bridge arm includes multiple half-bridge sub-modules and an inductor. The multiple half-bridge sub-modules are connected in series, one end of the inductor is connected to the output end of the tailmost half-bridge sub-module, and the other end of the inductor serves as the output end of the bridge arm, and the input end of the frontmost half-bridge sub-module serves as the input end of the bridge arm.

[0011] Furthermore, the above-mentioned half-bridge submodule includes two IGBT switching tubes connected in series and a capacitor connected in parallel at the ends of the two IGBT switching tubes.

[0012] Furthermore, the above-mentioned converter valve group includes multiple converter valves connected in series.

[0013] Furthermore, the above-mentioned converter valve is an IGBT anti-parallel diode, an IGCT switch tube or a bidirectional thyristor.

[0014] The control method of the three-port high-voltage DC-DC converter with an active filtering bridge arm comprises:

[0015] Charging control:

[0016] Open the high-pressure side valve group S 1H The medium-voltage and low-voltage side valve groups are kept closed, and the sum of the output voltages of all half-bridge sub-modules is adjusted so that the current flowing through the energy transfer bridge arm is a trapezoidal wave, thereby synchronously charging the half-bridge sub-modules in the energy transfer bridge arm;

[0017] Discharge control:

[0018] Open the medium pressure side valve group S 2MAnd low pressure side valve group S 2L , and keep the high pressure side valve group S 1H Shut down and adjust the sum of the output voltages of all half-bridge sub-modules so that the current flowing through the energy transfer bridge arm is a trapezoidal wave. The half-bridge sub-modules in the lower bridge arm discharge to the low-voltage side port, and all half-bridge sub-modules in the energy transfer bridge arm discharge to the medium-voltage side port.

[0019] Furthermore, the charging control includes:

[0020] Open the high-pressure side valve group S 1H And keep the medium-pressure side and low-pressure side valve groups closed;

[0021] Adjust the sum of the output voltages of all half-bridge submodules in the upper bridge arm A1 to U A1 -L1×I1÷T c The sum of the output voltages of all half-bridge submodules in the lower bridge arm A2 is U H -U A1 -L2×I1÷T c , so that the current i flowing through the upper bridge arm A1 A1 and the current i of the lower bridge arm A2 A2 All are I1÷T c The speed changes from 0 to I1, adjusting the high voltage side bridge arm A H The sum of the output voltages of all half-bridge submodules is U H +L H ×I1÷T c , so that the current flows through the high-voltage side bridge arm A H The current i AH I1÷T c The speed from I H Change to I H -I1;

[0022] When the current i flowing through the upper bridge arm A1 A1 and the current i of the lower bridge arm A2 A2 When it rises to I1, the sum of the output voltages of all half-bridge submodules in the upper bridge arm A1 is adjusted to U A1 , adjust the sum of the output voltages of all half-bridge submodules in the lower bridge arm A2 to U H -U A1 , so that the current i flowing through the upper bridge arm A1 A1 and the current i of the lower bridge arm A2 A2 Maintain both at I1 and adjust the high voltage side bridge arm A H The sum of the output voltages of all half-bridge submodules in the H , flows through the high voltage side bridge arm A H The current is maintained at I H -I1;

[0023] Among them, UA1 is the terminal voltage of the upper bridge arm A1, I1 is the current flowing through the energy transfer bridge arm during charging, I H is the high voltage side current, L1 and L2 are the bridge arm reactances of the upper bridge arm A1 and the lower bridge arm A2 respectively, U H is the DC voltage of the high-voltage side port, L H High voltage side bridge arm A H The bridge arm reactance, T c It is the time it takes for the current flowing through the energy transfer bridge arm to rise or fall.

