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

Abstract

The invention discloses a three-port high-voltage DC-DC converter with an active filtering bridge arm and a control method thereof, and relates to the field of power electronics. The invention aims to solve the problems that a multi-port topological structure needs a high-capacity magnetic element and the transmission efficiency is low. Two energy buffer bridge arms are connected in series; the energy transfer bridge arm is connected in parallel with the high-voltage-side and medium-voltage-side bridge arms; the low-voltage-side bridge arms are connected in parallel with two ends of the lower bridge arm; one ends of the high-pressure side valve group and the medium-pressure side valve group are connected with the energy transfer bridge arm, the other ends are respectively connected with the high-pressure side bridge arm and the medium-pressure side bridge arm, and two ends of the low-pressure side valve group are respectively connected with the low-pressure side bridge arm and the lower bridge arm. And the valve group is adjusted to be switched on or switched off, and the sum of output voltages of all half-bridge sub-modules is adjusted, so that the current flowing through the energy transfer bridge arm is trapezoidal wave, and charging or discharging is realized.

Description

Technical Field

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

[0002] With the continuous breakthroughs in power electronic devices and equipment technology, flexible DC transmission technology based on voltage source converters has developed rapidly. Flexible DC transmission has the characteristics of fast and independent control of active power and reactive power and flexible operation mode. It is a key technology to solve the large-scale consumption of new energy and optimize regional energy utilization. At the current stage, DC / DC converters are mainly used in low / medium voltage applications, which are difficult to expand to the power range of hundreds of kilovolts and megawatts. Therefore, many recent studies have focused on studying new DC / DC converter topologies for high-voltage applications.

[0003] However, due to factors such as the scale of renewable energy, the current high-voltage DC transmission lines have different voltage levels such as ±320kV, ±420kV, ±500kV, ±800kV and ±1100kV, so the expansion of its scale requires the use of DC transformers for voltage conversion. Unlike the AC transformers in the AC power grid, the DC power grid cannot use the principle of electromagnetic induction and needs to use 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 the DC power 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 lower volume. However, there are currently few feasible technical solutions. The patent "Ultra-high transformation ratio multi-port DC converter topology based on single-phase MMC" with authorization announcement number CN114362542A proposes to use multi-port independent input and series output solutions, and use MMC sub-module multi-port input to achieve power aggregation, but this multi-port topology requires large-capacity magnetic components, resulting in high construction costs and large volume and weight. The patent "A multi-port back-to-back DC-DC converter" with publication number CN104022499A 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, but the topology uses two-stage power transmission of the intermediate AC transformer, with low transmission efficiency, and large volume and cost. Summary of the invention

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

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

[0007] The energy transfer bridge arm comprises 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 high-pressure side, medium-pressure side and low-pressure side bridge arms, and the three converter valve groups are respectively high-pressure side, medium-pressure side and low-pressure side valve groups;

[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 to 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 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.

[0010] Furthermore, the structures of the energy buffer bridge arm and the 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 half-bridge sub-module at the tail end, and the other end of the inductor serves as the output end of the bridge arm, and the input end of the half-bridge sub-module at the front end serves as the input end of the bridge arm.

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

[0012] Furthermore, the above-mentioned converter valve group includes a plurality of 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 active filtering bridge arm comprises:

[0015] Charging control:

[0016] Open the high pressure side valve group S 1H The valve groups on the medium-voltage side and the low-voltage side are kept closed, and the sum of the output voltages of all the 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, 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 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 output voltage 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 A is the high voltage side bridge arm 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 continuous charging for a period of time, 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 output voltage 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 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 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 Shut down;

[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 The 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 the current flows through the medium voltage side bridge arm A M The current i AM Take I A1 ÷T c The speed from -I M Change to I A1 -I M ;

[0030] When the current flowing through the upper bridge 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 the current 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 The 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 output voltage 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 The speed from -I A1 changes to 0, the current i of the lower bridge arm A2 A2 Take I A2 ÷T c The 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 the current 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 active filtering bridge arm of the present invention has the advantages of not requiring a transformer and filtering inductor, not requiring AC voltage to be injected into the bridge arm, and requiring a small number of components. It can realize energy transfer between three ports with different DC voltage levels, and is suitable for realizing the interconnection of three DC systems with different voltage levels. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0037] Figure 2 It is the circuit principle diagram of the converter valve;

[0038] Figure 3 The schematic diagram of the circuit in which the IGBT switch tube in the converter valve is replaced by a bidirectional thyristor;

[0039] Figure 4 The schematic diagram of the circuit in which the IGBT switch tube in the converter valve is replaced by the IGCT switch tube;

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

[0041] Figure 6It is a schematic 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 described embodiments are only part of the embodiments of the present invention, rather than 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 belong to 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 without 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] The energy buffer bridge arms A1 and A2 are connected in series to form an energy transfer bridge arm. The energy buffer bridge arm A1 is located at the input end, and the 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 is connected to 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] The structures of all energy buffer bridge arms and active filter bridge arms are the same. Each bridge arm is composed of multiple half-bridge sub-modules and a bridge arm reactor in series. The circuit structures of multiple half-bridge sub-modules are the same. Each half-bridge sub-module includes two IGBT switch tubes connected in series and a capacitor connected in parallel at the ends of the two IGBT switch tubes. Figure 5 The output end of each half-bridge submodule is connected to the input end of the next half-bridge submodule, the input end of the first half-bridge submodule serves as the input end of the bridge arm, the output end 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 end 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, and each converter valve group includes a plurality of converter valves connected in series, and the converter valves are IGBT anti-parallel diodes, IGCT switch 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 active filtering bridge arm described in this embodiment includes:

[0049] Step 1: Trigger and open 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 current of the energy buffer bridge arms A1 and A2, 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 Keep the voltage and current of the high-voltage side port continuous. 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 Keep the voltage and current continuity of the medium voltage side and low voltage side ports respectively.