[0024] Furthermore, in the charging control stage, after a period of continuous charging, the sum of the output voltages of all half-bridge submodules in the upper bridge arm A1 is adjusted to U A1 +L1×I1÷T c , adjust the sum of the output voltages of all half-bridge submodules in the lower bridge arm A2 to U H -U A1 +L2×I1÷T c , so that the current i flowing through the upper bridge arm A1 A1 and the current i of the lower bridge arm A2 A2 All are I1÷T c The speed changes from I1 to 0, and the sum of the output voltages of the half-bridge submodules in the upper bridge arm A1 becomes U M -U L , the sum of the output voltages of the half-bridge submodules in the lower bridge arm A2 becomes U L ;

[0025] Adjust the high voltage side bridge arm A H The sum of the output voltages of all half-bridge submodules is U H -L H ×I1÷T c , high voltage side bridge arm A H The current i AH I1÷T c The speed from I H -I1 changes to I H ;

[0026] Among them, U M and U L are the DC voltages of the medium voltage side port and the low voltage side port respectively.

[0027] Furthermore, the above-mentioned discharge control includes:

[0028] Open the medium pressure side valve group S 2M And low pressure side valve group S 2L , and keep the high pressure side valve group S 1H Shutdown;

[0029] Adjust the sum of the output voltages of all half-bridge submodules in the upper bridge arm A1 to UM -U L +L1×I A1 ÷T c The sum of the output voltages of all half-bridge submodules in the lower bridge arm A2 is U L +L2×I A2 ÷T c , so that the current i flowing through the upper bridge arm A1 A1 Take I A1 ÷T c The speed changes from 0 to -I A1 , the current i flowing through the lower bridge arm A2 A2 Take I A2 ÷T c The speed changes from 0 to -I A2 , adjust the low voltage side bridge arm A L The sum of the output voltages of all half-bridge submodules is U L -L L ×(I A2 -I A1 )÷T c , so that the current flows through the low-voltage side bridge arm A L The current i AL With (I A2 -I A1 )÷T c Speed ​​from -I L Change to I A2 -I A1 -I L , adjust the medium voltage side bridge arm A M The sum of the output voltages of all half-bridge submodules is U M -L M ×I A1 ÷T c , so that it flows through the medium voltage side bridge arm A M The current i AM Take I A1 ÷T c Speed ​​from -I M Change to I A1 -I M ;

[0030] When the current flowing through the upper arm A1 rises to -I A1 When the output voltage of all half-bridge submodules in the upper bridge arm A1 is adjusted to U M -U L , so that the current i flowing through the upper bridge arm A1 A1 Maintain at -I A1 , when the current flowing through the lower bridge arm A2 rises to -I A2 When the output voltage of all half-bridge submodules in the lower bridge arm A2 is adjusted to U L, so that the current i flowing through the lower bridge arm A2 A2 Maintain at -I A2 , adjust the low voltage side bridge arm A L The sum of the output voltages of all half-bridge submodules is U L , so that the current flows through the low-voltage side bridge arm A L The current i AL Maintain at I A2 -I A1 -I L , medium voltage side bridge arm A M The sum of the output voltages of all half-bridge submodules is U M , so that it flows through the medium voltage side bridge arm A M The current i AM Maintain at I A1 -I M ;

[0031] Among them, I A1 and I A2 are the currents flowing through the energy buffer bridge arms A1 and A2 during discharge, L L Low voltage side bridge arm A L The bridge arm reactance, I M and I L They are the currents of the medium voltage side port and the low voltage side port respectively.

[0032] Furthermore, in the discharge control stage, after a period of continuous discharge, the sum of the output voltages of all half-bridge submodules in the upper bridge arm A1 is adjusted to U M -U L -L1×I A1 ÷T c , adjust the sum of the output voltages of all half-bridge submodules in the lower bridge arm A2 to U L -L2×I A2 ÷T c , so that the current i flowing through the upper bridge arm A1 A1 Take I A1 ÷T c Speed ​​from -I A1 Changes to 0, the current i of the lower bridge arm A2 A2 Take I A2 ÷T c Speed ​​from -I A2 The sum of the output voltages of the half-bridge submodules in the upper bridge arm A1 becomes U A1 , the sum of the output voltages of the bridge submodules in the lower bridge arm A2 becomes U H -U A1 ;

[0033] Adjust the low voltage side bridge arm A L The sum of the output voltages of all half-bridge submodules is U L+L L ×(I A2 -I A1 )÷T c , so that the current flows through the low-voltage side bridge arm A L The current i AL With (I A2 -I A1 )÷T c The speed from I A2 -I A1 -I L Change to -I L , adjust the medium voltage side bridge arm A M The sum of the output voltages of all half-bridge submodules u AM Control is U M +L M ×I A1 ÷T c , so that it flows through the medium voltage side bridge arm A M The current i AM Take I A1 ÷T c The speed from I A1 -I M Change to -I M .

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] The three-port high-voltage DC-DC converter with an active filtering bridge arm described in this invention has the advantages of eliminating the need for transformers and filter inductors, eliminating the need for AC voltage injection into the bridge arm, and requiring a small number of components. It enables energy transfer between three ports with different DC voltage levels and is suitable for interconnecting three DC systems with different voltage levels. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The schematic diagram of the three-port high-voltage DC-DC converter with active filtering bridge arm;

[0037] Figure 2 This is the circuit schematic diagram of the converter valve;

[0038] Figure 3 This is the circuit schematic diagram of replacing the IGBT switch tube in the converter valve with a bidirectional thyristor;

[0039] Figure 4 This is a circuit schematic diagram of replacing the IGBT switch tube in the converter valve with an IGCT switch tube;

[0040] Figure 5 This is the circuit schematic diagram of the energy buffer bridge arm;

[0041] Figure 6Schematic diagram of the DC-DC converter topology current working waveform;

[0042] Figure 7 Schematic diagram of the DC-DC converter topology voltage operating waveform. DETAILED DESCRIPTION

[0043] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only 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 making creative work are within the scope of protection of the present invention. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other in the absence of conflict.

[0044] Specific implementation method 1: refer to Figures 1 to 5 Specifically describing this embodiment, the three-port high-voltage DC-DC converter with active filtering bridge arms described in this embodiment includes: two energy buffer bridge arms A1 and A2 for transferring energy, three active filtering bridge arms A M 、A L 、A H , and three converter valve groups S 1H 、S 2M 、S 2L .

[0045] Energy buffer bridge arms A1 and A2 are connected in series to form an energy transfer bridge arm. Energy buffer bridge arm A1 is located at the input end, and energy buffer bridge arm A2 is located at the output end. H and A M are connected in parallel, and the energy transfer bridge arm is located at A H and A M Between, active filter bridge arm A L Connected in parallel at both ends of the energy buffer bridge arm A2. 1H and S 2M One end of each is connected to the input end of the energy buffer bridge arm A1, and the converter valve group S 1H and S 2M The other end of the active filter bridge arm A H and A M The input end is connected to the converter valve group S 2L The two ends of the active filter bridge arm A are connected L and the input end of the energy buffer bridge arm A2.

[0046] All energy buffer bridge arms and active filter bridge arms have the same structure. Each bridge arm consists of multiple half-bridge sub-modules and a bridge arm reactor in series. The circuit structure of multiple half-bridge sub-modules is the same. Each half-bridge sub-module includes two IGBT switches in series and a capacitor connected in parallel at the ends of the two IGBT switches. Figure 5 The output of each half-bridge submodule is connected to the input of the next half-bridge submodule. The input of the first half-bridge submodule serves as the input of the bridge arm. The output of the last half-bridge submodule is connected to one end of the bridge arm reactor, and the other end of the bridge arm reactor serves as the output of the bridge arm.

[0047] like Figure 2 、 Figure 3 and Figure 4 As shown, the structures of the three converter valve groups are the same. Each converter valve group includes multiple converter valves connected in series, and the converter valves are IGBT anti-parallel diodes, IGCT switching tubes or bidirectional thyristors.

[0048] Specific implementation method 2: refer to Figure 6 and Figure 7 Specifically describing this embodiment, the control method of the three-port high-voltage DC-DC converter with an active filtering bridge arm described in this embodiment includes:

[0049] Step 1: Trigger the opening of the high-pressure side converter valve group S 1H , keep the other two converter valve groups closed, then the energy buffer bridge arms A1 and A2 are connected to the high-voltage side port as a whole, and the high-voltage side current I H Flowing through the high-pressure side converter valve S 1H And energy buffer bridge arms A1, A2, filter bridge arm A H The current is responsible for compensating the difference between the high-voltage side current and the energy buffer bridge arm A1, A2 current, that is, I H -I1. By controlling the sum of the output voltages of all half-bridge sub-modules, the currents of the energy buffer bridge arms A1 and A2 are controlled to be trapezoidal waves, and the half-bridge sub-modules in the energy buffer bridge arms are charged synchronously. In this process, the energy buffer bridge arms A1 and A2 jointly bear the DC voltage U of the high-voltage side port. H , filter bridge arm A H Maintain the continuity of voltage and current at the high-voltage side port. Filter bridge arm A M 、A L They are connected in parallel with the medium voltage side and the low voltage side respectively. Since the energy buffer bridge arm is not connected with the medium voltage side and the low voltage side at this time, the filter bridge arm A M 、A L Maintain continuity of voltage and current at the medium voltage side and low voltage side ports respectively.

[0050] The specific method is as follows:

[0051] (1) Trigger the opening of the high-pressure side converter valve group S 1H At the same time, the sum of the output voltages of all half-bridge submodules in the energy buffer bridge arm A1 is u A1 Control is U A1 -L1×I1÷T c , the sum of the output voltages of all half-bridge submodules in the energy buffer bridge arm A2 is u A2 Control is U H -U A1 -L2×I1÷T c , at this time the current i flowing through the energy buffer bridge arm A1 A1 and the current i of the energy buffer bridge arm A2 A2 All are I1÷T c The speed changes from 0 to I1. Filter bridge arm A H The sum of the output voltages of all half-bridge submodules u H Control is U H +L H ×I1÷T c , then it flows through the filter bridge arm A H The current i AH I1÷T c The speed from I H Change to I H -I1 is used to compensate the current difference between the high voltage side and the energy buffer bridge arm. c is the current rise or fall time of the current trapezoidal wave, L1 and L2 are the bridge arm reactances of the energy buffer bridge arms A1 and A2 respectively, L H Filter bridge arm A H The bridge arm reactance, U A1 is the terminal voltage of the energy buffer bridge arm A1, and I1 is the current flowing through the energy buffer bridge arms A1 and A2 during charging.

[0052] (2) When the current i flowing through the energy buffer bridge arm A1 A1 and the current i of the energy buffer bridge arm A2 A2 When it rises to I1, the output voltage u of all half-bridge submodules in the energy buffer bridge arm A1 is A1 Control is U A1 , the sum of the output voltages u of all half-bridge submodules in the energy buffer bridge arm A2 A2 Control is U H -U A1 , then the current i flowing through the energy buffer bridge arm A1 A1 and the current i of the energy buffer bridge arm A2 A2 All are maintained at I1, during which time the filter bridge arm A H The sum of the output voltages of all half-bridge submodules u AH Keep UH , flows through filter bridge arm A H The current i AH Maintain at I H -I1.

[0053] (3) After continuous charging for a period of time, the sum of the output voltages of all half-bridge submodules in the energy buffer bridge arm A1 is u A1 Control is U A1 +L1×I1÷T c , the sum of the output voltages u of all half-bridge submodules in the energy buffer bridge arm A2 A2 Control is U H -U A1 +L2×I1÷T c , at this time the current i flowing through the energy buffer bridge arm A1 A1 and the current i of the energy buffer bridge arm A2 A2 All are I1÷T c The speed changes from I1 to 0, and then after a period of time, the converter valve group S 1H Then the sum of the output voltages of the energy buffer bridge arm A1 half-bridge submodules gradually becomes U M -U L The sum of the output voltages of the half-bridge submodules in the energy buffer bridge arm A2 gradually becomes U L , prepare for step 2 to open the converter valve at zero voltage. During this period, the filter bridge arm A H The sum of the output voltages of all half-bridge submodules u AH Control is U H -L H ×I1÷T c , flows through filter bridge arm A H The current i AH I1÷T c The speed from I H -I1 changes to I H .

[0054] (4) During this process, the filter bridge arm A M The sum of the output voltages of all half-bridge submodules u AM Control is U M , flows through filter bridge arm A M The current i AM Maintain at -I M , filter bridge arm A L The sum of the output voltages of all half-bridge submodules u AL Control is U L , flows through filter bridge arm A L The current i AL Maintain at -I L, respectively, to maintain the continuity of voltage and current at the medium voltage side and low voltage side ports. M and I L They are the currents of the medium voltage side port and the low voltage side port respectively.