[0050] The specific method is as follows:

[0051] (1) Triggering the opening of the high-pressure side converter valve group S 1H , and 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 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, 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 is the 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 a period of continuous charging, the sum of the output voltages of all half-bridge sub-modules 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 I1÷T c The speed changes from I1 to 0, and then after a period of time, the conversion valve group S 1H Then the sum of the output voltages of the half-bridge submodules of the energy buffer bridge arm A1 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 the zero voltage opening of the converter valve in step 2. 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, 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 keep the voltage and current continuity of 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 Shutdown, then the energy buffer bridge arm A2 is connected to the low-voltage side port, the energy buffer bridge arms A1 and A2 are connected to the medium-voltage side port, and 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 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 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. In 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. In 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. Filter bridge arm A 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 Keep the voltage and current of the high-voltage side port continuous. The specific method is 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 , and 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 The 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 The 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 is the 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 sub-modules is 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 sub-modules is 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 sub-modules 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 The speed from -I A1 changes to 0, the current i of the energy buffer bridge arm A2 A2 Take I A2 ÷T c The speed from -I A2Changes to 0, and after a period of time, the converter valve S 2L , S 2M The reliable shutdown of the energy buffer bridge arm A1 and the output voltage of the half-bridge submodule gradually become 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, 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 configuration of the active filter bridge arm is 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, so 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 It is 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 keeps connected 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 capacitor in the converter is kept balanced as a whole, so that energy can be transferred between DC ports of three different DC voltage levels.

[0071] In summary, the present invention discloses a three-port high-voltage DC-DC converter with an active filtering bridge arm, wherein the three-port high-voltage DC-DC converter with an active filtering bridge arm 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 the bridge arms, the energy buffer bridge arms A1 and A2 in the 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 It is always connected to the high-voltage side, the low-voltage side and the 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 submodule capacitors in the energy buffer bridge arm and the filter bridge arm are equal, and the energy stored in the capacitor in the converter is balanced as a whole, so that energy can be transferred between DC ports of three different DC voltage levels. The three-port high-voltage DC-DC converter with an active filter bridge arm of the present invention can realize energy transfer between three ports of different DC voltage levels, and does not need to be configured with an AC transformer, and has the characteristics of light weight, small size and high efficiency; it is suitable for realizing the interconnection of DC systems of three 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 examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that the features described in conjunction with a single embodiment may be used in other described embodiments.

Claims

1. A three-port high-voltage DC-DC converter with an active filter bridge arm, characterized in that: include: Energy transfer bridge arm, three active filter bridge arms and three converter valve groups; The energy transfer bridge arm comprises 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 high-pressure side, medium-pressure side and low-pressure side bridge arms, and the three converter valve groups are respectively high-pressure side, medium-pressure side and low-pressure side valve groups; 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 to both ends of the lower bridge arm; 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 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.

2. The three-port high-voltage DC-DC converter with active filtering bridge arm according to claim 1, characterized in that: 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 a reactor. The multiple half-bridge sub-modules are connected in series. One end of the reactor is connected to the output end of the half-bridge sub-module at the rear end, and the other end of the reactor serves as the output end of the bridge arm. The input end of the half-bridge sub-module at the front end serves as the input end of the bridge arm.

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

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

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

6. The control method of the three-port high-voltage DC-DC converter with active filtering bridge arm according to claim 2, characterized in that: include: Charging control: Open the high pressure side valve group S 1H The valve groups on the medium-voltage side and the low-voltage side are kept closed, and the sum of the output voltages of all the 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 S 2M And low pressure side valve group S 2L , and keep the high pressure side valve group S 1H Shut down, 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.

7. The control method of the three-port high-voltage DC-DC converter with active filtering bridge arm according to claim 6, characterized in that: The charging control includes: Open the high pressure side valve group S 1H And keep the medium-pressure side and low-pressure side valve groups closed; 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 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; 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; Among them, U A1 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 A is the high voltage side bridge arm 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.

8. The control method of the three-port high-voltage DC-DC converter with active filtering bridge arm according to claim 7, characterized in that: In the charging control stage, after charging for a period of time, 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 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 ; 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 ; Among them, U M and U L are the DC voltages of the medium voltage side port and the low voltage side port respectively.

9. The control method of the three-port high-voltage DC-DC converter with active filtering bridge arm according to claim 8, characterized in that: The discharge control comprises: 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 Shut down; Adjust the sum of the output voltages of all half-bridge submodules in the upper bridge arm A1 to U M -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 The 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 the current flows through the medium voltage side bridge arm A M The current i AM Take I A1 ÷T c The speed from -I M Change to I A1 -I M ; When the current flowing through the upper bridge 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 the current flows through the medium voltage side bridge arm A M The current i AM Maintain at I A1 -I M ; Among them, I A1 and I A2 are the currents flowing through the energy buffer bridge arms A1 and A2 during discharge, L L The 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.

10. The control method of the three-port high-voltage DC-DC converter with active filtering bridge arm according to claim 9, characterized in that: 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 The speed from -I A1 changes to 0, the current i of the lower bridge arm A2 A2 Take I A2 ÷T c The speed from -I A2 changes to 0, and 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 ; 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 the current 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 .

Images