[0055] Step 2: Trigger the opening of the medium-voltage side converter valve group S 2M and low-pressure side converter valve group S 2L , keep the high-pressure side converter valve group S 1H If it is turned off, then the energy buffer bridge arm A2 is connected to the low-voltage side port, and the energy buffer bridge arms A1 and A2 are connected to the medium-voltage side port. The low-voltage side current I L Flowing through the low-pressure side converter valve group S 2L and energy buffer bridge arm A2, filter bridge arm A L The current is responsible for compensating the low-voltage side current I L and the current I of the energy buffer bridge arm A2 A2 Subtract the current I of the energy buffer bridge arm A1 A1 The difference, that is (I A2 -I A1 )-I L . Medium voltage side current I M Flowing through the medium pressure side converter valve S 2M And energy buffer bridge arms A1, A2, filter bridge arm A M The current is responsible for compensating the medium voltage side current I M and the current I of the energy buffer bridge arm A1 A1 The difference, that is, I A1 -I M By controlling the sum of the output voltages of all half-bridge submodules, the currents of the energy buffer bridge arms A1 and A2 are controlled to be trapezoidal waves. The half-bridge submodules in the energy buffer bridge arm A2 discharge to the low-voltage side port. During this process, the energy buffer bridge arm A2 bears the DC voltage U of the low-voltage side port. L The half-bridge submodules in the energy buffer bridge arms A1 and A2 discharge to the medium voltage side port. During this process, the energy buffer bridge arms A1 and A2 bear the DC voltage U of the medium voltage side port. M , then the voltage borne by the energy buffer bridge arm A1 is U M -U L , filter bridge arm A L 、A M Ensure the current continuity of the low-voltage side port and the medium-voltage side port. H In parallel with the high voltage side, since the energy buffer bridge arm is not connected to the high voltage side at this time, the filter bridge arm A H Maintain the continuity of voltage and current at the high-voltage side port. The specific methods are as follows:

[0056] (1) Trigger the opening of the second converter valve S 2L 、The third converter valve S2M , keep the first converter valve closed S 1H At the same time, the sum of the output voltages of all half-bridge submodules of the energy buffer bridge arm A1 is u A1 Control is U M -U L +L1×I A1 ÷T c , the sum of the output voltages of all half-bridge submodules of the energy buffer bridge arm A2 u A2 Control is U L +L2×I A2 ÷T c , at this time the current i flowing through the energy buffer bridge arm A1 A1 Take I A1 ÷T c The speed changes from 0 to -I A1 , the current i of the energy buffer bridge arm A2 A2 Take I A2 ÷T c The speed changes from 0 to -I A2 During this period, filter bridge arm A L The sum of the output voltages of all half-bridge submodules u AL Control is U L -L L ×(I A2 -I A1 )÷T c , flows through filter bridge arm A L The current i AL With (I A2 -I A1 )÷T c Speed ​​from -I L Change to I A2 -I A1 -I L , filter bridge arm A M The sum of the output voltages of all half-bridge submodules u AM Control is U M -L M ×I A1 ÷T c , flows through filter bridge arm A M The current i AM Take I A1 ÷T c Speed ​​from -I M Change to I A1 -I M ; where T c is the current rise or fall time of the current trapezoidal wave, L L Filter bridge arm A L The bridge arm reactance, I A1 and I A2They are the currents flowing through the energy buffer bridge arms A1 and A2 during discharge respectively.

[0057] (2) When the current flowing through the energy buffer bridge arm A1 rises to -I A1 When the output voltage of all half-bridge submodules is u A1 Control is U M -U L , then the current i flowing through the energy buffer bridge arm A1 A1 Maintain at -I A1 ; When the current flowing through the energy buffer bridge arm A2 rises to -I A2 When the output voltage of all half-bridge submodules is u A2 Control is U L , then the current i flowing through the energy buffer bridge arm A2 A2 Maintain at -I A2 ; During this period, filter bridge arm A L The sum of the output voltages of all half-bridge submodules u AL Control is U L , flows through filter bridge arm A L The current i AL Maintain at I A2 -I A1 -I L ; Filter bridge arm A M The sum of the output voltages of all half-bridge submodules u AM Control is U M , flows through filter bridge arm A M The current i AM Maintain at I A1 -I M ;

[0058] (3) After a period of continuous discharge, the sum of the output voltages of all half-bridge submodules of the energy buffer bridge arm A1 is maintained at u A1 Equal to U M -U L -L1×I A1 ÷T c , maintain the sum of the output voltages u of all half-bridge submodules of the energy buffer bridge arm A2 A2 Equal to U L -L2×I A2 ÷T c , at this time the current i flowing through the energy buffer bridge arm A1 A1 Take I A1 ÷T c Speed ​​from -I A1 Changes to 0, the current i of the energy buffer bridge arm A2 A2 Take I A2 ÷T c Speed ​​from -I A2Changes to 0, and then after a period of time, the converter valve S 2L 、S 2M The reliable shutdown of the energy buffer bridge arm A1 half-bridge sub-module gradually changes to U A1 The sum of the output voltages of the energy buffer bridge arm A2 half-bridge submodules gradually becomes U H -U A1 , prepare for the zero voltage opening of the converter valve in step 1 of the next cycle. During this period, the filter bridge arm A L The sum of the output voltages of all half-bridge submodules u AL Control is U L +L L ×(I A2 -I A1 )÷T c , flows through filter bridge arm A L The current i AL With (I A2 -I A1 )÷T c The speed from I A2 -I A1 -I L Change to -I L , filter bridge arm A M The sum of the output voltages of all half-bridge submodules u AM Control is U M +L M ×I A1 ÷T c , flows through filter bridge arm A M The current i AM Take I A1 ÷T c The speed from I A1 -I M Change to -I M ;

[0059] (4) During this process, the filter bridge arm A H The sum of the output voltages of all half-bridge submodules u AH Control is U H , flows through filter bridge arm A H The current i AH Maintain at I H , keep the voltage and current of the high-voltage side port continuous.

[0060] (5) Relevant parameter representation

[0061] The active filter bridge arm is configured to keep the current flowing through the DC port side smooth and continuous. In each operating cycle, the energy increment of the SM capacitor should be zero. Therefore, the integral of the power of the energy buffer bridge arm and the filter bridge arm in one cycle should be zero, that is:

[0062] Power of energy buffer bridge arm A1

[0063] Power of energy buffer bridge arm A2

[0064] Filter bridge arm A H Power

[0065] Filter bridge arm A M Power

[0066] Filter bridge arm A L Power

[0067] Where, T h is the operating period of the active filter CET multi-port DC / DC converter, T c is the rise or fall time, T1 is the charging or discharging time of the energy buffer bridge arm A1, and T2 is the charging or discharging time of the energy buffer bridge arm A2. According to the above formula and T=T1+T2+4T c +2T d , amplitude I1, I A1 , I A2 and U A1 Expressed as:

[0068]

[0069]

[0070] The above two steps are repeated. The energy buffer bridge arms A1 and A2 in the topology are alternately connected to three different DC ports through the above method. The filter bridge arm A H 、A L and A M It always maintains connection with the high-voltage side, low-voltage side and medium-voltage side respectively, and is responsible for compensating the current difference between the DC port and the energy buffer bridge arm. The charging and discharging power of the half-bridge sub-module capacitors in the energy buffer bridge arm and the filter bridge arm are equal, and the energy stored in the capacitors in the converter is kept balanced as a whole, thereby realizing the mutual energy transfer between the DC ports of three different DC voltage levels.

[0071] In summary, the present invention discloses a three-port high-voltage DC-DC converter with active filtering bridge arms, which is composed of two energy buffer bridge arms, three active filtering bridge arms, and three converter valves. Through the coordinated control of the converter valves and bridge arms, the energy buffer bridge arms A1 and A2 in this topology are alternately connected to three different DC ports through the above method, and the filter bridge arm A H 、A L and A M The three-port high-voltage DC-DC converter with an active filtering bridge arm can achieve energy transfer between three DC ports with different DC voltage levels without the need for an AC transformer. It is lightweight, compact, and highly efficient, and is suitable for interconnecting three DC systems with different voltage levels.

[0072] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the invention. It should be understood that many modifications may be made to the illustrative embodiments, and that other arrangements may be devised, without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in ways other than those described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be used in conjunction with other described embodiments.

Claims

1. A control method for a three-port high-voltage DC-DC converter with an active filtering bridge arm, the three-port high-voltage DC-DC converter with an active filtering bridge arm comprising: Energy transfer bridge arm, three active filter bridge arms and three converter valve groups; The energy transfer bridge arm includes two energy buffer bridge arms connected in series, the two energy buffer bridge arms are respectively an upper bridge arm and a lower bridge arm, the three active filter bridge arms are respectively a high-pressure side, a medium-pressure side and a low-pressure side bridge arm, and the three converter valve groups are respectively a high-pressure side, a medium-pressure side and a low-pressure side valve group; The energy transfer bridge arm is connected in parallel with the high-voltage side and medium-voltage side bridge arms, and the energy transfer bridge arm is located between the high-voltage side and medium-voltage side bridge arms, and the low-voltage side bridge arm is connected in parallel at both ends of the lower bridge arm; One end of the high-pressure side and medium-pressure side valve groups are both connected to the input end of the energy transfer bridge arm, the other ends of the high-pressure side and medium-pressure side valve groups are respectively connected to the input ends of the high-pressure side and medium-pressure side bridge arms, and the two ends of the low-pressure side valve group are respectively connected to the input end of the low-pressure side bridge arm and the input end of the lower bridge arm; the structures of the energy buffer bridge arm and the active filter bridge arm are the same, each bridge arm includes multiple half-bridge sub-modules and an inductor, the multiple half-bridge sub-modules are connected in series, one end of the inductor is connected to the output end of the half-bridge sub-module at the rear end, the other end of the inductor serves as the output end of the bridge arm, and the input end of the front-end half-bridge sub-module serves as the input end of the bridge arm; The invention is characterized in that a control method of a three-port high-voltage DC-DC converter with an active filtering bridge arm comprises: Charging control: Open the high-pressure side valve group The medium-voltage and low-voltage side valve groups are kept closed, and the sum of the output voltages of all half-bridge sub-modules is adjusted so that the current flowing through the energy transfer bridge arm is a trapezoidal wave, thereby synchronously charging the half-bridge sub-modules in the energy transfer bridge arm; Discharge control: Open the medium pressure side valve group and low-pressure side valve group , and maintain the high pressure side valve group Shut down and adjust the sum of the output voltages of all half-bridge sub-modules so that the current flowing through the energy transfer bridge arm is a trapezoidal wave. The half-bridge sub-modules in the lower bridge arm discharge to the low-voltage side port, and all half-bridge sub-modules in the energy transfer bridge arm discharge to the medium-voltage side port.

2. The control method of a three-port high-voltage DC-DC converter with an active filtering bridge arm according to claim 1, characterized in that: The half-bridge submodule includes two IGBT switching tubes connected in series and a capacitor connected in parallel at the ends of the two IGBT switching tubes.

3. The control method of a three-port high-voltage DC-DC converter with an active filtering bridge arm according to claim 1 or 2, characterized in that: The converter valve group includes a plurality of converter valves connected in series.

4. The control method of a three-port high-voltage DC-DC converter with an active filtering bridge arm according to claim 3, characterized in that: The converter valve is an IGBT anti-parallel diode, an IGCT switch tube or a bidirectional thyristor.

5. The control method of a three-port high-voltage DC-DC converter with an active filtering bridge arm according to claim 1, characterized in that: The charging control includes: Open the high-pressure side valve group And keep the medium-pressure side and low-pressure side valve groups closed; Adjust the upper bridge arm The sum of the output voltages of all half-bridge submodules is , lower bridge arm The sum of the output voltages of all half-bridge submodules is , so that the current flowing through the upper arm Current and lower bridge arm Current All The speed changes from 0 to , adjust the high voltage side bridge arm The sum of the output voltages of all half-bridge submodules is , so that the current flows through the high-voltage side bridge arm Current by The speed from Change to ; When the flow passes through the upper arm Current and lower bridge arm Current Rise to When adjusting the upper bridge arm The sum of the output voltages of all half-bridge submodules is , adjust the lower bridge arm The sum of the output voltages of all half-bridge submodules is , so that the current flowing through the upper arm Current and lower bridge arm Current Maintained , adjust the high voltage side bridge arm The sum of the output voltages of all half-bridge submodules in the , flows through the high voltage side bridge arm The current is maintained at ; in, Upper arm The terminal voltage, is the current flowing through the energy transfer bridge arm during charging, is the high voltage side current, and Upper arm and lower bridge arm The bridge arm reactance, is the DC voltage at the high-voltage side port, High-voltage side bridge arm The bridge arm reactance, It is the time it takes for the current flowing through the energy transfer bridge arm to rise or fall.

6. The control method of the three-port high-voltage DC-DC converter with active filtering bridge arm according to claim 5, characterized in that: In the charging control stage, after continuous charging for a period of time, adjust the upper bridge arm The sum of the output voltages of all half-bridge submodules is , adjust the lower bridge arm The sum of the output voltages of all half-bridge submodules is , so that the current flowing through the upper arm Current and lower bridge arm Current All The speed from Change to 0, upper arm The sum of the output voltages of the half-bridge submodules becomes , lower bridge arm The sum of the output voltages of the half-bridge submodules becomes ; Adjust the high-voltage side bridge arm The sum of the output voltages of all half-bridge submodules is , high voltage side bridge arm Current by The speed from Changes to ; in, and are the DC voltages of the medium voltage side port and the low voltage side port respectively.

7. The control method of a three-port high-voltage DC-DC converter with an active filtering bridge arm according to claim 6, characterized in that: The discharge control includes: Open the medium pressure side valve group and low-pressure side valve group , and maintain the high pressure side valve group Shutdown; Adjust the upper bridge arm The sum of the output voltages of all half-bridge submodules is , lower bridge arm The sum of the output voltages of all half-bridge submodules is , so that the current flowing through the upper arm Current by The speed changes from 0 to , flows through the lower bridge arm Current by The speed changes from 0 to , adjust the low voltage side bridge arm The sum of the output voltages of all half-bridge submodules is , so that the current flows through the low-voltage side bridge arm Current by The speed from Changes to , adjust the medium voltage side bridge arm The sum of the output voltages of all half-bridge submodules is , so that the current flows through the medium voltage side bridge arm Current by The speed from Changes to ; When the flow passes through the upper arm The current rises to When adjusting the upper bridge arm The sum of the output voltages of all half-bridge submodules is , so that the current flowing through the upper arm Current Maintain , when flowing through the lower bridge arm The current rises to When adjusting the lower bridge arm The sum of the output voltages of all half-bridge submodules is , so that the current flows through the lower arm Current Maintain , adjust the low voltage side bridge arm The sum of the output voltages of all half-bridge submodules is , so that the current flows through the low-voltage side bridge arm Current Maintain , medium voltage side bridge arm The sum of the output voltages of all half-bridge submodules is , so that the current flows through the medium voltage side bridge arm Current Maintain ; in, and The energy flowing through the buffer bridge arm during discharge is and The current, Low voltage side bridge arm The bridge arm reactance, and They are the currents of the medium voltage side port and the low voltage side port respectively.

8. The control method of a three-port high-voltage DC-DC converter with an active filtering bridge arm according to claim 7, characterized in that: In the discharge control stage, after a period of continuous discharge, adjust the upper bridge arm The sum of the output voltages of all half-bridge submodules is , adjust the lower bridge arm The sum of the output voltages of all half-bridge submodules is , so that the current flowing through the upper arm Current by The speed from Change to 0, lower bridge arm Current by The speed from Change to 0, upper arm The sum of the output voltages of the half-bridge submodules becomes , lower bridge arm The sum of the output voltages of the bridge submodules becomes ; Adjust the low-voltage side bridge arm The sum of the output voltages of all half-bridge submodules is , so that the current flows through the low-voltage side bridge arm Current by The speed from Changes to , adjust the medium voltage side bridge arm The sum of the output voltages of all half-bridge submodules Control , so that the current flows through the medium voltage side bridge arm Current by The speed from Changes to .

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